^ 


aP34- 


Digitized  by  the  Internet  Archive 

in  2010  with  funding  from 

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http://www.archive.org/details/textbookofhumanp1889land 


A    TEXT-BOOK 


HUMAN     PHYSIOLOGY, 


STANDARD   MEDICAL  WORKS. 


ANDERSON  (Prof.  T.  McCall).  A  Treatise  on  Diseases  of  the  Skin;  with 
Special  Reference  to  Diagnosis  and  Treatment.  With  several  full-page  Plates, 
two  of  which  are  colored,  and  numerous  Wood  Engravings.     Octavo. 

Cloth,  ^4.50;  Leather,  1^5.50. 

BYFORD  (Prof.  W.  H.).  The  Diseases  of  Women.  Fourth  Edition.  Re- 
vised and  rewritten.  With  306  Illustrations,  over  100  of  which  are  original 
with  this  work.     Octavo.  Cloth,  $5.00  ;  Leather,  ^6.00. 

CAZEAUX  AND  TARNIER'S  Midwifery,  with  Appendix  by  Paul  F. 
MuNDE.  Eighth  American,  from  the  Eighth  French  and  First  Italian 
Editions.  Elegantly  Illustrated  with  seven  beautifully  colored  and  five  other 
full-page  Plates,  and  many  Wood   Engravings.     Octavo.     Students'  Edition. 

Cloth,  $5.00;   Leather,  $6.00. 

FAGGE  (Chas.  Hilton,  m.  d.).  The  Principles  and  Practice  of  Medicine. 
Edited  by  P.  H.  Pye-Smith,  m.  d.  Including  a  Section  on  Skin  Diseases 
by  the  Editor,  and  a  Chapter  on  Cardiac  Diseases  by  Samuel  Wilkes,  m.  d. 
2  Vols.     Octavo.  Cloth,  ^8.00;  Leather,  $10.00  ;  Half  Russia,  $12.00. 

GOWERS  (Prof.  W^m.  R.).  Manual  of  Diseases  of  the  Nervous  System. 
A  Complete  Text-book.     341  Illustrations.     Octavo. 

Cloth,  $6.50;  Leather,  57.50. 

HOLDEN  (Luther,  f.r.c.s.).  A  Manual  of  Anatomy.  Fifth  Edition.  Care- 
fully revised  and  enlarged.     208  Illustrations.     Octavo. 

Oilcloth,  S4.50;  Cloth,  $5.00;  Leather,  $6.00. 

JACOBSON  (W.  H.  A.,  f.r.c.s.).  The  Operations  of  Surgery.  A  Systematic 
Handbook  for  Practitioners,  Students  and  Hospital  Surgeons.  199  Illustra- 
tions (describing  over  230  operations  as  performed  at  Guy's  Hospital, 
London).     Octavo.      1000  pages.  Cloth,  $5.00 ;  Leather,  56.00. 

MEYER  (Dr.  Edouard).  A  Manual  of  Diseases  of  the  Eye.  Translated  from 
the  Third  Edition  by  A.  Freedland  Fergus,  m.  b.  (Glasgow).  270  Illustra- 
tions and  two  Colored  Plates  (by  Liebreich).     Octavo. 

Cloth,  54.50;  Leather,  $5.50. 

ROBERTS  (Prof.  Fred.).  The  Theory  and  Practice  of  Medicine.  Seventh 
Edition.     Thoroughly  revised  and  Enlarged.     Illustrated.     Octavo. 

Cloth,  55.50;  Leather,  56.50. 

WINCKEL  (Prof.  F.).  Text-book  on  Midwifery,  including  the  Diseases  of 
Childbed.  Authorized  Translation  by  J.  Clifton  Edgar,  m.  d..  Lecturer  on 
Obstetrics,  University  Medical  College,  New  York.  With  190  Illustrations, 
the  majority  of  which  are  original  with  this  work.     Octavo.       Nearly  Ready. 

*^*  These  books  may  be  obtained  through  any  bookseller,  or  upon  receipt  of 
the  price  any  book  w^ill  be  sent,  postage  prepaid.  Complete  Catalogues  upon  appli- 
cation. 

P.  BLAKISTON,  SON  &  CO.,  Medical  Publishers  and  Booksellers, 
1012   WALNUT   STREET,   PHILADELPHIA. 


A  TEXT-BOOK 


HUMAN    PHYSIOLOGY 


INCLUDING 


HISTOLOGY  AND   MICROSCOPICAL  ANATOMY ; 

WITH 

SPECIAL   REFERENCE   TO    THE   REQUIREMENTS    OF 

PRACTICAL  MEDICINE. 


DR.  L.  LANDOIS, 

PROFESSOR   OF   PHYSIOLOGY   AND   DIRECTOR    OP   THE   PHYSIOLOGICAL   INSTITUTE, 
UNIVERSITY   OF    GREIFSWALU. 


THIRD   AMERICAN, 
TRANSLATED    FROM    THE    SIXTH    GERMAN    EDITION. 

WITH   ADDITIONS    BY 

WILLIAM  STIRLING.  M.D.,  Sc.D., 

BRACKENBURY    PROFESSOR    OF    PHYSIOLOGY    AND    HISTOLOGY     IN    THE    OWENS    COLLEGE,    AND    PROFESSOR    IN    THE 
VICTORIA   UNIVERSITY,   MANCHESTER  ;    EXAMINER   IN   PHYSIOLOGY,   UNIVERSITY   OF   OXFORD. 

WITH  SIX  HUNDRED  AND  NINETY-TWO  ILLUSTRATIONS. 
PHILADELPHIA : 

P.    BLAKISTON,    SON    &    CO., 

IOI2    WALNUT     STREET. 

1889. 

[^//  Rights  Reserved. '\ 


WUl.^VIl  t'  /I"  *  ^ 


L232- 


Press  of  Wm.  F.  Fell  &  Oo., 

1220-24  SANSOM  ST., 

PHILAOCLPHIA. 


TO 

SIR   JOSEPH    LISTER,    Baronet, 

M.D.,  D.C.L.,  LL.D.,  F.R.SS.  (lOND.  AND  EDIN.), 

PROFESSOR  OF   CLINICAL  SURGERY   IN   KING'S   COLLEGE,    LONDON,   SURGEON-EXTRAORDINARY  TO   THE   QUEEN; 

FORMERLY   REGIUS   PROFESSOR   OF   CLINICAL   SURGERY   IN  THE   UNIVERSITY   OF   EDINBURGH, 

IN  ADMIRATION  OF 

Wht  Pan  of  ^(itnstf 

WHOSE  BRILLIANT  DISCOVERIES  HAVE  REVOLUTIONIZED 

MEDICAL  PRACTICE,  AND  CONTRIBUTED  INCALCULABLY  TO  THE 

WELL-BEING  OF  MANKIND  ; 

AND     IN     GRATITUDE    TO 

^Jxt  ®ieadter, 

WHOSE  NOBLE  EARNESTNESS  IN  INCULCATING 

THE  SACREDNESS  OF  HUMAN  LIFE 

STIRRED  THE  HEARTS  OF  ALL  WHO  HEARD  HIM  : 

BY  HIS  FORMER  PUPIL, 

THE  TRANSLATOR. 


PREFATORY  NOTE  TO  THE  THIRD  EDITION. 


In  offering  to  the  Profession  this  Third  English  Edition,  I  would  only  say  that 
the  whole  work  has  again  been  thoroughly  revised  and  in  many  parts  extended. 
In  all  respects  I  have  endeavored  to  keep  it  abreast  of  the  latest  investigations  in 
Physiology  and  their  bearing  on  Practical  Medicine  and  Surgery. 

I  have  again  to  thank  my  publishers  for  enabling  me  to  enhance  the  usefulness 
of  the  work  by  very  numerous  additions  to  the  Illustrations,  which  now  number 
692  as  compared  with  the  494  of  the  First  Edition.  Many  of  these  new  engrav- 
ings are  original ;  others  are  derived  from  the  Sixth  German  Edition  of  the  work, 
from  Stohr's  Lehrbuch  der  Histoiogie^OndUn^?,  Anatomy,  Ferrier's  Functions  of  the 
Brain  (Second  Edition),  H.  Obersteiner's  Anleitung  beim  Sttidium  des  Baues  der 
nervosen  Centralorgane,  Rollett's  Article  on  "Muscle"  in  the  Real-Encyclop(Bdie, 
Gowers'  Diseases  of  the  Nervous  System,  and  most  of  those  for  the  chapter  on 
Reproduction  from  Haddon's  Introductio?i  to  Embryology. 

In  addition,  I  have  to  tender  special  acknowledgments  to  my  colleagues  and 
friends,  Professors  A.  H.  Young,  James  Ross,  A.  W.  Hare  and  Dr.  Aug.  D. 
Waller;  as  well  as  to  Messrs.  Carl  Reichert,  of  Vienna;  W.  Petzold,  of  Leipzic; 
Rothe,  of  Prague;  Maw,  Cassella,  Krohne  and  Sesemann,  Evans  &  Wormall,  of 
London,  and  Ferries  &  Co.,  of  Bristol. 

For  the  first  time  the  work  appears  here  in  one  volume — an  arrangement 
adopted  both  to  meet  the  wishes  of  Students  and  to  facilitate  easy  reference.  I 
can  but  express  a  hope  that  the  present  Edition,  in  its  new  form,  will  meet  with 
the  same  very  kind  reception  accorded  to  its  predecessors. 

WILLIAM  STIRLING. 

The  Owens  College, 

Manchester. 


PREFACE  TO  THE  FIRST  EDITION. 


The  fact  that  Professor  Landois'  ^'  Lehrbtich  der  Physiologie  des  Menschen'^ 
has  already  passed  through  four  large  Editions  since  its  first  appearance  in  1880, 
shows  that  in  some  special  way  it  has  met  the  wants  of  Students  and  Practitioners 
in  Germany.  The  characteristic  which  has  thus  commended  the  work  will  be 
found  mainly  to  lie  in  its  evamQwi  pracitcaltty ;  and  it  is  this  consideration  which 
has  induced  me  to  undertake  the  task  of  putting  it  into  an  English  dress  for 
English  readers. 

Landois'  work,  in  fact,  forms  a  Bridge  between  Physiology  and  the  Practice 
of  Medicine.  It  never  loses  sight  of  the  fact  that  the  Student  of  to-day  is  the 
practicing  Physician  of  to-morrow.  Thus,  to  every  Section  is  appended — after  a 
full  description  of  the  normal  processes — a  short  resume  of  the  pathological  varia- 
tions, the  object  of  this  being  to  direct  the  attention  of  the  Student,  from  the 
outset,  to  the  field  of  his  future  practice,  and  to  show  him  to  what  extent  patho- 
logical processes  are  a  disturbance  of  the  normal  activities. 

In  the  same  way,  the  work  offers  to  the  busy  physician  in  practice  a  ready 
means  of  refreshing  his  memory  on  the  theoretical  aspects  of  Medicine.  He  can 
pass  backward  from  the  examination  of  pathological  phenomena  to  the  normal 
processes,  and,  in  the  study  of  these,  find  new  indications  and  new  lights  for  the 
appreciation  and  treatment  of  the  cases  under  consideration. 

With  this  object  in  view,  all  the  methods  of  investigation  which  may  with 
advantage  be  used  by  the  Practitioner,  are  carefully  and  fully  described ;  and 
Histology,  also,  occupies  a  larger  place  than  is  usually  assigned  to  it  in  Text-books 
of  Physiology. 

A  word  as  to  my  own  share  in  the  present  version  : — 

(i)  In  the  task  of  translating,  I  have  endeavored  throughout  to  convey  the 
author's  meaning  accurately,  without  a  too  rigid  adherence  to  the  original.  Those 
who  from  experience  know  something  of  the  difficulties  of  such  an  undertaking 
will  be  most  ready  to  pardon  any  shortcomings  they  may  detect. 

(2)  Very  considerable  additions  have  been  made  to  the  Histological,  and 
also  (where  it  has  seemed  necessary)  to  the  Physiological  sections.  All  such 
additions  are  enclosed  within  square  brackets  [  ].  I  have  to  acknowledge  my 
indebtedness  to  many  valuable  Papers  in  the  various   Medical  Journals — British 


X  PREFACE. 

and  Foreign — and  also  to  the  Histological  Treatises  of  Cadiat,  Ranvier,  and  Klein; 
Qnain's  A/i(7/o//iy,  Vol.  ii,  Ninth  Edition;  Herma-nn's  /fan(/hfc/i  t/er  Pkysio/ogt'e; 
and  the  Text-books  on  Physiology,  by  Rutherford,  Foster,  and  Kirkes;  Gamgee's 
Physiological  Chemistry;  Ewald's  Digestion  ;  and  Roberts'  Digestive  Ferments. 

(3)  The  Illustrations  have  been  greatly  increased  in  number,  viz.,  from  275 
in  the  Fourth  German  Edition  to  494  in  the  English  version.  These  additional 
Diagrams,  with  the  sources  whence  derived,  are  distinguished  in  the  List  of  Wood- 
cuts by  an  asterisk. 

There  only  remains  for  me  now  to  express  my  thanks  to  all  who  have  kindly 
helped  in  the  progress  of  the  work,  either  by  furnishing  Illustrations  or  otherwise 
— especially  to  Drs.  Byrom  Bramwell,  Dudgeon,  Lauder  Brunton,  and  Knott; 
Mr.  Hawksley ;  Professors  Hamilton  and  McKendrick ;  to  my  esteemed  teacher 
and  friend,  Professor  Ludwig,  of  Leipzic  ;  and,  finally,  to  my  friend,  Mr.  A. 
W.  Robertson,  m.a.,  formerly  Assistant  Librarian  in  the  University,  and  now 
Librarian  of  the  Aberdeen  Public  Library,  for  much  valuable  assistance  while  the 
work  was  passing  through  the  press. 

In  conclusion — and  forgetting  for  the  moment  my  own  connection  with  it — I 
heartily  commend  the  woxV  per  se  to  the  attention  of  Medical  men,  and  can  wish 
for  it  no  better  fate  than  that  it  may  speedily  become  as  popular  in  this  country 
as  it  is  in  its  Fatherland. 

WILLIAM  STIRLING. 
Aberdeen  University. 


GENERAL  CONTENTS. 


INTRODUCTION. 

PAGK 

The  Scope  of  Physiology  and  its  Relations  to  other  Branches  of  Natural  Science, 33 

Matter, 34 

Forces, 35 

Law  of  the  Conservation  of  Energy, 3^ 

Animals  and  Plants, 39 

Vital  Energy  and  Life, 4^ 

I.  PHYSIOLOGY  OF  THE  BLOOD. 

SECTION 

1 .  Physical  Properties  of  the  Blood, 42 

2.  Microscopic  Examination  of  the  Blood, 44 

3.  Histology  of  the  Human  Red  Blood  Corpuscles,      46 

4.  Effects  of  Reagents  on  the  Blood  Corpuscles, 47 

5.  Preparation  of  the  Stroma — Making  Blood  "  Lake  Colored," 49 

6.  Form  and  Size  of  the  Blood  Corpuscles  of  Different  Animals 50 

7.  Origin  of  the  Red  Blood  Corpuscles, 5^ 

8.  Decay  of  the  Red  Blood  Corpuscles, 53 

9.  The  Colorless  Corpuscles — Leucocytes — Blood  Plates — Granules, 53 

10.  Abnormal  Changes  of  the  Blood  Corpuscles, 5^ 

11.  Chemical  Constituents  of  the  Red  Blood  Corpuscles, 59 

12.  Preparation  of  Hsemoglobin  Crystals, 59 

13.  Quantitative  Estimation  of  Haemoglobin, 60 

14.  Use  of  Spectroscope, 61 

15.  Compounds  of  Haemoglobin — Methfemoglobin, 62 

16.  Carbonic  Oxide  Haemoglobin — Poisoning  with  Carbonic  Oxide, 65 

17.  Other  Compounds  of  Hemoglobin, 66 

18.  Decomposition  of  Hsemoglobin, 66 

19.  Haemin  and  Blood  Tests, 67 

20.  Hasmatoidin, 68 

21.  The  Colorless  Proteid  of  Haemoglobin, 68 

22.  Proteids  of  the  Stroma, 69 

23.  The  other  Constituents  of  Red  Blood  Corpuscles, •  69 

24.  Chemical  Composition  of  the  Colorless  Corpuscles, 69 

25.  Blood  Plasma,  and  its  Relation  to  Serum, ^o 

26.  Preparation  of  Plasma, • •  7° 

27.  Fibrin — Coagulation  of  the  Blood, 7^ 

28.  General  Phenomena  of  Coagulation, 7^ 

29.  Cause  of  Coagulation  of  the  Blood, 74 

30.  Source  of  the  Fibrin  Factors, 77 

31.  Relation  of  the  Red  Blood  Corpuscles  to  the  Formation  of  Fibrin, 77 

32.  Chemical  Composition  of  the  Plasma  and  Serum, 7^ 

33.  The  Gases  of  the  Blood, • ,  80 

34.  Extraction  of  the  Blood  Gases, 81 

35.  Quantitative  Estimation  of  the  Blood  Gases, 82 

36.  The  Blood  Gases, 83 

37.  Is  Ozone  (O3)  present  in  Blood? ^4 

38.  Carbon  dioxide  and  Nitrogen  in  Blood, 85 

39.  Arterial  and  Venous  Blood, °6 

40.  Quantity  of  Blood, "    ' -  86 

41.  Variations  firom  the  Normal  Conditions  of  the  Blood, 87 


Xll  CONTENTS. 

II.   PHYSIOLOGY   OF  THE  CIRCULATION. 

SECTION  PACK 

42.  (leneral  View  of  the  Circulation, 91 

43.  The   Heart 92 

44.  Arrangement  of  the  Cardiac  Muscular  Fibres, 92 

45.  Arrangement  of  the  Ventricular  Fibres 94 

46.  Pericanlium.  Endocardium,  Valves, 95 

47.  Automatic  Regulation  of  the  Heart, 96 

48.  The  Movements  of  the  Heart, 98 

49.  Pathological  Disturbances  of  Cardiac  Action, loi 

50.  The  Ajiex  Beat— The  Cardiogram, 102 

51.  The  Time  Occupied  by  the  Cardiac  Movements, 107 

52.  Pathological  Disturbance  of  the  Cardiac  Impulse, no 

53.  The  Heart  Sounds, 112 

54.  Variations  of  the  Heart  Sounds, 114 

55.  The  Duration  of  the  Movements  of  the  Heart, 116 

56.  Physical  Examination  of  the  Heart, 1 17 

57".  Innervation  of  Heart — Cardiac  Nerves, 117 

58.  The  Automatic  Motor  Centres  of  the  Heart 119 

59.  The  Cardiopneumatic  Movements, 128 

60.  Influence  of  the  Respiratory  Pressure  on  the  Heart, 129 

THE   CIRCULAnON. 

61.  The  Flow  of  ?'luids  through  Tubes, 132 

62.  Propelling  Force,  Velocity  of  Current,  Lateral  Pressure, 132 

63.  Currents  through  Capillary  Tubes 134 

64.  Movements  of  Fluids  and  Wave  Motion  in  Elastic  Tubes,    .    .                    134 

65.  Structure  and  Properties  of  the  Blood  Vessels, 134 

66.  Investigation  of  the  Pulse, 139 

67.  Pulse  Tracing,  or  Sphygmogram, 144 

68.  Origin  of  the  Dicrotic  Wave,    .    .     • 145 

69.  Dicrotic  Pulse, 14^ 

70.  Characters  of  the  Pulse, •  149 

71.  Variations  in  the  Strength,  Tension,  and  Volume  of  the  Pulse, 150 

72.  The  Pulse  Curves  of  various  Arteries, I5' 

73.  Anacrotism, '5^ 

74.  Influence  of  the  Respiratory  Movements  on  the  Pulse  Curve, 153 

75.  Influence  of  Pressure  upon  the  Form  of  the  Pulse  Wave, 155 

76.  Rapidity  of  Transmission  of  Pulse  Weaves, 156 

77.  Propagation  of  the  Pulse  Wave  in  Elastic  Tubes, 156 

78.  Velocity  of  the  Pulse  Wave  in  Man, 156 

79.  Other  Pulsatile  Phenomena, 157 

80.  Vibrations  communicated  to  the  Body  by  the  Action  of  the  Heart, 158 

8i.  The  Blood  Current 159 

82.  Schemata  of  the  Circulation, 161 

83.  Capacity  of  the  Ventricles, 161 

84.  Estimation  of  the  Blood  Pressure, 161 

85.  Blood  Pressure  in  the  Arteries, 165 

86.  Blood  Pressure  in  the  Capillaries, 171 

87.  Blood  Pressure  in  the  Veins, 171 

88.  Blood  Pressure  in  the  Pulmonary  Artery, 173 

89.  Measurement  of  the  Velocity  of  the  Blood  Stream, 175 

90.  Velocity  of  the  Blood  in  Arteries,  Capillaries,  and  Veins 177 

91.  Estimation  of  the  Capacity  of  the  Ventricles, 179 

92.  The  Duration  of  the  Circulation, 179 

93.  Work  of  the  Heart, 180 

94.  Blood  Current  in  the  Smallest  Vessels, 180 

95.  Passage  of  the  Blood  Corpuscles  out  of  the  Vessels  [Diapedesis], 182 

96.  Movement  of  the  Blood  in  the  Veins, 183 

97.  Sounds  or  Bruits  within  Arteries, 184 

98.  Venous  Murmurs 185 

99.  The  Venous  Pulse — Phlebogram 185 

100.  Distribution  of  the  Blood, 187 

101.  Plethysmography, 187 

102.  Transfusion  of  Blood, 189 


CONTENTS.  XIU 
THE  BLOOD  GLANDS. 

SECTION  PAGK 

103.  The  Spleen — Thymus — Thyroid — Suprarenal  Capsules — Hypophysis  Cerebri — Coccygeal 

and  Carotid  Glands, 102 

104.  Comparative, 201 

105.  Historical  Retrospect, ,    .  202 

III.   PHYSIOLOGY   OF    RESPIRATION. 

106.  Structure  of  the  Air  Passages  and  Lungs, 203 

107.  Mechanism  of  Respiration, 209 

108.  Quantity  of  Gases  Respired, 210 

109.  Number  of  Respirations, 211 

no.  Time  occupied  by  the  Respiratory  Movements, 212 

111.  Pathological  Variations  of  the  Respiratory  Movements, 215 

112.  General  View  of  the  Respiratory  Muscles, 216 

113.  Action  of  the  Individual  Respiratory  Muscles, 217 

114.  Relative  Size  of  the  Chest, 220 

115.  Pathological  Variations  of  the  Percussion  Sounds, 222 

116.  The  Normal  Respiratory  Sounds, 223 

117.  Pathological  Respiratory  Sounds, 224 

118.  Pressure  in  the  Air  Passages  during  Respiration, 225 

119.  Appendix  to  Respiration, 226 

120.  Peculiarly  Modified  Respiratory  Sounds, 226 

121.  Quantitative  Estimation  of  CO2,  O,  and  Watery  Vapor, 227 

122.  Methods  of  Investigation, 228 

123.  Composition  and  Properties  of  Atmospheric  Air, 230 

124.  Composition  of  Expired  Air 231 

125.  Daily  Quantity  of  Gases  Exchanged, 232 

126.  Review  of  the  Daily  Gaseous  Income  and  Expenditure, 232 

127.  Conditions  Influencing  the  Gaseous  Exchanges, 232 

128.  Diffusion  of  Gases  within  the  Lungs, 234 

129.  Exchange  of  Gases  between  the  Blood  and  Air, 235 

130.  Dissociation  of  Gases, 237 

131.  Cutaneous  Respiration, 238 

132.  Internal  Respiration, 238 

133.  Respiration  in  a  Closed  Space 240 

134.  Dyspnoea  and  Asphyxia, 241 

135.  Respiration  of  Foreign  Gases, 244 

136.  Accidental  Impurities. of  the  Air, 244 

137.  Ventilation  of  Rooms, 245 

138.  Formation  of  Mucus, 245 

139.  Action  of  the  Atmospheric  Pressure, 247 

140.  Comparative  and  Historical, 249 

IV.   PHYSIOLOGY    OF   DIGESTION. 

141.  The  Mouth  and  its  Glands, 250 

142.  The  SaUvary  Glands, 252 

143.  Histological  Changes  in  Salivary  Glands, 253 

144.  The  Nerves  of  the  Salivary  Glands, 255 

145.  Action  of  Nerves  on  the  Salivary  Secretion, 256 

146.  The  Saliva  of  the  Individual  Glands, 260 

147.  The  Mixed  Saliva  in  the  Mouth, 261 

148.  Physiological  Action  of  Saliva, 262 

149.  Tests  for  Sugar, 264 

150.  Quantitative  Estimation  of  Sugar, 265 

151.  Mechanism  of  the  Digestive  Apparatus, 266 

152.  Introduction  of  the  Food, 267 

153.  The  Movements  of  Mastication 267 

154.  Structure  and  Development  of  the  Teeth, 268 

155.  Movements  of  the  Tongue, 271 

156.  Deglutition, .' 272 

157.  Movements  of  the  Stomach, 275 

158.  Vomiting, 276 

159.  Movements  of  the  Intestine, 277 


XIV  CONTENTS. 

SECTION  PACK 

160.  Excretion  of  Fecal  Matter, 278 

161.  Conditions  inlluencing  the  Movements  of  the  Intestine 280 

162.  Structure  of  the  Stomach, 284 

i6j.  The  Gastric  Juice, 287 

164.  Secretion  of  Gastric  Juice, 288 

165.  Methods  of  obtaining  Gastric  Juice, 291 

166.  Process  of  Gastric  Digestion, 292 

167.  (iases  in  the  Stomach, 297 

168.  Structure  of  the  Pancreas, 297 

169.  The  Pancreatic  Juice, 298 

170.  Digestive  Action  of  the  Pancreatic  Juice, 299 

171.  The  Secretion  of  the  Pancreatic  Juice, 302 

172.  Preparation  of  Peptonized  Food, 303 

173.  Structure  of  the  Liver, 303 

174.  Chemical  Composition  of  the  Liver  Cells, 307 

175.  Diabetes  Mellitus,  or  Glycosuria, 310 

176.  The  Functions  of  the  Liver 311 

177.  Constituents  of  the  Bile 312 

178.  Secretion  of  Pile, 315 

179.  Excretion  of  Bile, 316 

180.  ReabsoriHion  of  Bile — Jaundice, 317 

iSl.   Functions  of  the  Bile, 319 

1S2.   Fate  of  the  Bile  in  the  Intestine, 320 

183.  The  Intestinal  Juice, 321 

184.  Fermentation  Processes  in  the  Intestine, 324 

185.  Processes  in  the  Large  Intestine, 328 

1S6.   Pathological  Variations, 331 

187.  Comparative  Physiology, 333 

188.  Historical  Retrospect, 334 

V.  PHYSIOLOGY  OF  ABSORPTION. 

189.  The  Organs  of  Absorption, 336 

190.  Structure  of  the  Small  and  Large  Intestines, 336 

191.  Absorption  of  the  Digested  Food, 342 

192.  Absorptive  Activity  of  the  Wall  of  the  Intestine, 344 

193.  Influence  of  the  Nervous  System. 347 

194.  Feeding  with  "  Nutrient  Enemala  " 347 

195.  Chyle  Vessels  and  Lymphatics, 348 

196.  Origin  of  the  Lymphatics 348 

197.  The  Lymph  Glands, 351 

198.  Properties  of  Chyle  and  Lymph, 353 

199.  Quantity  of  Lymph  and  Chyle,. 354 

200.  Origin  of  Lymph, 355 

201.  Movement  of  Chyle  and  Lymph, 356 

202.  Absorption  of  Parenchymatous  Effusions, 359 

203.  Dropsy,  CEdema,  Serous  Effusions, 359 

204.  Comparative  Physiology, 360 

205.  Historical  Retrospect 361 

VL    PHYSIOLOGY  OF  ANIMAL  HEAT. 

206.  Sources  of  Heat, 362 

207.  Homoiothermal  and  Poikilothermal  Animals, 365 

208.  Methods  of  Estimating  Temperature — Thermometry 366 

209.  Temperature  Topography, 369 

210.  Conditions  Influencing  the  Temperature  of  Organs, 370 

211.  Estimation  of  the  Amount  of  Heat — Calorimetry 371 

212.  Thermal  Conductivity  of  Animal  Tissues, 373 

213.  Variations  of  the  Mean  Temperature, 373 

214.  Regulation  of  the  Temperature, 376 

215.  Income  and  Expenditure  of  Heat, 379 

216.  Variations  in  Heat  Production, 380 

217.  Relation  of  Heat  Production  to  Bodily  Work, 381 

218.  Accommodations  for  Different  Temperatures, 381 

219.  Storage  of  Heat  in  the  Body, 382 


CONTENTS.  XV 

SECTION  PAGE 

220.  Fever, 383 

221.  Artificial  Increase  of  the  Temperatvtre, 384 

222.  Employment  of  Heat, 384 

223.  Increase  of  Temperature /^jAi'«(7;'/^w, 385 

224.  Action  of  Cold  on  the  Body, 385 

225.  Artificial  Lowering  of  Temperature, 386 

226.  Employment  of  Cold, 387 

227.  Heat  of  Inflamed  Parts, 387 

228.  Historical  and  Comparative, 387 

VII.   PHYSIOLOGY  OF  THE  METABOLIC  PHENOMENA 
OF  THE  BODY. 

229.  General  View  of  Food  Stuifs, 388 

230.  Structure  and  Secretion  of  the  Mammary  Glands, 390 

231.  Milk  and  its  Preparations, 392 

232.  Eggs, 395 

233.  Flesh  and  its  Preparations, 396 

234.  Vegetable  Foods, • 397 

235.  Condiments — Coffee,  Tea,  and  Alcohol, 400 

236.  Equilibrium  of  the  Metabolism, 402 

237.  Metabolism  during  Hunger  and  Starvation,      408 

238.  Metabolism  during  a  purely  Flesh  Diet, 409 

239.  A  Diet  of  Fat  or  of  Carbohydrates, 410 

240.  Mixture  of  Flesh  and  Fat, 411 

241.  Origin  of  Fat  in  the  Body, 411 

242.  Corpulence, .  413 

243.  The  Metabolism  of  the  Tissues, ' 414 

244.  Regeneration  of  Organs  and  Tissues, 416 

245.  Transplantation  of  the  Tissues, 419 

246.  Increase  in  Size  and  Weight  during  Growth, 419 

GENERAL  VIEW  OF  THE  CHEMICAL  CONSTITUENTS  OF 
THE   ORGANISM. 

247.  Inorganic  Constituents, 4?^ 

248.  Organic  Compounds — Proteids, 423 

249.  The  Animal  and  Vegetable  Proteids  and  their  Properties, 424 

250.  The  Albuminoids, 426 

251.  The  Fats, 429 

252.  The  Carbohydrates 430 

253.  Historical  Retrospect, 433 

VIII.   THE  SECRETION  OF  URINE. 

254.  Structure  of  the  Kidney, 434 

255.  The  Urine, 440 

256.  Organic  Constituents  of  Urine — Urea, 443 

257.  Qualitative  and  Quantitative  Estimation  of  Urea, 446 

258.  Uric  Acid, 447 

259.  Qualitative  and  Quantitative  Estimation  of  Uric  Acid, 449 

260.  Kreatinin  and  other  Substances, 449 

261.  Coloring  Matters  of  the  Urine, 452 

262.  Indigo,  Phenol,  Kresol,  Pyrokatechin, 453 

263.  Spontaneous  Changes  in  Urine,  Fermentations, 456 

264.  Albumin  in  Urine, 457 

265.  Blood  in  Urine 460 

266.  Bile  in  Urine, 462 

267.  Sugar  in  Urine, 462 

268.  Cystin, 465 

269.  Leucin,  Tyrosin, ,    .  • 465 

270.  Deposits  in  Urine, 465 

271.  General  Scheme  for  Detecting  Urinary  Deposits, 4^7 

272.  Urinary  Calculi, •    .  468 

273.  The  Secretion  of  Urine, 4^9 


XVI  CONTENTS. 

SECTION  PAGE 

274.  The  Formation  of  Urinary  Constituents, 473 

275.  Passage  of  Various   Substances  into  the  Urine, 475 

276.  Influence  of  Nerves  on  the  Renal  Secretion, 47^ 

277.  Uri\;mia,  Ammoniivmia,      479 

278.  Structure  and  Functions  of  the  Ureter, 480 

279.  Urinary  Bladder  and  Urethra, 481 

280.  Accumulation  and    Retention  of  Urine, 483 

281.  Retention  and  Incontinence  of  Urine, 486 

282.  Comparative  and  Historical, 486 

IX.  FUNCTIONS  OF   THE  SKIN. 

283.  Structure  of  the  Skin,  Nails,  and  Hair, 487 

284.  The  Glands  of  the  Skin, 492 

285.  The  Skin  as  a  Protective  Covering, 493 

286.  Cutaneous   Respiration  and  Secretion — Sweat, 493 

287.  Conditions  Influencing  the  Secretion  of  Sweat 495 

288.  Pathological  Variations, 497 

289.  Cutaneous  Absorption — Galvanic  Conduction, 498 

290.  Comparative — Historical, 499 

X.  PHYSIOLOGY  OF  THE  MOTOR  APPARATUS. 

291.  Ciliary  Motion,  Pigment  Cells, 5°° 

292.  Structure  and  Arrangement  of  the  Muscles, • 502 

293.  Physical  and  Chemical  Properties  of  Muscle, 511 

294.  Metabolism  in  Muscle, 5 '3 

295.  Rigor  mortis 5'5 

296.  Muscular   Excitability, S'9 

297.  Changes  in  a  Muscle  during  Contraction, 5^4 

298.  Muscular  Contraction, S^" 

299.  Rapidity  of  Transmission  of  a  Muscular  Contraction, 537 

300.  Muscular  Work, 538 

301.  The  Elasticity  of  Muscle, 54^ 

302.  Formation  of  Heat  in  an  Active  Muscle, 543 

303.  The   Muscle  Sound, 545 

304.  Fatigue  and   Recovery  of  Muscle,   .    .    .    .  • 545 

305.  The  Mechanism  of  the  Joints, 547 

306.  Arrangement  and  Uses  of  the  Muscles  of  the  Body, 549 

307.  Gymnastics — Pathological  Motor  Variations 553 

308.  Standing, 554 

309.  Silting, 555 

310.  Walking,  Running,  and  Leaping, • 555 

311.  Comparative, 55^ 

XI.   VOICE  AND  SPEECH. 

312.  Voice  and  Speech, 559 

313.  Arrangement  of  the  Larynx, 5^° 

314.  Organs  of  Voice — Laryngoscopy, 5^5 

315.  Conditions  Modifying  the  Laryngeal  Sounds, 5^8 

316.  Range  of  the  Voice, 5^9 

317.  Speech — The  Vowels, 5^9 

318.  The  Consonants, 57^ 

319.  Pathological  Variations  of  Voice  and  Speech, 573 

320.  Comparative — Historical, 573 

XII.  GENERAL  PHYSIOLOGY  OF  THE  NERVES  AND 
ELECTRO-PHYSIOLOGY. 

321.  Structure  and  Arrangement  of  the  Nerve  Elements, 575 

322.  Chemical  and  Mechanical  Properties  of  Nerve  Substance, • 581 

323.  Metabolism  of  Nerves, 582 

324.  Excitability  of  Nerves — Stimuh, 583 

325.  Diminution  of  Excitability — Degeneration  and  Regeneration  of  Nerves, 587 


CONTENTS.  XVll 

SECTION  PAGE 

326.  The  Galvanic   Current, 591 

327.  Action  of  the  Galvanic   Current — Galvanometer, 593 

328.  Electi-olysis, , • 594 

329.  Induction — Extra-Current — Magneto-Induction, 599 

330.  Du   Bois-Reymond's   Inductorium 601 

331.  Electrical  Currents  in  Passive  ^Muscle  and  Nerve, 603 

332.  Currents  of  Stimulated  Muscle  and  Nerve, 607 

333.  Currents  in   Nerve  and  Muscle  during  Electrotonus, 611 

334.  Theories  of  Muscle  and  Nerve  Currents, 613 

335.  Electrotonic  Alteration  of  the  Excitability, 615 

336.  Electrotonus — Law  of  Contraction, 617 

337.  Rapidity  of  Transmission  of  Nervous  Impulses, 620 

338.  Double  Conduction  in  Nerves, 623 

339.  Therapeutical  Uses  of  Electricity — Reaction  of  Degeneration, 624 

340.  Electrical  Charging  of  the  Body, 629 

341.  Comparative- — Historical, 629 

XIII.  PHYSIOLOGY  OF  THE  PERIPHERAL  NERVES. 

342.  Classification  of  Nerve  Fibres, 631 

343.  Nervus  Olfactorius, 634 

344.  Nervus  Opticus, 634 

345.  Nervus  Oculomotorius, 637 

346.  Nervus   Trochlearis, 639 

347.  Nervus    Trigeminus, 640 

348.  Nervus  Abducens, 649 

349.  Nervus  Facialis, 649 

350.  Nervus  Acusticus, 653 

351.  Nervus  Glosso-pharyngeus, 655 

352.  Nervus  Vagus, 656 

353.  Nervus  Accessorius, 664 

354.  Nervus  Hypoglossus, 664 

355.  The  Spinal  Nerves, 665 

356.  The  Sympathetic    Nerve, 670 

357.  Comparative — Historical, 673 


XIV.  PHYSIOLOGY  OF    THE  NERVE  CENTRES. 

358.  General, ,    .    , 675 

359.  Structure  of  the   Spinal  Cord, 676 

360.  Spinal  Reflexes, •  .    .    .    .     • 686 

361.  Inhibition  of  the  Reflexes, 689 

362.  Centres  in  the  Spinal  Cord,  ^ 693 

363.  Excitability  of   the  Spinal  Cord, 695 

364.  The  Conducting  Paths  in  the  Spinal  Cord, 696 

365.  General  Schema  of  the  Brain, 7°° 

366.  The  Medulla  Oblongata, 705 

367.  Reflex  Centres  of  the  Medulla  Oblongata, Jio 

368.  The  Respiratory  Centre, ' 7^2 

369.  The  Cardio-Inhibitory  Centre, 7"^ 

370.  The  Accelerans  Cordis  Centre, 720 

371.  Vasomotor  Centre  and  Vasomotor  Nerves, 7^2 

372.  Vaso- dilator  Centre  and  Vaso-dilator  Nerves, 729 

373.  The  Spasm  Centre — The  Sweat  Centre, 73° 

374.  Psychical  Functions  of  the  Cerebrum, 73^^ 

375.  Structure  of  the  Cerebrum — Motor  Cortical  Centres, 737 

376.  The  Sensory  Cortical  Centres, 75^ 

377.  The  Thermal  Cortical  Centres, 755 

378.  Topography  of  the  Cortex  Cerebri, 756 

379.  The  Basal  Gangha— The  Mid-brain, 765 

380.  The  Structure  and  Functions  of  the  Cerebellum, 772 

381.  The  Protective  Apparatus  of  the  Brain, 776 

382.  Comparative — Historical, 779 

2 


XVlll  CONTENTS. 

XV.   PHYSIOLOGY    OF    THE    SENSE    ORGANS. 
I.  SIGHT. 

SECTION  PAGE 

383.  Intraductory  Observations 781 

384.  Histology  of  the  Eye, 783 

385.  Dioptric  Observations 792 

386.  Formation  of  a  Retinal  Image, 796 

387.  Accommodation  of  the  Eye, 799 

388.  Normal  and  Abnormal  Refraction, 803 

389.  The  Power  of  Accommodation, 805 

390.  Spectacles, 806 

391.  Chromatic  Aberration  and  Astigmatism, 807 

392.  The  Iris, 808 

393.  Entoptical  Phenomena, 812 

394.  Illumination  of  the  Eye — The  Ophthalmoscope, 814 

395.  Activity  of  the  Retina  in  Vision, 818 

396.  Perception  of  Colors, 823 

397.  Color    Blindness 828 

398.  Stimulation  of  the  Retina 829 

399.  Movenientsof  the  Eyeballs, S^^ 

400.  Binocular  Vision, 837 

401.  Single  Vision — Identical  Points, 837 

402.  Stereoscopic  Vision, 839 

403.  Estimation  of  Size  and  Distance, 841 

404.  Protective  Organs  of  the  Eye, 843 

405.  Comparative  — Historical, 845 

2.  HEARING. 

406.  Structure  of  the  Organ  of  Hearing, 847 

407.  Physical  Introduction, 848 

408.  Ear  Muscles 849 

409.  Tympanic   Membrane, 849 

410.  The  Auditory  Ossicles  and  their  Muscles, 851 

411.  Eustachian  Tube — Tympanum, 855 

412.  Conduction  of  Sound  in  the  Labyrinth, 856 

413.  Structure  of  the  Labyrinth, 857 

414.  Auditory  Perceptions  of  Pitch, 860 

415.  Perception  of  Quality — Vowels, 863 

416.  Action  of  the  Labyrinth, 867 

417.  Harmony — Discords — Beats, 868 

418.  Perception  of  Sound, 869 

419.  Comparative — Historical, 870 

3.  SMELL. 

420.  Structure  of  the  Organ  of  Smell, 87 1 

421.  Olfactory  Sensations, 872 

4.  TASTE. 

422.  Position  and  Structure  of  the  Organs  of  Taste, 874 

423.  Gustatory  Sensations, 876 

5.  TOUCH, 

424.  Terminations  of  Sensory  Nerves 878 

425.  Sensory  and  Tactile  Sensations, 881 

426.  The  Sense  of  Locality, 882 

427.  The  Pressure  Sense, 885 

428.  The  Temperature  Sense 887 

429.  Common   Sensation — Pain, 889 

430.  The  Muscular  Sense,      891 


CONTENTS.  XIX 
XVI.  PHYSIOLOGY  OF  REPRODUCTION  AND  DEVELOPMENT. 

SECTION                                                      _  PAGE 

431.  Forms  of  Reproduction, 893 

432.  Testis — Seminal  Fluid,   .    .    .    , 896 

433.  The  Ovary — Ovum — Uterus, 901 

434.  Puberty, 906 

435.  Menstruation, 007 

436.  Penis — Erection, 909 

437.  Ejaculation — Reception  of  the  Semen, 911 

438.  Fertilization  of  the  Ovum, 912 

439.  Impregnation  and  Cleavage  of  the  Ovum, 913 

440.  Structures  formed  from  the  Epiblast, 917 

441.  Structures  formed  from  the  Mesoblast  and  the  Hypoblast, 919 

442.  Formation  of  the  Heart  and  Embryo, 921 

443.  Further  fonnation  of  the  Body, 922 

444.  Formation  of  the  Amnion  and  Allantois, 923 

445.  Human  Fcetal  Membranes — Placenta, 925 

446.  Chronology  of  Human  Development, 929 

447.  Formation  of  the  Osseous  System, 930 

448.  Development  of  the  Vascular  System, 934 

449.  Formation  of  the  Intestinal  Canal, 938 

450.  Development  of  Genito-Urinary  Organs, 940 

451.  Formation  of  the  Central  Nervous  vSystem, 943 

452.  Development  of  the  Sense  Organs, 944 

453.  Birth, 946 

454.  Comparative — Historical, 947 

Appendix  A. ;  Bibliography, 950 

Appendix  B. ;  Tables  of  Measure  (Metric  and  Ordinary)  and  of  Temperature, 954 

Index, 955 


LIST  OF  ILLUSTRATIONS. 


FIGURE  PAGE 

1.  Human  colored  blood  corpuscles, - 44 

2.  Apparatus  of  Abbe  and  Zeiss  for  estimating  the  blood  corpuscles, 45 

3.  Mixer, 45 

*4.   Gower's  hjemacytometer  {^Haivksle)'), 46 

*5.  Crenation  of  human  blood  corpuscles, 47 

6.  Red  blood  corpuscles  showing  various  changes  of  shape,       48 

*7.  Effect  of  reagents  on  blood  corpuscles  [Stirling), 49 

8.  Vaso-formative  cells, 52 

9.  White  blood  corpuscles  and  fibrin, 54 

*io.  White  blood  corpuscles  (A7«w), 55 

11.  Amcehoid  movements  of  colorless  corpuscles, 56 

12.  Blood  plates  and  their  derivatives, 57 

13.  Haemoglobin  crystals, 59 

*I4.  Gowers'  haemoglobinometer  (Hawksley), 60 

*I5.  Fleischl's  ha;mometer  {^Reicherf), 61 

16.  Scheme  of  a  spectroscope, 62 

17.  Various  spectra  of  haemoglobin  and  its  compounds, ,    .    .    .  63 

18.  Haemin  crystals, 67 

19.  Hcemin  ciystals  prepared  from  traces  of  blood, 67 

20.  Hfematoidin  crystals, 68 

*2i.   Hewson's  experiment, 74 

22.  Scheme  of  Pfliiger's  gas  pump, 82 

*23.   Micrococcus,  bacterium,  vibrio, 90 

*24.  Bacillus  anthracis, 90 

25.  Scheme  of  the  circulation, 91 

26.  Muscular  fibres  from  the  heart, 92 

27.  Muscular  fibres  in  the  left  auricle, 93 

28.  Muscular  fibres  in  the  ventricles, 94 

*29.  Lymphatic  from  the  pericardium  {Cadiat), 95 

*30.   Section  of  the  endocardium  {Cadiat), 95 

*3I.  Purkinje's  fibres  {Ranvier), 96 

32.  Cast  of  the  ventricles  of  the  human  heart, 99 

33.  The  closed  semilunar  valves, 100 

*34.  Gaule's  maximum  and  minimum  manometer  (^Gscheidlen), loo 

*35.  Manometer  of  Gaul e  (  6^jc^(?Z£f/f«), 100 

*36.  Various  cardiographs  {^Hermann), 103 

*37.  Cardiogram, 103 

*38.  Arteriogram  and  Cardiogram, 104 

39.  Curves  of  the  apex  beat, ' 104 

40.  Changes  of  the  heart  during  systole,  and  sections  of  thorax, 105 

*4I.   Dog's  heart,  posterior  surface  [L^cdwig  and  Hesse), 106 

*42.  Left  lateral  surface  (^Ludwig  and  Hesse), 106 

*43.  Anterior  surface  {Liidwig  and  Hesse), 106 

*44.   Base  of  heart  i^Ludiuig  arid  Hesse), , 107 

*45.  Base  of  heart  in  systole  and  diastole  (Ze^fl^w?^  rtw^  i^i-jf), 107  _ 

46.  Curves  from  a  rabbit's  ventricle, I08 

*47.  Marey's  registering  tambour  [Hermann), 109 

48.  Curs'es  obtained  with  a  cardiac  sound, no 

49.  Curves  from  the  cardiac  impulse, iii,  112 

*5o.  Scheme  of  cardiac  cycle, 112 

*5i.   Position  of  the  heart  in  the  chest  (Z^«f/iia  a«(/  CazV^/wfr), 115 

*52.  Curves  of  excised  rabbits'  hearts  (iVzV/zwo-,  <2/?fr  Waller), 1 16 

*53.  Heart  of  frog  from  the  front  (Z'ci^r), 1 18 

xxi 


XXll  LIST    OF    ILLUSTRATIONS. 

FIGURE  PAGE 

*54.  Heart  of  frog  from  behind  I^Ecker), Ii8 

*55.  Auricular  septum  [Ecker], 119 

*56.  Bipolar  nerve  cells  from  a  frog's  heart, 1 19 

*57.  Scheme  of  frog's  heart  {Bntntnn), 1 19 

*58.  Stannius's  experiment  i^Bnutton), 1 19 

*59.  Luciani's  groups  of  cardiac  pulsations  (//<?r»/fl««), 123 

*6o.  Scheme  of  a  frog  manometer  (5//r//«4'^), 123 

*6l.   Perfusion  cannula  [Kronec/cer  and  Stirling), 124 

*62.  Roy's  tonometer  (S/ir/im^'-), 124 

*6^.  Curves  of  a  frog's  heart  at  different  temperatures  (/[''^rwrtMw), 125 

64.  Cardio-pneumograph  of  Landois, 1 28 

65.  Apparatus  for  showing  the  effect  of  respiration, 130 

66.  Cylindrical  vessel  filled  with  water, 133 

67.  Cylindrical  vessel  with  manometers, 133 

6S.  Small  artery  with  its  various  coats, 135 

69.  Capillaries  injected  with  silver  nitrate, , 135 

*70.   Longitudinal  section  of  a  vein  at  a  valve  [Cadin/), 136 

71.  Sphygmometer  of  Herisson, 139 

72.  Scheme  of  Marey's  sphygmograph, 140 

*73.  Marey's  improved  sphygmograph  [B.  Bramwell^, 140 

*74.  Ludwig's  sphygmograph, 141 

*75.  Dudgeon's  sphygmograph  [Dudgeon), 141 

76.  Scheme  of  Brondgeest's  pansphygmograph, 142 

77.  Scheme  of  Landois'  angiograph, 142 

78.  Pulse  curves  of  the  carotid,  radial,  and  posterior  tibial  arteries, 143 

*79.  S.  Mayer's  gas  sphygmoscope 143 

80.  Hoemautographic  curve, 143 

*8l.  Sphygmogram  of  radial  artery  [Dudgeon), I44 

*82.  Irregular  pulse,  mitral  regurgitation, 145 

83.  Sphygmograms  of  various  arteries, 146 

*84.   Pulse  tracings  after  amyl  nitrite  (Stirling,  after  Murrell), 147 

*85.  Aortic  regurgitation, 147 

86.  Pulsus  dicrotus,  P.  caprizans,  P.  monocrotus, 148 

*87.  Hyperdicrotic  pulse, 149 

88.  Pulsus  alternans, 150 

89.  Curves  of  the  posterior  tibial  artery, 151 

90.  Anacrotic  pulse  curves, 152 

91.  Anacrotic  pulse  curves, 152 

92.  Influence  of  the  respiration  on  the  sphygmogram, 153 

93.  Pulse  curves  during  Miiller's  and  Valsalva's  experiments, 154 

94.  Pulsus  paradoxus, 155 

95.  Various  radial  curves  altered  by  pressure, 155 

96.  Pulse  tracings  of  the  radial  artery, 157 

97.  Tracings  from  the  posterior  tibial,  and  carotid  arteries, 157 

98.  Apparatus  for  registering  the  molar  motions  of  the  body, 158 

99.  Vibration  and  heart  curves, 159 

icxD.  Ludwig  and  Pick's  kymographs, 162 

*loi.  Ludwig's  improved  revolving  cylinder  f.^rwa««), 162 

*I02.  Blood-pressure  tracing  of  the  carotid  of  a  dog  (Zi'^/'/wrt««), 163 

*I03.  Fick's  spring  manometer,  by  Hering  [Hermanii), 164 

104.  Fick's  flat-spring  kymograph, 165 

*I05.  Scheme  of  height  of  blood  pressure, 166 

*lo6.   Depressor  curve  [Stirling). 167 

*I07.  Blood  pressure  and  respiration  tracings  taken  simultaneously  (Stirling), 168 

*lo8.   Blood-pressure  tracing  during  stimulation  of  the  vagus  (Stirling), 170 

*I09.  Apparatus  of  V.  Kries  for  capillary  pressure  (C  Z?<rtW?^), 17^ 

*iio.  Scheme  of  the  blood  pressure, 172 

111.  Volkmann's  haemadromometer, ■ 175 

112.  Ludwig  and  Dogiel's  rheometer, I7S 

113.  Vierordt's  hrematachometer — Dromograph, 176 

114.  Photohsematachometer, 177 

*ii5.  Scheme  of  sectional  area  (after  Yeo), 178 

116.  Diapedesis, 182 

117.  Various  forms  of  venous  pulse, 186 

118.  Mosso's  plethysmograph, 188 


LIST   OF    ILLUSTRATIONS.  XXIII 

FIGURE  PAGE 

*ii9.  Section  of  spleen  (^Stohr), 192 

*I20.  Trabeculas  of  the  spleen  [Cadiat), 193 

*I2I.  Adenoid  tissue  of  spleen  [Cadiat), 193 

*I22.  Malpighian  corpuscle  of  the  spleen  (Crta'?'(2/), 193 

*I23.  Elements  of  splenic  pulp  (Stohr), 194 

*I24.  Tracing  of  the  splenic  curve  [Roy), 196 

*I25.  Thymus  gland  [Cadiat), I97 

*I26.  Elements  of  the  thymus  gland  [Cadiat), 197 

*I27.  Thyroid  gland  [Cadiat), 198 

*I28.  Supra-renal  capsule  [Cadiat), 200 

129.  Schemata  of  the  circulation, 201 

*I30.   Human  bronchus  [Hai?iilton), 204 

*I3I.  Air  vesicles  injected  with  silver  nitrate  [Hamilton), 206 

132.  Scheme  of  the  air  vesicles  of  lung, 207 

*I33.   Interlobular  septa  of  lung  [Hatniltoii) , 208 

134.  Scheme  of  Hutchinson's  spii'ometer, 21 1 

135.  Brondgeest's  tambour  and  curve, 212 

136.  Marey's  stethograph  [A'P Kendrick), • 213 

137.  Pneumatograms, 214 

138.  Section  through  diaphragm  [Hermanu^, 217 

139.  Action  of  intercostal  muscles, 218 

140.  Cyrtometer  curve, 221 

141.  Sibson's  thoracometer 221 

142.  Topography  of  the  lungs  and  heart,   . 222 

143.  Andral  and  Gavarret's  respiration  apparatus, 228 

144.  Scharling's  apparatus, , 229 

145.  Regnault  and  Reiset's  apparatus, 229 

146.  V.  Pettenkofer's  apparatus, 230 

147.  Valentin  and  Brunner's  apparatus, 231 

148.  Ciliated  epithelium, 244 

149.  Objects  found  in  sputum, 246 

*l5o.   Squamous  epithelium  from  the  mouth  [Stirling), • 250 

151.  Mucous  follicle  and  salivary  corpuscles  [Schenk) 250 

*I52.   Section  of  tonsil  (6'A)^r), 251 

*I53.   Scheme  of  glands, 252 

154.  Rodded  epithehum  of  a  salivary  duct, 252 

155.  Histology  of  the  salivary  glands, 252 

*I56.   Human  submaxillary  gland  [Heidenhain), 253 

*I57.  Parotid  gland  of  rabbit  at  rest  [Heide7tJiai7i), 254 

*I58.  Parotid  gland  of  rabbit,  active  phase  Heidejihain), 254 

*I59.  Scheme  of  the  nerves  of  the  salivary  glands  [Stirling), 255 

*l6o.   Diagram  of'a  salivary  gland  [Stirling), 259 

161.  Apparatus  for  estimation  of  sugar, 265 

162.  Polarization  apparatus,      ' 266 

163.  Vertical  section  of  a  tooth, 268 

164.  Dentine, 269 

165.  Interglobular  spaces, 269 

166.  Dentine  and  enamel, 269 

167.  Dentine  and  crusta  petrosa, 269 

168.  \ 

169.  I  Development  of  a  tooth, 270 

170.  J 

171.  Section  of  oesophagus  [Schenk), 274 

172.  Perineum  and  its  muscles, 278 

173.  Levator  ani  externus  and  internus, 279 

*I74.  Vertical  section  of  Auerbach's  plexus  (Crta'z'a^), •    • 280 

*I75.  Auerbach's  plexus  [Cadiat), 281 

*I76.   Meissner's  plexus  [Cadiat), 282 

*I77.  Vertical  section  of  stomach  [Stohr], 284 

178.  Goblet  cells, 284 

179.  Surface  section  of  gastric  mucous  membrane, 284 

180.  Fundus  gland  of  the  stomach,. 285 

181.  Pyloric  gland, 285 

182.  Scheme  of  the  gastric  mucous  membrane, 286 

^183.  Pyloric  mucous  membrane  [Hermanri),     .    . 287 


Xxiv  LIST    OF    ILLUSTRATIONS. 

FIGIRE  ''*o^ 

*i84.   pyloric  glands  during  digenion  [Hennann), 287 

*l85.  Scheme  of  pyloric  fistula  {Stirling), 2S9 

*l86.  Section  of  the  acini  of  the  pancreas  (Hermann) 297 

187.  Changes  of  the  pancreatic  cells  during  activity, 297 

*lS8.   Section  of  human  liver  {St'o/ir), 303 

1 89.  Scheme  of  a  liver  lobule, 3^4 

*I90.   Human  liver  cells  (Cadiat), 3^5 

*I9I.  Liver  cells  during  fasting  (//<?/-///(?««), 305 

192.  Bile  ducts, 3°$ 

*I93.   Liver  cells  [Stirling,  after  Stolnikoff), 3°^ 

194.  Various  appearances  of  the  liver  cells, 3°^ 

195.  Interlobular  bile  duct 3°? 

*I96.  Cholesterin  [Stirling), 3'4 

*I97.   Biliary  fistula  {Stirling), 3'^ 

*I9S.  Section  of  duodenum  {Stohr), 3^1 

*I99.   Lieberkiihn's  gland  [Hermann), 3^2 

200.  Transverse  section  of  Lieberkiihn's  follicles  (^f^c"/?/'), 3^2 

*20I.   Schemata  of  intestinal  fistul.-e  [Stirling), 3^2 

*202.   Moreau's  fistula  [after  Briinton) 3^3 

203.  Bacterium  aceti  and  B.  butyricus 3^5 

204.  Bacillus  subtilis, 3^^ 

205.  Bacteria  of  fjeces, 33° 

*2o6.  Scheme  of  intestinal  absorption  [Beaunis) 33^ 

*207.  Longitudinal  section  of  small  intestine  [Schenk), 337 

208.  Scheme  of  an  intestinal  villus, 33^ 

209.  Injected  villus  [Schenk), 33^ 

*2io.  Villi  of  small  intestine  injected  (Cad!'/<i/), 339 

*2II.   Duodenum  injected  [Stohr), 34° 

*2I2.   Section  of  a  solitary  follicle  [Cadiat), 34° 

*2i3.  Section  of  a  Peyer's  patch  [Cadiat), 34^ 

214.  Section  of  large  intestine  [Schenk), 34* 

215.  Endosmometer, 342 

216.  Origin  of  lymphatics  in  the  tendon  of  diaphragm, 349 

*217.   Lymphatics  of  diaphragm  silvered  [Jianvier), 349 

218.  Perivascular  lymphatics, 35° 

219.  Stomata  from  lymph  sac  of  frog, 35° 

220.  Section  of  two  hniph  follicles, 35' 

'*22i.  Scheme  of  a  hTiiphatic  gland  [Sharpey), 35' 

222.   Part  of  a  lymphatic  gland, 35^ 

*223.  Section  of  the  central  tendon  of  diaphragm  [Briinton), 357 

*224.  Section  of  fascia  lata  of  a  dog  [Bruntoji), 357 

*225.  Lymph  hearts  [Eckcr), 35^ 

226.  Water  calorimeter  of  Lavre  and  Silbermann, 3^2 

*227.  Water  calorimeter  of  Dulong  [Rosenthal), Z^Z 

*228.  Clinical  Thermometers, 3^7 

229.  Walferdin"s  metastatic  thermometer, ■    • 3^7 

230.  Scheme  of  thermo-electric  arrangements, 3^° 

231.  Kopp's  apparatus  for  specific  heat 372 

232.  Daily  variations  of  temperature, 374 

*233.  Acini  of  the  mammary  gland  of  a  sheep  [Cadiat), •    .  39° 

234.  Milk  glands  during  inaction  and  secretion, 39' 

*235.   Milk  and  colosinmi  [Stirling), 39^ 

*236.  Section  of  a  grain  of  wheat  [Blyth), 39^ 

237.  Yeast-cells  growing, 401 

238.  Composition  of  animal  and  vegetable  food.-, 4^4 

*239.   Starch  grains, 43^ 

*240.  Longitudinal  section  of  the  kidney  (A''i?«/(f), 434 

*24I.   Malpighian  pyramid  [Tyson,  after  Ludwig), 435 

*242.  Scheme  of  the  uriniferous  tubules  [Klein  and  Noble  Smith), 43^ 

243.  Scheme  of  the  structure  of  the  kidney 437 

244.  Glomerulus  and  renal  tubules, 43^ 

*245.  Convoluted  renal  tubule  (/!'if?d't'«//<7?«),      43^ 

*24b.  Irregular  tubule  [Tyson,  after  Klein), 43^ 

*247.  Transverse  section  of  the  apex  of  a  Malpighian  pyramid  [Cadiat), 439 

'*248.  Development  of  a  glomerulus  [Cadiat), 44' 


LIST   OF   ILLUSTRATIONS.  XXV 

FIGURE  PAGE 

249.  Graduated  minar)'  flask, 441 

250.  Urinometer 441 

251.  Graduated  burette, 443 

252.  Urea  and  urea  nitrate, 444 

*253.  Oxalate  of  urea  [afler  Beale), 446 

*254.  Ureameter  [Charteris), 446 

255.  Graduated  pipette, • 447 

256.  Uric  acid, 448 

257.  Kreatinin  zinc  chloride, 450 

*258.  Oxalate  of  lime, 450 

259.  Hippuric  acid, 451 

260.  Deposit  in  urine  during  the  "  acid  fermentation,"      456 

261.  Deposit  in  ammoniacal  urine, 456 

262.  Micrococcus  ureze, 457 

263.  Esbach's  albumimeter,      459 

264.  Blood  corpuscles  in  urine, 460 

265.  Peculiar  fomis  of  blood  corpuscles, 460 

266.  Colored  and  colorless  corpuscles  in  urine,      460 

267.  Blood  corpuscles  and  triple  phosphate, 460 

268.  Spectroscopic  examination  of  urine, 461 

*269.   Picro-saccharimeter  [G.  Johnson), 464 

*270.   Inosit  [Beale,  afler  Fiinke), 464 

271.  Cystin  and  oxalate  of  lime,      465 

272.  Leucin,  tyrosin,  and  ammonium  urate, 465 

273.  Fungi  in  urine, 466 

274.  Epithelial  casts, 466 

275.  Blood  casts, 466 

276.  Leucocyte  cast, 466 

277.  Cast  of  urate  of  soda, 466 

278.  Finely  granular  casts, 466 

279.  Coarsely  granular  casts, 467 

280.  Hyaline  casts, 467 

2S1.  Calcic  carbonate  and  phosphate, 467 

282.  Triple  phosphate, 467 

283.  Imperfect  forms  of  triple  phosphate, 467 

284.  Acid  ammonium  urate, 468 

285.  Basic  magnesic  phosphate, 468 

*286.  Oncometer  [Stirling,  after  Roy), 477 

*287.  Oncograph  [Stirling,  after  Roy), 477 

*288.  Renal  oncograph  curve  [Stirling,  after  Roy), 47^ 

*289.   Section  of  ureter  [Sto/ir), 4S0 

*290.  Transitional  epithelium  [Beale), 481 

291.  View  of  the  trigone  of  the  bladder, 482 

*292.  Nervt)us  mechanism  of  micturition  [Stirling,  after  Gowers), 4^5 

*293.  Section  of  epidermis  and  its  nerves  [Ranvier), 487 

294.  Scheme  of  the  structure  of  the  skin, 4^8 

*295.  Papillie  of  the  skin  injected, 489 

296.  Transverse  section  of  a  nail, 4^9 

297.  Transverse  section  of  a  hair  follicle, 490 

298.  Longitudinal  section  of  a  hair  follicle, 491 

299.  Sebaceous  gland, 492 

300.  Ciliated  epithelium, y^o 

*30i.  Pigment  and  guanin  cells  of  frog  [Stirling), 5°^ 

302.  Histology  of  muscular  tissue, 5°3 

■^303.   Muscular  fibre  [Quain), 504 

*304.  Insect's  muscle  [Rollett),      5°S 

*305.  Insect's  muscle  [Rollett), 505 

*3o6.  Network  in  muscle  [Melland), 5°^ 

307.  Tendon  attached  to  a  muscle, 5°^ 

*3o8.  Injected  blood  vessels  of  muscle  (^o7/?y^^r), 5°^ 

309.  Motorial  end  plates,      5°7 

*3io.  Termination  of  a  nerve  in  a  frog's  muscle  (.A;?2/^«^), 5°^ 

*3ii.  Scheme  of  nerve  ending  in  muscle  (i^o/Zf/"/,  a/?^r  ^^/^w^), 5°^ 

*3I2.  Smooth  muscle, 5^° 

*3I3.  Non-striped  m.uscle  cell  [Stirling^, 5^° 


XXvi  LIST    OF    ILLUSTRATIONS. 

FIGURE                                                                                                                _  PAGB 

*3I4.  Nerve  ending  in  smooth  muscle  (Cr7(//V?/),      510 

■■■•J15.  Frog  with  its  sciatic  arter>- ligatured  (.S'//;7/«^'-) 521 

*3l6.   Scheme  of  the  curara  experiment  (^t//^/- AW/z^/yi^rd'), 521 

*3I7.   Excitability  in  a  frog's  sartorius  {SdrHui^,  after  Pollitzer), 522 

*3l8.   Exci  ability  in  a  curarized  sartorius  {Stirling^  after  Pollitzer'), 522 

319.  Microscopic  appearances  in  contracting  muscle, 525 

320.  Helmholtz's  myograph, 526 

*32i.   Pendulum  myogiMjih, 5^7 

*322.   Scheme  of  the  jicndulum  myograph  {Stirling), 528 

*323.   Du  Hois- Reymond's  spring  myograph 529 

324.  Muscle  curve, 5^9 

*325.  Muscle  curve  of  pendulum  myograph  {Stirling), 530 

*326.   Method  of  studying  a  muscular  contraction  («/?«■;- /\?«/'//i';/(5r,/) 531 

*327.  Effect  of  make  and  break  induction  shocks  {Stirling), 531 

328.  Muscle  curves, Si^ 

329.  Muscle  curve,  opening  and  closing  shocks, 532 

*330.   Veratrin  curve  {Stirling), ■     .  533 

331.  Muscle  curves,  tetanus, 534 

*332.   Staircase    contractions   {Buckiiiaster) 535 

333.  Curves  of  voluntary  impulses, 535 

*334.  Curves  of  a  red  and  pale  muscle  (A'rowifrXw  ««(/ ^//V/iM^), 536 

*33S-  Muscle  curves  {Kronecker  and  Stirling), 536 

*336.  Tone  inductorium  (A'/-ow^C/^i?r  rt«rt' ^^/r/z«^), 537 

*337-  Muscle  curves  (yl/rt;-(?)'), 53^ 

*338.  Height  of  the  hft  by  a  muscle, 539 

*339-  Dynamometer, 54t> 

*340.  Curve  of  elasticity  (^y/^r  y]/rtr^ji'), 54' 

*34i.  Curve  of  elasticity  of  a  muscle  {after  Alar ey), 54" 

*342.   Curve  of  elasticity  {A/arey), 54^ 

*343.  Fatigue  curve  {Stirling),    . 54^ 

*344.   Fatigue  curve  ( JValler), •   .    .    .     •  547 

*34S-  Vertical  section  of  articular  cartilage  (6'/i>//«^), 54^ 

*346.  Orders  of  levers, 55' 

*347.  Scheme  of  the. action  of  muscles  on  bones, 551 

348.  Phases  of  walking, 55^ 

349.  Instantaneous  photograph  of  a  person  walking, 556 

350.  Instantaneous  photograph  of  a  runner, 557 

351.  Instantaneous  photograph  of  a  person  jumping, 55^ 

352.  Larynx  from  the  front, 5^' 

353.  Larynx  from  behind, 5^' 

354.  Larynx  from  behind 5^2 

355.  Nerves  of  the  larynx, 5^2 

356.  Action  of  the  posterior  crico-arytenoid  muscles, 563 

357.  Action  of  the  arytenoid  muscles, 5^3 

358.  Action  of  the  lateral  crico-arytenoid  muscles, 5^3 

359.  Vertical  section  of  the  head  and  neck,    ......     •   .    .         5^5 

360.  Examination  of  the  larynx, 5^6 

361.  Laryngoscopic  view  of  the  larynx, 5^6 

362.  View  of  the  larynx  during  a  high  note, 5^7 

363.  View  of  the  larynx  during  a  deep  inspiration, 5^7 

364.  Rhinoscopy, 5^7 

365.  View  of  the  posterior  nares, • 5^^ 

366.  Parts  concerned  in  phonation, 57' 

367.  Tumors  on  the  vocal  cords 573 

368.  Histology  of  nervous  tissues, 57^ 

*369.  Transverse  section  of  nerve  fibres  (Ca^//rt/), 57^ 

*370.   Sympathetic  nerve  fibre  {Panvier), 57^ 

*37I.   Medullated  nerve  fibre  (Stirling), 57^ 

372.  Medullated  nerve  fibre, 57^ 

*373    Medullated  nerve  fibres  {Schwalbe), 57^ 

*374.   Ranvier's  crosses  (Ranvier), 579 

375.  Transverse  section  of  a  nerve, 579 

*376.  Cell  from  the  Gasserian  ganglion  (5(r//7<y«/(5f),    .    .         5^° 

377.   Degeneration  and  regeneration  of  nerve  fibres, 5^^ 

*378.  Waller's  experiments  {after  Dalton), 5^^ 


LIST   OF    ILLUSTRATIONS.  XXVll 

FIGURE  PAGE 

379.  Rheocord  of  du  Bois-Reymond, 593 

380.  Scheme  of  a  galvanometer, 594 

*38i.  Large  Grove's  battery  [Gscheidlen), 595 

*382.  Daniell's  cell  {Stirling), : 596 

*383.  Grennet's  battery  (6^5c/i^Z(//^«), 596 

*384.  Leclanche's  element  [Gscheidlen), 596 

*385.  Non-polarizable  electrodes  (j5'//tW^' ^/-^M^rj), 597 

*386.  Fleibchl's  non-polarizable  electrodes  {Pe(zoldi), 597 

*387.  Thomson's  galvanometer  [EHiott  Brothers), 597 

'^388.  Lamp  and  scale  [Elliott  Brothers), 598 

*389.  Galvanometer  shunt  {Elliott  Brothers), 598 

*390.  Scheme  of  the  induced  currents  {Hermann), 600 

*39I.   Helmholtz's  modification  {Herviann), 600 

392.   Scheme  of  an  induction  machine, 601 

*393.  Inductorium   {Elliott   Brothers), 602 

*394.  Inductorium  {Petzoldt), 602 

395.  Stohrer's  apparatus, 603 

*396.  Yx\(i\:\o-Q.\&-^  {Elliott  Brothers), 603 

*397.  Plug  key  {Elliott  Brothers), 603 

*398.   Capillary  contact  {Kro7iecker  and  Stirling), 603 

399.  Scheme  of  the  muscle  current, 604 

400.  Capillary  electrometer,      604 

*40i.  Nerve-muscle  pi-eparation, 606 

*402.   Kiihne's  experiment  {Stirling), 606 

*403.  Electrometer  curve,  frog's  muscle  {Waller), 608 

*404.  Electrometer  curve,  frog's  heart  {Waller), 608 

*405.  Secondary  contraction,      609 

406.  Bernstein's  differential  rheotome, 610 

407.  Nerve  current  in  electrotonus, .    .  611 

408.  Scheme  of  electrotonic  excitability, 6i5 

409.  Method  of  testing  electrotonic  excitability, 616 

410.  Distribution  of  an  electrical  current, 617 

411.  Velocity  of  nerve  energy, 621 

*4I2.  Scheme  for  testing  velocity  of  a  nerve  impulse, 621 

*4I3.  Curves  of  a  nerve  impulse  (^/a;r_j'), 622 

*4I4.  Kiihne's  gracilis  experiment, 624 

*4I5.   Sponge  rheophores  Weiss), 624 

*4i6.  Disk  rheophore  ( fFfm), 624 

*4I7.   Metallic  brush  ( IVeiss) 624 

418.  Motor  points  of  the  arm,      625 

419.  Motor  points  of  the  arm, 625 

420.  Motor  points  of  the  leg, 626 

421.  Motor  points  of  the  leg, 627 

*422.  Scheme  of  a  reflex  act  (^/zV/m^), 633 

423.  Optic  chiasma, 635 

^424.  Relation  of  field  of  vision,  retina,  and  optic  tracts  (6^d7Wf/'-j-), 635 

*425.  Decussation  of  the  optic  tracts  {Charcot), 636 

*426.  Scheme  of  images  in  squinting  (^;-w/owi?), 638 

427.  Medulla  oblongata, 639 

*428.   Under  surface  of  the  brain, 640 

429.  Connections  of  the  cranial  nerves, 642 

430.  Sensory  nerves  of  the  face, 647 

431.  Motor  points  of  the  face  and  neck, 651 

*432.   Disposition  of  the  semicircular  canals  {Stirling),      654 

433.  Scheme  of  the  branches  of  vagus  and  accessorius, 658 

*434.  Cardiac  nerves  of  the  rabbit  {Stirling), 660 

*435.  Diagram  of  a  spinal  nerve  {Ross),      . 666 

*436.  Spinal  ganglion  {Cadiai), 666 

437.  Cutaneous  nerves  of  the  arm, 668 

438.  Cutaneous  nerves  of  the  leg  {Henle), 668 

*439.  Visceral  nerves  of  the  dog  ((Jrtj/?'^//), 671 

440.  Transverse  section  of  the  spinal  cord, 676 

*44I.  Transverse  section  of  the  white  matter  {Obersteiner),      •  677 

■*442.  Multipolar  nerve  cells  of  the  cord  {Cadiat), 677 

*443.  Relation  of  white  and  gray  matter  of  the  cord  {Schdfer), 677 


XXviii  LIST   OF    ILLUSTRATIONS. 

FIGURE  PAG8 

*444.  Transverse  sections  of  the  spinal  cord, 678 

*445.  Cell  from  Clarke's  column  [Ol>ersUiner'), 679 

♦446.  Transverse  section  of  the  cord  {Cadiat), 679 

*447.  Longitudinal  section  of  the  cord  [Qidial) 680 

*448.  Multipolar  nerve  cell, 680 

*449.  Scheme  of  fibres  in  cord  {Obersteiner), 680 

*450.  Glia  cell  [Ol>ersteiner), 681 

*45I.  Glia  cells  of  cord  {Ol>t-rsh'iner), 681 

*452.  Spinal  cord  injected  [Ob^rsteiner), 682 

*453.  Injected  blood  vessels  of  the  cord  {^Kolliker) 682 

454.  Conducting  paths  in  the  cord, 683 

*455.  Degeneration  paths  in  the  cord  [Brainwell), 685 

♦456.  Scheme  of  a  retlex  act  {Stirling), 686 

*457.  Sectijn  of  a  spinal  segment  {Stirling), 686 

*458.  Propagation  of  reflex  movements  [Beaunis), 687 

*459.  Effect  of  section  of  half  of  the  cord  {Erb), 699 

*46o.  Brain,  ventricles,  and  basal  ganglia, 7°° 

461.  Scheme  of  the  brain, "joi 

*462.  Connections  of  the  cerebellum, 702 

■*463.  Diagram  of  a  spinal  segment  {Bramwell), "jod 

*464.  Section  across  the  pyramids  {Schwalbe), 7^7 

*465.  Section  of  the  medulla  oblongata  [Schwalbe), 708 

*466.  Section  of  the  olivary  body  {Schwalbe), 708 

*467.  Scheme  of  the  respiratory  centres  {Rutherford'), 713 

*46S.  Action  of  vagus  on  frog's  heart  {Stirling), 7^9 

*469.  Scheme  of  the  accelerans  fibres  {Stirling), 7^1 

*470.  Cardiac  plexus  of  a  cat  {Bohin), 721 

*47I.  YvQg  wiihoxxi  Ms  c&re.hr\\m  {Stirling,  after  Goltz), 733 

*472.  Frog  without  its  cerebrum  (^/2>//«,^,  rt/?^r  Goltz), 733 

*473.  Pigeon  with  its  cerebrum  removed  {after  Dalton), 734 

*474.  Motor  area  of  cerebral  convolution  (/vr^'/V/- rt'«(i'^.  Zif.yw), 73^ 

*475.  Cerebral  convolution  ;  s^nsoxy  zxt2.{Ferrier  and  B.  Lewis), 73^ 

■*476.  Perivascular  lymph  spaces  {Obersteiner), 73^ 

*477.  Frontal  convolution  by  Weigert's  method  {Obersteitier),      73^ 

*478.  Cerebral  convolution  injected, 739 

'*479.  Left  side  of  the  human  brain  {Ecker), 74° 

*4So.  Inner  aspect  of  right  hemisphere  {Ecker), 74^ 

*4Sl.  Left  frontal  lobe  and  island  of  Reil  ( 7>/r«^r), 742 

*482.  Brain  from  above  {Ecker), 743 

483.  Cerebrum  of  dog,  carp,  frog,  pigeon,  and  rabbit,      745 

484.  Relation  of  the  cerebral  convolutions  to  the  skull, 747 

*485.  Motor  areas  of  a  monkey's  brain  (//^;-j/^j' rtwo' 6"r//<iy('r), 748 

*48G.  Motor  areas  of  the  marginal  convolution  {Horsley  and  Schdfer), 74^ 

*487.  Psyciio-optic  fibres  {Miink), 752 

*488.  Motor  areas  {after  Gowers), 756 

*489.  Motor  centres  {after  Schdfer  and  Horsley^, 75^ 

*490.  Section  of  a  cerebral  hemisphere  {Horsley), 757 

*49i.  Innervation  of  associated  muscles  {Ross), 757 

*492.  Secondar}'  degeneration  in  a  crus  {Charcot), 759 

*493.  Transverse  section  of  the  crus  cerebri  {Charcot), 759 

*494.  Scheme  of  aphasia  {Lichtheim), 761 

■*495.  Scheme  of  aphasia  (Z/c/i/Z/^w), 7^1 

*496.  Scheme  of  aphasia  {Ross), 762 

*497.  Relation  of  the  convolutions  to  the  skull  {R.  W.  Reid), 7^4 

*498.  Relation  of  motor  centres  to  skull  {Hare), 765 

*499.  Outline  markings  on  skull  {Hare), 7^5 

*500.  Basal  ganglia  and  the  ventricles, 767 

*5oi.  Transverse  section  of  the  right  hemisphere  (Cif^-^M/'rtM;-), 7^8 

*502.  Transverse  section  of  the  crura  (  Wernicke  and  Go'vers), 769 

*503.  Transverse  section  of  the  pons  (  f^r«iV>^^), 769 

*504.  Course  of  the  fibres  in  pons  {Erb'), 7^9 

*505.  Longitudinal  section  of  a  human  brain  (  ff'/V(/frj//d'm), 77^ 

*5o6.  Section  of  the  cerebellum  {Sankey), 773 

*507.  Purkinje's  cell  (  Obersteiner), 773 

*So8.  Pigeon  with  its  cerebellum  removed  {Dalton), 774 


LIST   OF    ILLUSTRATIONS.  XXIX 

FIGTJRE  PAGE 

*509.  Cortex  cerebri  and  its  membranes  [Sckwalbe), 776 

*5lo.  Circle  of  Willis  [Charcot), 778 

*5II.   Ganglionic  axxerie?,  [Charcot), 779 

*5I2.   Corneal  corpuscles  [Ranvier), 783 

*5I3.  Corneal  spaces  [Ranvier), 783 

514.  Junction  of  the  cornea  and  sclerotic, 478 

*5I5.  Vertical  section  of  cornea  with  nerve  fibuli  (i?rt«?>'zV;-), 785 

*5l6.   Horizontal  section  of  cornea  with  nerve  't^wXx  [Ranvier), 786 

*5I7.  Vertical  section  of  choroid  and  sclerotic  (6'z't)7zrJ, 786 

518.  Bloodvessels  of  the  eyeball, 787 

*5I9.  Vertical  section  human  retina  [Cadiat), 788 

520.  Layers  of  the  retina, 788 

*52I.  Vertical  section  of  the  fovea  centralis  [Cadiat), 789 

*522.  Fibres  of  the  lens  [Kolliker),      790 

523.  Section  of  the  optic  nerve, 791 

524.  Action  of  lenses  on  light, 793 

525.  Refraction  of  light, 794 

526.  Construction  of  the  refracted  ray, 794 

527.  Optical  cardinal  points, 795 

528.  Construction  of  the  refracted  ray, 796 

529.  Construction  of  the  image, 79^ 

530.  Refracted  ray  in  several  media 797 

531.  Visual  angle  and  retinal  image, 797 

532.  Scheme  of  the  ophthalmometer, 798 

533.  Horizontal  section  of  the  eyeball, 800 

534.  Scheme  of  accommodation, 801 

535.  Sanson-Purkinje's  images, 801 

*536.   Phakoscope  [AP Kendrick), 802 

537.  Scheiner's  experiment, 803 

538.  Refraction  of  the  eye, • 804 

539.  Myopic  eye, 804 

540.  Hypermetropic  eye, 804 

541.  Power  of  accommodation, 805 

*542.  Diagram  of  astigmatism  [Frost), 808 

543.  Cylindrical  glasses, 808 

*544.  Scheme  of  the  nerves  of  the  iris  [Erb), 810 

*545.  Pupilometer  [Gorhavi), 81 1 

*546.  Pupilometer  [Gorhavi), 81 1 

547.  Entoptical  shadows, 812 

548.  Scheme  of  the  original  ophthalmoscope, 814 

549.  Scheme  of  tne  indirect  method, 815 

550.  Action  of  a  divergent  lens, 815 

551.  Action  of  a  divergent  lens, 815 

552.  View  of  the  fundus  oculi, ^ 816 

*553.   Morton's  ophthalmoscope  (/"/(T/Jari/rtw^  G^rry), 816 

*554.  Frost's  artificial  eye  (/''rwi'), 817 

*555-  Action   of  the  orthoscope, 817 

*556.  Mariotte's  experiment, S18 

*557.  Horizontal  section  of  the  right  eye, 820 

*558.  WB.z.TAYsY>&r\mettx  [Pickard  and  Curry), 821 

*559-   Priestley  Smith's  perimeter  [Pickard  and  Curry), 821 

560.  Perimetric  chart, 822 

561.  Geometrical  color  zone, 825 

562.  Action  of  light  rays  on  the  retina, 826 

*563.  Cones  of  the  retina  [Stirling  after  Engelmanri), 829 

*564.   Irradiation, 831 

■^565.   Irradiation, 831 

566.  Scheme  of  the  action  of  the  ocular  muscles, 835 

567.  Identical  points  of  the  retina, 838 

568.  The  horopter, 838 

569.  Two  stereoscopic  drawings, 839 

570.  Wheatstone's  stereoscope, 840 

571.  Brewster's  stereoscope, •  840 

572.  Telestereoscope, 841 

573.  Wheatstone's  pseudoscope, 841 


XXX  LIST    OF    ILLUSTRATIONS. 

FIGURE  ^^'^^ 

574.  Rollett's  apparatus, <^42 

*575.   Zollner's  lines, 843 

576.  Section  of  an  eyelid, S44 

577.  Scheme  of  the  organ  of  hearing, 847 

578.  External  auditory  meatus,    •    •  •  • 849 

579.  Left  tympanic  membrane  and  ossicles, '. 850 

580.  Membrana  tympani  and  ossicles, 850 

581.  Tympanic  membrane  from  within, 850 

♦582.   Ear  specula  (A>('//;/^  rtW(/  Sesemann), 850 

*583-  Toynbee's  artificial  membrana  tympani  {^Kro/tne  and  Sesemann), 851 

584.  Right  auditoi-y  ossicles 851 

585.  Tympanum  and  auditory  ossicles, 852 

586.  Tensor  tynnpani  and  Eustachian  tube, • 853 

587.  Right  stapedius  muscle, 854 

*58S.  Eustachian  catheter, 856 

*589.   Politzer's  ear  bag  [A'rohne  and  Sesemann) 856 

590.  Right  labyrinth, 856 

591.  Scheme  of  the  cochlea 858 

*592.   Interior  of  the  right  labyrinth, 858 

*593.  Semicircular  canals, 858 

*594.  Section  of  the  macula  acustica  (A^ewt^/Vr), 859 

595.  Scheme  of  the  canalis  cochlearis, 860 

*596.   Qs2\X.orC%vi\i\^\\^  [Krohne  and  Sesemann), 862 

597.   Curve  of  a  muscle  note  and  its  overtones, 864 

*598.   Kcenig's  manometric  capsule  {Kcenig), 865 

*599.   Flame  pictures  of  vowels  (A'lvnig), 865 

•*6oo.  Kcenig's  analyzing  apparatus  (A'(i'«2>), 866 

601.   Nasal  and  pharyngo-nasal  cavities, 871 

*6o2.   Section  of  the  olfactory  region  (5/<;//y-), 87 1 

603.  Olfactory  cells, 872 

*6o4.   Filiform  papill?e(i.7o//r), 874 

*6o5.   Fungiform  papillae  [Stohr), 874 

606.   Circumvallate  papilla  and   taste  bulbs, 875 

*6o7.   Papilla;  fohatre   {S/dhr), 875 

608.  Vertical  section  of  skin, 878 

609.  Wagner's  touch  corpuscle  [Ranvier), 878 

610.  Pacini's  corpuscle, 879 

*6li.   End  bulb  from  conjunctiva  ((2«rt?'«), 879 

*6i2.  Tactile  corpuscle  from  clitoris,  (^«rt««), 879 

*6i3.  Tactile  corpuscles  from  a  duck's  bill  [Quain), 8S0 

*6l4.   Bouchon  epidermique   {Hanvier), 880 

615.  ^Esthesiometer, 882 

*6i6.  /Esthesiometer  of  Sieveking 883 

*6i7.  Aristotle's  experiment, 884 

618.  Pressure  spots, 885 

619.  Landois'  pressure  mercurial  balance, 886 

620.  Cold  and  hot  spots, 887 

621.  Cold  and  hot  spots, ■••....  887 

622.  Topography  of  temperature  spots, 889 

*623.   Karyokinesis  [Gegenliaitr), 893 

*624.  Typical  nucleated  cell  {Camay), 893 

*625.   Mitosis  or  nuclear  division  [Fleniming) , 894 

626.  Ovum  of  Tania  solium, 895 

627.  Cysticercus, 895 

628.  Cysticerci  of  Taenia  solium, 896 

629.  Scolex, 896 

630.  Echinococcus, 896 

631.  Taenia  solium. 896 

*632.  Section  of  testis  {Schenk), 897 

*633.  Tubule  of  testis  {Schenk), 898 

*634.  Section   of  epididymis,   [Schenk), 898 

635.  Spermatic  crystals,  • 899 

636.  Spermatozoa, 9°° 

637.  Spermatogenesis, 9°° 

*638.  A  cat's  ovary  {Hart  and  Barbour,  after  Schron), 9°' 


LIST    OF    ILLUSTRATIONS.  XXXI 

FIGURE  _  PAGE 

*639.   Section   of  an  ovary  {Turner), 901 

640.  Ripe  ovum  of  rabbit, ■ 902 

641.  Ovary  and  polar  globules, 903 

642.  Scheme  of  a  meroblastic  ovum, 904 

643.  White  and  yellow  yelk, 904 

*644.   Hen's  egg  {Kolliker),  .        .    : 905 

*645.   Mucous  mtmhvan&  of  the  uterus  (Jlanf  and  Bariour,  a/ier  7 urner), 905 

""646.   Fallopian  tube  and   its  annexes  {Henle), 905 

*647.   Section  of  Fallopian  tube  {Schenk), 906 

*648.   Uterus  before  menstruation  {J.  Williams), 907 

*649.   Uterus  after  menstruation  {J.  WilHa?ns), 907 

650.  Fresh  corpus  luteum, 908 

651.  Corpus  luteum  of  a  cow, 908 

652.  Lutein  cells, 90S 

*653.  Erectile  tissue   [Cadiat), 909 

654.  The  urethra  and  adjoining  muscles, 910 

*655.   Formation  of  polar  globules, 913 

656.  Extrusion  of  a  polar  globule, .  913 

657.  Polar  globules,  male  and  female  pronucleus, 914 

*658.  Segmentation  of  2.  x2kkis!C s  osuva.  {Quain,  after  v.  Beneden), 914 

659.  Cleavage  of  the  yelk, 914 

*66o.   'Q\2iStoAerxmc.\es\c\.e  oix^a^xt  Quain,  after  V.Ben  ederi), 915 

661.  The  blastoderm, 915 

*66?.  Primitive  streak  {^Balfour), -. 916 

*663.  Transverse  section  of  an  embryo  newt  {Hertwig), 916 

*664.  Vertical  section  of  a  blastoderm  (TT/fm), 917 

665.   Schemata  of  development, 918 

*666.  Embryo  fowl,  2d  day  [Kollike!-), 919 

*667.  Transverse  section  of  an  embryo  duck  (^Balfour), 920 

*668/  Uterine  mucous  membrane  {Coste), 925 

*669.  Placental  villi  {Cadiat), 926 

*670.  Foetal  circulation  [Clelana) 928 

*67i.   Head  of  embryo  rabbit  [Kolliker), 931 

672.  Hare  lip, 931 

*673.  Meckel's  cartilage  ( ^K  K.  Parke?'), 931 

674.  Centres  of  ossification  in  the  innominate  bone, 933 

675.  Development  of  the  heart, 935 

676.  The  aortic  arches, 936 

677.  Veins  of  the  embryo, 936 

678.  Development  of  the  veins  and  portal  system, 937 

679.  Development  of  the  intestine, 938 

680.  Development  of  the  lungs, 938 

681.  Formation  of  the  omentum, ; 938 

682.  Development  of  the  internal  generative  organs, 939 

*683.  Development  of  ova  ( IViedersheim'), 940 

684.  Development  of  the  external  genitals, 942 

*685.    1  ^  r   942 

*f\9.i'     \  Changes  in  the  external  organs  of  generation  in  the  female  [after  Sckroeder),     .    .     -  ^ 

*688.    J  L    942 

*689.  Transverse  section  of  an  embryo  brain  [Kolliker), 943 

*690.  ILmhxyohvxn  oi  io^\  [Qiiain,  after  Mikalkowics), 944 

691.   Development  of  the  eye,      945 

*692.  Development  of  the  vertebrate  ear  i^Haddon), 945 

[The  illustrations  indicated  by  the  word  Herviann,  are  from  Hermann's  Handbuch  der  Physiolo- 
gie  ;  by  Cadiat,  from  Cadiat's  Traite  d' Anato/iiie  Generate ;  by  Ranvier,  from  Ranvier's  Traite 
Technique  d" Histologie  ;  by  Brunton,  from  Brunton's  Text-book  of  Pharmacology,  Therapeutics, 
and  Materia  Medica  ;  by  Schenk,  from  Schenk's  Grundriss  der  normalen  Histologie  ;  by  Ecker, 
irom  Ecker's  Anatomie  des  Frosches,  2d  ed.  ;  by  Quain,  firom  Quain's  Anatoiny  ;  by  Stohr,  from 
Stohr's  Lehrbuch  der  Histologie,  Jena,  1887  ;  by  Obersteiner,  from  H.  Obersteiner's  Anleitung 
beim  Studium  des  Baties  der  nervosen  Cejitralorgane,  Wien,  1888.] 


INTRODUCTION. 


THE  SCOPE  OF  PHYSIOLOGY  AND  ITS  RELATIONS  TO  OTHER  BRANCHES  OF 

NATURAL  SCIENCE. 

Physiology  is  the  science  of  the  vital  phenomena  of  organisms,  or,  broadly,  it  is 
the  Doctrine  of  Life.  Correspondingly  to  the  divisions  of  organisms,  we  distin- 
guish— (i)  Animal  Physiology ;  (2)  Vegetable  Physiology ;  and  (3)  the  Physiology 
of  the  Lowest  Living  Organisms,  which  stand  on  the  border  line  of  animals  and 
plants,  /.  e.,  the  so-called  Protistce  of  Haeckel,  micro-organisms,  and  those  ele- 
mentary organisms  or  cells  which  exist  on  the  same  level. 

The  object  of  Physiology  is  to  establish  these  phenomena,  to  determine  their 
regularity  and  causes,  and  to  refer  them  to  the  general  fundamental  laws  of 
Natural  Science,  viz.,  the  Laws  of  Physics  and  of  Chemistry, 

The  following  Scheme  shows  the  relation  of  Physiology  to  the  allied  branches 
of  Natural  Science  : — 

BIOLOGY. 

The  science  of  organized  beings  or  organisms  (animals,  plants,  protistse,  and 
elementary  organisms). 


I.  Morphology. 

The  doctrine  of  the  form  of  organ- 
isms. 

General 
Morphology. 

The  doctrine  of  the 
formed  elementary 
constituents  of  or- 
ganisms. 

(Histology) — 

(a)  Histology  of  Plants. 


Special 
Morphology. 

The  doctrine  of  the 
parts  and  organs  of 
organisms. 

(Organology — 
Anatomy) — 
[a)  Phytotomy. 


{b)  Histology  of  Animals,  [b)  Zootomy. 


II.  Physiology. 

The    doctrine    of    the    vital   phe- 


nomena of  organisms. 


General 
Physiology. 

The  doctrine  of  vital 
phenomena  in  gene- 
ral— 

{a)  Of  Plants. 

[b]  Of  Animals. 


Special 
Physiology. 

The  doctrine  of  the 
activities  of  the  in- 
dividual organs — 

{a)  Of  Plants. 

[b)  Of  Animals. 


III.  Embryology. 

The  doctrine  of  the  generation  and  development  of  organisms. 


Morphological  part  of  the 
doctrine  of  development, 
i.  e.,  the  doctrine  of  fo7-m 
in  its  stages  of  develop- 
ment— 

{a)  General. 

[b]  Special. 


r  I 


History   of  the   development  of  ] 
single  beings,  of  the   individual 
[e.  g.,  of  man)  from  the    ovum 
onward  (Ontogeny) — 

(a)  In  Plants. 

(b)  In  Animals. 

History  of  the  development  of 
a  w/io/e  stock  of  organisms  from 
the  lovv^est  forms  of  the  series 
upward  (Phylogeny) — 

{a)  In  Plants. 

[b)  In  Animals.  J 


Physiological  part  of  the 
doctrine  of  development, 
i.  e.,  the  doctrine  of  the 
activity  during  develop- 
ment— 

(a)  General. 

{b)  Special. 


Morphology  and  Physiology  are  of  equal  rank  in  biological  science,  and  a 
previous  acquaintance  with  Morphology  is  assumed  as  a  basis  for  the  comprehen- 
3  33 


34  INTRODUCTION. 

sion  of  Physiology,  since  the  work  of  an  organ  can  only  be  properly  understood 
when  its  external  form  and  its  internal  arrangements  are  known.  Development 
occupies  a  middle  place  between  Morphology  and  Physiology ;  it  is  a  morpho- 
logical discipUne  in  so  far  as  it  is  concerned  with  the  description  of  the  parts  of 
the  developing  organism;  it  is  a  physiological  doctrine  in  so  far  as  it  studies  the 
activities  and  vital  phenomena  during  the  course  of  development. 

MATTER. — The  entire  visible  world,  including  all  organisms,  consists  of 
matter,  /.  e.,  of  substance  which  occupies  space. 

We  distinguish  ponderable  matter  which  has  weight,  and  imponderable  matter 
which  cannot  be  weiglied  in  a  balance.     The  latter  is  generally  termed  ether. 

In  ponderable  materials,  again,  we  distinguish  \.\\^\x  form,  i.e.,  the  nature  of 
their  limiting  surfaces;  further,  their  volume,  i.e.,  the  amount  of  space  which 
they  occupy  ;  and  lastly,  their  aggregate  condition,  i.  e.,  whether  they  are  solid, 
fluid,  or  gaseous  bodies. 

Ether. — The  ether  fills  the  space  of  the  universe,  certainly  as  far  as  the  most 
distant  visible  stars.  This  ether,  notwithstanding  its  imponderability,  possesses 
distinct  mechanical  properties;  it  is  infinitely  more  attenuated  than  any  known 
kind  of  gas,  and  behaves  more  like  a  solid  body  than  a  gas,  resembling  a  gelati- 
nous mass  rather  than  the  air.  It  participates  in  the  luminous  phenomena  due  to 
the  vibrations  of  the  atoms  of  the  fixed  stars,  and  hence  it  is  the  transmitter  of 
light,  which  is  conducted  by  means  of  its  vibrations,  with  inconceivable  rapidity 
(42,220  geographical  miles  per  second),  to  our  visual  organs  i^Tyndall). 

Imponderable  matter  (ether)  and  ponderable  matter  are  not  separated  sharply 
from  each  oth^r ;  rather  does  the  ether  penetrate  into  all  the  spaces  existing 
between  the  smallest  particles  of  ponderable  matter. 

Particles. — Supposing  that  ponderable  matter  were  to  be  subdivided  con- 
tinuously into  smaller  and  smaller  portions,  until  we  reach  the  last  stage  of 
division  in  which  it  is  possible  to  recognize  the  aggregate  condition  of  the  matter 
operated  upon,  we  should  call  the  finely-divided  portions  of  matter  in  this  state 
particles.  Particles  of  iron  would  still  be  recognized  as  solid,  particles  of  water  as 
fluid,  particles  of  oxygen  as  gaseous. 

Molecules. — Supposing,  however,  the  process  of  division  of  the  particles  to 
be  carried  further  still,  we  should  at  last  reach  a  limit,  beyond  which,  neither  by 
mechanical  nor  by  physical  means,  could  any  further  division  be  effected.  We 
should  have  arrived  at  the  molecules.  A  molecule,  therefore,  is  the  smallest 
amcrunt  of  matter  which  can  still  exist  in  a  free  condition,  and  which  as  a  unit  no 
longer  exhibits  the  aggregate  condition. 

Atoms. — But  even  molecules  are  not  the  final  units  of  matter,  since  every 
molecule  consists  of  a  group  of  smaller  units,  called  atoms.  An  atom  cannot 
exist  by  itself  in  a  free  condition,  but  the  atoms  unite  with  other  similar  or  dis- 
similar atoms  to  form  groups,  which  are  called  molecules.  Atoms  are  incapable 
of  further  subdivision,  hence  their  name.  We  assume  that  the  atoms  are  invari- 
ably of  the  same  size,  and  that  they  are  solid.  From  a  chemical  point  of  view, 
the  atom  of  an  elementary  body  (element)  is  the  smallest  amount  of  the  element 
which  can  enter  into  a  chemical  combination.  Just  as  ponderable  matter  consists 
in  its  ultimate  parts  of  ponderable  atoms,  so  does  the  ether  consist  of  analogous 
small  ether-atoms. 

Ponderable  and  Imponderable  Atoms. — The  ponderable  atoms  within 
ponderable  matter  are  arranged  in  a  definite  relation  to  the  ether-atoms.  The 
ponderable  atoms  mutually  attract  each  other,  and  similarly  they  attract  the 
imponderable  ether-atoms  ;  but  the  ether-atoms  repel  each  other.  Hence,  in 
ponderable  masses,  ether-atoms  surround  every  ponderable  atom.  These  masses, 
in  virtue  of  the  attraction  of  the  ponderable  atoms,  tend  to  come  together,  but 
only  to  the  extent  permitted  by  the  surrounding  ether-atoms.  Thus  the  ponderable 
atoms  can  never  come  so  close  as  not  to  leave  interspaces.     All  matter  must. 


INTRODUCTION.  35 

therefore,  be  regarded  as  more  or  less  loose  and  open  in  texture,  a  condition  due 
to  the  interpenetrating  ether-atoms,  which  resist  the  direct  contact  of  the 
ponderable  atoms. 

Aggregate  Condition  of  Atoms. — The  relative  arrangement  of  the  molecules, 
/.  e.,  the  smallest  particles  of  matter  which  can  be  isolated  in  a  free  condition, 
determines  the  aggregate  condition  of  the  body. 

Within  a  solid  body,  characterized  by  the  permanence  of  its  volume  as  well  as 
by  the  independence  of  its  form,  the  molecules  are  so  arranged  that  they  cannot 
readily  be  displaced  from  their  relative  positions. 

Fluid  bodies,  although  their  volume  is  permanent,  readily  change  their  shape, 
and  their  molecules  are  in  a  condition  of  continual  movement. 

When  this  movement  of 'the  molecules  takes  so  wide  a  range  that  the  individual 
molecules  fly  apart,  the  body  becomes  gaseous,  and  as  such  is  characterized  by 
the  instability  of  its  form  as  well  as  by  the  changeableness  of  its  volume. 

Physics  is  the  study  of  these  molecules  and  their  motions. 

FORCES. 

I.  Gravitation — Work  done. — All  phenomena  appertain  to  matter.  These 
phenomena  are  the  appreciable  expression  of  the  forces  inherent  in  matter.  The 
forces  themselves  are  not  appreciable,  they  are  the  causes  of  the  phenomena. 

Gravitation. — The  law  of  gravitation  postulates  that  every  particle  of  ponder- 
able matter  in  the  universe  attracts  every  other  particle  with  a  certain  force. 
This  force  is  inversely  as  the  square  of  the  distance.  Further,  the  attractive  force 
is  directly  proportional  to  the  amount  of  the  attracting  matter,  without  any  refer- 
ence to  the  quality  of  the  body.  We  may  estimate  the  intensity  of  gravitation 
by  the  extent  of  the  movement  which  it  communicates  to  a  body  allowed  to  fall, 
for  one  second,  through  a  given  distance,  in  a  space  free  from  air.  Such  a  body 
will  fall  in  vacuo  9.809  metres  per  second.  This  fact  has  been  arrived  at  experi- 
mentally. 

Let  us  represent  g^  9.809  metres,  the  final  velocity  of  the  freely  falling  body  at  the  end  of  one 
second.     The  velocity,  V,  of  the  freely  falling  body  is  proportional  to  the  time,  t,  so  that 

^=gt (0; 

2.  e.,  at  the  end  of  the  ist  sec,  and  V  =^,  i  =^  =  9.809  M — the  distance  traversed — 

5  =  ^/2 (2)  : 

2  ■    ' 

i.  e.,  the  distances  are  as  the  square  of  the  times.  Hence,  from  (i)  and  (2)  it  follows  (by  eliminat- 
ing t)  that — 

V  -  V~'^^ (3)- 

The  velocities  are  as  the  square  roots  of  the  distances  traversed — 

Therefore  —   =j (4). 

The  freely  falling  body,  and  in  fact  every  freely  moving  body,  possesses  kinetic 
energy,  and  is  in  a  certain  sense  a  magazine  of  energy.  The  kinetic  energy  of 
any  moving  body  is  always  equal  to  the  product  of  its  weight  (estimated  by  the 
balance),  and  the  height  to  which  it  would  rise  from  the  earth,  if  it  were  thrown 
from  the  earth  with  its  own  velocity. 

Let  W  represent  the  kinetic  energy  of  the  moving  body,  and  P  its  weight,  then  W  =  P.  s,  so  that 
from  (4)  it  follows  that — 

W  =  pJ (5). 

Hence,  the  kinetic  energy  of  a  body  is  proportional  to  the  square  of  its  velocity. 

'Work. — If  a  force  (pressure,  strain,  tension)  be  so  applied  to  a  body  as  to 

move  it,  a  certain  amount  of  work  is  performed.     The  amount  of  work  is  equal 


36  INTRODUCTION. 

to  the  product  of  the  amount  of  the  pressure  or  strain  which  moves  the  body, 
and  of  the  distance  through  which  it  is  moved. 

Let  K  represent  the  force  acting  on  the  body,  and  S  the  distance,  then  the  work  W  =  KS.  The 
attraction  between  the  earth  and  any  body  raised  above  it  is  a  source  of  work. 

It  is  usual  to  express  the  vahie  of  K  in  kilogrammes,  and  S  in  metres,  so  that 
the  "unit  of  work  "  is  the  kilogramme-metre,  i.e.,  the  force  which  is 
required  to  raise  i  kilo,  to  the  height  of  i  metre. 

2.  Potential  Energy. —  The  transformation  of  Potential  into  Kinetic  Energy, 
and  conversely  :  Besides  kinetic  energy,  there  is  also  "potential  energy,"  or 
energy  of  position.  By  this  term  are  meant  various  forms  of  energy,  which  are 
suspended  in  their  action,  and  which,  although  they  may  cause  vnoUon,  are  not  in 
themselves  motion.  A  coiled  watch-spring  kept  in  this  position,  a  stone  resting 
upon  a  tower,  are  instances  of  bodies  possessing  potential  energy,  or  the  energy  of 
position.  It  requires  merely  a  push  to  develop  kinetic  from  the  potential  energy, 
or  to  transform  potential  into  kinetic  energy. 

Work,  7v,  was  performed  in  raising  the  stone  to  rest  upon  the  tower. 

7u  =  p,  s,  where/  ^  the  weight  and  s  =  the  height, 
p  z=  m.  ^,  is  ^=  the  product  of  the  mass  {m),  and  the  force  of  gravity  (^),  so  that  tv  =^  tn  g  s. 

This  is  at  the  same  time  the  expression  for  the  potential  energy  of  the  stone. 
This  potential  energy  may  readily  be  transformed  into  kinetic  energy  by  merely 
pushing  the  stone  so  that  it  falls  from  the  tower.  The  kinetic  energy  of  the  stone 
is  equal  to  the  final  velocity  with  which  it  impinges  upon  the  earth. 

V   •=  i/2g  s  (see  above  (3)  ). 
V«  =     2g  s. 
wV*  =     2;«  g  s. 

—  V  *  =     m  g  s. 
2 

m  g  s  was  the  expression   for  the  potential  energy  of  the  stone  while  it  was  still 

in       .  .       . 

resting  on  the  height ;        V2  is  the  kinetic  energy  corresponding  to  this  potential 

energy  {Briicke).  ^ 

Potential  energy  may  be  transformed  into  mechanical  energy  under  the  most 

varied  conditions ;  it  may  also  be  transferred  from  one  body  to  another. 

The  movement  of  a  pendulum  is  a  striking  example  of  the  former.  When  the  pendulum  is  at 
the  highest  point  of  its  excursion,  it  must  be  regarded  as  absolutely  at  rest  for  an  instant,  and  as 
endowed  with  potential  energy,  thus  correspondmg  with  the  raised  stone  in  the  previous  instance. 
During  the  swing  of  the  pendulum  this  potential  energy  is  changed  into  kinetic  energy,  which  is 
greatest  when  the  pendulum  is  moving  most  rapidly  toward  the  vertical.  As  it  rises  again  from  the 
vertical  position,  it  moves  more  slowly,  and  the  kinetic  energy  is  changed  into  potential  energy, 
which  once  more  reaches  its  maximum  when  the  pendulum  comes  to  rest  at  the  utmost  limit  of  its 
excursion.  Were  it  not  for  the  resistances  continually  opposed  to  its  movements,  such  as  the 
resistance  of  the  air  and  friction,  the  movement  of  the  jjendulum,  due  to  the  alternating  change  of 
kinetic  into  potential  energy  and  vice  versa,  \\ov\d  continue  uninterruptedly,  as  with  a  mathematical 
pendulum.  Suppose  the  swinging  ball  of  the  pendulum,  when  exactly  in  a  vertical  position, 
impinged  upon  a  resting  but  movable  sphere,  the  potential  energy  of  the  ball  of  the  pendulum  would 
be  transferred  directly  to  the  sphere,  provided  that  the  elasticity  of  the  ball  of  the  pendulum  and  the 
sphere  were  complete;  the  pendulum  would  come  to  rest,  while  the  sphere  would  move  onward 
with  an  equal  amount  of  kinetic  energy,  provided  there  were  no  resistance  to  its  movement.  This 
is  an  example  of  the  transference  of  kinetic  energy  from  one  body  to  another.  Lastly,  suppose  that 
a  stretched  watch-spring  on  uncoiling  causes  another  spring  to  become  coiled ;  and  we  have  another 
example  of  the  transference  of  kinetic  energy  from  one  body  to  another. 

The  following  general  statement  is  deducible  from  the  foregoing  examples :  If, 
in  a  system,  the  individual  moving  masses  approach  the  final  position  of  equi- 
librium, then  in  this  system  the  sum  of  the  kinetic  energies  increases  ;  if,  on  the 
other  hand,  the  particles  move  away  from  the  final  position  of  equilibrium,  then 


INTRODUCTION.  37 

the  sum  of  the  potential  energies  is  increased  at  the  expense  of  the  kinetic  energies, 
/.  e.,  the  kinetic  energies  diminish  {Brilcke^. 

The  pendulum,  which,  after  swinging  from  the  highest  point  of  its  excursion,  approaches  the 
vertical  position,  i.  e.,  the  position  of  equilibrium  of  a  passive  pendulum,  has  in  this  position  the 
largest  amount  of  potential  energy;  as  it  again  ascends  to  the  highest  point  of  its  excursion  on  the 
other  side,  it  again  gradually  receives  the  maximum  of  potential  energy  at  the  expense  of  the 
gradually  diminishing  movement,  and  therefore  of  the  kinetic  energy. 

3.  Heat. — Its  Relation  to  Potential  and  Kinetic  E7iei-gy. — If  a  lead  weight  be 
thrown  from  a  high  tower  to  the  earth,  and  if  it  strike  an  unyielding  substance,  the 
movement  of  the  mass  of  lead  is  not  only  arrested,  but  the  kinetic  energy  (which 
to  the  eye  appears  to  be  lost)  is  transformed  into  a  lively  vibratory  movement  of 
the  atoms.  When  the  lead  meets  the  earth,  heat  is  produced.  The  amount  of 
heat  produced  is  proportional  to  the  kinetic  energy  which  is  transformed  through 
the  concussion.  At  the  moment  when  the  lead  weight  reaches  the  earth,  the 
atoms  are  thrown  into  vibrations ;  they  impinge  upon  each  other ;  then  rebound 
again  from  each  other  in  consequence  of  their  elasticity,  which  opposes  their  direct 
juxtaposition ;  they  fly  asunder  to  the  maximum  extent  permitted  by  the  attractive 
force  of  the  ponderable  atoms,  and  thus  oscillate  to  and  fro.  All  the  atoms  vibrate 
like  a  pendulum,  until  their  movement  is  communicated  to  the  ethereal  atoms 
surrounding  them  on  every  side,  i.  e.,  until  the  heat  of  the  heated  mass  is 
' '  radiated. ' '     Heat  is  thus  a  vibratory  movement  of  the  atoms. 

As  the  amount  of  heat  produced  is  proportional  to  the  kinetic  energy  which  is 
transformed  through  the  concussion,  we  must  find  an  adequate  measure  for  both 
forces. 

Heat-Unit. — As  a  standard  of  measure  of  heat,  we  have  the  "heat-unit"  or 
calorie.  The  "heat-unit"  or  calorie  is  the  amount  of  energy  required  to  raise 
the  temperature  of  i  gramme  of  water  1°  Centigrade.  The  "heat-unit"  corres- 
ponds to  425.5  gramme-metres,  i.  e.,  the  same  energy  required  to  heat  i  gramme 
of  water  1°  C.  would  raise  a  weight  of  425.5  grammes  to  the  height  of  i  metre; 
or,  a  weight  of  425.5  grammes,  if  allowed  to  fall  from  the  height  of  i  metre,  would 
by  its  concussion  produce  as  much  heat  as  would  raise  the  temperature  of  i  gramme 
of  water  1°  C.  The  "  mechanical  equivalent  "  of  the  heat-unit  is,  therefore, 
425.5  gramme-metres. 

It  is  evident  that  from  the  collision  of  moving  masses  an  immeasurable  amount  of  heat  can  be 
produced.  Let  us  apply  what  has  already  been  said  to  the  earth.  Suppose  the  earth  to  be  disturbed 
in  its  orbit,  and  suppose  further  that,  owing  to  the  attraction  of  the  sun,  it  were  to  impinge  on  the 
latter  (whereby,  according  to  J.  R.  Mayer,  its  final  velocity  would  be  85  geographical  miles  per 
second),  the  amount  of  heat  produced  by  the  collision  would  be  equal  to  that  produced  by  the 
combustion  of  a  mass  of  pure  charcoal  more  than  5000  times  as  heavy  [Jtilius  Robert  Mayer, 
HebnhoUz). 

Thus,  the  heat  of  the  sun  itself  can  be  produced  by  the  collision  of  masses  of  cold  matter.  If  the 
cold  matter  of  the  universe  were  thrown  into  space,  and  there  left  to  the  attraction  of  its  particles, 
the  collision  of  these  particles  would  ultimately  produce  the  light  of  the  stars.  At  the  present  time, 
numerous  cosmic  bodies  collide  in  space,  while  innumerable  small  meteors  (94,000  to  188,000 
billions  of  kilos,  per  minute)  fall  into  the  sun.  The  force  of  gravity  is  perhaps,  in  fact,  the  only 
source  of  all  heat  (_/.  R.  Mayer,  Tyndall). 

We  have  a  homely  example  of  the  transformation  of  kinetic  energy  into  heat  in  the  fact  that  a 
blacksmith  may  make  a  piece  of  iron  red  hot  by  hammering  it.  Of  the  conversion  of  heat  into 
kinetic  energy  we  have  an  example  in  the  hot  watery  vapor  (steam)  of  the  steam  engine  raising  the 
piston.  An  example  of  the  conversion  of  potential  energy  into  heat  occurs  in  a  metallic  spring, 
when  it  uncoils  and  is  so  placed  as  to  rub  against  a  rough  surface,  producing  heat  by  friction. 

4.  Chemical  Affinity  :  Relation  to  Heat. — While  gravity  acts  upon  the 
particles  of  matter  without  reference  to  the  composition  of  the  body,  there  is 
another  atomic  force  which  acts  between  atoms  of  a  chemically  different  nature ; 
this  is  chemical  affinity.  This  is  the  force  in  virtue  of  which  the  atoms  of 
chemically  different  bodies  unite  to  form  a  chemical  compound.  The  force 
itself  varies  greatly  between  the  atoms  of  different  chemical  bodies  ;  thus  we  speak 


38  INTRODUCTION. 

of  strong  chemical  affinities  and  weak  affinities.  Just  as  we  were  able  to  estimate 
the  potential  energy  of  a  body  in  motion  from  the  amount  of  heat  which  was 
produced  when  it  collided  with  an  unyielding  body,  so  we  can  measure  the  amount 
of  heat  which  is  formed  when  the  atoms  of  chemically  different  bodies  unite  to 
form  a  chemical  compound.  As  a  rule,  heat  is  formed  when  sejjarate  chemically- 
different  atoms  form  a  compound  body.  When,  in  virtue  of  chemical  affinity, 
the  atoms  of  i  kilo,  of  hydrogen  and  8  kilos,  of  oxygen  unite  to  form  the  chemical 
compound  water,  an  amount  of  heat  is  thereby  evolved  which  is  equal  to  that 
produced  by  a  weight  of  47,000  kilos,  falling  and  colliding  with  the  earth  from  a 
height  of  1000  feet  above  the  surface  of  the  earth.  If  i  gramme  of  H  be  burned 
along  with  the  requisite  amount  of  O  to  form  water,  it  yields  34,460  heat-units  or 
calories :  and  i  gramme  carbon  burned  to  carbonic  acid  (carbon  dioxide)  yields 
8080  heat-units.  Wherever,  in  chemical  processes,  strong  chemical  affinities  are 
satisfied,  heat  is  set  free,  i.  e.,  chemical  affinity  is  changed  into  heat.  Chemical 
affinity  is  a  form  of  potential  energy  obtaining  between  the  most  different  atoms, 
which  during  chemical  processes  is  changed  into  heat.  Conversely,  in  those 
chemical  processes  where  strong  affinities  are  dissolved,  and  chemically-united 
atoms  thereby  pulled  asunder,  there  must  be  a  diminution  of  temperature,  or,  as 
it  is  said,  heat  becomes  latent — that  is,  the  energy  of  the  heat  which  has  become 
latent  is  changed  into  chemical  energy,  and  this,  after  decomposition  of  the 
compound  chemical  body,  is  again  represented  by  the  chemical  affinity  between 
its  isolated  different  atoms. 

LA^A/'  OF  THE  CONSERVATION  OF  ENERGY.— Julius  Robert 
Mayer  and  Helmholtz  have  established  the  important  law  that,  in  a  system  which 
does  not  receive  any  influence  and  impression  from  without,  the  sum  of  all  the 
forces  acting  within  it  is  always  the  same.  The  various  forms  of  energy  can  be 
transformed  one  into  the  other,  so  that  kinetic  cne7-gy  may  be  transformed  into  poten- 
tial energy  and  vice  versa,  but  there  is  never  any  part  of  the  energy  lost.  The 
transformation  takes  place  in  such  measure  that,  from  a  certain  definite  amount 
of  one  form  of  energy  a  definite  amount  of  another  can  be  obtained. 

The  various  forms  of  energy  acting  in  organisms  occur  in  the  following 
modifications: — 

1.  Molar  motion  (ordinary  movements),  as  in  the  movements  of  the  whole 
body,  of  the  limbs,  or  of  the  intestines,  and  even  those  observable  microscopically 
in  connection  with  cells. 

2.  Movements  of  Atoms  as  Heat. — We  know,  in  connection  with  the 
vibration  of  atoms,  that  the  number  of  vibrations  in  the  unit  of  time  determines 
whether  the  oscillations  appear  as  heat,  light,  or  chemically-active  vibrations. 
Heat-vibrations  have  the  smallest  number,  while  chemically-active  vibrations 
have  the  largest  number,  light-vibrations  standing  between  the  two.  In  the 
human  body  we  only  observe  heat-vibrations,  but  some  of  the  lower  animals  are 
capable  of  exhibiting  the  phenomena  of  light. 

In  the  human  organism  the  molar  movements  in  the  individual  organs  are  con- 
stantly being  transformed  into  heat,  e.g.,  the  kinetic  energy  in  the  organs  of  the 
circulation  is  transformed  by  friction  into  heat.  The  measure  of  this  is  the 
"unit  of  work"  =  i  gramme-metre,  and  the  "unit  of  heat"  =:=  425.5 
gramme-metres. 

3.  Potential  Energy. — The  organism  contains  many  chemical  compounds 
which  are  characterized  by  the  great  complexity  of  their  constitution,  by  the 
imperfect  saturation  of  their  affinities,  and  hence  by  their  great  tendency  to  split 
up  into  simpler  bodies. 

The  body  can  transform  the  potential  energy  into  heat  as  well  as  into  kinetic 
energy,  the  latter  always  in  conjunction  with  the  former,  but  the  former  always 
by  itself  alone.  The  simplest  measure  of  the  potential  energy  is  the  amount  of  heat 
which  can   be    obtained    by  complete    combustion   of  the  chemical  compounds 


INTRODUCTION.  39 

representing  the  potential  energy.  The  number  of  work-units  can  then  be  calcu- 
lated from  the  amount  of  heat  produced. 

4.  The  phenomena  of  electricity,  magnetism,  and  diamagnetism  may  be 
recognized  in  two  directions,  as  movements  of  the  smallest  particles,  which  are  recog- 
nized in  the  glowing  of  a  thin  wire  when  it  is  traversed  by  strong  electrical  currents 
(against  considerable  resistance),  and  also  as  molar  movement,  as  in  the  attraction 
or  repulsion  of  the  magnetic  needle.  Electrical  phenomena  are  manifested  in  our 
bodies  by  muscle,  nerve,  and  glands,  but  these  phenomena  are  relatively  small  in 
amount  when  compared  with  the  other  forms  of  energy.  It  is  not  improbable 
that  the  electrical  phenomena  of  our  bodies  become  almost  completely  transformed 
into  heat.  As  yet  experiment  has  not  determined  with  accuracy  "a  unit  of  elec- 
tricity" directly  comparable  with  the  "heat-unit"  and  the  "work-unit." 

It  is  quite  certain  that  within  the  organism  one  form  of  energy  can  be  trans- 
formed into  another  form,  and  that  a  certain  amount  of  one  form  will  yield  a 
definite  amount  of  another  form  ;  further,  that  new  energy  never  arises  spontane- 
ously, nor  is  energy  already  present  ever  destroyed,  so  that  in  the  organism  the 
law  of  the  conservation  of  energy  is  continually  in  action. 

ANIMALS  AND  PLANTS. — The  animal  body  contains  a  quantity  of 
chemically-potential  energy  stored  up  in  its  constituents.  The  total  amount  of 
the  energy  present  in  the  human  body  might  be  measured  by  burning  completely 
an  entire  human  body  in  a  calorimeter,  and  thereby  determining  how  many  heat- 
units  are  produced  when  it  is  reduced  to  ashes  (see  Animal  Heat). 

The  chemical  compounds  containing  the  potential  energy  are  characterized  by 
the  complicated  relative  position  of  their  atoms,  by  a  comparatively  imperfect 
saturation  of  the  affinities  of  their  atoms,  by  the  relatively  small  amount  of 
oxygen  which  they  contain,  by  their  great  tendency  to  decomposition,  and  the 
facility  with  which  they  undergo  decomposition. 

If  a  man  were  not  supplied  with  food  he  would  lose  50  grammes  of  his  body 
weight  every  hour ;  the  material  part  of  his  body,  which  contains  the  potential 
energy,  is  used  up,  oxygen  is  absorbed,  and  a  continual  process  of  combustion 
takes  place;  by  the  process  of  combustion  simpler  substances  are  formed  from  the 
more  complex  compounds,  whereby  potential  is  converted  into  kinetic  energy. 
It  is  immaterial  whether  the  combustion  is  rapid  or  slow;  the  same  amount  of 
the  same  chemical  substances  always  produces  the  same  amonnt  of  kinetic  energy, 
i.e.,  of  heat. 

A  person,  when  fasting,  experiences  after  a  certain  time  the  disagreeable  feeling 
of  exhaustion  of  his  reserve  of  potential  energy,  hunger  sets  in,  and  he  takes  food. 
All  food  for  the  animal  kingdom  is  obtained,  either  directly  or  indirectly,  from  the 
vegetable  kingdom.  Even  carnivora,  which  eat  the  flesh  of  other  animals,  only 
eat  organized  matter  which  has  been  formed  from  vegetable  food.  The  existence 
of  the  animal  kingdom  presupposes  the  existence  of  the  vegetable  kingdom. 

All  substances,  therefore,  necessary  for  the  food  of  animals  occur  in  vegetables. 
Besides  water  and  the  inorganic  constituents,  plants  contain,  among  other 
organic  compounds,  the  following  three  chief  representatives  of  foodstuffs — fats, 
carbohydrates,  and  proteids. 

All  these  contain  stores  of  potential  energy,  in  virtue  of  their  complex  chemical 
constitution. 

The  fats  contain  — I  ^"^^■>-^^^^^  =  ^^"y^^^^'l    (§  2=;0 
ine  tats.contam.— |_^  ^^j.j_^Qjj^^^g^y^^j.j^        |    ^S  251;. 

The  carbohydrates  contain  : — CeHjoOj         .         .         (§  252). 

rC.  5I-5-54-51 
I  H.     6.9-  7-3 

The  proteids  contain  per  cent.  : —  \  N.   15. 2-17.0  \     (§§  248  and  249"). 

■  O.  20.9-23.5  I 
S.      0.3-  2.0J 


40  INTRODUCTION. 

A  man  who  takes  a  certain  amount  of  this  food  adds  thereto  oxygen  from  the 
air  in  the  process  of  respiration.  Combustion  or  oxidation  then  takes  place, 
whereby  chemically-potential  energy  is  transformed  into  heat. 

Tt  is  evident  that  the  products  of  this  combustion  must  be  bodies  of  simpler 
constitution — bodies  with  less  complex  arrangement  of  their  atoms,  with  the 
greatest  possible  saturation  of  the  affinities  of  their  atoms,  of  greater  stability, 
partly  rich  in  O,  and  possessing  either  no  potential  energy,  or  only  very  little. 
These  bodies  are  carbon  dioxide,  CO., ;  water,  H.O  ;  and  as  the  chief  repre- 
sentative of  the  nitrogenous  excreta,  urea  ( CO(NHo)._,),  which  has  still  a  small 
amount  of  potential  energy,  but  which  outside  the  body  readily  splits  into  CO, 
and  ammonia  (NH.,). 

The  human  body  is  an  organism  in  which,  by  the  phenomena  of  oxidation,  the 
complex  nutritive  materials  of  the  vegetable  kingdom,  which  are  highly  charged 
with  potential  energy,  are  transformed  into  simple  chemical  bodies,  whereby  the 
potential  energy  is  transformed  into  the  equivalent  amount  of  kinetic  energy 
(heat,  work,  electrical  phenomena). 

But  how  do  plants  form  these  complex  food-stuffs  so  rich  in  potential  energy? 
It  is  plain  that  the  potential  energy  of  plants  must  be  obtained  from  some  other 
form  of  energy.  This  potential  energy  is  supplied  to  plants  by  the  rays  of  the 
sun,  whose  chemical  light-rays  are  absorbed  by  plants.  Without  the  rays  of  the 
sun  there  could  be  no  plants.  Plants  absorb  from  the  air  and  the  soil  CO.,,  H.^O, 
NH3,  and  X,  of  which  carbon  dioxide,  water,  and  ammonia  (from  urea)  are  also 
produced  by  the  excreta  of  animals.  Plants  absorb  the  kinetic  energy  of  light  from 
the  sun^ s  rays  and  transform  it  into  potential  energy,  which  is  accumulated  during 
the  growth  of  the  plant  in  its  tissues,  and  in  the  food-stuffs  produced  in  them 
during  their  growth.  This  formation  of  complex  chemical  compounds  is  accom- 
panied by  the  simultaneous  excretion  of  O. 

Occasionally,  kinetic  energy,  such  as  we  universally  meet  with  in  animals,  is  liberated  in  plants. 
Many  plants  develop  considerable  quantities  of  heat  in  their  flowers,  e.^^.,  the  arum  tribe.  We  must 
also  remember  that  during  the  formation  of  the  solid  parts  of  plants,  when  fluid  juices  are  changed 
into  solid  masses,  heat  is  set  free.  In  plants,  under  certain  circumstances,  O  is  absorbed,  and  CO.^ 
is  excreted,  but  these  processes  are  so  trivial  as  compared  with  the  typical  condition  in  the  vegetable 
kingdom,  that  they  may  be  regarded  as  of  small  moment. 

Plants,  therefore,  are  organisms  which,  by  a  reduction  process,  transform 
simple  stable  combinations  into  complex  compounds,  whereby  potential  solar 
energy  is  transformed  into  the  chemically-potential  energy  of  vegetable  tissues. 
Animals  are  living  beings,  which  by  oxidation  decompose  or  break  up  the  com- 
plex grouping  of  atoms  manufactured  by  plants,  whereby  potential  is  transformed 
into  kinetic  energy.  Thus,  there  is  a  constant  circulation  of  matter  and  a  con- 
stant exchange  of  energy  between  plants  and  animals.  All  the  energy  of  animals 
is  derived  from  plants.  All  the  energy  of  plants  arises  from  the  sun.  Thus  the 
sun  is  the  cause,  the  original  source  of  all  energy  in  the  organism,  /,  e.,  of  the 
whole  of  life. 

As  the  formation  of  solar  heat  and  solar  light  is  explicable  by  the  gravitation  of 
masses,  gravity  \s perhaps  the  original  form  of  energy  of  all  life. 

We  may  thus  represent  the  formation  of  kinetic  energy  in  the  animal  body 
from  the  potential  energy  of  plants.  Let  us  suppose  the  atoms  of  the  substances 
formed  in  organisms,  as  simple  small  bodies,  balls,  or  blocks.  As  long  as  these 
lie  in  a  single  layer,  or  in  a  few  layers,  upon  the  surface,  there  is  a  stable  arrange- 
ment, and  they  continue  to  remain  at  rest.  If,  however,  an  artificial  tower  be 
built  of  these  blocks,  so  that  an  unstable  erection  is  produced,  and  the  same  tower 
be  afterward  knocked  down,  then  for  this  purpose  we  require  (i)  the  motor 
power  of  the  workman  who  lifts  and  carries  the  blocks;  (2)  a  blow  or  other 
impulse  from  without  applied  to  the  unstable  structure — when  the  atoms  will  fall 
together,  and  as   they  fall  collide  with  each  other  and  produce  heat.     Thus,  the 


INTRODUCTION.  41 

energy  employed  by  the  workman  is  again  transformed  into  the  last-named  form 
of  energy. 

In  plants  the  complex  unstable  building  of  the  groups  of  atoms  is  carried  on, 
the  constructer  being  the  sun.  In  animals,  which  eat  plants,  the  complex  groups 
of  the  atoms  are  tumbled  down,  with  the  liberation  of  kinetic  energy. 

Vital  Energy  and  Life. — The  forces  which  act  in  organisms,  in  plants,  and 
animals  are  exactly  the  same  as  are  recognizable  as  acting  in  dead  matter.  A  so- 
called  "  vital  force,"  as  a  special  force  of  a  peculiar  kind,  causing  and  governing 
the  vital  phenomena  of  living  beings,  does  not  exist.  The  forces  of  all  matter,  of 
organized  as  well  as  unorganized,  exist  in  connection  with  their  smallest  particles 
or  atoms.  As,  however,  the  smallest  particles  of  organized  matter  are,  for  the  most 
part,  arranged  in  a  very  complicated  way,  compared  with  the  much  simpler  com- 
position of  inorganic  bodies,  so  the  forces  of  the  organism  connected  with  the 
smallest  particles  yield  more  complicated  phenomena  and  combinations,  whereby 
it  is  excessively  difficult  to  ascribe  the  vital  phenomena  in  organisms  to  the  simple 
fundamental  laws  of  physics  and  chemistry. 

The  Exchange  of  Material,  or  Metabolism  {"  Sioffwechser')  as  a  Sign 
of  Life. — Nevertheless,  there  appears  to  be  a  special  exchange  of  matter  and 
energy  peculiar  to  living  beings.  This  consists  in  the  capacity  of  organisms  to 
assimilate  the  matter  of  their  surroundings,  and  to  work  it  up  into  their  own  con- 
stitution, so  that  it  forms  for  a  time  an  integral  part  of  the  living  being,  to  be 
given  off  again.  The  whole  series  of  phenomena  is  called  metabolism  or 
"  StofTwechsel,"  which  consists  in  the  introduction,  assimilation,  integration, 
and  excretion  of  matter. 

We  have  already  shown  that  the  metabolism  of  plants  and  that  of  animals  are 
quite  different.  The  processes,  as  already  described,  actually  occur  in  the  typical 
higher  plants  and  animals. 

But  there  is  a  large  group  of  organisms  which,  throughout  their  entire  organiza- 
tion, exhibit  so  low  a  degree  of  development,  that  by  some  observers  they  are 
considered  as  undifferentiated  "ground-forms."  They  are  regarded  as  neither 
plants  nor  animals,  and  are  the  most  simple  forms  of  animated  matter.  Haeckel 
has  called  these  organisms  Protistse,  as  being  the  original  and  primitive  forms. 

We  must  assume  that,  corresponding  with  their  simpler  vital  conditions,  their 
metabolism  is  also  simpler,  but  on  this  point  we  still  require  further  observations 
and  experiments. 


Physiology  of  the  Blood. 


[The  blood  is  aptly  described  by  Claude  Bernard  as  an  internal  medium 
which  acts  as  a  "go-between"  or  medium  of  exchange  for  the  outer  world 
and  the  tissues.  Into  it  are  poured  those  substances  which  have  been  subjected 
to  the  action  of  the  digestive  fluids,  and  in  the  lungs  or  other  respiratory  organs 
it  receives  oxygen.  It  thus  contains  7iew  substances,  but  in  its  passage  through 
the  tissues  it  gives  up  some  of  these  new  substances,  and  receives  in  exchange 
certain  waste  products  which  have  to  be  got  rid  of.  Its  composition  is  thus 
highly  complex.  Besides  carrying  the  neiv  nutrient  fluids  to  the  tissues,  it  is  also 
the  great  oxygen  carrier,  as  well  as  the  medium  by  which  some  of  the  waste 
products,  e.g.,  C0._,,  urea,  are  removed y>v///  the  tissues,  and  brought  to  the  organs, 
e. g.,  the  lungs,  kidneys,  skin,  which  eliminate  them  from  the  body.  It  is  at  once 
a  great  pabulum-supplying  medium  and  a  channel  for  getting  rid  of  useless  mate- 
rials. As  the  composition  of  the  organs  through  which  the  blood  flows  varies,  it 
is  evident  that  its  composition  must  vary  in  different  parts  of  the  circulatory 
system ;  and  it  also  varies  in  the  same  individual  under  different  conditions. 
Still,  with  slight  variations,  there  are  certain  general  physical,  histological,  and 
chemical  properties  which  characterize  blood  as  a  whole. '\ 

I.  PHYSICAL  PROPERTIES.— (i)  Color.— The  color  of  blood  varies 
from  a  bright  scarlet-red  in  the  arteries  to  a  deep,  dark,  bluish-red  in  the  veins. 
Oxygen  (and,  therefore,  the  air)  makes  the  blood  bright  red]  want  of  oxygen 
makes  it  dark.  Blood  free  from  oxygen  (and  also  venous  blood)  is  dichroic — /.  e., 
by  reflected  light  it  appears  dark  red,  while  by  transmitted  light  it  is  green. 
[Arterial  blood  is  monochroic] 

In  thin  layers  blood  is  opaque,  as  is  easily  shown  by  shaking  blood  so  as 
to  form  bubbles,  or  by  allowing  blood  to  fall  upon  a  plate  with  a  pattern  on  it, 
and  pouring  it  off  again,  [Printed  matter  cannot  be  read  through  a  thin  layer  of 
blood  spread  on  a  glass  slide.]  Blood  behaves,  therefore,  like  an  "opaque  color," 
as  its  coloring  matter  is  suspended  in  the  form  of  fine  particles — the  blood 
corpuscles. 

Hence,  it  is  possible  to  separate  the  coloring  matter  from  the  fluid  part  of  the  blood  by  filtration. 
This  is  accomplished  by  mixing  the  blood  with  fluids  which  render  the  blood  corpuscles  sticky  or 
rough.  If  mammalian  blood  be  treated  with  one-seventh  of  its  volume  of  solution  of  sodic  sulphate, 
or  if  frog's  blood  be  mixed  with  a  2  per  cent,  solution  of  sugar  {Joh.  Ali'dler)  and  filtered,  the 
shriveled  corpuscles,  now  robbed  of  part  of  their  water,  remain  upon  the  filter. 

(2)  Reaction. — The  reaction  is  alkaline,  owing  to  the  presence  of  disodic 
phosphate,  Na.HPOi,  and  bicarbonate  of  soda.  After  blood  is  shed,  its  alkalinity 
rapidly  diminishes,  and  this  occurs  more  rapidly  the  greater  the  alkalinity  of  the 
blood.  This  is  due  to  the  formation  of  an  acid,  in  which,  perhaps,  the  colored 
corpuscles  take  part,  owing  to  the  decomposition  of  their  coloring  matter.  A  high 
temperature  and  the  addition  of  an  alkali  favor  the  formation  of  the  acid  (iV. 
Zuntz). 

The  alkaline  reaction  of  blood  is  diminished:  (a)  by  great  muscular  exertion,  owing  to  the 
formation  of  a  large  amount  of  acid  in  the  muscles;  (/3)  during  coagulation;  (y)  in  old  blood,  or 
blood  dissolved  by  water  from  old  blood  stains,  such  blood  being  usually  acid ;  fresh  cruor  has  a 

42 


PHYSICAL    PROPERTIES    OF   THE   BLOOD.  4S 

stronger  alkaline  reaction  than  serum ;  (d)  after  the  prolonged  use  of  soda  the  alkalinity  is  increased 
after  the  use  of  acids  it  is  decreased. 

Methods. — Owing  to  the  color  of  the  blood  we  cannot  employ  ordinary  litmus  paper  to  test  its 
reaction.  One  of  the  following  methods  maybe  used:  (i)  Moisten  a  strip  of  glazed  red  litmus 
paper  with  solution  of  common  salt,  and  allow  a  drop  of  blood  to  fall  on  the  paper;  then  rapidly 
wipe  it  off  before  its  coloring  matter  has  time  to  penetrate  and  tinge  the  paper  l^Zuniz).  (2)  Lie- 
breich  used  thin  plates  of  plaster- of- Paris  of  a  perfectly  neutral  reaction.  These  are  dried,  and 
afterward  moistened  with  a  neutral  solution  of  litmus.  When  a  drop  of  blood  is  placed  upon  the 
porous  plate,  the  fluid  part  of  the  blood  passes  into  it,  while  the  corpuscles  are  washed  off  with 
water,  and  the  altered  color  of  the  litmus-stained  slab  is  apparent.  [(3)  Schafer  uses  dry,  faintly- 
reddened,  glazed  litmus  paper,  and  on  it  is  placed  a  drop  of  blood,  which  is  wiped  off  after  a  few 
seconds.  The  place  where  the  blood  rested  is  indicated  by  a  blue  patch  upon  a  red  or  violet 
ground.] 

Estimation  of  the  Alkalinity. — A  very  dilute  solution  of  tartaric  acid  (i  cubic  centimetre 
combines  with  3. 1  milligrams  of  soda,  /.  e.,  I  litre  of  water  contains  7.5  grams  of  crystallized 
tartartic  acid)  is  added  to  blood  until  a  blue  litmus  paper  is  turned  red  (by  Zuntz's  method).  100 
grams  of  rabbit's  blood  have  an  alkalinity  corresponding  to  150  milligrams  of  soda;  the  blood 
of  carnivora  to  about  180  milligrams  [Lassar),  while  loo  c.c.  of  normal  human  blood  have  an 
alkalinity  equal  to  260-300  milligrams  of  soda  (v.  Jakscli). 

The  following  method  can  be  used  with  a  few  drops  of  blood  :  To  neutralize  the  blood,  tartaric 
acid  in  the  above  concentration  is  used.  Prepare  the  following  mixture  by  mixing  it  with  a 
concentrated  solution  of  sodic  sulphate,  and  then  adding  sodic  sulphate  until  the  mixture  is  com- 
pletely saturated.  I,  10  parts  of  solution  of  tartaric  acid  to  100  parts  of  concentrated  sodic  sulphate 
solution;  II,  20  parts  tartaric  acid  solution  to  90  sodic  sulphate  solution;  III  contains  these  sub- 
stances in  the  proportion  of  30  to  80;  IV,  40  to  70;  V,  50  to  60;  VI,  60  to  50;  VII,  70  to  40; 
VIII,  80  to  30;  IX,  90  to  20;  and  X,  loo  to  10.  Excess  of  sodic  sulphate  is  present  in  all  the 
flasks. 

A  known  volume  of  the  blood  to  be  investigated  is  mixed  with  an  equal  volume  of  each  of  the 
mixtures,  in  a  small  tube,  which  is  made  by  drawing  out  a  glass  tube  i  millimetre  in  diameter  to  a 
fine  point.  To  calibrate  this  tube,  suck  up  water,  say,  to  the  height  of  8  mm.,  make  a  mark  on  the 
tube  with  a  fine  file,  then  suck  up  the  water  until  its  lower  level  corresponds  with  the  mark.  Again 
mark  the  upper  limit  of  the  water.  To  test  the  blood,  suck  a  drop  of  the  mixture  I  up  to  the  level 
of  the  first  mark  on  the  glass  pipette,  and,  after  wiping  its  point,  suck  up  an  equal  quantity  of  blood. 
Again  clean  the  point  of  the  pipette,  and  blow  its  contents  into  a  watch  glass;  then  mix,  and  test 
the  reaction  with  sensitive  violet-colored  litmus  paper.  Proceed  in  the  same  way  with  the  several 
mixtures,  II  to  X,  until  the  alkaline  reaction  disappears  or  the  acid  appears.  The  narrow  strips  of 
litmus  paper  are  dipped  into  each  of  the  mixtures,  the  corpuscles  remain  in  the  wetted  part  of  the 
paper,  while  the  fluid  permeates  further  and  shows  the  reaction.  As  a  rule,  the  degree  of  alkalinity 
in  human  blood  corresponds  to  VI.  Human  blood  can  be  sucked  directly  from  a  small  wound 
made  by  a  needle,  either  by  attaching  an  elastic  tube  or  a  small  hypodermic  syringe  to  the  pipette 
{^Latidois). 

Pathological. — The  alkalinity  is  increased  during  persistent  vomiting,  and  decreased  in  pro- 
nounced anaemia,  cachexia,  uraemia,  rheumatism,  high  fever,  diabetes,  and  cholera.  [Immediately 
before  death  by  cholera  it  may  be  acid  {^Cantani).'\ 

(3)  Odor. — Blood  emits  a  peculiar  odor,  the  halitus  sanguinis,  which  differs  in 
animals  and  man. 

It  depends  upon  the  presence  of  volatile  fatty  acids.  If  concentrated  sulphuric  acid  be  added 
to  blood,  whereby  the  volatile  fatty  acids  are  set  free  from  their  combinations  with  alkalies,  the 
characteristic  odor,  somewhat  similar  to  that  of  butyric  acid,  becomes  much  more  perceptible. 

(4)  Taste. — Blood  has  a  saline  taste,  depending  upon  the  salts  dissolved  in  the 
fluid  of  the  blood. 

(5)  Specific  Gravity. — The  specific  gravity  is  1056-1059  in  man,  1051-1055 
in  woman  ;  in  children  less.  The  specific  gravity  of  the  blood  corpuscles  is  1105, 
that  of  the  plasma  1027.     Hence  the  corpuscles  tend  to  sink. 

Clinical  Method. — A  thin  glass  tube  is  drawn  out  till  it  is  of  small  calibre,  and  then  bent  at  a 
right  angle,  and  closed  above  with  a  caoutchouc  cap.  Press  slightly  on  the  caoutchouc  cap,  and 
suck  up  a  drop  of  the  freshly-drawn  blood  obtained  by  pricking  the  finger.  The  fine  capillary  tube 
is  at  once  immersed  in  a  solution  of  sodic  sulphate,  and  a  drop  of  the  blood  expressed  into  the 
saline  solution.  It  is  necessary  to  prepare  several  solutions  of  sodic  sulphate  with  specific  gravities 
varying  from  1050-1070.  The  solution  in  which  the  corpuscles  remain  suspended  indicates  the 
specific  gravity  of  the  blood  {Hoy,  Landois). 

The  drinking  of  water  and  hunger  diminish  the  specific  gravity  temporarily,  while  thirst  and  the 
digestion  of  dry  food  raise  it.     If  blood  be  passed  through  an  organ  artificially,  its  specific  gravity 


44 


MICROSCOPIC    EXAMINATION    OF   THE    I5LOOD. 


rises  in  consequence  of  the  absorption  of  dissolved  matters  and  the  giving  off  of  water.  It  falls 
after  hemorrhage,  and  is  diminished  in  badly-nourished  individuals.  [By  working  with  solutions 
of  glycerine,  Jones  finds  that  it  is  highest  at  birth,  is  at  a  minimum  between  the  second  week  and 
the  second  year;  it  rises  gradually  until  the  35th-45th  year.  It  is  usually  higher  in  the  male  than 
the  female,  is  diminished  by  pregnancy,  the  ingestion  of  solid  or  liquid  food,  and  gentle  exercise.] 

[(6)  Temperature. — Blood  is  viscid,  and  its  temperature  varies  from  36.5"  C. 
(97.7°  F.)  to  37.8°  C.  (100°  F.).  The  wannest  blood  in  the  body  is  that  of  the 
hepatic  vein  (ij  210^.] 

2.  MICROSCOPIC  EXAMINATION.— [Blood,  when  examined  by  the 
microscope,  is  seen  to  consist  of  an  enormous  number  of  corpuscles — (  olored 
and  colorless — floating  in  a  transparent  fluid,  the  plasma,  or  liquor  san- 
guinis. 

Human  Red  Blood  Corpuscles. — (a)  Form. — They  are  circular,  coin- 
shaped,  homogeneous  disks,  with  saucer-like  depressions  on  both  surfaces,  and 
with  rounded  margins ;  in  other  words,  they  are  bi-concave,  circular,  non-nucle- 
ated disks. 

Fig.  I. 

A  B 


A,  human  colored  blood  corpuscles — i,  on  the  flat;  2,  on  edge;  3,  rouleau  of  colored  corpuscles.  B,  amphibian 
colored  blood  corpuscles — i,  on  the  flat  ;  2,  on  edge.  C,  ideal  transverse  section  of  a  human  colored  blood 
corpuscle  magnified  50C0  times  linear —  ai,  diameter;  erf,  thickness. 

(d)  Size. — The  diameter  (ad)  is  7.7/j'-,*  (6.7-9.3/7.)  the  greatest  thickness  (cd) 
1.9,'i  (Fig.  I,  C),  [/.<f. ,  it  is  YTWo  ^°  3 0^0 0  of  ^"  inch  in  diameter,  and  about  one- 
fourth  of  that  in  thickness]. 

They  are  slightly  diminished  in  size  by  septic  fever,  inanition,  morphia,  increased  bodily  tem- 
perature, and  COo ;  and  increased  by  O,  watery  condition  of  the  blood,  cold,  consumption  of 
alcohol,  quinine,  and  hydrocyanic  acid.     Compare  \   lo,  3. 

If  the  total  amount  of  blood  in  a  man  be  taken  at  4400  cubic  centimetres,  the  corpuscles  therein 
contained  have  a  surface  of  2816  square  metres,  which  is  equal  to  a  square  surface  with  a  side  of 
80  paces;  176  cubic  centimetres  of  blood  pass  through  the  lungs  in  a  second,  and  the  blood  cor- 
puscles in  this  amount  of  blood  have  a  superficies  of  81  square  metres,  equal  to  a  square  surface 
with  a  side  of  13  paces  ( IVelcker). 

(ri  The  weight  of  a  blood  corpuscle  is  o-oooo8  milligramme. 

id )  The  number  exceeds  5,000,000  per  cubic  millimetre  in  the  male,  and 
4,500,000  in  the  female;  so  that,  in  10  lbs.  of  blood,  there  are  25  billions  of 
corpuscles.  The  number  is  in  inverse  ratio  to  the  amount  of  plasma  ;  hence,  the 
number  must  vary  with  the  state  of  contraction  of  the  blood  vessels,  the  pressure, 
diffusion  currents,  and  other  conditions. 

*  The  Greek  letter  /z  represents  one-thousandth  of  a  millimetre  (//  =  0001  mm.),  and  is  the  sign 
of  a  micro-millimetre,  or  a  micron. 


MICROSCOPIC    EXAMINATION    OF    THE    BLOOD. 


45 


The  number  of  red  corpuscles  is  increased ;  in  venous  blood  (especially  in  the  small  cutaneous 
veins),  after  the  use  of  sohd  food,  after  much  sweating,  and  the  excretion  of  much  \vater  by  the 
bowel  and  kidneys;  during  inanition,  because  the  blood  plasma  undergoes  decomposition  sooner 
than  the  blood  corpuscles  themselves;  in  the  blood  of  the  newly-born  child,  especially  when  the 
umbilical  cord  is  long  in  being  tied  (^  40),  from  the  4th  day  onward  the  number  is  diminished; 
in  persons  of  robust  constitution,  and  in  those  who  live  in  the  country.  The  number  is  diminished, 
during  pregnancy,  after  copious  draughts  of  water.  In  the  earlier  period  of  fcetal  life  the  number 
is  only  )4-i  million  in  i  cubic  millimetre.     (For  the  pathological  conditions  see  ^  10.) 

Methods  of  Counting  the  Blood  Corpuscles.— The  pointed  end  of  a  glass  pipette  (Fig.  3), 
the  mixer,  is  dipped  into  the  blood,  and  by  sucking  the  elastic  tube/,  blood  is  drawn  into  the  tube 
until  it  reaches  the  mark  )4,on  the  stem  of  the  pipette,  or  until  the  mark  i  is  reached.  The  carefully- 
cleaned  point  of  the  pipette  is  dipped  into  the  artificial  serum,  and  this  is  sucked  into  the  pipette 


Fig.  2. 


Fig.  3. 


^ 


Apparatus  of  Abbe  and  Zeiss  for  counting  the  cor- 
puscles. A,  in  section ;  C,  surface  view  without 
cover-glass ;  B,  microscopic  appearance  with  the 
blood  corpuscles. 


Melangeur,    pipette     or 
mixer. 


until  it  reaches  the  mark,  loi.  The  artificial  serum  consists  of  l  vol.  of  solution  of  gum  arable 
(sp.  gr.  1020)  and  3  vols,  of  a  solution  of  equal  parts  of  sodic  sulphate  and  sodic  chloride  (sp,  gr. 
1020).  The  process  of  mixing  the  two  fluids  is  aided  by  the  presence  of  a  little  glass  ball  {a)  in 
the  bulb  of  the  pipette.  If  blood  is  sucked  up  to  the  mark  ^,  the  strength  of  the  mixture  is  i  :  200 ; 
if  to  the  mark  l,  it  is  1  :  100;  a  small  drop  of  the  mixture  is  allowed  to  run  into  the  counting 
chamber  of  Abbe  and  Zeiss  (Fig.  2).  The  first  portions  are  not  used,  in  order  to  obtain  a  uniform 
sample  from  the  bulb  of  the  pipette.  This  chamber  consists  of  a  glass  receptacle  o.i  mm.  deep, 
with  its  base  divided  into  squares  and  cemented  to  a  glass  slide,  the  whole  being  covered  with  a 
thin  covering  glass.  The  space  over  each  square  ^  :^L_  cubic  millimetre.  Count,  with  the  aid 
of  a  microscope,  the  number  of  blood  corpuscles  in  each  square,  and  the  number  found,  multiplied 
by  4000,  will  give  the  number  of  blood  corpuscles  in  i  c.mm.  This  number,  again,  must  be  multi- 
plied by  100  or  200,  according  as  the  blood  was  diluted  lOO  or  200  times.  To  ensure  greater 
accuracy,  it  is  well  to  count  the  number  in  several  squares,  and  to  take  the  mean  of  these. 


41) 


HISTOLOGY    OF    THE    HUMAN    RED    BLe)OD    CORPUSCLES. 


[Gowers'  Method. — "The  Haemacytometer  {V'xq.  4)  consists  of  (l)  a  small  pipette,  which, 
when  tilled  to  the  mark  on  its  stem,  holds  exactly  995  cubic  millimetres.  It  is  furnished  with  an 
india-rubber  tube  and  mouthpiece  to  facilitate  tilling  and  emptying.  (2)  A  capillary  tube  marked 
to  contain  exactly  5  cubic  millimetres,  with  india-rubber  tube  for  filling,  etc.  (3)  A  small  glass  jar 
in  which  the  dilution  is  made.  (4)  A  glass  stirrer  for  mixing  the  blood  and  solution  in  the  glass 
jar.  (5)  A  brass  stage  plate,  carrying  a  glass  slip,  on  which  is  a  cell,  1  of  a  millimetre  deep.  'I'he 
bottom  of  this  is  divided  into  ,15  millimetre  scjuares.  Upon  the  top  of  the  cell  rests  the  cover-glass, 
which  is  kept  in  its  place  by  the  pressure  of  two  springs  proceeding  from  tlie  ends  of  the  stage 
plate."  The  diluting  solution  used  is  a  solution  of  sodic  sulphate  in  distilled  water,  sp.  gr.  1025, 
or  the  following — sodic  sulphate,  104  grains;  acetic  acid,  i  drachm  ;  distilled  water,  4  oz. 

"  995  cubic  millimetres  of  the  solution  are  placed  in  the  mixing  jar ;  5  cubic  millimetres  of  blood 
are  drawn  into  the  capillary  tube  from  the  puncture  in  the  finger,  and  then  blown  into  the  solution. 
The  two  fluids  are  well  mixed  by  rotating  the  stirrer  between  the  thumb  and  finger,  and  a  small 
drop  of  this  dilution  is  placed  in  the  centre  of  the  cell,  the  covering  glass  gently  put  upon  the  cell, 
and  secured  by  the  two  springs,  and  the  plate  placed  upon  the  stage  of  the  microscope.  The  lens 
is  then  focused  for  the  squares.  In  a  few  minutes  the  corpuscles  have  sunk  to  the  bottom  of  the 
cell,  and  are  seen  at  rest  on  the  squares.  The  number  in  ten  s^piares  is  then  counted,  and  this, 
multiplied  by  10,000,  gives  the  number  in  a  cubic  millimetre  of  blood." 

Fig.  4. 


Gowers'  apparatus.  A,  pipette  for  measuring  the  diluting  solution;  B,  capillary  tube  for  measuring  the  blood; 
C,  cell  with  divisions  on  the  floor,  mounted  on  a  slide ;  D,  vessel  in  which  the  dilution  is  made ;  E,  glass 
stirrer ;  F,  guarded  spear-pointed  needle. 

To  estimate  the  colorless  corpuscles  only,  mix  the  blood  with  10  parts  0-5  per  cent,  solution  of 
acetic  acid,  which  destroys  all  the  red  corpuscles.  ( Thoma). 

[e)  Red  blood  corpuscles  are  characterized  by  their  great  elasticity,  flexi- 
bility, and  softness.  [The  elastic  property  is  shown  by  the  extent  to  which  red 
corpuscles  while  circulating  may  be  distorted,  and  yet  resume  their  original  form 
as  soon  as  the  pressure  is  removed.] 

3.  HISTOLOGY  OF  THE  HUMAN  RED  BLOOD  CORPUS- 
CLES.— When  observed  singly,  human  red  blood  corpuscles  are  bi-concave 
circular  disks  of  a  yellow  color  with  a  slight  tinge  of  green  ;  they  seem  to  be 
devoid  of  an  envelope,  are  certainly  non-nucleated,  and  appear  to  be  homogene- 
ous throughout.  Each  corpuscle  consists  (i)  of  a  framework,  an  exceedingly  pale, 
transparent,  soft  protoplasm — the  stroma;  and  (2)  of  the  red  pigment,  or 
haemoglobin,  which  impregnates  the  stroma,  much  as  fluid  passes  into  and  is 
retained  in  the  interstices  of  a  bath  sponge. 


EFFECT    OF    REAGENTS    ON    THE    BLOOD    CORPUSCLES. 


47 


4.   EFFECT  OF   REAGENTS.— (A)  On  their   Vital  Phenomena. 

— The  blood  corpuscles  present  in  shed  blood — or  even  in  defibrinated  blood, 
when  it  is  reintroduced  into  the  circulation — retain  their  vitality  and  functions 
undiminished.  Heat  acts  powerfully  on  their  vitality,  for  if  blood  be  heated  to 
52°  C,  the  vitality  of  the  red  corpuscles  is  destro3'ed.  Mammalian  blood  may 
be  kept  for  four  or  five  days  in  a  vessel  under  iced  water,  and  still  retain  its  func- 
tions ;  but  if  it  be  kept  longer,  and  reintroduced  into  the  circulation,  the  corpus- 
cles rapidly  break  up — '-a.  proof  that 

they  have  lost  their  vitality.     The  I'ig.  5. 

red  corpuscles  in  freshly  shed  blood 
sometimes  exhibit  a  peculiar  mul- 
berry-like appearance  (Figs.  5,  6,g, 
h).  [This  is  called  crenation  of 
the  colored  corpuscles.  It  occurs 
in  cases  of  poisoning  with  Calabar 
bean ;  and  also  by  the  addition  of 
a  2  per  cent,  solution  of  common 
salt.]  The  blood  of  many  persons 
crenates  spontaneously — a  condi- 
tion ascribed  to  an  active  contrac- 
tion of  the  stroma,  but  it  is  doubtful 
if  this  is  the  cause.  The  red  cor- 
puscles of  the  embryo  chick  undergo 
active  contraction. 

(B)  On  their  external  char- 
acters.— {a)  The  color  is  changed 
by  many  gases.  O  makes  blood 
scarlet,  want  of  O  renders  it  dark 
bluish-red,  CO  makes  it  cherry-red, 
NO  violet-red.  There  is  no  difference  between  the  shape  of  the  corpuscles  in 
arterial  and  venous  blood.  All  reagents  {e.  g.,  a  concentrated  solution  of  sodic 
sulphate),  which  cause  great  shrinking  of  the  colored  corpuscles,  produce  a  very 
bright  scarlet  or  brick-red  color.  The  red  color  so  produced  is  quite  different 
from  the  scarlet-red  of  arterial  blood.  Reagents  which  render  blood  corpuscles 
globular  darken  the  blood,  e.g.,  water. 

[The  contrast  is  very  striking,  if  we  compare  blood  to  which  a  10  per  cent,  solution  of  common 
salt  has  been  added  with  blood  to  which  water  has  been  added.  With  reflected  light  the  one  is 
bright  red,  and  the  other  a  very  dark,  deep  crimson,  almost  black. 

(3)  Formation  of  Rouleaux. — A  very  common  phenomenon  in  shed  blood 
is  the  tendency  of  the  corpuscles  to  run  into  rouleaux  (Fig.  i,  A,  3). 

Conditions  that  increase  the  coagulability  of  the  blood  favor  this  phenomenon,  which  is  ascribed 
by  Dogiel  to  the  attraction  of  the  disks  and  the  formation  of  a  sticky  substance.  [The  cause  of  the 
formation  of  rouleaux  is  by  no  means  clear.  The  corpuscles  may  be  detached  from  each  other  by 
gently  touching  the  cover-glass,  but  the  rouleaux  may  re-form.  Lister  suggested  that  the  surfaces 
of  the  corpuscles  were  so  altered  that  they  became  adhesive.  Norris  made  experiments  with  corks 
weighted  with  tacks  or  pins,  so  as  to  produce  partial  submersion  of  the  cork  disks.  These  disks 
rapidly  cohere,  owing  to  capillarity,  and  form  rouleaux.  If  the  disks  be  completely  submerged 
they  remain  apart,  as  occurs  with  unaltered  blood  corpuscles  within  the  blood  vessels.  If,  how- 
ever, the  corpuscles  be  dipped  in  petroleum,  and  then  placed  in  water,  rouleaux  are  formed.] 
If  reagents  which  cause  the  corpuscles  to  swell  up  be  added  to  the  blood,  the  corpuscles  become 
globular  and  the  rouleaux  break  up.  According  to  E.  Weber  and  Suchard,  the  uniting  medium  is 
not  fibrin  (although  it  may  sometimes  assume  a  fibrous  form),  but  belongs  to  the  peripheral  layer 
of  the  corpuscles. 

{c)  Changes  of  Form. — The  discharge  of  a  Leyden  jar  causes  the  cor- 
puscles to  crenate,  so  that  their  surfaces  are  beset  with  coarse  or  fine  projections 
(Fig.  6,  c,  d,  e,  g,  h)  ;  it  also  causes  the  corpuscles  to  assume  a  spherical  form  (/,  /), 


Crenation  of  human  red  blood  corpuscles. 


48 


EFFECT   OF    REAGENTS    ON    THE    BLOOD    CORPUSCLES. 


and  they  become  smaller  than  normal.  The  corpuscles  so  altered  are  sticky,  and 
run  together  like  drops  of  oil,  forming  larger  si)heres.  The  prolonged  action  of 
the  electrical  spark  causes  the  haemoglobin  to  separate  from  the  stroma  (/&), 
whereby  the  fluid  part  of  the  blood  is  reddened,  while  the  stroma  is  recognizable 
only  as  a  faint  shadow  (/).  Similar  forms  are  to  be  found  in  decomposing  blood, 
as  well  as  after  the  action  of  many  other  reagents.     Heat. — Wlien  blood  is  heated, 

Fic.  6. 


Red  blood  corpuscles,  a,  b,  normal  human  red  corpuscles,  the  central  depression  more  or  less  in  focus  ;  c,  d,  e,  mvX- 
berry,  and  ^,  A,  crenated  forms;  A,  pale  corpuscles  decolorized  by  water;  /,  stroma ;  y",  frog's  blood  corpuscle 
acted  on  by  a  strong  saline  solution. 

on  a  warm  stage,  to  52°  C.  the  corpuscles  exhibit  remarkable  changes.  Some  of 
them  become  spherical,  others  biscuit-shaped  ;  some  are  perforated,  while  in  others 
small  portions  become  detached  and  swim  about  in  the  surrounding  fluid,  a  proof 
that  heat  destroys  the  histological  individuality  of  the  corpuscles.  If  the  heat 
be  continued,  the  corpuscles  are  ultimately  dissolved  (§  10,  3). 

Heat  acts  like  the  addition  of  a  concentrated  solution  of  urea  to  blood.  If  strong  pressure  be 
exerted  upon  a  microscopic  preparation,  the  blood  corpuscles  may  break  in  pieces.  The  latter  pro- 
cess is  called  haemocytotrypsis,  in  contradistinction  to  that  of  solution  of  the  corpuscles  or 
haemocytolysis. 

If  a  finger  moistened  with  blood  be  rapidly  drawn  across  a  warm  slip  of  glass,  so  that  the  fluid 
dries  rapidly,  the  corpuscles  exhibit  very  remarkable  shapes,  showing  their  great  ductility  and 
softness. 

Cytozoon — Gaule's  Experiment. — A  few  drops  of  freshly  shed  frog's  blood  are  mixed  with  5 
c.c.  of  0.6  per  cent,  solution  of  common  salt,  and  the  mixture  defibrinated  by  shaking  it  along 
with  a  few  c.c.  of  mercury.  A  drop  of  the  defibrinated  blood  is  examined  on  a  hot  stage  (30°-32° 
C.)  under  a  microscope,  when  a  protoplasmic  mass,  the  so-called  "  lVur?nchen,^'  escapes  with  a 
lively  movement  from  many  corpuscles,  and  ultimately  dissolves.  Similar  "  cytozoa  "  were  discov- 
ered by  Gaule  in  the  epithelium  of  the  cornea,  of  the  stomach  and  intestine,  in  connective  tissue, 
in  most  of  the  large  glands,  and  in  the  retina  (frog,  triton).  In  mammals  also  he  found  similar  but 
smaller  structures.  Most  probably  these  structures  are  parasitic  in  their  nature,  as  suggested  by  Ray 
Lankester,  who  called  the  parasite  Drepanidium  ranarum. 

[Staining  Reagents. — Such  reagents  as  magenta,  picro-carmine,  carmine,  and 
many  of  the  aniline  dyes,  stain  the  nucleus  deeply  when  such  is  present,  and  although 
they  must  traverse  the  hcemoglobin  to  reach  the  nucleus,  the  hsemoglobin  itself  is 
not  stained.  When  no  nucleus  is  present,  therefore,  the  corpuscles  are  not  stained. 
Magenta  causes  one  or  more  small  spots  or  maculas  to  appear  on  the  edge  of  the 
corpuscles  (Fig.  7,  a).  What  its  significance  is,  is  entirely  unknown.  Normal 
saline  solution  (0.6  per  cent.  NaCl),  tinged  with  methyl  violet,  is  a  good  staining 
and  preservative  agent.] 

[Agitation  with  Mercury. — If  ox  blood  be  shaken  up  with  mercury  for  7  or  8  hours,  the  cor- 
puscles completely  disappear,  no  trace  of  stroma  or  corpuscles  being  found  in  the  fluid  [Meltzer  and 
Welch).  The  addition  of  pyrogallic  acid  (20  per  cent.)  potassic  chlorate  (6  per  cent.),  and  silver 
nitrate  (3  per  cent.),  completely  prevents  dissolution  of  the  corpuscles,  even  though  the  shaking  be 
kept  up  for  fourteen  days.] 

If  blood  be  mixed  with  concentrated  gum  solution,  and  if  concentrated  salt  solution  be  added  to 
it  under  the  microscope,  the  corpuscles  assume  elongated  forms.     Similar  forms  are  obtained  by 


STROMA LAKE-COLORED    BLOOD.  49 

mixing  blood  with  an  equal  volume  of  gelatine  at  36°  C.,  allowing  it  to  cool,  and  then  making  sec- 
tions of  the  coagulated  mass.  The  corpuscles  may  be  broken  up  by  pressing  firmly  on  the  cover- 
glass.  In  all  these  experiments  no  trace  of  an  envelope  around  the  corpuscles  is  observed.  [An 
excellent  reagent  for  "  fixing  "  the  blood  corpuscles  is  either  a  dilute  solution  or  the  vapor  of  osmic 
acid.] 

Conservation  of  the  Corpuscles. — In  investigating  blood  with  the  microscope  for  forensic 
purposes,  it  is  necessary  to  have  a  solvent  for  the  blood  when  it  occurs  as  stains  on  a  garment  or 
instrument.     Dried  stains  are   dissolved  by  a  concentrated,  or  a  30  per  cent,  solution  of  caustic 

Fig.  7. 


a,  i,  human  red  blood  corpuscles  ;  a,  acted  on  by  magenta  ;  i,  by  tannic  acid.  The  others  are  amphibian  red  blood 
corpuscles  ;  c,d,  ^,  effect  of  tannic  acid.-y,  of  dilute  acetic  acid  ;  g-,  of  dilute  alcohol;  </,  by  boracic  acid. — Stirling. 

potash,  or  with  one  of  the  preserving  fluids.  If  the  stain  be  softened  with  concentrated  tartaric 
acid,  colorless  corpuscles  are  specially  distinct  [Stmwe).  Nevertheless,  corpuscles  are  often  not 
found  in  such  stains.  If  the  corpuscles  have  become  very  pale,  their  color  may  be  improved  by 
adding  a  solution  of  iodide  of  potassium,  a  saturated  solution  of  picric  acid,  20  per  cent,  pyrogallic 
acid,  or  3  per  cent,  solution  of  silver  nitrate. 

5.  STROMA— LAKE-COLORED  BLOOD.— Many  reagents  cause  the 
hsemoglobin  to  separate  from  the  stroma.  The  hccmoglobin  dissolves  in  the 
serum;  the  blood  becomes  dark  red  and  transparent,  as  it  contains  its  coloring 
matter  in  solution,  and  hence  it  is  called  "  lake-colored  "  (^Rollett).  The  aggre- 
gate condition  of  the  hsemoglobin  is  not  altered  when  the  corpuscles  are  dissolved 
— it  only  changes  its  place,  leaving  the  stroma  and  passing  into  the  serum.  Hence, 
the  temperature  of  the  blood  is  not  lowered  thereby. 

Methods. — To  obtain  a  large  quantity  of  the  stroma  for  chemical  purposes,  add  10  vols,  ot 

a  solution  of  common  salt  (i  vol.  concentrated  solution,  and    15   to  20  vols,  of  water)  to   i   vol.  of 

defibrinated  blood,  when  the  stromata  are  thrown  down  as  a  whitish  precipitate. 

For  microscopical   purposes,  mix  blood  with  an  equal  volume  of  a  concentrated  solution  of 

sodic  sulphate,  and  cautiously  add  a  i  per  cent,  solution  of  tartaric  acid. 

The  following  reagents  cause  a  separation  of  the  stroma  from  the  haemoglobin,  and  thus  make 

blood  transparent : — 

(a)  Physical  Agents. —  i.  Heating  the  blood  to  60°  C.  [Sc/ndtze);  the  temperature,  however, 
varies  for  the  blood  of  different  animals.  2.  Repeated  freezing  and  thawing  of  the  blood  [Rol- 
lett).  3.  Sparks  from  an  electrical  machine  (but  not  after  the  addition  of  salts  to  the  blood) 
[Rolleit) ;  the  constant  and  induced  currents  [NetiDiann). 

{b)  Chemically  active  Substances  produced  within  the  Body. — 4.  Bile  {Hi'mefeld),  or  bile 
salts  [Platlner,  v.  Dusch).  5.  Serum  of  other  species  or  animals  {Landois) ;  thus  dog's  serum 
and  frog's  serum  dissolve  the  blood  corpuscles  of  the  rabbit  in  a  few  minutes.  6.  The  addition 
of  lake-colored  blood  of  many  species  of  animals  { Latzdois) . 

(c)  Other  Chemical  Reagents. — 7.  Water.  8.  The  vapor'of  chloroform  [Bdttcher);  ether  (t/. 
Wittich)  ;  amyls,  small  quantities  of  alcohol  {RoUett)  ;  thymol  {Marchand)  ;  nitrobenzol,  ethy- 
lic  ether,  aceton,  petroleum  ether,  etc.  (Z.  Lezuhi).  9.  Antimoniuretted  hydrogen,  arseniuretted 
hydrogen;  carbon  bisulphide;  boracic  acid  (2  per  cent.)  added  to  amphibian  blood,  causes  the 
red  mass  (which  also  encloses  the  nucleus  when  such  is  present),  the  so-called  zooid,  to  sepa- 
rate  from  the  cecoid  (Fig.  7,  ^).  The  zooid  may  shrink  from  the  periphery  of  the  corpuscle,  or  it 
may  pass  out  of  the  corpuscle  altogether  [Brilcke)  ;  Briicke  regards  the  stroma  in  a  certain 
sense  as  a  house,  in  which  the  remainder  of  the  substance  of  the  corpuscle,  the  chief  part 
endowed  with  vital  phenomena,  lives.  Ii.  Strong  solutions  of  acids  dissolve  the  corpuscles; 
more  dilute  solutions  cause  precipitates  in  the  hsemoglobin.  This  is  easily  seen  with  carbolic 
acid  [HiUs  and  Landois,  Stirling  and  Raiinie).  12.  Alkalies  of  moderate  strength  cause 
sudden  solution.  A  ten  per  cent,  solution  of  potash,  placed  at  the  edge  of  a  cover-glass,  shows 
the  process  of  solution  going  on  under  the  microscope.  At  first  the  corpuscles  become  globular, 
and  so  appear  smaller,  but  afterward  they  burst  like  soda  bubbles.  [13.  NH^Cl  injected  into  the 
blood  causes  vacuolation  of  the  red  corpuscles  [Bobritzky).  14.  Sodic  salicylate,  benzoate  and 
colchicin,  dissolve  the  red  corpuscles  [N.  Raton).'] 
4 


50  FORM    AND    SIZE    OF    THE    BLOOD    CORPUSCLES. 

[Tannic  Acid. — A  freshly  prepared  solution  of  tannic  acid  has  a  remarkaUle  effect  on  the  col- 
ored blood  corpuscles  of  man  and  animals— causing  a  se])aration  of  the  hx>moglobin  from  the 
stroma  ( IT.  J\ol>frfs).  The  usual  effect  is  to  produce  one  or  more  granular  buds  of  hii^moglobin 
on  the  side  of  the  corpuscles  (Fig.  7, /',  f) ;  more  rarely  the  hremoglobin  collects  around  the 
nucleus,  if  such  be  present  (Fig.  7,  d),  or  is  extruded,  as  shown  in  Fig.  7,  e,'\ 

[Ammonium  or  Potassium    Sulpho-cyanide  removes  the  hivmoglobin,  and  reveals  a  reticular 

structure iiitra-nttclcar  plexus  of  fibrils  [Stir/itig  and  Rannie).'\ 

The  Amount  of  Gases  in  the  blood  exercises  an  important  influence  on  their  solubility.     The 

corpuscles  of  venous   blood,  which    contains   much   CO.^,  are  more  easily  dissolved  than  those  of 

arterial  blood  ;  while  between   both  stands  blood  containing  CO.     When  the  gases  are  completely 

removed  from  the  blood,  it  becomes  lake-colored. 

Salts  increase  the  resistance  of  the  corpuscles  to  physical  means  of  solution, 
while  they  facilitate  the  action  of  chemical  solvents. 

If  certain  salts  be  added  in  substance  to  blood,  they  make  blood  lake-colored;  potassic  sulpho- 
cyanide,  sodic  chloride,  etc.  [Kowaiewsky). 

Resistance  to  Solvents. — The  red  blood  corpuscles  offer  a  certain  degree  of 
resistance  to  the  action  of  solvents. 

Method. — Mix  a  small  drop  of  blood  with  an  equal  volume  of  a  3  per  cent,  solution  of  sodic 
chloride,  and  then  add  distilled  water  until  all  the  colored  corpuscles  are  dissolved.  Fill  the 
mixer  (Fig.  3)  up  to  the  mark  l  with  blood  obtained  by  picking  the  finger,  and  blow  this  blood 
into  an  equal  volume  of  a  3  per  cent,  solution  of  NaCl  previously  placed  in  a  hollow  in  a  glass 
slide.  Mix  the  fluids,  and  the  corpuscles  will  remain  undissolved.  By  means  of  the  pipette  add 
distilled  water,  and  go  on  doing  so  until  all  the  corpuscles  are  dissolved  ;  which  is  ascertained  with 
the  microscope.  In  normal  blood,  solution  of  the  corpuscles  occurs  after  30  volumes  of  distilled 
water  have  been  added  to  the  blood  {LtinJois). 

There  are  some  individuals  whose  blood  is  more  soluble  than  that  of  others;  their  corpuscles 
are  soft,  and  readily  undergo  changes.  Many  conditions,  such  as  cholcemia,  poisonmg  with  sub- 
stances which  dissolve  the  corpuscles,  and  a  markedly  venous  condition  of  the  blood,  affect  the 
corpuscles.  Interesting  observations  may  be  made  on  the  blood  in  infectious  diseases,  hemoglobin- 
uria, and  in  cases  of  burning.  In  an.-emia  and  fever,  the  capacity  for  resistance  seems  to  be 
diminished. 

6.  FORM  AND  SIZE  OF  THE  BLOOD  CORPUSCLES  OF 
ANIMALS. — All  marnmals  (with  the  exception  of  the  camel,  llama,  alpaca, 
and  their  allies),  and  the  cyclostomata  among  fishes,  e.g.,  Petromyzon,  possess 
circular,  bi-concave,  non-nucleated,  disk-shaped  corpuscles.  Elliptical  corpuscles 
without  a  nucleus  are  found  in  the  above-named  mammals,  while  all  birds,  reptiles, 
amphibians  (Fig.  i,  B,  i,  2),  and  fishes  (except  cyclostomata)  have  nucleated, 
elliptical,  bi-convex  corpuscles. 

j  Size  (n  =  o.ooi  Millimetre) 


Of  the  Disk-shaped 
Corpuscles. 


Of  the  Elliptical  Corpuscles. 


Short  Diameter. 


Long  Diameter. 


Elephant 9.4  u  j      Llama, 4.0  jx  8.0  fi 

Man, 7-7  "  Dove, 6.5  "  14.7 

Dog. 7.3  "  Frog 15-7  "  22.3 

Rabbit, 6.9  "  Triton, 19.5  "  29.3 

I     Cat, 6.5  "  Proteus, 35.0  "  58.0 

Sheep, 5-0  "  | 

Goat, 41"  The  corpuscles  of  -Amphiuma  are   nearly  one-third  larger 

Musk-deer,    ....  2.5  "        than  those  of  Proteus  (/vV(/r/^/). 

Among  vertebrates,  amphioxus  has  colorless  blood.  The  large  blood  corpuscles  of  many 
amphibia,  e.g.,  amphiuma,are  visible  to  the  naked  eye.  The  blood  corpuscles  of  the  frog  contain, 
in  addition  to  a  nucleus,  a  nucleolus  {Auerbach,  Jianvier),  [and  the  same  is  true  of  the  colored 
corpuscles  of  the  newt  {Stirling).  The  nucleolus  is  revealed  by  acting  on  the  corpuscles  with 
dilute  alcohol  (i,  alcohol;  2,  water;  Ranvier's  ^^  alcool  ait  tiers'''  (Fig.  7,^.).]  It  is  evident  that 
the  larger  the  blood  corpuscles  are,  the  smaller  must  be  the  number  and  total  superficies  of  the  cor- 
puscles in  a  given  volume  of  blood.     In  birds,  however,  the  number  is  relatively  larger  than  in 


ORIGIN    OF   THE    RED    BLOOD    CORPUSCLES.  51 

other  classes  of  vertebrates,  notwithstanding  the  larger  size  of  their  corpuscles ;  this,  doubtless,  has 
a  relation  to  the  very  energetic  metabolism  that  takes  place  in  birds  {Malassez).  Among 
mammals,  carnivora  have  more  blood  corpuscles  than  herbivora.  Goat's  blood  contains  9,720,000 
corpuscles  per  cubic  millimetre;  llama's,  13,000,000;  bullfinches,  3,600,000;  lizard's,  1,420,000; 
frog's,  404,000;  and  that  of  proteus,  36,000  (  J^/it/J^;?-).  In  hibernating  animals,  the  number 
diminishes  from  7,000,000  to  2,000,000  per  cubic  millimetre.  No  relation  exists  between  the  size 
of  the  animal  and  that  of  its  blood  corpuscles. 

The  invertebrata  generally  have  colorless  blood,  with  colorless  corpuscles  ;  but  the  earth-worm, 
and  the  larva  of  the  large  gnats,  etc.,  have  red  blood  whose  plasma  contains  haemoglobin,  while  the 
blood  corpuscles  themselves  are  colorless.  Many  invertebrates  possess  red,  violet,  brown  or  green 
opalescent  blood  with  colorless  corpuscles  (amceboid  cells).  In  cephalopods,  and  some  crabs,  the 
blood  is  blue,  owing  to  the  presence  of  a  coloring  matter  (haemocyanin),  which  contains  copper, 
and  combines  with  O. 

7.  ORIGIN  OF  THE  RED  BLOOD  CORPUSCLES.— (xV)  Dur- 
ing Embryonic  Life. — Blood  corpuscles  are  developed  in  the  fowl  during  the 
first  days  of  embryonic  life.  [They  appear  in  groups  within  the  large  branched 
cells  of  the  mesoblast,  in  the  vascular  area  of  the  blastoderm,  outside  the  develop- 
ing body  of  the  chick,  where  they  form  the  "  blood-islands  "  of  Pander.  The 
mother-cells  form  an  irregular  network  by  the  union  of  the  processes  of  adjoining 
cells,  and  meantime  the  central  masses  split  up,  and  the  nuclei  multiply.  The 
small  nucleated  masses  of  protoplasm,  which  represent  the  blood  corpuscles, 
acquire  a  reddish  hue,  while  the  surrounding  protoplasm,  and  also  that  of  the 
processes,  becomes  vacuolated  or  hollowed  out,  constituting  a  branching  system 
of  canals  ;  the  outer  part  of  the  cells  remaining  with  their  nuclei  to  form  the  walls 
of  the  future  blood  vessels.  A  fluid  appears  within  this  system  of  branched  canals 
in  which  the  corpuscles  lie,  and  gradually  a  communication  is  established  with 
the  blood  vessels  developed  in  connection  with  the  heart.  According  to  Klein, 
the  nuclei  of  the  protoplasmic  wall  also  proliferate,  and  give  rise  to  new  cells, 
which  are  washed  away  to  form  blood  corpuscles.]  At  first  the  corpuscles  exhibit 
amoeboid  movements,  are  devoid  of  pigment,  nucleated,  globular,  larger  and 
more  irregular  than  the  permanent  corpuscles.  They  become  colored,  retain 
their  nucleus,  and  are  capable  of  undergoing  multiplication  by  division  ;  Remak 
observed  all  the  stages  of  the  process  of  division,  which  is  best  seen  from  the  third 
to  the  fifth  day  of  incubation.  Increase  by  division  also  takes  place  in  the  larvae 
of  the  salamander,  triton  and  toad  (^Flemming) ;  and  during  the  intra-uterine  life 
of  a  mammal,  in  the  spleen,  bone-marrow,  the  liver,  and  the  circulating  blood 
{^izzozero). 

Neumann  found  in  the  liver  of  the  embryo  protoplasmic  cells  containing  red 
blood  corpuscles.  Cells,  some  with,  others  without,  haemoglobin,  but  with  large 
nuclei,  have  been  found.  These  cells  increase  by  division,  their  nucleus  shrivels, 
and  they  ultimately  form  blood  corpuscles  {Lowif)  The  spleen  is  also  regarded 
as  a  centre  of  their  formation,  but  this  seems  to  be  the  case  only  during  embryonic 
life  {Neumami).  Here  the  red  corpuscles  are  said  to  arise  from  yellow,  round, 
nucleated  cells,  which  represent  transition  forms.  Foa  and  Salvioli  found  red 
corpuscles  forming  endogenously  within  large,  protoplasmic  cells  in  lymphatic 
glands.  In  the  later  period  of  embryonic  life,  the  characteristic  non-nu- 
cleated corpuscles  seem  to  be  developed  from  the  nucleated  corpuscles.  The 
nucleus  becomes  smaller  and  smaller,  breaks  up,  and  gradually  disappears.  In 
the  human  embryo  at  the  fourth  week,  only  nucleated  corpuscles  are  found  ;  at 
the  third  month  their  number  is  still  ]4,-yi  of  the  total  corpuscles,  while  at  the 
end  of  foetal  life  nucleated  blood  corpuscles  are  very  rarely  found.  Of  course,  in 
animals  with  nucleated  blood  corpuscles,  the  nucleus  of  the  embryonic  blood 
corpuscles  remains. 

(B)  During  Post-Embryonic  Life. — Kolliker  assumed  that  in  the  tail  of 
the  tadpole  capillaries  are  formed  by  the  anastomoses  of  the  processes  of  branched 
and  radiating  connective-tissue  corpuscles.  These  corpuscles  lose  their  nuclei 
and  protoplasm,  become  hollowed  out,  join  with  neighboring  capillaries,  and  thus 


52 


ORIGIN    OF   THE    RED    BLOOD    CORPUSCLES. 


Fig.  S. 


Formation  of  red  blood  corpuscles  within  "  vaso-formative  cells," 
from  the  omentum  of  a  rabbit  seven  days  old.  r,  r,  the 
formed  corpuscles;  K,  K,  nuclei  of  the  vaso-formative  cell  ; 
a,  a,  processes  which  ultimately  unite  to  form  capillaries. 


form  new  blood  channels.  J.  Arnold  and  Golubew  oppose  thi.s  view,  asserting 
that  the  blood  capillaries  in  the  tail  of  the  tadpole  give  off  solid  buds  at  different 
places,  which  grow  more  and  more  into  the  surrounding  tissues,  and  anastomose 
with  each  other;  after  their  i)rotoplasm  and  contents  disappear  they  become  hol- 
low, and  a  branched  system  of  capillaries  is  formed  in  the  tissues.  Ranvier 
noticed  the  same  mode  of  growth  in  the  omentum  of  newly-born  kittens. 

Young  rabbits,  a  week  old,  have,  in  their  omentum,  small  white  or  milk  spots 
{Ra/ivier),  in  which  lie  "vaso-formative  cells,"  ;.  e.,  highly  refractive  cells 
of  variable  shape,  with  long  cylindrical  protoplasmic  processes  (Fig.  8).     In  its 

refractive  power  the  protoplasm  of 
these  cells  resembles  that  of  lymph 
corpuscles.  Long  rod-like  nuclei 
lie  within  these  cells  (K,  K),  and 
also  red  blood  corpuscles  (r,  r),  and 
both  are  surrounded  with  proto- 
plasm. These  vaso-formative  cells 
give  off  protoplasmic  processes  {a, 
a),  some  of  which  end  free,  while 
others  form  a  network.  Here  and 
there  elongated  connective-tissue 
corpuscles  lie  on  the  branches,  and 
ultimately  form  the  adventitia  of  the 
blood  vessel.  The  vaso-formative 
cells  have  many  forms:  they  may 
be  elongated  cylinders  ending  in 
points,  or  more  round  and  oval, 
resembling  lymph  cells,  or  modi- 
fied connective-tissue  corpuscles.  These  cells  are  ahoays  the  seat  of  origin  oj 
non-nucleated  red  blood  corpuscles,  which  arise  in  the  protoplasm  of  vaso-formative 
cells,  as  chlorophyll  grains  or  starch  granules  arise  within  the  cells  of  plants.  The 
corpuscles  escape,  and  are  washed  into  the  circulation  when  the  cells,  by  means  of 
their  processes,  form  connections  with  the  circulatory  system.  Probably  the 
vessels  so  formed  in  the  omentum  are  only  temporary.  May  it  not  be  that  there 
are  many  other  situations  in  the  body  where  blood  is  regenerated  ? 

[The  observations  of  Schiifer  also  prove  the  intra-cellular  origin  of  red 
blood  corpuscles,  and  although  this  mode  usually  ceases  before  birth,  still  it  is 
found  in  the  rat  at  birth.  The  protoplasm  of  the  subcutaneous  connective- 
tissue  corpuscles,  which  are  derived  from  the  mesoblast,  has  in  it  small  colored 
globules  about  the  size  of  a  colored  corpuscle.  The  mother  cells  elongate,  be- 
come pointed  at  their  ends,  and  unite  with  processes  from  adjoining  cells.  The 
cells  become  vacuolated  ;  fluid  or  plasma,  in  which  the  liberated  corpuscles  float, 
appears  in  their  interior,  and  ultimately  a  communication  is  established  with  the 
general  circulation.] 

Neumann  observed  similar  formations  in  the  embryonic  liver;  Wissotzky  in  the  rabbit's  amnion; 
Klein  in  the  embryo  chick  ;  and  Bayerl  in  ossifying  cartilage.  All  these  observations  go  to  show 
that  at  a  certain  early  period  of  development  blood  corpuscles  are  formed  within  other  large  cells 
of  the  mesoblast,  and  that  part  of  the  protoplasm  of  these  blood-forming  cells  remains  to  form  the 
wall  of  the  future  blood  vessel. 

(C)  Later  Formation. — Most  observers  agree  that  the  red  blood  corpuscles 
are  formed  from  special  nucleated  cells,  which  gradually  assume  the  form  and 
color  of  the  perfect  red  corpuscle.  According  to  Neumann,  however,  these  cor- 
puscles are  pigmented  from  the  first.  In  the  tailed  amphibians  and  fishes,  the 
spleen,  in  all  other  vertebrates  the  red  marrow  of  bone,  are  the  seats  of 
formation  of  these  corpuscles,  which  subsequently  increase  by  division  {Neumann, 
Rindfleisch,  Bizzozero).     In  the  red  marrow  of  bone  we  can  study  all  the  stages 


THE  COLORLESS  BLOOD  CORPUSCLES.  53 

of  the  transformation ;  especially  pale  contractile  cells  similar  to  colorless  corpus- 
cles, and  also  red  nucleated  corpuscles,  which  are  similar  to  the  nucleated  corpus- 
cles of  the  embryo,  and  the  progenitors  of  the  red  corpuscles.  These  transition 
cells  are  said  by  Erb  to  be  more  numerous  after  severe  hemorrhage,  the  number 
of  them  occurring  in  the  blood  corresponding  with  the  energy  of  the  formative 
process.  After  copious  hemorrhage,  these  transition  forms  appear  in  numbers  in 
the  blood  stream.  The  small  veins,  and,  perhaps,  the  capillaries  of  the  red  mar- 
row of  bone  and  the  spleen  have  no  proper  walls,  so  that  the  red  corpuscles  when 
formed  can  pass  into  the  circulation. 

Red  or  blood-forming  marrow  occurs  in  the  bones  of  the  skull,  and  in  most  of  the  bones  of 
the  trunk,  while  the  bones  of  the  extremities  either  contain  yellow  marrow  (which  is  essentially 
fatty  in  its  nature),  or,  at  most,  it  is  only  the  heads  of  the  long  bones  that  contain  red  marrow. 
Where  the  blood-regeneration  process  is  very  active,  however,  the  yellow  marrow  may  be  changed 
into  red,  even  throughout  all  the  bones  of  the  extremities  [Netimamt). 

8.  DECAY  OF  THE  RED  BLOOD  CORPUSCLES.— The  blood 
corpuscles  undergo  decay  within  a  limited  time,  and  the  liver  is  regarded  as  one 
of  the  chief  places  in  which  their  disintegration  occurs,  because  bile  pigments  are 
formed  from  haemoglobin,  and  the  blood  of  the  hepatic  vein  contains  fewer  red 
corpuscles  than  the  portal  vein. 

The  splenic  pulp  contains  cells  which  indicate  that  colored  corpuscles  are 
broken  up  within  it.  These  are  the  so-called  "  blood-corpuscle-containing  cells  " 
(§  102),  Quincke's  observations  go  to  show  that  the  red  corpuscles — which  may 
live  from  three  to  four  weeks — when  about  to  disintegrate,  are  taken  up  by  the 
white  blood  corpuscles  in  the  hepatic  capillaries,  by  the  cells  of  the  spleen  and 
the  bone  marrow,  and  are  stored  up  chiefly  in  the  capillaries  of  the  liver,  in 
the  spleen,  and  in  the  marrow  of  bone.  They  are  transformed,  partly  into 
colored,  and  partly  into  colorless  proteids  which  contain  iron,  and  are  either  de- 
posited in  a  granular  form,  or  are  dissolved.  Part  of  the  products  of  decompo- 
sition is  used  for  the  formation  of  new  blood  corpuscles  in  the  marrow  and  in  the 
spleen,  and  also  perhaps  in  the  liver,  while  a  portion  of  the  iron  is  excreted  by 
the  liver  in  the  bile. 

That  the  normal  red  blood  corpuscles  and  other  particles  suspended  in  the  blood  stream  are  not 
taken  up  in  this  way,  may  be  due  to  their  being  smooth  and  polished.  As  the  corpuscles  grow 
older  and  become  more  rigid,  they,  as  it  were,  are  caught  by  the  amoeboid  cells.  As  cells  contain- 
ing blood  corpuscles  are  very  rarely  found  in  the  general  circulation,  one  may  assume  that  the 
occurrence  of  these  cells  within  the  spleen,  liver,  and  marrow  of  bone  is  favored  by  the  slowness 
of  the  circulation  in  these  organs  [Quincke). 

Pathological. — In  certain  pathological  conditions,  ferruginous  substances  derived  from  the  red 
blood  corpuscles  are  found  in  masses  in  the  spleen,  the  marrow  of  bone,  and  the  capillaries  of  the 
liver:  (i)  When  the  disintegration  of  blood  corpuscles  is  increased,  as  in  ansemia  [Stahel). 
(2)  When  the  formation  of  red  blood  corpuscles  from  the  old  material  is  diminished.  If  the 
excretion  from  the  liver  cells  be  prevented,  iron  accumulates  within  them ;  it  is  also  more  abundant 
in  the  blood  serum,  and  it  may  even  accumulate  in  the  secretory  cells  of  the  cortex  of  the  kidney 
and  pancreas,  in  gland  cells,  and  in  the  tissue  elements  of  other  organs.  When  the  amount  of 
blood  in  dogs  is  greatly  increased,  after  four  weeks  an  enormous  number  of  granules  containing 
iron  occur  in  the  leucocytes  of  the  liver  capillaries,  the  cells  of  the  spleen,  bone-marrow,  lymph 
glands,  liver  cells,  and  the  epithelium  of  the  cortex  of  the  kidney.  The  iron  reaction  in  the  last 
two  situations  occurs  after  the  introduction  of  hsemoglobin,  or  of  salts  of  iron  into  the  blood  ( Glae- 
veck,  V.  Shirk). 

When  we  reflect  how  rapidly  large  quantities  of  blood  are  replaced  after 
hemorrhage  and  after  menstruation,  it  is  evident  that  there  must  be  a  brisk  manu- 
factory somewhere.  As  to  the  number  of  corpuscles  which  daily  decay,  we  have 
in  some  measure  an  index  in  the  amount  of  bile  pigment  and  urine  pigment 
resulting  from  the  transformation  of  the  liberated  haemoglobin  (§  20). 

9.  COLORLESS  CORPUSCLES,  BLOOD  PLATES  AND  GRAN- 
ULES.— White  Blood  Corpuscles. — Blood,  like  many  other  tissues,  con- 
tains a  number  of  cells  or  corpuscles  which  reach  it  from  without ;  the  corpuscles 


54 


THE  COLORLESS  BLOOD  CORPUSCLES. 


^ 


Y 


vary  somewhat  in  form,  and  are  called  colorless  or  white  blood  corpuscles, 
or  "leucocytes"  {^Hewson,  1770).  Similar  corpuscles  are  found  in  lymph, 
adenoid  tissue,  marrow  of  bone,  and  as  wandering  cells  or  leucocytes  in  connective 
tissue,  and  also  between  glandular  and  epithelial  cells.  So  that  these  corpuscles 
are  by  no  means  peculiar  to  blood  alone.  They  all  consist  of  more  or  less  spher- 
ical masses  of  protoplasm,  which  is  sticky,  highly  refractile,  soft,  capable  of  move- 
ment, and  devoid  of  an  envelope  (Fig.  9).     When  they  are  quite  fresh  (A)  it  is 

difficult  to  detect  the  nucleus,  but 
Fu;.  9.  after  they  have  been  shed  for  some 

C  time,  or  after  the  addition  of  water 

(B),  or  acetic  acid,  the  nucleus 
(which  is  usually  a  compound  one) 
appears  ;  acetic  acid  clears  up  the 
perinuclear  protoplasm,  and  reveals 
the  presence  of  the  nuclei,  of  which 
the  number  varies  from  one  to  four, 
although  generally  three  are  found. 
The  subsequent  addition  of  ma- 
genta solution  causes  the  nuclei  to 
stain  deeply.  Water  makes  the 
contents  more  turbid,  and  causes 
the  corpuscles  to  swell  up.  One 
or  more  nucleoli  may  be  present 
in  the  nucleus.  The  size  of  the 
corpuscles  varies  from  4-13  m,  and 
■'.  ^  ^  _  as  a  rule  they  are  about  -gxoir  ^^  ^" 
'  \  ^ ',  inch  in  diameter;  in  the  smallest 
*  u  T  forms  the  layer  of  the  proto- 
plasm is  extremely  thin.  They  all 
exhibit  amoeboid    movements 

A,  human  white  blood  corpuscles,  without  any  reagent;   B,  after  -,,l,;„u     „_„     ,rorir     ar>r>ar*^nf-      in     tVip 

the   action   of  water ;    C,   after   acetic  acid;   D,   frog's   cor-  WhlCh     are     Very     apparent      in     tUe 

puscles,  changes  of  shape  due  to  amoeboid   movement;   E,  larger  COrpUSCleS,   and  WCre  dlSCOV- 
fibrils  of  fibrin  from  coagulated  blood ;  F,  elementary  gran-  °,     .  \,,,  -,  •  , 

i,ies  "  ered    by    Wharton    Jones    in    the 

skate  (1846),  and  by  Davine  in  the 
corpuscles  of  man  (1850).  Max  Schultze  describes  three  different  forms  in 
human  blood : — 

(i)  The  smallest,  spherical  forms,  less  than  the  red  corpuscles,  with  one  or  two 
nuclei,  and  a  very  small  amount  of  protoplasm. 

(2)  Spherical  forms,  the  same  size  as  the  colored  blood  corpuscles. 

(3)  The  large  amoeboid  corpuscles,  with  much  protoplasm  and  distinctly  evi- 
dent movements. 

[On  examining  human  blood  microscopically,  more  especially  after  the  colored  blood  corpuscles 
have  run  into  rouleaux,  the  colorless  corpuscles  may  readily  be  detected,  there  being  usually  three 
or  four  of  them  visible  in  the  field  at  once.  They  adhere  to  the  glass  slide,  for  if  the  cover-glass 
be  moved,  the  colored  corpuscles  readily  glide  over  each  other,  while  the  colorless  can  be  seen  still 
adhering  to  the  slide.] 

[White  Corpuscles  of  Newt's  Blood. — The  characters  of  the  colorless  corpuscles  are  best 
studied  in  a  drop  of  newt's  blood,  which  contains  the  following  varieties : — 

(i)  The  large,  finely  granular  corpuscle,  which  is  about  yj|j  of  an  inch  in  diameter,  irregu- 
lar in  outline,  with  fine  processes  or  pseudopodia  projecting  from  its  surface.  It  rapidly  changes 
its  shape  at  the  ordinary  temperature,  and  in  its  interior  a  bi-  or  tri-partite  nucleus  may  be  seen,  sur- 
rounded with  fine  granular  protoplasm,  whose  outline  is  continually  changing.  Sometimes  vacuoles 
are  seen  in  the  protoplasm. 

(2)  The  coarsely  granular  variety  is  less  common  than  the  first-mentioned,  but  when  detected  its 
characters  are  distinct.  The  protoplasm  contains,  besides  a  nucleus,  a  large  number  of  highly 
refractive  granules,  and  the  corpuscle  usually  exhibits  active  amoeboid  movements  ;  suddenly  the 
granules  may  be  seen  to  rush  from  one  side  of  the  corpuscle  to  the  other.     The  processes  are 


AMCEBOID    MOVEMENTS    OF   THE    COLORLESS    CORPUSCLES. 


55 


usually  more  blunt  than  those  emitted  by  (i^ 
has  not  been  ascertained. 


The  relation  between  these  two  kinds  of  corpuscles 


Fig.  io. 


(3)  The  small  colorless  corpuscles  are  more  like  the  ordinary  human  colorless  corpuscle,  and 
they,  too,  exhibit  amoeboid  movements.] 

Two  kinds  of  colorless  corpuscles  like  (i)  and  (2)  exist  in  frog's  blood.  In  the  coarsely  granu- 
lar corpuscles  the  glancing  granules  may  be  of  a  fatty  nature,  since  they  dissolve  in  alcohol  and 
ether,  but  other  granules  exist  which  are  insoluble  in  these  fluids.  The  nature  of  the  latter  is 
unknown.     Very  large  colorless  corpuscles  exist  in  the  axolotl's  blood. 

[Action  of  Reagents. — (a)  Water,  when  added  slowly,  causes  the  colorless 
corpuscles  to  become  globular,  and  the  granules  within  them  to  exhibit  Brownian 
movements.  {^)  Pigments,  such  as  magenta  or  carmine,  stain  the  nuclei  very 
deeply,  and  the  protoplasm  to  a  less  extent,  (c)  Dilute  Acetic  Acid  clears  up 
the  surrounding  protoplasm  and  brings  clearly  into  view  the  composite  nucleus, 
which  may  be  stained  thereafter  with  magenta,  {d)  Iodine  gives  a  faint  port- 
wine  color,  especially  in  horse's  blood,  indicating  the  presence  of  glycogen.  (/) 
Dilute  Alcohol  causes  the  formation  of  clear  blebs  on  the 
surface  of  the  corpuscles,  and  brings  the  nuclei  into  view 
(yRanvier,  Stir  ling). '\ 

[A  delicate  plexus  of  the  fibrils — intra-nuclear  plexus 
— exists  within  the  nucleus,  just  as  in  other  cells.  It  is 
very  probable  that  the  protoplasm  itself  is  pervaded  by  a 
similar  plexus  of  fibrils,  and  that  it  is  continuous  with  the 
intra-nuclear  plexus  (Fig.  10).]  The  colorless  corpuscles 
divide,  and  in  this  way  reproduce  themselves. 

The  Number  of  Colorless  Corpuscles  is  very  much 
less  than  that  of  the  red  corpuscles,  and  is  subject  to  con- 
siderable variations.  It  is  certain  that  the  colorless  cor- 
puscles are  very  much  fewer  in  shed  blood  than  in  blood  still 
within  the  circulation.  Immediately  after  blood  is  shed, 
an  enormous  number  of  white  corpuscles  disappear  (§  31). 

Al.  Schmidt  estimates  the  number  that  remain  at  ^-^  of  the  whole  originally  present  in  the  circu- 
lating blood.  The  proportion  is  greater  in  children  than  in  adults.  The  following  table  gives  the 
number  in  shed  blood  ; — 


Plexus  of  fibrils  in  a  colorless 
blood  corpuscle. 


Number  of  White  in  Proportion  to  Red  Blood  Corpuscles  : — 


In  Normal  Conditions. 


In  Different  Places. 


In  DiflFerent  Conditions. 


335  {Welcker). 
357  \MoleschoU). 


Splenic  Vein,      i  :  60 
Splenic  Artery,  I  :  2260 
Hepatic  Vein,    i  :  170 
Portal  Vein,        i  :  740 
Generally   more   numerous 
in  Veins  than  Arteries. 


Increased  by  Digestion,  Loss 
of  Blood,  Prolonged  Sup- 
puration, Parturition,  Leu- 
ksemia,  Quinine,  Bitters. 

Diminished  by  Hunger,  Bad 
Nourishment. 


[The  number  also  varies  with  the  Age  and  Sex  : — 


Age.    Sex. 

White.     Red. 

1 

General  Conditions. 

White.     Red. 

Girls, 

Boys, 

Adults,    ........ 

Old  Age, 

I  :  405 
I  :  226 

I  :  335 
I  :  381 

! 

While  fasting, 

After  a  meal, 

During  pregnancy,     .    .    . 

1  :  716 

I  :  347 
I  :  281] 

1 
1 

II.  The  amceboid  movements  of  the  white  corpuscles  (so  called  because  they 
resemble  the  movements  of  amoeba)  consist  in  an  alternate  contraction  and  relax- 


56 


AMCliBOID    MOVEMENTS    OF   THE    COLORLESS    CORPUSCLES. 


Fig  II. 


Human  leucocytes,  showing  amoeboid  movements. 


ation  of  the  protoplasm  surrounding  the  nucleus.  Processes  are  given  off  from  the 
surface,  and  are  retracted  again.  There  is  an  internal  current  in  the  protoplasm, 
and  the  nucleus  has  also  been  observed  to  change  its  form  [and  exhibit  contractions 

without  the  corpuscle  dividing.  The  karyo- 
kinetic  aster,  and  convolution  of  the  intra- 
nuclear plexus  have  been  seen.]  Two  series 
of  phenomena  result  from  these  move- 
ments: (i)  The  "wandering"  or  loco- 
motion of  the  corpuscles  due  to  the  exten- 
sion and  retraction  of  their  processes  ;  (2) 
the  absorption  of  small  particles  into 
their  interior  (fat,  pigment,  foreign  bodies). 
The  particles  adhere  to  the  sticky  external 
surface,  are  carried  into  the  interior  by  the 
internal  currents,  and  may  eventually  be 
excreted,  just  as  particles  are  taken  up  by 
amceba  and  the  effete  particles  excreted. 
[Max  Schultze  observed  that  colored  par- 
ticles were  readily  taken  up  by  these  cor- 
puscles. Conditions  for  movement. — 
In  order  that  the  amoeboid  movements  of  the  leucocytes  may  take  place,  it  is 
necessary  that  there  be — (i)  a  certain  temperature  and  normal  atmospheric 
pressure;  (2)  the  surrounding  medium,  within  certain  limits,  must  be  "indiffer- 
ent," and  contain  a  sufficient  amount  of  water  and  oxygen;  (3)  there  must  be  a 
basis  or  supjDort  to  move  on.] 

Struggle  between  Microbes  and  the  Organism. — Metschnikoff  emphasizes  the  activity  of 
the  leucocytes  in  retrogressive  processes,  whereby  the  parts  to  be  removed  are  taken  up  by  them 
in  fine  granules,  and,  as  it  were,  are  ''eaten."  Hence,  he  calls  such  cells  "phagocytes."  Thev 
may  be  found  in  the  atrophied  tails  of  batrachians,  the  cells  containing  in  their  interior  whole 
pieces  of  nerve  fibre  and  primitive  muscular  bundles.  Schizomycetes  which  have  found  their  way 
into  the  blood  {\  183)  have  been  found  to  be  partly  taken  up  by  the  colorless  corpuscles.  [The 
spores  of  a  kind  of  yeast  are  similarly  attacked  in  the  transparent  tissues  of  the  water  flea  by  the 
leucocytes,  and  the  connective-tissue  cells  also  destroy  microbes.] 

Effect  of  Reagents. — On  a  hot  stage  (3S°-4o°  C.)  the  colorless  corpuscles 
of  warm-blooded  animals  retain  their  movements  for  a  long  time  ;  at  40°  C. 
for  two  to  three  hours;  at  50°  C.  the  proteids  are  coagulated  and  cause  "heat 
rigor"  and  death  [when  their  movements  no  longer  recur  on  lowering  the  tem- 
perature]. In  cold-blooded  animals  (frogs),  colorless  corpuscles  may  be  seen 
to  crawl  out  of  small  coagula,  in  a  moist  chamber,  and  move  about  in  the  serum. 
[Draw  a  drop  of  newt's  blood  into  a  capillary  tube,  seal  up  the  ends  of  the  latter 
and  allow  the  blood  to  coagulate.  After  a  time,  examine  the  tube  in  clove  oil, 
when  some  of  the  colorless  corpuscles  will  be  found  to  have  made  their  way  out 
of  the  clot.]  Induction  shocks  cause  them  to  withdraw  their  processes  and 
become  spherical,  and,  if  the  shocks  be  not  too  strong,  their  movements  recom- 
mence. Strong  and  continued  shocks  kill  them,  causing  them  to  swell  up,  and 
completely  disintegrating  them. 

Diapedesis. — These  amoeboid  movements  are  of  special  interest  on  account 
of  the  "wandering  out"  (diapedesis)  of  colorless  blood  corpuscles  through  the 
walls  of  the  blood  vessels  (§  95). 

[Effect  of  Drugs. — Acids  and  Alkalies,  if  very  dilute,  at  first  increase,  but  afterward  arrest 
their  movements.  Sodic  chloride  in  a  i  per  cent,  solution  at  first  accelerates  their  movements, 
but  afterward  produces  a  tetanic  contraction,  and,  it  may  be,  expulsion  of  any  food  particles  they 
contain.  The  Cinchona  alkaloids — quinine,  quinidine,  cinchonidine  (i  :  1500) — quickly  arrest 
the  locomotive  movements,  as  well  as  the  protrusion  of  pseudopodia,  although  the  leucocytes  of 
different  animals  vary  somewhat  in  their  resistance  to  the  action  of  drugs.  Quinine  not  only  arrests 
the  movements  of  the  leucocytes  when  applied  to  them  directly,  but  when  injected  into  the  circu- 
lation of  a  frog  the  leucocytes  no  longer  pass  through  the  walls  of  the  capillaries  (Binz). 


THE    BLOOD    PLATES.  57 

The  chyle  contains  leucocytes,  which  are  more  resistant  than  those  of  the  blood,  but  less  so  than 
those  of  the  coagulable  transudations.  The  leucocytes  of  the  lymphatic  glands  may  also  be  dissolved 
{^RauschenbacJi). 

Relation  to  Aniline  Pigments. — Ehrlich  has  observed  a  remarkable  relation  of  the  white 
corpuscles  to  acid  (eosin,  picric  acid,  aurantia),  basic  (dahlia,  acetate  of  rosanilin),  or  neutral  (picrate 
of  rosanilin)  reactions.  The  smallest  protoplasmic  granules  of  the  cells  have  different  chemical 
affinities  for  these  pigments.  Thus  Ehrhch  distinguishes  "  eosinophile,"  "  basophile,"  and  "  neu- 
trophile  "  granules  within  the  cells.  Eosinophile  granules  occur  in  the  leucocytes  which  come  from 
bone  marrow,  the  myelogenic  leucocytes.  The  small  leucocytes,  i.  e.,  those  about  the  size  of  a 
colored  blood  corpuscle  or  sHghtly  larger,  are  formed  in  the  lymphatic  glands,  the  lymphogenic. 
The  large  amoeboid  multi- nucleated  cells,  which  are  found  outside  the  vessels  in  inflammations, 
exhibit  a  neutrophile  reaction.  Their  origin  is  unknown,  and  so  is  that  of  the  large  uni-nucleated 
cells,  and  the  large  cells  with  constricted  nuclei.  The  eosinophile  corpuscles  are  considerably 
increased  in  leuksemia.  The  basophile  granules  occur  also  in  connective-tissue  corpuscles,  especially 
in  the  neighborhood  of  epithelium;  they  are  always  greatly  increased  where  chronic  inflammation 
occurs. 

III.  Blood  Plates. — Special  attention  has  recently  been  directed  to  a  third 
element  of  the  blood,  the  "blood  plates"  or  "blood  tablets"  of  Bizzozero  ; 
pale,  colorless,  oval,  round,  or  lenticular  disks  of  variable  size  (mean,  3  ,a).     In 


Fig.  12. 


I 


© 


O 


©        ^wlj 


"Blood  plates"  and  their  derivatives,  i,  a  red  blood  corpuscle  on  the  flat;  2,  on  the  side;  3,  unchanged  blood 
plates ;  4,  lymph  corpuscle,  surrounded  by  blood  plates  ;  5,  altered  blood  plates ;  6,  lymph  corpuscle  with  two 
heads  'of  fused  blood  plates  and  threads  of  fibrin;  7,  group  of  fused  blood  plates;  8,  small  group  of  partially 
dissolved  blood  plates  with  fibrils  of  fibrin. 

a  healthy  man  Fusari  found  18,000  to  250,000  in  i  cubic  millimetre  of  blood. 
These  blood  plates  may  be  recognized  in  the  circulating  blood  of  the  mesentery 
of  a  chloralized  guinea-pig  and  the  wing  of  the  bat.  They  are  precipitated  in 
enormous  numbers  upon  threads  suspended  in  fresh  shed  blood.  They  may  be 
obtained  from  blood  flowing  directly  from  a  blood  vessel,  on  mixing  it  with  i  per 
cent,  solution  of  osmic  acid.  They  rapidly  change  in  shed  blood  (Fig.  12,  5), 
disintegrating,  forming  small  particles,  and  ultimately  dissolving.  When  several 
occur  together  they  rapidly  unite,  form  small  groups  (7),  and  collect  into  finely 
granular  masses.  These  masses  may  be  associated  in  coagulated  blood  with  fibrils 
of  fibrin  (Fig.  12). 

[These  blood  plates  are  best  seen  in  the  shed  blood  of  the  guinea-pig,  especially  if  it  be  mixed 
with  a  solution  of  sodic  sulphate  (sp.  gr.  1022)  or  )^  per  cent.  NaCl  tinged  with  methyl-violet. 
Bizzozero  regards  them  as  the  agents  which  immediately  induce  coagulation  and  take  part  in  the 
formation  of  fibrin  during  coagulation  of  the  blood ;  Eberth  and  Schimraelbusch  ascribe  the  initial 
formation  of  white  thrombi  to  them.  According  to  Lowit  they  are  formed  from  partially  disinte- 
grated leucocytes,  as  a  consequence  of  alteration  of  the  blood.  Along  with  the  leucocytes  they  are 
concerned  in  the  formation  of  fibrin  {Hlava).  These  structures  were  known  to  earlier  observers; 
but  their  significance  has  been  variously  interpreted.     Hayem  called  them  haematoblasts.     Halla 


58  CHANGES    OF    THE    BLOOD    CORPUSCLES. 

found  that  they  increased  in  pregnancy,  Afanassiew  in  conditions  of  regeneration  of  the  blood,  and 
Fusari  in  febrile  anrijmia  ;  they  are  diminished  in  fever. 

[As  to  the  haematoblasts,  or,  as  they  have  also  been  called,  the  "  globules  of  Donnd  "  by 
Pouchet,  there  seems  to  be  some  confusion,  for  both  colored  and  colorless  granules  are  described 
under  these  names.  As  Gibson  suggests,  the  former  are,  perhaps,  parts  of  disintegrated  colored 
corpuscles,  while  the  latter  are  the  blood  plates.  The  "  invisible  blood  corpuscles"  described  by 
Norris  seem  to  be  simply  decolorized  red  corpuscles  [Hart,  Git>son).'\ 

IV.  Elementary  Granules. — Blood  contains  elementary  granules  (Fig. 
9,  F),  \_i.c.,  the  elementary  particles  of  Zinimermann  and  Deale.  They  are  ir- 
regular bodies,  much  smaller  than  the  ordinary  corpuscles,  and  appear  to  consist 
of  masses  of  protoplasm  detached  from  the  surface  of  leucocytes,  or  derived  from 
the  disintegration  of  these  corpuscles,  or  of  the  blood  plates.  Others,  again,  are 
coiTipletely  spherical  granules,  either  consisting  of  some  proteid  substance  or  fatty 
in  their  nature.  The  protoplasmic  and  the  proteid  granules  disai)pear  on  the 
addition  of  acetic  acid,  while  the  fatty  granules  (which  are  most  numerous  after 
a  diet  ricli  in  fats)  dissolve  in  ether]. 

V.  In  coagulated  blood,  delicate  threads  of  fibrin  (Figs.  9,  E,  and  12,  6, 
7,  8)  are  seen,  more  especially  after  the  corpuscles  have  run  into  rouleaux.  At 
the  nodes  of  these  fibres  are  found  granules  which  closely  resemble  those  described 
under  III. 

[When  the  blood-forming  process  is  particularly  active,  "  nucleated  colored  corpuscles " 
or  the  "  corpuscles  of  Neumann,"  are  sometimes  found  in  the  blood.  They  are  identical  with  the 
nucleated  colored  blood  corpuscles  of  the  fcetus,  being  somewhat  larger  than  the  non-nucleated 
colored  corpuscle  (§  7).] 

10.  ABNORMAL  CHANGES  OF  THE  BLOOD  CORPUSCLES.— (i)  Hemor- 
rhages diminish  the  number  of  red  corpuscles  (at  most  one-half),  and  so  does  menstruation. 
The  loss  is  partly  covered  by  the  absorption  of  fluid  from  the  tissues.  Menstruation  shows  us  that 
a  moderate  loss  of  red  corpuscles  is  replaced  withm  twenty-eight  days.  When  a  large  amount  of 
blood  is  lo.st,  so  that  all  the  vital  processes  are  lowered,  the  time  may  be  extended  to  five  weeks.  In 
acute  fevers,  as  the  temperature  increases,  the  number  of  red  corpuscles  diminishes,  while  the 
white  corpuscles  increase  in  number.  By  greatly  cooling  peripheral  parts  of  the  body,  as  by  keep- 
ing the  hands  in  iced  water,  in  some  individuals  possessing  red  blood  corpuscles  of  low  resisting 
power,  these  corpuscles  are  dissolved,  the  blood  plasma  is  reddened,  and  even  hivmoglobinuria 
may  occur  (^  265). 

Diminished  production  of  new  red  corpuscles  causes  a  decrease,  since  blood  corpuscles  are 
continually  being  used  up.  In  chlorotic  females  there  seems  to  be  a  congenital  weakness  in  the 
blood-forming  and  blood-propelling  apparatus,  the  cause  of  which  is  to  be  sought  for  in  some  faulty 
condition  of  the  mesoblast.  In  them  the  heart  and  the  blood  vessels  are  small,  and  the  absolute 
number  of  corpuscles  may  be  diminished  one-half,  although  the  relative  number  may  be  retained, 
while  in  the  corpuscles  themselves  the  haemoglobin  is  diminished  almost  one-third ;  but  it  rises 
again  after  the  administration  of  iron  {Ilayem).  The  administration  of  iron  increases  the  amount 
of  haemoglobin  in  the  blood.  [The  action  of  iron  in  anaemic  persons  has  been  known  since  the 
time  of  Sydenham..  Hayem  also  finds  in  certain  forms  of  anix-mia  that  there  is  considerable  varia- 
tion in  the  size  of  the  red  corpuscles,  and  that  in  chronic  anaemia  the  mean  diameter  of  the  cor- 
puscles is  always  less  than  normal  (7  //  to  6  u).  There  i;,  moreover,  a  persistent  alteration  in  the 
volume,  coloring  pcnuer,  and  consistence  of  the  corpuscles,  consequently  a  want  of  accord  between 
the  number  of  the  corpuscles  and  their  coloring  power,  i.e.,  tlie  amount  of  haemoglobin  which 
they  contain.  In  pernicious  anaemia,  in  which  the  continued  decrease  in  the  red  corpuscles 
may  ultimately  produce  death,  there  is  undoubtedly  a  severe  affection  of  the  blood-forming  appa- 
ratus. The  corpuscles  assume  many  abnormal  and  bizarre  forms,  often  being  oval  or  tailed, 
irregularly  shaped,  and  sometimes  very  pale;  while  numerous  cells  containing  blood-corpuscles 
are  found  in  the  marrow  of  bone.  In  this  disease,  altiiough  the  red  blood  corpuscles  are  diminished 
in  number,  some  may  be  larger  and  contain  more  haemoglobin  than  normal  corpuscles.  The 
number  of  colored  corpuscles  is  also  diminished  in  chronic  poisoning  by  lead  or  miasmata,  and 
also  by  the  poison  of  syphilis. 

(2)  The  size  of  the  corpuscles  varies  in  disease  from  2.9-12.9  n  (mean  6-8  /z) ;  "dwarf  cor- 
puscles" or  microcytes  (6  ti  and  less)  are  regarded  as  young  forms,  and  occur  plentifully  in  nearly 
all  cases  of  anaemia.  "  Giant  blood  corpuscles  "  or  macrocytes  (10  //  and  more)  are  constant  in 
pernicious  anremia,  and  sometimes  in  leuka-mia,  chlorosis,  and  liver  cirrhosis  [Gram). 

(3)  Abnormal  forms  of  the  red  corpuscles  have  been  observed  after  severe  burns  [Lesser) ; 
the  corpuscles  are  much  smaller,  and  under  the  influence  of  the  heat,  particles  seem  to  be  detached 
Irom  them  just  as  can  be  seen  happening  under  the  microscope  as  the  eflfect  of  heat.     Disintegra- 


PREPARATION    OF    IL^MOGLOBIN    CRYSTALS. 


59 


tion  of  the  corpuscles  into  fine  droplets  has  been  observed  in  various  diseases,  as  in  severe 
malarial  fevers.  The  dark  granules  of  a  pigment  closely  related  to  haematin  are  derived  from  the 
granules  arising  from  the  disintegration  of  the  blood  corpuscles,  and  these  particles  float  in  the  blood 
(melanaem-ia).  This  condition  can  be  produced  artificially  by  injecting  bisulphide  of  carbon  (7  to 
70  of  oil)  subcutaneously  into  rabbits  [Schwalbe).  They  are  partly  absorbed  by  the  colorless 
corpuscles,  but  they  are  also  deposited  in  the  spleen,  liver,  brain,  and  bone  marrow. 

(4)   Sometimes  the  red  corpuscles  are  abnormally  soft,  and  readily  yield  to  pressure. 

Parasites  of  Blood  Corpuscles.— Within  the  red  blood  corpuscles  of  birds,  fishes,  and  tor- 
toises, parasites  are  occasionally  developed  in  the  form  of  round  "  pseudo-vacuoles  "  from  which 
free  parasites  are  subsequently  discharged  {Danilewsky).  In  malarial  conditions  in  man,  proto- 
zoon-like  organisms  have  been  seen  within  the  red  corpuscles,  the  plasmodium  malaria  {Mar- 
chiafava). 

The  white  corpuscles  are  enormously  increased  in  number  in  leukaemia  {J.  H.  Bennett, 
Virchow).  In  some  cases  the  blood  looks  as  if  it  were  mixed  with  milk.  The  colorless  cor- 
puscles seem  to  be  formed  chiefly  in  bone-marrow  (^E.  Ahimiami),  and.  also  in  the  spleen  and 
lymphatic  glands  (myelogenic,  splenic,  and  lymphatic  leukjemia). 

II.  CHEMICAL  CONSTITUENTS  OF  THE  RED  BLOOD 
CORPUSCLES.— (i)  The  coloring  matter  or  hemoglobin  (Hb)  is 
the  cause  of  the  red  color  of  blood ;  it  also  occurs  in  muscle,  and  in  traces  in  the 
fluid  part  of  blood,  but  in  the  last  case  only  as  the  result  of  the  solution  of  some 
red  corpuscles.  Its  percentage  composition  is:  C  53.85,  H  7.32,  N  16.17, 
Fe  0.42,  S  0.39,  O  21.84  (dog).      Its  rational  formula  is  unknown,  but  Preyer 


Although  it  is  a  colloid 
Fig.  13. 


gives  the  empirical  formula  Cgoo,  Hgeo,  N154,  Fe,  S3,  Oi 
substance  it  crystallizes  in  all  classes  of  verte- 
brates, according  to  the  rhombic  system,  and 
chiefly  in  rhombic  plates  or  prisms;  in  the  guinea- 
pig  in  rhombic  tetrahedra;  in  the  squirrel,  how- 
ever, it  yields  hexagonal  plates.  The  varying 
forms,  perhaps,  correspond  to  slight  differences 
in  the  chemical  composition  in  different  cases. 
Crystals  separate  from  the  blood  of  all  classes  of 
vertebrata  during  the  slow  evaporation  of  lake- 
colored  blood,  but  with  varying  facility  (Fig  13). 

The  coloring  matter  crystallizes  very  readily  from  the 
blood  of  man,  dog,  mouse,  guinea-pig,  rat,  cat,  hedgehog, 
horse,  rabbit,  birds,  fishes ;  with  difficulty  from  that  of  the 
sheep,  ox,  and  pig.  Colored  crystals  are  not  obtained  from 
the  blood  of  the  frog.  More  rarely  a  crystal  is  formed  from 
a  single  corpuscle  enclosing  the  stroma.  Crystals  have  been 
found  near  the  nucleus  of  the  large  corpuscles  of  fishes,  and 
in  this  class  of  vertebrates  colorless  crystals  have  been  ob- 
served. 


Dichroism. — Hsemoglobin  crystals  are  doub- 
ly refractive   and  pleo-chromatic;   they  are  Haemogi^in  crystals  from  biood. 
bluish-red   with  transmitted   light,  scarlet-red  by        human ;  c,  cat ,- ^,  guinea-pig ; 

.    °  •^  ster ;  f,  squirrel. 

reflected  light.     They  contam  from   3  to  9  per 

cent,  water  of  crystallization,  and  are  soluble  in  water,  but  more  so  in  dilute 
alkalies.  They  are  insoluble  in  alcohol,  ether,  chloroform,  and  fats.  The  solu- 
tions are  dichroic :   red  in  reflected  light,  and  green  in  transmitted  light. 

In  the  act  of  crystallization  the  haemoglobin  seems  to  undergo' some  internal  change.  Before  it 
crystallizes  it  does  not  diffuse  like  a  true  colloid,  and  it  also  rapidly  decomposes  hydric  peroxide. 
If  it  be  redissolved  after  crystallization,  it  diff"uses,  although  only  to  a  small  extent,  but  it  no  longer 
decomposes  hydric   peroxide,  and  is  decolorized  by  it.     [The  presence  of  O  favors  crystallization.] 

12.  PREPARATION  OF  HAEMOGLOBIN  CRYSTALS.— Method  of  Rollett.— Put 
defibrinated  blood  in  a  platinum  capsule  placed  on  a  freezing  mixture,  freeze  the  blood,  and  then 
thaw  it;  pour  the  lake-colored  blood  into  a  plate,  until  it  forms  a  stratum  not  more  than  l^'^  mm. 
in  thickness,  and  allow  it  to  evaporate  slov^'Iy  in  a  cool  place,  when  crystals  will  separate. 

Method  of  Hoppe-Seyler.— Mix  defibrinated  blood  with  10  volumes  of  a  20  per  cent,  salt 
solution,  and  allow  it  to  stand  for  two  days.     Remove  the  clear  upper  fluid  with  a  pipette,  wash 


ham- 


60 


QUANTITATIVE    ESTIMATION    OF    H.EMOGLOBIN. 


the  thick  deposit  of  blood  corpuscles  wilh  water,  and  afterward  shake  it  for  a  long  time  with  an 
equal  volume  of  ether,  which  dissolves  the  blood  corpuscles.  Remove  the  ether,  filter  the  lake- 
colored  bloml,  add  to  it  )+  of  its  volume  of  cold  alcohol  (o°),  and  allow  the  mixture  to  stand  in  the 
cold  for  several  days.  The  numerous  crystals  can  be  collected  on  a  filter  and  pressed  between  folds 
of  blotting  p.iper. 

Method  of  Gscheidlen. — Take  defibrinated  blood,  which  has  been  exposed  for  twenty-four 
hours  to  the  air,  and  keep  in  a  closed  tube  of  narrow  calibre  for  several  days  at  37°  C.  Wiien  the 
blood  is  spread  on  glass,  the  crystals  form  rapidly.     [Vaccine  tubes  answer  very  well.] 

[Method  of  Stirling  and  Brito. — It  is  in  many  cases  sufficient  to  mix  a  drop  of  blood  wilh  a 
few  drops  of  water  on  a  glass  slide,  and  to  seal  up  the  preparation.  After  a  few  days  beautiful 
cr)'Stals  are  developed.  The  addition  of  water  to  the  blood  of  some  animals,  such  as  the  rat  and 
the  guinea])ig,  is  rapidly  followed  by  the  formation  of  crystals  of  luvmoglobin.  Very  large  crystals 
may  be  obtained  from  the  stomach  of  the  leech  several  days  after  it  has  sucked  blood.] 

13.  QUANTITATIVE  ESTIMATION  OF  HAEMOGLOBIN.— («)  From  the 
Amount  of  Iron. — As  dry  (100°  C.)  lutmoglobin  contains  0.42  per  cent,  of  iron,  the  amount  of 
h.vmoglobin  may  be  calculated  from  the  amount  of  iron.     If  m  represents  the  percentage  amount 

\oom 
of  metallic  iron,  then  the  percentage  of  hemoglobin  in  blood  is  =  ^~.^-     The  procedure  is  the 

following :  Calcine  a  weighed  quantity  of  blood,  and  exhaust  the  ash  with  HCl  to  obtain  ferric 
chloride,  which  is  transformed  into  ferrous  chloride.  The  solution  is  then  titrated  with  potassic 
permanganate. 

(^)  Colorimetric  Method. — Prepare  a  dilute  watery  solution  of  hemoglobin  crj'stals  of  a  known 
strength.  With  this  compare  an  aqueous  dilution  of  the  blood  to  be  investigated,  by  adding  water 
to  it  until  the  color  of  the  test  solution  is  obtained.  Of  course,  the  solutions  must  be  compared  in 
vessels  with  parallel  sides  and  of  exactly  the  same  width,  so  as  to  give  the  same  thickness  of  fluid 
(Hoppe-Scvlfr).  [In  the  vessel  with  parallel  sides,  or  hsematinometer,  the  sides  are  exactly  i 
centimetre  apart.  Instead  of  using  a  standard  solution  of  oxyhemoglobin,  a  solution  of  picro- 
carminate  of  ammonia  may  be  used  {Rajewsky,  Malaisez)^^ 

{c)  By  the  Spectroscope. — Preyer  found  that  an  0.8  per  cent,  watery  solution  (i  cm.  thick), 
allowed  the  red,  the  yellow,  and  the  first  strip  of  green  to  be  seen  (Fig.  17,  l).  Take  the  blood  to 
be  investigated  (about  0.5  c.cm.),  and  dilute  it  with  water  until  it  shows  exactly  the  same  optical 
effects  in  the  spectroscope.  If  k  is  the  percentage  of  lib,  which  allows  green  to  pass  through  (0.8 
l)er  cent.),  b,  the  volume  of  blood  investigated  (about  0.5  c.cm.),  iu,  the  necessary  amount  of  water 
added  to  dilute  it,  then  x  =  the  percentage  of  Hb  in  the  blood  to  be  investigated — 

k{w  +  b) 


Fig.  14. 


IJ 


B, 


It  is  very  convenient  to  add  a  drop 
of  caustic  potash  to  blood  and  then  to 
saturate  it  with  CO. 

[((/)  The  Haemoglobinometerof 
Gowers  is  used  for  the  clinical  esti- 
mation of  hemoglobin  (Fig.  14). 
"  The  tint  of  the  dilution  of  a  given 
volume  of  blood  with  distilled  water 
is  taken  as  the  index  of  the  amount 
of  hemoglobin.  The  distilled  water 
rapidly  dissolves  out  all  the  hemo- 
globin, as  is  shown  by  the  fact  that 
the  tint  of  the  dilution  undergoes  no 
change  on  standing.  The  color  of  a 
dilution  of  average  normal  blood  one 
hundred  times  is  taken  as  the  standard. 
The  quantity  of  hemoglobin  is  indi- 
cated by  the  amount  of  distilled 
water  needed  to  obtain  the  tint  with 
the  same  volume  of  blood  under  ex- 
amination as  was  taken  of  the  stand- 
ard. On  account  of  the  instability  of 
a  standard  dilution  of  blood,  tinted 


(lowers'  hxmoglobinomctcr.     A,  pipette  boltle  for  distilled  water     „, 

capilhry  pipette :   C,  graduated  tube :   D,  tube  with  standard  dilu-      glycerine  jelly   is    employed    instead 

t.on  :  F.  lance,  for  pricking  the  finger.  T,,is  j^  perfectly  Stable,  and  by  means 

,..,,,,,,  of    carmine    and    picro-carmine    the 

exact  tint  of  dduted  blood  can  be  obtained.     The  apparatus  consists  of  two  glass  tubes  of  exactly 

the  same  sue.     One  contains  (D)  a  standard  of  the  tint  of  a  dilution  of  20  cubic  mm.  of  blood,  in 

2  cubic  centimetres  of  water  (i   in   loo).     The  second  tube  (Cj  is  graduated,  1 00  degrees  =  2 


USE    OF   THE    SPECTROSCOPE. 


61 


Fig.  15. 


centimetres  (100  times  20  cubic  millimetres).  The  20  cubic  millimetres  of  blood  are  measured  by 
a  capillary  pipette  (B).  This  quantity  of  the  blood  to  be  tested  is  ejected  into  the  bottom  of  the 
tube,  a  few  drops  of  distilled  water  being  first  placed  in  the  latter.  The  mixture  is  rapidly  agitated 
to  prevent  the  coagulation  of  the  blood.  The  distilled  water  is  then  added  drop  by  drop  (from  the 
pipette  stopper  of  a  bottle  (A)  supplied  for  that  purpose),  until  the  tint  of  the  dilution  is  the  same 
as  that  of  the  standard,  and  the  amount  of  water  which  has  been  added  [i.  e.,  the  degree  of 
dilution)  indicates  the  amount  of  haemoglobin." 

"  Since  average  normal  blood  yields  the  tint  of  the  standard  at  loo  degrees  of  dilution,  the 
number  of  degrees  of  dilution  necessary  to  obtain  the  same  tint  with  a  given  specimen  of  blood  is 
the  percentage  proportion  of  the  hsemoglobin  contained  in  it,  compared  to  the  normal.  For  instance, 
the  20  cubic  millimetres  of  blood  from  a  patient  with  anemia  gave  the  standard  tint  of  30  degrees 
of  dilution.  Hence  it  contained  only  30  per  cent,  of  the  normal  quantity  of  hsemoglobin.  By 
ascertaining  with  the  hjemacytometer  the  corpuscular  richness  of  the  blood,  we  are  able  to  compare 
the  two.  A  fraction,  of  which  the  numerator  is  the  percentage  of  haemoglobin,  and  the  denomi- 
nator the  percentage  of  corpuscles,  gives  at  once  the  average  value  per  corpuscle.  Thus  the  blood 
mentioned  above  containing  30  per  cent,  of  hsemoglobin,  contained  60  per  cent,  of  corpuscles; 
hence  the  average  value  of  each  corpuscle  was  l^  or  ^  of  the  normal.  Variations  in  the  amount 
of  h2emoglobin  may  be  recorded  on  the  same  chart  as  that  employed  for  the  corpuscles.  The 
instrument  is  only  expected  to  yield  approximate  results,  accurate  within  2  or  3  per  cent.  It  has, 
however,  been  found  of  much  utility  in  clinical  observation."] 

{e)  Fleischl's  Haemometer.— For  clinical  purposes  this  instrument  (Fig.  15)  is  useful.  A 
cylinder  G,  of  two  compartments  a  and  a^ ,  rests  on  a  metallic  table.  Both  compartments  are  filled 
with  water,  but  in  one  [a)  is  placed  a 
known  quantity  of  blood  measured  in  a 
measuring  tube  of  known  capacity.  The 
red  color  of  the  solution  of  hsemoglobin 
thus  obtained  is  compared  with  a  red 
wedge  of  glass  (K),  which  is  moved  by 
means  of  a  wheel  (R  and  T)  under  the 
other  compartment  [a')  until  the  two 
colors  are  identical.  The  illumination  of 
the  dilute  blood  solution  and  the  red 
glass  wedge  is  done  from  below  by  lamp 
light  reflected  from  the  white  reflecting 
surface  (S).  The  frame  in  which  the 
red  glass  wedge  is  fixed  bears  numbers, 
and  when  the  color  is  identical  in  the  two 
compartments  a  and  a^,  the  percentage 
of  hiemoglobin  as  compared  with  normal 
blood  can  be  read  off"  directly.  Suppose 
it  to  be  80  on  the  scale,  then  the  blood 
examined  contains  80  per  cent,  of  the 
hsemoglobin  of  normal  blood. 

The  amount  of  haemoglobin 
in  man  is  13.77  per  cent.,  in  the 
woman  12.59  per  cent.,  during 
pregnancy  9  to  12  per  cent. 
\Preyer).  According  to  Leich- 
tenstern,  Hb  is  in  greatest  amount 
in  the  blood  of  a  newly-born 
infant,  but  after  ten  weeks  the 
excess  disappears.  Between  six  months  and  five  years  it  is  smallest  in  amount; 
it  reaches  its  second  highest  maximum  between  twenty-one  and  forty-five,  and 
then  sinks  again.  From  the  tenth  year  onward,  the  blood  of  the  female  is  poorer 
in  Hb.  The  taking  of  food  causes  a  temporary  decrease  of  the  Hb,  owing  to  the 
dilution  of  the  blood. 

In  Animals.— In  the  dog,  9.7  ;  ox,  9.9  ;  sheep,  10.3  ;  pig,  12.7  ;  horse,  13. i ;  birds,  16-17  per  cent. 

Pathological. A   decrease   is  observable   during  recovery  from   febrile   conditions,  and  also 

during  phthisis,  cancer,  ulcer  of  the  stomach,  cardiac  disease,  chronic  diseases,  chlorosis,  leukaemia, 
pernicious  ansemia,  and  during  the  rapid  mercurial  treatment  of  syphilitic  persons. 

14.  THE  SPECTROSCOPE.— As  the  spectroscope  is  frequently  used  in  the  investigation 
of  blood  and  other  substances,  a  short  description  of  the  instrument  is  given  here   (Fig.  16).     It 


Fleischl's  h3emometer.  K,  red  colored  wedge  of  glass  moved 
by  R  ;  G,  mixing  vessel  with  two  compartments  a  and  a' ;  M, 
table  with  hole  to  read  off  the  percentage  of  haemoglobin  on 
the  scale  P ;   T,  to  move  K;   S,  mirror  of  plaster-of-Paris. 


62 


COMPOUNDS    OF    H.EMOGLOBIN. 


consists  of — (i)  a  tube,  A,  which  has  at  its  peripheral  end  a  slit,  S  (that  can  be  narrowed  or 
widened).  At  the  other  end  a  collecting  lens,  C  (called  a  collimator),  is  placed,  so  that  its  focus 
is  in  exact  line  with  the  slit.  Light  (from  the  sun  or  a  lamp)  passes  through  the  slit,  and  thus  goes 
parallel  through  C  to  (2)  the  prism,  P,  which  decomposes  the  ]>arallel  rays  into  a  colored  spec- 
trum, r,  V.  (3)  An  astronomical  telescope  is  directed  to  the  sjiectrum  /-,  r',  and  the  observer,  h, 
with  the  aid  of  the  telescope,  sees  the  spectrum  magnified  from  six  to  ciglit  times.  (4)  A  third 
tube,  D,  contains  a  delicate  scale,  M,  on  glass,  whose  image,  when  illuminated,  is  reflected  from 
the  prism  to  the  eye  of  the  observer,  so  that  he  sees  the  spectrum,  and  over  or  above  it  the  scale. 
To  keep  out  other  rays  of  light  the  inner  ends  of  the  three  tubes  are  covered  by  metal  or  by  a  dark 
cloth  (see  also  i,  265). 

[The  micro-spectroscope,  t-.^.,  as  made  by  Browning  or  Zeiss,  may  be  used  when  small  quan- 
tities of  a  solution  are  to  be  examined.  Every  spectroscope  ought  to  give  two  spectra,  so  that  the 
position  of  any  absorjition  band  may  be  definitely  ascertained.  The  spectroscope  is  fitted  into  the 
ocular  end  of  the  tube  of  a  microscope  instead  of  the  eye-piece.  Small  cells  for  containing  the 
fluid  to  be  ex.imined  are  made  from  short  pieces  of  barometer  tubes  cemented  to  a  plate  of  glass.] 

Absorption  Spectra. — If  a  colored  medium  (<?..?•.,  a  solution  of  blood)  be  placed  between  the 
slit  and  a  source  of  light,  all  the  rays  of  colored  light  do  not  pass  through  it — some  are  absorbed  ; 
many  yellow  rays  are  absorbed  by  blood,  hence  that  part  of  the  spectrum  appears  dark  to  the 
observer.     On  account  of  this  absorption,  such  a  spectrum  is  called  an  '^^  absorption  spectrum'^ 

Fig.  16. 


Scheme  of  a  spectroscope  for  observing  the  spectrum  01    blood.       X,  tube;    S,  slit;    m,  m,  layer  of  blood  with 
ti.inic  m  front  of  it;    P,  prism;    M,  sc.tle  ;    B,  eye  of  observer  looking  through  a  telescope;    r,  v,  spectrum. 

Flame  Spectra.— If  mineral  substances  be  burned  on  a  platinum  wire  in  a  non-luminous  flame 
or  Bunsen's  burner  in  front  of  the  slit,  the  elements  present  in  the  mineral  or  ash  give  special 
colored  band  or  bands,  which  have  a  definite  position.     Sodium  gives  a  yellow,  potassium  a  red 


spectr 


(Fraun- 

,      ,     ,  .    .,    ^  •-  •  •'I- ••      -..-.,- w..^o  „.^  indicated 

by  the  letters  A,  B,  C,  D,  etc.,  a,  b,  c,  etc.  (Fig.  17). 

15.  COMPOUNDS  OF  Hb  WITH  O;  OXYHiEMOGLOBIN  AND 
METHiEMOGLOBIN.— I.  Oxyhaemoglobin  (O.Hb)  behaves  as  a  weak 
acid,  and  occurs  to  the  extent  of  86.78  to  94.30  per  cent,  in  dry  human  red  cor- 
puscles (Jiidell).  It  IS  formed  very  readily  whenever  Hb  comes  into  contact  with 
O  or  atmospheric  air.  According  to  Bohr,  i  gramme  Hb  unites  with  1.56  cubic 
centimetre  of  O  at  0°  and  760  mm.  Hg  pressure,  the  union  being  stronger  in 
weak  than  in  concentrated  solutions.  Oxyh?emoglobin  is  a  very  loose  chemical 
compound  and  is  slightly  less  soluble  than  Hb;  its  spectrum  shows  in  the 
yellow  and  the  green  two  dark  absorption-bands,  whose  length  and  breadth 
in  an  0.18  per  cent,  solution  are  given  in  Fig.  17  (2}. 


COMPOUNDS    OF    HEMOGLOBIN. 


6( 


It  occurs  in  the  blood  corpuscles  circulating  in  arteries  and  capillaries,  as  can 
be  shown  by  the  spectroscopic  examination  of  the  ear  of  a  rabbit,  of  the  prepuce, 
and  the  web  of  the  fingers  (  Vierordt). 

[Spectrum  of  Oxyhaemoglobin.— In  the  spectrum  of  a  dilute  solution  of 
hemoglobin  crystals  or  arterial  blood,  part  of  the  red  and  violet  rays  are  absorbed, 
but  two  well-marked  absorption-bands  exist  between  D  and  E.  The  line 
nearest  D,  i.e.,  next  the  red  end  of  the  spectrum,  sometimes  designated  by  the 
letter  (a)  is  narrow,  sharply  defined,  and  black  at  its  centre,  and  its  position  cor- 


FiG.  17. 


Red.     Orange. 


Green. 


Cyan  Blue. 


0-xy.= 

Hamoglobin 

0.8  <* 


Oxy,= 

Hamoglobin 

0.18    ■ 


HEemo- 

chromogen 

in  Alkaline 

Solution. 

Reduced 

Hamatin. 

1111111111111  ji.um.u.iiii.Lilui  III  i.i.iiiii  i|iLiiiiii  111  I'. yiiii 
50  60  70  80  qo  100  wo 

D  E  F 

Spectra  of  hsemoglobin  and  its  compounds. 

responds  to  the  wave-length  579.  The  other  absorption-band  near  E,  conveniently 
designated  by  (/?),  is  broader,  not  so  dark,  and  its  edges  are  less  sharply  defined. 
Its  centre  corresponds  to  the  wave-length  553.8.  In  very  dilute  solutions  the  a 
band  is  the  only  one  visible.  In  a  strong  solution,  as  shown  in  Fig.  17,  the  two 
bands  fuse,  but  are  again  made  visible  as  two  on  dilution  of  the  blood.] 

Reduction  of  Oxyhaemoglobin. — It  gives  its  O  very  readily,  however,  even 
when  means  which  set  free  absorbed  gases  are  used.  It  is  reduced  by  the  removal 
of  the  gases  by  the  air-pump,  by  the  conduction  through  its  solution  of  other  gases 


54  METH^MOGLOBIN. 

(CO),  and  by  heating  to  the  boiling  point.  In  the  circulating  blood  its  O  is  very 
rapidly  given  up  to  the  tissues,  so  that  in  suffocated  animals  only  reduced  /nemo- 
globin  is  found  in  the  arteries.  Some  constituents  of  the  serum  and  sugar  remove 
its  O.  By  adding  a  solution  of  oxyhoemoglobin  reducing  substances — e.g., 
ammonium  sulphide,  iron  filings,  or  Stokes's  fluid  [tartaric  acid,  iron  proto-sulphate, 
and  excess  of  ammonia] — the  two  absorption-bands  of  the  spectrum  disappear,  and 
reduced  hictnoglobin  (gas-free),  with  one  absorption-band,  is  formed.  The  color 
changes  from  a  bright  red  to  a  purplish  or  claret  tint.  The  two  bands  are 
reproduced  by  shaking  the  reduced  haemoglobin  with  air,  whereby  0,,Hb  is  again 
formed.  Solutions  of  oxyha;mogIobin  are  readily  distinguished,  by  their  scarlet 
color,  from  the  jmrplish  tint  of  reduced  haemoglobin. 

[The  single  absori)tion-band  (Fig.  17,  4)  designated  by  the  letter  {-f),  lying  about 
midway  between  the  j)osition  of  the  two  previous  bands,  is  broader,  fainter,  less 
deeply  shaded,  and  its  centre  is  about,  but  not  quite,  intermediate  between  D  and 
E.  It  extends  between  the  wave-lengths  595  and  538,  and  is  blackest  opposite  the 
wave-length  550,  so  that  it  lies  nearer  D  than  E.  At  the  same  time  more  of  the 
blue  rays  are  transmitted.  On  dilution  the  band  is  not  resolved  into  two,  but 
simply  becomes  fainter  and  disappears.] 

[Haemoglobin  has  certain  remarkable  characters :  ( i )  Although  it  is  a  crystalloid 
body  it  diffuses  with  difficulty  through  an  animal  membrane,  owing  to  the  large 
size  of  its  molecule.  (2)  It  readily  combines  with  O  to  form  an  unstable  and  loose 
chemical  compound,  oxyhgemoglobin,  (3)  This  O  it  gives  up  readily  to  the  tissues 
or  other  deoxidizing  reagents.  (4)  Its  composition  is  very  complex,  for,  in  addition 
to  the  ordinary  elements  present  in  proteids,  it  contains  a  remarkable  amount  of 
iron  (0.4  per  cent).] 

If  a  string  be  tied  round  the  base  of  two  fingers  so  as  to  intetrrupt  the  circulation,  spectroscopic 
examination  shows  that  the  oxyha-moglobin  rapidly  passes  into  reduced  lib  (  F/Vr^n//).  Cold 
delays  this  reduction;  it  is  accelerated  in  youth,  during  muscular  activity,  or  by  suppressed  respira- 
tion, and  usually  also  during  fever. 

The  spectroscopic  examination  of  small  blood-stains  is  often  of  the  utmost  forensic  importance. 
A  minimal  drop  is  sufficient.  Dissolve  the  stain  in  a  few  drops  of  distilled  water,  and  place  the 
solution  in  a  thin  glass  tube  in  front  of  the  slit  of  the  spectroscope. 

Parahaemoglobin. — If  O.JIb  be  preserved  under  alcohol  it  passes  into  a  modified  form,  which 
is  insoluble  in  water  [.Wnc/ci  and  Sieber.) 

2.  Methaemoglobin  is  a  more  stable,  crystalline  compound  (^Hoppe-Seyler.^  It 
contains  the  same  amount  of  O  as  O.^Hb,  but  in  a  different  chemical  union,  while 
the  O  is  also  more  firmly  united  with  it.  It  shows  four  absorption-bands  like 
haematin  in  acid  solution  (Fig.  17,  5),  of  which  that  between  C  and  D  is  distinct ; 
the  second  is  very  indistinct,  while  the  third  and  fourth  readily  fuse,  so  that  these 
last  two  bands  are  only  well  seen  with  good  apparatus. 

It  is  produced  spontaneously  in  old  brown  blood  stains,  in  the  crusts  of  bloody  wounds,  in  blood 
cysts,  and  in  bloody  urine.  Chemically,  it  can  be  prepared  from  a  solution  of  Hb,  by  the  action 
of  potassic  ferri-cyanide  (Jaderholm)  or  potassic  chlorate  {Marchand),  [or  by  adding  to  a  solution 
of  lib  a  freshly  prepared  solution  of  potassic  i)ermanganate],  and  in  non-laky  blood  by  alloxantin 
i Knvale-Msky).  It  crystallizes  if  defibrinated  blood  is  shaken  with  amyl  nitrite  and  the  mahogany- 
brown  laky  fluid  be  allowed  to  evaporate  slowly  {Halliburton). 

If  a  trace  of  ammonia  be  added  to  a  solution  of  methjemogoblin,  it  gives  an  alkaline  solution 
of  methxmogoblin,  which  shows  two  bands  like  oxyhsemoglobin,  of  which  the  first  one  is  the 
broader,  and  extends  more  toward  the  red.  If  ammonium  sulphide  be  added  to  the  methcemo- 
globin  solution,  reduced   Hb  is  formed. 

[Action  of  Nitrites.— The  addition  of  amyl  nitrite  dissolved  in  alcohol,  or 
sodic  potassic  nitrite  to  defibrinated  blood  causes  the  latter  to  assume  a  chocolate 
color,  which,  on  the  addition  of  ammonia,  changes  to  red.  The  chocolate-colored 
fluid  shows  one  well-defined  band  in  the  red,  and  less  distinctly  other  three  bands 
like  methremoglobin  {Gamgee).'\ 

[The  nitrites  therefore  form  a  compound  with  its  oxygen  more  firmly  fixed  than  the  O  in  HbO,, 
so  that  large  doses  of  nitrites  arrest  the  internal  respiration  and  are  poisonous.     It  is,  however, 


CARBONIC    OXIDE    HAEMOGLOBIN.  Q5 

affected  by  the  products  formed  in  the  blood  during  asphyxia,  while  CO-Hb  is  not,  the  methsemoglobin 
formed  by  the  nitrites  is  reduced  by  these  products  to  Hb,  which  as  it  passes  through  the  lungs 
takes  up  O.] 

i6.    CARBONIC  OXIDE  HEMOGLOBIN,  POISONING  WITH 

CO. — 3.  CO-Haemoglobin  is  a  more  stable  chemical  compound  than  the  fore- 
going, and  is  produced  at  once  when  carbonic  oxide  is  brought  into  contact  with  the 
pure  Hb  or  OaHb  (C/.  Bernard,  185  7).  It  has  an  intensely  florid  or  cherry-red cqXox , 
is  not  dichroic,  and  its  spectrum  shows  two  absorption-bands,  very  like  those 
of  O.^Hb,  but  they  are  slightly  closer  together  and  lie  more  toward  the  violet  (Fig. 
17,  3).  Reducing  substances  which  act  upon  HbOa,  ^•g-',  ammonium  sulphide  or 
Stokes's  fluid,  do  not  affect  these  bands,  i.e.,  they  cannot  convert  the  CO-Hb  into 
reduced  Hb.  If  a  10  per  cent,  solution  of  caustic  soda  be  added  to  a  solution  of 
CO-Hb,  and  heated,  it  gives  a  dnfiabar-red  color  ;  while,  with  an  HbOa  solution, 
it  gives  a  dark  brown,  greenish,  greasy  mass.  Oxidizing  substances  [solutions  of 
potassic  permanganate  (0.025  P^^  cent.),  potassic  chlorate  (5  percent.),  and  dilute 
chlorine  solution]  make  solutions  of  CO-Hb  cherry-red  in  color,  while  they  turn 
solutions  of  OjHb  pale  yellow.  After  this  treatment  both  solutions  show  the 
absorption-bands  of  methsemogoblin,  but  those  of  the  CO-Hb  appear  considerably 
later.     If  ammonium  sulphide  be  added,  O.jKh  and  CO-Hb  are  re-formed. 

On  account  of  its  stability,  CO-Hb  resists  external  influences  and  even  putrefaction  for  a  long 
time,  and  the  two  bands  of  the  spectrum  may  be  visible  after  many  months.  Landois  obtained  the 
soda  test  and  spectroscopic  bands  in  the  blood  of  a  woman  poisoned  eighteen  months  previously  by 
CO,  and  after  great  putrefaction  of  the  body  had  taken  place.  [Stirling  has  kept  CO-Hb  in  a 
stoppered  bottle  for  five  years  without  putrefaction  taking  place.] 

If  CO  or  air  containing  it  be  inspired,  it  gradually  displaces  the  O,  volume  for 
volume,  out  of  the  red  blood  corpuscles,  and  death  soon  occurs;  1000  c.cm. 
inspired  at  once  will  kill  a  man.  A  very  small  quantity  in  the  air  (4^-10^00) 
suffices,  in  a  relatively  short  time,  to  form  a  large  quantity  of  CO-Hb.  As  con- 
tinued contact  with  other  gases  (such  as  the  passing  of  O  through  it  for  a  very  long 
time)  gradually  separates  the  CO  from  the  Hb,  with  the  formation  of  OaHb,  it 
happens  that,  in  very  partial  poisoning  with  CO,  the  blood  gradually  gets  rid 
of  the  CO  by  the  respiratory  organs.  It  is  uncertain  if  any  part  is  excreted  as 
COo.  [CO-Hsemoglobin,  being  a  stable  compound  when  once  formed,  circulates 
in  the  blood  vessels ;  but  it  neither  gives  up  oxygen  to  the  tissues,  nor  takes  up 
oxygen  in  the  lungs,  hence  its  very  poisonous  properties.  The  real  cause  of  death 
in  animals  poisoned  with  it  is,  that  the  internal  respiration  is  arrested.] 

Poisoning  with  Carbonic  Oxide. — Carbonic  oxide  is  formed  during  the  incomplete  combustion 
of  coal  or  coke,  and  passes  into  the  air  of  the  room,  provided  there  is  not  a  free  outlet  for  the 
products  of  combustion.  It  occurs  to  the  extent  of  12-28  per  cent,  in  ordinary  gas,  which  largely 
owes  its  poisonous  properties  to  the  presence  of  CO.  If  the  O  be  gradually  displaced  from  the 
blood  by  the  respiration  of  air  containing  CO,  life  can  only  be  maintained  as  long  as  sufficient  O  can 
be  obtained  from  the  blood  to  support  the  oxidations  necessary  for  life.  Death  occurs  before  all  the 
O  is  displaced  from  the  blood.  CO  has  no  effect  when  directly  applied  to  muscle  and  nerve.  When 
it  is  mixed  with  air,  as  in  coal-gas  poisoning,  and  inhaled,  there  is  first  stimulation  and  afterward 
paralysis  of  the  nervous  system,  as  shown  by  the  symptoms  induced,  e.g.,  violent  headache,  great 
restlessness,  excitement,  increased  activity  of  the  heart  and  respiration,  salivation,  tremors,  and 
spasms.  Later,  unconsciousness,  weakness,  and  paralysis  occur,  labored  respiration,  diminished 
heart-beat,  and  lastly,  complete  loss  of  sensibility,  cessation  of  the  respiration  and  heart-beat, 
and  death.  At  first  the  temperature  rises  several  tenths  of  a  degree,  but  it  soon  falls  1°  or 
more.  The  pulse  is  also  increased  at  first,  but  afterward  it  becomes  very  small  and  frequent. 
In  poisoning  with  pure  CO  there  is  no  dyspnoea,  but  sometimes  muscular  spasms  occur,  the  coma 
not  being  very  marked.  There  is  also  temporary  but  pronounced  paralysis  of  the  limbs,  followed 
by  violent  spasms.  After  death  the  heart  and  brain  are  congested  with  intensely  florid  blood.  In 
poisoning  with  the  vapor  of  charcoal,  where  CO  and  COo  both  occur,  there  is  a  varying  degree 
of  coma  ;  pronounced  dyspnoea,  muscular  spasms  which  may  last  several  minutes,  gradual  paralysis 
and  asphyxia,  moniliform  contractions  and  subsequent  dilatation  of  the  blood  vessels,  with  congestion 
of  various  organs,  occur,  accompanied  by  a  fall  of  the  blood  pressure  [J^lebs),  indicating  initial 
stimulation  and  subsequent  paralysis  of  the  vaso-motor  centre.      This  also  explains  the  variations  in 

5 


66  DECOMPOSITION    OF    HAEMOGLOBIN. 

ilie  temperature  and  the  occasional  occurrence  of  sugar  in  the  urine  after  poisoning  with  CO.  After 
death,  tlie  blood  vessels  are  found  to  be  tilled  with  fluid  blood  of  an  exf|uisitely  bright  cherry-red 
color,  while  all  the  muscles  and  viscera  and  exposed  parts  of  the  body  (such  as  the  lips)  have  the 
same  color.  The  brain  is  soft  and  friable ;  there  is  catarrh  of  the  respiratory  organs  and  degenera- 
tion of  the  muscles,  and  great  congestion  and  degeneration  of  the  liver,  kidneys,  and  spleen.  The 
spots  of  lividity, /('.t/-///('^/<•w,  are  blight  red.  After  recovery  from  poisoning  with  CO  there  may  be 
parajilcgia  and  (alliiough  more  rarely)  disturbances  of  the  cerebral  activity. 

17.  OTHER  COMPOUNDS  OF  HEMOGLOBIN.— 4.  Nitric 
Oxide  Haemoglobin  (NO-Hb)  is  formed  when  NO  is  brought  into  contact 
witli  Hb  (^Z.  Uomann). 

As  NO  has  a  great  aftlnity  for  O,  red  fumes  of  nitrogen  jieroxide  (NO.^)  being  formed  whenever 
the  two  gases  meet,  it  is  clear  that,  in  order  to  prepare  NO- lib,  the  0  must  first  be  removed.  This 
may  be  done  by  passing  H  through  it  [or  anmionia  may  be  added  to  the  blood,  and  a  stream  of 
NC)  passed  through  it;  the  ammonia  combines  with  all  the  acid  formed  by  the  union  of  the  NO 
with  the  O  of  the  blood].  NO-IIb  is  a  more  stable  chemical  compound  than  CO-IIb,  which,  as  we 
have  seen,  is  again  more  stable  than  O.^Hb.  It  has  a  bluiih-violet  tint,  and  also  gives  two  absorption- 
bands  in  the  spectrum  similar  to  those  of  the  other  two  compounds,  but  not  so  intense.  These 
bands  are  not  abolished  by  the  action  of  reducing  agents.  As  NO-Hb  cannot  be  formed  in  the 
body,  it  has  no  practical  significance. 

The  three  compounds  of  Hb,  with  O,  CO,  and  NO  are  crystalline,  like 
reduced  Hb  ;  they  are  isomorphous,  and  their  solutions  are  not  dichroic. 
All  three  gases  unite  in  equal  volumes  with  Hb.  If  O  be  conducted  tlirough  a 
concentrated  solution  of  Hb  devoid  of  gases,  a  crystalline  mass  of  O..Hb  is 
thereby  readily  formed. 

5.  Cyanogen,  CNH  {Hoppe-Seyler),  and  acetylene,  C.^II^  [Bistrow  and  Liebreich),  form  easily 
decomposable  compounds  with  lib.  The  former  occurs  in  poisoning  with  hydrocyanic  acid,  and 
has  a  spectrum  nearly  identical  with  that  of  O^Hb,  and,  like  (j„Hb,  it  is  reduced,  but  very  slowly, 
by  special  reagents.     [The  existence  of  these  compounds  is,  however,  highly  doubtful  {^Gamgee^.'\ 

18.  DECOMPOSITION  OF  HAEMOGLOBIN.— In  solution  and  in 
the  dry  state  Hb  gradually  becomes  decomposed,  whereby  the  iron-containing 
pigment  hcematin  (along  with  certain  bye-products,  formic,  lactic,  and  butyric 
acids)  is  formed.  Hcemoglobin,  however,  may  be  decomposed  at  once  into  (i) 
Haematin,  a  body  containing  iron,  and  (2)  a  colorless  proteid  closely  related 
to  globulin  ;  by  (a)  the  addition  of  all  acids,  even  by  COa  in  the  presence  of 
plenty  of  water  ;  {b)  strong  alkalies;  (r)  all  reagents  which  coagulate  albumin, 
and  by  heat  at  7o°-8o°  C.  ;  {(i)  by  ozone. 

(A)  Haematin,  Q),M.-i{i^^tOi(^Nencki  and  Sieber),  is  a  bluish-black  amorphous 
body,  which  forms  about  4  per  cent,  of  haemoglobin  (dog).  It  is  insoluble  in 
water,  alcohol,  and  ether  ;  soluble  in  dilute  alkalies  and  acids,  and  in  acidulated 
ether  and  alcohol. 

(i )  Acid  Haematin. — Lecanu  extracted  it  from  dry  blood  corpuscles  by  using 
alcohol  containing  sulphuric  and  tartaric  acids.  [If  acetic  acid  be  added  to  a 
solution  of  Hb  and  slightly  heated,  a  mahogany-brown  fluid  is  obtained,  contain- 
ing hicmatin  in  acid  solution,  which  gives  a  spectrum  with  one  absorption-band 
to  the  red  side  of  D  near  C  (Fig.  17,  5).  There  is  at  the  same  lime  a  considerable 
absorption  of  the  blue  end  of  the  spectrum.  If  an  ethereal  extract  of  the  acid 
haematin  be  made,  the  ether  is  colored  brown  and  shows  four  absorption-bands, 
as  in  Fig.  17,  5.] 

(2)  Alkali  Haematin. — [If  to  the  above  solution  ammonia  or  caustic  soda  be 
added,  on  heating  gently,  the  color  changes,  and  the  fluid  becomes  dichroic, 
showing  a  greenish  tinge.  On  mixing  the  solution  thoroughly  with  air  the  spec- 
trum of  oxy-alkali  haematin  is  obtained,  /.  e.,  one  absorption-band  just  to  the 
red  side  of  D  (Fig.  17,  6),  so  that  it  is  much  nearer  D  than  the  corresponding 
band  of  acid  haematin.    Much  of  the  blue  end  of  the  spectrum  is  absorbed  as  well.] 

[(3)  Reduced  Alkali  Haematin  or  Haemochromogen. — If  the  solution  of 
alkali  haematin  be  reduced  by  ammonium  sulphide,  the  spectrum  of  h^mochro- 


HJEMIN    AND    BLOOD    TESTS. 


67 


mogen  is  obtained,  viz.,  two  absorption-bands  between  D  and  E,  but  they  are 
nearer  the  violet  end  than  in  the  case  of  HbOa  and  Hb-CO  (Fig.  17,  7).] 

[(4)  Haematoporphyrin  or  Iron-free  Haematin. — On  adding  blood  to 
concentrated  sulphuric  acid  a  clear  purplish-red  solution  is  obtained,  which  shows 
two  absorption-bands,  one  close  to  and  on  the  red  side  of  D,  and  a  second 
half-way  between  D  and  E.  If  water  be  added  a  brown  precipitate  is  thrown 
down.  When  this  precipitate  is  dissolved  in  caustic  soda,  it  gives  a  fluid  which 
shows /t'z/r  absorption-bands.] 

Action  of  CO2.  —  If  CO2  be  passed  through  a  solution  of  oxyhssmoglobin  for  a  considerable 
time,  reduced  Hb  is  first  formed  ;  but  if  the  process  be  prolonged  the  Hb  is  decomposed,  a  pre- 
cipitate of  globulin  is  thrown  down,  and  an  absorption-band,  similar  to  that  obtained  when  Hb  is 
decomposed  with  acids,  is  observed  (p.  66). 

An  alkaline  solution  of  haematin,  when  reduced  by  tin  and  hydrochloric  acid, 
yields  urobilin  (compare  §  261). 

When  haemoglobin  is  extravasated  into  the  subcutaneoiis  tissue,  it  becomes  so  altered  that  at  first 
haematoidin(§  20),  and  ultimately  hydrated  oxide  of  iron,  appear  in  its  place. 

19.  H^MIN  AND  BLOOD  TESTS.— In  1853  Teichmann  prepared 
crystals  of  haemin  from  blood,  which  Hoppe-Seyler  showed  to  be  chloride  of 


Fig.  18. 


/' 


.♦.< 


Haemin  crystals,     i,  human  ;  2,  seal ;   3,  calf;  4,  pig  ; 
S,lamb;  5,  pike;    7, rabbit. 


Fig.  19 


V 


Haemin  crystals  prepared 
from  traces  of  blood. 


haematin  (Haematin,  +  2HCI),  with  the  formula  CgaHgiClN^FeOg  {Nencki  and 
Sieber).  The  presence  of  these  crystals  is  used  as  a  test  for  blood  stains  or  blood 
in  solution.  They  (Fig.  18)  are  prepared  by  adding  a  small  crystal  of  common 
salt  to  dry  blood  on  a  glass  slide,  and  then  an  excess  of  glacial  ^^.c^tvc  acid  ;  the 
whole  is  gently  heated  until  bubbles  of  gas  are  given  off.  On  allowing  the  prepa- 
ration to  cool,  the  characteristic  haemin  crystals  are  obtained. 

Characters. — When  well  formed,  the  crystals  are  small  microscopic  rhombic 
plates,  or  rods ;  sometimes  they  are  single — at  other  times  they  are  aggregated  in 
groups,  often  crossing  each  other.  Some  kinds  of  blood  (ox  and  pig)  yield  very 
irregular,  scarcely  crystalline,  masses.  The  crystalline  forms  of  haemin  are  iden- 
tical in  all  the  different  kinds  of  blood  that  have  been  examined.  They  are  doubly- 
refractive  ;  under  the  polarization  microscope  they  are  a  glancing  yellow,  appear- 
ing raised  on  the  dark  field,  with  a  strong  absorption  of  the  light  parallel  to  the  long; 
axis  of  the  crystals  (^Falk  and  Morache).  They  are  pleochromatic  ;  by  trans- 
mitted light  they  are  mahogany-brown,  and  by  reflected  light  bluish-black,  glanc- 
ing like  steel. 

(i)  Preparation  from  Dry  Blood  Stains. — Place  a  few  particles  of  the  blood  stain  on  a  glass 
slide,  add  2  to  3  drops  of  glacial  acetic  acid  and  a  small  crystal  of  common  salt ;  cover  with 
a  cover-glass,  and  heat  gently  over  the  flame  of  a  spirit  lamp  until  bubbles  of  gas  are  given  off.  On 
cooling,  the  crystals  appear  in  the  preparation  (Fig.  19). 


68  THE    COLORLESS    PROTEID   OF    H.EMOGLOBIN. 

(2)  From  Stains  on  Porous  Bodies. — The  stained  object  (cloth,  wood,  hlolting  paper,  earth) 
is  extracted  witli  a  small  ciuantity  of  dilute  caustic  potash,  and  afterwards  with  water  in  a  watch- 
glass.  Hoth  solutions  are  carefully  fdtcred,  and  tannic  acid  and  glacial  acetic  acid  are  added  until 
an  acid  reaction  is  obtained.  The  dark  precipitate  which  is  formed  is  collectetl  on  a  filter  and 
washed.  A  small  part  of  it  is  ])laced  on  a  microscope  slide,  a  granule  of  common  salt  is  added, 
and  the  whole  dried  ;  the  dry  stain  is  treated  as  in  (i )  (S/rtrwe). 

(3)  From  Fluid  Blood. —  Dry  the  blood  slowly  at  a  low  temjierature,  and  proceed  as  in  (i). 

(4)  From  Dilute  Solutions  of  Haemoglobin. — (a)  Stnrwd's  MellioJ. — .Vdd  to  the  fluid, 
ammonia,  tannic  acitl,  and  afterwards  glacial  acetic  acid,  until  it  is  acid ;  a  black  precipitate  of 
tannate  of  luvmatin  is  thrown  down.  This  is  isolated,  washed,  dried,  and  treated  as  in  (l),  but 
instead  of  NaCl  a  granule  of  ammonium  chloride  is  added. 

Hcemin  crystals  may  sometimes  be  prepared  from  putrefying  or  lake-colored 
blood,  but  tliey  are  very  small,  and  the  test  often  fails.  When  mixed  with  iron- 
rust,  as  on  iron  weapons,  the  blood  crystals  are  generally  not  formed.  In  such 
cases,  scrape  off  the  stains  and  boil  theni  with  dilute  caustic  potash.  If  blood  be 
present,  the  dissolved  hceniatin  forms  a  fluid,  which  in  a  thin  layer  is  green,  in  a 
thick  layer  red  ^H.  Rose). 

ILvmin  crystals  have  been  prepared  from  all  classes  of  vertebrates  and  from  the  blood  of  the 
earth-worm.      From  tlie  blood  of  the  ox  and  pig  they  may  be  almost  amorphous. 

Chemical  Characters. — They  are  insoluble  in  water,  alcohol,  ether,  chloroform  ;  but  concen- 
trated H.,SO,  dissolves  them,  expelling  the  IICl,  and  giving  a  violet-red  color.  Ammonia  al.so 
dissolves  "them,  and  if  the  resuhing  solution  be  evaporated,  heated  to  130°  C,  and  treated  with 
boiling  water  (which  extracts  the  ammonium  chloride),  haematoporphyrin — identical  with 
Mulder's  iron-free  haematoin,  and  with  Preyer's  haematoin,  is  obtained  {Iloppc-Seyler).  It  is 
a  bluish-black  substance,  which  on  being  pounded  forms  a  brown  and  amorphous  powder.  Its 
solutions  in  caustic  alkalies  are  dichroic  ;  in  reflected  light,  brownish-red  ;  in  transmitted  light. 
in  a  thick  stratum,  red — in  a  thin  one,  olive-green.  The  acid  solutions  are  monochromatic  and 
brown. 

Preparation  in   Bulk. — To  obtain   it  in  quantity,  heat  dried  horse's  blood  with   10  parts  of 

formic  acid.     If  the  crystals  be  suspended  in  methyl  alcohol,  on  adding  iodine  and  heating  them 

„  they  dissolve   with  a  purple   color;   after   adding   bromine,  brown  ; 

and  after  passing  chlorine  gas,  green  ;  all  these  give  a  characteristic 

spectrum  [Axeii/t'ld). 

The  glacial  acetic  acid  may  be  replaced  by  oxalic  or  tartaric 
acid,  the  common  salt  by  salts  of  iodine  or  bromine;  in  the  latter 
case  similar  bromine-  or  iodine-luvmatin  is  formed  [Bikfak'i). 


20.  H>EMATOIDIN.— Virchow  discovered  this 
important  derivative  of  hemoglobin.  It  occurs  in  the 
body  wherever  blood  stagnates  outside  the  circulation, 
and   becomes   decomposed — as  when    blood    is  extra- 

Hxmatoidin  crystals.  ...  ,  .'  1         1        ■  •  i-i-/-i 

vasated  into  the  tissues — e.g.,  the  brain — in  solidified 
blood  plugs  or  thrombi ;  especially  in  veins  ;  invariably  in  the  Graafian  follicles. 
It  contains  no  iron  ( C3,,H.„;N406),  and  crystallizes  in  clino-rhombic  prisms  (Fig. 
20)  of  a  yellowish-brown  color.  It  is  soluble  in  warm  alkalies  and  chloroform. 
Very  probably  it  is  identical  with  the  bile-pigment — bilirubin.  [When  acted 
upon  by  impure  nitric  acid  (Gmelin's  reaction),  it  gives  the  same  play  of  colors 
as  bile.] 

Pathological. — In  cases  where  a  large  amount  of  blood  has  undergone  solution  within  the 
blood  vessels  (as  by  injecting  foreign  blood)  hrematoidin  crystals  have  been  found  in  the  urine. 
For  their  occurrence  in  the  urine  in  jaundice  (^  180),  and  in  the  sputum  (^  138). 

21.  (B.)  THE  COLORLESS  PROTEID  OF  HiEMOGLOBIN.— 

It  is  closely  related  to  globulin  ;  but,  while  the  Jatter  is  preci])itated  by  all  acids, 
even  by  CO,,  and  re-dissolved  on  passing  O  through  it,  the  proteid  of  hemoglobin, 
on  the  other  hand,  is  not  dissolved  after  precipitation  on  passing  through  it  a 
stream  of  O. 

As  crystals  of  hcemoglobin  can  be  decolorized  under  special  circumstances,  it  is  probable  that 
these  owe  their  crystalline  form  to  the  proteid  which  they  contain.  Landois  placed  crystals  of 
hemoglobin  along  with  alcohol  in  a  dialyser,  putting  ether  acidulated  with  sulphuric  acid  outside, 
and  thereby  obtained  colorless  crystals.     [If  frogs'  blood  be  sealed  up  on  a  microscopic  slide  along 


COMPOSITION    OF   THE    WHITE    CORPUSCLES.  69 

with   a  few  drops  of  water  for  several  days,  long,  colorless,  acicular  crystals  are  developed  in  it 
{^Stirling  and  Brito).'\ 

22.  II.  PROTEIDS  OF  THE  STROMA.— Dry  red  human  blood  cor- 
puscles contain  from  5. 10-12. 24  per  cent,  of  these  proteids,  but  little  is  known 
about  them  {y^ildeil').  One  of  them  is  globulin,  which  is  combined  with  a  body 
resembling  nuclein  {^Wooldridge),  and  traces  of  a  diastatic  ferment  {v.  WitticK). 
The  stroma  tends  to  form  masses  which  resemble  fibrin. 

L.  Brunton  found  a  body  resembling  mucin  in  the  nuclei  of  red  blood  corpuscles,  and  Miescher 
detected  nuclein  (|  250,  2). 

23.  OTHER  CONSTITUENTS  OF  RED  BLOOD  COR- 
PUSCLES.— III.  Lecithin  (0.35-0.72  per  cent.)  in  dry  blood  corpuscles 
(§  250,  2).     Cholesterin  (0.25  per  cent.)  (§  250,  III.),  no  Fats. 

Lecithin  is  regarded  as  a  glycero-phosphate  of  neurin,  in  which,  in  the  radical  of  glycero- 
phosphoric  acid,  two  atoms  of  H  are  replaced  by  two  of  the  radical  of  stearic  acid.  By  gentle  heat 
glycero-phosphoric  acid  is  split  up  into  glycerine  and  phosphoric  acid  (§  250). 

These  substances  are  obtained  by  extracting  old  stromata  or  isolated  blood  corpuscles  with  ether. 
When  the  ether  evaporates,  the  characteristic  globular  forms  ("  my elin-forms  ")  of  lecithin,  and 
crystals  of  cholesterin  are  recognized.  The  amount  of  lecithin  may  be  determined  from  the 
amount  of  phosphorus  in  the  ethereal  extract. 

IV.   Water  (681.63  pe^"  1°°° — C.  Schmidt'). 

V.  Salts  (7.28  per  1000),  chiefly  compounds  oi  potash  and  phosphoric  acid ; 
the  phosphoric  acid  is  derived  only  from  the  burned  lecithin  ;  while  the  greater 
part  of  the  sulphuric  acid  is  derived  from  the  burning  of  the  haemoglobin  in 
the  analysis. 

Analysis  of  Blood. — 1000  parts,  by  weight,  of  horse's  blood  contain — 

344.18  blood  corpuscles  (containing  about  128  per  cent,  of  solids). 
655.82  plasma  (containing  about  10  per  cent,  of  solids). 

1000  parts,  by  weight,  of  moist  blood  corpuscles  contain — 

Solids, 367.9  (pig);  400.1  (ox). 

Water, 632.1     "       599-9     " 

The  solids  are — 

Pig.  Ox. 

Hsemoglobin, , 261  280.5 

Proteids, 86.1  107 

Lecithin,  Cholesterin,  and  other  Organic  Bodies,  .    .    .  12.0  7.5 

Inorganic  salts, 8.09  4.8 

f  Potash, 5.543  0.747 

I  Magnesia, 0.158  0.017 

Including -j  Chlorine, i-504  1-635 

Phosphoric  Acid, 2.067  o-7°3 

Soda, o  2.og;^[B2e>2ge). 

[An  approximate  estimate  of  the  composition  of  human  blood  is  given  in 
the  following  table  : — 

Composition  of  Human  Blood  as  a  Whole. 

Water, 780 

Solids — of  these — 

Corpuscles, 134      1 

Serum-albumin,      "I 

Serum-globulin,      j '  | 

Fibrin  of  Clot  (?  Fibrinogen) 2.2    [-  220 

Inorganic  Salts  (of  serum), 6.0   I 

Extractives, 6.2   | 

Fatty  matters, 1.4  J 

Gases,  O,  COj,  N.] 

24.  CHEMICAL  COMPOSITION  OF  THE  WHITE  CORPUS- 
CLES.— Investigations  have  been  made  on  pus  cells,  which  closely  resemble 
colorless  blood  corpuscles.     They  contain  several  proteids  ;  alkali-albuminate,  a 


70  PREPARATION    OF    PLASMA. 

proteid  which  coagulates  at  48°  C,  an  albuminate  resembling  myosin,  paraglobu- 
lin,  peptone,  and  a  coagulating  ferment;  nuclein  in  the  nuclei  (§  250,  2),  gly- 
cogen (§252),  lecithin,  cerebrin,  cholesterin,  and  fat. 

ICO  parts,  hy  weight,  of  dry  pus,  contain  the  following  Salts : — 

Earthy  Phosphates, 0.416  Potash, 0.201 

Sodic  Phosphate, 0.606     I     Sodic  Chloride, 0.143 

25.  BLOOD  PLASMA  AND  ITS  RELATION  TO  SERUM.— The 

unaltered  tluid  in  which  the  blood  corpuscles  float  is  called  blood  plasma,  or 
liquor  sanguinis.  This  fluid,  however,  after  blood  is  withdrawn  from  the  vessels, 
rapidly  undergoes  a  change,  owing  to  the  formation  of  a  solid  fibrous  substance — 
fibrin.  After  this  occurs,  the  new  fluid  which  remains,  no  longer  coagulates  sponta- 
neously (it  is  plasma,  vii7ms  the  fibrin  factors),  and  is  called  serum.  Apart  from 
the  presence  of  the  fibrin  factors,  the  chemical  composition  of  plasma  and  serum  is 
the  same. 

[When  blood  coagulates,  Table  I  shows  w-hat  takes  place,  while  Table  II  shows  what  occurs 
when  it  is  beaten  :  — 

I. 


Coagulation. 

Blood. 
I 


Plasma.  Corpuscles. 


II. 
When  beaten. 


Blood. 
I 


Plasma.  Corpuscles. 


Serum.  Fibrin  factors.  Fibrin  factors.  Serum. 

I  I  i  I 


Blood  Clot.  Fibrin.  Deiibrinated  Blood. 

Plasma  is  a  clear,  transparent,  slightly  thickish  fluid,  which,  in  most  animals 
(rabbit,  ox,  cat,  dog),  is  almost  colorless ;  in  man  it  is  yellow,  and  in  the  horse 
citron  jellow. 

26.  PREPARATION    OF    PLASMA.— (A)  Without  Admixture.- 

Taking  advantage  of  the  fact  that  plasma,  when  cooled  to  0°  outside  the  body,  does 
not  coagulate  for  a  considerable  time,  Brilcke  prepares  the  plasma  thus  :  The  blood 
of  the  horse  (because  it  coagulates  slowly,  and  its  corpuscles  sink  rapidly  to  the  bot- 
tom) is  received,  as  it  flows  from  an  artery,  into  a  tall,  narrow  glass,  placed  in  a 
freezing  mixture,  and  cooled  to  0°.  The  blood  remains  fluid,  the  colored  cor- 
puscles subside  in  a  few  hours,  while  the  plasma  remains  above  as  a  clear  layer, 
which  can  be  removed  with  a  cooled  pipette.  If  this  plasma  be  then  passed 
through  a  cooled  filter,  it  is  robbed  of  all  its  colorless  corpuscles.  [Burdon- 
Sanderson  uses  a  vessel  consisting  of  three  compartments — the  outer  and  inner 
contain  ice,  while  the  blood  is  caught  in  the  central  compartment,  which  does  not 
exceed  half  an  inch  in  diameter.]  The  quantity  of  plasma  may  be  roughly  (but 
only  roughly)  estimated  by  using  a  tall,  graduated  measuring  glass.  If  the  plasma 
be  warmed,  it  soon  coagulates  (owing  to  the  formation  of  the  fibrin),  and  passes 
into  a  trembling  jelly.  If,  however,  it  be  beaten  with  a  glass  rod,  the  fibrin  is 
obtained  as  a  white,  stringy  mass,  adhering  to  the  rod.  The  quantity  of  fibrin  in 
a  given  volume  of  plasma  is  very  small  (p.  71),  although  it  varies  much  in  difterent 
cases. 

(B)  With  Admixture. — Blood  flowing  from  an  artery  is  caught  in  a  tall  vessel 
containing  4-  of  its  volume  of  a  concentrated  solution  of  sodic  sulphate  {Hewsoti) 
—or  in  a  25  per  cent,  solution  of  magnesic  sulphate  (t  vol.  to  4  vols,  blood — 
Simmer) — or  i  vol.  blood  with  2  vols,  of  a  4  per  cent,  solution  of  monophosphate 
of  potash  (Masia).  When  the  blood  is  mixed  with  these  fluids  and  put  in  a  cool 
place,  the  corpuscles  subside,  and  the  clear  stratum  of  plasma  mixed  with  the  salts 


COAGULATION    OF    THE    BLOOD.  71 

may  be  removed  with  a  pipette.  [The  plasma  so  obtained  is  called  "  salted 
plasma."]  If  the  salts  be  removed  by  dialysis,  coagulation  occurs  ;  or  it  maybe 
caused  by  the  addition  of  water  {J^oh.  Midler).  Blood  which  is  mixed  with  a  4 
per  cent,  solution  of  common  salt  does  not  coagulate,  so  that  it  also  may  be  used 
for  the  preparation  of  plasma.  [For  frogs'  blood  Johannes  Miiller  used  a  ^  per 
cent,  solution  of  cane  sugar,  which  permits  the  corpuscles  to  be  separated  from 
the  plasma  by  filtration.  The  plasma  mixed  with  the  sugar  coagulates  in  a  short 
time.] 

27.  FIBRIN— COAGULATION  OF  THE  BLOOD— General  Char- 
acters.— Fibrin  is  that  substance  which,  becoming  solid  in  shed  blood,  in  plasma 
and  in  lymph  causes  coagulation  of  these  fluids.  In  these  fluids,  when  left  to  them- 
selves, fibrin  is  formed,  consisting  of  innumerable,  excessively  delicate,  closely 
packed,  microscopic,  doubly  refractive  fibrils  (Fig.  7,  E).  These  fibrils  entangle  the 
blood  corpuscles  as  in  a  spider's  web,  and  form  with  them  a  jelly-like  solid  mass  called 
the  blood  clot  or  placenta  sanguinis.  At  first  the  clot  is  very  soft,  and  after 
the  first  2  to  15  minutes  a  few  fibres  may  be  found  on  its  surface ;  these  may  be 
removed  with  a  needle,  while  the  interior  of  the  clot  is  still  fluid.  The  fibres 
ultimately  extend  throughout  the  entire  mass,  which,  in  this  stage,  has  been  called 
cruor.  After  from  12  to  15  hours  the  fibrin  contracts,  or,  at  least,  shrinks  more 
and  more  closely  round  the  corpuscles,  and  a  fairly  solid,  trembling,  jelly-like  clot, 
which  can  be  cut  with  a  knife,  is  formed.  During  this  time  the  clot  takes  the 
shape  of  the  vessel  in  which  the  blood  coagulates,  and  expresses  from  its  substance 
a  fluid — the  blood  serum.  Fibrin  may  be  obtained  by  washing  away  the  cor- 
puscles from  the  clot  with  a  stream  of  water. 

Crusta  Phlogistica. — If  the  corpuscles  subside  very  rapidly,  and  if  the  blood 
coagulates  slowly,  the  upper  stratum  of  the  clot  is  not  red,  but  only  yellowish,  on 
account  of  the  absence  of  colored  corpuscles.  This  is  regularly  the  case  in  horse's 
blood,  and  in  human  blood  it  is  observed  especially  in  inflammations;  hence  this 
layer  has  been  called  crusta  phlogistica.  Such  blood  contains  more  fibrin,  and 
so  coagulates  more  slowly. 

The  crusta  is  formed  under  other  circumstances,  e.g.,  with  increased  sp.  gr.  of  the  corpuscles, 
or  diminished  sp.  gr.  of  the  plasma  (as  in  hydrsemia  and  chlorosis),  whereby  the  corpuscles  sink 
more  rapidly,  and  also  during  pregnancy.  The  taller  and  narrower  the  glass,  the  thicker  is 
the  crusta  (compare  |  41).  The  upper  end  of  the  clot,  where  there  are  few  corpuscles,  shrinks 
more,  and  is  therefore  smaller  than  the  rest  of  the  clot.  This  upper,  lighter- colored  layer  is 
called  the  "  buffy  coat ;"  but  it  gradually  passes,  both  in  size  and  color,  into  the  normal  dark- 
colored  clot.  [Sometimes  the  upper  surface  of  the  clot  is  concave  or  "  cupped."  The  older 
physicians  attached  great  importance  to  this  condition,  and  also  to  the  occurrence  of  the  buffy 
coat.] 

Defibrinated  Blood. — If  freshly-shed  blood  be  beaten  or  whipped  with  a  glass 
rod,  or  with  a  bundle  of  twigs,  fibrin  is  deposited  on  the  rod  or  twigs  in  the  form 
of  a  solid,  fibrous,  yellowish-white,  elastic  mass,  and  the  blood  which  remains  is 
called  ^''  defibrinated  blood''''  (p.  70).  [The  twigs  and  fibrin  must  be  washed  in  a 
stream  of  water  to  remove  adhering  corpuscles.] 

Coagulation  of  Plasma. — Plasma  shows  phenomena  exactly  analogous,  save 
that  the  clot  is  not  so  well  marked,  owing  to  the  absence  of  the  resisting  corpus- 
cles ;  there  is,  however,  always  a  soft  trembling  jelly  formed  when  plasma  coagu- 
lates. [In  Hewson's  experiment  on  the  blood  of  a  horse  tied  in  a  vein,  he  found 
that  the  plasma  coagulated — fibrin  being  formed,  so  that  he  showed  coagulation 
to  be  due  to  changes  in  the  plasm.a  itself  (§  29).] 

Properties  of  Fibrin. — Although  the  fibrin  appears  voluminous,  it  only 
occurs  to  the  extent  of  0.2  per  cent.  (o. i  to  0.3  per  cent.)  in  the  blood.  The 
amount  varies  considerably  in  two  samples  of  the  same  blood.  It  is  insoluble  in 
water  and  ether  ;  alcohol  shrivels  it  by  extracting  water ;  dilute  hydrochloric  acid 
(o.  I  per  cent.)  causes  it  to  swell  up  and  become  clear,  and  changes  it  into  syntonin 


72  GENERAL    TIIENOMENA   OF    COAGULATION. 

or  acid  albumin  (§  249,  III).  When  fresh,  it  has  a  grayish-yellow,  fibrous  appear- 
ance, and  is  elastic  ;  when  dried,  it  is  horny,  transparent,  brittle,  and  friable. 

When  fresh  it  dissolves  in  6-S  per  cent,  solutions  of  sodium  nitrate  or  sulphate,  in  dilute  alkalies, 
and  in  ammonia,  thus  formint;  aikali-albuminate.  Ileat  does  not  coagulate  these  solutions.  [It 
is  also  solul)le  in,  or  rather  decomposed  by,  5-10  i)er  cent,  solutions  of  neutral  salts,  f.^>;:,  NaCl, 
yielding  two  fibro-globulins  (  G'r<-c-n).'\  llydric  peroxide  is  rapidly  decomposed  by  fibrin  into  water 
and  O  {VViiiinn/ ).  Fibrin  which  has  been  exposed  to  the  air  for  a  long  lime  is  no  longer  soluble 
in  solution  of  potassic  nitrate,  but  in  neurin  I^Maiilhner).  During  putrefaction  it  passes  into  solu- 
tion, albumin  being  formed.  I'ibrin  contains, entangled  in  it,  ferric, calcic,  and  magnesic  phosphates, 
and  calcium  sulphate  whose  origin  is  unknown. 

Time  for  Coagulation. — The  first  appearance  of  a  coagulum  occurs  in  man's  blood  after  3 
minutes  45  seconds,  in  woman's  blood  after  2  min.  20  sec.  (yV.  A'asse).  Age  has  no  effect;  with- 
drawal of  food  accelerates  coagulation  (  //.  l'ic'7-orJf). 

28.  GENERAL  PHENOMENA  OF  COAGULATION.— I.  Blood 
in  direct  contact  with  living  unaltered  blood  vessels  does  not  coagu- 
late. [Hewson  (1772)  found  that  when  he  tied  the  jugular  vein  of  a  horse  in 
two  places,  and  e.xcised  it,  the  blood  did  not  coagulate  for  a  long  time.]  Briicke 
filled  tlie  heart  of  a  tortoise  with  blood  which  had  stood  15  minutes  e.xposed  to 
the  air  at  0°,  and  kept  it  in  a  moist  chamber ;  at  0°  C.  the  blood  was  still  unco- 
agulated  in  the  contracting  heart  after  eight  days.  Blood  in  a  contracting  frog's 
heart  preserved  under  mercury  does  not  coagulate.  If  the  wall  of  the  vessel  be 
altered  by  pathological  processes  (^.^.,  if  the  intima  becomes  rough  and  uneven, 
or  undergoes  inflammatory  change),  coagulation  is  apt  to  occur  at  these  places. 
Blood  rapidly  coagulates  in  a  dead  heart,  or  in  blood  vessels  (but  not  in  capillaries) 
or  other  canals  (e.g.,  the  ureter).  If  blood  stagnates  in  a  living  vessel,  coagu- 
lation begins  in  the  central  axis,  because  here  there  is  no  contact  with  the  wall  of 
the  living  blood  vessel. 

II.  Conditions  which  Hinder  or  Delay  Coagulation. — {a)  The  addition 
of  small  quantities  o(  alka/ics,  ammonia,  or  concentrated  solutions  of  neutral  salts 
of  the  alkalies  a//^/ <?rzr///i- (alkaline  chlorides,  sulphates,  phosphates,  nitrates,  carbo- 
nates). Magnesic  sulphate  acts  most  favorably  in  delaying  coagulation  (i  vol. 
solution  of  28  per  cent,  to  3I0  vols,  blood  of  the  horse). 

(/;)  Precipitation  of  the  fibrino-plastin  by  adding  weak  acids,  or  CO2. 

By  the  addition  of  acetic  acid  until  the  reaction  is  acid,  coagulation  is  coni])letely  arrested.  A 
large  amount  of  CO.^  delays  it,  hence  venous  blood  coagulates  more  slowly  than  arterial,  and  the 
blood  of  suffocated  persons  remains  fluid  for  the  same  reason. 

(<r)  The  addition  of  egg-albtanin,  syrup,  glycerine,  and  much  water.  If  unco- 
agulated  blood  be  brought  into  contact  with  a  layer  of  already-formed  fibrin, 
coagulation  occurs  later. 

(</)  By  cold  (0°  C.)  coagulation  may  be  delayed  for  one  hour.  If  blood  is 
frozen  at  once,  after  thawing  it  is  still  fluid,  and  then  coagulates  {^Heivson). 
When  shed  blood  is  under  Jiigh  pressure  it  coagulates  slowly. 

{/)  Blood  of  embryo  fowls  does  not  coagulate  before  the  twelfth  or  fourteenth 
day  of  incubation  {Boll)  ;  that  of  the  hepatic  vein  very  slightly ;  menstrual  blood 
shows  little  tendency  to  coagulate  when  alkaline  mucus  from  the  vagina  is  mixed 
with  it.  If  it  be  rapidly  discharged,  it  coagulates  in  masses.  Fcetal  blood  at  the 
moment  of  birth  coagulates  soon. 

(/)  Blood  rich  in  fibrin  from  inflamed  parts  coagulates  slowly,  but  the  clot  so 
formed  is  firm. 

{g  )  [P>lood  coagulates  more  slowly  in  a  smooth  than  a  rough  vessel,  and  also  in 
a  shallow  vessel  than  in  a  deep  one.] 

Hamophilia.— A  very  slight  scratch  in  some  persons  may  cause  very  free  bleeding.  These 
persons  are  called  colloquially  "bleeders,"  and  are  said  to  have  haemophilia  or  the  hemorrhagic 
diathesis.  In  "bleeders"  coagulation  seems  not  to  take  place,  owing  to  a  want  of  the  substances 
producing  fibrin ;  hence,  in  these  cases,  wounds  of  vessels  are  not  plugged  with  fibrin.  [A  tendency 
to  hemorrhage  occurs  in  scurvy,  purpura,  in  some  infectious  diseases,  such  as  typhus,  plague,  yellow 
fever,  and  in  poisoning  with  phosphorus.] 


GENERAL    PHENOMENA   OF    COAGULATION.  73 

Injection  of  Peptones. — Albertoni  observed  that  if  tryptic  pancreas  ferment  (dissolved  in 
glycerine)  be  injected  into  the  blood  of  an  animal,  the  blood  does  not  coagulate.  Schmidt-Miilheim 
found  that  after  the  injection  oi pni-e  peptone  into  the  blood  (0.5  gram  per  kilo.)  of  a  dog,  the  blood 
lost  its  power  of  coagulating.  [This  occurs  in  the  dog,  but  not  in  the  rabbit.  Peptonized  blood 
coagulates  when  it  is  treated  with  COj  or  water.  It  appears,  however,  that  it  is  not  the  peptone 
which  prevents  the  coagulation,  but  the  albumoses  adhering  to  it  which  do  so.]  A  substance  is 
formed  in  the  plasma,  which  prevents  coagulation,  but  which  is  precipitated  by  COj.  Lymph 
behaves  similarly  [Faiio).  After  peptones  are  injected,  there  is  a  great  solution  of  leucocytes  in  the 
blood  (v.  Samson- Himmehtjenia).  The  secretion  of  the  mouth  of  the  medicinal  leech  [although 
its  action  is  not  due  to  a  ferment  {Hayc7-afi)'\  and  snake  poison  also  prevent  coagulation  (  Wall). 
[Diastatic  ferment  also  prevents  coagulation  [Salvioli).'] 

III.  Coagulation  is  accelerated — (a)  By  contact  with  foreign  Sub- 
stances of  all  kinds,  but  only  when  the  blood  adheres  to  them,  hence,  threads 
or  needles  introduced  into  arteries  are  rapidly  covered  with  fibrin.  Blood  does 
not  coagulate  in  contact  with  bodies  covered  with  fat  or  vaseline  {^Freund').  Even 
the  introduction  of  air  bubbles  into  the  circulation  or  the  passage  of  indifferent 
gases,  N  or  H,  through  blood,  accelerates  it.  The  pathologically  altered  wall  of 
a  vessel  acts  like  a  foreign  body.  Blood  shed  from  an  artery  rapidly  coagulates 
■on  the  walls  of  vessels,  on  the  surfaces  exposed  freely  to  air,  and  on  the  rods  or 
twigs  used  to  beat  it. 

(Jb)  The  products  of  the  retrogressive  metabolism  of  proteids  (uric  acid,  glycin, 
leucin,  taurin,  kreatin,  sarkin,  but  not  urea)  favor  coagulation  by  increased  ferment 
formation  ;  but  if  they  are  added  in  excess,  they  retard  the  process. 

From  a  watery  extract  of  the  testis  or  thymus,  on  the  addition  of  acetic  acid,  is  precipitated  a 
substance  which  is  soluble  in  sodic  carbonate.  It  is  a  mixture  of  lecithin  and  albumin,  and  when 
it  is  injected  into  the  blood  stream  it  causes  almost  instantaneous  death  by  intravascular  coagulation 
(  Wooldridge) . 

(c)  During  rapid  hemorrhage,  the  last  portions  of  blood  coagulate  most  rapidly 
(^Holzmami). 

{d)  Heating  the  blood  from  39°  to  55°  C.  {Heiosoii). 

{e)  Agitation  of  the  blood  {HewsoJi  and  Hunter'). 

[(_/)  The  addition  of  a  small  quantity  of  water. 

\g)  A  watery  condition  of  the  blood.     The  clot  is  small  and  soft. 

{h)  Contact  with  oxygen.] 

IV.  Rapidity  of  Coagulation. — Among  vertebrates,  the  blood  of  birds 
(especially  of  the  pigeon)  coagulates  almost  momentarily;  in  cold-blooded  animals 
coagulation  occurs  much  more  slowly,  while  man:imals  stand  midway  between  the 
two. 

[The  blood  of  a  fowl  begins  to  coagulate  in  J^  to  i  y'^  minute ;  pig,  sheep,  rabbit,  in.  }4  to  i]4 
minute;  dog,  l  to  3  minutes;  horse  and  ox,  5  to  13  mmutes;  man,  3  to  4  minutes;  solidification 
is  completed  in  9  to  1 1  minutes  [A^asse).^  The  blood  of  invertebrates,  which  is  usually  colorless 
when  it  is  oxidized  (|  32),  forms  a  soft,  whitish  clot  of  fibrin.  Even  in  lymph  and  chyle,  a  small 
soft  clot  is  formed. 

V.  When  coagulation  occurs,  the  aggregate  condition  of  the  fibrin  factors  is 
altered,  so  that  heat  must  be  set  free  {Valentin,  1844). 

VI.  In  blood  shed  from  an  artery,  the  degree  of  alkalinity  diminishes  from 
the  time  of  its  being  shed  until  coagulation  is  completed  {Pflilger  and  Zuntz). 
This  is  probably  due  to  a  decomposition  in  the  blood,  whereby  an  acid  is  devel- 
oped, which  diminishes  the  alkalinity  (p.  72). 

VII.  During  coagulation  there  is  a  diminution  of  the  O  in  the  blood, 
although  a  similar  decrease  also  occurs  in  non-coagulated  blood.  Traces  of  ain- 
nwnia  are  also  given  off,  which  Richardson  erroneously  supposed  to  be  the  cause 
of  the  coagulation  of  the  blood. 

[This  is  refuted — (i)  by  the  fact  that  blood,  when  collected  under  mercury  (whereby  no  escape 
of  ammonia  is  possible),  also  coagulates;  and  (2)  by  the  following  experiment  of  Lister:  He 
placed  two  ligatures  on  a  vein  containing  blood,  moistening  one-half  of  the  outer  surface  of  the 


74 


CAUSE    OF   COAGULATION    OF    BLOOD. 


FlO.    21. 


Vein  of  horse  tied  be- 
tween two  ligatures. 
P.    plasma  ;    W  C, 


vein  with  ammonia,  leaving  the  other  half  intact.  The  blood  coagulated  in  the  first  half,  and  not 
in  the  other,  owing  to  the  properties  of  the  wall  of  the  vein  of  the  former  being  altered.  Neither 
the  decrea<;e  of  O  nor  the  evolution  of  ammonia  seems  to  have  any  causal  connection  with  the 
formation  of  fibrin.] 

Pathological. — When  the  blood  coagulates  within  the  vessels  during  life,  the  process  is  called 
thrombosis,  and  the  coagulum  or  plug  so  formed  is  termed  a  thrombus.  When  a  clot  of  blood 
or  other  bodv  is  carried  by  the  blood  stream  to  another  part  of  the  vascular  system  where  it  blocks 
up  a  vessel,  the  plug  is  called  an  embolus,  and  the  result  embolism. 

29.  CAUSE  OF  THE  COAGULATION  OF  BLOOD.— [Hewson's  Experiments 
(1--2.) Hewson  tied  the  jugular  vein  of  a  horse  between  two  ligatures,  removed  it,  and  then  sus- 
pended it  by  one  end  (Fig.  21).  He  found  that  the  blood  remained  fluid  for 
a  long  time  (48  hours),  the  red  corpuscles  sank  (RC)  and  left  a  clear  layer  of 
plasma  on  the  surface  (I*).  On  drawing  off  some  of  this  clear  plasma  it  co- 
agulated, thus  proving  coagulation  to  be  due  to  changes  in  the  plasma.  Lister 
repeated  this  experiment,  and  found  that,  even  if  the  upper  end  of  the  tube 
be  opened  and  the  blood  freely  exposed  to  the  air,  coagulation  is  but  slightly 
hastened.  He  showed  that  the  blood  might  be  poured  from  one  vein  into 
another,  just  as  one  might  pour  fluid  from  one  test  tube  into  another.  In  this 
case  there  were  two  test  tubes,  i.e.,  the  veins — and  although  the  blood,  on 
being  poured  from  the  one  to  the  other,  came  into  contact  with  the  air,  it  did 
not  coagulate.  Hewson,  however,  found  that  blood  poured  from  the  vein 
into  a  glass  vessel  coagulated,  so  that,  in  his  opinion,  the  blood  vessels  exerted 
a  restraining  influence  on  coagulation.  By  cooling  the  blood  and  preventing  it 
from  coagulating,  he  proved  that  coagulation  was  not  due  to  the  loss  of  heat. 
Nor  could  it  be  a  vital  act,  as  sodic  sulphate  or  other  neutral  salt  prevented 
coagulation  indefinitely,  but  coagulation  took  place  when  the  blood  was 
diluted  with  water.] 

[Buchanan's  Researches. — The  serous  sacs  of  the  body  contain  a  fluid 
which  in  some  respects  closely  resembles  lymph.      The  pericardial  fluid  of 
some  animals  coagulates   spontaneously  {e.g.,  in  the  rabbit,  ox,  horse,  and 
sheep)  if  the  fluid  be  removed  immediately  after  death.     If  this  be  not  done 
white.and  R C,  red    till  sez-eral  hours  after  death  the  fluid  does  not  coagulate  spontaneously.     The 
corpiLscles.  fluid  of  the  tunica  vaginalis  of  the  testis  sometimes  accumulates  to  a  great 

extent,  and  constitutes  hydrocele,  but  this  fluid  shows  no  tendency  to  coagulate 
spontaneously.  Andrew  Buchanan  found,  however,  that  if  to  the  fluid  of  ascites,  pleuritic  fluid,  or 
hydrocele  fluid,  there  be  added  clear  blood  serum,  then  coagulation  takes  place,  i.  e.  two  fluids — 
neither  of  which  shows  any  tendency  l>y  itself  to  coagulate — form  a  clot  when  they  are  mixed 
(1831).  He  also  found,  that  if  "washed  blood  clot"  (which  consists  of  a  mixture  of  fibrin  and 
colorless  corpuscles)  be  added  to  hydrocele  fluid,  coagulation  occurred.  He  compared  the  action 
of  washed  blood  clot  to  the  action  of  rennet  in  coagulating  milk,  and  he  imagined  the  agents  which 
determined  the  coagulation  to  he  colorless  corpuscles.  Thus,  the  bufi"y  coat  of  horses'  blood  is  a 
IX)werfuI  agent,  and  it  contains  numerous  colorless  corpuscles.  He  finally  concluded  that  some 
constituent  in  the  plasma,  to  which  he  gave  the  name  of  a  "  soluble  fibrin,"  is  acted  upon  by  the 
colorless  corpuscles  and  converted  into  fibrin.  The  soluble  fibrin  of  Buchanan  is  comparable  to  the 
fibrinogen  in  Hammarsten's  theory.     Buchanan,  however,  did  not  separate  the  substance.] 

[Denis's  Plasmine  (1859). — Denis  mixed  uncoagulated  blood  with  a  saturated  solution  of 
sodic  sulphate,  and  allowed  the  corpuscles  to  subside.  The  salted  plasma  thus  obtained  he  pre- 
cipitated with  sodic  chloride.  The  precipitate,  when  washed  with  a  saturated  solution  of  sodic 
chloride,  he  called  plasmine.  If  plasmine  be  mixed  with  water,  it  coagulates  spontaneously, 
resulting  in  the  formation  of  fibrin,  while  another  proteid  remains  in  solution.  According  to  the 
view  of  Denis,  fibrin  is  produced  by  the  splitting  up  of  plasmine  into  two  bodies — fibrin  and  a 
soluble  proteid.] 

[A.  Schmidt's  Researches  (1S61). — This  observer  re-discovered  the  chief  facts  already  known 
to  Buchanan,  viz.,  that  some  fluids  which  do  not  coagulate  spontaneously,  clot  when  mixed  with 
other  fluids  which  show  no  tendency  to  coagulate  spontaneously,  ^.^.,  hydrocele  fluid  and  blood 
serum.  He  isolated  from  these  fluids  the  bodies  described  as  fibrinogen  and  fibrino-plastin.  The 
bodies  so  obtained  were  not  pure,  but  Schmidt  supposed  that  the  formation  of  fibrin  was  due  to  the 
interaction  of  these  two  proteids.  The  reason  hydrocele  fluid  does  not  coagulate,  he  says,  is  that 
it  contains  fibrinogen  and  no  fibrino  plastin,  while  blood  serum  contains  the  latter,  but  not  the 
former.  Schmidt  afterwards  discovered  that  these  two  substances  may  be  present  in  a  fluid,  and  yet 
coagulation  may  not  occur  {e.g.,  occasionally  in  hydrocele  fluid).  He  supposed,  therefore,  that 
blood  or  blood  serum  contained  some  other  constituent  necessary  for  coagulation.  This  he  after- 
wards isolated  in  an  impure  condition  and  called  fibrin-ferment.'] 

A.  Schmidt's  theory  is  that  fibrin  is  formed  by  the  coming  together  of  two 
proteid  substances  which  occur  dissolved  in  the  plasma,  viz.  :      (i)  fibrinogen, 


THE    FIBRIN    FACTORS.  75 

/.  e.,  the  substance  which  yields  the  chief  mass  of  the  fibrin,  and  (2)  fibrino- 
plastic  substance  or  fibrino-plastin  (serum-globulin  or  paraglobulin,  §  32).  In 
order  to  determine  the  coagulation  a  ferment  seems  to  be  necessary,  and  this  is 
supplied  by  (3)  the  fibrin-ferment. 

1.  Properties. — Fibrinogen  and  fibrino-plastin  belong  to  the  group  of  pro- 
teids  called  globulins,  i.e.,  they  are  insoluble  in  pure  water,  but  are  soluble  in 
dilute  solutions  of  common  salt  (§  249),  and  are  not  distinguished  from  each 
other  by  well-marked  chemical  characters.     Still  they  differ,  as  follows: — 

Fibrino-plastin  is  more  easily  precipitated  from  its  solutions  than  fibrinogen. 
It  is  more  readily  redissolved  when  once  it  is  precipitated.  It  forms  when  pre- 
cipitated a  very  light  granular  powder. 

Fibrinogen  adheres  as  a  sticky  deposit  to  the  side  of  the  vessel.  It  coagulates 
at  56°  C. 

On  account  of  their  great  similarity,  both  substances  are  not  usually  prepared 
from  blood  plasma.  Fibrinogen  is  prepared  from  serous  transudations  (pericardial, 
abdominal,  or  pleuritic  fluid,  or  the  fluid  of  hydrocele),  which  contain  no  fibrino- 
plastin.  Fibri7io-plastin  is  most  readily  prepared  from  serum,  in  which  there  is 
still  plenty  of  fibrino-plastin,  but  no  fibrinogen. 

2.  Preparation  of  Fibrino-plastin,  Serum-globulin,  or  Paraglobulin. 
— {a)  Dilute  blood  serum  with  twelve  times  its  volume  of  ice-cold  water,  and 
almost  neutralize  it  with  acetic  acid  [add  4  drops  of  a  25  per  cent,  solution  of 
acetic  acid  to  every  120  c.  c.  of  diluted  serum]  ;  or  (J?)  pass  a  stream  of  carbon 
dioxide  through  the  diluted  serum,  which  soon  becomes  turbid ;  after  a  time  a  fine 
white  powder,  copious  and  granular,  is  precipitated. 

[(<;)  Method  of  Hammarsten. — All  the  fibrino-plastin  in  serum  is  not  pre- 
cipitated either  by  adding  acetic  acid  or  by  COj.  Hammarsten  found,  however, 
that  if  crystals  of  magnesium  sulphate  be  added  to  complete  saturation,  it  precipi- 
tates the  whole  of  the  serum-globulin,  but  does  not  precipitate  serum-albumin  ; 
serum-globulin  is  more  abundant  than  serum-albumin  in  the  serum  of  the  ox  and 
horse,  while  in  man  and  the  rabbit  the  reverse  obtains ;  (compare  §  32).] 

Schmidt  found  that  100  c.c.  of  the  serum  of  ox  blood  yielded  0.7  to  0.8  grm.;  horse's  serum, 
0.3  to  0.56  grm.  of  dry  fibrino-plastin.  Fibrino-plastin  occurs  not  only  in  serum,  but  also  in  red 
blood  corpuscles,  in  the  fluids  of  connective  tissue,  and  in  the  juices  of  the  cornea. 

3.  Preparation  of  Fibrinogen. — This  is  best  prepared  from  hydrocele 
fluid,  although  it  may  also  be  obtained  from  the  fluids  of  serous  cavities,  e.g.,  the 
pleura,  pericardium,  or  peritoneum.  It  does  not  exist  in  blood  serum,  although 
it  does  exist  in  blood  plasma,  lymph,  and  chyle,  from  which  it  may  be  obtained 
by  a  stream  of  CO2,  after  the  paraglobulin  is  precipitated,  {ci)  Dilute  hydrocele 
fluid  with  ten  to  fifteen  times  its  volume  of  water,  and  pass  a  stream  of  CO2  through 
it  for  a  longtime,  {b)  Add  powdered  conwion  salt  to  saturation  to  a  serous  trans- 
udation, when  a  sticky,  glutinous  (not  very  abundant)  precipitate  of  fibrinogen  is 
obtained. 

[Hammarsten  and  Eichwald  find  that,  although  paraglobulin  and  fibrinogen  are  soluble  in  solu- 
tions of  common  salt  (containing  5  to  8  per  cent,  of  the  salt),  a  saline  solution  of  12  to  16  per 
cent,  is  required  to  precipitate  the  fibrinogen,  leaving  still  in  solution  paraglobulin,  which  is  not 
precipitated  until  the  amount  of  salt  exceeds  20  per  cent.] 

Properties  of  the  Fibrin  Factors.— They  are  insoluble  in  pure  water,  but 
dissolve  in  water  containing  O  in  solution.  Both  are  soluble  in  very  dilute 
alkalies,  e.  g.,  caustic  soda,  and  are  precipitated  from  this  solution  by  CO2.  They 
are  soluble  in  dilute  common  salt — like  all  globulins — but  if  a  certain  amount  of 
common  salt  be  added  in  excess,  they  are  precipitated.  Very  dilute  hydrochloric 
acid  dissolves  them,  but  after  several  hours  they  become  changed  into  a  body 
resembling  syntonin  or  acid  albumin  (§  249,  III.).  Fibrinogen  held  in  solution 
by  common  salt  coagulates  at  52°  to  55°  C.     [Fredericq  finds   that  fibrinogen 


76  THE    FIBRIN    FACTORS. 

exists  as  such  in  the  plasma  ;  it  coagulates  at  56°  C,  and  the  plasma  thereafter  is 
uncoagulable.] 

4.  Preparation  of  the  Fibrin-Ferment. — {a)  Mix  blood  serum  (ox)  with 
twenty  times  its  volume  of  strong  alcohol,  and  alter  one  month  filter  off  the 
deposit  thereby  i)roduced.  The  deposit  on  the  filter  consists  of  coagulated  insolu- 
ble albumin  and  the  ferment  ;  dry  it  carefully  over  sulpiiuric  acid,  and  reduce  to 
a  powder.  Triturate  i  gram  of  the  powder  with  65  c.c.  of  water  for  ten  minutes, 
and  filter.  The  ferment  is  dissolved  by  the  water,  and  passes  through  the  filter, 
while  the  coagulated  albumin  remains  behind  (Sc/uniW/). 

[(/')  Gamgee's  Method. — Buchanan's  "washed  blood  clot"  (p.  74)  is  digested  in  an  8  per 
cent,  solution  of  common  salt.  The  solution  so  obtained  possesses  in  an  intense  degree  the  proper- 
ties of  Schmidt's  fibnn- ferment.] 

In  the  preparation  of  fibrino-plastin,  the  ferment  is  carried  down  with  it  mechanically.  The 
ferment  seems  to  be  formed  first  in  fluids  outside  tlie  body,  very  probably  by  the  solution  of  the 
colorless  corpuscles.  More  ferment  is  formed  in  the  blood  the  longer  the  interval  between  its  being 
shed  and  its  coagulation.  It  is  destroyed  at  70°  C.  Blood  flowing  directly  from  an  artery  into 
alcohol  contains  no  ferment.  It  is  also  formed  in  other  protoplasmic  parts  [Raiischenbach),  e.g.,  in 
dead  muscle,  brain,  suprarenal  capsule,  spermatozoa,  testicle  [Foa  and  Pe/lacani),  and  in  vegetable 
micro  organisms  [^.  f^.,  yeast]  and  protozoa  (^Grohiiiann)  [so  that  it  would  seem  to  be  a  general 
product  of  protoplasm.  As  the  ferment  does  not  pre- exist  in  colorless  blood  corpuscles,  it  seems 
to  be  formed  from  some  mother  substance  in  them,  the  blood  plasma  itself  decomposing  this  sub- 
stance.] 

Coagulation  Experiments. — According  to  A.  Schmidt,  if  pure  solutions  of 
(i;  fibrinogen,  (2)  fibrino-plastin,  and  (3)  fibrin-ferment  be  mixed,  fibrin  is 
formed.  The  process  goes  on  best  at  the  temperature  of  the  body ;  it  is  delayed 
at  0°  ;  and  the  ferment  is  destroyed  at  the  boiling  point.  The  presence  of  O 
seems  necessary  for  coagulation.  The  amount  of  the  ferment  appears  to  be  imma- 
terial ;  large  quantities  produce  more  rapid  coagulation,  but  the  amount  of  fibrin 
formed  is  not  greater. 

[Foa  and  Pellacani  find  that  a  filtered  watery  extract  of  fresh  brain,  capsule  of  the  kidneys,  testes, 
and  some  other  tissues,  when  injected  into  the  blood  vessels  of  a  rabbit,  causes  coagulation  of  the 
blood  in  the  jiulmonary  circulation  and  the  heart,  death  being  caused  by  the  action  of  a  substance 
identical  with  the  fibrin-ferment.] 

The  amount  of  salts  present  has  a  remarkable  relation  to  coagulation.  Solu- 
tions of  the  fibrin  factors  deprived  of  salts,  and  redissolved  in  very  dilute  caustic 
soda,  when  mixed,  do  not  coagulate  until  sufficient  NaCl  be  added  to  make  a  i 
per  cent,  solution  of  this  salt  {Schmidt).  [Green  finds  that  calcium  sulphate 
brings  about  coagulation  in  plasma  which  shows  little  or  no  tendency  to  clot, 
while  coagulation  in  its  absence  is  almost  or  quite  prevented.] 

When  blood  or  blood  plasma  coagulates,  all  the  fibrinogen  is  used  up,  so  that 
the  serum  contains  only  fibrino-plastin  and  fibrin-ferment ;  hence,  the  addition  of 
hydrocele  fluid  (which  contains  fibrinogen)  to  serum  causes  coagulation. 

[Hammarsten's  Theory. — Hammarsten's  researches  led  him  to  believe  that 
fibrino-plastin  is  quite  unnecessary  for  coagulation.  According  to  him,  fibrin  is 
formed  from  one  body,  \\z.,  fibrinogen,  which  is  present  in  plasma  when  it  is  acted 
upon  by  \.\\t  fibrin-fermetit ;  the  latter,  however,  has  not  been  obtained  in  a  pure 
state.  Neither  he  nor  Schmidt  asserts  that  this  body  is  of  the  nature  of  a  ferment, 
although  they  use  the  term  for  convenience.  It  is  quite  certain  that  fibrin  may 
be  formed  when  no  fibrino-plastin  is  present,  coagulation  being  caused  by  the 
addition  of  calcic  chloride  or  casein  prepared  in  a  special  way.  But,  whether  one 
or  two  proteids  be  required,  in  all  cases  it  is  clear  that  a  certain  quantity  of  salts, 
especially  of  NaCl,  is  necessary.] 

[The  main  drift  of  the  foregoing  evidence  points  to  the  presence  of  one  proteid 
—fibrinogen~\n  the  plasma,  which  under  certain  circumstances  yields  fibrin.  In 
shed  blood  this  act  seems  to  be  determined  by  a  ferment,  perhaps  derived  from 
the  disintegration  of  colorless  corpuscles.] 


SOURCE    OF    THE    FIBRIN    FACTORS.  77 

[Theory  of  Wooldridge. — Wooldridge  attributes  great  importance  to  lecithin.  In  shed  blood 
the  coagulation  is  brought  about  by  the  interaction  of  the  plasma  and  the  colorless  corpuscles.  If 
lecithin  (which  is  present  in  considerable  amount  in  the  colorless  corpuscles)  diffuses  into  the  blood, 
coagulation  takes  place.  When  peptone  is  injected  into  the  blood  of  the  dog,  the  blood  does  not 
clot ;  this  is  due,  according  to  Wooldridge,  to  the  peptone  "  preventing  the  interaction  of  leucocytes 
and  plasma."  If,  however,  the  corpuscular  elements  are  removed  by  the  centrifugal  machine,  the 
peptone  plasma  can  be  made  to  clot.  He  also  believes  that  fibrin-ferment  does  not  pre-exist  in 
normal  plasma,  but  that  "  it  may  make  its  appearance  in  that  plasma  in  the  absence  of  all  cellular 
elements,  and  must  therefore  come  from  some  constituent  or  constituents  of  the  plasma  itself."] 

30.  SOURCE  OF  THE  FIBRIN  FACTORS.— Al.  Schmidt  maintains 
that  all  the  three  substances  out  of  which  fibrin  is  said  to  be  formed,  arise  from 
the  breaking  up  of  colorless  blood  corpuscles.  In  the  blood  of  man  and  mammals, 
fibrinogen  exists  dissolved  in  the  circulating  blood  as  a  dissolution  product  of  the 
retrogressive  changes  of  the  white  corpuscles.  Plasma  contains  dissolved  fibrino- 
gen and  serum-albumin.  The  circulating  blood  is  very  rich  in  colorless  blood 
corpuscles,  much  richer,  indeed,  than  was  formerly  supposed.  As  soon  as  blood 
is  shed  from  an  artery,  enormous  numbers  of  the  colorless  corpuscles  are  dissolved 
— according  to  Al.  Schmidt  71.7  per  cent,  (horse).  First  the  body  of  the  cell 
disappears,  and  then  the  nucleus.  The  products  of  their  dissolution  are  dissolved 
in  the  plasma,  and  one  of  these  products  vi  fibrino-plastin.  At  the  same  time  the 
fibrin-ferment  is  also  produced,  so  that  it  would  seem  not  to  exist  in  the  intact 
blood  corpuscles.  Fibrino-plastin  and  fibrin-ferment  are  also  produced  by  the 
"  transitio?i  forms  "  of  blood  corpuscles,  t.  e.,  those  forms  which  are  intermediate 
between  the  red  and  the  white  corpuscles.  They  seem  to  break  up  immediately 
after  blood  is  shed.  The  blood  plates  (p.  57)  are  also  probably  sources  of  these 
substances. 

In  amphibians  and  birds  the  red  nucleated  corpuscles  rapidly  break  up  after  blood  is  shed,  and 
yield  the  substance  or  substances  which  form  fibrin.  Al.  Schmidt  convinced  himself  that  in  these 
animals  fibrinogen  is  originally  a  constituent  of  the  blood  corpuscles. 

It  is  clear,  therefore,  according  to  Schmidt's  view,  that  as  soon  as  the  blood 
corpuscles,  white  or  red,  are  dissolved,  the  fibrin  factors  pass  into  solution,  and 
the  formation  of  fibrin  by  the  interaction  of  the  three  substances  will  ensue. 

If  a  large  number  of  leucocytes  be  introduced  into  the  circulation  of  an  animal, 
the  leucocytes  are  dissolved  in  great  numbers  in  the  blood,  so  that  death  takes 
place  by  diffuse  coagulation.  Should  the  animal  survive  the  immediate  danger 
of  death,  the  blood,  owing  to  the  want  of  leucocytes,  is  completely  incapable  of 
coagulating  i^Groth). 

[And.  Buchanan  thought  that  the  potential  element  of  his  "  washed  bloo'd  clot"  resided  in  the 
colorless  corpuscles,  "  primary  cells  or  vesicles."  He,  like  Schmidt,  found  that  the  buffy  coat  of 
horses'  blood,  which  is  very  rich  in  white  corpuscles,  produced  coagulation  rapidly.  Buchanan  com- 
pared the  action  of  his  washed  clot  to  that  of  rennet  in  coagulating  milk.] 

Pathological. — Al.  Schmidt  and  his  pupils  have  shown  that  some  ferment,  probably  derived 
from  the  dissolution  of  colorless  corpuscles,  is  found  in  circulating  blood,  and  that  it  is  more  abund- 
ant in  venous  than  in  arterial  blood,  while  it  is  most  abundant  in  shed  blood.  It  is  specially 
remarkable  that  in  septic  fever  the  amount  of  ferment  in  blood  may  increase  to  such  an  extent  as  to 
permit  the  occurrence  of  spontaneous  coagulation  (thrombosis),  which  may  even  produce  death 
(Ai-n.  K'dhler).  In  febrile  cases  generally,  the  amount  of  ferment  is  somewhat  more  abundant 
\Edelberg  and  B irk).  After  the  injection  of  ichor  into  the  blood  an  enormous  number  of  colorless 
corpuscles  are  dissolved  [F.  Hoff/nann).  The  injection  of  peptone,  Hb,  and  to  a  less  degree  of 
distilled  water,  is  followed  by  dissolution  of  numerous  leucocytes. 

There  are  changes  in  the  blood,  constituting  true  blood  diseases,  in  which  the  physiological 
metabolism  of  the  colorless  corpuscles  is  enormously  increased,  so  that  the  metabolic  products 
accumulate  in  the  blood  {Alex.  Schmidt).  The  result  of  this  is  spontaneous  coagulation  within  the 
circulatory  system,  and  death  even  may  occur;  there  is  always  an  increase  of  temperature.  After 
such  a  condition,  the  coagulability  of  the  blood  is  diminished. 

31.  FORMATION  OF  FIBRIN. — After  several  observers  had  shown  that  the  red  blood  cor- 
puscles (bird,  horse,  frog)  participate  in  the  production  of  fibrin,  Landois  observed,  in  1874,  under 
the  microscope,  that  the  stromata  of  the  red  blood  corpuscles  of  mammals  passed  into  fibrin.     If  a 


78  COMTOSITION    OF    PLASMA    AND    SERUM. 

drop  of  defibrinated  rabbit's  blood  be  placed  in  serum  of  frog's  blood,  without  mixing  them,  the 
red  corpuscles  can  be  seen  collecting  together ;  their  surfaces  are  sticky,  and  they  can  only  be 
separated  by  a  certain  pressure  on  the  cover-glass,  whereby  some  of  the  now  spherical  corpuscles 
are  drawn  out  into  threads.  The  corpuscles  soon  become  spherical,  and  those  at  the  margin 
allow  the  hamoglobin  to  escape,  the  decolorizalion  progresses,  from  the  margin  inward,  until  at 
last  there  remain  masses  of  stroma  adhering  together.  The  stroma  substance  is  very  sticky,  but 
soon  the  cell  contours  disappear,  and  the  stromata  adhere  and  form  (hie  fibres.  Thus  (according 
to  Landois)  the  formation  of  fibrin  from  red  blood  corpuscles  can  be  traced  step  by  step.  The  red 
corpuscles  of  man  and  animals,  when  dissolved  in  the  serum  of  other  animals,  show  much  the 
same  phenomena. 

Stroma-Fibrin  and  Plasma-Fibrin. — Landois  calls  fibrin  formed  direct  from  stroma,  stromn- 
fibrin  .  fibrin  formed  in  the  usual  way  plasma-fibrin.  The  stroma  fibrin  is  closely  related  chemi- 
cally to  stroma  itself ;  as  yet,  however,  the  two  kinds  of  fibrin  have  not  been  sharply  distinguished 
chemically.  Substances  which  rapidly  dissolve  red  corpuscles  cause  extensive  coagulation,^.^., 
injection  of  bile  or  bile  salts,  or  lake-colored  blood,  into  arterjes.  After  the  injection  of  foreign 
blood  the  newly-injected  blood  often  breaks  up  in  the  blood  vessels  of  the  recipient,  while  the  finer 
vessels  are  frequently  found  plugged  with  small  thrombi  (§  102). 

Coagulable  Fluids. — With  regard  to  coagulability,  fluids  containing  proteids 
may  be  classified  thus:  — 

(i)  Those  that  coagtilaie  spontaneously,  i.  e.,  blood,  lymph,  chyle. 

(2)  Those  capable  of  coagulating,  c.  g.,  fluids  secreted  pathologically  in  serous  cavities  ;  for 
example,  hydrocele  fluid,  which,  as  usually  containing  fii)rinogen  only,  does  not  coagulate  spontane- 
ously, but  it  coagulates  on  the  addition  of  fibrino-plastin  and  ferment  (or  of  blood  serum  in  which 
both  occur). 

(3)  Those  which  do  not  coagulate,  e.  g.,  milk  or  seminal  fluid,  which  do  not  seem  to  contain 
fibrinogen. 

32.  CHEMICAL  COMPOSITION   OF   PLASMA  AND  SERUM. 

— I.  Proteids  occur  to  the  amount  of  8  to  10  per  cent,  in  the  plasma.  Only 
0.2  per  cent,  of  these  go  to  form  fibrin.  After  the  formation  of  the  fibrin  the 
plasma  is  converted  into  serum.  The  sp.  gr,  of  human  serum  is  1027  to  1029. 
It  contains  several  proteids.  [According  to  Hammarsten,  huma7i  serum  contains 
9.207  percent,  of  solids, — of  these,  3.103  =  serum-globulin,  and  4.516  =  serum- 
albumin,  /.  e.,  in  the  ratio  of  i  :  1.511.  In  horse  serum  the  proportion  is  4.5  :  2.6, 
in  o.x  serum  4. 16  :  3.29,  and  rabbit  serum  6.22  :  1.78.  The  total  amount  of  pro- 
teids in  blood  seems  to  be  much  more  constant  than  are  the  relative  proportions 
of  serum-albumin  and  serum-globulin  (.S't?/?^//).] 

(a)  Serum-globulin  or  Paraglobulin  (2  to  4  per  cent.).  If  crystals  of 
magnesium  sulphate  be  added  to  saturation  to  serum  at  35°  C.,  serum-globulin 
is  precipitated,  but  not  serum-albumin.  It  is  soluble  in  10  per  cent,  solution  of 
common  salt,  and  coagulates  at  69-75°  C.  Its  specific  rotatory  power  is  —  47-8° 
i^Fredcncif). 

[Serum-globulin  was  described  by  Panuin  under  the  name  of  "serum-casein"  ;  by  Al.  Schmidt, 
as  •' fibrino-plastic  substance  " ;  and  by  Kuhne,  as  "  paraglobulin."]  During  hunger  the  globulin 
increases  and  the  albumin  diminishes. 

i^b)  Serum-albumin  (3-4  per  cent.).  Its  solutions  begin  to  be  turbid  at 
60°  C,  and  coagulation  occurs  at  73°  C,  the  fluid  becoming  slightly  more  alka- 
line at  the  same  time.  If  sodium  chloride  be  cautiously  added  to  serum,  the 
coagtilating  temperature  may  be  lowered  to  50°  C.  Its  specific  rotatory  power  is 
from  —  62.6  to  64.5°  {Starke).  It  is  changed  into  syntonin  or  acid  albumin  by  the 
action  of  dilute  HCl,  and  by  dilute  alkalies  into  alkali-albuminate. 

Serum-albumin  is  absent  from  the  blood  of  starving  snakes ;  and  reappears  after  they  are  fed 
{Tiegel). 

[Serum-Albumin  -■.  Egg-Albumin— Although  serum-albumin  is  closely  related  to  egg- 
albumin  they  differ— f,7)  as  regards  their  action  upon  polarized  light;  {b)  the  precipitate  pro- 
duced by  adding  HCl  or  HNU.,  is  readily  soluble  in  4  c.c.  of  the  reagent  in  the  case  of  serum- 
albumm,  while  the  precipitate  in  egg-albumin  is  dissolved  with  very  great  difficulty ;  {c)  egg- 
albumin,  mjected  into  the  veins,  is  excreted  in  the  urine  as  a  foreign  body,  while  serum-albu- 
minis  not;   (t/)  serum-albumin   is   not  coagulated   by  ether,  while   egg-albumin   is,  if  the  solution 


PROTEIDS    OF    THE    SERUM.  79 

is  not  alkaline  (|  249).     Serum-albumin  has  never  been  obtained  free  from  salts,  even  when  it  is 
dialysed  for  a  very  long  time.] 

After  all  the  serum-globulin  in  serum  is  precipitated  by  magnesium  sulphate,  serum-albumin 
still  remains  in  solution.  If  this  solution  is  heated  to  40  or  50°  C.  a  copious  precipitate  of  non- 
coagulated  serum-albumin  is  obtained,  which  is  soluble  in  water.  If  the  serum-albumin  be  filtered 
from  the  fluid,  and  if  the  clear  fluid  be  heated  to  over  60°  C,  Fredericq  found  that  it  becomes 
turbid  from  the  precipitation  of  other  proteids ;  the  amount  of  these  other  bodies,  however,  is 
small. 

[Proteids  of  the  Serum. — Halliburton  has  shown  by  the  method  of  "  frac- 
tional heat  coagulation  "  (/.  <?.,  ascertaining  the  temperature  at  which  a  pro- 
teid  is  coagulated,  filtering  the  fluid  and  again  heating  the  filtrate  to  a  higher 
temperature),  that  from  the  same  fluid  perhaps  two  or  more  proteids,  all  with 
different  temperatures  of  coagulation,  may  be  obtained.  Care  must  be  taken  to 
keep  the  reaction  constant.  He  finds  that  serum-globulin  coagulates  at  75°  C, 
while  serum-albumin  in  reality  consists  of  three  proteids,  which  coagulate  at 
different  temperatures;  (a)  at  73°,  (/S)  at  77°,  and  (y)  at  84°  C] 

[Precipitation  by  Salts. — Sulphate  of  magnesia  not  only  precipitates  seriim-globulin  but 
also  fibrinogen.  The  fluid  must  be  shaken  for  several  hours  to  get  complete  saturation.  Sodic 
sulphate,  when  added  to  serum  deprived  of  its  globulin  by  MgSO^,  precipitates  serum-albumin, 
but  it  produces  no  precipitate  with  pure  serum.  In  this  way  serum-albumin  may  be  obtained 
in  a  pure,  uncoagulated,  and  still  soluble  condition.  Serum-globulin  is  thrown  down  by  sodic 
nitrate,  acetate,  or  carbonate ;  while  a//  the  proteids  of  the  serum  are  precipitated  by  potassic 
acetate  or  phosphate,  and  the  same  result  is  brought  about  by  adding  two  salts,  e.g.,  MgSO^ 
and  NajSO^  (in  this  case  sodio-magnesic  sulphate  is  formed) ;  MgSO^  and  NaNOg ;  MgSO^  and 
KI ;  NaCl  and  NagSO^.  After  serum-globulin  is  thrown  down  by  MgSO^,  the  addition  of 
MgSO^  and  Na2S04  or  the  double-salt,  precipitates  the  serum-albumin,  which  is  still  soluble  in 
water.     As  sulphate  of   ammonia    precipitates  all  the  proteids  except  peptones,  it   may  be   used 

[The  plasma  of  Invertebrata  (decapod  crustaceans,  some  gasteropods,  cephalopods,  etc.)  clots 
like  vertebrate  blood,  and  contains  fibrinogen,  but,  in  addition,  there  is  found  in  it  a  substance 
corresponding  to  haemoglobin,  and  called  by  Fredericq,  haemocyanin.  It  exists  like  Hb  in 
two  conditions,  one  reduced  and  the  other  oxy-hsemocyanin,  the  former  being  colorless,  the  latter 
blue.  In  its  general  characters  it  resembles  Hb,  although  it  contains  copper  instead  of  iron,  and 
gives  no  absorption-bands  [Halliburton).  In  the  blood  of  some  decapod  crustaceans  there  is  a 
reddish  pigment,  tetronerythrin,  which  is  identical  with  that  in  the  exoskeleton  and  hypoderm. 
It  belongs  to  the  group  of  lipochromes,  like  some  of  the  pigments  of  the  retina.  The  haemocyanin 
is  respiratory  in  function,  and  it  is  remarkable  that  it  is  contained  in  the  plasma,  and  not  in  the 
formed  elements  like  the  Hb  of  vertebrates.  So  that,  stated  broadly,  in  these  invertebrates  the 
plasma  is  both  nutritive  and  respiratory  in  its  functions,  while  in  vertebrates  the  red  blood  cor- 
puscles chiefly  are  respiratory  and  the  plasma  nutritive.] 

II.  Fats  (o.i  to  0.2  per  cent.). — Neutral  fats  (tristearin,  tripalmitin,  trio- 
lein) occur  in  the  blood  in  the  form  of  small  microscopic  granules,  which,  after  a 
meal  rich  in  fat  (or  milk)  render  the  serum  quite  milky. 

[The  amount  of  fat  in  the  serum  of  fasting  animals  is  about  0.2  per  cent. ;  during  digestion 
0.4  to  0.6  per  cent.;  and  in  dogs  fed  on  a  diet  rich  in  fat  it  may  be  1. 25  per  cent.  There  are 
also  minute  traces  of  fatty  acids  (succinic).  Rohrig  showed  that  soluble  soaps,  i.e.,  alkaline 
salts  of  the  fatty  acids,  cannot  exist  in  the  blood.  Cholesterin  may  be  considered  along  with  the 
fats.  It  occurs  in  considerable  amount  in  nerve  tissues,  and,  like  fats,  is  extracted  by  ether  from 
the  dry  residue  of  blood  serum.  Hoppe-Seyler  found  0.019  ^o  0.314  per  cent,  in  the  serum  of  the 
blood  of  fattened  geese.  There  is  no  fat  in  the  red  blood  corpuscles.  Lecithin  (its  decomposi- 
tion products,  glycerin-phosphoric  acid  and  protagon)  occur  in  serum  and  also  in  the  blood 
corpuscles.] 

III.  Traces  of  Grape  Sugar  [o.i  to  0.15  per  cent,  (more  in  the  hepatic  vein, 
0.23  per  cent.)]  derived  from  the  liver  and  muscles,  and  increased  after  hemor- 
rhage (§  175)  ]  some  glycogen,  and  another  reducing  fermentative  substance  also 
increased  by  hemorrhage. 

The  amount  of  grape  sugar  in  the  blood  increases  with  the  absorption  of  sugar  from  the 
intestine,  and  this  increase  is  most  obvious  in  the  blood  of  the  portal  and  hepatic  veins ;  there 
is  also  a  slight  increase  in  the  arterial  blood,  but  there  it  is  rapidly  changed.  The  presence  of 
sugar  is  ascertained  by  coagulating  blood   by  boiling  it  with  sodium  sulphate,  pressing  out   the 


Sodic  Phosphate,   . 

0.15  per  1000 

Calcic  Phosphate,  . 
Magnesic   " 

;    •   }o.73        " 

30  GASES    OF    TMF.    HLO(  »D. 

fluid  and  testing  it  for  sugar  with  Keliling's  solution  (C/.  Bernard).     Pavy  coagulates  the  blood  with 
alcohol. 

IV.  Extractives. — Kreatin,  urea  (0.016  per  cent.,  increased  after  nitrogenous 
food),  succinic  acid,  and  uric  acid  (more  abundant  in  gouty  conditions),  guanin 
(?),  carbamic  acid,  sarcolactic  acid  ;  all  occur  in  very  small  amounts. 

V.  Salts  (0.S5  per  cent.),  especially  x<p<//V  t7/AW^/^  (0.5  percent.)  and  sodic 
carbonate.  [It  is  most  important  to  note  that  the  soda  salts  are  far  more  abundant 
in  the  serum  than  the  potassium  salts.  The  ratio  may  be  as  high  as  10  :  1.] 
Animal  diet  increases  the  amount  of  salts,  vegetable  food  diminishes  it  tempo- 
rarily. 

Salts  in  luiman  blood  serum  (Ifoppe-Seyler). 
Sodic  Chloride,    ....  4. 92  per  1000 
"        Sulphate,     ....  0.44       " 
'«        Carbonate,  ....  0.2 1        " 

If  large  quantities  of  salts  are  introduced  into  the  blood,  they  almost  entirely  disappear  from  tlie 
blood  stream  within  a  few  minutes,  chiefly  by  diffusion  into  the  tissues.  They  are  gradually  elimi- 
nated by  the  kidneys.     The  same  is  true  of  sugar  and  peptones  {Luthoig  and  Klicou<icz). 

VI.   Water  about  90  per  cent. 
VII.  A  yellow  pigment. 

The  pigment  may  be  extracted  with  methylic  alcohol.  It  shows  two  absorption-bands  of  a  lijjo- 
chronie  like  lutein  {Krukenherg).  Tluidichum  regards  the  pigment  of  the  serum  as  lutein;  Maly, 
as  hydrobilirubin ;  and  MacMunn  as  choletelin. 

33.  THE  GASES  OF  THE  BLOOD. — Absorption  by  Solid  Bodies. — A  considerable 
attraction  exists  between  the  jiarticles  of  solid  porous  bodies  and  gases,  whereby  the  latter  are 
attracted  and  condensed  within  the  pores  of  solid  bodies,  /.  e.^  the  gases  are  absorbed.  Thus,  I  vol- 
ume of  boxwood  charcoal  (at  12°  C.  and  ordinary  barometric  pressure)  absorbs  35  volumes  CO,^,  9.4 
vol.  O,  7.5  vol.  N,  1.75  vol.  II.  //if<7/ is  always  formed  when  gases  are  absorbed,  and  the  amount  of 
heat  evolved  bears  a  relation  to  the  energy  with  which  the  absorption  takes  place.  Non-porous 
bodies  are  similarly  invested  by  a  layer  of  condensed  gases  on  their  surface. 

By  Fluids. — Fluids  can  also  absorb  gases.  A /cno7vn  quantity  of  fluid  at  diff'erent  pressures 
always  absorbs  the  same  volume  of  gas.  Whether  the  pressure  be  great  or  small,  the  volume  of  the 
gas  absorbed  is  equally  great  (  W.  Henry).  IJut  according  to  Boyle  (1662)  and  Mariotte's  law  (1679) 
on  the  compression  of  gases,  when  the  pressure  within  the  same  volume  of  gas  is  increased,  the 
volume  varies  inversely  as  the  pressure.  Hence  it  follows  that,  with  varying  pressure,  the  volume 
of  gas  absorbed  remains  the  same,  but  the  quantity  of  gas  [weight)  is  directly  proportional  to  the 
pressure.  If  the  pressure  =  o,  the  weight  of  the  gas  absorbed  must  also  =  0.  As  a  necessary 
result  of  this,  we  see  that  [l)  fluids  can  be  freed  of  t/ieir  absorbed  gases  in  a  vacuum  under  an  air- 
pump. 

Coefficient  of  Absorption  means  the  volume  of  a  gas  (0°  C.)  which  is  absorbed  by  a  unit  of 
volume  of  a  liquid  (at  760  mm.  Hg)  at  a  given  temperature.  The  volume  of  a  gas  absorbed,  and 
therefore  the  coefficient  of  absoqition,  is  quite  independent  of  the  pressure,  while  the  'weight  of  the 
gas  is  proportional  to  it.  Temperature  has  an  important  influence  on  the  coefficient  of  absorption. 
With  a  low  temperature  it  is  greatest;  it  diminishes  as  the  temperature  increases;  and  at  the  boiling 
point  W.  z=  o.  Hence,  it  follows  that  (2)  absorbed  gases  may  be  expelled  from  fluids  simply  by 
causing  the  fluids  to  boil.  The  coeflicient  of  absorption  diminishes  for  different  fluids  and  gases, 
with  increasing  temperature,  in  a  special,  and  by  no  means  uniform,  manner,  which  must  be  deter- 
mined empirically  for  each  liquid  and  gas.  Thus  the  coefficient  of  absorption  for  CO.^  in  water 
diminishes  with  an  increasing  temperature,  while  that  for  H  in  water  remains  unchanged  between  0° 
and  20°  C. 

Diffusion  of  Gases. — Gases  which  do  not  enter  into  chemical  combinations  with  each  other 
mix  with  each  other  in  definite  proportions.  If  the  necks  of  two  flasks  be  placed  in  communication 
by  means  of  a  glass  or  other  tube,  and  if  the  lower  flask  contain  CO.^,  and  the  upper  one  H,  the 
gases  mix  quite  independently  of  their  different  specific  gravities,  both  gases  forming 'in  each  flask  a 
perfectly  uniform  mixture.  The  phenomenon  is  called  \!nt  diffusion  of  gases.  \{  ts.  porous  mem- 
brane be  previously  inserted  between  the  gases,  the  exchange  of  gases  still  goes  on  through  the 
membrane.  But  (as  with  endosmosis  in  fluids)  the  gases  pass  with  unequal  rapidity  through  the 
pores,  so  that  at  the  beginning  of  the  experiment  a  larger  amount  of  gas  is  found  on  one  side  of  the 
membrane  than  on  the  other.  According  to  Graham,  the  rapidity  of  the  diffusion  of  the  gases  through 
the  pores  is  inversely  proportional  to  the  square  root  of  their  specific  gravities.  (According  to  Bun- 
sen,  however,  this  is  not  quite  correct.) 


EXTRACTION    OF   THE    BLOOD    GASES.  81 

Different  Gases  in    a  Gaseous  Mixture  do  not  Exert  Pressure  upon  one  another. — 

Gases,  therefore,  pass  into  a  space  filled  with  another  gas,  as  they  would  pass  into  a  vacuum.  If 
the  surface  of  a  fluid  containing  absorbed  gases  be  placed  in  contact  with  a  very  large  quantity  of 
another  gas,  the  absorbed  gases  diffuse  into  the  latter.  Hence,  absorbed  gases  can  be  removed  by 
(3)  p^tssmg  a  stream  of  ajiother  gas  through  the  fluid,  or  by7?ierefy  shaking  up  the  fltiid  with  another 
gas. 

Partial  Pressure. — If  izvo  or  more  gases  are  mixed  in  a  closed  space  over  a  fluid,  as  the  differ- 
ent gases  existing  in  a  gaseous  mixture  exert  no  pressure  upon  each  other,  the  several  gases  are 
absorbed.  The  vi'eight  of  each  absorbed  is  proportional  to  the  pressure  under  which  each  gas  would 
be,  were  it  the  only  gas  in  the  space.  This  pressure  is  called  the.  pa7-tial pressure oi  z.  gas  [Bunsen). 
The  absorption  of  gases  from  their  mixtures,  therefore,  is  proportional  to  the  partial  pressure.  The 
partial  pressure  of  a  gas  in  a  space  is  at  the  same  time  the  expression  for  the  tension  of  the  gas 
absorbed  by  a  fluid. 

The  air  contains  0.2096  volume  of  O,  and  0.7904  volume  N.  If  I  volume  of  the  air  be  placed 
under  a  pressure,  P,  over  water,  the  partial  pressure  under  which  O  is  absorbed  =:  0.2096  P;  that 
for  N  ^0.7904  P.  At  0°  C,  and  760  mm.  pressure,  I  volume  of  water  absorbs  0.02477  volume  of 
air,  consisting  of  0.00862  volume  0,  and  0.01615  volume  N.  It  contains,  therefore,  34  per  cent.  O 
and  66  per  cent.  N.  Therefore,  water  absorbs  from  the  air  a  mixture  of  gases  containing  a  larger 
percentage  of  O  than  the  air  itself. 

34.  EXTRACTION  OF  THE  BLOOD  GASES.— [The  blood  to  be  analyzed  must  be 
collected  over  mercury  so  as  to  avoid  contact  with  air.  This  is  done  by  means  of  a  special 
apparatus,  consisting  of  a  graduated  tube  filled  with  mercury  and  communicating  with  a  glass  globe 
also  filled  with  mercury,  which  can  be  lowered  as  the  blood  flows  into  the  graduated  tube.]  The 
extraction  of  the  gases  from  the  blood,  and  their  collection  for  chemical  analysis,  are  carried  out  by 
means  of  the  mercurial  pump  (C  Ludwig).  Fig.  22  shows  in  a  diagrammatic  form  the  arrangement 
of  Pfliiger's  gas  pump. 

It  consists  of  a  receptacle  for  the  blood,  or  ' '  blood-bulb  "  (A),  a  glass  globe  capable  of  containing 
250  to  300  c.c,  connected  above  and  below  with  tubes,  each  of  which  is  provided  with  a  stop-cock, 
a  and  b  ;  b  \s  an  ordinary  stop-cock,  while  a  has  through  its  long  axis  a  perforation  which  opens  at 
X,  and  is  so  arranged  that,  according  to  the  position  of  the  handle,  it  leads  up  into  the  blood-bulb 
(position  a',  a),  or  downward  through  the  lower  tube  (position  x^,a').  This  blood-bulb  is  first 
completely  emptied  of  air  (by  means  of  a  mercurial  air  pump),  and  then  carefully  weighed.  One  end 
(x^)  of  it  is  tied  into  an  artery  or  a  vein  of  an  animal,  and  when  the  lower  stop-cock  is  placed  in  the 
position  X,  a,  blood  flows  into  the  receptacle.  When  the  necessary  amount  of  blood  is  collected,  the 
lower  stop-cock  is  put  into  the  position  x\  a' ,  and  the  blood-bulb,  after  being  cleaned  most  carefully, 
is  weighed  to  ascertain  the  weight  of  the  amount  of  blood  collected.  The  second  part  of  the  appa- 
ratus consists  of  the  froth-chamber,  B,  leading  upward  and  downward  into  tubes,  each  of  which 
is  provided  with  an  ordinary  stop-cock,  c  and  d.  The  froth- chamber,  as  its  name  denotes,  is  to 
catch  the  froth  which  is  formed  during  the  energetic  evolution  of  the  gases  from  the  blood.  The 
lower  aperture  of  the  froth-chamber  is  connected  by  means  of  a  well-ground  tube  with  the  blood- 
bulb,  while  above  it  communicates  with  the  third  part  of  the  apparatus,  the  drying-chamber,  G. 
This  consists  of  a  U-shaped  tube,  provided  below  with  a  small  glass  bulb,  which  is  half  filled  with 
sulphuric  acid,  while  in  its  limbs  are  placed  pieces  of  pumice-stone  also  moistened  with  sulphuric  acid. 
As  the  blood  gases  pass  through  this  apparatus  (which  may  be  shut  off  by  the  stop-cocks  e  andy), 
they  are  freed  from  their  watery  vapor  by  the  sulphuric  acid,  so  that  they  pass  quite  dry  through  the 
stop-cock, y.  The  short,  well-ground  tube,  D,  is  fixed  to/",  and  to  the  former  is  attached  the  small 
barometric  tube  or  manofjieter ,  y ,  which  indicates  the  extent  of  the  vacuum.  From  D  we  pass  to 
the  pump  proper.  This  consists  of  two  large  glass  bulbs,  which  are  continued  above  and  below 
into  open  tubes;  the  lower  tubes,  Z  and  w,  being  united  by  a  caoutchouc  tube,  G.  Both  the  bulbs 
and  the  caoutchouc  tube  contain  mercury — the  bulbs  being  about  half  full,  and  F  being  larger  than 
E.  The  bulb,  E,  is  fixed;  but  F  can  be  raised  or  lowered  by  means  of  a  pulley  with  a  rack  and 
pinion  motion.  If  F  be  raised,  E  is  filled;  if  F  be  lowered,  E  is  emptied.  The  upper  end  of  E 
divides  into  two  tubes,  g  and  h,  of  which  g  is  united  to  D.  The  ascending  tube,  h  (gas-delivery 
tube),  is  very  narrow,  and  is  bent  so  that  its  free  end  dips  into  a  vessel  containing  mercury,  v  (a 
pneumatic  trough),  and  the  opening  is  placed  exactly  under  the  tube  for  collecting  the  gases,  the 
eudiometer,  J,  which  is  also  tilled  with  mercury.  Where  g  and  H  unite,  there  is  a  two-way  stop- 
cock, which  in  one  position,  H,  places  E  in  communication  with  A,  B,  G,  D,  the  chambers  to  be 
exhausted,  and  in  the  position  K  shuts  off  A,  B,  G,  D,  and  places  the  bulb,  E,  in  communication 
with  the  gas-delivery  tube,  /z,  and  the  eudiometer,  J.  B,  G,  D  are  completely  emptied  of  air,  thus: 
The  stop-cock  is  placed  in  the  position,  K;  raise  F  until  drops  of  mercury  issue  from  the  fine  tube, 
i  (not  yet  placed  under  J) ;  place  the  stop-cock  in  the  position  H,  lower  F;  stop-cock  in  position,  K, 
and  so  on  until  the  barometer,  y,  indicates  a  complete  vacuum.  J  is  now  placed  over  z.  Open  the 
cocks,  c  andiJ,  so  that  the  blood-bulb,  A,  communicates  with  the  rest  of  the  apparatus,  and  the  blood 
gases  froth  up  in  B,  and  after  being  dried  in  G  pass  toward  E.  Lower  F,  and  they  pass  into  E ; 
stop-cock  in  position,  K,  raise  F,  and  the  gases  are  collected  in  J  under  mercury.  The  repeated 
lowering  and  raising  of  F  with  the  corresponding  position  of  the  stop -cocks  ultimately  drives  all  the 
6 


82 


ESTIMATION    OF    THE    BLOOD    GASES. 


gases  into  J.  The  removal  of  the  gases  is  greatly  facilitated  by  placing  the  blood-bulb,  A,  in  a 
vessel  containing  water  at  60°  C. 

It  is  well  to  remove  the  gases  from  the  blood  immediately  after  it  is  collected  from  a  blood  vessel, 
because  the  O  undergoes  a  diminution  if  the  blood  be  kept.  Of  course,  in  making  several  analyses, 
it  is  difficult  to  do  this,  and  the  best  plan  to  pursue  in  that  case  is  to  keep  the  recejitacles  containing 
the  blood  on  ice. 

Mayow  (1670)  observed  that  gases  were  given  off  from  blood  in  vacuo.     Magnus  (1837)  investi- 

Yir,.  22. 


Scheme  of  Pflijger's  gas-pump.  A,  blood-bulb ;  a,  stop-cock,  with  a  longitudinal  perforation  opening  upward;  a', 
the  same  opening  downward;  (5  and  c,  stop-cocks  ;  B,  froth-chamber ;  d",  ^,y,  stop-cocks  ;  G,  drying-chambers, 
containing  sulphuric  acid  and  pumice-stone  ;  D,  tube,  with  manometer,^. 

gated  the  percentage  composition  of  the  blood  gases.    The  more  important  recent  investigations  have 
been  made  by  Lothar  Meyer  (1857),  and  by  the  pupils  of  C.  Ludwig  and  E.  Ptiiiger. 

35.  QUANTITATIVE  ESTIMATION  OF  THE  BLOOD  GASES. 

— The  gases  obtained  from    blood  consist  of  O,  CO.^,  and  N.     Pfliiger  obtained 
(at  0°  C.  and  i  metre  Hg  pressure)  47.3  volumes  per  cent.,  consisting  of — 
O,  16.9  per  cent.  ;   CO,,  29  per  cent.  ;   N,  1.4  per  cent. 


THE    BLOOD    GASES.  83 

As  is  shown  in  Fig.  22,  J,  the  gases  are  obtained  in  an  eudiometer,  i.e.,  in  a 
narrow  tube,  closed  at  one  end,  and  with  a  very  exact  scale  marked  on  it,  and  having 
two  fine  platinum  wires  melted  into  its  upper  end,  with  their  free  ends  projecting 
into  the  tube  (/  and  11). 

(i)  Estimation  of  the  COj. — A  small  ball  oi  fused  caustic  potash,  fixed  on  a  platinum  wire,  is 
introduced  into  the  mixture  of  gases  through  the  lower  end  of  the  eudiometer  under  cover  of  the 
mercury.  The  surface  of  the  potash  ball  is  moistened  before  it  is  introduced.  The  CO,  unites 
with  the  potash  to  form  potassium  carbonate.  The  potash  bulb  is  withdrawn  after  24  hours".  The 
diminution  in  volume  indicates  the  amount  of  COj  absorbed. 

(2)  Estimation  of  the  O. — {a)  Just  as  in  estimating  the  CO.^,  a  ball  oi phosphorus  on  a  platinum 
wire  is  introduced  into  the  eudiometer;  it  absorbs  the  O  and  forms  phosphoric  acid.  Another 
plan  is  to  employ  a  small  papier-mache  ball  saturated  with  pyi'ogaHic  acid  iji  caustic  potash,  which 
rapidly  absorbs  O.     After  the  ball  is  removed,  the  diminution  in  volume  indicates  the  quantity  of  O. 

{b)  The  O  is  most  easily  and  accurately  estimated  by  exploding  it  in  the  ezidiot?ieter.  Introduce  a 
sufficient  quantity  of  H  into  the  eudiometer,  and  accurately  ascertain  its  volume  ;  an  electrical  spark 
is  now  passed  between  the  wires,/  and  «,  through  the  mixture  of  gases  ;  the  O  and  H  unite  to  form 
water,  which  causes  a  diminution  in  the  volume  of  the  gases  in  the  eudiometer,  of  which  y^  is  due 
to  the  O  used  to  form  water  (H2O). 

{c)  Estimation  of  the  N. — When  the  CO^  and  O  are  estimated  by  the  above  method,  the 
remainder  is  pure  N. 

36.  THE  BLOOD  GASES— [In  human  blood,  the  average  total  gases 

are  estimated  to  be,  at  0°  C.  and  i  metre  pressure, 

O  CO2  N 

Arterial  blood,  17  30  i  to  2  per  cent. 

Venous  blood,       6  to  10  35  i  to  2       " 

or,  calculated  at  0°  C.  and  760  mm,  pressure, 

Arterial  blood,  20  39  1.4  per  cent. 

Venous  blood,       8  to  12  46  1.4       "       ] 

I.  Oxygen  exists  in  arterial  blood  (dog)  on  an  average  to  the  extent  of  17 
volumes  per  cent,  (at  0°  C.  and  i  metre  Hg  pressure)  {Ffliiger).  According  to 
Pfliiger,  arterial  blood  (dog)  is  saturated  to  -^  with  O,  while,  according  to  Hiifner, 
it  is  saturated  to  the  extent  of  \^.  In  venous  blood  the  quantity  varies  very 
greatly ;  in  the  blood  of  a  passive  muscle  6  volumes  per  cent,  have  been  found ; 
while  in  the  blood  after  asphyxia  it  is  absent,  or  occurs  only  in  traces.  It  is  cer- 
tainly more  abundant  in  the  comparatively  red  blood  of  active  glands  (salivary 
glands,  kidney),  than  in  ordinary  dark  venous  blood. 

[Modifying  Conditions. — The  amount  of  O  obtainable  from  the  blood  depends  upon  the 
organ  from  which  the  blood  comes,  or  whether  the  organ  be  active  or  at  rest.  Thus  the  O  present 
in  the 

Carotid  artery  is    .         •         21  per  cent.     I       Renal  vein  (kidney  active),  17  per  cent. 
Renal  artery,  .  .  19       "  |       Renal  vein  (kidney  at  rest),    6       " 

Bert  finds  that  increase  of  the  atmospheric  pressure  from  I  to  10  atmospheres  raises  the  amount 
of  O  in  arterial  blood  from  20  to  over  24  per  cent.,  and  the  N  from  1.8  to  over  9  per  cent.,  while 
the  COj  is  but  slightly  affected.] 

The  O  in  Blood  occurs — (jx)  simply  absorbed  in  the  plasma.  This  is  only  a 
minimal  amount,  and  does  not  exceed  what  distilled  water  at  the  temperature  of 
the  body  would  take  up  at  the  partial  pressure  of  the  O  in  the  air  of  the  lungs 
{Lothar  Meyer). 

(F)  Almost  the  total  O  of  the  blood  is  chemically  united,  and  therefore  not 
subject  to  the  law  of  absorption.  It  is  loosely  united  to  the  haemoglobin  of  the 
red  corpuscles,  with  which  it  forms  oxyhmnoglobin  (§  15).  With  regard  to  the 
taking  up  of  O,  the  total  quantity  of  blood  behaves  exactly  like  a  solution  of 
hsemoglobin  free  from  O  {Preyef).  The  absorption  of  O  is  more  rapid  in  blood 
than  in  a  solution  of  Hb. 

The  absorption  of  this  quantity  of  O  is  completely  independent  of  pressure  ;  hence,  animals 
confined  in  a  closed  space,  until  they  are   nearly  asphyxiated,  can  use  up  almost  all  the  O  from  the 


34  IS    OZONE    PRESENT    IN    BLOOn  ? 

surrounding  atmosphere.  The  fact  of  the  union  being  independent  of  pressure  is  proved  by  the 
following  :  The  blood  only  gives  oft"  copiously  its  chemically  united  O  when  the  atmospheric  pres- 
sure is  lowered  to  20  millimetres,  I Ig  {IVonii  Miiller) ;  and,  conversely,  blood  only  takes  up  a 
little  more  O  when  the  jiressure  is  increased  to  6  atmospheres  [Bert). 

Physical  Methods  of  Obtaining  O  from  Blood. — Notwithstanding  the 
chemical  union  between  the  Hb  and  O,  all  the  O  of  the  blood  can  be  expelled 
from  its  state  of  combination  by  those  means  which  set  free  absorbed  gases — (a) 
by  introducing  blood  into  a  Torricellian  vacuum  ;  {I?)  by  boiling  ;  {c)  by  the 
conduction  of  other  gases  [H,  N,  CO,  or  NO]  through  the  blood,  because  the 
oxyheemaglobin  compound  is  so  loose  that  it  is  decomposed  even  by  these  physical 

means. 

Reducing  Reagents. — Among  chemical  reagents  the  following  redi/ci/ig  swh- 
stances — ammonium  sulphide,  sulphuretted  hydrogen,  alkaline  solutions  of  sub- 
salts  or  Stokes's  fluid,  iron  filings,  etc.,  rob  blood  of  its  O  (§  15). 

Relation  to  Fe. — The  amount  of  iron  in  the  blood  (0.55  in  1000  parts)  stands  in  direct  rela- 
tion to  the  amount  of  lib;  this  to  the  quantity  of  lilood  corpuscles  ;  and  this,  in  turn,  to  the  specific 
gravity  of  the  blood.  The  amount  of  O  in  the  blood,  therefore,  is  nearly  proportional  to  the 
specific  gravity  of  the  blood,  and  it  is  also  in  proportion  to  the  amount  of  iron  in  the  blood.  Picard 
affirms  that  2.36  grams  of  iron  in  the  blood  can  fix  chemically  i  gram  O ;  while,  according  to 
Iloppe-Seyler,  the  proportion  is  i  atom  iron  to  2  atoms  O. 

During  morphia  narcosis  the  amount  of  O  in  the  blood  is  diminished  [E-waU);  after  hemor- 
rhage the  arterial  blood  is  saturated  with  O  {J.  G.  Oil). 

Disappearance  of  O  in  Shed  Blood.— Even  immediately  after  blood  is  shed,  there  is  a  slight 
disappearance  of  O,  as  a  physiological  index  of  respiration  of  the  tissues  within  the  living  blood 
itself  il  132).  When  blood  is  kept  long  outside  of  the  blood  vessels,  the  quantity  of  O  gradually 
diminishes,  and  if  it  be  kept  for  a  length  of  time  at  a  high  temperature  it  may  disappear  altogether. 
This  depends  upon  decomposition  occurring  in  the  blood,  whereby  reducing  substances  are  fornied 
which  consume  the  O.  All  kinds  of  blood,  however,  do  not  act  with  equal  energy  in  consuming 
O,  f.g.,  venous  blood  from  active  muscles  acts  most  energetically,  while  that  from  the  hepatic  vein 
has  very  little  effect.  COj  appears  in  the  blood  in  place  of  the  O,  and  the  color  darkens.  The 
amount  of  CO.,  produced  is  sometimes  greater  than  that  of  the  O  consumed. 

Relation  to"  Acids. — If  blood  (or  a  solution  of  oxyhemoglobin)  be  acted  upon  by  acids  {e.g., 
tartaric  acid)  until  it  is  strongly  acid,  O  can  be  pumped  out  in  considerably  less  amount,  while  the 
formation  of  CO.,  is  not  increased.  We  must,  therefore,  assume  that,  during  the  decomposition  of 
the  Hb  caused  by  the  acids  (?.  18),  a  decomposition  product  becomes  more  highly  oxidized  by  the 
intense  chemical  union  of  the  O  at  the  moment  of  its  origin  {Lothar  Meyer,  Zuntz,  Strassbiirg). 
The  same  phenomenon  occurs  when  oxyhemoglobin  is  decomposed  by  boiling. 

37.  IS  OZONE  PRESENT  IN  BLOOD  ?— On  account  of  the  numer- 
ous and  energetic  oxidations  which  occur  in  connection  with  the  blood,  the  ques- 
tion has  often  been  raised  as  to  whether  the  O  of  the  blood  exists  in  the  form  of 
ozone  (O3).  Ozone,  however,  is  contained  neither  in  the  blood  \\.%q\(  {Sc/wnbehi) 
nor  in  the  blood  gases  obtained  from  it.  Nevertheless,  the  red  corpuscles  (and 
Hb)  have  a  distinct  relation  to  ozone. 

(i)  Tests  for  Ozone. — Hxmo^ohm  2iCis  zs  z.  conveyer  of  ozone,  i.e.,\i  is  able  to  remove  the 
active  O  of  other  bodies  and  to  convey  or  transfer  it  at  once  to  other  easily  oxidizable  substances. 
(</)  Turpentine  which  has  been  exposed  to  the  air  for  a  long  time  always  contains  ozone.  The  tests 
for  the  latter  are  starch  and  potassium  iodide,  the  ozone  decomposing  the  iodide,  when  the  iodine 
strikes  a  blue  with  the  starch,  (h)  Freshly-prepared  tincture  of  guaiacum  is  also  rendered  blue  by 
ozone.  If  some  tincture  of  guaiacum  be  added  to  turpentine  there  is  no  reaction,  but  on  adding  a 
drop  of  blood  a  deep  blue  color  is  immediately  produced,  i.e.,  blood  takes  the  ozone  from  the  tur- 
pentine and  conveys  it  at  once  to  the  dissolved  guaiacum,  which  becomes  blue.  It  is  immaterial 
whether  the  Hb  contains  O  or  not. 

(2)  It  is  also  asserted  that  hemoglobin  acts  as  an  ozone-producer,  i.e.,  that  it  can  convert  the 
ordinary  O  of  the  air  into  ozone.  Hence  the  reason  why  red  blood  corpuscles  alone  render  guaia- 
cum blue.  This  reaction  succeeds  best  when  the  guaiacum  solution  is  allowed  to  dry  on  blotting- 
paper,  and  a  few  drops  of  blood  (diluted  5  to  10  times)  are  poured  on  it.  That  the  Hb  forms 
ozone  from  the  surrounding  O,  is  shown  by  the  fact  that  red  blood  corpuscles  containing  carbonic 
oxide  cause  the  blue  color  {A'iihne  and  Scholz).  According  to  Pfliiger,  however,  these  reactions 
only  occur  from  decomposition  of  the  Hb,  so  that  on  this  view  the  blood  corpuscles  cannot  be 
regarded  as  producers  of  ozone. 

Sulphuretted  hydrogen  is  decomposed  by  blood  (as  by  ozone  itself)  into  sulphur  and   water. 


CARBON    DIOXIDE    AND    NITROGEN    IN    BLOOD.  85 

Hydric  peroxide  is  decomposed  by  blood  into  0  and  water  [but  this  reaction  is  prevented  by  the 
addition  of  a  small  amount  of  hydrocyanic  acid  (Schdnbeiti)\.  Crystallized  Hb  does  not  do  this, 
and  HjOj  may  be  cautiously  injected  into  the  blood  vessels  of  animals.  This  would  show  that 
unchanged  Hb  does  not  produce  ozone. 

Various  Forms  of  Oxygen. — There  are  three  forms  of  oxygen  :  (i)  The  ordinary  oxygen(02) 
in  the  air.  (2)  Active  or  nascent  oxygen  (O),  which  never  can  occur  in  the  free  state,  but  the 
moment  it  is  formed  acts  as  a  powerful  oxidizing  agent  and  produces  chemical  compounds.  It  con- 
verts water  into  hydric  peroxide — the  N  of  the  air  into  nitrous  and  nitric  acids,  and  even  CO  into 
CO.,,  which  ozone  does  not.  It  certainly  plays  an  important  part  in  the  organism.  (3)  Ozone  (O3), 
which  is  formed  by  the  decomposition  of  several  molecules  of  ordinary  oxygen  (O.,)  into  two  atoms 
of  O,  and  the  appropriation  of  each  of  these  atoms  by  a  molecule  of  undecomposed  oxygen.  It  is 
oxygen  condensed  to  f  of  its  volume. 

38.  CO,  AND    N    IN    BLOOD.— II.    Carbon    Dioxide.— In    arterial 

blood  there  are  about  30  volumes  per  cent,  of  CO,  at  o*^  C.  and  i  metre  pressure 
(^Seischenow) ;  but  in  venous  blood  the  amount  is  very  variable,  e.g.,  in  the 
venous  blood  of  passive  muscles  there  are  35  volumes  per  cent.  {Sczelkow'),  while 
in  the  blood  of  asphyxia  there  may  be  52.6  volumes  per  cent.  The  CO2  in  the 
lymph  of  asphyxia  is  less  than  that  in  the  blood  {Btuhner,  Gaule).  The  CO2  of 
the  blood  may  be  extracted  from  it  or  completely  pumped  out,  but  during  the  pro- 
cess of  evacuation,  or  removal  of  the  gas,  a  new  property  of  the  red  blood 
corpuscles  is  produced,  whereby  they  assume  the  function  of  an  acid,  and  thus 
aid  in  the  chemical  expulsion  of  the  CO2.  This  acid-like  property  of  the  red 
corpuscles  occurs  especially  in  the  presence  of  O  and  heat. 

(A)  The  CO2  in  the  Plasma. — The  largest  portion  of  the  CO.,  belongs  to  the 
plasma  (or  serum),  and  it  all  appears  to  be  in  a  state  of  chemical  combination. 
Serum  takes  up  CO2  quite  independently  of  pressure,  hence  it  cannot  be  merely 
absorbed.  A  certain  part  of  the  CO,  can  be  removed  from  the  serum  (plasma)  by 
the  Torricellian  vacuum,  while  another  part  is  obtained  only  after  the  addition  of 
an  acid.  [The  latter  is  called  the  "  fixed  "  CO2,  while  the  former  is  known  as 
the  "  loose  "  CO2.]     The  CO2  in  the  serum  exists  in  the  following  conditions  : — 

(i)  CO2  is  united  to  the  soda  of  the  plasma  in  the  form  of  "  netitral  sodic  car- 
bonate.^'' This  portion  of  the  CO2  can  only  be  displaced  from  its  combination 
by  the  addition  of  an  acid,  (In  depriving  blood  of  its  gases  the  red  corpuscles 
play  the  role  of  an  acid.) 

(2)  A  portion  of  the  CO,  is  loosely  united  to  sodic  carbonate  in  the  form  of 
sodic  bicarbonate ;  the  carbonate  takes  up  i  equivalent  of  CO2 ;  Na2C03  +  CO2  -f- 
H2O  =  2NaHC03.  This  CO2  may  be  pumped  out,  as  in  the  process  the  bicarbon- 
ate splits  up  again  into  the  neutral  carbonate  and  COj. 

Preyer  has  objected  to  this  view  on  the  ground  that  blood  is  alkaline  in  reaction,  while  all  solu- 
tions that  contain  COj  in  a  state  of  absorption,  or  loose  chemical  combinations,  are  always  acid. 
Pfliiger  and  Zuntz  showed  that  blood,  after  being  completely  saturated  with  CO2,  still  remains 
alkaline. 

As  the  bicarbonate  only  gives  up  its  COj  very  slowly  in  vacuo,  while  blood  gives  off  its  COj 
very  energetically,  perhaps  the  soda,  united  with  an  albuminous  body,  combines  with  the  CO2  and 
forms  a  complex  compound,  from  which  the  CO,  is  rapidly  given  off  in  vacuo. 

(3)  A  minimal  portion  of  the  CO,  may  be  chemically  united  with  neutral  so aic 
phosphate  in  the  plasma  {^Fernet^.  One  equivalent  of  this  salt  can  fix  one  equiva- 
lent of  CO,,  so  acid  sodium  phosphate  and  acid  sodium  carbonate  are  formed, 
Na2HP0,  +  CO,  +  H2O  =  NaH2P04  +  NaH,  CO3  {Hermannn).  When  the  gases 
are  removed  the  CO2  escapes,  and  neutral  sodic  phosphate  remains. 

It  is  probable,  however,  that  almost  all  the  sodic  phosphate  found  in  the  blood-ash  arises  from 
the  burning  of  lecithin ;  we  have,  therefore,  to  consider  only  the  very  small  amount  of  this  salt  which 
occurs  in  the  plasma  {^HoppeSeyler  and  Sertoli). 

(B)  The  CO2  in  the  Blood  Corpuscles. — The  red  corpuscles  contain  CO2 
in  loose  chemical  combination ;  for  (i)  a  volume  of  blood  can  fix  nearly  as  much 
CO2  as  an  equal  volume  of  serum  {Ltidwig,  Al.  Schtnidt) ;  and  (2)  with  increasing 


86  QUANTITY    OF    BLOOD. 

])ressure  the  absorption  of  CO2  by  blood  takes  place  in  a  different  ratio  from  what 
occurs  with  serum  {Pfliiger,  Zuniz).  The  red  corpuscles  can  fix  more  CO.,  than 
their  own  volume,  and  tlie  union  of  the  CO,,  seems  to  depend  upon  the  Hb,  for 
Setschenow  found  that,  when  Hb  was  acted  on  by  CO.^,  its  power  of  fixing  the 
latter  was  increased,  which  is  perhaps  due  to  the  formation  of  some  substance  more 
suited  for  fixing  CO..  The  colorless  corpuscles,  after  the  manner  of  the  serum 
constituents,  also  fix  CO.,  to  the  extent  of  yi  to  ^V  of  the  absorbing  power  of  serum. 

After  the  use  of  I,  Hg,  sodic  oxalate,  and  nitrite,  there  is  a  diminution  of  COj  in  arterial  blood 
[Ffitelberg),  and  also  in  fever  [Geppert,  Minkowski).  [In  the  last  case  it  is  perhaps  due  to  the 
diminished  alkalinity,  and  this  is  in  part  owing  to  the  acid  products  formed  during  the  decomposition 
of  the  tissues.] 

III.  Nitrogen  exists  in  the  blood  to  the  extent  of  1.4  to  1.6  vol.  per  cent., 
and  it  appears  to  be  simply  absorbed. 

It  is  doubtful  if  any  part  of  the  N  exists  chemically  united  in  the  red  corpuscles.  Blood  warmed 
outside  the  body,  and  with  a  free  supply  of  oxygen,  gives  off  a  minute  quantity  of  ammonia,  which 
is  perhaps  derived  from  the  decomposition  of  some  salt  of  ammonia  as  yet  unknown  [/Cii/itte  and 
Strauch). 

39.  ARTERIAL  AND  VENOUS  BLOOD.— Arterial  blood  contains 
in  sohition  all  those  substances  which  are  necessary  for  the  nutrition  of  the  tissues, 
those  which  are  employed  in  secretion,  and  it  also  contains  a  rich  supply  of  O. 
Venous  blood  must  contain  less  of  all  these,  but  in  addition  it  holds  the  used,-up 
or  effete  substances  derived  from  the  tissues,  and  the  products  of  their  retrogressive 
metabolism  are  more  numerous;  there  is  in  venous  blood  a  larger  amount  of  CO2. 
It  is  evident,  also,  that  the  blood  of  certain  veins,  the  portal  and  hepatic,  must  have 
special  characters. 

The  following  are  the  most  important  points  of  difference  between  arterial  blood 
and  venous  blood  :  — 

Arterial  Blood  contains — 
more  O,  1      more  extractives,  I      less  urea, 

less  CO.^,  I       more  salts,  |       It    is    bright    red    and    not 

more  water,  more  sugar,  |  dichroic. 

more  fibrin,  |       fewer  blood  corpuscles,       |       As  a  rule  it  is  1°  C.  warmer. 

The  bright-red  color  of  arterial  blood  depends  on  the  presence  of  oxyhsemo- 
globin,  while  the  dark  color  of  venous  blood  is  due  to  its  smaller  proportion  of 
oxyht-emoglobin,  and  the  quantity  of  reduced  haemoglobin  which  it  contains.  The 
dark  change  of  color  is  not  to  be  attributed  to  the  larger  quantity  of  CO.,  in  venous 
blood  {Marchand)  ;  for  if  equal  quantities  of  O  be  added  to  two  portions  of  blood, 
and  if  COj  be  added  to  one  of  them,  the  color  is  not  changed  (Ffliiger). 

[According  to  C.  Schmidt,  the  blood  of  the  portal  vein  contains  more  water,  plasma,  salts,  and 
fats,  but  less  extractives  and  corpuscles  than  the  blood  of  the  hepatic  vein;  while  (when  an  animal 
is  not  digesting)  sugar  is  absent  or  at  least  only  in  traces  in  the  portal  vein,  and  in  considerable 
amount  in  the  hepatic  vein  (^  175)  ] 

40.  QUANTITY  OF  BLOOD.— In  the  adult  the  quantity  of  blood  is 
equal  to  -^  part  of  the  body  weight  {Bischoff),  in  newly-born  children  ^ 
(  Wekker). 

According  to  Schiicking,  the  amount  of  blood  in  a  newly-born  child  depends  to  some  extent  upon 
the  time  at  which  the  umbilical  cord  is  ligatured.  The  amount  =  yV  of  the  body  weight  when  the 
cord  is  tied  at  once,  while  if  it  is  tied  somewhat  later  it  may  be  1.  Immediate  ligature  of  the  cord 
may,  therefore,  deprive  a  newly-born  child  of  100  grams  of  blood.  Further,  the  number  of  cor- 
puscles IS  less  in  a  child  after  immediate  ligature  of  the  umbilical  cord  than  when  it  is  tied  somewhat 
later  {Helol). 

The  methods  of  Valentin  (1838),  and  Ed.  Weber  (1S50),  are  not  now  used,  as  the  results  obtained 
are  not  sufficiently  accurate. 

Method  of  Welcker  (1S54).— Begin  by  taking  the  weight  of  the  animal  to  be  experimented 
on;  place  a  cannula  in  the  carotid,  and  allow  the  blood  to  run  into  a  flask  previously  weighed,  and 
in  which  small  pebbles  (or  Hg)  have  been  placed  in  order  to  defibrinate  the  blood  by  shaking. 


ABNORMAL    CONDITIONS    OF    THE    BLOOD.  87 

Take  a  part  of  this  defibrinated  blood,  and  make  it  cherry-red  in  color  by  passing  through  it  a 
stream  of  CO  (because  ordinary  blood  varies  in  color  according  to  the  amount  of  O  contained  in  it — 
Gsckeidlen,  Ueidenham).  Tie  a  |—  shaped  cannula  in  the  two  cut  ends  of  the  carotid,  and  allow  a 
0.6  per  cent,  solution  of  common  salt  to  flow  into  the  vessel  from  a  pressure  bottle;  collect  the 
colored  fluid  issuing  from  the  jugular  veins  and  inferior  vena  cava  until  the  fluid  is  quite  clear.  The 
entire  body  is  then  chopped  up  (with  the  exception  of  the  contents  of  the  stomach  and  intestines, 
which  are  weighed,  and  their  weight  deducted  from  the  body  weight),  and  extracted  with  water, 
and  after  twenty-four  hours  the  fluid  is  expressed.  This  water,  as  well  as  the  washings  with  salt 
solution,  are  collected  and  weighed,  and  part  of  the  mixture  is  saturated  with  CO.  A  sample  of 
this  dilute  blood  is  placed  in  a  vessel  with  parallel  sides  (l  cm.  apart)  opposite  the  light  (the 
so-called  hsematinometer),  and  in  a  second  vessel  of  the  same  dimensions  a  sample  of  the  undiluted 
CO  blood  is  diluted  with  water  from  a  burette,  until  both  fluids  give  the  same  intensity  of  color. 
From  the  quantity  of  water  required  to  dilute  the  blood  to  the  tint  of  the  washings  of  the  blood 
vessels,  the  quantity  of  blood  in  the  washings  is  calculated.  On  chopping  up  the  muscles  alone,  we 
obtain  the  amount  of  Hb  present  in  them,  which  is  not  taken  into  calculation. 

Quantity  of  Blood  in  Various  Animals. — The  quantity  of  blood  in  the 
mouse  =  T^y  to^V ;  guinea-pig  =Ti.y  (^V  to  2V)  ^  rabbit  =2^,^  (to  to  2V)  '>  dog 
=  T3  (tt  to  iV)  ^  cat  =  2T. 5  ;  birds  =  ^  iq  ^;  frog  =  J^  to  ^L ;  fishes  = 
-jL  to  Y^-g-of  the  body  weight  (without  the  contents  of  the  stomach  and  intestines). 

The  specific  gravity  of  the  blood  ought  always  to  be  taken  when  estimating  the  amount  of  blood. 
The  amount  of  blood  is  diminished  during  inanition  ;  fat  persons  have  relatively  less  blood ;  after 
hemorrhage  the  loss  is  at  first  replaced  by  a  watery  fluid,  while  the  blood  corpuscles  are  gradually 
regenerated. 

Blood  in  Organs. — The  estimation  of  the  qiianiiiy  of  blood  in  different  organs 
is  done  by  suddenly  ligaturing  their  blood  vessels  intra  vitam.  A  watery  extract 
of  the  chopped-up  organ  is  prepared,  and  the  quantity  of  blood  estimated  as 
described  above.  [Roughly  it  may  be  said  that  the  lungs,  heart,  large  arteries, 
and  veins  contain  y^;  the  muscles  of  the  skeleton,  y^;  the  liver,  i^;  and  other 
organs,  ^  {Ranke')j\ 

41.  ABNORMAL  CONDITIONS  OF  THE  BLOOD.— (A)  i  Polysemia.— (i)  An 
increase  in  the  entire  mass  of  the  blood,  uniformly  in  all  organs,  constitutes /(^/j/^wm  ox  plethora, 
and  in  over- nourished  individuals  it  may  approach  a  pathological  condition.  A  bluish-red  color  of 
the  skin,  swollen  veins,  large  arteries,  hard,  full  pulse,  injection  of  the  capillaries  and  smaller  vessels 
of  the  visible  mucous  membranes  are  signs  of  this  state,  and,  when  accompanied  by  congestion  of 
the  brain,  there  is  vertigo,  congestion  of  the  lungs,  and  breathlessness.  After  major  amputations 
with  little  loss  of  blood  a  relative  but  transient  increase  of  blood  has  been  found  (?)  {plethora 
apocoptica). 

Transfusion. — Polysemia  may  be  produced  artificially  by  the  injection  of  blood  of  the  same 
species.  If  the  normal  quantity  of  blood  be  increased  83  per  cent,  no  abnormal  condition  occurs, 
because  the  blood  pressure  is  not  permanently  raised.  The  excess  of  blood  is  accommodated  in 
the  greatly  distended  capillaries,  which  may  be  stretched  beyond  their  normal  elasticity.  If  it  be 
increased  to  150  per  cent,  there  are  variations  in  the  blood  pressure,  life  is  endangered,  and  there 
may  be  sudden  rupture  of  blood  vessels  ( Worm  Midler). 

Fate  of  Transfused  Blood. — After  the  transfusion  of  blood  the  formation  of  lymph  is  greatly 
increased ;  but  in  one  or  two  days  the  serum  is  used  up,  the  water  is  excreted  chiefly  by  the  urine, 
and  the  albumin  is  partly  changed  into  urea.  Hence,  the  blood  at  this  time  appears  to  be  relatively 
richer  in  blood  corpuscles  [Panum,  Lesser,  Worm  Miiller).  The  red  corpuscles  break  up  much 
more  slowly,  and  the  products  thereof  are  partly  excreted  as  urea  and  partly  (but  not  constantly)  as 
bile  pigments.  Even  after  a  month  an  increase  of  colored  blood  corpuscles  has  been  observed 
{Tschirjew).  That  the  blood  corpuscles  are  broken  up  slowly  in  the  economy  is  proved  by  the 
fact,  that  the  amount  of  urea  is  much  larger  when  the  same  quantity  of  blood  is  swallowed  by  the 
animal  than  when  an  equal  amount  is  transfused  [Tschirjew,  Landois).  In  the  latter  case  there 
is  a  moderate  increase  of  the  urea,  lasting  for  days,  a  proof  of  the  slow  decomposition  of  the  red 
corpuscles.  Pronounced  over-filling  of  the  vessels  causes  loss  of  appetite  and  a  tendency  to  hemor- 
rhage of  the  mucous  membranes. 

(2)  Polyaemia  serosa  is  that  condition  in  which  the  amount  of  serum,  i.e.,  the  amount  of  water 
in  the  blood,"  is  increased.  This  may  be  produced  artificially  by  the  transfusion  of  blood  serum 
from  the  same  species.  The  water  is  soon  given  off  in  the  urine,  and  the  albumin  is  decomposed 
into  urea,  without,  however,  passing  into  the  urine.  An  animal  forms  more  urea  in  a  short  time 
from  a  quantity  of  transfused  serum  than  from  the  same  quantity  of  blood,  a  proof  that  the  blood 
corpuscles  remain  longer  undecomposed  than  the  serum  [Forsier,  Landois).  If  serum  from  another 
species  of  animal  be  used  {e.g.,  dog's  serum  transfused  into  a  rabbit),  the  blood  corpuscles  of  the 


88  ABNORMAL    CONDITIONS    OF    THE    BLOOD. 

recipient  are  dissolved  ;  haemoglobinuria  is  produced  [Ponjick) ;  and  if  there  be  general  dissolution 
of  the  corpuscles,  death  may  occur  (/..att Jot's). 

(3)  Polyaemia  aquosa  is  a  simple  increase  of  the  water  of  the  blood,  and  occurs  temporarily 
after  copious  drinking,  but  increased  diuresis  soon  restores  the  normal  condition.  Diseases  of  the 
kidneys,  which  destroy  their  secreting  parenchyma,  produces  this  condition,  and  often  general 
ilropsy,  owing  to  the  passage  of  water  into  the  tissues.  Ligature  of  the  ureter  produces  a  watery 
condition  of  the  blood. 

(4)  Plethora  polycythaemica,  Hyperglobulie. — An  increase  of  the  red  corpuscles  has  been 
assumed  to  occur  when  periodically  recurring  hemorrhages  are  interrupted,  <r,f^.,  menstruation, 
bleeding  from  the  nose,  etc. ;  but  the  increase  of  corpuscles  has  not  been  definitely  proved. 
There  is  a  proved  case  of  temjwrary  f>olycythxmia,  viz.,  when  similar  blood  is  transfused,  a  part 
of  the  fluid  being  used  up,  while  the  corpuscles  remain  unchanged  for  a  considerable  time. 
There  is  a  remakable  increase  in  the  number  of  blood  corpuscles  (to  S.82  millions  per  cubic  milli- 
metre) in  certain  severe  cardiac  affections  svhere  there  is  great  congestion,  and  much  water  trans- 
udes through  the  vessels.  In  cases  of  hemiplegia,  for  the  same  reason,  the  number  of  corpuscles 
is  greater  on  the  paralyzed  congested  side  (Penso/t//).  After  diarrhcea,  which  diminishes  the 
water  of  the  blood,  there  is  also  an  increase  \Broitardel),  and  the  same  is  the  case  after  profuse 
sweating  and  polyuria.  Drugs  (alcohol,  chloral,  amyl  nitrite)  which  act  on  the  blood  vessels  aflect 
the  number  of  corpuscles ;  during  contraction  of  the  blood  vessels  their  number  increases,  during 
dilatation  they  diminish  in  number  [Andit'esen).  There  is  a  temporary  increase  in  the  hwmato- 
blasts  as  a  reparative  process  after  severe  hemorrhage  (^  7),  or  after  acute  diseases.  In  cachectic 
conditions  this  increase  continues,  owing  to  the  diminished  non- conversion  of  these  corpuscles  into 
red  coqiuscles.  In  the  last  stages  of  cachexia  the  number  diminishes  more  and  more  until  the 
formation  of  ha-matoblasts  ceases  [Hayen). 

(5)  Plethora  hyperalbuminosa  is  a  term  applied  to  the  increase  of  albumins  in  the  plasma, 
such  as  occurs  after  taking  a  large  amount  of  food.  A  similar  condition  is  produced  by  transfusing 
the  serum  of  the  same  species,  whereby,  at  the  same  time,  the  urea  is  increased.  Injection  of  egg- 
albumin  produces  albuminuria  (S/oA'tis,  Lehmann). 

[The  subcutaneous  injection  of  human  blood  has  been  practiced  with  good  results  in  anaemia 
(:■.  Zieiiisscn).  When  defibrinated  human  blood  is  injected  subcutaneously,  while  its  passage  into 
the  circulation  is  aided  by  massage,  it  causes  neither  pain  nor  inflammation,  but  the  blood  of  animals, 
and  a  solution  of  hemoglobin,  always  induce  abscess  [Benczur).  Blood  is  also  rapidly  absorbed 
when  injected  in  small  amount  into  the  respiratory  passages.] 

Mellitaemia. — The  sugar  in  the  blood  is  partly  given  off"  by  the  urine,  and  in  "  diabetes 
mellitus  "  i  kilo.  (2.2  lbs.)  may  be  given  off  daily,  when  the  quantity  of  urine  may  rise  to  25 
kilos.  To  replace  this  loss  of  grape  sugar  a  large  amount  of  food  and  drink  is  required,  whereby 
the  urea  may  be  increased  threefold.  The  increased  production  of  sugar  causes  an  increased 
decomposition  of  albuminous  tissues;  hence  the  urea  is  always  increased,  even  though  the  supply 
of  albumin  be  insufficient.  The  patient  loses  flesh ;  all  the  glands,  and  even  the  testicles,  atrophy 
or  degenerate  (pulmonar)'  phthisis  is  common) ;  the  skin  and  bones  become  thinner ;  the  nervous 
system  holds  out  longest.  The  teeth  become  carious  on  account  of  the  acid  saliva,  the  crystal- 
line lens  becomes  turbid  from  the  amount  of  sugar  in  the  fluid  of  the  eye  which  extracts  water 
from  the  lens,  and  wounds  heal  badly  because  of  the  abnormal  condition  of  the  blood.  Absence 
of  all  carbohydrates  in  the  food  causes  a  diminution  of  the  sugar  in  the  blood,  but  does  not 
cause  it  to  disappear  entirely.  [The  sugar  in  the  blood  is  also  increased  after  the  inhalation 
of  chloroform  or  amyl  nitrite,  and  after  the  use  of  curara,  nitro-benzole,  and  chloral  [\  175)]  An 
excessive  amount  of  inosite  has  been  found  in  the  blood  and  urine  (^  267),  constituting  mellituria 
inosita  ( ]'ohl). 

Lipjemia,  or  an  Increase  of  the  Fat  in  the  Blood,  occurs  after  every  meal  rich  in  fat  {e.g., 
in  sucking  kittens),  so  that  the  serum  may  become  turbid  like  milk.  Pathologically,  this  occurs  in  a 
high  degree  in  drunkards  and  in  corpulent  individuals.  When  there  is  great  decomposition  of 
albumin  in  the  body  (and  therefore  in  very  severe  diseases),  the  fat  in  the  blood  increases,  and  this 
also  takes  place  after  a  liberal  supply  of  easily  decomposable  carbohydrates  and  much  fat. 

After  injuries  to  bones  affecting  the  marrow,  not  unfrequently  fatty  granules  pass  from  the  marrow 
through  the  imperfect  walls  of  the  blood  vessels  into  the  blood  stream.  These  fatty  particles  may 
form  fat  emboli,  e.g.,  in  the  liver  or  lungs,  or  they  may  appear  in  the  urine. 

If  granules  of  cinnabar  or  indigo  are  injected  'into  the  blood,  they  are  taken  up  by  the  leucocytes, 
and  by  them  are  carried  outside  the  blood  stream.  The  cells  of  the  splenic  pulp,  marrow  of  bone, 
and  the  liver  also  take  up  these  particles  [Siebei). 

The  salts  remain  very  persistently  in  the  blood.  The  withdrawal  of  common  salt  produces 
albuminuria,  and,  if  all  salts  be  withheld,  paralytic  phenomena  occur  {Forster).  'Over- feeding 
with  salted  food,  such  as  salt  meat,  has  caused  death  through  fatty  degeneration  of  the  tissues, 
especially  of  the  glands.  Withdrawal  of  lime  and  phosphoric  acid  produces  atrophy  and  softening 
of  the  bones.  In  infectious  diseases  and  dropsies  the  salts  of  the  blood  are  often  increased,  and 
diminished  in  inflammation  and  cholera.  [NaCl  is  absent  from  the  urine  in  certain  stages  of  pneu- 
monia, and  It  IS  a  good  sign  when  the  chlorides  begin  to  return  to  the  urine.]     [In  scurvy  the 


ABNORMAL    CONDITIONS    OF   THE    BLOOD.  89 

corpuscular  elements  are  diminished  in  amount,  but  we  have  not  precise  information  as  to  the  salts, 
although  this  disease  is  prevented,  in  persons  forced  to  live  upon  preserved  and  salted  food,  by  a 
liberal  use  of  the  salts — especially  potash  salts — of  the  organic  acids,  as  contained  in  lime-juice. 
In  gout  the  blood,  during  an  acute  attack,  and  also  in  chronic  gout,  contains  an  excess  of  uric 
acid   {Garrod).'\ 

The  amount  of  fibrin  is  increased  in  inflammations  of  the  lung  and  pleura  [croupous  pneu- 
monia, erysipelas],  hence  such  blood  forms  a  criista  phlogistica  {\  27).  In  other  diseases,  where 
decomposition  of  the  blood  corpuscles  occurs,  the  fibrin  is  increased,  perhaps  because  the  dissolved 
red  corpuscles  yield  material  for  the  formation  of  fibrin.  After  repeated  hemorrhages,  Sigm. 
Mayer  found  an  increase  of  fibrin.  Blood  rich  in  fibrin  is  said  to  coagulate  more  slowly  than  when 
less  fibrin  is  present — still  there  are  many  exceptions. 

(B)  (I.)  Diminution  of  the  Quantity  of  Blood,  or  its  Individual  Constituents. — (i) 
Oligaemia  vera,  Anaemia,  or  diminution  of  the  quantity  of  blood  as  a  whole,  occurs  whenever 
there  is  hemorrhage.  Life  is  endangered  in  newly-born  children  when  they  lose  a  few  ounces  of 
blood;  in  children  a  year  old,  on  losing  half  a  pound;  and  in  adults,  when  one-half  of  the  total 
blood  is  lost.  Women  bear  loss  of  blood  much  better  than  men.  The  periodical  formation  of  blood 
after  each  menstruation  seems  to  enable  blood  to  be  renewed  more  rapidly  in  their  case.  Stout 
persons,  old  people,  and  children  do  not  bear  the  loss  of  blood  well.  The  more  rapidly  blood  is 
lost,  the  more  dangerous  it  is.  [A  moderate  loss  of  blood  is  soon  made  up,  but  the  fluid  part  is 
more  quickly  restored  than  are  the  corpuscles.] 

Symptoms  of  Loss  of  Blood. — Great  loss  of  blood  is  accompanied  by  general  paleness  and 
coldness  of  the  cutaneous  surface,  increased  oppression,  twitching  of  the  eyeballs,  noises  in  the  ears 
and  vertigo,  loss  of  voice,  great  breathlessness,  stoppage  of  secretions,  coma;  dilatation  of  the 
pupils,  involuntary  evacuations  of  urine  and  fasces,  and  lastly,  general  convulsions,  are  sure  signs 
of  death  by  hemorrhage.  In  the  gravest  cases  recovery  is  only  possible  by  means  of  trans- 
fusion. Animals  can  bear  the  loss  of  one-fourth  of  their  entire  blood  without  the  blood  pressure 
in  the  arteries  permanently  falling,  because  the  blood  vessels  contract  and  accommodate  them- 
selves to  the  smaller  quantity  of  blood  (in  consequence  of  the  stimulation  of  the  vasomotor  centre 
in  the  medulla).  The  loss  of  one-third  of  the  total  blood  diminishes  the  blood  pressure  consid- 
erably (one-fourth  in  the  carotid  of  the  dog).  If  the  hemorrhage  is  not  such  as  to  cause  death, 
the  fluid  part  of  the  blood  and  the  dissolved  salts  are  restored  by  absorption  from  the  tissues, 
the  blood  pressure  gradually  rises,  and  then  the  albumin  is  restored,  though  a  longer  time  is 
required  for  the  formation  of  red  corpuscles.  At  first,  therefore,  the  blood  is  abnormally  rich  in 
water  (hydraemia),  and  at  last  abnormally  poor  in  corpuscles  (oligocythaemia,  hypoglobulie). 
With  the  increased  lymph  stream  which  pours  into  the  blood,  the  colorless  corpuscles  are  consider- 
ably increased  above  norma),  and  during  the  period  of  restitution  fewer  red  corpuscles  seem  to  be 
used  up  {e.g.,  for  bile). 

After  moderate  bleeding  from  an  artery  in  animals,  Buntzen  observed  that  the  volume  of  the 
blood  was  restored  in  several  hours;  after  more  severe  hemorrhage  in  24  to  48  hours.  The  red 
blood  corpuscles,  after  a  loss  of  blood  equal  to  i.i  to  4.4  per  cent,  of  the  body  weight,  are  restored 
only  after  7  to  34  days.  The  regeneration  begins  after  24  hours.  During  the  period  of  regene- 
ration the  number  of  the  blood  corpuscles  in  an  early  stage  of  development  is  increased.  The 
newly.formed  corpuscles  contain  less  Hb  than  normal  {Jac.  G.  OU).  Even  in  man  the  duration 
of  the  period  of  regeneration  depends  upon  the  amount  of  blood  lost  {Lyon).  The  amount  of 
haemoglobin  is  diminished  nearly  in  proportion  to  the  amount  of  the  hemorrhage  {Bizzozero  and 
Sakdoli). 

Metabolism  in  Anaemia. — The  condition  of  the  metabolistn  within  the  bodies  of  ansemic 
persons  is  important.  The  decomposition  of  proteids  is  increased  (the  same  is  the  case  in  hunger), 
hence  the  excretion  of  urea  is  increased  {Bauer).  The  decomposition  of  fats,  on  the  contrary,  is 
diminished,  which  stands  in  relation  with  the  diminution  of  COj  given  off".  Ansemic  and  chlorotic 
persons  put  on  fat  easily.  The  fattening  of  cattle  is  aided  by  occasional  bleedings  and  by  inter- 
current periods  of  hunger  {Aristotle). 

(2)  An  excessive  thickening  of  the  blood  through  loss  of  water  is  called  Oligaemia  sicca. 
This  occurs  in  man  after  copious  watery  evacuations,  as  in  cholera,  so  that  the  thick  tarry  blood 
stagnates  in  the  vessels.  Perhaps  a  similar  condition — though  to  a  less  degree — may  exist  after 
very  copious  perspiration. 

(3)  If  the  proteids  in  blood  be  abnormally  diminished  the  condition  is  called  Oligaemia  hyp- 
albuminosa  ;  they  may  be  diminished  about  one-half.  They  are  usually  replaced  by  an  excess  of 
water  in  the  blood  [so  that  the  blood  is  watery,  constituting  hydraemia].  Loss  of  albumin  from 
the  blood  is  caused  directly  by  albuminuria  (25  grams  of  albumin  may  be  given  off"  by  the  urine 
daily),  persistent  suppuration,  great  loss  of  milk,  extensive  cutaneous  ulceration,  albuminous  diar- 
rhoea (dysentery).  Frequent  and  copious  hemorrhages,  however,  by  increasing  the  absorption  of 
water  into  the  vessels,  at  first  produce  oligemia  hypalbuminosa. 

For  the  abnormal  changes  of  the  red  and  white  blood  corpuscles,  see  ?  10 ;  for  Haemophilia, 
a  28. 


90 


ORGANISMS    IN    THE    BLOOD. 


[Organisms  in  the  Blood. — The  presence  of  animal  and  vegetable  parasites  in  the  blood 
gives  rise  to  certain  diseases.  Some  of  these,  and  esiiecially  the  vegetable  organisms,  have  the 
power  of  multiplying  in  the  blood.  The  vegetable  forms  belonging  to  the  schizomycetes  are  fre- 
quently spoken  of  collectively  under  the  title  bacteria.     They  are  classified  by  Cohn  into 

I.  Spharobacteria.  I        }"•  Desmobacterial^^j^j^^;^  ^^^^^^^^^^^^ 

II.  Microbacteria,  exhibit  movements.  |        I\ .    Spirobacteria    j 

These  forms  are  shown  in  Fig.  23.  The  micrococci  (A)  are  examples  of  I;  while  Uacterium 
termo  (B)  is  an  example  of  II.     In  III  the  members  are  short  cylindrical  rods,  straight  (Bacillus, 


Fig.  23. 


Fig.  24. 


micrococcus  ;    B,   bacterium  ;    C,  vibrios  ; 
D,  bacilli;  E,  spirillum. 


Bacillus  anthracis  from  the  blood  (ox)  in 
splenic  fever. 


D)  or  wavy  (Vibrio,  C).  Splenic  fever  of  cattle  is  due  to  the  presence  of  Bacillus  anthracis  (Fig. 
24).  These  rod-shaped  bodies  under  proper  conditions  divide  transversely  and  elongate,  but  they 
also  form  spores  in  their  interior,  which  in  turn  under  appropriate  conditions  may  germinate  (Fig. 
24).  Class  IV  is  represented  by  two  genera,  Spirochxta  and  Spirillum  (Fig.  23),  the  former  with 
close,  and  the  later  with  open  spirals.  The  Spirochasta  Obermeieri  (often  spoken  of  as  "  Spirillum") 
is  present  in  the  blood  during  the  paroxysms  in  persons  suffering  from  relapsing  fever.  Among 
animal  parasites  are  Filaria  sanguinis,  and  Bilharzia  Ha^matobia,  which  occurs  in  the  portal  vein 
and  in  the  veins  of  the  urinary  apparatus.] 


Physiology  of  the  Circulation. 


Fig.  25. 


42.  GENERAL  VIEW. — The  blood  within,  the  vessels  is  in  a  state  of 
continual  motion,  being  carried /r^;^z  the  ventricles  by  the  large  arteries  (aorta  and 
pulmonary)  and  their  branches  to  the  system  of 
capillary  vessels,  from  which  again  it  passes  into 
the  veins  that  end  in  the  atria  of  the  auricles  (  W. 
Harvey,  1628). 

The  cause  of  the  circulation  is  the  difference 
of  pressure  which  exists  between  the  blood  in  the 
aorta  and  pulmonary  artery  on  the  one  hand,  and 
the  two  venae  cavse  and  the  four  pulmonary  veins 
on  the  other.  The  blood,  of  course,  moves  con- 
tinually in  its  closed  tubular  system  in  the  direction 
of  least  resistance.  The  greater  the  difference  of 
pressure,  the  more  rapid  the  movement  will  be. 
The  cessation  of  the  difference  of  pressure  (as  after 
death)  naturally  brings  the  movement  to  a  stand- 
still (§  81).  The  circulation  is  usually  divided 
into — 

(i)  The  greater,  or  systemic  circulation, 
which  includes  the  course  of  the  blood  from  the 
left  auricle  and  left  ventricle,  through  the  aorta  and 
all  its  branches,  the  capillaries  of  the  body  and  the 
veins,  until  the  two  vense  cavs  terminate  in  the 
right  auricle. 

(2)  The  lesser,  or  pulmonic  circulation, 
which  includes  the  course  from  the  right  auricle 
and  right  ventricle,  the  pulmonary  artery,  the  pul- 
monary capillaries,  and  the  four  pulmonary,  veins 
springing  from  them,  until  these  open  into  the  left 
auricle. 

(3)  The    portal    circulation    is    sometimes  -^^^'-ft  :4icTerT:'S^^^ 

spoken    of  as  a  special    circulatory  system,   although  tricle;  i,  pulmonary  artery:  2,  aorta: 

it  represents  only  a  second  set  of  capillaries  (within        femic''  cLdLTionT^'<.!^thT^superio'r 
the  liver)  introduced  into  the  course  of  a  venous        y^"^  <^a™:  g,  area  supplying  the 

,            4                  .                       ,  .  ,  interior  vena  cava,  a;  a,  «:,  intestine ; 

trunk.        It  consists    of    the    vena    portarum formed  ?«,  mesenteric  artery  ;  ^,  portal  vein  ; 

by  the  union  of  the  intestinal  or  mesenteric  and        l,  hver ,- a,  hepatic  vein. 
splenic  veins,  and  it  passes  into  the  liver,  where  it  divides  into  capillaries,  from 
which  the  hepatic  veins  arise.     The  hepatic  vein  joins  the  inferior  vena  cava. 

Strictly  speaking,  however,  there  is  no  special  portal  circulation.  Similar  arrangements  occur 
in  other  animals  in  different  organs,  e.  g.,  snakes  have  such  a  system  in  their  supra- renal  capsules, 
and  the  frog  in  its  kidneys.  When  an  artery  splits  up  into  fine  branches  during  its  course,  and 
these  branches  do  not  form  capillaries,  but  reunite  into  an  arterial  trunk,  a  rete  mirabile  is  formed, 
such  as  occurs  in  apes  and  the  edentata.  Microscopic  retia  mirabilia  exist  in  the  human  mesentery 
[Sck'dbl).  Similar  arrangements  may  exist  in  connection  with  veins,  giving  rise  to  venous  retia 
mirabilia. 

91 


92 


ARRANGEMENT    OF   THE    CARDIAC    MUSCULAR    FIBRES. 


X3_  THE  HEART. The  muscular  fibres  of  the  mammalian  heart  consist  of  short  (50  to 

-o  /(  in  man),  very  line,  transversely  striated  tihres,  which  are  actual  unicellular  elements,  devoid  of 
a  sarcolemma  (15  to  25  //  broad),  and  usually  divided  at  their  blunt  ends,  by  which  means  they 
anastomose  and  form  a  network  (Fig.  26,  A,  B).  The  individual  muscle  cells  contain  in  their  centre 
an  oval  nucleus,  and  are  held  together  by  a  cement  which  is  blackened  by  silver  nitrate,  and  dis- 
solved by  a  ^;i  per  cent,  solution  of  caustic  potash.  This  cement  is  also  dissolved  by  a  40  per  cent, 
solution  of  nitric  acid.  The  transverse  strix-  are  not  very  distinct,  and  not  unfreciuently  there  is 
an  appearance  of  longitudinal  striation,  produced  by  a  number  of  very  small  granules  arranged  in 
rows  within  the  fibres.  The  fibres  are  gathered  lengthwise  in  bundles,  or  fasciculi,  surrounded 
and  separated  from  each  other  by  delicate  processes  of  the  perimysium.  \Vhen  the  connective 
tissue  is  dissolved  by  prolonged  boiling,  these  bundles  can  be  isolated,  and  constitute  the  so-called 
"fibres"  of  the  heart.  The  transverse  sections  of  the  bundles  in  the  auricles  are  polygonal  or  rounded, 
while  in  the  ventricles  they  are  somewhat  flattened.  [The  muscular  mass  of  the  heart  is  called  the 
myocardium,  and  is  invested  by  filirous  tissue.  It  is  important  to  notice  that  the  connective  tissue 
of  the  visceral  pericardium  (epicardium)  is  continuous  with  that  of  the  endocardium  by  means  of 
the  perimysium  surrounding  the  bundles  of  muscular  fibres.]  The  fine  spaces  which  exist  between 
these  bundles  form  narrow  lacunne,  lined  with  epithelium,  and  constituting  part  of  the  lymphatic  sys- 
tem of  the  heart. 

[The  cardiac  muscular  fibres  occupy  an  intermediate  position  between  striped  and  plain  muscular 
fibres.  Although  they  are  striped,  they  are  involuntary,  not  being  directly  under  the  intluence  of  the 
will,  while  they  contract  more  slowly  than  a  voluntary  muscle  of  the  skeleton.]     In  the  frog's  heart 


Fig.  26. 


A,  muscular  fibres  from  the  heart  of  a  mammal,  and  C  from  a  frog;   B,  transverse  section  of  the  cardiac  fibres; 
/>,  connective-tissue  corpuscles  ;  c,  capillaries. 

the  muscular  fibres  are  in  shape  elongated  spindles,  or  fusiform,  in  this  respect  resembling  the  plain 
muscle  cells,  but  they  are  transversely  striped  (Fig.  26,  C).  They  are  easily  isolated  by  means  of  a 
2S  per  cent,  solution  of  potash  or  dilute  alcohol. 

44.  ARRANGEMENT  OF  THE  CARDIAC  MUSCULAR  FI- 
BRES.— The  study  of  the  embryonic  heart  is  the  key  to  a  proper  understanding 
of  the  complicated  arrangement  of  the  fibres  in  the  adult  heart.  The  simple  tubu- 
lar heart  of  the  embryo  has  an  ou/er  circular  and  an  inner  loni:;itiidinal  layer  of 
fibres.  The  septum  is  formed  later ;  hence,  it  is  clear  that  a  part,  at  least,  of  the 
fibres  must  be  common  to  the  two  auricles,  and  a  part  also  to  the  two  ventricles, 
since  there  is,  originally,  but  one  chamber  in  the  heart.  The  muscular  fibres  of 
the  auricles  are,  however,  completely  separated  from  those  of  the  ventricles  by 
the  fibro-cartilaginous  rings.  In  the  auricles  the  fundamental  arrangement  of 
the  embryonic  fibres  partly  remains,  while  in  the  ventricles  it  becomes  obscured 
as  the  cavities  undergo  a  sac-like  dilatation,  and  also  become  twisted  in  a  spiral 
manner. 

(i)  The  muscular  fibres  in  the  auricles  are  completely  separated  from  the 
fibres  of  the  ventricles  by  \.\\^  fibrous  rings  which  surround  the  auriculo-ventricular 
orifices,  and  which  serve  as  an  attachment  for  the  auriculo-ventricular  valves 
(Fig.  27,  I).  The  auricles  are  much  thinner  than  the  ventricles,  and  their  fibres 
are  generally  arranged  in  two  layers  ;  the  o\x\.tx  tra?isverse  layer  is  continuous  over 


ARRANGEMENT    OF    THE    CARDIAC    MUSCULAR    FIBRES. 


93 


both  auricles,  while  the  inner  one  is  directed  iongiiudinaHy.  The  outer  transverse 
fibres  may  be  traced  from  the  openings  of  the  venous  trunks  anteriorly  and  poste- 
riorly over  the  auricular  walls.  The  longitudinal  fibres  are  specially  well  marked 
where  they  are  inserted  into  the  fibro-cartilaginous  rings,  while  in  some  parts  of 
the  anterior  auricular  wall  they  are  not  continuous.  In  the  auricular  septum,  some 
fibres,  circularly  disposed  around  the  fossa  ovalis  (formerly  the  embryonic  opening 
of  the  foramen  ovale),  are  well  marked.  Circular  bands  of  striped  muscle  exist 
around  the  veins  where  they  open  into  the  heart ;  these  are  least  marked  on  the 
inferior  vena  cava,  and  are  stronger  and  reach  higher  (2.5  cm.)  on  the  superior 
vena  cava  (Fig.  27,  II).  Similar  fibres  exist  around  the  pulmonary  veins,  where 
they  join  the  left  auricle,  and  these  fibres  (which  are  arranged  as  an  inner  circular 
and  an  outer  longitudinal  layer)  can  be  traced  to  the  hilus  of  the  lung  in  man  and 
some  mammals ;  in  the  ape  and  rat  they  extend  on  the  pulmonary  veins  right  into 
the  lung.  In  the  mouse  and  bat,  again,  the  striped  muscular  fibres  pass  so  far  into 
the  lungs  that  the  walls  of  the  smaller  veins  are  largely  composed  of  striped  muscle 
(Stieda). 

Fig.  27. 


I.  Course  of  the  muscular  fibres  on  the  left  auricle  with  the  outer  transverse  and  inner  longitudinal  fibres,  the  circular 
fibres  on  the  pulmonary  veins  {v.  p.) ;  V,  the  left  ventricle  {yohn  Reid).  II.  Arrangement  of  the  striped  muscu- 
lar fibres  on  the  superior  vena  cava  (Elischer) — a,  opening  of  vena  azygos;  v,  auricle. 

Circular  muscular  fibres  are  found  where  the  vena  magna  cordis  enters  the  heart, 
and  in  the  Valvula  Thebesii  which  guards  it. 

Physiological  Significance. — (i)  The  auricles  contract  independently  of 
the  ventricles.  This  is  seen  when  the  heart  is  about  to  die ;  when  there  may  be 
several  auricular  contractions  for  one  ventricular,  and  at  last  only  the  auricles 
pulsate.  The  auricular  portion  of  the  right  auricle  beats  longest ;  hence  it  is  called 
the  "ultimum  moriens."  Independent  rhythmical  contractions  of  the  ven»  cavae 
and  pulmonary  veins  are  often  noticed  after  the  heart  has  ceased  to  beat.  [This 
beating  can  also  be  observed  in  those  veins  in  a  rabbit  after  the  heart  is  cut  out  of 
the  body.] 

(2)  The  double  arrangement  of  the  fibres  (transverse  and  longitudinal)  produces 
a  simultaneous  and  uniform  diminution  of  the  auricular  cavity  (such  as  occurs  in 
most  of  the  hollow  viscera). 

(3)  The  contraction  of  the  circular  muscular  fibres  around  the  venous  orifices, 
and  the  subsequent  contraction  of  the  auricle,  cause  these  veins  to  empty  themselves 
into  the  auricle  ;  and  by  their  presence  and  action  they  prevent  any  large  quantity 
of  blood  from  passing  backward  into  the  veins  when  the  auricle  contracts.  [No 
valves  are  present  in  the  superior  and  inferior  vena  cava  in  the  adult  heart,  or  in  the 
pulmonary  veins ;  hence  the  contraction  of  these  circular  muscular  fibres  plays  an  im- 
portant part  in  preventing  any  reflux  of  blood  during  the  contraction  of  the  auricles.] 


94 


ARRANGEMENT   OF    THE   VENTRICULAR    FIBRES. 


45.  ARRANGEMENT    OF    THE    VENTRICULAR    FIBRES.— 

(2)  The  muscular  fibres  in  the  thick  wall  of  the  ventricles  are  arranged  in 
several  layers  (Fig.  28,  A)  under  the  pericardium.  First,  there  is  an  outer  longi- 
ttuiinal  layer  (A)  which  is  in  the  form  of  single  bundles  on  the  right  ventricle, 
but  forms  a  complete  layer  on  the  left  ventricle,  where  it  measures  about  one- 
eighth  of  the  thickness  of  the  ventricular  wall.  A  second  lotigiiudinal  layer  of 
fibres  lies  on  the  inner  surface  of  the  ventricles,  distinctly  visible  at  the  orifices, 
and  within  the  vertically  placed  papillary  muscles,  while  elsewhere  it  is  replaced 
by  the  irregularly  arranged  trabeculae  carneae.  Between  these  two  layers  there 
lies  the  thickest  layer,  consisting  of  more  or  less  transversely  arranged  bundles, 
which  may  be  broken  up  into  single  layers  more  or  less  circularly  disposed.  The 
deep  lymphatic  vessels  run  between  the  layers,  while  the  blood  vessels  lie  within 
the  substance  of  the  layers,  and  are  surrounded  by  the  primitive  bundles  of  mus- 
cular fibres.     All  three  layers  are  not  completely  independent  of  each  other ;  on 

Fig.  2S. 


Course  of  the  ventricular  muscular  fibres.     A,  on  the   anterior   surface;  B,  view  of  the  apex  with  the  vortex-  C 
course  of  the  fibres  within  the  ventricular  wall ;  D,  fibres  passing  into  a  papillary  muscle.  '      ' 


the  contrary,  the  fibres  which  run  obliquely  form  a  gradual  transition  between  the 
transverse  layers  and  the  inner  and  outer  longitudinal  layers.  It  is  not,  however, 
quite  correct  to  assume  that  the  outer  longitudinal  layer  gradually  passes  into  the 
transverse,  and  this  again  into  the  inner  longitudinal  layer  (as  is  shown  schemat- 
ically in  C) ;  because,  as  Henle  pointed  out,  the  transverse  fibres  are  relatively 
far  greater  in  amount.  In  general,  the  outer  longitudinal  fibres  are  so  arranged  as 
to  cross  the  inner  longitudinal  layer  at  an  acute  angle.  The  transverse  layers 
lying  between  these  two  form  gradual  transitions  between  these  directions.  At  the 
apex  of  the  left  ventricle,  the  outer  longitudinal  fibres  bend  or  curve  so  as  to  meet 
at  the  so-called  vortex  B,  where  they  enter  the  muscular  substance,  and,  taking  an 
upward  and  inward  direction,  reach  the  papillary  muscles,  P,  D  ;  although  it  is  a 
mistake  to  say  that  all  the  bundles  which  ascend  to  the  papillary  muscles  arise 
trom  the  vertical  fibres  of  the  outer  surface:  many  seem  to  arise  independently 
within  the  ventricular  wall.     According  to   Henle,  all   the  external  longitudinal 


PERICARDIUM,    ENDOCARDIUM,  VALVES. 


95 


fibres  do  not  arise  from  the  fibrous  rings  or  the  roots  of  the  arteries.     The  mitral 
orifice  is  surrounded  by  circular  fibres  which  act  like  a  sphincter  {Henle). 

[The  assumption  that  the  muscles  of  the  ventricle  are  arranged  so  as  to  form  a  figure  of  8,  or  in 
loops,  seems  to  be  incorrect ;  thus,  fibres  are  said  to  arise  at  the  base  of  the  ventricle,  to  pass  over 
it,  and  to  reach  the  vortex,  where  they  pass  into  the  interior  of  the  muscular  substance,  to  end  either 
in  the  papillary  muscles  or  high  up  on  the  inner  surface  of  the  heart  at  its  base.  Figs.  C  and  D 
give  a  schematic  representation  of  this  view.] 

Only  the  general  arrangement  of  the  ventricular  muscular  fibres  has  been  indicated.  According 
to  Pettigrew,  there  are  seven  layers  in  the  ventricle,  viz.,  three  external,  a  fourth  or  central  layer, 
and  three  internal.  These  internal  layers  are  continuous  with  the  corresponding  external  layers  at 
the  apex,  thus — one  and  seven,  two  and  six. 

46.  PERICARDIUM,  ENDOCARDIUM,  VALVES.— The  pericardium  encloses 
within  its  two  layers  [visceral  and  parietal]  a  lymph  space — the  pericardial  space — which  contains 
a   small  quantity  of  lymph — the   pericardial 

fluid.     It  has  the  structure   of  a  serous  mem-  Fig.  29. 

brane,  i.  e.,  it  consists  of  connective  tissue 
mixed  with  fine  elastic  fibres  arranged  in  the 
form  of  a  thin  delicate  membrane,  and  cov- 
ered on  its  free  surfaces  with  a  single  layer  of 
epithelium  or  endothelium,  composed  of  ir- 
regular, polygonal,  flat  cells.  A  rich  lymphatic 
network  lies  under  the  pericardium  (Fig.  29) 
and  endocardium ;  also  in  the  deeper  layers 
of  the  visceral  pericardium  next  the  heart  and 
between  muscular  bundles  [Salvioli).  No 
stomata  exist  either  on  its  visceral  or  parietal 
layers.  Around  the  coronary  arteries  of  the 
heart  exist  lymph  vessels  and  deposits  of  fat, 
which  lie  in  the  furrows  and  grooves  in  the 
subserosa  of  the  epicarditim  (visceral  layer). 

The  endocardium,  next  the  cavity  of  the 
heart,  consists  of  a  single  layer  of  polygonal, 
flat,  nucleated  endothelial  cells.  [Under  this 
there  is  a  nearly  homogeneous  hyaline  layer 
(Fig.  30,  a),  slightly  thicker  on  the  left  side, 
which  gives  the  endocardium  its  polished  ap- 
pearance.] Then  follows,  as  the  basis  of  the  membrane,  a  layer  oifine  elastic  fibres — stronger  in  the 
auricles,  and  in  some  places  thereof  assuming  the  characters  of  a  fenestrated  membrane.  Between 
these  fibres  a  small  quantity   of  connective 

Fig. 


Lymphatic  of  the  pericardium,  epithelium  stained  with 
nitrate  of  silver. 


30. 


tissue  exists,  which  is  in  larger  amount  and 
more  areolar  in  its  characters  next  the  myo- 
cardium. Bundles  of  non-striped  muscular 
fibres  (few  in  the  auricles)  are  scattered  and 
arranged  for  the  most  part  longitudinally  be- 
tween the  elastic  fibres.  These  seem  evi- 
dently meant  to  resist  the  distention  which  is 
apt  to  occur  when  the  heart  contracts  and 
great  pressure  is  put  upon  the  endocardium. 
In  all  cases  where  high  pressure  is  put  upon 
walls  composed  of  soft  parts,  we  always  find 
muscular  fibres  present,  and  never  elastic 
fibres  alone.  No  blood  vessels  occur  in  the 
endocardium  [Longer). 

The  valves  also  belong  to  the 
endocardium — both  the  semilunar 
valves  of  the  aorta  and  pulmonary 
artery,  which  prevent  the  blood  from 

passing  back  into  the  ventricles,  and  the  tricuspid  (right  auriculo-ventricular)  and 
mitral  (left  auriculo-ventricular),  which  protect  the  auricles  from  the  same  result. 
The  lower  vertebrata  have  valves  in  the  orifices  of  the  venae  cavse,  which  prevent 
regurgitation  into  them  ;  while  in  birds  and  some  mammals  these  valves  exist  in  a 
rudimentary  condition.     The  valves  are  fixed  by  their  base  to  xt?,\sidint  fibrous 


Section  of  the  endocardium,  a.  hyaline  layer  ;  b,  network  of 
fine  elastic  fibres  ;  c,  network  of  stronger  elastic  fibres;  d, 
myocardium  with  blood  vessels,  which  do  not  pass  into 
the  endocardium. 


96 


AUTOMATIC    KEt.ULATlUN    OF    THE    HEART. 


Fi( 


rings,  consisting  of  elastic  and  fibrous  tissue.  They  are  formed  of  two  layers — 
(I )  ihtjibrous,  which  is  a  direct  continuation  of  the  fibrous  rings,  and  (2)  a  layer 
of  elastic  elements.  The  elastic  layer  of  the  auriculo-ventricular  valves  is  an 
immediate  prolongation  of  the  endocardium  of  the  auricles,  and  is  directed 
toward  the  auricles.  The  semilunar  valves  have  a  thin  elastic  layer  directed 
toward  the  arteries,  which  is  thickest  at  their  base.  The  connective-tissue  layer 
directed  toward  the  ventricle  is  about  half  the  thickness  of  the  valve  itself. 

The  auriculo-ventricular  valves  also  contain  striped  muscular  fibres.  Ra- 
diating fibres  proceed  from  the  auricles  and  pass  into  tlie  valves,  which,  when  the 
atria  contract,  retract  the  valves  toward  their  base,  and  thus  make  a  larger 
opening  for  the  passage  of  the  blood  into  the  ventricles  ;  according  to  Paladino, 
they  raise  the  valves  after  they  have  been  pressed  down  by  the  blood  current. 
This  observer  also  described  some  longitudinal  fibres  which  proceed  from  the 
ventricles  to  enter  these  valves.  There  is  also  a  concentric  layer  of  fibres  arranged 
near  their  point  of  attachment,  and  directed  more  toward  their  ventricular  sur- 
face. These  fibres  seem  to  contract  sphincter-like  when  the  ventricle  contracts, 
and  thus  approximate  the  base  of  the  valves,  and  so  prevent  too  great  tension 
being  put  upon  them.  The  larger  chordae  tendineae  also  contain  striped  muscle, 
while  a  delicate  muscular  network  exists  in  the  valvula  Thebesii  and  valvula 
Eustachii. 

Purkinje's  Fibres  consist  of  an  anastomosing  system  of  grayish  fibres  which  exist  in  the  sub- 
endocardial tissue  of  the  ventricles,  especially  in  the  heart  of  the  sheep  and  ox.  The  fibres  are 
made  up  of  polyhedral  clear  cells,  containing  some  granular  protoplasm,  and  usually  two  nuclei 
(f^'g-  3')-     The  margins  of  the  cells  are  striated.     Transition  forms  are  found  between  these  cells 

and  the  ordinary  cardiac  fibres;  in  fact, 
these  cells  become  continuous  with  the 
true  fully  developed  cardiac  fibres.  They 
represent  cells  which  have  been  arrested 
in  their  development.  They  are  absent 
in  man  and  the  lower  vertebrates,  but  in 
birds  and  some  mammals  they  are  well 
marked  {ScJnc<cig:;er-Siidel,  Kani'icr). 

Blood  Vessels  occur  in  the  auriculo- 
ventricular  valves  only  where  muscular 
fibres  are  present,  while  the  semilunar 
valves  are  usually  devoid  of  vessels  except 
at  their  base.  The  best  figures  of  the 
blood  vessels  of  the  valves  are  given  by 
Langer.  The  network  of  lymphatics 
in  the  endocardium  reaches  toward  the 
middle  of  the  valves. 

Weight  of  the   Heart. — •\ccording 
Purkinje's  fibres  isolated  with  dilute  alcohol,    c,  cell :  y,  stri.-ited  *°  ^^  •  ^'""er  the  proportion  between  the 
substance;  «,  nucleus.    X  300. '  '  weight  of  the  body  and  the  heart  in  the 

anan*  ^hild,  and  until  the  body  reaches  40  kilos., 
is  5  grms.  of  heart  substance  to  i  kilo,  of  body  weight ;  when  the  body  weight  is  from  50  to  90  kilos, 
the  ratio  is  I  kilo,  to  4  grms.  of  heart  substance;  at  loo  kilos.  3.5  grms.  As  age  advances,  the 
auricles  become  stronger.  The  right  ventricle  is  half  the  weight  of  the  left.  The  weight  of  the 
heart  of  an  adult  man  is  about  309  grms. ;  female,  274  grms.  [According  to  Laennec  the  heart  is 
al>out  the  sue  of  the  closed  fist  of  the  individual.]  Blosfeld  and  Dieberg  give  346  grms.  for  the 
male,  and  310  to  340  grms.  for  the  female  heart.  The  specijic  gravity  of  the  heart  muscle  is  1.069. 
Ihe  thickness  of  the  left  ventricle  in  the  middle  in  man  is  11.4  mm.,'  and  in  woman  11. 15;  that  of 
the  right  is  4.1  and  3.6  mm.  respectively. 

47-  AUTOMATIC  REGULATION  OF  THE  HEART.— Anatomical  Investiga- 
tions.— The  two  coronary  arteries  arise  from  the  first  part  of  the  aoita  in  the  re-ion  of  the  sinus 
of  \alsalva.  The  position  of  origin  varies— (i)  either  the  orifices  lie  within  the  sinus,  or  (2) 
their  openings  are  only  partially  reached  by  the  margins  of  the  semilunar  valves  (which  is  usually 
the  case  in  the  left  coronary  artery  of  man  and  the  ox),  or  (3)  their  orifices  lie  clear  above  the 
margins  of  the  valves.  Post-mortem  observations  seem  to  show  that  during  contraction  of  the 
ventricle  it  is  very  improbable  that  the  semilunar  valves  constantly  cover  the  origin  of  the  coro- 
nary arteries. 


LIGATURE    OF   THE    CORONARY   ARTERIES.  97 

Automatic  Regulation  of  the  Heart. — Briicke  attempted  to  show  that 
during  the  systole,  or  contraction  of  the  ventricle,  the  semilunar  valves  covered 
the  openings  of  the  coronary  arteries,  so  that  these  vessels  could  be  filled  with 
blood  only  during  the  diastole  or  relaxation  of  the  ventricle.  To  him  it  seemed 
that  (a)  the  diastolic  filling  of  the  coronary  arteries  would  help  to  dilate  the  ven- 
tricles ;  (d)  on  the  contrary,  a  systolic  filling  of  these  arteries  would  oppose  the 
contraction,  because  the  systolic  filling  and  expulsion  of  the  blood  from  the 
coronary  arteries  would  diminish  the  force  of  the  ventricular  contraction.  [To 
this  supposed  arrangement  Briicke  gave  the  name  "Selbststeuerung,"  which  may 
be  rendered  as  above,  or  as  "self-controlling"  action  of  the  heart  by  the  aortic 
valves.  ] 

Arguments  against  Briicke's  View. — The  following  considerations  militate  against  this 
theory  :  (i)  Filling  the  coronary  vessels  under  a  high  pressure  in  a  dead  heart  causes  a  diminution 
of  the  ventricular  cavity  [v.  Wiltick).  (2)  The  chief  trunks  of  the  coronary  arteries  lie  in  loose 
sub- pericardial  fatty  tissue  in  the  cardiac  sulci,  hence  a  dilatation  of  the  ventricle  through  this 
agency  is  most  unlikely  [Landois).  (3)  Experiments  on  animals  have  shown  that  a  coronary 
artery  spouts,  like  all  arteries,  during  the  systole  of  the  ventricle.  Von  Ziemssen  found  that  in  the 
case  of  a  woman  who  had  a  large  part  of  the  anterior  wall  of  the  thorax  removed  by  an  operation, 
the  heart  being  covered  only  by  a  thin  membrane,  the  pulse  in  the  coronary  arteries  was  synchro- 
nous with  the  pulse  in  the  pulmonary  artery.  H.  N.  Martin  and  Sedgwick  placed  a  manometer  io 
connection  with  the  coronary  artery,  and  another  with  the  carotid  in  a  large  dog,  and  they  found 
that  the  pulsations  occurred  sinmltaneonsly.  When  a  coronary  artery  is  divided,  the  blood  flows 
out  continuously,  but  undergoes  acceleration  during  the  systole  of  the  ventricles  [Endemann, 
Perls).  (4)  If  a  strong  intermittent  current  of  water  be  allowed  to  flow  through  a  sufficiently  wide 
tube  into  the  left  auricle  of  a  fresh  pig's  heart,  so  that  the  water  passes  into  the  aorta,  and  if  the 
aorta  be  provided  with  a  vertical  tube,  the  water  flows  continuously  from  the  coronary  arteries,  and 
is  accelerated  during  the  systole.  (5)  It  is  exceedingly  improbable  that  the  coronary  arteries  should 
be  filled  during  the  diastole,  while  all  the  other  arteries  are  filled  during  systole  of  the  ventricle.  (6) 
There  is  always  a  sufficient  quantity  of  blocd  in  the  sinus  of  Valsalva  to  fill  the  arteries  during  the 
first  part  of  the  systole.  (7)  The  valves,  when  raised,  are  not  applied  directlv  to  the  aortic  wall 
[Hamberger,  Rildinger)  even  by  the  most  energetic  pressure  from  the  ventricle  [Sandborg  and 
Worm  Mailer).  (8)  Observations  on  voluntary  muscles  have  shown  that  the  small  arteries  dilate 
during  contraction  of  the  muscle,  and  the  blood  stream  is  accelerated.  (9)  By  the  systolic  filling 
of  the  aorta  the  arterial  path  is  elongated — this  elastic  distention  is  compensated  before  the  diastole 
occurs.  By  the  recoil  of  the  aortic  walls  the  layer  of  blood  in  them  is  driven  backward  and  closes 
the  valves  \Ceradini).  According  to  Sandborg  and  Worm  Miiller,  the  semilunar  valves  close  just 
after  the  ventricles  have  begun  to  relax,  which  agrees  with  the  curve  obtained  from  the  cardiac 
impulse  (Fig.  39,  A). 

During  the  systole,  the  small  arterial  trunks  lying  next  the  ventricular  cavities 
have  to  bear  a  higher  pressure  than  that  borne  by  the  aorta,  and  their  lumen  must 
be  compressed  during  the  systole  so  that  their  contents  are  propelled  toward  the 
veins. 

Peculiarities  of  the  Cardiac  Blood  Vessels. — The  capillary  vessels  of  the  myocardium  are 
very  numerous,  corresponding  to  the  energetic  activity  of  the  heart.  Where  they  pass  into  veins, 
several  unite  at  once  to  form  a  wide  venous  trunk,  whereby  an  easy  passage  is  offered  to  the  blood. 
The  veins  are  provided  with  valves  so  that  (i)  during  systole  of  the  right  auricle  the  venous 
stream  is  interrupted;  (2)  during  contraction  of  the  ventricles,  the  blood  in  the  coronary  veins  is 
similarly  accelerated  as  in  the  veins  of  muscles.  The  coronary  arteries  are  characterized  by 
their  very  thick  connective  tissue  and  elastic  intima,  which  perhaps  accounts  for  the  frequent 
occurrence  of  atheroma  of  these  vessels  (^Henle).  Some  observers  -maintain  that  the  coronary 
arteries  do  not  anastomose,  but  this  is  denied  by  Langer  and  Krause.  [West  has  injected  the  one 
artery  from  the  other.]  Many  of  the  small  lower  vertebrates  have  no  blood  vessels  in  their  heart 
muscle,  e.  g.,  frog  [Ilyrtl). 

Ligature  of  the  Coronary  Arteries. — The  phenomena  produced  by  par- 
tial obliteration  or  ligature  of  the  coronary  arteries  are  most  important.  In  man 
analogous  conditions  occur,  as  in  atheroma  or  calcification  of  these  arteries.  See 
and  others  have  ligatured  the  coronary  arteries  in  dogs,  and  found  that  after  two 
minutes  the  cardiac  contractions  gave  place  to  twitchings  of  the  muscular  fibres, 
and  ultimately  the  heart  ceased  to  beat.  Ligature  of  the  anterior  coronary  artery 
alone,  or  of  both  its  branches,  is  sufficient  to  produce  this  result.  If  the  coro- 
7 


98  MOVEMENTS    OF    THE    HEART. 

nary  arteries  be  compressed  or  tied  in  a  rabbit  in  the  angle  between  the  bulbus 
aortse  and  the  ventricle,  the  heart's  action  is  soon  weakened,  owing  to  the  sudden 
anaemia  and  to  the  retention  of  the  decomposition  products  of  the  metabolism  in 
the  heart  muscle.  Ligature  of  one  artery  first  affects  the  corresjionding  ventricle, 
then  the  otlier  ventricle,  and,  last  of  all,  the  auricles.  Hence,  compression  of 
the  left  coronary  artery  (with  simultaneous  artificial  respiration  in  a  curarized 
animal)  causes  slowing  of  the  contractions,  esjjecially  of  tiie  left  ventricle,  while 
the  right  one  at  first  contracts  more  quickly,  and  then,  gradually,  its  rhythm  is 
slowed.  The  contractions  of  the  left  ventricle  are  not  only  slowed  but  also 
weakened,  while  the  right  pulsates  with  undiminished  force.  Hence  it  follows 
that,  as  the  left  half  of  the  heart  cannot  expel  the  blood  in  sufficient  quantity, 
the  left  auricle  becomes  filled,  while  the  right  ventricle,  not  being  affected, 
pumps  blood  into  the  lungs.  (Edema  of  the  lungs  is  produced  by  the  high  pres- 
sure in  the  pulmonary  circulation,  which  is  propagated  from  the  right  heart 
through  the  pulmonary  vessels  into  the  left  auricle  {Samurlson  and  Grinihagen). 
According  to  Sig.  Mayer,  protracted  dyspncea  causes  the  left  ventricle  to  beat 
more  feebly  sooner  than  the  right,  so  that  the  left  side  of  the  heart  becomes  con- 
gested. Perhaps  this  may  explain  the  occurrence  of  pulmonary  oedema  during 
the  death  agony. 

Cohnheim  and  v.  Scliulthess-Rechberg  found,  after  ligature  of  one  of  the  large  branches  of  a 
coronar\'  artery  in  a  dog,  that  at  the  end  of  a  minute  the  pulsations  become  intermittent.  This 
intermittence  becomes  more  pronounced,  the  two  sides  of  the  heart  do  not  contract  simultaneously 
(arhythmia),  the  heart  beats  more  slowly,  and  the  blood  pressure  falls.  Suddenly,  about  105 
seconds  after  the  ligature  is  applied,  both  ventricles  cease  to  beat,  and  there  is  a  great  fall  of  the 
blood  pressure.  After  an  arrest  lasting  for  10  to  20  seconds,  twitching  movements  occur  in  the 
ventricles,  while  the  auricles  pulsate  regularly,  and  may  continue  to  do  so  for  many  minutes,  but 
the  ventricles  cease  to  beat  altogether  after  50  seconds.  According  to  Lukjanow,  there  is  a  peri- 
staltic condition  which  operates  upward  and  downward,  and  occurs  in  the  period  between  the 
regular  contraction  and  the  twitching  vibratory  movement.  Stimulation  of  the  vagus  does  not  arrest 
these  peristaltic  movements. 

Pathological. — In  so-called  sclerosis  of  the  coronary  arteries  in  old  age,  there  are  attacks  of 
diminished  cardiac  activity,  weakness  of  the  heart,  an  altered  rhythm  and  frequency,  with  conse- 
quent breathlessness  ;  there  may  also  be  loss  of  consciousness,  congestions,  and  attacks  of  pulmonary 
cedema.     Death  may  take  place  unexpectedly  from  sudden  arrest  of  the  heart's  action. 

48.  MOVEMENTS    OF    THE    HEART.— Cardiac    Revolution.— 

The  movement  of  the  heart  is  characterized  by  an  alternate  contraction  and 
relaxation  of  its  walls.  The  total  cardiac  movement  is  called  a  "  cardiac 
revolution"  or  a  "cardiac  cycle,"  and  consists  of  three  acts — the  contraction 
or  systole  of  the  auricles,  tlie  contraction  or  systole  of  the  ventricles,  and  the  pause 
(Fig.  50).  During  the  pause,  the  auricles  and  ventricles  are  relaxed  ;  during  the 
contraction  of  the  auricles  the  ventricles  are  at  rest ;  while  during  the  contraction 
of  the  ventricles  the  auricles  are  relaxed.  The  rest  during  the  phase  of  relaxation 
is  called  the  diastole.  Tlie  following  is  the  sequence  of  events  in  the  heart  during 
a  cardiac  revolution  :  — 

(A)  The  blood  flows  into  the  auricles,  and  thus  distends  them  and  the 
auricular  appendices.     This  is  caused  by — 

(i)  ^\\t  pressure  of  the  blood  in  the  venae  cavae  (right  side)  and  the  pulmonary 
veins  (left  side)  being  greater  than  the  pressure  in  the  auricles.  (2)  The  elastic 
traction  of  the  lungs  (§  68),  which,  after  complete  systole  of  the  auricles,  pulls 
asunder  the  now  relaxed  and  yielding  auricular  walls.  The  auricular  appendages 
are  also  filled  at  the  same  time,  and  they  act  to  a  certain  extent  as  accessory 
reservoirs  for  the  large  supply  of  blood  streaming  into  the  auricles. 

(B)  The  auricles  contract,  and  we  observe  in  rapid  succession — 

(i)  The  contraction  and  emptying  of  the  auricular  appendix  toward  the  atrium. 
Simultaneously  the  mouths  of  the  veins  become  narrowed,  owing  to  the  contraction 
of  their  circular  muscular  fibres  (more  especially  the  superior  vena  cava  and  the 
pulmonary  veins)  ;    (2)  the  auricular  walls  contract  simultaneously  toward   the 


MOVEMENTS    OF    THE    HEART. 


99 


auriculo-ventricular  valves  and  the  venous  orifices,  whereby  (3)  the  blood  is  driven 
into  the  relaxed  ventricles,  which  are  considerably  distended  thereby. 

The  contraction  of  the  auricles  is  followed  by 

(a)  A  slight  stagnation  of  the  blood  in  the  large  venous  trunks,  as  can  be 
observed  in  a  rabbit  after  division  of  the  pectoral  muscles  so  as  to  expose  the 
junction  of  the  jugular  with  the  subclavian  vein.  There  is  no  actual  regurgitation 
of  the  blood,  but  only  a  partial  interruption  of  the  inflow  into  the  auricles,  because 
the  mouths  of  the  veins  are  contracted,  and  the  pressure  in  the  superior  vena  cava 
and  pulmonary  veins  soon  holds  in  equilibrium  any  reflux  of  blood ;  and  lastly. 

Fig.  32. 


Cast  of  the  ventricles  of  the  human  heart  viewed  from  behind  and  above ;  the  walls  have  been  removed,  and  only  the 
fibrous  rings  and  the  auriculo-ventricular  valves  are  retained.  L,  left,  R,  right  ventricle ;  S,  septum ;  F,  left 
fibrous  ring,  with  mitral  valve  closed  ;  D,  right  fibrous  ring,  with  tricuspid  closed ;  A,  aorta,  with  the  left  (Ci) 
and  right  (C)  coronary  arteries  ;  S,  sinus  of  Valsalva;  P,  pulmonary  artery. 

because  any  reflux  into  the  cardiac  veins  is  prevented  by  valves.  The  movement 
of  the  heart  causes  a  regular  pulsatile  phenomenon  in  the  blood  of  the  vense  cavse, 
which  under  abnormal  circumstances  may  produce  a  venous  pulse  (see  §  99). 

{F)  The  chief  motor  effect  of  the  contraction  of  the  auricles  is  the  dilatation  of 
the  relaxed  ventricle,  which  has  already  been  dilated  to  a  slight  extent  by  the  elastic 
traction  of  the  lungs. 

Aspiration  of  the  Ventricles. — The  dilatation  of  the  ventricles  has  been  ascribed  to  the 
elasticity  of  the  muscular  walls — the  strongly  contracted  ventricular  walls  (like  a  compressed  india- 
rubber  bag),  in  virtue  of  their  elasticity,  are  supposed,  in  returning  to  their  normal  resting  form,  to 


100 


MOVEMENTS    OF    THE    HEART. 


suck  in  or  aspirate  the  blood  under  a  negative  pressure;  this  power  on  the  part  of  the  ventricle  is 
not  great  (see  below). 

(c)  When  the  ventricles  are  distended  by  the  inflowing  blood,  the  auriculo- 
ventricular  valves  are  floated  up,  partly  by  the  recoil  or  reflexion  of  the  blood  from 
the  ventricular  wall,  and  partly  owing  to  their  lighter  specific  gravity,  whereby 
they  easily  float  into  a  more  or  less  horizontal  position.  The  valves  are  also  raised 
to  a  slight  extent  by  the  longitudinal  muscular  fibres,  which  pass  from  the  auricles 
into  the  cusps  of  the  valve. 

(C)  The  ventricles  now  contract,  and  simultaneously  the  auricles  relax, 
whereby — 

(i)  'hie  muscular  walls  contract  forcibly  from  all  sides,  and  thus  diminish  the 
ventricular  cavity.  (2)  The  blood  is  at  once  pressed  against  the  under  surface  of 
tlie  auriculo-ventricular  valves,  whose  curved  margins  are  opposed  to  each  other 
like  teeth,  and  are  pressed  hermetically  against  each  other  (Fig.  32).  It  is  impos- 
sible for  tiie  blood  to  push  the  cusps  backward  into  the  auricle,  as  the  chordae 
tendinese  hold  fast  their  margins  and  surfaces  like  a  taut  sail.  The  margins  of  the 
neigliboring  cusps  are  also  kept  in  apposition,  as  the  chordoe  tendineoe  from  one 
papillary  muscle  always  pass  to  the  adjoining  edges  of  two  cusps.  The  extent  to 
which  the  ventricular  wall  is  shortened  is  compensated  by  the  contraction  of  the 
])apillary  muscle,  and  also  of  the  large  muscular  chorda;,  so  that  the  cusps  cannot 
be  pushed  into  the  auricle.  When  the  valves  are  closed,  their  surfaces  are  hori- 
zontal, so  that,  even  when  the  ventricles  are  contracted  to  their  greatest  extent, 
there  remains  in  the  supra-papillary  space  a  small  amount  of  blood  which  is  not 
expelled  {Sandborg^  and  Worm  Miiller).  (3)  When  the  i)ressure  within  the  ven- 
tricles exceeds  that  in  the  arteries,  the  semilunar  valves  are  forced  open  and 
stretched  like  a  sail  across  the  pocket-like  sinus,  without,  however,  being  directly 
applied  to  the  wall  of  the  arteries  (pulmonary  and  aorta),  and  thus  the  blood  enters 
the  arteries. 

(D)  Pause. — As  soon  as  the  ventricular  contraction  ends,  and  the  ventricles 
begin  to  relax,  the  semilunar  valines  close  (  Vig.  t^i).  The 
diastole  of  the  ventricles  is  followed  by  the  pause.  Un- 
der normal  circumstances,  the  right  and  left  halves  of  the 
heart  always  contract  or  relax  uniformly  and  simultane- 
ously. 

Negative  Pressure  in  the  Ventricle. — Goltz  and  Gaule  found 
that  there  was  a  ttei^ative pjessiire  of  23.5  mm.  Hg  (dog)  in  the  in- 
terior of  the  ventricle  during  a  certain  ])hase  of  the  heart's  action. 
This  they  determined  by  a  maximal  and  minimal  manometer.  They 
surmised  that  this  phase  coincided  with  the  diastolic  dilatation,  for 
which  they  assumed  a  consideral^le  power  of  aspiration.  Moens  is 
of  o]iinion  that  this  negative  pressure  within  the  ventricle  obtains 
shortly  before  the  systole  has  reached  its  heit^ht,  i.  ^.,  just  before  the 
inner  surface  of  the  ventricles  and  the  valves,  after  the  blood  is  ex- 
]:)elled,  are  nearly  in  ap])osition.  He  explains  this  aspiration  as  being 
due  to  the  formation  of  an  empty  space  in  the  ventricle  caused  by  the 
energetic  expulsion  of  the  blood  through  the  aorta  and  pulmonary 
artery. 

Fig.  35. 


Fig 


,,,..:  of  the 

11  Irom  be- 


Fig.  34. 


laximum  and  minimum  manometer. 


[Maximum  and  Minimum  Manometer. — Into  the  tube  connecting  the  interior  of  the  ventricle 
of  the  heart  with  the  ordinary  U-shaped  mercury  manometer,  is  introduced  the  maximum  manome- 


PATHOLOGICAL    CARDIAC    ACTION.  101 

• 
ter,  which  is  constructed  on  the  principle  of  a  ball  and  cup  valve  (Fig.  34),  the  ball  A  being  kept 
closed  in  B  by  a  spring  C.  To  make  it  a  maximum  manometer,  the  end  A  is  connected  with  the 
heart,  and  B  with  the  mercurial  manometer  (Fig.  35).  When  a  clamp  is  placed  on  the  upper  limb 
the  valve  is  acted  on  only  at  each  systole  of  the  heart,  blood  is  driven  beyond  it,  but  during  diastole 
it  closes  and  no  blood  can  return.  This  goes  on  until  the  pressure  beyond  the  valve  in  the  mercury 
manometer  is  the  same  as  in  the  heart.  If  the  valve  be  reversed,  it  is  converted  into  a  minimum 
manometer.] 

49.  PATHOLOGICAL  CARDIAC  ACTION.— Cardiac  Hypertrophy.— All  resistances 
to  the  movement  of  the  blood  through  the  various  chambers  of  the  heart,  and  through  the  vessels 
communicating  with  it,  cause  a  greater  amount  of  work  to  be  thrown  upon  the  portion  of  the  heart 
specially  related  to  this  part  of  the  circulatory  system  ;  consequently,  there  is  produced  an  increase  in 
the  thickness  of  the  muscular  walls  and  dilatation  of  the  heart.  If  the  resistance  or  obstacle  does  not 
act  upon  one  part  of  the  heart  alone,  but  on  parts  lying  in  the  omuard  direction  of  the  blood  stream, 
these  parts  also  subsequently  undergo  hypertrophy.  If,  in  addition  to  the  muscular  thickening  of  a 
part  of  the  heart,  the  cavity  is  simultaneously  dilated,  it  is  spoken  of  as  eccentric  hypertrophy  or 
hypertrophy  with  dilatation.  The  obstacles  most  likely  to  occur  in  the  blood  vessels  are  narrowing 
of  the  lumen  or  want  of  elasticity  in  their  walls ;  in  the  heart,  narrowing  of  the  arterial  or  venous 
orifices  or  insufficiency  or  incompetency  of  the  valves.  Incompetencyof  the  valves  forms  an  obstruction 
to  the  movement  of  the  blood,  by  allowing  part  of  the  blood  to  flow  back  or  regurgitate,  thus  throw- 
ing extra  work  upon  the  heart. 

Thus  arise — (i)  Hypertrophy  of  the  left  ventricle,  owing  to  resistance  in  the  area  of  the  sys- 
temic circulation,  especially  in  the  arteries  and  capillaries — not  in  the  veins.  Among  the  causts 
are — constriction  of  the  orifice  or  other  parts  of  the  aorta,  calcification,  atheroma,  and  want  of  elas- 
ticity of  the  large  arteries  and  irregular  dilatations  or  aneurisms  in  their  course ;  insufficiency  of  the 
aortic  valves,  in  which  case  the  same  pressure  always  obtains  within  the  ventricle  and  in  the  aorta  ; 
and,  lastly,  cirrhosis  of  the  kidneys,  whereby  the  excretion  of  water  by  these  organs  is  diminished. 
Even  in  mitral  insufficiency,  compensatory  hypertrophy  of  the  left  ventricle  must  occur,  owing  10 
the  hypertrophy  of  the  left  atrium  in  consequence  of  the  increased  blood  pressure  in  the  pulmonary 
circuit. 

(2)  Hypertrophy  of  the  left  auricle  occurs  in  stenosis  or  constriction  of  the  left  auriculo-ven- 
tricular  orifice,  or  in  insufficiency  of  the  mitral  valve,  and  it  occurs  also  as  a  result  of  aoriic 
insufficiency,  because  the  auricle  has  to  overcome  the  continual  aortic  pressure  within  the  ven- 
tricle. 

(3)  Hypertrophy  of  the  right  ventricle  occurs  [a)  when  there  is  resistance  to  the  blood  stream 
through  the  pulmonary  circuit.  The  resistance  may  be  due  to  (a)  obliteration  of  large  vascular 
areas  in  consequence  of  destruction,  shrinking  or  compression  of  the  lungs,  and  the  disappearance 
of  numerous  capillaries  in  emphysematous  lungs;  (/?)  overfilling  of  the  pulmonary  circuit  with  blood 
in  consequence  of  stenosis  of  the  left  auriculo-ventricular  orifice,  or  mitral  insufficiency — consequent 
upon  hypertrophy  of  the  left  auricle  resulting  from  aortic  insufficiency,  [b]  When  the  valves 
of  the  pulmonary  artery  are  insufficient,  thus  permitting  the  blood  to  flow  back  into  the  ven- 
tricle, so  that  the  pressure  within  the  pulmonary  artery  prevails  within  the  right  ventricle  (very 
rare). 

(4)  Hypertrophy  of  the  right  auricle  occurs  in  consequence  of  the  last-named  condition,  and 
also  from  stenosis  of  the  tricuspid  orifice,  or  insufficiency  of  the  tricuspid  valve  (rare). 

Artificial  Injury  to  the  Valves.  —  If  the  aortic  valves  are  perforated,  with  or  without 
simultaneous  injury  to  the  mitral  or  tricuspid  valves,  the  heart  does  more  work;  thus  the  physical 
defect  is  overcome  for  a  time,  so  that  the  blood  pressure  does  not  fall.  The  heart  seems  to  have 
a  store  of  reserve  energy  which  is  called  into  play.  Soon,  however,  dilatation  takes  place, 
on  account  of  the  regurgitation  of  the  blood  into  the  heart.  Hypertrophy  then  occurs,  but 
the  compensation  meanwhile  must  be  obtained  through  the  reserve  energy  of  the  heart  [O. 
Rosenhacli). 

Impeded  Diastole. — Among  causes  which  hinder  the  diastole  of  the  heart  are — copious  effusion 
into  the  pericardium,  or  the  pressure  of  tumors  upon  the  heart.  The  systole  is  greatly  interfered  with 
when  the  heart  is  united  to  the  pericardium  and  to  the  connective  tissue  in  the  mediastinum.  As  a 
consequence  the  connective  tissue,  and  even  the  thoracic  wall,  are  drawn  in  during  contraction 
of  the  heart,  so  that  there  is  a  retraction  of  the  region  of  the  apex  beat  during  systole,  and  a  protrusion 
of  this  part  during  the  diastole. 

[Palpitation  is  a  symptom  indicating  generally  very  rapid  and  quick  action  of  the  heart,  the 
pulsations  often  being  unequal  in  time  and  intensity,  while  the  person  is  generally  conscious  of  the 
irregularity  of  the  cardiac  action.  It  may  be  due  to  some  organic  condition  of  the  heart  itself,  espe- 
cially where  the  cardiac  muscles  are  weak,  in  cases  of  dilatation  and  hypertrophy  of  the  left  ventricle, 
where  the  heart  is  gradually  becoming  unable  to  overcome  the  resistances  offered  to  its  work,  and 
especially  during  exertion  when  the  heart  is  taxed  above  its  strength.  It  may  also  occur  where  the 
blood  pressure  is  low,  as  in  anaemia,  so  that  the  heart  contracts  quickly,  there  being  little  resistance 
ooposed  to  its  action.     The  excitability  of  the  cardiac  muscle  may  be  increased,  as  in  fatty  heart, 


102  THE    CARDIOGRAM. 

• 
when  very  slight  exertion  may  excite  it  often  in  a  paroxysmal  way.  In  other  cases,  it  is  nervous  in 
its  origin,  l)eing  either  diect  or  reflex.  In  very  emotional  and  excitable  people  (especially  in  women) 
it  is  easilv  set  up,  and  in  some  people  it  may  be  produced  rellexly  by  gastric  or  intestinal  irritation 
or  dyspepsia.  It  also  fre(iuently  results  from  excesses  of  all  kinds  and  the  over-use  of  tobacco. 
The  remedies  to  be  used  obviously  depend  on  the  cause.  Where  the  blood  pressure  is  low,  as  in 
anixMiiia,  digitalis  and  iron  will  do  good;  the  former  by  increasing  the  blood  [iressure,  and  the 
latter  i>y  imjiroving  the  general  nutrition  of  the  body  and  the  blood  in  particular.  In  neurotic  cases 
cardiac  sedatives  are  indicated,  while  in  cases  due  to  indigestion  hydrocyanic  acid  is  useful 
{Brun/on).^ 

[Fainting  or  Syncope. — In  fainting,  the  person  loses  consciousness,  owing  to  a  sudden  arrest 
of  the  biooti  supjjly  to  the  brain,  the  face  is  pallid,  the  respiration  is  feeiile  or  ceases,  while  the 
heart  beats  but  feebly  or  not  at  all.  The  defective  supply  of  blood  to  the  brain  may  depend  upon 
sudden  arrest  of  the  hearts  action,  caused,  it  may  be,  by  a  fright,  or  the  heart's  action  may  be 
arrested  reflexly.  Any  cause  which  suddenly  diminishes  the  blood  pressure  may  produce  it,  or 
when  jjressure  is  suddenly  removed  from  the  large  vessels,  as  in  tapping  the  abdomen  in  ascites, 
without  at  the  same  time  giving  sufticient  support  to  the  abdominal  viscera.  When  a  person  has 
been  long  in  the  recumbent  position,  on  being  rapidly  set  up  in  bed  he  may  faint.  In  some  forms 
of  heart  liisease,  sudden  exertion  or  change  of  posture  may  produce  it.] 

[Treatment. — The  oiiject  is  to  restore  consciousness  and  the  action  of  the  heart.  Place  the 
person  in  the  horizontal  position,  keep  the  head  low,  even  lower  than  the  body,  and  do  not  support 
it  with  pillows.  Dashing  cold  water  on  the  face,  so  as  to  stimulate  the  fifth  nerve,  usually  succeeds 
in  causing  the  person  to  take  a  deep  inspiration.  In  other  cases  a  snitf  of  smelling  salts  or  am- 
monia, acting  through  the  nasal  branch  of  the  fifth  nerve,  will  excite  the  cardiac  and  respiratory 
functions  (g  36S).] 

50.  THE  APEX  BEAT,  CARDIOGRAM.— Cardiac  Impulse.— By 
the  term  "  apex  beat  "  or  "  cardiac  impulse  "  is  understood,  under  normal 
circumstances,  an  elevation  (perceptible  to  touch  and  sight)  in  a  circumscribed 
area  of  the  Ji/ih  left  intercostal  space,  and  caused  by  the  movement  of  the  heart. 
[The  apex  beat  is  felt  in  the  fifth  left  intercostal  space,  2  inches  below  the  nipple, 
and  I  inch  to  its  sternal  side,  or  at  a  point  2  inches  to  the  left  of  the  sternum.] 
The  impulse  is  more  rarely  felt  in  the  fourth  intercostal  space,  and  it  is  much  less 
distinct  when  the  heart  beats  against  the  fifth  rib  itself.  The  position  and  force 
of  the  cardiac  impulse  vary  with  changes  in  the  position  of  the  body. 

[The  cardiac  impulse  is  synchronous  with  the  systole  of  the  heart,  but  although  this  name  and 
apex  beat  are  frequently  used  as  synonymous  terms,  it  is  to  be  remembered  that  the  impulse  may 
be  caused  by  different  parts  of  the  heart  being  in  contact  with  the  chest  wall.  The  cardiac 
impulse  is  usually  higher  than  normal  in  children,  while  it  is  lower  during  inspiration  than  expira- 
tion.] 

[Methods. — To  obtain  a  curve  of  the  apex  beat  or  a  cardiogram,  we  may  use  one  or  other  of 
the  following  cardiographs  (Fig.  36).  Fig.  36,  A,  is  the  first  form  used  by  Marey,  and  it  consists 
of  an  oval  wooden  capsule  applied  in  an  air-tight  manner  over  the  apex  beat.  The  disk,  /, 
capable  of  being  regulated  by  the  screw,  s,  presses  upon  the  region  of  the  apex  beat,  while  /  is 
a  tube  which  may  be  connected  with  a  recording  tambour  (Fig.  47).  B  is  an  improved  form  of 
the  instrument,  consisting  essentially  of  a  tambour,  while  attached  to  the  membrane  is  a  button, 
/,  to  be  applied  over  the  apex  beat.  Tiie  movements  of  the  air  within  the  capsule  are  com- 
municated by  the  tube,  /,  to  a  recording  tambour.  Fig.  36,  C,  is  the  pansphygmograph  of 
Brondgeest,  which  consists  of  a  Marey's  tambour,  in  an  iron  horse-shoe  frame,  and  adjustable 
Viy  means  of  a  screw,  J.  Burdon  Sanderson's  cardiograph  is  shown  in  D.  The  button, /,  carried 
by  the  spring,  e,  does  not  rest  upon  the  caoutchouc  membrane,  but  on  an  aluminium  plate 
attached  to  it.  The  apparatus  is  adjusted  to  the  chest  by  three  supports.  Fig.  36,  E,  shows 
a  modified  instrument  on  the  same  principle,  by  Clrummach  and  v.  Knoll.  In  all  these  figures 
the  /  indicates  the  exit  tube  communicating  with  a  recording  tambour  (Fig.  47).  D  and  E  may 
be  used  for  other  purposes,  e.  i^.,  for  the  pidse,  so  that  they  are  polygraphs.     .See  also  Fig.  76.] 

Fig.  39,  A,  shows  the  cardiogram  or  the  impulse  curve  of  the  heart  of  a  healthy 
man  ;  B,  that  of  a  dog,  obtained  by  means  of  a  sphygmograph.  In  both  the 
following  points  are  to  be  noticed :  ab,  corresponds  to  the  time  of  the  pause 
and  the  contraction  of  the  auricles.  As  the  atria  contract  in  the  direction  of  the 
axis  of  the  heart  from  the  right  and  above  toward  the  left  and  below,  the  apex 
of  the  heart  moves  toward  the  intercostal  space.  The  two  or  three  smaller 
elevations  are  perhaps  caused  by  the  contractions  of  the  ends  of  the  veins,  the 
auricular  appendices,  and  the  atria  themselves. 


THE    CARDIOGRAM. 


103 


The  portion  be,  which  communicates  the  greatest  impulse  to  the  instrument, 
and  also  to  one's  hand  when  it  is  placed  on  the  apex  beat,  is  caused  by  the  con- 
traction of  the  ventricles,  and  during  it  the  first  sound  of  the  heart  occurs.     Fre- 

FiG.  36. 


Cardiographs.     A,  Marey's  original  form  ;  B,  Marey's  improved  form  ;  C,pansphygmograph  (Brondgeest) ;  D,  cardio- 
graph (Biirdon-Sanderson) ;  E,  that  of  v.  Knoll. 

quently,  but  erroneously,  the  cardiac  impulse  has  been  ascribed  to  the  contraction  of 
the  ventricles  alone.  It,  however,  is  due  to  all  those  conditions  which  cause  an 
elevation  in  the  region  of  the  cardiac  impulse. 

[Edgren  recorded  a  human  cardiogram,  and  listened  at  the  same  time  to  the  heart  sounds,  re- 
cording the  latter  by  means  of  an  electric  signal.     The  curve  rises  at  a,  with  the  beginning  of 

Fig.  37. 


Cardiogram,     a-f:   i,  beginning  of  ist,  and  2,  2d  sound. 


the  first  sound,  i.  e.,  with  the  contraction  of  the  ventricles,  and  reaches  the  abscissa  at  /  with  the 
beginning  of  the  second  sound,  i.e.,  when  the  semilunar  valves  are  closed.  The  relation  between 
a  and  the  points  intermediate  between  it  andy,  and  to  the  pulse  curve  of  the  carotid,  is  shown  in 
Fig.  38.     The  letters  with  the  dash  correspond  to  the  unmarked  letters  in  the  cardiogram.] 


104 


CAUSE    OF   THE    CARDIAC    IMPULSE. 


Fi( 


The    cause   of  the    ventricular   impulse    has  been    much   discussed.     It 

depends  upon  the  following  :  — 

(i )  The  base  of  the  heart  (auric- 
ulo-ventricular  groove)  represents 
during  diastole  a  irausversely- 
placed  ellipse  (Fig.  40,  I,  FCi), 
while  during  contraction  it  has  a 
more  circular  figure,  ab.  Thus, 
the  long  diameter  of  the  ellipse 
(FG)  is  diminished,  the  small 
diameter  dc  is  increased,  while 
the  base  is  brought  nearer  to  the 
chest  wall  e.  This  alone  does  not 
cause  the  impulse,  but  the  basis  of 
the  heart,  being  hardened  during 
the  systole  and  brought  nearer  to 
the  chest  wall,  allows  the  apex 
to  execute  the  movement  which 
causes  the  impulse  (p.  102). 

(2)   During  relaxation,  the  ventricle  lies  with  its  apex  (Fig.  40,  II,  0  obliquely 


The  upper  curve  (n.ui  the  human  carotid  ;   the  lower  a  cardio- 
gram taken  simultaneously. 


Y-.c.  39 


Curves  from  the  apex  beat.  A,  normal  curve  (man) ;  B,  from  a  dog;  C,  very  rapid  curve  (dog) ;  Dand  E,  normal  curves 
(man)  registered  on  a  vibrating  glass  plate  where  each  indentation  =  0.01613  sec.  '"  ^"  '^^  curves  ab  means 
contraction  of  the  auricles,  and  be  of  the  ventricles  ;  d,  closure  of  the  aortic,  and  e,  of  the  pulmonary  valves  ;  ef, 
diastole  of  the  ventricle. 

downward,  and  with  its  long  axis  in  an  oblitjue  direction — so  that  the  angles  {bci, 
aci)  formed  by  the  axis  of  the  ventricles  with  the  diameter  of  the  base  are  unequal 


CAUSE    OF   THE    CARDIAC    IMPULSE. 


105 


— during  systole  it  represents  a  regular  cone,  with  its  axis  at  right  angles  to  its 
base.  Hence,  the  apex  (/)  must  be  erected  from  below  and  behind  (/),  forward 
and  upward  (Harvej — "cor  sese  erigere  "),  and  when  hardened  during  systole 
presses  itself  into  the  intercostal  space  (Fig.  40,  II). 

(3)  The  ventricles  undergo  during  systole  a  slight  spiral  twisting  on  their  long 
axis  ("  lateralem  inclinationem  " — Harvey),  so  that  the  apex  is  brought  from  be- 
hind more  forward,  and  thus  a  greater  portion  of  the  left  ventricle  is  turned  to 
the  front.  This  rotation  is  caused  by  the  muscular  fibres  of  the  ventricles,  which 
proceed  from  that  part  of  the  fibrous  rings  between  the  auricles  and  ventricles 
which  lies  next  the  anterior  thoracic  wall.  The  fibres  pass  from  above  obliquely 
downward,  and  to  the  left,  and  also  run  in  part  upon  the  posterior  surface  of  the 
ventricles.     When   they  contract  in   the  axis  of   their    direction,  they  tend   to 

Fig.  40. 


I.  Schematic  horizontal  section  through  the  heart,  lungs,  and  thorax,  to  show  the  change  of  shape  which  the  base  ot 
the  heart  undergoes  during  contraction  of  the  ventricle — F,  G,  transverse  diameter  of  the  ventricle  during  dias- 
tole; c,  position  of  the  thoracic  wall  :  a,  i^,  transverse  diameter  of  the  heart  during  systole,  with  ^,  position  ot 
the  anterior  thoracic  wall  during  systole.     II.  Side  view  of  the  heart — i,  apex  during  diastole  ;  /,  during  systole. 


raise  the  apex,  and  also  to  bring  more  of  the  posterior  surface  of  the  heart  in 
relation  with  the  anterior  thoracic  wall.  It  is  favored  by  the  slightly  spiral 
arrangement  of  the  aorta  and  pulmonary  artery. 

These  are  the  most  important  causes,  but  the  minor  causes  are — 

(4)  The  "  reaction  iniptilse  "  or  "  recoil,'"  or  that  movement  which  the  ventricles 
are  said  to  undergo  (like  an  exploded  gun  or  rocket),  at  the  moment  when  the 
blood  is  discharged  into  the  aorta  and  pulmonary  artery,  whereby  the  apex  goes 
in  the  opposite  direction,  i.  e.,  downward  and  slightly  outward.  Landois,  how- 
ever, has  shown  that  the  mass  of  blood  is  discharged  into  the  vessels  0.08  of  a 
second  after  the  beginning  of  the  systole,  while  the  cardiac  impulse  occurs  with 
the  first  sound. 

(5)  When  the  blood  is  discharged  into  the  aorta  and  pulmonary  artery,  these 


106  CHANGE  IN  SHAPE  OF  HEART. 

vessels  are  slightly  elongated,  owing  to  the  increased  blood  pressure.  As  the  heart 
is  suspended  from  above  by  these  vessels,  the  apex  is  pressed  slightly  down- 
ward and  forward  toward  the  intercostal  space  (?). 

As  the  cardiac  impulse  is  observed  in  the  empty  hearts  of  dead  animals,  (4)  and  (5)  are  certainly 
of  only  second  rate  importance.  Filehne  and  Pentzoldt  maintain  that  the  apex  during  systole  does 
not  move  to  the  left  and  downward,  as  must  be  the  case  in  (4)  and  (5),  but  that  it  moves  upward 
and  to  the  riglit — a  result  corroborated  by  v.  Ziemssen.  [Harr  attributes  the  cause  of  the  impulse 
to  the  rigidity  or  hardening  of  the  ventricle  during  systole,  to  the  rotatory  movement  and  lengthening 
downward  of  the  blood  column  in  the  aorta  and  pulmonary  artery,  while  toward  the  end  of  the 
systole  the  maximum  of  recoil  takes  place  and  also  contributes  to  cause  it.] 

It  is  to  be  remembered  that  as  the  apex  is  always  applied  to  the  chest  wall,  separated  from  it 
merely  by  the  thin  margin  of  the  lung,  it  only  presses  against  the  intercostal  space  during  systole 
(A'lWjr//). 

After  the  apex  of  the  curve,  c,  has  been  reached  at  the  end  of  the  systole,  the 
curve  falls  rapidly,  as  the  ventricles  quickly  become  relaxed.  In  the  descending 
part  of  the  curve,  at  ^/and  e,  are  two  elevations,  which  occur  simultaneously  with 
the  second  sound.  These  are  caused  by  the  sudden  closure  of  the  semilunar 
valves,  whereby  an  impulse  is  propagated  through  the  axis  of  the  ventricle  to  its 
apex,  and  thus  causes  a  vibration  of  the  intercostal  space  ;  (^/corresponds  to  the 
closure  of  the  aortic  valves,  and  e  to  the  closure  of  the  pulmonary  valves.  The 
closure  of  the  valves  in  these  two  vessels  is  not  simultaneous,  but  is  separated  by 
an  interval  of  0.05  to  0.09  sec.  The  aortic  valves  close  sooner  on  account  of  the 
greater  blood  ])ressure  there.  Complete  diastolic  relaxation  of  the  ventricle 
occurs  from  e  iof  in  the  curve. 

It  is  clear,  then,  that  the  cardiac  impulse  is  caused  chiefly  by  the  contraction  of 
the  ventricles,  while  the  auricular  systole  and  the  vibration  caused  by  the  closure 
of  the  semilunar  valves  are  also  concerned  in  its  production. 

[Change  in  Shape  of  Heart. — The  experiments  of  Ludwig  and  Hesse  on 
the  heart  of  the  dog  show  that  the  shape  of  the  ventricles  varies  remarkably  in 
systole  and  diastole,  and  that  the  shape  of  the  heart  as  found  post-mortem  is  not 
its  natural  shape.] 

[Method. — Bleed  a  dog  rapidly  from  the  carotids,  defibrinate  the  blood,  expose  the  heart,  tie 
graduated  straight  tubes  into  the  pulmonary  artery  and  aorta,  and  ligature  the  auricular  vessels. 
I'our  the  blood  into  the  heart  until  it  is  dilated  under  a  pressure  equal  to  the  mean  arterial  pressure 

Fig.  41.  Fig.  42.  Fig.  43. 


Projection  of  a  dog's  heart.  Anterior  surface.  Left  lateral  surface. 

Posterior  surface. 

(150  mm.).  The  ventricles  are  in  the  diastolic  phase,  the  auricles  still  pulsate.  A  plaster  cast  is 
now  rapidly  made  of  the  ventricles.  This  represents  the  diastolic  phase.  To  obtain  what  may  be 
regarded  as  the  systolic  phase,  a  heart,  similarly  prepared  but  emptied  of  blood,  is  suddenly  plunged 
into  a  hot  (50°  C.)  saturated  solution  of  potassic  bichromate,  when  the  heart  gives  one  rapid  and 
final  contraction  and  remains  permanently  contracted,  owing  to  the  heat  rigor,  its  proteids  being 
coagulated  [\  295).  This  is  the  systolic  phase.  Little  pins  with  twisted  points  are  previously 
inserted  in  the  organ  to  mark  certain  parts  of  both  hearts  for  comparison.] 

[In  diastole,  the  shape  of  the  ventricle  is  hemispheroidal,  the  apex  being  rounded, 
while  the  posterior  surface  is  flatter  than  the  anterior  (Fig.  41).     In  the  plane  of 


THE    TIME    OF   THE    CARDIAC    MOVEMENTS.  107 

the  ventricular  base,  the  greatest  diameter  is  from  right  to  left,  and  the  shortest 
from  base  to  apex.  The  conus  arteriosus  is  above  the  plane  of  the  base.  During 
systole,  the  apex  is  more  pointed,  the  ventricle  more  conical,  while  all  the  diameters 
in  the  plane  of  the  base  are  equally  diminished,  hence  the  vertical  measurement 
from  base  to  apex  is  longer  now  than  either  of  the  diameters  at  the  base  (Fig.  43). 
The  conus  arteriosus  sinks  toward  the  plane  of  the  base,  while  the  base  of  the 
ventricle  becomes  more  circular,  so  that  the  difference  of  the  curvatures  of  the 
anterior  and  posterior  surfaces  van- 
ishes (Fig.  42).  In  all  these  figures  Fig.  44.  Fia45. 
the  shaded  part  represents  diastole 
and  the  clear  part  systole.  The  most 
remarkable  point  is  that  the  vertical 
measurement  remains  unchanged. 
This  refers  to  the  left  ventricle,  which 
of  course  forms  the  apex;  the  right 
is  shortened.  The  plane  of  the  ven- 
tricular base  in  systole  is  about  one- 
half  of  what  it  is  in  diastole,  as  is 

„!,„  „  ,■„  T?,'™  .  .  T'U.,^  i-U^  V.^^^*-  ,'r.  Projection  of  the  base  in  sys-  A,  aorta;  PA,  pulmonary 
shown  m  Fig.  44.         i  huS  the  heart  is  •'tole    and     diastole.      RV,  artery;  M,  mitral,  and 

diminished  in  all  its  diameters  except  right,  and  lv,  left  ventri-  t,  tricuspid  orifice. 

one,  the  arterial  orifices  are  scarcely 

affected,  while  the  area  of  the  auriculo-ventricular  orifices  (M,  T)  is  diminished 
about  one-half  (Fig.  45).  This  is  most  important  in  connection  with  the  closure 
of  the  auriculo-ventricular  valves ;  as  it  shows  that  the  muscular  fibres  of  the  heart, 
by  diminishing  these  orifices  during  systole,  greatly  aid  in  the  perfect  closure  of 
these  valves.  Thus  we  explain  why  defective  nutrition  of  the  cardiac  muscle  may 
give  rise  to  incompetency  of  these  valves,  without  the  valves  themselves  being 
diseased  {Macalisier).'] 

[In  order  to  account  for  the  vertical  diameter  remaining  unchanged,  we  may 
represent  the  ventricular  fibres  as  consisting  of  three  layers,  viz.,  an  inner  and 
outer  set,  more  or  less  longitudinal,  and  a  middle  set,  circular.  Both  sets  will 
tend,  when  they  contract,  to  diminish  the  cavity,  but  the  shortening  of  the  longi- 
tudinal layers  is  compensated  for  by  the  contraction,  t.  e.,  the  elongation  produced 
by  the  circular  set.] 

[In  order  to  obtain  the  shape  of  the  cavities,  dogs  were  taken  of  the  same  litter  and  as  nearly 
alike  as  possible.  One  heart  was  filled  with  blood,  as  already  described,  and  placed  in  a  cool 
solution  of  potassic  bichromate,  whereby  it  was  slowly  hardened  in  the  diastolic  form,  while  the 
other  was  plunged,  as  before,  into  a  hot  solution.     Casts  were  then  made  of  the  cavities.] 

51.  THE  TIME  OF  THE  CARDIAC  MOVEMENTS.— Methods.— The  time  occupied 
by  the  various  phases  of  the  move)?ienls  of  the  heart  may  be  determined  by  studying  the  apex  beat 
curve. 

(i)  If  we  know  at  what  rate  the  plate  on  which  the  curve  was  obtained  moved  during  the 
experiment,  of  course  all  that  is  necessary  is  to  measure  the  distance,  and  so  calculate  the  time 
occupied  by  any  event  (see  Pulse,  |  67). 

(2)  It  is  preferable,  however,  to  cause  a  tuning  fork,  whose  rate  of  vibration  is  known,  to  write 
its  vibrations  under  the  curve  of  the  apex  beat,  or  the  curve  may  be  written  upon  a  plate  attached 
to  a  vibrating  tuning  fork  (Fig.  39,  D,  E).  Such  a  curve  contains  fine  teeth  caused  by  the  vibrations 
of  the  tuning  fork.  D  and  E  are  curves  obtained  from  the  cardiac  impulse  in  this  way  from  healthy 
students.  In  D  the  notch  d  is  not  indicated.  Each  complete  vibration  of  the  tuning  fork,  reckoned 
from  apex  to  apex  of  the  teeth  =  0.01613  second,  so  that  it  is  simply  necessary  to  count  the  number 
of  teeth  and  multiply  to  obtain  the  time.  The  values  obtained  vary  within  certain  limits  even  in 
health. 

The  value  oi  a  b  ^=  pause  +  contraction  of  the  auricles,  is  subject  to  the 
greatest  variation,  and  depends  chiefly  upon  the  number  of  heart  beats  per  minute. 
The  more  quickly  the  heart  beats,  the  shorter  is  the  pause,  and  conversely.  In 
some  curves,  even  when  the  heart  beats  slowly,  it  is  scarcely  possible  to  distinguish 


108  THE    TIME    OF   THE    CARDIAC    MOVEMENTS. 

the  auricular  contraction  (indicated  by  a  rise)  from  the  ])art  of  the  curve  corres- 
ponding to  the  pause  (indicated  by  a  horizontal  line).  In  one  case  (heart  beats 
55  per  minute)  the  pause  =  0.4  second,  the  auricular  contraction  =  0.177  second, 
in  Fig.  39,  A,  the  time  occupied  by  the  pause  -f-  the  auricular  contraction  (74 
beats  per  minute)  =  0.5  second.  In  D,  a  />:^  19  to  20  vibrations^  0.32  second  ; 
in  E  =  26  vibrations  =  0.42  second. 

The  ventricular  systole  is  calculated  from  the  beginning  of  the  (  ontraction 
d,  to  e  wiien  the  semilunar  valves  are  closed  ;  it  lasts  from  the  first  to  the  second 
sound.  It  also  varies  somewhat,  but  is  more  constant.  Wlien  the  heart  beats 
rapidly,  it  is  somewhat  shorter — during  slow  action  longer.  In  E  =  0.32  second  ; 
in  D  =:  0.29  second  ;  with  55  beats  per  minute  Landois  found  it  =  0.34,  with  a 
very  high  rate  of  beating  =  0.199  second. 

When  the  ventricles  beat  feebly,  they  contract  more  slowly,  as  can  be  shown  by  applying  the 
registering  apparatus  to  the  heart  of  an  animal  just  killed.  In  Fig.  46,  from  the  ventricle  of  a  rabbit 
just  killed,  the  slow  heart  beats,  B,  are  seen  to  last  longest.  In  cases  of  enormous  hypertrophy  and 
dilatation  of  the  left  ventricle,  the  duration  of  the  ventricular  systole  is  not  longer  than  normal 

(Z(7«./M.f). 

In  calculating  the  lime  occupied  by  the  ventricular  systole  we  must  remember — (i)  T/te  time 
between  the  two  sounds  of  the  heart,  i.  e.,  from  the  beginning  of  the  first  to  the  end  of  the  second 
sound  [/>  to  e).  (2)  T/ie  time  the  blood  flows  into  the  aorta,  which  comes  to  an  end  at  the  depression 
between  c  and  d  (in  Fig.  39,  E).  Its  commencement,  however,  does  not  coincide  with  b,  as  the 
aortic  valves  open  0.085  to  0.073  second  after  the  beginning  of  the  ventricular  systole.  Hence  the 
aortic  current  lasts  0.08  to  0.09  second.     This  is  calculated  in  the  following  way :  The  time  between 

Fig.  46. 


Curves  recorded  by  the  ventricle  of  a  rabbit,  upon  a  vil)ratinf;  plate  attached  to  a  tuning  fork  (vibration  =  0.01613 
sec).     A,  soon  after  death  ;  B,  from  the  dying  ventricle. 

the  first  sound  of  the  heart  and  the  pulse  in  the  axillary  artery  is  0.137  second,  and  of  this  time  0.052 
second  is  occupied  in  the  propagation  of  the  pulse  wave  along  the  30  cm.  of  artery  lying  betsveen  the 
root  of  the  aorta  and  the  axilla.  Thus  the  pulse  wave  in  the  aorta  occurs  0.137  minus  0.052  = 
0.085  second  after  the  beginning  of  the  first  sound.  The  current  in  the  pulmonary  artery  is  inter- 
rupted in  the  depression  between  d  and  e.  (3)  Lastly,  the  time  occupied  by  the  muscular  contraction 
of  the  ventricle,  which  begins  at  /',  reaches  its  greatest  extent  at  c,  and  is  completely  relaxed  at  f. 
The  apex  of  the  curve,  <r,  may  be  higher  or  lower  according  to  the  flexibility  of  the  intercostal  space, 
hence  the  position  of  c  varies.  In  hypertrophy  with  dilatation  of  the  left  ventricle,  the  duration  of 
the  ventricular  contraction  does  not  greatly  exceed  the  normal. 

The  time  which  elapses  between  //and  e,  i.e.,  between  the  complete  closure  of 
the  aortic  and  pulmonary  valves,  is  greater  the  more  the  pressure  in  the  aorta 
exceeds  that  in  the  pulmonary  artery,  as  the  valves  are  closed  by  the  pressure 
from  above,  and  the  difference  in  time  may  be  0.05  second,  or  even  double  that 
time,  in  which  case  the  second  sound  appears  double  (compare  §  54),  If  the  aortic 
pressure  diminishes  while  that  in  the  pulinonary  artery  rises,  d  and  e  may  be  so 
near  each  other  that  they  are  no  longer  marked  as  distinct  eleinents  in  the  curve. 

The  time,  ef,  during  which  the  ventricles  relax  varies  somewhat :  o.  i  second 
may  be  taken  as  a  mean. 

Accelerated  Cardiac  Action. — When  the  action  of  the  heart  is  greatly  accelerated,  the  pause 
is  considerably  shortened  in  the  first  instance  {Bonders),  and  to  a  less  extent  the  time  of  con- 
traction of  the  auricles  and  ventricles.  When  the  pulse  rate  is  very  rapid,  the  .systole  of  the  atria 
coincides  with  the  closure  of  the  arterial  valves  of  the  preceding  contraction,  as  is  shown  in  Fig.  39, 
C  (dog). 


ENDOCARDIAL    PRESSURE. 


109 


Fig.  47. 


Marey's  re^^isteruig  laniUuur.  T,  metallic  capsule, 
with  thin  india-rubber  stretched  over  it,  and 
bearing  an  aluminium  disk,  which  acts  upon  the 
writing  lever,  H.  By  means  of  a  thick-walled 
caoutchouc  tube,  it  may  be  connected  with  any 
system  containing  air,  so  as  to  record  variations 
of  pressure. 


In  registering  the  cardiac  impulse,  the  apparatus  is  separated  by  a  greater  or  less  depth  of  soft 
parts  from  the  heart  itself,  so  that  in  all  cases  the  intercostal  tissues  do  not  follow  exactly  the  move- 
ments of  the  heart,  and  thus  the  curve  obtained  may  not  coincide  mathematically  with  the  move- 
ments of  the  heart.  It  is  desirable  that  curves  be  obtained  from  persons  whose  hearts  are  exposed, 
i.e.,  in  cases  of  ectopia  cordis. 

Cleft  Sternum. — Gibson  inscribed  cardiograms 
from  the  heart  of  a  man  with  cleft  sternum.  The 
following  were  the  results  obtained  :  Auricular  con- 
traction =  o.i  15  ;  ventricular  contraction  {^b,d)^= 
0.28;  difference  between  closure  of  vsXwes  {d,  e)  = 
0.C9;  ventricular  diastole  {e,f)=o.ii;  pause  = 
0.45  second. 

Endocardial  Pressure. — In  large  mam- 
mals, such  as  the  horse,  Chauveau  and 
Marey  (1861)  determined  the  duration  of 
the  events  that  occur  within  the  heart,  and 
also  the  endocardial  pressure  by  means  of  a 
cardiac  sound.  Small  elastic  bags  at- 
tached to  tubes  were  introduced  through  the 
jugular  vein  into  the  right  auricle  and 
ventricle.  Each  of  these  tubes  was  con- 
nected with  a  registering  tambour  (Fig.  47), 
and  simultaneous  tracings  of  the  variations 
of  pressure  within  the  cavities  of  the  heart 
were  obtained  by  causing  the  writing  points 
of  the  levers  of  the  tambours  to  write  upon  a  revolving  cylinder. 

Fig.  48,  A,  gives  the  result  obtained  when  one  elastic  bag  was  placed  in  the  right  auricle, 
being  introduced  through  the  jugular  vein  and  superior  vena  cava  ;  B,  when  the  other  bag  pushed 
through  the  tricuspid  orifice  was  in  the  right  ventricle ;  D,  in  the  root  of  the  aorta,  pushed  in 
through  the  carotid ;  C,  pushed  past  the  semilunar  valves  into  the  left  ventricle ;  while  at  E  a 
similar  bag  has  been  placed  externally  between  the  heart's  apex  and  the  inner  wall  of  the  chest.  In 
all  cases  v^  auricular  contraction  ;  V,  that  of  the  ventricle  ;  s,  closure  of  semilunar  valves,  sooner 
in  C  than  B  ;  P  =^  pause. 

Methods. — (i)  The  cardiac  sound  consists  of  a  tube  containing  two  separate  air  passages,  and 
in  connection  with  each  of  thei.e  there  is  a  small  elastic  bag  or  ampulla.  One  of  the  bags  is  fixed 
to  the  free  end  of  the  sound,  and  communicates  with  one  of  the  air  passages.  The  other  bag  is 
placed  in  connection  vi^ith  the  second  air  passage  in  the  sound,  and  at  such  a  distance  that,  when 
the  former  bag  lies  within  the  ventricle,  the  latter  is  in  the  auricle.  Each  bag  and  air  tube  com- 
municating with  it  is  connected  with  a  Marey's  tambour  (Fig.  47),  provided  with  a  lever  which 
inscribes  its  movements  upon  a  revolving  cylinder.  Any  variation  of  pressure  within  the  auricle  or 
ventricle  will  affect  the  elastic  ampullae,  and  thus  raise  or  depress  the  lever.  Care  must  be  taken  that 
the  writing  points  of  the  levers  are  placed  exactly  above  each  other.  A  tracing  of  the  cardiac  impulse 
is  taken  simultaneously  by  means  of  a  cardiograph  attached  to  a  separate  tambour. 

It  has  still  to  be  determined  whether  the  auricles  and  ventricles  act  alternately, 
so  that  at  the  moment  of  the  beginning  of  the  ventricular  contraction  the  auricles 
relax,  or  whether  the  ventricles  are  contracted  while  the  auricles  still  remain  slightly 
contracted,  so  that  the  whole  heart  is  contracted  for  a  short  time  at  least.  The 
latter  view  was  supported  by  Harvey,  Bonders,  and  others,  while  Haller  and  many 
of  the  more  recent  observers  support  the  view  that  the  action  of  the  auricles  and 
ventricles  alternates.  In  the  case  of  Frau  Serafin,  whose  heart  was  exposed,  v. 
Ziemssen  obtained  curves  from  the  auricles,  which  showed  that  the  contraction  of 
the  auricles  continued  even  after  the  commencement  of  the  ventricular  systole.  In 
Marey's  curve  the  contraction  of  the  ventricle  is  represented  as  following  that  of 
the  auricle  (Fig.  48). 

[(2)  Rolleston  used  a  special  apparatus  which  was  connected  with  the  interior  of  the  heart,  and 
he  finds  that  there  is  no  distinct  rise  of  pressure  in  the  dog  within  the  ventricles  corresponding  to 
the  auricular  systole  such  as  was  obtained  by  Marey  in  the  horse.  During  the  ventricular  diastole 
in  certain  cases  the  pressure  falls  below  the  atmospheric  pressure,  and  may  be  equal  to  — 20  mm, 
mercury  or  more  in  the  left  ventricle  (|  48).     It  is  probably  caused  by  the  elastic  expansion  of  the 


110 


PATHOLOGICAL    CARDIAC    IMPULSES. 


ventricle  continuing  after  the  blood  in  the  auricle  at  the  moment  of  the  cessation  of  the  ventricular 
systole  has  entered  the  ventricle,  i.e.,  the  quantity  of  blood  in  the  auricle  is  not  sufficient  in  all  cases 
to  distend  the  left  ventricle  to  the  jioint  at  which  its  suction  action  ceases.  Magini,  operating  on 
dogs  with  a  trocar  which  perforated  the  cavities  of  the  heart,  found  none  of  the  secondary  elevations 
obtained  by  Marey  with  his  sound.] 

A.  Fick  regards  the  alternating  contraction  as  a  means  whereby  the  pressure  in  the  large  venous 
trunks  is  kept  nearly  constant.  At  the  moment  of  ventricular  systole  the  auricles  relax,  and  the 
venous  blood  flows  freely  into  the  latter,  while  if  the  auricles  remained  contracted,  the  blood  in  the 
veins  would  be  kept  back.  Further,  at  the  moment  of  ventricular  diastole  the  auricles  contract, 
so  that  there  is  not  an  abnormal  diminution  of  the  pressure  in  the  veins.  Thus  the  pressure 
in  the  auricle  is  more  etjuable,  while  the  current  in  the  terminal  parts  of  the  veins  is  kept  more 
constant. 

Fig.  48. 


—  Right  Auricle. 


.Right  Ventricle. 


.-  Left  Ventricle. 


—  Aorta. 


.Cardiac  Impulse. 


Curves  obtained  from  the  hiart  of  a  horse  by  the  cardiac  sO'JnJ. 


52.  PATHOLOGICAL  CARDIAC  IMPULSES.— Change  in  the  Position  of  ;the 
Apex  Beat.— The  position  of  the  cardiac  impulse  is  changed — (i)  by  the  accumulation  of  fluids 
(serum,  pus,  blood)  or  gas  in  one  pleural  cavity.  A  copious  effusion  into  the  left  pleural  cavity 
compresses  the  lung,  and  may  displace  the  heart  toward  the  right  side,  while  effusion  on  the  right 
side  may  push  the  heart  more  to  the  left.  As  the  right  heart  must  make  a  greater  effort  to  propel 
the  blood  through  the  compressed  lung,  the  cardiac  impulse  is  usually  increased.  Advanced 
emphyseina  of  the  lung,  causing  the  diaphragm  to  be  pressed  downward,  displaces  the  heart 
doNvnward  and  mward,  while  pushing  or  pulling  up  of  the  diaphragm  (by  contraction  of  the  lung, 
or  through  pressure  from  below)  causes  the  apex  beat  to  be  displaced  upward,  and  also  slightly  to 
the  left.  Thickenmg  of  the  muscular  walls  with  dilatation  of  the  cavities  of  the  left  ventricle  makes 
that  ventricle  longer  and  broader,  while  the  increased  cardiac  impulse  may  be  felt  in  the  axillary 
hne  m  the  sixth,  seventh,  or  even  eighth  intercostal  space  to  the  left  of  the  mammary  line.  Hyper- 


VARIATIONS    OF   THE    CARDIAC    IMPULSE. 


Ill 


trophy,  with  dilatation  of  the  rjght  side,  increases  the  breadth  of  the  heart,  so  that  the  cardiac  impulse 
is  felt  more  to  the  right,  even  to  the  right  of  the  sternum.  In  the  rare  cases  where  the  heart  is 
transposed,  the  apex  beat  is  felt  on  the  right  side.  When  the  cardiac  impulse  goes  to  the  left  of  the 
left  mammary  line,  or  to  the  right  of  the  parasternal  line,  the  heart  is  increased  in  breadth,  and  there 
is  hypertrophy  of  the  heart.  A  greatly  increased  cardiac  impulse  may  extend  to  several  inter- 
costal spaces. 

The  cardiac  impulse  is  abnormally  weakened  in  cases  of  atrophy  and  degeneration  of  the  car- 
diac muscle,  or  by  weakening  of  the  innervation  of  the  cardiac  ganglia.  It  is  also  weakened  when  the 
heart  is  separated  from  the  chest  wall  owing  to  the  collection  of  fluids  or  air  in  the  pericardium, 
or  by  a  greatly  distended  left  lung ;  and,  indeed,  when  the  left  side  of  the  chest  is  filled  with 
fluid,  the  cardiac  impulse  may  be  extinguished.  The  same  occurs  when  the  left  ventricle  is  very 
imperfectly  filled  during  its  contraction  (in  consequence  of  marked  narrowing  of  the  mitral 
orifice),  or  when  it  can  only  empty  itself  very  slowly  and  gradually,  as  during  marked  narrowing 
of  the  aortic  orifice. 

An  increase  of  the  cardiac  impulse  occurs  during  hypertrophy  of  the  walls,  as  well  as  under  the 
influence  of  various  stimuli  (psychical,  inflammatory,  febrile,  toxic)  which  affect  the  cardiac  ganglia. 
Great  hypertrophy  of  the  left  ventricle  causes  the  heart  to  heave,  ^o  that  a  part  of  the  chest  wall  may 
be  raised  and  also  vibrate  during  systole. 

A  pulling  in  of  the  anterior  wall  of  the  chest  during  the  cardiac  systole  occurs  in  the  third  and 
fourth  interspaces,  not  unfrequently  under  normal  circumstances,  sometimes  during  increased  cardiac 
action,  and  in  eccentric  hypertrophy  of  the  ventricles.  As  the  heart's  apex  is  slightly  displaced, 
and  the  ventricle  becomes   slightly  smaller   during   its   systole,  the  empty  space  is  filled  by  the 


Fig 


yielding  soft  parts  of  the  intercostal  space.  When  the  heart  is  united  with  the  pericardium  and 
the  surrounding  connective  tissue,  which  renders  systolic  locomotion  of  the  heart  impossible, 
retraction  of  the  chest  wall  during  systole  takes  the  place  of  the  cardiac  impulse  {Skoda).  During 
the  diastole,  a  diastolic  cardiac  impulse  of  the  corresponding  part  of  the  chest  wall  may  be  said 
to  occur. 

Clinically,  changes  in  the  cardiac  impulse  are  best  ascertained  by  taking  graphic  representations 
of  the  cardiac  impulse,  and  studying  the  curves  so  obtained  (Figs.  49  A  and  49  b). 

In  curve  P  (much  reduced),  from  a  case  of  marked  hypertrophy  with  dilatation,  the  ventric- 
ular contraction,  be,  is  usually  very  great,  while  the  time  occupied  by  the  contraction  is  not  rnuch 
increased.  P  and  Q  were  obtained  from  a  case  of  marked  eccentric  hypertrophy  of  the  left  ventricle, 
due  to  insufficiency  of  the  aortic  valves.  Curve  Q  was  taken  intentionally  over  the  auriculo- 
ventricular  groove,  where  retraction  of  the  chest  wall  occurred  during  systole ;  nevertheless  the 
individual  events  occurring  in  the  heart  are  indicated. 

Fig.  E  is  from  a  case  of  aortic  stenosis.  The  auricular  contraction  {ab)  lasts  only  a  short  time; 
the  ventricular  systole  is  obviously  lengthened,  and  after  a  short  elevatian  {be)  shows  a  series 
of  fine  indentations  {e,  e)  caused  by  the  blood  being  pressed  through  the  narrow  and  rough- 
ened aorta. 

Fig.  F,  from  a  case  of  insuflEiciency  of  the  mitral  valve,  shows  {ab)  well  marked  on  account 
of  the  increased  activity  of  the  left  auricle,  while  the  shock  {d)  from  the  closure  of  the  aortic 
valves  is  small,  on  account  of  the  diminished  arterial  tension.  On  the  other  hand,  the  shock  from 
the  accentuated  pulmonary  sound  (<?)  is  very  great,  and  is  in  the  apex  of  the  curve.  On  account 
of  the  great  tension  in  the  pulmonary  artery,  the   second  pulmonary  tone  may  be  so  strong,  and 


112 


THE    Hi: ART    SOUNDS. 


succeed  the  second  aortic  sound  [<i)  so  rapidly,  that  hoth  almost  merge  completely  into  each  other 
(H  and  K). 

The  curve  of  stenosis  of  the  mitral  orifice  ((!)  sliows  a  loiifji  irregular,  notched,  auricular 
contraction  [('/•),  caused  by  the  blood  being  forced  through  an  irregular  narrow  orifice.  The  ven- 
tricular contraction  ((>c)  is  feelile  because  the  ventricle  is  imperfectly  fdicd.  The  ciosufes  of  the  two 
valves,  </ and  <-,  are  relatively  far  apart,  and  one  can  hear  distinctly  a  redu|ilicated  second  sound. 
The  aortic  valves  close  rapidly,  because  the  aorta  is  imperfectly  supplied  with  blood,  whde  the  more 
copious  inflow  of  blood  into  the  pulmonary  artery  causes  its  valves  to  close  later. 

If  the  heart  beats  rapidly  and  feebly — if  the  blood  pressure  in  the  aorta  and  pulmonary  artery  De 
low,  the  signs  of  closure  of  tlie  pulmonary  valves  may  be  absent — as  in  curve  L — taken  from  a  girl 
suffering  from  nervous  palpitation  and  morbus  IJasedowii. 

In  verv  rare  cases  of  insufficiency  of  the  mitral  valve,  it  has  been  observed  that  at  certain  times 
both  ventricles  contract  simultaneously,  as  in  a  normal  heart,  but  that  this  alternates  with  a  condi- 
tion where  the  right  ventricle  alone  seems  to  contract.  Curve  M  is  such  a  curve  obtained  by  Mal- 
branc,  who  called  this  condition  intermittent  hemisystole.  The  first  curve  (I)  is  like  a  normal 
curve,  during  which  the  whole  heart  acted  as  usual.  Tlie  curve  II,  however,  is  caused  by  tlie  right 
side  of  the  heart  alone ;  it  wants  the  closure  of  the  aortic  valves,  </,  and  there  was  no  pulse  in  the 
arteries.  Owing  to  insufficiency  of  the  tricuspid  valve,  the  same  person  had  a  venous  pulse  with 
every  cardiac  impulse,  so  that  the  arterial  and  venous  pulses  first  occurred  together,  and  then  the 
venous  pulse  alone  occurred.     In  these  cases  the  mitral  insufficiency  leads  to  the  right  ventricle 


Fi( 


KiGS.  49  A  AND  49  II.— Curves  of  the  cardiac  impulses,  ab,  contraction  of  auricles  ;  l>c,  ventricular  sysKilc  :  d,  closure 
of  aortic,  and  ,-,  of  pulmonary  valves  ;  e/,  diastole  of  ventricle  :  P,  y,  hypertroi)hy  and  dilatation  of  the  left 
ventricle;  E,  stenosis  of  the  aortic  orifice;  K,  mitral  insufficiency;  G,  mitral  stenosis;  L,  nervous  palpitation 
in  Ba.sedow's  disease;  M,  so-called  hemisystole. 

being  overdistended,  while  the  left  is  nearly  empty,  so  that  the  right  side  requires  to  contract  more 
energetically  than  the  left.  It  does  not  seem  that  the  right  ventricle  alone  contracts  in  these  cases, 
but  rather  that  the  action  of  the  left  side  is  very  feeble. 

53.  THE  HEART  SOUNDS.— On  listening  over  the  region  of  the  heart 
in  a  healthy  man,  either  with  the  ear  applied  directly  to 
the  chest  wall  {Harvey),  or  by  means  of  a  stethoscope 
{Laennec,  1819),  we  hear  two  characteristic  sounds,  the 
so-called  "heart  sounds,"  The  two  sounds  are  called 
first  and  second,  and  together  they  correspond  to  a  single 
cardiac  cycle.  These  sounds  are  separated  by  silences. 
[Fig.  50  shows  the  relation  of  the  events  occurring  in  the 
heart  during  a  cardiac  cycle  to  the  sounds  and  silences.] 

1.  The  first  sound. 

2.  The  first  or  short  silence. 

3.  The  second  sound. 

4.  The  second  or  long  silence. 

[Relative  Duration, — There  is  no  absolute  duration 
of  each  phase  of  a  cardiac  cycle,  but  we  may  take  the  aver- 


Scheme  of  a  canliac  cycle.  The 
inner  circle  shows  what  events 
occur  in  the  heart,  and  the 
outer,  the  relation  of  the  sounds 
and  silences  to  these  events. 


CAUSES    OF   THE    HEART    SOUNDS.  113 

age  duration  calculated  from  the  measurements  of  Gibson,  in  a  case  of  fissure  of 
the  sternum,  to  be  as  follows : — 

Auricular  systole, 112  sec. 

Ventricular  systole, 368    " 

Ventricular  diastole, • 57^    " 


Cardiac  cycle, 1.058  sec. 

Suppose  we  divide  the  cycle  into  tenths  (  Walshe),  then  the  first  sound  will  last 
^,  the  first  silence  -^y  the  second  sound  -^,  and  the  long  silence  -^  of  the  entire 
period.] 

The  first  sound  [long  or  systolic]  is  twice  as  long  as,  somewhat  duller,  and 
one-third  or  one-fourth  deeper  than,  the  second  sound  ;  it  is  less  sharply  defined 
at  first,  and  is  synchronous  with  the  systole  of  the  ventricles. 

The  second  sound  [short  or  diastolic]  is  clearer,  sharper,  shorter,  more  sud- 
den, and  is  one-third  to  one-fourth  higher;  it  is  sharply  defined  and  synchronous 
with  the  closure  of  the  semilunar  valves.  The  sounds  emitted  during  each  cardiac 
cycle  have  been  compared  to  the  pronunciation  of  the  syllables  lubb,  dUp.  Or  the 
result  may  be  expressed  thus — 


to 


lili^^^^^ 


^ 


Bu       -       tup.  Bu      -      tap. 

[It  is  to  be  remembered  that  in  reality  four  sounds  are  produced  in  the  heart, 
but  the  two  first  sounds  occur  together  and  the  two  second,  so  that  only  a  single 
first  and  a  single  second  sound  are  heard.] 

The  causes  of  the  first  sound  are  due  to  two  conditions.  As  the  sound  is 
heard,  although  enfeebled,  in  an  excised  heart  in  which  the  movements  of  the 
valves  are  arrested,  and  also  when  the  finger  is  introduced  into  the  auriculo-ven- 
tricular  orifices  so  as  to  prevent  the  closure  of  the  valves  (C.  Ludwig  and  Dogiel), 
one  of  the  chief  factors  lies  in  the  ^'muscle  sound '^  produced  by  the  contracting 
muscular  fibres  of  the  ventricles.  This  sound  is  supported  and  increased  by  the 
sound  produced  by  the  tension  and  vibration  of  the  auriculo-ventricular  valves 
and  their  chordae  tendinese,  at  the  moment  of  the  ventricular  systole.  Wintrich, 
by  means  of  proper  resonators,  has  analyzed  the  first  sound  and  distinguished  the 
clear,  short,  valvular  part  from  the  deep,  long,  muscular  sound. 

The  muscle  sound"  produced  by  transversly  striped  muscle  does  not  occur  with  a  si?nple  contrac- 
tion (p.  127),  but  only  when  several  contractions  are  superposed  to  produce  tetanus  (§  303).  The 
ventricular  contraction  is  only  a  simple  contraction,  but  it  lasts  considerably  longer  than  the  contrac- 
tion of  other  muscles,  and  herein  lies  the  cause  of  the  occurrence  of  the  muscle  sound  during  the 
ventricular  contraction. 

Defective  Heart  Sounds. — In  certain  conditions  (typhus,  fatty  degeneration  of  the  heart),, 
where  the  muscular  substance  of  the  heart  is  much  weakened,  the  first  sound  may  be  completely 
inaudible.  In  aortic  insufficiency,  in  consequence  of  the  reflux  of  blood  from  the  aorta  into  the 
ventricle,  the  mitral  valve  is  gradually  stretched,  and  sometimes  even  before  the  beginning  of  the 
ventricular  systole,  the  first  sound  may  be  absent.  Such  pathological  conditions  seem  to  show  that> 
for  the  production  of  the  first  sound,  muscle  sound  and  valve  sound  must  eventually  work  together^ 
and  that  the  tone  is  altered,  or  may  even  disappear,  when  one  of  these  causes  is  absent.  [Yeo  and 
Barrett  state  that  the  sound  is  purely  muscular  (?).] 

The  cause  of  the  second  sound  is  undoubtedly  due  to  the  prompt  closure, 
and  therefore  sudden  stretching  or  tension,  of  the  semilunar  valves  of  the  aorta 
and  pulmonary  artery,  so  that  it  is  purely  a  valvular  sound.  Perhaps  it  is  aug- 
mented by  the  sudden  vibration  of  the  fluid  particles  in  the  large  arterial  trunks. 
[The  second  sound  has  all  the  characters  of  a  valvular  sound.  That  the  aortic 
8 


114  VARIATIONS    OF   THE    HEART   SOUNDS. 

valves  are  concerned  in  its  production,  is  proved  by  introducing  a  curved  wire 
through  the  left  carotid  artery  and  hooking  up  one  or  more  segments  of  the  valve, 
when  the  sound  is  modified,  and  it  may  disappear  or  be  replaced  by  an  abnormal 
sound  or  "  murmur."  Again,  when  these  valves  are  diseased,  the  sound  is  altered, 
and  it  may  be  accompanied  or  even  displaced  by  murmurs.]  Although  the 
aortic  and  pulmonary  valves  do  not  close  simultaneously,  usually  the  difference  in 
time  is  so  small  that  both  valves  make  one  sound,  but  the  second  sound  may  be 
double  or  divided  when,  through  increase  of  the  difference  of  pressure  in  the 
aorta  and  pulmonary  artery,  the  interval  becomes  longer.  Even  in  health  this 
may  be  the  case,  as  occurs  at  the  end  of  inspiration  or  the  beginning  of  expira- 
tion yv.  Dusch). 

Where  the  Sounds  are  Heard  Loudest. — The  sound  produced  by  the 
tricuspid  valvr  is  heard  loudest  at  the  junction  of  the  lower  right  costal  cartilages 
with  the  sternum  ;  as  the  mitral  valve  lies  more  to  the  left  and  deeper  in  the 
chest,  and  is  covered  in  front  by  the  arterial  orifice,  the  mitral  sound  is  best 
heard  at  the  apex  beat,  or  immediately  above  it,  where  a  strip  of  the  left  ventricle 
lies  next  the  chest  wall.  [The  sound  is  conducted  to  the  part  nearest  the  ear  of 
the  listener  by  the  muscular  substance  of  the  heart.]  The  aortic  and  pulmonary 
orifices  lie  so  close  together  that  it  is  convenient  to  listen  for  the  second  {aortic) 
sound  in  the  direction  of  the  aorta,  where  it  comes  nearest  to  the  surface,  i.e., 
over  the  second  right  costal  cartilage  or  aortic  cartilage  close  to  its  junction  with 
the  sternum.  The  sound,  although  produced  at  the  semilunar  valves,  is  carried 
upward  by  the  column  of  blood  and  by  the  walls  of  the  aorta.  The  sound 
produced  by  the  pulmonary  artery  is  heard  most  distinctly  over  the  third  left 
costal  cartilage,  somewhat  to  the  left  and  external  to  the  margin  of  the  sternum 
(Fig.  50- 

54.  VARIATIONS  OF  THE  HEART  SOUNDS.— Increase  of  the  first  sound  of  both 
ventricles  indicates  a  more  energetic  contraction  of  the  ventricles  and  a  simultaneously  greater  and 
more  sudden  tension  of  the  auriculo-ventricular  valves.  Increase  of  the  second  sound  is  a  sign  of 
increased  tension  in  the  interior  of  the  corresponding  large  arteries.  Hence  increase  of  the  second 
(pulmonary)  sound  indicates  overfilling  and  excessive  tension  in  the  pulmonary  circuit.  A  feeble 
action  of  the  heart,  as  well  as  abnormal  want  of  blood  in  the  heart,  causes  weak  heart  sounds, 
which  is  the  case  in  degenerations  of  the  heart  muscle. 

Irregularities  in  structure  of  the  individual  valves  may  cause  the  heart  sounds  to  become  "  im- 
pure." If  a  pathological  cavity,  filled  with  air,  be  so  placed,  and  of  such  a  form  as  to  act  as  a 
resonator  to  the  heart  sounds,  they  may  assume  a  "metallic"  character.  The  first  and  second 
sounds  may  be  "  reduplicated  "  or  [although  "  duplication  "  is  a  more  accurate  term  [Barry\ 
doubled.  The  reduplication  of  the  first  sound  is  explained  by  the  tension  of  the  tricuspid  and  that 
of  the  mitral  valves  not  occurring  simultaneously.  Sometimes  in  disease  a  sound  is  produced  by  a 
hypertrophied  auricle  producing  an  audible  presystolic  sound,  /.  e.,  a  sound  or  "  murmur  "  pre- 
ceding the  first  sound.  [This  has  been  questioned  quite  recently.]  As  the  aortic  and  pulmonary 
valves  do  not  close  quite  simultaneously,  a  reduplicated  second  sotind\?,  only  an  increase  of  a  physio- 
logical condition.  All  conditions  which  cause  the  aortic  valves  to  close  rapidly  (diminished 
amount  of  blood  in  the  left  ventricle)  and  the  pulmonary  valves  to  close  later  (congestion  of  the 
right  ventricle — both  conditions  together  in  mitral  stenosis),  favor  the  production  of  a  reduplicated 
second  sound. 

Cardiac  Murmurs. — If  irregularities  occur  in  the  valves,  either  in  cases  of  stenosis  or  in  insuf- 
ficiency, so  that  the  blood  is  subjected  to  vibratory  oscillations  and  friction,  then,  instead  of  the 
heart  sounds,  other  sounds — murmurs  or  bruits — arise  or  accompany  these.  A  combination  of 
these  sounds  is  always  accompanied  by  disturbances  of  the  circulation.  [These  murmurs  may  be 
produced  within  the  heart,  when  they  are  termed  endocardial ;  or  outside  it,  when  they  are  called 
exocardial  murmurs.  But  other  murmurs  are  due  to  changes  in  the  quality  or  amount  of  the 
blood,  when  they  are  spoken  of  ashaemic  murmurs.  In  the  study  of  all  murmurs,  note  their  rhythm 
or  exact  relation  to  the  normal  sounds,  \k\€\i  point  of  »iaxi»iiim  intensity,  and  the  direction  in  which 
the  tnurniur  is  propagated.']  It  is  rare  that  tumors  or  other  deposits  projecting  into  the  ventricles 
cause  murmurs,  unless  there  be  present  at  the  same  time  lesions  of  the  valves  and  disturbances  of 
the  circulation.  The  cardiac  murmurs  are  always  related  to  the  systole  or  diastole,  and  usually  the 
systolic  are  more  accentuated  and  louder.  Sometimes  they  are  so  loud  that  the  thorax  trembles 
under  their  irregular  oscillations  {fremitus,  fr^missement  cataire). 

In  cases  where  diastolic  murmurs  are  heard,  there  are  always  anatomical  changes  in  the  car- 


VARIATIONS    OF    THE    HEART    SOUNDS. 


115 


diac  mechanism.  These  are  insufficiency  of  the  arterial  valves,  or  stenosis  of  the  auriculo -ventricu- 
lar orifice  (usually  the  left).  Systolic  murmurs  do  not  always  necessitate  a  disturbance  in  the 
cardiac  mechanism.  They  may  occur  on  the  left  side,  owing  to  insufficiency  of  the  mitral  valve, 
stenosis  of  the  aorta,  and  in  the  calcification  and  dilatation  of  the  ascending  part  of  the  aorta. 
These  murmurs  occur  very  much  less  frequently  on  the  right  side,  and  are  due  to  insufficiency  of 
the  tricuspid  and  stenosis  of  the  pulmonary  orifice. 


Fig.  51, 


The  heart — its  several  parts  and  great  vessels  in  relation  to  the  front  of  the  thorax.  The  lungs  are  collapsed  to 
their  normal  extent,  as  after  death,  exposing  the  heart.  The  outlines  of  the  several  parts  of  the  heart  are  indi- 
cated by  very  fine  dotted  lines.  The  area  of  propagation  of  valvular  murmurs  is  marked  out  by  more  visible 
dotted  lines.  A,  the  circle  of  mitral  murmur,  corresponds  to  the  left  apex.  The  broad  and  somewhat  diffused 
area,  roughly  triangular,  is  the  region  of  tricuspid  murmurs,  and  corresponds  generally  with  the  right  ventricle, 
where  it  is  least  covered  by  lung.  The  letter  C  is  in  its  centre.  The  circumscribed  circular  area,  D,  is  the 
part  over  which  the  pulmonic  arterial  murmurs  are  commonly  heard  loudest.  In  many  cases  it  is  an  inch,  or  even 
more,  lower  down,  corresponding  to  the  conus  arteriosus  of  the  right  ventricle,  where  it  touches  the  wall  of  the 
thorax.  The  internal  organs  and  parts  of  organs  are  indicated  by  letters  as  follows  : — r.  au,  right  auricle,  traced 
in  fine  dotting  ;  ao,  arch  of  aorta,  seen  in  the  first  intercostal  space,  and  traced  in  fine  dotting  on  the  sternum  ; 
V.  i.,  the  two  innominate  veins  ;  r.  v.,  right  ventricle  ;  I.  v.,  left  ventricle. 

Functional  Murmurs. — Systolic  murmurs  often  occur  without  any  valvular  lesion,  although 
they  are  always  less  loud,  and  are  caused  by  abnormal  vibrations  of  the  valves  or  arterial  walls. 
They  occur  most  frequently  at  the  orifice  of  the  pulmonary  artery  [and  are  generally  heard  at  the 
base],  less  frequently  at  the  mitral,  and  still  less  frequently  at  the  aortic  or  the  tricuspid  orifice. 
Ansemia,  general  malnutrition,  acute  febrile  affections,  are  the  causes  of  these  murmurs.     [Some  of 


116 


DURATION  OF  THE  MOVEMENTS  OF  THE  HEART. 


Fig.  52. 


these  are  due  to  an  altered  condition  of  the  blood,  and  are  called  hsemic,  and  others  to  defective" 
cardiac  muscular  nutrition,  and  are  called  dynamic  {lV(i/s/ic).'\ 

Sounds  may  also  occur  during  a  certain  stage  of  inflammation  of  the  pericardium  (pericarditis) 
from  the  roughened  surfaces  of  this  membrane  rubbing  upon  each  other.  Audible  friction  sounds 
are  thus  produced,  and  the  vibration  may  even  be  perceptible  to  toucli.  [These  are  "  friction 
sounds,"  and  quite  distinct  from  sounds  produced  within  the  heart  itself.] 

55.  DURATION  OF  THE  MOVEMENTS  OF  THE  HEART.— 

The  heart  continues  to  beat  for  some 
time  after  it  is  cut  out  of  the  body. 
The  movement  lasts  longer  in  cold- 
blooded animals  (frog,  turtle) — extend- 
ing even  to  days — than  in  mammals.  A 
rabbit's  heart  beats  from  3  minutes  up 
to  36  minutes  after  it  is  cut  out  of  the 
body.  The  average  of  many  experi- 
ments is  about  II  minutes.  [Waller 
and  Reid  recorded  the  ventricular  con- 
tractions of  a  rabbit's  heart  72  minutes 
after  its  excision.  Fig.  52  shows  the 
prolongation  of  the  ventricular  systole 
Curves  of  excised  r.-ibbit's  heart,  i,  6  mins.  after  excision ;  in  an  cxcised  rabbit's  heart,  the  move- 
2,  lo  mins  :  3, 20  mins. ;  4. 7°  m'ns.    (After  iVaiier  j^gnts  being  recordcd  by  a  Icver  resting 

and  Retd.)  1  n        -n,  r  1 

on  the  heart. J  Panum  found  the  last 
trace  of  contraction  to  occur  in  the  right  auricle  (rabbit)  15  hours  after  death  ;  in 
a  mouse's  heart,  46  hours  ;  in  a  dog's,  96  hours.  An  excised  frog's  heart  beats, 
at  the  longest,  2^  days  {Valentin).  In  a  human  embryo  (third  month)  the  heart 
was  found  beating  after  4  hours.  In  this  condition  stimulation  causes  an  increase 
and  acceleration  of  the  action.  The  ventricular  contraction  weakens,  and  soon 
each  auricular  contraction  is  not  followed  by  a  ventricular  contraction,  two  or 
more  of  the  former  being  succeeded  by  only  one  of  the  latter.  At  the  same  time 
the  ventricles  contract  more  slowly  (Fig.  46),  and  soon  stop  altogether,  while  the 
auricles  continue  to  beat.  If  the  ventricles  be  stimulated  directly,  as  by  pricking 
them  with  a  pin,  they  may  execute  a  contraction.  The  left  auricle  soon  ceases  to 
beat,  while  the  right  auricle  still  continues  to  contract.  The  right  auricular  ap- 
pendix continues  to  beat  longest,  as  was  observed  by  Galen  and  Cardanus  (1550), 
and  it  is  termed  "  ultimum  moriens."  Similar  observations  have  been  made  upon 
the  hearts  of  persons  who  have  been  executed. 

If  the  heart  has  ceased  to  beat,  it  may  be  excited  to  contract  for  a  short  time 
by  direct  stimulation,  more  especially  by  heat  (^Harvey)  ;  even  under  these  cir- 
cumstances the  auricles  and  their  appendices  are  the  last  parts  to  cease  contracting. 
As  a  general  rule,  direct  stimulation,  although  it  may  cause  the  heart  to  act  more 
vigorously  for  a  short  time,  brings  it  to  rest  sooner.  In  such  cases,  therefore,  the 
regular  sequence  of  events  ceases,  and  there  is  usually  a  twitching  movement  of  the 
muscular  fibres  of  the  heart.  C.  Ludwig  found  that,  even  after  the  excitability 
is  extinguished  in  the  mammalian  heart,  it  may  be  restored  by  injecting  arterial 
blood  into  the  coronary  arteries ;  conversely  lesion  of  these  vessels  is  followed  by 
enfeebled  action  of  the  heart  (§  47).  Hammer  found  that  in  a  man  whose  left 
coronary  artery  was  plugged  the  pulse  fell  from  80  to  8  beats  per  minute. 

[The  beats  of  the  excised  heart  of  a  rabbit  gradually  decline  in  force  and  frequency,  the  latent 
period  and  contraction  become  longer  and  the  excitability  more  obtuse.  The  duration  of  a  con- 
traction may  be  6  sec,  the  normal  being  .3  sec.  The  beats  have  often  a  bigeminal  character.  An 
excised  heart  may  be  frozen  quite  hard,  yet  on  being  thawed  it  contracts  spontaneously.  The  con- 
traction proceeds  in  a  wave  from  the  spot  stimulated  in  the  frog's  heart  at  8°  to  12°  C.  at  30  to  90 
mm.  per  sec. ;  in  the  mammalian  excised  heart  about  8  metres  per  sec.   (  Waller  and  Iieid)J] 

Action  of  Gases  on  the  Heart. — During  its  activity  the  heart  uses  O,  and  produces  COj,  so 
that  it  beats  longest  in  pure  O  (12  hours),  and  not  so  long  in  N, — H  (i  hour) — CO,  (10  minutes) 


INNERVATION    OF   THE    HEART.  117 

— CO  (42  minutes) — CI  (2  minutes),  or  in  a  vacuum  (20  to  30  minutes),  even  when  there  is  watery- 
vapor  present  to  prevent  evaporation.  If  the  heart  be  reintroduced  iato  O  it  begins  to  beat  again. 
[A  frog's  heart  ceases  to  beat  in  compressed  O  (10  to  12  atmospheres)  in  about  one-third  of  the 
time  it  would  do  were  it  simply  excised  and  left  to  itself.  An  excised  heart  suspended  in  ordinary 
air  beats  three  to  four  times  as  long  as  a  heart  which  is  placed  upon  a  glass  plate.] 

[56.  PHYSICAL  EXAMINATION  OF  THE  HEART.— The  phy- 
sical methods  of  diagnosis  enable  us  to  obtain  precise  knowledge  regarding  the 
actual  state  of  the  heart.     The  methods  available  are  :  — 


1.  Inspection. 

2.  Palpation. 


3.  Percussion. 

4.  Auscultation. 


To  arrive  at  a  correct  diagnosis  all  the  methods  must  be  employed.] 

[Inspection. — The  person  is  supposed  to  have  his  chest  exposed  and  to  be  in  the  recumbent 
position.  It  is  important  to  remember  the  limits  of  the  heart.  The  base  corresponds  to  a  line 
joining  the  upper  margins  of  the  third  costal  cartilages,  the  apex  to  the  fifth  interspace,  while 
transversely  it  extends  from  a  little  to  the  right  of  the  sternum  to  within  a  little  of  the  left  nipple ; 
this  area  occupied  by  the  heart  being  called  the  deep  cardiac  region.  By  the  eye  we  can 
detect  any  alteration  in  the  configuration  of  the  prsecordia,  bulging  or  retraction  of  the  region  as 
a  whole  or  of  the  intercostal  spaces,  and  we  may  detect  variations  in  the  position,  character, 
extent  of  the  cardiac  impulse,  or  the  presence  of  other  visible  pulsations.] 

[Palpation. — By  placing  the  whole  hand  flat  upon  the  prsecordia,  we  can  ascertain  the  presence 
or  absence,  the  situation  and  extent,  and  any  alterations  in  the  characters  of  the  apex  beat ;  or  we 
may  detect  the  existence  of  abnormal  pulsations,  vibrations,  thrills,  or  friction  in  this  region.  In 
feeling  for  the  apex  beat,  if  it  be  at  all  feeble,  it  is  well  to  make  the  patient  lean  forward.  Of 
course,  it  must  be  remembered  that  the  whole  heart  may  be  displaced  by  tumors  or  accumulations 
of  fluids  pressing  upon  it,  i.  <?.,  conditions  external  to  itself,  or  the  apex  beat  may  be  displaced  from 
causes  within  the  heart  itself,  as  in  hypertrophy  of  the  left  ventricle.] 

[Percussion. — As  the  heart  is  a  solid  organ,  and  is  surrounded  by  the  lungs  which  contain  air, 
it  is  evident  that  the  sound  emitted  by  striking  the  chest  over  the  region  of  the  former  must  be 
different  from  that  produced  over  the  latter.  Not  only  is  there  a  difference  in  the  sound  or  note 
emitted,  but  the  "sensation  of  resistance"  which  one  feels  on  percussing  the  two  organs  is  different. 
We  may  ascertain — 

1.  The  superficial  or  absolute  cardiac  dullness. 

2.  The  deep  or  relative  dullness. 

[Superficial  Cardiac  Dullness. — This  theoretically  is  the  part  of  the  heart  in  direct  contact 
with  the  chest  wall  and  uncovered  by  lung,  but  obviously  as  the  lungs  vary  in  size  during  respira- 
tion, it  must  be  smaller  during  inspiration  and  larger  during  expiration.  It  forms  a  roughly  tri- 
angular space,  whose  base  cannot  be  accurately  determined,  as  the  heart  dullness  merges  into  that 
of  the  liver,  situate  below  it,  but  it  corresponds  to  a  horizontal  line  2j^  inches  long,  extending  from 
the  apex  beat  to  the  middle  of  the  sternum.  The  internal  side  corresponding  to  the  left  edge  of 
the  sternum  is  2  inches  long,  and  reaches  from  the  junction  of  the  fourth  costal  cartilage  with  the 
sternum — apex  of  the  triangle — to  the  sternal  end  of  the  base  line.  The  superior,  outer,  or  oblique 
line,  3  inches  in  length,  is  somewhat  curved,  and  passes  downward  and  outward  from  the  apex 
of  the  triangle  to  the  apex  of  the  heart.] 

[Deep  Cardiac  Dullness. — By  this  method  theoretically  we  seek  to  define  the  exact  limits  of 
the  heart  as  a  whole,  and  thus  to  ascertain  its  absolute  size,  and  of  course  percussion  has  to  be  done 
through  a  certain  thickness  of  lung  tissue,  and  hence  one  must  strike  the  pleximeter  forcibly.  It 
extends  vertically  from  the  third  rib  and  ends  at  the  sixth,  but  owing  to  the  cardiac  merging  in  the 
hepatic  dullness,  this  lower  limit  cannot  be  accurately  ascertained ;  while  transversely  at  the  fourth 
rib  it  extends  from  just  within  the  nipple  line  to  slightly  beyond  the  right  of  the  sternum.  By  these 
means  we  may  detect  increase  in  the  size  of  the  heart  or  alterations  in  the  relation  of  the  lungs  to 
the  heart,  fluid  in  pericardium,  etc.] 

[Auscultation. — This  is  one  of  the  most  valuable  methods,  for  by  it  we  can  detect  variations 
and  modifications  in  the  healthy  sounds  of  the  heart,  the  rhythm  and  frequency  of  the  heart  beat, 
the  existence  of  abnormal  sounds,  and  their  exact  relation  to  the  normal  sounds,  also  their  char- 
acters and  relation  to  the  cardiac  cycle,  and  the  direction  in  which  these  sounds  are  propagated 
(I  54)0 

57.  INNERVATION  OF  THE  HEART.— [Intra-  and  Extra-Car- 
diac Nervous  Mechanism. — When  the  heart  is  removed  from  the  body,  or 
when  all  the  nerves  which  pass  to  it  are  divided,  it  still  beats  for  some  time,  so 
that  its  movements  must  depend  upon  some  mechanism  situated  within  itself. 
The  ordinary  rhythmical  movements  of  the  heart  are  undoubtedly  associated  with 
the  presence  of  nerve  ganglia,  which  exist  in  the  substance  of  the  heart — the 


118 


THE    FROG  S    HEART. 


intra-cardiac  ganglia.  But  the  movements  of  the  heart  are  influenced  by  nervous 
impulses  which  reach  it  from  without,  so  that  there  falls  to  be  studied  an  inira- 
caiiiiac  and  an  iwira-caitUac  nervous  mechanism.] 

The  cardiac  plexus  is  composed  of  the  following  nerves:  (i)  The  cardiac 
branches  of  the  vagus,  the  branch  of  the  same  name  from  the  external  branch  of 
the  superior  laryngeal,  a  branch  from  the  inferior  laryngeal,  and  sometimes 
branches  from  the  pulmonary  plexus  of  the  vagus  (more  numerous  on  the  right 
side)  ;  (2)  the  superior,  middle,  inferior,  and  lowest  cardiac  branches  of  the 
three  cervical  ganglia  and  the  first  thoracic  ganglia  of  the  sympathetic;  (3)  the 
inconstant  twig  of  the  descending  branch  of  the  hypoglossal  nerve,  which,  accord- 
ing to  Luschka,  arises  from  the  upper  cervical  ganglion.  From  the  plexus  there 
proceed — the  deep  and  the  superfieial  nerves  (the  latter  usually  at  the  division  of 
the  pulmonary  artery  under  the  arch  of  the  aorta,  and  containing  the  ganglion 
of  Wrisberg)  (§  370).  The  following  nerves  may  be  separately  traced  from  the 
plexus: — 

{a)  The  plexus  coronarius  dexter  and  sinister,  which  contains  the  vaso- 
motor fien'es  for  the  coronary  vessels  (physiological  proof  still  wanting)  as  well  as 
the  nerves  (sensory?)  proceeding  from  them  (to  the  pericardium?). 

{h)  Intra-cardiac  nerves  and  ganglia. — The  nerves  lying  in  i\\Q  grooves  of 
the  heart  and  in  its  substatice  contain  numerous  ganglia  {Remak),  and  are  regarded 
as  the  automatic  motor  centres  of  the  heart.  A  nervous  ring  containing  numerous 
ganglia  corresponds  to  the  margin  of  the  septum  atriorum  ;  there  is  another  in 
the  auriculo-ventricular  groove.  Where  the  two  meet,  they  exchange  fibres. 
The  ganglia  usually  lie  near  the  pericardium.  In  mammals,  the  two  largest  gan- 
glia lie  near  the  orifice  of  the  superior  vena  cava — in  birds,  the  largest  ganglion 
(containing  thousands  of  ganglionic  cells)  lies  posteriorly  where  the  longitudinal 
and  transverse  sulci  cross  each  other.  Fine  branches,  also  provided  with  small 
ganglia,  proceed  from  these  ganglia,  and  penetrate  the  muscular  walls  of  the  auri- 
cles and  ventricles. 

[Frog's  Heart. — The  frog's  heart  consists  of  the  sinus  venostis,  into  which  open  the  single 
inferior  and  the  two  superior  venK  cavK  (Fig.  54).  There  are /7w  auricles;  the  right  one  coni- 
municates   with   the   sinus  venosus,   and  opens   into  the  single   ventricle ;    the  left    auricle    also 


Fig.  53. 


Fig.  54. 


Heart  of  frog  from  the  front.  V,  single  ventricle;  Ad, 
^  J,  right  and  left  auricles  ;  B,  bulbus  arteriosus:  i, 
carotid,  2,  aorta,  and  3,  pulmo-cutaneous  arteries; 
C,  carotid  gland. 


Heart  of  frog  from  behind,  j.z/.,  sinus  venosus  opened  ; 
ci,  inferior ;  csd,  ess,  right  and  left  superior  venae 
cavse  ;  7'^.,  pulmonary  vein  ;  Ad,  3ind  >Jj,  right  and 
left  auricles  ;  /}/,  communication  between  the  right 
and  left  auricle. 


opens  into  the  singte  ventricle  (Fig.  53,  zi),  and  in  the  latter  are  mixed  the  venous  blood  returned 
by  the  right  auricle  and  the  arterial  blood  from  the  left  auricle.  The  aorta  with  its  bulbus 
arteriosus  conducts  the  blood  from  the  ventricle.  The  various  orifices  are  guarded  by  projec- 
tioiis  of  tissue,  which  act  like  valves.  The  two  auricles  are  completely  separated  by  a  septum. 
This  septum  ends  posteriorly  in  a  free  concave  margin  so  as  to  divide  the  auriculo-ventricular 
orifice  into  a  right  and  a  left  orifice.  Each  orifice  is  guarded  by  two  thick,  fleshy  valves,  which 
close  it.] 


MOTOR  CENTRES  OF  THE  HEART. 


119 


[Nerves. — The  two  cardiac  branches  of  the  vagi — the  nervi  cardiaci — proceed  to  the  posterior 
surface  of  the  sinus  venosus,  and  where  the  latter  joins  the  auricle  they  interlace,  and  are  mixed 
with  a  number  of  ganglion  cells  (Fig.  57).  This  spot  is  called  Remak's  ganglion,  is  sometimes 
single,  at  others  double,  and  it  can  be  seen  as  a  white  "  crescent  '■  when  the  heart  is  lifted  up  and 
looked  at  from  behind  (Fig.  54).     The  cardiac  nerves  proceed  downward  on  the  auricular  septum, 


Fig.  55. 


Fig.  56. 


Auricular  septum  of  a  frog's  heart,  a,  anterior,  and/, 
posterior  branch  of  the  cardiac  vagus  ;  B,  Bidder's 
ganglion. 


Pyriform  ganglionic  bi-polar  nerve  cell  from  the 
heart  of  a  frog.  »z,  sheath  ;  «,  straight  process  ; 
o,  spiral  process. 


exchanging  fibres  in  their  course  to  join  two  ganglia  at  the  auriculo-ventricular  groove,  and  known 
as  Bidder's  ganglia  (Fig.  57).  It  has  been  stated  by  one  observer  that  the  bulbus  arteriosus 
contains  ganglionic  cells,  but  this  is  denied  by  others.] 

According  to  Openchowsky,  every  part  of  the  heart  (frog,  triton,  tortoise)  contains  nerve  fibres 
which  are  connected  with  every  muscular  fibre.  In  the  auricles,  at  the  end  of  the  non-medul- 
lated  fibre,  a  tri-radiate  nucleus  exists  which  gives  off  fibrils  to  the  muscular  bundles.     There  is  a 

Fig.  58. 


B.A 


Scheme  of  nerves  of  frog's  heart.  R. 
Remak's,  and  B.  Bidder's  ganglia  ; 
S.V.,  sinus  venosus  ;  A,  auricles  ; 
V,  ventricle;  B.A. ,  bulbus  arterio- 
sus ;  z'ag;  vagi. 


Stannius's  experiment.  A,  auricle;  V, 
ventricle;  S.V.,  sinus  venosus.  The 
zig-zag  lines  indicate  which  parts  con- 
tinue to  beat ;  in  2  the  ventricle  beats  at 
a  different  rate. 


network  of  fine  nerve  fibres  distributed  immediately  under  the  endocardium — these  fibres  act  partly 
in  a  centripetal  direction  on  the  cardiac  ganglia,  and  are  partly  motor  for  the  endocardial  muscles. 
The  parietal  layer  of  the  pericardium  contains  (sensory)  nerve  fibres.  The  following  kinds  of 
nerve  cells  are  found — unipolar  cells,  the  single  processes  of  which  afterward  divide ;  bipolar  pyri- 
form cells   (Fig.   56),  which  in  the  frog  possess  a  straight  («)  and  usually  also  a  spiral  process  {0). 

58.  THE  AUTOMATIC  MOTOR  CENTRES  OF  THE  HEART.— 

(i)  It  is  generally  assumed  that  the  nervous  centres  which  excite  the  cardiac 
movements,  and  maintain  the  rhythm  of  these  movements,  lie  within  the  heart, 
and  that  they  are  probably  represented  by  the  ganglia. 

(2)  There  are — not  one,  but  several  of  these  centres  in  the  heart,  which  are 
connected  with  each  other  by  conducting  paths.      As  long  as  the  heart  is  intact, 


120  MOTOR  CENTRES  OF  THE  HEART. 

all  its  parts  move  in  rhythmical  sequence  from  a  principal  central  point,  an  impulse 
being  conducted  from  this  centre  through  the  conducting  paths.  What  the  "dis- 
charging forces"  of  these  regular  progressive  movements  are,  is  unknown.  If, 
however,  the  heart  be  subjected  to  the  action  of  diffuse  stimuli  {e.g.,  strong  elec- 
trical currents),  all  the  centres  are  thrown  into  action,  and  a  spasm-like  action  of 
the  heart  occurs.  The  dotninating  centre  lies  in  the  an  fides,  hence  the  regular  pro- 
gressive movement  usually  starts  from  them.  If  the  excitability  is  diminished,  as 
by  touching  the  septum  with  opium,  other  centres  seem  to  undertake  this  function, 
in  which  case  the  movement  may  extent  from  the  ventricles  to  the  auricles.  Ac- 
cording to  Kronecker  and  Schmey,  in  the  do^ s  heart  there  is  a  spot  above  the 
lower  limit  of  the  upper  third  of  the  ventricular  septum,  which,  when  it  is  injured, 
e.g.,  by  destroying  it  with  a  stout  needle,  brings  the  heart  to  a  standstill  ;  this  has 
been  called  a  coordinating  centre. 

(3)  All  stimuli  of  moderate  strength  applied  directly  to  the  heart  cause  at  first 
an  increase  of  the  rhythmical  heart  beats  ;  stronger  stimuli  cause  a  diminution,  and 
it  may  be  paralysis,  which  is  often  preceded  by  a  convulsive  movement.  Increased 
activity  exhausts  the  energy  of  the  heart  sooner. 

(4)  Single  very  weak  stimuli,  which  have  no  effect  on  the  heart  when  applied 
singly,  if  repeated  sufficiently  often,  may  become  active,  owing  to  "  summation  of 
the  stimuli  "  {v.  Basch). 

(5)  Even  the  weakest  stimulus  which  can  excite  a  contraction  always  causes  an 
energetic  contraction,  /.  <?.,  "the  minimal  stimulus  causes  a  maximal  effect" 
{^Bowditch,  Ki-ojiecker  and  Stirling). 

(6)  After  every  contraction  of  the  heart  there  is  a  short  period  of  "diminished 
excitability"  or  Marey's  "refractory  period,"  during  which  the  heart  is  less  sus- 
ceptible to  further  stimulation. 

(7)  The  non-ganglionic  apex  of  the  heart,  when  it  is  not  stimulated,  no  longer 
beats  spontaneously,  but  it  responds  each  time  by  a  single  contraction  to  a  single 
direct  stimulus.  If,  however,  a  continuous  stimulus,  e.g.,  a  continuous  current  of 
electricity,  be  applied  to  it,  it  executes  a  series  of  beats.  Such  continuous  stimuli 
are  obtained  through  a  continuous  pressure  of  fluid,  exerted  on  the  interior  of  the 
heart  or  by  moistening  the  heart  with  chemical  substances. 

(8)  The  auricular  centres  seem  to  be  more  excitable  than  those  of  the  ventricle  ; 
hence,  in  a  heart  left  to  itself  the  auricles  pulsate  longest. 

(9)  The  heart  may  be  excited  (reflexly)  from  its  inner  surface.  Weak  stimuli 
applied  to  the  inner  surface  of  the  lieart  greatly  accelerate  the  heart's  action,  the 
stimulus  required  being  much  feebler  than  that  applied  to  the  external  surface 
of  the  heart.  Strong  stimuli,  which  bring  the  heart  to  rest,  also  act  more  easily 
when  applied  to  the  inner  surface  than  when  they  are  applied  to  its  outer  surface. 
The  ventricle  is  always  the  first  part  to  be  paralyzed. 

(10)  In  order  that  the  heart  may  continue  to  contract,  it  is  necessary  that 
it  be  supplied  with  a  fluid  which,  in  addition  to  O,  must  contain  the  neces- 
sary nutritive  7naterials.  The  most  perfect  fluid,  of  course,  is  blood.  Hence 
the  heart  after  a  time  ceases  to  beat  in  an  indifferent  fluid  (0.6  per  cent,  sodium 
chloride),  but  its  activity  may  be  revived  by  supplying  it  with  a  proper  nutri- 
tive fluid. 

Cardiac  Nutritive  Fluids. — These  nutritive  fluids  are  such  as  contain  serum-albumin,  e.g., 
blood,  serum,  or  lymph.  Serum  retains  its  nutritive  properties  even  after  it  has  been  subjected  to 
diffusion  {Martins  and  Kronecker).  Milk  and  whey  (z/.  C//),  normal  saline  solution  mixed  with 
blood,  albumin,  or  peptone,  and  0.3  per  cent,  solution  carbonate  [Kronecker,  Mertinowicz  and  Stie- 
non),  a  trace  of  caustic  soda  [Gaule),  or  a  solution  of  the  salts  of  serum,  are  suitable.  Alkaline 
solution  of  soda  revives  a  feebly  beating  heart  by  neutralizing  the  acid  formed  in  the  cardiac  muscle, 
or  normal  saline  containing  calcic  phosphate  and  potassic  chloride  {S.  dinger). 

(11)  The  independent  pulsations  of  parts  of  the  heart  which  are  devoid  of  gan- 
glia, show  that  the  presence  of  ganglia  is  not  absolutely  necessary  in  order  to  have 


EXPERIMENTS  ON  THE  HEART.  121 

rhythmical  pulsation.  Direct  stimulation  of  the  heart  may  cause  these  movements. 
But  the  ganglia  are  more  excitable  than  the  heart  muscle  itself,  and  they  conduct 
the  impulses  which  lead  to  the  regular  alternating  action  of  the  various  parts  of  the 
heart,  so  that,  under  normal  circumstances,  we  must  assume  that  the  action  of  the 
heart  is  governed  by  the  ganglia. 

(12)  If  a  heart  be  cut  into  pieces,  so  that  the  individual  pieces  still  remain  con- 
nected with  each  other,  the  regular  peristaltic  or  wave-like  movements  proceeding 
from  the  auricles  to  the  ventricle  may  continue  for  a  long  time  {Danders,  Engel- 
manti).  If  the  heart,  however,  be  completely  divided  into  two  distinct  pieces 
(auricle  and  ventricle),  the  movements  of  both  parts  continue,  but  not  in  the  same 
sequence — they  beat  at  different  rates. 

The  chief  experiments  upon  which  the  above  statements  are  based  are  as  fol- 
lows : — 

I.  Experiments  by  cutting  and  ligaturing  the  heart.  These  experiments  have 
been  made  chiefly  upon  the  heart  of  the  frog.  The  ligature  experiments  are 
performed  by  tightening  and  then  relaxing  a  ligature  placed  around  the  heart,  so 
that  the  physiological  connection  is  destroyed,  while  the  anatomical  or  mechanical 
connections  (continuity  of  the  cardiac  wall,  intact  condition  of  its  cavities)  still 
exist.     The  most  important  of  these  experiments  are — 

(i)  Stannius's  Experiment. — If  the  sinus  venosus  of  a  frog's  heart  be  sepa- 
rated from  the  auricles,  either  by  an  incision  or  by  a  ligature,  the  auricles  and  ven- 
tricle stand  still  in  diastole,  while  the  veins  and  the  remainder  of  the  sinus  continue 
to  beat  (Fig.  58,  i).  If  a  second  incision  be  made  at  the  auriculo-ventricular 
groove,  as  a  rule  the  ventricle  begins  at  once  to  beat  again,  while  the  auricles 
remain  in  the  condition  of  diastolic  rest.  [Thus  the  sinus  venosus  and  ventricle 
continue  to  beat,  while  the  auricle  stands  still,  but  the  two  former  no  longer  beat 
with  the  same  rhythm,  the  ventricle  usually  beats  more  slowly,  as  is  shown  in 
Fig.  58,  2,  by  the  large  zig-zags.]  According  to  the  position  of  the  second  liga- 
ture or  incision,  the  auricles  may  also  beat  along  with  the  ventricles,  or  the  auri- 
cles alone  may  beat,  while  the  ventricles  remain  at  rest. 

Theoretical. — Various  explanations  of  these  experiments  have  been  given  :  (a)  Remak's 
ganglion  in  the  sinus  venosus  is  distinguished  by  its  great  excitability,  while  Bidder's  ganglion 
in  the  auriculo-ventricular  groove  is  less  excitable ;  in  the  normal  condition  of  the  heart  the  motor 
impulse  is  carried  from  the  former  to  the  latter.  If  the  sinus  venosus  be  separated  from 
the  heart,  Remak's  ganglion  has  no  action  on  the  heart.  The  heart  stops  for  two  reasons — 
first,  because  Bidder's  ganglion  alone  has  not  sufficient  energy  to  excite  it  to  action,  and  because 
the  inhibitory  fibres  of  the  vagus  going  to  the  heart  have  been  stimulated  by  being  divided  at 
this  point  [Heidenhain) .  [That  stimulation  of  the  inhibitory  fibres  of  the  vagus  is  not  the 
cause  of  the  standstill,  is  proved  by  the  fact  that  the  standstill  occurs  even  after  the  adminis- 
tration of  atropine,  which  paralyzes  the  cardiac  inhibitory  mechanism.]  The  passive  heart, 
however,  may  be  made  to  contract  by  mechanically  stimulating  Bidder's  ganglion,  e.g.,  by  a 
slight  prick  with  a  needle  in  the  auriculo-ventricular  groove,  or  by  the  action  of  a  constant 
current  of  moderate  strength  [Eckhaj-d),  the  ventricular  pulsation  at  the  same  time  preceding 
the  auricular  iv.  Bezold,  Bernstein).  If  the  auriculo-ventricular  groove  be  divided,  the  ventricle 
pulsates  again,  because  Bidder's  ganglion  has  been  stimulated  by  the  act  of  dividing  it;  while, 
at  the  same  time,  the  ventricle  is  withdrawn  from  the  inhibitory  influence  of  the  vagus  produced 
by  the  first  division  at  the  sinus  venosus.  If  the  line  of  separation  is  so  made  that  Bidder's 
ganglion  remains  attached  to  the  auricles,  these  pulsate,  and  the  ventricle  rests ;  if  it  be  divided 
into  halves,  the  auricles  and  ventricles  pulsate,  each  half  being  excited  by  the  portion  of  the 
ganglion  in  relation  with  it.  [b)  According  to  another  view,  both  Remak's  [a)  and  Bidder's 
ganglia  [b)  are  motor  centres,  but  in  the  auricles  there  is  in  addition  an  inhibitory  ganglionic 
system  [c)  [Bezold,  Traube).  Under  normal  circumstances  a -{-  b  \s  stronger  than  c,  while  c  is 
stronger  than  a  ox  b  separately.  If  the  sinus  venosus  be  separated,  it  beats  in  virtue  of  a  ;  on  the 
other  hand,  the  heart  rests  because  c  is  stronger  than  b.  If  the  section  be  made  at  the  level 
of  the  auriculo-ventricular  groove,  the  auricles  stand  still,  owing  to  c,  while  the  ventricle  beats, 
owing  to  b. 

(2)  If  the  ventricle  of  a  frog's  heart  be  separated  from  the  rest  of  the  heart 
by  means  of  a  ligature,  or  by  an  incision  carried  through  it  at  the  level  of  the 


122  EXPERIMENTS    ON    THE    HEART. 

auriculo-ventricular  groove,  the  sinus  and  atria  pulsate  undisturbed  as  before 
{Descartes,  1644),  but  the  ventricle  stands  still  in  diastole.  A  single  local 
stimulus  applied  to  the  ventricle  is  responded  to  by  a  sing/e  contraction.  If  the 
incision  be  so  made  that  the  lower  margin  of  the  auricular  septum  remains 
attached  to  the  ventricle,  the  latter  pulsates.  Even  the  ventricles  of  a  rabbit's 
heart,  when  separated  with  a  part  of  the  auricles  in  connection  with  them,  pulsate 
{Ttgersteiit). 

[Gaskell's  Clamp. — Gaskell  uses  a  clamp,  regulated  by  a  millimetre  screw,  to  compress  the 
heart,  and  thus  to  obstruct  the  passage  of  impulses  from  one  part  of  the  heart  to  the  other,  or 
to  "block"  the  way,  the  pulsations  of  the  auricles  and  ventricles  being  separately  registered. 
By  compressing  the  heart  at  the  auriculo-ventricular  groove,  the  ratio  of  auricular  and  ventricular 
beats    alters,  and    instead    of  being  i  :  1,  there    may  be  2,  3,  or   more  auricular  beats  for  each 

beat  of  the  ventricle,  expressed  thus:        >       »  --— »  —    •     After  the  heart  is  fixed  by  the  clamp, 

levers  are  placed  horizontally  above  and  below  the  heart.  These  levers  are  fixed  to  part  of  the 
auricles  and  to  the  apex  by  means  of  threads.  Each  part  of  the  heart  attached  to  a  lever,  as  it 
contracts,  pulls  upon  its  own  lever,  so  that  the  extent  and  duration  of  each  contraction  may  be 
registered.  This  method  is  applicable  for  studying  the  efifect  of  the  vagus  and  other  nerves  upon 
the  heart.] 

(3)  Section. — \.  Pick  showed  that  the  process  of  excitement  in  the  con- 
tractile tissue  of  the  frog's  heart  is  propagated  in  all  directions  (1874),  so  that  to 
a  certain  extent  the  whole  frog's  heart  behaves  like  one  continuous  muscular  fibre  ; 
thus  one  transverse  cut  into  the  ventricle  does  not  prevent  contraction  from 
taking  place  in  the  separated  parts.  Engelmann's  experiments  also  show  that  if 
the  ventricle  of  a  frog's  heart  be  cut  up  into  two  or  more  strips  in  a  zig-zag 
way,  so  that  the  individual  parts  still  remain  connected  with  each  other  by 
muscular  tissue,  the  strips  still  beat  in  a  regularly  progressive  rhythmical  manner, 
provided  one  strip  is  caused  to  contract.  The  rapidity  of  the  transmission  is 
about  10  to  15  mm.  per  sec.  Hence,  it  appears  that  the  conducting  paths  for 
the  impulse  causing  the  contraction  are  not  nervous,  but  must  be  the  contractile 
mass  itself.  It  has  not  been  proved  that  nerve  fibres  proceed  from  the  ganglia  to 
all  the  muscles. 

[.\ccording  to  Marchand's  experiments,  it  takes  a  very  long  time  for  the  excitement  to  pass  from 
the  auricles  to  the  ventricle — a  much  longer  time,  in  fact,  than  it  would  require  to  conduct  the  ex- 
citement through  muscle — so  that  it  is  probable  that  the  propagation  of  the  impulse  from  the 
auricles  to  the  ventricle  is  conducted  by  nervous  channels  to  the  auriculo-ventricular  nervous  appara- 
tus. In  fact,  in  the  mammalian  heart  the  muscular  fibres  of  the  auricles  are  quite  distinct  from  those 
of  the  ventricles.] 

(4)  When  the  apex  of  a  frog's  heart  is  ligatured  off  from  the  rest  of  the  heart, 
it  no  longer  pulsates  {Heidenhain,  Goltz),  but  such  an  apex,  if  stimulated  directly, 
e.  g.,  by  a  prick  of  a  pin,  responds  with  a  single  contraction.  If  the  "heart  apex" 
be  filled  with  normal  saline  solution  under  pressure,  which  acts  as  a  stimulus,  the 
heart  begins  to  pulsate,  and  the  same  is  the  case  with  a  solution  of  delphinin  or 
quinine.  If  a  cannula  be  tied  into  the  heart  over  the  auriculo-ventricular  groove, 
the  ventricle  does  not  beat,  but  if  the  ventricle  be  filled  through  the  cannula  with 
blood  containing  oxygen,  under  a  constant  and  sufficient  pressure,  it  also  pulsates 
{Ludwig  and  Alerurioiuicz). 

(5)  Luciani  found  that  a  heart  ligatured  above  the  auriculo-ventricular  groove, 
when  filled  with  pure  serum,  produced  groups  of  pulsations  with  a  long  diastolic 
pause  between  every  two  groups  (Fig.  59).  The  successive  beats  in  each  group 
assume  a  "staircase  "  character  (p.  126).  These  periodic  groups  undergo  many 
changes ;  they  occur  when  the  heart  is  filled  with  pure  serum  free  from  blood 
corpuscles,  and  they  disappear  and  give  place  to  regular  pulsations  when  defibrin- 
ated  blood  or  serum  containing  hemoglobin  or  normal  saline  solution  is  used 
{Rossbach).  They  also  occur  when  the  blood  within  the  heart  has  become  dark- 
colored,  /,  e.,  when  it  has  been  deprived  of  certain  of  its  constituents,  and  if  a 
trace  of  veratrin  be  added  to  bright  red  blood  they  occur.] 


ACTION    OF    FLUIDS    ON    THE    HEART. 


123 


(6)  An  apex  preparation,  when  stimulated  with  even  a  weak  induction  shock, 
always  gives  its  maximal  contraction,  and  when  a  tetanizing  current  is  applied, 
tetanus  does  not  occur  {Kronecker  and  Stirling).  When  the  opening  and  closing 
shocks  of  a  sufficiently  strong  constant  current  are  applied  to  the  heart  apex,  it 
contracts  with  each  closing  or  opening  shock.  [When  a  constant  current  is  applied 
to  the  lower  two-thirds  of  the  ventricle  (heart  apex),  under  certain  conditions  the 
apex  contracts  rhytJunically.  This  is  an  important  fact  in  connection  with  any 
theory  of  the  cardiac  beat.] 

Fig.  59. 


Four  groups  of  pulsations  with  intervening  pauses,  with  their  "  staircase"  character. 

were  marked  every  10  seconds. 


The  points  on  the  abscissa 


Fig.  60. 


(7)  If  the  bulbus  aortae  (frog)  be  ligatured,  it  still  pulsates,  provided  the  inter- 
nal pressure  be  moderate.  Should  it  cease  to  beat,  a  single  stimulus  makes  it 
respond  by  a  series  of  contractions.  Increase  of  temperature  to  35°  C,  and  rais- 
ing the  pressure  within  it,  increase  the  number  of  pulsations  {Engelmanti). 

Action  of  Fluids. — Haller  was  of  opinion  that  the  venous  blood  was  the 
natural  stimulus  which  caused  the  heart  to  contract.  That  this  is  not  so,  is  proved 
at  once  by  the  fact  that  the  heart  beats  rhythmically  when  it  contains  no  blood. 
Blood  and  other  fluids  which  are  supplied  to  an  excised  heart  are  not  the  cause  of 
its  rhythmical  movements,  but  only  the  conditions  on  which  these  movements 
depend. 

[Methods. — The  study  of  the  action  of  fluids  upon  the  excised  frog's  heart  has  been  rendered 
possible  by  the  invention  of  Ludwig's  "  frog  manometer."  The  apparatus  (Fig.  60)  consists  of 
(i)  a  double. way  cannula,  c,  which  is  tied  into  the  heart,  h  ; 
(2)  a  manometer,  ?ii,  connected  with  c,  and  registering  the 
movements  of  its  mercury  on  a  revolving  cylinder,  cyl ;  (3) 
two  Mariotte's  flasks,  a  and  b,  which  are  connected  with  the 
other  limb  of  the  cannula.  Either  a  or  b  can  be  placed 
in  communication  with  the  interior  of  the  heart  by  means  of 
the  stop-cock,  s.  The  fluid  in  one  graduated  tube  may  be 
poisoned,  and  the  other  not;  ^is  a  glass  vessel  for  fluid,  in 
which  the  heart  pulsates,  e^  and  e  are  electrodes,  e  is  inserted 
into  the  fluid  in  d,  e'  is  attached  to  the  German  silver  cannula 
which  is  shown  in  Fig.  6r.] 

[In  the  tonometer  of  Roy  (Fig.  62)  the  ventricle,  h,  or 
the  whole  heart,  is  placed  in  an  air-tight  chamber,  o,  filled 
with  oil.  Asbefore,  a  "  perfusion  "  cannula  is  tied  into  the 
heart.  A  piston,^,  works  up  and  down  in  a  cylinder,  and 
is  adjusted  by  means  of  a  thin  flexible  animal  membrane, 
such  as  is  used  by  perfumers.  Attached  to  the  piston  by 
means  of  a  thread  is  a  writing  lever,  /,  which  records  the 
variations  of  pressure  within  the  chamber,  0.  When  the 
ventricle  contracts,  it  becomes  smaller,  diminishes  the  pres- 
sure within  0,  and  hence  the  piston  and  lever  rise ;  con- 
versely, when  the  heart  dilates,  the  lever  and  piston  descend. 
Variations  in  the  volume  of  the  ventricle  may  be  registered, 
without  in  any  way  interfering  with  the  flow  of  fluids  through  Scheme  of  a  trog  manometer,  a,  b,  Mari- 
it.l  ott-'s  flasks  for  the  nutrient  tiuids ;  s, 

[Two  preparations  of  the  frog's  heart  have  been  used—  stop-cock;  c,  cannula;  .«  manometer; 

I    <r  •T.T  ,  ,,  •         1-1  1  ...  ,  ,  «,  heart;  d,  glass  cup  tor  A;  e  ,e,  elec- 

\\)    ihe  "heart,     in  which  case  the  cannula  is  introduced  trodes ;  cj//,  revolving  cylinder. 

into  the  heart  through  the  sinus  venosus,  and  a  ligature  is 

tied  over   it    a7-ound  the  auricle,  i.  e.,  above  the  auriculo- ventricular  groove.     Thus  the  auriculo- 
ventricular  ganglia  and  other  nervous  structures  remain  in  the  preparation.     This  was  the  heart 


^e(r&^^' 


124 


ACTION    OF    DRUGS    ON    THE    HEART, 


preparation  employed  by  Luciani  and  Rossbach.  (2)  In  the  '•  heart  apex,"  or  apex  preparation, 
the  cannula  is  introduced  as  before,  but  the  ligature  is  tied  on  it  over  the  ventricle,  several  milli- 
metres bt-low  the  auriculo-ventricular  groove,  so  that  this  preparation  contains  none  of  the  auriculo- 
ventricular  ganglia,  and,  according  to  the  usual  statement,  this  pari  of  the  heart  is  devoid  of  nerve 
ganglia.  This  is  the  preparation  which  was  used  by  Howditch,  Kronecker  and  Stirling,  Meruno- 
wicz,  and  others.  The  first  effect  of  the  application  of  the  ligature  in  both  cases  is,  that  both  prepa- 
rations cease  to  beat,  but  the  "  heart  "  usually  resumes  its  rhythmical  contractions  wiihin  several 
minutes,  while  the  "  heart  apex  "  does  not  contract  sjiontaneously  until  after  a  much  longer  time 
(10  to  90  mins.).] 

[If  the  "  heart  apex  "  be  filled  with  a  0.6  per  cent,  solution  of  common  salt,  the  contractions  are 
irst  of  greater  extent,  but  they  afterward  cease,  and  the  preparation  passes  into  a  condition  of 
"  apparent  death,"  lasting  30-90  mins.;  while,  if  the  action  of  the  fluid  be  prolonged,  the  heart 
may  not  contract  at  all,  even  when  it  is  stimulated  electrically  or  mechanically.  It  may  be  made, 
however,  to  pulsate  again,  if  it  be  supplied  with  saline  solution  containing  blood  (i  to  10  percent.). 
If  the  ventricle  be  nipped  with  wire  forceps  at  the  junction  of  the  upper  with  its  midiile  third,  so  as 
to  separate  the  lower  two-thirds  of  the  ventricle,  physiologically  but  not  anatomically,  from  the  rest 
of  the  heart,  then  the  apex  will  cease  to  contract,  although  it  is  still  supplied  with  the  frog's  own 
blood  (Bernstein,  BoxvdiUh).  The  ]>hysiologically  isolated  apex  may  be  made  to  beat  by  clamping 
the  aortic  branches  so  as  to  prevent  blood  passing  out  of  the  heart,  and  thus  raising  the  intra-cardiac 


Fig.  61. 


Fig.  62. 


K 


\i 


^ 


d 


^ 


Periusiun  c.inmila  for  a  frog's  heart. 
C,  for  fixing  an  electrode;  rf, 
the  heart  is  tied  over  the  flanges, 
preventing  it  from  slipping  out ; 
f,  section  of  d. 


Roy's  heart  tonometer,   /t,  heart  ;   o,  air-tight  chamber  ;  />,  piston  ;  /, 
writing  lever  ;  e,  outflow  tube. 


pressure.  The  rate  of  the  beat  of  the  apex  is  independent  of  and  slower  than  that  of  the  rest  of 
the  heart.  This  experiment  proves  that  the  amount  of  pressure  within  the  apex  cavity  is  an  im- 
portant factor  in  the  causation  of  the  spontaneous  beats  of  the  apex.  If  blood  serum,  to  which  a 
trace  of  delphinin  is  added,  be  transfused  or  "/>er/iised"  through  the  heart,  it  begins  to  beat 
within  a  minute,  continues  to  beat  for  several  seconds,  and  then  stands  still  in  diastole  [Bo^vditch). 
Quinine  and  a  mixture  of  atropine  and  muscarin  have  a  similar  action.  These  experiments  show 
\.hzi,  prozided  no  nervom  apparatus  exists  7uithin  the  heart  apex,  the  cause  of  the  varying  contrac- 
tion is  to  be  sought  for  in  the  musculature  of  the  heart,  and  that  the  stimulus  necessary  for  the 
systole  of  the  heart's  apex  may  arise  within  itself.  If  there  is  no  nervous  apparatus  of  any  kind 
present,  then  we  must  assume  that  the  heart  muscle  may  execute  rhythmical  movements  independently 
of  the  presence  of  any  nervous  mechanism,  although  it  is  usually  assumed  that  the  ganglia  excite 
the  heart  muscle  to  pulsate  rhythmically.  It  is  by  no  means  de/uiite/y  proved  Xhai  the  heart  apex  is 
devoid  of  all  nervous  structures,  which  may  act  as  originators  of  these  rhythmical  impulses.] 

[Action  of  Drugs. — If  the  heart  apex  contains  no  nervous  structures,  it  must  form  a  good  object 
for  the  study  of  the  action  of  drugs  on  the  cardiac  muscle.  Some  of  these  have  been  mentioned 
already.  Ringer  finds  that  a  calcium  salt  makes  the  contractions  higher  and  longer.  Dilute  adds 
added  to  saline  solution,  e.g.,  lactic,  cause  complete  relaxation  of  the  cardiac  musculature,  while 
dilute  alkalies  produce  an  opposite  effect  or  tonic  contraction,  even  though  the  apex  be  not  pulsating. 
The  action  of  a  dilute  acid  may  be  set  aside  by  a  dilute  alkali,  and  vice  versa.     Digitalin,  antiarin, 


ACTION    OF    MECHANICAL   AND    ELECTRICAL    STIMULI. 


125 


barium,  and  veratria  act  like  alkalies,  while  saponin,  muscarin,  and  pilocarpin  have  the  effect  of 
acids  (^  65).  An  isolated  frog's  heart,  fatigued  after  being  supplied  with  a  solution  of  blood,  is 
caused  to  beat  more  vigorously  by  a  solution  of  kreatinin,  or  extract  of  meat  (Mays).'] 

[The  "  heart "  preparation  in  many  respects  behaves  like  the  foregoing,  i.e.,  it  is  exhausted  after 
a  time  by  the  continued  application  of  normal  saline  solution  (0.6  per  cent.  NaCl),  while  its  activity 
may  be  restored  by  supplying  it  with  albuminous  and  other  fluids  (p.  120).] 

II.  Direct  Stimulation  of  the  Heart. — All  direct  cardiac  stimuli  act  more 
energetically  on  the  inner  than  on  the  outer  surface  of  the  heart.  If  strong 
stimuli  are  applied  for  too  long  a  time,  the  ventricle  is  the  part  first  paralyzed. 

(a)  Thermal  Stimuli. — [Heat  affects  the  number  or  fre- 
quency and  the  amplitude  of  the  pulsations,  as  well  as  the 
duration  of  the  systole  and  diastole  and  the  excitability  of  the 
heart.]  Descartes  (1644)  observed  that  heat  increases  the 
number  of  pulsations  of  an  eel's  heart.  As  the  temperature 
increases,  the  number  of  beats  is  at  first  considerably  increased, 
but  afterward  the  beats  again  become  fewer,  and  if  the  tempera- 
ture is  raised  above  a  certain  limit  the  heart  stands  still,  the 
myosin  of  which  its  fibres  consist  is  coagulated,  and  "  heat 
rigor"  occurs.  Even  before  this  stage  is  reached,  however, 
the  heart  may  stand  still,  the  muscular  fibres  appearing  to  re- 
main contracted.  The  ventricles  usually  cease  to  beat  before 
the  auricles  [Sckelske).  The  size  and  extent  oi  the  contractions 
increase  up  to  about  20°  C,  but  above  this  point  they  diminish 
(Fig.  63).  The  time  occupied  by  any  single  contraction  at  20° 
C.  is  only  about  -^^  of  the  time  occupied  by  a  contraction  occur- 


A,  contractions  of  a  frog's  heart  at  19°  C. ;    B,  at  34°  C.  ;    C,  at  3°  C. 

ring  at  5°  C.  A  heart  which  has  been  warmed  is  capable  of  reacting  pretty  rapidly  to  intermittent 
stimuli,  while  a  heart  at  a  low  temperature  reacts  only  to  stimuli  occurring  at  a  considerable 
interval  [Gaule). 

Cold. — When  the  temperature  of  the  blood  is  diminished,  the  heart  beats  more  slowly.  A  frog's 
heart,  placed  between  two  watch  glasses  and  laid  on  ice,  beats  very  much  more  slowly.  The  pul- 
sations of  a  frog's  heart  stop  when  the  heart  is  exposed  to  a  temperature  of  4°  C.  to  0°.  If  a  frog's 
heart  be  taken  out  of  warm  water,  and  suddenly  placed  upon  ice,  it  beats  more  rapidly,  and  con- 
versely, if  it  be  taken  from  ice  and  placed  over  warm  water,  it  beats  more  slowly  at  first  and  more 
rapidly  afterward  [Aristow). 

[Methods. — The  effect  of  heat  on  a  heart  may  be  studied  by  the  aid  of  the  frog  manometer, 
the  fluid  in  which  the  heart  is  placed  being  raised  to  any  temperature  required.  For  demonstration 
purposes,  the  heart  of  a  pithed  frog  is  excised  and  placed  on  a  glass  slide  under  a  light  lever,  such 
as  a  straw.  The  slide  is  warmed  by  means  of  a  spirit  lamp.  In  this  way  the  frequency  and  ampli- 
tude of  the  contractions  are  readily  made  visible  at  a  distance.] 

{b)  Mechanical  Stimuli. — Pressure  applied  to  the  heart  from  without  accelerates  its  action.  In 
the  case  of  Frau  Serafin,  v.  Ziemssen  found  that  slight  pressure  on  the  auriculo-ventricular  groove 
caused  a  second  short  contraction  of  both  ventricles  after  the  heart  beat.  Strong  pressure  causes  a 
very  irregular  action  of  the  cardiac  muscle.  This  may  readily  be  produced  by  compressing  the 
freshly- excised  heart  of  a  dog  between  the  fingers.  The  intra-cardiac  pressure  also  affects  the 
heart  beat  (p.  124).  If  the  pressure  within  the  heart  be  increased,  the  heart  beats  are  gradually 
increased,  if  it  be  diminished  the  number  of  beats  diminishes  (Ludzvig  and  Tkiry').  If  the  intra- 
cardiac pressure  be  very  greatly  increased,  the  heart's  action  becomes  very  irregular  and  slower.  A 
heart  which  has  ceased  to  Ijeat  may,  under  certain  circumstances,  be  caused  to  execute  a  sitigle 
contraction  if  it  be  stimulated  mechanically. 

{c)  Electrical  Stimuli. — A  constant  electrical  current  of  moderate  strength  increases  the 
number  of  heart  beats.     V.  Ziemssen  found,  in  the  case  of  Frau  Serafin  (§  47,  3),  that  the  number 


126  ACTION    OF    CHEMICAL   STIMULI. 

of  beats  was  doubled  when  a  constant  uninterrupted  strong  current  was  passed  through  the  ventri- 
cles. If  the  constant  current  be  very  strong,  or  if  tetanizing  induction  currents  be  used,  the  cardiac 
muscle  assumes  a  condition  resembling,  but  not  iilentical  with,  tetanus  {Ludwi;^  and  Hoffa), 
and,  of  course,  this  results  in  a  fall  of  the  blood  pressure.  If  the  auriculo-ventricular  groove  be 
compressed  so  as  to  cause  the  ventricle  of  a  frog's  heart  to  cease  to  beat,  on  placing  one  electrode 
of  a  constant  current  on  the  ventricular  wall  and  the  other  electrode  on  an  indifferent  part  of  the 
body,  we  obtain,  on  making  the  current,  a  systolic  contraction  of  the  ventricle  only  when  the 
cathode  touches  the  ventricle ;  and  conversely  on  breaking,  only  when  the  anode  is  on  the  heart 
[Biedermatin). 

When  a  single  induction  shock  is  applied  to  the  ventricle  of  a  frog's  heart  during  systole,  it 
has  no  apparent  etTect ;  but  if  it  is  applied  during  diastole,  the  succeeding  contraction  takes  place 
sooner.  The  auricles  and  also  the  apex  behave  in  a  similar  manner.  While  they  are  contracted, 
an  induction  shock  has  no  effect ;  if,  however,  the  stimulus  is  applied  during  diastole,  it  causes  a 
contraction,  which  is  followed  by  systole  of  the  ventricle.  Even  when  strong  tetanizing  induction 
shocks  are  applied  to  the  heart,  they  do  not  produce  ietantix  of  the  entire  cardiac  musculature,  or 
as  it  is  said,  "the  heart  knows  no  tetanus  "  {A'ronecl-er  and  Slirlin>^).  Small,  white,  local,  wheal-like 
elevations — such  as  occur  when  the  intestinal  musculature  is  stimulated — appear  between  the  elec- 
trodes. They  may  last  several  minutes.  A  frog's  heart,  which  yields  weak  and  irregular  contrac- 
tions, may  be  made  to  execute  regular  rhythmical  contractions  synchronous  with  the  stimuli,  if 
electrical  stimuli  are  used  i^Bowdilch). 

[Break  induction  shocks,  if  of  sufficient  strength,  cause  the  heart  to  contract,  while  weak  stimuli 
have  no  effect ;  on  the  other  hand,  moderate  stimuli,  when  they  do  cause  the  heart  to  contract, 
always  cause  a  maximal  contraction,  so  that  a  minimal  stimulus  acts  at  the  same  time  like  a  ma^^i- 
mal  stimulus.  The  heart  either  contracts  or  it  does  not  contract,  and  when  it  contracts,  the  result 
is  always  a  "maximal"  contraction  [Kronecker  and  S(i?-iini;).  Bowditch  found  that  the  excita- 
bility of  the  heart  was  increased  by  its  own  movements,  so  that  after  a  heart  had  once  contracted, 
the  strength  of  the  stimulus  required  to  excite  the  next  contraction  may  be  greatly  diminished,  and 
yet  the  stimulus  be  effectual.  Usually  the  amplitude  of  the  first  beat  so  produced  is  not  so  great  as 
the  second  beat,  and  the  second  is  less  than  the  third,  so  that  a  "  staircase"  ("Treppe")  of  beats 
of  successively  greater  extent  was  produced  (Fig.  59).  Under  certain  circumstances,  however, 
a  skeletal  muscle  gives  contractions  of  a  "staircase"  character.  This  staircase  arrangement  occurs 
even  when  the  strength  of  the  stimulus  is  kept  constant,  so  that  the  production  of  one  contraction 
facilitates  the  occurrence  of  the  succeeding  one.  A  staircase  arrangement  of  the  pulsations  is  also 
seen  in  Luciani's  groups  (p.  122).  The  question,  whether  a  stimulus  will  cause  a  contraction, 
depends  upon  what  particular  phase  the  heart  is  in  when  the  shock  is  applied.  Even  comparatively 
weak  stimuli  will  cause  a  heart  to  contract,  provided  the  stimuli  are  applied  at  the  proper  moment 
and  in  the  proper  tempo,  i.e.,  to  say,  they  become  what  are  called  "infallible."  If  stimuli  are 
applied  to  the  heart,  at  intervals  which  are  longer  than  the  time  the  heart  takes  to  execute  its  con- 
traction, they  are  effectual  or  "adequate,"  but  if  they  are  applied  before  the  period  of  pulsation 
comes  to  an  end,  then  they  are  ineffectual  [Kronecker).  It  is  quite  clear,  therefore,  that  the 
relation  of  the  strength  of  the  stimulus  to  the  extent  of  the  contraction  of  the  cardiac  muscle,  is 
quite  different  from  what  occurs  in  a  muscle  of  the  skeleton,  where  within  certain  limits  the  ampli- 
tude of  the  contraction  bears  a  relation  to  the  stimulus,  while  in  the  heart  the  contraction  is  always 
maxt>naL'\ 

Human  Heart. — V.  Ziemssen  found  that  he  could  not  alter  the  heart  beats  of  the  human  heart 
{Fran  Serafin,  \  47,  3),  even  with  strong  induction  currents.  The  ventricular  diastole  seemed  to 
be  less  complete,  and  there  were  irregularities  in  its  contraction.  By  opening  and  closing,  or  by 
reversing  a  strong  constant  current  applied  to  the  heart,  the  number  of  beats  was  increased,  and  the 
increase  corresponded  with  the  number  of  electrical  stimuli;  thus,  when  the  electrical  stimuli  were 
120, 140, 180,  the  number  of  heart  beats  was  the  same,  the  pulse  beforehand  being  80.  The  normal 
pulse  rate  of  80  was  reduced  to  60  and  50  when  the  number  of  shocks  was  reduced  in  the  .same 
ratio.  [In  Frau  Serafin's  case  the  electrodes  were  applied  to  the  heart,  separated  from  it  merely 
by  the  pericardium.  Ziemssen  found  that  the  Faradic  current  did  not  modify  the  heart's  action 
when  the  thorax  was  intact,  but  that  the  constant  current  did,  if  of  sufficient  strength.  Herbst  and 
Dixon  Mann  obtained  negative  results  with  both  kinds  of  electricity  in  the  normal  thorax.] 

[d]  Chemical  Stimuli. — Many  chemical  substances,  when  applied  in  a  dilute  solution  to  the 
inner  surface  of  the  heart,  increase  the  heart  beats,  while  if  they  are  concentrated,  or  allowed  to  act 
too  long,  they  diminish  the  heart  beats,  and  paralyze  it.  Bile  and  bile  salts  diminish  the  heart 
beats  (also  when  they  are  absorbed  into  the  blood,  as  in  jaundice) ;  in  very  dilute  solutions  both 
increase  the  heart  beats.  A  similar  result  is  produced  by  acetic,  tartaric,  citric,  and  phosphoric 
acids.  Chloroform  and  ether,  applied  to  the  inner  surface,  rapidly  diminish  the  heart  beats,  and 
then  paralyze  it;  but  very  small  quantities  of  ether  (i  per  cent.)  accelerate  the  heart  beat  of  the  frog 
{Kronecker  and  M' Gregor- Robertson),  while  a  solution  of  l^  to  2  per  cent,  passed  through  the 
heart  arrests  it  temporarily  or  completely.  Dilute  solutions  of  opium,  strychnia,  or  alcohol  applied 
to  the  endocardium, increase  the  heart  beats;  if  concentrated  they  rapidly'arrest  its  action.  Chloral 
hydrate  paralyzes  the  heart. 


NATURE    OF    A   CARDIAC    CONTRACTION.  127 

Action  of  Gases. — When  blood  containing  different  gases  was  passed  through  a  frog's  heart, 
Klug  found  that  blood  containing  sulphurous  acid  rapidly  and  completely  killed  the  heart ;  chlorine 
stimulated  the  heart  at  first,  and  ultimately  killed  it ;  and  laughing  gas  rapidly  killed  it  also.  Blood 
containing  sulphuretted  hydrogen  paralyzed  the  heart  without  stimulating  it.  Carbonic  oxide  also 
paralyzed  it,  but  if  fresh  blood  was  transfused  the  heart  recovered.  [Blood  containing  O  excites  the 
heart  [Castell),  while  the  presence  of  much  COj  paralyzes  it,  and  the  presence  of  COj  is  more 
injurious  than  the  want  of  O.  Blood  or  serum  completely  saturated  with  CO2  exhausts  the  heart 
{Saltei  and  Kronecker),  but  it  recovers  itself  when  the  CO,  is  removed.     H  and  N  have  no  effect.] 

Cardiac  Poisons  are  those  substances  whose  action  is  characterized  by  special  effects  upon  the 
movements  of  the  heart.  Among  these  are  neutral  potash  salts,  which  cause  the  heart  to  stand 
still  in  diastole.  An  excised  frog's  heart  ceases  to  beat  after  one-half  to  one  minute  when  it  is  placed 
in  a  2  per  cent,  solution  of  potassic  chloride.]  Even  a  very  dilute  solution  of  yellow  prussiate  of 
potash  injected  into  the  heart  of  a  frog  causes  the  ventricle  to  stand  still  in  systole.  Antiar  (Java 
arrow  poison)  causes  the  ventricle  to  stand  still  in  systole  and  the  auricles  in  diastole.  Some  heart 
poisons,  in  small  doses,  diminish  the  heart's  action,  and  in  large  doses  not  unfrequently  accelerate 
it,  e.  g.,  digitalis,  morphia,  nicotin.  Others,  when  given  in  small  doses,  accelerate  its  action,  and  in 
large  doses  slow  it — veratria,  aconitin,  camphor. 

Special  Actions  of  Cardiac  Poisons. — The  complicated  actions  of  various  poisons  upon  the 
heart  have  led  observers  to  suppose  that  there  are  various  intra-cardiac  mechanisms  on  which  these 
substances  may  act.  Besides  the  fiiuscular  fibres  of  the  heart  and  its  automatic  ganglia,  some  toxi- 
cologists  assume  that  there  are  inhibitory  ganglia  into  which  the  inhibitory  fibres  of  the  vagus  pass, 
and  accelerator  ganglia,  which  are  connected  with  the  accelerating  nerve  fibres  of  the  heart.  Both  the 
inhibitory  and  accelerator  ganglia  are  cotmected  with  the  atitoi?iatic  ganglia  by  conducting  channels. 

Muscarin  and  all  other  trimethylammonium  bases  stimulate  permanently  the  inhibitory  ganglia, 
so  that  the  heart  stands  still  {Schmiedeberg  atid  Koppe).  [According  to  Gaskell,  however,  when 
the  action  of  the  sinus  is  arrested  by  muscarin,  there  is  no  deflection  of  the  galvanometer  similar  to 
that  produced  by  the  excitation  of  the  vagus.  He  infers  that  muscarin  does  not  cause  arrest  of  the 
beat  by  acting  as  an  excitant  of  inhibitory  mechanisms,  but  as  a  depressant  to  motor  activity.]  As 
atropin  and  daturin  paralyze  these  ganglia,  the  standstill  of  the  heart  brought  about  by  muscarin 
rnay  be  set  aside  by  atropin.  [If  a  frog's  heart  be  excised  and  placed  in  a  watch  glass,  and  a  few 
drops  of  a  very  dilute  solution  of  muscarin  be  placed  on  it  with  a  pipette,  it  ceases  to  beat  withir^  a 
few  minutes,  and  will  not  beat  again.  If,  however,  the  muscarin  be  removed,  and  a  solution  of 
atropine  applied  to  the  heart,  it  will  resume  its  contractions  after  a  short  time.]  Physostigmin  or 
Calabar  bean  excites  the  energy  of  the  cardiac  muscle  to  such  an  extent,  that  stimulation  of  the 
vagus  no  longer  causes  the  heart  to  stand  still.  lodine-aldehyd,  chloroform,  and  chloral  hydrate 
paralyze  the  automatic  ganglia.  The  heart  stands  still,  and  it  cannot  be  made  to  contract  again  by 
atropine.  The  cardiac  muscle  itself  remains  excitable  after  the  action  of  muscarin  and  iodine- 
aldehyd,  so  that  if  it  be  stimulated  it  contracts.  [According  to  Gaskell,  antiarin  and  digitalin 
solutions  produce  an  alteration  in  the  condition  of  the  muscular  tissue  of  the  apex  of  the  heart  of 
the  same  nature  as  that  produced  by  the  action  of  a  very  dilute  alkali  solution,  while  the  action  of  a 
blood  solution  containing  muscarin  closely  resembles  that  of  a  dilute  acid  solution  (p.  138,  \  65).] 

[Nature  of  a  Cardiac  Contraction. — The  question  as  to  whether  this  is  a 
simple  contraction  or  a  compound  tetanic  contraction  has  been  much  discussed. 
So  much  is  certain,  that  the  systolic  contraction  of  the  heart  is  of  very  much  longer 
duration  (8  to  10  times)  than  the  contraction  of  a  skeletal  muscle  produced  by 
stimulation  of  its  motor  nerve.  When  the  sciatic  nerve  of  a  nerve-muscle  prepa- 
ration is  adjusted  upon  a  contracting  heart,  a  simple  secondary  twitch  of  the  limb, 
and  not  a  tetanic  spasm,  is  produced  when  the  heart  (auricle  or  ventricle)  con- 
tracts. This  of  itself  is  not  sufficient  proof  that  the  systole  is  a  simple  spasm,  for 
tetanus  of  a  muscle  does  not  in  all  cases  give  rise  to  secondary  tetanus  in  the  leg 
of  a  rheoscopic  limb.  Thus,  a  simple  "initial"  contraction  occurs  when  the 
nerve  is  applied  to  a  muscle  tetanized  by  the  action  of  strychnia,  and  the  con- 
tracted diaphragm  gives  a  similar  result.  The  question  whether  the  heart  can  be 
tetanized  has  been  answered  in  the  negative,  and  as  yet  it  has  not  been  shown 
that  the  heart  can  be  tetanized  in  the  same  way  that  a  skeletal  muscle  is  tetanized.] 

[Mac William  finds,  when  the  quadriceps  extensor  cruris  contracts  to  cause  the  knee  jerk,  that  a 
sound  similar  to  the  first  sound  of  the  heart  is  heard.  As  the  former  is  regarded  as  a  simple  con- 
traction, it  is  argued  that  a  simple  contraction  can  produce  a  muscle  sound.  Fredericq  regards  the 
ventricular  systole  not  as  a  simple  contraction,  but  as  composed  of  three  or  more  fused  contractions 
corresponding  to  tetanus.  This  he  concludes  from  a  study  of  cardiograms  as  well  as  from  the 
electro-motive  phenomena  of  the  heart.] 

The  peripheral  or  extra-cardiac  nerves  (§§  369  and  370). 


128 


THE    CARDIO-PNEUMATIC    MOVEMENT. 


59.   CARDIO-PNEUMATIC   MOVEMENT.— As  the  heart  within  the 

thorax  occupies  a  smaller  space  during  the  systole  than  during  the  diastole,  it 
follows  that,  when  the  glottis  is  open,  air  must  be  drawn  into  the  chest  when  the 
heart  contracts;  whenever  the  heart  relaxes, /.<?.,  during  diastole,  air  must  be 
expelled  through  the  open  glottis.  But  we  must  also  take  into  account  the  degree 
to  which  the  larger  intra-thoracic  vessels  are  filled  with  blood.  These  movements 
of  the  air  within  the  lungs,  although  slight,  seem  to  be  of  importance  in  hiber- 
nating animals.  In  animals  in  this  condition,  the  agitation  of  the  gases  in  the 
lungs  favors  the  exchange  of  CO^  and  O  in  the  lungs,  and  this  slow  current  of  air 
is  sufficient  to  aerate  the  blood  passing  through  the  lungs.  [Ceradini  called  the 
diminution  of  the  volume  of  the  entire  heart  which  occurs  during  systole  meio- 
cardia,  and  the  subsequent  increase  of  volume,  when  the  heart  is  distended  to  its 
maximum,  auxocardia.] 

Method. — A  manometric  Jlame  may  be  used.  Insert  one  limb  of  a  Y-tube  into  the  opened 
trachea  of  an  animal,  while  the  other  limb  passes  to  a  small  gas  jet,  and  connect  the  other  tube  with 
the  gas  supply.  The  movements  of  the  heart  affect  the  column  of  gas,  and  thus  affect  the  flame. 
It  may  also  be  done  in  man  by  inserting  the  tube  into  one  nostril,  while  the  other  nostril  and  the 
mouth  are  closed.  [A  simpler  and  less  irritating  plan  is  to  fill  a  wide  curved  glass  tube  with  tobacco 
smoke,  and  insert  one  end  of  the  tube  into  one  nostril  while  the  other  nostril  and  the  mouth  are 
closed.  If  the  glottis  be  kept  open,  and  respiration  be  stopped,  then  the  movements  of  the  column 
of  smoke  within  the  tube  are  obvious.  Or  a  manometer  containing  a  drop  of  a  colored  fluid  may  be 
used  under  the  same  conditions.] 

Fig.  64. 


Landois'  cardio-pneumograph,  and  the  curves  obtained  therewith.        A  and  B,  from  man,  1  and  2  correspond  to 
the  periods  of  the  first  and  second  heart  sounds  ;   C,  from  dag;   D,  method  of  using  the  apparatus. 

The  cardiac  pneumograph  (Fig.  64)  consists  of  a  tube  (D),  about  1  inch  in  diameter  and  6  to 
8  inches  in  length ;  the  tube  is  bent  at  a  right  angle,  and  communicates  with  a  small  metal  capsule 
about  the  size  of  a  saucer  (T),  over  which  a  membrane  composed  of  collodion  and  castor  oil  is 
loosely  stretched.  To  this  membrane  is  attached  a  glass  rod  (H)  used  as  a  writing  style,  which 
records  its  movements  on  a  glass  plate  (S)  moved  by  clock  work.  A  small  valve  (K)  is'p'aced  on 
the  side  of  the  tube  (D),  which  enables  the  experimenter  to  breathe  when  necessary.  The  tube 
(D)  is  held  in  an  air-tight  manner  between  the  lips,  the  nostrils  being  closed,  the  gLttis  open,  and 
respiration  stopped.     In  the  curves  (Fig.  64,  A,  B)  we  observe  that— 

( I )  At  the  moment  of  the  first  sound  ( i)  the  respiratory  gases  undergo  a  sharp  expiratory  move- 
ment, because  at  the  moment  of  the  first  part  of  the  ventricular  systole  the  blood  of  the  ventricle  has 
not  left  the  thorax,  while  venous  blood  is  .streaming  into  the  right  auricle  through  the  venre  cavae, 
and  because  the  dilating  branches  of  the  pulmonary  artery  compress  the  accompanving  bronchi. 
The  blood  of  the  right  ventricle  has  not  yet  left  the  thorax,  it  passes  merely  into  the  pulmonary 
circuit.     The  expiratory  movement  is  diminished  somewhat  (a)  by  the  muscular  mass  of  the  ven- 


INFLUENCE    OF    RESPIRATORY    PRESSURE    ON    THE    HEART.         129 

tricle  occupying  slightly  less  bulk  during  the  contraction,  and  (,3)  owing  to  the  thoracic  cavity  being 
slightly  increased  by  the  fifth  intercostal  space  being  pushed  forward  by  the  cardiac  impulse. 

(2)  Immediately  after  (l)  there  follows  a  strong  inspiratory  current  of  the  respiratory  gases.  As 
soon  as  the  blood  from  the  root  of  the  aorta  reaches  that  part  of  the  aorta  lying  outside  the  thorax, 
more  blood  leaves  the  chest  than  passes  into  it  simultaneously  through  the  vense  cav:e. 

(3)  After  the  second  sound  (at  2),  indicated  sometimes  by  a  slight  depression  in  the  apex  of  the 
curve,  the  arterial  blood  accumulates,  and  hence  there  is  another  expiratory  movement  in  the  curve. 

(4)  The  peripheral  wave  movements  of  the  blood  from  the  thorax  cause  another  inspiratory 
movement  of  the  gases. 

(5)  More  blood  flows  into  the  chest  through  the  veins,  and  the  next  heart  beat  occurs. 

60.  INFLUENCE  OF  THE  RESPIRATORY  PRESSURE  ON 
THE  HEART. — The  variation  in  pressure  to  which  all  the  intra-thoracic 
organs  are  subjected,  owing  to  the  increase  and  decrease  in  the  size  of  the  chest 
caused  by  the  respiratory  movements,  exerts  an  influence  on  the  movements  of 
the  heart.  Examine  first  the  relations  in  different  passwe  conditions  of  the  thorax, 
when  the  glottis  is  open. 

The  diastolic  dilatation  of  the  cavities  of  the  heart,  besides  the  pressure  of  the 
venous  blood  and  the  elastic  stretching  of  the  relaxed  muscle  wall,  is  fundamen- 
tally due  to  the  elastic  traction  of  the  lungs.  This  is  stronger  the  more  the 
lungs  are  distended  (inspiration),  and  is  less  active  the  more  the  lungs  are  con- 
tracted (expiration).     Hence  it  follows — 

(i)  When  the  greatest  possible  expiratory  effort  is  made  (of  course,  with  the 
glottis  open,  only  a  small  amount  of  blood  flows  into  the  heart ;  the  heart  in 
diastole  is  small  and  contains  a  small  amount  of  blood.  Hence  the  systole  must 
also  be  small,  thus  causing  a  small  pulse  beat. 

(2)  On  taking  the  greatest  possible  inspiration  (with  the  glottis  open),  and 
therefore  causing  the  greatest  stretching  of  the  elastic  tissue  of  the  lungs,  the 
elastic  traction  of  the  lungs  is,  of  course,  greatest  =  30  mm.  Hg  {Donders^,  and 
may  interfere  with  the  contraction  of  the  thin-walled  atria  and  appendices,  in 
consequence  of  which  these  cavities  do  not  completely  empty  themselves  into  the 
ventricles.  The  heart  is  in  a  state  of  great  diastolic  distention,  and  filled  with 
blood ;  nevertheless,  in  consequence  of  the  limited  action  of  the  auricles,  only 
small  pulse  beats  are  observed.  In  several  individuals  Bonders  found  the  pulse 
to  be  smaller  and  slower;  afterward  it  became  larger  and  faster. 

(3)  When  the  chest  is  in  a  position  of  moderate  rest,  whereby  the  elastic 
traction  is  moderate  =  7.5  mm.  Hg,  we  have  the  condition  most  favorable  to  the 
action  of  the  heart — sufficient  diastolic  dilatation  of  the  cavities  of  the  heart,  as 
well  as  unhindered  emptying  of  them  during  systole. 

Voluntary  increase  or  diminution  of  the  intra-thoracic  pressure 
affects  the  action  of  the  heart. 

(i)  Valsalva's  Experiment  (1740). — If  the  thorax  is  fixed  in  the  position 
of  deepest  inspiration,  and  the  glottis  be  then  closed,  and  if  a  powerful  expiratory 
effort  be  made  by  bringing  into  action  all  the  expiratory  muscles,  so  as  to  contract 
the  chest,  the  cavities  of  the  heart  are  so  compressed  that  the  circulation  of  the 
blood  is  temporarily  interrupted.  In  this  expiratory  phase  the  elastic  traction  is 
very  limited,  and  the  air  in  the  lungs  being  under  a  high  pressure  also  acts  upon 
the  heart  and  the  intra-thoracic  great  vessels.  No  blood  can  pass  into  the  thorax 
from  without;  hence  the  visible  veins  swell  up  and  become  congested,  the  blood 
in  the  lungs  is  rapidly  forced  into  the  left  ventricle  by  the  compressed  air  in  the 
lungs,  and  the  blood  soon  passes  out  of  the  chest,  so  that  the  heart  and  lungs  con- 
tain little  blood,  thus  leading  to  a  greater  supply  of  blood  in  the  systemic  than  in 
the  pulmonary  circulation  and  the  heart.  The  heart  sounds  disappear,  and  the 
pulse  is  absent  (^E.  H.   Weber,  Danders'). 

(2)  J.  Miiller's  Experiment  (1838). — Conversely,  if  after  the  deepest 
possible  expiration  the  glottis  be  closed,  and  the  chest  be  now  dilated  with  a  great 
inspiratory  effort,  the  heart  is  powerfully  dilated,  the  elastic  traction  of  the  lungs, 
9 


130 


INFLUENCE    OF    RESPIRATORY    PRESSURE    ON    THE    HEART. 


and  the  very  attenuated  air  in  these  organs,  act  so  as  to  dilate  the  cavities  of  the 
heart.  More  blood  flows  into  the  right  heart,  and,  in  proportion  as  the  right 
auricle  and  ventricle  can  overcome  the  traction  outward,  the  blood  vessels  of  the 
lungs  become  filled  with  blood,  and  thus  partly  occupy  the  lung  space.  Much  less 
blood  is  driven  out  of  the  left  heart,  so  that  the  pulse  may  disappear.  Hence 
the  heart  is  distended  with  blood  and  the  lungs  are  congested,  while  the  aortic 
system  contains  a  small  amount  of  blood,  /".  e.,  the  systemic  circulation  is 
comjiaratively  empty,  while  the  heart  and  the  pulmonary  vessels  are  engorged 
with  blood. 

In  normal  respiration,  the  air  in  the  lungs  during  inspiration  is  under  slight 
pressure,  while  during  expiration   the  pressure  is  higher,  so  that  these  conditions 


Fig.  65. 


Apparatus  for  demonstrating  the  action  of  inspiration,  II,  and  expiration,  I,  on  the  heart  and  blood  stream.  P,  /, 
lungs;  H,  A,  heart;  L, /,  closed  glottis;  Si,  w,  manometers;  E.  ^,  ingoing  blood  stream,  vein;  A,  a,  outgoing 
blood  stream,  artery;  D,  diaphragm  during  expiration;  rf,  during  inspiration. 


favor  the  circulation  ;  inspiration  favors  the  occurrence  of  diastole,  the  supply  of 
blood  (and  lymph)  through  the  venae  cavae.  In  operations  where  the  axillary  or 
jugular  vein  is  cut,  air  may  be  sucked  into  the  circulation  during  inspiration,  and 
cause  death.  Expiration  favors  the  flow  of  blood  in  the  aorta  and  its  branches, 
and  aids  the  systolic  emptying  of  the  heart. 

The  elastic  traction  of  the  lungs  aids  the  lesser  circulation  through  the  lungs  ; 
the  blood  of  the  pulmonary  capillaries  is  exposed  to  the  pressure  of  the  air  in  the 
lungs,  while  the  blood  in  the  pulmonary  veins  is  exposed  to  a  less  pressure,  as  the 
elastic  traction  of  the  lungs,  by  dilating  the  left  auricle,  favors  the  outflow  from 
the  capillaries  into  the  left  auricle.  The  elastic  traction  of  the  lungs  acts  slightly 
as  a  disturbing  agent  on  the  right  ventricle,  and,  therefore,  on  the  movement  of 


INFLUENCE    OF    RESPIRATORY    PRESSURE    ON    THE    HEART.         131 

blood  through  the  pulmonary  artery,  owing  to  the  overpowering  force  of  the  blood 
stream  through  the  pulmonary  artery,  as  against  the  elastic  traction  of  the  lungs 
(JDonders). 

The  above  apparatus  (Fig.  65)  shows  the  effect  of  the  inspiratory  and  expiratory  movements  on 
the  dilatation  of  the  heart,  and  on  the  blood  stream  in  the  large  blood  vessels.  The  large  glass 
vessel  represents  the  thorax;  the  elastic  membrane,  D,  the  diaphragm;  P, /,  the  lungs;  L,  the 
trachea  supplied  with  a  stop-cock  to  represent  the  glottis;  H,  the  heart ;  E,  the  vense  cavse ;  A,  the 
aorta.  If  the  glottis  be  dosed,  and  the  expiratory  phase  imitated  by  pushing  up  D  as  in  I,  the  air 
in  P,  P  and  the  heart  H  are  compressed,  the  venous  valve  closes,  the  arterial  is  opened,  and  the 
fluid  is  driven  out  through  A.  The  manometer,  M,  indicates  the  intra-thoracic  pressure.  If  the 
glottis  be  closed,  and  the  inspiratoiy  phase  imitated,  as  in  11,/,/ and  h  are  dilated,  the  venous 
valve  opens,  the  arterial  valve  closes ;  hence,  venous  blood  flows  from  e  into  the  heart.  Thus,  inspi- 
ration always  favors  the  venous  stream,  and  hinders  the  arterial ;  while  expiration  hinders  the  venous, 
and  favors  the  arterial  stream.  If  the  glottis  L  and  /  be  open,  the  air  in  P,  P,  p,  p  will  be  changed 
during  the  respiratory  movements  D  and  d,  so  that  the  action  on  the  heart  and  blood  vessels  will  be 
diminished,  but  it  will  still  persist,  although  to  a  much  less  extent. 


THE  CIRCULATION  OF  THE  BLOOD. 


6i.  FLOW  OF  FLUIDS  THROUGH  TUBES.— Toricelli's  Theorem  states  that  the 
velocity  of  efllux  (?')  of  a  fluid — through  an  opening  at  the  bottom  of  a  cylindrical  vessel — is  exactly 
the  same  as  the  velocity  which  a  body  falling  freely  would  acijuire,  were  it  to  fall  from  the  surface  of 
the  fluid  to  the  base  of  the  orifice  of  the  outflow.  If  h  be  the  height  of  the  ])ropelling  force,  the 
velocity  of  eBlux  is  given  by  the  formula — 

-'  ^=  I  2gh  (where  s;  =  9.8  metres). 
The  rapidity  of  outilow  increases  with  increase  in  the  height  of  the  propelling  force,  A.  The 
former  occurs  in  the  ratio  i,  2,  3,  when  /t  increases  in  the  ratio  i,  4,  9,  i.e.,  the  velocity  of  efflux 
is  as  the  square  root  of  the  height  of  the  propelling  force.  Hence,  it  follows  that  the  velocity  of 
efflux  depends  upon  the  height  of  the  liquid  above  the  orifice  of  outflow,  and  not  upon  the  nature  of 
the  fluid. 

Resistance. — Toricelli's  theorem,  however,  is  only  valid  when  all  resistance  to  the  outflow  is 
absent ;  but  in  every  physical  experiment  such  resistance  exists.  Hence,  the  propelling  force,  //,  has 
not  only  to  cause  the  efflux  of  the  fluid,  but  has  also  to  overcome  resistance.  These  two  forces  may 
be  expressed  by  the  heights  of  two  columns  of  water  placed  over  each  other,  viz.,  by  the  height  of 
the  column  of  water  causing  the  outflow,  F,  and  the  height  of  the  column,  D,  which  overcomes  the 
resistance  opposed  to  the  outflow  of  the  fluid.     So  that 

/;  =  F  +  D. 

62.  VELOCITY  OF  THE  CURRENT.  RESISTANCE.— In  the  case  of  a  fluid  flow- 
ing through  a  tube,  which  it  fills  completely,  we  have  to  consider  the  propelling  force,  //,  causing 
the  fluid  to  flow  through  the  various  sections  of  the  tube.  The  amount  of  the  propelling  force 
depends  upon  two  factors  : — 

(1)  On  the  velocity  of  the  current,  v  ;  (2)  on  the  pressure  (amount  of  resistance)  to  which  the 
fluid  is  subjected  at  the  various  parts  of  the  tube,  D. 

(i)  The  velocity  of  the  current,  z',  is  estimated — (a)  from  the  lumen, /,  of  the  tube  ;  and  (b) 
from  the  quantity  of  fluid,  (/,  which  flows  through  the  tube  in  the  unit  of  time.  So  that  z'  ■=  (/  :  I. 
Both  values,  (/  as  well  as  /,  can  be  accurately  measured.     (The  circumference  of  a   circular  tube, 

whose  diameter  ^  f/ is  3.14.0'.     The  sectional  area  (lumen  of  the  tube)  is  1=:^'  ^.d^).     Having  in 

4 
this  way  determined  v,  from  it  we  may  calculate  the  height  of  the  column  of  fluid,  F,  which  will 
give   this  velocity,  i.e.,  the  height  from  which  a  body  must  fall  in  vacuo,  in  order  to  attain  the 

velocity  z/.  In  this  case  F  =  -'  (where^  =  the  distance  traversed  by  a  falling  body  in  i  sec.  =  4.9 
metre).  Ag 

(2)  The  pressure,  D  (amount  of  resistance),  is  measured  directly  by  placing  manometers  at 
different  parts  of  the  tube  (Fig.  67).  _2 

The  propelling  force  at  any  part  of  the  tube  is  /^  =  F  -f  D  ;  or,  h  —  ^    -f  D  {Donders).  This 

IS  proved  experimentally  by  taking  a  tall  cylindrical  vessel.  A,  of  sufficient  size,  which  is  kept 
filled  with  water  at  a  constant  level,  h.  The  rigid  outflow  tube,  ab,  has  in  connection  with  it  a 
number  of  tubes  placed  vertically,  i,  2,  3,  constituting  a  piezometer.  At  the  end  of  the  tube,  b, 
there  is  an  opening  with  a  yhort  tube  fixed  in  it,  from  which  the  water  issues  to  a  constant  height, 
provided  the  level  of  //  is  kept  constant.  The  height  to  which  it  rises  depends  on  the  height  of 
the  column  of  fluid  causing  the  velocity,  F.  As  the  pressure  in  the  manometric  tubes,  D',  D^,  DS, 
can  be  read  off  directly,  the  propelling  force  of  the  water  at  the  sections  of  the  tubes,  I,  II,  III,  is — 

/i  =  F  +  Di ;  F  +  D2 ;  F  +  D3. 
At  the  end  of  the  tube,  b,  where  D<  =  O,  //  =  F  -f  O,  i.e.,  h  —  F.  In  the  cylinder  itself  it  is  the 
constant  pressure,  h,  which  causes  the  movement  of  the  fluid.  It  is  clear  that  the  propelling  force 
of  the  water  gradually  diminishes  as  we  pass  from  the  inflow  toward  the  outflow  of  the  tube,  b.  The 
water  in  the  pressure  cylinder,  falling  from  the  height,  h,  only  rises  as  high  as  F  at  b.  This 
diminution  of  the  propelling  power  is  due  to  the  presence  of  resistances,  which  oppose  the  current 
in  the  tube,  i.e.,  part  of  the  energy  is  transformed  into  heat.  As  the  propelling  force  at  b  is  repre- 
sented only  by  F,  while  in  the  vessel  it  is  h,  the  difference  must  be  due  to  the  sum  of  the  resistances, 
D  =  ^  —  F ;  hence  it  follows  that  /^  =  F  +  D. 

132 


VELOCITY   OF    THE    CURRENT RESISTANCE. 


133 


Estimation  of  the  Resistance. — When  a  fluid  flows  through  a  tube  of  uniform  calibre,  the 
propelling  force,  h,  diminishes  from  point  to  point  on  account  of  the  uniformly  acting  resistance, 
hence  the  sum  of  the  resistance  in  the  whole  tube  is  directly  proportional  to  its  length.  In  a  uni- 
formly wide  tube,  fluid  flows  through  each  sectional  area  with  equal  velocity,  hence  v  and  also  F 
are  equal  in  all  parts  of  the  tube.  The  diminution  which  h  (propelling  force)  undergoes  can  only 
occur  from  a  diminution  of  pressure  D,  as  F  remains  the  same  throughout  (and  /^  =  F  +  D) 
Experiment  with  the  pressure  cylinder  shows  that  the  pressure  toward  the  outflow  end  of  the  tube 
gradually  diminishes.  In  a  uniformly  wide  tube,  the  height  of  the  pressure  in  the  manometers 
expresses  the  resistances  opposed  to  the  current  of  fluid  which  it  has  to  overcome  in  its  course  from  the 
point  itivestigated  to  the  free  orifice  of  efflux. 

Nature  of  the  Resistance. — The  resistance  opposed  to  the  flow  of  a  fluid  depends  upon  the 
cohesion  of  the  particles  of  the  fluid  among  themselves.  During  the  current,  the  outer  layer  of  fluid 
■which  is  next  the  wall  of  the  tube,  and  which  moistens  it,  is  at  rest.  All  the  other  layers  of  fluid, 
which  may  be  represented  as  so  many  cylindrical  layers,  one  inside  the  other,  move  more  rapidly  as 
we  proceed  toward  the  axis  of  the  tube,  the  axial  thread  or  stream  being  the  most  rapidly  moving 
part  of  the  liquid.  On  account  of  the  movement  of  the  cylindrical  layers,  one  within  the  other,  a 
part  of  the  propelling  energy  must  be  used  up.  The  amount  of  the  resistance  greatly  depends  upon 
the  amount  of  the  cohesive  force  vfh.\ch.  the  particles  of  the  fluid  have  for  each  other;  the  more  firmly 
the  particles  cohere  the  greater  will  be  the  resistance,  and  vice  versa.  Hence,  the  sticky  blood  cur- 
rent experiences  greater  resistance  than  water  or  ether. 

Heat  diminishes  the  cohesion  of  the  particles,  hence  it  also  diminishes  the  resistance  to  the 
onflow.     These  resistances  are  first  developed  by,  and  result  from,  the  movement  of  the  particles 


Fig.  66. 


Fig.  67. 


TT 


ur 


Cylindrical  vessel  filled  with  water,  h,  height  01 
the  column  of  fluid;  D,  height  required  to 
overcome  the  resistance ;  F,  height  causing 
the  efflux. 


A,  cylindrical  vessel  filled  with  water,  ab,  outflow 
tube,  along  which  are  placed  at  intervals  vertical 
tubes,  I,  2,  3,  to  estimate  the  pressure. 


of  the  fluid,  they  being,  as  it  were,  torn  from  each  other.  The  more  rapid  the  czirrent,  there- 
fore, i.  e.,  the  larger  the  number  of  particles  of  fluid  which  are  pulled  asunder  in  the  unit  of 
time,  the  greater  will  be  the  sum  of  the  resistance.  As  the  layer  of  fluid  lying  next  the  tube, 
and  moistening  it,  is  at  rest,  the  material  which  composes  the  tube  exerts  no  influence  on  the 
resistance. 

Tubes  of  Unequal  Diameter. — When  the  velocity  of  the  current  is  uniform,  the  resistance 
depends  upon  the  diameter  of  the  tube — the  smaller  the  diameter  the  greater  the  resistance  ;  the 
greater  the  diameter  the  less  the  resistance.  The  resistance  in  narrow  tubes,  however,  increases  more 
rapidly  than  the  diameter  of  the  tube  decreases,  as  has  been  proved  experimentally.  In  tubes  of 
unequal  calibre,  at  different  parts  of  their  course,  the  velocity  of  the  current  varies — it  is  slower  in  the 
wide  part  of  the  tube,  and  more  rapid  in  the  narrow  parts.  As  a  general  rule,  in  tubes  of  unequal 
diameter  the  velocity  of  the  current  is  inversely  proportional  to  the  diameter  of  the  corresponding 
section  of  the  tube;  i.  e.,  if  the  tube  be  cylindrical,  it  is  inversely  proportional  to  the  square  of  the 
diameter  of  the  circular  transverse  section.  In  tubes  of  uniform  diameter,  the  propelling  force  of  the 
moving  fluid  diminishes  uniformly  from  point  to  point,  but  in  tubes  of  unequal  calibre  it  does  tiot 
diminish  tiniformly.  As  the  resistance  is  greater  in  narrow  tubes,  of  course  the  propelling  force 
must  diminish  more  rapidly  in  them  than  in  wide  tubes.  Hence,  within  the  wide  parts  of  the  tube 
the  pressure  is  greater  than  the  sum  of  the  resistances  still  to  be  overcome,  while  in  the  narrow  por- 
tions it  is  less  than  these. 

Tortuosities  and  bending  of  the  vessels  add  new  resistance,  and  the  fluid  presses  more 
strongly  on  the  convex  side  than  on  the  concave  side  of  the  bend,  and  there  the  resistance  to  the  flow 
is  greater  than  on  the  convex  side. 


134  FLOW    IN    RIGID    AND    ELASTIC    TUBES. 

Division  of  a  tube  inlo  two  or  more  branches  is  a  source  of  resistance,  and  diminishes  the  pro- 
pelling power.  When  a  tube  divides  into  two  smaller  tubes,  of  course  some  of  the  particles  of  the 
fluid  are  retarded,  while  others  are  accelerated  on  account  of  the  unetiual  velocities  of  the  different 
layers  of  the  fluid.  Many  particles  which  had  the  i;reatest  velocity  in  the  axial  layer  come  to  lie 
more  toward  the  side  of  the  lube,  where  they  move  more  slowly ;  and  conversely  many  of  those 
lying  in  the  outer  layers  reach  the  centre,  where  they  move  more  rapitlly.  Hence,  some  of  the 
propelling  force  is  used  up  in  this  process,  and  the  pulling  asunder  of  the  particles  where  the  tube 
divides  acts  in  a  similar  manner.  If  two  inhes  join  to  form  o/te  tube,  new  resistance  is  thereby 
caused,  which  must  diminish  the  propelling  force.  The  sum  of  the  mean  velocities  in  both  branches 
is  independent  of  the  atigh-  at  which  the  division  takes  place  [j^in-o/>son).  If  a  branch  ije  ojiened 
from  a  tube,  the  princijial  current  is  accelerated  to  a  considerable  extent,  no  matter  at  what  angle  the 
branch  may  be  given  olT. 

63.  FLOW  IN  CAPILLARY  TUBES.— Poiseuille  proved  experimentally  that  the  flow  in 
the  capillaries  is  subject  to  special  conditions  : — 

( 1 )  The  quantity  of  fluid  which  flows  out  of  the  S(jf/ie  capillary  tube  is  proportional  to  the  pressure. 

(2)  The  time  necessary  for  a  given  quantity  of  fluid  to  flow  out  (withthe  like  pressure,  diameter 
of  tube  and  temperature),  is  proportional  to  the  length  of  the  tubes. 

(3)  The  product  of  the  outflow  (other  things  being  equal)  is  as  the  fourth  power  of  the  diameter. 

(4)  The  velocity  of  the  current  is  proportional  to  the  pressure  and  to  the  square  of  the  diameter, 
and  inversely  proportional  to  the  length  of  the  tube. 

(5)  The  resistance  in  the  cipillaries  is  proportional  to  the  velocity  of  the  current. 

64.  FLOW  IN  ELASTIC  TUBES.— (i)  When  an  uninterrupted  unifortn  current  flows 
through  an  elastic  tube,  it  follows  exactly  the  satne  la~u's  as  if  the  tube  had  rigid  'walls.  If  the  pro- 
pelling power  increases  or  diminishes,  the  elastic  tubes  become  wider  or  narrower,  and  they  behave, 
as  far  as  the  movement  of  the  fluid  is  concerned,  as  wider  or  narrower  rigid  tubes. 

(2)  Wave  Motion. — If,  however,  more  fluid  be  forced  in  jerks  into  an  elastic  tube,  /.  e.,  inter- 
ruptedly, the  first  part  of  the  tube  dilates  suddenly,  corresponding  to  the  quantity  of  fluid  propelled 
into  it.  The  jerk  communicates  an  oscillatory  movement  to  the  particles  of  the  fluid,  which  is  com- 
municated to  all  the  fluid  particles  from  the  beginning  to  the  end  of  the  tube ;  a  positive  -•.uave  is  thus 
rapidly  propagated  throughout  the  'whole  length  of  the  tube.  If  we  imagine  the  elastic  tube  to  be 
closed  at  its  peripheral  end,  the  positive  wave  will  be  reflected  from  the  point  of  occlusion,  and  it 
may  be  propagated  to  and  fro  through  the  tube  until  it  finally  disappears.  In  such  a  closed 
tube  a  sudden  jet  of  fluid  produces  only  a  wave  movement,  i.  e.,  only  a  vibratory  movement,  or  an 
alteration  in  the  shape  of  the  liquid,  there  being  no  actual  translation  of  the  particles  along  the  tube. 

(3)  If,  however,  fluid  be  pumped  interruptedly  or  by  jerks  into  an  elastic  tube  filled  with  fluid, 
in  which  there  is  already  a  continuous  current,  the  movement  of  the  current  is  combined  with  the 
wave  movement.  We  must  carefully  distinguish  the  movement  of  the  current  of  the  fluid,  i.  e.,  the 
translation  of  a  mass  of  fluid  through  the  tube,  from  the  luave  movement,  iht  oscillatory  movement, 
or  movement  of  change  of  form  in  the  column  of  fluid.  In  the  former,  the  particles  are  actually 
translated,  while  in  the  latter  they  merely  vibrate.  The  current  in  elastic  tubes  is  slower  than  the 
wave  movement,  which  is  propagated  with  great  rapidity.  This  last  case  obtains  in  the  arterial  sys- 
tem. The  blood  in  the  arteries  is  already  in  a  state  of  continual  movement,  directed  from  the  aorta  to 
the  capillaries ;  by  means  of  the  systole  of  the  left  ventricle  a  quantity  of  fluid  is  suddenly  pumped 
into  the  aorta,  and  causes  &  positive  7oa7'e,  the  pulse  wave,  which  is  propagated  with  great  rapidity 
to  the  terminations  of  the  arteries,  while  the  current  of  the  blood  itself  moves  much  more  slowly. 

Rigid  and  Elastic  Tubes. — If  a  quantity  of  fluid  be  forced  into  a  rigid  tube  under  a  certain 
pressure,  the  same  quantity  of  fluid  will  flow  out  at  once  at  the  other  end  of  the  tube,  provided  there 
be  no  special  resistance.  In  an  elastic  tube,  immediately  after  the  forcing  in  of  a  quantity  of  fluid,  at 
first  only  a  small  quantity  flows  out,  and  the  remainder  flows  out  only  after  the  propelling  force  has 
ceased  to  act.  If  an  equal  quantity  of  fluid  be  periodically  injected  into  a  rigid  tube,  with  each 
jerk  an  equal  quantity  is  forced  out  at  the  other  end  of  the  tube,  and  the  outflow  lasts  exactly  as 
long  as  the  jerk  or  the  contraction,  and  the  pause  between  two  periods  of  outflow  is  exactly  the  same 
as  between  the  two  jerks  or  contractions.  In  an  elastic  tube  it  is  difi'erent,  as  the  outflow  continues 
for  a  time  after  the  jerk ;  hence,  it  follows  that  a  continuous  outflow  current  will  be  produced  in 
elastic  tubes,  when  the  time  between  two  jerks  is  made  shorter  than  the  duration  of  the  outflow  after 
the  jerk  has  been  completed.  When  fluid  is  pumped  periodically  into  rigid  tubes,  it  causes  a  sharp 
abrupt  outflow  synchronous  with  the  inflow,  and  the  outflow  becomes  continuous  only  when  the 
inflow  is  continuous  and  uninterrupted.  In  elastic  tubes,  an  intermittent  current  under  the  above 
conditions  causes  a  continuous  outflow,  which  is  increased  with  the  systole  or  contraction. 

65.  STRUCTURE  AND  PROPERTIES  OF  THE  BLOOD  VES- 
SELS.— In  the  body  the  large  vessels  carry  the  blood  to  and  from  the  various 
tissues  and  organs,  while  the  thin-walled  capillaries  bring  the  blood  into  intimate 
relation  with  the  tissues.  Through  the  excessively  thin  walls  of  the  capillaries  the 
fluid  part  of  the  blood  transudes,  to   nourish  the  tissues  outside  the  capillaries. 


STRUCTURE    OF   ARTERIES. 


135 


[At  the  same  time  fluids  pass  from  the  tissues  into  the  blood.  Thus  there  is  an 
exchange  between  the  blood  and  the  fluids  of  the  tissues.  The  fluid  after  it 
passes  into  the  tissues  constitutes  the  lymph,  and  acts  like  a  stream  irrigating  the 
tissue  elements.] 

I.  The  arteries  are  distinguished  from  veins  by  their  thicker  walls,  due  to  the 
greater  development  of  smooth  muscular  and  elastic  tissues — the  middle  coat 
(tunica  media)  of  the  arteries  is  specially  thick,  while  the  outer  coat(t.  adventitia) 
is  relatively  thin.    [The  absence  of  valves  is  by  no  means  a  characteristic  feature.] 

A  typical  artery  consists  of  three  coats  (Fig.  68).  (i)  The  tunica  intima,  or  inner  coat, 
consists  of  a  layer  of  {a)  irregular,  long,  fusiform,  nucleated,  squamous  cells  forming  the  excessively 
thin,  transparent  endothelium,  immediately  in  contact  with  the  blood  stream.  [Like  other  endo- 
thelial cells,  these  cells  are  held  together  by  a  cement  substance,  which  is  blackened  by  the  action 
of  silver  nitrate.]  Outside  this  lies  a  very  thin,  more  or  less  fibrous,  layer — sub -epithelial  lay €7- — in 
which  numerous  spindle  or  branched  protoplasmic  cells  lie  embedded  within  a  corresponding  system 
of  plasma  canals.     Outside  this  is  an  elastic  lamina  [b],  which  in  the  smallest  arteries  is  a  structure- 


FiG.  69. 


Capillaries.  The  outlines  of  the  nucleated  endothelial  cells 
with  the  cement  blackened  by  the  action  of  silver 
nitrate. 

Coats  of  a  small  artery,  a,  endothelium  ; 
b,  internal  elastic  lamina ;  c,  circular 
muscular  fibres  of  the  middle  coat ;  d, 
the  outer  coat. 

less  or  fibrous  elastic  membrane — in  arteries  of  medium  size  it  is  a  fenestrated  membrane  [JJenle), 
while  in  the  largest  arteries  there  may  be  several  layers  of  elastic  laminse  or  fenestrated  elastic  mem- 
brane mixed  with  connective  tissue.  [In  some  arteries  the  elastric  membrane  is  distinctly 
fibrous,  the  fibres  being  chiefly  arranged  longitudinally.  It  can  be  stripped  off,  when  it  forms  a 
brittle  elastic  membrane,  which  has  a  great  tendency  to  curl  up  at  its  margins.  In  a  transverse 
section  of  a  middle-sized  artery  it  appears  as  a  bright  wavy  line,  but  the  curves  are  probably 
produced  by  the  partial  collapse  of  the  vessel.  It  forms  an  important  guide  to  the  pathologist, 
in  enabling  him  to  determine  which  coat  of  the  artery  is  diseased.]  In  middle-sized  and  large 
arteries  a  few  non-striped  muscular  fibres  are  disposed  longitudinally  between  the  elastic  plates  or 
laminae.  Along  with  the  circular  muscular  fibres  of  the  middle  coat,  they  may  act  so  as  to  narrow 
the  artery,  and  they  may  also  aid  in  keeping  the  lumen  of  the  vessel  open  and  of  uniform  calibre. 

(2)  The  tunica  media,  or  middle  coat,  contains  much  non-striped  muscle  (f),  which  in  the 
smallest  arteries  consists  of  transversely  disposed  non-striped  muscular  fibres  lying  between  the 
endothelium  and  the  T.  adventitia,  while  a  finely  granular  tissue  with  few  elastic  fibres  forms  the 
bond  of  union  between  them.     As  we  proceed  from  the  very  smallest  to  the  small  arteries,  the 


136 


STRUCTURE    OF    VEINS. 


Fig 


number  of  muscular  fibres  becomes  so  great  as  to  form  a  well  marked  fibrous  ring  of  non-sti-iped 
luiisile,  in  which  there  is  comparatively  little  connective  tissue.  In  the  large  arteries  the  amount  of 
connective  tissue  is  considerably  increased,  and  between  the  layers  of  fine  connective  tissue  numer- 
ous (as  many  as  fifty)  thick,  elastic,  fibrous  or  fenestrated  laniin;\?  are  concentrically  arranged.  A  few 
non-striped  fibres  lie  scattered  among  these,  and  some  of  them  are  arranged  transversely,  while  a 
few  have  an  obli(iue  or  longitudinal  direction. 

The  first  part  of  the  aorta  and  pulmonary  artery,  and  the  retinal  arteries,  are  devoid  of  muscle.  The 
descending  aorta,  common  iliac,  and  po]iliteal  have  longitudinal  libres  between  the  transverse  ones. 
Longitudinal  bundles  lying  inside  the  media  occur  in  llie  renal,  sulenic,  and  internal  spermatic 
arteries.  Longitudinal  bundles  occur  both  on  the  outer  and  inner  surfaces  of  the  umbilical  arteries, 
which  are  very  muscular. 

(3)  The  tunica  adventitia,  or  outer  coat,  in  the  sinalhst  arteries  consists  of  a  structureless 
membrane  with  a  few  connective- tissue  corpuscles  attached  to  it;  in  ioiiteichat  larger  arteries  there 
is  a  layer  of  fine  fibrous  elastic  tissue  mi.\ed  with  bundles  of  fibrillar  connective  tissue  (a).  In 
arteries  of  »iuii/!e  size,  and  in  the  laigest  arteries,  the  chief  mass  consists  of  bundles  of  fibrillar 
connective  tissue  containing  connective-tissue  corpuscles.  The  bundles  cross  each  other  in  a  variety 
of  directions,  and  fat  cells  often  lie  between  them.  Next  the  media  there  are  numerous  fibrous  or 
fenestrated  elastic  lamellte.  In  medium-sized  and  small  arteries  the  elastic  tissue  next  the  media 
takes  the  form  of  an  independent  clastic  membrane  (Ilenle's  external  elastic  membrane).  Hundles 
of  non-striped  muscle,  arranged  longitudinally,  occur  in  the  adventitia  of  the  arteries  of  the  penis, 
and  in  the  renal,  s[5lenic,  spermatic,  iliac,  hypogastric,  and  superior  mesenteric  arteries. 

II.  The  capillaries,  while  retaining  their  diameter,  divide  and  reunite  so  as  to  form  networks, 
whose  shape  and  arrangement  differ  considerably  in  different  tissues.  The  diameter  of  the  capil- 
laries varies  considerably,  but  as  a  general  rule  it  is  such  as  to  admit  freely  a  single  row  of  blood 
corpuscles.  In  the  retina  and  the  muscles  the  diameter  is  5-6  //,  and  in  bone  marrow,  liver,  and 
choroid  10-20 ,«.     The  tubes  consist  of  a  single  layer  of  transparent,  excessively  thin,  nucleated, 

endothelial  cells  joined  to  each  other  by  their  margins.  [The 
nuclei  contain  a  well  marked  intranuclear  ])lexus  of  fibrils, 
like  other  nuclei.]  The  cells  are  more  fusiform  in  the  smaller 
capillaries  and  more  polygonal  m  the  larger.  The  body 
of  the  cells  presents  the  characters  of  very  faintly  refractive 
protoplasm,  but  it  is  doubtful  whether  the  body  of  the  cell 
is  endowed  with  the  property  of  contractility  (p.  138). 

If  a  dilute  solution  (^  per  cent.)  of  silver  nitrate  be 
injected  into  the  blood  vessels,  the  cement  substance  of  the 
endothelium  [and  of  the  muscular  fibres  as  well]  is  re- 
vealed by  the  presence  of  the  black  "  silver  lines."  The 
blackened  cement  substance  shows  little  specks  and  large 
black  slits  at  different  points.  It  is  not  certain  whether 
these  are  actual  holes  through  which  colorless  corpuscles 
may  pass  out  of  the  vessels,  or  are  merely  larger  accumula- 
tions of  the  cement  substance.  [If  a  capillary  is  examined 
in  a  perfectly  fresh  condition  (while  living)  and  without  the 
addition  of  any  reagent,  it  is  impossible  to  make  out  any 
line  of  demarcation  Ijetween  adjacent  cells,  owing  to  the 
uniform  refractive  index  of  the  entire  wall  of  the  tube.] 

[Arnold  called  these  small  areas  in  the  black  silver  lines, 
when  they  are  large,  stomata,  and  when  small,  stigmata. 
They  are  most  numerous  after  venous  congestion,  and  after 
the  disturbances  which  follow  inflammation  of  apart.  They 
are  not  always  present.  The  existence  of  cement  substance 
between  the  cells  may  also  be  inferred  from  the  fact  that 
indigo-sulphate  of  soda  is  deposited  in  it  (  7/ioma),  and 
jiarticles  of  cinnabar  and  China  ink  are  fixed  in  it,  when 
tlicse  substances  are  injected  into  the  blood  i^Foa).'\ 

Fine  anastomosing  fibrils  derived  from   non-medullated 
nerves  terminate  in  small  end-buds  in  relation  with  the 
capillary  wall;    ganglia  in  connection  with   the  nerves  of 
\  7    capillaries  occur  only  in  the  region  of  the  sympathetic. 

The  small  vessels  next  in  size  to  the  capillaries,  and  con- 
tinuous with  them,  have  a  completely  structureless  covering 
in  addition  to  the  endothelium. 

Longitudinal  section  of  a  vein  at  the  level  of  a  tit      »t>i-  •  11        j-   ^'  •   1      j 

valve,  a.hyalinelayerof  the  internal  coat;  ^''^-     The     VCinS     are    generally    distinguished 

^;,l!?fiKl^'"l'•"'^J''i^''''"'"°^T°°i^'""^"  from  the  arteries  by  \.\\e\r  h/men  being  wide?-  than 

cular  hbres  divided  transversely ;  d,  longi-      ,         ,  r      i  t  •  i       • 

tudinai  muscular  fibres  in  the  adventitia.    the  luiiien  01  the  Corresponding  artcrics ;  their 


STRUCTURE    OF   VEINS.  137 

walls  are  thinner  on  account  of  the  smaller  amount  of  non-striped  muscle  and 
elastic  tissue  (the  non-striped  muscle  is  not  unfrequently  arranged  longitudinally 
in  veins).  They  are  also  more  extensile  (with  the  same  strain).  The  adventitia  is 
usually  the  thickest  coat.  The  occurrence  of  valves  is  limited  to  the  veins  of 
certain  areas. 

Structure. — (i)  The  tunica  intima  consists  of  a  layer  oi shorter  and  broader  endothelial  cells, 
under  which  in  the  smallest  veins  there  is  a  structureless  elastic  membrane,  sub-epithelial  layer, 
which  is  fibrous  in  veins  somewhat  larger  in  size,  but  in  all  cases  is  thinner  than  in  the  arteries.  In 
large  veins  it  may  assume  the  characters  of  a  fenestrated  membrane,  which  is  double  in  some  parts 
of  the  crural  and  iliac  veins.  Isolated  muscular  fibres  exist  in  the  intima  of  the  femoral  and 
popliteal  veins. 

(2)  The  t.  media  of  the  larger  veins  consists  of  alternate  layers  of  elastic  and  muscular  tissue 
united  to  each  other  by  a  considerable  amount  of  connective  tissue,  but  this  coat  is  always  thinner 
than  in  the  corresponding  arteries.  This  coat  diminishes  in  the  following  order  in  the  following 
vessels :  popliteal,  veins  of  the  lower  extremity,  veins  of  the  upper  extremity,  superior  mesenteric, 
other  abdominal  veins,  hepatic,  pulmonary,  and  coronary  veins.  The  following  veins  contain  no 
muscle:  veins  of  bone,  central  nervous  system  and  its  membranes,  retina,  the  superior  cava,  with 
the  large  trunks  that  open  into  it,  the  upper  part  of  the  inferior  cava.  Of  course,  in  these  cases  the 
media  is  very  thin.  In  the  smallest  veins  the  media  is  formed  of  fine  connective  tissue,  with  very 
few  muscular  fibres  scattered  in  the  inner  part. 

.(3)  The  t.  adventitia  is  thicker  than  that  of  the  corresponding  arteries;  it  contains  much  con- 
nective tissue,  usually  arranged  longitudinally,  and  not  much  elastic  tissue.  I>ongitudinally  arranged 
muscular  Jibres  occur  in  some  veins  (renal,  portal,  inferior  cava  near  the  liver,  veins  of  the  lower 
extremities).  The  valves  consist  of  fine  fibrillar  connective  tissue  with  branched  cells.  An  elastic 
netwurk  exists  on  their  convex  surface,  and  both  surfaces  are  covered  by  endothelium.  The  valves 
contain  many  muscular  fibres  (Fig.  70).  [Ranvier  has  shown. that  the  shape  of  the  epithelial  cells 
on  the  side  over  which  the  blood  passes  is  more  elongated  than  on  the  cardiac  side  of  the  valve, 
where  the  long  axes  of  the  cells  are  placed  transversely.] 

The  sinuses  of  the  dura  mater  are  spaces  covered  with  endothelium.  The  spaces  are  either 
duplicatures  of  the  membrane,  or  channels  in  the  substance  of  the  tissue  itself. 

Cavernous  spaces  we  may  imagine  to  arise  by  numerous  divisions  and  anastomoses  of  tolerably 
large  veins  of  unequal  calibre.  The  vascular  wall  appears  to  be  much  perforated  and  like  a  sponge, 
the  internal  space  being  traversed  by  threads  and  strands  of  tissue,  which  are  covered  with  endo- 
thelium on  their  surfaces,  that  are  in  contact  with  the  blood.  The  surrounding  wall  consists  of  con- 
nective tissue,  which  is  often  very  tough,  as  in  the  corpus  cavernosum,  and  it  not  unfrequently 
contains  non-striped  muscle. 

Cavernous  formations  of  an  analogous  nature  on  artei'ies  are  the  carotid  gland  of  the  frog, 
and  a  similar  structure  on  the  pulmonary  arteries  and  aorta  of  the  turtle,  and  the  coccygeal  gland 
of  man.  The  last  structure  is  richly  supplied  with  sympathetic  nerve  fibres,  and  is  a  convoluted 
mass  of  ampullated  or  fusiform  dilatations  of  the  middle  sacral  artery,  surrounded  and  permeated 
by  non-striped  muscle. 

Vasa  Vasorum. — [These  are  small  vessels  which  nourish  the  coats  of  the  arteries  and  veins. 
They  arise  from  one  part  of  a  vessel  and  enter  the  walls  of  the  same,  or  another  vessel  at  a  lower 
level.  They  break  up  chiefly  in  the  outer  coat,  and  none  enter  the  inner  coat.]  In  structure  they 
resemble  other  small  blood  vessels.  The  blood  circulating  in  the  arterial  or  venous  wall  is  returned 
by  small  veins. 

[Lymphatics. — There  are  no  lymphatics  on  the  inner  surface  of  the  muscular  coat,  or  under 
the  intima  in  large  arteries.  They  are  numerous  in  a  gelatinous  layer  immediately  outside  the 
muscular  coat,  and  the  same  relation  obtains  in  large  muscular  veins  and  lymphatic  trunks 
{Hoggan).'] 

Intercellular  Blood  Channels. — Intercellular  blood  channels  of  narrow  calibre,  and  without 
walls,  occur  in  the  granulation  tissue  of  healing  wounds.  At  first  blood  plasma  alone  is  found 
between  the  formative  cells,  but  afterwards  the  blood  current  forces  blood  corpuscles  through  the 
channels.  The  first  blood  vessels  in  the  developing  chick  are  formed  in  a  similar  way,  from  the 
formative  cells  of  the  mesoblast. 

Properties  of  the  Blood  Vessels. — The  larger  blood  vessels  are  cylin- 
drical tubes  composed  of  several  layers  of  various  tissues,  more  especially  elastic 
tissue  and  smooth  muscular  fibres,  and  the  whole  is  lined  by  a  smooth  polished 
layer  of  endothelium.  One  of  the  most  important  properties  is  the  contractility 
of  the  vascular  wall,  in  virtue  of  which  the  calibre  of  the  vessel  can  be  varied, 
and  therefore  the  supply  of  blood  to  a  part  is  altered.  The  contractility  is  due  to 
the  plain  muscular  fibres,  which  are,  for  the  most  part,  arranged  circularly.  It  is 
most  marked  in   the  small  arteries,  and  of  course  is  absent  where  no  muscular 


138  PROPERTIES   OK   THE    liLOOD    VESSELS. 

tissue  occurs.  The  amount  and  intensity  of  the  contraction  depend  upon  the  de- 
velopment of  the  muscular  tissue  ;  in  fact,  the  two  go  hand  in  hand.  [If  an  artery 
be  exposed  in  the  living  body  it  soon  contracts  under  the  stimulus  of  the  atmos- 
phere acting  upon  the  muscular  fibres.] 

[Action  of  Drugs  on  the  Vascular  System. — Gaskell  finds  that  a  very  dilute  solution  of 
lactic  acid  1 1  :  10,000  parts  of  saline  solution),  passed  through  the  blood  vessels  of  a  frog, 
alwavs  enlarges  the  calibre  of  the  blood  vessels,  while  an  alkaline  solution  (i  part  sodium 
hydrate  to  10,000  saline  solution)  always  diminishes  their  size,  usually  to  absolute  closure,  and 
indeed  the  artificial  constriction  of  the  blood  vessels  may  be  almost  complete.  These  fluids  are 
antagonistic  to  each  other  as  far  as  regards  their  action  on  the  calibre  of  the  arteries.  Dilute  alka- 
line solutions  act  on  the  heart  in  the  same  way.  After  a  series  of  beats  the  ventricle  stops  beating, 
the  standstill  being  in  a  state  of  contraction.  Very  dilute  lactic  acid  causes  the  ventricle  to  stand 
still  in  the  phase  of  complete  relaxation.  Thfe  acid  and  alkaline  saline  solutions  are  antagonistic  in 
their  action  on  the  ventricle.  Cash  and  Brunton  find  that  dilute  acids  have  a  tendency  to  increase 
the  transudation  through  the  vessels  and  produce  adenta  of  the  surrounding  tissues.  They  also 
observed  that  barium,  calcium,  strontium,  copper,  iron,  and  tin  produce  contraction  of  the  blood 
vessels  when  solutions  of  their  salts  are  driven  through  them,  while  the  same  effect  is  produced  by 
very  dilute  solutions  of  potassium.  Nicotin,  atropin,  and  chloral  differ  in  their  action  according  to 
the  dose.  In  these  experiments  the  effect  was  ascertained  by  the  amount  of  fluid  which  flowed  out 
of  the  vessels  in  a  given  time.]  If  blood  containing  certain  drugs  be  perfused  through  the  blood 
vessels  of  a  freshly  excised  organ,  the  blood  vessels  are  dilated;  e.  s;.,  by  amyl  nitrite,  chloral 
hydrate,  morphia,  CO,  paraldehyde,  kairin,  quinine,  atropin,  ferricyanide  of  potassium,  (urea  and 
sodic  chloride  in  the  renal  vessels), — they  are  contracted  by  digitalin,  veratria,  helleborin  [A'obert). 
Heat  causes  contraction  of  the  blood  vessels  of  the  frog's  mesentery  [Gartner).  According  to  Roy 
the  blood  vessels  shorten  when  heated. 

That  the  capillaries  undergo  dilatation  and  contraction,  owing  to  variations 
in  the  size  of  the  protoplasmic  elements  of  their  walls,  must  be  admitted. 

Strieker  has  described  capillaries  as  "protoplasm  in  tubes,"  and  observed  that  in  the  tadpole  they 
exhibited  movements  when  stimulated.  Golubew  described  an  active  state  of  contraction  of  the 
capillary  wall,  but  he  regarded  the  nuclei  as  the  parts  which  underwent  change.  Rouget  observed 
the  same  result  in  the  capillaries  of  newborn  mammals.  Tarchanoff  found  that  mechanical  or 
electrical  stimulation  caused  a  change  in  the  shape  and  size  of  the  nuclei,  so  that  he  regards 
these  as  the  actively  contractile  parts.  [Severini  also  attaches  great  importance  to  the  contrac- 
tility of  the  capillaries  and  especially  of  their  nuclei  as  influencing  the  blood  stream.  Oxygen 
acts  on  the  nuclei  of  the  capillary  wall  (membrana  nictitans  of  frog)  and  causes  them  to  swell, 
while  CO2  has  an  opposite  effect.  The  circulation  through  a  lung  suddenly  filled  with  O  or  atmos- 
pheric air  is  at  first  very  rapid,  but  soon  diminishes,  while  with  CO.,  the  circulation  remains  con- 
stant.] As  the  capillaries  are  excessively  thin,  soft,  and  delicate,  it  is  obvious  that  the  form  of 
the  individual  cells  must  depend  to  a  considerable  extent  upon  the  degree  to  which  the  vessels  are 
filled  with  blood.  In  vessels  which  are  distended  with  blood  the  endothelial  cells  are  flattened,  but 
when  the  capillaries  are  collapsed  they  project  more  or  less  into  the  lumen  of  the  vessel  (A't'naut). 

[It  is  well  known  that  the  capillaries  present  great  variations  in  their  diameter  at  different 
times.  As  these  variations  are  usually  accompanied  by  a  corresponding  contraction  or  dilatation 
of  the  arterioles,  it  is  usually  assumed  that  the  variations  in  the  diameter  of  the  capillaries  are  due 
to  differences  of  the  pressure  within  the  capillaries  themselves,  viz.,  to  the  elasticity  of  their  walls. 
Every  one  is  agreed  that  the  capillaries  are  very  elastic,  but  the  experiments  of  Roy  and  Graham 
Brown  show  that  they  are  contractile  as  well  as  elastic,  and  these  observers  conclude  that,  under 
normal  conditions,  it  is  by  the  contractility  of  the  capillary  wall  as  a  whole  that  the  diameter  of 
these  vessels  is  changed,  and  to  all  appearance  their  contractility  is  constantly  in  action.  "The 
individual  capillaries  (in  all  probability)  contract  or  expand  in  accordance  with  the  requirements  of 
the  tissues  through  which  they  pass.  The  regulation  of  the  vascular  blood  flow  is  thus  more  com- 
plete than  is  usually  imagined."] 

Physical  Properties. — Among  the  physical  properties  of  the  blood  vessels, 
elasticity  is  the  most  important;  their  elasticity  is  s/na//  in  amotint,  i.e.,  they 
otter  little  resistance  to  any  force  applied  to  them  so  as  to  distend  or  elongate 
them,  but  it  \% perfect  in  quality,  i.e.,  the  blood  vessels  rapidly  regain  their  original 
size  and  form  after  the  force  distending  them  is  removed. 

[Uses  of  Elasticity. — The  elasticity  of  the  arteries  is  of  the  utmost  importance  in  aiding  the 
conversion  of  the  unequal  movement  of  the  blood  in  the  large  arteries  into  a  uniform  flow  in  the 
capillaries.  E.  H.  Weber  compared  the  elastic  wall  of  the  arteries  with  the  air  in  the  air  chamber 
of  a  fire  engine.  In  both  cases  an  elastic  medium  is  acted  upon — the  air  in  the  one  case  and  the 
elastic  tissue  in  the  other — which  in  turn  presses  upon  the  fluid,  propelling  it  onward  continually, 


THE    PULSE. 


139 


while  the  action  of  the  pump  or  the  heart,  as  the  case  may  be,  is  intermittent.  The  ordinary  spray 
producer  acts  on  this  principle.  A  uniform  spray  or  jet  is  obtained  by  pumping  intermittently,  but 
only  when  the  resistance  is  such  as  to  bring  into  action  the  elasticity  of  the  bag  between  the  pump 
and  the  spray  orifice.] 

According  to  E.  H.  Weber,  Volkmann,  and  Wertheim,  the  elongation  of  a  blood  vessel  and  moist 
tissues  generally  is  not  proportional  to  the  weight  used  to  extend  it,  the  elongation  being  relatively 
less  with  a  large  weight  than  with  a  small  one,  so  that  the  curve  of  extension  is  nearly  [or,  at  least 
bears  a  certain  relation  to]  a  hyperbola.  According  to  Wundt,  we  have  not  only  to  consider  the 
extension  produced  -aX  first  by  the  weight,  but  also  the  subsequent  "elastic  after-effect,"  which 
occurs  gradually.  The  elongation  which  takes  place  during  the  last  few  moments  occurs  so  slowly 
and  so  gradually  that  it  is  well  to  observe  the  effect  by  means  of  a  magnifying  lens.  Variations 
from  the  general  law  occur  to  this  extent,  that  if  a  certain  weight  is  exceeded,  less  extension,  and, 
it  may  be,  permanent  elongation  of  the  artery  not  unfrequently  occur.  K.  Bardeleben  found,  espe- 
cially in  veins  elongated  to  40  or  50  per  cent,  of  their  original  length,  that  when  the  weight 
employed  increased  by  an  equal  amount  each  time,  the  elongation  was  proportional  to  the  square 
root  of  the  weight.  This  is  apart  from  any  elastic  after-effect.  Veins  may  be  extended  to  at  least 
50  per  cent,  of  their  length  without  passing  the  limit  of  their  elasticity. 

[Roy  experimented  upon  the  elastic  properties  of  the  arterial  7vall.  A  portion  of  an  artery,  so 
that  it  could  be  distended  by  any  desired  internal  pressure,  was  enclosed  in  a  small  vessel  contain- 
ing olive  oil  arranged  in  the  same  way  as  in  Fig.  62,  for  the  heart.  The  variations  of  the  contents 
were  recorded  by  means  of  a  lever  writing  on  a  revolving  cylinder.  The  instrument  is  termed  a 
sphygmotonometer.  The  ao7-ta  and  other  large  arteries  are  most  elastic  and  most  distensible  at 
pressures  corresponding  more  or  less  exactly  to  their  normal  blood  pressure,  while  in  veins  the  rela- 
tion between  internal  pressure  and  the  cubic  capacity  is  very  different.  In  them  the  maximum 
of  distensibility  occurs  with  pressures  immediately  above  zero.  Speaking  generally,  the  cubic 
capacity  of  an  artery  is  greatly  increased  by  raising  the  intra-arterial  tension,  say  from  zero  to  about 
the  normal  internal  pressure  which  the  artery  sustains  during  life.  Thus  in  the  rabbit,  the  capacity 
of  the  aorta  was  qtiadrupled  by  raising  the  intra-arterial  pressure  from  zero  to  200  mm.  Hg.,  while 
that  of  the  carotid  was  more  than  six  times  greater  at  that  pressure  than  it  was  in  the 
undistended  condition.  The  pulmonary  artery  is  distinguished  by  its  excessive  elastic 
distensibility.  Its  capacity  (rabbit)  was  increased  more  than  twelve  times  on  raising 
the  internal  pressure  from  zero  to  about  36  mm.  Hg.  Veins,  on  the  other  hand,  are 
distinguished  by  the  relatively  small  increase  in  their  cubic  capacity  produced  by 
greatly  raising  the  internal  pressure,  so  that  the  enormous  changes  in  the  capacity  of 
the  veins  during  life  are  due  less  to  differences  in  the  pressure  than  to  the  great  differ- 
ences in  the  quantity  of  blood  which  they  contain.] 

Pathological. — Interference  with  the  nutrition  of  an  artery  alters  its  elasticity, 
[and  that  in  cases  where  no  structural  changes  can  be  found].  Marasmus  preceding 
death  causes  the  arteries  to  become  wider  than  normal.  In  some  old  people  they 
become  atheromatous  and  even  calcified. 

Cohesion. — The  cohesion  of  blood  vessels  is  very  great,  and  in 
virtue  of  this  they  are  able  to  resist  even  considerable  internal  pres- 
sure without  giving  way.  The  carotid  of  a  sheep  is  ruptured  only 
when  fourteen  times  the  usual  pressure  it  is  called  upon  to  bear  is  put 
upon  it  (Volkmami).  Given  a  vein  and  an  artery  of  the  same  thick- 
ness, a  greater  pressure  is  required  to  rupture  the  former  than  the  lat- 
ter. The  human  carotid  or  iliac  artery  resists  a  pressure  of  8  atmos- 
pheres, the  veins  about  the  half  of  this. 


Fig.  71, 


66.  INVESTIGATION  OF  THE  PULSE.— [The  charac- 
ters of  the  pulse  maybe  investigated  by — (i)  the  eye  {inspectioii)  ;  (2} 
the  finger  (^palpatioti)  ;  (3)  instruments. 

Two  or  three  fingers  are  placed  over  the  course  of  the  radial  artery, 
and  the  various  phenomena  in  connection  with  the  pulse  are  noted. 
It  takes  much  practice  for  the  physician  to  acquire  the  tactus  eruditus,      Sphygmome- 
and  notwithstanding  the  value  of  instruments,  every  physician  should         ^^^^°l  ^^^ 
make  a  careful  study  of  the  pulse  beat  with  his  finger.     In  order  to         Cheiius. 
feel  the  pulse  beat  or  to  take  a  pulse  tracing,  there  must  be  some  resist- 
ant body,  e.g.,  a  bone  behind  the  artery,  and  a  certain  degree  of  pressure  must 
be  exerted  on  the  artery.] 

The  individual  phases  of  the   movement  of  the  pulse  can  only  be  accurately 
investigated  by  the  application  of  instruments  to  the  arteries. 


140 


INSTRUMENTS    FOR    INVESTIGATING   THE    PULSE, 


(i)  Poiseuille's  Box  Pulse  Measurer  (1829). — An  artery  is  exposed  and  placed  in  an  oblong 
box  filled  with  an  indifferent  Huid.  A  vertical  tube  witli  a  scale  attached  communicates  with  the 
interior  of  the  box.     The  cuhiiun  of  fluid  undert^ocs  a  variation  with  every  pulse  heat. 

(2)  Herisson's  Tubular  Sphygmometer  consists  of  a  gla.ss  tube  whose  lower  end  is  covered 
with  an  ela.stic  membrane  (Fig.  71;.  The  tube  is  partly  fdied  with  llg.  The  membrane  is  placed 
over  the  position  of  a  pulsating  artery,  so  that  its  beat  causes  a  movement  in  the  Mg.  Chelius  u.sed 
a  similar  instrument,  and  he  succeeded  with  this  instrument  in  showing  the  existence  of  the  double 
beat  (dicrotism)  in  the  normal  pulse  (1S50). 

(3)  Vierordt's  Sphygmograph  (1855^— In  ''"«.  one  of  the  earliest  sphygmographs,  Vierordt 
departed  from  the  principle   of  a  fluctuating  fluid  column,  and  adopted   the  prmciple  of  the  lever. 


Fic.  72. 


Scheme  of  M.irey's  sphygmograph.  A.  spring  with  ivory  pad,  j',  which  rests  on  the  artery  ;  e,  weak  spring  pressing 
k  into  /  ;  V,  writing  lever  ;  P,  piece  of  smoked  glass  or  paper  moved  by  clockwork,  U  ;  H,  screw  to  limit  excur- 
sion of  A  ;  S,  arrangement  for  fixing  the  instrument  to  the  arm  of  the  patient. 

Upon  the  artery  rested  a  small  pad,  which  moved  a  complicated  system  of  levers.  At  first  he  used 
a  straw  6  inches  long,  which  rested  on  the  artery.  The  point  of  one  of  the  levers  inscribed  its 
movements  upon  a  revolving  cylinder.     This  instrument  was  soon  discarded. 

(4)  Marey's  Sphygmograph  consists  of  a  combination  of  a  lever  with  an  elastic  spring.  The 
elastic  sjiring  (Fig.  72,  A)  is  fixed  at  one  end,  2,  free  at  the  other  end,  and  provided  with  an  ivory 
pad,  y,  wliich  is  pressed  by  the  spring  upon  the  radial  artery.  On  the  upper  surface  of  the  pad 
there  is  a  vertically  placed  fine-toothetl  rod,  k,  wliich  is  pressed  upon  by  a  weak  spring,  e,  so  that  its 
teeth  dovetail  with  similar  teeth  in  tlie  small  wheel,  /,  from  whose  axis  there  projects  a  long,  light, 

Fig.  73. 


Marey's  improved  sphygmograph.  A,  steel  spring;  B,  first  lever;  C,  WTiting  lever;  C,  its  free  writing  end  ;  D, 
screw  for  bringing  B  in  contact  with  C  ;  G,  slide  with  smoked  paper;  H,  clockwork;  L,  screw  for  increasing 
the  pressure  ;  M,  dial  indicating  the  pressure;  K,  K,  straps  for  fi.xing  the  instrument  to  the  arm,  and  the  arm 
to  the  double  inclined  plane  or  support. 

wooden  lever,  v,  running  nearly  parallel  with  the  elastic  spring.  This  lever  has  a  fine  style  at  its 
free  end,  s,  which  writes  upon  a  smoked  plate,  P,  moved  by  clockwork,  U,  in  front  of  the  style. 
Marey's  instrument,  as  improved  by  Mahomed  and  others,  has  been  very  largely  used. 

[Its  more  complete  form,  as  in  Fig.  73,  where  it  is  shown  applied  to  the  arm,  consists  of  (i)  a 
steel  spring.  A,  which  is  provided  with  a  pad  resting  on  the  artery,  and  moves  with  each  movement 
of  the  artery  ;  (2)  the  lever,  C,  which  records  the  movement  of  the  artery  and  spring  in  a  magnified 
form  on  the  smoked  paper,  G;  (3)  an  arrangement,  L,  whereby  the  exact  pressure  exerted  upon 
the  artery  is  indicated  on  the  dial,  M  ;  (4)  the  clockwork,  H,  which  moves  the  smoked  paper,  G, 
at  a  uniform  rate  ;  (5)  a  framework  to  which  the  various  parts  of  the  instrument  are  attached,  and 
by  means  of  which  the  instrument  is  fastened  to  the  arm  by  straps  K,  K  (Byrom  Bramwell).'\ 


INSTRUMENTS    FOR    INVESTIGATING   THE    PULSE. 


141 


[Application. — In  applying  the  sphj'gmograpli,  cause  the  patient  to  seat  himself  beside  a  low 
table,  and  place  his  arm  on  the  double  inclined  plane  (Fig.  73).  In  the  newer  form  of  instrument, 
the  lid  of  the  box  is  so  arranged  as  to  unfold  to  make  this  support.  The  fingers  ought  to  be  semi- 
flexed.    Mark  the  position  of  the  radial  artery  with  ink.     See  that  the  clockwork  is  wound  up, 

Fig.  74. 


Ludwig's  Sphygmograph. 

and  apply  the  ivory  pad  exactly  over  the  radial  artery  where  it  lies  upon  the  radius,  fixing  it  to  the 
arm  by  the  non-elastic  straps,  K,  K.  Fix  the  slide  holding  the  smoked  paper  in  position.  The 
best  paper  to  use  is  that  with  a  very  smooth  surface,  or  an  enameled  card  smoked  over  the  flame  of  a 
turpentine  lamp,  over  a  piece  of  burning  camphor,  or  over  a  fan-tailed  gas  burner.     The  writing 

Fig.  75. 


Dudgeon's  Sphygmograph. 

style  is  so  arranged  as  to  write  upon  the  smoked  paper  with  the  least  possible  friction.  It  is  most 
important  to  regulate  the  pressure  exerted  upon  the  artery  by  means  of  the  milled  head,  L.  This 
must  be  determined  for  each  pulse,  but  the  rule  is  to  graduate  the  pressure  until  the  greatest  ampli- 
tude of  movement  of  the  lever  is  obtained.     Set  the   clockwork  going,  and  a  tracing  is  obtained. 


142 


INSTRUMENTS    FOR    INVESTIGATING    THE    PULSE. 


which  must  be  "  fixed  "  by  dipping  it  in  a  rapidly  drying  varnish,  ^.  j-.,  photographic.     In  every 
case  scratch  on  the  tracing,  with  a  needle,  the  name,  date,  and  amount  of  pressure  employed.] 

[(5)  Dudgeon's  Sphygmograph. — This  is  a  convenient  form  of  sphygmograph,  although 
Broadbent  regards  its  results  as  untrustworthy.  The  instrument  after  being  carefully  adjusted  upon 
the  radial  arter)'  is  kept  in  position  by  an  inelastic  strap.     The  pressure  of  the  spring  is  regulated, 


Scheme  of  Brondgeest's  sphygmograph.     S,  S',  receiving  and  recording  (S,  S')  tambours  with  writing  levers,  Z  .ind 
Z';   K,  K',  conducting  tubes:  /,  over  heart,/',  over  a  distant  artery. 

by  the  eccentric  wheel,  to  any  amount  from  i  to  5  ounces.     As  in  other  instruments  the  tracing 
paper  is  moved  in  front  of  the  writing  needle  by  means  of  clockwork.     The  writing  levers  are  so 
adjusted  that  the  movements  of  the  artery  are  magnified  fifty  times  (Fig.  75).] 
(6)   [Ludv^fig's  improved  form  is  a  very  serviceable  instrument  (Fig.  74).] 

Fig.  77. 


Scheme  of  Landois'  Angiograph. 

(7)  Marey's  tambours  are  also  employed  for  registering  the  movements  of  the  pulse.  They 
*'^^"^ed  in  the  same  way  as  the  pansphygmograph.  Two  pairs  of  metallic  cups  (Fig.  76,  S,  S, 
and  S',  S^,  Lpham's  capsules)  are  pierced  in  the  middle  by  thin  metal  tubes,  whose  free  ends  are 
connected  with  caoutchouc  tubes,  K  and  K^.  All  the  four  metallic  vessels  are  covered  with  an 
elastic  membrane.     On  S  and  S^  are  fixed  two  knob-like  pads,/  and/',  which  are  applied  to  the 


INSTRUMENTS    FOR    INVESTIGATING    THE    PULSE. 


143 


pulsating  arteries,  and  the  metal  arcs,  B  and  B',  retain  them  in  position.  On  the  other  tambours 
are  arranged  the  writing  levers,  Z  and  Z^.  Pressure  on  tlie  one  tambour  necessarily  compresses  the 
air,  and  makes  the  other,  with  which  it  is  connected,  expand,  so  as  to  move  the  writing  lever.  This 
arrangement  does  not  give  absolutely  exact  results  ;  still,  it  is  very  easily  used,  and  is  convenient. 
In  Fig.  76  a  double  arrangement  is  shown,  whereby  one  instrument,  B,  may  be  placed  over  the 
heart  and  the  other,  B^,  on  a  distant  artery. 

(8)  Landois'  Angiograph. — To  a  basal  plate,  G,  G,  are  fixed  two  upright  supports,/,  which 
carry  between  them  at  their  upper  part  the  movable  lever,  d,  r,  carrying  a  rod  bearing  a  pad,  e, 
directed  downward,  which  rests  on  the  pulse.  The  short  arm  carries  a  counterpoise,  d,  so  as  exactly 
to  balance  the  long  arm.  The  long  arm  has  fixed  to  it  at  r  a  vertical  rod  provided  with  teeth,  h, 
which  is  pressed  against  a  toothed  wheel  firmly  fixed  on  the  axis  of  the  very  light  writing  lever,  e,f, 
which  is  supported  between  two  uprights,  q,  fixed  to  the  opposite  end  of  the  basal  plate,  G,  G.  The 
■writing  lever  is  equilibrated  by  means  of  a  light  weight.  The  writing  needle,  k,  is  fixed  by  a  joint 
to  e,  and  it  writes  on  the  plate,  t.     The  first  mentioned 

lever,  d,  r,  carries  a  shallow  cup,  Q,  just  above  the  pad,  FiG.  78. 

into  which  weights  may  be  put  to  press  on  the  pulse. 
In  this  instrument  the  weight  can  be  measured  and 
varied ;  the  writing  lever  moves  vertically,  and  not  in 
a  curve  as  in  Marey's  apparatus,  which  greatly  facili- 
tates the  measuring  of  the  curves  (Fig.  77). 

Other  sphygmographs  are  used,  both  in  this  country 
and  abroad,  including  that  of  Sommerbrodt,  which  is 
a  complicated  form  of  Marey's  sphygmograph,  and 
those  of  Pond  and  Mach. 

In  every  pulse  curve — sphygmogram 
or  arteriogram — we  can  distinguish  the 
ascending  part  (ascent)  of  the  curve,  the 
apex,  and  the  descending  part  (descent). 
Secondary  elevations  scarcely  ever  occur  in 
the  ascent,  which  is  usually  represented  by  a 


Normal  pulse  curve  of  the  radial  artery,  obtained 
by  the  angiograph  writing  upon  a  plate  at- 
tached to  a  vibrating  tuning-fork.  Each  double 
vibration  ^  0.01613  sec. 


Fig.  80. 


Fig.  79. 


Gas  Sphygraoscope  of  S.  Mayer. 


Haemautographic  curve  of  the  posterior 
tibial  artery  of  a  dog.  P,  primary 
pulse  wave  ;  R,  dicrotic  wave ;  e,  e, 
elevations  due  to  elasticity. 

Straight  line,  while  they  are  always  present  in  the  descent.  Such  elevations 
occurring  in  the  descent  are  called  catacrotic,  and  those  in  the  ascent,  ana- 
crotic. When  the  recoil  elevation  or  dicrotic  wave  occurs  in  a  well-marked  form 
in  the  descent,  the  pulse  is  said  to  be  dicrotic,  and  when  it  occurs  twice,  tricrotic. 


144  THE    rULSE    CURVE. 

Measuring  Pulse  Curves. — If  the  smoked  surface  on  which  the  tracing  is  inscribed  is  moved 
at  a  uniform  rate  tiy  means  of  the  clockwork,  then  the  height  and  length  of  the  curve  are  measured 
by  means  of  an  ordinary  rule.  If  we  know  the  rate  at  which  the  paper  was  moved,  then  it  is  easy 
to  calculate  the  duration  of  any  event  in  the  curve. 

The  curve  may  be  recorded  on  a  plate  of  glass  fixed  to  a  tuning-fork  kept  in  vibration.  Every 
part  of  the  curve  shows  little  elevations  (whose  rate  of  vibration  is  known  beforehand).  All  that  is 
reiiuiretl  is  to  count  the  number  of  vibrations  in  order  to  ascertain  the  duration  of  any  part  of  the 
curve  (Fig.  78). 

Gas  Sphygmoscope. — A  small  metallic  or  glass  capsule  (Fig.  79),  provided  with  an  inlet  and 
an  outlet  tube,  and  closed  below  Ijy  a  fine  membrane,  is  placed  over  an  artery.  The  inlet  tube  is 
connected  to  a  gas  supply,  and  the  outlet  to  a  rat-tail  gas  burner  (/>).  The  gas  jet  responds  to  every 
pulse  beat.     C/erinac  f>hotoj:;rtiplted  a  beam  of  light  set  in  motion  by  the  movements  of  the  pulse. 

Haemautography. — Expose  a  large  artery  of  an  animal,  and  divide  it  so  that  the  stream  of 
blood  issuing  from  it  strikes  against  a  piece  of  paper  drawn  in  front  of  the  blood  stream.  The  curve 
so  obtained  (Fig.  80)  shows,  in  addition  to  the  primary  wave,  P,  a  distinct  dicrotic  wave,  R,  and 
slight  vibrations,  e,  e,  due  to  the  variations  in  the  elasticity  of  the  arterial  wall,  which  shows  that 
the  movements  occur  in  tiie  blood  itself,  and  are  communicated  as  waves  to  the  arterial  wall.  Hy 
estimating  the  amount  of  blood  in  the  various  parts  of  the  curve,  we  obtain  a  knowledge  of  the 
amount  of  blood  discharged  by  the  divided  artery  during  the  systole  and  diastole  [i.e.,  the  narrowing 
and  dilatation)  of  the  artery — the  ratio  is  7  :  10.  Thus  in  the  tatil  of  time,  during  arterial  dilata- 
tion, rather  more  than  t-Mice  as  much  blooil  flows  out  as  compared  with  what  occurs  during  arterial 
contraction. 

67.  PULSE  TRACING  OR  SPHYGMOGRAM.— [The  Pulse.— With 
each  systole  of  the  heart,  a  certain  quantity  of  blood  is  forced  into  the  already 
filled  and  partially  distended  arteries,  the  resistance  in  the  vessels  is  lowest  between 
the  pulsations,  and  at  this  time  the  arterial  tubes  are  somewhat  flattened,  but  with 
each  systole  of  the  left  ventricle  the  pulse  wave,  or  rather  the  liquid  pressure  within 

the  vessel,  is  increased,  thus  forcing 
Fig.  81.  the  artery  back  into  the  circular  form. 

"  The  change  of  shape,  from  the  flat- 
tened condition  impressed  upon  the 
vessel  by  the  finger  or  the  sphygmo- 
graph  lever,  to  the  round  cylindrical 
shape  which  it  assumes  under  the  dis- 
tending force  of  the  blood  within  it, 
constitutes    the  pulse  "  and  it    in- 

Sphygmogram  of  radi.il  artery:    pressure    2  oz.     Each         dicatCS    the    degree    and   duratioH    of 
pare  01  the  curve  between  the  base  of  one  up-stroke  ,  .  ,"  .  , 

and  the  base  of  the  next  up-stroke  corresponds  to  a        the       increased         preSSUre         in        the 

beats°aXari'of  a°s[xi'h."'''  '''^"'''  '^°''"  ^'"^ ''"''"''      arterial  System  caused  by  the  ventri- 
cular systole  {Broadbent').'\ 
Analysis. — A    sphygmogram    or    pulse  tracing   consists   of  a   series  of 
curves  (Fig.  81)  each  of  whicii  corresponds  with  one  beat  of  the  heart.     Each 
pulse  curve  consists  of — 

1.  The  line  of  ascent  {a  to  b  in  Fig.   81). 

2.  The  apex  (P  in  Fig.   Zt^,  and  b  in  Fig.   81). 

3.  The  line  of  descent  (^  to  k). 

(i)  The  line  of  ascent,  up-stroke,  or  percussion  stroke,  is  nearly  vertical, 
and  occurs  during  the  dilatation  of  the  artery  produced  by  the  systole  of  the  left 
ventricle,  when  the  aortic  valves  are  forced  open  and  the  ventricular  contents  are 
projected  into  the  arterial  system.  [The  ascent  is  nearly  vertical,  but  in  some 
cases,  where  the  ventricle  contracts  very  suddenly,  as  occasionally  happens  in 
aortic  regurgitation,  it  is  quite  vertical  (Fig.   85).] 

(2)  The  apex  or  percussion  ^vave  in  a  normal  pulse  is  pointed. 
.(3)  The  line  of  descent  is  gradual,  and  corresponds  to  the  diminution  of 
diameter  or  contraction  of  the  artery.  It  is  interrupted  by  two  cotnpletely  distinct 
elevations  ox  secondary  waves.  Such  elevations  are  called  "  catacrotic."  The 
more  distinct  of  the  two  occurs  as  a  well-marked  elevation  about  the  middle  of  the 
descent   (R  in   Fig.  83  and  /  in  Fig.  81)  ;  it  is  called  the  dicrotic  wave,  or. 


ORIGIN    OF   THE   DICROTIC    WAVE.  145 

with  reference  to  its  mode  of  origin,  the  "  recoil  wave.''''  [As  the  descent  cor- 
responds to  the  time  when  blood  is  flowing  out  of  the  arteries  at  the  periphery 
into  the  capillaries,  its  direction  will  depend  on  the  rapidity  of  the  outflow.  Thus 
it  will  be  more  rapid  in  paralysis  of  the  arterioles  and  very  rapid  in  aortic  regurgi- 
tation, where,  of  course,  much  of  the  blood  flows  backward  into  the  left  ventricle 
(Fig.  85).  In  this  case,  the  artery  will  recoil  suddenly  from  under  the  finger  or 
pad  of  the  instrument,  and  this  constitutes  the  "  pulse  of  empty  arteries."] 

The  dicrotic  ■wave,  or  recoil  wave,  corresponds  to  the  time  following  the 
closure  of  the  aortic  valves,  and  is  preceded  in  the  descent  by  a  slight  depression, 
the  aortic  notch. 

[The  tidal  wave,  or  pre-dicrotic,  occurs  between  the  apex  and  the  dicrotic 
wave  (Fig.  81,  rt^).  It  occurs  on  the  descent,  and  during  the  contraction  of 
the  ventricle.  The  tidal  wave  is  best  marked  in  a.  hard  pulse,  i.e.,  where  the 
blood  pressure  is  high,  so  that  it  is  usually  well  marked  in  cirrhotic  disease  of  the 
kidney,  accompanied  by  hypertrophy  of  the  left  ventricle.] 

[In  some  cases,  e.g.,  mitral  regurgitation,  the  pre-dicrotic  wave  may  be  present  in  some  pulse 
beats  and  absent  in  others  (Fig.  82),  where  the  tidal  wave  is  present  in  the  largest  pulse,and  absent 
in  the  others,  while  the  base  line  is  uneven.  In  mitral  stenosis  the  amount  of  blood  discharged 
into  the  left  ventricle  frequently  varies,  hence  the  variations  in  the  characters  of  the  arterial  pulse.] 

There  may  be  other  secondary  waves  in  the  lower  part  of  the  descent. 
[Respiratory  or  Base  Line. — If  a  line  be  drawn  so  as  to  touch  the  bases  of 

Fig.  82. 


Irregular  pulse  of  mitral  regurgitation. 

all  the  up-strokes,  we  obtain  a  straight  line,  hence  called  by  this  name.     The 
base  line  is  altered  in  disease  and  during  forced  respiration  (§  74).] 

The  pulse  curve  indicates  the  variations  of  pressure  which  the  blood  exerts  on  the  arterial  walls, 
for  the  lever  rises  and  falls  with  the  pressure,  hence  v.  Kries  calls  it  the  "  pressure  pulse." 

68.  ORIGIN  OF  THE  DICROTIC  WAVE.— The  dicrotic  or  recoil 
wave,  which  is  always  present  in  a  normal  pulse,  is  caused  thus :  During  the 
ventricular  systole  a  mass  of  blood  is  propelled  into  the  already  full  aorta,  where- 
by a  positive  wave  is  rapidly  transmitted  from  the  aorta  throughout  the  arterial 
system,  even  to  the  smallest  arterioles,  in  which  this  primary  wave  is  extinguished. 
As  soon  as  the  semilunar  valves  are  closed,  and  no  rhore  blood  flows  into  the 
arterial  system,  the  arteries,  which  were  previously  distended  by  the  mass  of  blood 
suddenly  thrown  into  them,  recoil  or  contract,  so  that  in  virtue  of  the  elasticity 
(and  contractility)  of  their  walls,  they  exert  a  counter-pressure  upon  the  column 
of  blood,  and  thus  the  blood  is  forced  onward.  There  is  a  free  passage  for  it 
toward  the  periphery,  but  toward  the  centre  (heart)  it  impinges  upon  the  already 
closed  semilunar  valves.  This  develops  a  new  positive  wave,  which  is  propagated 
peripherally  through  the  arteries,  where  it  disappears  in  their  finest  branches.  In 
those  cases  where  there  is  sufficient  time  for  the  complete  development  of  the 
pulse  curve  (as  in  the  short  course  of  the  carotids,  and  in  the  arteries  of  the 
upper  arm,  but  not  in  those  of  the  lower  extremity,  on  account  of  their  length), 
a  second  reflected  wave  may  be  caused  in  exactly  the  same  way  as  the  first.  Just 
as  the  pulse  occurs  later  in  the  more  peripherally  placed  arteries  than  in  those 
near  the  heart,  so  the  secondary  wave  reflected  from  the  closed  aortic  valves 
10 


146 


CHARACTERS    OF   THE    DICROTIC    WAVE. 


must  appear  later  in  the  peripheral  arteries.  Both  kinds  of  waves,  the  pri- 
mary pulse  wave,  the  secondary,  and  eventually  even  the  tertiary  reflected  wave, 
arise  in  the  same  place,  and  take  the  same  course,  and  the  longer  the  course 
they  have  to  travel  to  any  part  of  the  arterial  system,  the  later  they  arrive  at 
their  destination. 

Fig.  83. 


XII  XIII  XIV  XV 

I,  II,  111.  sphyemograms  ot  carotid   arter>- :    IV,  axillary  ;   V  to  IX,   radial;   X,  dicrotic  radial  pulse;    XI.  XII. 
crural:   XIII,  posterior  tibial;    XIV,  XV,  pedal.     In  all  the  curves  P  indicates  apex  ;    R,  dicroti. 
elevations  due  to  elasticity ;  K.  elevation  caused  by  the  closure  of  the  semilunar  valves  of  the  aorta. 


tic  wave  ;  e,  e. 


[The  conditions  which  favor  dicrotism  are  low  blood  pressure  and  a  rapid,  sharp  cardiac  con- 
traction. When  the  blood  pressure  is  low,  there  is  less  resistance  to  the  inflow  of  blood  at  the 
aorta  from  the  left  ventricle,  so  that  its  systole  occurs  sharply,  forcing  on  the  blood  and  distend- 
ing the  arterial  walls.  The  elastic  coats  rebound  on  the  contained  blood,  and  thus  start  a  wave 
from  the  closed  semilunar  valves.] 


CONDITIONS    INFLUENCING   ARTERIAL   TENSION, 


147 


The  following  points  regarding  the  dicrotic  wave  have  been  ascertained  experi- 
mentally, chiefly  by  Landois  : — 

1.  The  dicrotic  wave  occurs  later  in  the  descending  part  of  the  curve,  the  further 
the  artery  experimented  upon  is  distant  from  the  heart.  Compare  the  curves. 
Fig.  83. 

The  shortest  accessible  course  is  that  of  the  carotid;  where  the  dicrotic  wave  reaches  its 
maximum  0.35  to  0.37  sec.  after  the  beginning  of  the  pulse.  .  In  the  upper  extremity  the  apex 
of  the  dicrotic  wave  is  0.36  to  0.38.  to  0.40  sec.  after  the  beginning  of  the  pulse  beat.  The 
longest  course  is  that  of  the  arteries  of  the  lower  extremity.  The  apex  of  the  dicrotic  wave 
occurs  0.45  to  0.52  to  0.59  sec.  after  the  beginning  of  the  curve.  It  varies  with  the  height  of 
the  individual. 

2.  The  dicrotic  elevation  in  the  descent  is  lower,  and  is  less  distinct,  the  further 
the  artery  is  situated  from  the  heart,  so  that  the  longer  the  distance  which  the 
wave  has  to  travel  the  less  distinct  it  becomes. 

3.  It  is  best  marked  in  a  pulse  where  the  primary  pulse  wave  is  short  and 
energetic.  It  is  greatest  relatively  when  the  systole  of  the  heart  is  short  and 
energetic. 

4.  It  is  better  marked  the  lower  the  tension  of  the  blood  within  the  arteries  [and 
is  best  developed  in  a  soft  pulse].  In  Fig.  ^i,  IX  and  X  were  obtained  when  the 
tension  of  the  arterial  was  low ;  V  and  VI,  medium;  and  VII  with  high  tension. 

Conditions  influencing  Arterial  Tension. — It  is  diminished  at  the  beginning  of  inspiration 
[\  74),  by  hemorrhage,  stoppage  of  the  heart,  heat,  an  elevated  position  of  parts  of  the  body,  amyl 
nitrite,  nitro-glycerine,  and  the  nitrites  generally.     [Both  drugs  accelerate  the  pulse  beats  and 

Fig.  84. 


Fig.  8";. 


Pulse  tracings.     A,  normal ;  A',  one  minute  after  inhalation  ot  amyl  nitrite ;  B,  normal ;  B',  after  a  dose  ot  nitro- 
glycerine {Stirling,  after  Murrell). 

produce  marked  dicrotism;  with  amyl  nitrite  the  full  effect  is  obtained  in  from  15  to  20  sec.  after 
the  inhalation  of  the  dose  (Fig.  84,  A,  A^),  but  with  nitro-glycerine  not  until  6  or  7  min.  (Fig.  84, 
B,  W)  and  in  the  latter  case  the  effects  last  longer.]  It  is  increased  at  the  beginning  of  expiration, 
by  accelerated  action  of  the  heart,  stimulation  of  vaso-motor  nerves,  diminished  outflow  of  blood  at 
the  periphery,  and  by  inflammatory  congestion  by  certain  poisons,  as  lead ;  compression  of  other 
large  arterial  trunks,  action  of  cold  and  electricity  on  the  small  cutaneous  vessels,  and  by  impeded 
outflow  of  venous  blood.  When  a  large  arterial  trunk  is  ex- 
posed, the  stimulation  of  the  air  causes  it  to  contract,  resulting 
in  an  increased  tension  within  the  vessel.  In  many  diseased 
conditions  the  arterial  tension  is  greatly  increased — \_e-g-i  in 
Bright's  disease,  where  the  kidney  is  contracted  ("  granular  "), 
and  where  the  left  ventricle  is  hypertrophied] . 

In  all  these  conditions  increased  arterial  tension  is  indicated 
by  the  dicrotic  wave  being  less  high  and  less  distinct,  while 
with  diminished  arterial  tension  it  is  a  larger  and  appar- 
ently more  independent  elevation.  Moens  has  shown  that 
the  time  between  the  primary  elevation  ^nd  dicrotic  wave  in- 
creases with  increase  in  the  diameter  of  the  tube,  with  diminu- 
tion of  its  thickness,  and  when  its  coefficient  of  elasticity 
diminishes. 

[The  dicrotic  wave  is  absent  or  but  slightly  marked  in  cases 
of  atheroma  and  in  aortic  regurgitation  (Fig.  85).     In  this  figure  observe  also  the  vertical  character  ot 
the  up-stroke.] 

Elastic  Elevations. — Besides   the  dicrotic  wave,  a  number   of  small  less- 
marked  elevations  occur  in  the  course  of  the  descent  in  a  sphygmogram  (Fig. 


Aortic  Regurgitation. 


148  DICROTIC    PULSE. 

83,  e,  e).  These  elevations  are  caused  by  the  elastic  tube  being  thrown  into  vibra- 
tions by  the  rapid,  energetic  pulse  wave,  just  as  an  elastic  membrane  vibrates  when 
it  is  suddenly  stretched.  The  artery  also  executes  vibratory  movements  when  it 
passes  suddenly  from  the  distended  to  the  relaxed  condition.  These  small  eleva- 
tions in  the  pulse  curve,  caused  by  the  elastic  vibrations  of  the  arterial  wall,  are 
called  "elastic  elevations  "  by  Landois. 

(i)  The  elastic  vibrations  increase  in  number  in  one  and  the  same  artery 
with  the  degree  of  tension  of  the  elastic  arterial  wall.  A  very  high  tension  occurs 
in  the  cold  stage  of  intermittent  fever,  in  which  case  these  elevations  are  well 
marked. 

(2)  If  the  tension  of  the  arterial  wall  be  greatly  diminished,  these  elevations 
may  disappear,  so  that,  while  diminished  tension  favors  the  production  of  the 
dicrotic  wave,  it  acts  in  the  opposite  way  with  reference  to  the  "  elastic  elevations." 
(3)  In  diseases  of  the  arterial  walls  affecting  their  elasticity,  these  elevations  are 
either  greatly  diminished  or  entirely  abolished.  (4)  The  further  the  arteries  are 
distant  from  the  heart,  the  higher  are  the  elastic  elevations.  (5)  When  the  mean 
pressure  within  the  arteries  is  increased  by  preventing  the  outflow  of  blood  from 
them,  the  elastic  vibrations  are  higher  and  nearer  the  apex  of  the  curve.  (6)  They 
vary  in  number  and  length  in  the  pulse  curves  obtained  from  different  arteries  of 
the  body. 

When  the  arm  is  held  in  an  upright  position,  after  five  minutes  the  blood  vessels  empty  themselves 
and  collapse,  while  the  elasticity  of  the  arteries  is  diminished. 

69.  DICROTIC  PULSE. — Sometimes  during  fever,  especially  when  the  temperature  is  high,  a 
dicrotic  pulse  may  be  felt,  each  pulse  beat,  as  it  were,  being  composed  of  two  beats  (Fig.  83,  X),  one 
beat  being  large  and  the  other  small,  and  more  like  an  after  beat.  Both  beats  correspond  to  one 
beat  of  the  heart.  The  two  beats  are  quite  distinguishable  by  the  touch.  The  phenomenon  is 
only  an  exaggerated  condition  of  what  occurs  in  a  normal  pulse.     The  sensible  second  beat  is  nothing 

_    •.  Fig.  86. 


Development  of  the  Pulsus  dicrotus — P.  caprizans  ;  P.  monocrotus. 

more  than  the  greatly  increased  dicrotic  elevation,  which,  under  ordinary  conditions,  is  not  felt  by 
the  finger. 

Condi;ions. — The  occurrence  of  a  dicrotic  pulse  is  favored  (i)  by  a  short  primary  pulse  wave, 
as  in  fevers,  where  the  heart  beats  rapidly. 

•  (2)  'By  diminished  arterial  tension.  A  short  systole  and  diminished  arterial  blood  pressure  are 
the  most  favorable  conditions  for  causing  a  dicrotic  pulse.  [So  that  dicrotism  is  best  marked  in  a 
soft  pulse.]  The  double  beat  may  be  felt  only  at  certain  parts  of  the  arterial  system,  while  at  other 
parts  only  a  single  beat  is  felt.  A  favorite  site  is  the  radial  artery  of  one  or  other  side,  where  condi- 
tions favorable  to  its  occurrence  appear  to  exist.  This  seems  to  be  due  to  a  local  diminution  of  the 
blood  pressure  in  this  area,  owing  to  the  paralysis  of  its  vasomotor  nerves  {Landois).  If  the 
tension  be  increased  by  compressing  other  large  arterial  trunks  or  the  veins  of  the  part,  the  double 
beat  becomes  a  simple  pulse  beat.  The  dicrotic  pulse  in  fever  seems  to  be  due  to  the  increased 
temperature  (39°  to  40°  C),  whereby  the  artery  is  more  distended,  and  the  heart  beat  is  shorter 
and  more  prompt. 

(3)  It  is  absolutely  necessary  that  the   elasticity  of  the  arterial  wall  be  normal.     The  dicrotic 
pulse  does  not  occur  in  old  persons  with  atheromatous  arteries. 

Monocrotic  Pulse.— In  Fig.  86,  A,  B,  C,  we  observe  a  gradual  passage  of  the  normal  radial 
curve,  A,  mto  the  dicrotic  beat,  B,  and  C,  where  the  dicrotic  wave,  r,  appears  as  an  independent 


CONDITIONS   AFFECTING   THE    PULSE    RATE. 


149 


Hyperdicrotic  Pulse. 


elevation.     If  the  frequency  of  the  pulse  increases  more  and  more  in  fever,  the  next  following 

pulse  beat  may  occur  in  the  ascending  part  of  the  dicrotic  wave,  D,  E,  F,  and  it  may  even  occur 

close  to  the  apex,  G  (P.   caprizans).     If  the  next  following  beat  occurs  in  the  depression,  i, 

between  the  primary  elevation,  p,  and  the 

dicrotic  elevation,  r,  the  latter  entirely  dis-  •^^*^-  °1- 

appears,  and  the  curve,  H,  assumes  what 

Landois  calls  the  "  monocrotic  type." 

[Degrees  of  Dicrotism. — When  the 
aortic  notch  reaches  the  respiratory  or  base 
line,  the  tidal  wave  having  disappeared, 
the  pulse  is  said  to  be  fully  dicrotic.  When 
the  aortic  notch  falls  below  the  base  line, 
i.  e.,  below  where  the  up-stroke  begins,  the  pulse  is  said  to  be  hyperdicrotic  (Fig.  87).  This 
form  occurs  during  high  fever  (104°  F.),  and  is  usually  a  grave  sign,  indicating  exhaustion  and  the 
need  for  stimulants.  ] 

70.  CHARACTERS  OF  THE  PULSE.— [The  three  factors  concerned  in  the  produc- 
tion of  the  pulse  are,  (i)  the  action  of  the  heart,  (2)  the  elasticity  of  the  large  vessels.  (3)  the 
resistance  in  the  small  arteries  and  capillaries.  Any  or  all  or  several  of  these  factors  may  be 
modified.]  (i)  Frequency. — According  as  a  greater  or  less  number  of  beats  occurs  in  a  given 
time,  e.  g.,  per  minute,  the  pulse  is  said  to  be  frequent  or  infrequent.  The  normal  rate,  in  man 
=  71  per  minute,  and  somewhat  more  in  the  female;  in  fever  it  may  exceed  120  (250  have  been 
counted  by  Bowles),  while  in  other  diseases  it  may  fall  to  40,  and  even  10  to  15;  but  such 
cases  are  rare,  and  are  probably  due  to  an  affection  of  the  cardiac  nerves  (§  41).  The  frequency 
of  the  pulse  is  usually  increased  when  the  respirations  are  deeper,  but  not  more  numerous,  i.  e., 
rapid  shallow  respirations  do  not  affect  the  frequency  of  the  pulse,  but  deep  respirations  do.  [The 
frequency  may  be  regular  or  irregular  with  regard  to  time.] 

(2)  Celerity  or  Rapidity. — If  the  pulse  wave  is  developed,  so  that  the  distention  of  the  artery 
slowly  reaches  its  height,  and  the  relaxation  also  takes  place  gradually,  we  have  the  p.  tardus  or 
slow  or  long  pulse;  the  opposite  condition  gives  rise  to  the  p.  celer  or  quick  or  short  pulse.  The 
rapidity  of  the  pulse  is  increased  by  quick  action  of  the  heart,  power  of  expansion  of  the  arterial 
walls,  easy  efflux  of  blood  owing  to  the  dilatation  of  the  small  arteries,  and  by  nearness  to  the  heart. 
[The  quickness  has  reference  to  a  single  pulse  beat,  ihtfreqiiency  to  a  nutnber  of  beats.]  In  a  quick 
pulse,  the  curve  is  high  and  the  angle  at  the  apex  is  acute,  while  in  a  slow  pulse  the  ascent  is  low 
and  the  angle  at  the  apex  is  large. 

(3)  Conditions  Affecting  the  Pulse  Rate. — Frequency  in  Health. — In  man  the  normal 
pulse  rate  ^71  to  72  beats  per  minute,  in  the  female  about  80.  In  some  individuals  the  pulse 
rate  may  be  higher  (90  to  100),  in  others  lower  (50),  and  such  a  fact  must  be  borne  in  mind. 

{a)  Age:— 

Beats  per 
Minute. 

5  years, 94  to  90 

10      "' about  90 

10  to  15  years 78 

15  to  20     "        70 

20  to  25      "        70 


Beats  per 
Minute. 
Newly  born,  ,    .    .     130  to  140 

1  year, 120  to  130 

2  years, 105 

3  "       100 

4  "       97 


Beats  per 
Minute 

25  to  50  years,     ....  70 

60  years, 74 

80     "      79 

80  to  90  years,    .    .  over  80 


{b')  The  length  of  the  body  has  a  certain  relation  to  the  frequency  of  the  pulse.     The  following 
results  have  been  obtained  by  Czarnecki  from  the  formulae  of  Volkmann  and  Rameaux : — 


Length  of  Body 
in  10  cm. 

140  to  150, 69 

150  to  160, 67 

160  to  170, 65 

170  to  180, 63 

Above  180, 60 


Pulse. 
Calculated.     Observed. 

74 
68 


65 
64 
60 


Length  of  Body  Pulse. 

in  10  cm.  Calculated.     Observed. 

80  to    90, 90  103 

90  to  100, 86  91 

IOC  to  no 81  87 

no  to  120, 78  84 

120  to  130, 75  78 

130  to  140, 72  86 

(c)  The  pulse  rate  is  increased  by  muscular  activity,  by  every  increase  of  the  artei-ial  blood 
pressure,  by  taking  of  food,  increased  temperature ,  painful  sensations,  by  psychical  disturbances,  and 
\in  extreine  debility^.  Increased  heat,  fever,  or  pyrexia  increases  the  frequency,  and  as  a  rule  the 
increase  varies  with  the  height  of  the  temperature.  [Dr.  Aitken  states  that  an  increase  of  the  tem- 
perature of  1°  F.  above  98°  F.  corresponds  with  an  increase  of  ten  pulse  beats  per  minute;  thus — 


Temp.  F. 
98°    . 

99°    . 
100°    . 


Pulse  Rate. 
.     .     60 
-     .     70 
.     .     80 


Temp.  F. 
101°  . 
102°  . 
103°  . 


Pulse  Rate. 
.    .     90 
.     .  100 
.     .  1 10 


Temp.  F. 
104°  . 
105°  . 
106°  . 


Pulse  Rate. 
.     .  120 

.     .  140 


150 


VARIATIONS    IN    THE    CHARACTERS   OF   THE    PULSE. 


This  is  merely  an  approximate  estimate.]  It  is  more  frequent  when  a  person  is  standing  than  when 
he  lies  down.  Music  accelerates  the  pulse  and  increases  the  blood  pressure  in  dogs  and  men. 
Increased  barometric  pressure  diminishes  the  frequency. 

The  Variation  of  the  Pulse  Rate  during  the  Day. — 3  to  6  a.m.  =:  61  beats;  8  to  11^  a.m. 
=  74.     It  then  falls  toward  2  r.M. ;  toward  3  (at  dinner  time)  another  increase  takes  place  and 
goes  on  until  6  to  8  i-.M.  =^  70;  and  it  falls  until  midnight  rT=  54.     It  then  rises  again  toward  2 
A.M.,  when  it  soon  fnlls  again,  and  afterward  rises  as  before  toward  3  to  6  a.m. 
[Pulse  Rate  in  Animals. — {Colin.)'\ 

Per  Mil).  Per  Min. 

Lioness 68 

Tiger 74 

Sheep, 70-80 

Goat, 70-80 

Leopard 60 

Wolf  (female),   .    .  96 

Hyivna, 55 


Elephant, 25-28 

Camel 28-32 

Giraffe, 66 

Horse, 36-40 

Ox 45-50 

Tapir, 44 

Ass, 46-50 

Pig 70-80 

Lion, 40 


Dog, 90-100 

Cat, 120-140 


Rabbit,    .  . 

Mouse,    .  . 

Goose,     .  . 

Pigeon,  .  . 

Hen,  .    .  . 

Snake,    .  . 

Carp,  .    .  , 

Frog,  .    .  . 
Salamander, 


Per  Min. 

.  .  120-150 
120 
no 
136 

.  .     140 

•  •  24 
.  .  20 
.  .     80 

•  •  77 
(4)  Variations  in  the  Pulse  Rhythm  ( AUorhythmia). — On  applying  the  fingers  to  the  normal 

pulsfe,  we  feel  beat  after  beat  occurring  at  apparently  equal  intervals.  Sometimes  in  a  normal  series 
a  beat  is  omitted  =  pulsus  intermittens,  or  intermittent  pulse.  [In  feeling  an  intermittent  pulse, 
we  imagine  or  have  the  impression  that  a  beat  is  omitted.  This  may  be  due  to  a  reflex  arrest  of  the 
ventricular  contraction,  caused  by  digestive  derangement,  in  which  case  it  has  no  great  significance; 
but  if  it  be  due  to  failure  of  the  ventricular  action,  intermittent  pulse  is  a  serious  symptom,  being 
frequently  present  when  the  muscular  walls  are  degenerated.]  At  other  times  the  beats  become 
smaller  and  smaller,  and  after  a  certain  time  begin  as  large  as  before  ^=  p.  myurus.  When  an 
extra  beat  is  intercalated  in  a  normal  series  =  p.  intercurrens.  The  regular  alternation  of  a  high 
and  a  low  beat  =  p.  alternans  (Fig.  88).     In  the  p.  bigeminus  of  Traube  the  beats  occur  in 

Fic.  88. 


Pulsus  alternans. 


pairs,  so  that  there  is  a  longer  pause  after  every  two  beats.  Traube  found  that  he  could  produce  this 
form  of  pulse  in  curarized  dogs  by  stopping  the  artificial  respiration  for  a  long  time.  The  p. 
trigeminus  and  quadrigeminus  occur  in  the  same  way,  but  the  irregularities  occur  after  every 
third  and  fourth  beat.  Knoll  found  that  in  animals  such  irregularities  of  the  pulse  were  apt  to 
occur,  as  well  as  great  irregularity  in  the  rhythm  generally,  when  there  is  much  resistance  to  the 
circulation,  and  consequently  the  heart  has  great  demands  upon  its  energy.  The  same  occurs  in 
man  when  an  improper  relation  exists  between  the  force  of  the  cardiac  muscle  and  the  work  it  has 
to  do  {Rtegel).     Complete  irregularity  of  the  heart's  action  is  called  arhythmia  cordis. 

71.  VARIATIONS  IN  THE  CHARACTERS  OF  THE  PULSE.— Compressibility. 
— The  relative  strength  or  compressibility  of  the  pulse  (p.  fortis  and  debilis),  ;".  e.,  whether  the 
pulse  is  strong  or  weak,  is  estimated  by  the  weight  which  the  pulse  is  able  to  raise.  A  sphygmo- 
graph,  provided  with  an  index  indicating  the  amount  of  pressure  exerted  upon  the  spring  pressing 
upon  the  artery,  may  be  used  (Fig.  73).  In  this  case,  as  soon  as  the  pressure  exerted  upon  the 
artery  overcomes  the  pulse  beat,  the  lever  ceases  to  move.  The  -weight  employed  indicates  the  strength 
of  the  pulse.  [The  finger  may  be,  and  generally  is  used.  The  finger  is  pressed  upon  the  artery 
until  the  pulse  beat  in  the  artery  beyond  the  point  of  pressure  is  obliterated.  In  health  it  requires 
a  pressure  of  several  ounces  to  do  this.  Handheld  Jones  uses  a  sphygmometer  for  this  purpose. 
It  is  constructed  like  a  cylindrical  letter  weight,  and  the  pressure  is  exerted  by  means  of  a  spiral 
spring  which  has  been  carefully  graduated.]  The  pulse  is  hard  or  soft  when  the  artery,  according 
to  the  mean  blood  pressure,  gives  a  feeling  of  greater  or  less  resistance  to  the  finger,  and  this  quite 
independent  of  the  energy  of  the  individual  pulse  beats  (p.  durus  and  mollis).  In  estimating  the 
tension  of  the  artery  and  the  pulse,  i.  e.,  whether  it  is  hard  or  soft,  it  is  important  to  observe  whether 
the  artery  has  this  quality  only  during  the  pulse  wave,  i.  e.,  if  it  is  hard  during  diastole,  or  whether 
It  IS  hard  or  soft  during  the  period  of  rest  of  the  arterial  wall.  All  arteries  are  harder  and  less  com- 
pressible during  the  pulse  beat  than  during  the  period  of  rest,  but  an  artery  which  is  very  hard  during 
the  pulse  beat  may  be  hard  also  during  the  pause  between  the  pulse  beats,  or  it  may  be  very  soft,  as 
in  msufficiency  of  the  aortic  valves.     In  this  case,  after  the  systole  of  the  left  ventricle,  owing  to  the 


THE    PULSE    CURVES    OF    VARIOUS   ARTERIES.  151 

incompetency  of  the  aortic  semilunar  valves,  a  large  amount  of  blood  flows  back  into  the  ventricle, 
so  that  the  arteries  are  thereby  suddenly  rendered  partially  empty.  [The  sudden  collapse  of  the 
artery  gives  rise  to  the  characteristic  "pulse  of  unfilled  arteries"  (Fig.  85).] 

Under  similar  conditions,  the  volume  of  the  pulse  is  obvious  from  the  size  of  the  sphygmogram, 
so  that  we  speak  of  a  large  and  a  small  pulse  (p.  magnus  and  parvus).  Sometimes  the  pulse  is  so 
thready  and  of  such  diminished  volume  that  it  can  scarcely  be  felt.  A  large  pulse  occurs  in  disease 
when,  owing  to  hypertrophy  of  the  left  ventricle,  a  large  amount  of  blood  is  forced  into  the  aorta. 
A  jwa// pulse  occurs  under  the  opposite  condition,  when  a  small  amount  of  blood  is  forced  into  the 
aorta,  either  from  a  diminution  of  the  total  amount  of  the  blood,  or  from  the  aortic  orifice  being 
narrowed  [aortic  stenosis],  or  from  disease  of  the  mitral  valve;  again,  where  the  ventricle  contracts 
feebly,  the  pulse  becomes  small  and  thready. 

Compare  the  two  radials.  Sometimes  the  pulse  differs  on  the  two  sides,  or  it  may  be  absent  on 
one  side.  [The  pulse  wave  in  the  two  radials  is  often  different  when  an  aneurism  is  present  on  one 
side.] 

Angiometer. — Waldenburg  constructed  a  "pulse  clock,"  to  register  the  tension,  the  diameter  of 
the  artery,  and  the  volume  of  the  pulse  upon  a  dial.  It  does  not  give  a  graphic  tracing,  the  results 
being  marked  by  the  position  of  an  indicator. 

72.  THE  PULSE  CURVES  OF  VARIOUS  ARTERIES.— i.  Carotid  (Fig  83,  I,  II, 
III;  Fig.  93,  C  and  C^).  The  ascending  part  is  very  steep — the  apex  of  the  curve  (Fig.  83,  P)  is 
sharp  and  high.  Below  the  apex  there  is  a  small  notch — the  "  aortic  notch  "  (Fig.  83,  K) — which 
depends  on  a  positive  wave  formed  in  the  root  of  the  aorta,  owing  to  the  closure  of  the  aortic  valves, 
and  propagated  with  almost  wholly  undiminished  energy  into  the  carotid  artery.  Quite  close  to  this 
notch,  if  the  curve  be  obtained  with  minimal  friction,  the  first  elastic  vibration  occurs  (Fig.  83,  II,  e). 
Above  the  middle  of  the  descending  part  of  the  curve  is  the  dicrotic  elevation,  R,  produced  by 
the  reflection  of  a  positive  wave  from  the  already  closed  semilunar  valves.  The  dicrotic  wave  is 
relatively  small  on  account  of  the  high  tension  in  the  carotid  artery.  After  this  the  curve  falls 
rapidly,  but  in  its  lowest  third  two  small  elevations  may  be  seen.  Of  these  the  former  is  due  to 
elastic  vibration.  The  latter  represents  a  second  dicrotic  wave  (Fig.  83,  III,  R).  Here  there  is  a 
true  tricrotism,  which  is  more  easily  obtained  from  the  carotid  on  account  of  the  shortness  of  the 
arterial  channel. 

2.  Axillary  Artery  (Fig.  83,  IV).  In  this  curve  the  ascent  is  very  steep,  while  in  the  descent  near 
the  apex  there  is  a  small  (aortic)  elevation,  K,  caused  by  a  positive  wave,  produced  by  the  closure 
of  the  aortic  valves.  Below  the  middle  there  is  a  tolerably  high  dicrotic  elevation,  R,  higher  than 
in  the  carotid  curve ;  because  in  the  axillary  artery  the  arterial  tension  is  less,  and  permits  a  greater 
development  of  the  dicrotic  wave.     Further  on,  two  or  three  small  elastic  vibrations  occur,  e,  e. 

3.  Radial  Artery  (Fig.  78;  Fig.  83,  V  to  X;  Fig.  93,  R  and  RJ.  The  line  of  ascent  (Fig. 
83)  is  tolerably  high  and  sudden — somewhat  in  the  form  of  a  long/".  The  apex,  P,  is  well  marked. 
Below  this,  if  the  tension  be  high,  two  elastic  vibrations  may  occur  (V,  e,  e),  but  if  it  be  low,  only 
one  (VI  to  IX,  e).  About  the  middle  of  the  curve  is  the  well-marked  dicrotic  elevation,  R.  This 
wave  is  least  pronounced  in  a  small  hard  pulse,  and  when  the  artery  is  much  distended  (Fig.  83, 
VII,  Rj) ;  it  is  larger  when  the  tension  is  low  (Fig.  83,  IX,  R), 
and  is  greatest  of  all  when  the  pulse  is  dicrotic  (X,  R).  Two  Fig. 
or  three  small  elastic  elevations  occur  in  the  lowest  part  of  the 
curve. 

4.  Femoral  Artery  (Fig.  83,  XI,  XII).  The  ascent  is 
steep  and  high — the  apex  of  the  curve  is  not  unfrequently 
broad,  and  in  it  the  closure  of  the  aortic  valves  (K)  is  indi- 
cated. The  curve  falls  rapidly  toward  its  lowest  third.  The 
dicrotic  elevation,  R,  occurs  late  after  the  beginning  of  the 
curve,  and  there  are  also  small  elastic  elevations  [e,  e). 

5.  Pedal  Artery  (Fig.  83,  XIV,  XV),  and  Posterior  Tibial 
(Fig.  89  and  Fig.  83,  XIII).     In  pulse  curves  obtained   from         ^-^^^^by^r  angiograph^'upon 
these  arteries,  there  are  well-marked  indications  that  the  appara-  a  vibrating  plate. 

tus  (heart)  producing  the  waves  is  placed  at  a  considerable  dis- 
tance.    The  ascent  is  oblique  and  low — the  dicrotic  elevation  occurs  late.     Two  elastic  vibrations 
(Fig.  83,  XIV,  e,  e)  occur  in  the  descent,  but  they  are  very  close  to  the  apex,  ^jrhile  the  elastic 
vibrations  at  the  lower  part  of  the  curve  are  feebly  marked.     Fig.  89  is  from  the  posterior  tibial. 
When  measured  it  gives  the  following  result : — 

I  to  2 9.5  1 

I    to    '2  20 

^     -^ -  r    I  vibration  is  ^  0.01613  sec. 

.  I  to  4 30.5  I  -5 

[  I  to  6 61     J 

73,  ANACROTISM. — As  a  general  rule,  the  line  of  ascent  of  a  pulse  curve  has  the  form  of 
any,  and  is  nearly  vertical.  The  arterial  walls  are  thrown  into  elastic  vibration  by  the  pulse  beat, 
and  the  number  of  vibrations  depends  greatly  upon  the  tension  of  the  arterial  walls.     The  disten- 


152 


ANACROTISM. 


tion  of  the  artery,  or  what  is  the  same  thing,  the  ascent  of  the  sphygmogram  usually  occurs  so 
ra|>iiily  that  it  is  equal  to  onf  elastic  vibration.  The  elongated  /-shape  of  the  ascent  is  fundament- 
ally just  a  |irolonged  elastic  vibration.  When  the  number  of  vibrations  causing  the  elastic  variation 
is  small,  and  when  the  line  of  ascent  is  prolonged,  two  elevations  occasionally  occur  in  the  line  of 
ascent.  Such  a  condition  may  occur  normally  (Fig.  S3,  V'lII,  at  I  and  2;  X,  at  I  and  2).  When 
a  series  of  closely-placed  elastic  vibrations  occur  in  the  upper  part  of  the  line  of  ascent,  so  that  the 
aoex  appears  dentate  and  forms  an  angle  with  the  line  of  ascent,  then  the  condition  becomes  one 
of  anacrotism  (Fig.  90,  <;,  a),  which,  when  it  is  so  marked,  may  be  characterized  as  pathological. 
Anacrotism  of  the  pulse  occurs  when  the  time  of  the  intlux  of  the  blood  is  longer  than  the  time 
occupied  bv  an  elastic  vibration.      Hence  it  takes  |ilace — 

(i)  In  dilatation  and  hypertrophy  of  the  left  ventricle,  e.g.,  Fig.  90,  A,  a  tracing  from  the 


Anacrotic  radial  curves,     a,  a,  llie  anacrotic  parli. 

radial  artery  of  a  man  suffering  trom  contracted  kidney.  The  large  volume  ol  blood  expelled  with 
each  svstole  requires  a  long  time  to  dilate  the  tense  arteries. 

1 21  When  the  extensibility  of  the  arterial  wall  is  diminished,  even  the  normal  amount  ot 
blood  expelled  from  the  heart  at  every  systole  requires  a  long  time  to  dilate  the  artery.  This  occurs 
in  old  people  where  the  arteries  tend  to  become  rigid,  e.  g.,  in  atheroma.  Cold  also  stimulates  the 
arteries,  so  that  they  become  less  extensile.  Within  one  hour  after  a  tepid  bath,  the  pulse  assumes 
the  anacrotic  form  (Fig.  90,  D)  G.  v.  Liebig). 

(3)  When  the  blood  stagnates  in  consequence  of  great  diminution  in  the  velocity  of  the  blood 
stream,  as  occurs  in  paralyzed  limbs,  the  volume  of  blood  propelled  into  the  artery  at  every  sys- 

Fn:   9r. 


1.  II.  III. 

I,  II.  Ill,  curves  with  anacrotic  elevations  a,  in  insufficiency  ot  the  aortic  valves. 


tole  no  longer  produces  the  normal  distention  of  the   arterial   coats,  and  anacrotic  notches  occur 
(Fig.  90.  B). 

(4)  After  ligature  of  an  artery,  when  blood  slowly  reaches  the  peripheral  part  of  the  vessel 
through  a  relatively  small  collateral  circulation,  it  also  occurs.  If  the  brachial  artery  be  com- 
pressed so  that  the  blood  slowly  reaches  the  radial,  the  radial  pulse  may  become  anacrotic.  It  often 
occurs  in  stenosis  of  the  aorta,  as  the  blood  has  difficulty  in  getting  into  the  aorta  (Fig.  90,  C). 

Recurrent  Pulse. — If  the  radial  artery  be  compressed  at  the  wrist,  the  pulse 
beat  reappears  on  the  distal  side  of  the  point  of  pressure  through  the  arteries  of 
the  palm  of  the  hand  {Janaud,  Neidert).  The  curve  is  anacrotic,  and  the 
dicrotic  wave  is  diminished,  while  the  elastic  elevations  are  increased.  : 


INFLUENCE    OF    RESPIRATION    ON    THE    PULSE    CURVE.  153 

(5)  A  special  form  of  anacrotism  occurs  in  cases  of  well-marked  insufficiency  of  the  aortic 
valves.  Practically,  in  these  cases,  the  aorta  remains  permanently  open.  The  contraction  of  the 
left  auricle  causes  in  the  blood  a  wave  motion,  which  is  at  once  propagated  through  the  open  mouth 
of  the  aorta  into  the  large  blood  vessels.  This  wave  is  followed  by  the  wave  caused  by  the  con- 
traction of  the  hypertrophied  left  ventricle,  but  of  course  the  former  wave  is  not  so  large  as  the 
latter.  In  insufficiency  of  the  aortic  valves,  the  auricular  wave  occurs  before  the  ventricular  wave 
in  the  ascending  part  of  the  curve.  The  auricular  is  well  marked  only  in  the  large  vessels,  for  it 
soon  becomes  lost  in  the  peripheral  vessels.  Fig.  91,  I,  was  obtained  from  the  carotid  of  a  man 
suffering  from  ■well-marked  insufficiency  of  the  aortic  valves,  with  considerable  hypertrophy  of  the 
left  ventricle  and  left  auricle.  The  ascent  is  steep,  caused  by  the  force  of  the  contracting  heart.  In 
the  apex  of  the  curve  are  two  projections;  A  is  the  anacrotic  auricular  wave,  and  V  is  the  ventricu- 
lar wave.  Fig.  91,  II,  is  a  curve  obtained  from  the  subclavian  artery  of  the  same  individual.  In 
the  femoral  artery  the  auricular  projection  is  only  obtained  when  the  friction  of  the  writing  style  is 
reduced  to  the  minimum,  and  when  it  occurs  it  immediately  precedes  the  beginning  of  the  ascent 
(Fig.  86,  III,  a).  The  pulse  curve,  in  cases  of  aortic  insufficiency,  is  also  characterized  by  (i) 
its  considerable  height ;  (2)  the  rapid  fall  of  the  lever  from  the  apex  of  the  curve,  because  a  large 
part  of  the  blood  which  is  forced  into  the  aorta  regurgitates  into  the  left  ventricle  when  the  ventricle 
relaxes;  (3)  not  unfrequently  a  projection  occurs  at  the  apex,  due  to  the  elastic  vibration  of  the 
tense  arterial  wall;  (4)  the  dicrotic  wave  (R)  is  small  compared  with  the  size  of  the  curve  itself, 
because  the  pulse  wave,  owing  to  the  lesion  of  the  aortic  valves,  has  not  a  sufficiently  large  surface 
to  be  reflected  from  (Fig.  85).  The  great  height  of  the  curve  is  explained  by  the  large  amount  of 
blood  projected  into  the  aortic  system  by  the  greatly  hypertrophied  and  dilated  ventricle. 

74.  INFLUENCE  OF  RESPIRATION  ON  THE  PULSE 
CURVE. — The  respiratory  movements  influence  the  pulse  (i)  in  a  purely- 
physical  way.  Stated  broadly,  the  blood  pressure  rises  during  inspiration  and 
falls  during  expiration,  but  when  we  consider  the  effect  on  the  pulse  curve,  it  is 
found  that  it  varies  with  the  depth,  rapidity,  and  ease  of  respiration  ;  (2)  the  res- 

FiG.  92. 


Influence  of  the  respiration  upon  the  pulse.      J,  inspiration;  E,  expiration. 

piratory  movements  are  accompanied  by  stimulation  of  the  vasomotor  centre, 
which  produces  variations  of  the  blood  pressure. 

1.  Normal  Respiration. — Fig.  92  shows  what  sometimes,  but  by  no  means 
always,  happens.  During  inspiration,  owing  to  the  dilatation  of  the  thorax, 
more  arterial  blood  is  retained  within  the  chest,  while  at  the  same  time  venous 
blood  is  sucked  into  the  right  auricle  by  the  aspiration  of  the  thorax ;  as  a  conse- 
quence of  this,  the  tension  in  the  arteries  during  inspiration  must  be  less.  The 
diminution  of  the  chest  during  expiration  favors  the  flow  in  the  arteries,  while 
it  retards  the  flow  of  the  venous  blood  in  the  venae  cavse,  two  factors  which  raise 
the  tension  in  the  arterial  system.  The  difference  of  pressure  explains  the  differ- 
ence in  the  form  of  the  pulse  curve  obtained  during  inspiration  and  expiration,  as 
in  Fig.  92  and  Fig.  83, 1,  III,  IV,  in  which  J  indicates  the  part  of  the  curve  which 
occurred  during  inspiration,  and  E  the  expiratory  portion.  The  following  are 
the  points  of  difference:  (i)  The  greater  distention  of  the  arteries  during  expi- 
ration causes  all  the  parts  of  the  curve  occurring  during  this  phase  to  be  higher; 
(2)  the  line  of  the  ascent  is  lengthened  during  expiration,  because  the  expiratory- 
thoracic  movement  helps  to  increase  the  force  of  the  expiratory  wave ;  (3)  owing 
to  the  increase  of  the  pressure,  the  dicrotic  wave  must  be  less  during  expiration ; 
{4)  for  the  same  reason  the  elastic  elevations  are  more  distinct  and  occur  higher 
in  the  curve  near  its  apex.  The  frequency  of  the  pulse  is  slightly  greater 
during  expiration  than  during  inspiration. 

2.  This  purely  mechanical  effect  of  the  respiratory  movements  is  modified  by 
the  simultaneous  stimulation  of  the  vasomotor  centre  which  accompanies  these 


154 


INFLUENCE    OF    RESPIRATION    ON    THE    PULSE    CURVE. 


movements.  At  the  beginning  of  inspiration  the  blood  pressure  in  the  arteries  is 
lowest,  but  it  begins  to  rise  during  inspiration,  and  increases  until  the  end  of  the 
inspiratory  act,  reaching  its  maximum  at  the  beginning  of  expiration  ;  during  the 
remainder  of  the  expiration  the  blood  pressure  falls  until  it  reaches  its  lowest  level 
again  at  the  beginning  of  inspiration  (compare  §  85,/) ;  the  pulse  curves  are 
similarly  modified,  and  exhibit  the  signs  of  greater  or  less  tension  of  the  arteries 
corresponding  to  the  phases  of  the  respiratory  movements.  [There  is,  as  it  were, 
a  displacement  of  the  blood-pressure  curve  relative  to  the  respiratory  curve.] 

Forced  Respiration. — With  regard  to  the  effect  produced  on  the  pulse  curve 
by  a  powerful  expiration  and  a  forced  inspiration,  observers  are  by  no  means  agreed. 

Valsalva's  Experiment. — Strong  expiratory  pressure  is  best  produced  by 
closing  the  mouth  and  nose,  and  then  making  a  great  exi)iratory  effort  (§  60) ;  at 
first  there  is  increase  of  blood  pressure,  while  the  form  of  the  pulse  waves  resem- 
bles that  which  occurs  in  ordinary  expiration,  the  dicrotic  wave  being  less  devel- 
oped ;  but,  when  the  forced  pressure  is  long  continued,  the  pulse  curves  have  all 
the  signs  of  diminished  tension.  This  effect  is  due  to  the  action  of  the  vasomotor 
centre,  which  is  affected  reflexly  from  the  pulmonary  nerves.     We  must  assume 


Fig.  93. 


C,  cunretrom  the  carotid,  and  R,  radial,  during  Miiller's  experiment;  Q  and  Rj,  during  Valsalva's  experiment. 

Curves  written  on  a  vibrating  surface. 


that  forced  expiration,  such  as  occurs  in  Valsalva's  experiment,  acts  by  depressifi^t^ 
the  activity  of  the  vasomotor  centre  (§  371,  II).  Coughing,  singing,  and 
declaiming  act  like  Valsalva's  experiment,  while  the  frequency  of  the  pulse  is 
increased  at  the  same  time.  After  the  cessation  of  Valsalva's  experiment,  the 
blood  pressure  rises  above  the  normal  state  {Sommerbrodt),  almost  as  much  as  it 
fell  below  it ;  the  normal  condition  being  restored  within  a  few  minutes  {Lenz- 
mann). 

Miiller's  Experiment, — When  the  thorax  is  in  the  expiratory  phase,  close 
the  mouth  and  nose,  and  take  a  deep  inspiration  so  as  forcibly  to  expand  the  chest 
(§  60).  At  first  the  pulse  curves  have  the  characteristic  signs  of  diminished 
tension,  viz.,  a  higher  and  more  distinct  dicrotic  wave;  then  the  tension  can,  by 
nervous  influences,  be  increased,  just  as  in  Fig.  93,  where  C  and  R  are  tracings 
taken  from  the  carotid  and  radial  arteries  respectively,  during  Miiller's  experiment, 
in  which  the  dicrotic  waves,  r,  r,  indicate  the  diminished  tension  in  the  vessels. 
In  Ci  and  R,,  taken  from  the  same  person  during  Valsalva's  experiment,  the 
opposite  condition  occurs. 

Compressed  Air. — On  expiring  into  a  vessel  resembling  a  spirometer  (see  Respiration),  (Wal- 
denburg's  respiration  apparatus),  and  filled  with  compressed  air,  the  same  result  is  obtained  as  in 


INFLUENCE    OF    PRESSURE    ON    THE    PULSE    CURVE. 


155 


Valsalva's  experiment — the  blood  pressure  falls  and  the  pulse  beats  increase ;  conversely,  the  inspi- 
ration from  this  apparatus  of  air  under  less  pressure  acts  like  Miiller's  experiment,  i.  e.,  it  increases 
the  effect  of  the  inspiration,  and  afterward  increases  the  blood  pressure,  which  may  either  remain 
increased  on  continuing  the  experiment,  or  may  fall  [Lenzmann). 

The  inspiration  of  compressed  air  diminishes  the  mean  blood  pressure  [Zuntz),  and  the  after- 
effect continues  for  some  time.  The  pulse  is  more  frequent  both  during  and  after  the  experiment. 
Expiration  in  rarefied  air  increases  the  blood  pressure.  The  effects  which  depend  upon  the  action 
of  the  nervous  system  do  not  occur  to  the  same  extent  in  all  cases.  Exposure  to  compressed  air  in 
a  pneumatic  cabinet  lowers  the  pulse  curve,  the  elastic  vibrations  become  indistinct,  and  the 
dicrotic  wave  diminishes  and  may  disappear  {v.  Vivenot).  The  heart's  beat  is  slowed  and  the 
blood  pressure  raised  [Bert).  Exposure  to  rarefied  air  causes  the  opposite  result,  which  is  assign 
of  diminished  arterial  tension. 

Pulsus  Paradoxus. — Under  pathological  conditions,  especially  when  there  is  union  of  the 
heart  or  its  large  vessels  with  the  surrounding  parts,  the  pulse  during  inspiration  may  be  extremely 

Fig.  94. 


Pulsus  paradoxus  (after  Kussmaul).      E,  expiration  ;  J,  inspiration. 

small  and  changed,  or  may  even  be  absent  (Fig.  94).  This  condition  has  been  called  pulsus 
paradoxus  [Griesinger,  Kussmaul).  It  depends  upon  a  diminution  of  the  arterial  lumen  during 
the  inspiratory  movement.  Even  in  health,  it  is  possible  by  a  change  of  the  inspiratory  movement 
to  produce  the  p.  paradoxus  {^Riegel,  Sommerbrodt). 

75.  INFLUENCE  OF  PRESSURE  ON  THE  PULSE  CURVE.— It  is  most  important 
to  know  the  actual  pressure  which  is  applied  to  an  artery  while  a  sphygmogram  is  being  taken. 
The  changes  affect  i\ieform  of  the  curve  as  well  as  the  relation  of  individual  parts  thereof.  In 
Fig.  95,  a,  b,  c,  d,  e  are  radial  curves;  a  was  taken  with  a  minimal  pressure,  b  with  loo,  c  200, 
d  250,  and  e  450  grams  pressure,  while  A,  B,  C,  D  show  the  relations  as  to  the  time  of  occur- 
rence of  the  individual  phenomena  where  the  weight  was  successively  increased.  The  study  of 
these  curves  yields  the  following  results:  (i)  When  the  weight  is  small,  the  dicrotic  wave  is 
relatively  less;  the  whole  curve  is  high;  (2)  with  a  moderate  weight  (100  to  200  grams)  the 


Fig.  95. 


Various  forms  01  curves  (radial)  obtained  by  gradually  increasing  the  pressure. 

dicrotic  wave  is  bestmarked,  the  whole  curve  is  somewhat  lower;  (3)  on  increasing  the  "ttrei^t  the 
size  of  the  dicrotic  wave  again  diminishes ;  (4)  the  fine  elastic  vibrations  preceding  the  dicrotic 
wave  appear  first  when  a  weight  of  220  to  300  grams  is  used;  (5)  the  rapidity  of  the  pulse  changes 
with  increasing  weight,  the  time  occupied  by  the  ascent  becoming  shorter,  the  descent  becoming 
longer;  (6)  the  height  of  the  entire  curve  decreases  as  the  weight  increases.  In  every  sphygmo- 
gram the  pressure  under  which  it  was  obtained  ought  always  to  be  stated.  In  Fig.  95,  A,  B  are 
curves  obtained  from  the  radial  artery  of  a  healthy  student.  The  pressure  exerted  upon  the  artery 
for  A  was  icx);  B,  220  grms.  (i  vibration  =  0.01613  sec). 


156  VELOCITY    OF   THE    PULSE    WAVE    IN    MAN.    " 

If  pressure  be  exerted  upon  an  artery  for  a  long  time,  the  strength  of  the  pulse  is  gradually 
increased.  If,  after  subjecting  an  artery  to  considerable  pressure,  a  lighter  weight  be  used,  not 
unfrequently  the  pulse  curve  assumes  the  form  of  a  dicrotic  pulse,  owing  to  the  greater  develop- 
ment of  the  dicrotic  elevation.  When  strong  pressure  is  applied,  the  blood  is  forced  to  find  its 
way  through  collateral  channels.  When  the  chief  artery  ceases  to  be  compressed,  the  total  area 
is,  of  course,  considerably  and  suddenly  enlarged,  which  results  in  the  production  of  a  dicrotic 
elevation.  Kig.  83,  X,  is  such  a  dicrotic  curve  obtained  after  considerable  pressure  had  been 
applied  to  the  artery. 

76.  TRANSMISSION  OF  PULSE  V^AVES.— The  pulse  wave 
proceeds  throughout  the  arterial  system  from  the  root  of  the  aorta,  so  that  the 
])ulse  is  felt  sooner  in  parts  lying  near  the  heart  than  in  the  peripheral  arteries. 
E.  H.  Weber  calculated  the  velocity  of  the  pulse  wave  as  9.240  metres 
[28'.'^  feet]  per  second,  from  the  difference  in  time  between  the  pulse  in  the 
external  maxillary  artery  and  the  dorsal  artery  of  the  foot.  Czermak  showed 
that  the  elasticity  was  not  equal  in  all  the  arteries,  so  that  the  velocity  of  the 
pulse  wave  cannot  be  the  same  in  all.  The  pulse  wave  is  propagated  more 
slowly  in  the  arteries  with  soft  extensile  walls  than  in  arteries  with  resistant  and 
thick  walls,  so  that  it  is  transmitted  more  rapidly  in  the  arteries  of  the  lower 
extremities  than  in  those  of  the  upper.     It  is  still  slower  in  children. 

77.  PULSE  WAVE  IN  ELASTIC  TUBES. — Waves  similar  to  the  pulse  may  be  pro- 
duced in  elastic  tubes,  (i)  According  to  E.  H.  Weber  the  velocity  of  propagation  of  the  waves  is 
11.205  metres  per  sec;  according  to  Bonders,  11-13  metres  (34-42  feet).  (2)  According  to  E. 
H.  Weber  increased  internal  tension  causes  only  an  inconsiderable  decrease;  Rive  found  a  great 
decrease;  Donders  found  no  obvious  difference;  while  Marey  found  an  increased  velocity.  (3) 
Bonders  found  the  velocity  to  be  the  same  in  tubes  2  mm.  in  diameter  as  in  wider  tubes,  but 
Marey  believes  that  the  velocity  varies  when  the  diameter  of  the  tube  changes.  (4)  The  velocity 
is  less,  the  smaller  the  elastic  coeflicient.  (5)  The  velocity  increases  with  increased  thickness  of 
the  wall,  while  it  diminishes  when  the  specific  gravity  of  the  fluid  increases. 

Moens  has  recently  formulated  the  following  laws  as  to  the  velocity  of  propagation  of  waves  in 
elastic  tubes:  (i)  It  is  inversely  proportioml  to  the  square  root  of  the  specific  gravity  of  the 
fluid;  (2)  it  is  as  the  square  root  of  the  thickness  of  the  wall,  the  lateral  pressure  being  the 
same ;  (3)  it  is  inversely  as  the  square  root  of  the  diameter  of  the  tube,  the  lateral  pressure  being 
the  same;  (4)  it  is  as  the  square  root  of  the  elastic  coefficient  of  the  wall  of  the  tube,  the  lateral 
pressure  being  the  same  (  Valentin"). 

(A)  The  velocity  of  the  wave  is  11.809  nietres  per  second. 

(B)  The  inlra-vascular  pressure  has  a  decided  influence  on  the  velocity:  thus,  in  the  tube,  A, 
with  18  cm.  (Hg.)  pressure,  the  velocity  per  metre  :=  0.093  second,  while  with  21  cm.  pressure 
{Hg.)  ^0.095  second  per  metre. 

(C)  The  specific  gravity  of  the  liquid  influences  the  velocity  of  the  pulse  wave.  In  mercury 
the  wave  is  propagated  four  times  more  slowly  than  in  water. 

(D)  The  velocity  in  a  tube  which  is  more  rigid  and  not  so  extensile  is  greater  than  in  a  tube 
which  is  easily  distended. 

78.  VELOCITY  OF  THE  PULSE  WAVE  IN  MAN.— Landois  obtained  the  follow- 
ing results  in  a  student :  Difference  between  carotid  and  radial  =  0.074  second  (the  distance 
being  taken  as  62  centimetres) ;  carotid  and  femoral  ^=  0.068  second;  femoral  (inguinal  region)  and 
posterior  tibial  =  0.097  second  (distance  estimated  at  91  centimetres).  [Waller  obtained  between 
the  heart  and  carotid  o.io  second ;  heart  and  femoral,  0.18  sec. ;  heart  and  dorsalis  pedis,  0.22.] 

The  velocity  of  the  pulse  wave  in  the  arteries  of  the  upper  extremities 
=  8.43  metres  per  second,  and  in  those  of  the  lower  extremity  9.40  metres  per 
second,  {i.e.,  about  30  feet  per  second].  The  velocity  is  greater  in  the  less 
extensile  arteries  of  the  lower  extremities  than  in  those  of  the  upper  limb.  For 
the  same  reason  it  is  less  in  the  peripheral  arteries  and  in  the  yielding  arteries  of 
children  {Czennak). 

E.  H.  Weber  estimated  the  velocity  at  9.24  metres  per  second;  Garrod,  9-10.8  metres;  Grashey, 
8.5  metres;  Moens,  S. 3  metres,  and  with  diminished  pressure  during  Valsalva's  experiment  7.3 
metres  (?  60,  §  74). 

Influencing  Conditions. — In  animals,  hemorrhage,  slowing  of  the  heart  produced  by  stimula- 
tion of  the  vagus  {Moens),  section  of  the  spinal  cord,  deep  morphia  narcosis,  and  dilatation  of  the 
blood  vessels  by  heat,  produce  slowing oi  the  velocity,  while  stimulation  of  the  spinal  cord  accelerates 
it  [Grunmach). 


OTHER    PULSATILE    PHENOMENA. 


157 


The  wave  length  of  the  pulse  wave  is  obtained  by  multiplying  the  dura- 
tion of  the  inflow  of  blood  into  the  aorta  rrr  0.08  to  0.09  second  (§  51),  by  the 
velocity  of  the  pulse  wave. 

Method. — Place  the  knobs  of  two  tambours  (Fig.  76)  upon  the  two  arteries  to  be  investigated, 
or  place  one  over  the  apex  beat  and  the  other  upon  an  artery.  These  receiving  tambours  are 
connected  with  two  registering  tambours,  as  in  Brondgeest's  pansphygmograph  (§  67,  Fig.  76),  so 
that  their  writing  levers  are  directly  over  each  other,  and  so  arranged  as  to  write  simultaneously  on 
one  vibrating  plate  attached  to  a  tuning-fork.  [Or  they  may  be  made  to  write  upon  a  revolving 
cylinder,  whose  rate  of  movement  is  ascertained  by  causing  a  tuning-fork  of  a  known  rate  of  vibra- 
tion to  write  under  them.]  The  apparatus  is  improved  by  using  rigid  tubes  and  filling  them  with 
water,  in  which  all  impulses  are  rapidly  communicated.     In  arteries  which  are  distant  from  each 


Fig.  96. 


A,  curve  of  radial  artery  on  a  vibrating  surface  (i  vib.  =  0.01613  sec.) ;  P,  apex  cf  curve  ;  e,  e,  elastic  vibrations  ;  R, 
dicrotic  wave.     B,  curve  of  same  radial  taken  along  with  the  heart  beat;  v,  H,  P,  contraction  of  the  ventricle. 

other,  or  in  the  case  of  the  heart  and  an  artery,  the  two  knobs  of  the  receiving  tambours  may  be 
connected  by  means  of  a  Y-tube  with  one  writing  lever.  In  Fig  96,  B  is  a  curve  from  the  radial 
artery  taken  in  this  way.  In  it  z/  H  P  indicates  contraction  of  the  ventricle;  H,  the  apex  of  the 
ventricular  contraction  ;  P,  the  primary  apex  of  the  radial  curve;  v,  the  beginning  of  the  ventricular 
contraction  ;  /,  of  the  radial  pulse.  A  is  the  curve  of  the  radial  artery  alone.  From  these  curves 
it  is  evident  that  in  this  instance  nine  vibrations  occur  between  the  beginning  of  the  ventricular 
contraction  and  the  beginning  of  the  pulse  in  the  radial  artery  =  0.15  sec. 

In  Fig.  97  the  difference  between  the  carotid  and  the  posterior  tibial  pulse  =  0.137  sec. 

Pathological. — In  cases  of  diminished  extensibility  of  the  arteries,  e.  g.,  in  atheroma  (^  77,  D), 
the  pulse  wave  is  propagated  more  rapidly.  Local  dilatations  of  the  arteries,  as  in  aneurisms, 
cause  a  retardation  of  the  wave,  and  a  similar  result  arises  from  local  constrictions.  Relaxation  of 
the  walls  of  the  vessels  in  high  fever  retards  the  movement  {Uamernik). 

Fig.  97. 


Tib.fost.  I 

:  Garot.    : 


Curves  ot  the  carotid  and  posterior  tibial  tal<en  simultaneously  with  Brondgeest's  pansphygmograph  writing  upon  a 
vibrating  plate  attached  to  a  tuning-fork.     The  arrows  indicate  the  identical  moment  of  time  in  each  curve. 

79.  OTHER  PULSATILE  PHENOMENA.— i.  In  the  mouth  and  nose,  when  they 
are  filled  with  air,  and  the  glottis  closed,  pulsatile  phenomena  (due  to  the  arteries  in  their  soft 
parts)  may  be  found  communicating  a  movement  to  the  contained  air.  The  curves  obtained  are 
relatively  small,  and  closely  resemble  the  curve  of  the  carotid.  A  similar  pulse  is  obtained  in  the 
tympanum  with  intact  membrana  tympani,  and  when  the  soft  parts  of  the  tympanum  are  congested 
{Schwartze,  Troltsch). 

2.  Entoptical  Pulse. — After  violent  exercise,  an  illumination,  corresponding  to  each  pulse  beat, 
occurs  on  a  dark  optical  field.  When  the  optical  field  is  bright,  an  analogous  darkening  occurs. 
The  ophthalmoscope  occasionally  reveals  pulsation  of  the  retinal  arteries  {Jager),  which  becomes 
marked  in  insufficiency  of  the  aortic  valves.  .      : 


158 


VIBRATIONS   OF   THE    BODY    DUE   TO    THE    HEART. 


3.  Pulsatile  Muscular  Contraction. — The  orbicularis  palpebrarum  muscle  contracts  under 
sirnilar  conditions  synchronously  with  the  pulse ;  and  it  is  perhaps  due  to  the  pulse  beat  exciting 
the  sensory  nerves  reflexly.  The  Brothers  Weber  found  that  not  unfrequently,  while  walking,  the 
step  and  pulse  gradually  and  involuntarily  coincide. 

4.  When  the  legs  are  crossed  as  one  sits  in  a  chair,  the  leg  which  is  supported  is  raised  with  each 
pulse  beat,  and  it  gives  also  a  second  or  dicrotic  elevation. 

5.  If,  while  a  person  is  quite  (luiet,  the  incisor  teeth  of  the  lower  jaw  be  made  just  to  touch  the 
upj>er  incisors  very  lightly,  we  detect  a  double  beat  of  the  lower  against  the  upper  teeth,  owing  to 
the  pulse  beat  in  the  external  iDaxillary  artery  raising  the  lower  jaw.  The  second  elevation  is  due  to 
the  closure  of  the  semilunar  valves,  and  not  to  a  dicrotic  wave. 

6.  Brain  and  Fontanelles. — The  large  arteries  at  the  base  of  the  brain  communicate  a  move- 
ment to  it,  while  similar  movements  occur  with  respiration — rising  during  expiration  and  falling 
during  inspiration.  These  movements  are  visible  in  the  fontanelles  of  infants.  The  respiratory 
movements  depend  upon  variations  in  the  amount  of  blood  in  the  veins  of  the  cranial  cavity,  and 
also  upon  the  respiratory  variations  of  the  blood  pressure. 

7.  Among  pathological  phenomena  are  (a)  the  beating  in  the  epigastrium,  e.  _q:,  in  the  hyper- 
trophy of  the  right  or  left  ventricle,  caused,  it  may  be,  by  deep  insertion  of  the  diaphragm,  and  it 
may  be,  partly,  by  the  beating  of  a  dilated  abdominal  aorta  or  coeliac  axis. 

t.  (b)  Aneurisms  or  abnormal  dilalations  of  the  arteries  cause  an  abnormal  pulsation,  while  they 

Fig.  98. 


1.  Elastic  support  for  registering  the  molar  motions  of  the  body — K,  woodenjbox  ;  B,  feet  of  patient ;  /.cardiograph  ; 
a  ^,  elastic  tubing.  II.  Vibration  curves  of  a  healthy  person.  III.  Curve  obtained  from  a  patient  with  insuffi- 
ciency of  the  aortic  valves  and  great  hypertrophy  of  the  heart. 

produce  a  slowing  in  the  velocity  of  the  pulse  wave  in  the  corresponding  artery.  Hence  the  pulse 
appears  later  in  such  an  artery  than  in  the  artery  on  the  healthy  side.  Hypertrophy  and  dilatation 
of  the  left  ventricle  cause  the  arteries  near  the  heart  to  pulsate  strongly.  In  the  analogous  condition 
of  the  right  ventricle,  the  beat  of  the  pulmonary  artery  may  be  seen  and  felt  in  the  second  left  inter- 
costal space. 

80.  VIBRATIONS  OF  THE  BODY  DUE  TO  THE  HEART.— The  beating  of  the 
heart  and  large  arteries  communicates  vibrations  to  the  body  as  a  whole ;  the  vibration  being  not 
simple  but  compound.  Gordon  was  the  first  to  represent  this  pulsatory  vibration  graphically.  If  a 
person  be  placed  in  an  erect  attitude  in  the  scale-pan  of  a  large  balance,  the  index  oscillates,  and  its 
movements  coincide  with  the  heart's  movements. 

Method.— Take  a  long  four-sided  box,  K,  open  at  the  top,  and  arrange  several  coils,  a,  b,  ot 
stout  caoutchouc  tubing  round  one  end  (Fig.  98).  A  wooden  board,  B,  is  so  placed  that  it  rests 
with  one  end  on  the  caoutchouc  tubing,  and  with  the  other  on  the  narrow  end  of  the  box.  The 
person  to  be  experimented  upon,  A,  stands  vertically  and  firmly  on  this  board.  A  receiving  tam- 
bour,/, is  placed  against  the  surface  of  the  board  next  the  elastic  tube,  which  registers  the  vibrations 
of  the  foot  support.  Fig.  Ill  is  a  curve  showing  such  vibrations,  each  heart  beat  being  followed  in 
this  case  by  four  oscillations.  To  ascertain  the  relations  and  causes  of  these  vibrations,  it  is  necessary 
to  obtain,  simultaneously,  a  tracing  of  the  heart  and  the  vibratory  curve.     For  this  purpose  use  the 


THE    BLOOD    CURRENT.  159 

two  tambours  of  Brondgeest's  pansphygmograph  (§  67,  76),  placing  one  knob  or  pad  over  the  heart 
and  the  other  on  the  foot  support,  and  allow  the  writing  tambours  to  inscribe  their  vibrations  on  a 
glass  plate  attached  to  a  tuning-fork. 

In  the  lower  or  cardiac  impulse  curve  (Fig.  99),  the  rapidly  rising  part  is  due  to  the  ventricular 
systole.  It  contains  eight  vibrations  (i  vib.  =  0.01613  sec).  The  beginning  of  the  ventricular  systole 
is  indicated  in  the  figure  by  -36,  -3,  -17. 

If  the  corresponding  numbers  in  the  upper  or  vibratory  curve  are  studied,  it  is  obvious  that  at  the 
moment  ef  ventricular  systole  the  body  makes  a  downward  vibration,  i.  e.,  it  exercises  greater  pres- 
sure upon  the  foot  support.  Gordon  interprets  his  curve  as  giving  exactly  the  opposite  result.  This 
downward  motion,  however,  lasted  only  during  five  vibrations  of  the  tuning-fork ;   during  the  last 

Fig.  99. 


The  upper  curve  is  the  vibration  curve  of  a  healthy  person,  and  the  lower  one  a  tracing  of  the  apex  beat. 

three  vibrations,  corresponding  to  the  systole,  there  is  an  ascent  of  the  body  corresponding  to  a  less 
pressure  upon  the  foot  plate.  When  the  ventricle  empties  itself,  it  undergoes  a  movement  in  a 
downward  and  outward  direction. — Gutbrodt's  "  reaction  impulse." 

In  the  upper  curve  analogous  numbers  are  employed  to  indicate  the  vibrations  occurring  simul- 
taneously, viz., -28, -11,  -10.  The  closure  of  the  semilunar  valves  is  well  marked  in  the  three 
heart  beats  at  20,  -20.  This  closure  is  indicated  in  analogous  points  in  both  curves,  after  which 
there  is  a  descent  of  the  foot  support,  and  this  corresponds  to  the  downward  propagation  of  the 
pulse  wave  through  the  aorta  to  the  vessels  of  the  feet. 

Pathological. — In  insufficiency  of  the  aortic  valves,  as  shown  in  Fig.  98,  III,  the  vibration  com- 
municated to  the  body  is  very  considerable. 

81.  THE  BLOOD  CURRENT.— Cause.— The  closed  and  much- 
branched  vascular  system,  whose  walls  are  endowed  with  elasticity  and  contrac- 
tility, is  not  only  completely  filled  with  blood,  but  it  is  over-filled.  The  total 
volume  of  the  blood  is  somewhat  greater  than  the  capacity  of  the  entire  vascular 
system.  Hence  it  follows  that  the  mass  of  blood  must  exert  pressure  on  the 
walls  of  the  entire  system,  thus  causing  a  corresponding  dilatation  of  the  elastic 
vascular  walls  {Brunner).  This  occurs  during  life  ;  after  death  the  muscles  of  the 
vessels  relax,  and  fluid  passes  into  the  tissues,  so  that  the  blood  vessels  come  to 
contain  less  fluid,  and  some  of  them  may  be  empty. 

If  the  blood  were  uniformly  distributed  throughout  the  vascular  system  and 
under  the  same  pressure,  it  would  remain  in  a  position  of  equilibrium  (as  after 
death).  If,  however,  the  pressure  be  raised  in  one  section  of  the  tube,  the  blood 
will  move  from  the  part  where  the  pressure  is  higher  to  where  it  is  lower ;  so  that 
the  blood  current  is  a  result  of  the  difference  of  pressure  within  the 
vascular  system.  If  either  the  aorta  or  the  venae  cavse  be  suddenly  ligatured  in 
a  living  animal,  the  blood  continues  to  flow,  but  gradually  more  slowly,  until  the 
difference  of  pressure  is  equalized  throughout  the  entire  vascular  system. 

The  velocity  of  the  current  will  be  greater  the  greater  the  difference  of  pres- 
sure, and  the  less  the  resistance  opposed  to  the  blood  stream. 

The  difference  of  pressure  which  causes  the  current  is  produced  by 
the  heart.  Both  in  the  systemic  and  pulmonary  circulation  the  point  of  greatest 
pressure  is  in  the  root  or  beginning  of  the  arterial  system,  while  the  point  of 


160  THE    BLOOD    CURRENT. 

lowest  pressure  is  in  the  terminal  portion  of  the  venous  orifices  at  the  heart.  Hence 
the  blood  flows  continually  from  the  arteries  through  the  capillaries  into  the  venous 
trunks.  The  heart  keeps  up  the  difference  of  pressure  required  to  produce  this 
result ;  with  each  systole  of  the  ventricles  a  certain  quantity  of  blood  is  forced 
into  the  beginning  of  the  arteries,  while  at  the  same  time  an  equal  amount  flows 
from  the  venous  orifices  into  the  auricles  during  their  diastole  {E.  H.   Weber). 

Bonders  showed  that  the  action  of  the  heart  not  only  causes  the  difference  of 
pressure  necessary  to  establish  a  blood  current,  but  also  raises  the  mean  pres- 
sure within  the  vascular  system.  The  terminations  of  the  veins  at  the  heart  are 
wider  and  more  extensible  than  the  arteries  where  they  arise  from  the  heart  (Fig. 
133).  As  the  heart  propels  a  volume  of  blood  into  the  arteries  equal  to  that 
which  it  receives  from  the  veins,  it  follows  that  the  arterial  pressure  must  rise 
more  rapidly  than  the  venous  pressure  diminishes,  since  the  arteries  are  not  so 
wide  nor  so  extensible  as  the  veins.     Thus  the  total  pressure  must  also  increase. 

Cause  of  Continuous  Flow. — The  volume  of  blood  expelled  from  the  ven- 
tricles at  every  systole  would  give  rise  to  2.  jerky  or  intermittent  movement  of  the 
blood  stream  (i)  if  the  tubes  had  rigid  walls,  as  in  such  tubes  any  pressure  ex- 
erted upon  their  contents  is  propagated  momentarily  throughout  the  length  of  the 
tube,  and  the  motion  of  the  fluid  ceases  when  the  propelling  force  ceases  ;  (2) 
the  flow  would  also  be  intermittent  in  character  in  elastic  tubes  if  the  time  between 
two  successive  systoles  were  longer  than  the  duration  of  the  current  necessary  for 
the  compensation  of  the  diff"erence  of  pressure  caused  by  the  systole.  If  the  time 
between  two  successive  systoles  be  shorter  than  the  time  necessary  to  equilibrate 
the  pressure,  the  current  will  become  continuous,  provided  the  resistance  at  the 
periphery  of  the  tube  be  sufficiently  great  to  bring  the  elasticity  of  the  tube 
into  action.  The  more  rapidly  systole  follows  systole,  the  greater  the  diff'erence 
of  pressure  becomes,  and  the  more  distended  the  elastic  walls.  Although  the 
current  thus  produced  is  continuous,  a  sudden  rise  of  pressure  is  caused  by  the 
forcing  in  of  a  mass  of  blood  at  every  systole,  so  that  with  every  systole  there  is  a 
sudden  jerk  and  acceleration  of  the  blood  streaiti  corresponding  to  the  pulse  (com- 
pare §  64). 

The  sudden  jerk-like  acceleration  of  the  blood  current  is  propagated  throughout 
the  arterial  system  with  the  velocity  of  the  pulse  wave  ;  both  phenomena  are  due 
to  the  same  fundamental  cause.  Every  pulse  beat  causes  a  temporary  rapid  pro- 
gressive acceleration  of  the  particles  of  the  fluid.  But  just  as  the  form  movement 
of  the  pulse  is  not  a  simple  movement,  neither  is  the  pulsatile  acceleration  a 
simple  acceleration.  It  follows  the  course  of  the  development  of  the  pulse  wave. 
The  pulse  curve  is  the  graphic  representation  of  the  pulsatory  acceleration  of  the 
blood  stream.  Every  rise  in  the  curve  corresponds  to  an  acceleration,  every 
depression  to  a  retardation  of  the  current. 

[Method  :  Ri^d  and  Elastic  Tubes. — These  facts  are  easily  demonstrated.  Tie  a  Higgin- 
son's  sjTinge  to  a  piece  of  an  ordinary  gas  pipe.  On  forcing  water  through  the  tube,  by  compress- 
ing the  elastic  pump,  the  water  will  flow  out  at  the  other  end  of  the  tube  in  jets,  while  during  the 
intervals  of  pulsation  no  water  will  flow  out.  As  the  walls  of  the  tube  are  rigid,  just  as  much  fluid 
flows  out  as  is  forced  into  the  tube.  If  a  similar  arrangement  be  made,  and  a  long  elastic  tube  be 
nsed,  a  continuous  outflow  is  obtained,  pro%-ided  the  pulsations  occur  with  sufiicient  rapidity  and 
the  length  of  the  tube,  or  the  resistance  at  its  periphery-,  be  sufiScient  to  bring  the  elasticity  of  the 
tube  into  action.  This  can  be  done  by  putting  a  narrow  cannula  in  the  outflow  end  of  the  tube,  or 
by  placing  a  clamp  on  it  so  as  to  diminish  the  exit  aperture.  This  apparatus  converts  the  intermit- 
tent flow  into  a  continuous  current.]  The  fire-engine  is  a  good  example  of  the  conversion  of  an 
intennittent  inflow  into  a  uniform  outflow.  The  air  in  the  reser^'oir  is  in  a  state  of  elastic  tension, 
and  it  represents  the  elasticity  of  the  vascular  walls,  ^^■hen  the  pump  is  worked  slowly,  the  out- 
flow of  the  water  occurs  in  jets,  and  is  interrupted.  If  the  pumping  movement  be  sufficiently  rapid, 
the  compressed  air  in  the  reservoir  causes  a  continuous  outflow,  which  is  distinctly  accelerated  at 
every  movement  of  the  pump.     [The  ordinary  spray-producer  is  another  good  example.] 

[Thuii,  there  are  two  factors — a  central  one,  the  heart,— and  a  peripheral 


ESTIMATION    OF    THE    BLOOD    PRESSURE.  161 

one,  the  amount  of  resistance  in  the  arterioles.     Either  or  both  may  be  varied, 

and  as  this  is  done,  so  will  the  pressure  and  velocity  vary.] 

Current  in  the  Capillaries. — In  the  capillaries  the  pulsatile  acceleration  of 
the  current  ceases  with  the  extinction  of  the  pulse  wave.  The  great  resistance 
which  is  offered  to  the  current  toward  the  capillary  area  causes  both  to  disappear. 
It  is  only  when  the  capillaries  are  greatly  dilated,  and  when  the  arterial  blood  pres- 
sure is  high,  that  the  pulse  is  propagated  through  the  capillaries  into  the  beginning 
of  the  veins.  A  venous  pulse  is  observed  in  the  veins  of  the  sub-maxillary  gland 
after  stimulation  of  the  chorda  tympani  nerve,  which  contains  the  vaso-dilator 
nerves  for  the  blood  vessels  of  this  gland.  If  the  finger  be  constricted  with  an 
elastic  band,  so  as  to  hinder  the  return  of  the  venous  blood,  and  to  increase  the 
arterial  blood  pressure,  while  at  the  same  time  dilating  the  capillaries,  an  inter- 
mittent increased  redness  occurs,  which  corresponds  with  the  well-known  throb- 
bing sensation  in  the  swollen  finger.  This  is  due  to  the  capillary  pulse.  [Roy 
and  Graham  Brown  found  that  pulsatile  phenomena  were  produced  in  the  capil- 
laries by  increasing  the  extra-vascular  pressure  (§  86).  Quincke  called  attention 
to  the  capillary  pulse,  which  can  often  be  seen  under  the  finger  nails.  Extend 
the  fingers  completely,  when  a  whitish  area  appears  under  the  nails.  A  red  area 
near  the  free  margin  of  the  nail  advances  and  retires  with  each  pulse  beat.  It  is 
well  marked  in  some  diseased  conditions  of  the  heart,  especially  in  incompetence 
of  the  aortic  valves,  and  is  probably  produced  by  increased  extra-vascular  pres- 
sure.] 

82.  SCHEMATA  OF  THE  CIRCULATION.— E.  H.  Weber  constructed  a  scheme  of 
the  circularion.  It  consisted  of  a  force  pump  with  properly  arranged  valves  to  represent  the  heart, 
portions  of  gut  for  the  arteries  and  veins,  and  a  piece  of  glass  tubing  containing  a  piece  of  sponge 
to  represent  the  capillaries.  Various  schemes  have  been  invented,  including  the  very  complicated 
one  of  Marey  [the  extremely  ingenious  one  of  v.  Thanhoffer,  and  the  thoroughly  practical  one  of 
Rutherford] . 

83.  CAPACITY  OF  THE  VENTRICLES.— Since  the  right  and  left 
ventricles  contract  simultaneously,  and  just  the  same  volume  of  blood  passes 
through  the  pulmonary  as  through  the  systemic  circulation,  it  follows  that  the 
right  ventricle  must  be  just  as  capacious  as  the  left.  The  capacity  of  the  ventri- 
cles has  been  estimated  in  the  following  ways  : — 

Methods. — (i)  Directly,  by  filling  the  dead  relaxed  ventricle  with  blood  or  an  injection  mass. 
This  method  is  unsatisfactory  and  inaccurate. 

(2)  Indirectly.  Volkmann  11850)  estimated  it  thus:  Estimate  the  sectional  area  of  the  aoita, 
and  the  velocity  of  the  blood  stream  in  it  (?.  i).  From  this  calculate  the  amount  of  blood  passing 
through  the  aorta  in  the  unit  of  time.  As  the  total  quantity  of  blood  in  the  body  is  known  ( =r  ^ 
of  the  body  weight),  we  can  easily  calculate  how  long  this  takes  to  flow  through  the  aorta.  We 
must  also  know  the  number  of  beats  during  the  time  of  the  circulation.  From  these  data,  and 
from  experiments  on  animals,  Volkmann  estimated  the  volume  of  blood  discharged  at  each  systole 
by  the  ventricle  to  be  xo-o  °f  '^^  body  weight.  For  a  man  weighing  75  kilos,  this  is  187.5  grams. 
This  estimate  still  leaves  much  to  be  desired. 

Place  calculates  it  in  the  following  manner  :  A  man  uses  about  500  litres  of  O  in  24  hours.  To 
absorb  this  into  the  venous  blood  (which  contains  about  7  vols,  per  cent  less  O  than  arterial),  about 
7000  litres  of  blood  must  pass  through  the  lungs  in  24  hours.  If  one  calculates  100,000  heart 
beats  in  24  hours,  then  at  each  systole  only  70  cubic  centimetres  are  discharged. 

84.  ESTIMATION  OF  THE  BLOOD  PRESSURE.— (A)  In  Animals  :  (i)  Methods 
of  Hales. — The  Rev.  Stephen  Hales  (1727)  was  the  first  to  introduce  a  long  glass  tube  into  a  blood 
vessel  in  order  to  estimate  the  blood  pressure  by  measuring  the  height  of  the  column  of  blood. 

The  tube  was  provided  at  its  tower  end  with  a  copper  tube  bent  at  a  right  angle  (Pitot's  tube). 
[The  tube  he  used  was  one- sixth  of  an  inch  bore  and  about  9  feet  long,  and  was  inserted  into  the 
femoral  artery  of  a  horse.  The  height  to  which  the  blood  rose  in  the  tube  was  noted,  as  well  as  the 
oscillations  that  occurred  with  every  pulsation.  From  the  height  of  the  column  of  flcdd  he  calcu- 
lated the  force  of  the  heart.] 

(2)  The  Haemadynamometer  of  PoiseuUIe  (1828). — This  observer  used  a  U-shaped  tube 
partiallv  filled  with  mercury — a  manometer — which  was  brought  into  connection  with  a  blood 
vessel  by  means  of  a  rigid  tube.  [The  merctiry  oscillated  with  every  pulsation,  and  the  extent  of 
II 


162 


LUDWIG  S    KYMOGRAPH. 


the  oscillations  was  read  off  by  means  of  a  scale  attached  to  the  bent  tube.     He  called  the  instru- 
ment a  humaityiiamoiiielerr^ 

[(3)  Vierordt  used  a  tube  5  or  6  feet  long,  and  filled  it  with  a  solution  of  sodium  carbonate, 
thus  preventing  much  blood  from  entering  the  tube,  while  at  the  same  time  the  soda  solution 
])revented  the  coagulation  of  the  blood.] 

Fig.  100. 


r\ 


c- 


b 

I.  Scheme  of  C.  Ludwig's  kymograph.     II.  Kick's  spring  kyniogriiph. 


Fig.   lor. 


P^T^ISST^ 


Ludwig's  improved  revolving  cylinder,  R,  moved  by  the 
clockwork  in  the  box  A,  and  regulated  by  a  Foucault's 
regulator  placed  on  the  top  of  the  box.  The  disk,  D, 
moved  by  the  clockwork,  presses  upon  the  wheel,  n, 
which  can  be  raised  or  lowered  by  the  screw,  L,  thus 
altering  the  position  of  «  on  D,  so  as  to  cause  the 
cylinder  to  rotate  at  different  rates.  The  cylinder  it- 
self can  be  raised  by  the  handle,  U.  On  the  left  side  of 
the  figure  is  a  mercurial  manometer.  When  the  cylin- 
der is  used,  it  is  covered  with  smoked  smooth  paper. 


(4)  C.  Ludwig's  Kymograph. — 
C.  Ludwig  employed  a  U-shaped 
manometer,  but  he  placed  a  light  float 
(Fig.  100,  d,  s)  upon  the  surface  of  the 
mercury  in  the  open  limb  of  the  tube. 
A  writing  style,/,  placed  transversely 
on  the  free  end  of  the  float,  inscribed 
the  movements  of  the  float — and,  there- 
fore, of  the  mercury — upon  a  cylinder, 
c,  caused  to  revolve  at  a  uniform  rate. 
This  apparatus  registered  the  height  of 
the  blood  pressure,  as  well  as  the  pulsa- 
tile and  other  oscillations  occurring  in 
the  mercury.  Volkmann  called  this 
instrument  a  kymograph  or  "  wave 
writer."  The  difference  of  the  height 
of  the  column  of  mercury,  c,  d,  in  both 
limbs  of  the  tube  indicates  the  pressure 
within  the  vessel.  If  the  height  of  the 
column  of  mercury  be  multiplied  by 
13.5,  this  gives  the  height  of  the  cor- 
responding column  of  blood.  Setsche- 
now  placed  a  stop-cock  in  the  lower 
bend,  h,  of  the  tube.  If  this  be  closed 
so  as  just  to  permit  a  small  aperture  of 
communication  to  remain,  the  pulsatile 
vibrations  no  longer  appear,  and  the 
apparatus  indicates  the  mean  pressure. 


METHOD    OF    ESTIMATING    BLOOD    PRESSURE. 


163 


By  the  term  mea?i  pressure  is  meant  the  limit  of  pressure,  above  and  below  which 
the  oscillations  occurring  in  an  ordinary  blood-pressure  tracing  range.  [Briefly, 
it  is  the  average  elevation  of  the  mercurial  column.] 

In  a  blood-pressure  tracing,  such  as  Fig.  102,  each  of  the  smaller  waves  corresponds  to  a 
heart  beat,  the  ascent  corresponds  to  the  systole  and  the  descent  to  the  diastole.  The  large 
undulations  are  due  to  the  respiratory  movements.  It  is  clear  that  the  heart  beat  is  expressed 
as  a  simple  rise  and  fall  (Fig.  102),  so  that  the  curve  of  the  heart  beat  obtained  with  a  mercurial 
kymograph  differs  from  a  sphygmographic  curve. 

Faults  of  a  Mercurial  Manometer. — A  perfect  recording  instrument  ought  to  indicate  the 
height  of  the  blood  pressure,  and  also  the  size,  form,  and  duration  of  any  wave  motion  communicated 
to  it.  The  mercurial  manometer  does  not  give  the  true  form  of  the  pulse  wave,  as  the  mercury, 
when  once  set  in  motion,  executes  vibrations  of  its  own,  owing  to  its  great  inertia,  and  thus  the  finer 
movements  of  the  pulse  wave  are  lost.  Hence  a  mercurial  kymograph  is  used  for  registering  the 
blood  pressure,  and  not  for  obtaining  the  exact  form  of  the  pulse  wave.  Instruments  with  less 
inertia,  and  with  no  vibrations  pecuUar  to  themselves,  are  required  for  this  purpose. 


Fig.  102. 


Blood-pressure  curve  of  the  carotid  of  a  dog  obtained  with  a  mercurial  manometer.  C-;f==  line  of  no  pressure, 
zero  line,  or  abscissa  ■  y-y  is  the  blood-pressure  tracing  with  small  waves,  each  one  caused  by  a  heart  beat,  and 
the  large  waves  due  to  the  respiration.  A  millimetre  scale  shows  the  height  of  the  pressure  in  millimetres  of 
mercury. 

[Method. — Expose  the  carotid  of  a  chloralized  rabbit,  and  isolate  a  portion  of  the  vessel  between 
two  ligatures,  or  two  spring  clamps.  With  a  pair  of  scissors  make  an  oblique  slit  in  the  artery,  and 
into  it  tie  a  straight  glass  cannula,  directing  the  pointed  end  of  the  cannula  toward  the  heart.  Fill 
the  cannula  with  a  saturated  solution  of  sodium  carbonate,  taking  care  that  no  air  bubbles  enter, 
and  connect  it  with  the  lead  tube  which  goes  to  the  ascending  limb  of  the  manometer.  The  tube 
which  connects  the  artery  with  the  manometer  must  be  flexible  and  yet  inelastic,  and  a  lead  tube  is 
best.  It  is  usual  to  connect  a  pressure  bottle,  containing  a  saturated  solution  of  sodium  carbonate, 
by  means  of  an  elastic  tube,  with  the  tube  attached  to  the  manometer.  This  bottle  can  be  raised  or 
lowered.  Before  beginning  the  experiment,  raise  the  pressure  bottle  until  there  is  a  positive 
pressure  of  mercury  in  the  manometer  about  equal  to  the  estimated  blood  pressure,  and  then  clamp 
the  tube  of  the  pressure  bottle  where  it  joins  the  lead  tube.  This  positive  pressure  prevents  the 
escape  of  blood  from  the  artery  into  the  solution  of  sodium  carbonate.  When  all  is  ready,  the 
ligature  on  the  cardiac  side  of  the  cannula  is  removed,  and  immediately  the  float  begins  to  oscillate 
and  inscribe  its  movements  upon  the  recording  surface.  The  fluid  within  the  artery  exerts  pressure 
latterly  upon  the  sodium  carbonate  solution,  and  this  in  turn  transmits  it  to  the  mercury.     Peptones, 


164 


SPRING    KYMOGRAPH. 


or  rather  the  albumoses,  when  injected  into  the  blood  keep  it  from  coagulating  (p.  73).  Roy  finds 
that  oil  may  take  the  place  of  sodic  carbonate.] 

[Precautions. — In  taking  a  blood-pressure  tracing,  after  seeing  that  the  apparatus  is  perfect, 
care  must  be  taken  that  the  animal  is  perfectly  quiescent,  as  every  movement  causes  a  rise  of  blood 
pressure.  This  may  be  secured  by  giving  curara  and  keeping  up  artilicial  respiration,  or  by  the 
carefully  regulated  inhalation  of  ether.  When  a  drug  is  to  be  injected  to  test  its  action,  if  it  be 
introduced  into  the  jugular  vein  it  is  apt  to  afl'ect  the  heart  directly.  This  may  be  avoided  by 
injecting  it  into  a  vein  of  the  leg,  or  under  the  skin.  The  solution  of  the  drug  must  not  contain 
particles  which  will  block  up  the  capillaries.  Care  should  also  be  taken  that  the  carbonate  of  soda 
does  not  flow  back  into  the  artery.] 

[Continuous  Tracing. — When  we  have  occasion  to  take  a  tracing  for  any  length  of  time,  it 
must  be  written  upon  a  strip  of  paper  which  is  moved  at  a  uniform  rate  in  front  of  the  writing  style 
on  the  float  (Fig.  100).  Various  arrangements  are  employed  for  this  purpose,  but  it  is  usual  to  cause 
a  cylinder  to  revolve,  so  as  to  unfold  a  roll  or  riband  of  paper  placed  on  a  movable  bobbin.  As  the 
cylinder  revolves,  it  gradually  winds  oflT  the  strip  of  paper,  which  is  kept  applied  to  the  revolving 
surface  by  ivory  friction  wheels.  In  Ilering's  complicated  kymograph  a  long  strip  of  smoked  paper 
is  used.  The  writing  style  may  consist  of  a  sable  brush,  or  a  tine  glass  pen  filled  with  aniline  blue 
disM)lved  in  water,  to  which  a  little  alcohol  and  glycerine  are  added.] 

[In  order  to  measure  the  height  of  the  pressure,  we  must  know  the  position  of  the  abscissa  or 
line  of  no  pressure,  and  it  may  be  recorded  at  the  same  time  as  the  blood  pressure,  or  afterward. 
In  Fig.  102  O  -  X  is  the  zero  line  or  the  abscissa,  and  the  height  of  the  vertical  lines  or  ordinates 
may  be  measured  by  the  millimetre  scale  on  the  left  of  the  figure.  The  height  of  the  blood  pressure 
is  obtained  by  drawing  ordinates  from  the  curve  to  the  abscissa,  measuring  their  length,  and  multi- 
plying by  two.] 

(5)  Spring  Kymograph. — A.  Fick  (1864)  uses  a  "hollow  spring  kymo- 
graph "  on  the  principle  of  Bourdon's  manometer  (Fig.  100,  II). 

A  hollow  C-shaped  metallic  spring,  F,  is  filled  with  alcohol.  One  end  of  the  hollow  spring  is 
closed,  and  the  other  end,  covered  by  a  membrane,  is  brought  into  connection  with  a  l>lood  vessel 
by  a  junction  piece  filled  with  a  solution  of  sodium  carbonate.  As  soon  as  the  communication  with 
the  artery  is  opened,  the  pressure  rises,  and  the  spring,  of  course,  tends  to  straighten  itself.  To  the 
closed  end,  d,  there  is  fixed  a  vertical  rod  attached  to  a  series  of  levers,  //,  ?',  ^,  e,  one  of  which  writes 
its  movements  upon  a  surface  moving  at  a  uniform  rate.  The  blood  pressure  and  the  periodic 
variations  of  the  pulse  are  both  recorded,  although  the  latter  is  not  done  with  absolute  accuracy. 

[Hering  improved  Fick's  instrument  (Fig.  103).     a,l>,  c,  is  the  hollow  spring  filled  with  alcohol, 

and  communicating  at  a  with  the  lead 


Fig.  103. 


lube,  (/,  passing  to  the  cannula  in  the 
artery.  To  c  is  attached  a  series  of  light 
wooden  levers  with  a  writing  style,  s. 
The  lower  part  of  4  dips  into  a  vessel, 
<?,  filled  with  oil  or  glycerine,  which 
serves  to  damp  the  vibrations  of  the 
levers.  At /is  a  syringe  communicating 
with  the  tube,  ^,  filled  with  solution  of 
sodic  carbonate,  and  used  for  regulating 
the  amount  of  fluid  in  the  tube  con- 
necting the  manometer  with  the  blood 
vessel.  The  whole  apparatus  can  be 
raised  or  lowered  on  the  toothed  rod,  A, 
Ijy  means  of  the  mill-head  opposite, _^,  to 
which  all  the  parts  of  the  apparatus  are 
attached.] 

(6)  Fick's  Flat  Spring  Kymo- 
graph.— The  narrow  tube  a,  a  {l  mm. 
diam.)  is  placed  in  connection  with  a 
blood  vessel  by  means  of  the  cannula, 
c,  and  over  its  vertical  expanded  end, 
A,  is  fixed  a  caoutchouc  membrane,  with 
a  projecting  point,  s,  which  presses 
against  a  horizontal  spring,  F,  joined  to 
a  writing  lever,  H,  by  an  intermediate 
piece,  d.  The  whole  is  held  in  the 
metallic  frame,  R  R  (Fig.  104).  In 
order  to  estimate  the  absolute  pressure, 
the  instrument  must  be  compared  previously  with  a  mercurial  manometer. 

(B)  In  man  the  blood  pressure  may  be  estimated   by  means  of  (i)  a  properly 


Fick's  spring  manometer,  as  improved  by  Hering. 


BLOOD    PRESSURE    IN    THE    ARTERIES. 


165 


graduated  sphygmograph  (§  67).  The  pressure  required  to  abolish  the 
movement  of  the  lever  indicates  approximately  the  vascular  tension.  The  mean 
blood  pressure  in  the  radial  artery  is  equal  to  550  grams. 

(2)  Sphygmomanometer  of  v.  Basch. — A  capsule  containing  fluid  was 
placed  upon  a  pulsating  artery,  while  the  capsule  itself  communicated  with  a 
mercurial  manometer.  As  soon  as  the  pressure  within  the  manometer  slightly 
exceeded  that  within  the  artery,  the  artery  was  compressed  so  that  a  sphygmograph 
placed  on  a  peripheral  portion  of  the  vessel  ceased  to  beat.  Both  arrangements 
do  not  give  the  exact  pressure  within  the  artery ;  they  only  indicate  the  pressure 
which  is  required  to  compress  the  artery  and  the  overlying  soft  parts.  The 
pressure  required  to  compress  the  arterial  walls,  however,  is  very  small  compared 
with  the  blood  pressure.  It  is  only  4  mm.  Hg.  V.  Basch  estimated  the  pressure 
in  the  radial  artery  of  a  healthy  man  to  be  135  to  165  millimetres  of  mercury. 

Variations. — In  children  the  blood  pressure  increases  with  age,  height  and  weight.  In  the 
superficial  temporal  artery,  at  2  to  3  years,  it  is  =  97  mm. ;   12  to  13  years,  1 13  mm.  Hg.  {A.  Eckert, 

Fig.  104. 


Pick's  flat  spring  kymograph. 

c.  \  100).  The  blood  pressure  is  raised  immediately  after  bodily  movements  ;  it  is  higher  when  a 
person  is  in  the  horizontal  position  than  when  sitting,  and  in  sitting  than  in  standing.  After  a  cold  as 
well  as  after  a  warm  bath,  the  first  effect  is  an  increase  of  blood  pressure  and  of  the  quantity  of  urine. 

85.  BLOOD  PRESSURE  IN  THE  ARTERIES.— The  following 
results  have  been  obtained  by  experiment  on  systemic  arteries  : — 

{a)  Mean  Blood  Pressure. — The  blood  pressure  is  very  considerable,  vary- 
ing within  pretty  wide  limits;  in  the  large  arteries  of  large  mammals,  and  perhaps 
in  man,  it  =  140  to  160  millimetres  [5.4  to  6.4  inches]  of  a  mercurial  column. 

The  following  results  have  been  obtained,  those  marked  thus  *  by  Poiseuille,  and  those  +  by 
Volkmann : — 


*  Carotid,  Horse,   161  mm. 


+ 


Dog, 

Goat, 
Rabbit. 


122  to  214  mm. 
151  mm. 

130  to  190  mm.  [Ludwig 
118  to  135  mm. 
90  mm. 


4-  Carotid,  Fowl,  88  to  171  mm. 
-j-  Aorta  of  Frog,  22  to  29  mm. 
-)-  Gill  artery  of  Pike,  35  to  84  mm. 

Brachial  artery  of  Man  during  an  operation, 

no  to  1-20  mm.  [Faivre).     Perhaps  too 

low,  owing  to  the  injury. 


+ 
+ 

E.  Albert  estimated  the  blood  pressure  by  means  of  a  manometer,  placed  in  connection  with  the 
anterior  tibial  artery  of  a  boy  whose  leg  was  to  be  amputated,  to  be  100  to  160  mm.  Hg.  The 
elevation  with  each  pulse  beat  was  17  to  20  mm. ;  coughing  raised  it  to  20  or  30  mm. ;  tight  band- 
aging of  the  healthy  leg,  15  mm.;  while  passive  elevation  of  the  body,  whereby  the  hydrostastic 
action  of  the  column  of  blood  was  brought  into  play,  raised  it  40  mm. 

The  pressure  in  the  aorta  of  mammals  varies  from  200  to  250  mm.  Hg.  As  a  general  rule,  the 
blood  pressure  in  large  animals  is  higher  than  in  small  animals,  because  in  the  former  the  blood 
channel  is  considerably  longer,  and  there  is  greater  resistance  to  be  overcome.  In  very  young  and 
in  very  old  animals  the  pressure  is  lower  than  in  individuals  in  the  prime  of  life. 

The  arterial  pressure  in  the  foetus  is  scarcely  half  that  of  the  newly-born,  while  the  venous 
pressure  is  higher,  the  difference  of  pressure  between  arterial  and  venous  blood  being  scarcely  half 
so  great  as  in  adult  animals  [Cohnsiein  and  Zuntz). 


166 


BLOOD    PRESSURE    IN    THE    ARTERIES. 


The  arterial  blood  pressure  is  highest  in  the  aorta,  and  falls  toward  the 
smaller  vessels,  but  the  tall  is  very  gradual,  as  sliown  in  Fig.  105.  A  great  fall 
takes  place  on  i)assing  from  the  area  of  the  arterioles  into  the  capillary  area  (C), 
while  it  is  less  in  tiie  venous  area,  and  negative  near  the  heart,  as  indicated  in  the 
dotted  line  passing  below  the  abscissa,  so  that  the  pressure  is  lowest  in  the  cardiac 
ends  of  the  venre  cavx  (compare  V\ix.  iii). 

(d)  Branching  of  the  Blood  Vessels. — Within  the  large  arteries  the  blood 
pressure  diminishes  relatively  little  as  we  pass  toward  the   jjeriphery,  because  the 

difference  of  the  resistance  in  the 
Fig-  I05-  different  sections  of  large  tubes  is 

very  small.     As  soon,  however,  as 
the   arteries   begin    to   divide   fre- 
quently, and   undergo  a  consider- 
\  able  diminution  in  their  lumen,  the 

blood    pressure    in    them    rapidly 
I    T'"'"---...  diminishes,  because  the  propelling 

energy  of  the  blood  is  much  weak- 
ened, owing  to  the  resistance  which 
it  has  to  overcome  (§  99). 

(r)  Amount  of  Blood.— The 
blood    pressure    is    increased    with 


B.R 


H  A  C  V  ^^^^H 

L.V.  R.  A. 

Scheme  of  the  blood  pressure,  in  A,  the  arteries  ;  C,  capil- 
laries, and  V,  veins;  O-O,  is  the  abscissa  or  line  of  no 
pressure;  L.  V.,  left  ventricle,  and  R.  A.  right  auricle; 
li.  P.,  the  height  of  the  blood  pressure. 


greater  filling  of  the  arteries,  and  vice  versa  ;  hence  it — 

Increases. 

1.  With  increased  and  accelerated  action  of  the 

heart ; 

2.  In  plethoric  persons; 

3.  After  considerable  increase  of  the  quantity 

of  blood  by  direct  transfusion,  or  after 
a  copious  meal. 


Decreases. 

1.  During  diminished  and  enfeebled  action  of 
the  heart ; 

2.  In  ana;mic  persons ; 

3.  After  hemorrhage  or  considerable  excretions 
from  the  blood  by  sweating,  the  urine, 
severe  diarrhrea. 


The  blood  pressure  does  not  vary  in  the  same  proportion  as  the  variations  in  the  amount  of  blood. 
The  vascular  system,  in  virtue  of  its  muscular  tissue,  has  the  property,  within  liberally  wide  limits, 
of  accommodating  itself  to  larger  or  smaller  quantities  of  blood  {C.  Ludtvig  and  Worm  Miiller, 
I  102,  d).  [In  fact,  a  large  amount  of  blood  may  be  transfused  without  materially  raising  the 
blood  pressure.]  Small  and  moderate  hemorrhages  (in  the  dog  to  2.8  per  cent,  of  the  body  weight) 
have  no  obvious  effect  on  the  blood  pressure.  After  a  slight  loss  of  blood  the  pressure  may  even 
rise  ( IVorw  Miiller).  If  a  large  amount  of  blood  be  withdrawn,  it  causes  a  great  fall  of  the  blood 
pressure,  and  when  hemorrhage  occurs  to  4-6  per  cent,  of  the  body  weight,  the  blood  pressure  =  0. 
The  transfusion  of  a  moderate  amount  of  blood  does  not  raise  the  mean  arterial  blood  pressure. 
There  are  important  practical  deductions  from  these  experiments,  viz.,  that  the  arterial  blood 
pressure  cannot  be  diminished  directly  by  moderate  bloodletting,  and  that  the  blood  pressure  is  not 
necessarily  high  in  plethoric  persons.] 

(//)  Capacity  of  the  Vessels. — The  arterial  pressure  rises  when  the  capacity 
of  the  arterial  system  is  diminished,  and  conversely.  The  circularly-disposed 
smooth  muscular  fibres  of  the  arteries  are  the  chief  agents  concerned  in  this  pro- 
cess. When  they  relax,  the  arterial  blood  pressure  falls,  and  when  they  contract, 
it  rises.  These  actions  of  muscular  fibres  are  controlled  and  regulated  by  the 
action  of  the  vasomotor  nerves  (§  371). 

{e~)  Collateral  Vessels. — The  arterial  pressure  within  a  given  area  of  the 
vascular  system  must  ri.se  or  fall  according  as  the  neighboring  areas  are  dimin- 
ished, whether  by  the  application  of  pressure,  or  a  ligature,  or  are  rendered 
impervious,  or  as  these  areas  dilate.  The  application  of  cold  or  warmth  to  limited 
areas  of  the  body — increasing  or  diminishing  the  atmospheric  pressure  on  a  part 
— the  paralysis  or  stimulation  of  certain  vasomotor  areas  (§  371),  all  produce 
remarkable  variations  in  the  blood  pressure.  [The  effect  of  dilatation  of  a  large 
vascular  area  on  the  arterial  pressure  is  well  shown  by  what  happens  when  the 
blood  vessels  of  the  abdomen  are  dilated.     Divide  both  vagi  in  the  neck  of  a 


RESPIRATORY   UNDULATIONS. 


167 


rabbit  and  stimulate  the  central  end  of  the  superior  cardiac  or  depressor 
nerve  ;  after  a  few  seconds,  the  blood  vessels  of  the  abdomen  dilate,  and  gradually 
there  is  a  steady  fall  of  the  blood  pressure  in  the  systemic  arteries.  Fig.  io6  is  a 
blood-pressure  tracing  showing  the  height  of  the  blood  pressure  before  stimulation, 
a.  The  stimulation  was  continued  from  a  to  b,  and  after  a  certain  latent  period 
there  is  a  steady  fall  of  the  blood  pressure.] 

(/)  Respiratory  Undulations. — The  arterial  pressure  also  undergoes  regular 
variations  or  undulations  owing  to  the  respiratory  movements.  These  undulations 
are  called  respiratory  undulatiofis  (Figs.  102  and  107).  Stated  broadly,  during 
every  strong  inspiration  the  blood  pressure  rises,  and  during  expiration  it  falls 
(§  74).  This  is  not  quite  correct.  These  undulations  may  be  explained  by  the 
fact  that,  with  every  expiration,  the  blood  in  the  aorta  is  subjected  to  an  increase 
of  pressure  through  the  compressed  air  in  the  chest ;  with  every  inspiration,  on  the 
other  hand,  it  is  diminished,  owing  to  the  rarefaction  of  the  air  in  the  lungs  acting 

Fig.  106. 


Kymographic  traciag  showing  the  effect  on  the  blood  pressure  of  stimulation  of  the  central  end  of  the  depressor 
nerve  in  the  rabbit  after  section  of  both  vagi  in  the  neck.  Stimulation  began  at  a  and  ended  at  ^;  o-x, 
the  abscissa. 


upon  the  aorta.  Besides,  the  inspiratory  movements  of  the  chest  aspirate  blood 
from  the  venae  cavge  toward  the  heart,  while  expiration  retards  it,  and  thus 
influences  the  blood  pressure.  The  undulations  are  most  marked  in  the  arteries 
lying  nearest  to  the  heart.  The  respiratory  undulations  are  due  in  part  to  a 
stimulation  or  condition  of  excitement  of  the  vasomotor  centre,  which  runs 
parallel  with  the  respiratory  movements.  This  stimulation  of  the  vasomotor 
centre  causes  the  arteries  to  contract,  and  thus  the  blood  pressure  is  raised.  The 
variations  in  the  pressure  which  depend  upon  a  varying  activity  of  the  vasomotor 
centre  are  known  as  the  "curves  of  Traube  and  Hering."  Fig.  107  shows  the 
carotid  blood-pressure  tracing  of  a  dog.  In  this  curve,  when  inspiration  begins 
(I)  the  blood  pressure  is  still  falling  slightly,  but  gradually  rises  until  it  reaches  its 
maximum  shortly  after  the  beginning  of  expiration  (E).  [The  maxima  and 
minima  of  the  respiratory  and  blood-pressure  curves  do  not  coincide  exactly,  but 
in  addition  the  tiumber  of  pulse  beats  is  greater  in  the  ascent  than  in  the  descent. 


168  TRAUBE-HERING    CURVES. 

This  is  well  marked  in  a  blood -pressure  tracing  from  a  dog's  carotid  (Fig.  107), 
while  in  a  rabbit  this  difference  of  the  pulse  rate  is  but  slightly  marked  (Fig.  106). 
The  smaller  number  of  pulse  beats  during  the  descent,  i.e.,  during  the  greater 
part  of  expiration — is  due  to  the  activity  of  the  cardio-inhibitory  centre  in  the 
medulla  oblongata.  This  is  proved  by  the  fact  that  section  of  both  vagi  in  the 
dog  causes  the  difference  of  pulse  rate  to  disappear,  while  other  conditions  remain 
the  same  as  before,  except  that  the  heart  beats  more  rapidly.  It  would  seem  that, 
during  the  ascent,  the  cardio-inhibitory  centre  is  comparatively  inactive.  It  is 
clear,  therefore,  that  the  respiratory  and  cardio-inhibitory  centres  in  the 
medulla  oblongata  act  to  a  certain  extent  in  unison,  so  that  it  is  reasonable  to 
suppose  that  other  centres  situated  in  close  proximity  to  these  may  also  act  in 
unison  with  them,  or,  as  it  were,  "in  sympathy."  As  already  stated,  the  vaso- 
motor centre  is  also  in  action  during  a  particular  part  of  the  time.] 

[If  a  dog  be  curarized  and  artificial  respiration  established,  the  respiratory 
undulations  still  occur,  although  in  a  modified  form.  In  artificial  respiration,  the 
mechanical  conditions,  as  regards  the  intra-thoracic  pressure,  are  exactly  the 
reverse  of  those  which  obtain  during  ordinary  respiration.  Air  is  forced  into  the 
chest  during  artificial  respiration,  so  that  the  pressure  within  the  chest  is  increased 
during  inspiration,  while  in  ordinary  inspiration  the  pressure  is  diminished.  Thus, 
the  same  mechanical  explanation  will  not  suffice  for  both  cases.] 

Fig.  107. 


Carotid  blood-pressure  tracing  of  dog;   vagi  not  divided;   I  =  inspiration,  E  =  expiration  (Jitirling). 

If  the  artificial  respiration  be  suddenly  interrupted  in  a  curarized  animal,  the 
blood  pressure  rises  steadily  and  rapidly.  This  rise  is  due  to  the  stimulation  of  the 
vasomotor  centre  in  the  medulla  oblongata  by  the  impure  blood.  This  causes 
contraction  of  the  small  arteries  throughout  the  body,  which  retards  the  outflow 
from  the  large  arteries,  and  thus  the  pressure  within  them  is  raised.  [Stated  broadly, 
the  arterial  pressure  depends  on  the  central  organ — the  heart,  and  on  the  con- 
dition of  the  peripheral  organs — the  small  arteries.  Both  are  influenced  by 
the  nervous  system.  If  the  action  of  the  vasomotor  centre  be  eliminated  by 
dividing  the  spinal  cord  in  the  cervical  region,  arrest  of  the  respiration,  causes  a 
very  slight  rise  of  the  blood  pressure;  hence,  it  is  evident  that  venous  blood  acts 
but  slightly  on  the  heart,  or  on  any  local  peripheral  nervous  mechanism,  or  on  the 
muscular  fibres  of  the  arteries.  This  experiment  shows  that  it  is  the  vasomotor 
centre  which  is  specially  acted  upon  by  the  venous  blood.] 

[Traube-Hering  Curves. — The  following  experiment  proves  that  the  varying 
activity  of  the  vasomotor  centre  suffices  to  produce  undulations  in  the  blood- 
pressure  tracing.  Take  a  dog,  curarize  it,  expose  both  vagi  and  establish  artificial 
respiration  ;  then  estimate  the  blood  pressure  in  the  carotid.  After  section  of  the 
vagi,  the  heart  will  continue  to  beat  more  rapidly,  but  it  will  be  undisturbed  by 
the  cardio-inhibitory  centre.  Thus  the  central  factor  in  the  causation  of  the 
blood  pressure  remains  constant.  Suddenly  interrupt  the  respiration,  and,  as  al- 
ready stated,  the  blood  pressure  will  rise  steadily  and  uniformly,  owing  to  the  stimu- 


ARREST   OF   THE    HEART's    ACTION.  169 

lation  of  the  vasomotor  centre  by  the  venous  blood.  In  this  case  the  peripheral 
factor,  or  state  of  tension  of  the  small  arteries  throughout  the  body,  is  influenced 
by  the  condition  of  the  nerve  centre,  which  controls  their  action.  After  a  time, 
the  blood-pressure  tracing  shows  a  series  of  bold  curves  higher  than  the  original 
tracing.  These  can  only  be  due  to  an  alteration  in  the  state  of  the  small  arteries, 
brought  about  by  a  condition  of.  rythmical  activity  of  the  vasomotor  centre. 
These  curves  were  described  and  figured  by  Traube,  and  are  called  the  Traube  or 
Traube-Hering  curves.  As  in  other  conditions,  stimulation  causes  exhaustion,  and 
soon  the  venous  blood  paralyzes  the  vasomotor  centre  and  the  small  arteries  relax, 
blood  flows  freely  out  of  the  larger  arteries,  and  the  blood  pressure  rapidly  sinks. 
Variations  in  the  blood  pressure  have  been  observed  after  a  mechanical  pump  has 
been  substituted  for  the  heart,  i.e.,  after  all  respiratory  movements  have  been  set 
aside,  so  that  the  only  factor  which  would  account  for  the  phenomena  of  the  Traube- 
Hering  curves  is  the  variation  in  the  peripheral  resistance  in  the  small  arteries, 
determined  by  the  condition  of  the  vasomotor  centre.] 

Variations. — The  respiratory  undulations  of  the  blood  pressure  become  more  pronounced  the 
greater  the  force  of  the  respirations,  which  produce  greater  variations  of  the  intra-thoracic  pres- 
sure. In  man,  the  diminution  of  the  pressure  within .  the  trachea  is  i  mm.  Hg.  during  tranquil 
inspiration);  while  during  forced  respiration,  when  the  respiratory  passage  is  closed,  it  may  be  57 
mm.  Conversely,  during  ordinary  expiration,  the  pressure  is  increased  within  the  trachea  2-3  mm. 
Hg.,  while  during  forced  expiration,  owing  to  the  compression  of  the  abdominal  muscles,  it  may 
reach  87  mm.  Hg. 

Other  Factors. — The  increase  of  the  blood  pressure  during  inspiration,  as  well  as  the  fall  during 
expiration,  must  in  part  depend  upon  the  pressure  within  the  abdomen.  As  the  diaphragm  descends 
during  inspiration,  it  presses  upon  the  abdominal  contents,  including  the  abdominal  vessels,  whereby 
the  blood  pressure  must  be  increased.  The  reverse  effect  occurs  during  expiration  [Sckweinburg). 
[Section  of  both  phrenic  nerves  and  opening  of  the  abdominal  cavity  cause  the  respiratory  undula- 
tions almost  entirely  to  disappear.  The  respiratory  undulations,  therefore,  depend  in  great  part  upon 
the  changes  of  the  abdominal  pressure  and  the  effect  of  these  changes  on  the  amount  of  blood  in 
the  abdominal  vessels.  When  making  a  blood-pressure  experiment,  pressure  upon  the  abdomen  of 
the  animal  with  the  hand  causes  the  blood  pressure  to  rise  rapidly.] 

(g)  Variations  with  each  Pulse  Beat. — The  mean  arterial  pressure  undergoes 
a  variation  with  each  heart  beat  ox  pulse  ^^rt-/,  causing  the  so-called  pulsatory  un- 
dulations (Fig.  107).  The  mass  of  blood  forced  into  the  arteries  with  each 
ventricular  systole  causes  a  positive  wave  and  an  increase  of  the  pressure  corres- 
ponding with  it,  which,  of  course,  corresponds  in  its  development  and  in  its  form 
with  the  pulse  curve. 

In  the  large  arteries,Volkmann  found  the  increase  during  the  heart  beat  to  be  =  Jg  (horse)  and  -^^ 
(dog)  of  the  total  pressure. 

None  of  the  apparatus  described  in  |  84  gives  an  exact  representation  of  the  pulse  curve.  They 
all  show  simply  a  rise  and  fall,  a  simple  curve.  The  sphygmograph  alone  gives  a  true  expression 
of  the  undulations  in  the  blood  pressure  which  are  due  to  the  heart  beat. 

(/%)  Arrest  of  the  Heart's  Action.— If  the  heart's  action  be  arrested  or  in- 
terrupted by  continued  stimulation  of  the  vagus,  or  by  high  positive  respiratory 
pressure,  the  arterial  blood  pressure  falls  enormously,  while  it  rises  in  the  veins  as 
the  blood  flows  into  them  from  the  arteries  to  equilibrate  the  difference  of  pressure 
in  the  two  sets  of  vessels.  This  experiment  shows  that,  even  when  the  difference 
of  pressure  is  almost  entirely  set  aside,  the  passive  blood  presses  upon  the  arterial 
walls,  i.e.,  on  account  of  the  overfilling  of  the  blood  vessels  a  slight  pressure  is 
exerted  upon  the  walls,  even  when  there  is  no  circulation.  [As  already  stated,  the 
arterial  pressure  depends  on  the  condition  of  the  central  organ— the  heart — and  on 
the  peripheral  organs — the  small  arteries.  If  the  action  of  the  heart  be  arrested, 
then  the  blood  pressure  rapidly  falls.  Fig.  108  shows  the  effect  on  the  blood  pressure 
of  arresting  the  action  of  the  heart  by  stimulation  of  the  peripheral  end  of  the 
vagus.  There  is"  a  sudden  fall  of  the  arterial  pressure,  as  shown  by  the  rapid  fall 
of  the  curve  from  «.] 


170       RELATION  OF  BLOOD  PRESSURE  TO  PULSE  RATE. 

[Variations  in  Animals.— The  pressure  in  the  arterial  system  depends  upon  the  balance  be- 
tween the  niflow  and  outflow,  i.  c,  upon  the  heart  and  the  state  of  the  arterioles.  But  it  is  to  be 
noted  that  the  central  factor,  the  heart,  varies  in  different  animals.  In  the  rabbit,  the  heart  normally 
beats  rapidly,  so  that  section  of  the  vagi  does  not  cause  any  great  increase  in  the  number  of  beats 
nor  IS  the  blood  pressure  much  raised  thereby.  In  the  dog,  on  the  other  hand,  the  beats  are  con- 
siderably increased  by  section  of  the  vagi,  while  the  blood  pressure  rises  considerably  Atropin 
paralyzes  the  cardiac  terminations  of  the  vagus,  and  thereby  trebles  the  number  of  heart  beats  in  the 
dog,  while  It  only  raises  it  25  per  cent,  in  the  rabbit ;  in  man,  again,  the  number  may  be 
doubled.  As  Brunton  has  shown,  this  difference  of  the  initial  number  of  heart  beats  and  the  action 
of  the  vagus  have  important  relations  to  the  action  of  drug?  on  the  blood  pressure.  For  example, 
if  an  mtact  rabbit  be  caused  to  inhale  amy!  nitrite,  the  blood  pressure  falls  at  once  and  rapidly' 
whde  m  the  dog  the  fall  may  be  slight.  The  pulse  of  the  dog,  however,  is  greatly  accelerated,  so 
much  so  as  to  be  nearly  as  rapid  as  that  of  the  rabbit.  In  both,  the  vessels  are  dilated,  but  In  the 
dog,  notwithstandmg  this  dilatation,  which/,?;-  se  would  cause  the  pressure  to  fall,  the  heart  of  the 
dog  beats  now  so  rapidly  as  to  compensate  for  this,  and  thus  keeps  the  blood  pressure  nearly  normal ; 
whde  the  mcreased  rate  of  beating  in  the  rabbit  is  not  sufficient  for  this  purpose.  If  the  vagi  in  the 
dog  be  divided,  the  subsequent  inhalation  of  amyl  nitrite  causes  a  fall  of  blood  pressure  like  that  in 
the  rabbit  {Brunton).^ 


Fig.  108. 


Blood-pressure  tracing  taken  with  a  mercurial   kymograph  from  the  carotid  of  a  rabbit. 
o-  X,  abscissa  ;  stimulation  of  vagus  begun  at  a  and  stopped  at  b. 

[Relation  of  Blood  Pressure  to  Pulse  Rate.— When  the  blood  pressure 
rises  m  an  intact  animal,  as  a  rule  the  pulse  rate  falls,  owing  to  stimulation  of  the 
vagus  centre  increasing  the  cardio-inhibitory  action,  while  a  fall  of  blood  pressure 
is  accompanied  by  an  increase  of  the  number  of  pulse  beats  for  the  opposite 
reason,  the  action  of  the  medullary  cardio-inhibitory  centre  being  increased.  But 
the  blood  pressure  may  be  increased  either  by  the  action  of  the  heart  or  the  arteri- 
?u  "vi  A^^^  "^^  ^^^  ^^^^  ^^^  P"l'^  b^^^s  more  quickly,  and  in  some  animals 
the  blood  pressure  rises  ;  in  this  case,  the  rise  in  the  two  curves  occurs  together, 
and  If  the  vagi  be  stimulated  there  is  a  sudden  fall  of  the  blood  pressure,  due  to 
arrest  ot  the  heart  s  action,  so  that  again  the  two  curves  are  parallel.  If  the 
arterioles  contract  the  blood  pressure  rises,  but  by  and  by  the  pulse  rate  falls, 
owing  to  the  cardio-inhibitory  action  of  the  vagus  ;  while,  on  the  other  hand,  if 
the   arterioles  are  dilated,  the  blood  pressure  falls,  and   the  heart  beats  faster. 


BLOOD    PRESSURE    IN    THE   VEINS.  171 

Thus,  in  both  of  these  cases  the  pulse  curve  and  blood-pressure  curve  run  in  opposite 
directions.     These  results  only  obtain  when  the  vagi  are  intact  (yBrunton).'\ 

[The  increase  in  the  pulse  rate  and  blood  pressure  following  section  of  the  vagi  do  not  run 
parallel.  Both  sooner  or  later  reach  a  maximum,  but  the  blood  pressure  gradually  falls  to  or  below 
the  normal,  while  the  pulse  rate  remains  above  the  normal  {^Mimzel).'\ 

For  the  effects  of  the  nervous  system  upon  the  blood  pressure  see  ^371. 

Pathological. — In  persons  suffering  from  granular  or  contracted  kidney  and  sclerosis  of  the 
arteries,  in  lead  poisoning,  and  after  the  injection  of  ergotin,  which  causes  contraction  of  the  small 
arteries,  it  is  found,  on  employing  the  method  of  v.  Basch,  that  the  blood  pressure  is  raised.  It  is 
also  increased  in  cases  of  cardiac  hypertrophy  with  dilatation,  and  by  digitalis  in  cardiac  affec- 
tions, while  it  falls  after  the  injection  of  morphia.  The  blood  pressure  falls  in  fever,  a  fact  also 
indicated  in  the  sphygmogram  (^  69),  and  it  is  low  in  chlorosis  and  phthisis. 

86.  BLOOD  PRESSURE  IN  THE  CAPILLARIES.— Methods.— Direct  estimation 
of  the  capillary  pressure  is  not  possible,  on  account  of  the  smallness  of  the  capillary  tubes.  If  a 
glass  plate  of  known  dimensions  be  placed  on  a  portion  of  the  skin  rich  in  blood  vessels,  and  if  it 
be  weighted  until  the  capillaries  become  pale,  we  obtain  approximately  the  pressure  necessary  to 
overcome  the  capillary  pressure.  N.  v.  Kries  placed  a  small  glass  plate  (Fig.  109)  2.5-5  ^'\-  nrni-j 
on  a  suitable  part  of  the  skin,  e.  g.,  the  skin  at  the  root  of  the  nail  on  the  terminal  phalanx,  or  on  the 
ear  in  man,  and  on  the  gum  in  rabbits.  Into  a  scale  pan  attached  to  this,  weights 
were  placed  until  the  skin  became  pale.  The  pressure  in  the  capillaries  of  the 
hand,  when  the  hand  is  raised,  Kries  found  to  be  24  mm.  Hg. ;  when  the  hand 
hangs  down,  54  mm.  Hg.  :  in  the  ear,  20  mm.,  and  in  the  gum  of  a  rabbit,  32  mm. 

Roy  and  Graham  Brown  compressed  from  below  transparent  vascular  membranes 
against  a  glass  plate  by  means  of  an  elastic  bag  connected  with  a  manometer,  while 
the  variations  in  the  capillaries  were  observed  from  above  by  a  microscope. 

Conditions  influencing  Capillary  Pressure. — The  capillary 
blood  pressure  in  a  given  area  increases  (i)  When  the  afferent 
small  arteries  dilate,  so  that  the  blood-pressure  within  the  large 
arteries  is  propagated  more  easily  into  them.  (2)  By  increasing  the 
pressure  in  the  small  afferent  arteries.  (3)  By  narrowing  the  diam- 
eter of  the  veins  leading  from  the  capillary  area.  Closure  of  the 
veins  may  quadruple  the  pressure.  (4)  By  increasing  the  pressure 
in  the  veins  (<?,  g.,  by  altering  the  position  of  a  limb).  A  diminu- 
tion of  the  capillary  pressure  is  caused  by  the  opposite  conditions. 

Changes  in  the  diameter  of  the  capillaries  influence  the  internal  pressure.  We 
have  to  consider  the  movements  of  the  capillary  wall  itself  as  well  as  the  pressure, 
swelling,  and  consistence  of  the  surrounding  tissues.  The  resistance  to  the  blood  v.  Kries's  appara- 
stream  is  greatest  in  the  capillary  area,  and  it  is  evident  that  the  blood  in  a  long  tus  for  capillary- 
capillary  must  exert  more  pressure  at  the  commencement  than  at  the  end  of  the  Luare  of  glass'^' 
■capillary;  in  the  middle  of  the  capillary  area  the  blood  pressure  is  just  about  one- 
half  of  the  pressure  within  the  large  arteries  (Z?tJ«a'^rj).  The  capillary  pressure  must  also  vary  in 
different  regions  of  the  body.  Thus,  the  pressure  within  the  intestinal  capillaries,  in  those  constitut- 
ing the  glomeruli  of  the  kidney,  and  in  those  of  lower  limbs  when  the  person  is  in  the  erect  posture, 
must  be  greater  than  in  other  regions,  depending  in  the  former  cases  partly  upon  the  double  resist- 
ance caused  by  two  sets  of  capillaries,  and  in  the  latter  case  partly  on  purely  hydrostatic  causes. 

87.  BLOOD  PRESSURE  IN  THE  VEINS.— In  the  large  venous 
trunks  near  the  heart  (innominate,  subclavian,  jugular)  a  mean  negative 
pressure  of  about  — o.i  mm.  Hg.  prevails  (ZT.  Jacobson).  Hence,  the  lymph 
stream  can  flow  unhindered.  As  the  distance  of  the  veins  from  the  heart  increases, 
there  is  a  gradual  increase  of  the  lateral  pressure  ;  in  the  external  facial  vein 
(sheep)  =  -)-  3  mm.  ;  brachial,  4.1  mm.,  and  in  its  branches  9  mm.;  crural, 
1 1.4  mm.  [The  pressure  is  said  to  be  negative  when  it  is  less  than  that  of  the 
atmosphere.  The  gradual  fall  of  the  blood  pressure  from  the  capillary  area  (C)  to 
the  venous  area  (V)  is  shown  in  Fig.  108,  while  within  the  thorax,  where  the  veins 
terminate  in  the  right  auricle,  the  pressure  is  negative.] 

Modifying  Conditions. — (i)  All  conditions  which  diminish  the  difference  of 
j>ressure  between  the  arterial  and  venous  systems  increase  the  venous  pressure,  and 
vice  versa. 


172 


BLOOD    PRESSURE    IN    THE    VEINS. 


(2)  General  plethora  of  blood  increases  it ;  aniemia  diminishes  it. 

(3)  Respiration,  or  the  aspiration  of  the  thorax,  affects  specially  the  pres- 
sure in  the  veins  near  the  heart  ;  during  inspiration,  owing  to  the  diminished 
tension,  blood  flows  toward  the  chest,  while  during  expiration  it  is  retarded.  The 
effects  are  greater,  the  deeper  the  respiratory  movement,  and  these  may  be  very 
great  when  the  respiratory  passages  are  closed  (§  60). 

[When  a  vein  is  exposed  at  the  root  of  the  neck,  it  collapses  during  inspiration,  and  fills  during 
expiration.  The  respiratory  movements  do  not  affect  the  venous  stream  in  peripheral  veins.  The 
veins  of  the  neck  and  face  become  distended  with  blood  during  crying,  and  on  making  violent 
expiratory  efforts,  as  in  blowing  upon  a  wind  instrument.  Every  surgeon  is  acquainted  with  the 
fact  that  air  is  particularly  liable  to  be  sucked  into  the  veins,  especially  in  operations  near  the  root 
of  the  neck.     This  is  due  to  the  negative  intra-thoracic  pressure  occurring  during  inspiration.] 

(4)  Aspiration  of  the  Heart. — Blood  is  sucked  or  aspirated^  into  the  auricles 
when  they  dilate  (p.  100),  so  that  there  is  a  double  aspiration — one  synchronous 
with  inspiration,  and  the  other,  which  is  but  slight,  synchronous  with  the  heart 
beat.  There  is  a  corresponding  retardation  of  the  blood  stream  in  the  venae  cavae^ 
caused  by  the  contraction  of  the  auricle  (p.  99,  a).  The  respiratory  and  cardiac 
undulations  are  occasionally  observable  in   the  jugular  vein  of  a  healthy  person 

(§99)- 

YiQ   ,,0  (5)  Change  in  the /<?j"/'//^«  of  the  limbs  or  ot 

the  body,  for  hydrostatic  reasons,  greatly  alters 
the  venous  pressure.     The  veins  of  the  lower  ex- 
tremity bear  the  greatest  pressure,  while  at  the 
same  time  they  contain    most  muscle  (jST.   Bar- 
\        delehen,  §  65).     Hence,  when  these  muscles  from 
any  cause  become  insufficient,  dilatations  occur 
\     in   the  veins,  giving   rise   to   the  production    ol 
';    varicose  veins. 


BR 


Scheme  of  the  blood  pressure.  H,  heart; 
a,  auricle  ;  v,  ventricle  ;  A,  arterial ;  C, 
capillary  ;  and  V,  venous  areas.  The 
circle  indicates  the  parts  within  the 
thorax  ;  B.  P., pressure  in  the  aorta. 


[Braune  showed  that  the  femoral  vein  under  Poupart's 
ligament  collapsed  when  the  lower  limb  was  rotated  out- 
ward and  backward,  but  tilled  again  when  the  limb  was 
restored  to  its  former  position.  All  the  veins  which  open 
into  the  femoral  vein  have  valves,  which  permit  blood  to 
pass  into  the  femoral  vein,  but  prevent  its  reflux.  This 
mechanism  acts  to  a  slight  degree  as  a  kind  of  suction  and 
pressure  apparatus  when  a  person  walks,  and  thus  favors  the 
onward  movement  of  the  blood.] 

[(6)  Muscular  Movements. — Veins  which 
lie  between  muscles  are  compressed  when  these 
muscles  contract,  and  as  valves  exist  in  the  veins, 
the  flow  of  blood  is  accelerated  toward  the  heart ;  if  the  outflow  of  the  blood  be 
obstructed  in  any  way,  then  the  venous  pressure  on  the  distal  side  of  the  obstruc- 
tion may  be  greatly  increased.  When  a  fillet  is  tied  on  the  upper  arm,  and  the 
person  moves  the  muscles  of  the  forearm,  the  superficial  veins  become  turgid,  and 
can  be  distinctly  traced  on  the  surface  of  the  limb.] 

(7)  Gravity  exercises  a  greater  eff"ect  upon  the  blood  stream  in  the  extensile 
veins  than  upon  the  stream  in  the  arteries.  It  acts  on  the  distribution  of  the 
blood,  and  thus  indirectly  on  the  motion  of  the  blood  stream.  It  favors  the 
emptying  of  descending  veins,  and  retards  the  emptying  of  ascending  veins,  so 
that  the  pressure  becomes  less  in  the  former  and  greater  in  the  latter.  If  the 
position  of  the  limb  be  changed,  the  conditions  of  pressure  are  also  altered.  If  a 
person  be  suspended  with  the  head  hanging  downward,  the  face  soon  becomes- 
turgid,  the  position  of  the  body  favoring  the  inflow  of  blood  through  the  arteries, 
and  retarding  the  outflow  through  the  veins.  If  the  hand  hangs  down  it  contains 
more  blood  in  the  veins  than  if  it  is  held  for  a  short  time  over  the  head,  when  it 
becomes  pale  and  bloodless.     [As  Lister  has  shown,  the  condition  of  the  vessels 


BLOOD    PRESSURE    IN    THE    PULMONARY   ARTERY.  173 

in  the  limb  is  influenced  not  only  by  the  position  of  the  limb,  but  also  by  the 
fact  that  a  nervous  mechanism  is  called  into  play.] 

[Ligature  of  the  portal  vein  causes  congestion  of  the  rootlets  and  dilatation  of  all  the  blood 
vessels  in  the  abdomen ;  gradually  nearly  all  the  blood  of  the  animal  accumulates  within  its  belly, 
so  that,  paradoxical  as  it  may  seem,  an  animal  may  be  bled  into  its  own  belly.  As  a  consequence 
of  sudden  and  complete  ligature  of  this  vein,  the  arterial  blood  pressure  gradually  and  rapidly  falls, 
and  the  animal  dies  very  quickly.  If  the  ligature  be  removed  before  the  blood  pressure  falls  too 
much,  the  animal  may  recover.  Schiff  and  Lautenbach  regard  the  symptoms  as  due  chiefly  to  the 
action  of  a  poison,  for  when  the  blood  of  the  portal  vein  in  an  animal  treated  in  this  way  is  injected 
into  a  frog,  it  causes  death  within  a  few  hours,  while  the  ordinary  blood  of  the  portal  vein  has  no 
effect.] 

[Ligature  of  the  Veins  of  a  Limb. — The  effect  of  ligaturing  or  compressing  all  the  veins  of 
a  limb  is  well  seen  in  cases  where  a  bandage  has  been  applied  too  tightly.  It  leads  to  congestion 
and  increase  of  pressure  within  the  veins  and  capillaries,  increased  transudation  of  fluid  through 
the  capillaries,  and  c'onsequent  cedetna  of  the  parts  beyond  the  obstruction.  Ligature  of  one  vein 
does  not  always  produce  oedema,  but  if  several  veins  of  a  limb  be  ligatured,  and  the  vasomotor 
nerves  be  divided  at  the  same  time,  the  rapid  production  of  oedema  is  ensured.  In  pathological 
cases  the  pressure  of  a  tumor  upon  a  large  vein  may  produce  similar  results  (^  203).] 

88.  BLOOD  PRESSURE  IN  THE  PULMONARY  ARTERY.— Methods.— (i) 
Direct  estimation  of  the  blood  pressure  in  the  pulmonary  artery  by  opening  the  chest  was  made 
by  C.  Ludwig  and  Beutner  (1850).  Artificial  respiration  was  kept  up,  and  the  manometer  was 
placed  in  connection  with  the  left  branch  of  the  pulmonary  artery.  The  circulation  through  the 
left  lung  of  cats  and  rabbits  was  thereby  completely  cut  off,  and  in  dogs  to  a  great  extent  interrupted. 
There  was  an  additional  disturbing  element,  viz.,  the  removal  of  the  elastic  force  of  the  lungs,  owing 
to  the  opening  of  the  chest,  whereby  the  venous  blood  no  longer  flowed  normally  into  the  right 
heart,  while  the  heart  itself  was  under  the  full  pressure  of  the  atmosphere.  The  estimated  pressure 
in  the  dog  =z  29.6  ;  in  the  cat  =  17. 7  ;  in  the  rabbit,  12  mm.  Hg.,z'.  e.,  in  the  dog  3  times,  the 
rabbit  4  times,  and  the  cat  5  times  less  than  the  carotid  pressure. 

(2)  Hering  (1850)  experimented  upon  a  calf  with  ectopia  cordis.  He  introduced  glass  tubes 
directly  into  the  heart,  by  pushing  them  through  the  muscular  walls  of  the  ventricles.  The  blood 
rose  to  the  height  of  21  inches  in  the  right  tube,  and  33.4  inches  in  the  left. 

(3)  Faivre  (1856)  introduced  a  catheter  through  the  jugular  vein  into  the  right  ventricle,  and 
placed  it  in  connection  with  a  recording  tambour. 

Indirect  measurements  have  been  made  by  comparing  the  relative  thickness  of  the  walls  of 
the  right  and  left  ventricles,  or  the  walls  of  the  pulmonary  artery  and  aorta. 

Beutner  and  Marey  estimated  the  relation  of  the  pulmonary  artery  to  the  aortic 
pressure  as  i  to  3  ;  Goltz  and  Gaule  as  2  to  5  ;  Fick  and  Badoud  found  a  pressure 
of  60  mm.  in  the  pulmonary  artery  of  the  dog,  and  in  the  carotid  iii  mm.  Hg. 
The  blood  pressure  within  the  pulmonary  artery  of  a  child  is  relatively  higher 
than  in  the  adult. 

Elastic  Tension  of  Lungs. — The  lungs  within  the  chest  are  kept  in  a  state 
of  distention,  owing  to  the  fact  that  a  negative  pressure  exists  on  their  outer 
pleural  surface.  When  the  glottis  is  open,  the  inner  surface  of  the  lung  and  the 
walls  of  the  capillaries  in  the  pulmonary  air  vesicles  are  exposed  to  the  full  pres- 
sure of  the  air.  The  heart  and  large  blood  vessels  within  the  chest  are  not  ex- 
posed to  the  full  pressure  of  the  atmosphere,  but  only  to  the  pressure  which  cor- 
responds to  the  atmospheric  pressure  minus  the  pressure  exerted  by  the  elastic 
traction  of  the  lungs  (§  60).  The  trunks  of  the  pulmonary  artery  and  veins  are 
subjected  to  the  same  conditions  of  pressure.  The  elastic  traction  of  the  lungs 
is  greater  the  more  they  are  distended.  The  blood  of  the  pulmonary  capillaries 
will,  therefore,  tend  to  flow  toward  the  large  blood  vessels.  As  the  elastic  traction 
of  the  lungs  acts  chiefly  on  the  thin-walled  pulmonary  veins,  while  the  semilunar 
valves  of  the  pulmonary  artery,  as  well  as  the  systole  of  the  right  ventricle,  pre- 
vent the  blood  from  flowing  backward,  it  follows  that  the  blood  in  the  capillaries  of 
the  lesser  circulation  must  flow  toward  the  pulmonary  veins. 

If  tubes  with  thin  walls  be  placed  in  the  walls  of  an  elastic  distensible  bag,  the 
lumen  of  these  tubes  changes  according  to  the  manner  in  which  the  bag  enclosing 
them  is  distended.  If  the  bag  be  directly  inflated  so  as  to  increase  the  pressure 
within  it,  the  lumen  of  the  tubes  is  diminished  {Funke  and  Latschenberger').     If 


174  BLOOD    PI^SSURE    IN    THE    PULMONARY    ARTERY. 

the  bag  be  placed  within  a  closed  space,  and  the  tension  within  this  space  be 
diminished  so  that  the  bag  thereby  becomes  distended,  the  tubes  in  its  wall 
dilate.  In  the  latter  case — viz.,  by  negative  aspiration — the  lungs  are  kept 
distended  within  the  thorax,  hence  the  blood  vessels  of  the  lungs  containing  air 
are  wider  than  those  of  collapsed  lungs  {Quincke  and  Pfeiffer,  Bowiiiich  and 
Garland,  De  J^agef).  Hence  also,  more  blood  flows  through  the  lungs  dis- 
tended within  the  thorax  than  through  collapsed  lungs.  The  dilatation  which 
takes  place  during  inspiration  acts  in  a  similar  manner.  The  negative  pressure 
that  obtains  within  the  lungs  during  inspiration  causes  a  considerable  dilatation 
of  the  pulmonary  veins,  into  which  the  blood  of  the  lungs  flows  readily,  while 
the  blood  under  high  pressure  in  the  thick-walled  pulmonary  artery  scarcely 
undergoes  any  alteration.  The  velocity  of  the  blood  stream  in  the  pulmonary 
vessels  is  accelerated  during  inspiration  (Z><?  yager,  Lalesqiie).  The  blood 
pressure  in  the  pulmonary  circuit  is  raised  when  the  lungs  are  inflated.  Con- 
traction of  small  arteries,  which  causes  an  increase  of  the  blood  pressure  in  the 
systemic  circulation,  also  raises  the  pressure  in  the  pulmonary  circuit,  because 
more  blood  flows  to  the  right  side  of  the  heart. 

The  vessels  of  the  pulmonary  circulation  are  very  distensible  and  their  tonus 
is  slight.  [Occlusion  of  one  branch  of  the  pulmonary  artery  does  not  raise  the 
pressure  within  the  aorta.  Even  when  one  pulmonary  artery  is  plugged  with  an 
embolon  of  paraffin,  the  pressure  within  the  aortic  system  is  not  raised  {Lichtheini). 
When  a  large  branch  of  the  pulmonary  artery  becomes  impervious,  the  obstruc- 
tion is  rapidly  compensated  for,  and  this  is  not  due  to  the  action  of  the  nervous 
system.  The  vasomotor  system  has  much  less  eff"ect  upon  the  pulmonary  blood 
vessels  than  upon  those  of  the  systemic  circulation.  The  compensation  seems 
to  be  due  chiefly  to  the  great  distensibility  and  dilatation  of  the  pulmonary 
vessels  {Lichtheim).'\  We  know  little  of  the  effect  of  physiological  conditions 
upon  the  pulmonary  artery.  According  to  Lichtheim  suspension  of  the  respira- 
tion causes  an  increase  of  the  pressure.  [In  one  experiment  he  found  that  the 
pressure  within  the  pulmonary  artery  was  increased,  while  it  was  not  increased  in 
the  carotid,  and  he  regards  this  experiment  as  proving  the  existence  of  vasomotor 
nerves  in  the  lung.] 

During  the  act  of  great  straining,  the  blood  at  first  flows  rapidly  out  of  the  pulmonary  veins, 
and  afterward  ceases  to  flow,  because  the  inflow  of  blood  into  the  pulmonary  vessels  is  inter- 
fered with.  As  soon  as  the  straining  ceases,  blood  flows  rapidly  into  the  pulmonary  vessels 
{^LaUsiine). 

Severini  found  that  the  blood  stream  through  the  lungs  is  greater  and  more  rapid  when  the 
lungs  are  filled  with  air  rich  in  C()2  than  when  the  air  within  them  is  rich  in  O.  He  supposes 
that  these  gases  act  upon  the  vascular  ganglia  within  the  lung,  and  thus  aff'ect  the  diameter  of 
the  vessels. 

Pathological. —  Increase  of  the  pressure  within  the  area  of  the  pulmonary  artery  occurs  fre- 
quently in  man,  in  certain  cases  of  heart  disease.  In  these  cases  the  second  pulmonary  sound  is 
always  accentuated,  while  the  elevation  caused  thereby  in  the  cardiogram  is  always  more  marked 
and  occurs  earlier  (|  52).  Electrical  and  mechanical  stimulation  of  abdominal  organs  raises  the 
blood  pressure  in  the  pulmonary  artery  [Morel). 

[The  action  of  drugs  on  the  pulmonary  circulation  may  be  tested  by  Holmgren's  apparatus 
(?  94)1  which  permits  of  distention  of  the  lung  and  retention  of  the  normal  circulation  in  the 
frog.  Cold  contracts  the  pulmonary  capillaries  to  one-third  of  their  diameter,  and  anaesthetics 
arrest  the  pulmonary  circulation,  chloroform  being  most  and  ether  least  active,  while  ethidene  is 
intermediate  in  its  effect.] 

[Influence  of  the  Nervous  System. — The  pulmonary  circulation  is  much 
less  dependent  on  the  nervous  system  than  the  systemic  circulation.  Very  con- 
siderable variations  of  the  blood  pressure  within  the  other  parts  of  the  body  may 
occur,  while  the  pressure  within  the  right  heart  and  pulmonary  artery  is  but 
slightly  affected  thereby.  The  pressure  is  increased  by  electrical  stimulation  of 
the  medulla  oblongata,  and  it  falls  when  the  medulla  is  destroyed.  Section  and 
stimulation   of  the  central  or  peripheral  ends  of  the  vagi,   stimulation   of   the 


VELOCITY   OF   THE    BLOOD    STREAM. 


175 


splanchnics,  and  of  the  central  end  of  the  sciatic,  have  but  a  minimal  influence 
on  the  pressure  of  the  pulmonary  artery  (^Auberi).~\ 

89.  VELOCITY  OF  THE  BLOOD  STREAM.— Methods :  (i)  A.  W.  Volkmann's 
Haemadromometer  (1850). — A  glass  tube  of  the  shape  of  a  hair-pin,  60-130  cm.  long  and  2  or 
3  mm.  broad,  with  a  scale  etched  on  it,  or  attached  to  it,  is  fixed  to  a  metallic  basal  plate,  B,  so 


Fig.  III. 


Volkmann's  haemadromometer  (B).  I,  blood  flows  from  artery  to 
artery ;  II,  blood  must  pass  through  the  glass  tube  of  B ;  c,  c, 
cannulas  for  the  divided  artery. 


Sww 


Ludwig  and  Dogiel's  rheometer. 
X,  Y,  axis  of  rotation  ;  A,  B, 
glass  bulbs ;  h,  k,  cannulas 
inserted  in  the  divided  artery; 
e,  ei,  rotates  on  g;  f;  c,  d, 
tubes. 

that  each  limb  passes  to  a  stop-cock  with  three  channels.  The  basal  plate  is  perforated  along  its- 
length,  and  carries  at  each  end  short  cannulse,  c,  c,  which  are  tied  into  the  ends  of  a  divided  artery. 
The  whole  apparatus  is  first  filled  with  water  [or,  better,  with  salt  solution].  The  stop-cocks  are 
moved  simultaneously,  as  they  are  attached  to  a  toothed  wheel,  and  have  at  first  the  position  given 
in  Fig.  Ill,  I,  so  that  the  blood  simply  flows  through  the  hole  in  the  basal  piece,  i.  e.,  directly 
from  one  end  of  the  artery  to  the  other.     If  at  a  given  moment  the  stop-cock  is  turned  in  the  direc- 


176       MEASUREMENT   OF    THE    VELOCITY    OF   THE    BLOOD    STREAM. 

tion  indicated  in  Fig.  in,  II,  the  blood  has  to  pass  through  the  glass  tube,  and  the  time  it  takes  to 
make  the  circuit  is  noted  ;  and  as  the  length  of  the  tube  is  known,  we  can  easily  calculate  the 
velocity  of  the  blood.  The  method  has  very  obvious  defects  arising  from  the  narrowness  of  the 
tube;  the  introduction  of  such  a  tube  offers  new  resistance,  while  there  are  no  respiratory  or  pulse 
variations  observable  in  the  stream  in  the  glass  tube. 

Volkmann  found  the  velocity  to  be  in  the  carotid  (dog)  =  205  to  357  mm.  ; 
carotid  (horse)  =  306  ;  maxillary  (horse)  =:  232  ;  metatarsal  ^  56  mm.  per 
second. 

(2)  C.  Ludwig  and  Dogiel  (1867)  devised  a  "  stromuhr  "  or  rheometer  for 
measuring  the  amount  of  blood  which  passed  through  an  artery  in  a  given  time 
(Fig.   112). 

It  consists  of  two  glass  bulbs,  A  and  B,  of  exactly  the  same  capacity.  These  bulbs  communi- 
cate with  each  other  above,  their  lower  ends  being  fi.\ed  by  means  of  the  tubes,  c  and  d,  to  the 
metal  disk,  e,  f,.  This  disk  rotates  round  the  axis,  X,  Y,  so  that,  after  a  complete  revolution,  the 
tube  c  communicates  with  f,  and  d  with  g\  y"and  g  are  provided  with  horizontally  placed  cannula;, 
h  and  k,  which  are  tied  into  the  ends  of  the  divided  artery.     The  cannula  //  is  fixed  in  the  central 


Fig.   113. 


I.  Vierordt's  haematachometer.  A,  glass  ;  e.  entrance;  a,  exit  cannula;  /,  pendulum.  II.  Dromograph.  A,  B, 
tube  inserted  in  artery  ;  C,  lateral  tube  connected  with  a  manometer  ;  ^,  index  moving  in  a  caoutchouc  membrane, 
a;  G,  handle.     III.  Curve  obtained  by  dromograph. 

end,  and_>^  in  the  peripheral  end  of  the  artery  [e.  g.,  carotid) ;  the  bulb,  A,  is  filled  with  oil,  and  B 
with  dehbrinated  blood ;  at  a  certain  moment  the  communication  through  h  is  opened,  the  blood 
flows  in,  driving  the  oil  before  it,  and  passes  into  B,  while  the  defibrinat'ed  blood  flows  through  k 
into  the  peripheral  part  of  the  artery.  As  soon  as  the  oil  reaches  m — a  moment  which  is  instantly 
noted,  or,  what  is  better,  inscribed  upon  a  revolving  cylinder— the  bulbs.  A,  B,  are  rotated  upon 
the  axis,  X,  Y,  so  that  B  comes  to  occupy  the  position  of  A.  The  same  experiment  is  repeated, 
and  can  be  continued  for  a  long  time.  The  quantity  of  blood  which  passes  in  the  unit  of  time 
(I  sec.)  IS  calculated  from  the  time  necessary  to  fill  the  bulb  with  blood.  Important  results  are 
obtained  by  means  of  this  instrument. 

[Suppose  50  c.cm.  of  blood  are  delivered  in  100  sees.,  then  i  c.cm.  flows  through  in  2  sees. 
Suppose  the  sectional  area  of  the  artery  to  be  3^  mm.  As  the  velocity  is  measured  by  the  ratio  of 
the  quantity  to  the  sectional  area,  then  5°°° 


314 


159  mm.  per  second.] 


[As  peptone  injected  into  the  blood  prevents  it  from  coagulating  (dog),  this  fact  has  been  turned 
to  account  in  using  the  rheometer.] 

(3)  Vierordt's  Haematachometer  (1858)  consists  of  a  small  metal  box  (Fig.  113,  I)  with 
parallel  glass  sides.  To  the  narrow  sides  of  the  box  are  fitted  an  inlet,  <?,  and  an  exit  cannula,  a. 
In  its  intenor  is  suspended,  against  the  entrance  opening,  a  pendulum,  /,  whose  vibrations  may  be 


VELOCITY   OF   THE    BLOOD. 


177 


read  off  on  a  curved  scale.     [This  instrument,  as  well  as   Volkmann's  apparatus,  has  only  an 
historical  interest.] 

(4)  Chauveau  and  Lortet's  Dromograph  (i860)  is  constructed  on  the  same  principle.  A  tube 
A,  B  (Fig.  113),  of  sufficient  diameter,  with  a  side  tube  fixed  to  it,  C,  which  can  be  placed  in  con- 
nection with  a  manometer,  is  introduced  into  the  carotid  artery  of  a  horse.  At  a  a  small  piece  is 
cut  out  and  provided  with  a  covering  of  gutta-percha  which  has  a  small  hole  in  it ;  through  this  a 
light  pendulum,  a,  b,  with  a  long  index,  b,  projects  into  the  tube,  i.  e.,  into  the  blood  current,  which 
causes  the  pendulum  to  vibrate,  and  the  extent  of  the  vibrations  can  be  read  off  on  a  scale,  S,  S.  G 
is  an  arrangement  to  permit  the  instrument  to  be  held.  Both  this  and  the  former  instrument  are 
tested  beforehand  with  a  stream  of  water  sent  through  them  with  varying  velocities. 

(5)  Cybulski's  Photohaematachometer. — When  fluid  flows  into  a  tube  (Fig.  114,11,  de)  in  the 
direction  of  the  arrow,  the  fluid  stands  higher  in  the  manometer /than  in  m.  The  tube  my  indicates 
the  lateral  pressure,  but/x  gives  this  plus  the  velocity  of  the  fluid  (p.  132).  The  velocity  of  the 
current  may  be  estimated  from  the  difference  in  the  level  in  the  two  tubes. 

Bitot's  tube  as  used  by  Cybuhki  is  bent  at  a  right  angle  (I,  cp),  the  end  c  being  inserted  and  tied 
into  the  central,  and/  into  the  peripheral,  part  of  a  divided  artery.  As  the  blood  flows  through  the 
tube,  the  blood  rises  higher  in  a  than  b. 

To  avoid  having  the  manometers  a  and  b  too  long,  they  are  connected  with  each  other  by  a 
capillary  tube  filled  with  air  and  provided  above  with  a  stop-cock  i.  The  blood  is  allowed  to  rise 
to    the  height  of  i   and  2,  the  stop-cock  i  is 


Fig.  114, 
I. 


closed,  and  practically  an  air  manometer  is 
made,  which  shows  a  marked  difference  in  the 
level  of  the  blood  of  the  two  tubes.  The  level 
of  the  blood  in  i  and  2  is  continually  changed 
by  the  movements  of  the  heart  and  those  of 
respiration,  and  these  variations  are  photo- 
graphed by  means  of  a  camera  n  with  a  rapidly 
moving  plate  k. 

Fig.  114,  C,  shows  a  curve  obtained 
from  the  carotid  of  a  dog.  The  velocity 
of  the  current  at  ij-  i  =  238  mm.,  in  the 
phase  2i-  2  ==  225  mm.,  and  at  31-3 
=  177  mm.  The  velocity  is  greatest 
at  the  end  of  inspiration  and  the  be- 
ginning of  expiration.  Asphyxia  in- 
creases it  at  first.  Paralysis  of  the 
sympathetic  increases  it,  while  stimula- 
tion of  this  nerve  diminishes  it.  Section 
of  the  vagi  increases  the  velocity,  while 
stimulation  diminishes  it. 

The  curve  of  the  velocity  may  be  written  off 
on  a  smoked  glass  plate,  moving  parallel  with 
the  index  b.  The  dromograph  curve.  Fig.  113, 
III,  shows  the  primary  elevation,  B,  and  the 
dicrotic  elevation  R. 

90.  VELOCITY  OF  THE 
BLOOD.— Division  of  Vessels- 
Arteries. — In  estimating  the  velocity 
of  the  blood,  it  is  important  to  remem- 
ber that  the  sectional  area  of  all  the 
branches  of  the  aorta  becomes  greater 
as  we  proceed  from  the  aorta  toward 
the  capillaries,  so  that  the  capillary  j 
area  is  700  times  greater  than  the  sec- 
tional area  of  the  aorta.     As  the  veins 

join  and  form  larger  trunks,  the  venous  area  gradually  becomes  smaller,  but  the 
sectional  area  of  the  venous  orifices  at  the  heart  is  greater  than  that  of  the  cor- 
responding arterial  orifices.  [We  may  represent  the  result  as  two  cones  placed 
base  to  base  (Fig.  115),  the  bases  meeting  in  the  capillary  area.     The  sectional 


Scheme  of  the  photohaematachometer;  II.  Pilot's  tube. 


178  VELOCIT\'  OF  THE  BLOOD. 

area  of  the  venous  orifice  (V)  is  represented  larger  than  that  of  the  arterial  (A). 
The  increased  sectional  area  influences  the  velocity  of  the  blood  current, 
while  the  resistance  affects  the  pressure.] 

The  common   iliacs  are  an  exception;  the  sum  of  their  sectional  areas  is  less  than  that  of  the 
aorta ;  the  sections  of  the  four  pulmonary  veins  are  together  less  than  that  of  the  pulmonary  artery. 

(2}  Sectional  Area. — An  equal  quantity  of  blood  must  pass  through  every 

section    of   the    circulatory    system,    through 
pjg  ,,-  the   pulmonic   as   well    as   through    the    sys- 

temic circulation,  so  that  the  same  amount 
of  blood  must  pass  through  the  pulmonary 
artery  and  aorta,  notwithstanding  the  very 
unequal  blood  pressure  in  these  two  vessels. 

(3)  Lumen. — The  velocity  of  the  current, 
therefore,  in  various  sections  of  the  vessels, 
must  be  inversely  as  their  lumen. 

(4)  Capillaries. — Hence,  the  velocity 
must  diminish  very  considerably  as  we  pass 
from  the  root  of  the  aorta  and  the  pulmonary 
artery    toward    the    capillaries,  so    that    the 

Scheme  ofthesec^ionaUrea^^^A,  arterial,  ^^^      vclocity  in  the  capillaHes  of  mammals  = 

0.8  millimetre  per  sec;  frog  =  o.53  mm. 
{E.  H.  Weber^  ;  man  =  0.6  to  0.9  (C  Vierordt).  According  to  A.  W.  Volktiiann, 
the  blood  in  mammalian  capillaries  flows  500  times  slower  than  the  blood  in  the 
aorta,  so  that  the  total  sectional  area  of  all  the  capillaries  must  be  500  times  greater 
than  that  of  the  aorta.  Bonders  found  the  velocity  of  the  stream  in  the  small 
afferent  arteries  to  be  10  times  faster  than  in  the  capillaries. 

Veins. — The  current  becomes  accelerated  in  the  veins,  but  in  the  larger  trunks 
it  is  0.5  to  0.75  times  less  than  in  the  corresponding  arteries. 

(5)  Mean  Blood  Pressure. — The  velocity  of  the  blood  does  not  depend 
upon  the  mean  blood  pressure,  so  that  it  may  be  the  same  in  congested  and  in 
anaemic  parts  {Volkmann,  Hering). 

(6)  Difference  of  Pressure. — On  the  other  hand,  the  velocity  in  any  section 
of  a  vessel  is  dependent  on  the  difference  of  the  pressure  which  exists  at  the  com- 
mencement and  at  the  end  of  that  particular  section  of  a  blood  vessel ;  it  depends, 
therefore,  on  (i)  the  vis  a  tergo  {i.e.,  the  action  of  the  heart),  and  (2)  on  the 
amount  of  the  resistance  at  the  periphery  (dilatation  or  contraction  of  the  small 
vessels). 

Corresponding  to  the  smaller  difference  in  the  arterial  and  venous  pressure  in  the  foetus  (g  85), 
the  velocity  of  the  blood  is  less  in  this  case  [Cohnslein  and  Zuntz). 

(7)  Pulsatory  Acceleration. — With  every  pulse  beat  z.  corresponding  accel- 
eration of  the  blood  current  (as  well  as  of  the  blood  pressure)  takes  place  in  the 
arteries  (pp.  169,  176).  In  large  vessels,  Vierordt  found  the  increase  of  the 
velocity  during  the  systole  to  be  greater  by  ^  to  Yi  than  the  velocity  during  the 
diastole.  The  variations  in  the  velocity  caused  by  the  heart  beat  are  recorded  in 
Fig.  113,  obtained  by  Chauveau's  dromograph  from  the  carotid  of  a  horse.  The 
velocity  curve  corresponds  with  a  sphygmogram — P  represents  the  primary  eleva- 
tion and  R  the  dicrotic  wave.  This  acceleration,  as  well  as  the  pulse,  disappears 
in  the  capillaries.  A  pulsatory  acceleration,  more  rapid  during  its  first  phase,  is 
observable  in  the  small  arteries,  although  the  arteries  themselves  are  not  distended 
thereby. 

(8;  Respiratory  Effect. — Every  ifispiration  retards  the  velocity  in  the 
arteries,  every  expiration  aids  it  somewhat ;  but  the  -value  of  these  agencies  is  very 
small. 


THE   DURATION    OF   THE    CIRCULATION.  179 

If  we  compare  what  has  already  been  said  regarding  the  effect  of  the  respiration  on  the  contraction 
and  dilatation  of  the  heart  and  on  the  blood  stream  (^  60),  it  is  clear  that  respiration  favors  the 
blood  stream,  and  so  does  artificial  respiration.  When  artificial  respiration  is  interrupted,  the 
blood  stream  becomes  slower  {Dogiel).  If  the  suspension  of  respiration  lasts  somewhat  longer,  the 
current  is  again  accelerated  on  account  of  the  dyspnceic  stimulation  of  the  vasomotor  centre  [Heiden- 
ham)  \\  371,  I). 

(9)  Modifying  Conditions. — Many  circumstances  affect  the  velocity  of  the 
blood  in  the  veins.  (1)  There  are  regzi/ar  variations  in  the  large  veins  near  the 
heart  due  to  the  respiratioti  and  the  movements  of  the  heart  (§§  50  and  60).  (2) 
Irregular  vzxizXioxis  due  to  pressure,  e.  g.,  from  contracting  muscles  (§  87),  fric- 
tion on  the  skin  in  the  direction  or  against  the  direction  of  the  venous  current ; 
\he  position  oi  a  limb  or  of  the  body.  The  pump-like  action  of  the  veins  of  the 
groin  on  moving  the  leg  has  been  referred  to  (§  87).  When  the  lower  limb  is 
extended  and  rotated  outward,  the  femoral  vein  in  the  iliac  fossa  collapses,  owing 
to  an  internal  negative  pressure  ;  when  the  thigh  is  flexed  and  raised,  it  fills  under 
a  positive  pressure  {Braune').     A  similar  condition  obtains  in  walking. 

91.  CAPACITY  OF  THE  VENTRICLES.— Vierordt  calculated  the  capacity  of  the  left 
ventricle  from  the  velocity  of  the  blood  stream,  and  the  amount  of  blood  discharged  per  second  by 
the  right  carotid,  right  subclavian,  the  two  coronary  arteries,  and  the  aorta  below  the  origin  of  the 
innominate  artery.  He  estimated  that  with  every  systole  of  the  heart,  172  cubic  centimetres  (equal 
to  I  So  grammes)  of  blood  were  discharged  into  the  aorta  ;  this,  therefore,  must  be  the  capacity  of 
the  left  ventricle  (compare  \  83). 

92.  THE  DURATION  OF  THE  CIRCULATION.— The  time  re- 
quired by  the  blood  to  make  a  complete  circuit  through  the  course  of  the  cir- 
culation was  first  determined  by  Hering  (1829),  in  the  horse.  He  injected  a  2 
per  cent,  solution  of  potassium  ferrocyanide  into  a  special  vein,  and  ascertained 
(by  means  of  ferric  chloride)  when  this  substance  appeared  in  the  blood  taken 
from  the  corresponding  vein  on  the  opposite  side  of  the  body.  The  ferrocyanide 
may  also  be  injected  into  the  central  or  cardiac  end  of  the  jugular  vein,  and  the 
time  noted  at  which  its  presence  is  detected  in  the  blood  of  the  peripheral  end  of 
the  same  vein.  Vierordt  (1858)  improved  this  method  by  placing  under  the  cor- 
responding vein  of  the  opposite  side  a  rotating  disk,  on  which  was  fixed  a  number 
of  cups  at  regular  intervals.  The  first  appearance  of  the  potassium  ferrocyanide 
is  detected  by  adding  ferric  chloride  to  the  serum  which  separates  from  the  samples 
of  blood  after  they  have  stood  for  a  time.  The  duration  of  the  circulation  is  as 
follows : — 

Horse, 31.5  seconds. 

Dog, 16.7         " 

Rabbit,     ....    7.79      " 


Hedgehog,  .    .    .    7.61  seconds. 

Cat, 6.69 

Goose 10.86        " 


Duck,  ....  10.64  seconds. 
Buzzard,       .    .     6.73      " 
Fowl,   ....     5.17      " 


Results. — When  these  numbers  are  compared  with  the  frequency  of  the  normal 
pulse  beat  in  the  corresponding  animals,  the  following  deductions  are  obtained  : — 

(i)  The  mean  time  required  for  the  circulation  is  accomplished  during  27  heart 
beats,  /.  <?.,  for  man  =  32.2  seconds,  supposing  the  heart  to  beat  72  times  per 
minute. 

(2)  Generally,  the  mean  time  for  the  circulation  in  two  warm-blooded  animals 
is  inversely  as  the  frequency  of  the  pulse  beats. 

Modifying  Conditions. — The  time  is  influenced  by  the  following  factors  :  — 

1.  Long  vascular  channels  {e.  g.,  from  the  metatarsal  vein  of  one  foot  to  the  other  foot)  re- 
quire a  longer  time  than  short  channels  (as  between  the  jugulars).  The  difference  may  be  equal  to 
10  per  cent,  of  the  time  required  to  complete  the  entire  circuit. 

2.  In  young  animals  (with  shorter  vascular  channels  and  higher  pulse  rate)  the  time  is  shorter 
than  in  old  animals. 

3.  Rapid  and  energetic  cardiac  contractions  (as  during  muscular  exercise)  diminish  the  time. 
Hence  rapid  and  at  the  same  time  less  energetic  contractions  (as  after  section  of  both  vagi),  and 
slow  but  vigorous  systoles  [e.  g.,  after  slight  stimulation  of  the  vagus),  have  no  effect. 

C.  Vierordt  estimated  the  quantity  of  blood  in  a  man,  in  the  following  manner  :  In  all  warm- 
blooded animals,  27  systoles  correspond  to  the  time  for  completing  the  circulation.     Hence,  the 


180  BLOOD    CURRENT    IN    THE    SMALLER    VESSELS. 

total  mass  of  the  blood  must  be  equal  to  27  times  the  capacity  of  the  ventricle,  i.  e.,  in  man,  187.5 
grms.  X  27  =  5062.5  grms.  This  is  equal  to  j',  of  the  body  weight  in  a  person  weighing  65.8 
kilos,  (compare  ^.  49.) 

It  is  not  to  be  forgotten  that  the  salt  used  is  to  some  extent  poisonous,  but  Hermann  uses  the 
corresi)ondin<;  innocuous  soda  salt  (25  ])ercent.). 

Pathological.  — Tlie  duration  of  the  circulation  seems  to  be  increased  during  septic  fever  {£. 
IVolff). 

93.  WORK  OF  THE  HEART.— The  left  ventricle  expels  0.188  kilo, 
of  blood  with  each  systole,  and  in  doing  so  it  overcomes  the  pressure  in  the  aorta, 
which  is  equal  to  a  column  of  blood  3.21  metres  in  height.  [The  amount  of 
blood  expelled  from  each  ventricle  during  the  systole  is  about  180  grms.  (6  oz.).  It 
is  forced  out  against  a  pressure  of  250  mm.  Hg.  =  3.21  metres  of  blood.]  The 
work  of  the  heart  at  each  systole  is  0.188  X  3- 21  =  0.604  kilogramme-metre.  If 
the  number  of  beats  =  75  per  minute,  then  the  work  of  the  left  ventricle  in  24 
hours  =  (0.604  X  75  X  60  X  24)=  65,230  kilogramme-metres;  while  the 
"  work  "  done  by  the  righl  ventricle  is  about  one-third  that  of  the  left,  and  there- 
fore =  21,740  kilogramme-metres.  Both  ventricles  do  work  equal  to  86,970  kilo- 
gramme-metres. A  workman  during  eight  hours  produces  300,000  kilogramme- 
metres,  /.  (?.,  about  four  times  as  much  as  the  heart.  As  the  whole  of  the  work  of 
the  heart  is  consumed  in  overcoming  the  resistance  within  the  circulation,  or 
rather  is  converted  into  heat,  the  body  must  be  partly  warmed  thereby — (425.5 
gramme-metres  are  equal  to  i  heat  unit,  /.  e.,  the  force  required  to  raise  425.5 
grammes  to  the  height  of  i  metre  may  be  made  to  raise  the  temperature  of  i 
cubic  centimetre  of  water  1°  C).  So  that  204,000  "  heat  units"  are  obtained 
from  the  transformation  of  the  kinetic  energy  of  the  heart. 

One  gramme  of  coal  when  burned  yields  S680  heat  units,  so  that  the  heart 
yields  as  much  energy  for  heating  the  body  as  if  about  25  grammes  of  coal  were 
burned  within  it  to  produce  heat. 

94.  BLOOD  CURRENT  IN  THE  SMALLER  VESSELS.— 

Methods. — The  most  important  observations  for  this  purpose  are  made  by  means 
of  the  microscope  on  transparent  parts  of  living  animals.  Malpighi  was  the 
first  to  observe  the  circulation  in  this  way  in  the  lung  of  a  frog  (1661). 

The  following  parts  have  been  employed :  The  tails  of  tadpoles  and  small  fishes ;  the  web, 
tongue,  mesentery,  and  lungs  of  curarized  frogs;  the  wing  of  the  bat;  the  third  eyelid  of  the 
pigeon  or  fowl ;  the  mesentery  ;  the  vessels  of  the  liver  of  frogs  and  newts,  pia  mater  of  rabbits, 
the  skin  on  the  belly  of  the  frog,  the  mucous  membrane  of  the  inner  surface  of  the  human  lip 
(Hater's  Cheilangioscope,  1S79)  ;  the  conjunctiva  of  the  eyeball  and  eyelids.  All  these  may  be 
examined  by  reflectt-d  light. 

[Holmgren's  Method. — In  studying  the  circulation  in  the  frog's  lung,  it  must  be  inflated.  A 
cannula  with  a  bulge  on  its  free  end  is  placed  in  the  larynx,  while  to  the  other  end  is  fixed  a  piece 
of  caoutchouc  tubing.  The  lung  is  inflated  and  then  the  caoutchouc  tube  is  closed,  after  which  the 
lung  is  placed  in  a  chamber  with  glass  above  and  below,  and  examined  microscopically.] 

[Entoptical  appearances  of  the  circulation  [Purkinje,  1815).  Under  certain  conditions  a 
person  may  detect  the  movement  of  the  blood  corpuscles  within  the  blood  vessels  of  his  own  eye. 
The  best  method  is  that  of  Rood,  viz.,  to  look  at  the  sky  through  a  dark  blue  glass,  or  through 
several  pieces  of  cobalt  glass  placed  over  each  other  [Helm/ioltz].'] 

Form  and  Arrangement  of  Capillaries. —  Regarding  the  form  and  arrangement  of  the  capil- 
laries, we  find  that — 

1.  The  diameter  which,  in  the  finest,  permits  only  the  passage  of  single  corpuscles  in  a  row — one 
behind  the  other — may  vary  from  5  /i  to  2  a,  so  that  2  or  more  corpuscles  may  move  abreast  when 
the  capillary  is  at  its  widest. 

2.  The  length  is  about  0.5  mm.     They  terminate  in  small  veins. 

3.  The  number  is  very  variable,  and  the  capillaries  are  most  numerous  in  those  tissues  where 
the  metabohsm  is  most  active,  as  in  lungs,  liver,  muscles — less  numerous  in  the  sclerotic  and  in  the 
nerve  trunks. 

4.  They  form  numerous  anastomoses,  and  give  rise  to  networks,  whose  form  and  arrangement 
are  largely  determined  by  the  arrangement  of  the  tissue  elements  themselves.  They  form  simple 
loops  in  the  skin,  and  polygonal  networks  in  the  serous  membranes,  and  on  the  surface  of  many 
gland  tubes;  they  occur  in  the  form  of  elongated  networks,  with   short  connecting  branches  in 


CAPILLARY    CIRCULATION.  181 

muscle  and  nerve,  as  well  as  between  the  straight  tubules  of  the  kidney;  they  converge  radially 
toward  a  central  point  in  the  lobules  of  the  liver,  and  form  arches  in  the  free  margins  of  the  iris, 
and  on  the  limit  of  the  sclerotic  and  cornea. 

[Direct  Termination  of  Arteries  in  Veins. — Arteries  sometimes  terminate  directly  in  veins, 
without  the  intervention  of  capillaries,  e.g.,  in  the  ear  of  the  rabbit,  in  the  terminal  phalanges  of 
the  fingers  and  toes  in  man  and  some  animals,  in  the  cavernous  tissue  of  the  penis.  They  may  be 
regarded  as  secondary  channels  which  protect  the  circulation  of  adjacent  parts,  and  they  may  also 
be  related  to  the  heat-regulating  mechanisms  of  peripheral  parts  {Hoyer).'\ 

In  connection  with  the  termination  of  arteries  in  capillaries,  it  is  important  to  ascertain  if  the 
arterioles  are  terminal  arteries,  i.e.,\l  they  do  not  form  any  further  anastomoses  with  other 
similar  arterioles,  but  terminate  directly  in  capillaries,  and  thus  only  communicate  by  capillaries 
with  neighboring  arterioles — or  the  arteries  may  anastomose  with  other  arteries  just  before  they 
break  up  into  capillaries.  This  distinction  is  important  in  connection  with  the  nutrition  of  parts 
supplied  by  such  arteries  {^Cohnheini). 

Capillary  Circulation. — On  observing  the  capillary  circulation,  we  notice 
that  the  red  corpuscles  move  only  in  the  axis  of  the  current  (axial  current), 
while  the  lateral  transparent  plasma  current  flowing  on  each  side  of  this  central 
thread  is  free  from  these  corpuscles.  [The  axial  current  is  the  more  rapid.]  This 
plasma  layer  or  "  Poiseuille's  space  "  is  seen  in  the  smallest  arteries  and  veins, 
where  f  are  taken  up  with  the  axial  current,  and  the  plasma  layer  occupies  \  on 
each  side  of  it  (Fig.  ii6).  A  great  many,  but  not  all,  of  the  colorless  corpuscles 
move  in  this  layer.  It  is  much  less  distinct  in  the  capillaries.  Rud.  Wagner 
stated  that  it  is  absent  in  the  finest  vessels  of  the  lung  and  gills  [although  Gunning 
was  unable  to  confirm  this  statement].  The  colored  corpuscles  move  in  the 
smallest  capillaries  in  single  file,  one  after  the  other ;  in  the  larger  vessels,  several 
corpuscles  may  move  abreast,  with  a  gliding  motion,  and  in  their  course  they  may 
turn  over  and  even  be  twisted  if  any  obstruction  is  offered  to  the  blood  stream. 
As  a  general  rule,  in  these  vessels  the  movement  is  uniform,  but  at  a  sharp  bend 
of  the  vessel  it  may  partly  be  retarded  and  partly  accelerated.  Where  a  vessel 
divides,  not  unfrequently  a  corpuscle  remains  upon  the  projecting  angle  of  the 
division,  and  is  doubled  over  it  so  that  its  ends  project  into  the  two  branches  of 
the  tube.  There  it  may  remain  for  a  time,  until  it  is  dislodged,  when  it  soon 
regains  its  original  form  on  account  of  its  elasticity.  Not  unfrequently  we  see  a 
red  corpuscle  becoming  bent  where  two  vessels  meet,  but  on  all  occasions  it 
rapidly  regains  its  original  form.  This  is  a  good  proof  of  the  elasticity  of  the 
colored  corpuscles.  The  motion  of  the  colorless  corpuscles  is  quite  different 
in  character ;  they  roll  directly  on  the  vascular  wall,  moistened  on  their  peripheral 
zone  by  the  plasma  in  Poiseuille's  space,  their  other  surface  being  in  contact  with 
the  thread  of  colored  corpuscles  in  the  centre  of  the  stream.  Schklarewsky 
(1868)  has  shown  by  physical  experiments,  that  the  particles  of  least  specific 
gravity  in  all  capillaries  {e.g.,  of  glass)  are  pressed  toward  the  wall,  while  those 
of  greater  specific  gravity  remain  in  the  middle  of  the  stream.  [Graphite  and 
particles  of  carmine  were  supended  in  water,  and  caused  to  circulate  through  capil- 
lary tubes  placed  under  a  microscope,  when  the  graphite  kept  the  centre  of  the 
stream,  and  the  carmine  moved  in  the  layer  next  the  wall  of  the  tube.] 

When  the  colorless  corpuscles  reach  the  wall  of  the  vessel,  they  must  roll  along, 
partly  on  account  of  their  surface  being  sticky,  whereby  they  readily  adhere  to  the 
vessel,  and  partly  because  one  surface  is  directed  toward  the  axis  of  the  vessel 
where  the  movement  is  most  rapid,  and  where  they  receive  impulses  directly  from 
the  rapidly  moving  colored  blood  corpuscles  {Donders).  The  rolling  motion  is 
not  always  uniform,  not  unfrequently  it  is  retrograde  in  direction,  which  seems  to 
be  due  to  an  irregular  adhesion  to  the  vascular  wall.  Their  slower  movement  (10 
to  1 2  times  slower  than  the  red  corpuscles)  is  partly  due  to  their  stickiness,  and 
partly  to  the  fact  that,  as  they  are  placed  near  the  wall,  a  large  part  of  their  sur- 
face lies  in  the  peripheral  threads  of  the  fluid,  which,  of  course,  move  more  slowly 
(in  fact  the  layer  of  fluid  next  the  wall  is  passive — p.  133). 

[D.  J.  Hamilton  finds  that,  when  a  frog's  web  is  examined  in  a  vertical  position,  by  far  the 


182 


DIAPEDESIS. 


greater  proportion  of  leucocytes  float  on  the  upper  surface,  and  only  a  few  on  the  lower  surface,  of 
a  small  blood  vessel.  In  experiments  to  determine  why  the  colored  corpuscles  float  or  glide 
exclusively  in  the  axial  stream,  wliile  a  great  many,  but  not  all,  of  tlie  leucocytes  roll  in  the 
peripheral  layers,  Hamilton  ascertained  that  the  nearer  the  suspended  body  approaches  to  the 
specific  gravity  of  the  liquid  in  which  it  is  immersed,  the  more  it  tends  to  occupy  the  centre  of  the 
stream.  He  is  of  opinion  that  the  phenomenon  of  the  separation  of  the  blood  corpuscles  in 
the  circulating  fluid  is  due  to  the  colorless  corpuscles  being  specifically  lighter,  and  the  colored 
either  of  the  same  or  of  very  slightly  greater  specific  gravity,  than  the  blood  plasma.  Hamilton 
controverts  the  statement  of  Schklarewsky,  and  he  finds  that  it  is  the  relative  specific  gravity  of  a 
body  which  ultimately  determines  its  position  in  a  tube.  These  experiments  point  to  the  immense 
importance  of  a  due  relation  subsisting  between  the  specific  gravity  of  the  blood  plasma  and  that  of 
the  corpuscles.] 

In  the  vessels  first  formed  in  the  incubated  egg,  as  well  as  in  young  tadpoles,  the  movement  of 
the  blood  from  the  heart  occurs  in  jerks  [Spallanzani,  1768). 

The  velocity  of  the  blood  stream  is  influenced  by  the  diameter  of  the  vessels, 
which  undergo  periodic  changes  of  calibre.  This  change  occurs  not  only  in 
vessels  provided  with  muscular  fibres,  but  also  in  the  capillaries,  which  vary  in 
diameter,  owing  to  the  contraction  of  the  cells  composing  their  walls  (p.  138). 

The  amount  of  7vaier  in  the  blood  is  of  importance  ;  when  it  is  increased,  the 
circulation  is  facilitated  and  accelerated  (§  62). 

The  velocity  of  the  blood  is  greater  in  the  pulmonary  than  in  the  systemic 
capillaries;  so  that  the  total  sectional  area  of  the  pulmonary  capillaries  is  less  than 
that  of  all  the  systemic  capillaries. 

95.  DIAPEDESIS. — If  the  circulation  be  studied  in  the  vessels  of  the  mesentery,  we  may 
observe  colorless  corpuscles  passing  out  of  the  vessels  in  greater  or  less  numbers  (Fig.  116). 
The  mere  contact  with  the  air  suffices  to  excite  slight  inflammation.  At  first,  the  colorless  corpus- 
cles in  the  plasma  space  move  more  slowly;  several  accumulate  near  each  other,  and  adhere  to  the 
walls — soon  they  bore  into  the  wall,  ultimately  they  pass  quite  through  it,  and  may  wander  for  a 

distance  into  the  perivascular  tissues.  It  is  doubt- 
ful whether  they  pass  through  the  so-called  "  sto- 
mata  "  which  exist  between  the  endothelial  cells, 
or  whether  they  simply  pass  through  the  cement 
substance  between  the  endothelial  cells  (p.  136). 
This  process  is  called  diapedesis,  and  consists  of 
several  acts :  {a)  The  adhesion  of  lymph  cells  or 
colorless  corpuscles  to  the  inner  surface  of  the 
vessel  (after  moving  more  slowly  along  the  wall  up 
to  this  point),  {b)  They  send  processes  into  and 
through  the  vascular  wall,  (c)  The  body  of  the 
cell  is  drawn  after  or  follows  the  processes,  whereby 
the  corpuscle  appears  constricted  in  the  centre  (Fig. 
116,  f).  (d)  The  complete  passage  of  the  corpus- 
cle through  the  wall,  and  its  further  motion  in  virtue 
of  its  own  amoeboid  movements.  Hering  observed 
that  in  large  vessels  with  perivascular  lymph  spaces, 
the  corpuscles  passed  into  the  spaces,  hence  cells 
Small  vessel  of  a  frog's  mesenterj-  showing  diapedesis.  are  found  in  lymph  before  it  has  passed  through 
■w.iv,  vascular  walls  :  a, a,  Poiseuille's  space;  r,  Ivmphatic  glands.  The  cause  of  the  diapedesis 
,  To  '^^X^'dili:^:^^:^^^^^,  is  partly  due  to  the  independent  locomotion  of  the 
y,y,  extruded  corpuscles.  corpuscles,  and  it  is  partly  a  physical  act,  viz.,  a 

filtration  of  the  colloid  mass  of  the  cell  under  the 
force  of  the  blood  pressure  {Hering) — in  the  latter  respect  depending  upon  the  intravascular  pres- 
sure and  the  velocity  of  the  blood  stream.  Hering  regards  this  process,  and  even  the  passage 
of  the  colored  corpuscles  through  the  vascular  wall,  as  a  normal  process.  The  red  corpuscles 
pass  out  of  the  vessels  when  the  venous  outflow  is  obstructed,  which  also  causes  the  transuda- 
tion of  plasma  through  the  vascular  wall.  The  plasma  carries  the  colored  corpuscles  along  with 
It,  and  at  the  moment  of  their  passage  through  the  wall  they  assume  extraordinary  shapes,  owing  to 
the  tension  put  upon  them,  regaining  their  shape  as  soon  as  they  pass  out  {Cohnkeim).  This 
remarkable  phenomenon  was  described  by  Waller  in  1846.  It  was  re-described  by  Cohnheim,  and 
according  to  him  the  out-wandering  is  a  sign  of  inflammation,  and  the  colorless  corpuscles  which 
accumulate  in  the  tissues  are  to  be  regarded  as  true  pus  corpuscles,  which  may  undergo  further 
increase  by  division. 

Stasis. — When  a  strong  stimulus  acts  on  a  vascular  part,  hyperaemic  redness  and  szvelling  occur. 


Fig.  116. 


MOVEMENT   OF   THE    BLOOD    IN    THE    VEINS.  183 

Microscopic  observation  shows  that  the  capillaries  and  the  small  vessels  are  dilated  and  over- 
filled v}'\'Ca.  blood  corpuscles;  in  some  cases,  a  temporary  narrowing  precedes  the  dilatation;  simul- 
taneously the  velocity  of  the  stream  changes,  rarely  there  is  a  temporary  acceleration,  more  frequently 
it  beco77ies  slower.  If  the  action  of  the  stimulus  or  irritant  be  continued,  the  retardation  becomes 
considerable,  the  stream  moves  in  jerks,  then  follows  a  to-and-fro  movement  of  the  blood  column — 
a  sign  that  stagnation  has  taken  place  in  other  vascular  areas.  At  last  the  blood  stream  comes  com- 
pletely to  a  stand-still — stasis — and  the  blood  vessels  are  plugged  with  blood  corpuscles.  Numer- 
ous colorless  blood  corpuscles  are  found  in  the  stationary  blood.  While  these  various  processes  are 
taking  place,  the  colorless  corpuscles — more  rarely  the  red — pass  out  of  the  vessels.  Under  favor- 
able circumstances  the  stasis  may  disappear.  The  swelling  which  occurs  in  the  neighborhood  of 
inflamed  parts  is  chiefly  due  to  the  exudation  of  plasma  into  the  surrounding  tissues. 

96.  MOVEMENT  OF  THE    BLOOD    IN   THE  VEINS.— In  the 

smallest  veins  coming  from  the  capillaries,  the  blood  stream  is  more  rapid  than  in 
the  capillaries  themselves,  but  less  so  than  in  the  corresponding  arteries.  The 
stream  is  uniform,  and  if  no  other  conditions  interfered  with  it,  the  venous  stream 
toward  the  heart  ought  to  be  uniform,  but  many  circumstances  affect  the  stream 
in  different  parts  of  its  course.  Among  these  are  :  (1)  The  relative  laxness,  great 
distensibility,  and  the  ready  compressibility  of  the  walls,  even  of  the  thickest  veins. 
(2)  The  incofiiplete  filliiig  oi  the  veins,  which  does  not  amount  to  any  considerable 
distention  of  their  walls.  (3)  The  numerous  and  free  anastomoses\it\.-^ttri  adjoin- 
ing veins,  not  only  between  veins  lying  in  the  same  plane,  but  also  between 
superficial  and  deep  veins.  Hence,  if  the  course  of  the  blood  be  obstructed 
in  one  direction,  it  readily  finds  another  outlet.  (4)  The  presence  of  numerous 
valves  which  permit  the  blood  stream  to  move  only  in  a  centripetal  direction. 
They  are  absent  from  the  smallest  veins,  and  are  most  numerous  in  those  of 
middle  size. 

Position  of  Valves. — The  venous  valves  always  have  two  pouches,  and  are  placed  at  definite 
intervals,  which  correspond  to  the  i,  2,  3,  or  nth  power  of  a  certain  "  fundamental  distance,"  which 
is  =  7  mm.  for  the  lower  extremity  and  5.5  mm.  for  the  upper.  Many  of  the  original  valves  dis- 
appear. On  the  proximal  side  of  every  valve  a  lateral  branch  opens  into  the  vein,  while  on  the 
distal  side  of  each  branch  lies  a  valve.     The  same  is  true  for  the  lymphatics  (if.  Bardeleben) . 

Effect  of  Pressure. — As  soon  as  pressure  is  applied  to  the  veins,  the  next 
lowest  valves  close,  and  those  immediately  above  the  seat  of  pressure  open  and 
allow  the  blood  to  move  freely  toward  the  heart.  Tht  pressure  may  be  exerted 
from  without,  as  by  anything  placed  against  the  body ;  the  thickened,  contracted 
muscles,  especially  the  muscles  of  the  limbs,  compress  the  veins.  That  the  blood 
flows  out  of  a  divided  vein  more  rapidly  when  the  muscles  contract,  is  shown  during 
venesection.  If  the  muscles  are  kept  contracted,  the  venous  blood  passing  out  of 
the  muscles  collects  in  the  passive  parts,  e.g.,  in  the  cutaneous  veins.  The  pulsa- 
tile pressure  of  the  arteries  accompanying  the  veins  favors  the  venous  current. 
From  a  hydrostatic  point  of  view  the  valves  are  of  considerable  importance,  as 
they  serve  to  divide  the  column  of  blood  into  segments  {e.g.,  in  the  crural  vein  in 
the  erect  attitude),  so  that  the  fine  blood  vessels  in  the  foot  are  not  subjected  to 
the  whole  amount  of  the  hydrostatic  pressure  in  the  veins. 

The  velocity  of  the  venous  blood  has  been  measured  directly  (with  the  hsemadromometer  and  the 
rheometer — \  89).  Volkmann  found  it  to  be  225  mm.  per  sec.  in  the  jugular  vein.  Reil  observed 
that  2]/^  times  more  blood  flowed  from  an  arterial  orifice  than  from  a  venous  orifice  of  the  same  size. 
The  velocity  of  the  venous  current  obviously  depends  upon  the  sectional  area  of  the  vessel.  Borelli 
estimated  the  capacity  of  the  venous  system  to  be  4  times  greater  than  that  of  the  arterial ;  while, 
according  to  Haller,  the  ratio  is  9  to  4. 

Large  Veins. — As  we  proceed  from  the  small  veins  toward  the  vense  cavae, 
the  sectional  area  of  the  veins,  taken  as  a  whole,  becomes  less,  so  that  the  velocity 
vf  the  current  increases  in  the  same  ratio.  The  velocity  of  the  current  in  the  vense 
cavae  may  be  about  half  of  that  in  the  aorta  {Haller).  As  the  pulmonary 
veins  are  narrower  than  the  pulmonary  artery,  the  blood  moves  more  rapidly  in 
the  former. 


184  SOUNDS    WITHIN    ARTERIKS. 

97.  SOUNDS  WITHIN  ARTERIES.— The  sounds  proiluced  within  arteries  are,  speaking 
strictly  from  a  physical  point  of  view,  only  noises  or  bruits.  Still,  following  Skoda's  lead,  they  are 
spoken  of  by  physicians  as  "  tones."  Clinically,  there  is  no  sharp  distinction  between  "tones," 
sounds,  noises,  or  bruits.  In  four-fifths  of  all  healthy  men  two  sounds — corresponding  in  duration 
and  other  characters  to  the  two  heart  sounds — are  heard  in  the  carotid  {Conrad,  Weil).  Sometimes 
only  the  second  heart  sound  is  distinguishable,  as  its  place  of  origin  is  near  to  the  carotid.  They 
are  not  true  arterial  sounds,  but  are  simply  "  propagated  heart  sounds."  Sometimes  the  sound 
of  the  pulmonary  artery  can  be  heard  in  this  way  (  Weil,  Belli-lheim').  These  murmurs,  sounds,  or 
bruits  occur  either  spontaneously,  or  are  produced  by  the  application  of  external  pressure,  whereby 
the  lumen  of  the  vessel  is  diminished.  Hence  one  distinguishes:  (i)  Spontaneous  Murmurs^ 
and  (2)  Pressure  Murmurs. 

Arterial  Sounds  or  murmurs  are  readily  produced  by  pressing  upon  a  strong 
artery,  e.g.,  the  crural  in  the  inguinal  region,  so  as  to  leave  only  a  narrow  passage 
for  the  blood  ("  stenosal  murmur").  A  fine  blood  stream  passes  with  great 
rapidity  and  force  through  this  narrow  part,  into  a  wider  portion  of  the  artery 
lying  behind  the  point  of  compression.  Thus  arises  the  "pressure  stream" 
{F.  Nicmeyer),  or  the  "  fluid  vein  "  ("  veine  fluide  "  of  Chauveau).  The  particles 
of  the  fluid  are  thrown  into  rapid  oscillation,  and  undergo  vibratory  movements, 
and  by  their  movements  produce  the  sound  within  the  peripheral  dilated  portion 
of  the  tube.  A  sound  is  produced  in  the  fluid  by  pressure  (yCorrigati).  The  sounds 
are  not  caused  by  vibrations  of  the  vascular  wall,  as  supposed  by  Bouillaud. 

A  murmur  of  this  sort  is  the  "sub-clavicular  murmur"  [Roser),  occasionally  heard  during 
systole  in  the  subclavian  artery ;  it  occurs  when  the  two  layers  of  the  pleura  adhere  to  the  apex  of 
the  lung  (especially  in  tubercular  diseases  of  the  lungs),  whereby  the  subclavian  artery  undergoes  a 
local  constriction  due  to  its  being  made  tense  and  slightly  curved  [Friedreich).  This  result  is 
indicated  in  a  diminution  or  absence  of  the  pulse  wave  in  the  radial  artery  (  Weil). 

It  is  obvious  that  arterial  murmurs  will  occur  in  the  human  body — [a]  When,  owing  to  patho- 
logical conditions,  the  arterial  tube  is  dilated  at  one  part,  into  which  the  blood  current  is  forcibly- 
poured  from  the  normal  narrow  tube.  Dilatations  of  this  sort  are  called  aneurisms,  in  which 
murmurs  are  generally  audible.  (l>)  When  pressure  is  exerted  upon  an  artery,  e.  g.,  by  the  pressure 
of  the  greatly  enlarged  arteries  during  pregnancy,  or  by  a  large  tumor  pressing  upon  a  large  artery. 

Spontaneous  Murmurs. — In  cases  where  no  source  of  external  pressure  is  discoverable,  and 
when  no  aneurism  is  present,  the  spontaneously  occurring  sounds  are  favored,  when  at  the  moment 
of  arterial  rest  (cardiac  systole)  the  arterial  walls  are  distended  to  the  slightest  extent,  and  when 
during  the  movement  of  the  pulse  (cardiac  diastole)  the  tension  is  most  rapid  [Traul>e,  ll^eil),  i.  e.,. 
when  the  low  systolic  minimum  tension  of  the  arterial  wall  passes  rapidly  into  the  high  maximum 
tension.  This  is  especially  the  case  in  insufficiency  of  the  aortic  valves,  in  which  case  the  sounds 
in  the  arteries  are  audible  over  a  wide  area.  If  the  minimum  tension  of  the  arterial  wall  is  relatively 
great,  even  during  diastole,  the  sounds  in  the  arteries  are  greatly  diminished. 

Arterial  murmurs  are  favored  by  (i)  Sufficient  delicacy  and  elasticity  of  the 
arterial  walls.  (2)  Diminished  peripheral  resistance,  e.g.,  an  easy  outflow  of  the 
fluid  at  the  end  of  the  stream.  (3)  Accelerated  current  in  the  vascular  system 
generally.  (4)  A  considerable  difference  of  the  pressure  in  the  narrow  and  wide 
portions  of  the  tube.     (5)  Large  calibre  of  the  arteries. 

In  normal  pulsating  arteries,  sounds  may  be  heard  especially  at  an  acute  bend  of  the  artery. 
Murmurs  of  this  sort  are  loudest  where  several  large  arteries  lie  together;  hence,  during  pregnancy, 
we  hear  the  uteriiie  murmur,  or  placental  bruit,  or  souffle  in  the  greatly  dilated  uterine  arteries. 
It  is  much  less  distinct  in  the  umbilical  arteries  of  the  cord  (umbilical  murmurs).  Similar  sounds 
are  heard  through  the  thin  walls  of  the  head  of  infants,  and  a  murmur  is  sometimes  heard  in  the 
enlarged  spleen  in  ague  [Maissurianz). 

Auscultation  of  the  Normal  Pulse. — On  auscultating  the  radial  artery  under  favorable  cir- 
cumstances, and  especially  in  old,  thin  persons  with  wide  arteries  and  dicrotic  pulse,  one  may  hear 
two  sounds  corresponding  to  the  primary  and  dicrotic  waves. 

In  insufficiency  of  the  aortic  valves,  characteristic  sounds  may  be  heard  in  the  crural  artery. 
If  pressure  be  exerted  upon  the  artery,  a  double  blowing  murmur  is  heard;  the  first  one  is  due  to  a 
large  mass  of  blood  being  propelled  into  the  artery  synchronously  with  the  heart  beat,  the  second 
to  the  fact  that  a  large  quantity  of  blood  flows  back  into  the  heart  during  diastole.  If  no  pressure 
be  exercised  two  sounds  are  heard,  and  these  seem  to  be  due  to  a  wave  propagated  into  the  arteries 
by  the  auricles  and  ventricles  respectively— compare  f  73,  Fig.  86,  III.  In  atheroma  a  double 
sound  may  sometimes  be  heard  (g  73,  2). 


THE  VENOUS  PULSE PHLEBOGRAM.  185 

98.  VENOUS  MURMURS.— I.  Bruit  de  Diable.— This  sound  is  heard 
above  the  clavicles  in  the  furrow  between  the  two  heads  of  the  sterno-mastoid, 
most  frequently  on  the  right  side,  and  in  40  per  cent,  of  all  persons  examined. 
It  is  either  a  continuous  or  a  rhythmical  murmur,  occurring  during  the  diastole  of 
the  heart  or  during  inspiration  ;  it  has  a  whistling  or  rushing  character,  or  even  a 
musical  quality,  and  arises  within  the  bulb  of  the  common  jugular  vein.  When 
this  sound  is  heard  without  pressure  being  exerted  by  the  stethoscope,  it  is  a 
pathological  phenomenon.  If,  however,  pressure  be  exerted,  and  if,  at  the  same 
time,  the  person  examined  turn  his  head  to  the  opposite  side,  a  similar  sound  is 
heard  in  nearly  all  cases.  The  pathological  bruit  de  diable  occurs  especially  in 
anaemic  persons,  in  lead  poisoning,  in  syphilitic  and  scrofulous  persons,  sometimes 
in  young  persons,  and  less  frequently  in  elderly  people.  Sometimes  a  thrill  of 
the  vascular  wall  may  be  felt. 

Causes. — It  is  due  to  the  vibration  of  the  blood  flowing  in  from  the  relatively 
narrow  part  of  the  common  jugular  vein  into  the  wide  bulbous  portion  of  the 
vessel,  and  seems  to  occur  chiefly  when  the  walls  of  a  thin  part  of  the  vein  lie  close 
to  each  other,  so  that  the  current  must  purl  through  it.  It  is  clear  that  pressure 
from  without,  or  lateral  pressure,  as  by  turning  the  head  to  the  opposite  side,  must 
favor  its  occurrence.  Its  intensity  will  be  increased  when  the  velocity  of  the 
stream  is  increased,  hence  inspiration  and  the  diastolic  action  of  the  heart  (both  of 
which  assist  the  venous  current)  increase  it.  The  erect  attitude  acts  in  a  similar 
manner.  A  similar  bruit  is  sometimes,  though  rarely,  heard  in  the  subclavian, 
axillary,  thyroid,  facial,  innominate  and  crural  veins,  and  superior  cava. 

II.  Regurgitant  Murmurs. — On  making  a  sudden  effort,  a  murmur  may  be  heard  in  the  crural 
vein  during  expiration,  which  is  caused  by  a  centrifugal  current  of  blood,  owing  to  the  incompetence 
or  absence  of  the  valves  in  this  region.  If  the  valves  at  the  jugular  bulb  are  not  tight,  there  may 
be  a  bruit  with  expiration  (expiratory  '■\\x'gv\2x  vein  bruit — Hamernjk),  or  during  the  cardiac  systole 
(jyj^o/iV  jugular  vein  bruit — v.  Bat?iberger). 

III.  Valvular  Sounds  in  Veins. — When  the  tricuspid  valve  is  incompetent,  during  the  ven- 
tricular systole,  a  large  volume  of  blood  is  propelled  backward  into  the  venae  cavse.  The  venous 
valves  are  closed  suddenly  thereby  and  a  sound  produced.  This  occurs  at  the  bulb  or  dilatation  on 
the  jugular  vein  (v.  Bamberger^,  and  in  the  crural  vein  at  the  groin  (N.  Friedreich),  i.  e.,  only  as 
long  as  the  valves  are  competent.  Forced  expiration  may  cause  a  valvular  sound  in  the  crural  vein. 
No  sound  is  heard  in  the  veins  under  perfectly  normal  circumstances. 

99.  THE  VENOUS  PULSE— PHLEBOGRAM.— Methods.— A  tracing  of  the  move- 
ments of  a  vein,  taken  with  a  lightly  weighted  sphygmograph,  has  a  characteristic  form,  and  is  called 
a  phlebogram  (Fig.  117).  In  order  to  interpret  the  various  events  of  the  phlebogram,  it  is  most 
important  to  record  simultaneously  the  events  that  take  place  in  the  heart.  The  auricular  contraction 
(compare  Fig.  39)  is  synchronous  with  a  b  ;  be,  with  the  ventricular  systole,  during  which  time  the 
first  sound  occurs,  while  a  ^  is  a  presystolic  movement.  The  carotid  pulse  coincides  nearly  with 
the  apex  of  the  cardiogram,  i.  e.,  almost  simultaneously  with  the  descending  limb  of  the  phlebogram 
(^Riegel). 

Occasionally  in  healthy  individuals  a  pulsatile  movement,  synchronous  with  the 
action  of  the  heart,  may  be  observed  in  the  common  jugular  vein.  It  is  either 
confined  to  the  lower  part  of  the  vein,  the  so-called  bulb,  or  extends  further  up 
along  the  trunk  of  the  vein.  In  the  latter  case,  the  valves  above  the  bulb  are 
insufficient,  which  is  by  no  means  rare,  even  in  health.  The  wave  motion  passes 
from  below  upward,  and  is  most  obvious  when  the  person  is  in  the  passive  hori- 
zontal position,  and  it  is  more  frequent  on  the  right  side,  because  the  right  vein 
lies  nearer  the  heart  than  the  left.  It  is  propagated  more  slowly  than  the  arterial 
pulse  wave.  The  venous  pulse  resembles  very  closely  the  tracing  of  the  cardiac 
impulse.     Compare  Fig.  117,  i,  with  Fig.  39. 

It  is  obvious  that,  as  the  jugular  vein  is  in  direct  communication  with  the  right 
auricle,  and  as  the  pressure  within  it  is  low,  the  systole  of  the  right  auricle  must 
cause  a  positive  wave  to  be  propagated  toward  the  peripheral  end  of  the  jugular 
vein.  Fig.  117,  9  and  10,  are  venous  pulse  tracings  of  a  healthy  person  with 
insufficiency  of  the  valves  of  the  jugular  vein.     In  these  curves,  the  part  a  b  cor- 


186 


LIVER    PULSE. 


responds  to  the  contraction  of  the  auricle.  Occasionally  this  part  consists  of  two 
elevations,  corresponding  to  the  contraction  of  the  atrium  and  auricle  respectively. 
As  the  blood  in  the  right  auricle  receives  an  impulse  from  the  sudden  tension  of 
tlie  tricuspid  valve,  synchronous  with  the  systole  of  the  fight  ventricle,  there  is  a 
positive  wave  in  the  jugular  vein  in  Fig.  117,  9  and  10,  indicated  by  b,  c.  Lastly, 
the  sudden  closure  of  the  pulmonary  valves  may  even  be  indicated  (^).  As  the 
aorta  lies  in  direct  relation  with  the  pulmonary  artery,  the  sudden  closure  of  its 
valves  may  also  be  indicated  (Fig.  91,  9,  at  d^.  During  the  diastole  of  the  auricle 
and  ventricle,  blood  flows  into  the  heart,  so  that  the  vein  partly  collapses  and  the 
lever  of  the  recording  instrument  descends. 

Sinus  and  Retinal  Pulse. — The  blood  in  the  sinuses  of  the  brain  also  undergoes  a  pulsatile 
movement,  owing  to  the  fact  that  during  cardiac  diastole  much  blood  flows  into  the  veins  (^Mosso). 
L'nder  favorable  circumstances,  this  movement  may  be  propagated  into  the  veins  of  the  retina, 
constituting  the  zenous  retinal  tulse  of  the  older  observers  {/lelfreich) . 


Fig.  117. 


'\cDO\is,  ■p\i\s<£A  (J-'riedreich).  i-3,  trom  insufficiency  ot  the  tricuspid;  9,  10,  pulse  ot  the  jugular  vein  ol  a  healthy 
person.  In  all  the  curves,  a  b  =  contraction  of  the  right  auricle  ;  6  c,  oi  the  right  ventricle ;  d,  closure  of  the 
aortic  valves  ;  f,  closure  of  the  pulmonary  valves  ;  ^,^,  diastole  of  the  right  ventricle. 

Pathological  Jugular  Vein  Pulse. — The  venous  pulse  in  the  jugular  vein  is  far  better  marked 
in  insufficiency  of  the  tricuspid  valve, zx\A  the  vein  may  pulsate  violently,  but  if  its  valves  be  perfect, 
the  pulse  is  not  propagated  along  the  vein,  so  that  a  pulse  in  the  jugular  vein  is  not  necessarily  a 
sign  of  insufficiency  of  the  tricuspid  valve,  but  only  of  insufficiency  of  the  valve  of  the  jugular  vein 
{^Friedreich). 

Liver  Pulse. — The  ventricular  systole  is  propagated  into  the  valveless  inferior  vena  cava,  and 
causes  the  liver  pulse.  With  each  systole  blood  passes  into  the  hepatic  veins,  so  that  the  liver 
undergoes  a  systolic  swelling  and  injection. 

Fig.  117,  2-8,  are  curves  of  the  pulse  in  the  common  jugular  vein.  Although  at  first  sight  the 
curves  appear  to  be  very  different,  they  all  agree  in  this,  that  the  various  events  occurring  in  the 
heart  during  a  cardiac  revolution  are  indicated  more  or  less  completely.  Li  all  the  curves,  ab  = 
auricular  contraction.  The  auricle,  when  it  contracts,  excites  a  positive  wave  in  the  veins.  The 
elevation,  b  c,  is  caused  by  the  large  blood  wave  produced  in  the  veins,  owing  to  the  emptying  of 
the  ventricle.  It  is  always  greater,  of  course,  in  insufficiency  of  the  tricuspid  valves  than  under  normal 
circumstances  (Fig.  117,  9  and  10).  In  the  laUer  case,  the  closure  of  the  tricuspid  valve  causes 
only  a  slight  wave  motion  in  the  auricle.     The  apex,  c,  of  this  wave  may  be  higher  or  lower,  accord- 


DISTRIBUTION    OF   THE    BLOOD.  187 

ing  to  the  tension  in  tlie  vein  and  the  pressure  exerted  by  the  sphygmograph.  As  a  general  rule,  at 
least  one  notch  (4,  5,  6,  e)  follows  the  apex,  due  to  the  prompt  closure  of  the  valves  of  the 
pulmonary  artery.  The  closure  of  the  closely  adjacent  aortic  valves  may  cause  a  small  secondary 
wave  near  to  e  (as  in  i  and  2,  d).  The  curve  falls  toward  /,  corresponding  to  the  diastole  of  the 
heart. 

A  well-marked  venous  pulse  occurs  when  the  r?^k(  auricle  is  greatly  congested,  as  in  cases  of 
insufficiency  of  the  mitral  valve  or  stenosis  of  the  same  orifice.  In  rare  cases,  in  addition  to  the 
pulse  in  the  common  jugular  vein,  the  external  jugular,  the  facial,  thyroid,  external  thoracic  veins,  or 
even  the  veins  of  the  upper  and  lower  extremities  may  pulsate.  A  similar  pulsation  must  occur  in 
the  pulmonary  veins  in  mitral  insufficiency,  but  of  course  the  result  is  not  visible. 

On  rare  occasions,  a  pulse  occurs  in  the  veins  on  the  back  of  the  hand  and  foot,  owing  to  the 
arterial  pulse  being  propagated  through  the  capillaries  into  the  veins.  This  may  occur  under  normal 
circumstances,  when  the  peripheral  ends  of  the  arteries  become  dilated  and  relaxed  [Quincke^,  or 
when  the  blood  pressure  within  these  vessels  rises  rapidly  and  falls  as  suddenly,  as  in  insufficiency 
of  the  aortic  valves. 

In  progressive  effusion  into  the  pericardium  the  carotid  pulse  at  iirst  becomes  smaller  and  the 
venous  pulse  larger;  beyond  a  certain  stage  of  pressure  the  latter  ceases  {^Riegel). 

100.  DISTRIBUTION  OF  THE  BLOOD.— In  the  rabbit,  one-fourth 
of  the  total  amount  of  the  blood  is  found  in  each  of  the  following :  a,  in  the 
passive  muscles  ;  b,  in  the  liver ;  c,  in  the  organs  of  the  circulation  (heart  and 
vessels)  ;  d,  in  all  other  parts  together. 

Methods. — The  methods  adopted  do  not  give  exact  results.  J.  Ranke  ligatured  the  parts  during 
life,  removed  them,  and  investigated  the  amount  of  blood  while  the  tissues  were  still  warm. 

Influencing  Conditions. — The  amount  of  blood  is  influenced  by  (i)  the  anatomical  distribu- 
tion of  the  vessels  (vascularity  or  the  reverse)  as  a  whole ;  (2)  the  diameter  of  the  vessels,  which 
depends  upon  physiological  causes  {a)  on  the  blood  pressure  within  the  vessels ;  {b)  on  the  condi- 
tion of  the  vasomotor  or  vaso -dilator  nerves;  (f)  on  the  condition  of  the  tissues  themselves,  d".^., 
the  vessels  of  the  intestine  during  absorption ;  by  the  vessels  of  muscle  during  muscular  contraction  ; 
of  vessels  in  inflamed  parts. 

The  most  important  factor,  however,  is  the  state  of  activity  of  the  organ 
itself;  hence,  the  saying,  "  ubi  irritatio,  ibi  afifiuxus."  We  may  instance  the 
congestion  of  the  salivary  glands  and  the  gastric  mucous  membrane  during  diges- 
tion, and  the  increased  vascularity  of  muscles  during  contraction.  As  the  activity 
of  organs  varies  at  different  times,  the  amount  of  blood  in  the  part  or  organ  goes 
hand  in  hand  with  the  variations  in  its  states  of  activity.  When  some  organs  are 
congested,  others  are  at  rest ;  during  digestion,  there  is  muscular  relaxation  and 
less  mental  activity  :  violent  muscular  exertion  retards  digestion — during  great 
congestion  of  the  cutaneous  vessels  the  activity  of  the  kidneys  diminishes.  Many 
organs  (heart,  muscles  of  respiration,  certain  nerve  centres)  seem  always  to  be  in 
a  nearly  uniform  state  of  activity  and  vascularity.  During  the  activity  of  an  organ, 
the  amount  of  blood  in  it  may  be  increased  30  per  cent.,  nay,  even  47  per  cent. 
The  motor  organs  of  young  muscular  persons  are  relatively  more  vascular  than 
those  of  old  and  feeble  persons  (y.  Ranke^.  In  the  condition  of  increased  activity 
a  more  rapid  renewal  of  the  blood  seems  to  occur ;  after  muscular  exertion  the 
duration  of  the  circulation  diminishes  {Vierordt'). 

During  a  condition  of  mental  activity,  the  carotid  is  dilated,  the  dicrotic  wave  in  the  carotid 
curve  is  increased  (the  radial  shows  the  opposite  condition),  and  the  pulse  is  increased  in  frequency 
{Gley). 

Age. — The  development  of  the  heart  and  large  vessels  determines  a  different  distriburion  of  the 
blood  in  the  child  from  that  which  obtains  in  the  adult.  The  heart  is  relatively  small  from  infancy 
up  to  puberty,  the  vessels  are  relatively  large ;  while  after  puberty  the  heart  is  large,  and  the  vessels 
are  relatively  smaller.  Hence  it  follows  that  the  blood  pressure  in  the  arteries  of  the  systemic 
circulation  must  be  lower  in  the  child  than  in  the  adult.  The  pulmonary  artery  is  relatively  wide 
in  the  child,  while  the  aorta  is  relatively  small;  after  puberty  both  vessels  have  nearly  the  same  size. 
Hence,  it  follows  that  the  blood  pressure  in  the  pulmonary  vessels  of  the  child  is  relatively  higher 
than  that  in  the  adult  [Berteke). 

loi.  PLETHYSMOGRAPHY.— In  order  to  estimate  and  register  the 
amount  of  blood  in  a  limb  Mosso  devised  an  instrument  (Fig.  118),  which  he 
termed  a  plethysmograph. 


188 


PLETHYSMOGRAPHY. 


It  consists  of  a  long  cylindrical  glass  vessel,  G,  suited  to  accommodate  a  limb.  The  opening 
through  which  the  limb  is  introduced  is  closed  with  caoutchouc,  and  the  vessel  is  filled  with  water. 
There  is  an  opening  in  the  side  of  the  vessel  in  which  a  manometer  tube,  filled  to  a  certain 
height  with  water,  is  fixed.  As  the  arm  is  enlarged  owing  to  the  increased  supply  of  arterial 
blood  passing  into  it  at  each  pulse  beat,  of  course  the  water  column  in  the  manometer  is  raised. 
Kick  placed  a  float  upon  the  surface  of  the  water,  and  thus  enabled  the  variations  in  the  volume 
of  the  fluid  to  be  inscribed  on  a  revolving  cylinder.  The  curve  obtained  resembled  the  pulse 
curve;  it  was  even  dicrotic.  In  Fig.  ii8  the  movement  of  the  fluid  is  represented  as  conveyed  to 
a  Marey's  tambour,  T,  similar  to  the  recording  apparatus  employed  in  Brondgeest's  pansphygmo- 
graph  (Fig.  76). 

The  cylinder  C  may  be  filled  with  air.  Kries  fills  it  with  gas  and  connects  the  tube  leading  to 
T  to  a  gas  burner.     The  variations  in  the  gas  flame  are  then  photographed. 

Results. — (t)  Pulsatile  Variations  in  the  Volume. — As  the  venous  cur- 
rent is  regarded  as  uniform  in  the  passive  limb,  every  increase  of  the  volume  curve 
indicates  a  greater  velocity  of  the  arterial  current  toward  the  periphery,  and  vice 
versa  (^Fick).  The  curves  registered  by  the  apparatus  are  volume  pulses,  and 
they  resemble  the  curve  of  the  dromograph  (Fig.  113,  III).  The  ascent  of  the 
curve  indicates  a  greater,  the  descent  a  diminished  inflow  of  arterial  blood. 

At  first  sight  the  plethysmograph  curve  (volume  pulse,  ^  90,  7)  is  very  like  the  pulse  curve 
(pressure  pulse) ;  both  are  dicrotic.  But  there  are  differences;  the  volume  pulse  curve  beyond  the 
apex  falls  more  rapidly.  This  rapid  fall,  which  is  not  accompanied  by  a  corresponding  fall  of  the 
pressure,  is  attributed  by  v.  Kries  to  peripheral  reflexion.  The  dicrotic  wave  occurs  sooner  in  the 
volume  pulse  than  in  the  pulse  curve. 

Fig.  118. 


Mosso's  plethysmograph.     G,  glass  vessel  for  holding  a  limb  ;  F,  flask  for  varying  the  water  pressure  in  G  ; 

T,  recording  apparatus. 

(2)  The  respiratory  undulations  correspond  to  similar  variations  in  the 
blood  pressure  tracing  (§  85,/).  Vigorous  respiration  and  cessation  of  the  respi- 
ration cause  a  diminution  of  the  volume.  The  limb  swells  during  straining  and 
coughing,  but  diminishes  during  sighing.  (3)  Certain  periodic  undulations 
occur,  due  to  the  regular  periodic  contractions  of  the  small  arteries.  (4)  Other 
undulations,  due  to  various  accidental  causes,  affect  the  blood  pressure  :  changes 
of  the  position  of  a  limb  acting  hydrostatically,  and  dilatation  or  contraction  of 
the  vessels  in  other  vascular  regions.  (5)  Movement  of  the  muscles  of  the  limb 
under  observation  causes  diminution  of  volume,  as  the  venous  current  is  accele- 
rated, the  musculature  is  also  very  slightly  diminished  in  volume,  even  when  the 
mtra-muscular  vessels  are  dilated.  (6)  Menial  exercise  causes  a  diminution  in  the 
volume  of  the  limb,  and  so  does  sleep  (Mosso).  Music  influences  the  blood 
pressure  in  dogs,  the  pressure  rising  or  falling  under  different  conditions.  The 
stimulation  of  the  auditory  nerve  is  transmitted  to  the  medulla  oblongata,  where 
it  acts  so  as  to  cause  acceleration  of  the  action  of  the  heart  (Dogiel).  (7)  Com- 
pression  of  the  afferent  artery  causes  a  decrease,  and  compression  of  the  vein  an 
mcrease  in  the  volume  of  the  limb  {^Mosso).  (8)  Stimulation  of  the  vasomotor 
nerves  causes  a  decrease,  that  of  the  vaso-dilators  an  increase  in  the  volume  {Bow- 
ditch  and  Warren'). 


TRANSFUSION    OF   BLOOD.  189 

102.    TRANSFUSION    OF   BLOOD.— Transfusion  is  the  introduction 

of  blood  from  one  animal  into  the  vascular  system  of  another  animal. 

(a)  The  red  corpuscles  are  the  most  important  elements  in  connection  with 
the  restorative  powers  of  the  blood.  They  seem  to  preserve  their  functions  even 
in  blood  which  has  been  defibrinated  outside  the  body  (§  4,  A). 

(^b)  With  regard  to  the  gases  present  in  the  blood,  arterial  blood  never  acts 
injuriously ;  but  venous  blood  overcharged  with  carbonic  acid  ought  only  to  be 
transfused  when  the  respiration  is  sufficient  to  oxygenate  the  blood  as  it  passes 
through  the  pulmonary  capillaries,  whereby  venous  is  transformed  into  arterial 
blood.  If  the  respiratory  movements  have  ceased,  or  are  imperfectly  performed, 
the  blood  becomes  rapidly  richer  in  carbonic  acid,  and  in  this  condition  reaches 
the  heart ;  thence  it  is  propelled  into  the  blood  vessels  of  the  medulla  oblongata, 
where  it  acts  as  a  powerful  stimulus  of  the  respiratory  centre,  causing  dyspnoea, 
convulsions,  and  death. 

(^)  The  fibrin,  and  the  substances  from  which  it  is  formed,  do  not  seem  to 
play  any  part  in  connection  with  the  restorative  powers  of  the  blood ;  hence  de- 
iibrinated  blood  performs  all  the  functions  of  non-defibrinated  blood  within  the 
body  {^Paniim,  Landois). 

{d)  The  investigations  of  Worm  Miiller  showed  that  an  excess  of  83  per  cent, 
of  blood  may  be  transfused  into  the  vascular  system  of  an  animal  (dog)  without 
producing  any  injurious  effects.  Hence  it  follows  that  the  vascular  system  has  the 
power  of  accommodating  large  quantities  of  blood  within  it.  That  the  vascular 
system  can  accommodate  itself  to  a  diminished  amount  of  blood  has  been  known 
for  a  long  time  (§  85,  c).  [It  is  very  important  to  observe  that  the  transfusion 
of  a  large  quantity  of  blood  does  not  materially  or  permanently  raise  the  blood 
pressure.] 

When  Employed. — The  transfusion  of  blood  is  used  (i)  in  acute  anaemia 
(§  41,  I),  e.g.,  after  copious  hemorrhage.  New  blood  (150  to  500  c.  c),  from 
the  same  species  of  animal,  is  introduced  directly  into  the  vessels,  to  supply  the 
place  of  the  blood  lost  by  the  hemorrhage. 

(2)  In  cases  of  poisoning,  where  the  blood  has  been  rendered  useless  by 
being  mixed  with  a  poisonous  substance,  and  hence  is  unable  to  support  life.  In 
such  cases  remove  a  considerable  quantity  of  the  blood,  and  replace  it  by  fresh 
blood.  Carbonic  oxide  is  a  poison  of  this  kind,  and  its  effects  on  the  body  have 
already  been  described  (§16).  A  similar  practice  is  indicated  in  poisoning  with 
ether,  chloral,  chloroform,  opium,  morphia,  strychnine,  cobra  poison,  and  such 
substances  as  dissolve  the  blood  corpuscles,  e.g.,  potassic  chlorate. 

(3)  Under  certain  pathological  conditions,  the  blood  may  become  so  altered 
in  quality  as  to  be  unable  to  support  life.  The  morphological  elements  of  the 
blood  may  be  altered,  and  so  may  the  relative  proportion  of  its  other  constituents. 
Among  these  conditions  may  be  cited  the  pathological  condition  of  uraemia,  due, 
it  may  be,  to  the  accumulation  of  urea  or  the  products  of  its  decomposition  within 
the  blood ;  accumulation  of  the  biliary  constituents  in  the  blood,  and  great 
increase  of  the  carbonic  acid.  All  these  three  conditions,  when  very  pronounced, 
may  cause  death.  In  these  cases,  part  of  the  impure  blood  may  be  replaced  by 
normal  human  blood. 

Among  conditions  where  the  morphological  constituents  of  the  blood  are  altered 
qualitatively  or  quantitatively  are  :  hydrsemia  (excessive  amount  of  water  in  the 
blood,  §  41,  i)  ;  oligocythaemia  (abnormal  diminution  of  red  blood  corpuscles). 
When  these  conditions  are  highly  developed,  more  especially  in  pernicious 
anaemia  (§  10,  2),  healthy  blood  may  be  substituted.  Transfusion  is  not  suited 
for  persons  suffering  from  leukaemia  (compare  p.  59). 

After- Effects. — A  quarter  or  half  an  hour  after  normal  blood  has  been 
injected  into  the  blood  vessels  of  a  man,  there  is  a  greater  or  less  febrile  reaction, 
according  to  the  amount  of  blood  transfused  (Fever,  §  220). 


190  TRANSFUSION    OF    BLOOD. 

Operation. — The  operative  procedure  to  be  adopted  in  the  process  of  transfusion  varies  according 
as  defibrinated  or  nondetibrinated  blood  is  used.  In  order  to  defibrinate  blood,  some  blood  is 
withdrawn  from  a  vein  of  a  healthy  man  in  the  ordinary  way,  collected  in  an  open  vessel,  and 
whipped  or  beaten  with  a  glass  rod  until  all  the  fibrin  is  completely  removed  from  it.  It  is  then 
filtered  through  an  atlas  filter,  heated  to  the  temperature  of  the  body  (by  placing  it  in  a  vessel  in 
warm  water),  and  injected  by  means  of  a  syringe  into  an  artery  ojiened  for  the  purpose.  A  vein 
{e.!^.,  basilic  or  great  saphenous)  may  be  selected  for  the  transfusion,  in  which  case  the  blood  is 
driven  inward  in  the  direction  of  the  heart;  if  an  artery  is  selected  (radial  or  posterior  tibial)  the 
blood  is  injected  toward  the  periphery  {Hiiter),  or  toward  the  heart  {Landois,  Schd/er). 

If  non-defibrinated  human  blood  is  used,  the  blood  may  be  passed  directly  from  the  arm  of 
the  giver  to  the  arm  of  the  receiver  by  means  of  a  flexible  tube.  The  tube  used  must  be  filled  with 
normal  saline  solution  to  prevent  the  entrance  of  air.  [J.  Duncan  collects  the  blood  shed  during 
an  operation  in  a  5  per  cent,  solution  of  sodic  phosphate  {Pavy'),  and  injects  the  mixture  especially 
where  much  blood  has  been  lost  previously.] 

Dangers. — It  is  most  important  that  no  air  be  allowed  to  pass  into  the  circulation,  for  if  it  be 
introduced  in  sufficient  quantity  it  may  cause  death.  When  air  enters  the  circulation  it  reaches 
the  right  side  of  the  heart,  where,  owing  to  the  movement  of  the  blood,  it  forms  air  bubbles  and 
makes  a  froth.  The  air-bubbles  are  pumped  into  the  branches  of  the  pulmonary  artery,  in  which 
they  become  impacted,  arrest  the  pulmonary  circulation,  and  rapidly  cause  death. 

Peritoneal  Transfusion. — Recently,  the  injection  of  defibrinated  blood  into  the  peritoneal 
cavity  has  been  recommended.  The  blood  so  injected  is  absorbed  {Fonfick).  Even  after  twenty 
minutes  the  number  of  blood  corpuscles  in  the  blood  of  the  recipient  (rabbit)  is  increased,  and  the 
number  is  greatest  on  the  first  or  second  day.  The  operation,  however,  may  cause  death,  and  one 
fatal  case,  owing  to  peritonitis,  is  recorded  [Afosler).  It  is  evident  that  this  method  of  transfusion 
is  not  applicable  in  cases  where  blood  must  be  introduced  into  the  circulation  as  rapidly  as  possible 
{e.g.,  after  severe  hemorrhage  or  in  certain  cases  of  poisoning).  [Blood  has  been  injected  into  the 
subcutaneous  cellular  tissue  of  the  abdomen  in  cases  of  great  debility.] 

Heterogeneous  Blood. —  The  blood  of  animals  ought  never  to  be  transfused  into  the  blood 
7'essels  of  man.  It  is  to  be  remembered,  however,  that  the  blood  corpuscles  of  the  sheep  are 
rapidly  dissolved  by  human  blood,  so  that  tlie  active  constituents  of  the  blood  are  rendered  useless 
{La/tdois).  As  a  general  rule,  the  blood  serum  of  some  mammals  dissolves  the  blood  corpuscles 
of  other  mammals  (§  5,  5). 

Solution  of  the  Blood  Corpuscles. — The  serum  of  dog's  blood  is  a  powerful  solvent,  while 
that  of  the  blood  of  the  horse  and  rabbit  dissolves  corpuscles  relatively  slowly.  The  blood  cor- 
puscles of  mammals  vary  very  greatly  with  reference  to  their  power  to  resist  the  solvent  action  of 
the  serum  of  other  animals.  The  red  blood  corpuscles  of  rabbits'  blood  are  rapidly  dissolved  by 
the  blood  serum  of  other  animals,  while  those  of  the  cat  and  dog  resist  the  solvent  action  much 
longer.  Solution  of  the  corpuscles  occurs  in  defibrinated  as  well  as  in  ordinary  blood.  When  the 
blood  of  a  rabbit  or  lamb  is  injected  into  the  blood  vessels  of  a  dog,  the  red  blood  corpuscles  are 
dissolved  in  a  few  minutes.  If  blood  be  withdrawn  by  pricking  the  skin  with  a  needle,  the  par- 
tially dissolved  corpuscles  may  be  detected. 

Liberation  of  Haemoglobin  and  Haemoglobinuria. — As  a  result  of  the  solution  of  the  colored 
corpuscles,  the  blood  plasma  is  reddened  by  the  liberated  haemoglobin.  Part  of  the  dissolved 
material  may  be  used  up  in  the  body  of  the  recipient,  some  of  it  for  the  formation  of  bile,  but 
if  the  solution  of  the  corpuscles  has  been  extensive,  the  haemoglobin  is  excreted  in  the  urine 
(haemoglobinuria),  in  less  amount  in  the  intestine,  the  bronchi,  and  the  serous  cavities.  Bloody 
urine  has  been  observed  in  man  after  the  injection  of  lOO  grammes  of  lamb's  blood.  Even  some 
of  the  recipient's  blood  corpuscles  are  dissolved  by  the  serum  of  the  transfused  blood,  e.  g.,  on 
transfusing  dog's  blood  into  man.  In  the  rabbit,  whose  corpuscles  are  readily  dissolved,  the 
transfusion  of  tiie  blood  scrum  of  the  dog,  man,  pig,  sheep,  or  cat  produces  serious  symptoms,  and 
even  death.  The  dog,  whose  corpuscles  are  more  resistant,  bears  transfusion  of  other  kinds  of 
blood  well. 

Dangers. — When  foreign  or  heterogeneous  blood  {i.  <?.,  blood  from  a  different  species)  is  trans- 
fused, two  phenomena  which  may  be  dangerous  to  life  occur: — 

(i)  Before  the  corpuscles  are  dissolved,  they  usually  run  together  and  form  sticky  masses,  con- 
sisting of  10  or  12  corpuscles,  which  are  apt  to  occlude  the  capillaries.  After  a  time  they  give 
up  their  haemoglobin,  leaving  the  stroma,  which  yields  a  sticky,  fibrin-like  mass  that  may  occlude 
fine  vessels  (^  31). 

(2)  The  presence  of  a  large  quantity  of  dissolved  haemoglobin  may  cause  extensive  coagulation 
within  the  blood  vessels.  The  injection  of  dissolved  haemoglobin  causes  extensive  coagulations 
{Naunyn  and  Franc  ken). 

The  coagulation  occurs  usually  in  the  venous  system  and  in  the  larger  vessels,  and  may  cause 
death  either  suddenly  or  after  a  considerable  time. 

Dissolved  haemoglobin  seems  greatly  to  increase  the  activity  of  the  fibrin-ferment  (§  30),  perhaps 
by  accelerating  the  disintegration  of  the  colorless  corpuscles.     Haemoglobin  exposed  to  the  air 


TRANSFUSION    OF    BLOOD.  191 

gradually  loses  this  property;  and  the  fibrin-ferment,  when  in  contact  with  haemoglobin,  is  either 
destroyed  or  rendered  less  active  {^Sachssendahl). 

Vascular  Symptoms. — As  a  result  of  the  above-named  causes  of  occlusion  of  the  vessels, 
there  are  often  signs  of  the  circulation  being  impeded  in  various  organs.  In  man,  after  transfusion 
of  lambs'  blood,  the  skin  is  bluish-red,  in  consequence  of  the  stagnation  of  blood  in  the  cutaneous 
vessels.  Difficulty  of  breathing  occurs  from  obstruction  in  the  capillaries  of  the  lung;  while  there 
may  be  rupture  of  small  bronchial  vessels,  causing  sanguineous  expectoration.  The  dyspnoea  may 
increase,  especially  when  the  circulation  through  the  medulla  oblongata — the  seat  of  the  respiratory 
centre — is  interfered  with.  In  the  digestive  tract,  for  the  same  reason,  increased  peristalsis,  evacua- 
tion of  the  contents  of  the  rectum,  vomiting,  and  abdominal  pain  may  occur.  These  phenomena 
are  explained  by  the  fact  that  disturbances  of  the  circulation  in  the  intestinal  vessels  cause  increased 
peristaltic  movements.  Degeneration  of  the  parenchyma  of  the  kidney  occurs  as  a  result  of  the 
occlusion  of  some  of  the  renal  vessels.  The  uriniferous  tubules  become  plugged  with  cylinders 
of  coagulated  albumin  {Fonjick).  Owing  to  the  occlusion  of  numerous  small  muscular  branches, 
the  muscles  may  become  stiff,  or  coagulation  of  their  myosin  may  occur.  Other  symptoms,  refer- 
able to  the  nervous  system,  sense  organs,  and  heart,  are  all  due  to  the  interference  with  the  circula- 
tion through  them.  An  important  symptom  is  the  occurrence  of  a  considerable  amount  oi  fever 
half  an  hour  or  so  after  the  transfusion  of  heterogeneous  blood  (§  200).  When  many  vessels 
are  occluded,  rupture  of  some  small  blood  vessels  may  take  place.  This  explains  the  occurrence 
of  slight,  yet  persistent  hemorrhages,  which  occur  on  the  free  surfaces  of  the  mucous  and  serous 
membranes,  and  in  the  parenchyma  of  organs,  as  well  as  in  wounds.  The  blood  coagulates  with 
difficulty,  and  imperfectly. 

Transfusion  of  other  Fluids. — Other  substances  have  been  transfused.  Normal  saline  solu- 
tion (0.6  per  cent.  NaCl),  or  serum  from  the  same  species,  aids  the  circulation  in  a  purely 
mechanical  way  ( 6^(?/^s),  and  it  even  excites  the  circulation  {Kronecker).  In  severe  ansemia  this 
fluid  cannot  maintain  life  [Eulenburg  and  Landois).  The  injection  of  peptone,  even  in  moderate 
amount,  is  dangerous  to  life,  as  it  causes  paralysis  of  the  vessels  (p.  73). 


THE  BLOOD  GLANDS. 


Fig.  119. 


Capsul; 


Trabecule. 


"':^ 
^ 


103. — I.  THE  SPLEEN. — Structure. — The  spleen  is  covered  by  the  peritoneum,  except  at 
the  liilum.     Under  this  serous  covering   there  is  a  tough,  thick,  elastic,    fibrous  capsule,  which 

closely  invests  the  organ  and  gives  a  covering  to 
the  vessels  which  enter  or  leave  it  at  the  hilum,so 
that  fibrous  tissue  is  carried  into  the  organ  along 
the  course  of  the  vessel?  (Fig.  1 19).  [The  capsule 
cannot  be  separated  without  tearing  the  splenic 
pulp.]  Numerous  trabeculae  pass  into  the  spleen 
from  the  deep  surface  of  the  capsule,  where  they 
l)ranch  and  anastomose  so  as  to  produce  a  network 
of  sustentacular  tissue,  which  is  continuous  with 
the  connective  tissue,  prolonged  inward  and  sur- 
rounding the  blood  vessels  (Fig.  120).  Thus,  the 
connective  tissue  in  the  spleen,  as  in  other  viscera, 
is  continuous  throughout  the  organ.  In  this  way 
an  irregular  dense  network  is  formed,  comparable 
to  the  meshes  of  a  bath  sponge.  [This  network 
is  easily  demonstrated  by  washing  out  the  pulp 
lying  in  its  meshes  by  means  of  a  stream  of  water, 
when  a  beautiful,  soft,  semi-elastic  network  or 
frainework  of  rounded  and  flattened  threads  is 
obtained.]  The  capsule  (Fig.  119)  is  composed 
of  interlacing  bundles  of  connective  tissue  mixed 
with  numerous  fine  fibres  of  elastic  tissue  and 
some  non-striped  muscular  fibres. 

Reticulum. — Within  the  meshes  of  the  trabe- 
cular framework  there  is  disposed  a  very  delicate 
network  or  reticulum  of  adenoid  tissue,  which, 
with  the  other  colored  elements  that  fill  up  the 
meshes,  constitutes  the  splenic  pulp  (Fig.  121). 
The  reticulum  is  continuous  with  the  fibres  of  the 
trabecula:.  [If  a  fine  section  of  the  spleen  be 
"penciled"  in  water,  so  as  to  remove  the  cellular 
elements,  the  preparation  presents  much  the  same 
characters  as  a  section  of  a  lymph  gland  similarly 
treated,  viz.,  a  very  fine  network  of  adenoid  tissue,  continuous  with,  and  surrounding  the  walls  of, 
the  blood  vessels.     The  spaces  of  this  tissue  are  filled  with  lymph  and  blood  corpuscles.] 

The  pulp  is  a  dark,  reddish-colored,  semi-fluid  materia!,  which  may  be  squeezed  or  washed  out 
of  the  meshes  in  which  it  lies.  It  contains  a  large  number  of  colored  blood  corpuscles,  and  becomes 
brighter  when  it  is  exposed  to  the  action  of  the  oxygen  of  the  air. 

Blood  Vessels  and  Malpighian  Corpuscles. — The  large  splenic  artery,  accompanied  by  a 
vein,  splits  up  into  several  branches  before  it  enters  the  spleen.  Both  vessels  and  their  branches 
are  enclosed  in  a  fibrous  sheath,  which  becomes  continuous  with  the  trabecule.  The  smaller 
branches  of  the  artery  gradually  lose  this  fibrous  investment,  and  each  one  ultimately  divides  into 
a  group  or  pencil  of  arterioles  or  penicilli,  which  do  ttot  anastomose  with  each  other.  [Thus  each 
branch  is  terminal — a  condition  which  is  of  great  importance  in  connection  with  the  pathology  of 
embolism  or  infarction  of  the  vessels  of  the  spleen.]  At  the  points  of  division  of  the  branches  of 
the  artery,  or  scattered  along  their  course,  are  small  oval  or  globular  masses  of  adenoid  tissue  (^\j  to 
2'jj  inch  in  diameter),  the  Malpighian  corpuscles.  [These  bodies  are  visible  to  the  naked  eye 
as  small,  round,  or  oval  white  structures,  about  the  size  of  millet  seed,  in  a  section  of  a  fresh 
spleen.  They  are  verj-  numerous — [70,000  in  man] — and  are  readily  detected  in  the  dark  reddish 
pulp.  One  must  be  careful  not  to  mistake  sections  of  the  trabecular  for  them.  These  corpuscles 
consist  of  adenoid  tissue,  whose  meshes  are  filled  with  lymph  corpuscles,  and  they  present  exactly 
the  same  structure  as  the  solitary  follicles  of  the  intestine  (\  197).     They  are  small  lymphatic 

192 


Malpighian 
corpuscles. 


Splenic  pulp. 


Trabecula. 


Blood  vessel  in 
a  trabecula. 


Section  of  human  spleen  X  10  times. 


BLOOD    VESSELS    OF   THE    SPLEEN. 


193 


accumulations  around  the  arteries — periarterial  masses  of  adenoid  tissue  similar  to  those  masses 
that  occur  in  a  slightly  different  form  in  other  organs,  e.  g.,  the  lungs.  In  a  section  of  the  spleen 
the  artery  may  pass  through  the  centre  of  the  mass  or  through  one  side  of  it,  and  in  some  cases  the 
tissue  is  collected  unequally  on  opposite  sides  of  the  vessel,  so  that  it  is  lop-sided.  They  are  not 
surrounded  by  any  special  envelope.  In  some  animals  the  lymphatic  tissue  is  continued  for  some 
distance  along  the  small  arteries,  so  that  to  some  extent  it  resembles  a  perivascular  sheath  of  ade- 


FiG.  1 20. 


Fig.  121. 


Trabeculae  of  the  spleen  of  a  cat  witli  the  splenic  pulp  washed  out. 
a,  trabecula;  b,  vein. 


Adenoid  reticulum  of  spleen 
of  cat. 


noid  tissue.  In  a  well-injected  spleen,  a  few  fine  capillaries  are  to  be  found  within  these  corpuscles. 
The  capillaries  distributed  in  the  substance  of  the  Malpighian  corpuscle  (Fig.  122)  form  a  network, 
and  ultimately  pour  their  blood  into  the  spaces  in  the  pulp.  According  to  Cadiat,  the  corpuscles 
are  separated  from  the  splenic  pulp  by  a  lymphatic  sinus,  which  is  traversed  by  efferent  capillaries 
passing  to  the  pulp  (Fig.  122).] 

Connection  of  Arteries  and  Veins. — It  is  very  difficult  to  determine  what  is  the  exact  mode 
of  termination  of  the  arteries  within  the  spleen, 

more  especially  as  it  is  extremely  difScult  to  FiG.   122. 

inject  the  blood  vessels  of  the  spleen.  Accord- 
ing to  Stieda  and  others,  the  fine  "  capillary 
arteries"  formed  by  the  division  of  the  small 
arteries  do  not  open  directly  into  the  capillary 
veins,  but  the  connection  between  the  arteries 
and  veins  is  by  means  of  the  "  intermediary 
intercellular  spaces  "  of  the  reticulum  of 
the  spleen,  so  that,  according  to  this  view, 
there  is  no  continuous  channel  lined  through- 
out by  epithelium  connecting  these  vessels  one 
with  another.  Thus  the  blood  of  the  spleen 
flows  into  the  spaces  of  the  adenoid  reticulum 
just  as  the  lymph  stream  flows  through  the 
spaces  in  a  lymph  gland.  According  to  Bill- 
roth and  K5lliker,  a  closed  blood  channel  act- 
ually does  exist  between  the  capillary  arteries 
and  the  veins,  consisting  of  dilated  spaces 
(similar  to  those  of  erectile  tissue).  These 
intermediary  spaces  are  said  to  be  completely 
lined  by  spindle-shaped  epithelium,  which 
abuts  externally  on  the  reticulum  of  the  pulp. 
[According  to  Frey,  owing  to  the  walls  of  the 
terminal  vessels  being  incomplete,  there  being 
clefts  or  spaces  between  the  cells  composing 
them,  the  blood  passes  freely  into  spaces  of  the  adenoid  tissue  of  the  pulp  "in  the  same  way 
as  the  water  of  a  river  finds  its  way  among  the  pebbles  of  its  bed,"  these  "  intermediary  pass- 
ages "  being  bounded  directly  by  the  cells  and  fibres  of  the  network  of  the  pulp.  From  these  passages 
the  venous  radicals  arise.  At  first,  their  walls  are  imperfect  and  cribriform,  and  they  often  present 
peculiar  transverse  markings,  due  to  the  circular  disposition  of  the  elastic  fibres  of  the  reticulum. 
The  small  veins  have  at  first  a  different  course  from  the  arteries.  They  anastomose  freely,  but  they 
soon  become  ensheathed,  and  accompany  the  arteries  in  their  course.] 

13 


Malpighian  corpuscle  of  a  cat's  spleen  injected,  a,  artery  ; 
b,  meshes  of  the  pulp  injected ;  c,  the  artery  of  the  cor- 
puscle ramifying  in  the  lymphatic  tissue  composing  it. 


194  FUNCTIONS    OF   THE    SPLEEN. 

Elements  of  the  Pulp  (Fig.  123.) — The  morphological  elements  are  very  various — (l)  Lymph 
corpuscles  of  various  sizes,  sometimes  partly  swollen,  and  at  other  times  with  granular  contents.  (2) 
Red  blood  corpuscles.  (3)  Transition  forms  between  l  and  2  [although  this  is  denied  by  some 
observers  (^  7,  C)].  (4)  Cells  containing  red  blood  corpuscles  and  pigment  granules,  [These  cells 
exhibit  am(cboid  movements.]     (Compare  ^  8.) 

[Lymphatics  undoubtedly  arise  within  the  spleen,  but  they  are  not  numerous.  There  are  two 
systems — a  superficial  or  capsular,  and  trabecular  system  ;  and  a  perivascular  set.  The  superficial 
lymphatics  in  the  capsule  are  rather  more  numerous.  Some  of  them  seem  to  communicate  with  the 
lymphatics  within  the  organ  [Toinsu  Kolliker).  In  the  horse's  spleen  they  communicate  with  the 
lymphatics  in  the  trabecul.v,  and  with  the  perivascular  lymphatics.  The  exact  mode  of  origin  of 
the  perivascular  system  is  unknown,  but  in  part  at  least  it  begins  in  the  spaces  of  the  adenoid 
tissue  of  the  Malpighian  corpuscles  and  perivascular  adenoid  tissue,  and  runs  along  the  arteries 
toward  the  hdum.  There  seem  to  be  no  afferent  lymphatics  in  the  spleen  such  as  exist  in  a  lym- 
phatic gland. 

The  nerves  of  the  spleen  are  composed  for  the  most  part  of  non-medullated  nerve  fibres,  and 
run  along  with  the  artery.     Their  exact  mode  of  termination  is  un- 
Fic.  123.  known,  but  they  probably  go  to  the  blood  vessels  and  to  the  muscular 

tissue  in  the  capsule  and  trabecular.  [They  are  well  seen  in  the 
spleen  of  the  ox,  and  in  their  course  very  small  ganglia,  placed  wide 
apart,  have  been  found  by  Remak  and  W.  Stirling.] 

Chemical  Composition. — Several  of  the  more  highly  oxidized 
stages  of  albuminous  bodies  exist  in  the  spleen.  Besides  the  ordin- 
ary constituents  of  the  blood,  there  exist  leucin,  tyrosin,  xanthin, 
hypoxanthin;  lactic,  butyric,  acetic,  formic,  succinic,  and  uric  acids, 
and  perhaps  glycero-phosphoric  acid  {Saiko-u>ski);  cholesterin,  a 
gluten-like  body,  inosit,  a  pigment  containing  iron,  and  even  free 
iron  oxide  [N'asse).  The  ash  is  rich  in  phosphoric  acid  and  iron  (p. 
195) — poor  in  chlorine  compounds.  The  splenic  juice  is  alkaline  in 
reaction  ;  the  specific  gravity  of  the  spleen  =r  1059-1066. 

The  functions  of  the  spleen  are  obscure,  but  we 
know  some  facts  on    which  to    form   a   theory.     [The 

Elements  of  human  splenic  pulp.  i  j'cr         r  ..u  ■       ii      i.  t 

I,  colorless  cells:  2, endothe-    splceu  differs  from  Other  organs  ni  that  no  very  apparent 
lium;  3,  colored  blood  cor-    effect  is  pfoduced  by  it,  so  that  we  must  determine  its 

puscles  ;    4,   cells    Containing  .         \  ■'  ^  ...  .  ,       . 

granules,  the  upper  one  with    uscs  lu  the  ccouomy  from  a  Consideration  of  such  facts 
end!,°ser"°°'^'°''^"'''^''^'    ^s  the  followiug :   (i)  The  effects  of  its  removal  or  ex- 
tirpation.    (2)  The  changes  which  the  blood  undergoes 
as  it  passes  through  it.     (3)  Its  chemical  composition.     (4)  The  results  of  experi- 
ments upon  it.     (5)  The  effects  of  diseases.] 

(i)  Extirpation. — The  spleen  may  be  removed  from  an  animal — old  or  young 
— without  the  organism  suffering  any  very  obvious  change  {Galen).  The  human 
spleen  has  been  successfully  removed  by  Koberle,  Fean,  and  others.  As  a  result 
(compensatory  ?)  the  lymphatic  glands  enlarge,  but  not  constantly,  while  the 
blood-forming  activity  of  the  red  marrow  of  bone  is  increased.  Small  brownish- 
red  patches  were  observed  in  the  intestines  of  frogs  after  extirpation  of  the  spleen. 
These  new  formations  are  regarded  by  some  observers  as  compensatory  organs. 
Tizzoni  asserts  that  new  splenic  structures  are  formed  in  the  omentum  (horse, 
dog)  after  the  destruction  of  the  parenchyma  and  blood  vessels  of  the  spleen. 
The  spleen  is  absent  extremely  seldom. 

[The  weight- of  the  animal  (dog)  diminishes  after  the  operation,  but  afterward  increases.  The 
number  of  red  blood  corpuscles  is  lessened,  reaching  its  minimum  about  the  150th  to  the  200th  day, 
while  the  colorless  corpuscles  are  increased  in  number.  The  lymphatic  glands  (especially  the  in- 
ternal, and  those  in  the  neck,  mesentery,  and  groin)  enlarge,  while  on  section  the  cortical  substance 
of  these  structures  is  redder,  owing  to  the  great  number  of  red  corpuscles,  many  of  them  are  nu- 
cleated in  the  lymph  spaces  {Gibson).  The  marrow  of  all  the  long  bones  (those  of  the  foot  ex- 
cepted), becomes  very  red  and  soft,  with  the  characters  of  embryonic  bone-marrow.  Such  animals 
withstand  hemorrhage  (to  r^  of  the  total  amount  of  blood)  without  any  specially  bad  results 
( Ttzzoni,  Winogradcnu).  Schindeler  observed  that  animals  after  extirpation  of  the  spleen  became 
very  ravenous.] 

[Regeneration. — After  entire  removal  of  the  spleen,  nodules  of  splenic  tissue  are  reproduced 
(fox) ;  while  new  adenoid  tissue  is  formed  in  the  lymphatic  glands,  and  in  Peyer's  patches,  the  pa- 
renchyma of  the  former  coming  to  resemble  splenic  tissue  ( Tizzoni,  Eternod.)^ 


CONTRACTION    OF   THE    SPLEEN.  195 

(2)  According  to  Gerlach  and  Funke  the  spleen  is  a  blood-forming  gland. 
The  blood  of  the  splenic  vein  contains  far  more  colorless  corpuscles  than  the  blood 
of  the  splenic  artery  (p.  55).  Many  of  these  corpuscles  undergo  fatty  degenera- 
tion, and  disappear  in  the  blood  stream.  That  colorless  blood  corpuscles  are 
formed  within  the  spleen  seems  to  be  proved  by  the  enormous  number  of  these 
corpuscles  which  are  found  in  the  blood  in  cases  of  leukaemia  {Beiineit  (\%'^2), 
Virchow).  Bizzozero  and  Salvioli  found  that,  several  days  after  severe  hemor- 
rhage, the  spleen  became  enlarged,  and  its  parenchyma  contained  numerous  red 
nucleated  hsematoblasts. 

(3)  Other  observers  {^Kolliker  and  Ecker)  regard  the  spleen  as  an  organ  in  which 
colored  blood  corpuscles  are  destroyed,  and  they  consider  the  large  proto- 
plasmic cells  containing  pigment  granules  as  a  proof  of  this  (p.  53).  According 
to  the  observations  of  Kusnetzow,  these  structures  are  merely  lymph  corpuscles, 
which,  in  virtue  of  their  amceboid  movements,  have  entangled  colored  blood  cor- 
puscles. [Such  corpuscles  exhibit  similar  properties  when  placed  upon  a  warm 
stage.]  Similar  cells  occur  in  extravasations  of  blood.  The  colored  blood  cor- 
puscles within  the  lymph  cells  gradually  become  disintegrated,  and  give  rise  to  the 
production  of  granules  of  hsematin  and  other  derivatives  of  haemoglobin.  [The 
spleen  contains  so  much  free  iron  that  a  section  of  this  organ,  especially  from  a 
young  animal,  when  treated  with  Tizzoni's  fluid,  /.  ^.,  with  potassic  ferrocyanide 
and  hydrochloric  acid,  gives  a  distinct  blue  color  (§  174,  4).]  Hence,  the  spleen 
contains  more  iron  than  corresponds  to  the  amount  of  blood  present  in  it.  When 
we  consider  that  the  spleen  contains  a  large  number  of  extractives  derived  from 
the  decomposition  of  proteids,  it  is  very  probable  that  colored  blood  corpuscles 
are  destroyed  in  the  spleen.  Further,  the  juice  of  the  spleen  contains  salts  similar 
to  those  that  occur  in  the  red  blood  corpuscles. 

The  blood  from  the  spleen  is  said  to  have  undergone  other  changes,  but  the  following  statement 
must  be  accepted  with  caution:  The  blood  of  the  splenic  vein  contains  more  water  and  fibrin,  its 
red  blood  corpuscles  are  smaller,  brighter,  less  flattened,  more  resistant,  and  do  not  form  rouleaux ; 
its  haemoglobin  crystallizes  more  easily,  and  there  is  a  large  proportion  of  O  during  digestion. 

[The  spleen  has  therefore  very  direct  relations  to  the  blood ;  in  it  colored  blood 
corpuscles  undergo  disintegration,  it  produces  colorless  corpuscles,  and  it  is  said 
to  transform  white  corpuscles  into  red.] 

(4)  Contraction. — In  virtue  of  the  plain  muscular  fibres  in  its  capsule  and 
trabeculae,  the  spleen  undergoes  variations  in  its  volume.  Stimulation  of  the  spleen 
or  its  nerves,  by  cold,  electricity,  quinine,  eucalyptus,  ergot  of  rye,  and  other 
"splenic  reagents"  causes  it  to  contract,  whereby  it  becomes  paler,  and  its 
surface  may  even  appear  granular.  After  a  meal,  the  spleen  increases  in  size,  and 
it  is  usually  largest  about  five  hours  after  digestion  has  begun,  z.  <?.,  at  a  time  when 
the  digestive  organs  have  almost  finished  their  work,  and  have  again  become  less 
vascular.  After  a  time  it  regains  its  original  volume.  For  this  reason  the  spleen 
was  formerly  regarded  as  an  apparatus  for  regulating  the  amount  of  blood  in  the 
digestive  organs.  [The  congestion  of  the  spleen  after  a  meal  is  more  probably 
related  to  the  formation  of  new  colorless  corpuscles  than  to  the  destruction  of  red 
corpuscles.  It  may  be,  however,  that  some  of  the  products  of  digestion  are  par- 
tially acted  upon  in  the  spleen,  and  undergo  further  change  in  the  liver.]  There 
is  a  relation  between  the  size  of  the  spleen  and  that  of  the  liver,  for  it  is  found 
that  when  the  spleen  contracts — e.  g.,  by  stimulation  of  its  nerves — the  liver 
becomes  enlarged,  as  if  it  were  injected  with  more  blood  than  usual  {Drosdow  and 
BotschetschkaroTJu) . 

[Oncograph. — Botkin,  and  more  recently  Roy,  have  studied  various  conditions 
which  affect  the  size  of  the  spleen.  Roy  enclosed  the  spleen  of  a  dog  in  a  box 
with  rigid  walls,  the  oncograph  {oyy-oq,  volume),  and  filled  with  oil  after  the  manner 
of  the  plethysmograph  (§§  loi,  276).  Any  variations  in  the  size  of  the  organ 
caused  a  variation  in  the  amount  of  oil  within  the  box,  and  these  variations  were 


196 


INFLUENCE    OF   NERVES   ON    THE    SPLEEN. 


recorded.  The  blood  pressure  was  recorded  at  the  same  time.  The  circulation 
through  the  spleen  is  peculiar,  and  is  not  due  to  the  blood  pressure  within  the 
arteries,  but  is  carried  on  chiefly  by  a  rhythmical  contraction  of  the  muscular 
fibres  of  the  capsule  and  trabecule.  The  spleen  undergoes  very  regular  rhyth- 
mical contractions  (systole)  and  dilatations  (diastole).  This  alternation  of 
systole  and  diastole  may  last  for  hours,  and  the  two  events  together  occupy  about 
one  minute  (Fig.  124).  Changes  in  the  arterial  blood  pressure  have  comparatively 
little  influence  on  the  volume  of  the  spleen.  The  rhythmical  contractions,  although 
modified,  still  go  on  after  section  of  the  splenic  nerves.  This  would  seem  to 
indicate  that  the  spleen  has  an  independent  (nervous)  mechanism  within  itself, 
causing  its  movements.] 

[Influence  of  Nerves. — Section  of  the  splenic  nerves  is  followed  by  an 
increase  in  the  size  of  the  spleen.  The  nerves  have  their  centre  in  the  medulla 
oblongata.  Stimulation  of  the  medulla  oblongata,  either  directly  or  by  means  of 
asphyxiated  blood,  causes  contraction  of  the  spleen,  hence  the  spleen  is  "small 
and  contracted"  in  death  from  asphyxia.     The  fibres  proceed  down  the  cord, 

Fig.  124. 


Abscissa  of  Blood  prcssu  re- cm /c  2  secf   inter/als 


Tracing  of  a  splenic  curve,  reduced  one-half,  taken  with  the  oncograph.  The  upper  line  with  large  waves  is  the 
splenic  curve;  each  ascent  corresponds  to  an  increase,  and  each  descent  to  a  diminution  in  the  volume  of  the 
spleen.  The  curve  beneath  is  a  blood-pressure  tracing  from  the  carotid  artery.  The  lowest  line  indicates  the 
time,  the  interruptions  of  the  marker  occurring  every  two  seconds.  The  vertical  lines,  a  and  b,  give  the  relative 
positions  of  the  lever  point  of  the  oncograph,  and  of  the  point  of  the  recording  style  of  the  kymograph  respectively 
(Koy). 

and  leaving  it  in  the  dorsal  region,  enter  the  left  splanchnic,  pass  through  the 
semilunar  ganglion,  and  thus  reach  the  splenic  plexus.  Stimulation  of  the  periph- 
eral ends  of  these  nerves  causes  contraction  of  the  spleen,  and  so  does  cold  applied 
to  the  spleen  directly  or  over  the  region  of  the  organ.  In  the  last  case  the  result 
is  brought  about  reflexly.  Botkin  found  that  the  application  of  the  induced 
current  to  the  skin  over  the  spleen,  in  a  case  of  leuknemia,  caused  well-marked 
contraction  of  the  spleen  in  all  its  dimensions,  and  the  result  lasted  some  time. 
After  every  stimulation  the  number  of  colorless  corpuscles  in  the  blood  increased, 
and  the  condition  of  the  patient  improved.] 

[There  is  a  popular  notion  that  the  spleen  is  influenced  by  the  condition  of  the 
nervous  system.  Botkin  found  that  depressing  emotions  increased  its  size,  while 
exhilarating  ideas  diminished  it.  The  causes  of  these  changes  are  referable  not 
only  to  changes  in  the  amount  of  blood  in  the  spleen,  but  also  to  the  greater  or 
less  degree  of  contraction  of  its  muscular  tissue.  And  it  would  appear  that,  like 
the  small  arteries,  the  muscular  tissue  of  the  spleen  is  in  a  state  of  tonic  con- 


THE   THYMUS. 


197 


traction.  The  size  of  the  spleen  may  be  influenced  reflexly.  Thus,  Tarchanoff 
found  that  stimulation  of  the  central  ^nd.  of  the  vagus,  when  the  splanchnics  were 
intact,  caused  contraction  of  the  spleen,  while  stimulation  of  the  central  end  of 
the  sciatic  also  caused  contraction,  but  to  a  less  degree.  It  is  quite  certain  that 
all  the  phenomena  are  not  due  to  the  action  of  vasomotor  nerves  on  the  splenic 
blood  vessels.  There  is  a  certain  amount  of  independent  action  of  the  muscular 
fibres  of  the  organ,  and  it  is  not  improbable  that  the  innervation  of  the  spleen  is 
similar  to  the  innervation  of  arteries,  and  that  it  has  a  motor  centre  in  the  cord 
capable  of  being  influenced  reflexly  by  afferent  nerves,  while  it  also  sends  out 
efferent  impulses.] 

[Stimulation  of  (i)  the  central  end  of  a  sensory  nerve  ;  (2)  of  the  peripheral 
ends  of  both  splanchnics  ;  (3)  of  the  peripheral  ends  of  both  vagi,  causes  contrac- 
tion of  the  spleen.  But  even  after  section  of  the  splanchnics  and  vagi,  stimulation 
of  a  sensory  nerve  still  causes  contraction,  so  that  there  must  be  some  other  channel 
as  yet  unknown  {Roy).  Bochefontaine  found  that  electrical  stimulation  of  certain 
parts  of  the  cortex  cerebri  produced  contraction  of  the  spleen.]  Sensory  nerves 
seem  to  occur  only  in  the  peritoneum  covering  the  spleen. 

Pressure  on  the  splenic  vein  causes  enlargement  of  the  spleen,  hence,  increased  pressure  in  this 
vein  (congestion  of  the  portal  vein,  cessation  of  haemorrhoidal  and  menstrual  discharges)  also  causes 
its  enlargement.  With  regard  to  the  action  of  "  splenic  reagents,"  such  as  quinine,  on  the  con- 
traction of  the  spleen,  Binz  is  of  opinion  that  this  drug  retards  the  formation  of  the  colorless  blood 
corpuscles,  so  that  its  chief  function  is  interfered  with  and  the  organ  becomes  less  vascular.  It  is 
not  definitely  decided,  however,  whether  it  is  contraction  or  dilatation  of  the  spleen  that  alters  the 
proportion  of  red  and  white  corpuscles  in  the  blood. 

Splenic  Tumors. — The  increase  in  size  of  the  spleen  in  various  diseases  early  attracted  the 
attention  of  physicians.  The  healthy  spleen  undergoes  several  variations  in  volume  during  the 
course  of  a  day,  corresponding  with  the  varying  activity  of  the  digestive  organs.  In  this  respect 
the  spleen  resembles  the  arteries.  In  many  fevers  the  spleen  becomes  greatly  enlarged,  probably 
due  to  paralysis  of  its  nerves.  It  is  greatly  increased  in  intermittent  fever  or  ague,  and  often  during 
the  course  of  typhus.  When  it  becomes  abnormally  enlarged,  and  remains  so  alter  repeated  attacks 
of  the    ague,  it   is   greatly  hypertrophied,  and    constitutes    "  ague  cake."     In    cases  of  splenic 

leukremia  it  is  greatly  enlarged,  and  at  the  same  time  there  is  a 
Fig.  125.  great  increase  in  the  number  of  colorless  corpuscles  in  the  blood 

and  also  a  decrease  of  the  colored  ones  f|  10). 

II.  The  Thymus. — During  foetal  life  this  gland  is  largely  de- 
veloped, and  it  increases  during  the  first  two  or  three  years  of 
life,  remaining  stationary  until  the  tenth  or  fourteenth  year,  when  it 

Fig.  126. 


Section  of  the  thymus  gland  of  a  cat, 
with  one  complete  lobule  with  a 
cortical  part  a,  and  a  centre,  i5.  a, 
lymphoid  tissue  ;  c,  blood  vessels 
injected;  «^,  connective  tissue. 


Elements  of  the  thymus 
(X  300).  a.  lymph  cor- 
puscles ;  b,  concentric 
corpuscle  of  Hassall. 


begins  to  atrophy  and  undergo  fatty  degeneration,     [The  degeneration  begins  at  the  outer  part  of 
each  lobule  and  progresses  inward  (j^w).] 

Structure. — "  It  consists  of  an  aggregation  of  lymph  follicles  (resembling  the  glands  of  Peyer) 
or  masses  of  adenoid  tissue  held  together  by  a  framework  of  connective  tissue  which  contains  blood 
vessels,  lymphatics,  and  a  few  nerves  (Fig.  125).  The  framework  of  connective  tissue  gives  off 
septa  which  divide  the  gland  into  lobes,  these  being  further  subdivided  by  finer  septa  into  lobules, 
-the  lobules  being  separated  by  fine  intra-lobular  lamellse  of  connective  tissue  into  follicles  (0.5-1.5 


198 


THE   THYROID. 


mm.).  These  follicles  make  up  the  gland  substance,  and  they  are  usually  polygonal  when  seen  in 
a  section.  Each  follicle  consists  of  a  cortical  and  a  medullary  part,  and  the  matrix  or  frame- 
work of  both  consists  of  a  fine  adeniod  reticulum  whose  meshes  are  filled  with  lymph  corpuscles" 
(Fig.  126,  <?).]  Many  of  these  corpuscles  exhibit  various  stages  of  disintegration.  In  the  medulla 
are  found  the  concentric  corpuscles  of  Hassall.  ["  They  consist  of  a  central  granular  part, 
around  which  are  disposed  layers  of  llattened,  nucleated,  endothelial  cells  arranged  concentrically. 
When  seen  in  a  section  they  resemble  the  '  cell  nests  '  of  epithelioma  (Fig.  126,  />).  They  have  also 
been  compared  to  similar  bodies  which  occur  in  the  prostate.  They  are  most  numerous  when  the 
gland  undergoes  its  retrograde  metamorphosis."  Sig.  Mayer  finds  that  the  thymus  of  the  frog  con- 
tains structures,  with  transverse  markings,  identical  with  the  stripes  of  striped  muscular  fibres. 
The  structures  are  identical  with  those  called  "  sarcoplasts  "  by  Margo  and  Paneth,  and  "  sar- 
colytes"  by  Sig.  Mayer.  They  also  occur  in  large  numbers  in  the  tail  of  the  larvae  of  batrachians, 
when  the  tail  is  undergoing  a  retrograde  metamori^hosis.] 

Simon,  His,  and  others  described  a  convoluted  blind  canal,  the  "  central  canal,"  as  occurring 
within  the  gland,  and  on  it  the  follicles  were  said  to  be  placed.  Other  observers,  Jendrassik  and 
Klein,  either  deny  its  existence  or  regard  it  merely  as  a  lymphatic  or  an  artificial  product.  Numer- 
ous fine  lymphatics  penetrate  into  the  interior  of  the  organ,  and  many  are  distributed  over  its  sur- 
face, but  their  mode  of  origin  is  unknown.  [They  seem  to  be  channels  through  which  the  lymph 
corpuscles  are  conveyed  away  from  the  gland.]  Numerous  blood  vessels  are  also  distributed  to 
the  septa  and  follicles  (Fig.  125,  c). 

Chemical  Composition. — Besides  gelatin,  albumin,  soda  albumin,  there  are  sugar  and  fat, 
leucin,  xanthin,  hypoxanthin,  formic,  acetic,  butyric,  and  succinic  acids.  Potash  and  phosphoric 
acid  are  more  abundant  in  the  as/t  than  soda,  calcium,  magnesium  (?  ammonium),  chlorine,  and 
sulphuric  acid. 

Function. — As  long  as  it  exists,  it  seems  to  perform  the  functions  of  a  true  lymph  gland.  This 
view  is  supported  by  the  fact  that  in  reptiles  and  amphibians,  which  do  not  possess  lymph  glands, 
the  thymus  remains  as  a  permanently  active  organ.  [Extirpation  gave  few  positive  results,  but 
chemical  investigation  shows  that  the  i)arenchyma  contains  a  large  number  of  products  indicating 
considerable  metabolic  activity  {Fried/fben).'] 

III.  The  Thyroid. — Structure. — The  gland  consists  of  lobes  and  lobules  held  together  by 
connective  tissue   rich  in  cells.     Each  lobule  is  made  up  of  numerous  completely  closed  sacs 

(0.04    to  0.1   mm.  in  diameter),  which  in 


Fk; 


IT' 


•Ji--' 


:^ 


>' 


Section  of  ihe  thyroid  ghiiid.  a,  closed  vesicles;  b,  distended 
by  colloid  masses  and  lined  by  low  columnar  epithelium  ; 
c,  inter-vesicular  connective  tissue. 


the  embryo  and  the  newly-born  animal  are 
composed  of  a  membrana  propria  lined  by 
a  single  layer  of  nucleated  cells  (Fig.  127). 
The  sacs  contain  a  transparent,  viscid, 
albuminous  fluid.  [Not  unfrequently  the 
sacs  contain  many  colored  blood  corpuscles 
{Balfer).']  Each  sac  is  surrounded  by  a 
l)lexus  of  capillaries  which  do  not  penetrate 
the  membrana  propria.  There  are  also 
numerous  lymphatics.  At  an  early  period 
the  sacs  dilate,  their  cellular  lining  atro- 
phies, and  their  contents  undergo  colloid 
degeneration.  When  the  gland  vesicles  are 
greatly   enlarged,  "  goitre  "  is   produced. 

The  chemical  composition  of  this 
gland  has  not  been  much  investigated.  In 
addition  to  the  ordinary  constituents,  leucin, 
xanthin.  sarkin,  lactic,  succinic,  and  volatile 
fatty  acids  have  been  found. 

[Excision. — The  effects  differ  according 
to  the  animal  operated  on.  This  gland  has 
been  excised  in  the  human  subject  in  cases 
of  goitre.  Reverdin  pointed  out  that  a  pe- 
culiar  condition   results,  called  cachexia 


stumipriva,  and  practically  the  human  being  becomas  a  cretin.  This  operation,  therefore,  is  highly 
(|uestionable  when  performed  on  man.  Rabbits  endure  the  operation  well,  and  so  do  the  sheep, 
calf,  and  horse.  Of  dogs,  cats,  and  foxes,  only  a  very  small  number  survive,  nearly  all  die.  It 
appears  therefore  that  herbivora  bear  the  operation  and  suffer  fewer  after-effects  than  carnivora  [San- 
quirico  and  Orecchia).  The  immediate  effects  are  fibrillar  contractions,  which  ultimately  influence 
the  gait  of  the  animak.  convulsions,  anresthesia,  great  diminution  of  sensibility,  loss  of  flesh,  redness  of 
the  ears  and  intense  heat  of  the  skin  (which  disappear  after  several  days),  difficulty  in  seizing  and 
eatmg  food,  keratoconjunctivitis,  and  frequently  disturbance  of  the  rhythm  of  respiration  with  dysp- 
ntea  and  spasms  of  the  abdominal  muscles  {Schiff).  The  arterial  blood  contains  about  the  same 
amount  of  O  as  venous  blood.     Certain  parts  of  the  peripheral  nerves  undergo  a  kind  of  degenera- 


FUNCTIONS    OF   THE   THYROID    GLAND. 


199 


tion  similar  to  that  found  after  nerve  stretching.  There  is  albuminuria  and  fall  of  the  blood  pressure. 
Death  usually  occurs  between  the  third  and  fourth  day,  the  animals  being  comatose  ( Wagner). 
Schiff  found  that  if  one-half  of  the  gland  was  excised  at  once,  and  the  other  half  a  month  afterward, 
death  did  not  occur;  but  Wagner  denies  this,  for  he  asserts  that  the  remaining  half  hypertrophies, 
and  if  it  be  excised,  death  occurs  with  the  usual  symptoms.  In  monkeys,  five  days  after  the  opera- 
tion, there  are  symptoms  of  nervous  disturbance.  The  animals  have  lost  their  appetite,  there  are 
fibrillar  contractions  of  the  muscles  of  the  face,  hands,  and  feet,  but  the  tremors  disappear  on  volun- 
tary effort.  The  appetite  returns  and  is  increased,  but  notwithstanding,  the  animal  grows  thin  and 
pale  ;  while  the  tremors  increase  and  affect  all  the  muscles  of  the  body.  These  tremors  are  of  central 
origin,  because  they  disappear  on  dividing  the  nerve.  Thus  there  is  profound  alteration  of  the 
motor  powers.  Among  the  outward  symptoms  are  puffiness  of  the  eyelids,  swelling  of  the  abdo- 
men, increased  hebetude,  and  dyspnoea,  while  afterward  there  is  a  fall  of  the  temperature  and  im- 
becility ;  the  tremors  disappear,  there  is  a  pallor  of  the  skin,  and  ultimately  after  five  to  seven  weeks 
the  animals  die  comatose.  Thus  there  is  a  slow  onset  of  hebetude,  terminating  in  imbecility.  Very 
remarkable  changes  occur  in  the  blood.  There  is  a  steady  fall  of  the  blood  pressure ;  a  diminution 
of  the  red  blood  corpuscles,  or  rather  profound  ansemia ;  leucocythaemia,  the  colorless  corpuscles 
being  increased  to  the  ratio  of  four  to  fourteen ;  and  lastly  mucin  is  present  in  the  blood,  although 
normally  it  is  not  so.  The  salivary  glands  are  hypertrophied,  owing  to  the  presence  of  mucin, 
which  is  found  even  in  the  parotid,  although  this  is  normally  a  serous  gland  (§  141).  The  swelling 
of  the  abdomen  is  due  to  hypertrophy  of  the  great  omentum.  Mucin  is  found  in  the  peritoneal  fluid, 
and  the  spleen  is  also  enlarged.  Thus  these  symptoms  present  many  features  in  common  with  those 
of  myxcedema  as  described  by  Ord  {v.  Horsley).'] 

[Stages. — Horsley  distinguishes  three  stages.  In  the  first  or  neurotic  stage  the  animals  exhibit 
constant  tremors,  8  per  second,  and  young  animals  do  not  appear  to  survive  this  stage.  In  the  second 
or  mucinoid  stage,  mucin  is  deposited  in  the  tissues  and  blood ;  this  change,  however,  is  only 
seen  to  perfection  in  monkeys.  If  these  animals  be  kept  at  a  high  artificial  temperature,  their  life  is 
considerably  prolonged.  In  the  third,  atrophic,  or  marasmic  period,  the  animals  die  of  marasmus, 
while  they  lose  their  excess  of  mucin.  Age  seems  to  exert  an  important  influence  in  thyroidectomy ; 
young  dogs  survive  but  a  short  time,  while  old  dogs  merely  exhibit  symptoms  of  indolence  and 
incapacity ;  and^  as  a  matter  of  fact,  the  activity  of  the  gland  seems  to  be  most  active  when  tissue 
metabolism  is  most  active.] 

[The  following  table,  after  Horsley,  indicates  the  symptoms  that  follow  loss  of  the  function  of 
the  thyroid  gland : — 


Stages. 

Duration.                                  Symptoms. 

Remarks. 

I.  Neurotic. 

I  to  2  weeks  in  dogs; 

Tremors,  rigidity,  dysp- 

Young  dogs    and  monkeys 

I     to    3    weeks     in 

noea. 

alike  die  in  this  stage. 

monkeys. 

II.  Mucinoid. 

^  to  I  week  in  dogs; 

Commencing      hebetude 

Dogs    survive   only    to    the 

3    to    7    weeks     in      and   mucinoid   degen-      beginning  of    this   stage; 

monkeys.                          eration  of  the  connec- 

monkeys    die  at  the  end. 

tive  tissues. 

if  not  treated. 

III.  Atrophic. 

5  to  8  weeks  in  mon- 

Complete imbecility  and 

Monkeys  survive   according 

keys. 

atrophy  of  all  tissues. 

to  the  temperature  of  the 

especially  muscles. 

air-bath.] 

Functions. — The  functions  of  the  thyroid  gland  are  very  obscure.  Perhaps  it  may  be  an  appa- 
ratus for  regulating  the  blood  supply  to  the  head  (?).  It  becomes  enlarged  in  Basedow's  disease, 
in  which  there  is  great  palpitation,  as  well  as  protrusion  of  the  eyeball  or  exophthalmos,  which  seem 
to  depend  upon  a  simultaneous  stimulation  of  the  accelerating  nerve  of  the  heart,  and  the  sympa- 
thetic fibres  of  the  smooth  muscles  in  the  orbital  cavity  and  the  eyelids,  as  well  as  of  the  inhibitory 
fibres  of  the  vessels  of  the  thyroid.  In  many  localities  it  is  common  to  find  swelling  of  the  thyroid 
constituting  goitre,  which  is  sometimes,  but  far  from  invariably,  associated  with  idiocy  and  cretinism. 
[Horsley  finds  that  its  removal  is  the  essential  cause  of  myxoedema  and  cretinism.  He  regards  it 
(i)  as  a  blood-forming  gland,  so  that  it  has  a  hsemapoietic  function,  but  Gibson  finds  no  grounds 
for  supporting  this  view.  During  the  anemia  resulting  from  its  removal,  the  blood  of  the  thyroid 
vein  contains  7  per  cent,  more  red  blood  corpuscles  than  the  corresponding  artery  {Horsley). 
(2)  It  seems  to  regulate  the  formation  of  mucin  in  the  body.  After  its  removal  the  normal  meta- 
bolism is  no  longer  maintained,  and  there  is  a  corresponding  increasingly  defective  condition  of 
nutrition.] 

In  the  Tunicata,  this  gland,  represented  by  a  groove,  secretes  a  digestive  fluid.  In  vertebrates,  it  is 
an  organ  which  has  undergone  a  retrograde  change  [Gegenbaur). 


200 


THE  SUPRARENAL  CAPSULES. 


Fk 


IV.  The  Suprarenal  Capsules. — Structure. — These  organs  are  invested  by  a  thin  capsule 
which  sends  processes  into  the  substance  of  the  organ.  They  consist  of  an  outer  (broad)  or  cortical 
layer  and  an  inner  (narrow)  or  medullary  layer.  The  former  is  yellowish  in  color,  firm  and 
striated,  while  the  latter  is  softer  and  deeper  in  tint.  In  the  outermost  zone  of  the  cortex  (Fig.  128,  i), 
the  trabecuL-E  form  ix)lygonal  meshes,  which  contain  the  cellsof  the  gland  substance;  in  the  broader 
middle  zone  the  meshes  are  elongated,  and  the  cells  fdling  them  are  arranged  in  columns  radiating 
outward.  Here  the  cells  are  transparent  and  nucleated,  often  containing  oil  globules;  in  the  inner- 
most narrow  zone  the  j)olygonal  arrangement  prevails,  and  the  cells  often  contain  yellowish-brown 
pigment.  In  the  medulla  (c),  the  stroma  forms  a  reticulum  containing  groups  of  cellsof  very  irregu- 
lar shape.  Numerous  blood  vessels  occur  in  the  gland,  especially  in  the  corte.x.  [The  nerves 
are  extremely  numerous,  and  are  derived  from  the  renal  and  solar  plexuses.  Many  of  the  fibres  are 
medullated.  After  they  enter  the  gland,  numerous  ganglionic  cells  occur  in  the  plexuses  which 
they  form.  Indeed,  some  observers  regard  the  cells  of  the  medulla  as  nervous.  Undoubtedly, 
numerous  viiiltipoldr  nerve  cells  exist  within  the  gland.] 

Chemical  Composition. — The  suprarenals  contain  the  constituents  of  connective  and  nerve 
tissue  ;  also  leucin,  hypoxanthin,  benzoic,  hippuric,  and  taurocholic  acids,  taurin,  inosit,  fats,  and  a 
body  which  becomes  pigmented  by  oxidation.  Among  inorganic  substances  potash  and  phosphoric 
acid  are  most  abundant. 

The  function  of  the  suprarenal  bodies  is  very  obscure. 
It  is  noticeable,  however,  that  in  Addison's  disease 
("  bronzed  skin  "),  which  is  perhaps  primarily  a  nervous 
affection,  these  glands  have  frequently,  but  not  invariably, 
been  found  to  be  diseased.  Owing  to  the  injury  to  adjacent 
abdominal  organs,  extirpation  of  these  organs  is  often, 
although  not  always,  fatal ;  in  dogs  pigmented  patches  have 
been  found  in  the  skin  near  the  mouth.  Brown-Sequard 
IJiinks  they  may  be  concerned  in  preventing  the  over-pro- 
duction of  pigment  in  the  blood. 

[Spectrum. — MacMunn  finds  that  the  medulla  of  the 
suprarenal  bodies  (in  man,  cat,  dog,  guinea  pig,  rat,  etc.) 
gives  the  spectrum  of  hremochromogen  (^  18),  while  the 
cortex  shows  that  of  what  he  calls  histohaematin,  the 
latter  being  a  group  of  respiratory  pigments.  He  finds  that 
linsmochromogen  is  only  found  in  excretory  organs  (the 
liile,  the  liver),  hence  he  regards  the  medulla  as  excre- 
tory, so  that  part  of  the  function  of  the  adrenals  may  be 
"  to  metamorphose  effete  haemoglobin  or  hajmatin  into 
hsemochromogen,"  and  when  they  are  diseased,  the  effete 
pigment  is  not  removed,  hence  the  pigmentation  of  the 
skin  and  mucous  membranes.  Taurocholic  acid  has  been 
found  in  the  medulla  by  Vulpian,  and  pyrocatechin  by 
Krukenberg.  MacMunn  believes  that  "  they  have  a 
large  share  in  the  downward  metamorphosis  of  coloring 
matter."] 

V.  Hypophysis  Cerebri — Coccygeal  and  Carotid 
Glands. — The  hypophysis  cerebri,  or  pituitary  body, 
consists  of  an  anterior  lower  or  larger  lobe,  partly  embrac- 
ing the  posterior  lower  or  smaller  lobe.  These  two  lobes 
are  distinct  in  their  structure  and  development.  The 
posterior  lobe  is  a  part  of  the  brain,  and  belongs  to  the 
infundibulum.  The  nervous  elements  are  displaced  by  the 
Section  of  a  human  supraren.'il  capsule,  a,  ingrowth  of  Connective  tissue  and  blood  vessels.  The 
capsule ;  b,  gland   cells   of  the  cortex   ar-         .      •  _^-  ,  ■    a      ^    j         j  i_     i^        j 

ranged  in  columns  :<:,glandularnetwork  of  ''"'^^/''^'"PO^'O"  '■^P'^es^"'^  ^"   mflected   and   much  altered 
the  medulla;  d,  bloodvessels.  portion  of  ectoderm,  from  which  it  is  developed.     It  con- 

tains gland-like  structures,  with  connective  tissue,  lym- 
phatics, and  blood  vessels,  the  whole  being  surrounded  by  a  capsule.  According  to  Ecker  and 
Mihalkowicz,  it  resembles  the  suprarenal  capsule  in  its  structure,  while,  according  to  other  observers, 
in  some  animals  it  is  more  like  the  thyroid.  Its  functions  are  entirely  unknown.  [Excision. — 
Horsley  has  removed  this  gland  twice  successfully  in  dogs,  which  lived  from  five  to  six  months.  No 
nervous  or  other  symptoms  were  noticed,  but  when  the  cortex  of  the  brain  was  exposed  and  stimu- 
lated, a  great  increase  in  the  excitability  of  the  motor  regions  was  induced,  even  slight  stimulation 
bemg  followed  by  violent  tetanus  and  prolonged  epilepsy.] 

Coccygeal  and  Carotid  Glands. — The  former,  which  lies  on  the  tip  of  the  coccyx,  is  composed  to 
a  large  exient  of  plexuses  of  small,  more  or  less  cavernous,  arteries,  supported  and  enclosed  by  septa 
and  a  capsule  of  connective  tissue  {Luschka).  Between  these  lie  polyhedral  granular  cells  arranged 
in  networks.  The  carotid  gland  has  a  similar  structure  (p.  118).  Their  functions  are  quite  unknown. 
Perhaps  both  organs  may  be  regarded  as  the  remains  of  embryonal  blood  vessels  {Arnold). 


COMPARATIVE   ANATOMY   OF    THE    CIRCULATION. 


201 


104.  COMPARATIVE. — The  heart  in  fishes  (Fig.  129,  I),  as  well  as  in  the  larvse  of  amphi- 
bians with  gills,  is  a  simple  venous  heart,  consisting  of  an  auricle  and  a  ventricle.  The  ventricle 
propels  the  blood  to  the  gills,  where  it  is  oxygenated  (arterialized) ;  thence  it  passes  into  the  aorta 
to  be  distributed  to  all  parts  of  the  body,  and  returns  through  the  capillaries  of  the  body  and  the 
veins  to  the  heart.  The  amphibians  (frogs)  have  two  auricles  and  one  ventricle  (Frog,  II). 
From  the  latter  there  proceeds  one  vessel  which  gives  off  the  pulmonary  arteries,  and  as  the  aorta 
supplies  the  rest  of  the  body  with  blood,  the  veins  of  the  systemic  circulation  carry  their  blood  to  the 
right  auricle,  those  of  the  lung  into  the  left  auricle.  In  fishes  and  amphibians  there  is  a  dilatation 
at  the  commencement  of  the  aorta,  the  bulbus  arteriosus,  which  is  partly  provided  with  strong 
muscles.  The  reptiles  (III)  possess  two  separate  auricles,  and  two  imperfectly  separated  ventricles. 
The  aorta  and  pulmonary  artery  arise  separately  from  the  two  latter  chambers.     The  venous  blood 

Fig.  129. 


Schemata  of  the  circulation.  \.  Fish.— A,  auricle;  .S,  sinus  venosus  ;  K,  ventricle  ;  ^,  bulbus  aortae  :  c,  branchial 
arteries  ;  /,  branchial  vessels ;  Vv,  branchial  veins  ;  E,  circulns  cephalicus  aortae  ;  F,  common  aorta ;  G,  caudal 
artery;  //,  duct  of  Cuvier  ;  /,  anterior,  and  iT,  posterior  cardinal  veins  ;  Z,  caudal  vein  ;  ^,  Af,  kidneys.  II. 
Frog. — I,  sinus  venosus;  II  and  III,  right  and  left  auricles;  IV,  ventricle  ;  V,  aorta  with  the  bulb  ;  _i,  pul- 
monary arteries;  2,  arch  of  the  aorta;  3,  carotid  ;  4,  lingual;  s,  carotid  gland,  and  6,  axillary  arteries;  7, 
common  aorta;  8,  cceliac  artery ;  9,  cutaneous  artery;  Vv,  pulmonary  veins;  /, /,  lungs.  III.  Saurians. — 
I,  right  auricle,  with  the  venae  cavs ;  II,  right  ventricle;  III,  left  auricle;  IV,  left  ventricle.  V,  anterior 
common  aorta  ;  i,  pulmonary  artery  ;  2,  arch  of  the  aorta;  3,  carotid  artery  ;  4,  posterior  common  aorta  ;  5, 
cceliac,  and  6,  subclavian,  arteries  ;  7,  pulmonary  veins  ;  8,  lungs.  IV.  Tortoise. — I,  right  auricle  with  the  venae 
cavae  ;  II,  right,  and  IV,  left  ventricles  ;  III,  left  auricle  ;  i  and  2,  right  and  left  aortae  ;  3,  posterior  common 
aorta;    4,  ccfiliac;   5,  subclavian ;    6,  carotid,  and   7,  pulmonary  arteries  ;    8,  pulmonary  veins. 

of  the  systemic  and  pulmonary  circulations  flows  separately  into  the  right  and  left  auricles,  and 
the  two  streams  are  mixed  in  the  ventricle.  In  some  reptiles  the  opening  in  the  ventricular  septum 
seems  capable  of  being  closed.  The  complete  separation  of  the  ventricle  into  two  is  seen  in  Fig.  IV, 
in  the  tortoise.  The  lower  vertebrates  have  valves  at  the  orifices  of  the  vense  cavse,  which  are 
rudimentary  in  birds  and  some  mammals.  All  birds  and  mammals  have  two  completely  separate 
auricles  and  two  separate  ventricles.  In  the  halicore  the  apex  of  the  ventricles  is  deeply  cleft. 
Some  animals  have  accessory  hearts,  e.g.,  the  eel  in  its  caudal  vein.  They  are  very  probably  lymph 
hearts  {Robin).  The  veins  of  the  wing  of  the  bat  pulsate  {Schiff).  The  lowest  vertebrate, 
amphioxus,  has  no  heart,  but  only  a  rhythmically  pulsating  vessel. 

Among  blood  glands,  the  thymus  and  spleen  occur  throughout  the  vertebrata,  the  latter  being 
absent  only  in  amphioxus  and  a  few  fishes. 


202  HISTORICAL    RETROSPECT   OF   THE    CIRCULATION. 

Among  invertebrata  a  closed  vascular  system^  with  pulsatile  movement,  occurs  here  and  there, 
e.s;.y  among  echinodermata  (star  fishes,  sea  urchins,  holothurians)  and  the  higher  worms.  The 
insects  have  a  pulsating  "  dorsal  vessel"  as  the  central  organ  of  the  circulation,  which  is  a  contractile 
tube  provided  with  valves  and  dilated  by  muscular  action ;  the  blood  being  propelled  rhythmically 
in  one  direction  into  the  spaces  whicn  lie  among  the  tissues  and  organs,  so  that  these  animals  do 
not  possess  a  closed  vascular  system.  The  mollusca  have  a  heart  with  a  lacunar  vascular  system. 
The  cephalopods  (cuttle  fish)  have  three  hearts — a  simple  arterial  heart,  and  two  venous  simple 
gill  hearts,  each  placed  at  the  base  of  the  gills.  The  vessels  form  a  completely  closed  circuit.  The 
Icnvest  animals  have  either  a  pulsatile  vesicle,  which  propels  the  colorless  juice  into  the  tissues  (in- 
fusoria), or  the  vascular  apparatus  may  be  entirely  absent. 

105.  HISTORICAL  RETROSPECT. — The  ancients  held  various  theories  regarding  the 
movement  of  the  blood,  but  they  knew  nothing  of  its  circulation.  According  to  Aristotle  (384  H.C.), 
the  heart,  the  acropolis  of  the  body,  prepared  in  its  cavities  the  blood,  which  streamed  through  the 
arteries  as  a  nutrient  fluid  to  all  parts  of  the  body,  but  never  returned  to  the  heart.  With  Herophilus 
and  Erasistratus  (300  B.C. ),  the  celebrated  physicians  of  the  Alexandrian  school,  originated  the 
erroneous  view  that  the  arteries  contain  air,  which  was  supplied  to  them  by  the  respiration  (hence 
the  name  artery).  They  were  led  to  adopt  this  view  from  the  empty  condition  of  the  arteries  after 
death.  By  experiments  upon  animals,  Galen  disproved  this  view  (131-201  a.d.) — "Whenever  I 
injured  an  artery,"  he  says,  "blood  always  flowed  from  the  wounded  vessel.  On  tying  part  of  an 
artery  between  two  ligatures,  the  part  of  the  artery  so  included  is  always  filled  with  blood." 

Still,  the  idea  of  a  single  centrifugal  movement  of  the  blood  was  retained,  and  it  was  assumed 
that  the  right  and  left  sides  of  the  heart  communicated  directly  by  means  of  openings  in  the  septum 
of  the  heart,  until  Vesalius  showed  that  there  are  no  openings  in  the  septum.  Michael  Servetus  (a. 
Spanish  monk,  burned  at  Geneva,  at  Calvin's  instigation,  in  1553)  discovered  the  pulmonary  circula- 
tion. Cesalpinus  confirmed  this  observation,  and  named  it  "  Circulatio."  Fabricius  ab  Aqua— 
pendente  (Padua,  1574)  investigated  the  valves  in  the  veins  more  carefully  (although  they  were 
known  in  the  5th  century  to  Theodoretus,  Bishop  in  Syria),  and  he  was  acquainted  with  the  centri- 
petal movement  of  the  blood  in  the  veins.  Up  to  this  time  it  was  imagined  that  the  veins  carried 
blood  from  the  centre  to  the  periphery,  although  Vesalius  was  acquainted  with  the  centripetal  direc- 
tion of  the  blood  stream  in  the  large  venous  trunks.  At  length  William  Harvey,  who  was  a 
pupil  of  Fabricius  (1604),  demonstrated  the  complete  circulation  (1616-1619),  and  published  his 
great  discovery  in  1628.  [For  the  history  of  the  discovery  of  the  circulation  of  the  blood,  see  the 
works  of  Willis  on  "  W.  Harvey,"  "  Servetus  and  Calvin,"  those  of  Kirchner,  and  the  various 
Harveian  orations.] 

According  to  Hippocrates,  the  heart  is  the  origin  of  all  the  vessels ;  he  was  acquainted  with  the 
large  vessels  arising  from  the  heart,  the  valves,  the  chordre  tendinere,  the  auricles,  and  the  closure  of 
the  semilunar  valves.  Aristotle  was  the  first  to  apply  the  terms  aorta  and  vtn-x.  cavK ;  the  school 
of  Erasistratus  used  the  term  carotid,  and  indicated  the  functions  of  the  venous  valves.  In  Cicero  a 
distinction  is  drawn  between  arteries  and  veins.  Celsus  mentions  that  if  a  vein  be  struck  below  the 
spot  where  a  ligature  has  been  applied  to  a  limb,  it  bleeds,  while  Aretaeus  (50  a.d.)  knew  that 
arterial  blood  was  bright  and  venous  dark.  Pliny  (179  a.d.)  described  the  pulsating  fontanelle  in 
the  child  Galen  (131-203  a.d.)  was  acquainted  with  the  existence  of  a  bone  in  the  septum  of  the 
heart  of  large  animals  (ox,  deer,  elephant).  He  also  surmised  that  the  veins  communicated  with 
the  arteries  by  fine  tubes.  The  demonstration  of  the  capillaries,  however,  was  only  possible  by  the 
use  of  the  microscope,  and  employing  this  instrument,  Malpighi  (1661)  was  the  first  to  demonstrate 
the  capillary  circulation.  Leuwenhoek  (1674)  described  the  capillary  circulation  more  carefully,  as 
it  may  be  seen  in  the  web  of  the  frog's  foot  and  other  transparent  membranes.  Blancard  (1676) 
proved  the  existence  of  capillary  passages  by  means  of  injections.  William  Cooper  (1697)  proved 
that  the  same  condition  exists  in  warm-blooded  animals,  and  Ruysch  made  similar  injections. 
Stenson  (born  1638)  established  the  muscular  nature  of  the  heart,  although  the  Hippocratic  and 
Alexandrian  schools  had  already  surmised  the  fact.  Cole  proved  that  the  sectional  area  of  the 
blood  stream  became  widertoward  the  capillaries  (1681).  Joh.  Alfons  Borelli  (1608-1679)  was  the 
first  to  estimate  the  amount  of  work  done  by  the  heart. 


Physiology  of  Respiration. 


The  object  of  respiration  is  to  supply  the  oxygen  necessary  for  the  oxidation 
processes  that  go  on  in  the  body,  as  well  as  to  remove  the  carbon  dioxide  formed 
within  the  body.  The  most  important  organs  for  this  purpose  are  the  lungs. 
There  is  an  outer  and  an  inner  respiration — the  former  embraces  the  exchange 
of  gases  between  the  external  air  and  the  blood  gases  of  the  respiratory  organs 
(lungs  and  skin) — the  latter,  the  exchange  of  gases  between  the  blood  in  the 
capillaries  of  the  systemic  circulation  and  the  tissues  of  the  body. 

[The  pulmonary  apparatus  consists  of  (i)  an  immense  number  of  small  sacs — 
the  air  vesicles — filled  with  air,  and  covered  externally  by  a  very  dense  plexus 
of  capillaries;  (2)  air  passages — the  nose,  pharynx,  larynx,  trachea,  and 
bronchi  communicating  with  (i)  ;  (3)  the  thorax  with  its  muscles,  acting  like  a 
pair  of  bellows,  and  moving  the  air  within  the  lungs.] 

106.  STRUCTURE  OF  THE  AIR  PASSAGES  AND  LUNGS.— The  lungs  are 
compound  tubular  glands,  which  separate  CO2  from  the  blood.  Each  lung  is  provided  with  an 
excretory  duct  (bronchus)  which  joins  the  common  respiratory  passage  of  both  lungs — the  trachea. 

Trachea. — The  trachea  and  extra-pulmonary  bronchi  are  similar  in  structure.  The  basis  of  the 
trachea  consists  of  16—20  C-shaped  incomplete  cartilaginous  hoops  placed  over  each  other.  These 
rings  consist  of  hyaline  cartilage,  and  are  united  to  each  other  by  means  of  tough  fibrous  tissue 
containing  much  elastic  tissue,  the  latter  being  arranged  chiefly  in  a  longitudinal  direction.  The 
function  of  the  cartilages  is  to  keep  the  tube  open  under  varying  conditions  of  pressure.  Pieces 
of  cartilage  having  a  similar  function  occur  in  the  bronchi  and  their  branches,  but  they  are  absent 
from  the  bronchioles,  which  are  less  than  i  mm.  in  diameter.  In  the  smaller  bronchi,  the  carti- 
lages are  fewer  and  scattered  more  irregularly.  [In  a  transverse  section  of  a  large  intra-pulmo- 
nary  bronchus,  two,  three,  or  more  pieces  of  cartilage,  each  invested  by  its  perichondrium,  may 
be  found.]  At  the  points  where  the  bronchi  subdivide,  the  cartilages  assume  the  form  of  irregular 
plates  embedded  in  the  bronchial  wall. 

An  external  fibrous  layer  of  connective  tissue  and  elastic  fibres  covers  the  trachea  and  the  extra- 
pulmonary bronchi  externally.  Toward  the  oesophagus,  the  elastic  elements  are  more  numerous, 
and  there  are  also  a  few  bundles  of  plain  muscular  fibres  arranged  longitudinally.  Within  this 
layer  there  are  bundles  of  non-striped  muscular  fibres  which  pass  transversely  between  the  carti- 
lages behind,  and  also  in  the  intervals  between  the  cartilages.  [These  pale  reddish  fibres  constitute 
the  trachealis  muscle,  and  are  attached  to  the  inner  surfaces  of  the  cartilages  at  a  little  distance 
from  their  free  ends.  The  arrangement  varies  in  different  animals — thus,  in  the  cat,  dog,  rabbit, 
and  rat  the  muscular  fibres  are  attached  to  the  external  surfaces  of  the  cartilages,  while  in  the  pig, 
sheep,  and  ox  they  are  attached  to  their  internal  surfaces  {Stirling).']  Some  muscular  fibres  are 
arranged  longitudinally  external  to  the  transverse  fibres.  The  function  of  these  muscular  fibres 
is  to  prevent  too  great  distention  when  there  is  great  pressure  within  the  air  passages. 

The  mucous  membrane  consists  of  a  basis  of  very  fine  connective  tissue,  containing  much 
adenoid  tissue  with  numerous  lymph  corpuscles.  Numerous  elastic  fibres  are  arranged  chiefly  in  a 
longitudinal  direction  under  the  basement  membrane.  They  are  also  abundant  in  the  deep  layers 
of  the  posterior  part  of  the  membrane  opposite  the  intervals  between  the  cartilages.  A  small  quan- 
tity of  loose  submucous  connective  tissue  containing  the  large  blood  vessels,  glands,  and  lymphatics 
unites  the  mucous  membrane  to  the  perichondrium  of  the  cartilages.  The  epithelium  consists  of 
a  layer  of  columnar  ciliated  cells  with  several  layers  of  immature  cells  under  them.  [The  super- 
ficial layer  of  cells  is  columnar  and  ciliated  (Fig.  130,  b),  while  those  lying  under  them  present  a 
variety  of  forms,  and  below  all  is  a  layer  of  somewhat  flattened  squames,  c,  resting  on  the  basement 
membrane,  d.  These  squames  constitute  a  layer  quite  distinct  from  the  basement  membrane,  and 
they  form  the  layer  described  as  D6bove's  membrane.  They  are  active  germinating  cells,  and 
play  a  most  important  part  in  connection  with  the  regeneration  of  the  epithelium,  after  the  super- 
ficial layers  have  been  shed,  in  such   conditions  as  bronchitis.     Not  unfrequently  a  little  viscid 

203 


204 


STRUCTURE    OF   THE    TRACHEA    AND    BRONCHI. 


mucus  (a)  lies  on  the  free  ends  of  the  cilia.  In  the  intermediate  layer,  the  cells  are  more  or  less 
pyriform  or  battledore-shaped,  with  their  long  tapering  process  inserted  among  the  deepest  layer 
of  squames.  According  to  Drasch,  this  long  process  is  attached  to  one  of  these  cells  and  is  an 
outgrowth  from  it,  the  whole  constituting  a  "foot  cell."] 

Under  the  epithelium  is  the  homogeneous  basement  membrane,  through  which  fine  canals 
pass,  connecting  the  cement  of  the  epithelium  with  spaces  in  the  mucosa.  [This  membrane  is 
well  marked  in  the  human  trachea,  where  it  plays  an  important  part  in  many  pathological  condi- 
tions, e.^i^.,  bronchitis.     It  is  stained  bright  red  with  picrocarmine.]     The  cilia  act  so  as  to  carry 

any  secretion  toward  the   larynx.     Goblet 


Fic.  no. 


z^ 


^^mm^^m 


cells  exist  between  the  ciliated  columnar 
cells.  Numerous  small  compound  tubular 
mucous  glands  occur  in  the  mucous 
membrane,  chietly  Ijetween  the  cartilages. 
Their  ducts  open  on  the  surface  by  means 
of  a  slightly  funnel  -  shaped  aperture, 
into  which  the  ciliated  epithelium  is  pro- 
longed for  a  short  distance.  [The  acini 
of  some  of  these  glands  lie  outside  the 
trachealis  muscle.  The  acini  are  lined  by 
cubical  or  columnar  secretoiy  epithelium. 
In  some  animals  (dog)  these  cells  are  clear, 
and  present  the  usual  characters  of  a  mucus- 
secreting  gland ;  in  man,  some  of  the  cells 
may  be  clear,  and  others  "granular,"  but 
the  appearance  of  the  cells  depends  upon 
the  physiological  state  of  activity.]  These 
glands  secrete  the  mucus,  which  entangles 
particles  inspired  with  the  air,  and  is  car- 
ried toward  the  larynx  by  ciliary  action. 
[Numerous  lymphatics  exist  in  the  mu- 
cous  and  submucous  coat,  and  not  unfre- 
quently  small  aggregations  of  adenoid  tissue 
occur  (especially  in  the  cat)  in  the  mucous 
coat,  usually  around  the  ducts  of  tiie  glands. 
They  are  comparable  to  the  solitary  follicles 
of  the  alimentary  tract.  The  blood  ves- 
sels are  not  so  numerous  as  in  some  other 
mucous  membranes.  [A  plexus  of  nerves 
containing  numerous  ganglionic  cells  at  the 
nodes  exists  on  the  posterior  surface  of  the 
trachealis  muscle.  The  fibres  are  derived 
from  the  vagus,  recurrent  laryngeal,  and 
sympathetic  ( C.  Frankenhatiser,  W.  Stir- 


Transverse  section  of  part  of  a  human  bronchus  (  X  450).   a,  pre 

cipitated    mucus;    h,   ciliated  columnar  epithelium;  c,  deep  //«</  ]\audarazi\.'\ 

germinal  layer  of  cells  (Debove's  membrane) ;  4/,  elastic  base-  'r\~-t  „ '„ >.„i,_„„„  „f  tt,<>  ♦..„ 

ment  membrane  ;  e,  elastic  fibres  divided  transversely  (inner  [^lie  mUCOUS    membrane  of  the  tra- 

fibrous  layer)  ;  f,  bronchial  muscle  ;  g,  outer  fibrous  layer  with  chea    and    extra  -  pulmonary    bronchl, 

leucocytes  and  pigment  granules  (black);  below  a  mass  of  therefore,  Consists  of  the  following  layers 

adenoid  tissue.  r  -^t  •  .         j  o       .< 

from  within  outward  :  — 

(i)  Stratified  columnar  ciliated  epithelium. 

(2J  A  layer  of  flattened  cells  (Debove's  membrane). 

(3)  A  clear  homogeneous  basement  membrane. 

(4)  A  basis  of  areolar  tissue,  with  adenoid  tissue  and  blood  vessels,  and  outside  this  a  layer  of 

longitudinal  elastic  fibres. 

Outside  this,  again,  is  the  submucous  coat,  consisting  of  loose  areolar  tissue,  with  the  larger 
vessels,  lymphatics,  ner\es,  and  mucous  glands.] 

[The  Bronchi. — In  structure  the  extra-pulmonary  bronchi  resemble  the  trachea.  As  they 
pass  into  the  lung  they  divide  very  frequently,  and  the  branches  do  not  anastomose.  In  the  intra- 
pulmonary  bronchi  the  subdivisions  become  finer  and  finer,  the  finest  branches  being  called 
terminal  bronchi,  or  bronchioles,  which  open  separately  into  clusters  of  air  vesicles.] 

[Eparterial  and  Hyparterial  Bronchi. — As  the  bronchi  proceed,  one  main  trunk  passes  into 
the  lung,  running  toward  its  base,  and  from  it  are  given  off  branches  dorsally  and  ventrally,  and 
these  branches  again  subdivide.  In  man  one  main  branch  comes  off  from  the  right  bronchus  and 
proceeds  to  the  upper  right  lobe,  above  the  place  where  the  pulmonary  artery  crosses  the  bronchus. 
Such  branches  are  called  eparterial,  and  they  are  more  numerous  in  birds.  In  man,  all  the  branches, 
both  on  the  right  and  left  side,  come  off  below  the  point  where  the  pulmonary  artery  crosses  the 
bronchus,  and  are  called  hyparterial  bronchi  (C.  Aeby).'\ 


STRUCTURE    OF   THE    BRONCHIOLES   AND    AIR    CELLS.  205 

[In  the  middle-sized  intra-pulmonary  bronchi,  the  usual  characters  of  the  mucous  membrane 
are  retained,  only  it  is  thinner;  the  cartilages  assume  the  form  of  irregular  plates  situated  in  the 
outer  wall  of  the  bronchus ;  while  the  muscular  fibres  are  disposed  in  a  complete  circle,  constituting 
the  bronchial  muscle  (Fig.  130,/).  When  this  muscle  is  contracted,  or  when  the  bronchus  as  a 
whole  is  contracted,  the  mucous  membrane  is  thrown  into  longitudinal  folds,  and  opposite  these 
folds  the  elastic  fibres  form  large  elevations.  This  muscle  is  particularly  well  developed  in  the 
smaller  microscopic  bronchi.  Numerous  elastic  fibres,  e,  disposed  longitudinally,  exist  under  the 
basement  membrane,  d.  They  are  continuous  with  those  of  the  trachea,  and  are  prolonged  onward 
into  the  lung.  The  mucous  membrane  of  the  larger  intra-pulmonary  bronchi  consists  of  the  fol- 
lowing layers  from  within  outward  : — 

(1)  Stratified  columnar  ciliated  epithelium  (Fig.  130,  F). 

(2)  Debove's  membrane  (Fig.  130,  c). 

(3)  Transparent  homogeneous  basement  membrane  (Fig.  130,  d'). 

(4)  Areolar  tissue  with  longitudinal  elastic  fibres  (Fig.  130,  e). 

(5)  A  continuous  layer  of  non-striped  muscular  fibres  disposed  circularly  [bronchial  muscle,  Fig. 

Outside  this  is  the  submucous  coat,  consisting  of  areolar  tissue  mixed  with  much  adenoid  tissue 
(Fig.  130,^),  sometimes  arranged  in  the  form  of  cords,  the  lymph-follicular  cords.  It  also  con- 
tains the  acini  of  the  numerous  mucous  glands,  blood  vessels,  and  lymphatics.  The  ducts  of  the 
glands  perforate  the  muscular  layer,  and  open  on  the  free  surface  of  the  mucous  membrane.  The 
submucous  coat  is  connected  by  areolar  tissue  with  the  perichondrium  of  the  cartilages.  Outside 
the  cartilages  are  the  nerves  and  nerve  ganglia  accompanying  the  bronchial  vessels.  The 
branches  of  the  pulmonary  artery  and  of  the  pulmonary  vein  usually  lie  on  opposite  sides  of  the 
bronchus,  while  there  are  several  branches  of  the  bronchial  arteries  and  veins.  Fat  cells  also 
occur  in  the  peribronchial  tissue.] 

In  the  small  bronchi  the  cartilages  and  glands  disappear,  but  the  circular  muscular  fibres  are 
well  developed.     They  are  lined  by  lower  columnar  ciliated  epithelium,  containing  goblet  cells. 

Bronchioles. — After  repeated  subdivision,  the  bronchi  form  the  "  smallest  bronchi"  (about  0.5 
to  I  mm.)  or  lobular  bronchial  tubes.  Each  tube  is  lined  by  a  layer  of  ciliated  epithelium,  but  the 
glands  and  cartilages  have  disappeared.  These  tubes  have  a  few  lateral  alveoli  or  air  cells  com- 
municating with  them.  Each  smallest  bronchus  ends  in  a"  respiratory  bronchiole  [Kolliker),  which 
gradually  becomes  beset  with  more  air  cells,  and  in  which  squamous  epithelium  begins  to  appear  be- 
tween the  ciliated  epithelial  cells.  [Each  bronchiole  opens  into  several  wider  alveolar  or  lobular 
passages.  Each  passage  is  completely  surrounded  with  air  cells,  and  from  it  are  given  off  several 
similar  but  wider  blind  branches,  the  infundibula,  which,  in  their  turn,  are  beset  on  all  sides  with 
alveoli  or  air  cells.  Several  infundibula  are  connected  with  each  bronchiole,  and  the  former  are 
wider  than  the  latter.  Each  bronchiole,  with  its  alveolar  passages,  infundibula,  and  air  vesicles,  is 
termed  a  lobule,  whose  base  is  directed  outward,  and  whose  apex  may  be  regarded  as  a  terminal 
bronchus.  The  lung  is  made  up  of  an  immense  number  of  these  lobules,  separated  from  each  other 
by  septa  of  connective  tissue,  the  interlobular  septa  (Fig.  133,  e)  which  are  continuous  on  the 
one  hand  with  the  sub-pleural  connective  tissue,  and  on  the  other  with  the  peribronchial  connective 
tissue.] 

[There  is  an  alteration  in  the  structure  of  the  bronchi,  as  we  proceed  from  the  larger  to  the 
smaller  tubes.  The  cartilages  and  glands  are  the  first  structures  to  disappear.  The  circular  bron- 
chial muscle  is  well  developed  in  the  smaller  bronchi  and  bronchioles,  and  exists  as  a  continuous 
thin  layer  over  the  alveolar  passages,  but  it  is  not  continued  over  and  between  the  air  cells.  Elastic 
fibres,  continuous,  on  the  one  hand,  with  those  in  the  smaller  bronchi,  and  on  the  other  with  those 
in  the  walls  of  the  air  cells,  lie  outside  the  muscular  fibres  in  the  bronchioles  and  infundibula.  In 
the  respiratory  bronchioles,  the  ciliated  epithelium  is  reduced  to  a  single  layer,  and  is  mixed  with 
the  stratified  form  of  epithelium,  while,  where  the  alveolar  passages  open  into  the  air  cells  or 
alveoli,  the  epithelium  is  non- ciliated,  low,  and  polyhedral.] 

Alveoli  or  Air  Cells. — The  form  of  the  cells,  which  are  250  ^i  {-^-^  inch)  in  diameter,  may  be 
more  or  less  spherical,  polygonal,  or  cup-shaped.  They  are  disposed  around  and  in  communication 
with  the  alveolar  passages.  Their  form  is  determined  by  the  existence  of  a  nearly  structureless 
membrane,  composed  of  slightly  fibrillated  connective  tissue  containing  a  few  corpuscles.  This  is 
surrounded  by  numerous  fine  elastic  fibres,  which  give  to  the  pulmonary  parenchyma  its  well-marked 
elastic  characters  (Fig.  132,  e,  e).  These  fibres  often  bifurcate,  and  are  arranged  with  reference  to 
the  alveolar  wall.  They  are  very  resistant,  and  in  some  cases  of  lung  disease  may  be  recognized 
in  the  sputum.  A  few  non-striped  muscular  fibres  exist  in  the  delicate  connective  tissue  between 
adjoining  air  vesicles.  These  muscular  fibres  sometimes  become  greatly  developed  in  certain  diseases 
{^Arnold,  W.  Stirling).  The  air  cells  are  lined  by  two  kinds  of  cells  ;  (i)  large,  transparent,  clear, 
polygonal  (nucleated  ?)  squames  or  placoids  (22-45  <")  lying  over  and  between  the  capillaries  in 
the  alveolar  wall  (Fig.  131,  a) ;  (2)  small,  irregular,  "  granular,"  nucleated  cells  (7-15  ,«)  arranged 
singly  or  in  groups  (two  or  three)  in  the  interstices  between  the  capillaries.  They  are  well  seen  in 
a  cat's  lung  (Fig.  131,  a;).  [When  acted  on  with  nitrate  of  silver  the  cement  substance  bounding 
the  clear  cells  is  stained,  but  the  small  cells  become  of  a  uniform  brown,  granular  appearance,  so 


206 


THE    BLOOD    VESSELS    OF   THE    LUNGS. 


that  they  are  readily  recognized.  Small  holes  or  "  pseudostomata  "  seem  to  exist  in  the  cement 
substance,  and  are  most  obvious  in  distended  alveoli.  They  open  into  the  lymph-canalicular  system 
of  llu-  alveolar  wall  [K'/ein),  and  through  them  the  lymph  corpuscles,  which  are  always  to  be 
founil  on  the  surface  of  the  air  vesicles,  migrate,  and  carry  with  them  into  the  lymphatics  particles  of 

carbon  derived  from  the  air.]    In  the  alve- 
Fic.  131.  olar  walls  is  a  very   dense  plexus  of  fine 

capillaries  (Fig.  132,  c),  which  lie  more 
toward  the  cavity  of  the  air  vesicle,  being 
covered  only  by  the  epithelial  lining  of 
the  air  cells.  I'.etween  two  adjacent  alve- 
oli there  is  only  a  single  layer  of  capillaries 
(man),  and  on  the  boundary  line  between 
two  air  cells  the  course  of  the  capillaries 
is  twisted,  thus  projecting  sometimes  into 
the  one  alveolus,  sometimes  into  the  other. 
[The  number  of  alveoli  is  stated  to  be 
about  725  millions,  a  result  obtained  by 
measuring  the  size  of  the  air  vesicles  and 
ascertaining  the  amount  of  air  in  the  lung 
after  an  ordinary  inspiration,  determining 
how  much  of  this  air  is  in  the  air  vesicles 
and  bronchi  respectively.  The  superficial 
area  of  the  air  vesicles  is  about  90  square 
metres,  or  100  times  greater  than  the  sur- 
face of  the  body  (.8  to  .9  s([.  metre).] 

The  Blood  vessels  of  the  lung  belong 
to  two  different  systems:  (A)  Pulmonary 
vessels  (lesser  circulation).  The  branches 
of  the  pulmonary  artery  accompany  the 
bronchi  and  are  closely  applied  to  them. 
[As  they  proceed  they  branch,  but  the 
branches  do  not  anastomose,  and  ultimately 
they  terminate  in  small  arterioles,  which 
supply  several  adjacent  alveoli,  each  arteri- 
ole splitting  up  into  capillaries  for  several 
air  cells  (Fig.  132,  z-,  c).  An  efferent  vein  usually  arises  at  the  opposite  side  of  the  air  cells,  and 
carries  away  the  purified  blood  from  the  capillaries.  In  their  course  these  veins  unite  to  form  the 
fulmonary  veins,  which,  again,  are  joined  in  their  course  by  a  few  small  bronchial  veins.  The  veins 
usually  anastomose  in  the  earlier  part  of  their  course,  while  the  corresponding  arteries  do  not.] 
Although  the  capillary  plexus  is  very  fine  and  dense,  its  sectional  area  is  less  than  the  sectional  area 
of  the  systemic  capillaries,  so  that  the  blood  stream  in  the  pulmonary  capillaries  must  be  more  rapid 
than  that  in  the  capillaries  of  the  body  generally.  The  pulmonary  veins,  unlike  veins  generally, 
are  collectively  narrower  than  the  pulmonary  artery  (water  is  given  off  in  the  lung),  and  they  have 
no  valves.  [The  pulmonary  artery  contains  venous  blood,  and  the  pulmonary- veins  pure  or  arterial 
blood.] 

(B)  The  bronchial  vessels  represent  the  nutrient  system  of  the  lungs.  They  (1-3)  arise  from 
the  aorta  (or  intercostal  arteries)  and  accompany  the  bronchi  without  anastomosing  with  the  branches 
of  the  pulmonary  artery.  In  their  course  they  give  branches  to  the  lymphatic  glands  at  the  hilum 
of  the  lung,  to  the  walls  of  the  large  blood  vessels  (vasa  vasorum),  the  pulmonary  pleura,  the  bron- 
chial walls,  and  the  interlobular  septa.  The  blood  which  issues  from  their  capillaries  is  returned 
— partly  by  the  pulmonary  veins — hence,  any  considerable  interference  with  the  pulmonary  circula- 
tion causes  congestion  of  the  bronchial  mucous  membrane,  resulting  in  a  catarrhal  condition  of  that 
membrane.  The  greater  part  of  the  blood  is  returned  by  the  bronchial  veins,  which  open  into  the 
vena  azygos,  intercostal  vein,  or  superior  vena  cava.  The  veins  of  the  smaller  bronchi  (fourth 
order  onward)  open  into  the  pulmonary  veins,  and  the  anterior  bronchial  also  communicate  with 
the  pulmonary  vein  {Zttckerkandl.) 

[The  Pleura. — Each  pleural  cavity  is  distinct,  and  is  a  large  serous  sac,  which  really  belongs  to 
the  lymphatic  system  of  the  lung.  The  pleura  consists  of  two  layers,  visceral  and  parietal.  The 
visceral  pleura  covers  the  lung ;  the  parietal  portion  lines  the  wall  of  the  chest,  and  the  two  layers 
of  the  corresponding  pleura  are  continuous  with  one  another  at  the  root  of  the  lung.  The  visceral 
pleura  is  the  thicker,  and  may  readily  be  separated  from  the  inner  surface  of  the  chest.  Structurally, 
the  pleura  resembles  a  serous  membrane,  and  consists  of  a  thin  layer  of  fibrous  tissue  covered  by  a 
layer  of  endothelium.  Under  this  layer,  or  the  pleura  proper,  is  a  deep  or  sub-serous  layer  of  looser 
areolar  tissue,  containing  many  elastic  fibres.  The  layer  of  the  pleura  pulmonalis  of  some  animals, 
as  the  guinea  pig,  contains  a  network  of  non-striped  muscular  fibres  {Klein).  Over  the  lung  it  is 
also  continuous  with  the  interlobular  septa.     The  interlobular  septa  (Fig.  133,  e)  consist  of  bands 


Air  vesicles  injected  with  silver  nitrate,  a.  outlines  of  squamous 
epithelium  ;  b,  alveolar  wall ;  c,  young  epithelium  cell ;  d,  ag- 
gregation of  young  epithelial  cells  germinating. 


THE    LYMPHATICS    OF   THE    LUNG. 


207 


of  fibrous  tissue  separating  adjoining  lobules,  and  they  become  continuous  with  the  peribronchial 
connective  tissue  entering  the  lung  at  its  hilum.  Thus  the  fibrous  framework  of  the  lung  is  con- 
tinuous throughout  the  lung,  just  as  in  other  organs.  The  connection  of  the  sub-pleural  fibrous  tissue 
with  the  connective  tissue  within  the  substance  of  the  lung  has  most  important  pathological  bearings. 
The  interlobular  septa  contain  lymphatics  and  blood  vessels.  The  endothelium  covering  the  parietal 
layer  is  of  the  ordinary  squamous  type,  but  on  the  pleura  pulmonalis  the  cells  are  less  flattened, 
more  polyhedral,  and  granular.  They  must  necessarily  vary  in  shape  with  changes  in  the  volume 
of  the  lung,  so  that  they  are  more  flattened  when  the  lung  is  distended,  as  during  inspiration.  The 
pleura  contains  many  lymphatics,  which  communicate  by  means  of  stomata  with  the  pleural 
cavity.] 

[The  Lymphatics  of  the  lung  are  numerous,  and  are  arranged  in  several  systems.  The  various 
air  cells  are  connected  with  each  other  by  very  delicate  connective  tissue,  and,  according  to  J. 
Arnold,  in  some  parts  this  interstitial  tissue  presents  characters  like  those  of  adenoid  tissue;  so  that 
the  lung  is  traversed  by  a  system  of  juice  canals  or  "  Saft-canalchen."]  [In  the  deep  layer  of 
the  pleura  there  is  a  (a)  sub-pleural  plexus  of  lymphatics  partly  derived  from  the  pleura,  but  chiefly 

Fig.  132. 


Semi-diagrammatic  representation  of  the  air  vesicles  of  the  lung,  v,  v,  blood  vessels  at  the  margins  of  an  alveolus  ; 
c,  c,  its  blood  capillaries;  E,  relation  of  the  squamous  epithelium  of  an  alveolus  to  the  capillaries  in  its  wall;  /, 
alveolar  epithelium  shown  alone ;  e,  e,  elastic  tissue  of  the  lung. 


from  the  lymph- canalicular  system  of  the  pleural  alveoli.  Some  of  these  branches  proceed  to  the 
bronchial  glands,  but  others  pass  into  the  interlobular  septa,  where  they  join  [b)  the  perivascular 
lymphatics  which  arise  in  the  lymph-canalicular  system  of  the  alveoli.  These  trunks,  pro\-ided 
with  valves,  run  alongside  the  pulmonary  artery  and  vein,  and  in  their  course  they  form  frequent 
anastomoses.  Special  vessels  arise  within  the  walls  of  the  bronchi,  and  occur  chiefly  in  the  outer 
coat  of  the  latter,  constituting  {c)  the  peri-bronchial  lymphatics,  which  anastomose  with  b.  The 
branches  of  these  two  sets  run  toward  the  bronchial  glands.  Not  unfrequently  (cat)  masses  of 
adenoid  tissue  are  found  in  the  course  of  these  lymphatics.]  The  lymph-canalicular  system  and  the 
lymphatics  become  injected  when  fine-colored  particles  are  inspired,  or  are  introduced  into  the  air 
cells  artificially.  The  pigment  particles  pass  through  the  semi-fluid  cement  substance  into  the  lymph- 
canalicular  system  and  thence  into  the  lymphatics ;  or,  according  to  Klein,  they  pass  through  actual 
holes  or  pores  in  the  cement  (p.  206).]  [This  pigmentation  is  well  seen  in  coal-miner's  lung  or 
anthracosis,  where  the  particles  of  carbon  pass  into  and  are  found  in  the  IjTnphatics.  Sikorski 
and  Kiittner  showed  that  pigment  reached  the  lymphatics  in  this  way  during  life.     If  pigment, 


208 


THE    NERVES   OF   THE    LUNG. 


China  ink,  or  indigo  carmine  be  introduced  into  a  frog's  lung,  it  is  found  in  the  lymphatic  system  of 
the  lung.  Ruppert,  and  also  Schotielius,  showed  that  the  same  result  occurred  in  dogs  after  the 
inhalation  of  charcoal,  cinnabar,  or  precipitated  Berlin  blue,  and  von  Ins  after  the  inhalation  of 
silica.  Schestopal  used  China  ink  and  cinnabar  suspended  in  }(  per  cent,  salt  solution.]  Exces- 
sively fine  lymph  canals  lie  in  the  wall  of  the  alveoli  in  the  interspaces  of  the  capillaries,  and  there 
are  slight  dilatations  at  the  points  of  crossing.  According  to  Pierrot  and  Renaut  every  air  cell  of  the 
lung  of  the  o.\  is  surrounded  by  a  large  lymph  space,  such  as  occurs  in  the  salivary  glands.  When 
a  large  (juantity  of  fluid  is  injected  into  the  lung,  it  is  absorbed  with  great  rapidity ;  even  blood 
corpuscles  rapidly  pass  into  the  lymphatics. 

The  superficial  lymphatics  of  the  pulmonary  pleura  communicate  with  the  pleural  cavity  by 
means  of  free  openings  or  stomata,  and  the  same  is  true  of  the  lymphatics  of  the  parietal  pleura, 
but  these  stomata  are  confined  to  limited  areas  over  the  diaphragmatic  pleura.     [The  lymphatics  in 

the  costal  pleura  occur  over  the  intercostal 
p-jg   ,,-,  spaces  and  not  over  the  ribs  (Z'j/^/'OT^/j/t/).] 

The  large  arteries  of  the  lung  are  provided 
with  lymphatics  which  lie  between  the 
middle  and  outer  coats.  [The  movements 
of  the  lung  during  respiration  are  most 
important  factors  in  moving  the  lymph 
onward  in  the  pulmonary  lymphatics. 
The  reflux  of  the  lymph  is  prevented  by 
the  presence  of  valves.] 

[The  nerves  of  the  lung  are  derived 
from  the  anterior  and  posterior  pulmonary 
plexuses,  and  consist  of  branches  from  the 
vagus  and  sympathetic.  They  enter  the 
lungs  and  follow  the  distribution  of  the 
bronchi,  several  sections  of  nerve  trunks 
being  usually  found  in  a  transverse  section 
of  a  large  bronchial  tube.  The  nerves 
lie  outside  the  cartilages,  and  are  in  close 
relation  with  the  branchesof  the  bronchial 
arteries.  jSIedullated  and  non-medullated 
nerve  fibres  occur  in  the  nerves,  which 
also  contain  numerous  small  ganglia 
[Remak,  Klehi,  Stirling).  In  the  lung 
of  the  calf  the  ganglia  are  large.  The 
exact  mode  of  termination  of  the  nerve 
fibres  within  the  lung  has  yet  to  be  ascer- 
tained in  mammals,  but  some  fibres  pass 
to  the  bronchial  muscle,  others  to  the 
large  blood  vessels  of  the  lung,  and  it  is 
highly  probable  that  the  mucous  glands 
are  also  supplied  with  nerve  filaments. 
In  the  comparatively  simple  lungs  of  the 
frog,  nerves  with  numerous  nerve  cells 
in  their  course  are  found  {Arnold,  Stir- 
ling), and  in  the  very  simple  lung  of  the 
newt,  there  are  also  numerous  nerve  cells 
disposed  along  the  course  of  the  intra- 
pulmonary  nerves.  Some  of  these  fibres 
terminate  in  the  uniform  layer  of  non-striped  muscle  which  forms  part  of  the  pulmonary  wall  in  the 
frog  and  newt,  and  others  end  in  the  muscular  coat  of  the  pulmonary  blood  vessels  {Stirling).  The 
functions  of  these  ganglia  are  unknown,  but  they  may  be  compared  to  the  nerve  plexuses  existing 
in  the  walls  of  the  digestive  tract.] 

The  Function  of  the  non-striped  muscle  of  the  entire  bronchial  system 
seems  to  be  to  offer  a  sufficient  amount  of  resistance  to  increased  pressure  within 
the  air  passages;  as  in  forced  expiration,  speaking,  singing,  blowing,  etc.  The 
vagus  ^is  the  motor  nerve  for  these  fibres,  and  according  to  Longet,  the  "  lung- 
tonus  "  during  increased  tension  depends  upon  these  muscles. 

[Effect  of  Nerves.— By  connecting  the  interior  of  a  small  bronchus  with  an  oncograph  (?  103) 
m  curanzed  dogs  (the  thorax  being  opened),  Graham  Brown  and  Roy  found  that  section  of  one 
vagus  causes  a  marked  expansion  of  the  bronchi  of  the  corresponding  lung,  while  stimulation  of 
the  peripheral  end  of  a  divided  vagus  causes  a  powerful  contraction  of  the  bronchi  of  both  lungs. 


Human  lung  (^  50  auil  reduced  >/).  a,  small  bronchus;  i,  b, 
pulmonarj-  artery  ;  c,  pulmonar>'  vein  ;  e,  interlobular  septa, 
continuous  with  the  deep  layer  of  the  pleura,/. 


MECHANISM    OF   RESPIRATION.  209 

Stimulation  of  the  central  end  of  one  vagus,  the  other  being  intact,  also  causes  a  contraction  (feebler) 
under  the  same  circumstances.  Especially  in  etherized  dogs,  expansion  and  not  contraction  results. 
If  both  vagi  be  divided,  no  effect  is  produced  by  stimulation  of  the  central  end  of  either  vagus.  It 
seems  plain  that  the  vagi  contain  centripetal  or  afferent  fibres,  which  can  cause  both  expansion  and 
contraction  of  the  bronchi.  Asphyxia  causes  contraction  provided  the  vagi  are  intact,  but  none  if 
they  are  divided,  although  in  etherized  dogs  expansion  frequently  occurs,  while  stimulation  of  the 
central  end  of  other  sensory  nerves  has  very  rarely  any,  or,  if  any,  but  a  slight,  effect  on  the  calibre 
of  the  bronchi,  so  that  in  the  dog  the  only  connection  between  the  cerebro-spinal  centres  and  the 
bronchi  is  through  the  vagi.] 

Pathological. — Stimulation  of  the  smooth  muscles,  whereby  a  spasmodic  narrowing  of  the 
smaller  bronchi  is  produced,  may  excite  asthmatic  attacks.  If  the  expiratory  blast  be  interfered  with, 
acute  emphysema  may  take  place  i^Bierniei'). 

Chemistry. — In  addition  to  connective,  elastic,  and  muscular  tissue,  the  lungs  contain  lecithin, 
inosit,  uric  acid  (taurin  and  leucin  in  the  ox),  guanin,  xanthin  (?),hypoxanthin  (dog) — soda,  potash, 
magnesium,  oxide  of  iron,  much  phosphoric  acid,  also  chlorine,  sulphuric  and  silicic  acids — in  dia- 
betes sugar  occurs — in  purulent  infiltration  glycogen  and  sugar — in  renal  degeneration  urea,  oxalic 
acid,  and  ammonia  salts ;  and  in  diseases  where  decomposition  takes  place,  leucin  and  tyrosin. 

[Physical  Properties  of  the  Lungs. — The  lungs,  in  virtue  of  the  large 
amount  of  elastic  tissue  which  they  contain,  are  endowed  with  elasticity;  and 
when  the  chest  is  opened  they  collapse.  If  a  cannula  with  a  small  lateral  opening 
be  tied  into  the  trachea  of  a  rabbit's  or  sheep's  lungs,  the  lungs  may  be  inflated 
with  a  pair  of  bellows,  or  elastic  pump.  After  the  artificial  inflation,  the  lungs, 
owing  to  their  elasticity,  collapse  and  expel  the  greater  part  of  the  air.  As  much 
air  remains  within  the  light  spongy  tissue  of  the  lungs,  even  after  they  are  removed 
from  the  body,  a  healthy  lung  floats  in  water.  If  the  air  cells  are  filled  with  patho- 
logical fluids  or  blood,  as  in  certain  diseased  conditions  of  the  lung  (pneumonia), 
then  the  lungs  or  parts  thereof  may  sink  in  water.  The  lungs  of  the  foetus,  before 
respiration  has  taken  place,  sink  in  water,  but  after  respiration  has  been  thoroughly 
established  in  the  child,  the  lungs  float.  Hence,  this  hydrostatic  test  is  largely 
used  in  medico-legal  cases,  as  a  test  of  the  child's  having  breathed.  If  a  healthy 
lung  be  squeezed  between  the  fingers,  it  emits  a  peculiar  and  characteristic  fine 
crackling  sound,  owing  to  the  air  within  the  air  cells.  A  similar  sound  is  heard 
on  cutting  the  vesicular  tissue  of  the  lung.  The  color  of  the  lungs  varies  much; 
in  a  young  child  it  is  rose-pink,  but  afterward  it  becomes  darker,  especially  in 
persons  living  in  towns  or  a  smoky  atmosphere,  owing  to  the  deposition  of  gran- 
ules of  carbon.     In  coal  miners  the  lungs  may  become  quite  black.] 

[Excision  of  the  Lung. — Dogs  recover  after  the  excision  of  one  entire  lung,  and  they  even  sur- 
vive the  removal  of  portions  of  lung  infected  with  tubercle  {Biondi).'] 

107.  MECHANISM  OF  RESPIRATION.— The  mechanism  of  respi- 
ration  consists  in  an  alternate  dilatation  and  contraction  of  the  chest.  The  dila- 
tation is  called  inspiration,  the  contraction  expiration.  As  the  whole  external 
surfaces  of  both  elastic  lungs  are  applied  directly,  and  in  an  air-tight  manner,  by 
their  smooth,  moist,  pleural  investment,  to  the  inner  wall  of  the  chest,  which  is  cov- 
ered by  the  parietal  pleura,  it  is  clear  that  the  lungs  must  be  distended  with  every 
dilatation  of  the  chest,  and  diminished  by  every  contraction  thereof.  The  move- 
ments of  the  lungs,  therefore,  are  entirely  passive,  and  are  dependent  on  the 
thoracic  movements. 

On  account  of  their  complete  elasticity  and  their  great  extensibility,  the  lungs 
are  able  to  accommodate  themselves  to  any  variation  in  the  size  of  the  thoracic 
cavity,  without  the  two  layers  of  the  pleura  becoming  separated  from  each  other. 
As  the  capacity  of  the  non-distended  chest  is  greater  than  the  volume  of  the  col- 
lapsed lungs  after  their  removal  from  the  body,  it  is  clear  that  the  lungs,  even  in 
their  natural  position  within  the  chest,  are  distended,  z.  e.,  they  are  in  a  certain 
state  of  elastic  tension  (§  60).  The  tension  is  greater  the  more  distended  the 
thoracic  cavity,  and  vice  versa.  As  soon  as  the  pleural  cavity  is  opened  by  per- 
foration from  without,  the  lungs,  in  virtue  of  their  elasticity,  collapse,  and  a  space 
14 


210  QUANTITY   OF    GASES    RESPIRED. 

filled  with  air  is  formed  between  the  surface  of  the  lungs  and  the  inner  surface  of 
the  thoracic  wall  (pneumothorax),  The  lungs  so  affected  are  rendered  useless 
for  respiration  ;  hence  a  double  pneumothorax  causes  death. 

Pneumothorax. — It  is  also  clear  that,  if  the  pulmonary  pleura  be  perforated  from  within  the 
Umil;.  air  will  pass  from  the  respiratory  passages  into  the  pleural  sac,  and  also  give  rise  to  pneumo- 
thorax. [Not  unfrequently  the  surgeon  is  called  on  to  open  the  chest,  say  by  removing  a  portion 
of  a  rib,  to  allow  of  the  free  exit  of  pus  from  the  pleural  cavity.  If  this  be  done  with  proper 
precautions,  and  if  the  external  wound  be  allowed  to  heal,  after  a  time  the  air  in  the  pleural 
cavity  becomes  absorbed,  the  collapsed  lung  tends  to  reign  its  original  form,  and  again  becomes 
functionally  active.] 

Estimation  of  Elastic  Tension. — If  a  manometer  be  introduced  through  an  intercostal  space 
into  the  pleural  cavity,  in  a  dead  subject,  we  can  measure,  by  means  of  a  column  of  mercury,  the 
amount  of  the  elastic  tension  required  to  keep  the  lung  in  its  position.  This  is  equal  to  6  mm.  in 
the  dead  subject,  as  well  as  in  the  condition  of  expiration.  If,  however,  the  thorax  be  brought  into 
the  position  of  inspiration  by  the  application  of  traction  from  without,  the  elastic  tension  may  be  in- 
creased to  30  mm.  Ilg  [Dottders). 

If  the  glottis  be  closed  and  a  deep  inspiration  taken,  the  air  within  the  lungs 
must  become  rarefied,  because  it  has  to  fill  a  greater  space.  If  the  glottis  be  sud- 
denly opened,  the  atmospheric  air  passes  into  the  lungs  until  the  air  within  the 
lungs  has  the  same  density  as  the  atmosphere.  Conversely,  if  the  glottis  be  closed, 
and  if  an  expiratory  effort  be  made,  the  air  within  the  chest  must  be  compressed. 
If  the  glottis  be  suddenly  opened,  air  passes  out  of  the  lungs  until  the  pressure  out- 
side and  inside  the  lung  is  equal.  As  the  glottis  remains  open  during  ordinary 
respiration,  the  equilibration  of  the  pressure  within  and  without  the  lungs  will  take 
place  gradually.  During  tranquil  inspiration  there  is  a  slight  negative  pressure; 
during  expiration,  a  slight  positive  pressure  in  the  lungs;  the  former  ^  i  mm., 
the  latter  2-3  mm.  Hg  in  the  human  trachea  (measured  in  cases  of  wounds  of  the 
trachea). 

108.  QUANTITY  OF  GASES  RESPIRED.— As  the  lungs  within  the 
chest  never  give  out  all  the  air  they  contain,  it  follows  that  only  a  part  of  the  air 
of  the  lungs  is  changed  during  inspiration  and  expiration.  The  volume  of  this  air 
will  depend  upon  the  depth  of  the  respirations. 


COMPl.EMENTAL 
AIR, 

no 


5  Hutchinson  defined  the  following  : — 

^^  (i)  Residual   air  is  the  volume  of  air  which  remains  in  the 

^  53  chest  a/ler  the  most  complete  expiration.     It  is  ;=  1 230-1 640  c.  c. 

o  ^  [100-130  cubic  inches]. 

§-  ^  (2)  Reserve  or  supplemental  air  is  the  volume  of  air  which 

-    o"  Kj  can  be  expelled  from   the  chest  after  a  normal  quiet  expiration. 

5' o  It  is  ^  1240-1S00  c.  c.  [100  cubic  inches]. 

RESERVE  AIR,       i       n"  ~  (3)  Tidal  air  is  the  volume  of  air  which  is  taken  in  and  given 

100                  I    "2  °"'  ^*  ^■&.c\\.  rfespiration.     It  is  ■^=:  500  cubic  centimetres  [20  cubic 
inches]. 


TIDAL   AIR, 
20 


RESIDUAL  AIR,      j  •  (4)  Complemental  air  is  the  volume  of  air  that  can  be  forcibly 

inspired  over  and  above  what  is  taken  in  at  a  normal   respiration. 
—  I  It  amounts  to  about  1500  c.  c.  [100-130  cubic  inches]. 


100 


(5)  Vital  Capacity  is  the  term  applied  to  the  volume  of  air  which  can  be 
forcibly  expelled  from  the  chest  after  the  deepest  possible  inspiration.  It  is  equal 
to  3772  c.  c.  (or  230  cubic  inches)  for  an  Englishman  {Hutchinson),  and  3222  for 
a  German  {Haeset-). 

Hence,  after  every  quiet  inspiration,  both  lungs  contain  (i  +  2  +  3)  =r=  3000 
to  3900  c.  cm.  [220  cubic  inches];  after  a  quiet  expiration  (i  -f  2)  =  2500  to 
3400  c.  cm.  [200  cubic  inches].  So  that  about  i  to  i  of  the  air  in  the  lungs  is 
subject  to  renewal  at  each  ordinary  respiration. 

_  Bonders  calculated  that  the  entire  bronchial  system  and  the  trachea  contain  about  500  c.  c.  of 


NUMBER    OF    RESPIRATIONS. 


211 


Fig, 


Estimation  of  Vital  Capacity. — This  was  formerly  thought  to  be  of  great 
utility,  but  at  the  present  time  not  much  importance  is  attached  to  it,  nor  is  it 
frequently  measured  in  cases  of  disease.  It  is  estimated  by  means  of  the  spiro- 
meter of  Hutchinson  (Fig.  134),  which  consists  of  a  graduated  cylinder  filled 
with  water  and  inverted  like  a  gasometer  over  water,  and  balanced  by  means  of 
a  counterpoise.  Into  the  cylinder  a  tube  projects,  and  this  tube  is  connected 
with  a  mouth-piece.  The  person  to  be  experimented  upon  takes  the  deepest 
possible  inspiration,  closes  his  nostrils,  and  breathes  forcibly  into  the  mouth- 
piece of  the  tube.  After  domg  so  the  tube  is  closed.  The  cylinder  is  raised 
by  the  air  forced  into  it,  and  after  the  water 
inside  and  outside  the  cylinder  is  equalized, 
the  height  to  which  the  cylinder  is  raised  indi- 
cates the  amount  of  air  expired,  or  the  vital  or 
respiratory  capacity.  In  a  man  of  average 
height,  5  feet  8  inches,  it  is  equal  to  230  cubic 
inches. 

The  foHowing  circumstances  affect  the  vital  capa- 
city : — 

(i)  The  Height. — Every  inch  added  to  the  height  of 
persons  between  5  and  6  feet  gives  an  increase  of  the 
vital  capacity  =^  130  c.  c.  [8  cubic  inches]. 

(2)  The  Body  weight. — When  the  body  weight 
exceeds  tlie  normal  by  7  per  cent,  there  is  a  dimi- 
nutioi'.  of  37  c.  c.  of  the  vital  capacity  for  every  kilo,  of 
increase. 

(3)  Age. — The  vital  capacity  is  at  its  maximum  at  35  ; 
there  is  an  annual  decrease  of  23.4  c.  c,  from  this  age 
onward  to  65,  and  backward  to  15  years  of  age. 

(4)  Sex. — It  is  less  in  women  than  men,  and  even 
where  there  is  the  same  circumference  of  chest,  and  the 
same  height  in  a  man  and  a  woman,  the  ratio  is  10  :  7. 

(5)  Position  and  Occupation. — More  air  is  respired 
in  the  erect  than  in  the  recumbent  position. 

(6)  Disease. — Abdominal  and  thoracic  diseases  di- 
minish it. 


Scheme  of  Hutchinson's  Spirometer. 


109.  NUMBER  OF  RESPIRATIONS.— In  the  adult,  the  number  ot 
respirations  varies  from  16  to  24  per  minute,  so  that  about  4  pulse  beats  occur 
during  each  respiration.  The  number  of  respirations  is  influenced  by  many  con- 
ditions :  — 

(i)  The  Position  of  the  Body. — In  the  adult,  in  the  horizontal  position,  Guy  counted  13, 
while  sitting  19,  while  standing  22,  respirations  per  minute. 

(2)  Age. — Quetelet  found  the  mean  number  of  respirations  in  300  individuals  to  be  : — 


Year. 

Respirations. 

Year. 

Respirations. 

0  to     I, 

44 

1            Average 

20  to  25, 

18.7               -) 

Average 

5> 

26 

V       Number  per 

25  to  30, 

16 

Number  per 

15  to  20, 

20 

)             Minute. 

30  to  50, 

18.I               J 

Minute. 

(3)  The  State  of  Activity. — Gorham  counted  in  children  of  2  to  4  years  of  age  during  standing 
32,  in  sleep  24,  respirations  per  minute.  During  bodily  exertion  the  number  of  respirations 
increases  before  the  heart  beats.  [Very  slight  nmscidar  exertion  suffices  to  increase  the  frequency 
of  the  respirations.] 

[(4)  The  Temperature  of  the  surrounding  medium. — The  respirations  become  more  numerous 
the  higher  the  surrounding  temperature,  but  this  result  only  occurs  when  the  actual  temperature  of 
the  blood  is  increased,  as  in  fever. 

(5)  Digestion. — There  is  a  slight  variation  during  the  course  of  the  day,  the  increase  being 
most  marked  after  mid-day  dinner  (  Vierordt). 

(6)  The  Will  can  to  a  certain  extent  modify  the  number  and  also  the  depth  of  the  respirations, 
but  after  a  short  time  the  impulse  to  respire  overcomes  the  voluntary  impulse. 

(7)  The  Gases  of  the  Blood  have  a  marked  effect,  and  so  has  the  heat  of  the  blood  in  fever.] 


212 


TIME    OCCUPIED    BY    THE    RESPIRATORY    MOVEMENTS. 


Rliinoccros, 
Hippopotamus 
Horse,    .    .    . 
Ass,    .    .    .    . 


Per  Mill. 

•    55 

.  2IO 
.    lOO 

6-IO 

'i 

IO-I2 

.      7 


Per  Min. 

Pigeon, 30 

Siskin, 100 

Canary, 18 


Birds. 
Condor,  .  . 
Sparrow,    .    . 


Reptiles. 
Snake,  .  .  .  . 
Tortoise,     .    .    . 


[(S)  In  Animals — 

Mammals.  !  ^^^^j 

I'er  Min.       ,>    »  /        1  •       \ 

TiL-er  6  '   ^^^^  (waking) 

Lion,'  :    :    ;    :    :    :  lol   Rat(asleep), 

jaguar, II 

Panther 18 

Cat,       24  I 

Dog, 15 

Dromedary,      ...  1 1 
Giratle,     ....  S-lo 

Ox, 15-18 

Squirrel, 70 

[(9)  In  Disease. —  The  number  may  be  greatly  increased  from  many  causes,  e.  g.,  in  fever, 
pleurisy  and  pneumonia,  some  heart  diseases,  or  in  certain  cases  of  alteration  of  the  blood,  as 
in  ancemia;  and  diminished  where  there  is  pressure  on  the  respiratory  centre  in  the  medulla,  in 
coma.     It  is  important  to  note  the  ratio  of  pulse  beats  to  respirations.] 


6 
90 


Raja, 
Torpedo, 


Fish. 


Per  Min. 

Perch, 30 

Mullet, 60 

Eel 50 

Hippocampus,     .    .  33 

Invertebrata. 

Crab, 12 

Mollusca,     .    .     14-65 
{P.Beri.)'\ 


Fid.    135. 


A,  Brondgeest's  tambour  for  registering  the  respiratory  movements.  /5,  c,  inner  and  outer  caoutchouc  membranes; 
a,  the  capsule;  (/.(Z,  cords  for  fastening  the  instrument  to  the  chest;  5,  tube  to  the  recording  tambour.  BJ 
normal  respiratory  curve  obtained  on  a  vibrating  plate  (each  vibration  ^  0.01613  sec). 

no.  TIME  OCCUPIED  BY  THE  RESPIRATORY  MOVE- 
MENTS.— The  time  occupied  in  the  various  phases  of  a  respiration  can  only 
be  accurately  ascertained  by  obtaining  a  curve  or  pneumatogram  of  the 
respiratory  movements  by  means  of  recording  apparatus. 

Methods. — The  graphic  method  can  be  employed  in  three  directions:  (i) 
To  record  the  movements  of  individual  parts  of  the  chest  wall. 

(i)  Vierordt  and  C.  Ludwig  transferred  the  movements  of  a  part  of  the  chest  wall  to  a  lever 
which  inscribed  its  movements  upon  a  revolving  cylinder.  Reigel  (1873)  constructed  a  "double 
stethograph"  on  the  same  principle.  This  instrument  is  so  arranged  that  one  arm  of  the  lever 
may  be  applied  in  connection  with  the  healthy  side  of  a  person's  chest,  and  the  other  on  the  dis- 
eased  side.  In  the  case  of  animals  placed  on  their  backs,  Snellen  introduced  a  long  needle 
vertica  ly  through  the  abdominal  walls  into  the  liver.  Rosenthal  opened  the  abdomen  and 
apiilied  a  lever  to  the  under  surface  of  the  diaphragm,  and  thus  registered  its  movements 
(Phrenograph).  r       =>  o 

(2)  An  air  tambour,  such  as  is  used  in  Brondgeest's  pansphygmograph  (Fig.  135,  A)  may  be 
employed.     It  consists  of  a  brass  vessel,  a,  shaped  like  a  small  saucer.     The  mouth  of  the  brass 


TIME    OCCUPIED    BY   THE    RESPIRATORY    MOVEMENTS. 


213 


vessel  is  covered  vtritli  a  double  layer  of  caoutchouc  membrane,  b,  c,  and  air  is  forced  in  between 
the  two  layers  until  the  external  membrane  bulges  outward.  This  is  placed  on  the  chest,  and  the 
apparatus  is  fixed  in  position  by  means  of  the  bands,  d,  d.  The  cavity  of  the  tambour  communi- 
cates by  means  of  a  caoutchouc  tube,  .f,  with  a  recording  tambour,  which  inscribes  its  movements 
upon  a  revolving  cylinder.  Every  dilatation  of  the  chest  compresses  the  membrane,  and  thus  the 
air  within  the  tambour  is  also  compressed.  [A  somewhat  similar  apparatus  is  used  by  Burdon- 
Sanderson,  and  called  a  "recording  stethograph,"  By  it  movements  of  the  corresponding  points 
on  opposite  sides  of  the  chest  can  be  investigated.]  A  cannula  or  oesophageal  sound  may  be  intro- 
duced into  that  portion  of  the  oesophagus  which  lies  in  the  chest,  and  a  connection  estabhshed 
with  Marey's  tambour  [Rosenthal).  [This  method  also  enables  one  to  measure  the  inlra-thoracic 
pressure?^ 

Marey's  Stethograph  or  Pneumograph. — [There  are  two  forms  of  this  instrument,  one  modi- 
fied by  P.  Bert  and  tiie  more  modern  form  (Fig.  136).  A  tambour  {h)  is  fixed  at  right  angles  to  a 
thin  elastic  plate  of  steel  (/).  The  aluminium  disk  on  the  caoutchouc  of  the  tambour  is  attached 
to  an  upright  {b),  whose  end  lies  in  contact  with  a  horizontal  screw  [g).  Two  arms  [d,  c)  are 
attached  to  opposite  sides  of  the  steel  plate,  and  to  them  the  belt  {i)  which  fastens  the  instrument 
to  the  chest  is  attached.  When  the  chest  expands,  these  two  arms  are  pulled  asunder,  the  steel 
plate  is  bent,  and  the  tambour  is  affected,  and  any  movement  of  the  tambour  is  transmitted  to  a 
registering  tambour  by  the  air  in  the  tube  (a)]. 

(2)  To  record  variation  in  volume  of  the  thorax  or  of  the  respired  gases. 

For  this  purpose  E.  Hering  secures  the  animal,  and  places  it  in  a  tight  box  provided  with  two 
openings  in  its  side ;  one  hole  contains  a  tube,  which  is  connected  to  a  cannula  tied  into  the  trans- 
versely divided  trachea  of  the  ani- 
mal, so  that  respiration  can  go  on  FiG.   136. 
undisturbed.     In  the  other  orifice  is           ^.My:P>  f^6 
fixed  a  water  manometer  provided 
with  a  swimmer  arranged  to  write 
on  a  recording  surface.     Gad  regis- 
tered graphically  the  respired  air  by 
means  of  a   special   apparatus;  the 
expired  air  raised  a  very  light  and 
carefully  equipoised  box  placed  over 
water.     As  it  was  raised,  it  moved  a 
writing  style.       During    inspiration 
the  box  sank. 

(3)  To  record  the  rate  at 
which  the  respiratory  gases  are 
exchanged. 

If  the  trachea  of  an  animal,  or 
the  mouth  of  a  man  (the  nostrils 
being  closed),  be  connected  with  a 
tube  like  that  of  the  dromograph 
(Fig.  113),  then  during  inspiration 
and   expiration  the  pendulum  will 

be  moved  to  and  fro  by  the  air,  and  the  movements  of  the  pendulum  can  be  registered, 
years  ago,  an  instrument,  called  the  "  Anapnograph,"  was  constructed  on  this  principle.] 

The  curve  (Fig,  135,  B)  was  obtained  by  placing  the  tambour  of  a  Brondgeest's 
pansphygmograph  upon  the  xiphoid  process,  and  recording  the  movement  upon 
a  plate  attached  to  a  vibrating  tuning  fork.  The  inspiration  (ascending  limb) 
begins  with  moderate  rapidity,  is  accelerated  in  the  middle,  and  toward  the  end 
again  becomes  slower.  The  expiration  also  begins  with  moderate  rapidity,  is  then 
accelerated,  and  becomes  much  slower  at  the  latter  part,  so  that  the  curve  falls 
very  gradually. 

Inspiration  is  slightly  shorter  than  Expiration. — According  to  Sibson, 
the  ratio  for  an  adult  is  as  6  to  7  ;  in  women,  children,  and  old  people,  6  to  8  or 
6  to  9.  Vierordt  found  the  ratio  to  be  10  to  14.  i  (to  24.1)  ;  J.  R.  Ewald,  11  to 
12.  It  is  only  occasionally  that  cases  occur  where  inspiration  and  expiration  are 
equally  long,  or  where  expiration  is  shorter  than  inspiration.  When  respiration 
proceeds  quietly  and  regularly,  there  is  usually  no  pause  (complete  rest  of  the 
chest  walls)  between  the  ifispiration  and  expiration.     The  very  flat  part  of  the 


Marey's  Stethograph. 


[Some 


214 


TYPE    OV    RESPIRATION. 


expiratory  curve  has  been  wrongly  regarded  as  due  to  a  pause.  Of  course,  we 
may  make  a  voluntary  pause  between  two  respirations,  or  at  any  part  of  a  respi- 
ratory act. 

Some  observers,  however,  have  ilescribed  a  pause  as  occurring  between  the  end  of  expiration  and 
the  beginning  of  the  next  inspiration  (expiration  pause),  and  also  another  pause  at  the  end  of  inspi- 
ration (inspiration  pause).  The  latter  is  always  of  very  short  duration,  and  considerably  shorter 
than  the  former.  During  very  deep  and  slow  respiration,  there  is  usually  an  expiration  pause, 
while  it  is  almost  invariably  absent  during  ra[jid  breathing.  An  inspiration  pause  is  always  absent 
under  normal  circumstances,  but  it  may  occur  under  pathological  conditions. 

In  certain  parts  of  the  respiratory  curve  slight  irregularities  may  appear,  which  are  sometimes 
due  to  vibrations  communicated  to  the  thoracic  walls  by  vigorous  heart  beats  (Fig.  137). 

The  "type"  of  respiration  may  be  ascertained  by  taking  curves  from  various 
parts  during  the  respiratory  movements.     Hutchinson  showed  that,  in  the  female, 

Fin.  137. 


Pneiimatograms  obtained  by  means  of  Riegel's  stethograph.  I,  normal  curves;  II,  curve  from  a  case  ot  emphy- 
sema; a,  ascer.dmg  limb;  i,  apex;  <r,  descending  limb  of  the  curve.  The  small  elevations  are  due  to  the 
cardiac  impulse. 

the  thorax  is  dilated  chiefly  by  raising  the  sternum  and  the  ribs  (Respiratio 
costahs),  while  in  man  it  is  caused  chiefly  by  a  descent  of  the  diaphra^rm  (Respi- 
ratio diaphragmatica  or  abdominalis).  In  the  former,  there  is  the  so-called 
"  costal  type,"  in  the  latter  the  "  abdominal  or  diaphragmatic  type." 

This  difference  in  the  type  of  respiration  in  the  sexes  occurs  only  during  normal  quiet  respira- 
tion During  deep  and  forced  respiration,  in  both  sexes  the  dilatation  of  the  chest  is  caused 
chiefly  by  raising  the  chest  and  the  ribs.  In  man,  the  epigastrium  may  be  pulled  in  sooner  than  it 
IS  protruded.  During  sleep,  the  type  of  respiration  in  both  sexes  is  thoracic,  while  at  the  same  time 
the  inspiratory  dilatation  of  the  chest  precedes  the  elevation  of  the  abdominal  wall  (A/osso).  It  is 
not  determined  whether  the  costal  type  of  respiration  in  the  female  depends  upon  the  constriction  of 
the  chest  by  corsets  or  other  causes  (Stdson),  or  whether  it  is  a  natural  adaptation  to  the  child- 
Dearing  function  in  women  {Hutchinson).  Some  observers  maintain  that  the  diff^erence  of  type  is 
quite  distinct,  even  m  sleep,  when  all  constrictions  are  removed,  and  that  similar  differences  are 
noticeable  m  young  children.     This  is  denied  by  others,  while  a  third  class  of  observers  hold  that 


PATHOLOGICAL   VARIATIONS    OF    RESPIRATORY    MOVEMENTS.       215 

the  costal  type  occurs  in  children  of  both  sexes,  and  they  ascribe  as  a  cause  the  greater  flexibility  of 
the  ribs  of  children  and  women,  which  permits  the  muscles  of  the  chest  to  act  more  efficiently  upon 
the  ribs. 

III.  PATHOLOGICAL. — Examination  of  the  Lungs. — The  same  methods  that  are  ap- 
plicable to  the  heart,  viz.,  I,  Inspection;  II,  Palpation;  III,  Percussion;  and  IV,  Auscultation, 
apply  here  also.] 

[By  inspection  we  may  determine  the  presence  of  symmetrical  or  unilateral  alterations  in  the 
shape  of  the  chest,  the  presence  of  bulging  or  flattening  at  one  part,  and  variations  in  the  movement 
of  the  chest  walls.  By  palpation,  the  presence  or  absence,  character,  seat,  and  extent  of  any  move- 
ments are  more  carefully  examined.  But  we  may  also  study  what  is  called  vocal  fremitus  (^  II7). 
Percussion  (§  114),  Auscultation  (|  116).] 

[In  investigating  the  respiratory  movements,  we  should  observe  (i),  the  frequency  (§  109) ;  (2), 
the  type  (§  no) ;  (3),  the  nature,  character,  and  extent  of  the  movements,  noting  also  whether  they 
are  accompanied  by  pain  or  not  (^  no) ;  (4),  the  rhythm.] 

I.  Changes  in  the  Mode  of  Movement. — In  persons  suffering  from  disease  of  the  respiratory 
organs,  the  dilatation  of  the  chest  may  be  diminished  (to  the  extent  of  5  or  6  cm.)  on  both  sides  or 
only  on  one  side.  In  affections  of  the  apex  of  the  lung  (in  phthisis),  the  sub-normal  expansion  of  the 
upper  part  of  the  wall  of  the  chest  may  be  considerable.  Jielraction  of  the  soft  parts  of  the  thoracic 
wall,  the  xiphoid  process,  and  the  parts  where  the  lower  ribs  are  inserted,  occurs  in  cases  where  air 
cannot  freely  enter  the  chest  during  inspiration,  e.g.,  in  narrowing  of  the  larynx;  when  this  retraction 
is  confined  to  the  upper  part  of  the  thoracic  wall,  it  indicates  that  the  portion  of  the  lung  lying 
under  the  part  so  affected  is  less  extensile  and  diseased. 

Harrison's  Groove. — In  persons  suffering  from  chronic  difficulty  of  breathing,  and  in  whom,  at 
the  same  time,  the  diaphragm  acts  energetically,  there  is  a  slight  groove,  which  passes  horizontally 
outward  from  the  xiphoid  cartilage,  caused  by  the  pulling  in  of  the  soft  parts  and  corresponding  to 
the  insertion  of  the  diaphragm. 

The  duration  of  inspiration  is  lengthened  in  persons  suffering  from  narrowing  of  the  trachea 
or  larynx  ;  expiration  is  lengthened  in  cases  of  dilatation  of  the  lung,  as  in  emphysema,  where  all 
the  expiratory  muscles  must  be  brought  into  action  (Fig.  137,  II). 

II.  Variations  in  the  Rhythm. — When  the  respiratory  apparatus  is  much  affected,  there  is 
either  an  increase  or  a  deepening  of  the  respirations,  or  both.  When  there  is  great  difficulty  of 
breathing,  this  is  called  dyspnoea. 

Causes  of  Dyspnoea. — (i)  Limitation  of  the  exchange  of  the  respiratory  gases  in  the  blood 
due  to  (a)  diminution  of  the  respiratory  surface  (as  in  some  diseases  of  the  lungs)  ;  [b)  narrowing 
of  the  respiratory  passages;  (c)  diminution  of  the  red  blood  corpuscles;  [d)  disturbances  of  the 
respiratory  mechanism  [e.g.,  due  to  affections  of  the  respiratory  muscles  or  nerves,  or  painful 
affections  of  the  chest  wall)  ;  {e)  impeded  circulation  through  the  lungs  due  to  various  forms  of 
heart  disease.  (2)  Heat  dyspnoea. — The  frequency  of  the  respirations  is  increased  in  febrile 
conditions.  The  warm  blood  acts  as  a  direct  irritant  of  the  respiratory  centre  in  the  medulla 
oblongata,  and  raises  the  number  of  respirations  to  30-60  per  minute  ("Heal  dyspnoea  ").  If  the 
carotids  be  placed  in  warm  tubes,  so  as  to  heat  the  blood  going  to  the  medulla  oblongata,  the 
same  phenomena  are  produced  (^  368).  [When  a  child  sucks,  it  breathes  exclusively  through  the 
nose,  hence  catarrhal  conditions  of  the  nasal  mucous  membrane  are  fraught  with  danger  to  the 
child.] 

[Orthopnoea. — Sometimes  the  difficulty  of  breathing  is  so  great  that  the  person  can  only  respire 
in  the  erect  position,  i.e.,  when  he  sits  or  is  propped  up  in  bed.  This  occurs  frequently  toward  the 
close  of  some  heart  affections,  notably  in  mitral  lesions ;  dropsical  conditions,  especially  of  the 
cavities,  may  be  present.] 

Cheyne-Stokes'  Phenomenon. — This  remarkable  phenomenon  occurs  in  certain  diseases,  where 
the  normal  supply  of  blood  to  the  brain  is  altered,  or  where  the  quality  of  the  blood  itself  is  altered, 
e.g.,  in  certain  affections  of  the  brain  and  heart,  and  in  ursemic  poisoning.  Respiratory  pauses  of 
one-half  to  three-quarters  of  a  minute  alternate  with  a  short  period  {%—}{.  min.)  of  increased 
respiratory  activity,  and  during  this  time  20—30  respirations  occur.  The  respirations  constituting  this 
"  series  "  are  shallow  at  first ;  gradually  they  become  deeper  and  more  dyspnoeic,  and  finally  become 
shallow  or  superficial  again.  Then  follows  the  pause,  and  thus  there  is  an  alternation  of  pauses  and 
series  (or  groups)  of  modified  respirations.  During  the  pause,  the  pupils  are  contracted  and  inactive  ; 
and  when  the  respirations  begin,  they  dilate  and  become  sensible  to  light ;  the  eyeball  is  moved  as 
a  whole  at  the  same  time.  Hein  observed  that  consciousness  was  abolished  during  the  pause,  and 
that  it  returned  when  respiration  commmenced. 

Causes. — Luciani  and  Rosenbach  regard  variations  in  the  excitability  of  the  respiratory  centre 
as  the  cause  of  the  phenomenon,  which  they  compare  with  the  periodic  contraction  of  the  heart  (^  58). 
The  excitability  of  the  respiratory  centre  is  lowest  during  the  pause.  They  observed  this  phe- 
nomenon after  injury  to  the  medulla  oblongata  above  the  respiratory  centre,  and  after  apncea  produced 
in  animals  deeply  narcotized  with  opium,  and  in  the  last  stages  of  asphyxia,  during  respiration  in  a 
closed  space.  During  hibernation,  this  mode  of  respiration  is  normal  in  Myoxus,  the  hedgehog, 
and  the  caiman. 


216  THE    MUSCLES    OF    FORCED    RESPIRATION. 

Periodic  Respiration. — If  frogs  be  kept  under  water,  or  if  the  aorta  be  clamped,  after  several 
hours,  ihey  become  passive.  If  they  be  taken  out  of  the  water,  or  if  the  clamp  be  removed  from  the 
aorta,  they  gradually  recover  and  always  exhibit  the  Cheyne  Stokes'  phenomenon.  In  such  frogs 
the  blood  current  may  be  arrested  temporarily,  while  the  phenomenon  itself  remains  (So/^o/o-v  and 
Luchsin^er).  If  the  blood  current  be  arrested  by  ligature  of  the  aorta,  or  if  the  frogs  be  bled,  the 
respirations  occur  in  groups.  This  is  followed  by  a  few  single  respirations,  and  then  the  respiration 
ceases  completely.  During  the  pause  between  the  periods,  mechanical  stimulation  of  the  skin 
causes  the  discharge  of  a  group  of  respirations  (^Siebert  and  Langendorff). 

Action  of  Drugs. — Muscarin,  digitalin,  curara,  chloral,  sulphuretted  hydrogen,  and  the  poison 
of  many  infectious  diseases  (typhus,  diphtheria,  scarlet  fever)  may  also  cause  periodic  respiration 
in  frogs  [which  is  not  due  to  the  action  of  these  drugs  on  the  heart]. 

Periodic  respiration  wuhout  any  variation  in  the  size  of  the  individual  respirations — the  so-called 
"Blot's  respiration" — occurs  normally  during  sleep.  While  the  nervous  system  as  it  were 
strives  to  rest,  and  thus  forgets  the  respiration,  the  organism  does  not  observe  the  short  pauses 
[Mosso).  [There  is  a  periodic  increase  or  decrease  in  the  depth  of  the  respiration,  especially  in  old 
people  and  children,  even  to  the  extent  of  respiration  becoming  "  remittent,"  or  even"  intermittent," 
for  a  period  of  30  sec.  during  sleep.  During  periodic  respiration  the  action  of  the  several  respiratory 
muscles  does  not  coincide.  As  a  rule,  one  respires  more  than  is  required  by  the  organism.  Mosso 
calls  this  "  luxus  respiration."]  Periodic  irregularities  in  the  respiration  are  often  of  reflex 
origin  (Knoll). 

112.    GENERAL  VIEW  OF  THE   RESPIRATORY  MUSCLES. 

(A)  Inspiration. 
L  During  Ordinary  Inspiration. 

1.  The  diaphragm  (^Nervus phrcnicus). 

2.  The  Mm.  levatores  costariun  longi  et  breves  {Rami posteriores  Nn.  dorsaliuni). 

3.  The  Mm.  intercostales  externi  et  intercartilaginei  {^Nn.  intercostales). 

II.  During  Forced  Respiration. 
{a)  Muscles  of  the  Trunk. 

1 .  The  three  Mm.  scaleni  {Rami  musculares  of  the  plexus  cervicalis  etbrachialis). 

2.  M.  sternocleidomastoideus  (Ram.  externus  N.   accessorii). 

3.  M.  trapezius  (i?.  externus  N.  accessorii  et  Ram.  musculares  plexus  cervicalis^. 

4.  M.  pectoralis  minor  {Nn.  ihoracici  afiteriores). 

5.  M.  serratus  posticus  superior  {N.  dorsalis  scapulce). 

6.  Mm.  rhomboidei  {N.  dorsalis  scapulce). 

7.  Mm.  extensores  columnse  vertebralis  {Ram.  posteriores  nervorum  dorsalium). 
[8.   Mm.  serratus  anticus  major  {N.  tJwracicus  longus).  ??] 

(^)  Muscles  of  the  Larynx. 

1.  M.  sternohyoideus  (i?^;«.  descendens  hypoglossi). 

2.  M.  sternothyreoideus  {Ram.  descendens  hypoglossi). 

3.  M.  crico-arytaenoideus  posticus  {N.  laryngeus  inferior  vagi). 

4.  M.  thyreo-arytaenoideus  N.  {laryngeus  inferior  vagi). 

(c)  Muscles  of  the  Face. 

1.  M.  dilatator  narium  anterior  et  posterior  {N.  facialis). 

2.  M.  levator  alae  nasi  {N.  facialis). 

3.  The  dilators  of  the  mouth  and  nares,  during  forced  respiration  ["gasping 
for  breath  "],  {N.  facialis). 

(d)  Muscles  of  the  Pharynx. 

1.  M.  levator  veli  palatini  {N.  facialis). 

2.  M.  azygos  uvulae  {N.  facialis). 

3.  According  to  Garland,  the  pharynx  is  always  narrowed. 

(B)  Expiration. 
I.   During  Ordinary  Respiration. 
The  thoracic  cavity  is  diminished  by  the  weight  of  the  chest,  the  elasticity  of 
the  lungs,  costal  cartilages,  and  abdominal  muscles. 


ACTION    OF   THE    DIAPHRAGM. 


217 


II.  During  Forced  Expiration. 
The  Abdominal  Muscles. 

1.  The  abdominal  muscles  [including  the  obliquus  externus  and  internus,  and 
transversalis  abdominis]  {Nn.  abdominis  internis  anteriores  e  nervis  intercostalibus, 
8-12). 

2.  Mm.  intercostales  interni,  so  far  as  they  lie  between  the  osseous  parts  of  the 
ribs,  and  the  Mm.  infracostales  (^Nn.  intercostales'). 

3.  M.  triangularis  sterni  {Nn.  intercostales'). 

4.  M.  serratus  posticus  inferior  {Ram.  externi  nerv.  dorsalinm). 

5.  M.  quadratus  lumborum  {Ram.  muscular  e plexu  lumbali). 

113.  ACTION  OF  THE  INDIVIDUAL  RESPIRATORY  MUSCLES.— (A)  Inspi- 
ration.— (i)  The  Diaphragm  arises  from  the  cartilages  and  the  adjoining  osseous  parts  of  the 
lower  six  ribs  (costal  portion),  by  two  thick  processes  or  crura,  from  the  upper  three  or  four  lumbar 
vertebrae,  and  a  sternal  portion  from  the  back  of  the  ensiform  process.  It  represents  an  arched 
double  atpola  or  dome-shaped  partition,  directed  toward  the  chest ;  in  the  larger  concavity  on  the 
right  side  lies  the  liver,  while  the  smaller  arch  on  the  left  side  is  occupied  by  the  spleen  and 
stomach.  During  the  passive  condition,  these  viscera  are  pressed  against  the  under  surface  of  the 
diaphragm,  by  the  elasticity  of  the  abdominal  walls,  and  by  the  intra-abdominal  pressure,  so  that 
the  arch  of  the  diaphragm  is  pressed  upward  into  the  chest.  The  elastic  traction  of  the  lungs  also 
aids  in  producing  this  result.  The  greater  part  of  the  upper  surface  of  the  central  tendon  of  the 
diaphragm  is  united  to  the  pericardium.  The  part  on  which  the  heart  rests,  and  which  is  perforated 
by  the  inferior  vena  cava  (foramen  quadrilaterum)  is  the  deepest  part  of  the  middle  portion  of  the 
diaphragm  during  the  passive  condition. 

Action  of  the  Diaphragm. — When  the  diaphragm  contracts,  both  arched 
portions  become  flatter,  and  the  chest  is  thereby  elongated  from  above  downward. 
In  this  act,  the  lateral  muscular  parts  of  the  diaphragm  pass  from  an  arched  con- 
dition into  a  flatter   form  (Fig.   138),  and 
during  a  forced  inspiration  the  lowest  lateral 
portions,  which  during  rest  are  in  contact 
with  the  chest  wall,  become  separated  from 
it.     The    middle    of  the    central    tendon 
where  the  heart  rests  (fixed  by  means  of  the 
pericardium  and  inferior  vena  cava)  takes 
no   share   in    this   movement,  especially  in 
ordinary  quiet   breathing,  but    during    the 
deepest  inspiration  it  sinks  somewhat. 

Undoubtedly,  the  diaphragm  is  the  most  powerful 
agent  in  increasing  the  cavity  of  the  chest.  Briicke 
believes  that  in  addition  to  increasing  the  length  of 
the  thoracic  cavity  from  above  downward,  it  also  in- 
creases the  transverse  diameter  of  the  lower  part  of 
the  chest.  It  presses  upon  the  abdominal  viscera 
from  above,  and  strives  to  press  these  outward,  thus 
tending  to  push  out  the  adjoining  thoracic  wall.  If 
the  contents  of  the  abdomen  are  removed  from  a  liv- 
ing animal,  every  time  the  diaphragm  contracts  the 
ribs  are  drawn  inward.  This,  of  course,  hinders  the 
chest  from  becoming  wider  below,  hence  the  presence 
of  the  abdominal  viscera  seems  to  be  necessary  for 
the  normal  activity  of  the  diaphragm.  Every  con- 
traction of  the  diaphragm,  by  increasing  the  intra- 
abdominal pressure,  favors  the  venous  blood  current 
in  the  abdomen  toward  the  vena  cava  inferior. 

Phrenic  Nerve. — The  immense  importance  of  the 
diaphragm  as  the  great  inspiratory  muscle  is  proved 
by  the  fact  that,  after  both  phrenic  nerves  (third  and 
fourth  cervical  nerves)  are  divided,  death  occurs.  The 
phrenic  nerve  contains  some  sensory  fibres  for  the 

pleura,  pericardium,  and  a  portion  of  the  diaphragm.     The  contraction  of  the  diaphragm  is  not  to 
be  regarded  as  a  "  simple  muscular  contraction,"  since  it  lasts  4  to  8  times  longer  than  a  simple 


Sagittal  section  through  the  second  rib  on  the 
right  side.  When  the  arched  muscular  part 
of  the  diaphragm  contracts,  a  wedge-shaped 
space,  with  its  apex  downward,  is  formed 
around  the  circumference  of  the  lower  part  of 
the  chest. 


218 


CHANGES    IN    THE    CHEST. 


contraction;  it  is  rather  a  short  tetanic  contraction,  which  we  may  arrest  in  any  stage  of  its  activity, 
without  l)rint;ing  into  action  any  antagonistic  muscles  \Kronecker  and  Marckwald'). 

(2)  The  Elevators  of  the  Ribs. — The  ribs  at  their  vertebral  ends  (which  lie  much  higher  than 
their  sternal  emis)  are  uniteii  by  means  of  joints  by  their  heads  and  tubercles  to  the  bodies  and  trans- 
verse processes  of  the  vertebra:.  A  horizontal  axis  can  be  drawn  through  both  joints,  around  wliich 
the  ribs  can  rotate  upward  and  downward.  If  the  axis  of  rotation  of  each  pair  of  ribs  be  prolonged 
on  both  sides  until  they  meet  in  the  middle  line,  the  angles  so  formed  are  greatest  above  (125°), 
and  smallest  below  (88°).  Owing  to  the  ribs  being  curved,  we  can  imagine  a  plane  which,  in  the 
passive  (expiratory)  condition  of  the  chest,  has  a  slope  from  behind  and  inward  to  the  front  and 
outward.  If  the  ribs  move  on  their  axis  of  rotation,  this  plane  becomes  more  horizontal,  and  the 
thoracic  cavity  is  increased  in  its  transverse  diameter.  As  the  axis  of  rotation  of  the  upper  ribs 
runs  in  a  more  frontal,  and  that  of  the  lower  ribs  in  a  more  sagittal  direction,  the  elevation  of  the 
upper  ribs  causes  a  greater  increase  from  before  backward,  and  the  lower  ribs  from  within  outward 
(as  the  movements  of  ribs  which  are  directed  downward  are  vertical  to  the  axis).  The  costal  cartil- 
ages undergo  a  slight  tension  at  the  same  time,  which  brings  their  elasticity  into  play. 

Changes  in  the  Chest. — All  '^  inspiratory  muscles''  7vhicli  act  directly  upon 
the  clu'st  wall  do  so  by  raising  the  ribs  :  {a)  When  the  ribs  are  raised,  the  inter- 
costal spaces  are  widened,  {b)  When  the  upper  ribs  are  raised,  all  the  lower  ribs 
and  the  sternum  must  be  elevated  at  the  same  time,  because  all  the  ribs  are  con- 
nected with  each  other  by  means  of  the  soft  parts  of  the  intercostal  spaces,  {c) 
During  inspiration,  there  is  an  elevation  of  the  ribs  and  a  dilatation  of  the  inter- 
costal spaces,  (The  lowest  rib  is  an  exception  ;  during  forced  respiration,  at  least, 
it  is  drawn  downward.)  {d)  If",  on  a  preparation  of  the  chest,  the  ribs  be  raised 
as  in  insi)iration,  we  may  regard  all  those  muscles  as  elevators  of  the  ribs,  whose 
origin  and  insertion  become  approximated.  Every  one  is  agreed  that  the  scaleni 
and  levatores  costarum  longi  et  breves,  the  serratus  posticus  superior,  are  inspiratory 
muscles.    These  are  the  most  important  inspiratory  muscles  which  act  upon  the  ribs. 

Intercostal    Muscles. — With 
Fu;.  139.  regard  to  the  action  of  the  inter- 

f  costal  muscles,  there  is  a  great  dif- 

ference of  opinion.  According  to 
the  above  experiment,  the  external 
intercostals  and  the  intercartilagin- 
ous  parts  of  the  internal  intercostals 
act  as  inspiratory  muscles,  while  the 
remaining  portions  of  the  internal 
intercostals  (as  far  as  they  are  cov- 
ered by  the  external)  are  elongated 
when  the  ribs  are  raised,  while  they 
shorten  when  the  chest  wall  de- 
scends. A  muscle  shortens  only 
during  its  activity.  The  internal 
intercostals  were  regarded  by  Ham- 
berger  as  depressors  of  the  ribs  or 
expiratory  muscles. 

In  Fig.  139,  I,  when  the  rods,  a  and  b 
(which  represent  the  ribs), are  raised,  the  in- 
tercostal space  must  be  widened  {ef^  c  d). 
On  the  opposite  side  of  the  figure,  it  is  evi- 
dent that  when  the  rods  are  raised,  the  line, 
g  h,  is  shortened  {i  k  <l  g  h,  direction  of 
the  external  intercostals  ),/w  is  lengthened 
(/  m  <^  o  n,  direction  of  internal  intercos- 
tals.) Fig.  139,  II,  shows,  that  when  the 
ribs  are  raised,  the  intercartilaginei,  indi- 
.  cated  by  ^g' /i,  and  the  external  intercostals 

indicated  by  /  k,  are  shortened.     When  the  ribs  are  raised,  the  position  of  the  muscular  fibres  is 
indicated  by  the  diagonal  of  the  rhomb  becoming  shorter. 

The  mode  of  action  of  the  intercostal  muscles  is  an  old  story,  Galen   (131-203  a.  d.)  regarding 


0 

k 

\ 

^^ 

j  ^ 

/ 

Scheme  of  the  action  of  the  intercostal  muscles. 


MECHANISM    OF   ORDINARY   RESPIRATION.  219 

the  externals  as  inspiratory,  the  internals  as  expiratory.  Hamberger  (1727)  accepted  this  proposi- 
tion, and  considered  the  intercartilaginei  also  as  inspiratory.  Haller  looked  upon  both  the  external 
and  internal  intercostals  as  inspiratory,  while  Vesalius  (1540)  regarded  both  as  expiratory.  Lan- 
derer,  observing  that  the  upper  two  or  three  intercostal  spaces  became  narrower  during  inspiration, 
regarded  both  as  active  during  inspiration  and  expiration.  They  keep  one  lib  attached  to  the  other, 
so  that  their  action  is  to  transmit  any  strain  put  upon  them  to  the  wall  of  the  chest.  On  this  view 
they  will  be  in  action,  even  when  the  distance  between  their  points  of  attachment  becomes  greater. 
Landois  regards  the  external  intercostals  and  intercartilaginei  as  active  only  during  inspiration,  the 
internal  intercostals  only  during  expiration.  [Martin  and  Hartwell  exposed  the  internal  intercostals, 
and  observed  whether  they  contracted  along  with  the  diaphragm,  or  whether  the  contractions  of 
these  two  muscles  alternate.  As  the  result  of  their  experiments,  they  conclude  that  "  the  internal 
intercostal  muscles  are  expiratory  throughout  their  whole  extent,  at  least  in  the  dog  and  cat ;  and 
that  in  the  former  animal  they  are  almost  "ordinary  "  muscles  of  respiration,  while  in  the  latter 
they  are  '  extraordinary  '  respiratory  muscles."]  Landois  is  of  opinion  that  the  chief  z.Q.\\orv  of  these 
muscles  is  not  to  raise  or  depress  the  ribs,  but  rather  that  the  external  intercostals  and  the  inter- 
cartilaginei offer  resistance  to  the  inspiratory  dilatation  of  the  intercostal  spaces,  and  to  the  simul- 
taneously increased  elastic  tension  of  the  lungs.  The  internal  intercostals  act  during  powerful 
expiratory  efforts  [e.  g.,  coughing),  and  oppose  the  distention  of  the  lungs  and  chest  caused  by  this 
act.  Unless  muscles  were  present  to  resist  the  uninterrupted  tension  and  pressure,  the  intercostal 
substance  would  become  so  distended  that  respiration  would  be  impossible.  [According  to  Ruther- 
ford, the  internal  intercostals  are  probably  muscles  of  inspiration.] 

The  Pectoralis  minor  and  (?  Serratus  anticus  major)  can  only  act  as 
elevators  of  the  ribs  when  the  shoulders  are  fixed,  partly  by  the  rhomboidei,  and 
partly  by  fixing  the  shoulder  joint  and  supporting  the  arms,  as  is  done  instinctively 
by  persons  suffering  from  breathlessness. 

(3)  Muscles  acting  on  the  Sternum,  Clavicle,  and  Vertebral  Col- 
umn.— When  the  head  is  fixed  by  the  muscles  of  the  neck,  the  sternocleido- 
mastoid raises  the  manubrium  sterni  and  the  sternal  end  of  the  clavicle,  so  that 
the  thorax  is  raised  and  thereby  dilated.  The  scaleni  also  aid  in  this  act.  The 
clavicular  portion  of  the  trapezius  may  act  in  a  similar  although  less  energetic 
manner.  When  the  vertebral  column  is  straightened,  it  causes  an  elevation  of  the 
upper  ribs,  and  a  dilatation  of  the  intercostal  spaces  which  aid  inspiration. 
During  deep  respiration,  the  straightening  of  the  vertebral  column  takes  place 
involuntarily. 

(4)  Lfaryngeal  Movements. — During  labored  respiration,  with  every  inspi- 
ration, the  larynx  descends  and  the  glottis  is  opened.  At  the  same  time  the  palate 
is  raised,  so  as  to  permit  a  free  passage  to  the  air  entering  through  the  mouth. 

(5)  Facial  Movements. — During  labored  respiration,  the  facial  muscles  are 
involved  ;  there  is  an  inspiratory  dilatation  of  the  nostrils  (well  marked  in  the 
horse  and  rabbit).  When  the  need  for  respiration  is  very  great,  the  mouth  is 
gradually  widened,  and  the  person,  as  it  were,  gasps  for  breath.  During  expiration, 
the  muscles  that  are  active  during  (4)  and  (5)  relax,  so  that  a  position  of  equi- 
librium is  established  without  there  being  any  active  expiratory  movement  to 
counteract  the  inspiratory  movement.  During  inspiration  the  pharynx  becomes 
narrow  {Garland). 

(B)  Expiration. — Ordinary  expiration  occurs  without  the  aid  of  muscles, 
owing  to  the  weight  of  the  chest,  which  tends  to  fall  into  its  normal  position 
from  the  position  to  which  it  was  raised  during  inspiration.  This  is  aided  by  the 
elasticity  of  the  various  parts  of  the  chest.  When  the  costal  cartilages  are  raised, 
which  is  accompanied  by  a  slight  rotation  of  their  lower  margins  from  below 
forward  and  upward,  their  elasticity  is  called  into  play.  As  soon,  therefore,  as 
the  inspiratory  forces  cease,  the  costal  cartilages  return  to  their  normal  position, 
i.e.,  the  position  of  expiration,  and  tend  to  untwist  themselves;  at  the  same  time, 
the  elasticity  of  the  distended  lungs  draws  upon  the  thoracic  walls  and  the 
diaphragm.  Lastly,  the  tense  and  elastic  abdominal  walls,  which,  in  man 
chiefly,  are  stretched  and  pushed  forward,  tend  to  return  to  their  non-distended 
passive  condition  when  the  abdominal  viscera  are  relieved  from  the  pressure  of 
the  contracted  diaphragm.     (When  the  position  of  the  body  is  reversed,  the  action 


220  RELATIVE    DIMENSIONS   OF   THE   CHEST. 

of  the  weight  of  the  chest  is  removed,  but  in  place  of  it  there  is  the  weight  of  the 
viscera,  which  press  upon  the  diaphragm.) 

The  abdominal  muscles  [obliquus  internus  and  externus,  transversalis 
abdominis  and  levator  ani]  are  always  active  during  labored  respiration.  They 
act  by  diminishing  the  abdominal  cavity,  and  they  press  the  abdominal  contents 
upward  against  the  diaphragm.  When  they  act  simultaneously,  the  abdominal 
cavity  is  diminished  througliout  its  whole  extent.  The  triangularis  sterni 
depresses  the  sternal  ends  of  the  united  cartilages  and  bones,  from  the  third  to 
sixth  ribs  downward  ;  and  tlie  serratus  posticus  inferior  depresses  the  lowest 
four  ribs,  causing  the  other  to  follow.  It  is  aided  by  the  quadratus  lumborum, 
which  depresses  the  last  rib.  According  to  Henle,  the  serratus  i)osticus  inferior 
fixes  the  lower  ribs  for  the  action  of  the  slips  of  the  diaphragm  inserted  into  them, 
so  that  it  acts  during  inspiration.  According  to  Landerer,  the  downward  move- 
ment of  the  ribs  in  the  lower  part  of  the  thorax  dilates  the  chest. 

In  the  erect  posilion,  when  the  vertebral  column  is  fixed, deep  inspiration  and  expiration  naturally 
alter  the  position  of  tlie  centre  of  gravity,  so  that  durinj^  inspiration,  owing  to  the  protrusion  of  the 
thoracic  and  abdominal  wails,  the  centre  of  gravity  lies  somewhat  more  to  the  front.  Hence,  with 
each  respiration  there  is  an  involuntary  balancing  of  the  body.  During  very  deep  inspiration,  the 
accompanying  straightening  of  the  vertebral  column  and  the  throwing  backward  of  the  head  com- 
pensate for  the  protrusion  of  the  anterior  walls  of  the  trunk. 

114.  RELATIVE  DIMENSIONS  OF  THE  CHEST.— The  diameter  of  the  chest  is 
ascertained  by  means  of  callipers;  the  circumference  with  a  flexible  centimetre  or  other  measure. 

In  strong  men,  the  circumference  of  the  upper  part  of  the  chest  (immediately 
under  the  arms)  is  8S  centimetres  (34.3  inches),  in  females  82  centimetres  (32 
inches)  ;  at  the  level  of  the  ensiform  process  82  centimetres  (32  inches)  and  78 
centimetres  (30.4  inches)  respectively.  When  the  arms  are  placed  horizontally, 
during  moderate  expiration,  the  circumference  immediately  under  the  nipple  and 
the  angles  of  the  scapulae  is  equal  to  half  the  length  of  the  body  ;  in  man  82,  and 
during  deep  inspiration  89  centimetres.  The  circumference  at  the  level  of  the 
ensiform  cartilage  is  6  centmietres  less.  In  old  people,  the  circumference  of  the 
upper  part  of  the  chest  is  diminished,  so  that  the  lower  part  becomes  the  wider  of 
the  two.  The  right  half  of  the  chest  is  usually  slightly  larger  than  the  left  half, 
owing  to  the  greater  development  of  the  muscles  on  that  sifie.  The  long 
diameter  of  the  chest — from  the  clavicle  to  the  margin  of  the  lowest  rib — varies 
very  much. 

The  transverse  diameter  in  man,  above  and  below,  is  25  to  26  centimetres 
(9.7  to  10. 1  inches),  in  females  23  to  24  centimetres  (8.9  to  9.2  inches)  ;  above 
the  nipple  it  is  i  centimetre  more.  The  antero-posterior  diameter  (distance  of 
anterior  chest  wall  from  the  tip  of  a  spinous  process)  in  the  upper  part  of  the  chest 
is  =17  (6.6  inches),  in  the  lower  19  centimetres  (7.4  inches).  Valentin  found 
that  in  a  man,  during  the  deepest  inspiration,  the  chest  on  a  level  with  the  groove 
in  the  heart  was  increased  about  ^V  ^°  f  J  while  Sibson  estimates  the  increase  at 
the  level  of  the  nipple  to  be  ■^. 

Thoracometer. — In  order  to  obtain  a  knowledge  of  the  degree  of  movement — rising  or  falling — 
of  the  chest  wall  during  respiration,  various  instruments  have  been  invented.  The  thoracometer 
I  fig-  UO/n^^ures  the  elevation  in  different  parts  of  the  sternum.  It  consi.Ms  of  two  metallic  bars 
placed  at  right  angles  to  each  other  ;  one  of  them.  A,  is  placed  on  the  vertebral  column.  On  B 
there  is  placed  a  movable  transverse  bar,  C,  which  carries  on  its  free  end  a  toothed  rod,  Z,  directed 
downward.  The  lower  end  of  this  rod  is  provided  with  a  pad  which  rests  on  the  sternum,  while 
Its  toothed  edge  drives  a  small  wheel,  which  moves  an  index,  whose  excursions  are  indicated  on  a 
circle  with  a  scale  attached  to  it. 

.  '^^^  Cyrtometer  of  Woillez  consists  of  a  brass  chain  of  movable  links,  to  be  applied  in  a  defi- 
nite direction  to  part  of  the  chest  wall,  e.  ^ir.,  transversely  on  a  level  with  the  nipple,  or  vertically 
upon  the  mammiUary  or  axillary  lines  anteriorly.  There  are  freely  movable  links  at  two  parts, 
which  permit  the  chain  to  be  easily  removed,  so  that  as  a  whole  it  still  retains  its  form.  The  chain 
is  laid  upon  a  sheet  of  paper,  and  a  line  drawn  with  a  pencil  around  its  inner  margin  gives  the  form 
of  the  thorax  (Fig.  140).     [A  lead  wire  answers  the  same  purpose.] 


LIMITS    OF   THE    LUNGS. 


221 


Limits  of  the  Lungs. — The  extent  and  boundaries  of  the  lungs  are  ascer- 
tained in  the  living  subject  by  means  of  percussion,  which  consists  in  lightly 
tapping  the  chest  wall  by  means  of  a  hammer  (percussion  hammer).  A  small 
ivory  or  bone  plate  or  pleximeter,  held  in  the  left  hand,  is  laid  on  the  chest, 
and  the  hammer  is  made  to  strike  this  plate,  whereby  a  sound  is  emitted,  which 
sound  varies  with  the  condition  of  the  subjacent  lung  tissue.  Whenever  the  lung 
substance  in  contact  with  the  chest  wall  contains  air,  a  clear  resonant  tone  or  sound 
— such  as  is  obtained  by  striking  a  vessel  containing  air,  a  clear  percussion  sound 
— is  obtained.  Where  the  lung  does  not  contain  air,  a  dull  sound — like  striking 
a  limb — is  obtained.  If  the  parts  containing  air  be  very  thin,  or  only  partially 
filled  with  air,  the  sound  is  "  muffled." 

Fig.  142  indicates  the  relation  of  the  lungs  to  the  anterior  surface  of  the  chest. 
The  apices  of  the  lungs  reach  3  to  7  centimetres  (i.i  to  2.7  inches)  above  the 
clavicles  anteriorly,  while  posteriorly  they  extend  from  the  spines  of  the  scapulsi 
as  high  as  the  seventh  spinous  process.  The  lower  margin  of  the  right  lung  in  the 
passive  position  (moderate  expiration)  of  the  chest,  commences  at  the  right  margin 


Fig.  141. 


FlO.    I40 


Cyrtometer  curve.     Left  side  of  the  chest  retracted  in 
a  girl  aged  twelve. 


Sibson's  Thoracometer. 


of  the  sternum  at  the  insertion  of  the  sixth  rib,  runs  under  the  right  nipple,  nearly 
parallel  to  the  upper  border  of  the  sixth  rib,  and  descends  a  little  in  the  axillary 
line,  to  the  upper  margin  of  the  seventh  rib.  On  the  left  side  (apart  from  the 
position  of  the  heart),  the  lower  limit  reaches  as  far  down  anteriorly  as  the  right. 
In  Fig.  142  the  line  a,  t,  b  shows  the  lowest  limit  of  the  passive  lungs.  Poste- 
riorly both  lungs  reach  as  far  down  as  the  tenth  rib.  During  the  deepest  inspiration, 
the  lungs  descend  anteriorly  as  far  as  between  the  sixth  and  seventh  ribs,  and  pos- 
teriorly to  the  eleventh  rib — whereby  the  diaphragm  is  separated  from  the  thoracic 
wall  (Fig.  143).  During  the  deepest  expiration,  the  lower  margins  of  the  lungs  are 
elevated  almost  as  much  as  they  descend  during  inspiration.  In  Fig.  142, 
ni,  n  indicates  the  margin  of  the  right  lung  during  deep  inspiration  ;  h,  I,  during 
deep  expiration.  [The  part  of  the  chest  wall  covered  by  the  costal  pleura  is  con- 
siderably larger  than  the  circumference  of  the  lung.  This  is  specially  marked  at 
the  lower  margin  of  the  lung,  and  where  the  left  lung  is  incised  over  the  heart. 
In  these  regions,  during  expiration,  the  surfaces  of  the  visceral  and  parietal  pleurae 
are  in  contact,  but  during  inspiration  they  are  separated,  and  allow  the  thin  mar- 
gins of  the  lung  to  be  insinuated  between  them.     This  available  space  is  called 


222 


PATHOLOGICAL    PERCUSSION    SOUNDS. 


complemental  space  {Gerhardt),ox  "disposable  "  or  reserve  pleural  space 

by  Lusclika  i^Eiih/iorsf).'] 

It  is  important  to  observe  the  relation  of  the  margin  of  the  left  lung  to  the  heart. 
In  Fig.  142  a  somewhat  triangular  space,  reaching  from  the  middle  of  the  point  of 
insertion  of  the  fourth  rib  to  the  sixth  rib  on  the  left  side  of  the  sternum,  is  indi- 
cated. In  the  passive  chest,  the  heart  lies  in  contact  with  the  thoracic  wall  in  this 
triangular  area  (§  56).  This  area  is  represented  by  the  triangle  /,  /',  /",  and  per- 
cussion over  it  gives  a  dull  sound  (superficial  dullness). 

In  the  area  of  the  larger  triangle,  d,  d' ,  a",  where  the  heart  is  separated  from 
the  chest  wall  by  the  thin  anterior  margins  of  the  lung,  percussion  gives  a  muffled 
sound,  while  further  outward  a  clear  lung  percussion  sound  is  obtained.  During 
deep  inspiration,  the  inner  margin  of  the  left  lung  reaches  over  the  heart  as  far  as 

Fk;.  142. 


/ 


%. 


^\ 


/r 


Topography  of  the  lungs  and  heart,  h,  I,  upward  limit  of  inur^iii  ol  lung  during  deepest  expiration  ;  »t,  n,  lower 
limit  during  deepest  inspiration;  /,  i',  f ,  triangular  area  where  the  heart  is  uncovered  by  lung,  dull  percussion 
sound  ;  ci,  d,'  d" ,  muffled  percussion  sound  ;  /,  /',  anterior  margin  of  left  lung  reaches  this  line  during  deep  inspi- 
ration, and  during  deep  expiration  it  recedes  as  far  as  e,  «•'. 


the  insertion  of  the  mediastinum,  whereby  the  dull  sound  is  limited  to  the  smallest 
triangle,  /,  /,  /'.  Conversely,  during  very  complete  expiration,  the  margin  of  the 
lung  recedes  so  far  that  the  cardiac  dullness  embraces  the  space,  /,  e,  e! . 

115.  PATHOLOGICAL  PERCUSSION  SOUNDS.— Abnormal  Dullness.— The  nor- 
mal clear  resonant  percussion  sound  of  the  lungs  becomes  mutlled  when  intiltraiion  takes  place  into 
the  lungs,  so  as  to  diminish  the  normal  amount  of  air  witliin  them,  or  when  the  lungs  are  compressed 
from  without,  e.g.,  by  effusion  of  fluid  into  the  pleura.  The  percussion  sound  becomes  clearer  when 
the  chest  wall  is  very  thin,  as  in  spare  individuals,  during  very  deep  inspiration,  and  especially  in 
emphysema,  where  the  air  vesicles  of  certain  parts  of  the  lung  (apices  and  margins)  become  greatly 
dilated. 

The  pitch  of  the  percussion  sound  ought  also  to  be  noted.  It  depends  upon  the  greater  or  less 
tension  of  the  elastic  pulmonary  tissue,  and  on  the  elasticity  of  the  thoracic  wall.  The  tension  of 
the  elastic  tissue  is  increased  during  inspiration  and  diminished  during  expiration,  so  that  even 
under  physiological  conditions,  the  pitch  of  the  sound  varies. 


NORMAL   RESPIRATORY   SOUNDS.  223 

The  sound  is  said  to  be  tympanitic  when  it  has  a  musical  quality  resembling  in  its  timbre  the 
sound  produced  on  drums,  and  when  it  has  a  slight  variation  in  pitch.  If  a  caoutchouc  ball  be 
placed  near  the  ear,  on  tapping  it  gently,  a  well-marked  tympanitic  sound  is  heard,  and  the  sound  is 
of  higher  pitch  the  smaller  the  diameter  of  the  ball.  A  tympanitic  sound  is  always  produced  on 
tapping  the  trachea  in  the  neck.  A  tympanitic  sound  produced  over  the  chest  is  always  indica- 
tive of  a  diseased  condition.  It  occurs  in  cases  of  cavities  or  vomicae  within  the  substance  of  the 
lung  (the  sound  becomes  deeper  when  the  mouth,  or  better,  the  mouth  and  nose,  are  closed),  when 
air  is  present  in  one  pleural  cavity,  as  well  as  in  conditions  where  the  tension  of  the  pulmonary 
tissues  is  diminished.  The  tympanitic  sound  resembles  the  metallic  tinkling  which  is  heard  in 
large  pathological  cavities  in  the  lungs,  or  which  occurs  when  the  pleural  cavity  contains  air,  and 
when  the  conditions  which  permit  a  more  uniform  reflection  of  the  sound  waves  within  the  cavity 
are  present. 

[When  a  cavity,  freely  communicating  with  a  large  bronchus,  exists  in  the  upper  and  anterior 
part  of  the  lung,  a  peculiar  "  cracked-pot  sound  "  is  heard  on  percussing  over  the  part.  Some 
notion  of  this  sound  may  be  obtained  by  clasping  the  two  hands  so  as  to  bring  the  palms  nearly 
together,  leaving  an  air  space  between,  and  then  striking  them  on  the  knee.  When  percussion  is 
made  over  a  large  cavity  communicating  with  a  bronchus,  some  of  the  air  is  expelled,  and  the  sound 
thereby  emitted  is  blended  with  the  fundamental  note  of  the  air  in  the  cavity  itself,  the  combination 
of  these  two  sounds  thus  producing  the  "  cracked-pot "  sound.] 

Resistance, — When  percussing  a  chest,  we  may  determine  whether  the  substance  lying  under  the 
portion  of  the  chest  under  examination  presents  great  or  small  resistance  to  the  blow,  either  of  the 
percussion  hammer  or  of  the  tips  of  the  fingers,  as  the  case  may  be  \j.g.,  in  great  pleuritic  effusion 
exerting  much  pressure  on,  and  so  distending,  the  thoracic  walls]. 

Phonometry. — If  the  stem  of  a  vibrating  tuning  fork  be  placed  on  the  chest  wall,  over  a  part  con- 
taining air,  its  sound  is  intensified  ;  but  if  it  be  placed  over  a  portion  of  the  lung  which  contains  little 
or  no  air,  its  sound  is  enfeebled  ( Von  Baas). 

ii6.  THE  NORMAL  RESPIRATORY  SOUNDS.— If  the  ear  directly, 

or  through  the  medium  of  a  stethoscope,  be  placed  in  connection  with  the  chest 
wall,  we  hear  over  the  entire  area,  where  the  lung  is  in  contact  with  the  chest,  the 
so-called  "  normal  vesicular  sound,"  which  is  Sindihle  during  inspiration,  and 
its  typical  characters  may  be  studied  by  listening  in  the  infra-scapular  region  in  an 
adult.  It  is  a  fine  sighing  or  breezy  sound  [which  gradually  increases  in  intensity 
until  it  reaches  a  maximum,  and  falls  away  before  expiration  begins].  It  is  said 
to  be  caused  by  the  sudden  dilatation  of  the  air  vesicles  (hence  "  vesicular  ") 
during  inspiration,  and  it  is  also  ascribed  to  the  friction  of  the  current  of  air  enter- 
ing the  alveoli.  The  sound  has,  at  one  time,  a  soft,  at  another,  a  sharper  character  ; 
the  latter  occurs  constantly  in  children  up  to  12  years  of  age.  In  their  case  the 
sound  is  sharper,  because  the  air,  in  entering  vesicles  one-third  narrower,  is  sub- 
jected to  greater  friction.  This  is  followed  by  an  expiratory  sound,  which  may  be 
absent  during  quiet  breathing.  It  is  a  feeble  sighing  sound,  of  an  indistinct,  soft 
character,  caused  by  the  air  passing  out  of  the  air  vesicles,  is  three  or  four  times 
shorter  than  the  inspiratory,  is  loudest  at  first,  and  soon  disappears,  the  latter  part 
of  the  expiratory  act  giving  rise  to  no  audible  sound.  Its  absence  is  not  a  sign 
of  disease,  but  when  it  is  prolonged  and  loud,  suspicion  is  aroused.] 

Bronchial  Respiration. — Within  the  larger  air  passages — larynx,  trachea, 
bronchi — during  inspiration  and  expiration,  there  are  loud,  rough,  harsh  sounds 
like  a  sharp  h  or  ch — the  '^bronchial'''' — the  laryngeal,  tracheal,  or  "  tubular  " 
sound,  or  breathing.  [In  normal  bronchial  breathing,  as  heard  over  the  trachea, 
there  is  a  pause  between  the  inspiratory  and  expiratory  sounds,  which  are  of  nearly 
equal  duration  and  of  about  the  same  intensity  throughout.  These  sounds  are  also 
heard  between  the  scapulae,  at  the  level  of  the  fourth  dorsal  vertebra  (bifurcation 
of  trachea),  and  they  occur  also  during  expiration,  being  slightly  louder  on  the 
right  side,  owing  to  the  slightly  greater  calibre  of  the  right  bronchus.  At  all 
other  parts  of  the  chest,  the  vesicular  sound  obscures  the  tubular  or  bronchial 
sound.  If  the  air  vesicles  are  deprived  of  their  air,  the  tubular  breathing  becomes 
distinct. 

Bronchial  respiration  is  produced  chiefly  in  the  larynx,  owing  to  the  formation 
of  air  eddies  in  consequence  of  the  narrowing  of  the  respiratory  part  of  the  glottis. 
This  "  laryngeal  stenosis  sound  "  excites  resonance  of  the  tracheo-bronchial  column 


224  PATHOLOGICAL    RESPIRATORY   SOUNDS. 

of  air,  and  communicates  to  it  the  specific  character  of  bronchial  breathing  which 
is  heard  over  the  large  tubes  of  the  bronchial  system  (^Dchio). 

It  is  asserted  that,  when  lungs  containing  air  are  placed  over  the  trachea,  the  tubular  sound  there 
produced  becomes  vesicular.  In  this  case,  we  must  suppose  that  the  vesicular  sound  arises  from 
the  tubular  breathing  becoming  weakened,  and  acousiicaliy  altered  by  being  conducted  through  the 
lung  alveoli.  A  sighing  sound  is  often  produced  at  the  apertures  of  the  nose  and  mouth  during 
forced  inspiration. 

117.  PATHOLOGICAL  RESPIRATORY  SOUNDS.— [The  breath  sounds  heard  in 
disease  may  be  merely  modifications  of  the  normal  vesicular  or  bronchial  sounds,  or  new  sounds, 
such  as  friction  sounds,  rales,  or  rhonchi.] 

[Puerile  Breathing  is  merely  an  exaggerated  vesicular  sound,  so  called  because  it  resembles 
the  louder  vesicular  sound  heard  in  children.  It  occurs  when  some  part  of  the  lung  is  unable 
to  act,  and  there  is,  as  it  were,  extra  work  of  the  other  parts  to  compensate,  and  thus  the  sound  is 
exaggerated.] 

(i)  Bronchial  or  Tubular  Breathing  occurs  over  the  entire  area  of  the  lung,  either  when  the 
air  vessels  are  devoid  of  air,  which  may  be  caused  by  the  exudation  of  fluid  or  solid  constituents, 
or  when  the  lungs  are  compressed  from  without.  In  both  cases  vesicular  sounds  disappear,  and 
the  condensed  or  solidified  lung  tissue  conducts  the  tubular  sound  of  the  large  bronchi  to  the 
surface  of  the  chest.  [The  sound  heard  over  a  hepatized  lobe  of  the  lung  in  pneumonia  is  a 
typical  example  ]  It  also  occurs  in  large  cavities,  with  resistant  walls  near  the  surface  of  the  lung, 
provided  these  cavities  communicate  with  a  large  bronchus.  [In  this  case  it  is  termed  cavernous 
breathing.] 

(2)  The  amphoric  sound  is  compared  to  that  produced  by  blowing  over  the  mouth  of  an  empty 
bottle.  It  occurs  either  when  a  cavity — at  least  the  size  of  the  fist — exists  in  the  lung,  which  is  so 
blown  into  during  respiration  that  a  peculiar  amphoric-like  sound,  with  a  metallic  limbic,  called 
metallic  tinkling,  is  produced;  or  when  the  lung  still  contains  air,  and  is  capable  of  expansion; 
as  there  is  still  air  in  the  pleural  cavity,  it  acts  as  a  resonator,  and  causes  an  amphoric  sound, 
simultaneous  with  the  change  of  air  in  the  lungs.  [The  amphoric  sound  or  echo  and  metallic 
tinkling  are  the  only  certain  signs  of  the  existence  of  a  cavity  in  the  lung.] 

(3j  If  obstruction  occurs  in  the  course  of  the  air  passages  of  the  lungs,  various  results  may 
accrue,  according  to  the  nature  of  the  resistance :  ((z)  owing  to  various  causes,  e.  Q-.,  in  the  apices  of 
the  lungs,  there  may  be  partial  swelling  of  the  walls  of  the  air  lubes,  or  infiltration  into  the  air  cells, 
which  hinders  ihe  regular  supply  of  air.  In  these  cases  parts  of  the  lung  are  not  supplied  with  air 
continuously  ;  it  only  reaches  them  periodically,  when  a  cogwheel  sound  occurs.  A  similar  sound 
may  be  heard  occasionally  in  a  normal  lung,  when  the  muscles  of  the  chest  contract  in  a  periodic 
spasmodic  manner.  {/>)  When  the  air  entering  large  bronchi  causes  the  formation  of  bubbles  in  the 
mucus  which  may  have  accumulated  there  "  mucous  rales  "  are  produced.  They  also  occur  in 
small  spaces  when  the  walls  are  separated  from  their  fluid  contents  by  the  air  entering  during  inspira- 
tion,  or  when  the  walls,  being  adherent  to  each  other,  are  suddenly  pulled  asunder.  The  riles  are 
distinguished  as  tftoisi  (when  the  contents  are  fluid),  or  as  dry  (when  the  contents  are  sticky);  they 
may  be  inspiratory,  expiratory,  or  continuous,  or  they  may  be  coarse  or  fine;  funher,  there  is  the 
very  fine  crepitation,  or  crackling  sound,  and,  lastly,  the  metallic  tinkling  caused  in  large  cavities 
through  resonance.  [Crepitation  or  vesicular  rales  are  fine  crepitating  sounds  like  those  pro- 
duced by  rubbing  a  lock  oi^  hair  between  the  fingers  near  one's  ear;  they  occur  only  during  inspira- 
tion, and  are  a  proof  that  some  air  is  entering  the  air  vesicles.  It  is  heard  in  its  typical  form  during 
the  first  stage  of  pneumonia,  and  seems  to  be  produced  by  the  bursting  of  minute  bubbles  of  air  in 
a  fluid.]  (<-)  When  the  mucous  membrane  of  the  bronchi  is  greatly  swollen,  or  is  so  covered  with 
viscid  mucus  that  the  air  must  force  its  way  through,  deep  sonorous  rhonchi  (rhonchi  sonori)  may 
occur  in  the  large  air  passages,  and  clear,  shrill  sibilant  sounds  (rhonchi  sibilantes)  in  the  smaller 
ones.  [Rhonchi  are  usually  due  to  catarrh  or  to  affections  of  the  bronchial  mucous  membrane 
or  bronchitis  ]  When  there  is  extensive  bronchial  catarrh,  not  unfrequently  we  feel  the  chest  wall 
vibrating  with  the  rk\e  sounds  (bronchial  fremitus). 

(4)  If  fluid  and  air  occur  together  in  one  pleural  cavity  in  which  the  lung  is  collapsed,  on  shaking 
the  person's  thorax  vigorously  we  hear  a  sound  such  as  is  produced  when  air  and  water  are  shaken 
together  in  a  bottle.  This  is  the  succussion  sound  of  Hippocrates.  Much  more  rarely  this  sound 
is  heard  under  similar  conditions  in  large  pulmonary  cavities. 

(5)  Pleural  Friction. — When  the  two  opposed  surfaces  of  the  pleura  are  inflamed,  have  become 
soft,  and  are  covered  wiih  exudation,  they  move  over  each  other  during  respiration,  and  in  doing  so 
give  rise  to  friction  sounds,  which  can  be  felt  (often  by  the  patient  himself),  and  can  also  be  heard. 
The  sound  is  comparable  to  the  sound  produced  by  bending  new  leather. 

(6)  Pectoral  Fremitus. — When  we  speak  or  sing  in  a  loud  tone,  the  walls  of  the  chest  vibrate, 
because  the  vibration  of  the  vocal  cords  is  propagated  throughout  the  entire  bronchial  ramifications. 
The  vibration  is,  of  course,  greatest  near  the  trachea  and  large  bronchi.  The  ear  cannot  delect  the 
sounds  distinctly.  If  there  be  much  exudation  or  air  in  the  pleura,  or  great  accumulation  of  mucus 
in  the  bronchi,  the  pectoral  fremitus  is  diminished  or  altogether  absent.     [In  health,  when  a  person 


PRESSURE    IN    THE    AIR    PASSAGES   DURING    RESPIRATION.  225 

speaks,  the  vocal  resonance  over  the  trachea,  although  loud,  may  be  inarticulate ;  and  on  listening 
over  the  sternum  the  sound  is  diminished  and  quite  inarticulate ;  while  over  the  chest  wall  generally 
the  sound,  though  distinct,  is  feeble. 

All  conditions  which  cause  bronchial  breathing  increase  the  pectoral  fremitus.  Under  normal 
circumstances,  therefore,  it  is  louder  where  bronchial  breathing  is  heard  normally.  The  ear  hears 
an  intensified  sound,  called  bronchophony  [which  is  a  sound  like  that  heard  normally  over  the 
trachea  or  bronchi,  but  audible  over  the  vesicular  lung  tissue.  The  conditions  that  cause  it  are  the 
same  as  those  on  which  bronchial  breathing  depends,  so  that  it  is  heard  in  pneumonia  and  phthisis. 
If,  through  effusion  into  the  pleura  or  inflammatory  processes  in  the  lung  tissue,  the  bronchi  are 
pressed  flat,  a  peculiar  bleating  sound  (aegophony)  may  be  heard.] 

ii8.  PRESSURE  IN  THE  AIR  PASSAGES  DURING  RESPI- 
RATION.— Respiratory  Pressure. — If  a  manometer  be  tied  into  the  trachea 
of  an  animal,  so  that  the  respiration  goes  on  completely  undisturbed,  /.  e., 
normal  respiration,  during  every  inspiration  there  is  a  negative  pressure  (-3 
mm.  Hg)  and  during  expiration  a  positive  pressure.  Bonders  placed  the  U-shaped 
manometer  tube  in  one  nostril,  closed  his  mouth,  leaving  the  other  nostril  open, 
and  respired  quietly.  During  every  quiet  inspiration  the  mercury  showed  a  nega- 
tive pressure  of-  i  mm.,  and  during  expiration  a  positive  pressure  of  2-3  mm. 

Forced  Respiration. — As  soon  as  the  air  was  inspired  or  expired  with  greater 
force,  the  variations  in  pressure  became  very  much  greater,  e.  g.,  during  speaking, 
singing,  and  coughing.  The  inspiratory  pressure  was  =  -  57  mm.  (36-74),  the 
greatest  expiratory  pressure  -f  87  (82-iooj  mm.  Hg.  The  pressure  of  forced 
expiration,  therefore,  is  30  mm.  greater  than  the  inspiratory  pressure  {Donders). 

Resistance  to  Inspiration. — Notwithstanding  this,  we  must  not  conclude 
that  the  expiratory  muscles  act  more  powerfully  than  the  inspiratory ;  for  during 
inspiration  a  variety  of  resistances  have  to  be  overcome,  so  that  after  these  have 
been  met,  there  is  only  a  residue  of  the  force  for  the  aspiration  of  the  mercury. 
The  resistances  to  be  overcome  by  the  inspiratory  muscles  are :  (i)  The  elastic 
tension  of  the  lungs,  which  during  the  deepest  expirations  =  6  mm. ;  during  the 
deepest  inspirations  =  30  mm.  Hg  (§  107).  (2)  The  raising  of  the  weight  of 
the  chest.  (3)  The  elastic  torsion  of  the  costal  cartilages.  (4)  The  depression 
of  the  abdominal  contents,  and  the  elastic  distention  of  the  abdominal  walls. 
All  these  not  inconsiderable  resistances,  which  the  inspiratory  muscles  have  to 
overcome,  act  during  expiration,  and  aid  the  expiratory  muscles.  The  forces 
concerned  in  inspiration  are  decidedly  much  greater  than  those  of  expiration. 

Intra-thoracic  Pressure. — As  the  lungs  within  the  chest,  in  virtue  of  their 
elasticity,  continually  strive  to  collapse,  necessarily  they  must  cause  a  negative 
pressure  within  the  chest.  This  amounts  in  dogs,  during  inspiration,  to  -7.1  to 
-7.5  mm.  Hg,  and  during  expiration  to  -  4  mm.  Hg.  The  corresponding 
values  for  man  have  been  estimated  at  -  4.5  mm.  Hg  and  -  3  mm.  Hg,  by 
Hutchinson. 

[We  must  distinguish  between  the  respiratory  pressure  of  the  air  withui  the  respiratory 
passages,  and  the  intra-thoracic  pressure.  The  former  is  the  same  as  the  atmospheric  pressure  when 
the  chest  is  passive,  but  less  than  it  as  the  chest  is  being  enlarged,  and  greater  than  it  when  it  is 
being  diminished  in  size.  The  intra-thoracic  pressure  is  the  pressure  within  the  chest,  but  outside 
the  hings,  i.  e.,  in  the  pleura,  mediastinum,  etc.  It  is  negative,  i.  e.,  less  than  the  atmospheric  pres- 
sure, and  must  vary  with  the  degree  of  distention  of  the  lungs.] 

[Method. — A  direct  estimation  was  made  by  Adamkiewicz  and  Jacobson.  A  trocar  with  its 
stylet  was  forced  into  the  fourth  left  intercostal  space  near  the  sternum  and  pushed  into  the  peri- 
cardium (sheep).  The  stylet  was  then  withdrawn,  and  the  trocar  connected  with  a  manometer, 
and  the  negative  pressure  of  -  3  to  -  5  mm.  Hg  was  obtained.  During  severe  dyspnoea  it  was  -  9 
mm.  Hg.  Rosenthal  introduced  an  oesophageal  sound  with  an  elastic  ampulla  on  its  lower  end  into 
the  oesophagus,  so  that  the  ampulla  came  to  lie  opposite  the  posterior  mediastinum.  The  sound 
was  connected  with  a  registering  tambour  or  manometer.  During  inspiration  the  manometer  fell, 
and  during  expiration  it  rose.] 

Even  the  greatest  inspiratory  or  expiratory  pressure  is  always  much  less  than  the  blood  pressure 
in  the  large  arteries ;  but  if  the  pressure  be  calculated  upon  the  entire  respiratory  surface  of  the 
thorax,  very  considerable  results  are  obtained. 

15 


226  MODIFIED    RESPIRATORY    MOVEMENTS. 

Pneumatometer. — This  instrument  of  Waldenburg  is  merely  a  mercurial  manometer  fixed  to  a 
stand,  and  connected  to  an  elastic  tube  with  a  suitable  mouth-piece,  which  is  fitted  over  the  mouth 
and  nose,  while  the  variations  of  the  Hg  can  be  read  oft'  on  a  scale.  [In  the  male,  the  expiratory 
pressure  is  90-120  mm.  Ilg,  and  the  respiratory  70-100.  The  relation  of  the  pressures  during 
expiration  and  inspiration  is  more  important  than  the  absolute  j^ressure.]  The  inspiratory  pressure 
is  diminished  in  nearly  all  diseases  where  tlie  expansion  of  the  lung  is  impaired  [phthisis],  or  the 
expiratory  pressure  is  diminished,  as  in  emphysema  and  asthma. 

Effects  of  the  first  Respiration  on  the  Thorax. — Until  birth,  the  airless  lungs  are  completely 
collapsed  (atelectic)  within  the  chest,  and  fill  it,  so  that  on  opening  the  chest  in  a  dead  foetus, 
pneumothorax  does  not  occur  [Bernstein).  Supposing,  however,  respiration  to  have  been  fully 
established  after  birth,  and  air  to  have  freely  entered  the  lungs,  if  a  manometer  be  placed  in  con- 
nection with  the  trachea,  and  the  chest  be  opened,  the  manometer  will  register  a  pressure  of  6 
mm.  Hg,  due  to  the  collapse  of  the  elastic  lungs.  Bernstein  supposes  that  the  thorax  assumes  a 
new  permanent  form,  due  to  the  first  respiratory  distention ;  it  is  as  if,  owing  to  the  respiratory 
elevation  of  the  ribs,  the  thorax  had  become  permanently  too  large  for  the  lungs,  which  are,  there- 
fore, kept  permanently  distended,  but  collapse  as  soon  as  air  passes  into  the  pleura.  When  a  lung 
has  once  been  filled  with  air,  it  cannot  be  emptied  by  pressure  from  without,  as  the  small  bronchi 
are  compressed  before  the  air  can  pass  out  of  the  alveoli.  The  expiratory  muscles  cannot  jx)ssibly 
expel  all  the  air  from  the  lungs,  while  the  inspiratory  muscular  force  is  sufiicient  to  distend  the  lungs 
beyond  their  elastic  equilibrium.  Inspiration  distends  the  lungs,  increasing  their  elastic  tension, 
while  expiration  diminishes  the  tension  without  abolishing  it. 

119.  APPENDIX  TO  RESPIRATION.— Nasal  Breathing.— During 

quiet  respiration  we  usually  breathe — or  ought  to  breathe — through  the  nostrils, 
the  mouth  being  closed.  The  current  of  air  passes  through  the  pharyngo-nasal 
cavity — so  that,  in  its  course  during  inspiration,  it  is  (i)  wanned  and  rendered 
moist,  and  thus  irritation  of  the  mucous  membrane  of  the  air  passages  by  the  cold 
air  is  prevented  ;  (2)  ?,m3.\\  parficles  of  soot,  or  other  foreign  substances  in  the  air, 
adhere  to,  and  become  embedded  in  the  mucus  covering  the  somewhat  tortuous 
walls  of  the  respiratory  passages,  and  are  carried  outward  by  the  agency  of  the 
ciliated  epithelium  of  the  respiratory  passages ;  (3)  disagreeable  odors  and  certain 
impurities  are  detected  by  the  sense  of  smell. 

If  a  lung  be  inflated,  air  constantly  passes  through  the  walls  of  the  alveoli  and  trachea.  This 
also  occurs  during  violent  expiratory  efibrts  (cutaneous  emphysema  in  whooping  cough),  so  that 
pneumothorax  may  occur  [J.  R.  Ezuald  and  Kobert'). 

Pulmonary  CEdema,  or  the  exudation  of  lymph  into  the  pulmonary  alveoli,  occurs  (i)  \\Tien 
there  is  very  great  resistance  to  the  blood  stream  in  the  aorta  or  its  branches,  e.g.,  by  ligaturing  all 
the  arteries  going  to  the  head  or  the  arch  of  the  aorta,  so  that  only  one  carotid  remains  pervious. 
(2)  When  the  pulmonary  veins  are  occluded.  (3)  When  the  left  ventricle,  owing  to  meciianical 
injury,  ceases  to  beat,  while  the  right  ventricle  goes  on  contracting  (\  47).  These  conditions  pro- 
duce at  the  same  time  anxmia  of  the  vasomotor  centre,  which  results  m  stimulation  of  that  centre, 
and  consequent  contraction  of  all  the  small  arteries.  Thus  the  blood  stream  through  the  veins  to  the 
right  heart  is  favored,  and  this  in  its  turn  favors  the  production  of  oedema  of  the  lungs.  [The 
injection  of  muscarin  rapidly  causes  pulmonary  cedema,  due  to  the  increase  of  pressure  and  slowing 
of  the  blood  stream  in  the  pulmonary  capillaries.  It  is  set  aside  by  atropin  (  Weinzweig,  Gross- 
mann)."] 

120.  MODIFIED  RESPIRATORY  MOVEMENTS.— (i)  Coughing  consists  in  a 
sudden  violent  expiratory  explosion  after  a  previous  deep  inspiration  and  closure  of  the  glottis, 
whereby  the  glottis  is  forced  open,  and  any  substance,  fluid,  gaseous,  or  solid,  in  contact  with  the 
respiratory  mucous  membrane  is  violently  ejected  through  the  open  mouth.  It  is  produced  volun- 
tarily or  refiexly;  in  the  latter  case,  it  can  be  controlled  by  the  will  only  to  a  limited  extent. 

[Causes. — A  cough  may  be  discharged  reflexly  from  a  large  number  of  surfaces :  (i)  A 
draught  of  cold  air  striking  the  sitn,  especially  of  the  upper  part  of  the  body.  This  may  cause 
congestion  of  blood  in  the  air  passages,  this  in  turn  exciting  the  cough.  (2)  More  frequently  it  is 
discharged  from  the  respiratory  mucous  membrane,  especially  of  the  larynx,  the  sensory  branches 
of  the  vagus  and  the  superior  laryngeal  nerve  being  the  afferent  nerves.  A  cough  cannot  be  dis- 
charged from  every  part  of  the  larynx :  thus  there  is  none  from  the  true  vocal  cords,  but  only  from 
the  glottis  respiratoria.  All  other  parts  of  the  lar>-nx  are  inactive,  and  so  is  the  trachea  as  far  as  the 
bifurcation,  where  stimulation  excites  cough  {Kohts).  (3)  Sometimes  an  offending  body,  such  as  a 
pea  or  inspissated  cerumen  in  the  external  auditory  meatus,  gives  rise  to  coughing,  the  afferent  nerve 
being  the  auricular  branch  of  the  vagus.  (4)  There  seems  to  be  no  doubt  that  there  may  be  a  ''gas- 
tric or  stomach  cough,''  produced  by  stimulation  of  the  gastric  branches  of  the  vagus,  especially 
in  cases  of  indigestion,  accompanied  by  irritation  of  the  larynx  and  trachea.  (5)  Irritation  of 
the  costal  pleura  and  even  of  the  cesophagus  {Kohts).     (6)  Irritation  of  some  parts  of  the  nose. 


CHEMISTRY   OF    RESPIRATION.  227 

(7)  Sometimes  also  from  irritation  of  the  pharynx,  as  by  an  elongated  uvula.     (8)  In  some  diseases 
of  the  liver,  spleen,  and  generative  organs,  when  pressure  is  exerted  on  these  parts.] 

(2)  Hawking,  or  clearing  the  throat.  An  expiratory  current  is  forced  in  a  continuous  stream 
through  the  narrow  space  between  the  root  of  the  tongue  and  the  depressed  soft  palate,  in  order 
to  assist  in  the  removal  of  foreign  bodies.  When  the  act  is  carried  out  periodically,  the  closed 
glottis  is  suddenly  forced  open,  and  it  is  comparable  to  a  voluntary  gentle  cough.  This  act  can 
only  be  produced  voluntarily. 

(3)  Sneezing  consists  in  a  sudden  violent  expiratory  blast  through  the  nose,  for  the  removal  of 
mucus  or  foreign  bodies  (the  mouth  being  rarely  open)  after  a  simple  or  repeated  spasm-like  inspira- 
tion— the  glottis  remaining  open.  It  is  usually  caused  reflexly  by  stimulation  of  sensory  nerve  fibres 
of  the  nose  [nasal  branch  of  the  fifth  nerve],  or  by  sudden  exposure  to  a  bright  light  [the  afferent 
nerve  is  the  optic].  This  reflex  act  may  be  interfered  with  to  a  certain  extent,  or  even  prevented, 
by  stimulation  of  sensory  nerves,  or  firmly  compressing  the  nose  where  the  nasal  nerve  issues.  The 
continued  use  of  sternutatories,  as  in  persons  who  take  snuff,  dulls  the  sensory  nerves,  so  that  they 
no  longer  act  when  stimulated  reflexly. 

[Sternutatories  or  Errhines,  such  as  powdered  ipecacuanha,  snuff,  and  euphorbium,  also  in- 
crease the  secretion  from  the  nasal  glands.  The  afferent  impulses  sent  to  the  respiratory  centre 
also  affect  the  vasomotor  centre,  so  that,  even  when  sneezing  does  not  occur,  the  blood  pressure 
throughout  the  body  is  raised.] 

(4)  Snoring  occurs  during  respiration  through  the  open  mouth,  whereby  the  inspiratory  and 
expiratory  stream  of  air  throws  the  uvula  and  soft  palate  into  vibration.  It  is  involuntary,  and 
usually  occurs  during  sleep,  but  it  may  be  produced  voluntarily. 

(5)  Gargling  consists  in  the  slow  passage  of  the  expiratory  air  current  in  the  form  of  bubbles 
through  a  fluid  lying  between  the  tongue  and  the  soft  palate,  when  the  head  is  held  backward. 
It  is  a  voluntary  act. 

(6)  Crying,  caused  by  emotional  conditions,  consists  in  short,  deep  inspirations,  long  expirations 
with  the  glottis  narrowed,  relaxed  facial  and  jaw  muscles,  secretion  of  tears,  often  combined  with 
plaintive  inarticulate  expressions.  When  crying  is  long  continued,  sudden  and  spasmodic  involun- 
tary contractions  of  the  diaphragm  occur,  which  cause  the  inspiratory  sounds  in  the  pharynx  and 
larynx  known  as  sobbing.     This  is  an  involuntary  act. 

(7)  Sighing  is  a  prolonged  inspiration,  usually  combined  with  a  plaintive  sound,  often  caused 
involuntarily,  owing  to  painful  or  unpleasant  recollections. 

(8)  Laughing  is  due  to  short,  rapid  expiratory  blasts  through  the  tense  vocal  cords,  which 
cause  a  clear  tone,  and  there  are  characteristic  inarticulate  sounds  in  the  larynx,  with  vibra- 
tions of  the  soft  palate.  The  mouth  is  usually  open,  and  the  countenance  has  a  characteristic 
expression,  owing  to  the  action  of  the  M.  zygomaticus  major.  It  is  usually  involuntary,  and  can 
only  be  suppressed,  to  a  certain  degree,  by  the  will  (by  forcibly  closing  the  mouth  and  stopping 
respiration). 

(9)  Yawning  is  a  prolonged  deep  inspiration  occurring  after  successive  attempts  at  numerous 
inspirations — the  mouth,  fauces,  and  glottis  being  wide  open ;  expiration  shorter — both  acts  often 
accompanied  by  prolonged  characteristic  sounds.  It  is  quite  involuntary,  and  is  usually  excited  by 
drowsiness  or  ennui. 

[(10)  Hiccough  is  due  to  a  spasmodic  involuntary  contraction  of  the  diaphragm,  causing  an 
inspiration,  which  is  arrested  by  the  sudden  closure  of  the  glottis,  so  that  a  characteristic  sound  is 
emitted.  Not  unfrequently  it  is  due  to  irritation  of  the  gastric  mucous  membrane,  and  sometimes  it 
is  a  very  troublesome  symptom  in  ursemic  poisoning.] 

121.  CHEMISTRY  OF  RESPIRATION— CARBON  DIOXIDE,  OXYGEN,  and 
WATERY  VAPOR  GIVEN  OFF.— I.  Estimation  of  COj.— i.  The  volume  of  CO2  is 
estimated  by  means  of  the  anthracometer  (Fig.  143,  II).  The  volume  of  gas  is  collected  in  a 
graduated  tube,  ;',  r,  provided  with  a  bulb  at  one  end  (previously  filled  with  water  and  carefully 
calibrated,  i.  e.,  the  exact  amount  which  each  part  of  the  tube  contains  is  accurately  measured), 
and  the  tube  is  closed.  The  lower  end  has  a  stop-cock,  k,  and  to  this  is  screwed  a  flask,  n,  com- 
pletely filled  with  a  solution  of  caustic  potash ;  the  stop-cock  is  then  opened,  the  potash  solution  is 
allowed  to  ascend  into  the  tube,  which  is  moved  about  until  all  the  COj  unites  with  the  potash  to 
form  potassium  carbonate.  Hold  the  tube  vertically  and  allow  the  potash  to  run  back  into  the 
flask,  close  the  stop-cock,  and  remove  the  bottle  with  the  potash.  Place  the  stop-cock  under  water,, 
open  it,  and  allow  the  water  to  ascend  in  the  tube,  when  the  space  in  the  tube  occupied  by  the  fluid 
indicates  the  volume  of  CO2  which  is  combined  with  the  potash. 

2.  By  Weight. — A  large  quantity  of  the  mixture  of  gases  which  has  to  be  investigated  is  made 
to  pass  through  a  Liebig's  bulb  filled  with  caustic  potash.  The  potash  apparatus  having  been  care- 
fully weighed  beforehand,  the  increase  of  weight  indicates  the  amount  of  COj  which  has  been  taken 
up  by  the  potash  from  the  air  passed  through  it. 

3.  By  Titration. — A  large  volume  of  the  air  to  be  investigated  is  conducted  through  a  known 
volume  of  a  solution  of  barium  hydrate.  The  COj  unites  with  the  barium  and  forms  barium  car- 
bonate. The  fluid  is  neutralized  with  a  standard  solution  of  oxalic  acid,  and  the  more  barium  that 
has  united  with  the  COj  the  smaller  will  be  the  amount  of  oxalic  acid  used,  and  vice  versa. 


228 


ANDRAL   AND    GAVARRET  S    APPARATUS. 


II.  Estimation  of  Oxygen. — According  to  volume  (a)  Uy  the  union  of  the  O  with  potassium 
pyrogaliate.  The  same  procedure  is  adopted  as  for  the  estimation  of  CO^,  only  the  flask,  w,  is  filled 
with  the  pyrogaliate  solution  instead  of  potash.  {/>)  By  explosion  in  an  eudiometer  (see  Blood 
Gases,  ?  35). 

III.  Estimation  of  Watery  Vapor. — The  air  to  be  investigated  is  passed  through  a  bulb 
containing  concfntratc-d  su'if'huric  add,  or  through  a  tube  filled  with  pieces  of  calcititn  chloride. 
The  amount  of  water  is  directly  indicated  by  the  increase  of  weight. 

122.  METHODS  OF  INVESTIGATION.— I.  Collecting  the  Expired  Air.— (i)  The 
air  expired  may  be  collected  in  tlie  cylinder  of  the  spirometer,  which  is  suspended  in  concentrated 
salt  solution  to  avoid  the  absorption  of  CO.^  (?  108). 

Andral  and  Gavarret's  Apparatus. — The  operator  breathed  several  times  into  a  capacious 
cylinder  (Fig.  143).  A  mouth-piece  (M)  was  placed  air-tight  over  the  mouth,  while  the  nostrils 
were  closed?  The  direction  of  the  respiratory  current  was  regulated  by  two  so-called  "  Miiller's 
Valves  "  (mercurial),  (a  and  /').  With  every  inspiration  the  bottle  or  valve,  a  (filled  below  with 
Ilg  and  hermetically  closed  above),  permits  the  air  inspired  to  pass  to  the  lungs — during  every 
expiration  the  expired  air  can  pass  only  through  b  to  the  collecting  cylinder  C. 

(2)  If  the  gases  given  ofi"  by  the  skin  are  to  be  collected,  a  limb,  or  whatever  part  is  to  be  inves- 
tigated, is  secured  in  a  closed  vessel,  and  the  gases  so  obtained  are  analyzed. 


Fig.  143. 


O^ 


^ 


o 


^#9 
E 

I.  Apparatus  ot  Andral  and  Gavarret  for  collecting  the  expired  air.     C,  large  cylinder  to  collect  the  air  expired  ;   P, 
weight  to  balance  cylinder  ;  a,  b,  two  Miiller's  valves  ;  M,  mouth-piece.     II.  Anthracometer  of  Vierordt. 

II.  The  most  important  apparatus  for  this  purpose  are  those  of  («)  Scharling  (Fig.  144), 
which  consists  of  a  closed  box,  A,  of  suflicient  size  to  contain  a  man.  It  is  provided  %vith  an  inlet 
2  and  outlet  b.  The  latter  is  connected  with  an  aspirator,  C,  a  large  barrel  filled  with  water. 
When  the  stop-cock,  h,  is  opened  and  the  water  flows  out  of  the  barrel,  fresh  air  will  rush  in  con- 
tinuously into  the  box.  A,  and  the  air  mixed  with  the  expired  gases  will  be  drawn  toward  C.  A 
Liebig's  bulb,  d,  filled  with  caustic  potash,  is  connected  with  the  entrance  tube,  z,  through  which 
the  in-going  air  must  pass,  whereby  it  is  completely  deprived  of  CO.^,  so  that  the  person  experi- 
mented on  is  supplied  with  air  free  from  C()2.  The  air  passing  out  by  the  exit  tube,  b,  has  to  pass 
first  through  e,  where  it  gives  up  its  watery  vapor  to  sulphuric  acid,  whereby  the  amount  of  watery 
vapor  is  estimated  by  the  increase  of  the  weight  of  the  apparatus,  e.  Afterward  the  air  passes 
through  a  bulb,  /,  containing  caustic  potash,  which  absorbs  all  the  CO.^,  while  the  tube,  g,  filled 
with  sulphuric  acid,  absorbs  any  watery  vapor  that  may  come  from  /.  The  increase  in  weight 
of  /  and  g  indicates  the  amount  of  COj,  The  total  volume  of  air  used  is  known  from  the 
capacity  of  C. 

(^)  Regnault  and  Reiset's  Apparatus  is  more  complicated,  and  is  used  when  it  is  necessary 
to  keep  animals  for  some  time  under  observation  in  a  bell-jar.  It  consists  of  a  globe,  R,  in 
which  is  placed  the  dog  to  be  experimented  on  (Fig.   145).     Around  this  is  placed  a  cylinder, 


SCHARLING,  REGNAULT   AND    REISET's   APPARATUS. 


229 


g,g  (provided  with  a  thermometer,  /),  which  may  be  used  for  calorimetric  experiments.  A  tube, 
c,  leads  into  the  globe,  R  ;  through  this  tube  passes  a  known  quantity  of  pure  oxygen  (Fig.  145,  O). 
To  absorb  any  trace  of  COj,  a  vessel  containing  potash  (Fig.  145,  CO2)  is  placed  in  the  course  of 
the  tube.  The  vessel  for  measuring  the  O  is  emptied  toward  R,  through  a  solution  of  calcium 
chloride  from  a  large  pan  (CaClj)  provided  with  large  flasks.     Two  tubes,  d  and  e,  lead  from   R, 

Fig.  144. 


/ 

/ 

>■ 

Z_ 

A 

b 

d 

/ 

Scharling's  apparatus,  d,  bulb  containing  caustic  potash  to  absorb  COo  from  in-going  air;  A,  box  for  animal  experi- 
mented on  ;  e  and^,  tubes  containing  sulphuric  acid  to  absorb  watery  vapor  ;  /,  potash  bulb  to  absorb  COo  given 
off;  C,  vessel  filled  with  water  to  aspirate  air ;  h,  stop-cock. 

and  are  united  by  caoutchouc  tubes  with  the  potash  bulbs  (KOH,  K^^),  which  can  be  raised  or 
depressed  alternately  by  means  of  the  beam,  W.  In  this  way  they  aspirate  alternately  the  air  from 
R,  and  the  caustic  potash  absorbs  the  COj.  The  increase  in  weight  of  these  flasks  after  the 
experiment  indicates  the  amount  of  COj  expired.  The  manometer,  /,  shows  whether  there  is  a 
difference  of  the  pressure  outside  and  inside  the  globe,  R. 


Koh 


Scheme  of  tVie  respiration  apparatus  of  Regnault  and  Reiset.  R,  globe  for  animal ;  g,  g,  outer  casing  for  R .  provided 
with  a  thermometer,  t ;  d  and  e,  exit  tubes  to  movable  potash  bulbs,  KOH  and  Y^oh  ;  O,  in-going  oxygen  ;  CO2, 
vessel  to  absorb  any  carbonic  acid  ;  CaCla,  apparatus  for  estimating  the  amount  of  O  supplied  ;  y,  manometer. 


(c)  V.  Pettenkofer  has  invented  the  most  complete  apparatus  (Fig.  146).  It  consists  of  a 
chamber,  Z,  with  metallic  walls,  and  provided  with  a  door  and  a  window.  At  a  is  an  opening  for 
the  admission  of  air,  while  a  large  double  suction  pump,  PPj  (driven  by  means  of  a  steam  engine) 
continually  renews  the  air  within  the  chamber.     The  air  passes  into  a  vessel,  6,  filled  with  pumice- 


230 


COMPOSITION    OF    ATMOSPHERIC    AIR 


stone  saturated  with  sulphuric  acid,  in  which  it  is  dried;  it  then  passes  through  a  large  j^as  meter, 
c  which  measures  the  total  amount  of  the  air  passing  through  it.  After  the  air  is  measured,  it  is 
emptied  outward  by  means  of  the  pump,  I'P,.  From  the  chief  exit  tube,  .r,  of  the  chamber,  provided 
with  a  small  manometer,  </,  a  narrow  laterally  placed  tube,  «,  passes,  conducting  a  small  secondary 
stream,  which  is  chemically  investigated.  This  current  passes  through  the  suction  apparatus,  MM, 
^constructed  on  the  principle  of  Miiller's  mercurial  valve,  and  driven  by  a  steam  engine).     Before 


Fig.  146. 


Respiration  apparatus  of  V.  Pettenkofer.     Z,  chani:  .  1  experimented  on  ;    jr,  exit  tube  with  manometer,^  ; 

*,  vessel  with  sulphuric  acid;    C,  gas  meter;    PPi,  pump;    n,  secondary  current,  with,  ^'i  bulb ;    MMj,  suction 
appaiatus ;   u,  gas  meter;  N,  stream  for  investigating  air  before  it  enters  Z. 

reaching  this  apparatus,  the  air  passes  through  the  bulb,  K,  filled  with  sulphuric  acid,  whose  increase 
in  weight  indicates  the  amount  of  watery  vapor.  After  passing  through  MMj,  it  goes  through  the 
tube,  R,  filled  with  baryta  solution,  which  takes  up  COj.  The  quantity  of  air  which  passes  through 
the  accessor}'  current,  «,  is  measured  by  the  small  gas  meter,  u,  from  which  it  passes  outward.  The 
second  accessory  stream,  X,  enables  us  to  investigate  the  air  before  it  enters  the  chamber,  and  it  is 
arranged  in  exactly  the  same  way  as  «.  The  increase  of  CO.,  and  H^O  in  the  accessory  stream,  n 
(i.  e.,  more  than  in  X),  indicates  the  amount  of  CO.,  given  off  by  the  person  in  the  chamber,  Z. 

123.    COMPOSITION    OF    ATMOSPHERIC    AIR.— i.    Dry    Air 

contains :  — 

G.ns.  By  Weight.  Hy  Volume. 

0 23.015  20.96 

N 76.985  79.02 

CO.,, 0.03-0.034 

2.  Aqueous  vapor  is  always  present  in  the  air,  but  it  varies  greatly  in  amount, 
and  generally  increases  with  the  increase  of  the  temperature  of  the  air.  We 
distinguish  (a)  the  absolute  fnoisture,  i.  e.,  the  quantity  of  watery  vapor  which  a 
volume  of  air  contains  in  the  form  of  vapor;  and  (/')  the  relative  moisture,  i.  e., 
the  amount  of  watery  vapor  which  a  volume  of  air  contains  with  respect  to  its 
temperature. 

Experience  shows  that  people  generally  can  breathe  most  comfortably  in  an  atmosphere  which  is 
not  completely  saturated  with  aqueous  vapor  according  to  its  temperature,  but  is  only  saturated  to 
the  extent  of  70  j)er  cent.     If  the  air  be  too  drj',  it  irritates  the  respiratory  mucous  membrane ;  if 


COMPOSITION    OF    EXPIRED    AIR. 


231 


too  moist,  there  is  a  disagreeable  sensation,  and  if  it  be  too  warm,  a  feeling  of  closeness.  Hence, 
it  is  important  to  see  that  the  proper  amount  of  watery  vapor  is  present  in  the  air  of  our  sitting  rooms, 
bedrooms,  and  hospital  wards. 

The  absolute  amount  of  moisture  varies.  In  towns  during  the  day  it  increases  with  increase  of 
temperature,  and  diminishes  when  the  temperature  falls ;  it  also  varies  with  the  direction  of  the 
wind,  season  of  the  year,  and  the  height  above  sea  level. 

The  relative  amount  of  moisture  is  greatest  at  sunrise,  least  at  midday ;  small  on  high  mountains ; 
greater  in  winter  than  in  summer ;  larger  with  a  south  or  a  west  wind  than  with  a  north  or  an  east 
wind. 

The  air  in  midsummer  contains  absolutely  three  times  as  much  watery  vapor  as  in  midwinter, 
nevertheless  the  air  in  summer  is  relatively  drier  than  the  air  in  winter. 

3.  The  air  expands  by  heat.     Rudberg  found  that  1000  vol-       Fig.  147. 
umes  of  air,  at  0°,  expanded  to  1365  when  heated  to  100°  C.  ^ 

4.  The  density  of  the  air  diminishes  with  increase  of  the  height 
above  the  sea  level. 

124.  COMPOSITION  OF  EXPIRED  AIR.— i.  The  ex- 
pired air  contains  more  CO2 — in  normal  respiration  =r  4.38  vols, 
per  cent.  (3.3  to  5.5  per  cent.),  so  that  it  contains  nearly  100  times 
more  CO2  than  the  atmospheric  air. 

2.  It  contains  less  O  (4.782  vols,  percent,  less)  than  the  atmo- 
spheric air.  /.  e.,  it  contains  only  16.033  vols,  per  cent,  of  O. 

3.  Respiratory  Quotient. — Hence,  during  respiration,  more 
O  is  taken  into  the  body  from  the  air  than  COo  is  given  off;  so 
that  the  volume  of  the  expired  air  is  {^  to  Jq)  smaller  than  the 
volume  of  the  air  inspired,  both  being  calculated  as  dry,  at  the  same 
temperature,  and  at  the  same  barometric  pressure.  The  relation  of 
the  O  absorbed  to  the  CO2  given  off  is  4.38  :  4.782.  This  is  ex- 
pressed by  the  "respiratory  quotient" — 


CO2 
O 


\    4-782    J 


0.906. 


4.782 

4.  An  excessively  small  quantity  of  N  is  added  to  the  expired  air 
{^Regnault  and  Reiset).  Segen  found  that  all  the  N  taken  in  with 
the  food  did  not  reappear  in  the  excreta  (urine  and  faeces),  and  he 
assumed  that  a  small  part  of  it  was  given  off  by  the  lungs. 

5.  During  ordinary  respiration  the  expired  air  is  saturated 
■with  ^vatery  vapor.  It  is  evident,  therefore,  that  when  the 
watery  vapor  in  the  air  varies,  the  lungs  give  off  different  quantities 
of  water  from  the  body.  The  percentage  of  watery  vapor  falls 
during  rapid  respiration  {Moleschoff). 

6.  The  expired  air  is  warmer  (36.3°  C).     It  is  very  near  the 
temperature  of  the  body,  and  although  the  temperature  of  the  sur- 
rounding  atmosphere   be   very  variable,    the  temperature    of  the  B 
expired  air  still  remains  nearly  the  same. 

Fig.  147  shows  the  instrument  used  by  Valentin  and  Brunner  to  determine  the  temperature  of  the 
expired  air.  It  consists  of  a  glass  tube,  A,  A.,  with  a  mouth-piece,  B,  and  in  it  is  a  fine  thermom- 
eter, C.  The  operator  breathes  through  the  nose  and  expires  slowly  through  the  mouth-piece  into 
the  tube. 

Temperature  of  I'emperature  of  the 

the  Air.  Expired  Air. 

-  6.3°  C, +  29.8°  C 

+  17-19°  C., +  36.2-37°  c. 

+  44°  C.,   .    .    . ^  38.5°  C. 

7.  The  diminution  of  the  volume  of  the  expired  air  mentioned  under  (3)  is 
far  more  than  compensated  by  the  warming  which  the  inspired  air  undergoes  in 
the  respiratory  passages,  so  that  the  volume  of  the  expired  air  is  one-ninth  greater 
than  the  air  inspired. 


232 


CONDITIONS    INFLUENCING    THE    GASEOUS    EXCHANGES. 


8.  A  very  small  quantity  of  ammonia  is  found  in  the  expired  air  =  0.0204 
grammes  in  24  hours;  it  is  probal)ly  derived  from  the  blood. 

9.  Small  quantities  of  H  and  CH4  are  expired,  both  being  absorbed  from  the 
intestine.  In  herbivora,  Reiset  found  that  30  litres  of  CH4  were  expired  in  24 
hours. 

125.  QUANTITY  OF  GASES  EXCHANGED.— As  under  normal 
circumstances  more  O  is  absorbed  than  there  is  CO.^  given  off  (equal  volumes  of  O 
and  CO.,  contain  equal  quantities  of  O),  a  part  of  the  O  must  be  used  for  other 
oxidation  processes  in  the  body.  According  to  the  extent  of  these  latter  pro- 
cesses, the  ratio  of  the  O  taken  into  the  CO.,  given  out  — 


/CO, 

\  o 


0.906  normally)  must  vary. 


The  amount  of  CO.^  given  off  may  be  less  than  the  "  mean  "  above  stated.  The 
quantity  of  CO2  alone  is  not  a  reliable  indication  of  the  entire  exchange  of  gases 
during  respiration;  we  must  estimate  simultaneously  the  amount  of  O  absorbed 
and  the  CO,  given  off. 

126.   DAILY  GASEOUS  INCOME  AND  EXPENDITURE  :  — 

Income  in  24  hours. 


Oxygen — 

744  grms.  ^=  5 16.500  c.  cmtr. 


(  Vierordf). 


(At  0°  C.  and  mean  barometric  pressure.) 


Expenditure  in  24  hours. 
Carbonic  Acid^ 

900  grms.  =  455500  c.  cmtr.         (  Vierordt). 
36  grms.  per  hour    {Scharling). 

32.8  to  33.4  grms.  "       [LiebermeisterV 

34  grms.  .  .  "  .        {Pannm). 

3 '-5  to  33  grms.      .         "         .         {Ranke). 
Water. — 640  grms.  .         "         .     (  Valentin), 
330     "        .  "  .      (  Vierordt). 


127.  CONDITIONS  INFLUENCING  THE  GASEOUS  EX- 
CHANGES— The  formation  of  CO.^,  in  all  probability,  consists  of  two  distinct 
processes.  First,  compounds  containing  CO.,,  which  are  ^^.v/V/a/'/i?/; //■<7<///(:/x  of  sub- 
stances containing  carbon,  seem  to  be  formed  in  the  tissues.  The  second  process 
consists  in  the  separation  of  this  CO..,,  which,  however,  takes  place  without  the 
absorption  of  O.  Both  processes  do  not  always  occur  simultaneously,  and  the  one 
process  may  exceed  the  other  in  extent.     The  formation  of  CO.,  is  affected  by — 

I.  Age. — Until  the  body  is  fully  developed,  the  CO.^  given  off  increases,  but  it 
diminishes  as  the  bodily  energies  decay.  Hence,  in  young  persons  the  O  absorbed 
is  relatively  greater  than  the  CO,  given  off;  at  other  periods  both  values  are 
pretty  constant.     Example  : — 


Age — Years. 

In  24  Hours. 

COj,  Gram.  Excreted.  ==  Carbon. 

0  Absorbed,  Gram. 

8 

«5 

16 
18-20 
20-24 
40-60 
60-80 

443  gram.  =  121  Carbon 
766     "        =  209       " 
950     «'        =  259       '« 
1003     "        =  274       " 
1074     «'        =  293       " 
889     "        =  242       <' 
810     "        =  221       " 

375  grammes. 
652         " 
809 

854         " 
914 

757 
689 

The  absolute  amount  of  CO.^  given  off  is  less  in  children  than  in  adults;  but  if 
the  CO2  given  off  be  calculated  with  reference  to  body  weight,  then,  weight  for 
weight,  a  child  gives  off  twice  as  much  CO^  as  an  adult. 


CONDITIONS    INFLUENCING   THE    GASEOUS   EXCHANGES.  233 

2.  Sex. — Males,  from  the  eighth  year  onward  to  old  age,  give  off  about  one- 
third  more  CO2  than  females.  This  difference  is  more  marked  at  puberty,  when 
the  difference  may  rise  to  one-half.  After  cessation  of  the  menses,  there  is  an  in- 
crease, and  in  old  age  the  amount  of  CO^  given  off  diminishes.  Pregnancy  in- 
creases the  amount,  owing  to  causes  which  are   easily  understood   {^Andral  and 

Gavarret. ) 

3.  Constitution. — In  general,  muscular,  energetic  persons  use  more  O  and 
excrete  more  CO2  than  less  active  persons  of  the  same  weight. 

4.  Alternation  of  Day  and  Night. — The  CO2  given  off  is  diminished  about 
one-fourth  during  sleep,  due  to  the  constant  heat  of  the  surroundings  (bed),  dark- 
ness, absence  of  muscular  activity,  and  the  non-taking  of  food  (see  5,  6,  7,  9). 
O  is  not  stored  up  during  sleep  (S.  Lewiri).  After  awaking  in  the  morning,  the 
respirations  are  deeper  and  more  rapid,  while  the  amount  of  CO2  given  off  is 
increased.  It  decreases  during  the  forenoon,  until  dinner  at  mid-day  causes 
another  increase.     It  falls  during  the  afternoon,  and  increases  again  after  supper. 

During  hibernation,  when  no  food  is  taken,  and  when  the  respirations  cease,  or  are  greatly 
diminished,  the  respiratory  exchange  of  gases  is  carried  out  by  diffusion  and  the  cardio-pneumatic 
movements  (§  59).  The  CO2  given  off  falls  to  -^^,  the  O  taken  in  to  ^,  of  what  they  are  in  the 
waking  condition.  Much  less  COj  is  given  off  than  O  taken  in,  so  that  the  body  weight  may  increase 
through  the  excess  of  O. 

5.  Temperature  of  the  Surroundings. — Cold-blooded  animals  become 
warmer  when  the  temperature  of  their  environment  is  raised,  and  they  give  off 
more  CO2  in  this  condition  than  when  they  are  cooler;  e.g.,  a  frog  with  the 
temperature  of  the  surroundings  at  39°  C.  excreted  three  times  as  much  CO2  as 
when  the  temperature  was  6°  C.  Warm-blooded  animals  behave  quite  differ- 
ently when  the  temperature  of  the  surrounding  medium  is  changed.  When  the 
temperature  of  the  animal  is  lowered  thereby,  there  is  a  considerable  decrease  in 
the  amount  of  CO2  given  off,  as  in  cold-blooded  animals,  but  if  the  temperature 
of  the  animal  be  increased  (and  also  in  fever),  the  CO2  is  increased  (C.  Ludwig 
and  Sander s-Ezn).  Exactly  the  reverse  obtains  when  the  temperature  of  the  sur- 
roundings varies  and  the  bodily  temperature  remains  constant.  As  the  cold  of 
the  surrounding  medium  increases,  the  processes  of  oxidation  within  the  body  are 
increased  through  some  as  yet  unknown  reflex  mechanism ;  the  number  and  depth 
of  the  respirations  increase,  whereby  more  O  is  taken  in  and  more  CO2  is  given 
out.  A  man  in  January  uses  32.2  grammes  O  per  hour;  in  July  only  31.7 
grammes.  In  animals,  with  the  temperature  of  the  surroundings  at  8°  C.,  the 
CO2  given  off  was  one-third  greater  than  with  a  temperature  of  38°  C.  When  the 
temperature  of  the  air  increases — the  body  temperature  remaining  the  same — the 
respiratory  activity  and  the  COj  given  off  diminish,  while  the  pulse  remains  nearly . 
constant.  On  passing  suddenly  from  a  cold  to  a  warm  medium  the  amount  of 
CO2  is  considerably  diminished ;  and  conversely,  on  passing  from  a  warm  to  a 
cold  medium,  the  amount  is  considerably  increased  (§  214). 

6.  Muscular  exercise  causes  a  considerable  increase  in  the  CO2  given  out, 
which  may  be  three  times  greater  during  walking  than  during  rest  (^Ed.  Stnith). 
Ludwig  and  Sczelkow  estimated  the  O  taken  in  and  the  CO2  given  off  by  a  rabbit 
during  rest,  and  when  the  muscles  of  the  hind  limbs  were  tetanized.  During 
tetanus  the  O  and  CO2  were  increased  considerably,  but  in  tetanized  animals  more 
O  was  given  off  in  the  CO2  expired  than  was  taken  up  simultaneously  during 
respiration.  The  passive  animal  absorbed  nearly  twice  as  much  O  as  the  amount 
of  CO2  given  off  (§  294). 

7.  Taking  of  food  causes  a  not  inconsiderable  increase  in  the  CO2  given  off, 
which  depends  upon  the  quantity  taken ;  the  increase  generally  occurs  about  an 
hour  after  the  chief  meal — dinner.  During  inanition,  the  exchange  of  gases 
diminishes  considerably  until  death  occurs.  At  first  the  CO2  given  off  diminishes 
more  quickly  than  the  O  is  taken  up.     The  quality  of  the  food  influences  the 


234 


DIFFUSION    OF    GASES    WITHIN    THE    LUNGS. 


CO,  given  off  to  this  extent,  that  substances  rich  in  carbon  (carbohydrates  and 
fats)  cause  a  greater  excretion  of  CO.,  than  substances  which  contain  less  C  (albu- 
mins). Regnault  and  Reiset  found  that  a  dog  gave  off  79  per  cent,  of  the  O 
inspired  after  a  flesh  diet,  and  91  per  cent,  after  a  diet  of  starch.  If  easily 
oxidizable  substances  (glycerin  or  lactate  of  soda)  are  injected  into  the  blood, 
the  O  taken  in  and  the  CO,  given  off  undergo  a  considerable  increase  {Ludwig 
ami  Scheremetjewsky).  Alcohols,  tea,  and  ethereal  oils  diminish  the  CO;,  {Froui, 
Vierordt).  [Kd.  Smith  divided  foods,  with  reference  to  the  excretion  of  CO.^,  into 
two  classes.  The  respiratory  excitants  include  nitrogenous  foods,  rum,  beer, 
sugar,  stout,  etc.  ;  the  non-exciters  starch,  fat,  some  alcoholic  mixtures.  The 
most  powerful  respiratory  excitants,  however,  are  tea,  sugar,  coffee,  and  rum,  and 
the  maximum  effect  is  usually  experienced  within  an  hour.  He  also  found  that 
the  effects  produced  by  alcoholic  drinks  varied  with  the  nature  of  the  spirituous 
liquor.  Thus  brandy,  whisky,  and  gin  diminish  the  amount ;  while  pure  alcohol, 
rum,  ale,  and  i)orter  tend  to  increase  it. 

8.  The  number  and  depth  of  the  respirations  have  practically  no  influence 
on  the  formation  of  CO,  or  the  oxidation  processes  within  the  body,  these  being 
regulated  by  the  tissues  themselves,  by  some  mechanism  as  yet  unknown  {Pfluger). 
They  have  a  marked  effect,  however,  upon  the  removal  of  the  already  formed  CO, 
from  the  body.  An  increase  in  the  number  of  respirations  (their  depth  remaining 
the  same),  as  well  as  an  increase  of  their  depth  (the  number  remaining  the  same), 
causes  an  absolute  increase  in  the  amount  of  CO,  given  off,  which,  with  reference 
to  the  total  amount  of  gases  exchanged,  is  relatively  diminished.  The  following 
example  from  \'ierordt  illustrates  this:  — 


No.  of  Resps.  . 

Volume  of 

Amount  of 

per  cent. 

Depth  of 

Amount  of 

per  cent. 

per  Minute. 

Air. 

CO2. 

COo.            1 

1 

Resps. 

CO2. 

"      COj 

12 

6000 

258  C.cmtr 

=  4-3% 

500 

21  c.  cnitr. 

=  4-3^ 

24 

12000 

420       " 

=  3-5" 

1000 

36        " 

=  3.6"       1 

48 

24000 

744       " 

=  3t« 

1500 

51        " 

=  34" 

96 

48000 

1392       '• 

-2.9" 

2000 

64       " 

=  3-2" 

3000 

72        " 

=  1.4" 

g.  Exposure  to  bright  light  causes  an  increase  in  the  CO.^  given  off  in  frogs, 
in  mammals  and  birds,  even  in  frogs  deprived  of  their  lungs,  or  in  those  whose 
spinal  cord  has  been  divided  high  up.  The  consumption  of  O  is  increased  at  the 
same  time.  The  same  results  occur  in  blind  persons,  although  to  a  less  degree. 
Bluish-violet  light  is  almost  as  active  as  white  light,  while  red  light  is  less  active. 

10.  The  experiments  of  Grehant,  on  dogs,  seem  to  show  that  intense  inflammation  of  th^ 
bronchial  mucous  membrane  influences  the  COj  given  off". 

11.  Among  poisons,  thebaia  increases  the  CO2  given  off",  while  morphia,  codeia,narcein,narcotin, 
papaverin,  diminish  it  {Fiioini). 

128.  DIFFUSION   OF  GASES  WITHIN  THE  LUNGS.— The  air 

within  the  air  vesicles  contains  most  CO,  and  least  O,  and  as  we  pass  from  the  small 
to  the  large  bronchi  and  onward  to  the  trachea,  the  composition  of  the  air  gradu- 
ally approaches  more  closely  to  that  of  the  atmosphere.  Hence,  if  the  air  expired 
be  collected  in  two  portions,  the  first  half  (/.  e.,  the  air  from  the  larger  air  passages) 
contains  less  CO.,  (3.7  vols,  per  cent.)  than  the  second  half  (5.4  vols,  per  cent,). 
The  difference  in  the  percentage  of  gases  gives  rise  to  a  diffusion  of  the  gases  within 
the  air  passages ;  the  CO.,  must  diffuse  from  the  air  vesicles  outward,  and  the  O 
from  the  atmosphere  and  nostrils  inward  (§  t,;^).  This  movement  is  aided  by  the 
cardio-pneumatic  movement  (§  59).  In  hibernating  animals  and  in  persons  appa- 
rently but  not  actually  dead,  the  exchange  of  gases  within  the  lungs  can  only  occur 


EXCHANGE    OF    GASES    IN    THE    AIR   VESICLES.  235 

in  the  above-mentioned  ways.  For  ordinary  purposes  this  mechanism  is  insufficient, 
and  there  are  added  the  respiratory  movements  whereby  atmospheric  air  is  intro- 
duced into  the  larger  air  passages,  from  which  and  into  which  the  diffusion  currents 
of  O  and  CO2  pass,  on  account  of  the  difference  of  tension  of  the  gases. 

129.  EXCHANGE  OF    GASES  IN  THE  AIR  VESICLES.— The 

exchange  of  gases  between  the  gases  of  the  blood  and  those  in  the  air  vesicles 
occurs  almost  exclusively  through  the  agency  of  chemical  processes,  and  therefore 
independently  of  the  diffusion  of  gases. 

Method. — It  is  important  to  ascertain  the  tension  of  the  O  and  COj  in  the  venous  blood  of  the 
pulmonary  capillaries.  Pfliiger  and  Wolf  berg  estimated  the  tension  by  "  catheterizing  the 
lungs."  An  elastic  catheter  was  introduced  through  an  opening  in  the  trachea  of  a  dog  into  the 
bronchus  leading  to  the  lowest  lobe  of  the  left  lung.  An  elastic  sac  was  placed  round  the  catheter, 
and  when  the  latter  was  introduced  into  the  bronchus,  the  sac  around  the  catheter  was  distended  so 
as  to  plug  the  bronchus.  No  air  could  escape  between  the  catheter  and  the  wall  of  the  bronchus. 
The  outer  end  of  the  catheter  was  closed  at  first,  and  the  dog  was  allowed  to  respire  quietly.  After 
four  minutes  the  air  in  the  air  vesicles  was  completely  in  equilibrium  with  the  blood  gases.  The 
air  of  the  lung  was  sucked  out  of  the  catheter  by  means  of  an  air-pump,  and  afterward  analyzed. 

Thus  we  may  measure  indirectly  the  tension  of  the  O  and  CO2  in  the  venous 
blood  of  the  pulmonary  capillaries.  The  direct  estimation  of  the  gases  in  differ- 
ent kinds  of  blood  is  made  by  shaking  up  the  blood  with  another  gas.  The  gases 
so  removed  indicate  directly  the  proportion  of  blood  gases. 

The  following  statement  shows  the  tension  and  percentage  of  O  and  CO^  in 
arterial  and  venous  blood,  in  the  atmosphere,  and  in  the  air  of  the  alveoli :  — 

I.  i  V. 

O-Tension  in  arterial  blood  =::   29.6  mm.  Hg  j  O-Tension  in  the  air  of  the  alveoli  of  the  cathe- 

(corresponding  to  a  mixture    containing  3.9  j  terized  lung  --=  27.44  mm.  Hg  (correspond- 

vol.  percent,  of  O).  j  ing  to  3.6  vol.  per  cent.). 


II. 

COj-Tension  in  arterial  blood  ^   21  mm.  Hg 
(corresponding  to  2.8  vol.  percent.). 

III. 

O-Tension  in  venous    blood   =    12.   mm.  Hg 
(corresponding  to  2.9  vol.  per  cent.). 

IV. 
CO^-Tension  in  venous  blood  =  41  mm.  Hg 
(corresponding  to  5.4  vol.  per  cent.). 


VI. 

CQ^-Tension  in  the  air  of  the   alveoli  of    the 
catheterized  lung  =  27  mm.  Hg  (correspond- 
ing to  3.56  vol.  per  cent.). 
VII. 

O-Tension  in  the  atmosphere  =  158  mm.  Hg 
(corresponding  to  20.8  vol.  per  cent.). 
VIII. 

C02-Tension  in  the  atmosphere  =  0.38  mm. 
Hg  (corresponding  to  0.03-0.05  vol.  per 
cent.). 


When  we  compare  the  tension  of  the  O  in  the  air  (VII  ^158  mm.  Hg)  with 
the  tension  of  the  O  in  venous  blood  (III  =  22  mm.  Hg,  or  V  =  27.44  mm. 
Hg),  we  might  be  inclined  to  assume  that  the  passage  of  the  O  from  the  air  of  the 
air  vesicles  into  the  blood  was  due  solely  to  diffusion  of  the  gases  ;  and  similarly, 
we  might  assume  that  the  CO,  of  the  venous  blood  (IV  or  VI)  diffused  into  the 
air  vesicles,  because  the  tension  of  the  COj  in  the  air  is  much  less  (VIII).  There 
are  a  number  of  facts,  however,  which  prove  that  the  exchanges  of  the  gases  in 
the  lungs  is  chiefly  due  to  chemical  forces. 

[v.  Fleischl  finds  that  fluids  yield  up  their  gases  very  much  more  easily  when  they  receive  a  shock, 
and  he  regards  the  shock  communicated  to  the  blood  by  the  contraction  of  the  heart  as  an  import- 
ant factor  in  preparing  the  blood  for  the  diffusion  of  COj  from  the  blood  plasma  into  the  lungs.] 

[Changes  produced  in  the  Blood  by  Respiration. — The  blood  of  the 
pulmonary  artery  is  changed  from  venous  into  arterial  blood  (  §  39),  the  most 
obvious  alterations  being  (i)  the  change  in  color  from  dark  crimson  to  bright 
scarlet.  (2)  It  loses  CO2.  (3)  It  gains  O.  (4)  The  reduced  Hb  of  the  venous 
blood  is  converted  into  HbOa-  (5)  As  to  a  supposed  difference  of  temperature, 
see  §  209,  3.     (6)  Pawlow  finds  that  blood  which  passes  several  times  through  the 


236  ABSORPTION    OF   OXYGEN    IN    THE    LUNGS. 

lungs  loses  its  power  of  coagulation.     Are  we  to  assume  that  the  pulmonary  tissues 
have  the  property  of  destroying  the  fibrin-ferment? 

1.  Absorption  of  O. — Concerning  the  absorption  of  O  from  the  air  in  the 
alveoli  into  the  venous  blood  of  the  lung  capillaries,  whereby  the  blood  is  arteri- 
alized,  it  is  proved  that  this  is  a  chemical  process.  The  gas-free  (reduced) 
h;Emo£;lobin  takes  up  O  to  form  oxyha^moglobin  (i^  15,  i).  That  this  absorption 
has  nothing  to  do  directly  with  the  diffusion  of  gases,  but  is  due  to  a  chemical 
combination  of  the  atomic  compounds,  is  shown  by  the  fact  that,  when  pure  O  is 
respired,  the  blood  does  not  take  up  more  O  than  when  atmospheric  air  is  respired  ; 
further,  that  animals  made  to  breathe  in  a  limited  closed  space  can  absorb  almost 
all  the  O — even  to  traces — into  their  blood  before  suffocation  occurs.  Of  course, 
if  the  absorption  of  O  were  due  to  diffusion,  in  the  former  case  more  O  would  be 
absorbed,  while  in  the  latter  case  the  absorption  of  O  could  not  possibly  occur  to 
such  an  extent  as  it  does.  The  law  of  diffusion  comes  into  play  in  connection 
with  the  absorption  of  O  to  this  extent,  viz.,  that  the  O  diffuses  from  the  air  cells 
of  the  lung  into  the  blood  plasma,  where  it  reaches  the  blood  corpuscles  floating 
in  the  plasma.  The  haemoglobin  of  the  blood  corpuscles  forms  at  once  a  chemi- 
cal compound  (oxyhemoglobin)  with  the  O. 

Even  in  very  rarefied  air,  such  as  is  met  with  in  the  upper  regions  of  the  atmosphere  during  a 
balloon  ascent,  the  absorption  of  O  still  remains  independent  of  the  partial  pressure.  But  a  much 
longer  time  is  required  for  this  process  at  the  ordinary  temperature  of  the  body,  so  that  in  rarefied 
air  the  absorption  of  O  is  greatly  delayed,  but  it  is  not  diminished.  This  is  the  cause  of  death  in 
aeronauts  who  have  ascended  so  high  that  the  atmospheric  pressure  is  diminished  to  one-third 
{Setschettow). 

2.  Excretion  of  CO^. — With  regard  to  the  excretion  of  CO;^  from  the  blood, 
we  must  remember  that  the  CO.,  in  the  blood  exists  in  two  conditions.  Part  of 
the  CO.^  forms  a  loose  or  feeble  chemical  compound,  while  another  portion  is  more 
firmly  combined.  The  former  is  obtained  by  those  means  which  remove  gases 
from  fluids  containing  them  in  a  state  of  absorption,  so  that  in  removing  the  CO2 
from  the  blood  it  is  difficult  to  determine  whether  the  CO2  so  removed,  obeyed 
the  law  of  diffusion,  or  if  it  was  expelled  by  chemical  means. 

Although  it  is  convenient  to  represent  the  excretion  of  CO^  from  the  blood 
into  the  air  vesicles  of  the  lung,  as  due  to  equilibrium  of  the  tension  of  the  CO, 
on  opposite  sides  of  the  alveolar  membrane,  /.  e.,  to  diffusion — nevertheless, 
chemical  processes  play  an  important  part  in  this  act.  The  absorption  of  O 
by  the  colored  corpuscles  acts,  at  the  same  time,  in  expelling  CO.,.  This  is 
proved  by  the  fact  that  the  expulsion  of  CO2  from  the  blood  takes  place  more 
readily  when  O  is  simultaneously  admitted.  The  free  supply  of  O  not  only  favors 
the  removal  of  the  CO2,  which  is  loosely  combined,  but  it  also  favors  the  expul- 
sion of  that  portion  of  the  COo  which  is  more  firmly  combined,  and  which  can 
only  be  expelled  by  the  addition  of  acids  to  the  blood.  That  the  oxygenated 
blood  corpuscles  (/'.  e.,  their  oxyhaemoglobin)  are  concerned  in  the  removal  of 
CO2  is  proved  by  the  fact  that  CO.j  is  more  easily  removed  from  serum  which  con- 
tains oxygenated  blood  corpuscles  than  from  serum  charged  with  O. 

[The  following  scheme  may  serve  to  illustrate  the  extent  to  which  diffusion 
comes  into  play.  The  O  must  pass  through  the  alveolar  membrane,  AB — includ- 
ing the  alveolar  epithelium  and  the  wall  of  the  capillaries — as  well  as  the  blood 
plasma,  to  reach  the  hsemoglobin  of  the  blood  corpuscles.  Similarly,  the  CO, 
must  leave  the  salts  of  the  plasma  with  which  it  is  in  combination,  and  diffuse  in 
the  opposite  direction,  through  the  wall  of  the  capillaries,  the  alveolar  membrane, 
and  epithelium,  to  reach  the  air  vesicles.  Let  AB  represent  the  alveolar  mem- 
brane ;  on  the  one  side  of  it  is  represented  the  partial  pressure  of  the  CO^  and  O 
in  the  air  vesicles  ;  and  on  the  other,  the  partial  pressure  of  the  CO,  and  O  in  the 
venous  blood  entering  the  lung.     The  indexes  indicate  the  direction  of  diffusion.] 


DISSOCIATION    OF    GASES.  237 

Partial  pressure  of  air  in  J  ^ 

alveoli  of  lung.  1  ' 7 -44 

A 1^ J ^ B 


Tension  of  gases  in  venous  j  ^j 


22 


blood  of  lung.  1        CO2 O 

Nature  of  the  Process. — The  exchange  of  gases  between  the  blood  and  the 
air  in  the  lungs  has  been  represented  by  Bonders  as  due  to  the  process  of  dis- 
sociation. 

[Bohr  used  a  modified  rheometer  of  Ludwig's,  whereby  living  arterial  blood  was  brought  into 
direct  contact  with  a  volume  of  air  containing  a  greater  or  less  percentage  of  CO.^.  Even  when 
the  amount  of  CO^  in  the  air  in  direct  contact  with  the  blood  was  very  small,  it  was  found  that  very 
little  COj  diffused  from  the  blood  into  the  air  space.  Bohr  therefore  concludes  that  the  separation 
of  COj  from  the  venous  blood  in  the  lungs,  and  its  passage  into  the  air  vesicles,  are  not  explicable 
on  the  hypothesis  of  diffusion,  but  we  must  rather  regard  the  COj  as  removed  from  the  blood  by 
the  pulmonary  tissue  by  means  of  a  kind  of  secretory  process,  analogous  to  the  excretion  processes 
in  glands.] 

130.  DISSOCIATION  OF  GASES.— Many  gases  form  true  chemical 
compounds  with  other  bodies  (/.  e.,  they  combine  according  to  their  equivalents), 
when  the  contact  of  these  bodies  is  effected  under  conditions  such  that  the  partial 
pressure  of  the  gases  is  high.  The  chemical  compound  formed  under  these  con- 
ditions is  broken  up,  whenever  the  partial  pressure  is  diminished,  or  when  it 
reaches  a  certain  minimum  level,  which  varies  with  the  nature  of  the  bodies 
forming  the  compound.  Thus,  by  increasing  and  diminishing  the  partial  pressure 
alternately,  a  chemical  compound  of  the  gas  may  be  formed  and  again  broken  up. 
This  process  is  called  dissociation  of  the  gases.  The  minimal  partial  pressure 
is  constant  for  each  of  the  different  substances  and  gases,  but  temperature,  as  in 
the  case  of  the  absorption  of  gases,  has  a  great  effect  on  the  partial  pressure ; 
with  increase  of  temperature  the  partial  pressure,  under  which  dissociation  occurs, 
diminishes. 

As  an  example  of  the  dissociation  of  a  gas,  take  the  case  of  calcium  carbonate.  When  it  is 
heated  in  the  air  to  440°  C,  COj  is  given  oif  from  its  state  of  chemical  combination,  but  is  taken  up 
again  and  a  chemical  compound  formed,  which  is  changed  into  chalk  when  it  cools. 

Dissociation  in  the  Blood. — The  chemical  combinations  containing  CO2 
and  those  containing  O  within  the  blood  stream,  viz.,  the  salts  of  the  plasma, 
which  are  combined  with  CO2,  and  the  oxyhgemoglobin,  behave  in  a  similar 
manner.  If  these  compounds  of  O  and  CO2  are  placed  under  conditions  where 
the  partial  pressure  of  these  gases  is  very  low — i.  e.,\x\  a  medium  containing  a 
very  small  amount  of  these  gases,  the  compounds  are  dissociated,  i.  e.,  they  give 
off  CO2  or  O.  If  after  being  dissociated  they  are  placed  under  conditions  where, 
owing  to  the  large  amount  of  these  gases,  the  partial  pressure  of  O  or  of  CO2  is 
high,  these  gases  are  taken  up  again,  and  enter  into  the  condition  of  chemical 
combination. 

The  haemoglobin  of  the  blood  in  the  pulmonary  capillaries  finds  plenty  of  O  in 
the  alveoli ;  hence,  it  unites  with  the  O,  owing  to  the  high  partial  pressure  of  the 
O  in  the  lung,  and  so  forms  the  compound  oxyhaemoglobin.  On  its  course 
through  the  capillaries  of  the  systemic  circulation,  the  oxyhsemoglobin  of  the 
blood  comes  into  relation  with  tissues  poor  in  O ;  the  oxyhgemoglobin  is  disso- 
sociated,  the  O  is  supplied  to  the  tissues,  and  the  blood  freed  from  this  O  returns 
to  the  right  heart,  and  passes  to  the  lungs,  where  it  takes  up  the  new  O. 

The  blood  while  circulating  meets  with  most  CO2  in  the  tissues ;  the  high  par- 
tial pressure  of  the  CO2  in  the  tissues  causes  the  CO2  to  unite  with  certain  con- 
stituents in  the  blood  so  as  to  form  chemical  compounds,  which  carry  the  CO2 
from  the  tissues  to  the  lungs.  In  the  air  of  the  lungs,  however,  the  partial  pressure 
of  the  CO2  is  very  low,  dissociation  of  these  chemical  compounds  occurs  under 


238  INTERNAL    RESPIRATION. 

the  low  partial  pressure,  and  the  CO.;  passes  into  the  air  cells  of  the  lung,  from 
which  it  is  expelled  during  expiration.  It  is  evident  that  the  giving  up  of  O  from 
the  blood  to  the  tissues,  and  the  absorption  of  CO,,  from  the  tissues,  go  on  side  by 
side  and  take  place  simultaneously,  while  in  the  lungs  the  reverse  processes  occur 
almost  simultaneously. 

131.  CUTANEOUS  RESPIRATION.— Methods. — If  a  man  or  an  animal  be  placed  in 
the  chamber  of  the  respiratory  apparatus  (^  122),  and  if  tubes  be  so  arranged  that  the  respiratory 
gases  do  not  enter  the  chamber,  of  course  we  obtain  only  the  ^^perspiration  "  of  the  skin  in  the 
chamber.  It  is  less  satisfactory  to  leave  the  head  of  the  person  outside  the  chamber,  while  the  neck 
is  fixed  air-ti<^ht  in  the  wall  of  the  chamber.  The  extent  of  the  cutaneous  respiration  of  a  limb 
may  be  ascertained  by  enclosing  it  in  an  air-tight  vessel  i^Rohrig)  similar  to  that  used  for  the  arm  in 
the  plethysmograph  (j>  loi). 

Loss  by  Skin. — A  healthy  man  loses  by  the  skin,  in  24  hours,  ^  of  his  body 
weight,  which  is  greater  than  the  loss  by  the  lungs,  in  the  ratio  of  3  :  2.  Only  10 
grammes — 150  grains, — or  it  may  be  3.9  grammes,  60  grains, — of  the  entire  loss 
are  due  to  the  CO,,  given  off  by  the  skin.  The  remainder  of  the  excretion  from 
the  skin  is  due  to  \vater  [i.',-2  lb  daily]  containing  a  few  salts  in  solution.  When 
the  surrounding  temperature  is  raised,  the  CO2  is  increased,  in  fact  it  may  be 
doubled  ;  violent  muscular  exercise  has  the  same  effect. 

O  Absorbed. — The  O  taken  up  by  the  skin  is  either  equal  to,  or  slightly  less 
than,  the  CO,  given  off.  As  the  CO.  excreted  by  the  skin  is  only  ^^  of  that 
excreted  by  the  lungs,  while  the  O  taken  in  ^  y^l^  of  that  taken  in  by  the  lungs, 
it  is  evident  that  the  respiratory  activity  of  the  skin  is  very  slight.  Animals  whose 
skin  has  been  covered  by  an  impermeable  varnish  die,  not  from  suffocation,  but 
from  other  causes  (§  225). 

In  animals  with  a  thin,  moist  epidermis  (frog)  the  exchange  of  gases  is  much  greater,  and  in 
them  the  skin  so  far  supports  the  lungs  in  their  function,  and  may  even  partly  replace  them  func- 
tionally. In  mammals  with  thick,  dry  cutaneous  appendages,  the  exchange  of  gases  is,  again, 
much  less  than  in  man. 

132.    INTERNAL    RESPIRATION.— \A^here   CO,  is   formed.— By 

the  term  "internal  respiration  "  is  understood  the  exchange  of  gases  between 
the  capillaries  of  the  systemic  circulation  and  the  tissues  of  the  organs  of  the 
body.  As  organic  constituents  of  the  tissues,  during  their  activity,  undergo 
gradual  oxidation,  and  form  among  other  products,  CO,,;  we  may  assume  (i) 
that  the  chief  focus  for  the  absorption  of  O  and  the  formation  of  CO2  is  to  be 
soueht  for  within  the  tissues  themselves.  That  the  O  from  the  blood  in  the 
capillaries  rapidly  penetrates  or  diffuses  into  the  tissues,  is  shown  by  the  fact  that 
the  blood  in  the  capillaries  rapidly  loses  O  and  gains  CO,,,  while  blood  containing 
O,  and  kept  warm  outside  the  body,  changes  very  slowly  and  incompletely.  If 
portions  of  fresh  tissues  be  placed  in  defibrinated  blood  containing  O,  then  the  O 
rapidly  disai)pears.  Frogs  deprived  of  their  blood  exhibit  an  exchange  of  gases 
almost  as  great  as  normal.  This  shows  that  the  exchange  of  gases  must  take 
place  in  the  tissues  themselves.  If  the  chief  oxidations  took  place  in  the 
blood  and  not  in  the  tissues,  then,  during  suffocation,  when  O  is  excluded,  the 
substances  which  use  up  O,  i.e.,  those  substances  which  act  as  reducing  agents, 
ought  to  accumulate  in  the  blood.  But  this  is  not  the  case,  for  the  blood  of 
asphyxiated  animals  contains  mere  traces  of  reducing  materials  {FJliiger).  It  is 
difficult  to  say  how  the  O  is  absorbed  by  the  tissues,  and  what  becomes  of  it 
immediately  it  comes  in  contact  with  the  living  elements  of  the  tissues.  Perhaps 
it  is  temporarily  stored  up,  or  it  may  form  certain  intertnediate  less  oxidized  com- 
pounds. This  may  be  followed  by  a  period  of  rapid  formation  and  excretion  of 
CO^.  On  this  supposition,  it  is  evident  that  the  absorption  of  O  and  the  excre- 
tion of  CO,  need  not  occur  to  the  same  extent,  so  that  the  amount  of  CO.^  given 
off  at  any  period  is  not  necessarily  an  index  of  the  amount  of  O  absorbed  during 
the  same  period  (§  127). 


TENSION    OF    THE    GASES    IN    CAVITIES    AND    LYMPH.  239 

[There  are  two  views  as  to  where  the  CO2  is  formed  as  the  blood  passes  through 
the  tissues.  One  view  is  that  the  seat  of  oxidation  is  in  the  blood  itself,  and  the 
other  is  that  it  is  formed  in  the  tissues.  If  we  knew  the  tension  of  the  gases  in 
the  tissues,  the  problem  would  be  easily  solved,  but  we  can  only  arrive  at  a  know- 
ledge of  this  subject  indirectly,  in  the  following  ways]  : — 

CO2  in  Cavities. — That  the  CO2  is  formed  in  the  tissues,  is  supported  by  the  fact  that  the 
amount  of  CO2  in  the  fluids  of  the  cavities  of  the  body  is  greater  than  the  CO2  in  the  blood  of  the 
capillaries.     The  tension  of  CO2  in — 

Mm.  I  Mm. 

Arterial  blood,         .         .         12.28  Hg  tension.  |  Bile,         ....  50.0  Hg  tension. 

Peritoneal  cavity,     .  .  58.5     "  "  I  Hydrocele  fluid,        .  .  46.5     "  " 

Acid  urine,  .         .  68.0     "         "  |  {Pfli'tger  and  Slrassburg). 

The  large  amoicnl  of  CO.,  in  these  fluids  can  only  arise  fro7n  the  CO^  of  the  tissues  passing  into 
the7?i. 

Gases  of  Lymph. — In  the  lymph  of  the  ductus  thoracicus  the  tension  of  COj  =  33.4  to  37.2 
mm.  Hg,  which  is  greater  than  in  arterial  blood,  but  considerably  less  than  in  venous  blood  (41.0 
mm.  Hg).  [^Ltidwig  and  Hammarsten,  Tschirjew.']  This  does  not  entitle  us  to  conclude  that  in 
the  tissues  from  M^hich  the  lymph  comes  only  a  small  quantity  of  COj  is  formed,  but  rather  that  in 
the  lymph  there  is  less  attraction  for  the  COj  formed  in  the  tissues  than  in  the  blood  of  the  capil- 
laries, where  chemical  forces  are  active  in  causing  it  to  combine,  or  that  in  the  course  of  the  long 
lymph  current,  the  COj  is  partly  given  back  to  the  tissues,  or  that  CO2  is  formed  in  the  blood  itself. 
Further,  the  m.uscles,  which  are  by  far  the  largest  producers  of  CO3  contain  few  lymphatics,  never- 
theless they  supply  much  CO2  to  the  blood.  The  amount  of  free  "  non-fixed  "  CO2  contained  in  the 
juices  and  tissues  indicates  that  the  COj  passes  from  the  tissues  into  the  blood;  still,  Preyer  believes 
that  in  venous  blood  COj  undergoes  chemical  combination.  The  exchange  of  O  and  COj  varies 
much  in  the  different  tissues.  The  muscles  are  the  most  important  organs,  for  in  their  active  con- 
dition they  excrete  a  large  amount  of  CO2,  and  use  up  much  O.  The  O  is  so  rapidly  used  up  by 
them  that  no  free  O  can  be  pumped  out  of  muscular  tissue  (Z.  Hermattn).  The  exchange  of  gases 
is  more  vigorous  during  the  activity  of  the  tissues.  Nor  are  the  salivary  glands,  kidneys,  and  pan- 
creas any  exception,  for  although,  when  these  organs  are  actively  secreting,  the  blood  flows  out  of 
the  dilated  veins  in  a  bright  red  stream,  still  the  relative  diminution  of  COj  is  more  than  compen- 
sated by  the  increased  volume  of  blood  which  passes  through  these  organs. 

Reductions  by  the  Tissues. — The  researches  of  Ehrlich  have  shown  that  in  most  tissues  very 
energetic  reductions  take  place.  If  coloring  matters,  such  as  alizarin  blue,  indophenol  blue,  or 
methyl  blue,  be  introduced  into  the  blood  stream,  the  tissues  are  colored  by  them.  Those  tissues  or 
organs  which  have  a  particular  affinity  for  O  {e.g.,  liver,  cortex  of  the  kidney,  and  lungs),  absorb  O 
from  these  pigments,  and  render  them  colorless.  The  pancreas  and  sub-maxillary  gland  scarcely 
reduce  them  at  all. 

(2)  In  the  blood  itself,  as  in  all  tissues,  O  is  used  up  and  CO2  is  formed. 
This  is  proved  by  the  following  facts  :  That  blood  withdrawn  from  the  body 
becomes  poorer  in  O  and  richer  in  CO2 ;  that  in  the  blood  of  asphyxia,  free  from 
O,  and  in  the  blood  corpuscles,  there  are  slight  traces  of  reducing  agents,  which 
become  oxidized  on  the  addition  of  O.  Still,  this  process  is  comparatively  insig- 
nificant as  against  that  which  occurs  in  all  the  other  tissues.  That  the  walls  of  the 
vessels — more  especially  the  muscular  fibres  in  the  walls  of  the  small  arteries — use 
O  and  produce  CO2  is  unquestionable,  although  the  exchange  is  so  slight  that  the 
blood  in  its  whole  arterial  course  undergoes  no  visible  change. 

Ludwig  and  his  pupils  have  proved  that  CO2  is  actually  formed  in  the  blood.  If  the  easily  oxidiz- 
able  lactate  of  soda  be  mixed  with  blood,  and  this  blood  be  caused  to  circulate  in  an  excised  but 
living  organ,  such  as  a  lung  or  kidney,  more  O  is  used  up  and  more  COj  is  formed  than  in  unmixed 
blood  similarly  tran.sfused. 

(3)  That  the  tissues  of  the  living  lungs  use  O  and  give  off  CO2  is  probable. 
When  C.  Ludwig  and  Miiller  passed  arterial  blood  through  the  blood  vessels  of  a 
lung  deprived  of  air,  the  O  was  diminished  and  the  CO2  increased.  As  the  total 
amount  of  CO2  and  O  found  in  the  entire  blood  at  any  one  time  is  only  4 
grammes,  and  as  the  daily  excretion  of  CO2  =  900  grammes,  and  the  O  absorbed 
daily  =  744  grammes,  it  is  clear  that  exchange  of  gases  must  go  on  with  great 
rapidity,  that  the  O  absorbed  must  be  used  quickly,  and  the  CO2  must  be  rapidly 
excreted. 


1>4()  RESPIRATION    IN    A    LIMITED    SI'ACE. 

Still,  it  is  a  striking  fact  that  oxidation  processes  of  such  magnitude,  as  <■.(,■-.,  the  union  of  C  to  form 
CO,,  occur  at  the  relatively  low  temperature  of  the  blood  and  tissues.  It  has  been  surmised  that 
the  blood  acts  as  an  ozone  producer,  and  transforms  this  active  form  of  O  to  the  tissues.  Liebig 
showed  that  the  alkaline  reaction  of  most  of  the  juices  and  tissues  favors  the  processes  of  oxidation. 
Numerous  organic  substances,  which  are  not  altered  by  O  alone,  become  rapidly  oxidized  in 
the  presence  of  free  alkalies,  e.g.,  gallic  acid,  pyrogallic  acid,  and  sugar;  while  many  organic 
acids,  which  are  unaffected  by  ozone  alone,  are  changed  into  carbonates  when  in  the  form  of  alka- 
line salts  (  GorupBesanez) ;  and,  in  the  same  way,  when  they  are  introduced  into  the  body  in  the 
form  of  acids,  they  are  partly  or  wholly  excreted  in  the  urine,  but  when  they  are  administered  as 
alkaline  compounds  they  are  changed  into  carbonates. 

133.  RESPIRATION  IN  A  LIMITED  SPACE.— Respiration  in  a 
limited  space  causes  (i)  a  gradual  diminution  of  O  ;  (2)  a  simultaneous  in- 
crease of  CO.^ ;  (3)  a  diminution  in  the  volume  of  the  gases.  If  the  space  be  of 
moderate  dimensions,  the  animal  uses  up  almost  all  the  ©contained  therein,  and 
dies  ultimately  of  spasms  caused  by  the  asphyxia.  The  O  is  absorbed,  therefore — 
independently  of  the  laws  of  absorption — by  chemical  means.  The  O  in  the  blood 
is  almost  completely  used  up  (§  129).  In  a  larger  space,  the  CO.^  accumulates 
rapidly,  before  the  diminution  of  O  is  such  as  to  affect  the  life  of  the  animal.  As 
CO^  can  only  be  excreted  from  the  blood  when  the  tension  of  the  CO.,  in  the  blood 
is  greater  than  the  tension  of  CO.^  in  the  air,  as  soon  as  the  CO.^  m  the  surrounding 
air  in  the  closed  space  becomes  the  same  as  in  the  blood,  the  CO2  will  be  retained 
in  the  blood,  and  finally  CO.^  may  pass  back  into  the  body.  This  occurs  in  a  large 
closed  space,  when  the  amount  of  O  is  still  sufficient  to  support  life,  so  that  death 
occurs  under  these  circumstances  (in  rabbits)  through  poisoning  with  CO.^  causing 
diminished  excitability,  loss  of  consciousness,  and  lowering  of  temperature,  but 
no  spasms  {JVorm  Miiller).  In  pure  O  animals  breathe  in  a  normal  way;  the 
quantity  of  O  absorbed  and  the  CO,,  excreted  is  quite  independent  of  the  percent- 
age of  O,  so  that  the  former  occurs  through  chemical  agency  independent  of  pres- 
sure. In  limited  spaces  filled  with  O,  animals  died  by  absorption  of  the  CO.,, 
excreted.  Worm  Miiller  found  that  rabbits  died  after  absorbing  CO.,,  equal  to  half 
the  volume  of  their  body,  although  the  air  still  contained  50  per  cent.  O.  Animals 
can  breathe  quite  quietly  a  mixture  of  air  containing  14.8  percent.  (20.9  percent, 
normal);  with  7  per  cent,  they  breathe  with  difliculty  ;  with  4.5  per  cent,  there 
is  marked  dyspnoea;  with  3  per  cent.  O  there  is  tolerably  rapid  asphyxia.  The 
air  expired  by  man  normally  contains  1410  18  per  cent.  O.  According  to  Hemp- 
ner,  mammals  placed  in  a  mixture  of  gases  poor  in  O  use  slightly  less  O. 

Dyspnoea  occurs  when  the  respired  air  is  deficient  in  O,  as  well  as  when  it  is  overcharged  with 
CO.^,  but  the  dyspnoea  in  the  former  case  is  prolonged  and  severe ;  in  the  latter,  the  respiratory 
activity  soon  ceases.  The  want  of  O  causes  a  greater  and  more  prolonged  increase  of  the  blood 
pressure  than  is  caused  by  an  excess  of  CO.^.  Lastly,  the  consumption  of  O  in  the  body  is  less 
affected  when  the  O  in  the  air  is  diminished  than  when  there  is  an  excess  of  COj.  If  air  containing 
a  diminished  amount  of  O  be  respired,  death  is  preceded  by  violent  phenomena  of  excitement  and 
spasms,  which  are  absent  in  cases  of  death  caused  by  breathing  air  overcharged  with  COj.  In 
poisoning  with  CO^,  the  excretion  of  COj  is  greatly  diminished,  while  with  diminution  of  O  it  is 
almost  unchanged. 

If  animals  be  supplied  with  a  mixture  of  gases  similar  to  the  atmosphere,  in 
which  N  is  replaced  by  H,  they  breathe  quite  normally  {^Lavoisier  and  Segiiin)  ; 
the  H  undergoes  no  great  change. 

CI.  Bernard  found  that,  when  an  animal  breathed  in  a  limited  space,  it  became  partially  accustomed 
to  the  condition.  On  placing  a  bird  under  a  bell-jar,  it  lived  several  hours  ;  but  if  several  hours 
before  its  death,  another  bird  fresh  from  the  outer  air  were  placed  under  the  same  bell-jar,  the 
second  bird  died  at  once  of  convulsions. 

Frogs,  when  placed  for  several  hours  in  air  devoid  of  O,  give  off  just  as  muchCOj  as  in  air  con- 
taining O,  and  they  do  this  without  any  obvious  disturbance.  Hence,  it  appears  that  the  formation 
of  CO2  is  independent  of  the  absorption  of  O,  and  the  CO^  must  be  formed  from  the  decomposition 
of  other  compounds.  Ultimately,  however,  complete  motor  paralysis  occurs,  while  the  circulation 
remains  undisturbed  {Aubert). 


PHENOMENA   OF   ASPHYXIA.  241 

[134.  DYSPNCEA  AND  ASPHYXIA.— For  the  causes  of  dyspnoea  see 
§  III,  and  those  of  asphyxia  see  §  368.  If  from  any  cause  an  animal  be  not  sup- 
plied with  a  due  amount  of  air,  normal  respiration  becomes  greatly  altered,  passing 
through  the  phases  of  hyperpncEa,  or  increased  respiration,  dyspnoea,  or  diffi- 
culty of  breathing,  to  the  final  condition  of  suffocation  or  asphyxia.  The 
phenomena  of  asphyxia  may  be  developed  by  closing  the  trachea  of  an  animal 
with  a  clamp,  or  by  any  means  which  prevents  the  entrance  of  air  or  blood  into 
the  lungs. 

The  phenomena  of  asphyxia  are  usually  divided  into  several  stages:  i. 
During  the  first  stage  there  is  hyperpnoea,  the  respirations  being  deeper,  more 
frequent,  and  labored.  The  extraordinary  muscles  of  respiration — both  those  of 
inspiration  and  expiration  (§  118) — are  called  into  action,  dyspnoea  is  rapidly 
produced,  and  the  struggle  for  air  becomes  more  and  more  severe.  At  the  same 
time  the  oxygen  of  the  blood  is  being  used  up,  while  the  blood  itself  becomes 
more  and  more  venous.  The  venous  blood  circulating  in  the  medulla  oblongata 
and  spinal  cord  stimulates  the  respiratory  centres,  and  causes  the  violent  respira- 
tions.    This  stage  usually  lasts  about  a  minute,  and  gradually  gives  place  to — 

2.  The  second  stage,  when  the  inspiratory  muscles  become  less  active,  while 
those  concerned  in  labored  expiration  contract  energetically,  and  indeed  almost 
every  muscle  in  the  body  may  contract ;  so  that  this  stage  of  violent  expiratory 
efforts  ends  in  general  convulsions.  The  convulsions  are  due  to  stimulation  of 
the  respiratory  centres  by  the  venous  blood.  The  convulsive  stage  is  short,  and 
is  usually  reached  in  a  little  over  one  minute.     This  storm  is  succeeded  by — 

3.  The  third  stage,  or  stage  of  exhaustion,  the  transition  being  usually  some- 
what sudden.  It  is  brought  about  by  the  venous  blood  acting  on  and  paralyzing 
the  respiratory  centres.  The  pupils  are  widely  dilated,  consciousness  is  abolished, 
and  the  activity  of  the  reflex  centres  is  so  depressed  that  it  is  impossible  to  dis- 
charge a  reflex  act,  even  from  the  cornea.  The  animal  lies  almost  motionless, 
with  flaccid  muscles,  and  to  all  appearance  dead,  but  every  now  and  again,  at 
long  intervals,  it  makes  a  few  deep  inspiratory  efforts,  showing  that  the  respira- 
tory centres  are  not  quite,  but  almost  paralyzed.  Gradually  the  pauses  become 
longer  and  the  inspirations  feebler  and  of  a  gasping  character.  As  the  venous 
blood  circulates  in  the  spinal  cord,  it  causes  a  large  number  of  muscles  to  con- 
tract, so  that  the  animal  extends  its  trunk  and  limbs.  It  makes  one  great  inspira- 
tory spasm,  the  mouth  being  widely  opened  and  the  nostrils  dilated,  and  ceases 
to  breathe.  After  this  stage,  which  is  the  longest  and  most  variable,  the  heart 
becomes  paralyzed,  partly  from  being  over-distended  with  venous  blood,  and 
partly,  perhaps,  from  the  action  of  the  venous  blood  on  the  cardiac  tissues,  so 
that  the  pulse  can  hardly  be  felt.  To  this  pulseless  condition  the  term 
"asphyxia  "  ought  properly  to  be  applied.  In  connection  with  the  resuscitation 
of  asphyxiated  persons,  it  is  important  to  note  that  the  heart  continues  to  beat 
for  a  few  seconds  after  the  respiratory  movements  have  ceased. 

The  whole  series  of  phenomena  occupies  from  3  to  5  minutes,  according  to  the 
animal  operated  on,  and  depending  also  upon  the  suddenness  with  which  the 
trachea  was  closed.  If  the  causes  of  suffocation  act  more  slowly,  the  phenomena 
are  the  same,  only  they  are  developed  more  slowly. 

The  Circulation. — The  post-mortem  appearances  in  man  or  in  an  animal  are 
generally  well  marked.  The  right  side  of  the  heart,  the  pulmonary  artery,  the 
venge  cavse,  and  the  veins  of  the  neck  are  engorged  with  dark  venous  blood. 
The  left  side  is  comparatively  empty,  because  the  rigor  mortis  of  the  left  side  of 
the  heart,  and  the  elastic  recoil  of  the  systemic  arteries,  force  the  blood  toward 
the  systemic  veins.  The  blood  itself  is  almost  black,  and  is  deprived  of  almost 
all  its  oxygen,  its  haemoglobin  being  nearly  all  in  the  condition  of  reduced 
haemoglobin,  while  ordinary  venous  blood  contains  a  considerable  amount  of 
oxyhsemoglobin  as  well  as  reduced  Hb.  The  blood  of  an  asphyxiated  animal 
16 


242         THE    CHANGES   OF   THE    CIRCULATION    DURING    ASPHYXIA. 

practically  contains  none  of  the  former  and  much  of  the  latter.  It  is  important 
to  study  the  changes  in  the  circulation  in  relation  to  phenomena  exhibited  by  an 
animal  during  suffocation. 

We  may  measure  the  blood  pressure  in  any  artery  of  an  animal  while  it  is  being 
asphvxiated,  or  we  may  oj^en  its  chest,  maintain  artificial  res|)iration,  and  place  a 
manometer  in  a  systemic  artery,  e.  g.,  the  carotid,  and  another  in  a  branch  of  the 
pulmonary  artery.  In  the  latter  case,  we  can  watch  the  order,  of  events  in  the 
heart  itself,  when  the  artificial  respiration  is  interrupted.  It  is  well  to  study  the 
events  in  both  cases. 

If  the  blood  pressure  be  measured  in  a  systemic  artery,  e.  g.,  the  carotid,  it 
is  found  tiiat  the  blood  pressure  rises  very  rapidly,  and  to  a  great  extent  during 
the  first  and  second  stages ;  the  pulse  beats  at  first  are  quicker,  but  soon  become 
slower  and  more  vigorous.  During  the  third  stage  it  falls  rapidly  to  zero.  The 
threat  rise  of  the  blood  pressure,  during  the  first  and  second  stages,  is  chiefly  due 
to  the  action  of  the  venous  blood  on  the  general  vasomotor  centre,  causing  con- 
striction of  the  small  systemic  arteries.  The  peripheral  resistance  is  thus  greatly 
increased,  and  it  tends  to  cause  the  heart  to  contract  more  vigorously,  but  the 
slower  and  more  vigorous  beats  of  the  heart  are  also  partly  due  to  the  action  of 
the  venous  blood  on  the  cardio-inhibitory  centre  in  the  medulla. 

If  the  second  method  be  adopted,  viz.,  to  open  the  chest,  keep  up  artificial 
respiration,  and  measure  the  blood  pressure  in  a  branch  of  the  pulmonary  artery, 
as  well  as  in  a  systemic  artery — e.  g.,  the  carotid — we  find  that  when  the  artificial 
respiration  is  stopped,  in  addition  to  the  rise  of  the  blood  pressure  indicated  in 
the  carotid  manometer,  the  cavities  of  the  heart  and  the  large  veins  near  it  are 
engorged  with  venous  blood.  There  is,  however,  but  a  slight  comparative  rise 
in  the  blood  pressure  in  the  pulmonary  artery.  This  may  be  accounted  for,  either 
by  the  pulmonary  artery  not  being  influenced  to  the  same  extent  as  other  arteries 
by  the  vasomotor  centre,  or  by  its  greater  distensibility  (§  88).  But,  as  the  heart 
itself  is  supplied  through  the  coronary  arteries  with  venous  blood,  its  action  soon 
becomes  weakened,  each  beat  becomes  feebler,  so  that  soon  the  left  ventricle 
ceases  to  contract,  and  is  unable  to  overcome  the  great  peripheral  resistance  in 
the  systemic  arteries,  although  the  right  ventricle  may  still  be  contracting.  As 
the  blood  becomes  more  venous,  the  vasomotor  centre  becomes  paralyzed,  the 
small  systemic  arteries  relax,  and  the  blood  flows  from  them  into  the  veins,  while 
the  blood  pressure  in  the  carotid  manometer  rapidly  falls.  The  left  ventricle, 
now  relieved  from  the  great  internal  pressure,  may  execute  a  few  feeble  beats,  but 
they  can  only  be  feeble,  as  its  tissues  have  been  subjected  to  the  action  of  the 
very  impure  blood.  More  and  more  blood  accumulates  in  the  right  side  from 
the  causes  already  mentioned.  The  violent  inspiratory  efforts  in  the  early  stages 
aspirate  blood  from  the  veins  toward  the  right  side  of  the  heart,  but  of  course 
this  factor  is  absent  when  the  chest  is  opened.] 

[Convulsions  during  asphyxia  occur  only  in  warm-blooded  animals,  and  not 
in  frogs.  If  a  drug  when  injected  into  a  mammal  excites  convulsions,  but  does 
not  do  so  in  the  frog,  then  it  is  usually  concluded  that  the  convulsions  are  due 
to  its  action  on  the  circulation  and  respiration,  and  not  to  any  direct  stirnulating 
effect  upon  the  motor  centres.  But  if  the  drug  excites  convulsions  both  in  the 
mammal  and  frog,  then  it  probably  acts  directly  on  the  motor  centres  {J3runtoti).~\ 

[Recovery  from  the  condition  of  Asphyxia. — If  the  trachea  of  a  dog  be  closed  suddenly 
and  compleiely,  the  average  duration  of  the  respiratory  movements  is  4  minutes  5  seconds,  while 
the  heart  continues  to  beat  for  about  7  minutes.  Recovery  may  be  obtained  if  proper  means  be 
adopted  before  the  heart  ceases  to  beat;  but  after  this,  never.  If  a  dog  be  drowned,  the  result  is 
different.  After  complete  submersion  for  i^  minutes,  recovery  did  not  take  place.  In  drown- 
ing, air  passes  out  of  the  chest,  and  water  is  inspired  into  and  fills  the  air  vesicles.  It  is  rare 
for  recovery  to  take  place  in  a  person  deprived  of  air  for  more  than  five  minutes.  If  the  state- 
ments of  sponge  divers  are  to  be  trusted,  a  person  may  become  accustomed  to  the  deprival  of  air 
for  a  longer  time  than  usual.     In  cases  where  recovery  takes  place  after  a  much  longer  period  of 


ARTIFICIAL    RESPIRATION    IN    ASPHYXIA,  243 

submersion,  it  has  been  suggested  that,  in  these  cases,  syncope  occurs,  the  heart  beats  but  feebly 
or  not  at  all,  so  that  the  oxygen  in  the  blood  is  not  used  up  with  the  same  rapidity.  It  is  a 
well-known  fact  that  newly- born  and  young  puppies  can  be  submerged  for  a  long  time  before 
they  are  suffocated.] 

Artificial  Respiration  in  Asphyxia. — In  cases  of  suspended  animation,  artificial  respiration 
must  be  performed.  The  first  thing  to  be  done  is  to  remove  any  foreign  substance  from  the  respira- 
tory passages  (mucus  or  oedematous  fluids)  in  the  newly-born  or  asphyxiated.  In  doubtful  cases, 
open  the  trachea  and  suck  out  any  fluid  by  means  of  an  elastic  catheter  {v.  Hiiter').  Recourse 
must  in  all  cases  be  had  to  artificial  respiration.  There  are  several  methods  of  dilating  and 
compressing  the  chest  so  as  to  cause  an  exchange  of  gases.  One  method  is  to  compress  the  chest 
rhythmically  with  the  hands. 

[Marshall  Hall's  Method. — "After  clearing  the  mouth  and  throat,  place  the  patient  on  the 
face,  raising  and  supporting  the  chest  well  on  a  folded  coat  or  other  article  of  dress.  Turn  the  body 
very  gently  on  the  side  and  a  little  beyond,  and  then  briskly  on  the  face,  back  again,  repeating  these 
measures  cautiously,  efficiently,  and  perseveringly,  about  fifteen  times  in  the  minute,  or  once  every 
four  or  five  seconds,  occasionally  varying  the  side.  By  placing  the  patient  on  the  chest,  the  weight 
of  the  body  forces  the  air  out ;  when  turned  on  the  side,  this  pressure  is  removed,  and  air  enters  the 
chest.  On  each  occasion  that  the  body  is  replaced  on  the  face,  make  uniform  but  efficient  pressure 
with  brisk  movement  on  the  back  between  and  below  the  shoulder  blades  or  bones  on  each  side, 
removing  the  pressure  immediately  before  turning  the  body  on  the  side.  During  the  whole  of  the 
operations  let  one  person  attend  solely  to  the  movements  of  the  head  and  of  the  arm  placed 
under  it."] 

[Sylvester's  Method. — "Place  the  patient  on  the  back  on  the  flat  surface,  inclined  a  little 
upward  from  the  feet ;  raise  and  support  the  head  and  shoulders  on  a  small  firm  cushion  or  folded 
article  of  dress  placed  under  the  shoulder-blades.  Draw  forward  the  patient's  tongue,  and  keep  it 
projecting  beyond  the  lips;  an  elastic  band  over  the  tongue  and  under  the  chin  will  answer  this 
purpose,  or  a  piece  of  string  or  tape  may  be  tied  round  them,  or  by  raising  the  lower  jaw  the  teeth 
may  be  made  to  retain  the  tongue  in  that  position.  Remove  all  tight  clothing  from  about  the  neck 
and  chest,  especially  the  braces."  "  To  Imitate  the  Alovenients  of  Breathing. — Standing  at  the 
patient's  head  grasp  the  arms  just  above  the  elbows,  and  draw  the  arms  gently  and  steadily  upward 
above  the  head,  and  keep  them  stretched  upward  for  two  seconds.  By  this  means  air  is  drawn  into 
the  lungs.  Then  turn  down  the  patient's  arms,  and  press  them  gently  and  firmly  for  two  seconds 
against  the  sides  of  the  chest.  By  this  means  air  is  pressed  out  of  the  lungs.  Repeat  these 
measures  alternately,  deliberately,  and  perseveringly  about  fifteen  times  in  a  minute,  until  a  sponta- 
neous effort  to  respire  is  perceived,  immediately  upon  which  cease  to  imitate  the  movements  of 
breathing,  and  proceed  to  induce  circulation  a7id  zvarmtk"~\ 

Howard  advises  rhythmical  compression  of  the  chest  and  abdomen  by  sitting  like  a  rider  astride 
of  the  body,  while  Schiiller  advises  that  the  lower  ribs  be  seized  from  above  with  both  hands  and 
raised,  whereby  the  chest  is  dilated,  especially  when  the  thigh  is  pressed  against  the  abdomen  to 
compress  the  abdominal  walls.  The  chest  is  compressed  by  laying  the  hands  flat  upon  the  hypo- 
chondria. Artificial  respiration  acts  favorably  by  supplying  O  to,  as  well  as  removing  COj  from,  the 
blood ;  further,  it  aids  the  movement  of  the  blood  within  the  heart  and  in  the  large  vessels  of  the 
thorax.  If  the  action  of  the  heart  has  ceased,  recovery  is  impossible.  In  asphyxiated  newly-born 
children,  we  must  not  cease  too  soon  to  perform  artificial  respiration.  Even  when  the  result  appears 
hopeless,  we  ought  to  persevere.  PHiiger  and  Zuntz  observed  that  the  reflex  excitability  of  the  fcetal 
heart  continued  for  several  hours  after  the  death  of  the  mother. 

Resuscitation  by  compressing  the  heart. — Bohm  found  that  in  the  case  of  cats  poisoned  with 
potash  salts  or  chloroform,  or  asphyxiated,  so  as  to  arrest  respiration  and  the  action  of  the  heart — 
even  for  a  period  of  forty  minutes — and  even  when  the  pressure  within  the  carotid  had  fallen  to 
zero,  he  could  restore  animation  by  rhytlunical  compression  of  the  heart,  combined  with  artificial 
respiration.  The  compression  of  the  heart  causes  a  slight  movement  of  the  blood,  while  it  acts  at 
the  same  time  as  a  rhythmical  cardiac  stimulus.  After  recovery  of  the  respiration,  the  reflex  excita- 
bility and  gradually  also  voluntary  movements  are  restored.  The  animals  are  blind  for  several  days, 
the  brain  acts  slowly,  and  the  urine  contains  sugar.  These  experiments  show  how  important  it  is 
in  cases  of  asphyxia  to  act  at  the  same  time  upon  the  heart. 

For  physiological  purposes,  artificial  respiration  is  often  made  use  of,  especially  after  poi- 
soning with  curara.  Air  \%  forced  into  the  lungs  by  means  of  an  elastic  bag  or  bellows,  attached  to 
a  cannula  tied  in  the  trachea.  The  cannula  has  a  small  opening  in  the  side  of  it  to  allow  the 
expired  air  to  escape. 

Pathological.  — After  the  lungs  have  once  been  properly  distended  with  air,  it  is  impossible  by 
any  amount  of  direct  compression  of  them  to  get  rid  of  all  the  air.  This  is  probably  due  to  the 
pressure  acting  on  the  small  bronchi,  so  as  to  squeeze  them,  before  the  air  can  be  forced  out  of  the 
air  vesicles.  If,  however,  a  lung  be  filled  with  CO.,,  and  be  suspended  in  water,  the  CO2  is  absorbed  by 
the  water,  and  the  lungs  become  quite  free  from  air  and  are  atelectic  [Hermann  and  Kellej-).  '  The 
atelectasis,  which  sometimes  occurs  in  the  lung,  may  thus  be  explained  :  If  a  bronchus  is  stopped 
with  mucus  or  exudation,  CO.,  accumulates  in  the  air  vesicles  belonging  to  this  bronchus.     If  the 


244  ACCIDENTAL    IMPURITIES   OF    THE    AIR. 

CO  is  absorbed  by  ihe  blood  or  lymph,  the  corresponding  area  of  the  lung  will  become  atelectic. 
Sometimes  there  is  spasm  of  the  respiratory  muscles,  brouglit  about  by  direct  or  reflex  stimulation 
of  the  respiratory  centre. 

135.  RESPIRATION  OF  FOREIGN  GASES. — No  gas  wiihout  a  sufficient  admixture 
of  O  can  support  life.  Even  with  completely  innocuous  and  indifTerent  gases,  if  no  O  be  mixed 
with  tlitni,  thev  cause  sutTocation  in  2  to  3  minutes. 

I.  Completely  indifferent  Gases  are  N,  H,  CH^.  The  living  blood  of  an  animal  breathing 
these  gases  yields  no  O  to  them  {/'/liii^c!). 

II.  Poisonous  Gases. — O  displacing  Gases. — {a)  Those  that  displace  O,  and  form  a  stable 
compound  with  tlie  ha'moglobin  (I)  CO  (j;^  1 6  and  17).  (2)  CNIl  (hydrocyanic  acid)  displaces  (?) 
O  Irom  hremoglobm,  forming  a  more  stable  compound,  and  kdls  exceedingly  rapidly.  Blood 
corpuscles  charged  with  hydrocyanic  acid  lose  the  property  of  decomposing  hydric  peroxide  into 

water  and  O  ({;  I7<  5)- 

{b)  Narcotic  Gases.— (i)  CO.^. — v.  Peltenkofer  characterizes  atmospheric  air  containing  .1  per 
cent.  CO.,  as  "bad  air;"  still,  air  in  a  room  containing  this  amount  of  CO.,  produces  a  disagreeable 
feeling,  rather  from  the  impurities  mixed  with  it  than  from  the  actual  amount  of  CO.^  itself.  Air 
contaming  i  per  cent.  CO.,  produces  decided  discomfort,  and  with  10  per  cent,  it  endangers  life, 
while  larger  amounts  cause  death,  with  symptoms  of  coma.  (2)  N,/J  (nitrous  oxide),  respired, 
mixed  with  \  volume  O,  causes,  after  i  to  2  minutes,  a  short  temporary  stage  of  excitement  ^"  Laugh- 
ing gas"  oflL  Davy),  which  is  succeeded  by  unconsciousness,  and  afterward  by  an  increased 
excretion  of  CO.^.     (3)  Ozonized  air  causes  similar  effects  [Binz). 

{c)  Reducing  Gases. — (i)  H.^S  (sulphuretted  hydrogen)  rapidly  robs  blood  corpuscles  of  O, 
S  and  I1.,0  being  formed,  and  death  occurs  rapidly  before  the  gas  can  decompose  the  hivmoglobin 
to  form  a  sulphur-metha-moglobin  compound. 

(2)  PH3  (phosphuretted  hydrogen)  is  oxidized  in  the  blood  to  form  phosphoric  acid  and  water, 
with  decomposition  of  the  hamoglobin. 

(3)  AsH,  (arseniuretted  hydrogen)  and  SbH.,  (antimoniuretted  hydrogen)  act  like  PH3,  but  the 
hcemoglobin  passes  out  of  the  stroma  and  appears  in  the  urine. 

(4)  CNj  (cyanogen)  absorbs  O,  and  decomposes  the  blood. 

III.  iVrespirable  Gases,  z.  1?.,  gases  which,  on  entering  the  larynx,  cause  reflex  spasm  of  the 
glottis.  When  introduced  into  the  trachea,  they  cause  inflammation  and  death.  Under  this  cate- 
gory come  hydrochloric,  hydrofluoric,  sulphurous,  nitrous,  and  nitric  acids,  ammonia,  chlorine, 
fluorine,  and  ozone. 

136.  ACCIDENTAL  IMPURITIES  OF  THE  AIR.— Among  these  are  dust  particles, 
which  occur  in  enormous  amount  suspended  in  the  air,  and  thereby  act  injuriously  upon  llie  respi- 
ratory  organs.  The  ciliated  epithelium  of  the  respiratory  passages  eliminates  a  large  number  of 
them  (Pig.  148).     Some  of  them,  however,  reach  the  air  vesicles  of  the  lung,  where  they  penetrate 

the  epithelium, reach  the  interstitial  lung 
Fig.  148.  tissue  and  lymphatics,  and  so  pass  with 

.f,,    ,,  the    lymph  stream    into  the    bronchial 

,    i^.^Cll'Ii7il7v/"it;,  u,,,  glands.      Vziruclts  o(  coal  or  c/iarcoal 

Epithelium.  ■-    ;        r  ■-:-'  -'-    -L^i^. ^  ^_^^        are  found  in  the  lungs  of  all  elderly  in- 

"    '  ■  ^1  ^^^    '^  ■       dividuals,  and  blacken  the  alveoli.      In 

x'M  moderate  amount,  these  black  particles 

do  not  seem  to  do  any  harm  in  the  tis- 

\  sues,  but  when  there  are  large  accumu- 


VVVj*!^'  '  l^   '^'^Ari '  Intermedi-       lations  they  give  rise  to  lung  afiections, 

^    ■s^;^.''^'.:-'f):f^^         ate  forms.        which   lead  to   disintegration   of   these 
r),:hnvr'<:  ^^i  t         i  orijans.     [In  coal  miners,  for  example, 

i_/cuovc  s   -,    ^^  ^  -Oi". — • Inner  layer  ^  *-  ,  1       r     1. 

Membrane.  "  ^         _     ~%  -^^^  the  lung  tissues  along  the  track  ot  the 

Ciliated  tpithelium.  lymphatics  and  in  the  bronchial  glands 

are  quite  black,  constituting  '-coal 
miners'  lung."]  In  many  trades  various  particles  occur  in  the  air;  miners,  grinders,  .stone 
masons,  file  makers,  weavers,  si)inners,  tobacco  manufacturers,  millers,  and  bakers  suffer  fr<;m  lung 
afl'ections  caused  by  the  introduction  of  particles  of  various  kinds  inhaled  during  the  lime  they 
are  at  work. 

Germs. — There  seems  no  doubt  that  the  seeds  of  some  contagious  diseases  may  be  inhaled. 
Diphtheritic  bacteria  (Bacillus  diphtheria?)  become  localized  in  the  pharynx  and  in  the  larynx — 
glanders  in  the  nose — measles  in  the  bronchi — whooping  cough  in  the  bronchi — hay  monads  in 
the  nose— the  Bacillus  pneumoniae  of  pneumonia  in  the  pulmonary  alveoli.  Tuberculosis,  accord- 
mg  to  R.  Koch,  is  due  to  the  introduction  and  development  of  the  Bacillus  tuberculosis  in  the 
lungs,  the  bacillus  being  derived  from  the  dust  of  tuberculous  sputa.  The  same  seems  to  be  the 
case  with  the  Bacillus  of  leprosy  and  with  Bacillus  malaria,  which  is  the  cause  of  malaria.  The 
latter  organism  thus  reaches  the  blood  ;  it  changes  the  Hb  within  the  red  blood  corpuscles  into 
melanin  (|  10,  3),  and   causes  them  to  break  up.     The   Micrococcus  vaccinae  of  smallpox  gains 


VENTILATION    OF    ROOMS.  245 

access  to  the  blood  in  the  same  way,  also  the  Spirillum  of  remittent  fever  (Fig.  23),  the  Microbe  of 
scarlet  fever,  etc. 

Seeds  of  disease  passing  into  the  mouth  along  w^ith  air,  and  also  with  the  food,  are  swallowed, 
and  undergo  development  in  the  intestinal  tract,  as  is  probably  the  case  in  cholera  (Comma  bacillus 
of  R.  Koch),  dysentery,  typhoid,  and  anthrax  which  is  due  to  Bacterium  anthracis  (Fig.  24). 

137.  VENTILATION  OF  ROOMS. — Fresh  air  is  as  necessary  for  the  healthy  as  for  the 
sick.  Every  healthy  person  ought  to  have  a  cubic  space  of  at  the  very  least  800  cubic  feet,  and 
every  sick  person  at  the  very  least  1000  cubic  feet  of  space.  [The  cubic  space  allowed  per 
individual  varies  greatly,  but  1 000  cubic  feet  is  a  fair  average.  If  the  air  in  this  space  is  to  be 
kept  sweet,  so  that  the  CO.^  does  not  exceed  .06  per  cent.,  3000  cubic  feet  of  air  per  hour  must  be 
supplied,  i.  e.,  the  air  in  the  space  must  be  renewed  three  times  per  hour.] 

[Floor  Space. — It  is  equally  important  to  secure  sufficient  floor  space,  and  this  is  especially  the 
case  in  hospitals.  If  possible,  100-120  square  feet  of  floor  space  ought  to  be  provided  for  each 
patient  in  a  hospital  ward,  and  if  it  is  obtainable  a  cubic  space  of  1500  cubic  feet  (^Pa7'kes).  In 
all  cases  the  minimum  floor  space  should  not  be  less  than  J^  of  the  cubic  space.] 

Overcrowding. — When  there  is  overcrowding  in  a  room,  the  amount  of  COj  increases,  v. 
Pettenkofer  found  the  normal  amount  of  CO.,  (.04  to  .05  per  1000)  increased  in  comfortable  rooms 
to  0.54-0.7  per  1000 ;  in  badly  ventilated  sick  chambers  =  2.4;  in  overcrowded  auditoriums,  32; 
in  pits  =  4.9  ;  in  school  rooms,  7.2  per  1000.  Although  it  is  not  the  quantity  of  CO.,  which  makes 
the  air  of  an  overcrowded  room  injurious,  but  the  excretions  from  the  outer  and  inner  surfaces  of 
the  body,  which  give  a  distinct  odor  to  the  air,  quite  recognizable  by  the  sense  of  smell,  still  the 
amount  of  CO.^  is  taken  as  an  index  of  the  presence  and  amount  of  these  other  deleterious  sub- 
stances. Whether  or  not  the  ventilation  of  a  room  or  ward  occupied  by  persons  is  sufficient,  is  as- 
certained by  estimating  the  amount  of  COj.  A  room  which  does  not  give  a  disagreeable,  somewhat 
stuffy,  odor  has  less  than  0.7  per  1000  of  C0,2,  while  the  ventilation  is  certainly  insufficient  if  the 
CO2  =  I  per  1000.  As  the  air  contains  only  0.0005  cubic  metre  COj  in  i  cubic  metre  of  air,  and 
as  an  adult  produces  hourly  0.0226  cubic  metres  CO2,  calculation  shows  that  every  person  requires 
113  cubic  metres  of  fresh  air  per  hour,  if  the  COj  is  not  to  exceed  0.7  per  1000 ;  for  0.7  :  1000  =^ 
(0.0226  -(-  X  X  0.0005)  •  -^j  ^-  ^•,x=  113. 

[Vitiating  Products. — In  a  state  of  repose,  an  adult  man  gives  off  from  12  to  16  cubic  feet  of 
COj  in  twenty-four  hours,  or  on  an  average  .6  cubic  feet  per  hour.  To  this  must  be  added  a 
certain  quantity  of  organic  matter,  which  is  extremely  deleterious  to  health.  While  the  COj  dif- 
fuses readily  and  is  easily  disposed  of  by  opening  the  windows,  this  is  not  the  case  with  the  organic 
matter,  which  adheres  to  clothing,  curtains,  and  furniture;  hence,  to  get  rid  of  it,  a  room,  and  espe- 
cially a  sleeping  apartment,  requires  to  be  well  aired  for  a  long  time,  together  with  the  free  admission 
of  sunlight.  We  must  also  remember  that  an  adult  gives  off"  from  25  to  40  oz.  of  water  by  the 
skin  and  lungs.  The  nature  of  the  organic  matters  is  not  precisely  known,  but  some  of  it  is  par- 
ticulate, consisting  of  epithelium,  fatty  matters,  and  organic  vapors  from  the  lungs  and  mouth.  It 
blackens  sulphuric  acid,  and  decolorizes  a  weak  solution  of  potassic  permanganate.  As  a  test,  if 
we  expire  through  distilled  water,  and  this  water  be  set  aside  for  some  time  in  a  warm  place,  it  will 
soon  become  fcetid.  We  must  al^o  take  into  consideration  the  products  of  combustion  ;  thus  i 
cubic  foot  of  coal  gas,  when  burned,  destroys  all  the  O  in  8  cubic  feet  of  air  {Pa7'kes).'\ 

Methods. — In  ordinary  rooms,  where  every  person  is  allowed  the  necessary  cubic  space  (looo 
cubic  feet),  the  air  is  sufficiently  renewed  by  means  of  the  pores  in  the  walls  of  the  room,  by  the 
opening  and  shutting  of  doors,  and  by  the  fireplace,  provided  the  damper  is  kept  open.  It  is  most 
important  to  notice  that  the  natural  ventilation  be  not  interfered  with  by  dampness  of  the  walls,  for 
this  influences  the  pores  very  greatly.  At  the  same  time,  damp  walls  are  injurious  to  health  by  con- 
ducting away  heat,  and  in  them  the  germs  of  infectious  diseases  may  develop. 

[Natural  Ventilation. — By  this  term  is  meant  the  ventilation  brought  about  by  the  ordinary 
forces  acting  in  nature ;  such  as  diffusion  of  gases,  the  action  of  winds,  and  the  movements  excited 
■owing  to  the  different  densities  of  air  at  unequal  temperatures.] 

[Artificial  Ventilation. — Various  methods  are  in  use  for  ventilating  public  buildings  and  dwell- 
ing houses.  Two  principles  are  adopted  for  the  former,  viz.,  extraction  and  propulsion  of  air. 
In  the  former  method,  the  air  is  sucked  out  of  the  rooms  by  a  fan  or  other  apparatus,  while  in  the 
latter,  air  is  forced  into  the  rooms,  the  air  being  previously  heated  to  the  necessary  temperature.] 

[A  very  convenient  method  of  introducing  air  into  a  room  is  by  means  of  Tobin's  tubes, 
placed  in  the  walls.  The  air  enters  through  these  tubes  from  the  outside  near  the  floor,  and  is  car- 
ried up  six  or  more  feet,  to  an  opening  in  the  wall ;  the  cool  air  thus  descends  slowly.  For  a  sit- 
ting room,  a  convenient  plan  of  window  ventilation  is  H.  Bird's  Method  :  Raise  the  lower  sash 
and  place  under  it,  so  as  to  fill  up  the  opening,  a  piece  of  wood  3  or  4  inches  high.  Air  will  then 
pass  in,  in  an  upward  direction,  between  the  upper  part  of  the  lower  sash  frame  and  the  lower  part 
of  the  upper  one.] 

138.  FORMATION  OF  MUCUS— SPUTUM.— The  respiratory  mucous 

membrane  is  covered  normally  with  a  thin   layer  of  mucus  (Fig,  130,  a).     It  so 
far  inhibits  the  formation  of  new  mucus  by  protecting  the  mucous  glands  from  the 


246 


THE    SPUTUM. 


action  of  cold  or  other  irritative  agents.  New  mucus  is  secreted  as  that  already 
formed  is  removed.  An  increased  secretion  accompanies  congestion  of  the  res- 
piratory mucous  membrane  [or  any  local  irritation].  Division  of  the  nerves  on 
one  side  of  the  trachea  (cat)  causes  redness  of  the  tracheal  mucous  membrane  and 
increased  secretion  {Ross(?iuh),  [but  the  two  processes  do  not  stand  in  the  relation 
of  cause  and  effect].  [The  secretion  cannot  be  excited  by  stimulating  the  nerves 
going  to  the  mucous  membrane.  This  merely  causes  anaemia  of  the  mucous 
membrane,  while  the  secretion  continues]. 

Modifying  Conditions. — If  ice  be  placed  on  the  belly  of  an  aniinal  so  as  to  cause  the  animal 
"  to  take  (7  cold,"  the  respiratory  mucous  membrane  first  becomes  pale,  and  afterward  there  is  a 
copious  mucous  secretion,  the  membrane  becoming  deeply  congested.  The  injection  of  sodium 
carbonate  and  ammonium  chloride  into  the  blood  limits  the  secretion.  The  local  application  of 
alum,  silver  nitrate,  or  tannic  acid,  makes  the  mucous  membrane  turbid,  and  the  epithelium  is  shed. 
The  secretion  is  excited  by  apomorphin,  emetin,  pilocarpin,  and  ipecacuanha  when  given  internally, 
while  it  is  limited  by  atropin  and  morphia  [Hossbach). 

Fig.  149. 


Variou<;  objects  found  in  sputum,  i,  detritus  and  particles  of  dust :  2,  alveolar  epithelium  with  pigment;  3,  fatty 
and  pigmented  alveolar  epithelium  ;  4,  alveolar  epithelium  with  myclin-forms ;  5,  free  myelin-forms  ;  6,  7,  ciliated 
epithelium,  some  without  cilia;  8,  squamous  epithelium  from  the  mouth;  9,  leucocytes  ;  10,  elastic  fihres;  ii, 
fibrin  cast  of  a  small  bronchus  ;  12,  leptothrix  buccalis  with  cocci,  bacteria,  and  spirocha;tae  ;  a,  fatty  acid  crys- 
tals and  free  fatty  granules  ;  b,  ha:matoidin ;  c,  Charcot's  crystals  ;  d,  cholesterin. 

[Expectorants  favor  the -removal  of  the  secretions  from  the  air  passages.  This  they  may  do 
either  by  {a)  altering  the  character  and  qualities  of  the  secretion  itself,  or  {b)  by  affecting  the  expul- 
sive  mechanism.  Some  of  the  drugs  already  mentioned  are  examples  of  the  first  class.  The  second 
class  act  chiefly  by  influencing  the  respiratory  centre,  e.  g.,  ipecacuanha,  strychnia,  ammonia, 
senega;  emetics  also  act  energetically  as  expectorants,  as  in  some  cases  of  chronic  bronchitis; 
warmth  and  moisture  in  the  air  are  also  powerful  adjuncts.] 

Sputum. — Under  normal  circumstances,  some  mucus — mixed  with  a  little 
saliva — may  be  coughed  up  from  the  back  of  the  throat.  In  catarrhal  conditions 
of  the  respiratory  mucous  membrane,  the  sputum  is  greatly  increased  in  amount, 
and  is  often  mixed  with  other  characteristic  products.  Microscopically,  sputum 
contains — 

I.  Epithelial  Cells,  chiefly  squames  from  the  mouth  and  pharynx  (Fig.  149), 
more  rarely  alveolar  epithelium  and  ciliated  epithelium  (7)  from  the  respiratory 


ACTION    OF   THE    ATMOSPHERIC    PRESSURE.  247, 

passages.  They  are  often  altered  owing  to  maceration  or  other  changes.  Thus 
some  cells  may  have  lost  their  cilia  (6). 

The  epithelium  of  the  alveoli  (2)  is  squamous  epithelium,  the  cells  being  two  to- four  times 
the  breadth  of  a  colorless  blood  corpuscle.  These  cells  occur  chiefly  in  the  morning  sputum  in 
individuals  over  30  years  of  age.  In  younger  persons  their  presence  indicates  a  pathological  con- 
dition of  the  pulmonary  parenchyma. 

They  often  undergo  fatty  degeneration,  and  they  may  contain  pigment  granules  (3) ;  or  they  may 
present  the  appearance  of  what  Buhl  has  called  '■'■  viyeliii  degenerated  cells"  i.e.,  cells  filled  with 
clear  refractive  drops  of  various  sizes,  some  colorless,  others  with  colored  particles,  the  latter  having 
been  absorbed  (4).     Mucin  in  the  form  of  myelin  drops  (5)  is  always  present  in  sputum. 

2.  Lymphoid  cells  (9)  are  colorless  blood  corpuscles  which  have  wandered 
out  of  the  blood  vessels ;  they  are  most  numerous  in  yellow  sputum,  and  less 
numerous  in  the  clear,  mucus-like  excretion.  The  lymph  cells  often  present  altera- 
tions in  their  characters ;  they  may  be  shriveled  up,  fatty,  or  presei:it  a  granular 
appearance. 

The  fluid  substance  of  the  sputum  contains  much  mucus,  arising  from  the 
mucous  glands  and  goblet  cells,  together  with  nuclein,  and  lecithin,  and  the  con- 
stituents of  saliva,  according  to  the  amount  of  the  latter  mixed  with  the  secretion. 
Allmtiiin  occurs  only  during  the  inflammation  of  the  respiratory  passages,  and  its 
amount  increases  with  the  degree  of  inflammation.  Urea  has  been  found  in  cases 
of  nephritis. 

In  cases  of  catarrlj,  the  sputum  is  at  first  usually  sticky  and  clear  (sputa  cruda),  but  later  it 
becomes  more  firm  and  yellow  (sputa  cocta).  Under  pathological  conditions,  there  may  be 
found  in  the  sputum — («)  red  blood  corpuscles  from  rupture  of  a  blood  vessel,  [b)  Elastic 
fibres  (10)  from  disintegration  of  the  alveoli  of  the  lung;  usually  the  bundles  are  fine,  curved,  and 
the  fibres  branched.  [In  certain  cases  it  is  well  to  add  a  solution  of  caustic  potash,  which  dissolves 
most  of  the  other  elements,  leaving  the  elastic  fibres  untouched.]  Their  presence  always  indicates 
destruction  of  the  lung  tissue,  [c)  Colorless  plugs  of  fibrin  (xi),  casts  of  the  smaller  or  larger 
bronchi,  occur  in  some  cases  of  fibrinous  exudation  into  the  finer  air  passages,  {d)  Crystals  of 
various  kinds — crystals  o^  fatty  acids  in  bundles  of  fine  needles  (Fig.  149,  a).  They  indicate  great 
decomposition  of  the  stagnant  secretion.  Leucin  and  tyrosin  crystals  are  rare  {\  269).  Tyrosin 
occurs  in  considerable  amount  when  an  old  abscess  breaks  into  the  lungs.  Colorless,  sharp  pointed, 
octagonal  or  rhombic  plates — Charcot's  crystals  (c) — have  been  found  in  the  expectoration  in 
asthma,  and  exudative  affections  of  the  bronchi.  Hsematoidin  [b)  and  cholesterin  crystals  [d') 
occur  much  more  rarely. 

Fungi  and  other  lowly  organisms  are  taken  in  during  inspiration  (§  136).  The  threads  of 
Leptothrix  buccalis  (12),  detached  from  the  teeth,  are  frequently  found  (|  147).  Mycelium  and 
spores  are  found  in  thrush  (Oidium  albicans),  especially  in  the  mouths  of  sucking  infants.  In 
mal-odorous  expectoration  rod-shaped  bacteria  are  present.  In  pulmonary  gangrene  are  found 
monads,  and  cercomonads;  in  pulmonary  phthisis  the  tubercle  bacillus;  very  rarely  sarcina,  which, 
however,  is  often  found  in  gastric  catarrh  in  the  stomach  and  also  in  the  urine  (|  270). 

Physical  Characters. — Sputum,  with  reference  to  its  physical  characters,  is  described  as  mucous, 
muco-purulent,  or  purulent. 

Abnormal  coloration  of  the  sputum — red  from  blood ;  when  the  blood  remains  long  in  the  lung 
it  undergoes  a  regular  series  of  changes,  and  tinges  the  sputum  dark  red,  bluish  brown,  brownish 
yellow,  deep  yellow,  yellowish  green,  or  grass  green.  The  sputum  is  sometimes  yellow  in  jaundice. 
The  sputum  may  be  tinged  by  what  is  inspired  [as  in  the  case  of  the  "black  spit"  of  miners]. 

The  odor  of  the  sputum  is  more  or  less  unpleasant.  It  becomes  very  disagreeable  when  it  has 
remained  long  in  pathological  lung  cavities,  and  it  is  stinking  in  gangrene  of  the  lung. 

139.  ACTION   OF  THE   ATMOSPHERIC    PRESSURE.— At  the 

normal  pressure  of  the  atmosphere  (height  of  the  barometer,  760  millimetres  Hg), 
pressure  is  exerted  upon  the  entire  surface  of  the  body  =  15,000  to  20,000  kilos., 
according  to  the  extent  of  the  superficial  area.  This  pressure  acts  equally  on  all 
sides  upon  the  body,  and  also  occurs  in  all  internal  cavities  containing  air,  both 
those  that  are  constantly  filled  with  air  (the  respiratory  passages  and  the  spaces  in 
the  superior  maxillary,  frontal,  and  ethmoid  bones),  and  those  that  are  temporarily 
in  direct  communication  with  the  outer  air  (the  digestive  tract  and  tympanum). 
As  the  fluids  of  the  body  (blood,  lymph,  secretions,  parenchymatous  juices)  are 
practically  incompressible,  their  volume  remains  unchanged  under  the  pressure ; 


248  ACTION    OF   DIMINISHED    ATMOSPHERIC    PRESSURE. 

but  they  absorb  gases  from  the  air  corresponding  to  the  prevailing  pressure  (/'.  e., 
the  partial  pressure  of  the  individual  gases),  and  according  to  their  temperature 
(^  T^T^).  The  solids  consist  of  elementary  parts  (cells  and  fibres),  each  of  which 
jyresents  only  a  microscopic  surface  to  the  ])ressure,  so  that  for  each  cell  the  pre- 
vailing pressure  of  the  air  can  only  be  calculated  at  a  few  millimetres — a  pressure 
under  which  the  most  delicate  histological  tissues  undergo  development.  As  an 
example  of  the  action  of  the  pressure  of  the  atmospheric  i)ressure  upon  large  masses, 
take  that  brought  about  by  the  adhesion  of  the  smooth,  sticky,  moist,  articular 
surfaces  of  the  shoulder  and  hip  joints;  the  arm  and  the  leg  are  supported  without 
the  action  of  muscles.  The  thigh  bone  remains  in  its  socket  after  section  of  all  the 
muscles  and  its  capsule.  Even  when  the  cotyloid  cavity  is  perforated,  the  head 
of  the  femur  does  not  fall  out  of  its  socket.  The  ordinary  barometric  variations 
affect  the  respiration — a  rise  of  the  barometric  pressure  excites,  while  a  fall  dimin- 
ishes, the  resi)irations.     The  absolute  amount  of  CO2  remains  the  same  (§  127,  8). 

Great  diminution  of  the  atmospheric  pressure,  such  as  occurs  in  ballooning  (highest  ascent, 
8600  metres),  or  in  ascemling  mountains,  causes  a  series  of  characteristic  jilienomena  :  (l)  In  con- 
sequence of  the  diminution  of  tlie  pressure  upon  the  parts  directly  in  contact  with  the  air,  ihey 
become  greatly  congested,  hence  there  is  redness  and  swelling  of  the  skin  and  free  mucous  mem- 
branes; tiiere  maybe  hemorrhage  from  the  nose,  lungs,  gums;  turgidity  of  the  cutaneous  veins; 
copious  secretion  of  sweat;  great  secretion  of  mucus.  (2)  A  feeling  of  weight  in  the  limbs,  a 
pressing  outward  of  the  tympanic  membrane  (until  the  tension  is  equilibrated  by  opening  the 
Eustachian  tube),  and  as  a  consequence  noises  in  the  ears  and  difficulty  of  hearing.  (3)  In  conse- 
(pience  of  the  diminished  tension  of  the  O  in  the  air  (§  129),  there  is  difficulty  of  breathing,  pain  in 
the  chest,  whereby  the  respirations  (and  pulse)  becotne  more  rajjid,  deeper,  and  irregular.  When 
the  atmospheric  ]5resfure  is  diminished  Yz-y^,  the  amount  of  O  in  the  blood  is  diminished,  the  COj 
is  imperfectly  removed  from  the  blood,  and  in  consequence  there  is  diminished  o.xidation  within  the 
body.  When  the  atmospheric  pressure  is  diminished  to  one-half,  the  amount  of  CO.,  in  arterial 
blood  is  lessened  ;  and  the  amount  of  N  diminishes  proportionally  with  the  decrea.^e  of  the  atmos- 
l)heric  pressure.  The  diminished  tension  of  the  air  prevents  the  vibrations  of  the  vocal  cords  from 
occurring  so  forcibly,  and  hence  the  voice  is  feeble.  (4)  In  consequence  of  the  amount  of  blood  in 
the  skin,  the  internal  organs  are  relatively  anaemic;  hence,  there  is  diminished  secretion  of  urine, 
muscular  weakness,  disturbances  of  digestion,  dullness  of  the  senses,  and  it  may  be  unconsciousness, 
and  all  these  phenomena  are  intensified  by  the  conditions  mentioned  under  (3).  Some  of  these 
phenomena  are  modified  by  usage.  The  highest  limit  at  which  a  man  may  still  retain  his  senses  is 
placed  by  Tissandier  at  an  elevation  of  8000  metres  (2S0  mm.  Hg).  In  dogs  the  blood  pressure 
falls,  and  the  pulse  becomes  small  and  diminished  in  frequency,  when  the  atmospheric  pressure  falls 
to  200  mm.  Ilg. 

Those  who  live  upon  high  mountains  suffer  from  a  disease  "mal  de  montagne,"  which  consists 
essentially  in  the  above  symptoms,  although  it  is  sometimes  complicated  with  ananiiaof  the  internal 
organs.  Al.  v.  Humboldt  found  that  in  those  who  lived  on  the  Andes  the  thorax  was  capacious. 
At  6000  to  8000  feet  above  sea  level,  water  contains  only  one-third  of  the  absorbed  gases,  so  that 
fi>hes  cannot  live  in  it.  Animals  may  be  subjected  to  a  further  diminution  of  the  atmospheric 
pressure  by  being  placeil  under  the  receiver  of  an  air  pump.  Birds  die  when  the  pressure  is  reduced 
to  120  mm.  Hg  ;  mammals  at  40  mm.  Ilg;  frogs  endure  repeated  evacuations  of  the  receiver, 
whereby  they  are  much  di.stended,  owing  to  the  escape  of  gases  and  wafer,  but  after  the  entrance  of 
air  they  become  greatly  compressed.  The  cause  of  death  in  mammals  is  ascribed  by  Hoppe-Seyler 
lo  the  evolution  of  bubbles  of  gas  in  the  blood;  these  bubbles  stop  up  the  capillaries,  and  the  circu- 
lation is  arrested.  Local  diminution  of  the  atmospheric  pressure  causes  marked  congestion  and 
swelling  of  the  part,  as  occurs  when  a  cupping  gla.ss  is  used. 

Great  increase  of  the  atmospheric  pressure  causes  phenomena,  for  the  most  part,  the  reverse 
of  the  foregoing,  as  in  pneumatic  cabinets  and  in  diving  bells,  where  men  may  work  even  under  4)^ 
atmospheres  pressure,  (i )  Paleness  and  dryness  of  the  external  surfaces,  collapse  of  the  cutaneous 
veins,  diminution  of  perspiration,  and  mucous  secretions.  (2)  The  tympanic  membrane  is  pressed 
inward  (until  the  air  escapes  through  the  Eustachian  tube,  after  causing  a  sharp  sound),  acute  .sounds 
are  heard,  pain  in  the  ears,  and  difficulty  of  hearing.  (3)  A  feeling  oflightness  and  freshness  during 
respiration,  the  respiration  becomes  slower  (by  2-4  per  minute),  inspiration  easier  and  shorter, 
expiration  lengthened,  the  pause  distinct.  The  capacity  of  the  lungs  increases,  owing  to  the  freer 
movement  of  the  diaphragm,  in  con.sequence  of  the  diminution  of  the  intestinal  gases.  Owing  to 
the  more  rapid  oxidations  in  the  body,  muscular  movement  is  easier  and  more  active.  The  O 
absorbed  and  the  CO.^  excreted  are  increased.  The  venous  blood  is  reddened.  (4)  Difficulty  of 
speaking,  alteration  of  the  tone  of  the  voice,  inability  to  whistle.  (5)  Increase  of  the  urinary 
secretion,  more  muscular  energy,  more  rapid  metabolism,  increased  appetite,  subjective  feeling  of 
warmth,  pulse  beats  slower,  and  pulse  curve  is  lower  (compare  \   74).     In  animals  subjected  to 


COMPARATIVE    AND    HISTORICAL.  249 

excessively  high  atmospheric  pressure,  P.  Bert  found  that  the  arterial  blood  contained  30  vols,  per 
cent.  O  fat  760  mm.  Hg) ;  when  the  amount  rose  to  35  vol.  per  cent.,  death  occurred  with  convul- 
sions. Compressed  air  has  been  used  for  therapeutical  purposes,  but  in  doing  so  a  too  rapid  increase 
of  the  pressure  is  to  be  avoided.  Waldenburg  has  constructed  such  an  apparatus,  which  may  be 
used  for  the  respiration  of  air  under  a  greater  or  less  pressure. 

Frogs,  when  placed  in  compressed  O  (at  14  atmospheres),  exhibit  the  same  phenomena  as  if 
they  were  in  a  vacuum,  or  pure  N.  There  is  paralysis  of  the  central  nervous  system,  sometimes 
preceded  by  convulsions.  The  heart  ceases  to  beat  (not  the  lymph  hearts),  while  the  excitability 
of  the  motor  nerves  is  lost  at  the  same  time,  and  lastly  the  direct  muscular  excitability  disappears. 
An  excised  frog's  heart  placed  in  O  under  a  very  high  pressure  (13  atmospheres),  scarcely  beats 
one-fourth  of  the  time  during  which  it  pulsates  in  air.  If  the  heart  be  exposed  to  the  air  again,  it 
begins  to  beat,  so  that  compressed  O  renders  the  vitality  of  the  heart  latent  before  abolishing  it. 

Phosphorus  retains  its  luminosity  under  a  high  pressure  in  O,  but  this  is  not  the  case  with  the 
luminous  organisms,  e.  g.,  Lampyris,  and  luminous  bacteria.  High  atmospheric  pressure  is  also 
injurious  to  plants. 

140.  COMPARATIVE  AND  HISTORICAL.— Mammals  have  lungs  similar  to  those  of 
man.  The  lungs  of  birds  are  spongy,  and  united  to  the  chest  wall,  while  tliere  are  openings  on 
their  surface  communicating  with  thin- walled  "  air-sacs,''  which  are  placed  among  the  viscera. 
The  air  sacs  communicate  with  cavities  in  the  bones,  which  give  the  latter  great  lightness.  The 
diaphragm  is  absent.  In  reptiles  the  lungs  are  divided  into  greater  and  smaller  compartments; 
in  snakes  one  lung  is  abortive,  while  the  other  has  the  elongated  form  of  the  body.  The  amphi- 
bians (frog)  possess  two  simple  lungs,  each  of  which  represents  an  enormous  infundibulum  with 
its  alveoli.  The  frog  pumps  air  into  its  lungs  by  the  contraction  of  its  throat,  the  nostrils  being 
closed  and  the  glottis  opened.  When  young — until  their  metamorphosis — frogs  breathe  like  fishes 
by  means  of  gills.  The  perennibranchiate  amphibians  (Proteus)  retain  their  gills  throughout  life. 
Among  fishes,  which  breathe  by  gills  and  use  the  O  absorbed  by  the  water,  the  Dipnoi  have  in 
addition  to  gills  a  swim  bladder  provided  with  afferent  and  efferent  vessels,  which  is  comparable 
to  the  lung.  The  Cobitis  respires  also  with  its  intestine.  Insects  and  centipedes  respire  by 
"tracheae,''  which  are  branched  canals  distributed  throughout  the  body;  they  open  on  the  surface 
of  the  body  by  openings  (stigmata)  which  can  be  closed.  Spiders  respire  by  means  of  tracheae  and 
tracheal  sacs,  crabs  by  gills.  The  mollusks  and  cephalopods  have  gills ;  some  gasteropods  have 
gills  and  others  lungs.  Among  the  lower  invertebrata  some  breathe  by  gills,  others  by  means  of  a 
special  ''  water  vascular  system,"  and  others  again  by  no  special  organs. 

Historical. — Aristotle  (384  B.C.)  regarded  the  object  of  respiration  to  be  the  cooling  of  the 
body,  so  as  to  moderate  the  internal  warmth.  He  observed  correctly  that  the  warmest  animals 
breathe  most  actively,  but  in  interpreting  the  fact  he  reversed  the  cause  and  effect.  Galen 
(131-203  A.D.)  thought  that  the  "soot"  was  removed  from  the  body  along  with  the  expired 
water.  The  most  important  experiments  on  the  mechanics  of  respiration  date  from  Galen;  he 
observed  that  the  lungs  passively  follow  the  movements  of  the  chest ;  that  the  diaphragm  is  the 
most  important  muscle  of  inspiration ;  that  the  external  intercostals  are  inspiratory ;  and  the 
internal,  expiratory.  He  divided  the  intercostal  nerves  and  muscles,  and  observed  that  loss  of 
voice  occurred.  On  dividing  the  spinal  cord  higher  and  higher,  he  found  that  as  he  did  so  the 
muscles  of  the  thorax  lying  higher  up  became  paralyzed.  Oribasius  (360  A.D.)  observed  that  in 
double  pneumothorax  both  lungs  collapsed.  Vesalius  (1540)  first  described  artificial  respiration 
as  a  means  of  restoring  the  beat  of  the  heart.  Malpighi  (1661)  described  the  structure  of  the 
lungs.  J.  A.  Borelli  (f  1679)  gave  the  first  fundamental  description  of  the  mechanism  of  the 
respiratory  movements.  The  chemical  processes  of  respiration  could  only  be  known  after  the 
discovery  of  the  individual  gases  therein  concerned.  Van  Helmont  (f  1644)  detected  COg. 
[Joseph  Black  (1757)  discovered  that  CO,,  or  "  fixed  air,"  is  given  out  during  expiration.]  In 
1774  Priestley  discovered  O.  Lavoisier  detected  N  (1775),  and  ascertained  the  composition  of 
atmospheric  air,  and  he  regarded  the  formation  of  COj  and  H2O  of  the  breath  as  a  result  of  a  com- 
bustion within  the  lungs  themselves.  J.  Ingen-Houss  (1730-1799)  discovered  the  respiration  of 
plants.  Vogel  and  others  proved  the  existence  of  COj  in  venous  blood,  and  Hoffmann  and  others 
that  of  O  in  arterial  blood.  The  more  complete  conception  of  the  exchange  of  gases  was,  how- 
ever, only  possible  after  Magnus  had  extracted  and  analyzed  the  gases  of  arterial  and  venous 
blood  (§  36). 


Physiology  of  Digestion. 


141.  THE  MOUTH  AND  ITS  GLANDS.— The  mucous  membrane  of  the  cavity  of 
the  month,  which  becomes  continuous  with  the  skin  at  the  red  margin  of  tlie  lips,  lias  a  number  of 
sebaceous  glands  in  the  rei;ion  of  the  red  part  of  the  lip.  The  buccal  mucous  membrane  consists 
of  bundles  of  tine  fibrous  tissue  mixed  w^ith  elastic  fibres,  which  traverse  it  in  every  direction. 
Papillae — simple  or  compound — occur  near  the  free  surfaces.  The  submucous  tissue,  which 
is  directly  continuous  with  the  fibrous  tissue  of  the  mucous  membrane  itself,  is  thickest  where  the 
mucous  membrane  is  thickest,  and  densest  where  it  is  firmly  fixed  to  the  periosteum  of  the   bone 

Fig.   151. 


Kpithe- 
lium. 


Closed 
follicles. 


Mucous 
gland. 


Cells  of  stratified  squamous  epithe 
lium  detached  from  the  mouth 
s,  salivary  corpuscles. 


Section  of  a  mucous  follicle  from  the  tongue. 

and  to  the  gum;  it  is  thinnest  where  the  mucous  memljrane  is  most  movable,  and  where  there  are 
most  folds.  The  cavity  of  the  mouth  is  lined  by  stratified  squamous  epithelium  (Fig.  150), 
which  is  thickest,  as  a  rule,  where  the  longest  papillae  occur. 

All  the  glands  of  the  mouth,  including  the  salivary  glands,  may  be  divided 
into  different  classes,  according;  to  the  nature  of  their  secretions. 

1.  The  serous  or  albuminous  glands  [true  salivary],  whose  secretion 
contains  a  certain  amount  of  albumin,  e.  g.,  the  human  parotid. 

2.  The  mucous  glands,  whose  secretion,  in  addition  to  some  albumin,  con- 
tains the  characteristic  constituent  mucin. 

3.  The  mixed  [or  muco-salivary]  glands,  some  of  the  acini  secreting  an 
albuminous  fluid  and  others  mucin,  e.  g.,  the  human  maxillary  gland. 

Numerous  mucous  glands  (labial,  buccal,  palatine,  lingual,  molar)  have  the  appearance  of 
small  macroscopic  bodies  lying  in  the  sub-mucosa.  They  are  branched  tubular  glands,  and 
the  contents  of  their  secretory  cells  consist  partly  of  mucin,  which  is  expelled  from  them  during 
secretion.  The  excretory  ducts  of  these  glands,  which  are  lined  by  cylindrical  epithelium,  are 
constricted  where  they  enter  the  mouth.  Not  unfrequently  one  duct  receives  the  secretion  of  a 
neighboring  gland. 

The  glands  of  the  tongue  form  two  groups,  which  differ  morphologically  and  physiologically, 
(l)  The   mucous  glands   {IVeber's  glands),  occurring  chiefly  near  the  root  of  the  tongue,  are 

250 


THE  MOUTH  AND  ITS  GLANDS. 


251 


branched  tubular  glands  lined  with  clear,  transparent,  secretory  cells  whose  nuclei  are  placed  near 
the  attached  end  of  the  cells.  The  acini  have  a  distinct  membrana  propria.  (2)  The  serous  glands 
{Ebner's)  are  acinous  glands  occurring  in  the  region  of  the  circumvallate  papillee  (and  in  animals 
near  the  papillze  foliatse).  They  are  lined  with  turbid  granular  epithelium  with  a  central  nucleus 
and  secrete  saliva.  (3)  The  glands  of  Blandin  and  Nuhn  are  placed  near  the  tip  of  the  tongue, 
and  consist  of  mucous  and  serous  acini,  so  that  they  are  mixed  glands  {Pod-ioiso(zky). 

The  blood  vessels  are  moderately  abundant,  and  the  larger  trunks  lie  in  the  sub-mucosa,  while 
the  finer  twigs  penetrate  into  the  papillse,  where  tliey  form  either  a  capillary  network  or  simple 
loops. 

The  larger  lymphatics  lie  in  the  sub-mucosa,  while  the  finer  branches  form  a  fine  network 
placed  in  the  mucosa.  The  lymph  follicles  also  belong  to  the  lymphatic  system  (^  197).  On 
the  dorsum  of  the  posterior  part  of  the  tongue  they  form  an  almost  continuous  layer.  They  are 
round  or  oval  (1-1.5  mm.  in  diameter),  lying  in  the  sub-mucosa,  and  consist  of  adenoid  tissue 
loaded  with  lymph  corpuscles.  The  outer  part  of  the  adenoid  reticulum  is  compressed  so  as  to 
form  a  kind  of  capsule  for  each  follicle.  Similar  follicles  occur  in  the  intestine  as  solitary  follicles; 
in  the  small  intestine  they  are  collected  together  into  Peyer's  patches,  and  in  the  spleen  they  occur 
as  Malpighian  corpuscles.  On  the  dorsum  of  the  tongue  several  of  these  follicles  form  a  slightly 
oval  elevation,  which  is  surrounded  by  connective  tissue.  In  the  centre  of  this  elevation  there  is  a 
depression,  into  which  a  mucous  gland  opens,  which  fills  the  small  crater  with  mucus  (Fig.  151). 

The  tonsils  have  fundamentally  the  same  structure.  On  their  surface  are  a  number  of  depres- 
sions into  which  the  ducts  of  small  mucous  glands  open.  These  depressions  are  surrounded  by 
groups  (10-20)  of  lymph  follicles,  and  the  whole  is  environed  by  a  capsule  of  connective  tissue 
(Fig.  152).  Large  lymph  spaces,  communicating  with  lymphatics,  occur  in  the  neighborhood  of 
the  tonsils,  but  as  yet  a  direct  connection  between  the  spaces  in  the  follicles  and  the  lymph  vessels 
has  not  been  proved  to  exist.  Similar  structures  occur  in  the  tubal  and  pharyngeal  tonsils. 
[Stohr  asserts  that  an  enormous  number  of  leucocytes  wander  out  of  the  tonsils,  solitary  and  Peyer's 
glands,  and  the  adenoid  tissue  of  the  bronchial  mucous  membrane.  The  cells  pass  out  between  the 
epithelial  cells,  but  do  not  pass  into  the  interior  of  the  latter.] 

Nerves. — Numerous  medtiUated  nerve  fibres  occur  in  the  sub-mucosa,  pass  into  the  mucosa,  and 
terminate  partly  in  the  individual  papillae  in  Krause's  end  bulbs,  which  are  most  abundant  in  the 
lips  and  soft  palate,  and  not  so  numerous  in  the  cheeks  and   floor  of  the  mouth.     The   nerves 
administer  not  only  to  common   sensation,  but  they  are  also  the  organs  of  transmission  for  tactile 
(heat  and  pt'essure)   im- 
pressions.     It   is   highly  Fig.  152. 
probable,    however,    that                                      • — ^— '»»-^_ 
some  nerve  fibres  end  in                                        ^  ^ 
fine  terminal    fibrils,  be-                                       ^^-^ 
tween  the  epithelial  cells, 
as  in  the  cornea  and  else- 
where. 

[  Secretory  glands 
may  be  simple  (Fig.  153, 
B,  C,  D)  or  compound 
(E).  In  the  latter  case 
the  duct  is  branched.  In 
the  process  of  develop- 
ment, a  solid  process  of 
the  epithelium  sinks  into 
the  subjacent  fibrous  tis- 
sue, and,  to  form  a  simple 
gland,  a  cavity  appears  in 
this  bud,  but  for  a  com- 
pound gland,  other  epi- 
thelial buds  sprout  from 
its  blind  end.  Each  bud 
acquires  a  central  cavity, 
these  elongate  and  in- 
crease in  number,  tlius 
forming  a  much  branched 
system,  the  terminal  blind 
ends  forming  the  acini, 

alveoli  or  true  secretory  part.  If  the  alveoli  are  tubular  in  shape,  the  gland  is  called  a  compound 
tubular  gland.  Thus  in  the  compound  glands  some  parts  aie  secretory,  and  others  act  as  ducts, 
while  in  the  simple  glands,  all  the  parts  may  be  secretory.  All  the  glands  opening  on  the  surface 
of  the  body  are  of  epiblastic  origin.  The  secretory  cells  lining  the  acini  rest  on  a  basement  mem- 
brane, and  outside  this  are  the  lymph  spaces  and  capillary  blood  vessels.] 


Epithelium. 


A 


Tunica 
propria. 


Vertical  section  of  a  human  tonsil,  X  20.  i,  cavity;  2,  epithelium  infiltrated  with 
leucocytes  below  and  on  the  left,  but  free  on  the  right;  3,  adenoid  tissue  with  sec- 
tions a,  b,  c,  of  masses  of  it ;  4,  fibrous  sheath ;  5,  section  of  a  gland  duct ;  d, 
blood  vessel. 


252 


THE    SALIVARY    fJLANDS. 


142.  THE  SALIVARY  GLANDS. — The  three  pairs  of  salivary  glands,  sub-maxillary, 
sublingual,  ami  parotid,  are  coni|)ouiul  tiil)uiar  glands.  Fig.  155,  A,  shows  a  fine  duct,  termi- 
nalinLj  in  the  more  or  less  llask  siiaped  alveoli  or  acini.  [Kach  gland  consists  of  a  niimiier  of  lobes, 
and  each  lube  in  turn  of  a  number  of  lobules,  which,  again,  are  composed  of  acini.  All  these  are 
held  together  by  a  framework  of  connective  tissue.  The  larger  branches  of  the  duct  lie  between 
the  lobules,  and  constitute  the  interlobular  ducts,  giving  branches  to  each  lobule  which  they  enter, 
constituting  the  intralobular  liucts,  which  branch  and  finally  terminate  in  connection  with  the 
alveoli,  by  means  of  an  intermediary  or  intercalary  part.  The  larger  interlobar  and  interlobular 
ducts  consist  of  a  meml)rana  jnopiia,  strengtiiened  outside  with  fibrous  and  elastic  tissue,  and  in 
some  places  also  by  non  striped  muscle,  while  the  ducts  are  lined  by  columnar  e|)ithelial  cells.  In 
the  largest  branches,  there  is  a  second  row  of  smaller  cells,  lying  between  the  large  cells  and  the 
niembrana  propria.     The  intralobular  ducts  are  lined   by  a  single   layer  of  large  cylindrical 

epithelium  with  the  nucleus  about  the 


Fir,.  153. 


middle  of  the  cell,  while  the  outer  half 
of  the  cell  is  finely  striated  longitudi- 
nally, or  "rodded,"  which  is  due  to 
fibrillar  (Fig.  154) ;  the  inner  half  next 
the  lumen  is  granular.  The  interme- 
diary part  is  narrow,  and  is  lined  by  a 
single  layer  of  flattened  cells,  each  with 
an  elongated  oval  nucleus.  There  is 
usually  a  narrow  "neck,"  where  the 
intralobular  duct  becomes  continuous 
with  the  intermediary  part,  and  here  the 
cells  are  polyhedral.] 

Fic.  154. 


''"'//Iii;';i»'' 


Evolution  of  glands.  A,  schema  of  skin  ;  e/,  epidermis  ;  d,  cutis  with 
a  capillary  c;  B,  simple  gland  with  its  bloodvessels;  C,  D,  more 
complex  glands  ;   E,  compound  gland,  blood  vessels  omitted. 

Fig.  155. 


Rodded   epithelium    lining   the    duct   of 
salivary  gland. 


A,  duct  and  acini  of  the  parotid  gland  of  a  dog;  B,  acini  ol  the  sub-maxillary  gland  of  a  dog;  c,  refractive  mucous 
cells;  </,  granular  half-moons  of  Gianuzzi ;  C,  similar  alveoli  after  prolonged  secretion  ;  D,  basket-shaped  tissue 
investment  of  an  acuius  ;  F.  entrance  of  a  non-medullated  nerve  fibre  into  a  secretory  cell. 

The  acini,  or  alveoli,  are  the  parts  where  the  actual  process  of  secretion  takes  place.     They 
vary  somewhat  in  shape — some  are  tubular,  others  branched,  some  are  dilated  and  resemble  a 


THE    STRUCTURE    OF    THE    SALIVARY    GLANDS. 


253 


Florence  flask,  and  several  of  them  usually  open  into  one  intermediary  part  of  a  duct.  Each 
alveolus  is  bounded  by  a  basement  membrane,  with  a  reticulate  structure  made  up  of  nucleated, 
branched,  and  anastomosing  cells  so  as  to  resemble  a  basket  (D).  There  is  a  homogeneous  membrane 
bounding  the  alveoli  in  addition  to  this  basket  shaped  structure.  Immediately  outside  this  mem- 
brane is  a  lymph  space,  and  outside  this  again  the  network  of  capillaries  is  distributed.  [The 
extent  to  which  this  lymph  space  is  filled  \\ith  lymph  determines  the  distance  of  the  capillaries  from 
the  membrana  propria.  The  inter-alveolar  lymph  spaces  communicate  with  large  lymph  spaces 
between  the  lobules,  which  in  turn  communicate  with  perivascular  lymphatics  around  the  arteries 
and  veins.]     The  lymphatics  emerge  from  the  gland  at  the  hilum. 

The  secretory  cells  vary  in  structure,  according  as  the  salivary  gland  is  a 
mucous  [sub-maxillary  and  sublingual  of  the  dog  and  cat],  a  serous  [parotid 
of  man  and  mammals,  and  sub-maxillary  of  rabbit],  or  mixed  gland  [human 
sub-maxillary  and  sublingual]. 

Mucous  Acini. — The  secretory  cells  of  mucous  glands,  and  the  mucous  acini  of  mixed  glands 
(Fig.  156),  are  lined  by  a  single  layer  of  "  mucin  cells  "  (Fig.  155,  B,  c),  which  are  large  cells  dis- 
tended with  mucin, or  with  a  hypothetical  substance, 
mucigen,  which  yields  mucin.     The  mucin  cells 
are  more  or  less  spheroidal  in  shape,  clear,  shining, 
highly  refractive,  and  nearly  fill  the  acinus.     The 
flattened  nucleus  is   near  the  wall  of  the  acmus 
Each  cell   has  a  fine  process  which  overlaps  the 
fixed  parts  of  the   cell   next  to  it.     Owing  to  the 
body  of  each  cell   being  infiltrated  with   mucin 
these   cells  do   not  stain  with  carmine,  although 
the  nucleus  and  its  immediately  investing  prjto 
plasm  do.     Another  kind  of  cell   occurs  in   the 
sub-maxillary  gland  of  the  dog.      It  forms  a  half 
moon  shaped  strzei:/tere\ymg  indirect  contact  ^\uh    /^ 
the  wall  of  the  acinus  [GiaJiuzzi).     Each  "  half  ^S 
moon  "  or   "  crescent  "  consists  of  a  number 
of  small,  closely  packed,  angular,  highly  albumm 
ous  cells  with  small  oval  nuclei,  which,  ho\\e\er 
are  separated  only  with  difficulty.       Hence,  Hei 
denhain  has  called  them  "composite  marginal 
cells"  (B,  a').    They  are  granular,  darker,  de\oid 
of  mucin,  and  stain  readily  with  pigments.      [In 
the  sub-maxillary  gland  of  the  cat,  there  is  a  com 
plete  layer  of  these  "marginal"  carmine-staining 
cells   lying   between    the   mucous   cells   and   the 
membrana  propria.] 

[Serous  Acini. — In  true  serous  glands  (paro- 
tid of  man  and  mammals)  and  in  the  serous  acini 
of  mixed  glands,  the  acini  are  lined  by  a  single 
layer  of  secretory  columnar  finely-granular  cells, 
which  in  the  quiescent  condition  completely  fill  the  acinus,  so  that  scarcely  any  lumen  is  left.  Just 
before  secretion,  or  when  these  cells  are  quiescent,  Langley  has  shown  that  they  are  large  and  filled 
with  numerous  granules,  which  obscure  the  presence  of  the  nucleus.  As  secretion  takes  place, 
these  granules  seem  to  be  used  up  or  discharged  into  the  lumen ;  at  least,  the  outer  part  of  each  cell 
gradually  becomes  clear  and  more  transparent,  and  this  condition  spreads  toward  the  inner  part  of 
the  cell.] 

[In  the  mixed  or  muco-salivary  glands  {e.g.,  human  sub -maxillary)  some  of  the  alveoli  are 
mucous  and  others  serous  in  their  characters,  but  the  latter  are  always  far  more  numerous,  and  the 
one  kind  of  acinus  is  directly  continuous  with  the  others  (Fig.  156).] 

143.  HISTOLOGICAL  CHANGES  DURING  THE  ACTIVITY 
OF  THE  SALIVARY  GLANDS.— [The  condition  of  physiological  activity 
of  the  gland  cells  is  accompanied  by  changes  in  the  histological  characters  of  the 
secretory  cells.  Changes  in  serous  glands  have  been  carefully  studied  in  the 
parotid  of  the  rabbit,  but  the  appearances  vary  somewhat,  according  as  the  glands 
are  examined  in  the  fresh  condition  or  after  hardening  in  various  reagents,  such  as 
absolute  alcohol.  When  the  gland  is  at  rest,  in  a  preparation  hardened  in  alcohol, 
and  stained  with  carmine,  the  cells  consist  of  a  pale,  almost  uncolored  substance, 
with  a  few  fine   granules,  and  a  small,  irregular,    red-stained,  shriveled  nucleus 


Section  of  a  human  sub-maxillary  gland.  On  the  left  is  a 
group  of  serous  alveoli,  and  on  the  right  a  group  of 
mucous  alveoli. 


254  HISTOLOGICAL    CHANGES    IN    THE    SALIVARY    (ILANDS. 

devoid  of  a  nucleolus.  The  appearance  of  the  nucleus  suggests  the  idea  of  its 
being  shriveled  by  the  action  of  the  hardening  reagent  (Fig.  157).] 

[During  activity,  if  the  gland  be  caused  to  secrete  by  stimulating  the  sympa- 
thetic, all  parts  of  the  cells  undergo  a  change  (Figs.  157,  158).  In  preparations 
hardened  in  alcohol  (i)  the  cells  diminish  somewhat  in  size;  (2)  tlie  nuclei 
are  no  longer  irregular,  but  round,  with  a  sharp  contour  and  nucleoli  ;  (3)  the 
substance  of  the  cell  itself  is  turbid  owing  to  the  diminution  of  the  clear  substance, 
and  the  increase  of  the  granules,  especially  near  the  nuclei  ;  (4)  at  the  same  time, 
the  whole  cell  stains  more  deeply  with  carmine  {Hci({cnhain).'\ 

[On  studying  the  changes  which  occur  in  a  living  serous  gland,  Langley 
found  that  the  substance  of  the  cells  of  the  parotid  is  pervaded  by  fine  granules, 
which  are  so  numerous  as  to  obscure  the  nucleus,  while  the  outlines  of  the  cells  are 
indistinct.  No  lumen  is  visible  in  the  acini  during  activity,  the  granules  disap- 
pear from  the  outer  zone  of  the  cells,  the  cells  themselves  becoming  smaller  and 
more  distinct.  After  prolonged  secretion  the  granules  largely  disappear  from  the 
cell  substance  except  quite  near  the  inner  margin.  The  cells  are  smaller,  their 
outlines  more  distinct,  their  spherical  nuclei  apparent,  and  the  lumen  of  the  acini 
is  wide  and  distinct.     Thus,  it  is  evident  that,  during  rest,  granules  are  manu- 


FiG.  157. 


*-; 


*\L^' 


4 


'*  ""'f  y^i*.   .;■  ..  .:>**^^-*:^^« 


^   I.      tnim'^m^^Sr^ 


^^ 

Sections  of  a  "  serous"  gland.     The  parotid  of  a  rabbit.  Fig.  157,  at  rest;    Fig.  158,  after  stimulation  of  the 

cervical  sympathetic. 

factured,  which  disappear  during  the  activity  of  the  cells,  the  disappearance  taking 
place  from  without  inward.  Similar  changes  occur  in  the  cells  of  the  pancreas.] 
[More  complex  changes  occur  in  the  mucous  glands,  such  as  the  submaxillary 
or  orbital  glands  of  the  dog  (^Lavdovsky).  The  appearances  vary  according  to  the 
intensity  and  duration  of  the  secretory  activity.  The  mucous  cells  at  rest  are 
large,  clear,  and  refractive,  containg  a  flattened  nucleus  (Fig.  155,  C),  surrounded 
with  a  small  amount  of  protoplasm,  and  placed  near  the  basement  membrane.  The 
clear  substance  does  not  stain  with  carmine,  and  consists  of  mucigen  lying  in  the 
wide  spaces  of  an  intracellular  plexus  of  fibrils.  After  prolonged  secretion, 
produced,  it  may  be,  by  strong  and  continued  stimulation  of  the  chorda,  the 
mucous  cells  of  the  sub-maxillary  gland  of  the  dog  undergo  a  great  change.] 
The  distended,  refractive,  and  "mucous  cells,"  which  occur  in  the  quiescent 
gland,  and  which  do  not  stain  with  carmine,  do  not  appear  after  the  gland  has 
been  in  a  state  of  activity.  Their  place  is  taken  by  small,  dark,  protoplasmic 
cells  devoid  of  mucin  (Fig.  155,  C).  These  cells  readily  stain  with  carmine, 
while  their  nucleus  is  scarcely,  if  at  all,  colored  by  the  dye.  The  researches  of 
R.  Heidenhain  (1868)  have  shed  much  light  on  the  secretory  activity  of  the 
salivary  glands. 


THE    NERVES    OF   THE    SALIVARY    GLANDS. 


255 


The  change  maybe  produced  in  two  ways.  Either  it  is  due  to  the  "mucous  cells"  during 
secretion  becoming  broken  up,  so  that  Ihey  yield  their  mucin  directly  to  the  saliva;  in  saliva  rich 
in  mucin,  small  microscopic  pieces  of  mucin  are  found,  and  sometimes  mucous  cells  themselves  are 
present.  Or,  we  must  assume  that  the  mucous  cells  simply  eliminate  the  mucin  from  their  bodies 
{Ewald,  Stohr) ;  while,  after  a  period  of  rest,  new  mucin  is  formed.  Accordmg  to  this  view,  the 
dark  granular  cells  of  the  glands,  after  active  secretion,  are  simply  mucous  cells,  which  have  given 
out  their  mucin.  If  we  assume,  with  Heidenhain,  that  the  mucous  cells  break  up,  then  these 
granular  non-mucous  cells  must  be  regarded  as  new  formations  produced  by  the  proliferation  and 
growth  of  the  composite  marginal  cells,  i.  e.,  the  crescents,  or  half-moons  of  Gianuzzi. 

[During  rest,  the  protoplasm  seems  to  manufacture  mucigen,  which  is  changed 
into  and  discharged  as  mucin  in  the  secretion,  when  the  gland  is  actively  secreting. 
Thus,  the  cells  become  smaller,  but  the  protoplasm  of  the  cell  seems  to  increase, 
new  mucigen  is  manufactured  during  rest,  and  the  cycle  is  repeated.] 

144.  THE  NERVES  OF  THE  SALIVARY  GLANDS.— The  nerves 
are  for  the  most  part  medullated,  and  enter  at  the  hilum  of  the  gland,  where  they 
form  a  rich  plexus  provided  with  ganglia  between  the  lobules.  [There  are  no 
ganglia  in  the  parotid  gland  {KIein).'\ 

All  the  salivary  glands  are  supplied  by  branches  from  two  different  nerves — from 
the  sympathetic  and  from  a  cranial  nerve. 

Fig.  159. 


Scheme  of  the  nerves  of  the  salivary  glands.  P.,  pons  ;  M.  O.,  medulla  oblongata  ;  J.  N.,  nerve  of  Jacobson;  O.,  S. 
M.,  I.  M,,  ophthalmic,  superior,  and  inferior  maxillary  divisions  of  fifth  nerve,  V. ;  VII.,  seventh  nerve  ;  S.s.p., 
small  superficial  petrosal  nerve;  Vag,  vagus  ;  Sym.,  sympathetic  ;  O.  G.,  otic,  and  S.  G.,  sub-ina.xillary  ganglia; 
P.,  S.,  and  S.  L.,  parotid,  sub-maxillary,  and  sublingual  glands  :   T.,  tongue. 


1.  The  sympathetic  nerve  gives  branches  {a)  to  the  sub-maxillary  and  the 
sublingual  glands,  derived  from  the  plexus  on  the  external  maxillary  artery  ;  (F) 
to  the  parotid  gland  from  the  carotid  plexus  (Fig.  159). 

2.  The  facial  nerve  gives  branches  to  the  sub-maxillary  and  sublingual  glands 
from  the  chorda  tympani,  which  accompanies  the  lingual  branch  of  the  fifth  nerve 
(Fig.  159).  The  branches  to  the  parotid  arise  from  the  tympanic  branch  of  the 
glosso-pharyngeal  nerve  (dog).  The  tympanic  plexus  sends  fibres  to  the  small 
superficial  petrosal  nerve,  and  with  it  these  fibres  run  to  the  anterior  surface  of  the 
pyramid  in  the  temporal  bone,  emerging  from  the  skull  through  a  fissure  between 
the  petrous  and  great  wing  of  the  sphenoid,  and  then  joining  the  otic  ganglion. 
This  ganglion  sends  branches  to  the  auriculo-temporal  nerve  (itself  derived  from 
the  third  branch  of  the  trigeminus),  which,  as  it  passes  upward  to  the  temporal 
region  under  cover  of  the  parotid,  gives  branches  to  this  gland. 

The  sub-maxillary  ganglion,  which  gives  branches  to  the  sub-maxillary  and 
sublingual    glands,    receives  fibres   from    the    tympanico-lingual  nerve  (chorda 


256  ACTION    OF    NERVES    ON    THE    SECRETION    OF    SALIVA. 

tympani)  as  well  as  sympathetic  fibres  from  the  plexus  on  the  external  maxillary 
artery. 

Termination  of  the  Nerve  Fibres. — With  regard  to  the  ultimate  distribution 
of  these  nerves  we  can  distinguish  (i)  the  vasomotor  nerves,  which  give 
brandies  to  the  walls  of  the  blood  vessels,  and  (2)  the  secretory  nerves  proper. 

rflui^er  states,  with  regard  to  the  latter,  that  (a)  medullated  nerve  fibres  penetrate  tlie  acini ;  the 
sheath  of  Schwann  unites  with  the  membrana  propria  of  the  acinus;  the  medullated  fibre — still 
medullaieil — passes  between  the  secretory  cells,  where  it  divides  and  becomes  non-medullated,  and 
its  axial  cylinder  terminates  in  connection  with  the  nucleus  of  a  secretory  cell.  [This,  however,  is 
not  pr()ve<l]  (Fig.  155,  F).  [fi)  According  to  Plliiger,  some  of  the  nerve  fibres  end  in  multipolar 
ganL:;lii>n  celU,  which  lie  outside  the  wall  of  the  acinus,  and  these  cells  send  branches  to  the  secretory 
cells  of  the  acini.  [These  cells  probably  correspond  to  the  branched  cells  of  the  basket-shaped 
structure.]  (r)  Again,  he  describes  medullated  fibres  which  enter  the  attached  end  of  the  cylin- 
drical epithelium  lining  the  excretory  ducts  of  the  glands  (E).  Pfiiiger  thinks  that  those  fibres 
entering  the  acini  directly  are  cerebral,  wiiile  those  with  ganglia  in  their  course  are  derived  from  the 
sympatlietic  system.  [(</)  The  direct  termination  of  nerve  fibres  has  been  observed  in  the  salivary 
glanils  of  tlie  cockroach  by  Kupffer.] 

145.  ACTION  OF  THE  NERVOUS  SYSTEM  ON  THE  SECRE- 
TION OF  SALIVA.— A.  Sub-maxillaryGland.— Stimulation  of  the  facial 
nerve  at  its  origin  causes  a  profuse  secretion  of  a  thin,  watery  saliva,  which  con- 
tains a  very  small  amount  of  specific  constituents.  Simultaneously  with  the  act  of 
secretion,  the  blood  vessels  of  the  glands  dilate,  and  the  capillaries  are  so  distended 
that  the  pulsatile  movement  in  the  arteries  is  proj^agated  into  the  veins.  Nearly  four 
times  as  much  blood  flows  out  of  the  veins  (CY.  Bernard),  the  blood  being  of  a 
bright  red  color,  and  containing  one-third  more  O  than  the  venous  blood  of  the 
non-stimulated  gland.  Notwithstanding  this  relatively  high  percentage  of  O,  the 
secreting  gland  uses  more  O  than  the  passive  gland  (§  131,  i). 

[I.  Stimulation  of  Chorda. — If  a  cannula  be  placed  in  Wharton's  duct, 
e.  g.,  in  a  dog,  and  the  chorda  tympani  be  divided,  no  secretion  flows  from  the 
cannula.  On  stimulating  i\\Q  peripheral  end  0/  the  ehorda /j/npani  with  a.n  inter- 
rupted current  of  electricity,  the  same  results — copious  secretion  of  saliva  and 
vascular  dilatation,  with  increased  flow  of  blood  through  the  gland — occur  as  when 
the  origin  of  the  seventh  nerve  itself  is  stimulated.  The  watery  saliva  is  called 
chorda  saliva.] 

Tvv(j  functionally  different  kinds  of  nerve  fibres  occur  in  the  facial  nerve — (i) 
true  secretory  fibres,  (2)  vasodilator  fibres. 

II.  Stimulation  of  the  sympathetic  nerve  causes  a  scanty  amount  of  a 
very  thick,  sticky,  mucous  secretion,  in  which  the  specific  salivary  constituents, 
mucin,  and  the  salivary  corpuscles  are  very  abundant.  The  specific  gravity  of  the 
saliva  is  raised  from  1007  to  loio.  Simultaneously  the  blood  vessels  become  con- 
tracted, so  that  the  blood  flows  more  slowly  from  the  veins,  and  has  a  dark  bluish 
color. 

The  sympathetic  also  contains  itvo  kinds  of  nerve  fibres — (i)  true  secretory 
fibres,  and  (2)  vaso-constrictor  fibres. 

[Electrical  Variations  during  Secretion. — That  changes  in  the  electromotive  properties  ot 
glands  occur  during  secretion  was  shown  in  the  frog's  skin.  Bayliss  and  Bradford  find  that  the 
same  is  true  of  the  sub-maxillary  gland  (dog).  During  secretion,  the  excitatory  change  on 
stimulating  the  chorda  is  a  positive  variation  of  the  current  of  rest  (the  hilum  of  the  gland  becoming 
more  positive),  but  it  is  frequently  followed  by  a  second  phase  of  opposite  sign.  The  latent  period 
is  always  very  short,  about  o.y]" .  Atropin  abolishes  the  chorda  variation.  On  stimulating  the 
sympathetic,  the  excitatory  change  is  of  an  opposite  sign  to  that  of  the  chorda,  and  the  hilum 
becomes  less  positive,  so  that  there  is  a  negative  variation.  It  requires  a  more  powerful  stimulus,  is 
less  in  amount,  and  its  latent  period  is  longer  {2."-\'f),  while  atropin  lessens  but  does  not 
abolish  it.] 

Relation  to  Stimulus. — On  stimulating  the  cerebral  ner\GS,  at  first  with  a  weak  and  gradually 
with  a  stronger  stimulus,  there  is  a  gradual  development  of  the  secretion  in  which  the  solid  constitu- 
ents— ^^occasionally  the  organic — are  increased  {Heidenhain).  If  a  strong  stimulus  be  applied  for  a 
long  time,  the  secretion  diminishes,  becomes  watery,  and  is  poor  in  specific  constituents,  especially 


ACTION    OF    NERVES   ON    THE    SECRETION    OF    SALIVA.  257 

in  the  organic  elements,  which  are  more  affected  than  the  inorganic  (C.  Ludwig  and  Becker). 
After  prolonged  stimulation  of  the  sympathetic,  the  secretion  resembles  the  chorda  saliva.  It  would 
seem,  therefore,  that  the  chorda  and  sympathetic  saliva  are  not  specifically  distinct,  but  -vary  only 
in  degree.  On  continuing  the  stimulation  of  the  nerves  up  to  a  certain  maximal  limit,  the  rapidity 
of  secretion  becomes  greater,  and  the  percentage  of  salts  also  increases  to  a  certain  maximum,  and 
this  independently  of  the  former  condition  of  the  glands.  The  percentage  of  organic  constituents 
also  depends  on  the  strength  of  the  nervous  stimulation,  but  not  on  this  alone,  as  it  is  essentially 
contingent  upon  the  condition  of  the  gland  before  the  secretion  took  place,  and  it  also  depends  upon 
the  duration  and  intensity  of  the  previous  secretory  activity.  Very  strong  stimulation  of  the  gland 
leaves  an  "  after-effect,"  which  predisposes  it  to  give  off  organic  constituents  into  the  secretion 
[Heidenhain).  A  latent  period  of  1.2  sec.  to  24  sec.  may  elapse  between  the  nerve  stimulation  and 
the  beginning  of  the  secretion. 

[Langley  has  shown  that  in  the  cat  the  sympathetic  saliva  of  the  sub-maxillary  gland  is  less  viscid 
than  the  chorda  saliva.] 

Relation  to  Blood  Supply. — The  secretion  of  saliva  is  not  sitnply  the  result  oj 
the  amount  of  blood  in  the  glands  ;  that  there  is  a  factor  independent  of  the  changes 
in  the  state  of  the  vessels  is  shown  by  the  following  facts : — 

(i)  The  secretory  activity  of  the  glands  when  their  nerves  are  stimulated  continues  for  some  time 
after  the  blood  vessels  of  the  gland  have  been  ligatured.  [If  the  head  of  a  rabbit  be  cut  off,  stimula- 
tion of  the  seventh  nerve,  above  where  the  chorda  leaves  it,  causes  a  flow  of  saliva,  which  cannot 
be  accounted  for  on  the  supposition  that  the  saliva  already  present  in  the  salivary  glands  is  forced 
out  of  them.  Thus  we  may  have  secretion  without  a  blood  stream.  The  saliva  is  really 
secreted  from  the  lymph  present  in  the  lymph  spaces  of  the  gland  (^Ludwig).'] 

(2)  Atropin  and  daturin  abolish  the  activity  of  the  secretory  fibres  in  the 
chorda  tympani,  but  do  not  affect  the  vaso-dilator  fibres  {Jleidenhaifi).  The  same 
results  occur  after  the  injection  of  acids  and  alkalies  into  the  excretory  duct 
(^Gianuzzi). 

[Action  of  Atropin. — The  vascular  dilatation  and  the  increased  flow  of  saliva, 
due  to  the  activity  of  the  secretory  cells,  produced  by  stimulation  of  the  chorda 
tympani,  although  they  occur  simultaneously,  do  not  stand  in  the  relation  of  cause 
and  effect.  We  may  cause  vascular  dilatation  without  an  increased  flow  of  saliva, 
as  already  stated  (2).  If  atropin  be  given  to  an  animal,  stimulation  of  the  chorda 
produces  dilatation  of  the  blood  vessels,  but  no  secretion  of  saliva.  Atropin 
paralyzes  the  secretory  fibres,  but  not  the  vaso-dilator  fibres  (Fig.  160).  The 
increased  supply  of  blood,  while  not  causing,  yet  favors  the  act  of  secretion,  by 
placing  a  larger  amount  of  pabulum  at  the  disposal  of  the  secretory  elements,  the 
cells.] 

(3)  The  pressure  in  the  excretory  duct  of  the  salivary  gland — measured  by 
means  of  a  manometer  tied  into  it — may  be  nearly  twice  as  great  as  the  pressure 
within  the  arteries  of  the  glands,  or  even  in  the  carotid  itself  {Ludwig^.  The 
pressure  in  Wharton's  duct  may  reach  200  mm.  Hg. 

[Secretory  Pressure. — The  experiment  described  under  (3)  proves,  in  a 
definite  manner,  that  the  passage  of  the  water  from  the  blood  vessels,  or  at  least 
from  the  lymph  into  the  acini  of  the  gland,  cannot  be  due  to  the  blood  pressure  ; 
that,  in  fact,  it  is  not  a  mere  process  of  filtration,  such  as  occurs  in  the  glomeruli  of 
the  kidney.  In  the  case  of  the  salivary  gland,  where  the  pressure  within  the 
gland  may  be  double  that  of  the  arterial  pressure,  the  water  actually  moves  from 
the  lymph  spaces  against  very  great  resistance.  We  can  only  account  for  this 
result  by  ascribing  it  to  the  secretory  activity  of  the  gland  cells  themselves. 
Whether  the  activities  of  the  gland  cells,  as  suggested  by  Heidenhain,  are  governed 
directly  by  two  distinct  kinds  of  nerve  fibres,  a  set  of  solid-secreting  fibres,  and  a 
set  of  water-secreting  fibres,  remains  to  be  proved.] 

(4)  Just  as  in  the  case  of  muscles  and  nerves,  the  salivary  glands  become  fatigued  or  exhausted 
after  prolonged  action.  This  result  may  also  be  brought  about  by  injecting  acids  or  alkalies  into 
the  duct,  which  shows  that  the  secretory  activity  of  the  gland  is  independent  of  the  circulation 
[Gianuzzi). 

All  these  facts  lead  us  to  conclude  that  the  nerves  exercise  a  direct  effect  upon  the  secretory 
cells,  apart  from  their  action  on  the  blood  vessels. 

17 


1>58  REFLEX    SECRETION    OF    SALIVA. 

Extirpation  of  Salivary  Glands. — When  the  chorda  tympani  is  extirpated  on  one  side  in 
young  dogs,  the  sub-maxillary  gland  on  that  side  does  not  develop  so  much — its  weight  is  50  per 
cent,  less — while  the  mucous  cells  and  the  "crescents"  are  smaller  than  on  the  sound  side 
[Bitfitlini). 

During  secretion,  the  temperature  of  the  gland  rises  1.5°  C.  {Ludwig),  and 
the  blood  flowing  from  the  veins  is  often  warmer  than  the  arterial  blood.  [The 
electro-motive  changes  are  referred  to  on  p.  256.] 

"  Paralytic  Secretion  "  of  Saliva. — By  this  term  is  meant  the  continued 
secretion  of  a  thin,  watery  saliva  from  the  sub-maxillary  gland,  which  occurs  twenty- 
four  hours  after  the  section  of  the  cerebral  nerves  (chorda  of  the  seventh),  i.e., 
those  branches  of  them  that  go  to  this  gland,  whether  the  sympathetic  be  divided 
or  not  {CI.  Bernard).  It  increases  until  the  eighth  day,  after  which  it  gradually 
diminishes,  while  the  gland  tissue  degenerates.  The  injection  of  a  small 
quantity  of  curara  into  the  artery  of  the  gland  also  causes  it. 

[Heidenhain  showed  that  section  of  one  chorda  is  followed  by  a  continuous  secretion  of  saliva 
hova  bo(k  sub-maxillary  glands.  The  term  "paralytic"  secretion  is  applied  to  that  which  takes 
place  on  the  side  on  which  the  nerve  is  cut,  and  Langley  proposes  to  call  the  secretion  on  the 
opposite  side  the  antilytic.  Apnoea  (^  368)  stops  both  the  paralytic  and  antilytic  secretion,  while 
dyspnoea  increases  the  flow  in  both  cases;  and  as  section  of  the  sympathetic  fibres  to  the  gland  (where  the 
chorda  is  cut)  arrests  the  paralytic  secretion  excited  by  dyspncea,  it  is  evident  that  both  the  paralytic 
secretion  and  the  secretion  following  dyspncea  are  caused  by  stimuli  traveling  down  the  sympathetic 
fibres.  In  the  later  stages  of  the  paralytic  secretion,  the  cause  is  in  the  gland  itself,  for  it  goes  on 
even  if  all  the  nerves  passing  to  the  gland  be  divided,  and  is  probably  due  to  a  local  nerve  centre. 
In  this  stage  the  secretion  is  arrested  by  a  large  dose  of  chloroform.  The  paralytic  secretion  in  the 
first  stage  may  be  owing  to  a  venous  condition  of  the  blood  acting  on  a  central  secretory  centre 
whose  excitability  is  increased ;  and  in  the  latter  stages  probably  on  local  nerve  centres  within  the 
gland.  The  fibres  of  the  chorda  in  the  cat  are  only  partially  degenerated  thirteen  days  after  section 
{Langley).'] 

[Histological  Changes. — In  the  gland  during  paralytic  secretion,  the  gland  cells  of  the  alveoli 
(serous,  mucous,  and  demilunes)  diminish  in  size  and  show  the  typical  "  resting  "  appearance,  even 
to  a  greater  extent  than  the  normal  resting  gland  [Langley).'] 

B.  Sub-lingual  Gland. — Very  probably  the  same  relations  obtain  as  in  the 
sub-maxillary  gland. 

C.  Parotid  Gland. — In  the  dog,  stimulation  of  the  sympathetic  alone  causes 
no  secretion  ;  it  occurs  when  the  glosso-pharyngeal  branch  to  the  parotid  is 
simultaneously  excited.  This  branch  may  be  reached  within  the  tympanum  in  the 
tympanic  plexus.  A  thick  secretion  containing  much  organic  matter  is  thereby 
obtained.  Stimulation  of  the  cerebral  hra.nc\\  alone  yields  a  clear,  thin,  watery 
secretion,  containing  a  very  small  amount  of  organic  substances,  but  a  considerable 
amount  of  the  salts  of  the  saliva. 

[Stimulation  of  Jacobson's  Nerve  (Parotid  of  Dog) — 

Total  Solids.  Salts.  Organic  Matter. 

Without  sympathetic,  .  .  0.56  per  cent.  0.31  0.24 

With  sympathetic,   .  .  .  2.42  per  cent.  0.36  2.06] 

[Reflex  Secretion  of  Saliva. — If  a  cannula  be  placed  in  Wharton's  duct, 
e.g.,  in  a  dog,  during  fasting,  no  saliva  will  flow  out,  but  on  applying  a  sapid 
substance  to  the  mucous  membrane  of  the  mouth  or  the  tongue,  there  is  a 
copious  flow  of  saliva.  If  the  sympathetic  nerve  be  divided,  secretion  still 
takes  place  when  the  mouth  is  stimulated,  but  if  the  chorda  tympani  be  cut, 
secretion  no  longer  takes  place.  Hence,  the  secretion  is  due  to  a  reflex  act  ; 
in  this  case,  the  lingual  is  the  afferent,  and  the  chorda  the  efferent  nerve 
carrying  impulses  from  a  centre  situated  in  the  medulla  oblongata  (Fig.  160).] 
In  the  intact  body,  the  secretion  of  saliva  occurs  through  a  reflex  stimulation 
of  the  nerves  concerned,  whereby,  under  normal  circumstances,  the  secretion 
is  always  watery  (chorda  or  facial  saliva).  The  centripetal  or  afferent 
nerve  fibres  concerned  are  :  (i)  The  nerves  of  taste.  (2)  The  sensory  branches 
of  the  trigeminus  of  the  entire  cavity  of  the  mouth  and  the  glosso-pharyngeal 


REFLEX   SECRETION    OF    SALIVA. 


259 


Fig. 

1 60. 

Mucous  Membrane 

<=t-^=^ 

^.^ 

'" 

Afferent// 
>'ervey// 

5f  Duct  of  Gland. 

Nerve  i 

I^M. Secretory  N 

Centre. 

^^K.    — *"  "^^ 

^t           ^fl 

%  Secreting 
f     cells. 

Vai 

so.dilator\\^     1 
Nerve.           ^Jy 

Bloodvessels 
of  Gland. 

Diagram  of  a  salivary  gland. 


(which  appear  to  be  capable  of  being  stimulated  by  mechanical  stimuli,  pres- 
sure, tension,  displacement).  The  movements  of  mastication  also  cause  a 
secretion  of  saliva.  Pfliiger  found  that  one-third  more  saliva  was  secreted  on  the 
side  where  mastication  took  place  ;  and 
CI.  Bernard  observed  that  the  secre- 
tion ceased  in  horses  during  the  act  of 
drinking.  (3)  The  nerves  of  smell, 
excited  by  certain  odors.  (4)  The  gas- 
tric branches  of  the  vagus.  A  rush  of 
saliva  into  the  mouth  usually  precedes 
the  act  of  vomiting  (§  158). 

(5)  The  stimulation  of  distant  sensory 
nerves,  e.  g.,  the  central  end  of  the  sciatic — 
certainly  through  a  complicated  reflex  mechan- 
ism— causes  a  secretion  of  saliva  ( Owsjamtikow 
and  Tschierjew).  Stimulation  of  the  conjunc- 
tiva, e.  g.,  by  applying  an  irritating  fluid  to  the 
eye  of  carnivorous  animals,  causes  a  reflex  secre- 
tion of  saliva  (^Aschenbrandf).  Perhaps  the 
secretion  of  saliva  which  sometimes  occurs 
during  pregnancy  is  caused  in  a  similar  reflex 
manner. 

(6)  The  movements  of  mastication  excite 

secretion,  but  although,  during  the  act  of  rumination,  this  is  the  case  in  ruminants,  in  whom  the 
process  of  mastication  is  very  thorough,  there  is  no  secretion  from  the  sub-maxillary  gland,  although 
the  parotid  secretes  {Colin,  Ellenberger  and Hofmeister'). 

The  reflex  centre  for  the  secretion  of  saliva  lies  in  the  medulla  oblongata,  at 
the  origin  of  the  seventh  and  ninth  cranial  nerves.  The  centre  for  the  sympathetic 
fibres  is  also  placed  here.  This  region  is  connected  by  nerve  fibres  with  the  cere- 
brum ;  hence,  the  thought  of  a  savory  morsel,  sometimes,  when  one  is  hungry, 
causes  a  rapid  secretion  of  a  thin,  watery  fluid — [or,  as  we  say,  ''makes  the  mouth 
water  "].  If  the  centre  be  stimulated  directly  by  a  mechanical  stimulus  (puncture), 
salivation  occurs,  while  asphyxia  has  the  same  effect.  The  reflex  secretion  of 
.saliva  may  be  inhibited  by  stimulation  of  certain  sensory  nerves,  e.  g.,  by  pulling 
out  a  loop  of  the  intestine.  Stimulation  of  the  cortex  cerebri  of  a  dog,  near  the 
sulcus  cruciatus,  is  often  followed  by  secretion  of  saliva.  Disease  of  the  brain  in 
man  sometimes  causes  a  secretion  of  saliva,  owing  to  the  effects  produced  on  the 
intracranial  centre. 

So  long  as  there  is  no  stimulation  of  the  nerves,  there  is  no  secretion  of  saliva, 
as  in  sleep.  Immediately  a/Ur  the  section  of  all  nerves,  secretion  stops,  for  a  time 
at  least. 

Pathological  Conditions  and  Poisons. — Certain  affections,  as  inflammation  of  the  mouth, 
neuralgia,  ulcers  of  the  mucous  membrane,  and  affections  of  the  gums,  due  to  teething  or  the 
prolonged  administration  of  mercury,  often  produce  a  copious  secretion  of  saliva  or  ptyalism. 
Certain  poisons  cause  the  same  effect  by  direct  stimulation  of  the  nerves,  as  Calabar  bean 
(physostigmin),  digitalin,  and  especially  pilocarpin.  Many  poisons,  especially  the  narcotics — above 
all,  atropin — paralyze  the  secretory  nerves,  so  that  there  is  a  cessation  of  the  secretion  and  the  mouth 
becomes  dry ;  while  the  administration  of  muscarin  in  this  condition  causes  secretion.  Pilocarpin 
acts  on  the  chorda  tympani,  causing  a  profuse  secretion,  and  if  atropin  be  given,  the  secretion  is 
again  arrested.  Conversely,  if  the  secretion  be  arrested  by  atropin,  it  may  be  restored  by  the  action 
of  pilocarpin  or  physostigmin.  Nicotin,  in  small  doses,  excites  the  secretory  nerves,  but  in  large 
doses  paralyzes  them.  Daturin,  cicutin,  and  iodide  of  aethylstrychnin,  paralyze  the  chorda.  The 
saliva  is  diminished  in  amount  in  man,  in  cases  of  paralysis  of  the  facial  ox  sympathetic  nerves,  as 
is  observed  in  unilateral  paralysis  of  these  nerves. 

[Sialogogues  are  those  drugs  which  increase  the  secretion  of  saliva.  Some  are  topical,  and 
take  effect  when  applied  to  the  mouth.  They  excite  secretion  reflexly  by  acting  on  the  sensory 
nerves  of  the  mouth.  They  include  acids,  and  various  pungent  bodies,  such  as  mustard,  ginger, 
pyrethrum,  tobacco,  ether,  and  chloroform;  but  they  do  not  all  produce  the  same  effect  on  the 
amount  or  quality  of  the  saliva  ;  others,  the  general  sialogogues,  cause  salivation  when  introduced 


260  THE    PAROTID    SALIVA. 

into  the  blood ;  physostigmin,  nicotin,  pilocarpin,  muscarin.  The  drugs  named  act  after  all  the 
nerves  going  to  the  gland  are  divided,  so  that  they  stimulate  the  peripheral  ends  of  the  nerves  in 
the  glands.     The  two  former  also  excite  the  central  ends  of  the  secretory  nerves.] 

[Antisialics  are  those  substances  which  diminish  the  secretion  of  saliva,  and  they  may  take  effect 
upon  any  part  of  the  reflex  arc,  i.  e.,  on  the  mouth,  the  afterent  nerves,  the  nerve  centre  and  aflerent 
nerves,  or  upon  the  blood  stream  through  the  glands,  or  on  the  glands  themselves.  Opium  and 
morphia  affect  the  centre,  large  doses  of  physostigmin  affect  the  blood  supply,  but  atropin  is  the  most 
powerful  of  all,  as  it  paralyzes  the  terminations  of  the  secretory  nerves  in  the  glands,  e.g.,  the  chorda 
tympani,  and  even  the  sympathetic  in  the  cat  (but  not  in  the  dog).] 

[Excretion  by  the  Saliva. — Some  drugs  are  excreted  by  the  saliva.  Iodide  of  potassium  is 
rapidly  eliminated  by  the  kidneys,  and  by  the  salivary  glands,  and  so  also  is  iodide  of  iron.] 

Theory  of  Salivary  Secretion. — Ileindenhain  has  recently  formulated  the  following  theory 
regarding  the  secretion  of  saliva :  "  During  the  passive  or  quiescent  condition  of  the  gland,  the 
organic  materials  of  the  secretion  are  formed  from  and  by  the  activity  of  the  protoplasm  of  the 
secretory  cells.  A  quiescent  cell,  which  has  been  inactive  for  some  time,  therefore  contains  little 
protoplasm,  and  a  large  amount  of  these  secretory  substances.  In  an  actively  secreting  gland,  there 
are  two  processes  occurring  together,  but  independent  of  each  other,  and  regulated  by  two  different 
classes  of  nerve- fibres;  secretory  fibres  cause  the  act  of  secretion,  while  trophic  fibres  cause  chemical 
processes  within  the  cells,  partly  resulting  in  the  formation  of  the  soluble  constituents  of  the  secre- 
tion, and  partly  in  the  growth  of  the  protoplasm.  According  to  the  number  of  both  kinds  of  fibres 
present  in  a  nerve  passing  to  a  gland,  such  nerve  being  stimulated,  the  secretion  takes  place  more 
rapidly  (cerebral  nerve)  or  more  slowly  (sympathetic),  while  the  secretion  contains  less  or  more 
solid  constituents.  The  cerebral  ntrxts  contain  many  secretory  fibres  and  few  trophic  fibres,  while 
the  sympathetic  contain  more  trophic  but  few  secretory  fibres.  The  rapidity  and  chemical  com- 
position of  the  secretion  vary  according  to  the  strength  of  the  stimulus.  During  continued  secretion, 
the  supply  of  secretory  materials  in  the  gland  cells  is  used  up  more  rapidly  than  it  is  replaced  by 
the  activity  of  the  protoplasm  ;  hence,  the  amount  of  organic  constituents  diminishes,  and  the  micro- 
scopic characters  of  the  cells  are  altered.  The  microscopic  characters  of  the  cells  are  altered  also  by 
the  increase  of  the  protoplasm,  which  takes  place  in  an  active  gland.  The  mucous  cells  disappear, 
and  seem  to  be  dissolved  after  prolonged  secretion,  and  their  place  is  taken  by  other  cells  derived 
from  the  proliferation  of  the  marginal  cells.  The  energy  which  causes  the  current  of  fluid  depends 
upon  the  protoplasm  of  the  gland  cells." 

146.  THE  SALIVA  OF  THE  INDIVIDUAL  GLANDS.— (a) 
Parotid  saliva  is  obtained  by  placing  a  fine  cannula  in  Steno's  duct ;  it  has  an 
alkaline  reaction,  but  during  fasting,  the  first  few  drops  may  be  neutral  or  even 
acid  on  account  of  free  CO2;  its  specific  gravity  is  1003  to  1004.  After  standing 
it  becomes  turbid,  and  deposits,  in  addition  to  albuminous  matter,  calcium  car- 
bonate, which  is  present  in  the  fresh  saliva  in  the  form  of  bicarbonate.  It  contains 
small  quantities  (more  abundant  in  the  horse)  of  a  globulin-like  body,  and  never 
seems  to  be  without  CNKS,  /.  e.,  sulphocyanide  of  potassium  (or  sodium), — 
which,  however,  is  absent  in  the  sheep  and  dog. 

[The  sulphocyanide  gives  a  dark  red  color  (ferric  sulphocyanide)  with  ferric  chloride,  and  the 
color  is  discharged  by  mercuric  chloride,  but  this  is  not  the  case  with  meconic  acid,  which  gives  a 
similar  color  reaction.]  It  also  reduces  iodic  acid  when  added  to  saliva,  causing  a  yellow  color 
from  the  liberation  of  iodine,  which  may  be  detected  at  once  by  starch  [Solera). 

Among  the  organic  substances  the  most  important  are  ptyalin,  a  small 
amount  of  urea,  and  traces  of  a  volatile  acid.  Mucin  is  absent,  hence  the 
parotid  saliva  is  not  sticky,  and  can  readily  be  poured  from  one  vessel  into 
another.  It  contains  1.5  to  1.6  per  cent,  of  solids  in  man,  of  which  0.3  to  i.o 
per  cent,  is  inorganic. 

Of  the  inorganic  constituents — the  most  abundant  are  potassium  and  sodium  chlorides ;  then 
potassium,  sodium,  and  calcium  carbonates,  some  phosphates,  and  a  trace  of  an  alkaline  sulphate. 

Salivary  calculi  are  formed  in  the  ducts  of  the  salivary  glands  owing  to  the  deposition  of  lime 
salts,  and  they  contain  only  traces  of  the  other  salivary  constituents ;  in  the  same  way  is  formed  the 
tartar  of  the  teeth,  which  contains  many  threads  of  leptothrix,  and  the  remains  of  low  organisms 
which  live  in  decomp>osing  saliva  in  carious  cavities  between  the  teeth. 

{b)  Sub-maxillary  saliva  is  obtained  by  placing  a  cannula  in  Wharton's 
duct ;  it  is  alkaline,  and  may  be  strongly  so.  After  standing  for  a  time,  fine 
crystals  of  calcium  carbonate  are  deposited,  together  with  an  amorphous  albu- 
minous body.     It  always  contains  mucin  (which  is  precipitated  by  acetic  acid)  ; 


THE    MIXED    SALIVA    IN    THE    MOUTH.  261 

hence,  it  is  usually  somewhat  tenacious.  It  contains  ptyalin,  but  in  less  amount 
than  in  parotid  saliva;  and,  according  to  Oehl,  only  0.0036  percent,  of  potassium 
sulphocyanide. 

Chemical  Composition. — Sub-maxillary  saliva  (dog)  : — 
Water,  991-45  per  1000, 

Organic  Matter,         2.89  "         " 
Inorganic  Matter,      5.66/    4."'5o  NaCl  and  CaCl, . 

\    i.iSCaCOg,  Calcium  and  Magnesium  phosphates. 

Mixed  Saliva  Parotid  Sub-maxillary 

(Human)  (Human)  (Dog) 

(Jacudowzisck).  {Hopi>e-Seyler).  (Herter). 

[Water,      99-51  99-32  99.44 

Solids, 0.49  0.68  0.56 

Soluble  organic  bodies  (ptyalin),    .    .    ,  0.13    \  0.34  f  0.066 

Epithelium,  mucin, 0.16    J  1 0.17 

Inorganic  salts,  . 0.102  0.34  0.43 

Potassic  sulphocyanide, 0.006  0.03  .    . 

Potassic  and  sodic  chlorides,        ....  0.084  •    •  •    •  ] 

Gases. — Pfliiger  found  that  100  cubic  centimetres  of  the  saliva  contained  0.6  O ;  64.7  CO2  (part 
could  be  pumped  out,  and  part  required  the  addition  of  phosphoric  acid) ;  0.8  N. ;  or,  in  100  vol. 
gas,  0.91  O;  97.88  COj;  1.21  N.  [It  therefore  contains  much  more  COo  than  venous  blood. 
Kiilz  obtained  from  100  c.c.  of  human  saliva  7  c.c.  of  gas — O  =  i  c.c,  N  =  2.5  c.c.  and  COj  = 
3.5  c.c.     Besides  this  there  is  40-60  c.c.  of  fixed  COj  in  the  form  of  carbonates.] 

(<:)  Sub-lingual  saliva  is  obtained  by  placing  a  very  fine  cannula  in  the 
ductus  Rivinianus  ;  it  is  strongly  alkaline  in  reaction,  very  sticky  and  cohesive, 
contains  much  mucin,  numerous  salivary  corpuscles,  and  some  potassium  sulpho- 
cyanide. 

147.  THE  MIXED  SALIVA  IN  THE  MOUTH.— The  mixed 
saliva  in  the  mouth  is  a  mixture  of  the  secretions  from  the  salivary,  mucous,  and 
other  glands  of  the  mouth. 

(i)  Physical  Characters. — It  is  an  opalescent,  tasteless,  odorless,  slightly 
glairy  fluid,  with  a  specific  gravity  of  1004  to  1009,  and  an  alkaline  reaction.  The 
amount  secreted  in  twenty-four  hours  =  200  to  1500  grammes  (7  to  50  oz.)  ; 
according  to  Bidder  and  Schmidt,  however,  =  1000  to  2000  grammes.  The  solid 
constituents  =  5.8  per  1000. 

Composition. — The  solids  are  :  Epithelium  and  mucus,  2.2 ;  ptyalin  and  albumin,  1.4;  salts, 
2.2;  potassium  sulphocyanide,  0.04  per  1000.  The  ash  contains  chiefly  potash,  phosphoric  acid, 
and  chlorine  [Hamnierbacher). 

Decomposition  products  of  epithelium,  salivary  corpuscles,  or  the  remains  of  food,  may  render 
it  acid  iemp07-arily,  as  after  long  fasting,  and  after  much  speaking ;  the  reaction  is  acid  in  some 
cases  of  dyspepsia  and  in  fever,  owing  to  the  stagnation  and  insufficient  secretion. 

(2)  Microscopic  Constituents. — («)  The  salivary  corpuscles  are  slightly 
larger  than  the  white  blood  corpuscles  (8  to  11  /j.),  and  are  nucleated  protoplasmic 
globular  cells  without  an  envelope  (Fig.  150,  s).  During  their  living  condition, 
the  particles  in  their  interior  exhibit  molecular  or  Brownian  movement.  The 
dark  granules  lying  in  the  protoplasm  are  thrown  into  a  trembling  movement, 
from  the  motion  of  the  fluid  in  which  they  are  suspended.  This  dancing  motion 
stops  when  the  cell  dies. 

[The  Brownian  movements  of  these  suspended  granules  are  purely  physical,  and  are  exhibited 
by  all  fine  microscopic  particles  suspended  in  a  limpid  fluid,  e.  g.,  gamboge  rubbed  up  in  water, 
particles  of  carmine,  charcoal,  etc.] 

{b)  Pavement  epithelial  cells  from  the  mucous  membrane  of  the  mouth  and  tongue;  they  are 
very  abundant  in  catarrh  of  the  mouth  (Fig.  150). 

(c)  Living  organisms,  which  live  and  thrive  in  the  cavities  of  teeth,  nourished  by  the 
remains  of  food.  Among  these  are  Leptothrix  buccalis  (Fig.  149,  12)  and  small  bacteria-like  organ- 
isms. The  threads  of  the  leptothrix  penetrate  into  the  canals  of  the  dentine,  and  produce  dental 
caries.  [Miller  has  found  twenty-five  varieties  of  microorganisms,  including  cocci,  bacteria,  vibrios, 
spirilla,  and  spirochsetse,  eight  of  them  present  in  the  stomach  and  twelve  in  the  intestines.] 


262  PHYSIOLOGICAL    ACTION    OF    SALI\A. 

(3)  Chemical  Properties, — (a)  Organic  Constituents. — Senim-aUmmin 
is  precipitated  by  heat  and  by  the  addition  of  alcohol.  In  saliva,  mixed  with 
much  water  and  shaken  up  with  COj,  a  globulin-like  body  is  precipitated  ;  mucin 
occurs  in  small  amount.  Among  the  extractives,  the  most  important  is  ptyalin  ; 
fats  and  urea  occur  only  in  traces.  In  twenty-four  hours  130  milligrammes  of 
potassium  or  sodium  sulphocyanide  are  secreted. 

(/^)  Inorganic  Constituents. — Sodium  and  potassium  chlorides,  potassium 
sulphate,  alkaline  and  earthy  phosphates,  ferric  phosphate. 

According  to  Schonbein,  the  saliva  contains  traces  of  nitrites  (detected  by  adding  dilute  sulphuric 
acid  and  diamido-benzol  to  dilute  saliva),  which  give  a  yellow  color  {Gries).  There  are  also  traces 
of  ammonia  (Uriicke). 

Abnormal  Constituents. — In  diabetes  mellitus,  lactic  acid,  derived  from  a  further  decompo- 
sition of  £;rape  sugar,  is  found.  It  dissolves  the  lime  in  the  teeth,  giving  rise  to  diabetic  dental 
caries.  Frerichs  found  leucin,  and  Vulpian  increase  of  albumin  in  albuminuria.  Of  foreign  sub- 
stances taken  into  the  body,  the  following  appear  in  the  saliva :  Mercury,  potassium,  iodine,  and 
bromine. 

Saliva  of  New-born  Children. — In  new-born  children,  the  parotid  alone 
contains  ptyalin.  The  diastatic  ferment  seems  to  be  developed  in  the  sub-maxil- 
lary gland  and  pancreas,  at  the  earliest  after  two  months.  Hence,  it  is  not  advi- 
sable to  give  starchy  food  to  infants.  No  ptyalin  has  been  found  in  the  saliva  of 
infants  suffering  from  thrush  (O'l'dium  albicans — Zweifel).  The  diastatic  action  of 
saliva  is  not  absolutely  necessary  for  the  suckling,  feeding  as  it  does  upon  milk. 
The  mouth  durirfg  the  first  two  months  is  not  moist,  but  at  a  later  period  saliva  is 
copiously  secreted  {Korowin)  ;  after  the  first  six  months,  the  salivary  glands 
increase  considerably.  The  eruption  of  the  teeth — owing  to  the  irritation  of  the 
mucous  membrane — produce  a  copious  secretion  of  saliva. 

148.  PHYSIOLpGICAL    ACTION     OF    SALIVA.— I.    Diastatic 

Action. — Tlie  most  important  chemical  action  exerted  by  saliva  in  digestion  is 
its  diastatic  or  amylolytic  action  (Leuchs,  1831),  /.  e.,  the  transformation  of  starch 
into  dextrin  and  some  form  of  sugar.  This  is  due  to  the  ptyalin — a  hydrolytic 
ferment  or  enzym — which,  even  when  it  is  present  in  very  minute  quantity, 
causes  starch  to  take  up  water  and  become  soluble,  the  ferment  itself  undergoing 
no  essential  change  in  the  process.  [Ptyalin  belongs  to  the  group  of  unorganized 
ferments  (§  250,  9).  Like  all  other  ferments  it  acts  only  within  a  certain  range 
of  temperature,  being  most  active  about  40°  C.  Its  energy  is  permanently 
destroyed  by  boiling.     It  acts  best  in  a  slightly  alkaline  or  neutral  medium.] 

[Action  on  Starch. — Starch  grains  consist  of  granulose  or  starch  enclosed 
by_  coats  of  cellulose.  Cellulose  does  not  appear  to  be  affected  by  saliva,  so  that 
saliva  acts  but  slowly  on  raw,  unboiled  starch.  If  the  starch  be  boiled,  so  as  to 
swell  up  the  starch  grains  and  rupture  the  cellulose  envelopes,  the  amylolytic 
action  takes  place  rapidly.  If  starch  paste  or  starch  mucilage,  made  by  boiling 
starch  in  water,  be  acted  upon  by  saliva,  especially  at  the  temperature  of  the  body, 
the  first  physical  change  observable  is  the  liquefaction  of  the  paste,  the  mixture 
becoming  more  fluid  and  transparent.  The  change  takes  place  in  a  few  minutes. 
When  the  action  is  continued,  important  chemical  changes  occur.] 

According  to  O' Sullivan,  Musculus,  and  v.  Mering,  the  diastatic  ferment  of 
saliva  (and  of  the  pancreas),  by  acting  upon  starch  or  glycogen,  forms  dextrin 
and  maltose  (both  soluble  in  water).  Several  closely  allied  varieties  of  dextrin, 
distinguishable  by  their  color  reactions,  seem  to  be  produced  {Britcke).  Ery- 
throdextrin  is  formed  first,  it  gives  a  red  color  with  iodine  ;  then  a  reducing 
dextrin — achroodextrin,  which  gives  no  color  reaction  with  iodine.  The  sugar 
formed  by  the  action  of  ptyalin  upon  starch  is  maltose  (C,,Ho.,0„  -f  H^G), 
which  is  distinguished  from  grape  sugar  (C12H04O10)  by  containing  one  molecule 
less  of  water,  which,  however,  it  holds  as  a  molecule  of  water  of  hydration. 
[Maltose  also  differs  from  grape  sugar  in   its  greater  rotatory  power  on  polarized 


FUNCTIONS    OF    SALIVA.  263 

light,  the  former  =  +  150°,  the  latter  -j-  56°,  the  ratio  being  61  :  100  ;  and  in 
its  smaller  power  of  reducing  cupric  oxide.  Thus,  between  the  original  starch 
and  the  final  product,  maltose,  several  intermediate  bodies  are  formed.  The 
starch  gives  a  blue  with  iodine,  but  after  it  has  been  acted  on  for  a  time  it  gives  a 
red  or  violet  color,  indicating  the  presence  of  erythrodextrin,  there  being  a  sim- 
ultaneous production  of  sugar ;  but  ultimately  no  color  is  obtained  on  adding 
iodine — achroodextrin,  which  gives  no  color  with  iodine,  maltose  being  formed. 
The  presence  of  the  maltose  is  easily  determined  by  testing  with  Fehling's  solution.] 
[Brown  and  Heron  suggest  that  the  final  result  of  the  transformation  may  be 
represented  by  the  equation — 

io(Ci2H,oOio)  +  8H20  =  8(Ci2H,,On)  +  2(C,,H,oOio) 

Soluble  starch.  Water.  Maltose.  Achroodextrin. 

The  ferment  slowly  changes  maltose  into  grape  sugar  or  dextrose.  This  result 
may  be  brought  about  much  more  rapidly  by  boiling  maltose  with  dilute  sulphuric 
or  hydrochloric  acid.]  Achroodextrin  ultimately  passes  into  maltose,  and  this 
again  into  dextrose  ;  the  other  form  of  dextrin  does  not  seem  to  undergo  this 
change  (Seegen's  Dystropodextrin).  For  the  further  changes  that  maltose  under- 
goes in  the  intestine,  see  §  183,  II,  2. 

[The  formula  of  starch  is  usually  expressed  as  CgHjoOj,  but  the  researches  already  mentioned,  and 
those  of  Brown  and  Heron,  make  it  probable  that  it  is  more  complex,  which  we  may  provisionally 
represent  by  ^(Cj^HjjOk,).  According  to  Musculus  and  Meyer,  erythrodextrin  is  a  mixture  of  dex- 
trin and  soluble  starch.] 

Preparation  of  Ptyalin. — (i)  Like  all  other  hydrolytic  ferments,  it  is  carried  down  with  any 
copious  precipitate  that  is  produced  in  the  fluid  which  contains  it,  and  it  can  be  isolated  from  the 
precipitate.  The  saliva  is  acidulated  with  phosphoric  acid,  lime-water  is  added  until  the  reaction 
becomes  alkaline,  when  a  precipitate  of  the  basic  calcium  phosphate  occurs,  which  carries  the  ptya- 
lin along  with  it.  This  precipitate  is  collected  on  a  filter,  washed  with  water,  which  dissolves  the 
ptyalin,  and  from  its  watery  solution  it  is  precipitated  by  alcohol  as  a  white  powder.  It  is  redissolved 
in  water  and  reprecipitated,  and  is  obtained  pure  {Cohnheini). 

(2)  Glycerine  or  v.  Wittich's  Method. — The  salivary  glands  [rat]  are  chopped  up,  placed  in 
absolute  alcohol  for  twenty-four  hours,  taken  out  and  dried,  and  afterward  placed  in  glycerine 
for  several  days,  which  extracts  the  ptyalin.  It  is  precipitated  by  alcohol  from  the  glycerine 
extract. 

(3)  WilHam  Roberts  recommends  the  following  solutions  for  extracting  ferments  from  organs 
which  contain  them:  (i)  A  3  to  4  percent,  solution  of  a  mixture  of  2  parts  of  boracic  acid 
and  I  part  borax.  (2)  Water,  with  12  to  15  per  cent,  of  alcohol.  (3)  i  part  chloroform  to  200 
of  water. 

Diastatic  Action  of  Saliva. — {a)  The  diastatic  or  sugar-forming  action  is  known  by  (i)  The 
disappearance  of  the  starch.  When  a  small  quantity  of  starch  is  boiled  with  several  hundred 
times  its  volume  of  water,  starch  mucilage  is  obtained,  which  strikes  a  blue  color  with  iodine.  If  to 
a  small  quantity  of  this  starch  a  sufficient  amount  of  saliva  be  added,  and  the  mixture  kept  for  some 
time  at  the  temperature  of  the  body,  the  blue  color  disappears.  (2)  The  presence  of  sugar  is 
proved  directly  by  using  the  tests  for  sugar  (§  149)- 

{b)  The  action  takes  place  more  slowly  in  the  cold  than  at  the  temperature  of  the  body — its  action 
is  enfeebled  at  55°  C,  and  destroyed  at  75°  C.  [Paschutin).  The  most  favorable  temperature  is 
35°  to  39°  C. 

(c)  The  ptyalin  itself  does  not  seem  to  be  changed  during  its  action,  but  ptyalin  which  has  been 
used  for  one  experiment  is  less  active  when  used  the  second  time  [PaschtiHn). 

Ptyalin  differs  from  diastase — the  ferment  in  germinating  grains — in  so  far  that  the  latter  first  begins 
to  act  at  -j-  66°  C.  Ptyalin  decomposes  salicin  into  saligenin  and  grape  sugar  [Frerichs  and 
Stadler). 

{d)  Saliva  acts  best  in  an  exactly  neutral  medium,  but  it  also  acts  in  an  alkaline  and  even  in  a 
slightly  acid  fluid ;  strong  acidity  prevents  its  action.  The  ptyalin  is  only  active  in  the  stomach  when 
the  acidity  is  due  to  organic  acids  (lactic  or  butyric),  and  not  when  free  hydrochloric  acid  is  present 
{van  de  Velde).  In  both  cases,  however,  dextrin  is  formed.  Ptyalin  is  destroyed  by  hydrochloric 
acid  or  digestion  by  pepsin  [Chiftendefi  and  Griswold,  Langley).  Even  butyric  and  lactic  acids 
formed  from  grape  sugar  in  the  stomach  may  prevent  its  action  ;  but  if  the  acidity  be  neutralized, 
the  action  is  resumed  (C/.  Bernara). 

{e)  The  addition  of  common  salt,  ammonium  chloride,  or  sodium  .sulphate  (4  per  cent,  solution), 
increases  the  activity  of  the  ptyaHn,  and  CO2,  acetate  of  quinine,  strychnia,  morphia,  curara,  0.025  per 
cent,  sulphuric  acid,  have  the  same  effect. 


264  TESTS    FOR    SUGAR. 

{J)  Much  alcohol  and  caustic  potash  destroy  the  ptyalin ;  long  exposure  to  the  air  weakens  its 
action  ;  sodium  carbonate  and  magnesium  sulphate  delay  the  action  [Pfeiffer).  Salicylic  acid  and 
much  atropin  arrest  the  formation  of  sugar. 

[g)  Ptyalin  acts  very  feebly  and  very  gradually  upon  raw  starch,  only  after  2  to  3  hours  [Schiff); 
while  upon  boiled  starch  it  acts  rapidly.  [Hence  the  necessity  for  boiling  thoroughly  all  starchy 
foods.] 

(//)  The  various  kinds  of  starch  are  changed  more  or  less  rapidly  according  to  the  amount  of  cel- 
lulose which  they  contain  ;  raw  potato  starch  after  2  to  3  hours,  raw  maize  starch  after  2  to  3  minutes 
{^Haiinnarslen') ;  wheat  starch  more  quickly  than  that  of  rice.  When  the  starches  are  powdered  and 
boiled,  they  are  changed  with  equal  rapidity. 

(/')  A  mixture  of  the  saliva  from  all  the  glands  is  more  active  than  the  saliva  from  any  single  gland 
{Jakubo-oitsch),  while  mucin  is  inactive. 

[Effect  of  Tea. — Tea  has  an  intensely  inhibitory  effect  on  salivary  digestion,  which  is  due  to 
the  large  quantity  of  tannin  contained  in  the  tea-leaf.  Coffee  and  cocoa  have  only  a  slight 
effect  on  salivary  digestion.  The  only  way  to  mitigate  the  inhibitory  effect  of  tea  on  salivary 
digestion  is  "not  to  sip  the  beverage  with  the  meal,  but  to  eat  first  and  drink  afterward" 
{Roberts).'\ 

II.  Saliva  dissolves  those  substances  which  are  soluble  in  water ;  while  the  alka- 
line reaction  enables  it  to  dissolve  some  substances  which  are  not  soluble  in  water 
alone,  but  require  the  presence  of  an  alkali. 

III.  Saliva  moistens  dry  food  and  aids  the  formation  of  the  "bolus,"  while  by 
its  mucin  it  helps  the  act  of  swallowing,  the  mucin  being  given  off  unchanged  in 
the  faeces.     The  ultimate  fate  of  ptyalin  is  unknown. 

[IV.  Saliva  also  aids  articulation,  while  according  to  Liebig  it  carries  down 
into  the  stomach  small  quantities  of  O.] 

[V.  It  is  necessary  to  the  sense  of  taste  to  dissolve  sapid  substances,  and  bring 
them  into  relation  with  the  end  organs  of  the  nerves  of  taste.] 

Saliva  has  no  action  on  proteids  or  on  fats. 

The  presence  of  a  peptone-forming  ferment  has  recently  been  detected  in  saliva  {Hii/ner,  Munk, 
JCiihne).     [Perfectly  healthy  human  saliva  has  no  poisonous  properties.] 

149.  TESTS  FOR  SUGAR.— I.  Trommer's  test  depends  upon  the  fact 
that,  in  alkaline  solutions,  sugar  acts  as  a  reducing  agent ;  in  this  case  a  metallic 
oxide  is  changed  into  a  sub-oxide.  To  the  fluid  to  be  investigated,  add  ^  of  its 
volume  of  a  solution  of  caustic  potash  (soda),  specific  gravity  1.25,  and  a  few 
drops  of  a  weak  solution  of  cupric  sulphate,  which  causes  at  first  a  bluish  precipi- 
tate, consisting  of  hydrated  cupric  oxide,  but  it  is  redissolved,  giving  a  clear 
blue  fluid,  if  sugar  be  present.  Heat  the  upper  stratum  of  the  fluid,  and  a  yellow 
or  red  ring  of  cuprous  oxide  is  obtained,  which  indicates  the  presence  of  sugar; 
2CuO  — 0  =  Cu.,0. 

The  solution  of  hydrated  cupric  oxide  is  caused  by  other  organic  substances;  but  the  final 
stage,  or  the  production  of  cuprous  oxide,  is  obtained  only  with  certain  sugars — grape,  fruit  and 
milk  (but  not  cane)  sugar.  Fluids  which  are  turbid  must  be  previously  filtered,  and  if  they  are 
highly  colored,  they  must  be  treated  with  basic  lead  acetate ;  the  lead  acetate  is  afterward 
removed  by  the  addition  of  sodium  phosphate  and  subsequent  filtration.  If  very  small  quantities 
of  sugar  are  present  along  with  compounds  of  ammonia,  a  yellow  color  instead  of  a  yellow 
precipitate  may  be  obtained.  In  doing  the  test,  care  must  be  taken  not  to  add  too  much  cupric 
sulphate. 

[2.  Fehling's  Solution  is  an  alkaline  solution  of  potassio-tartrate  of  copper. 
Boil  a  small  quantity  of  the  deep-blue  colored  Fehling's  solution  in  a  test-tube, 
and  add  to  the  boiling  test  a  few  drops  of  the  fluid  supposed  to  contain  the  sugar. 
If  siigar  be  present,  the  copper  solution  is  reduced,  giving  a  yellow  or  reddish 
precipitate.  The  reason  for  boiling  the  test  itself  is,  that  the  solution  is  apt  to 
decompose  when  kept  for  some  time,  when  it  is  precipitated  by  heat  alone.  This 
is  one  of  the  best  and  most  reliable  tests  for  the  presence  of  sugar.  In  Pavy's 
modification  of  this  test,  ammonia  is  used  instead  of  a  caustic  alkali  (§  267).] 

(3)  Bottger's  Test. — .'Mkaline  bismuth  oxide  solution  is  best  prepared,  according  to  Nylander, 
as  follows:  2  grms.  bismuth  subnitrate,  4  grms.  potassic  and  sodic  tartrate,  100  grms.  caustic  soda 
of  8  per  cent.     Add  i  c.c.  to  every  10  c.c.  of  the  fluid  to  be  investigated.     When  boiled  for  several 


QUANTITATIVE    ESTIMATION    OF    SUGAR.  265 

minutes,  the  sugar  causes  the  reduction  and  deposits  a  black  precipitate  of  metallic  bismuth. 
[According  to  Salkowski,  the  urine  of  a  person  taking  rhubarb  gives  the  same  reaction  with  this 
test.] 

(4)  Moore  and  Heller's  Test. — Caustic  potash  or  soda  is  added  until  the  mixture  is  strongly 
alkaline ;  it  is  afterward  boiled.  If  sugar  be  present,  a  yellow,  brown,  or  brownish-black  coloration 
is  obtained.  If  nitric  acid  be  added,  the  odor  of  burned  sugar  (caramel)  and  formic  acid  is 
obtained. 

(5)  Mulder  and  Neubauer's  Test. — A  solution  of  indigo- carmine,  rendered  alkaline  with  sodic 
carbonate,  is  added  to  the  sugar  solution  until  a  slight  bluish  color  is  obtained.  When  the  mixture 
is  heated,  the  color  passes  into  purple,  red,  and  yellow.  When  shaken  with  atmospheric  air,  the 
fluid  again  becomes  blue. 

Molisch's  Test. — To  5  c.cm.  of  the  fluid  add  2  drops  of  a  17  per  cent,  alcoholic  solution  of 
a-naphthol,  or  a  solution  of  thymol.  Add  i  to  2  c.cm.  of  concentrated  sulphuric  acid,  and  shake 
the  mixture.  The  presence  of  sugar  colors  the  a-naphthol  mixture  deep  violet,  the  thymol 
deep  red.  The  subsequent  addition  of  water  causes  a  precipitate  of  similar  color,  which  is 
insoluble  in  concentrated  hydrochloric  acid.  Albumin,  casein  and  peptone  give  the  same 
reaction  [Seegen),  but  the  deposit  on  the  addition  of  water  is  soluble  in  concentrated  hydro- 
chloric acid. 

Other  tests  are  described  in  §  266. 

In  all  cases  where  albumin  is  present  it  must  be  removed — in  urine  by  acidulating  with  acetic 
acid  and  boiling ;  in  blood,  by  adding  four  times  its  volume  of  alcohol  and  afterward  filtering,  while 
the  alcohol  is  expelled  by  heat. 

150.  QUANTITATIVE  ESTIMATION  OF  SUGAR.— I.  By  Fermentation.— In  the 

glass  vessel  (Fig.  161,  a)  a  measured  quantity  (20  c.cm.)  of  the  fluid  (sugar)  is  placed  along  with 
some  yeast,  while  b  contains  concentrated  sulphuric  acid.  The  whole  apparatus  is  then  weighed. 
When  exposed  to  a  sufficient  temperature  (io°  to  40°  C),  the  sugar  splits  into  2  molecules  of 
alcohol  and  2  of  carbon  dioxide, 

C.HjA  =  2  (C^HgO)  -f       2  (CO,), 

Grape  sugar  =       2  alcohol      +   2  carbon  dioxide  ; 

and  in  addition  there  are  formed  traces  of  glycerine  and  succinic  acid.  The  CO,  escapes  from  b, 
and  as  it  passes  through  the  H2S0^,  the  CO,  yields  to  the  latter 

its  water.     The  apparatus  is  weighed  after  two  days,  when  the  Fig.  161. 

reaction  is  ended,  and  the  amount  of  sugar  is  calculated  from 
the  loss  of  weight  in  the  20  c.cm.  of  fluid.  100  parts  of  water- 
free  sugar  =  48.89  parts  CO.,,  or  100  parts  CO,  correspond  to 
204.54  parts  of  sugar. 

II.  Titration. — By  means  of  Fehling's  solution,  which  is 
made  of  such  strength  that  all  the  copper  in  10  cubic  centi- 
metres of  the  solution  is  reduced  by  0.05  gramme  of  grape 
sugar  (I  267). 

III.  Circumpolarization. — The   saccharimeter  of    Soleil- 
Ventzke  may  be  used  to  determine  the  amount  of  sugar  present.    Apparatus  for  the  quantitative  estimation 
It  may  also  be  used  for  the  quantitative  estimation  of  albumin.  of  sugar  by  fermentation. 
Sugar  rotates  the  ray  of  polarized  light  to  the  right  and  albumin 

to  the  left.  The  amount  of  rotation,  or  "specific  rotatory  power,"  is  directly  proportional  to  the 
amount  of  the  rotating  substance  present  in  the  solution,  so  that  the  amount  of  rotation  of  the  ray 
indicates  the  amount  of  the  substance  present.  By  the  term  "specific  rotatory  power"  is  meant  the 
degree  of  rotation  which  is  produced  by  i  grm.  of  the  substance  dissolved  in  i  c.cm  of  water,  when 
examined  in  a  layer  i  decimeter  thick.    For  yellow  light  the  specific  rotation  of  grape  sugar  is  -|-  56°. 

In  Fig.  162  the  light  from  the  lamp  falls  upon  a  crystal  of  calc-spar.  Two  Nicol's  prisms  are 
placed  at  v  and  s,  v  is  movable  round  the  axis  of  vision,  while  s  is  fixed.  In  m  Soleil's  double 
plate  of  quartz  is  placed,  so  that  one-half  of  it  rotates  the  ray  of  polarized  light  as  much  to  the  right 
as  the  other  rotates  it  to  the  left.  In  n  the  field  of  vision  is  covered  by  a  plate  of  left-rotatory 
quartz.  At  b  c\%  the  compensator,  composed  of  two  right-rotatory  prisms  of  quartz,  which  can  be 
displaced  laterally  by  the  milled  head,  g,  so  that  the  polarized  light  passing  through  the  apparatus 
can  be  made  to  pass  through  a  thicker  or  thinner  layer  of  quartz.  When  these  right-rotatory  prisms 
are  placed  in  a  certain  position,  the  rotation  of  the  left-rotatory  quartz  at  n  is  exactly  neutralized.  In 
this  position  the  scale  on  the  compensator  has  its  nonius  exactly  at  0,  and  both  halves  of  the  double 
plate  zXtn  appear  to  have  the  same  color  to  the  observer,  who  from  v  looks  through  the  telescope 
placed  at  e.  Rotate  the  Nicol's  prism  at  v  until  a  bright  rose-colored  field  is  obtained.  In  this 
position  the  telescope  must  be  so  adjusted  that  the  vertical  line  bounding  the  two  halves  shall  be 
distinctly  visible.     The  apparatus  is  now  ready  for  use. 

Fill  a  tube,  I  decimetre  in  length,  with  urine  containing  sugar  or  albumin,  the  urine  being  per- 
fectly clear.  The  tube  is  placed  between  m  and  n.  By  rotating  the  Nicol's  prisms,  v,  the  rose 
color  is  again  obtained.    The  compensator  at  g  is  then  rotated  until  both  halves  of  the  field  of  vision 


266 


MECHANISM    OF   THE    DIGESTIVE    APPARATUS. 


have  exactly  the  same  color.  When  this  is  obtained,  read  oft"  on  the  scale  the  number  of  degrees 
the  nonius  is  displaced  to  the  right  (sugar)  or  to  the  left  (albumin)  from  zero.  The  number  of 
degrees  indicates  directly  the  number  of  grammes  of  the  rotating  substance  present  in  loo  c.  c.  of 
the  fluid.  If  the  fluid  is  very  dark  colored,  it  must  be  decolorized  by  filtering  it  through  animal 
charcoal  (S^e^c-n),  [or  the  coloring  matter  may  be  precipitated  by  the  addition  of  lead  acetate].  If 
the  sugary  urine  contains  albumin,  the  latter  must  be  removed  by  boiling  and  filtration.  A  turbidity 
not  removed  by  filtration  may  be  got  rid  of  by  adding  a  drop  of  acetic  acid  or  several  drops  of  sodic 
carbonate  or  milk  of  lime,  and  afterward  filtering.  [One  may  also  employ  the  apparatus  of  Mit- 
scherlich,  or  the  "half-shadow  apparatus"  of  Laurent.] 


Fig.  162. 


Soleil-Ventzke's  Polarization  Apparatus. 


151.  MECHANISM  OF  THE  DIGESTIVE  APPARATUS.— This 

embraces  the  following  acts  :  — 

1.  The  introduction  and    mastication  of   the    food;    the  movements   of  the 

tongue ;  insalivation ;  formation  of  the  bolus  of  food. 

2.  Deglutition. 

3.  The  movements  of  the  stomach,  small  and  large  intestine. 
4-  The  excretion  of  fecal  matters. 


MASTICATION.  267 

152.  INTRODUCTION  OF  THE  FOOD.— Fluids  are  taken  into  the 
mouth  in  three  ways:  (i)  By  suction,  the  lips  are  applied  air-tight  to  the  vessel 
containing  the  fluid,  while  the  tongue  is  retracted  (the  lower  jaw  being  pften 
depressed)  and  acts  like  the  piston  in  a  suction  pump,  thus  causing  the  fluid  to 
enter  the  mouth.  Herz  found  that  the  negative  pressure  caused  by  an  infant 
while  sucking  ==  3  to  10  mm.  Hg.  (2)  The  fluid  is  lapped  when  it  is  brought 
into  direct  contact  with  the  lips,  and  is  raised  by  aspiration  and  mixed  with  air  so 
as  to  produce  a  characteristic  sound  in  the  mouth.  (3)  Fluid  may  be  poured 
into  the  mouth,  and  as  a  general  rule  the  lips  are  applied  closely  to  the  vessel 
containing  the  fluid. 

Solids,  when  they  consist  of  small  particles,  are  licked  up  with  the  lips,  aided 
by  the  movements  of  the  tongue.  In  the  case  of  large  masses,  a  part  is  bitten  off 
with  the  incisor  teeth,  and  is  afterward  brought  under  the  action  of  the  molar 
teeth  by  means  of  the  lips,  cheeks,  and  tongue. 

153.  MASTICATION. — The  articulation  of  the  jaw  is  provided  with  an  interarticular  carti- 
lage—  the  meniscus — which  prevents  direct  pressure  being  made  upon  the  articular  surface  when 
the  jaws  are  energetically  closed,  and  which  also  divides  the  joint  into  two  cavities,  one  lying 
over  the  other.  The  capsule  is  so  lax  that,  in  addition  to  the  raising  and  depressing  of  the  lower 
jaw,  it  permits  of  the  lower  jaw  being  displaced  forward,  whereby  the  meniscus  moves  with  it,  and 
covers  the  articular  surface. 

The  process  of  mastication  embraces:  («)  The  elevation  of  the  ja-w, 
accomplished  by  the  combined  action  of  the  Temporal,  Masseter,  and  Internal 
Pterygoid  Muscles.  If  the  lower  jaw  was  previously  so  far  depressed  that  its 
articular  surface  rested  upon  the  tubercle,  it  now  passes  backward  upon  the 
articular  surface. 

{d)  The  depression  of  the  lower  jaw  is  caused  by  its  own  weight,  aided 
by  the  action  of  the  anterior  bellies  of  the  Digastrics,  the  Mylo-  and  Genio-hyoid 
and  Platysma.  The  muscles  act  especially  during  forcible  opening  of  the  mouth. 
The  necessary  fixation  of  the  hyoid  bone  is  obtained  through  the  action  of  the 
Omo-  and  Sterno-hyoid,  and  by  the  Sterno-thyroid  and  Thyro-hyoid. 

When  the  articular  surface  of  the  lower  jaw  passes  forward  on  to  the  tubercle,  the  External 
Pterygoids  actively  aid  in  producing  this  (^Berard). 

if)  Displacement  of  the  Articular  Surfaces. — During  rest,  when  the 
mouth  is  closed,  the  incisor  teeth  of  the  lower  jaw  are  within  the  arch  of  the 
upper  incisors.  When  in  this  position  the  jaw  is  protruded  by  the  External 
Pterygoids,  whereby  the  articular  surface  passes  on  to  the  tubercle  (and,  there- 
fore, downward),  while  the  lateral  teeth  are  thereby  separated  from  each  other. 
The  jaw  is  retracted  by  the  Internal  Pterygoids  without  any  aid  from  the  posterior 
fibres  of  the  Temporals.  When  one  articular  surface  is  carried  forward,  the  jaw 
is  protruded  and  retracted  by  the  External  and  Internal  Pterygoid  of  the  same 
side.  At  the  same  time,  there  is  a  transverse  movement,  whereby  the  back  teeth 
of  the  protruded  side  are  separated  from  each  other. 

During  mastication,  the  individual  movements  of  the  lower  jaw  are  variously 
combined,  and  especially  with  lateral  grinding  movements,  while  the  food  to  be 
masticated  is  kept  from  passing  outward  by  the  action  of  the  muscles  of  the  lips 
(Orbicularis  oris)  and  the  Buccinators,  while  the  tongue  continually  pushes  the 
particles  between  the  molar  teeth.  The  energy  of  the  muscles  of  mastication  is 
regulated  by  the  sensibility  of  the  teeth,  and  the  muscular  sensibility  of  the 
muscles  of  mastication,  as  well  as  by  the  general  sensibility  of  the  mucous  mem- 
brane of  the  mouth  and  lips.  At  the  same  time,  the  mass  is  mixed  with  saliva, 
the  divided  particles  cohere,  and  are  formed  into  a  mass  or  bolus,  of  a  long, 
oval  shape,  by  the  muscles  of  the  tongue.  The  bolus  then  rests  on  the  back  of 
the  tongue,  ready  to  be  swallowed. 

Nerves  of  Mastication. — The  muscles  of  mastication  receive  their  motor  nerves  from  the 
third  branch  of  the  trigeminus,  the  mylo-hyoid  and  the  anterior  belly  of  the  digastric  being  sup- 


268 


STRUCTURE    AND    DEVELOPMENT   OF   THE   TEETH. 


Fig.  163. 


Pulp 
Cavitv. 


plied  from  the  same  source.  The  genio-,  omo-,  and  sterno-hyoid,  sternothyroid,  and  thyrohyoid 
are  supplied  by  the  hypoglossal,  while  the  facial  supplies  the  posterior  belly  of  the  digastric,  the 
stylohyoid,  the  platysma,  the  buccinator,  and  the  muscles  of  the  lips.  The  general  centre  for  the 
muscles  of  mastication  lies  in  the  medulla  oblongata  (^  367). 

\Vhen  the  mouth  is  closed,  the  jaws  are  kept  in  con- 
tact by  the  pressure  of  the  air,  as  the  cavity  of  the  mouth 
is  rendered  free  from  air,  and  the  entrance  of  air  is  pre- 
vented anteriorly  by  the  lips,  and  posteriorly  by  the  soft 
palate.  The  pressure  exerted  by  the  air  is  from  2  to  4 
mm.  Hg.  {Mc/z;^'cr  and  DoHcfers). 

[Effect  on  the  Circulation. — Marey  found  that  mas- 
tication trebled  the  velocity  of  the  blood  current  in  the 
carotid  (horse),  while  Francois  Frank  observed  that  the 
circulation  of  the  brain  (in  man)  is  increased ;  hence  it 
is  evident  that  mastication  implies  an  increased  supply 
of  blood  to  the  nerve  centres.] 

154.  STRUCTURE  AND  DEVELOPMENT 
OF  THE  TEETH.— .\  tooth  is  just  a  papilla  of  the 
mucous  membrane  of  the  gum,  which  has  undergone  a 
characteristic  development.  In  its  simplest  form,  as  in 
the  teeth  of  the  lamprey,  the  connective-tissue  basis  of 
the  papilla  is  covered  with  many  layers  of  corneous  epi- 
thelium. In  human  teeth,  part  of  the  papilla  is  trans- 
formed into  a  layer  of  calcified  dentine,  while  the  epi- 
thelium of  the  papilla  produces  the  enamel,  the  fang  of 
the  tooth  being  covered  by  a  thin  accessory  layer  of 
bone,  the  crusta  petrosa  or  cement. 

The  dentine  or  ivory  which  surrounds  the  pulp  cavity 
and  the  canal  of  the  fang  (Fig.  163)  is  very  firm,  elastic, 
and  brittle.  Dentine,  like  the  matrix  of  bone,  when 
treated  in  a  certain  way,  presents  a  fibrillar  structure.  It 
is  permeated  by  innumerable  long,  tortuous,  wavy  tubes 
— the  dentinal  tubules — each  of  which  communicates 
with  the  pulp  cavity  by  means  of  a  fine  opening,  and 
passes  more  or  less  horizontally  outward  as  far  as  the 
outer  layers  of  the  dentine.  The  tubules  are  bounded 
by  an  extremely  resistant,  thin,  cuticular  membrane, 
which  strongly  resists  the  action  of  chemical  reagents. 
These  tubules  are  filled  completely  by  soft  fibres,  the  "fibres  of  Tomes,"  which  are  merely 
greatly  elongated  and  branched  processes  of  the  odontoblasts  of  the  pulp. 

The  dentinal  tubules,  as  well  as  the  fibres  of  Tomes,  anastomose  throughout  their  entire  extent 
by  means  of  fine  processes.  As  the  fibres  approach  the  enamel,  which  they  do  not  penetrate,  some 
of  them  bend  on  themselves,  and  form  a  loop  (Fig.  166,  c),  while  others  pass  into  the  "inter- 
globular spaces  "  (Fig.  165)  which  are  so  abundant  in  the  outer  part  of  the  dentine.  The  inter- 
globular spaces  are  small  spaces  bounded  by  curved  surfaces.  Certain  curved  lines,  "  Schreger's 
lines,"  may  be  detected  with  the  naked  eye  in  the  dentine  {e.  g.,  of  the  elephant's  tusk)  running 
parallel  with  the  contour  of  the  tooth.  They  are  caused  by  the  fact  that  at  these  parts  all  the  chief 
curves  in  the  dentinal  tubules  follow  a  similar  course. 

The  enamel,  the  hardest  substance  in  the  body  (resembling  apatite),  covers  the  crown  of  the 
teeth.  It  consists  of  hexagonal  flattened  prisms  arranged  side  by  side  like  a  palisade  (Fig.  166,  B 
and  C).  They  are  3  to  5  /i  (soW  inch)  broad,  not  quite  uniform  in  thickness,  curved  slightly  in 
different  directions,  and,  owing  to  inequalities  of  thickness,  they  exhibit  transverse  markings.  They 
are  elongated,  calcified,  cylindrical,  epithelial  cells.  Retzius  described  dark  brown  lines  running 
parallel  with  the  outer  boundary  of  the  enamel,  due  to  the  presence  of  pigment  (Fig.  163).  The 
fully-formed  enamel  is  negatively  doubly  refractive  and  uniaxial,  while  the  developmg  enamel  is 
positively  doubly  refractive  [Hoppe-Seyler). 

The  cuticula  or  Nasmyth's  membrane  covers  the  free  surface  of  the  enamel  as  a  completely 
structureless  membrane  i  to  2  //  thick,  but  in  quite  young  teeth  it  exhibits  an  epithelial  structure, 
and  is  derived  from  the  outer  epithelial  layer  of  the  enamel  organ. 

The  cement  or  crusta  petrosa  is  a  thin  layer  of  bone  covering  the  fang  (Fig.  167,  a).  The 
bone  lacunae  communicate  directly  with  the  dental  tubules  of  the  fang.  Haversian  canals  and 
lamellae  are  only  found  where  the  layer  of  cement  is  thick,  and  the  former  may  communicate  with 
the  pulp  cavity.  Very  thin  layers  of  cement  may  be  devoid  of  bone  corpuscles.  Sharpey's  fibres 
occur  in  the  cement  of  the  dog's  tooth ;  while  in  the  horse's  tooth  single  bone  corpuscles  are 
developed  by  a  capsule.     In  the  periodontal  membrane,  which  is  just  the  periosteum  of  the 


Longitudinal  section  of  an  incisor  tooth. 


CHEMISTRY    OF    A   TOOTH. 


269 


alveolus,  coils  of  blood  vessels  similar  to  the  renal  glomeruli  occur.     They  anastomose  with  each 
other,  and  are  surrounded  by  a  delicate  capsule  of  connective  tissue. 

Chemistry  of  a  Tooth. — The  teeth  consist  of  a  gelatine-yielding  matrix  infiltrated  with  calcium 
phosphate  and  carbonate  (like  bone),  (i)  The  dentine  contains — organic  matter,  27.70;  calcium 
phosphate  and  carbonate,  72.06;  magnesium  phosphate,  0.75;  with  traces  of  iron,  fluorine,  and 
sulphuric  acid. 

Fig.  165. 


Fig.  164. 


Transverse  section  of  dentine.  The 
light  rings  are  the  walls  of  the 
dentinal  tubules  ;  the  dark  centres 
with  the  light  points  are  the  fibres 
of  Tomes  lying  in  the  tubules. 


Interglobular  spaces  in  dentine. 


Fig.  167. 


Section   of  a   tooth  between   the   dentine   and   enamel,     a,  enamel  ;     Transverse  section  of  the  fang,    a,  cement 
c,  dentinal  tubules  ;  B,  enamel  prisms  highly  magnified  ;   C,  trans-  with   bone  corpuscles  ;   b,  dentine    with 

verse  sections  of  enamel  prisms.  tubules  ;   c,  boundary  between  both. 


(2)  The  enamel  contains  anorganic  proteid  matrix  allied  to  the  substance  of  epithelium.  It 
consists  of  3.60  organic  matter  and  96.00  of  calcium  phosphate  and  carbonate,  1.05  magnesium 
phosphate,  with  traces  of  calcium  fluoride  and  an  insoluble  chlorine  compound. 

(3)  The  cement  is  identical  with  bone. 

The  pulp  in  a  fully-grown  tooth  represents  the  remainder  of  the  dental  papilla  around  which  the 
dentine  was  deposited.  It  consists  of  a  very  vascular,  indistinctly  fibrillar  connective  tissue,  laden 
with  cells.     The  layers  of  cells,  resembling  epithelium,  which  lie  in  direct  contact  with  the  dentine, 


270 


DEVELOPMENT   OK    A    TOOTH. 


are  called  odontoblasts,  /.  e.,  those  cells  which  build  up  the  dentine.  These  cells  send  off  long- 
branched  jirocesses  into  the  dentinal  tubules,  while  their  nucleated  bodies  lie  on  the  surface  of  the 
pulp,  and  form  connections  by  processes  with  other  cells  of  the  pulp  and  with  neighboring  odonto- 
blasts. Numerous  non-medilllated  nerve  fibres  (sensory  from  the  trigeminus),  whose  mode  of 
termination  is  unknown,  occur  in  the  pulp. 

The  periosteum  or  periodontal  membrane  of  the  fang  is,  at  the  same  time,  the  alveolar 
l>eriosteum,  and  consists  of  connective  tissue  with  elastic  fibres  and  many  nerves. 

The  gums  are  devoid  of  mucous  glands,  very  vascular,  and  often  provided  with  long  vascular 
papilhv,  wliich  are  sometimes  compound. 

Development  of  a  Tooth. — It  begins  at  the  end  of  the  second  month  of  foetal  life.  Along  the 
whole  length  of  the  fcptal  gum  is  a  thick  projecting  ridge  (Fig.  i6S,  a)  composed  of  many  layers 
of  epithelium.  A  depression,  the  dental  groove,  also  filled  with  epithelium,  occurs  in  the  gum, 
and  runs  along  under  the  ridge.  The  dental  groove  becomes  deeper  throughout  its  entire  length, 
and  on  transverse  section  presents  the  appearance  of  a  dilated  flask  {b),  while  at  the  same  time  it  is 
rilled  with  elongated  epithelial  cells,  which  form  the  "  enamel  organ."  A  conical  papilla,  the 
"  dentine  germ,"  grows  up  from  the  mucous  tissue,  of  which  the  gum  consists,  toward  the  enamel 
organ  (Fig.  169,  t),  so  that  the  apex  of  the  papilla  comes  to  have  the  enamel  organ  resting  upon  it 
like  a  double  cap.  Afterward,  owing  to  the  development  of  connective  tissue,  the  parts  of  the 
enamel  organ  lying  between  and  uniting  the  individual  dentine  germs,  disappear,  and  gradually  the 
connective  tissue  forms  a  tooth  sac  enclosing  the  papilla  and  its  enamel  organ  (d). 

Those  epithehal  cells  (Fig.  169,  3)  of  the  enamel  organ  which  lie  next  the  top  of  the  papilla,  are 
cylindrical,  and  become  calcifted  to  form  enamel  prisms.     The  layer  of  cells  of  the  double  cap,  which 


Fk;.  168. 


Fig.  169. 


Fig.  170. 


Fig.  168. — a.  Dental  ridge;  b,  enamel  organ;  c,  beginning  of  the  dentine  germ;  d,  first  indication  of  the  tooth  sac. 
Fig.  169. — a.  Dental  ridge  ;  t,  enamel  organ  with  (i)  outer  epithelium,  (2)  middle  stellate  layer,  (3)  enamel  prism- 
cell  layer;  c,  dentine  germ  with  blood  vessels  and  the  long  osteoblasts  on  the  surface ;  d,  tooth  sac ;  e,  secondary 
enamel  germ.  Fig.  170. — a.  Dental  ridge  :  b,  enamel  organ  ;  c,  dentine  germ  ;  /,  enamel ;  g,  dentine  ;  h,  interval 
between  enamel  organ  and  the  position  of  the  tooth  ;  k,  layer  of  odontoblasts. 


is  directed  toward  the  tooth  sac  (i),  becomes  flattened,  fuses,  undergoes  a  horny  transformation,  and 
becomes  the  cuticula,  while  the  cells  which  lie  between  both  layers  undergo  an  intermediate  meta- 
morphosis, so  that  they  come  to  resemble  the  branched  stellate  cells  of  the  mucous  tissue  (2),  and 
gradually  disappear  altogether. 

The  dentine  is  formed  in  the  most  superficial  layer  of  the  projecting  connective  tissue  of  the 
dental  papilla,  owing  to  the  calcification  of  the  continuous  layer  of  odontoblasts  which  occur  there 
(Figs.  169  and  170,  k).  During  the  process,  fibres  or  branches  of  these  cells  are  left  unaffected,  and 
remain  as  the  fibres  of  Tomes.  Exactly  the  same  process  occurs  as  in  the  formation  of  bone,  the 
odontoblasts  forming  around  themselves  a  calcified  matrix.  The  cement  is  formed  from  the  soft 
connective  tissue  of  the  dental  alveolus. 

Dentition. — During  the  development  of  the  first  temporary  or  milk  teeth  a  special  enamel 
organ  (Fig.  169,  <r)  is  formed  near  these,  but  it  does  not  undergo  development  until  the  milk  teeth 
are  shed;  even  the  papilla  is  wanting  at  first.  When  the  permanent  tooth  begins  to  develop,  it 
opens  into  the  alveolar  wall  of  the  milk  teeth  from  below.  The  tissue  of  this  dental  sac  causes 
erosion,  or  eating  away  of  the  fang  and  even  of  the  body  of  the  milk  teeth,  without  its  blood  vessels 
undergoing  atrophy.  The  chief  agents  in  the  absorption  are  the  amoeboid  cells  of  the  granulation 
tissue.     [Multinuclear  giant  cells  also  erode  the  fangs  of  the  teeth.] 

Eruption  of  the  Milk  Teeth.— The  following  is  the  order  in  which  the  twenty  milk  teeth  cut 
the  gum,  i.  e.,  from  the  seventh  month  to  the  second  year:  Lower  central  incisors,  upper  central 
incisors,  upper  lateral  incisors,  lower  lateral  incisors,  first  molar,  canine,  the  second  molars. 


MOVEMENTS   OF   THE    TONGUE. 
[The  figures  indicate  in  months  the  period  of  eruption  of  each  tooth.] 


271 


Molars. 

Canines. 

1   ■ 
Incisors.              ;            Canines. 

Molars. 

24      12 

18 

9  7  7  9                         18 

j 

24      12 

[The  permanent  teeth  succeed  the  milk  teeth,  the  process  beginning  about  the  seventh  year. 
Ten  teeth  in  each  jaw  take  the  place  of  the  milk  teeth,  while  six  teeth  appear  further  back  in  each 
jaw.  Thus  the  total  number  of  permanent  teeth  is  thirty-two.  As  the  sacs,  from  which  the  per- 
manent teeth  are  developed,  are  formed  before  birth,  they  merely  undergo  the  same  process  of 
development  as  the  temporary  teeth,  only  at  a  much  later  period.  The  last  of  the  permanent  molars 
— the  wisdom  tooth — may  not  cut  the  jaw  until  the  seventeenth  to  the  twenty-fifth  year.  At  the  sixth 
year  the  jaw  contains  the  largest  number  of  teeth,  as  all  the  temporary  teeth  are  present,  and,  in 
addition,  the  crowns  of  all  the  permanent  teeth,  except  the  wisdom  teeth,  making  forty-eight  in  all.] 

[Eruption  of  Permanent  Teeth. — The  age  at  which  each  tooth  cuts  the  gum  is  given  in 
years  in  the  following  table  : — 


Molars. 

Bicuspid. 

Canines. 

1 

j       Incisors. 

Canines. 

Bicuspid. 

Molars. 

17       12 
to      to     6 
25       13 

ID      9 

II    to    12 

1 
1 
j     8778 

i 

II    to    12 

9      10 

12      17 

6     to     to 

13  25 

[Action  of  Drugs  on  the  Teeth. — All  the  conditions  for  putrefaction  are  present  in  the  mouth; 
and  when  putrefaction  occurs,  the  products  (often  acid)  attack  the  dentine  and  hasten  its  decay. 
Hence,  the  necessity  for  thorough  daily  cleansing  of  the  teeth  and  mouth.  The  teeth  may  be 
cleaned  by  means  of  a  soft  tooth  brush  and  water,  with  or  without  the  use  of  any  of  the  numerous 
dentifrices,  such  as  powdered  chalk  or  charcoal.  Astringents,  such  as  catechu  and  areca-nut,  are 
sometimes  used.  Mineral  acids  attack  the  teeth,  and  ought,  when  taken,  to  be  sucked  through  a 
tube.] 

155.  MOVEMENTS  OF  THE  TONGUE.— The  tongue,  being  a 
muscular  organ,  and  extremely  mobile,  plays  an  important  part  in  the  process  of 
mastication  :  (i)  It  keeps  the  food  from  passing  from  between  the  molar  teeth, 
(2)  It  forms  into  a  bolus  the  finely  divided  food  after  it  is  mixed  with  saliva.  (3) 
When  the  tongue  is  raised,  the  bolus  lying  on  its  dorsum  is  pushed  backward  into 
the  pharynx  and  oesophagus. 

The  course  of  the  fibres  is  threefold — longitudinally,  from  base  to  tip  :  trans- 
versely, the  fibres  for  the  most  part  proceeding  outward  from  the  vertically  placed 
septum  linguae  ;  vertically,  from  below  upward.  Some  of  the  muscles  are  confined 
to  the  tongue  (intrinsic),  while  others  (extrinsic)  are  attached  beyond  it  to  the 
hyoid  bone,  lower  jaw,  the  styloid  process,  and  the  palate. 

Microscopically,  the  fibres  are  transversely  striated,  with  a  delicate  sarcolemma,  and  very  often 
they  are  branched  where  they  are  inserted  into  the  mucous  membrane.  The  muscular  bundles  cross 
each  other  in  various  directions,  and  in  the  interspaces  fat  cells  and  glands  occur. 

Changes  in  form  and  position  : — 

(i)  Shortening  and  broadening  by  the  longitudinal  muscle,  aided  by  the  hyo- 
glossus, 

(2)  Elongation  and  narrowing,  by  the  transversus  linguse. 

(3)  The  dorsum  is  rendered  concave  by  the  transversus  and  the  simultaneous 
action  of  the  median  vertical  fibres. 

(4)  Arching  of  the  dorsum  :  {a)  Transversely  by  the  lowest  transverse  bundles  ; 
(J))  longitudinally,  by  the  lowest  longitudinal  muscles. 

(5)  Protrusion,  by  the  genio-glossus,  while  at  the  same  time  the  tongue  usually 
becomes  narrower  and  longer  (2). 


272  DEGLUTITION. 

(6)  Retraciion,  hyi\\Q.  hyo-glossus  and  stylo-glossus,  and  (i)  usually  occurring  at 
the  same  time. 

(7)  Depression  into  the  floor  of  the  mouth,  by  the  hyo-glossus.  The  floor  of  the 
mouth  may  be  made  deeper  by  depressing  the  hyoid  bone. 

(8)  Elevation  of  the  tongue  toward  the  palate  :  {a)  At  the  tip  by  the  anterior 
part  of  the  longitudinal  fibres  ;  (/')  in  the  middle  by  elevating  the  entire  hyoid 
bone  by  the  mylo-hyoid  {N.  trigeminus)  ;  (r)  at  the  root  by  the  stylo-glossus  and 
palato-glossus,  as  well  as  indirectly  by  the  stylo-hyoid  (yN.  facialis). 

(9)  Lateral  movements,  the  tip  of  the  tongue  passing  to  the  right  or  left  ;  these 
are  caused  by  the  longitudinal  fibres  of  one  side. 

Motor  Nerves. — The  motor  nerve  of  the  tongue  is  the  hypoglossal.  When  this  nerve  is  divided 
or  paralyzed  on  one  side,  the  tip  of  the  tongue  lying  in  the  floor  of  the  mouth  is  directed  toward  the 
sound  side,  because  the  tonus  of  the  non-paralyzed  longitudinal  fibres  shortens  the  sound  side  slightly. 
If  the  tongue  h^  protruded,  however,  the  tip  passes  toward  iht  paralyzed  side.  This  arises  from  the 
direction  of  the  genio-glossus  (from  the  middle  downward  and  outward),  and  the  tongue  follows  the 
direction  of  its  action.  The  tongues  of  animals  which  have  been  killed  exhibit  fibrillar  contrac- 
tions of  the  muscles,  sometimes  lasting  for  a  whole  day.  [Stirling  has  frequently  found  nerve  gan- 
glia in  the  nerves  of  the  tongue.] 

156.  DEGLUTITION. — The  onward  movements  of  the  contents  of  the 
digestive  canal  are  effected  by  a  special  kind  of  action  whereby  the  tube  or  canal 
contracts  upon  its  contents,  and  as  this  contraction  proceeds  along  the  tube, 
the  contents  are  thereby  carried  along.  This  is  the  "  peristaltic  movement," 
or  peristalsis. 

In  the  first  and  most  complicated  part  of  the  act  of  deglutition,  we  distinguish 
in  order  the  following  individual  movements : — 

(i)  The  aperture  of  the  mouth  is  closed  by  the  orbicularis  oris  {N.  facialis). 

(2)  The  jaws  are  pressed  against  each  other  by  the  muscles  of  mastication  (iV. 
trigeminus),  while  at  the  same  time  the  lower  jaw  affords  a  fixed  point  for  the  action 
of  the  muscles  attached  to  it  and  the  hyoid  bone. 

(3J  The  tip,  middle,  and  root  of  the  tongue,  one  after  the  other,  are  pressed 
against  the  hard  palate,  whereby  the  contents  of  the  mouth  are  propelled  toward 
the  pharynx. 

(4)  When  the  bolus  has  passed  the  anterior  palatine  arch  (the  mucus  of  the  ton- 
sillar glands  making  it  slippery  again),  it  is  prevented  from  returning  to  the  mouth 
by  the  palato-glossi  muscles  which  lie  in  the  anterior  pillars  of  the  fauces,  coming 
together  like  two  side  screens  or  curtains,  meeting  the  raised  dorsum  of  the  tongue 
(Stylo-glossus). 

(5)  The  morsel  is  now  behind  the  anterior  palatine  arch  and  the  root  of  the 
tongue,  and  has  reached  the  pharynx,  where  it  is  subjected  to  the  successive  action 
of  the  three  pharyngeal  constrictor  muscles  which  propel  it  onward.  The  action 
of  the  superior  constrictor  of  the  pharynx  is  always  combined  with  a  horizontal 
elevation  (Levator  veli  palatini;  N.  facialis)  dind  tension  (Tensor  veli  palatini; 
iV.  trigeminus,  otic  ganglion)  of  the  soft  palate.  The  upper  constrictor  presses 
(through  the  pterygo-pharyngeus)  the  posterior  and  lateral  walls  of  the  pharynx 
tightly  against  the  posterior  margin  of  the  horizontal,  tense,  soft  palate,  whereby 
the  margins  of  the  posterior  palatine  arches  (palato-pharyngeus)  are  approximated. 
The  pharyngo- nasal  cavity  is  thus  completely  shut  off,  so  that  the  bolus  cannot  be 
pressed  backward  into  the  nasal  cavity. 

In  persons  with  congenital  or  acquired  defects  of  the  soft  palate,  or  cleft-palate,  during  swallow- 
ing, food  passes  into  the  nose. 

(6)  Falk  and  Kronecker  assert  that,  by  the  energetic  contraction  of  the  muscles 
which  diminish  the  cavity  of  the  mouth,  especially  the  mylo-hyoid,  the  bolus  is 
"  projected  "  through  the  pharynx  and  oesophagus.  [They  even  assert  that  the 
bolus  reaches  the  cardia  before  even  the  musculature  of  the  pharynx  or  oesophagus 
can  contract,  and  further  that  the  pharyngeal  muscles  of  a  dog  may  be  divided 


NERVOUS    MECHANISM    OF    DEGLUTITION.  273 

without  making  swallowing  impossible.]  If  we  make  a  series  of  efforts  to  swallow, 
one  after  the  other,  as  in  drinking,  contraction  of  the  pharynx  and  oesophagus  takes 
place  only  after  the  last  effort.  Thus  each  new  act  of  deglutition  in  the  mouth 
inhibits  (by  stimulation  of  the  glosso-pharyngeal  nerve)  the  movements  in  the  parts 
of  the  oesophageal  tube  situated  below  it. 

(7)  The  bolus  is  propelled  onward  by  the  successive  contraction  of  the  upper, 
middle,  and  lower  constrictors  of  the  pharynx  until  it  passes  into  the  oesophagus. 
At  the  same  time  the  entrance  to  the  glottis  is  closed,  else  the  morsel  would  pass 
into  the  larynx,  or,  as  is  generally  said,  would  "  pass  the  wrong  way." 

Duration. — According  to  Meltzer  and  Kronecker,  the  duration  of  deglutition  in  the  mouth  is 
0.3  sec.  ;  then  the  constrictors  of  the  pharynx  contract  0.9  sec. ;  afterward,  the  upper  part  of  the 
oesophagus;  then  after  1.8  sec.  the  middle;  and  after  another  3  sec.  the  lower  constrictor.  The 
closure  of  the  cardia,  after  the  entrance  of  the  bolus  into  the  stomach,  is  the  final  act  in  the  total 
series  of  movements. 

Sounds  during  Deglutition. — If  the  region  of  the  stomach  be  auscultated  during  the  act  of 
swallowing,  two  sounds  may  be  heard ;  the  first  one  is  produced  when  the  bolus  is  projected  into  the 
stomach;  the  second  occurs  when  the  peristalsis,  which  takes  place  at  the  end  of  swallowing, 
squeezes  the  contents  of  the  oesophagus  through  the  cardia  {^Meltzer,  Zenker,  jEwald).  [The  latter 
occurs  4-5  mins.  afterward.  In  man,  when  water  alone  is  swallowed,  there  is  no  sound,  but  when 
it  is  mixed  with  air  there  is,  and  it  is  generally  heard  because  air  is  usually  swallowed  with  the  food 
or  drink  [Qtdncke).'\ 

The  closure  of  the  glottis  is  effected  in  the  following  manner  :  (a)  The  whole 
larynx — the  lower  jaw  being  fixed — is  raised  upward  and  forward,  while  at  the 
same  time  the  root  of  the  tongue  hangs  over  it.  The  hyoid  bone  is  raised  forward 
and  upward  by  the  genio-hyoid,  anterior  belly  of  the  digastric,  and  mylo-hyoid  ; 
the  larynx  is  approximated  close  to  the  hyoid  bone  by  the  thyro-hyoid.  {b^  When 
the  larynx  is  raised,  so  that  it  comes  to  lie  below  the  overhanging  root  of  the 
tongue,  the  epiglottis  is  pressed  downward  over  the  entrance  to  the  glottis,  and 
the  bolus  passes  over  it.  The  epiglottis  is  also  pulled  down  by  the  special  muscular 
fibres  of  the  reflector  epiglottidis  and  aryepiglotticus.  (r)  The  closure  of  the  glottis 
by  the  constrictors  of  the  larynx  also  prevents  the  entrance  of  substances  into  the 
larynx  (§  313,  II,   2). 

Injury  to  the  Epiglottis. — Intentional  injury  of  the  epiglottis  in  animals,  or  its  destruction  in 
man,  may  cause  fluids  to  "go  the  wrong  way,"  i.  ,?.,  into  the  glottis,  while  solid  food  can  be 
swallowed  without  disturbance.  In  dogs,  colored  fluids  placed  on  the  root  of  the  tongue  have  been 
observed  to  pass  directly  into  the  pharynx  without  coming  into  contact  with  it,  so  as  to  tinge  the 
upper  surface  of  the  epiglottis  {Magendie).  [The  basis  of  the  epiglottis  is  yellow  elastic  cartilage, 
so  that  it  shows  no  tendency  to  ossify,  and  always  retains  its  elasticity  (§  313)-] 

In  order  that  the  descending  bolus  may  be  prevented  from  carrying  the  pharynx 
with  it,  the  stylo-pharyngeus,  salpingo-pharyngeus,  and  baseo-pharyngeus  contract 
upward  when  the  constrictors  act. 

Nervous  Mechanism. — Deglutition  is  voluntary  only  during  the  time  the 
bolus  is  in  the  mouth.  When  the  food  passes  through  the  palatine  arch  into  the 
gullet  the  act  becomes  involuntary,  and  is,  in  fact,  a  well-regulated  reflex  action. 
When  there  is  no  bolus  to  be  swallowed,  voluntary  movements  of  deglutition  cark 
be  accomplished  only  within  the  mouth  ;  the  pharynx  only  takes  up  the  move- 
ment, provided  a  bolus  (food  or  saliva)  mechanically  excites  the  reflex  act.  The- 
afferent  nerves,  which,  when  mechanically  stimulated,  excite  the  involuntary  act 
of  deglutition,  are,  the  palatine  branches  of  the  trigeminus  (from  the  spheno-pala- 
tine  ganglion)  and  the  pharyngeal  branches  of  the  vagus.  The  centre  for  the- 
nerves  concerned  (for  the  striped  muscles)  lies  in  the  superior  olives  of  the  medulla, 
oblongata.  Swallowing  can  be  carried  out  when  a  person  is  unconscious,  or  after- 
destruction  of  the  cerebrum,  cerebellum,  and  pons  (§  367,  6).  [Even  in  the 
deep  coma  of  alcoholism,  the  tube  of  a  stomach  pump  is  carried  into  the  stomach, 
reflexly,  provided  the  surgeon  passes  it  back  into  the  pharynx.]  The  nerves  of" 
the  pharynx  are  derived  from  the  pharyngeal  plexus,  which  receives  branches: 
from  the  vagus,  glosso-pharvngeal  and  sympathetic  (§  352.  4). 
18  ^  ' 


274 


STRUCTURE    OF    THE    CESOPHAGUS. 


Within  the  oesophagus,  whose  stratified  epithelium  is  moistened  with  the 
mucus  derived  from  tlie  mucous  glands  in  its  walls,  the  downward  movement  is 
involuntary,  and  depends  upon  a  complicated  reflex  movement  discharged  from 
the  centre  for  deglutition.  There  is  a  peristaltic  movement  of  the  outer  longitu- 
dinal and  inner  circular  non-striped  muscular  fibres. 

In  the  upper  part  of  the  cesophagus,  which  contains  striped  muscular  fibres,  the  peristalsis  takes 
place  more  quickly  than  in  the  lower  part.  The  movements  of  the  oesophagus  never  occur  inde- 
pendently, but  are  always  the  continuation  of  a  foregoing  act  of  deglutition.  If  food  be  introduced 
into  the  tcsophagus  through  a  hole  in  its  wall,  there  it  lies;  and  it  is  only  carried  downward  when 
a  movement  to  swallow  is  made.  The  peristalsis  extends  along  the  whole  length  of  the  oesophagus, 
even  when  it  is  ligatured  or  when  a  part  of  it  is  removed  (A/osso).  If  a  dog  be  allowed  to  swallow 
a  piece  of  flesh  tied  to  a  string,  so  that  the  llesh  goes  half-way  down  the  oesophagus,  and  if  the  flesh 
be  withdrawn,  the  peristalsis  still  passes  downward  (C  Ludwig  and  Wild). 

The  motor  nerve  of  the  cesophagus  is  the  vagus  (not  the  accessory  fibres)  [oesophageal,  whose 
branches  have  numerous  small  ganglia  in  their  course].  After  it  is  divided,  the  food  lodges  in  the 
lower  part  of  the  cesophagus.  V'ery  large  and  very  small  masses  are  swallowed  with  more  difficulty 
than  those  of  moderate  size.  Dogs  can  swallow  an  olive-shaped  body  weighted  with  a  counterpoise 
of  450  grammes  i^Mosso).  When  the  thorax  is  greatly  distended,  as  in  Miiller's  experiment,  or 
greatly  diminished,  as  in  Valsalva's  experiment  [\  60),  deglutition  is  rendered  more  difficult. 


Y\v..  171. 


Excretory  duct. 


Stratified 
epithelium 


Injected 
capillaries. 

Mucous  mem- 
brane   with 
muscularis 
mucosae. 


Siib-mucosa. 


Transverse  section  of  part  of  the  oesophagus. 


Goltz's  Experiments. — The  oesophagus  and  stomach  of  the  frog  become  more  excitable,  /.  e., 
the  excitability  of  the  ganglionic  plexuses  in  their  walls  is  increased,  when  the  brain  and  spinal  cord 
or  both  vagi  are  destroyed.  These  organs  contract  energetically  after  slight  stimulation,  while  frogs, 
whose  central  nervous  system  is  intact,  swallow  fluids  simply  by  peristalsis.  Females,  and  some- 
times men  also,  suffering  from  hysteria,  not  unfrequently  have  similar  spasmodic  contractions  of  the 
oesophageal  region  (globus  hystericus).  After  section  of  both  vagi  in  the  dog,  Schiff  observed 
spasmodic  contraction  of  the  oesophagus. 

Effect  on  Circulation. — Every  time  one  swallows,  the  heart's  action  is  accelerated,  the  blood 
pressure  falls,  the  necessity  for  respiration  diminishes,  while  many  movements  (labor  pains,  erection) 
are  inhibited.     These  effects  are  brought  about  reflexly  [Kronecker  and  Meltzer,  \  369). 

[Structure  of  the  CEsophagus. — The  walls  of  the  oesophagus  are  composed  of  four  coats — 
mucous,  sub-mucous,  muscular,  and  fibrous  (Fig.  171). 

(i)  The  mucous  coat  is  firm,  and  is  thrown  into  longitudinal  folds,  which  disappear  when  the 
tuhJe  is  distended.  It  is  lined  by  several  layers  of  stratified  squamous  epithelium.  The  mem- 
brane itself  is  composed,  especially  at  its  inner  part,  of  dense  fibrous  tissue,  which  projects,  in  the 
form  of  papillae,  into  the  stratified  epithelium.  The  papilki.'  are  present  in  the  child,  but  are  largest 
in  old  people.  At  its  outer  part  is  a  continuous  longitudinal  layer  of  non-striped  muscle,  the 
muscularis  mucosae.  The  layer  consists  of  small  bundles  of  non-striped  muscle  separate  from 
each  other. 


MOVEMENTS  OF  THE  STOMACH.  275 

(2)  The  sub-mucous  coat  is  thicker  than  the  foregoing,  and  consists  of  loose  connective  tissue, 
with  the  acini  of  small  mucous  glands  imbedded  in  it.  The  ducts  pierce  the  muscularis  mucosae  to 
open  on  the  inner  surface  of  the  tube. 

(3)  The  muscular  coat  consists  of  an  zww^r,  thicker,  circular,  and  an  outer,  thinner,  longitudinal 
layer  of  non-striped  muscle,  commencing  on  a  level  with  the  cricoid  cartilage.  In  man  the  upper  third 
of  the  gullet  consists  of  striped  muscular  fibres.  (4)  Outside  the  muscular  coat  is  a  layer  of  fibrous 
tissue  with  elastic  fibres.  The  structure  of  the  muscular  coat  of  the  oesophagus  varies  much  in 
different  animals.  In  the  rabbit,  in  the  first  quarter  of  its  length,  it  has  two  layers,  but  below  this 
there  are  three  layers,  i.  e.,  a  circular  between  an  outer  and  an  inner  longitudinal  layer,  while  the 
non-striped  fibres  are  confined  to  the  lowest  quarter  of  the  tube.] 

[Nerve  Plexuses. — As  in  the  intestine,  there  are  two  plexuses  of  nerves  with  ganglia ;  one  in 
the  sub-mucous  coat  i^Meissner' s)  and  the  other  between  the  two  muscular  coats  [AtierbacKs), 
which  are  continuous  with  those  in  the  stomach  and  intestine.  Blood  vessels  and  numerous  lymph- 
atics lie  in  the  mucous  and  sub-mucous  coats.] 

157.  MOVEMENTS    OF  THE  STOMACH.— Position.— When  the 

stomach  is  empty,  the  great  curvature  is  directed  downward  and  the  lesser 
upward  ;  but  when  the  organ  is  full,  it  rotates  on  an  axis  running  horizontally- 
through  the  pylorus  and  cardia,  so  that  the  great  curvature  appears  to  be  directed 
to  the  front  and  the  lesser  backward. 

Arrangement  of  the  Muscular  Fibres. — The  non-striped  muscular  fibres  of  the  stomach  are 
arranged  in  three  directions  or  layers,  an  outer  longitudinal  continuous  with  those  of  the  oeso- 
phagus. This  layer  is  best  developed  along  the  curvatures,  especially  the  lesser.  At  the  pylorus 
the  fibres  form  a  thick  layer,  and  become  continuous  with  the  longitudinal  fibres  of  the  duodenum. 
The  circular  fibres  form  a  complete  layer ;  at  the  pylorus  they  are  more  numerous,  and  constitute 
the  sphincter  muscle  or  pyloric  valve  ;  while  at  the  cardia  (inlet),  such  a  muscular  ring  is  absent. 
The  innermost  oblique  or  diagonal  layer  is  complete. 

The  Movements  of  the  Stomach  are  of  two  kinds — (i)  The  rotatory  or 
churning  movements,  whereby  the  parts  of  the  wall  of  the  stomach  in  contact 
with  the  contents  glide  to  and  fro  with  a  slow  rubbing  movement.  Such  move- 
ments seem  to  occur  periodically,  every  period  lasting  several  minutes  {^Beaumont). 
By  these  movements  the  contents  are  moistened  with  the  gastric  juice,  while  the 
masses  of  food  are  partly  broken  down.  The  formation  of  hair  balls  in  the 
stomach  of  dogs  and  oxen  indicates  that  such  rotatory  movements  of  the  contents 
of  the  stomach  take  place.  (2)  The  other  kind  of  movement  consists  in  a  periodi- 
cally occurring  peristalsis,  whereby,  as  with  a  push,  the  first  dissolved  portions 
of  the  contents  of  the  stomach  are  forced  into  the  duodenum.  They  begin  after 
a  quarter  of  an  hour,  and  recur  until  about  five  hours  after  a  meal.  This  peri- 
stalsis is  most  pronounced  toward  the  pyloric  end,  and  the  muscles  of  the  pyloric 
sphincter  relax  to  allow  the  contents  to  pass  into  the  duodenum.  According  to 
Rtidinger,  the  longitudinal  muscular  fibres,  when  they  contract,  especially  when 
the  pyloric  end  is  filled,  may  act  so  as  to  dilate  the  pylorus. 

Gizzard. — The  strongly  muscular  walls  of  the  stomach  of  grain-eating  birds  effect  a  trituration 
of  the  food.  The  older  physiologists  found  that  glass  balls  and  lead  tubes,  which  could  be  com- 
pressed only  by  a  weight  of  40  kilos,  were  broken  or  compressed  in  the  stomach  of  a  turkey. 

Influence  of  Nerves. — [The  stomach  is  supplied  by  the  vagi  and  by  the 
sympathetic,  the  right  vagus  being  distributed  to  the  posterior  surface,  and  the 
left  to  the  anterior  surface,  of  the  organs.]  Auerbach's  ganglionic  plexus  of 
nerve  fibres  and  nerve  cells,  which  lies  between  the  muscular  coats  of  the  stomach, 
must  be  regarded  as  its  proper  motor  centre,  and  to  it  motor  impulses  are  con- 
ducted by  the  vagi.  Section  of  both  vagi  does  not  abolish,  but  it  diminishes 
the  movements  of  the  stomach.  The  muscular  fibres  of  the  cardia  may  be  excited 
to  action,  or  their  action  inhibited  by  fibres  which  run  in  the  vagus  (Nn.  con- 
strictores,  et  dilatator  cardise).  [If  the  vagi  be  divided  in  the  neck,  there  is  a 
short  temporary  spasmodic  contraction  of  the  cardiac  aperture.  On  stimulating 
the  peripheral  end  of  the  vagus  with  electricity,  after  a  latent  period  of  a  few 
seconds,  the  cardiac  end  contracts,  more  especially  if  the  stomach  be  distended, 
but  the  movements  are  slight  if  the  stomach  be  empty.     In  curarized  dogs,  the 


276  VOMITING. 

pylorus  contracts  with  varying  intensity,  and  irregularly  whether  the  vagi  and 
splanchnics  be  intact  or  divided.  Stimulation  of  the  vagi  in  the  neck  causes  con- 
traction of  the  pylorus,  when  the  latent  period  may  be  seven  seconds.  Stimula- 
tion of  the  splanchnics  in  the  thorax  arrests  the  spontaneous  pyloric  contractions, 
the  left  splanchnic  being  more  active  than  the  right  (Oser).} 

Local  electrical  stimulation  of  the  surface  of  the  stomach  causes  circular  constrictions  of  the 
organ,  which  disappear  very  gradually,  while  the  movement  is  often  propagated  to  other  parts  of  the 
gastric  wall.  When  heated  to  25°  C,  the  excised  empty  stomach  exhibits  movements.  Injury  to 
the  pedunculi  cerebri,  optic  thalamus,  medulla  oblongata,  and  even  to  the  cervical  part  of  the  spinal 
cord,  according  to  Schiff,  causes  paralysis  of  the  vessels  of  certain  areas  of  the  stomach,  resulting 
in  congestion  and  subsequent  hemorrhage  into  the  mucous  membrane.  [It  is  no  uncommon  occur- 
rence to  tind  hemorrhage  into  the  gastric  mucous  membrane  of  rabbits,  after  they  have  been  killed 
by  a  violent  blow  on  the  head.] 

[Action  of  Drugs. — The  mitotnatic  centres  are  excited  by  emetin,  apomorphin,  tartar  emetic, 
while  muscarin  causes  general  contraction  of  the  stomach.  The  activity  of  the  automatic  centres 
is  diminished  by  chloral,  urethan,  morphin,  and  nicotin,  while  atropin  causes  paralysis  of  the  nerve 
endings  (.£".  Sch'utz).^ 

158.  VOMITING. — Mechanism. — Vomiting  is  caused  by  contraction  of 
the  walls  of  the  stomach,  the  pyloric  sphincter  being  closed.  It  occurs  most  readily 
when  the  stomach  is  distended — (dogs  usually  greatly  distend  the  stomach  by 
swallowing  air  before  they  vomit)  ;  it  readily  occurs  in  infants,  in  whom  the  cul- 
de-sac  at  the  cardia  is  not  developed.  It  is  quite  certain  that  in  children  vomiting 
occurs  through  contraction  of  the  walls  of  the  stomach,  without  the  spasmodic 
action  of  the  abdominal  walls.  When  vomiting  is  violent,  the  abdominal  muscles 
act  energetically.  [The  act  of  vomiting  is  generally  preceded  by  a  feeling  of 
nausea,  and  usually  there  is  a  rush  of  saliva  into  the  mouth,  caused  by  a  reflex 
stimulation  of  afferent  fibres  in  the  gastric  branches  of  the  vagus,  the  efferent  nerve 
for  the  secretion  of  saliva  being  the  chorda  tympani.  After  this  a  deep  inspiration 
is  taken  and  the  glottis  closed,  so  that  the  diaphragm  is  firmly  pressed  downward 
against  the  abdominal  contents,  and  it  is  kept  contracted  ;  the  lower  ribs  are' 
pulled  in.  The  diaphragm  being  kept  contracted  and  the  glottis  closed,  a  violent 
expiratory  effort  is  made,  so  that  the  contraction  of  the  abdominal  muscles  acts 
upon  the  abdominal  contents,  the  stomach  being  forcibly  compressed.  .  The 
cardiac  orifice  is  opened  at  the  same  time,  and  the  contents  of  the  stomach  are 
ejected.  The  chief  agent  seems  to  be  the  abdominal  compression,  but  the  walls 
of  the  stomach  also  help,  though  only  to  a  slight  extent.] 

The  contraction  of  the  walls  of  the  stomach,  which  causes  a  general  diminution  of  the  gastric 
cavity,  is  not  a  true  anti-peristalsis,  as  can  be  seen  in  the  stomach  when  it  is  exposed.  The  cardia 
is  opened  by  the  longitudinal  muscular  fibres,  which  pull  toward  the  lower  orifice  of  the  oesophagus, 
so  that  when  the  stomach  is  full  they  must  act  as  dilators.  The  act  of  vomiting  is  preceded  by  a 
ructus-like  dilating  movement  of  the  intra-thoracic  part  of  the  oesophagus,  which  is  caused  thus : 
The  glottis  is  closed,  inspiration  occurs  suddenly  and  violently,  whereby  the  cesophagus  is  distended 
by  gases  preceding  from  the  stomach.  The  larynx  and  hyoid  bone,  by  the  combined  action  of  the 
genio-hyoid,  stemo-hyoid,  sterno- thyroid,  and  thyro-hyoid  muscles,  are  forcibly  pulled  forward,  so 
that  the  air  passes  from  the  pharynx  downward  into  the  upper  section  of  the  resophagus.  If  the 
abdominal  walls  contract  suddenly,  and  if  this  sudden  impulse  be  aided  by  the  movements  of  the 
stomach  itself,  the  contents  of  the  stomach  are  forced  outward.  During  continued  vomiting,  anti- 
peristalsis  of  the  duodenum  may  occur,  whereby  bile  passes  into  the  stomach,  and  becomes  mixed 
with  its  contents. 

Children,  in  whom  the  fundus  is  absent,  vomit  more  easily  than  adults.  [In  them  also  the 
nervous  system  is  more  excitable.] 

Influence  of  Nerves. — The  centre  for  the  movements  concerned  in  vomiting 
lies  in  the  medulla  oblongata,  and  is  in  relation  with  the  respiratory  centre,  as  is 
shown  by  the  fact  that  nausea  may  be  overcome  by  rapid  and  deep  respirations. 
In  animals,  vomiting  may  be  inhibited  by  vigorous  artificial  respiration.  On  the 
other  hand,  the  administration  of  certain  emetics  prevents  the  occurrence  of 
apnoea. 

In  vomiting,  the  afferent  impulses  may  be  discharged  from  (i)  the  mucous 


MOVEMENTS    OF   THE    INTESTINE.  277 

membrane  of  the  soft  palate,  pharynx,  root  of  the  tongue  {glosso-pharyngeal  nerve), 
as  in  tickling  the  fauces  with  the  finger  ;  (2)  the  nerves  of  the  stomach  {vagus  and 
sympathetic)  ;  (3)  stimulation  of  the  uterine  nerves  (pregnancy)  ;  (4)  the  mesenteric 
nerves  (inflammation  of  the  abdomen  and  hernia)  ;  (5)  nerves  of  the  urinary 
apparatus  (passing  a  renal  calculus)  ;  (6)  nerves  to  the  liver  and  gall  duct  {vagus)] 
(7)  nerves  to  the  lungs  in  phthisis  {vagus).  Vomiting  is  also  produced  by  direct 
stimulation  of  the  vomiting  centre.  [The  efferent  impulses  are  carried  by  the 
phrenics  (diaphragm),  vagus  (oesophagus  and  stomach),  and  in tercostals  (abdominal 
muscles).] 

Vomiting,  produced  by  the  thought  of  something  disagreeable,  appears  to  be  caused  by  the  con- 
duction of  the  excitement  from  the  cerebrum  to  the  vomiting  centre.  [It  may  also  be  excited 
through  the  brain  by  a  disagreeable  smell,  shocking  sight,  or  by  other  impressions  on  the  nerves  of 
special  sense.]  Vomiting  is  very  common  in  diseases  of  the  brain  [tubercle,  inflammation,  hemor- 
rhage].    Section  of  both  vagi  generally,  but  not  always,  prevents  vomiting. 

Emetics  act  (i)  partly  by  mechanically  or  chemically  stimulating  the  ends  of  the  centripetal 
(afferent)  nerves  of  the  mucous  membrane.  [These  are  local  emetics.]  Tickling  the  fauces,  touch- 
ing the  surface  of  the  exposed  stomach  (dog) ;  and  many  chemical  emetics,  e.g.,  mustard,  cupric 
and  zinc  sulphate,  and  other  metallic  salts,  act  in  this  way.  (2)  Other  substances  cause  vomiting 
when  they  are  introduced  into  the  blood  (without  being  first  introduced  into  the  stomach),  and  act 
directly  upon  the  vomiting  centre,  f.^.,  apomorphin.  [These  are  ^fwd-r^/ emetics.]  (3)  Lastly, 
there  are  some  substances  which  act  in  both  ways,  e.g.,  tartar  emetic.  Emetics  may  also  remove 
mucus  from  the  lungs,  and  in  this  case  it  is  probable  that  the  emetic  acts  upon  the  respiratory 
centre,  and  so  favors  the  respirations.  The  ^^^fra/ emetics  usually  create  considerable  depression, 
while  the  vomiting  lasts  longer  than  with  local  emetics.  The  former  increase  the  salivary,  gastric, 
and  respiratory  secretions. 

[Uses  of  Emetics. — Emetics  are  useful  not  only  for  removing  from  the  stomach  any  offending 
body,  be  it  a  poison  or  the  products  of  imperfect  or  perverted  gastric  digestion,  or  bile  which  has 
passed  back  into  the  stomach,  but  foreign  bodies  impacted  in  the  oesophagus  may  be  got  rid  of  on 
exciting  vomiting  by  the  subcutaneous  injection  of  apomorphin.  As  the  diaphragm  contracts  vigor- 
ously during  vomiting,  it  compresses  the  liver,  and  thus  bile  is  expelled  into  the  duodenum,  or  the 
passage  of  a  small  calculus  along  the  bile  duct  may  be  aided.  They  also  are  useful  in  removing 
mucus  or  false  membranes  from  the  respiratory  passages.] 

[Anti-Emetics. — Vomiting  may  be  allayed  by  local  anti-emetics,  such  as  ice,  and  many  chemi- 
cal substances,  such  as  bismuth,  hydrocyanic  acid,  opium,  and  morphia,  as  well  as  by  general  reme- 
dies which  act  on  the  vomiting  centre.  Some  of  the  foregoing  drugs  perhaps  act  both  locally  and 
generally.] 

Vomiting  is  analogous  to  the  process  of  rumination  in  animals  that  chew  the  cud  {\  187).  Some 
persons  can  empty  their  stomach  in  this  way. 

159.  MOVEMENTS    OF    THE    INTESTINE.— Peristalsis.— The 

best  example  of.  peristaltic  movements  is  afforded  by  the  small  intestine  ;  the  pro- 
gressive narrowing  of  the  tube  proceeds  from  above  downward,  thus  propelling 
the  contents  before  it.  Frequently  after  death,  or  when  air  acts  freely  upon  the 
gut,  the  peristalsis  develops  at  various  parts  of  the  intestine  simultaneously, 
whereby  the  loops  of  intestine  present  the  appearance  of  a  heap  of  worms  creep- 
ing among  each  other.  The  advance  of  new  intestinal  contents  again  increases 
the  movement.  In  the  large  intestine,  the  movements  are  more  sluggish  and  less 
extensive.  The  peristaltic  movements  may  be  seen  and  felt  when  the  abdominal 
walls  are  very  thin,  and  also  in  hernial  sacs.  They  are  more  lively  in  vegetable 
feeders  than  in  carnivora.  The  peristalsis  is  perhaps  conducted  directly  through 
the  muscular  substance  itself,  as  in  the  heart  and  ureter.  The  movements  of  the 
stomach  and  intestine  cease  during  sleep  {BuscK). 

[Rate  of  Motion. — In  a  Thiry-Velly  fistula  {\  183,  II)  Fubini  estimated  the  rate  of  motion  of  a 
smooth  sphere  of  sealing  wax.  It  took  55  sec.  to  travel  i  ctm.  [|  in.]  ;  an  induction  current 
greatly  increases  the  motion,  to  i  ctm.  in  10  seconds;  NaCl  does  not  affect  it,  but  excites  secretion ; 
laudanum  paralyzes  it.] 

Method  of  Observation. — Open  the  abdomen  of  an  animal  under  a  .6  per  cent,  saline  solution 
to  prevent  the  exposure  of  the  gut  to  air  {^Sanders  and  Braam-Houckgeest'). 

The  ileo-colic  valve,  as  a  rule,  prevents  the  contents  of  the  large  intestine 
from  passing  backward  into  the  small  intestine. 


278 


EXCRETION  OF  FECAL  MATTER. 


When  fluid  is  slowly  introduced  into  the  rectum  through  a  tube,  it  passes  upward  into  the  intes- 
tine, and  even  goes  through  the  ileo-colic  valve  into  the  small  intestine.  Muscarin  excites  very 
lively  peristalsis  of  the  intestines,  which  may  be  set  aside  by  atropin  (Sc/iiniedeber^  and  Koppe). 

Pathological. — When  any  condition  excites  an  acute  inflammation  of  the  intestinal  mucous 
membrane,  catarrh  is  rapidly  produced,  and  very  strong  contractions  of  the  inflamed  parts  lllled  with 
food  take  place.  When  these  parts  of  the  gut  become  empty,  the  movements  are  not  stronger  than 
normal.  If  new  material  passes  into  the  inflamed  part,  the  peristalsis  recurs,  becomes  more  lively 
than  normal,  and  the  result  is  diarrhcea  {Nolhnagel).  Sometimes  a  greatly  contracted  part  of  the 
small  intestine  is  pushed  into  the  piece  of  gut  directly  continuous  with  it,  giving  rise  to  invagina- 
tion or  intussusception. 

Anti-peristalsis,  /.  c*.,  a  movement  which  travels  in  an  upward  direction  toward  the  stomach, 
does  not  occur  normally.  This  has  been  inferred  from  the  fact,  that  in  cases  where  the  intestine  is 
occluded,  called  ileus,  fecal  matter  is  vomited.  Nothnagel's  experiments  throw  doubts  upon  this 
view,  as  he  failed  to  observe  anti-peristalsis  in  cases  where  the  intestine  was  occluded  artificially. 
The  fecal  odor  of  the  ejecta  may  result  from  the  prolonged  retention  of  the  material  within  the 
small  intestine. 

i6o.  EXCRETION  OF  FECAL  MATTER.— The  contents  of  the 
small  intestine  remain  in  it  about  three  hours,  and  about  twelve  hours  in  the  large 
intestine,  where  they  become  less  watery,  and  they  assume  the  characters  of  faeces, 


Kk;.  17. 


I  he  perineum  and  its  muscles.  1,  anus  ;  2,  coccyx  ;  3,  tuberosity  ;  4,  >ciatn.  ii;;.iiiient ;  5,  cotyloid  cavity  ;  B,  bulbo- 
T^^^T°^"^  """scle  ;  Ts,  superficial  transverse  perineal  muscle ;  F,  fascia  of  the  deep  transverse  perineal  muscle; 
J,  ischio-cavernosus  muscle  ;  M,  obturator  internus  ;  S,  external  anal  sphincter  ;  L,  levator  ani  ;  P,  pyriformis. 

become  "formed  "  in  the  lower  part  of  the  great  intestine.  The  faeces  are  grad- 
ually carried  along  by  the  peristaltic  movement,  until  they  reach  a  point  a  little 
above  that  part  of  the  rectum  which  is  surrounded  by  both  sphincters,  the  internal 
sphincter  consisting  of  non-striped,  and  the  external  of  striped  muscle. 


EXCRETION    OF    FECAL    MATTER. 


279 


Immediately  after  the  expulsion  of  the  faeces  the  external  sphincter  (Fig.  172, 
S,  and  Fig.  173)  usually  contracts  vigorously,  and  remains  so  for  some  time. 
Afterward  it  relaxes,  when  the  elasticity  of  the  parts  surrounding  the  anal  opening, 
particularly  of  the  two  sphincters,  suffices  to  keep  the  anus  closed.  In  the  inter- 
val between  two  evacuations,  there  does  not  seem  to  be  a  continued  tonic  con- 
traction of  the  sphincters.  As  long  as  the  faeces  lie  above  the  rectum,  they  do  not 
excite  any  conscious  sensations,  but  the  sensation  of  requiring  to  go  to  stool  occurs 
when  the  faeces  pass  into  the  rectum.  At  the  same  time,  the  stimulation  of  the 
sensory  nerves  of  the  rectum  causes  a  reflex  excitement  of  the  sphincters.  The 
centre  for  these  movements  (Budge's  centrum  ano-spinale)  lies  in  the  lumbar  region 
of  the  spinal  cord  (§  362)  ;  in  the  rabbit  between  the  sixth  and  seventh,  and  in 
the  dog  at  the  fifth  lumbar  vertebra  (^Masius). 

Fig.  173. 


Levator  ani  and  sphincter  ani  externus. 


In  animals  whose  spinal  cord  is  divided  above  the  centre,  a  slight  touch  in  the  region  of  the  anus 
causes  this  orifice  to  contract,  but  after  this  lively  reflex  contraction,  the  sphincters  relax  again,  and 
the  anus  may  remain  open  for  a  time.  This  occurs  because  the  voluntary  impulses  which  proceed 
from  the  brain  to  cause  the  contraction  of  the  external  sphincter  are  absent.  Landois  observed  that 
in  dogs  with  the  posterior  roots  of  their  lower  lumbar  and  sacral  nerves  divided,  the  anus  remained 
open,  and  not  unfrequently  a  mass  of  fseces  remained  half  ejected.  As  the  sensibility  of  the  rectum 
and  anus  was  abolished  in  these  animals,  the  sphincters  could  not  contract  reflexly,  nor  could  there 
be  any  voluntary  contraction  of  the  sphincters,  the  result  of  sensory  impulses  from  the  rectum. 

The  external  sphincter  can  be  contracted  voluntarily,  like  any  voluntary  muscle, 
but  the  closure  of  the  anus  can  only  be  effected  up  to  a  certain  degree.  When 
the  pressure  from  above  is  very  great,  the  energetic  peristalsis  at  last  overcomes 
the  strongest  voluntary  impulses.     Stimulation  of  the  peduncles  of  the  cerebrum 


280 


DEFECATION. 


and  of  the   spinal    cord    below   this    point   causes   contraction  of  the   external 
sphincter. 

Defecation. — The  evacuation  of  the  faeces,  which  in  man  usually  occurs  at 
certain  times,  begins  with  a  lively  peristalsis  of  the  large  intestine,  which  passes 
downward  to  the  rectum.  In  order  that  the  mass  of  freces  may  not  excite  reflexly 
the  sphincter  muscles,  in  consequence  of  mechanical  stimulation  of  the  sensory 
nerves  of  the  rectum,  there  seems  to  be  a  centre  which  inhibits  the  reflex  action 
of  the  sphincters,  which  is  called  into  play,  owing,  as  it  appears,  to  voluntary 
impulses.  Its  seat  is  in  the  brain,  perhaps  in  the  optic  thalami.  When  this 
inhibitory  apparatus  is  in  action,  the  fecal  mass  passes  through  the  anus,  without 
causing  it  to  close  reflexely.  The  strong  peristalsis  which  precedes  defecation 
can  be  aided,  and  to  a  certain  degree  excited,  by  rapid  voluntary  movements  of 
the  external  sphincter  and  levator  ani,  whereby  the  plexus  myentericus  of  the  large 
intestine  is  stimulated  mechanically,  thus  causing  lively  peristaltic  movements  in 
the  large  intestine.  The  expulsion  of  the  freces  is  also  aided  by  the  pressure  of 
the  abdominal  muscles,  and  most  efificiently  when  a  deep  respiration  is  taken,  so 
as  to  fix  the  diaphragm,  whereby  the  abdominal  cavity  is  diminished  to  the 
greatest  extent.  The  soft  parts  of  the  floor  of  the  pelvis,  during  a  strong  eff"ort 
at  stool,  are  driven  downward  in  the  form  of -a  cone,  causing  the  mucous  mem- 
brane of  the  anus,  which  contains  much  venous  blood,  to  be  everted.  The 
function  of  the  levator  ani  (Figs.  172,  173)  is  to  raise  voluntarily  the  soft  parts 

Fir,.    174. 


Auerbach's  plexus  sliown  in  section  (human),    a.  ganglionic  cells  ;  t,  nerve  fibres  ;  c,  section  of  the  circular  muscul.tr 

fibres  ;  </,  longitudinal  muscular  fibres. 


of  the  floor  of  the  pelvis,  and  to  pull  the  anus  to  a  certain  extent  upward  over 
the  descending  fecal  mass.  At  the  same  time,  it  prevents  the  distention  of  the 
pelvic  fascia.  As  the  fibres  of  both  levatores  converge  below,  and  become  united 
with  the  fibres  of  the  external  sphincter,  they  aid  the  latter,  during  energetic 
contraction  of  the  sphincter;  or,  as  Hyrtl  put  it,  the  levatores  are  related  to  the 
anus,  like  the  two  cords  of  a  tobacco  pouch.  During  the  periods  between  the 
evacuation  of  the  gut,  the  faeces  appear  only  to  reach  the  lower  end  of  the  sig- 
moid flexure.  As  a  rule,  from  thence  downward,  the  rectum  is  normally  devoid 
of  faeces.  It  seems  that  the  strong  circular  fibres  of  the  muscular  coat,  which 
Nelaton  has  called  sphincter  ani  tertius,  when  they  are  well  developed,  contract 
and  prevent  the  entrance  of  the  faeces.  When  the  tendency  to  the  evacuation  of 
the  rectum  is  very  pressing,  the  anus  may  be  closed  more  firmly  from  without,  by 
energetically  rotating  the  thigh  outward,  and  contracting  the  muscles  of  the 
gluteal  region. 

161.  CONDITIONS  INFLUENCING  THE  INTESTINAL 
MOVEMENTS. — The  intestinal  canal  contains  an  auto7natic  motor  centre 
within  its  walls — the  plexus  myentericus  of  Auerbach^which  lies  between 
the  longitudinal  and  circular  muscular  fibres  of  the  gut.  It  is  this  plexus  which 
enables  the  intestine,  when  cut  out  of  the  body,  to  execute,  apparently  spontane- 
ously, movements  for  some  time. 


CONDITIONS    INFLUENCING    THE    INTESTINAL    MOVEMENTS.        281 

[Structure. — Auerbach's  Plexus  consists  of  non-medullated  nerve  fibres  whicli  form  a  dense 
network,  groups  of  ganglion  cells  occurring  at  the  nodes  (Fig.  175,  and  when  seen  in  vertical  sections 
between  the  muscular  coats  it  is  like  Fig.  174).  A  similar  plexus  extends  throughout  the  whole 
intestine  between  the  longitudinal  and  circular  muscular  coats  from  the  oesophagus  to  the  rectum. 
Branches  are  given  off  to  the  muscular  bundles.  A  similar,  but  not  so  rich  a  plexus  lies  in  the  sub- 
mucous coat,  Meissner's  plexus,  which  gives  branches  to  supply  the  muscularis  mucosae,  the 
smooth  muscular  fibres  of  the  villi,  and  the  glands  of  the  intestine  (Fig.  176). 

I.  If  this  centre  is  not  affected  by  any  stimulus,  the  movements  of  the  intestine 
cease — comparable  to  the  condition  of  the  medulla  oblongata  in  apnoea.  The 
same  is  true — ^just  as  in  the  case  of  the  respiration — during  intra-uterine  life,  in 
consequence  of  the  foetal  blood  being  well  supplied  with  O.  This  condition  may 
be  termed  aperistalsis.  It  also  occurs  during  sleep,  perhaps  on  account  of  the 
greater  amount  of  O  in  the  blood  during  that  state. 


Fig.  175. 


Plexus  of  Auerbach,  prepared  trom  the  small  intestine  of  a  dog,  by  the  action  of  gold  chloride.  The  nerve  cells  are 
shown  at  the  nodes,  while  the  fibrils  proceeding  from  the  ganglia,  and  the  anastomosing  fibres,  lie  between  the 
muscular  bundles. 


2.  When  blood  containing  the  normal  amount  of  blood  gases  passes  through 
the  intestinal  blood  vessels,  the  quiet  peristaltic  movements  of  health  occur 
(euperistalsis)  provided  no  other  stimulus  be  applied  to  the  intestine. 

3.  All  stimuli  applied  to  the  plexus  myentericus  increase  the  peristalsis,  which 
may  become  so  very  violent  as  to  cause  evacuation  of  the  contents  of  the  large 
gut,  and  may  even  produce  spasmodic  contraction  of  the  musculature  of  the  intes- 
tine. This  condition  may  be  termed  dysperistalsis,  corresponding  to  dyspnoea. 
The  condition  of  the  blood  flowing  through  the  intestinal  vessels  affects  the 
peristalsis. 

Condition  of  the  Blood. — Dysperistalsis  may  be  produced  by  (a)  interrupting  the  circulation  of 
the  blood  in  the  intestines,  no  matter  whether  anaemia  (  as  after  compressing  the  aorta — Schiff)  or 
venous  hyperaemia  be  produced.  The  stimulating  condition  is  the  want  of  O,  i.  e.,  the  increase  of 
COj.  Very  slight  disturbance  in  the  intestinal  blood  vessels,  e.  g.,  venous  congestion  after  copious 
transfusion  into  the  veins,   whereby   the  abdominal  and  portal  veins  become  congested,   causes 


282 


INFLUENCE    OF    NERVES    ON    THE    INTESTINE. 


increased  peristalsis.  The  intestines  become  nodulated  at  one  part  and  narrow  at  another, 
and  involuntary  evacuation  of  the  fxces  takes  place  when  there  is  congestion,  owing  to 
the  plugging  of  the  intestinal  blood  vessels  when  blood  from  another  species  of  animal   is  used 

for  transfusion  (ji  102).     The  marked  peri- 
Fi<;.   176.  stalsis   which    occurs   on    the  approach   of 

death  is  undoubtedly  due  to  the  derange- 
ments of  the  circulation,  and  the  consequent 
alteration  of  the  amount  of  gases  in  the 
blood  of  the  intestine.  The  same  is  true  of 
the  increased  movements  of  the  intestines 
which  occur  as  a  result  of  psychical  excite- 
ment, e.  g.,  grief.  The  stimulus,  in  this  case, 
passes  from  the  cerebrum  through  the 
medulla  oblongata  (vasomotor  centre)  to 
the  intestinal  nerves,  and  causes  anxmia  of 
the  intestine  (corresponding  to  the  pallor 
occurring  elsewhere).  When  the  normal 
condition  of  the  circulation  is  restored,  the 
peristalsis  diminishes,  {h)  Direct  stimula- 
tion of  the  intestine,  conducted  to  the  plexus 
myentericus,  causes  dysperistahis ;  direct 
exposure  of  the  intestines  to  the  air  (stronger 
when  CO2  or  CI  is  present) — introduction 
of  various  irritating  substances  into  the 
intestine — increased  filling  of  the  intestine 
when  there  is  any  difficulty  in  emptying  the 
gut  (often  in  man) — direct  stimulation  of 
various  kinds  (also  intlammation) — all  act 
upon  the  intestine,  either  from  without  or 
from  within.  Induction  shocks  applied  to 
a  loop  of  intestine  in  a  hernial  sac  cause 
lively  peristalsis  in  the  hernia.  The  intesti- 
nal movements  are  favored  by  heat. 

4.  The  continued  application  of 
strong  stimuli  causes  the  dysperi- 
stalsis  to  give  place  to  rest,  owing 
to  over-stimulation,  which  may  be 
called  "  intestinal  paresis,"  or 
exhaustion. 

This  condition  is  absolutely  different  from  the  passive  condition  of  the  intestine  in  aperistalsis. 
Continued  congestion  of  the  intestinal  blood  vessels  ultimately  causes  intestinal  paralysis,  e.  g.,  when 
transfusion  of  foreign  blood  causes  coagulation  within  these  vessels.  Filling  the  blood  vessels  with 
"indifferent"  fluids,  after  the  peristalsis  has  been  previously  brought  about  by  compressing  the 
aorta,  also  causes  cessation  of  the  movements  {O.  Nasse).  The  movements  cease  when  the 
intestines  are  cooled  to  19°  C.  {Horwath),  while  severe  inflammation  of  the  intestine  has  a  similar 
effect.  Under  favorable  circumstances,  the  intestine  may  recover  from  this  condition.  Arterial 
blood  admitted  into  the  vessels  of  the  exhausted  intestine  causes  peristalsis,  which  at  first  is  more 
vigorous  than  normal. 

5.  The  continued  application  of  strong  stimuli  causes  complete  paralysis  of 
the  intestine,  such  as  occurs  after  violent  peritonitis,  or  inflammation  of  the 
musculature  or  mucous  coat  in  man.  In  this  condition,  the  intestine  is  greatly 
distended,  as  the  paralyzed  musculature  does  not  offer  sufficient  resistance  to  the 
intestinal  gases  which  are  expanded  by  the  heat.  This  constitutes  the  condition 
of  meteorism. 

Influence  of  Nerves. — With  regard  to  the  nerves  of  the  intestine,  stimulation 
of  the  vagus  increases  the  movements  (of  the  small  intestine),  either  by  conduct- 
ing impressions  to  the  plexus  myentericus,  or  by  causing  contraction  of  the  stomach, 
which  stimulates  the  intestine  in  a  purely  mechannical  manner  {Braam-ffouck- 
geesf).  The  splanchnic  is  (i)  the  inhibitory  nerve  of  the  small  intestine  {PflUger), 
but  only  as  long  as  the  circulation  in  the  intestinal  blood-vessels  is  undisturbed, 
and  the    blood    in  the   capillaries  does  not  become  venous ;     when    the    latter 


Plexus  of  Meissner.     a,  ganglia  •    b,  anastomosing   fibres  ;    c, 
artery  ;    d,  vasomotor  nerve  fibres  accompanying  c. 


EFFECTS    OF    DRUGS    ON    THE    INTESTINE.  283 

condition  occurs,  stimulation  of  the  splanchnic  increases  the  peristalsis.  If  arterial 
blood  be  freely  supplied,  the  inhibitory  action  continues  for  some  time.  Stimu- 
lation of  the  origin  of  the  splanchnics,  of  the  spinal  cord  in  the  dorsal  region 
(under  the  same  conditions),  and  even  when  general  tetanus  has  been  produced 
by  the  administration  of  strychnia,  causes  an  inhibitory  effect.  It  is  inferred  that  the 
splanchnic  contains  (2)  inhibitory  fibres,  which  are  easily  exhausted  by  a  venous 
condition  of  the  blood,  and  also  motor  fibres,  which  remain  excitable  for  a  longer 
time,  because  after  death  stimulation  of  the  splanchnics  always  causes  peristalsis, 
just  like  stimulation  of  the  vagus.  (3)  It  is  the  vasomotor  nerve  of  the  intestinal 
blood  vessels,  so  that  it  governs  the  largest  vascular  area  in  the  body.  When  it  is 
stimulated,  all  the  vessels  of  the  intestine  which  contain  muscular  fibres  in  their 
walls  contract ;  when  it  is  divided,  they  dilate.  In  the  latter  case,  a  large  amount 
of  blood  accumulates  within  the  blood  vessels  of  the  abdomen,  so  that  there  is 
anaemia  of  the  other  parts  of  the  body,  which  may  be  so  great  as  to  cause  death — 
owing  to  the  deficient  supply  of  blood  to  the  medulla  oblongata.  (4)  It  is  the 
sensory  nerve  of  the  intestine,  and,  under  certain  circumstances,  it  may  give  rise 
to  very  painful  sensations. 

As  stimulation  of  the  splanchnic  contracts  the  blood  vessels,  von  Basch  has  raised  the  question 
whether  the  intestine  does  not  come  to  rest,  owing  to  the  want  of  the  blood,  which  acts  as  a  stimulus. 
But  when  a  weak  stimulus  is  applied  to  the  splanchnic,  the  intestine  ceases  to  move  before  the  blood 
vessels  contract  (van  Braam- Houckgeest) ;  it  would  therefore  seem  that  the  stimulation  diminishes 
the  excitabihty  of  the  plexus  myentericus.  According  to  Engelmann  and  v.  Brakel,  the  peristaltic 
movement  is  chiefly  propagated  by  direct  muscular  conduction,  as  in  the  heart  and  ureter,  without 
the  intervention  of  any  nerve  fibres. 

[Effect  of  Nerves  on  the  Rectum. — The  nervi  erigentes,  when  stimulated,  cause  the  longi- 
tudinal muscular  fibres  of  the  rectum  to  contract,  while  the  circular  muscular  fibres  are  supplied  by 
the  hyposgastric  nerves.  Stimulation  of  the  latter  nerves  also  exerts  an  inhibitory  effect  on  the 
longitudinal  muscles.  Stimulation  of  the  nervi  erigentes  inhibits  not  only  the  spontaneous  move- 
ments of  the  circular  fibres  of  the  rectum,  but  also  those  movements  excited  by  stimulation  of  the 
hypogastric  nerves  [Fellner).'] 

[Artificial  Circulation  in  the  Intestine. — Ludwig  and  Salvioli  excised  a  loop  of  intestine  from 
an  animal,  tied  a  cannula  into  an  artery  and  another  into  a  vein,  and  kept  it  in  a  warm  moist 
atmosphere.  The  arterial  cannula  was  connected  with  a  vessel  containing  defibrinated  blood,  to 
which  different  drugs  could  be  added.  A  lever  rested  on  the  intestine,  and  registered  its  movements 
on  a  recording  surface.  As  long  as  arterial  blood  was  transfused,  the  intestine  was  nearly  quiescent, 
but  when  it  was  arrested,  so  that  the  blood  became  venous,  a  series  of  contractions  occurred. 
Nicotin  diminished  the  flow  of  blood  and  quickened  the  intestinal  movements,  while  at  the  same 
time  the  circular  muscular  fibres  remained  contracted  or  tetanic.  Tincture  of  opium,  in  the  propor- 
tion of  .01  to  .04  in  the  blood,  causes  at  first  contraction  of  the  vessels,  and  lessens  the  amount  of 
blood  circulating  in  the  intestine  ;  but  it  very  rapidly  increases — even  to  six  times — the  amount  of 
blood  which  transfuses,  while  at  the  same  time  the  movements  of  the  intestine  cease,  the  walls  of 
the  intestine  being  contracted.     Peptone  caused  first  strong  and  then  irregular  contractions.] 

Effect  of  Drugs. — Among  the  reagents  which  act  upon  the  intestinal  movements  are:  (i)  Such 
as  diminish  the  excitability  of  the  plexus  myentericus,  i.  e.,  which  lessen  or  even  abolish  intestinal 
peristalsis,  e.g.,  belladonna.  (2)  Such  as  stimulate  the  inhibitory  fibres  of  the  splanchnic,  and  in 
large  doses  paralyze  them —opium,  morphia;  i  and  2  produce  constipation.  (3)  Other  agents 
excite  the  motor  apparatus — nicotin  (even  causing  spasm  of  the  intestine),  muscarin,  caffein,  and 
many  laxatives,  which  act  as  purgatives.  The  movements  produced  by  muscarin  are  abolished  by 
atropin.  These  substances  accelerate  the  evacuation  of  the  intestine,  and,  owing  to  the  rapid  move- 
ment of  the  intestinal  contents,  only  a  small  amount  of  water  is  absorbed  ;  so  that  the  evacuations 
are  frequently  fluid.  (4)  Among  purgatives,  colocynth  and  croton  oil  act  as  direct  irritants.  With 
regard  to  drugs  of  this  sort,  they  seem  to  cause  a  watery  transudation  into  the  intestine,  just  as 
croton  oil  causes  vesicles  when  applied  to  the  skin.  (5)  Calomel  is  said  to  limit  the  absorptive 
activity  of  the  intestinal  wall,  and  to  control  the  decompositions  in  the  intestine.  The  stools  are 
thin  and  greenish,  from  the  admixture  of  biliverdin.  (6)  Certain  saline  purgatives — sodium  sul- 
phate, magnesium  sulphate — cause  fluid  evacuations  by  retaining  the  water  in  the  intestine ;  and  it  is 
said  that  if  they  be  injected  into  the  blood  vessels  of  animals,  they  cause  constipation.  [When  a 
crystal  of  &  potash  salt  is  apphed  to  the  peritoneal  surface  of  the  intestine  of  an  animal,  it  causes 
merely  a  local  constriction  of  the  muscular  fibres  of  the  gut,  while  a  sodium  salt  excites  a  contrac- 
tion which  passes  upward  toward  the  stomach,  and  never  toward  the  rectum.  In  any  case  it  niay 
serve  as  a  useful  guide  to  the  surgeon,  in  determining  which  is  the  upper  end  of  a  piece  of  intestine 
during  an  operation  on  the  intestines  {Noihnagel).'] 


284 


STRUCTURE    OF    THE    STOMACH. 


[Saline  Cathartics. — A  salt  exerts  a  genuine  excitosecretory  action  on  the  glands  of  the  intes- 
tines, wliile  at  the  same  time,  in  virtue  of  its  low  difrusibility,  it  impedes  absorption.  Thus,  between 
stimulated  secretion  and  impeded  absorption  there  is  an  accumulation  of  fluid  within  the  canal,  which 
reaches  the  rectum  and  results  in  purgation.  Purgation  does  not  ensue  when  water  is  withheld 
from  the  diet  fur  one  or  two  days  previous  to  the  administration  of  tlie  salt  in  a  concentrated  form. 
When  a  concentrated  solution  of  a  salt  is  administered  to  an  animal  whose  alimentary  canal  is 
empty,  but  whose  blood  is  in  a  natural  state  of  dilution,  the  blood  becomes  rapidly  very  concen- 
trated, and  reaches  the  maximum  of  its  concentration  in  from  half  an  hour  to  an  hour  and  a  half; 
within  four  liours  the  blood  lias  gra<iually  returned  to  its  normal  state  of  concentration,  without 
having  reabsorbed  fluid  from  tlie  intestine.  It  apparently  recoups  itself  from  the  tissue  fluids.  The 
salt — sulphate  of  magnesia  or  sulphate  of  soda — becomes  split  up  in  the  small  intestine,  and  the 
acid  is  more  rapidly  absorbed  than  the  base  A  portion  of  the  absorbed  acid  shortly  afterward 
returns  to  the  intestines,  evidently  through  the  intestinal  glands.  The  salt  does  not  purge  when 
injected  into  the  blood,  and  excites  no  intestinal  secretion  ;  nor  does  it  purge  when  injected  subcu- 
taneously,  unless  on  account  of  its  causing  local  irritation  of  the  abdominal  subcutaneous  tissue, 
which  acts  reflexly  on  the  intestines,  dilating  their  blood  vessels,  and  perhaps  stimulating  their 
muscular  movements.  (M.  H(iy). 

162.  STRUCTURE  OF  THE  STOMACH.— [The  stoiTiach  receives 
the  bolus,  and  secretes  a  juice  which  acts  on  certain  constituents  of  the  food, 
while  by  its  muscular  walls  it  moves  the  latter  within  its  own  cavity,  and  after  a 
time  expels  the  partially  digested  products  toward  the  duodenum.] 


Seros:i 


Vertical  section  of  tlie  wall  of  the  human  stomach, 
X  IS-.  P-,  epithelium  ;  Gl.,  glands  ;  Mm.,  mus- 
cularis  mucosse. 


Surface  section  of  the  dog's  gastric  mucous  mem- 
brane, showing  pits,  /,  /;  a,  the  elevations 
round  ;,  i. 

Structure. — [The  walls  of  the  stomach  consist  of  four  coats,  which  are 
from  without  inward  (Fig.  177) — 

(i)  The  serous  layer,  from  the  peritoneum. 

(2)  The  muscular  layer,  composed  of  three  layers  of  non-striped  muscular  fibres — (aj  longi- 

tudinal, (h)  circular,  {c)  oblique  (§  15). 

(3)  The  sub-mucous  layer  of  loose  connective  tissue,  with  the  larger  blood  vessels,  lymphatics, 

and  nerves. 

(4)  The  mucous  layer.] 


STRUCTURE    OF   THE    STOMACH. 


285 


The  well- developed  mucous  membrane  of  the  stomach  is  thrown  into  a  series  of  folds  or 
rugae,  in  a  contracted  condition  of  the  organ.  With  the  aid  of  a  hand  lens,  it  is  seen  to  be  beset 
with  small  irregular  depressions  ox  pits  (Fig.  179).  Throughout  its  entire  extent  it  is  covered  by  a 
single  layer  of  moderately  tall,  narrow,  cylindrical  epithelium,  which  seems  to  consist  of  mucous- 
secreting  goblet  cells  (Fig.  178).  The  epithelium  is  sharply  defined  at  the  cardia  from  the  strati- 
fied epithelium  of  the  oesophagus,  and  also  at  the  pylorus,  from  the  true  cylindrical  epithelium  with 
the  striated  disk  in  the  duodenum,     [The  cells  contain  a  plexus  of  fibrils,  and  in  the  passive  condi- 

FiG.  180. 


I.  Transverse  section  of  a  duct  of  a  fundus  gland— a,  membrana  propria  ;  b,  mucous-secreting  goblet  cells  ;  c, 
adenoid  interstitial  substance.  II.  Transverse  section  of  a  fundus  gland — a,  chief,  h,  parietal  cells ;  r,  adenoid 
tissue ;  c,  capillaries. 


tion  seem  to  consist  of  two  zones,  an  outer  clear  part,  next  the  lumen 
of  the  organ,  consisting  of  a  substance  (mucigen)  which  yields  mucus, 
the  attached  end  of  the  cell  being  granular.]  The  oval  nucleus  lies 
about  the  centre  of  the  cells.  Spindle-shaped,  nucleated  cells,  proba- 
bly for  replacing  the  others,  are  said  by  Ebstein  to  occur  at  their  bases. 
All  the  cells  are  open  at  their  free  ends,  so  that  the  mucus  is  readily 
discharged,  leaving  the  cells  empty.  Numerous  tubular  glands  of 
two  distinct  kinds  are  placed  vertically,  like  rows  of  test-tubes,  in  the 
mucous  membrane. 

The  cardiac  portion  of  the  gastric  mucous  membrane  consists  of  a 
number  of  microscopic  tubular  glands  placed  side  by  side,  the  fundus 
glands  of  Heidenhain,  otherwise  called  peptic,  or  cardiac.  Several 
gland  tubes,  which  are  wider  below,  usually  open  into  the  duct  (Fig. 
182).  Each  gland  consists  of  a  structureless  membrana  propria  with 
anastomosing  branched  cells  in  relation  with  it.  The  duct  is  short, 
about  one -fifth  of  the  whole  tube,  and  is  lined  by  a  layer  of  cells  like 
those  lining  the  stomach,  while  the  secretory  part  of  the  tubes  is  lined 
throughout  by  a  layer  of  granular,  short,  small,  polyhedral,  or  col- 
umnar nucleated  cells.  These  cells  border  the  very  narrow  lumen,  and 
are  called  principal  [Heidenhain),  central  (Fig.  180,  II,  a),  or 
adelomorphous  cells  (ad^Aof,  hidden).  At  various  places,  between 
these  cells  and  the  membrana  propria,  are  large,  oval,  or  angular,  well- 
defined,  granular,  densely  reticulated,  nucleated  cells,  the  parietal 
cells  of  Heidenhain,  the  delomorphous  cells  of  RoUett,  or  the  oxyn- 
tic  (acid-forming)  cells  of  Langley  (Fig.  180,  II,  h).  They  are  most 
numerous  in  the  neck  of  the  glands,  and  least  so  in  the  deep  blind 
end  of  the  tubes.  These  cells  are  stained  deeply  by  osmic  acid  and 
aniline  blue,  so  that  they  are  readily  distinguished  from  the  other 
cells.  They  bulge  out  the  membrana  propria  of  the  gland  opposite 
where  they  are  placed.  The  parietal  cells  in  man  are  said  to 
reach  to  the  lumen  of  the  gland  tubes  [Stohr).  Isolated  cells  are 
sometimes  found  under  the  epithelium  of  the  surface  of  the  stomach, 
and  occasionally  in  individual  pyloric  glands.  The  fundus  glands  are 
most  numerous  (about  five  millions),  and  are  of  considerable  size  in 
the  fundus. 


Fig.  I 


Isolated  pyloric  gland. 


286 


PVI.ORIC    GLANDS    OF    THK    STOMACH. 


2.  The  pyloric  glands  occur  only  in  the  region  of  the  pylorus,  where  the  mucous  membrane  is 
more  yellowish-white  in  color  (Fig.  iSi,  A).  These  glands  are  generally  branched  at  their  lower 
ends,  so  that  several  tubes  open  into  a  single  duct  [which,  in  contradistinction  to  the  duct  of  the 
other  glands,  is  wide  and  long,  extending  often  to  half  the  depth  of  the  mucous  membrane.  The 
duct  is  lined  by  epithelium  like  that  lining  the  stomach,  while  the  secretory  part  is  lined  by  a 
single  layer  of  short,  finely  granular,  columnar  cells,  whose  secretion  is  quite  dilTerent  from  that  of 
the  cells  lining  the  duct.  The  lumen  is  well  defined.  Nussbaum  has  occasionally  found  other 
cells,  which  stain  deeply  with  osmic  acid,  between  the  base  of  these.  The  appearance  of  the  cells 
differs  according  to  their  state  of  physiological  activity  (Figs.  183,  184).  When  they  are  exhausted 
they  are  smaller  and  more  granular,  owing  to  the  denser  reticulation  of  their  network  ;  at  any  rate 
they  are  granular  in  ]ireparations  hardened  in  alcohol  (Fig.  184).     There  are  no  parietal  cells.] 


\  ertical  section  of  the  gastric  mucous  membrane.  g^,g^.  pits  on  the  surface  :  /.  neck  of  a  fundus  gland  opening  into  a 
duct,^;  X,  parietal.  and_y,  chief  cells  ;  a,  ;•,  c,  artery,  vein,  capillaries  ;  li,  d,  lymphatics,  emptying  into  a  large 
trunk,  e. 

The  glands  are  supported  by  verj- delicate  connective  tissue  mixed  with  adenoid  tissue  (Fig.  iSo). 
Below  this  are  two  layers,  circular  and  longitudinal,  of  non-striped  muscle,  the  muscularis  mucosae 
(Fig.  177,  Mm.),  and  from  it  fine  processes  of  smooth  muscular  fibres  pass  up  between  groups  of  the 
glands  toward  the  free  epithelial  surface  of  the  mucous  membrane.  Perhaps  these  processes 
are  concerned  in  emptying  the  glands.  [In  the  gastric  mucous  membrane  of  the  cat  there  is  a 
clear,  homogeneous  layer,  which  is  stained  red  by  picro-carmine,  and  placed  immediately 
internal  to  the  muscularis  mucosiv.  It  is  pierced  by  the  processes  passing  from  the  muscularis 
mucosje.] 


THE    GASTRIC    JUICE. 


287 


Masses  of  adenoid  tissue  occur  in  the  mucous  membrane,  especially  near  the  pylorus,  constituting 
lymph  follicles,  which  are  comparable  to  the  solitary  glands  of  the  small  intestine.  The  lymphatics 
are  numerous,  and  begin  close  under  the  epithelium  by  dilated  extremities  or  loops  (Fig.  182,  d); 
they  run  vertically,  and  anastomose  in  the  mucosa  between  the  gland  tubes,  which  they  envelop  in 
sinus-like  spaces.  They  join  large  trunks  in  the  mucosa  ;  another  plexus  of  large  vessels  exists  in 
the  sub-mucosa  [Loven). 

[The  Nerves. —  A  plexus  of  non-medullated  nerve  fibres  and  a  few  ganglion  cells  exist  in  the 
muscular  coat  [Auerbach's],  and  another  [Meissner's]  in  the  sub-mucosa.] 

The  blood  vessels  are  very  numerous.  Small  arterial  branches,  a,  run  in  the  sub-mucosa,  and 
ascend  between  the  glands  to  form  a  longitudinal  capillary  network,  c,c,  under  the  epithelium,  and 
between  its  meshes  the  gland-ducts  open,_§-.  The  veins  gradually  collect  from  this  horizontal  capil- 
lary network,  and  run  toward  the  large  veins  of  the  sub-mucosa,  v. 


Fig.  183. 


Fig.  I 


Sect  on  of  the  p)  lor  c  mucous  membrane. 


Pj'loric  glands  showing  changes  of  the  cells 
during  digestion. 


163.  THE  GASTRIC  JUICE.— Properties.— The  gastric  juice  is  a 
tolerably  clear,  colorless  fluid,  with  a  strong  acid  reaction,  sour  taste,  and  pecu- 
liar characteristic  odor ;  it  rotates  the  plane  of  polarized  light  to  the  left.  It  is 
not  rendered  turbid  by  boiling,  and  resists  putrefaction  for  a  long  time.  Its 
specific  gravity  =  1002.5  (dog,  1005),  and  it  contains  only  yi  per  cent,  of  solid 
constituents.  The  quantity  secreted  in  24  hours  was  estimated  by  Beaumont, 
from  observations  upon  Alexis  St.  Martin,  who  had  a  gastric  fistula  (1834) — at 
only  180  grms.  daily  (!)  ;  by  Grunewald  (1853),  in  a  similar  case,  as  equal  to 
26.4  per  cent,  of  the  body  weight ;  while  Bidder  and  Schmidt  (from  correspond- 


288 


THE    GASTRIC   JUICE. 


ing  obsen-ations  on  dogs)  estimated  it  as  equal  to  6_^<  kilos,  daily,  corresponding 
to  y'y  of  the  body  weight.     It  contains  : — 

(i )  Pepsin,  the  characteristic  hydrolytic  ferment  or  enzym,  which  dissolves 
proteids.  E.  Schiitz  obtained  0.41  to  1,17  per  cent,  from  a  fasting  person  by 
means  of  the  oesophageal  sound. 

(2)  Free  hydrochloric  acid  {Front,  1824),  0.2  to  0.3  (^Richet,  0.8  to  2.1) 
per  1000  ;  (in  the  dog,  0.52  per  cent.).  It  occwt%  free,  as  the  gastric  juice  always 
contains  more  free  chlorine  than  bases,  to  which  it  can  be  united  (C.  Schmiift). 
Lactic  acid  is  usually  met  with,  but  it  arises  from  the  fermentation  of  the  carbo- 
hydrates of  the  food. 

Tests. — Free  hydrochloric  acid  is  detected  by  the  following  reactions :  0.025  P^''  cent,  solu- 
tion of  methyl-violet  becomes  blue;  or  alkaline  solution  of  ootropaeolin  becomes  lilac;  or,  red 
Bordeaux  wine,  treated  with  amylic  alcohol  until  its  color  almost  disappears,  becomes  rose  colored. 
[Giinzburg  recommends  an  alcoholic  solution  of  phloroglucin-vanillin.  2  grammes  of  phloro- 
glucin  are  mixed  with  i  gramme  of  vanillin  in  30  grammes  of  absolute  alcohol,  which  gives  a  yel- 
lowish-red solution.  Concentrated  and  even  very  weak  mineral  acids  cause,  with  this  solution,  a 
bright  red  color  with  the  formation  of  bright  red  crystals,  while  concentrated  organic  acids  do  not 
affect  it.  For  gastric  juice  mix  equal  quantities  of  the  filtered  gastric  juice  and  the  above  solution 
in  a  watch  glass,  and  evaporate  carefully,  not  allowing  it  to  boil;  a  red  pellicle  with  red  crystals 
indicates  the  presence  of  minute  traces  of  hydrochloric  acid.  Congo  red,  either  in  solution  or  as 
Congo- red  papers,  becomes  blue,  but  the  reaction  is  interfered  with  by  the  presence  of  ammonia,  or 
ammoniacal  salts.] 

Lactic  Acid. — The  freshly  prepared  blue  solution  of  10  c.  c.  of  a  4  per  cent,  solution  of  carbolic 
acid,  with  20  c.  c.  of  distilled  water,  and  i  drop  of  liquor  ferri  perchloride,  is  changed  to  yellow 
by  lactic  acid  {Uffelmann). 

(3)  The  large  amount  of  mucus  covering  the  surface  of  the  mucous  membrane 
is  secreted  by  the  goblet  cells  of  the  mucous  membrane  (§  162),  (>;  136,  II). 

(4)  Mineral  salts  (2  per  1000),  and  a  milk-curdling  ferment. 

They  are  chiefiy  sodium  and  potassium  chlorides,  less  calcic  chloride  (ammonium  chloride,  also 
in  animals),  and  the  compounds  of  phosphoric  acid  with  lime,  magnesium  and  iron. 

Among  foreign  substances,  which  may  be  introduced  into  the  body,  the  following  appear  in  the 
gastric  juice — HI,  after  the  use  of  potassium  iodide — potassium  sulphocyanide,  ferric  lactate,  and 
sugar ;  and  ammonium  carbonate  in  uremia. 


[Composition  of  Gastric  Juice  {Hoppe-Scyler,  after  C.  Schmidt.). 


Constituents. 


Water,  .  .  .  . 
Organic  matter, 
Free  HCI,  .  . 
CaClj,  .  .  .  . 
NaCl,     .    .    .    . 

KCl, 

NH^Cl,  .  .  .  . 
Ca32(POj,  .  . 
Mg32(PO,).  .  . 
FePO, 


Human. 


Dog. 


III. 


994.404 

3-195 
0.200 
0.061 
1.465 
0.550 

I         °'^^     I  i 


With  saliva. 

971.171 

17336 

2-337 

I.66I 

3-147 
1-073 
0-537 
2.294 

0.323 
0.1 2 1 


No  saliva. 

973.062 
17.127 
3.050 
0.624 
2.507 
1. 125 
0.468 
1.729 
0.226 
0.082 


IV. 
Sheep. 


986.143 
4-055 
1-234 
0.II4 

4-369 
1. 518 

0.473 
1. 182 

0-577 
0.331 


Good  human  saliva  is  not  .so  dilute  or  so  poor  in  HCI  as  I.  Szabo  has  found  even  3  of  HCI  per 
1000  in  man.] 

164.  SECRETION  OF  GASTRIC  JUICE.— After  the  discovery  of  the 
two  kinds  of  glands  in  the  stomach  and  the  two  kinds  of  cells  in  the  fundus  glands, 
the  question  arose  as  to  whether  the  different  constituents  of  gastric  juice  were 
formed  by  different  histological  elements. 

Changes  of  the  Cells  during  Digestion. — During  the  course  of  digestion,  the  cells  of  the 
fundus  (and  pyloric  glands,  dog)  undergo  important  changes  [Jleidenhain).     During  hunger,  the 


SECRETION    OF    GASTRIC   JUICE.  289 

chief  cells  are  clear  and  large,  the  parietal  investing  cells  are  small,  the  pyloric  cells  clear  and  of 
moderate  size.  During  the  first  six  hours  of  digestion,  the  chief  cells  become  enla,rged  and  moder- 
ately turbid  or  granular,  the  parietal  cells  also  enlarge,  while  the  pyloric  cells  remain  unchanged. 
The  chief  cells  become  diinmisked  and  more  turbid  or  granular  until  the  ninth  hour,  the  parietal 
cells  are  still  swollen,  and  the  pyloric  cells  enlarge.  During  the  last  hours  of  digestion,  the  chief 
cells  again  become  larger  and  clearer,  the  parietal  cells  diminish,  the  pyloric  cells  decrease  in  size 
and  become  turbid  (Figs.  183  and  184). 

[Langley  gives  a  different  description  of  the  appearances  presented  by  these  cells.  The  results 
may  be  reconciled  by  remembering  that  the  gland  cells  were  examined  under  different  conditions. 
The  secretory  cells  consist  of  a  cell  substance  composed  of  {a)  a  framework  of  living  protoplasm, 
either  in  the  form  of  an  intracellular  fibrillar  network,  or  in  flattened  bands.  The  meshes  of  this 
framework  enclose  at  least  two  chemical  substances,  viz.,  [b)  a  hyaline  substance  in  contact  with 
the  framework,  and  [c)  spherical  granules  which  are  efnbedded  in  the  hyaline  substance.  During 
active  secretion,  the  granules  decrease  in  number  and  size,  the  hyaline  substance  increases  in 
amount,  the  network  grows.  This  is  the  reverse  of  what  is  stated  above  as  the  observation  of 
Heidenhain,  but  the  granular  appearance  described  by  Heidenhain  after  secretion  is  very  probably 
due  to  the  action  of  the  hardening  agent,  alcohol.  Langley  found  that  in  the  living  condition,  or 
after  the  use  of  osmic  acid,  in  some  animals  at  least,  the  chief  cells  are  granular  during  rest,  but 
during  a  state  of  activity  two  zones  are  differentiated,  an  outer  one,  which  is  clear,  owing  to  the  dis- 
appearance of  the  granules,  and  an  inner  more  or  less  granular  one.  Granules  reappear  in  the 
outer  part  after  rest.  During  digestion,  the  parietal  cells  increase  in  size,  but  do  not  become 
granular.  In  all  cells  containing  much  pepsinogen,  distinct  granules  are  present,  and  the  quantity 
of  pepsinogen  varies  directly  with  the  number  and  size  of  the  granules.  In  the  glands  of  some 
animals  there  is  little  difference  between  the  resting  and  active  phases.  Compare  Serous  Glands, 
\  143,  and  Pancreas,  \  168.] 

The  pepsin  is  formed  in  the  chief  cells  (^Heidenhain).  When  these  are  clear 
and  large,  they  contain  much  pepsin  ;  when  they  are  contracted  and  turbid,  the 
amount  is  small.  The  pyloric  glands  are  also  said  to  secrete  pepsin,  but  only  to 
a  small  extent.  Pepsin  accumulates  during  the  first  stage  of  hunger,  and  it  is 
eliminated  during  digestion  and  also  during  prolonged  hunger.  Pepsin,  as  such, 
is  not  present  within  the  cells,  but  only  as  a  "  mother  substance,"  a  pepsinogen 
substance  (zymogen),  or  pro-pepsin,  which  occurs  in  the  granules  of  the  chief 
cells.  This  zymogen,  or  mother  substance,  by  itself,  has  no  effect  upon  proteids ; 
but  if  it  be  treated  with  hydrochloric  acid  or  sodium  chloride,  it  is  changed  into 
pepsin.  Pepsin  and  pepsinogen  may  be  extracted  from  the  gastric  mucous  mem- 
brane by  means  of  water  free  from  acids. 

[Pepsinogen  and  Pepsin. — Glycerine  extracts  very  little  pepsin  from  the  perfectly  fresh 
gastric  mucous  membrane,  but  a  large  amount  is  afterward  obtained  by  extracting  it  with  dilute 
hydrochloric  acid,  or  with  this  acid  and  glycerine.  The  relative  amount  of  pepsinogen  and  pepsin 
in  a  fluid  may  be  determined  approximately  by  the  method  of  Langley  and  Edkins.  A  i  per  cent, 
solution  of  sodic  carbonate  exerts  a  greater  destructive  action  on  pepsin  than  on  pepsinogen,  while  a 
current  of  COj  destroys  pepsinogen  to  a  greater  extent  than  pepsin.  Both  substances  are  unaffected 
by  CO,  but  are  destroyed  at  54°  to  57°  C] 

The  pyloric  glands  secrete  pepsin,  but  no  acid.  Klemensiewicz  excised 
in  a  living  dog  the  pyloric  portion  of  the  stomach, 
and  afterward  stitched  together  the  duodenum  and 
the  remaining  part  of  the  stomach.  The  excised 
plyoric  part,  with  its  vessels  intact,  he  stitched  to  the 
abdominal  wall,  after  sewing  its  lower  end.  The 
animals  experimented  on  died,  at  the  latest,  after 
six  days.  The  secretion  of  this  part  was  thin,  alka- 
line, and  contained  2  per  cent,  of  solids,  including 
pepsin. 

[Pyloric   Fistula. — In  Fig.    185   P   represents  the   excised 
pyloric  portion,  C  the  cardiac.     The  parts  a,  a,  and  a'  a'  were 
then  stitched  together,  and  the  continuity  of  the  organ  established. 
The  lower  end  {d)  of  P  was  closed  by  sutures,  while  the  edges  of    Diagram  of  Klemensiewicz's  experi- 
P  at  O  were  stitched  to  the  abdominal  walls,  thus  making  a  py-  '"^"'  ^^^'''^'"s) 

loric  fistula.] 

In  the  frog  the  alkaline  glands  of  the  oesophagus  contain  only  chief  cells  which 

^9 


290  INFLUENCE    OF   THE    NERVES   ON    THE    SECRETION. 

produce  pepsin  ;   while  the  stomach  has  glands  which  secrete  acid  (and  perhaps 
some  pepsin),  and  are  lined  by  parietal  cells. 

Among  fishes  the  carps  have  no  fundus  glands  in  the  stomach  (^Luchau).  [The  secreting  por- 
tions of  glands  of  the  cardiac  sac  (crop)  of  the  herring  are  lined  by  a  single  layer  of  polygonal 
cells  {W.  Stirlins).\ 

The  hydrochloric  acid  is  formed,  according  to  Heidenhain,  by  the  parietal 
cells.  It  occurs  on  the  free  surface  of  the  gastric  mucous  membrane  as  well  as  in 
the  ducts  of  the  fundus  glands.  The  deep  parts  of  the  glands  are  usually  alkaline. 
Free  HCl  is  detected  in  human  gastric  juice,  within  45  minutes  to  i  to  2  hours 
after  a  moderate  meal,  but  in  10  to  15  minutes  in  a  fasting  condition  after  drink- 
ing water;  the  amount  gradually  increases  during  the  process  of  digestion.  Lactic 
acid,  perhaps  derived  from  the  food,  is  found  in  the  stomach  immediately  after 
taking  food,  after  half  an  hour  along  with  HCl,  while  after  an  hour  only  HCl  is 
found  {^Ejvald  and  Boas). 

CI.  Bernard  injected  potassium  ferrocyanide  and  afterward  lactate  of  iron  into  the  veins  of  a  dog. 
After  death,  blue  coloration  occurred  only  in  the  upper  acid  layers  of  the  mucous  membrane. 
Nevertheless,  we  must  assume  that  the  hydrochloric  acid  is  secreted  in  the  parietal  cells  of  the 
fundus  of  the  glands,  and  that  it  is  rapidly  carried  to  the  surface  along  with  the  pepsin. 
Briicke  neutralized  the  surface  of  the  gastric  mucous  membrane  with  magnesia  usta,  chopped 
up  the  mucous  membrane  with  water,  and  left  it  for  some  time,  when  the  fluid  had  again  an  acid 
reaction. 

As  to  the  formation  of  a  free  acid,  the  following  statements  may  be  noted  : 
The  parietal  cells  form  the  hydrochloric  acid  from  the  chlorides  which  the  mucous 
membrane  takes  up  from  the  blood.  According  to  Voit,  the  formation  of  acid 
ceases,  if  chlorides  be  withheld  from  the  food.  Maly  suggests  that  the  active 
agent  is  lactic  acid,  which  splits  up  sodium  chloride  and  forms  free  HCl.  The 
base  set  free  is  excreted  by  the  urine,  rendering  it  at  the  same  time  less  acid.  The 
formation  of  acid  is  arrested  during  hunger.  According  to  H.  Shultz,  watery 
solutions  of  alkaline  and  earthy  chlorides  are  decomposed,  even  at  a  low  tempera- 
ture, by  CO.,,  free  hydrochloric  acid  being  formed. 

[The  source  of  the  HCl  is  undoubtedly  the  sodic  chloride  in  the  blood  and  lymph,  but  what  other 
acid  displaces  the  HCl  is  a  matter  of  conjecture.  In  this  connection,  it  is  important  to  remember 
that  Jul.  Thomsen  has  shown  that  every  acid  can  displace  a  part  of  another  acid  from  its  combina- 
tion with  its  base,  and  the  weaker  acid  may  even  combine  with  the  greater  part  of  the  base.  Thomsen 
calls  this  "  avidity."  Even  strong  mineral  acids  may  be  displaced  by  weak  organic  ones.  Thus 
the  free  CO2  in  the  alkaline  blood  may  set  free  a  small  quantity  of  HCl  from  the  sodic  chloride. 
What  is  still  more  remarkable  is,  that  the  free  HCl  should  be  transferred  by  the  cells  toward  the 
gland  duct,  while  the  sodic  carbonate  diffuses  toward  the  blood  and  lymph. J 

Secretion. — When  the  stomach  is  empty,  there  is  usually  no  secretion  of  gastric 
juice  ;  this  takes  place  only  after  appropriate  (mechanical,  thermal,  or  chemical) 
stimulation.  In  the  normal  condition,  it  takes  place  immediately  on  the  introduc- 
tion of  food,  but  also  of  indigestible  substances,  such  as  pebbles.  The  mucous 
membrane  becomes  red,  and  the  circulation  more  active,  so  that  the  venous  blood 
becomes  brighter.  [That  the  vagi  are  concerned  in  this  vascular  dilatation,  is 
proved  by  the  fact,  that  if  both  nerves  be  divided  during  digestion,  the  gastric 
mucous  membrane  becomes  pale  {Ruiherford).']  The  secretion  is  probably  caused 
reflexly,  and  the  centre  perhaps  lies  in  the  wall  of  the  stomach  itself  (Meissner's 
plexus  in  the  submucous  coat).  It  is  asserted  that  the  idea  of  food,  especially 
during  hunger,  excites  secretion.  As  yet  we  do  not  know  the  effect  produced 
upon  the  secretion  by  stimulation  or  destruction  of  other  nerves,  e.g.,  vagus, 
sympathetic.  [There  is  no  nerve  passing  to  the  stomach,  whose  stimulation  causes 
a  secretion  of  gastric  juice,  as  the  chorda  tympani  does  in  the  sub-maxillary  gland. 
If  the  vagi  be  divided  sufficiently  low  down  not  to  interfere  with  respiration,  the 
introduction  of  food  still  causes  a  secretion  of  gastric  juice  ;  even  if  the  sympathetic 
branches  be  divided  at  the  same  time,  secretion  still  goes  on  {Heidenhaifi).  This 
experiinent  points  to  the  existence  of  local  secretory  centres  in  the  stomach.  But 
there  is  evidence  to  show  that  there  is  some  connection,  perhaps  indirect,  between 


METHODS    OF   OBTAINING    GASTRIC   JUICE.  291 

the  central  nervous  system  and  the  gastric  glands.  Richet  observed  a  case  of 
complete  occlusion  of  the  oesophagus  in  a  woman,  produced  by  swallowing  a  caustic 
alkali.  A  gastric  fistula  was  made,  through  which  the  person  could  be  nourished. 
On  placing  sugar  or  lemon  juice  in  the  person's  mouth,  Richet  observed  a  secretion 
of  gastric  juice.  In  this  case  no  saliva  could  be  swallowed  to  excite  secretion,  so 
that  it  must  have  taken  place  through  some  nervous  channels.  Even  the  sight  or 
smell  of  food  caused  secretion.  Emotional  states  also  are  known  to  interfere  with 
gastric  digestion.! 

Effect  of  Abiorption. — Heidenhain  isolated  apart  of  the  mucous  membrane 
of  the  fundus  so  as  to  form  a  blind  sac  of  it,  and  he  found  that  mechanical  stimu- 
lation caused  merely  a  scanty  local  secretion  at  the  spots  irritated.  If,  however, 
at  the  same  time,  absorption  of  digested  matter  also  occurred,  secretion  took  place 
over  larger  surfaces.  [He  distinguishes  a  primary  and  merely  local  secretion 
excited  by  the  mechanical  stimulus  of  the  ingesta,  and  a  secondary  depending  on 
absorption,  and  extending  to  the  whole  of  the  mucous  membrane.] 

The  statement  of  Schiff,  that  active  gastric  juice  is  secreted  only  after  absorption  of  the  so-called 
peptogenic  substances  (especially  dextrin),  is  denied. 

The  acid  contents  of  the  stomach  called  chyme,  which  pass  into  the  duodenum 
after  gastric  digestion  is  completed,  are  neutralized  by  the  alkali  of  the  intestinal 
mucous  membrane  and  the  pancreatic  juice  [at  the  same  time,  a  precipitate  is 
formed  and  deposited  on  the  walls  of  the  duodenum,  and  it  carries  the  pepsin  down 
with  it].  Part  of  the  pepsin  is  reabsorbed  as  such,  and  is  found  in  traces  in  the 
urine  and  muscle  juice  (Briicke).  If  the  gastric  juice  be  completely  discharged 
externally  through  a  gastric  fistula,  the  alkalinity  of  the  intestine  is  so  strong  that 
the  urine  becomes  alkaline  {^Maly). 

The  acid  gastric  juice  of  the  new-born  child  is  already  fairly  active ;  casein  is  most  easily  digested 
by  it,  then  fibrin  and  the  other  proteids  [Zweifel).  When  the  amount  of  acid  is  too  great  in  the 
stomach  of  sucklings,  large,  firm,  indigestible  masses  of  casein  are  apt  to  be  formed,  especially  after 
the  use  of  cow's  milk  (^  230). 

[Action  of  Drugs  on  Gastric  Secretion. — Dilute  alkalies,  if  given  before  food;  saliva;  some 
substances  called  peplogens  by  Schiff,  such  as  dextrin  and  peptones,  alcohol  and  ether,  all  excite 
secretion,  the  last  being  very  powerful.  When  the  secretion  is  excessively  acid,  antacids  are  given, 
some  diminishing  the  acidity  in  the  stomach,  as  the  carbonates  and  bicarbonates  of  the  alkalies, 
liquor  potassse,  and  the  carbonate  of  magnesia;  while  the  citrates  and  tartrates  of  the  alkalies,  be- 
coming converted  into  carbonates  in  their  passage  through  the  organism,  diminish  the  acidity  of  the 
urine.]  Small  doses  of  alcohol,  introduced  into  the  stomach,  increase  the  secretion  of  gastric  juice ; 
large  doses  arrest  it.  Artificial  digestion  is  affected  by  10  per  cent,  of  alcohol,  is  retarded  by  20  per 
cent.,  and  is  arrested  by  stronger  doses.  Beer  and  wine  hinder  digestion,  and  in  an  undiluted  form 
interfere  with  artificial  digestion. 

165.  METHODS  OF  OBTAINING  GASTRIC  JUICE.— Historical.— Spallanzani 
caused  starving  animals  to  swallow  small  pieces  of  sponge  enclosed  in  perforated  lead  capsules,  and 
after  a  time,  when  the  sponges  had  become  saturated  with  gastric  juice,  he  removed  them  from  the 
stomach.  To  avoid  the  admixture  of  saliva,  the  sponges  are  best  introduced  through  an  opening  in 
the  cesophagus.  Dr.  Beaumont  (1825),  an  American  physician,  was  the  first  to  obtain  humaa  gastric 
juice,  from  a  Canadian  named  Alexis  St.  Martin,  who  was  injured  by  a  gunshot  wound,  whereby 
a  permanent  gastric  fistula  was  established.  Various  substances  were  introduced  through  the  exter- 
nal opening,  which  was  partially  covered  with  a  fold  of  skin,  and  the  time  required  for  their  solu- 
tion was  noted.  Bassow  (1842),  Blondlot  (1843),  and  Bardeleben  (1849),  were  thereby  led  tO' 
make  artificial  gastric  fistulse. 

Gastric  Fistula. — The  anterior  abdominal  wall  is  opened  by  a  median  incision  just  below  the 
ensiform  cartilage,  the  stomach  is  exposed,  and  its  anterior  wall  opened  and  afterward  stitched  to 
the  margins  of  the  abdominal  walls.  A  strong  cannula  is  placed  in  the  fistula  thus  formed.  The 
tube  is  kept  corked.  If  the  ducts  of  the  salivary  glands  be  tied,  a  perfectly  uncomplicated  object 
for  investigation  is  obtained. 

According  to  Leube,  dilute  human  gastric  juice  may  be  obtained  by  means  of  a  siphon-like  tube 
introduced  into  the  stomach.     Water  is  introduced  first,  and  after  a  time  it  is  withdrawn. 

An  important  advance  was  made  when  Eberle  (1834)  prepared  artificial  gastric  juice,  by 
extracting  the  pepsin  from  the  gastric  mucous  membrane  with  dilute  hydrochloric  acid.  Four  litres 
of  solution  of  hydrochloric  acid,  containing  4  ,to  8  c.c.  HCl  per  looo,  are   sufficient  to  extract  the 


292  PROCESS    OF    GASTRIC    DIGESTION. 

chopped-up  mucous  membrane  of  a  pig's  stomach.  Half  a  litre  is  infused  with  the  stomach  and 
renewed  every  six  hours.  The  collected  fluid  is  afterward  filtered.  The  sub.stance  to  be  digested 
is  placed  in  this  fluid,  and  the  whole  is  kept  at  the  temperature  of  the  body,  but  it  is  necessary  to 
add  a  iitile  IICl  from  timetotime  (Si/nonnn).  The  HCl  maybe  replaced  by  ten  times  its  volume 
of  lactic  acid  and  also  by  nitric  acid;  while  oxalic,  sulphuric,  phosphoric,  acetic,  formic,  succinic, 
tartaric,  and  citric  acids  are  much  less  active  ;   butyric  and  salicyclic  acids  are  inactive. 

Von  Wittich's  Method. — (</)  Glycerine  extracts  pepsin  in  a  very  ])ure  form.  The  mucous 
membrane  is  rubbed  up  with  pondered  glass  until  it  forms  a  pulp,  mixed  with  glycerine,  and  allowed 
to  stanil  for  eight  days.  The  fluid  is  pressetl  through  cloth,  and  the  filtrate  mixed  with  alcohol, 
thus  ])recipitating  the  pepsin,  which  is  washed  with  alcohol  and  afterward  dissolved  in  the  dilute 
IICl,  to  form  an  artificial  digestive  fluid.  (/>)  Or  the  mucous  membrane  may  be  placed  for  twenty- 
four  hours  in  alcohol,  and  afterward  dried  and  extracted  for  eight  days  with  glycerine,  (c)  Wm. 
Roljerts  has  used  other  agents  for  extracting  enzymes  (^  148). 

Preparation  of  Pure  Pepsin. — Briicke  pours  on  the  pounded  mucous  membrane  of  the  pig's 
stomach  a  5  percent,  solution  of  phosphoric  acid,  and  afterward  adds  lime-water  until  the  acid  re- 
action is  scarcely  distinguishable.  A  copious  precipitate,  which  carries  the  pepsin  with  it,  is  pro- 
duced. This  precipitate  is  collected  on  cloth,  repeatedly  washed  with  water,  and  afterward  dissolved 
in  very  dilute  IICl.  A  copious  precipitation  is  caused  in  this  fluid  by  gradually  adding  to  it  a  mix- 
ture of  cholesterin  in  four  parts  of  alcohol  and  one  of  ether.  The  cholesterin  pulp  is  collected  on 
a  fdter,  washed  with  water  containing  acetic  acid,  and  afterward  with  pure  water.  The  cholesterin 
pulp  is  placed  in  ether  to  dissolve  the  cholesterin,  and  the  ether  is  then  removed.  The  small 
watery  deposit  contains  the  pepsin  in  solution. 

Pepsin  so  prepared  is  a  colloid  substance  ;  it  does  not  react  like  albumin  with 
the  following  tests,  viz.  :  It  does  not  give  the  xanthroprotein  reaction  (§  248),  is 
not  precipitated  by  acetic  acid  and  potassium  ferrocyanide,  nor  by  tannic  acid, 
mercuric  chloride,  silver  nitrate,  or  iodine.  In  other  respects  it  belongs  to  the 
group  of  albuminoids.  It  is  rendered  inactive  in  an  acid  fluid  by  heating  it  to 
55°  to  60°  C. 

166.  PROCESS  OF  GASTRIC  DIGESTION.— [In  the  process  of 
gastric  digestion  we  have  to  consider — 

1.  The  secretion  of  gastric  juice  and  its  action  on  food. 

2.  The  absorption  of  the  products  of  this  digestion. 

3.  The  movements  of  the  stomach  itself.] 

Chyme. — The  finely  divided  mixture  of  food  and  gastric  juice  is  called  chyme. 
The  gastric  juice  acts  upon  certain  constituents  of  chyme. 

I.  Action  on  Proteids. — Pepsin  and  the  dilute  hydrochloric  acid,  at  the 
temperature  of  the  body,  transform  proteids  into  a  soluble  form,  to  which  Lehmann 
(1850)  gave  the  name  of  *'  peptone"  (§  249,  III).  Fibrin  (or  coagulated  pro- 
teids) first  becomes  clear  and  swollen  up. 

[It  is  commonly  stated  that  the  first  product  formed  during  the  gastric  digestion 
of  proteids  is  syntonin  or  parapeptone,  then  hemi-albumose  or  propep- 
tone,  and  finally  peptone.  The  products  vary,  however,  with  the  proteid 
digested.  Kiihne  has  shown  that  the  proteid  molecule  is  split  up,  and  yields  two 
groups,  which  he  calls  anti-peptone  and  hemi-peptone  ;  the  former  can  be 
split  up  into  leucin  and  tyrosin  by  trypsin,  while  the  latter  does  not  undergo  this 
change.  A  mixture  of  the  two  he  calls  ampho-peptone.  The  intermediate 
body  or  propeptone,  is  really  a  mixture  of  several  bodies.  Kiihne  calls  it  hemi- 
albumose.  These  intermediate  bodies  from  albumin  are  called  albumoses,  from 
globulins  globuloses,  from  casein  caseoses.  Halliburton  calls  all  these  interme- 
diate bodies  "  proteoses."] 

Properties. — Hemi-albumose,  although  a  composite  body,  gives  the  following  reactions  :  It  is 
highly  soluble  in  water;  when  heated  to  50°  to  60°  it  becomes  somewhat  turbid,  but  when  boiled  it 
becomes  clear,  and  gets  turbid  again  on  cooling.  This  effect  is  most  marked  when  it  is  treated 
with  acetic  acid  and  sodic  chloride,  or  the  latter  alone.  It  is  precipitated  by  acetic  acid  and  potas- 
sic  ferrocyanide,  but  the  precipitate  disappears  on  heating  and  reappears  on  cooling.  It  gives  the 
biuret  rosy  tint  reaction  like  peptones.  It  is  precipitated  by  nitric  acid,  and  the  precipitate  adheres 
to  the  glass,  but  is  soluble  in  the  acid  with  the  aid  of  heat,  yielding  a  yellow  fluid,  but  is  precipitated 
on  cooling.     It  is  precipitated  by  boiling  with  acetic  acid  and  a  strong  solution  of  sodic  sulphate, 


PROCESS   OF    GASTRIC    DIGESTION.  293: 

raetaphosphoric  acid,  and  pyrogallic  acid  [Kuhne).     It  is  said  to  be  present  in  all  animal  tissues 
except  muscle  and  nerve  (^  293). 

[Albumoses  are  the  first  products  of  the  splitting  up  of  proteids  by  enzymes, 
and  from  them  peptones  are  ultimately  formed.  They  may  be  made  from  Witte's 
peptone,  or  by  the  peptic  digestion  of  fibrin.  Such  a  mixture,  on  being  neutral- 
ized with  sodic  carbonate,  gives  a  copious  precipitate  of  parapeptones,  which  can 
be  filtered  off,  leaving  a  clear  solution  of  albumoses.  On  saturating  the  clear 
fluid  with  NaCl,  a  dense  white  precipitate,  consisting  of  three  albumoses,  called 
proto-,  dys-,  and  hetero-albumose  is  obtained ;  a  fourth,  deutero-albu- 
mose,  remains  in  solution,  but  can  be  precipitated  by  adding  acetic  acid.  If  the 
albumose  precipitate  be  treated  with  10  percent.  NaCl  solution,  proto-  and  hetero- 
albumose  are  dissolved,  leaving  dys-albumose  undissolved.  Dialysis  of  the  saline 
solution  precipitates  hetero-albumose,  leaving  proto-albumose  in  solution.  It  is 
probable,  however,  that  hetero-  and  dys-albumose  are  identical,  or  that  the  former 
is  merely  an  insoluble  form  of  the  latter.  The  albumoses  are  bodies  intermediate 
between  albumins  and  peptones,  and  of  the  three,  deutero-albumose  is  nearest  to 
peptones.] 

[Properties. — Proto-albumose  is  soluble  in  distilled  water,  is  not  changed  by  heat,  but  is  pre-' 
cipitated  by  saturation  of  the  solution  with  sodic  chloride,  by  HNO3,  acetic  acid,  potassic  ferrocya- 
nide,  copper  sulphate,  mercuric  chloiide.  Deutero-albumose  is  very  like  the  foregoing,  but  it  is 
not  precipitated  by  HNO3  or  on  adding  sodic  chloride  to  saturation,  but  precipitation  occurs  when 
20  to  30  per  cent,  of  acetic  acid  is  added.  Hetero-albumose  resembles  a  globulin  in  its  proper- 
ties; it  is  insoluble  in  distilled  water,  but  is  soluble  in  saline  solutions  (10  to  15  per  cent.),  and  is 
partly  precipitated  from  its  solution  by  saturation  with  NaCl  or  dialysis.  It  is  coagulated  by  heat. 
All  give  the  rosy-pink  color  with  the  biuret  reaction,  and  they  are  all  precipitated  by  saturation  with 
neutral  ammonia  sulphate,  which  peptones  are  not  [Kuhne  and  Chittenden).'\ 

[Globuloses  from  the  globulin  of  ox  serum  are  obtained  in  the  same  way,  although  the  ferment 
has  much  less  action  on  globulin  than  on  albumin.  Speaking  generally,  they  resemble  the  albu- 
moses.] 

By  the  continued  action  of  the  gastric  juice,  the  propeptone  passes  into  a  true 
soluble  peptone.  The  unchanged  albumin  behaves  like  an  anhydride  with 
respect  to  the  peptone.  The  formation  of  peptone  is  due  to  the  taking  up  of  a 
molecule  of  water,  under  the  influence  of  the  hydrolytic  ferment  pepsin,  and  the 
action  takes  place  most  readily  at  the  temperature  of  the  body.  Gelatin  is 
changed  into  a  gelatin-peptone. 

According  to  Kiihne,  the  proteid  molecule  contains  two  substances  preformed :  anti- albumin 
and  hemi-albumin.  Gastric  juice  at  first  converts  them  into  anti-albumose  and  hemi-albumose, 
and  both  ultimately  into  anti-peptone  and  hemi-peptone  (^  170,  II).  Only  the  latter  is  split  up  by 
trypsin  into  leucin  and  tyrosin. 

The  greater  the  amount  of  pepsin  (within  certain  limits),  the  more  rapidly  does 
the  solution  take  place.  The  pepsin  suffers  scarcely  any  change,  and  if  care  be 
taken  to  renew  the  hydrochloric  acid,  so  as  to  keep  it  at  a  uniform  amount,  the 
pepsin  can  dissolve  new  quantities  of  albumin.  Still,  it  seems  that  some  pepsin 
is  used  up  in  the  process  of  digestion  {Griltzner).  Proteids  are  introduced  into 
the  stomach  either  in  a  solid  (coagulated)  or  fluid  condition.  Casein  alone  of  the 
fluid  forms  is  precipitated  or  coagulated,  and  afterward  dissolved.  The  non- 
coagulated  proteids  are  transformed  into  syntonin,  without  being  previously  coagu- 
lated, and  are  then  changed  into  propeptone  and  directly  peptonized,  i.  e.,  actually 
dissolved. 

When  albumin  is  digested  by  pepsin  at  the  temperature  of  the  body,  a  not  inconsiderable  amount 
of  heat  disappears,  as  can  be  proved  by  calorimetric  experiment  {Alaly).  Hence,  the  temperature 
of  the  chyme  in  the  stomach  falls  o°.2  to  o°.6  C.  in  two  to  three  hours  (v.  Vintschgau  and  Dieil). 

Coagulated  albumin  may  be  regarded  as  the  anhydride  of  the  fluid  form,  and 
the  latter  again  as  the  anhydride  of  peptone.  The  peptones,  therefore,  represent 
the  highest  degree  of  hydration  of  the  proteids. 


294  PROPERTIES   OK    I'EITONES. 

Hence  iMrrtones  may  be  fonncd  from  prolcids  by  those  reagents  which  usually  cause  hydration 
vi  "  .realS  "h  MroHR  .cids  (from  Lin.  with  0.2  HCl).  caust.c  alkal.es.  putrefact.ve  and 
various  other  ferments,  and  o/oiie. 

The  anhydride  proteid  has  been  prepared  from  the  hydrated  fortii.  Henniger 
and  Hofmeister.  by  boiling  pure  peptone  with  dehydrating  substances  (anhydrous 
acetic  acid  at  80°  C),  have  succeeded  in  decomposing  it  into  a  body  resembhng 

'^Peptoncs.-(  .  )  They  are  completely  soluble  in  water.  (2)  They  diffuse  very 
cas.U  through  tnembranes.  (3)  They  filter  quite  easily  through  the  pores  of 
animal  membranes.  (4)  They  are  no/  precipitated  \^y  boiling,  nitric  acid,  acetic 
acid  and  potassium  ferrocyanide,  acetic  acid  and  saturation  with  common  salt, 
(c)  They  are  precipitated  from  neutral  or  feebly  acid  solutions  by  mercuric 
chloride,  tannic  acid,  bile  acids,  and  phosphoro-molybdic  acid.  (6)  With 
Millon's  reagent  they  react  like  proteids,  and  give  a  red  color,  and  with  nitric 
acid  give  the  yellow  xanthoprotein  reaction.  (7)  With  caustic  potash  or  soda 
and  a  small  quantity  of  cupric  sulphate  [or  Fehling's  solution]  they  give  a 
beautiful  rosy-red  co\ox,  the  biuret  reaction.  (8)  They  rotate  the  plane  of  polar- 
ized light  to' the  left. 

[Kuhne  and  Chittenden,  making  use  of  the  fait  that  ammonium  sulphate  to 
saturation  precipitates  all  proteids  from  solution  except  peptone,  have  reinvesti- 
gated the  subject,  and  they  find  that  many  of  the  peptones  of  commerce  contain 
albumoses.  Pure  jjeptone  has  remarkable  properties.  When  dissolved  in  water, 
it  hisses  and  froths  like  phosphoric  anhydride,  heat  is  evolved,  and  a  brown  solu- 
tion IS  formed.  It  is  difiicult  to  preserve  it.  It  is  not  precipitated  by  NaCl,  or 
NaCl  and  acetic  acid,  but  is  completely  precipitated  by  phospho-tungstic  and 
phosi)ho-molybdic  acids,  tannin,  iodo-mercuric  iodide,  picric  acid.  Peptones 
have  a  cheesy  taste,  while  albumin  and  albumoses  are  tasteless.] 

The  biuret  reaction  is  obtained  with  propeptone,  as  well  as  with  a  form  of  albumin,  which  is 
formed  durinp  artificial  digestion  and  is  soluble  in  alcohol.  It  is  called  "  alkophyr  "  by  Briicke. 
[Darby's  fluid  meat  gives  all  the  above  reactions,  and  is  very  useful  for  studying  the  tests  for 
peptiines] 

The  rapidity  of  solution  of  fibrin  is  tested  by  placing  fibrin  which  is  swollen  up  by  the  action 
of  0.2  per  cent.  HCi  in  a  glass  funnel,  and  adding  the  digestive  fluid,  observing  the  rapidity  with 
which  the  fluid,  the  altere<i  fibrin,  drops  from  the  funnel,  and  the  fibrin  disappears  {Grunhagen). 
Or  the  fibrin  may  be  colored  with  carmine,  swollen  up  in  o.l  per  cent.  HCl,  and  placed  in  the 
digestive  tluid.     The  more  rapidly  the  fluid  is  colored  red,  the  more  energetic  is  the  digestion. 

Preparation. — I'ure  peptones  are  prepared  by  taking  fluid  which  contains  them  and  neutralizing 
it  with  barium  carfxmate,  evaporating  upon  a  water  bath,  and  filtering.  The  barium  is  removed 
from  the  filtrate  by  the  careful  addition  of  sulphuric  acid,  and  subsequent  filtration. 

Ptomaines. — Hriegcr  extracted  from  gastric  peptones  by  amylic  alcohol  a  peptone-free  poison, 
with  actions  like  those  of  curara.  It  belongs  to  the  group  of //cwrt/w^,  i.  e.,  alkaloids  obtained  from 
dead  l)o<lies  or  decomposing  proteids.  [I'lomaines  are  identical  with  the  alkaloids  in  plants,  and 
many  have  been  isolated.  The  term  leucomaine  has  been  applied  by  Gautier  to  alkaloids  formed 
by  the  decomjxjsition  of  albuminous  bodies  during  the  normal  metabolic  processes  taking  place  in 
the  iis>ues.  They  are  not  formed  by  the  activity  of  microorganisms.  .Some  seem  to  be  formed  in 
muscle,  and  are  cksely  allied  to  creatin  and  xanihin.] 

Peptones  are  undoubtedly  those  modifications  of  albumin  or  proteids  which, 
after  their  absorption  from  the  intestinal  canal  into  the  blood,  are  destined  to 
make  good  the  proteids  used  up  in  the  human  organism.  By  giving  peptones 
(instead  of  albumin)  as  food,  life  cannot  only  be  maintained,  but  there  may  even 
be  an  increase  of  the  body  weight  {Plbsz  and  Maty,  Adamkiewicz).  Very 
probably,  before  being  absorbed  into  the  blood  stream,  peptones  are  re-trans- 
formed into  serum  albumin  (§  192). 

Conditions  affecting  Gastric  Digestion.— The  presence  of  already-formed  peptones  interferes 
with  the  action  of  the  gastric  juice,  in  so  far  as  the  greater  concentration  of  the  fluid  interferes  with 
and  limits  the  mobility  of  the  fluid  particles.  Boiling,  concentrated  acids,  alum,  and  tannic  acid, 
ntkalinity  of  the  gastric  juice  (<•.  g.,  by  the  admixture  of  much  saliva),  abolish  the  action  ;  also  sul. 
phurous  and  arsenious  acids  and  potassic  iodide.     The  salts  of  the  heavy  metals,  which  cause  pre- 


ARTIFICIAL   DIGESTION    OF   THE    PROTEIDS. 


295 


cipitates  with  pepsin,  peptone,  and  mucin,  interfere  with  gastric  digestion,  and  so  do  concentrated 
solutions  of  alkaUne  salts,  common  salt,  magnesium  and  sodium  sulphates.  A  small  quantity  of 
NaCl  increases  the  secretion  [Griiizner)  and  favors  the  action  of  pepsin.  Alkalies  rapidly  destroy 
pepsin,  but  less  rapidly  pro-pepsin  [Langley).  Alcohol  precipitates  the  pepsin,  but  by  the  subsequent 
addition  of  water  it  is  redissolved,  so  that  digestion  goes  on  as  before.  Any  means  that  prevent 
the  proteid  bodies  from  swelUng  up,  as  by  binding  them  firmly,  impede  digestion.  Slightly 
over  half  a  pint  of  cold  water  does  not  seem  to  disturb  healthy  digestion,  but  it  does  so  in  cases  of 
disease  of  the  stomach.  Copious  draughts  of  water,  and  violent  muscular  exercise,  disturb  digestion ; 
while  warm  clothing,  especially  over  the  pit  of  the  stomach,  aids  it.  Menstruation  retards  gastric 
digestion.  [Oddi  finds  that  the  presence  of  large  quantities  of  ox  bile,  or  even  of  its  own  bile  in  the 
stomach  of  a  dog,  does  not  aff"ect  the  activity  of  the  gastric  juice,  does  not  precipitate  peptones,  and 
does  not  excite  vomiting.] 

[Artificial  Digestion. — The  action  of  gastric  juice  on  proteids  may  be 
observed  outside  the  body,  and  we  can  prove,  as  is  shown  in  the  following  table, 
after  Rutherford,  that  pepsin  and  an  acid — e.  g.,  hydrochloric,  along  with  water — 
are  essential  to  the  formation  of  gastric  peptones  : — 


Beaker  A. 

Beaker  B. 

Beaker  C. 

Water. 

Pepsin,  0.3  per  cent. 

Fibrin. 

Water. 

HCl,  0.2  per  cent. 

Fibrin. 

Water. 

Pepsin,  0.3  per  cent. 

HCl,     0.2 

Fibrin. 

Keep  all  in  water  bath  at  38°  C. 

Unchanged.                     Fibrin    swells     up,   becomes    clear,    and    is 
changed  into  acid  albumin  or  syntonin. 

Fibrin  ultimately  changed 
into  peptone.] 

[In  all  animals,  gastric  digestion  is  essentially  an  acid  digestion,  and  between 
the  native  proteid,  fibrin,  albumin,  or  any  other  form  of  proteid,  and  the  end 
product  peptone,  there  are  numerous  intermediate  substances,  many  of  whose 
properties  and  characters  have  still  to  be  investigated.] 

[Exclusion  of  the  Stomach. — Ogata  finds  that  if  the  stomach  be  divided  at  the  pyloric  end  so 
as  to  exclude  the  stomach  from  the  digestive  apparatus,  a  dog  can  be  nourished  for  a  long  time  by 
introducing  food  through  the  pylorus  into  the  duodenum.  A  dog  has  lived  several  years  after  excision 
of  its  stomach  [Czerny).  Raw  flesh  so  introduced  is  digested  more  rapidly  in  the  small  intestine 
than  in  the  stomach.  The  stomach  not  only  digests,  but  it  acts  on  the  connective  tissue  of  flesh  so  as 
to  prepare  the  latter  for  intestinal  digestion.] 

II.  Action  on  other  Constituents  of  Food. — Milk  coagulates  when  it 
enters  the  stomach,  owing  to  the  precipitation  of  the  casein,  and  in  doing  so  it 
entangles  some  of  the  milk  globules.  During  the  process  of  coagulation,  heat  is 
given  off.  The  free  hydrochloric  acid  of  the  gastric  juice  is  itself  sufficient  to  pre- 
cipitate it ;  the  acid  removes  from  the  alkali-albuminate  or  casein  the  alkali  which 
keeps  it  in  solution.  Hammarsten  separated  a  special  ferment  from  the  gastric 
juice — quite  distinct  from  pepsin — the  milk-curdling  ferment  which,  quite 
independently  of  the  acid,  precipitates  the  casein  either  in  neutral  or  alkaline  solu- 
tions. It  is  this  ferment  or  rennet  which  is  used  to  coagulale  casein  in  the 
making  of  cheese.  [Rennet  is  an  infusion  of  the  fourth  stomach  of  the  calf  in 
brine  (§  231).  The  ferment  which  coagulates  milk  is  quite  distinct  from  pepsin. 
If  magnesic  carbonate  be  added  to  an  infusion  of  calf's  stomach,  a  precipitate 
is  obtained.  The  clear  fluid  has  strongly  coagulating  properties,  while  the  pre- 
cipitate is  strongly  peptic] 

The  action  of  the  milk-curdling  ferment  is,  perhaps,  like  the  action  of  all  ferments,  a  hydration  of 
casein  ;  it  is  greater  in  the  presence  of  0.2  HCl. 

One  part  of  the  rennet  ferment  can  precipitate  800,000  parts  of  casein.  When  casein  coagulates, 
two  new  proteids  seem  to  be  formed — the  coagulated  proteid  which  constitutes  cheese,  and  a  body 
resembling  peptone  dissolved  in  the  whey.     The  addition  of  calcium  chloride  accelerates,  while 


29<;  ACTION    Ol-    GASTRIC   JUKE    ON    THE    VARIOUS   TISSUES. 

w.ter  retard*  the  coagulation  (?  231)  {Ihmmarsten).     [A  ferment  similar  to  rennet  is  contained 
in  the  sec«l»  of   W'ithama  iOHipilans  (S.  Lf<i)]  .     ■    r         j       j  c     n  . 

Casein  is  first  precipitated  in  the  stomach,  then  a  bodyl.We  syntonm  is  formed,  and  finally  peptone. 
During  the  process,  a  substance  conlainint:  phosphorus  and  resembling  nuclein  appears  {Lu(,avm). 

There  is  a  "lactic  acid  ferment  "  also  i)rescnt,  which  changes  milk  sugar 
into  lactic  acid  {Hammarsicn).  I'art  of  the  milk  sugar  is  changed  in  the  stomach 
and  intestine  into  grape  sugar. 

Action  on  Carbohydrates.— tlastric  juice  does  not  act  as  a  solvent  of  starch, 
inulin.  or  gums.  Cane  sugar  is  slowly  changed  into  grape  sugar.  According  to 
Uffelmann.  the  gastric  mucus,  and  according  to  Leube,  the  gastric  acid,  are  the 
chief  agents  in  this  process.  On  albuminoids.— During  the  digestion  of  true 
cartilage,  there  is  formed  a  chondrin  peptone,  and  a  body  which  gives  the  sugar 
reaction  with  Trommer's  test.  Perfectly  pure  elastin  yields  an  elastin  peptone, 
similar  to  albumin  pei)tone,  and  hemi-elastin  similar  to  hemi-albumose.  A  very 
minute  quantity  of  fat  is  broken  up  into  glycerine  and  fatty  acids.  [On  neutral 
olive  oil  being'injected  into  the  stomach  of  a  dog,  after  several  hours— the  pylorus 
being  plugged  with  an  elastic  bag— it  partly  splits  up  and  yields  oleic  acid  (yCash 
and  0^ata).'\ 

rWc  still  require  further  observations  on  the  gastric  digestion  of  fats.  Richet  observed  in  his 
case  of  fistula,  thai  fatty  matters  remained  a  long  time  in  the  stomach,  and  Ludwig  found  the  same 
result  in  the  dog.  In  some  dyspeptics,  rancid  eructations  often  take  place  toward  the  end  of  gastric 
digestion.] 

III.  Action  on  the  Various  Tissues.— (i)  The  gelatine-yielding  substances  (collagen)  of 
all  the  connective  tissues  (connective  tissue,  white  fibro-cartilage,  and  the  matrix  of  bone),  as  well 
as  glutin,  is  dissolved  and  peptonized  by  the  gastric  juice.  [Gelatin,  when  acted  on  by  gastric  juice, 
no  longer  sf>lidifies  in  the  cold,  but  a  ::;elatin-pcptonf  is  formed,  which  is  soluble  and  diffusible, 
although  it  differs  from  true  [leptonc.  In  the  dog,  connective  tissues  are  especially  acted  on  in  the 
stomach,  while  the  other  parts  of  organs  used  as  food  are  prepared  for  digestion  in  the  small  intestine, 
where  the  cellul.ir  and  nuclear  elements  are  digested  by  the  pancreatic  juice  [Bikfalvi).']  (2)  The 
Structureless  membranes  (menibranx  propria)  of  glands,  sarcolemma,  Schwann's  sheath  of 
nerve  fibres,  c.ipsule  of  the  lens,  the  elastic  laminx  of  the  cornea,  the  membranes  of  fat  cells  are 
dissolved,  but  the  true  elastic  (fenestrated)  membranes  and  fibres  are  not  affected.  (3)  Striped 
muscle,  after  solution  of  the  sarcolemma,  breaks  up  transversely  into  disks,  and,  like  non-striped 
muscle,  is  dissolved,  and  forms  a  true  soluble  pejMone,  but  parts  of  the  muscle  always  pass  into  the 
intestine.  (4)  The  albuminous  constituents  of  the  soft  cellular  elements  of  glands,  stratified  epi- 
thelium, endothelium,  and  lymph  cells,  form  peptones,  but  the  nuclein  of  the  nuclei  does  not  seem 
to  \tc  dissolved.  (5)  The  horny  parts  of  the  epidermis,  nails,  hair,  as  well  as  chitin,  silk,  conchioUn, 
and  s|x)ngin  of  the  lower  animals  are  indigestible,  and  so  are  amyloid  substance  and  wax.  (6)  The 
red  blood  corpuscles  are  dissolved,  the  haemoglobin  decomposed  into  haematin  and  a  globulin- 
like substance;  the  latter  is  peptonized,  while  the  former  remains  unchanged,  and  is  partly  absorbed 
and  transformed  into  bile  pigment.  Fibrin  is  easily  dissolved  to  form  hemi-  and  anti-peptone.  (7) 
Mucin,  which  is  .al>o  secreted  by  the  goblet  cells  of  the  stomach,  passes  through  the  intestines 
unchanged.  (S)  Vegetable  fats  are  not  affected  by  the  gastric  juice  ;  these  cells  yield  their  proto- 
pla.smic  contents  to  fonn  pei)tn!R-s,  while  the  cellulose  of  the  cell  wall,  in  the  case  of  man  at  least, 
remains  undigi-sti-*!  (■;  1S4). 

Why  the  Stomach  does  not  digest  itself.— That  the  stomach  can  digest  living  things  is  shown 
by  the  following  facts  :  l{cm.ard  intro<luced  the  leg  of  a  living  frog  through  a  gastric  fistula  into  the 
stomach  of  a  dog.  I'avy  did  the  same  with  the  car  of  a  rabbit,  and  in  both  the  objects  introduced 
were  digested.  [  Ircn/el  has  mo<lified  this  experiment,  and  shown  that  the  legs  of  a  living  frog  are 
digcstwl  by  artificial  ga.stric  juice,  the  tissues  being  first  killed  and  then  digested.  His  experiments  go 
to  show  that  the  alkalinity  of  the  blood  is  not  the  protective  medium.]  '1  he  margins  of  a  gastric  ulcer 
and  of  gastric  fi.stul.v  in  man  are  attacked  by  the  gastric  juice.  John  Hunter  (1772)  discussed  the 
micslion  why  the  stomach  docs  not  digest  itself.  Not  unfraiuently  after  death  the  posterior  wall  of 
the  stomach  is  found  dige-tetl  [more  especially  if  the  person  die  after  a  full  meal  and  the  body  be  kept 
in  a  warm  place,  whereby  the  contents  of  the  stomach  may  escape  into  the  peritoneum.  CI.  Bernard 
showcil,  that  if  a  rabbit  lie  kill.-d  and  placed  in  an  oven  at  the  temijerature  of  the  body,  the  walls 
of  the  stomach  are  attacked  by  its  own  gastric  juice.  Fishes  also  are  fref|uentlv  found  with 
their  stomach  partially  digeste<l  after  death].  It  would  seem,  therefore,  that  so  long  lis  the  circula- 
tion continues,  the  tissues  are  protected  from  the  action  of  the  acid  by  the  alka/ine  blood  •  this  action 
cannot  take  place  if  the  reaction  be  alkaline  ( Paw).  [This,  however,  does  not  explain  why  the 
pancreatic  juice  does  not  digest  the  pancreas.]  Ligature  of  the  arteries  of  the  stomach  causes 
digestive  softening  of  the  gastric  mucous  membrane.  '1  he  thick  laver  of  the  mucus  may  also  aid  in 
protecting  the  stomach  from  the  action  of  its  own  gastric  juice  (C/.  Bernard). 


STRUCTURE  OF  THE  PANCREAS. 


297 


167.  GASES  IN  THE  STOMACH.— The  stomach  always  contains  a 
certain  quantity  of  gas,  derived  partly  from  the  gases  swallowed  with  the  saliva, 
partly  from  gases  which  pass  backward  from  the  duodenum. 

The  air  in  the  stomach  is  constantly  undergoing  changes,  whereby  its  O  is 
absorbed  by  the  blood,  and  for  i  vol.  of  O  absorbed  2  vols,  of  CO.2  are  returned 
to  the  stomach  from  the  blood.  Hence,  the  amount  of  O  in  the  stomach  is  very 
small,  the  CO2  very  considerable  {Flane)-). 


Gases  in  the  Stomach. — Vol.  per  cent.  [Planer). 


Human  Subject  after  Vegetable  Diet. 


I. 


CO2, 20.79 

H, 6.71 

N      72.50 

O, 


3383 
27-58 
38.22 

0.37 


Dog. 


I. 

After  Animal  Diet . 


25.2 

68.7 
6.1 


II. 

After  Legumes. 


32.9 

66.3 
0.8 


By  the  acid  of  the  stomach  a  part  of  the  CO2  is  set  free  from  the  saliva,  which 
contains  much  CO2  (§  146).     The  N  acts  as  an  indifferent  substance. 

Abnormal  development  of  gases  in  persons  suffering  from  gastric  catarrh,  occurs  when  the 
gastric  contents  are  neutral  in  reaction ;  during  the  butyric  acid  fermentation  H  and  COj  are  formed ; 
the  acetic  acid  and  lactic  acid  fermentations  do  not  cause  the  formation  of  gases.  M  arsh  gas  (CH^) 
has  been  found,  but  it  comes  from  the  intestine,  as  it  can  only  be  formed  when  no  O  is  present 
{I  184). 

168.  STRUCTURE  OF  THE  PANCREAS.— The  pancreas  is  a  compound  tubular 
gland,  and  in  its  general  an-angement  into  lobes,  lobules,  and  system  of  ducts  and  acini,  it  corresponds 
exactly  to  the  tme  salivary  glands.  The  epithelium  lining  the  ducts  is  not  at  all,  or  only  faintly, 
striated.  The  acini  are  tubular  or  flasked-shaped,  and  often  convoluted.  They  consist  of  a  mem- 
brana  propria,  resembling  that  of  the  salivary  glands,  lined  by  a  single  layer  of  somewhat  cylindrical 
cells,  with  a  more  or  less  conical  apex,  directed  toward  the  very  narrow  lumen  of  the  acini.  [As  in 
the  salivary  glands,  there  is  a  narrow  intermediary  part  of  the  ducts  opening  into  the  acini,  and 
lined  by  flattened  epithelium.]     The  cells  lining  the  acini  consist  of  two  zones  (Fig.  186) : — 


Fig.  I 


Section  of  the  fresh  pancreas. 


Fig.  187. 


Changes  of  the  pancreatic  cells  in  various  stages  of  activity,  i.  During 
hunger;  2,  in  the  first  stage  of  digestion;  3,  in  the  second  stage;  4, 
during  paralytic  secretion. 


(l)  The  smaller  outer  or  parietal  layer  is  transparent,  homogeneous,  sometimes  faintly  striated,, 
and  readily  stained  with  carmine  and  logwood;  and  (2)  the  inner  layer  (Bernard's  granular  layer)  is 
granular,  and  stains  but  slightly  with  carmine  (Fig.  186).  It  undoubtedly  contributes  to  the  secretion 
by  giving  off  material,  the  granules  being  dissolved,  while  the  zone  itself  becomes  smaller.  The 
spherical  nucleus  lies  between  the  two  zones.  [The  lumen  of  the  acini  is  very  small,  and  spindle- 
shaped  or  branched  cells  (centro-acinar  cells)  lie  in  it,  and  send  their  processes  between  the 
secretory    cells,  thus  acting  as  supporting  cells  for  the  elements  of  the  wall  of  the  acini.     Dm-ing- 


298  THE    PANCREATIC   JUICE. 

secret » 

zone 
the  DUU 

inn"*unc"d^mi.ulhcl  irsire:Vh;%7a.rules  disappear,  while  fhe  striated  outer  zone  increases  in  size 
mclST  2).  In  the  ....m/ stage  (to  to  20  hours)  tl>c  inner  zone  ,s  j^reaily  enlarged  and  granular, 
whi^e  the  outer  zone  is  small  ( Kit;.  .87.3)-  I'^nng  hunger  the  outer  zone  agam  enlarges  (F.g. 
787  I)  In  a  glan.l  where  paralytic  secretion  takes  place,  the  gland  .s  much  dmi.n.shed  in  s.ze, 
Ihc  cells  are  shriveled  ( F.g.  1 87,  4)  and  greatly  changed.  According  to  Ogata,  some  cells  actually 
disai>i)car  durini?  secretion.  .  ,  n    <•  .• 

The  axially  placed  excretory  duct  consists  of  an  inner  th.ck  and  an  outer  loose  wa  1  of  connective 
and  elastic  tissues,  lined  by  a  single  layer  of  columnar  epithelium.  Small  mucous  glands  he  in  the 
Unrest  trunks.  Non-medullaied  nei^es,  with  ,c<7«;V/V7  in  their  course,  pass  to  the  acmi.  but  their 
mode  of  termination  is  unknown.  The  blood  vessels  form  a  rich  capillary  plexus  round  some 
acini  while  round  others  there  are  verv'  few.  Kiihne  and  I.ea  found  peculiar  small  cells  in  groups 
between  the  alveoli,  and  supplied  with  convoluted  cai.illaries  like  glomeruli.  1  heir  signihcance  is 
entirely  unknown.  [They  are  probably  lymphatic  in  their  nature  ]  The  lymphatics  resemble  those 
of  the'  salivar)-  glands.  When  a  coloretl  injection  is  forced  into  the  ducts  under  a  high  pressure,  fine 
intercellular  passages  between  the  secreting  cells  are  formed  {Saviolli's  canals),  but  they  are  artificial 

products.]  ...  ... 

[Number  of  Ducts.— In  making  evjieriments  upon  the  pancre.itic  secretion,  it  n  important  to 
rememU-r  that  the  number  of  pancreatic  ducts  varies  in  ditferent  animals.  In  man  there  is  one  duct 
oix-ning  along  with  tlie  common  bile  duct  at  \'ater's  ampulla,  at  the  junction  of  the  middle  and  lower 
thiril  of  the  duodenum.  The  r.ibbit  ha.s  two  ducts,  the  larger  oi>ening  .separately  aliout  14  inches  (30 
to  35  cm.)  below  the  entrance  of  the  bile  duct.  The  dog  and  cat  have  each  two  ducts  opening 
separately] 

Chemistry. — The  fresh  pancreas  contains  water,  proteids,  ferments,  fats,  and  salts.  In  a  gland 
which  has  l)cen  exjx)sed  for  some  time,  much  leucin,  isoleucin.  butalin,  tyrosin,  often  xanthin  and 
guanin,  are  found :  lactic  and  fatty  acids  seem  to  be  formed  from  chemical  decomix)sitions  taking 
place. 

169.  THE  PANCREATIC  JUICE.— Method.— Regner  de  Graaf  (1664)  tied  a  cannula  in 
the  pancreatic  duct  of  a  dog,  and  collected  the  juice  in  a  small  bag.  Other  experimenters  made  a 
temporary  fistula.  To  make  a  permanent  fistula,  the  abdomen  is  opened  (dog),  the  pancreatic 
duct  pulled  forward,  and  stitched  to  the  abdominall  wall,  with  which  it  unites.  Heidenhain  cuts  out 
the  part  of  the  duocienum  where  the  duct  opens  into  it,  from  its  continuity  with  the  intestine,  and  fixes 
it  out.side  the  alKiominal  wound. 

The  secretion  obtained  from  a  permanent  fistula  is  a  copious,  slightly 
active,  watery  secretion,  containing  much  sodium  carbonate;  while  the  thick  fluid 
obtained  from  the  fistula  before  inflammation  sets  in,  or  that  from  a  temporary 
fistula,  acts  far  more  energetically.  This  thick  secretion,  which  is  small  in 
amount,  is  the  «<?r//;a/ secretion.  The  copious  watery  secretion  is  perhaps  caused 
by  the  increased  transudation  from  the  dilated  blood  vessels  (possibly  in  conse- 
quence of  the  paralysis  of  the  vasomotor  nerves).  It  is,  therefore,  in  a  certain 
sense,  a  "paralytic  secretion  "  (§  145).  The  quantity  varies  much,  according 
as  the  fluid  is  thick  or  thin.  During  digestion,  a  large  dog  secretes  i  to  1.5 
gramme  of  a  thick  secretion  (C/.  Bernard).  Bidder  and  Schmidt  obtained  in 
twenty-four  hours  35  to  117  grammes  of  a  watery  secretion  per  kilo,  of  a  dog. 
When  the  gland  is  not  secreting,  and  is  at  rest,  it  is  soft,  and  of  a  pale  yellowish- 
red  color,  but  during  secretion  it  is  red  and  turgid  with  blood,  owing  to  the 
dilatation  of  the  blood  vessels. 

The  normal  secretion  is  transparent,  colorless,  odorless,  saltish  to  the  taste, 
and  has  a  strong  alkaline  reaction,  owing  to  the  presence  of  sodium  carbonate, 
so  that  when  an  ac  id  is  added,  CO.^  is  given  off.  It  contains  albumin  and  alkali- 
albuminate;  it  is  sticky,  somewhat  viscid,  flows  with  difficulty,  and  is  coagulated 
by  heat  into  a  white  ma.ss.  In  the  cold,  there  separates  a  jelly-like  albuminous 
coagulunri.  Nitric,  hydrochloric,  and  sulphuric  acids  cause  a  precipitate ;  while 
the  precipitate  caused  by  alcohol  is  redissolved  in  water.  CI.  Bernard  found  in 
the  pancreatic  juice  of  a  dog  8.2  per  cent,  of  organic  substances,  and  0.8  percent, 
of  ash.     The  juice  (dog)  analyzed  by  Carl  Schmidt  contained  in  1000  parts  : — 


ACTION    OF   THE    PANCREATIC   JUICE.  299 


f  Organic, 81.84 

Solids,  90.38  in  J   Inorganic,      ,    .    ,    .      8.54 
1000  parts.         I        (like  those  of  blood 
l^  serum). 


Sodic  chloride, 7.36 

"     phosphate, 0.45 

"     sulphate, o.io 

Soda, 0.32 

Lime, 0.22 

Magnesia, 0.05 

Potassic  sulphate, 0.02 

Ferric  oxide, 0.02 


The  more  rapid  and  more  profuse  the  secretion,  the  poorer  it  is  in  organic  substances,  while  the 
inorganic  remain  almost  the  same;  nevertheless,  the  total  quantity  of  solids  is  greater  than  when  the 
quantity  secreted  is  small  [^Bernstein).  Traces  of  leucin  and  soaps  are  present  in  the  fresh  juice. 
[It  usually  contains  few  or  no  structural  elements.  Any  structural  elements  present  in  the  fresh  juice, 
as  well  as  its  proteids,  are  digested  by  the  peptone-forming  ferment  of  the  juice,  especially  if  the  latter 
be  kept  for  some  time.  If  the  fresh  juice  is  allowed  to  stand  for  some  time,  and  then  mixed  with 
chlorine  water,  a  red  color  is  obtained.] 

Concretions  are  rarely  formed  in  the  pancreatic  ducts ;  they  usually  consist  of  calcic  carbonate. 
Dextrose  has  been  found  in  the  juice  in  diabetes,  and  urea  in  jaundice.  SchifPs  statement  that  the 
pancreas  secretes  only  after  the  absorption  of  dextrin,  has  not  been  confirmed.  The  secretory  activity 
of  the  pancreas  is  not  dependent  on  the  presence  of  the  spleen. 

170.  ACTION  OF  THE  PANCREATIC  JUICE.— The  presence  of 
at  least  four  enzymes,  or  hydrolytic  ferments,  makes  the  pancreatic  juice  one 
of  the  most  important  digestive  fluids  in  the  body. 

I.  Diastatic  action  is  due  to  the  diastatic  ferment,  amylopsin,  a  substance 
which  seems  to  be  identical  with  the  saliva  ferment ;  but  it  acts  much  more 
energetically  than  the  ptyalin  on  saliva,  on  raw  starch  as  well  as  upon  boiled 
starch ;  at  the  temperature  of  the  body  the  change  is  effected  almost  at  once, 
while  it  takes  place  more  slowly  at  a  low  temperature.  Glycogen  is  changed  into 
dextrin  and  grape  sugar;  and  achroodextrin  into  sugar.  Even  cellulose  is  said  to 
be  dissolved,  and  gum  changed  into  sugar  by  it,  but  inulin  remains  unchanged. 

According  to  v.  Mering  and  Musculus,  the  starch  (as  in  the  case  of  the  saliva,  \  148)  is  changed 
into  maltose,  and  a  reducing  dextrin;  so  also  is  glycogen.  Amylopsin  changes  achroodextrin  into 
maltose ;  at  40°  C.  maltose  is  slowly  changed  into  dextrose,  but  cane  sugar  is  not  changed  into  invert 
sugar.  The  ferment  is  precipitated  by  alcohol,  while  it  is  extracted  by  glycerine  without  undergoing 
any  essential  change.  All  conditions  which  destroy  the  diastatic  action  of  saliva  (^  148)  similarly 
affect  its  action,  but  the  admixture  with  acid  gastric  juice  (its  acid  being  neutralized)  or  bile  does  not 
seem  to  have  any  injurious  influence.  This  ferment  is  absent  from  the  pancreas  of  new-bom  children 
(JCorowin). 

Preparation. — The  ferment  is  isolated  by  the  same  methods  as  obtain  for  ptyalin  (^  148) ;  but  the 
tryptic  ferment  is  precipitated  at  the  same  time.  The  addition  of  neutral  salts  (4  per  cent,  solution), 
e.g.,  potassium  nitrate,  common  salt,  ammonium  chloride,  increases  the  diastatic  action. 

II.  Tryptic  action,  or  the  action  on  proteids,  depends  upon  the  presence  of 
a  hydrolytic  ferment  which  is  now  termed  trypsin  (^Kuhne).  Trypsin  acts  upon 
proteids  at  the  temperature  of  the  body,  when  the  reaction  is  alkaline,  and  changes 
them  first  into  a  globulin-like  substance,  then  into  propeptone  or  albumose,  and 
lastly  into  a  true  peptone,  sometimes  called  tryptone.  The  albumoses  are  not  so 
abundant  or  so  easily  separated  as  in  gastric  digestion  (see  also  p.  293).  The 
proteids  do  not  swell  up  before  they  are  changed  into  peptone  [but  they  are 
eroded  or  eaten  away  by  the  action  of  the  juice].  When  the  proteid  has  been 
previously  swollen  up  by  the  action  of  an  acid,  or  when  the  reaction  of  the  medium 
is  acid,  the  transformation  is  interfered  with. 

Substances  yielding  gelatin,  nuclein,  and  Hb,  resist  trypsin ;  glutin  and  swollen-up  gelatin-yielding 
substances  are  changed  into  gelatin-peptone,  but  the  latter  undergoes  no  further  change.  Hb-O.^  is 
split  up  into  albumin '  and  hsemochromogen.  In  other  respects,  trypsin  acts  on  tissues  containing 
albumins  just  like  pepsin  (^  166,  III). 

Trypsin  is  never  absent  from  the  pancreas  of  new-born  children  {Zweifel),  and  it  may  be 
extracted  by  water,  which,  however,  also  dissolves  the  albumin.  Kiihne  has  carefully  separated  the 
albumin  and  obtained  the  ferment  in  a  pure  state.  It  is  soluble  in  water,  insoluble  in  alcohol.  Pep- 
sin and  hydrochloric  acid  together  act  upon  trypsin  and  destroy  it ;  hence  it  is  not  advisable  to  admin- 
ister trypsin  by  the  mouth,  as  it  would  be  destroyed  in  the  stomach.  When  dried  it  may  be  heated 
to  160°  without  injury. 


300  ACTION    (^F   THE    I'ANCREATIC   JUICE. 

Trypsin  is  formed  within  the  pancreas  by  a  "mother  substance,"  or 
zymogen,  taking  up  oxvgcn.  The  zymogen  is  found  in  small  amount,  6  to  lo 
hours  aticr  a  meal,  in  the  inner  /one  of  the  secretory  cells,  but  after  i6  hours  it  is 
very  abundant  in  the  inner  zone  of  the  cells.  It  is  soluble  in  water  and  glycerine. 
Tryjwin  is  formed  in  the  watery  solution  from  the  zymogen,  and  the  same  result 
occurs  when  the  pancreas  is  chopped  up  and  treated  with  strong  alcohol  {Kiihne). 
The  addition  of  sodium  chloride,  carbonate,  and  glycocholate,  favors  the 
activity  of  the  tryptic  ferment  {Ifeidfnhain).  [The  following  facts  show  that 
zymogen  C-v*);,  ferment),  or,  as  it  has  been  called,  trypsinogen,  is  the  precursor 
of  trypsin,  that  it  exists  in  the  gland  cells,  and  requires  to  be  acted  upon  before 
trypsin  is  formed.  If  a  glycerine  extract  be  made  of  a  pancreas  taken  from  an 
animal  just  killed,  and  if  another  extract  be  made  from  a  similar  pancreas  which 
has  been  kept  for  24  hours,  it  will  be  found  that  an  alkaline  solution  of  the  former 
has  practically  no  effect  on  fibrin,  while  the  latter  is  powerfully  proteolytic.  If  a 
fresh  and  still  warm  pancreas  be  rubbed  up  with  an  equal  volume  of  a  i  per  cent, 
solution  of  acetic  acid,  and  then  extracted  with  glycerine,  a  powerfully  proteolytic 
extract  is  at  once  obtained.  Trypsin  is  formed  from  zymogen  by  the  action  of 
acetic  acid.  There  is  reason  to  believe  that  trypsin  is  formed  from  zymogen  by 
oxidation,  and  that  the  former  loses  its  proteolytic  power  after  removal  of  its 
oxygen.  The  amount  of  zymogen  present  in  the  gland  cells  seems  to  depend 
upon  the  number  and  size  of  the  granules  present  in  the  inner  granular  zone  of  the 
secretory  cells.] 

Further  Effects. — When  trypsin  is  allowed  to  act  upon  the  hemipeptone 
formed  by  its  own  action,  the  latter  is  partly  ciianged  into  the  amido-acid,  leucin, 
or  amido-caproic  acid  (C,,H,,iNOi),  and  tyrosin  (CsHnNO;,),  which  belongs 
to  the  aromatic  series  ( ij  252,  IV,  3).  Hypoxanthin,  xanthin,  and  aspartic  or 
amido-succinic  acid  (C.HjNO,),  are  also  formed  during  the  digestion  of  fibrin  and 
gluten,  and  so  are  glutamic  (QHaNO,)  and  amido-valerianic  acid  (CsHnNOa). 
Gelijiin  is  first  changed  into  a  gelatin-peptone,  and  afterward  is  decomposed  into 
ghiin  and  ammonia. 

Putrefactive  Phenomena. — If  the  action  of  the  pancreatic  juice  be  still 
furtlier  prolonged,  especially  if  the  reaction  be  alkaline,  a  body  with  a  strong, 
stinking,  disagreeable  fecal  odor,  indol  (C,H,N),  skatol  (QHyN),  and  phenol 
(CjHcO),  and  a  substance  which  becomes  red  on  the  addition  of  chlorine  water 
{Brrmirti),  [or  it  gives  with  bromine  water  first  a  pale  red  and  then  a  violet  tint 
(A'//////*-),]  volatile  fatty  acids  are  formed,  while,  at  the  same  time,  H,  CO,,  H.,S, 
CH„  and  N  are  given  off.  The  formation  of  indol  and  the  other  substances  just 
mentioned  depends  upon  putrefaction  (§  184,  III).  Their  formation  is  pre- 
vented by  the  addition  of  salicylic  acid,  or  thymol,  which  kills  the  organisms 
ujM)n  which  putrefai  tion  depends  {Kiiline). 

[Artificial  Digestion.— From  fibrin  placed  in  pancreatic  juice,  or  in  a  i  per 
cent,  solution  of  sodium  carbonate  containing  the  ferment  trypsin,  peptones  are 
rapidly  formed  at  40°  C.  When  we  compare  gastric  with  pancreatic 
digestion,  we  find  that  the  fibrin  in  pancreatic  digestion  is  eroded,  or  eaten  away, 
and  never  swells  up.  The  process  takes  place  in  an  alkaline  medium,  and  never 
in  an  acid  one.  In  fact,  a  i  per  cent,  solution  of  sodic  carbonate  seems  to  play 
the  same  part  in  assisting  trypsin  that  a  .2  percent,  solution  of  HCl  does  for 
pepsin  in  gastric  digestion.  In  gastric  digestion  acid  albumin  or  syntonin  is 
formed  in  addition  to  the  true  peptones.  In  pancreatic  digestion  a  body  resem- 
bling alkalt  albumin,  which  passes  into  a  globulin-like  body,  and  ultimately  into 
a  i^ptone,  is  formed.  Of  the  peptones  so  produced,  one  is  called  anti-peptone, 
and  It  IS  not  further  changed,  but  part  of  the  proteid  is  changed  into  hemi- 
peptone. 1  his  body,  when  acted  upon,  yields  leucin  and  tyrosin.  When  putre- 
faction takes  place,  the  bodies  above  mentioned  are  also  formed  We  might 
represent  the  action  of  trypsin  thus:    Proteid  -f  trypsin  +  i   per 'cent,  sodium- 


ACTION    OF   THE    PANCREATIC    JUICE. 


301 


carbonate,  kept  at  38°  C.  =  formation  of  a  globulin-like  body,  and  then  anti- 
peptone  and  hemi-peptone  are  formed. 


ANTI -PEPTONE 

yields 

Hemi-peptone 

yields 

Normal  Digestive  Products. 

Putrefactive  Products. 

undergoes  no  further 
change. 

Leucin, 

Tyrosin, 
Hypoxanthin, 
Aspartic  Acid. 

Indol, 
Skatol, 
Phenol. 

Volatile  Fatty  Acids, 
H,  CO2,  II^S, 
CH,,  N. 

It  seems  that  trypsin  in  pure  water  can  act  slowly  upon  fibrin  to  produce  pep- 
tone.    Pepsin  cannot  do  this  without  the  aid  of  an  acid.] 

[Kiihne's  Pancreas  Powder. — This  is  prepared  by  the  prolonged  extrac- 
tion of  fresh  pancreas  of  ox  with  alcohol  and  then  with  ether.  If  the  dry  pow- 
der be  extracted  for  several  hours  with  a  i  per  cent,  solution  of  salicylic  acid, 
and  filtered,  a  fluid  with  powerful  proteolytic,  but  no  diastatic,  properties  is 
obtained.  Several  hours  afterward  much  tyrosin  may  separate  out,  which,  of 
course,  must  be  removed  by  filtration.  The  clear  fluid,  when  mixed  with  flbrin 
and  a  i  per  cent,  solution  of  sodic  carbonate,  rapidly  digests  fibrin.  If  it  be 
desired  to  obtain  a  true  pancreatic  digestion,  with  none  of  the  products  of  putre- 
faction, the  mixture  must  be  strongly  "thymolized"  with  a  25  per  cent,  alcoholic 
solution  of  thymol  {Kuhne).'\ 

[Setschenow  finds  that  egg  albumin,  boiled  in  a  vacuum  at  35°-40°  C,  is  more  rapidly  digested 
than  fibrin  by  a  specially  prepared  tiypsin.]  AVhen  proteids  are  boiled  for  a  long  time  with  dilute 
HjSO^,  we  obtain  peptone,  then  leucin  and  tyrosin  ;  gelatin  yields  glycin.  Hjrpoxanthin  and  xanthin 
are  obtained  in  the  same  way  by  similarly  boiling  fibrin,  and  the  former  may  even  be  obtained  by 
boiling  fibrin  with  water  [^Chittenden). 

It  is  very  remarkable  that  the  juice  of  the  green  fruit  of  the  papaya  tree,  or  Carica  papaya, 
possesses  digestive  properties  [Roy,  Wittmack),  and  that  the  action  is  due  to  peptonizing  ferment, 
closely  related  to  trypsin,  and  called  caricin  or  papain.  [It  forms  a  true  peptone,  an  intermediate 
body,  and  leucin  and  tyrosin.  It  also  contains  a  milk-coagulating  ferment  [Martin).']  The  milky 
juice  of  the  fig  tree  has  a  similar  action.  Sprouting  malt,  vetch,  hop,  hemp  during  sprouting,  and 
the  receptacle  of  the  artichoke  contain  a  peptonizing  ferment.  Leucin,  tyrosin,  glutamic  and  aspartic 
acids,  and  xanthin  are  formed  in  the  seeds  of  some  plants;  hence  we  may  assume  that  the  processes 
of  decomposition  in  some  seeds  are  closely  allied  to  the  fermentative  actions  that  occur  in  the  intestine. 

III.  The  action  on  neutral  fats  is  twofold  :  (i)  It  acts  upon  fats  so  as  to 
form  a  fine  permanent  emulsion.  (2)  It  causes  neutral  fats  to  take  up  a 
molecule  of   water   and    split  into  glycerine  and  their  corresponding  fatty 

(C,,H,,oOe)  +  3  (H,0)  =  CC3HSO3)  +  3  (CisHsA). 

Tristearin.  Water.  Glycerine.  Stearic  Acid. 

The  latter  result  is  due  to  the  action  of  an  easily  decomposable  fat-splitting 
ferment  (C7.  Bernard),  also  called  steapsin.  Lecithin  is  decomposed  by  it 
into  glycero-phosphoric  acid,  neurin  and  fatty  acids.  The  fatty  acids  thus  lib- 
erated are  partly  saponified  by  the  alkali  of  the  pancreatic  and  intestinal  juices, 
and  partly  emulsionized  by  the  alkaline  intestinal  juice.  Both  the  soaps  and  emul- 
sions are  capable  of  being  absorbed  (§  191). 

Emulsification. — The  most  important  change  effected  on  fats  in  the  small  intestine  is  the  produc- 
tion of  an  emulsion,  or  their  subdivision  into  exceedingly  minute  particles  (^.  191)-  This  is  necessary 
in  order  that  the  fats  may  be  taken  up  by  the  lacteals.  If  the  fat  to  be  emulsified  contain  a  fi^ee  fatty 
acid,  i.e.,\i  it  be  slightly  rancid,  and  if  the  fluid  with  which  it  is  mixed  be  alkaline,  emulsifi- 
cation takes  place  extremely  rapidly  [B7-iicke).  A  drop  of  cod- liver  oil,  which  in  its  unpurified 
condition  always  contains  fatty  acids,  on  being  placed  in  a  drop  of  0.3  per  cent,  solution  of  soda, 
instantly  gives  rise  to  an  emulsion  [Gad).     The  excessively  minute  oil  globules  that  compose  the 


802  SECRETION    OK    PANCREATIC   JUICE. 

emulsion  arc  firs,  covered  with  a  layer  of  soap,  which  soon  dissolves,  and  in  the  process  small  Rlohul^ 
IrTdc,n"hcd  from  the  original  oil  glol-ules.  The  fresh  surface  .s  aga.n  covered  by  a  soap  him,  and 
Z  !r-K.-  is  rqH-at«l  over  and  over  a^ain  until  an  excessively  tuie  emuls.on  .s  obtamed.  If  the  fat 
contain  nu.ch  fatty  acid,  and  the  solution  of  scHla  be  more  concentrated,  *•  „o''/,n/orms  are  obtamed 
similar  to  tho>e  which  are  formed  when  fresh  nerve  fibres  are  texsed  >n  water  An.mal  ods  emuls.omze 
more  rcad.iv  than  vegetable  oils;  castor  oil  does  not  emuls.onue  (Go,/)-  [H  is  extremely  d.Hjcult  to 
oUain  a  ,K-rfectly  nelitrnl  oil.  xs  most  oils  contain  a  trace  of  a  fatty  acid.  In  fact,  if  on  addmg  a 
weak  volution  of  sckUc  carlK>nate  to  oil  or  fatty  matters,  tluid  at  the  temperature  of  the  body,  an  emul- 
sion is  obtaine.l.  one  may  Ik;  sure  that  the  oil  contained  a  fatty  acid,  so  that  Bernard  s  v,ew  about  an 
"cmuLsive  fennent"  being  neces^n'  is  not  endorsed.  The  fatty  acid  set  free  by  the  fat-splitting 
ferment  <-nabl.-s  the  alkaline  pancreatic  juice  at  once  to  produce  an  emulsion.] 

Fat-Splitting  Ferment.— This  is  a  very  unstable  body,  and  must  be  prepared  from  the 
perfectly  Ircsh  glan.l  by  rubbing  it  up  with  powdered  glass,  glycerine,  and  a  I  per  cert,  solution  of 
iodic  c'arlKmatc.  and  allowing  it  to  stand  for  a  day  or  two  (G/ii/zner).  [This  ferment  is  said  to 
cause  an  emulsion  of  oil  and  mucilage  tinged  blue  with  litmus  at  40°  C.  to  become  red  (Gamo^eg). 
In  performing  this  experiment  notice  that  the  mucilage  is  perfectly  neutral,  as  gum  arabic  is  fre- 
quently acid.] 

[Pancreatic  Extracts.— The  action  of  the  pancreas  may  be  tested  by  making  a  watery  extract 
of  a  perfectly  fresh  gland.  Such  an  extract  always  acts  upon  starch  and  generally  upon  fats,  but 
this  extract  and  also  the  glycerine  extract  vary  in  their  action  upon  proteids  at  different  times.  If 
the  extract— watery  or  glycerine — be  made  from  the  pancreas  of  a  fasting  animal,  the  tryptic  action 
is  slight  or  absent,  but  is  active  if  it  be  prepared  (rom  a  gland  4  to  10  hours  after  a  meal.  The 
pancreatic  preparations  of  Benger  of  Manchester,  Savory  and  Moore,  or  Burroughs  and  Welcome,  all 
possess  active  diastatic  and  proteolytic  properties.] 

[Pancreas  Salt. — Prosser-James  proposes  to  employ  common  salt  mixed  with  pepsin,  which  he 
calls  j)epiic  s.ilt ;  and  he  advocates  the  use  of  another  preparation  composed  of  the  pancreatic  ferments 
and  common  salt,  pancreatic  salt] 

The  pancreas  of  new  born  children  contains  trypsin  and  the  fat-decomposing  ferment,  but  not 
the  diastatic  one  {Zwtifel).  \  slight  diastatic  action  is  obtained  after  two  months,  but  the  full  effect 
is  not  obtained  until  after  the  first  year  [Koroivin). 

IV.  The  pancreas  contains  a  milk-curdling  ferment,  which  may  be  extracted 
by  means  of  a  concentrated  solution  of  common  salt. 

171.  THE  SECRETION  OF  THE  PANCREATIC  JUICE.— Rest 
and  Activity. — .Vs  in  other  glands,  we  distinguish  a  quiescent  state,  during 
which  the  gland  is  soft  and  pale,  and  a  state  of  secretory  activity,  during  which 
the  organ  swells  up  and  appears  pale  red.  The  latter  condition  only  occurs  after 
a  ineal,  and  is  caused  probably  reflexly,  owing  to  stimulation  of  the  nerves  of  the 
stomach  and  duodenum.  KUhne  and  I>ea  found  that  all  the  lobules  of  the  gland 
were  not  active  at  the  same  time.  The  pancreas  of  the  herbivora  secretes  unin- 
terruptedly [l)ul  in  the  dog  secretion  is  not  constant]. 

Time  of  Secretion. — According  to  Bernstein  and  Heidenhain,  the  secretion 
begins  to  flow  when  food  is  introduced  into  the  stomach,  and  reaches  its  maxi- 
mum 2  to  3  hours  thereafter.  The  amount  falls  toward  the  5th  or  7th  hour,, 
and  rises  again  (owing  to  the  entrance  of  the  chyme  into  the  duodenum),  toward 
the  Qlh  and  nth  hour,  gradually  falling  toward  the  17th  to  24th  hour,  until 
it  ceases  completely.  When  more  food  is  taken,  the  same  process  is  repeated. 
As  a  general  rule,  a  rapidly-formed  secretion  contains  less  solids  than  one  formed 
slowly. 

Condition  of  Blood  Vessels.— During  secretion,  the  blood  vessels  behave 
like  the  blood  vessels  of  the  salivary  glands  after  stimulation  of  the  chorda — 
they  dilate,  and  the  venous  blood  is  bright  red— thus,  it  is  probable  that  a 
similar  nervous  mechanism  exists  [but  as  yet  no  such  mechanism  has  been 
discovered].  The  secretion  is  excreted  at  a  pressure  of  more  than  17  mm.  Kg. 
(rabbit).  '  ^ 

Effect  of  Nerves.— The  nerves  arise  from  the  hepatic,  splenic,  and  superior 
mesenteric  plexuses,  together  with  branches  from  the  vagus  and  sympathetic. 
The  secretion  is  excited  by  stimulation  of  the  medulla  oblongata,  as  well  as  by 
direct  stimulation  of  the  gland  itself  by  induction  shocks.  [It  is  not  arrested 
by  section  of  the  cervical  spinal  cord.]     The  secretion  is  suppressed  by  atropin 


PREPARATION  OF  PEPTONIZED  FOOD 


303 


Sub-Iobular  Vein. 


Fig.  i88. 

Intra-Iobular  Vein. 


[in  the  dog,  but  not  the  rabbit],  by  producing  vomiting,  by  stimulation  of  the 
central  end  of  the  vagus,  as  well  as  by  stimulation  of  other  sensory  nerves,  e.  g.,  the 
crural  and  sciatic.  Extirpation  of  the  nerves  accompanying  the  blood  vessels 
prevents  the  above-named  stimuli  from  acting.  Under  these  circumstances,  a  thin 
"paralytic  secretion,"  with  feeble  digestive  powers,  is  formed,  but  its  amount 
is  not  influenced  by  the  taking  of  food.  [Secretion  is  excited  by  the  injection  of 
ether  into  the  stomach.] 

Extirpation  of  the  gland  may  be  performed,  or  the  duct  ligatured  in  animals,  without  causing 
any  very  great  change  in  their  nutrition;  the  absorption  of  fat  from  the  intestine  does  not  cease. 
After  the  duct  is  ligatured  it  may  be  again  restored.  Ligature  of  the  duct  may  cause  the 
formation  of  cysts  in  the  duct  and  atrophy  of  the  gland  substance.  Pigeons  soon  die  after  this 
operation. 

[172.  PREPARATION  OF  PEPTONIZED  FOOD.— Peptonized  food 
may  be  given  to  patients  whose  digestion  is  feeble  {Roberts).  Food  may  be  pep- 
tonized either  by  peptic  or 
tryptic  digestion,  but  the 
former  is  not  so  suitable  as 
the  latter,  because  in  pep- 
tic digestion  the  grateful 
odor  and  taste  of  the  food 
are  destroyed,  while  bitter 
by-products  are  formed,  so 
that  pancreatic  digestion 
yields  a  more  palatable  and 
agreeable  product.  As  tryp- 
sin is  destroyed  by  gastric 
digestion,  obviously  it  is  use- 
less to  give  extract  of  the 
pancreas  to  a  patient  along 
with  his  food.] 

[Peptonized  Milk. — "A  pint  of 
milk  is  diluted  with  a  quarter  of  a 
pint  of  water  and  heated  to  60°  C. 
Two  or  three  teaspoonfuls  of  Ben- 
ger's  liquor  pancreaticus,  together 
with  10  or  20  grains  of  bicarbonate  Section  of  human  liver,  X  20,  showing  the  liver  lobules  and  the  radiate 
of  soda    are  then  mixed  therewith."  arrangement  of  their  cells  from  the  central  or  intra-lobular  vein. 

Keep  the  mixture  at  38°  C.  for  about 
two  hours,  and  then  boil  it  for  two  or  three  minutes,  which  arrests  the  ferment  action.] 

[Peptonized  Gruel,  prepared  from  oatmeal,  or  any  farinaceous  food,  is  more  agreeable  than 
peptonized  milk,  as  the  bitter  flavor  does  not  appear  to  be  developed  in  the  pancreatic  digestion  of 
vegetable  proteids.] 

[Peptonized  Milk  Gruel  yielded  Roberts  the  most  satisfactory  results,  as  a  complete  and  highly 
nutritious  food  for  weak  digestions.  Make  a  thick  gruel  from  any  farinaceous  food,  e.g.,  oatmeal,  and 
while  still  hot  add  to  it  an  equal  volume  of  cold  milk,  when  the  mixtm-e  will  have  a  temperature  of 
52°  C.  (125°  F.).  To  each  pint  of  this  mixture  add  two  or  three  teaspoonfuls  of  liquor  pancreaticus 
and  20  grains  of  bicarbonate  of  soda.  It  is  kept  warm  for  two  hovus  under  a  "  cosey."  It  is  then 
boiled  for  a  few  minutes  and  strained.  The  bitterness  of  the  digested  milk  is  almost  completely  cov- 
ered by  the  sugar  produced  during  the  process.] 

[Peptonized  soups  and  beef  tea  have  also  been  made  and  used  with  success,  and  have  been  adminis- 
tered both  by  the  mouth  and  rectum.] 

[  I  'eptonizing  powders  containing  the  proper  proportions  of  ferment  and  sodic  bicarbonate  are  pre- 
pared by  Benger,  and  Burroughs  and  Welcome.] 

173.  STRUCTURE  OF  THE  LIVER. -The  liver,  the  largest  gland 
in  the  body,  consists  of  innuinerable  small  lobules  or  acini,  i  to  2  millimetres 
(t4"  to  tV  i"ch)  in  diameter.  These  lobules  are  visible  to  the  naked  eye.  All  the 
lobules  have  the  same  structure. 


304 


STRUCTURE    OK    THE    LIVER. 


1  The  Cosule  -The  liver  is  covered  by  a  thin,  f.brou.s.  tlrmly  adherent  capsule,  which  has 
onitsTrt  furFacealaye  of  en.lothelium  derived  from  the  peritoneum.  The  capsule  sends  fine 
«Va  int.^Se  orea'  Jween  ,hc  lobules,  but  it  is  also  continued  mto  the  .nter.or  at  the  transverse 
filTurc  where  U  surrounds  the  ,K.rtal  vein,  hepatic  artery,  and  b.le-duct  and  accompanies  these 
^ciur."«  the  capsule  of  Gl.Uon,  or  intcr-lobulnr  connective  tissue  1  he  spaces  in  which  hese 
S^T^c^u  cs  h/arc-  known  as  portal  canals.  In  some  animals  (pig,  camel,  polar  hear)  the 
£tSc>a"  ".mratoHromenchothcrbytho  x.mcwhat  lamcll.aled  connective  tissue  of  ^'I'^son  s  cai>- 
sule  but  in  man  this  is  but  sliRhllv  <levelo,Kxl.  so  that  adjoining  lobules  are  more  or  less  fused.  Very 
Sate  conmctivc  tis>ue.  but  small  in  amount,  is  also  found  w.thm  the  lobules.  Leucocytes  are 
somttinu-s  foun.l  in  the  tissue  of  Cdisson's  cai)sulc.  . 

T  Blood  Ves5els.-(-,)  Branches  of  the  Venous  System.-  1  Ik-  portal  vein  after  its  entrar^ce 
into  the  liver  at  the  ,x.rtal  hssurc,  gives  off  numerous  branches  lying  between  the  lobules,  and  ulti- 
mately fonning  small  trxmks  which  reach  the  periphery  of  the  lobuks.  where  they  form  a  ncli  plexus. 
These  are  the  inter-lobular  veins  (Figs.  iS8,  189.  r,i).     I-rom  these  vems  numerous  capillaries 

KiG.  189. 


1,  Scheme  of  a  liver  lobule — K.i,  K.;,  intcr-lohular  veins  (port.il)  :  f-'.c,  central  or  intra-lobular  vein  (hepatic) ;  c,c, 
capilLiries  between  both;  Ki,  sul>-lobular  vein ;  Kr',  vena  vascularis;  .-J,  .4,  hepatic  artery, giving  branches, 
r,  r,  to  Otiss'in's  capsule  and  the  larger  vessels,  and  ultimately  forming  the  venae  vasculares  at  i,  i,  opening 
into  the  intra-lobular  capillaries;  g,  bile  ducts;  jr,  x,  intra-lobular  biliary  channels  between  the  liver  cells  ;  d,  d, 
position  of  the  liver  cells  between  the  meshes  ot  the  blood  cipillaries.  11,  Isolated  liver  cells — c,  a  blood  capil- 
lary ;  a,  fine  bile-capillary  channel. 

[c,  f)  are  given  off  to  the  entire  periphery  of  the  lobule.  The  capillaries  converge  tow.ard  the  centre 
of  the  lobule.  .\s  they  proceed  inward,  they  form  elongated  me.shes,  and  between  the  capillaries  lie 
rows  or  columns  of  liver  cells  (</,  d).  The  capillaries  are  relatively  wide,  and  are  so  disposed  as  to 
lie  between  the  fdi:fs  of  the  columns  of  cells,  and  never  between  the  surfaces  of  two  neighboring 
cells.  The  capillaries  converge  toward  the  centre  of  each  lobule,  where  they  join  to  form  one  large 
vein,  the  intra-lobular,  hepatic,  or  central  vein  (  V.  c),  which  traverses  each  lobule,  reaches  its 
surface  at  one  point,  passes  out,  and  joins  similar  veins  from  other  lobules  to  form  the  sub-lobular 
veins  (  V.s).  These  in  turn  unite  to  form  wide  veins,  the  origins  of  the  hepatic  vein,  which  opens 
into  the  vena  cava  inferior. 

(b)  The  branches  of  the  hepatic  artery  accompany  the  branches  of  the  portal  vein  and  bile  duct  in 
the  portal  canals  l)etween  the  lobules,  and  in  their  course  give  off  capillaries  to  supply  the  walls  of  the 


STRUCTURE    OF   THE    LIVER. 


305 


portal  vein  and  larger  bile  ducts.  The  branches  of  the  hepatic  arteiy  anastomose  frequently  where 
they  lie  between  the  lobules.  On  reaching  the  peripher}-  of  the  lobules,  a  certain  number  of  capil- 
laries are  given  off,  which  penetrate  the  lobule  and  terminate  in  the  capillaries  of  the  portal  vein  (z,  i). 
These  capillaries,  however,  which  supply  the  walls  of  the  portal  vein  and  large  bile  ducts  (r,  r),  ter- 
minate in  veins  which  end  in  the  portal  vein  [V.v).  Several  branches— r(7/j'///<?/" — pass  to  the  surface 
of  the  liver,  where  they  form  a  wide-meshed  plexus  under  the  peritoneum.  The  blood  is  returned  by 
veins,  which  open  into  branches  of  the  portal  vein. 

[Hepatic  Zones. — Pathologists  draw  a  sharp  distinction  between  different  zones  within  a  hepatic 
lobule.  Thus  the  central  area,  capillaries  and  cells,  fonn  the  hepatic  vein  zone,  which  is  specially 
liable  to  cyanotic  changes ;  the  area  next  the  peripheiy  of  the  lobule  is  the    portal  vein  zone,  whose 


Human  liver  cells  containing  oil  globules,  t ;  d,  has  two  nuclei.         Liver  cells  after  withholding  food  for  36  hours. 


cells  under  certain  circumstances  are  particularly  apt  to  undergo  fatty  degeneration ;  while  there  is 
an  area  lying  naidway  between  the  two  foregoing — the  hepatic  artery  zone — which  is  specially  liable 
to  amyloid  or  waxy  degeneration.  ] 

3.  The  hepatic  cells  (Fig  189,  II,  a)  are  irregular  polygonal  cells  of  about  yJ^^  of  an  inch 
(34  to  45  //)  in  diameter  (  Hg.  190).  The  arrangement  of  the  capillaries  within  a  lobule  determines 
the  arrangement  of  the  liver  cells.  The  hver  cells  form  anastomosing  columns  which  radiate  from  the 
centre  to  the  periphery  of  each  lobule  (Fig.  191).  [The  liver  cells  are  usually  stated  to  be  devoid  of 
an  envelope,  although  Haycraft  states  that  they  possess  one.     They  usually  contain  a  single  nucleus. 

Fig.  192. 

Finest  bile  duct.     Finest  bile  duct  divided. 


Nucleus  of  a 
liver  cell. 

Blood  capillaries ;  finest  bile  ducts  in  their  relative  position  in  a  rabbit's  liver. 


with  one  or  more  nucleoh,  but  sometimes  two  nuclei  occur.     The  protoplasm  and  nucleus  of  each  cell 
contain  a  plexus  of  fibrils  just  like  other  epithelial  cells.      In  some  animals,  globules  of  oil  and  pigment 
granules  are  found  in  the  cell  protoplasm  (Fig.  190).     Each  cell  is  in  relation  with  the  wide-meshed 
blood  capillaries  [d,  d),  and  also  with  the  much  narrower  meshwork  of  bile  ducts  (I,  x). 
20 


306 


STRUCTURE   OF   THE    LIVER. 


Chanees  in  Liver  Cells.-n,e  np,^arance  of  the  cells  vanes  with  the  penod  of  d.ges  jon 
l>uri.rhun«rThe  l.vc-r  colls  arc  fi.u-lv  ^-ranular  an.l  ver)-  cloudy  (P.g.  191)  [and  contain  l.ttle 
ilmv' n  "«.  .i^MUcn.  Rranules.  and'  .he  nucleus  is  more  frequently  absent.  Often  free  nucleoh 
undV\c  nuc  ci  Ari  found  (£//r»fi.r,'.r  and  liou,,,^.  Durnig  activity.  ,  .after  a  full  meal, 
licSlv  of  st^hv  foo<l.  the  cells  are  larger  and  more  distinct,  slam  more  deeply  w,  h  eosm  and 
^E  ew  -r  granuk.!.  The  protoplasm  contains  coarse,  glancing  "passes  of  glyocen  ^^lg  194,  2), 
rin^.h  surface  of  the  cell  it  is  c'oiuUnse<l.  and  a  fine  network  stretches  toward  the  centre  of  the 
S  Z\  it  is  >us,K-nd«l  the  nucleus.  .Ml  the  hepatic  cells  are  not  in  the  same  phase  of  activity  at 
Z'Ll  time.  Afnna.ssiew  finds  that  if  the  fonnation  of  bile  m  the  liver  be  increa.sed  (..  g.,  by  section 
of  .he  hemtic  nerN-es.  or  feeling  with  proteids).  the  cells  are  moderately  enlarged  in  size,  and  contain 
numeroJ  granule.,  which  are  pro.eid  in  their  nature;  .uch  cells  resist  the  action  of  caus  ic  potash. 
When  there  is  a  grea.  formation  of  glycogen  (as  after  feeding  with  potatoes  and  sugar),  all  the  cells  are 
vrr>-  large  and  sh-oq^lv  definc-d,  and  contain  many  granules  of  glycogen,  the  cells  being  so  large  as  to 
compress  the  cnpillanes.     These  cells  dissolve  <iuickly  in  caustic  potash. 

Action  of  Drugs.— Some  substances  excite  the  cells  to  activity,  and  cause  them  to  present  the 
apKarancc  of  cells  in  activity,  t.g.,  pilocarpin.  muscarin,  aloes,  less  so  salicylate  and  benzoate  of 
soda  and  rhubarb,  while  atropin  and  lead  acetate  inhibit  the  signs  of  activity.  These  results  w-ere 
oUaincd  in  the  horse  by  KUenberger  and  Haum.  [Stolnikow,  by  using  the  quadruple-staining  method 
of  Claulc,  finds  that  the  hepatic  cells  of  the  frog  undergo  remarkable  changes  in  poisoning  by 
phosphorus.  It  is  well  known  that  this  drug  produces  fatty  degeneration  of  the  liver  cells,  but 
a  deeper  study  shows  that  the  changes  are  both  histological  and  chemical.  Besides  producing 
remarkable  changes  in  the  protoplasm  of  the  cell,  the  protoplasm  of  the  nucleus,  in  the  form  of  small 

IMG.   193. 


/^X 


c/C 


Liver  cells  of  frog,     a,  early,  and  (^.  late  sUgc  in  poisoning  by  phosphorus  ;   c,  liver  cell  of  frog  getting  water  only, 
d,  getting  sugar,  and  e,  peptone  {Stirling,  after  Stolnikmv.) 

masses  called  plasmosoma,  passes  out  into  the  cell  body,  perhaps  to  renew  the  latter.  The  cells  are 
increased  in  size,  both  after  poisoning  with  phosphorus  and  after  excision  of  the  fat  bodies  in  the 
frog  (Fig.  1931.  The  fat  present  in  the  liver  in  phosphorus  poisoning  is  not  present  as  droplets  of 
oil.  but  probably  in  a  loose  combination,  e.g.,  lecithin,  and  as  a  matter  of  fact  the  amount  of  liver 
lecithin  is  extraordinarily  increased.  There  is  also  an  increase  of  the  nuclein ;  while  glycogen  is 
absent.  The  season  of  the  year  also  affects  them.  There  is  a  period  of  growth  from  July  to 
Novcmlter,  and  one  of  decay  from  December  to  May  (^A.  Leonard).  Antipyrin  also  produces 
profound  changes,  especially  in  the  nuclei.] 

4.  The  Bile  Ducts. — The  finest  bile  capillaries,  channels,  or  canaliculi  arise  from  the  centre  of 
the  lobule,  and  indeed  throughout  the  whole  lobule  they  form  a 
regular  anastomosing  network  of  very  fine  tubes  or  channels.  Each 
cell  is  surrounded  by  a  polygonal — usually  hexagonal — mesh  (Fig. 
194,  3).  The  bile  capillaries  always  lie  in  the  middle  of  the  surface 
between  two  adjoining  cells  (II,  a),  where  they  form  actual  inter- 
cellular passages  (Fig.  192).  [According  to  some  observers,  they 
are  merely  excessively  narrow  channels  (i  to  2  /z  wide)  in  the 
cement  substance  between  the  cells,  while  according  to  others  they 
have  a  distinct  delicate  wall.  The  bile-capillary  network  is  much 
closer  than  the  blood-capillary  network.  [Thus,  there  are  three 
networks  within  each  lobule — 

( 1 )  A  network  of  blood  capillaries ; 

(2)  ''  hepatic  cells; 

.  (3)  "  bile  capillaries;  (Fig.  192).] 

Excessively  minute  intra-cellular  passages  are  said  to  pass  from  the  bile  capillaries  into  the 

interior  of  the  liver  cells,  where  they  communicate  with  certain  small   cavities  or   vacuoles  [Asp, 

KuCffer)  (Fig.  194.  3).     As  the  blood  capillaries  run  alon^  the  edge  of  the  liver  cells,  and  the  bile 

capillaries  between  the  opposed  surfaces  of  adjacent  cells,  the  two  systems  of  canals  within  the 


Fig. 


Liver  cell  during  fasting;  a. 
containing  masses  of  glycogen  ; 
\,  a  liver  cell  surrounded  with 
oile  channels,  from  which  fine 
twigs  proceed  into  the  cell 
substance  to  end  in  vacuoles. 


STRUCTURE  OF  THE  LIVER.  307 

lobule  are  kept  separate.  Some  bile  capillaries  run  along  the  edges  of  the  liver  cells  in  the  human 
liver,  especially  during  embryonic  life.  Toward  the  peripheral  part  of  the  lobule,  the  bile  capil- 
laries are  larger,  while  adjoining  channels  anastomose,  and  leave  the  lobule,  where  they  become 
inter- lobular  ducts  (g),  which  join  with  other  similar  ducts  to  form  larger  inter-lobular  bile  ducts. 
These  accompany  the  hepatic  artery  and  portal  vein,  and  leave  the  liver  at  the  transverse  fissure. 
The  finer  inter-lobular  ducts  frequently  anastomose  in  Glisson's  capsule,  possess  a  structureless 
basement  membrane,  and  are  lined  by  a  single  layer  of  low  polyhedral  epithelial  cells.  The  larger 
inter-lobular  ducts  have  a  distinct  wall,  consisting  of  connective  and  elastic  tissue,  mixed  with  circu- 
larly disposed  smooth  muscular  fibres  (Fig.  195).  Capillaries  are  supplied  to  the  wall,  which  is 
lined  by  a  single  layer  of  columnar  epithelium.  A  sub -mucosa  occurs  only  in  the  largest  bile  ducts, 
and  in  the  gall  bladder.  Smooth  muscular  fibres,  arranged  in  single  bundles,  occur  in  the  largest 
ducts,  and  as  longitudinal  and  circular  layers  in  the  gall  blad- 
der, whose  mucous  membrane  is  provided  with  numerous  folds  FiG.  195, 
and  depressions.  The  epithelium  lining  the  gall  bladder  is 
■cylindrical,  with  a  distinct,  clear  disk,  and  between  these  cells 
are  goblet  cells.  Small  branched  tubular  mucous  glands 
occur  in  the  larger  bile  ducts  and  in  the  gall  bladder.                     fib'^'^" 

Vasa  aberrantia  are  isolated  bile  ducts  which  occur  on  the 
surface  of  the  liver,  but  have  no  relation  to  any  system  of  liver 
lobules.  They  occur  at  the  sharp  margin  of  the  liver,  in  the 
region  of  the  inferior  vena  cava,  of  the  gall  bladder,  and  of  Cj'lindrical 
the  parts  near  the  portal  fissure.  It  seems  that  the  liver  epithelium. 
lobules  to  which  they  originally  belonged  have  atrophied  and 
disappeared  {^Zicckerkandl  and  Toldt). 

5.  The  lymphatics  begin  as  pericapillary  tubes  around 
the  capillaries  within  the  lobules,  emerge  from  the  lobule,  and  ''^^SS- ' 
run  within  the  wall  of  the  branches  of  the  hepatic  and  portal            Inter-lobular  bile  duct  (human), 
veins,  and  afterward  surround  the  venous  trunks,  thus  forming 

the  inter-lobular  lymphatics.  These  unite  to  form  larger  trunks,  which  leave  the  liver  partly  at  the 
portal  fissure,  partly  along  with  the  hepatic  veins,  and  partly  at  different  points  on  the  surface  of  the 
organ.  There  is  a  narrow,  superficial  meshwork  of  lymphatics  under  the  peritoneum — sub-peritoneal — 
which  communicate  with  the  thoracic  lymphatics,  through  the  triangular  ligament  and  suspensorium, 
while  on  the  under  surface  they  communicate  with  the  lymphatics  of  the  inter-lobular  connective 
tissue. 

6.  The  nerves  consist  partly  of  medullated  and  partly  of  non-medullated  fibres  from  branches 
of  the  sympathetic  and  left  vagus  to  the  hepatic  plexus.  They  accompany  the  branches  of  the 
hepatic  artery,  and  ganglia  occur  on  their  branches  within  the  liver.  Some  of  the  nerve  fibres  are 
vasomotor  in  function,  and,  according  to  Pfliiger,  other  nerve  fibres  terminate  directly  in  connection 
with  liver  cells.  [MacCallum  describes  an  inter-lobular  plexus  of  non-medullated  fibres  in  man  and 
menobranchus,  from  which  a  perivascular  and  inter-cellular  plexus  proceeds.  From  the  latter  fibrils 
pass  to  terminate  within  the  cells  near  the  nucleus.] 

Pathological. — The  connective  tissue  between  the  lobules  may  undergo  great  increase  in  amount, 
especially  in  alcohol  and  gin  drinkers,  and  thus  the  substance  of  the  lobules  may  be  greatly  com- 
pressed, owing  to  the  cicatricial  contraction  of  the  newly-formed  connective  tissue  (cirrhosis  of  the 
liver).     In  such  inter-lobular  connective  tissue,  newly-formed  bile  ducts  are  found. 

Ligature  of  the  ductus  choledochus  [causes  enlargement  of  the  spleen  (rabbit),  and  a  dimi- 
nution in  the  number  of  the  blood  corpuscles],  and,  after  a  time,  interstitial  inflammation  of  the  liver. 
In  rabbits  and  guinea  pigs  the  liver  parenchyma  disappears,  and  its  place  is  taken  by  newly-formed 
connective  tissue  and  bile  ducts  [Charcot  a?id  Go??ibault).  In  all  these  cases  of  interstitial  inflam- 
mation, there  is  proliferation  of  the  epithelium  of  the  bile  ducts. 

[Regeneration  of  the  Liver. — Tizzoni  finds  that  there  may  be  partial  regeneration  and  new 
formation  of  liver  lobules  in  the  dog,  the  process  being  the  same  as  that  which  occurs  in  the  em- 
bryonic development  of  the  organ,  i.  e.,  the  growth  of  solid  cylinders  of  liver  cells,  formed  by  the 
preexisting  liver  cells,  which  penetrate  into  the  connective  tissue  uniting  the  edges  of  the  woimd. 
These  cells  ultimately  differentiate  into  hepatic  cells  and  bile  ducts.  Other  observers  attribute  the 
new  formation  to  outgrowths  of  the  epithelial  cells  of  the  bile  cells,] 

174.  CHEMICAL  COMPOSITION  OF  THE  LIVER  CELLS.— 
(i)  Proteids. — The  fresh,  soft,  parenchyma  of  the  liver  \s  alkaline  in  reaction  ;  after 
death,  coagulation  occurs,  the  cell  contents  appear  turbid,  the  tissue  becomes  friable, 
and  gradually  an  acid  reaction  is  developed.  This  process  closely  resembles  what 
occurs  in  muscle,  and  is  due  to  the  coagulation  of  a  myosin-like  body,  which  is 
soluble  during  life,  but  after  death  undergoes  spontaneous  coagulation  {Fldsz). 
The  liver  contains  other  proteids;  one  coagulating  at  45°  C,  another  at  70°  C, 


308  CHEMICAL   COMPOSITION    OF   THK    LIVER    CELLS. 

and  one  which  is  slightly  soluble  in  dilute  acids  and  alkalies.     The  nuclei  contain 
nuclein.     The  connective  tissue  yields  gelatin.  ,    u   j     ♦ 

(.,  Glycogen  or  Animal  Starch-i. 2  to  2.6  per  cent.-,s  a  true  carbohydrate 
mos"t  dosdv  related  to  inulin,  soluble  in  water,  but  diffuses  with  difficulty,  and  has 
the  lonnula  6(C...H,oC).)  +  H,0.  It  is  stored  up  in  the  liver  eel  s  in  amorphous 
granules  around  the  nuclei  (Fig.  194,  2),  but  is  not  uniformly  distributed  in  all  parts 
of  the  liver  Like  inulin,  it  gives  a  deep  red  color  with  solution  of  iodine  in  iodide 
of  iKJtassium.  It  is  changed  into  dextrin  and  sugar  by  diastatic  ferments,  and 
when  boiled  with  dilute  mineral  acids,  it   yields  grape  sugar  (^5  148,  I;  ^  17°,  iJ 

^  252,  III). 

Preparation  of  Glycogen.-[Fced  a  ral.l.it  on  cinots  or  boiled  rice,  and  kill  it  three  or  four 
hour>  llurcnfur.  Ktinnve  ihc  liver  immediately  after  death,  cut  it  into  tme  pieces  and  pl.nce  these  in 
60,/inP  water,  and  Uil  it  for  some  time  in  order  to  ohtain  a  watery  extract  of  the  liver.  1  he  boiling 
water  destroys  the  ferment  su,,ix.sed  to  be  present  in  the  liver,  which  wouk  transform  the  glycogen 
into  craiK-  suL'.ar  To  the  col.l  filtrate  are  added  alternately  dilute  hydrochloric  acid  and  i^tassio- 
nu-rcuric  i.Kli.le.  which  precipitates  the  proteids.  Filter,  when  a  clear  opalescent  fluid,  containing 
the  glycogen  in  solution,  is  obtained.  The  glycogen  is  precipitated  from  the  t.ltrate.  as  a  white  amor- 
nhous'ix.w,ler.  on  adding  an  excess  of  70  to  80  jx^r  cent,  alcohol.  The  precipitate  is  wa.shed  with  60 
per  cent  and  afterward  with  95  ]xr  cent,  alcohol,  then  with  ether,  and  la.stly,  with  absolute  alcohol ; 
It  is  dried  over  sulphuric  acid  and  weighed  (Briicke).  Kiilz  modifies  the  method  somewhat.  After 
Imiling  the  liver  for  half  an  hour,  it  is  rubbed  up  with  liquor  jjota-sse  ( 100  grms.  liver.  4  grms.  KHO). 
Evaporate  in  the  water  bath  until  all  is  dissolved,  which  occurs  in  about  3  hours.  After  cooling,  neu- 
trali/c  with  HCl  and  precii)ilate  the  i)roteids  as  alwve.  V.  Eves  a-sserts  that  iht  post-mortem  conver- 
sion of  sugar  in  the  liver  is  not  attributable  to  a  ferment  action,  and  the  rapid  appearance  of  sugar  in 
the  liver  after  death  is  due  to  the  siKcific  metalx)lic  activity  of  the  dying  cells.] 

Sources.— The  "mother  substance"  of  the  glycogen  of  the  liver  has 
been  variously  stated  to  be  the  carbohydrates  of  the  food  {Fa7)y)  ;  fats  (olive  oil, 
Salomon) ;  glycerine,  taurin,  and  glycin  (the  latter  splitting  into  glycogen  and 
urea),  the  proteids  (C/.  Bernard)  ;  and  gelatin  {Salomon).  If  it  is  derived  from 
the  albumins,  it  must  be  formed  from  a  non-nitrogenous  derivative  thereof. 

Rohmann  found  that  the  use  of  ammonia  carlx)nate  and  asparagin  or  glycin,  along  with  a  carbo- 
hydrate diet,  in  rabbits  considerai)ly  increased  the  formation  of  glycogen.  The  excessive  formation  of 
acid  ol>served  by  Stadelmann  in  diabetes  unites  with  the  ammonia  and  diminishes  considerably  the 
fonnation  of  glycogen. 

Effects  of  Food. — Rabbits,  whose  livers  have  been  rendered  free  from  glyco- 
gen by  starvation,  yield  new  glycogen  from  their  livers  when  they  are  fed  with 
cane  sugar,  grape  sugar,  maltose,  or  starch.  Forced  muscular  movements  soon 
make  the  liver  of  dogs  free  from  glycogen,  exposure  to  cold  diminishes  its  amount. 
Dextrin  and  grape  sugar  occur  in  the  dead  liver,  but,  in  addition,  some  glycogen 
is  found  for  a  considerable  time  after  death  in  the  liver  and  in  the  muscles. 

If  glycogen  is  injected  into  the  l)lood,  achroodextrin  appears  in  the  urine,  and  also  haemoglobin,  as 
glycogen  dissolves  red  blood  corjjuscles.  Ligature  of  the  bile  duct  causes  decrease  of  the  glycogen 
in  the  liver. 

Other  Situations. — Glycogen  is  not  confined  to  the  liver  cells;  it  occurs  during  foetal  life  in  all  the 
tissui>  of  the  Irnly  of  the  emlirvo  [including  ihe  eml)rv-onic  skeleton],  in  young  animals  [A'ii/ine],  the 
placenta  1  Betnard  ).  [It  occurs  in  large  amount  in  the  liver  during  intra-uterine  life.]  In  the  adult 
it  occurs  in  the  testicle,  in  the  muscles  ( MacDounel,  O.  Nasi.e\,  in  numerous  pathological  products,  in 
inflamed  lungs  \  Kiihne\.  and  also  in  the  corresponding  tissues  of  the  lower  animals.  It  also  occurs 
in  the  chorionic  villi,  in  colorless  blood  corpuscles,  in  fre.sh  pus  cells  which  .still  exhibit  amoeboid  move- 
ments, and  in  fact  in  all  developing  animal  cells,  w  ith  amrtboid  movement ;  it  is  a  never  failing  con- 
stituent in  cartilage,  and  in  the  muscles  and  liver  of  invertebrata,  such  as  the  oyster.  There  is  none 
in  the  frc-sh  brain  of  the  dog  or  rabbit,  but  it  is  found  in  the  brain  in  diabetic  coma  (Abeles)l\ 

Modifying  Conditions. — If  large  quantities  of  starch,  milk-,  fruit-,  or  cane- 
sugar,  or  glycerine,  but  not  mannite,  or  glycol,  or  inosite,  be  added  to  the  pro- 
teids of  the  food,  the  amount  of  glycogen  in  the  liver  is  very  greatly  increased  (to 
12  per  cent,  in  the  fowl),  while  a  purely  albuminous  or  purely  fatty  diet  diminishes 
it  enormously.  During  hunger  it  almost  disappears.  The  injection  of  dissolved 
carbohydrates  into  a  me.senteric  vein  of  a  starving  rabbit  causes  the  liver  pre- 
viously free  from  glycogen  to  contain  glycogen. 


CHEMICAL    COMPOSITION    OF    THE    LIVER    CELLS.  309 

[Bffect  of  Drugs. — Arsenic,  phosphorus  and  antimony  destroy  the  glycogenic  function  of  the 
liver,  no  glycogen  being  present  in  the  liver  in  animals  poisoned  with  these  drugs,  so  that  punctiue  of 
the  iloor  of  the  fourth  ventricle  no  longer  causes  glycosuria  in  them.  In  animals  poisoned  by  strych- 
nia or  curara,  it  is  greatly  diminished,  both  in  the  liver  and  in  the  muscles.  Sugar  is  always  present 
in  the  lurine  in  the  latter  case  but  not  in  the  former.] 

During  life,  under  normal  conditions,  the  glycogen  in  the  liver  is  either  not 
transformed  into  grape  sugar  (^Pavy),  or,  what  is  more  probable,  only  a  very  small 
amount  of  it  is  so  changed.  The  normal  amount  of  sugar  in  blood  is  0.5  to  i 
per  1000,  although  the  blood  of  the  hepatic  vein  contains  somewhat  more.  A 
considerable  amount  is  transformed  into  sugar  only  when  there  is  a  decided 
derangement  of  the  hepatic  circulation,  and  in  these  circumstances  the  blood  of 
the  hepatic  vein  contains  more  sugar.  The  glycogen  undergoes  this  change  very 
rapidly  after  death,  so  that  a  liver  which  has  been  dead  for  some  time  always  con- 
tains more  sugar  and  less  glycogen. 

The  diastatic  ferment  in  the  liver  is  small  in  amount,  and  can  be  obtained 
from  the  extract  of  the  liver  cells  by  the  same  means  as  are  applicable  for  obtain- 
ing other  similar  ferments,  such  as  ptyalin ;  but  it  does  not  seem  to  be  formed 
within  the  liver  cells,  but  only  passes  very  rapidly  from  the  blood  into  them.  The 
ferment  seems  to  be  rapidly  formed  when  the  blood  stream  undergoes  considerable 
derangement.  A  similar  ferment  is  formed  when  red  blood  corpuscles  are  dis- 
solved (^Tiegel),  and,  as  red  blood  corpuscles  are  continually  destroyed  within  the 
liver,  there  is  one  source  from  which  the  ferment  may  be  formed,  whereby  minute 
quantities  of  sugar  would  be  continually  formed  in  the  liver. 

According  to  Seegen,  the  blood  of  the  hepatic  vein  contains  twice  as  much  sugar  (0.23  per  cent.) 
as  that  in  the  portal  vein  (0.II9  per  cent.);  observations  on  dogs  showed  that  the  blood  flowing 
through  the  liver  gives  up  over  400  grms.  sugar  in  24  hours.  Hence,  in  carnivora,  the  greatest  part 
of  the  C  of  the  animal  food  must  pass  into  sugar,  .so  that  the  formation  of  sugar  in  the  liver,  and  its 
decomposition  in  the  blood,  or  in  the  organs  traversed  by  the  blood,  must  be  a  very  important  function 
of  the  metabohsm.  Seegen  is  also  of  opinion  that  the  liver  glycogen  takes  no  part  in  the  formation  of 
sugar  in  the  liver. 

[Blood  when  perfused  through  a  freshly  excised  liver  (or  through  the  kidneys,  lungs,  or  muscles), 
gains  lactic  acid  {^G.Agiio  and  I'Vissokowitsch).'] 

(3)  Fats,  in  the  form  of  highly  refractive  granules,  occur  in  the  liver  cells,  as 
well  as  free  in  the  bile  ducts ;  sometimes,  when  the  food  contains  much  fat  (more 
abundant  in  drunkards  and  the  phthisical),  olein,  palmatin,  stearin,  volatile  fatty 
acids,  and  sarcolactic  acid  are  found. 

There  are  also  found  traces  of  cholesterin,  minute  quantities  of  urea,  uric  acid,  and  the  little-known 
body  jecorin.  [Jecorin,  discovered  by  Drechsel,  contains  S  and  P,  and  reduces  alkahne  solutions  of 
copper  like  grape  sugar.  It  is  also  found  in  the  spleen,  muscles,  and  blood  {Baldi).  The  Hver  of 
birds  contains  a  relatively  large  amount  of  uric  acid,  even  6  to  14  times  as  much  as  the  blood  {v. 
Sckrcede!').']  [Leucin  (Pguanin),  sarkin,  xanthin,  cystin,  and  tyrosin  occur  pathologically  in  certain 
diseases  where  marked  chemical  decompositions  occur.] 

[Fatty  Degeneration  and  Infiltration. — Fatty  gi-anules  are  of  common  occurrence  within  the 
cells  of  the  liver,  constituting  fatty  infiltration,  and  when  not  too  numerous  do  not  seem  to  interfere 
greatly  with  the  functions  of  the  liver  cells.  Fatty  particles  occur  if  too  much  fatty  food  be  taken, 
and  they  are  commonly  found  in  the  livers  of  stall-fed  animals;  t\\e  \\e\\-\ino\\'n pdte-de-foi gras  is 
largely  composed  of  the  livers  of  geese,  which  have  been  fed  on  large  amounts  of  farinaceous  food, 
and  which  have  been  subjected  to  other  unfavorable  hygienic  conditions.  Fatty  granules  are  recog- 
nized by  their  highly  refractive  appearance,  by  their  solubility  in  ether,  and  by  being  blackened  by 
osmic  acid.] 

(4)  The  inorganic  substances  in  the  human  liver  are — potassium,  sodium, 
calcium,  magnesium,  iron,  manganese,  chlorine,  and  phosphoric,  sulphuric,  car- 
bonic, and  silicic  acids ;  while  copper,  zinc,  lead,  mercury,  and  arsenic  may  be 
accidentally  deposited  in  the  hepatic  tissue. 

Tizzoni's  Reaction. — If  a  section  of  a  liver  (especially  of  a  young  animal)  hardened  in  alcohol 
be  treated  with  a  solution  of  potassic  ferrocyanide,  and  then  with  dilute  hydrochloric  acid,  as  a  general 
rule,  the  preparation  becomes  blue,  even  to  the  naked  eye  ;  but  failing  that,  one  can  usually  see  with 
the  microscope  granules  of  Prussian  blue  in  the  protoplasm  of  the  cells,  indicating  the  presence  of  free 
iron  oxide.] 


310  DIADETKS    MELI.ITUS    AND    GLYCOSURIA. 

175.  DIABETES  MELLITUS  AND  GLYCOSURIA.— [Glycosu- 
ria IS  tharattcri/cd  by  the  presence  of  grape  sugar  in  the  urine.  According 
to  Briicke  a  trace  of  sugar  exists  normally  in  urine,  and  when  this  amount  is 
increased  we  have  glycosuria.  When  the  normal  amount  of  grape  sugar  in  the 
blood  is  increased,  grape  sugar  appears  in  the  urine.  In  diabetes  mellitus, 
grape  sugar  also  appears  in  the  urine,  but  this  is  really  a  serious  disease,  involving 
the  alteration  of  many  tissues,  and  distinguished  by  profound  disturbance  of  the 
whole  metabolic  activity,  which  leads  to  numerous  pathological  changes  and  often 
to  death.  The  appearance  of  grape  sugar  in  urine  does  not  necessarily  mean  that 
a  person  is  suffering  tVom  this  disease.] 

The  formation  of  large  quantities  of  grape  sugar  by  the  liver,  and  its  passage 
into  the  blood,  and  from  the  blood  into  the  urine,  constitute  glycosuria.  Extirpa- 
tion of  the  liver  in  frogs,  or  destruction  of  the  hepatic  cells,  as  by  fatty  degeneration 
from  poisoning  with  phosphorus  or  arsenic,  does  not  cause  this  condition.  It 
occurs  for  several  hours  after  the  injury  of  a  certain  part — the  centre  for  the 
he|)atic  vasomotor  nerves — of  they?^^;^  of  the  lower  part  of  the  fourth  ventricle  {CI. 
Bernard's  "  piqflre  ") ;  also  after  section  of  the  vasomotor  channels  in  the  spinal 
cord,  from  above  down  as  far  as  the  exit  of  the  nerves  for  the  liver,  viz.,  to  the 
lumbar  region,  and  in  the  frog  to  the  fourth  vertebra  {Schiff).  When  the  vaso- 
motor nerves,  which  proceed  from  this  centre  to  the  liver,  are  cut  or  paralyzed  in 
any  part  of  their  course,  melhturia  or  glycosuria  is  produced.  All  the  nerve 
channels  do  not  run  through  the  spinal  cord  alone.  A  number  of  vasomotor 
nerves  leave  the  spinal  cord  higher  up,  pass  into  the  sympathetic,  and  thus  reach 
the  liver;  so  that  destruction  of  the  superior  {Favy),  as  well  as  of  the  inferior 
cervical  sympathetic  ganglion,  and  the  first  thoracic  ganglion  {Eckhara)  of 
the  abdominal  sympathetic,  and  often  of  the  splanchnic  itself  produces  it.  The 
paralysis  of  the  blood  vessels  causes  the  liver  to  contain  much  blood,  and  the 
intra-hepatic  blood  stream  is  slowed.  The  disturbance  of  the  circulation  causes- 
a  great  accumulation  of  sugar  in  the  liver,  as  the  blood  ferment  has  time  to  act 
upon  the  glycogen  and  transform  it  into  sugar.  By  stimulation  of  the  sympathetic 
at  the  lowest  cervical  and  first  thoracic  ganglion,  the  hepatic  vessels  at  the  periphery 
of  the  liver  lobules  become  contracted  and  pale  {Cyon).  It  is  remarkable  that 
glycosuria  when  present  may  be  set  aside  by  section  of  the  splanchnic  nerves. 
This  is  explained  by  supposing  that  the  enormous  dilatation  and  congestion,  or 
the  hyperiumia  of  the  abdominal  blood  vessels  thereby  produced,  renders  the  liver 
anaemic. 

Continued  stimulation  of  jx-riphcral  nen-es  may  act  reflexly  w^xyw  the  centre  for  the  vasomotor 
nenes  of  the  liver.  Dialietes  has  been  observed  to  occur  after  stimulation  of  the  central  end  of  the 
vagus  {CI.  Bernard),  and  also  after  stimulation  of  the  central  end  of  the  depressor  nerve  {Fihhne). 
Kven  section  and  sul)se<|uent  stimulation  of  the  cantral  end  of  the  sciatic  nerve  causes  diabetes.  This 
may  cxjilain  the  occurrence  of  diabetes  in  people  who  suffer  from  sciatica.  [It  may  occur  also  after 
perverteil  ner%ous  activity,  a.s  psychical  excitement,  neuralgias  (sciatica,  trigeminal  or  occipital), 
concussion  of  the  brain,  as  well  as  after  certain  injuries  to  the  skull  and  vertebral  column  and  some 
Ccrel>ral  diseases.] 

According  to  Schiff,  the  stagnation  of  blood  in  other  vascular  regions  of  the  body  may  cause  the 
fennent  to  accumulate  in  the  blood  to  such  an  extent  that  diabetes  occurs.  The  glycosuria  that 
occurs  after  compression  of  the  aorta  or  portal  vein  may  perhaps  be  ascribed  to  this  cause,  but  perhaps. 
the  pressure  caused  by  these  procedures  may  paraly/.e  certain  nerves.  According  to  Eckhard,  injury 
to  the  vermiform  process  of  the  cerebellum  of  the  rabbit  causes  diabetes.  In  man,  affections  of  the 
atx)ve- named  ner%ous  regions  cause  dial>etes. 

[In  most  individuals  the  use  of  a  large  quantity  of  sugar  in  the  food  is  not  followed  by  the  appear- 

Tr^m  „.?>"" '?  t  """''=•  T-^  u*""^  exceptional  cases  it  is  often  present,  e.g.,  in  persons  suffering: 
from  gastnc  catarrh,  especially  if  they  are  gouty.]  ^     &  1       v  s 

(Ji.  ""w*?""  "f  P°.'Sons  which  paralyze  the  hepatic  vasomotor  nerves  produce  diabetes ;  curara 
delDhin^  r  'c^^^T  "  T-  '"^'"'^Td)  CO,  amyl  nitrite,  ortho-nitro-propionic  acid,  and  methyl- 
delphinin  ;  less  certainly  morphia,  chloral  hydrate,  IICX,  and  some  other  drugs  ;  [phlorizin  [v.  Mer- 
^  •..•''"V'°'"'  '"^''/'""■'  "^T-"!'-  i^"t  congestion  of  the  liver  produced  in  o  he?  ways  appears  to 
cau.e  dialx^tes,  ..  g.,  after  mechanical  stimulation  of  the  liver.     To  this  class  belongs  th  J  in^e^ction  of 


THE    FUNCTIONS    OF    THE    LIVER.  311 

dilute  saline  solutions  into  tlie  blood  [Bock,  Hoffmann),  whereby  either  the  change  in  form  or  the 
solution  of  the  colored  blood  corpuscles  causes  the  congestion.  The  circumstance  that  repeated  blood 
letting  makes  the  blood  richer  in  sugar,  may  perhaps  be  explained  by  the  slowing  of  the  circulation. 

[Most  of  the  means  which  produce  glycosui-ia  in  other  animals  fail  to  do  so  in  birds;  even  the 
piqure  rarely  produces  it.  This  Thiel  and  Minkowski  attribute  to  the  intensely  active  oxidation 
processes  in  birds.  Phlorizin  causes  glycosuria,  even  after  extirpation  of  the  liver,  which  shows  that 
in  these  cases  there  are  other  causes  at  work  that  obtain  in  the  forms  of  glycosuria.]  Phlorizin  makes 
animals  which  are  free  from  carbohydrates  diabetic.  In  this  case  the  sugar  must  be  derived  from 
proteids  [v.  Mering  ). 

Theoretical. — In  order  to  explain  the  more  immediate  cause  of  these  phenomena  several  hypo- 
theses have  been  advanced  : — 

{a)  The  liver  glycogen  may  be  transformed  unhindered  into  sugar,  as  the  blood  in  its  passage  through 
the  liver  deposits  or  gives  up  the  ferment  to  the  liver  cells.  So  that  the  normal  function  of  the 
vasomotor  system  of  the  liver,  and  its  centre  in  the  floor  of  the  fourth  ventricle,  may  be  regarded  as, 
in  a  certain  sense,  an  "  inhibitory  system"  for  the  formation  of  sugar. 

(3)  If  we  assume  that,  normally  there  is  continually  a  small  quantity  of  sugar  passing  from  the  liver 
into  the  hepatic  vein,  we  might  explain  the  diabetes  as  due  to  the  disappearance  of  these  decom- 
positions— diminished  burning  up  of  the  sugar  in  the  blood,  which  are  constantly  removing  the  sugar 
from  the  blood.  In  fact,  diabetic  persons  have  been  found  to  consume  less  O  and  to  have  an  increased 
formation  of  urea. 

[Injection  of  Grape  Sugar  into  the  Blood. — ^^^len grape  sugar  is  injected  into  the  jugular  vein 
of  a  dog,  only  33  per  cent,  at  most  is  given  off  in  the  urine ;  within  2  to  5  hours  the  urine  is  free  from 
sugar.  Even  within  a  few  minutes  after  the  injection,  only  a  certain  proportion  (/^-X)  <^f  ^'^  sugar 
is  found  in  the  blood ;  part  of  the  sugar  has  been  detected  in  the  muscles,  liver,  and  kidneys,  but  the 
fate  of  the  remainder  is  not  known.  Immediately  after  the  injection,  the  amount  of  hsemoglobin  and 
also  of  serum-albumin  is  diminished  (50  per  cent.),  which  is  due  to  increase  of  the  quantity  of  water 
within  the  vessels ;  but  within  two  hours  the  normal  state  is  restored  ( Brasol) .  In  a  curarized  dog 
the  injection  of  grape  sugar  into  a  vein  increase  the  blood  pressure,  but  this  effect  is  not  observed  after 
the  injection  of  morphia  and  chloral.] 

Persons  suffering  from  diabetes  require  a  large  amount  of  food ;  they  suffer  greatly  from  thirst,  and 
drink  much  fluid.  They  exhibit  signs  of  marked  emaciation,  when  the  loss  of  the  body  is  gi'eater  than 
the  supply.  [In  advanced  diabetes  the  glycogenic  function  of  the  liver  is  almost  abolished,  as  was 
proved  by  removing  with  a  trocar  a  small  part  of  the  liver  from  man,  when  almost  no  glycogen  was 
found  {Eh7-lich).  The  absorbed  sugar  in  the  portal  vein  passes  directly  into  the  general  circulation 
without  being  submitted  to  the  action  of  the  liver  [v.  Freric/is).']  In  severe  cases,  toward  death,  not 
unfrequently  a  peculiar  comatose  condition — diabetic  coma — occurs,  when  the  breath  often  has  the 
odor  of  aceton,  which  is  also  fonnd  in  the  urine.  But  neither  aceton  nor  its  precursor,  aceto-acetie 
acid,  nor  jethyl-diacetic  acid,  nor  the  unknown  substance,  in  diabetic  urine,  which  gives  the  red  color 
with  ferric  chloride  {v.  Jakscli),  is  the  cause  of  the  coma  [Frerichs  and  Brieger). 

176.  THE  FUNCTIONS  OF  THE  LIVER.— [To  understand  the 
functions  of  the  liver,  we  must  remember  its  unique  relation  to  the  vascular 
and  digestive  systems,  whereby  many  of  the  products  of  gastric  and  intestinal 
digestion  have  to  traverse  it  before  they  reach  the  blood,  and  some  of  them  as 
they  traverse  the  liver  are  altered.  We  have  still  much  to  learn  regarding  the 
liver.  It  has  several  distinct  functions — some  obvious,  others  not.  (i)  The  liver 
secretes  bile,  which  is  formed  by  the  hepatic  cells,  and  leaves  the  organ  by  the 
bile  ducts,  to  pass  into  the  duodenum.  (2)  The  liver  cells  also  form  glycogen, 
which  does  not  pass  into  the  ducts,  but  in  some  altered  and  diffusible  form  passes 
into  the  blood  stream,  and  leaves  the  liver  by  the  hepatic  veins.  Hence,  the 
study  of  the  liver  materially  influences  our  conception  of  a  secreting  organ.  In 
this  case,  we  have  the  products  of  its  secretory  activity  leaving  it  by  two  different 
channels — the  one  by  the  ducts,  and  the  other  by  the  blood  stream.  The  liver, 
therefore,  is  a  great  storehouse  of  carbohydrates,  and  it  serves  them  out  to  the 
economy  as  they  are  required.  All  this  points  to  the  liver  as  being  an  organ 
intimately  related  to  the  general  metabolism  of  the  body.  (3)  In  a  certain 
period  of  development  it  is  concerned  in  the  formation  of  blood  corpuscles  (§  7). 
(4)  It  has  some  relation  to  the  breaking  up  of  blood  corpuscles  and  the  forma- 
tion of  urea  and  other  metabolic  products  (§  20,  §  177,  3).  (5)  Brunton 
attributes  some  importance  to  the  liver  in  connection  with  the  arrest  of  certain 
substances  absorbed  from  the  alimentary  canal,  whereby  they  are  either  destroyed, 
stored  up  in  the  liver,  or,  it  may  be,  prevented  from  entering  the  general  circula- 


312  CONSTITUENTS   OF   THE    BILE. 

tion  in  too  large  amount.     It  is  possible  that  ptomaines   may  be  arrested  in  this 
way  (§  166).] 

FThr  liv,T  ha>  no  special  nclion  on  ccrtnin  mineral  substances  which  traverse  it  in  the  blood,  e.  g., 
•,I..ri<k-.  but  It  rc-tains  the  vi-fjitabie  alkaloitls,  provided  they  are  not  present  in  too  large  an 
the  l.liKxl.      ihi-  ptoniaino  are  similarly  retained  in  the  liver.     The  liver  possesses  this 
j.i. .,,.,,    ..iilv  n-  Iniii,'  :\s  ji  contain-.  ^;lyci>i^in  ( //.  AV;v/-j).] 

177.  CONSTITUENTS  OF  THE  BILE.— Bile  is  a  yellowish-brown 
or  dark  grccn-t  olorcd  transparent  fluid,  with  sweetish,  strongly  bitter  taste, 
feeble  musk-like  odor,  and  neutral  reaction.  The  specific  gravity  of  human  bile 
from  the  gall  bladder  =  1026  to  1032,  while  that  from  a  fistula  =  1010  to  ion. 
It  contains  — 

(1)  Mucus,  which  gives  bile  its  sticky  character,  and  not  unfrequently  makes 
it  alkaline  ;  it  is  the  product  of  the  mucous  glands  and  the  goblet  cells  of  the 
mucous  membrane  of  the  larger  bile  ducts.  When  bile  is  exposed  to  the  air,  the 
mucus  causes  it  to  putrefy  rapidly.     It  is  precipitated  by  acetic  acid  or  alcohol. 

[The  bile  formed  in  the  ultimate  bile  ducts  does  not  seem  to  contain  mucin  or  mucus,  but  bile  from 
the  gall  blad<l<r  always  does.      It  is  foniied  by  the  mucous  glands  in  the  larger  bile  ducts  {'i,  173).] 

(2)  The  Bile  Acids. — Glycocholic and  taurocholic  acids,  so-called  conjugate 
acids,  are  united  with  soda  (in  traces  with  potash)  to  form  glycocholate  and 
taurocholateofsoda,  which  have  a  bitter  taste,  and  rotate  the  plane  of  polarized  light 
to  the  right.  In  human  bile  (as  well  as  in  that  of  birds,  many  mammals,  and 
amphibians)  taurocholic  acid  is  most  abundant;  in  other  animals  (pig,  ox)  gly- 
cocholic acid  is  most  abundant  but  is  absent  in  sucklings. 

(a)  Glycocholic  acid,  C',,r,Hj,,NOr, ;  when  boiled  with  caustic  potash,  or  baryta 
water,  or  with  dilute  mineral  acids,  it  takes  up  HoO  and  splits  into — 

tdycin  ( =  Glycocoll  ^  f  Jelatin  Sugar  =  Amido-acetic  acid)  =  C2HSNO2. 
4-  Cholalic  acid  (also  called  Cholic  acid), ^C,,H.„0=. 


—-  ( Hycocholic  acid  -|-  Water, —  C^gH^jNOg  -f  H^O. 

(/i)  Taurocholic  acid,  QsH^iNSO;,  when  similarly  treated,  takes  up  water 
and  splits  into — 

Ti»urinf=  .Xmido-xthyl-sulphuric  acid)  ::=  C^IKXSOj. 
--  Cholalic  .acid =  C,.H.„0.. 


=  Taurcxholic  acid  -|-  Water =  CjeM^sN'SO^  +  Hp  [Strec/cer.) 

[Solutions  of  Liurocholic  acid  are  antiseptic,  and  if  sufficiently  strong  interfere  with  the  development 
of  bacteria,  and  |)revcnt  the  .alcoholic  and  lactic  fermentations,  as  well  as  the  trj-ptic  and  diastatic 
action  of  the  jiaiicrcas  i  /■.«//<•// 1.] 

Preparation  of  the  Bile  Acids. — Evaporate  bile  to  '4^  of  its  volume,  rub  it  up  into  a  paste  with 
excevs  of  animal  charcoal  and  dry  at  100°  C.  Extract  the  black  mass  with  absolute  alcohol,  and 
filter,  .\fter  a  part  of  the  alcohol  has  l)een  removed  by  distillation,  the  bile  salts  are  precipitated  in  a 
resinous  fonn.  and  on  the  addition  of  excess  of  ether,  there  is  formed  immediately  a  crvstalline  ma.ss 
of  glancing  needles  1  Platner's  "  crystallized  bile  "].  The  alkaline  salts  of  the  bile  acids  are  freely 
.soluble  in  water  or  alcohol,  and  insohilile  in  t-llier.  Neutral  lead  acet.ate  precipitates  the  glycocholic 
aci<l— as  lead  glycochol.ate — from  the  solution  of  both  salts ;  the  precipitate  is  collected  on  a  filter, 
dLs.solved  in  hot  alcohol,  and  the  lead  is  precipitated  as  lead  sulphide  by  H.^S ;  after  removal  of  the 
lead  sulphide,  the  addition  of  water  precijiitates  the  isolated  glycocholic  acid.  If,  after  precipitating 
the  It-ad  glycfK:holatr,  the  liltrate  be  treated  with  basic  lead  .acetate,  a  precipitate  of  lead  taurocholate 
IS  fonne.l,  from  which  the  acid  may  be  obtained  in  the  saiiie  way  as  described  above  {Strecker). 

With  regard  to  the  decomposition  products  of  the  bile  acids,  glycin,  as 
such,  does  not  occur  in  the  body,  but  only  in  the  bile  in  combination  with  cholic 
acid,  in  urine  in  combination  with  benzoic  acid,  as  hippuric  acid,  and  lastly,  in 
gelatin  in  complex  combination. 

Cholalic  acid  rotates  the  ray  of  polarized  light  to  the  right,  and  its  chemical 
composition  is  unknown.  It  is  insoluble  in  water,  soluble  in  alcohol,  but  soluble 
with  difficulty  in  ether,  from  which  it  separates  in  prisms.  Its  crystalline  alkaline 
salts  are  readily  soluble  in  water.  It  is  colored  blue  by  iodine,  and  occurs  free 
onlv  in  the  intestine. 


THE    BILE    ACIDS    AND    PIGMENTS.  313 

Cholalic  acid  is  replaced  in  the  bile  of  many  animals  by  a  nearly  related  acid,  e.  g.,  in  pig's  bile 
by  hyo-cholalic  acid  [^Strecker) ;  in  the  bile  of  the  goose,  cheno-cholalic  acid  is  present  {^Alarsson, 
Otto). 

When  cholalic  acid  is  boiled  with  concentrated  HCl,  or  heated  dry  at  200°  C, 
it  becomes  an  anhydride,  thus  : — 

Cholalic  acid,  .    .    .  =  C^^H^qO^,  produces 
Choloidinic  acid,      .  =^  Q-^^^^^  -f-  HjO,  and  this  again  yields 
Dyslysin,      .    ,    .    ,  =  Cj^HjgOg  =  HjO. 
Choloidinic  acid  is,  however,  not  improbably  a  mixture  of  cholalic  acid  and  dyslysin ;  dyslysin, 
when  fused  with  caustic  potash,  is  changed  into  cholalate  of  potash.     By  oxidation  cholalic  acid  yields 
a  tribasic  acid,  as  yet  uninvestigated,  and  a  fair  amount  of  oxalic  acid,  but  no  fatty  acids  ( Cleve) . 

PettenkofFer's  Test. — The  bile  acids,  cholic  acid,  and  their  anhydrides, 
when  dissolved  in  water,  yield  on  the  addition  off  concentrated  sulphuric  acid 
(added  in  drops  so  as  not  to  heat  the  fluid  above  70°  C),  and  several  drops  of  a 
10  per  cent,  solution  of  cane  sugar,  a  reddish-purple,  transparent  fluid,  which  shows 
two  absorption  bands  at  E  and  F  {Schenk').  [A  very  good  method  is  to  mix  a 
few  drops  of  the  cane-sugar  solution  with  the  bile,  and  to  shake  the  mixture  until 
a  copious  froth  is  obtained.  Pour  the  sulphuric  acid  down  the  side  of  the  test 
tube,  and  then  the  characteristic  color  is  seen  in  the  froth.  Any  albumin  present 
must  be  removed  before  applying  the  test.] 

According  to  Drechsel,  it  is  better  to  add  phosphoric  acid,  instead  of  sulphuric  acid,  until  the  fluid 
is  syrupy,  then  add  the  cane  sugar,  and  afterward  place  the  whole  in  boiling  water.  When  investi- 
grating  the  amount  of  bile  acids  in  a  liquid,  the  albumin  must  be  removed  beforehand,  as  it  gives  a 
reaction  similar  to  the  bile  acids,  but  in  that  case  the  red  fluid  has  only  one  absorption  band.  If 
only  small  quantities  of  bile  acids  are  present,  the  fluid  must  in  the  first  place  be  concentrated  by 
evaporation. 

[Hay's  Test. — The  bile  acids  or  their  soluble  salts  lower  the  surface  tension  of  flnids  in  which 
they  are  dissolved.  Throw  a  small  quantity  of  sulphur  (sublimed  or  precipitated)  on  the  surface  of 
the  fluid  containing  bile  acids,  and  if  the  bile  acids  be  present,  the  sulphur  will  at  once  begin  to  sink, 
and  will  be  wholly  precipitated  within  a  few  minutes.     {^Privately  coinvmnicated.W 

The  bile  acids  are  formed  in  the  liver.  After  its  extirpation,  there  is  no 
accumulation  of  biliary  matters  in  the  blood. 

How  the  formation  of  the  nitrogenous  bile  acids  is  effected,  is  quite  unknown.  They  must  be 
obtained  from  the  decomposition  of  albuminous  materials,  and  it  is  important  to  note  that  the  amount 
of  bile  acids  is  increased  by  albuminous  food.  Taurin  contains  part  of  the  sulphur  of  albumin ;  bile 
salts  contain  4  to  4.6  per  cent.,  which  may  perhaps  be  derived  from  dissolved  red  blood  corpuscles. 

(3)  The  Bile  Pigments. — The  freshly  secreted  bile  of  man  and  many  animals 
has  a  yellowish-brown  color,  due  to  the  presence  of  bilirubin.  When  it  remains 
for  a  considerable  time  in  the  gall  bladder,  or  when  alkaline  bile  is  exposed  to 
the  air,  the  bilirubin  absorbs  O  and  becomes  changed  into  a  green  pigment, 
biliverdin.  This  substance  is  present  naturally,  and  is  the  chief  pigment  in  the 
bile  of  herbivora  and  cold-blooded  animals. 

{a)  Bilirubin  (CsoHgeN^Og)  is  perhaps  united  with  an  alkali ;  crystallizes  in 
transparent  fox-red  clinorhombic  prisms.  It  is  insoluble  in  water,  soluble  in  chloro- 
form, by  which  substance  it  may  be  separated  from  biliverdin,  which  is  insoluble 
in  chloroform.  It  unites  as  a  monobasic  acid  with  alkalies,  and  as  such  is  soluble. 
It  is  identical  with  Virchow's  haematoidin  (§  20). 

Preparation. — It  is  most  easily  prepared  from  the  red  (bilirubin  chalk)  gall  stones  of  man  or  the 
ox.  The  stones  are  pounded,  and  their  chalk  dissolved  by  hydrochloric  acid;  the  pigment  is  then 
extracted  with  chloroform.  That  bihrubin  is  derived  from  hffiraoglobin  is  very  probable,  considering 
its  identity  with  hsematoidin.  Very  probably  red  blood  corpuscles  are  dissolved  in  the  liver,  and  their 
hsemoglobin  changed  into  bilirubin. 

{b')  Biliverdin,  CaaHsgNiOg,  is  an  oxidized  derivative  of  the  former,  from 
which  it  can  be  obtained  by  various  oxidation  processes.  It  is  readily  soluble  in 
alcohol,  very  slightly  so  in  ether,  and  not  at  all  soluble  in  chloroform.  It  occurs 
in  the  placenta  of  the  bitch.  As  yet  it  has  not  been  re-transformed  by  reducing 
agents  into  bilirubin. 


314  CHOLESTERIN. 

Tests  for  Bile  Pigments.— Bilirubin  and  biliverdin  may  occur  in  other 
fluids,  f.  r.,  the  urine,  and  are  detected  by  the  Gmelin-Heintz'  reaction. 
When  nifrir  acU  containh,)^  some  nitrous  add  is  added  to  a  hquid  containing  these 
pigments,  a  play  of  colors  is  obtained,  beginning  with  green  (biliverdin),  blue, 
violet,  red,  ending  with  yellow.  [This  reaction  is  best  done  by  placing  a  drop  of 
the  liquid  on  a  white  porcelain  plate,  and  adding  a  drop  of  the  impure  nitric  acid.] 

(.-)  If  when  the  l.luc  color  is  rcnchcfl.  the  oxidation  ]m->ce.ss  is  arrested,  bilicyanin  {llcynsius, 
Camf>bel!),  in  acid  solution  l.lue  (in  alkaline  violet),  is  obtained,  which  shows  two  ill-dehned  absoqj- 

tion  bonds  near  1)  (Jajjf^)-  \^v     \  •      \    \^  t\ 

yd\   Bilifuscin  occurs  in  small  amount  in  decomposing  bile  and  m  gall  stones  =  bilirubm  +  H^U. 

(<■)   Biliprasin  (.V/.Tr/Zt-r)  also  occurs    -- Bilirubin  4- n.p  + (J. 

(/)  The  v.llow  pifjnunt.  which  ultimately  results  from  the  prolonged  action  of  the  oxidizing 
rcnRcnt.  is  tlie  choletelin  (C,eH„N,0,)  of  Maly;  it  is  amoqjhous,  and  soluble  in  water,  alcohol, 
aci<ls,  and  alkalies.  •      i        . 

I  Spectrum  of  Bile.— The  bile  of  carnivorous  animals  is  generally  free  from  absor])tion  bands,  except 
uhi-n  acKls  arc  added  to  it,  in  which  ca-se  the  band  of  bilirubin  is  revealed.  Bilirubin  and  biliverdin 
yielil  characteristic  sjxxtra  only  when  they  are  treated  with  nitric  acid.  The  bile  of  some  animals 
yields  bands,  but  when  this  is  the  case  they  are  due  to  the  presence  of  a  derivative  of  h;ematin,  and 
MncMunn  calls  this  body  cholohaematin,  which  gives  a  three-  or  four-banded  spectrum  (ox,  sheep).] 

{g)  Hilirubin  absorbs  W  +  H.O  (by  putrefaction,  or  by  the  treatment  of  alkaline 
watery  solutions  with  the  powerfully  reducing  sodium  amalgam),  and  becomes 
converted  into  Maly's  hydrobilirubin  (C32H40N4O;),  which  is  slightly  soluble  in 
water,  and  more  easily  soluble  in  solutions  of  salts,  or  alkalies,  alcohol,  ether, 
chloroform,  and  shows  an  absorption  band  at  b,  F.  This  substance,  which,  accord- 
ing to  Hammarsten,  occurs  in  normal  bile,  is  a  constant  coloring  matter  of  faeces, 
and  was  called  stercobilin  by  Vaulair  and  Masius,  but  is  identical  with  hydro- 
bilirubin {Maly).  It  is,  however,  probably  identical  with  the  urinary  pigment 
urobilin  of  Jaff6  {Stokvis,  §  20). 

[The  bile  of  invertebrates  contains  none  of  the  bile  pigments  present  in  vertebrates,  although 
hxmochromogen  is  found  in  the  cray  fish  and  pulmonale  mollusks.  In  some  organs,  and  in  bile,  a 
pipmeiu-like  vegetable  chlorophyll — entero-chlorophyll — is  found;  but  whether  it  is  derived  from 
without,  or  formed  within  the  organism,  is  not  certain  [^MacMunti).'\ 

(4)  Cholesterin,  C\6H4,0(H.jO),  is  a  monatomic  alcohol  which  rotates  the 
ray  of  polarized  light  to  the  left ;  it  occurs  also  in  blood, 
Fig.  196.  ,        yelk,  nervous  matter  [and  gall  stones].     It  forms  trans- 

parent rhombic  plates,  which  usually  have  a  small  oblong 
piece  cut  out  of  the  corner  (Fig.  196).  It  is  insoluble 
in  water,  soluble  in  hot  alcohol,  ether,  or  chloroform. 
It  is  kept  in  solution  in  the  bile  by  the  bile  salts. 


Preparation. — It  is  most  easily  prepared   from  so-called  white 
gall  stones,  which  not  unfrequently  consist  entirely  of  cholesterin,  by 
extracting  them  with  hot  alcohol  after  they  are  })ulverized.     Crystals 
are  excreted  after  evaporation  of  the  alcohol.     Tests. — They  give  a 
Crjstals  of  Cliulestcriii.  red  Color  with  sulphuric  acid  (5  vols,  to  I  vol.  M./)),  while  they  give 

a  blue — as  cellulose  does — with  sulphuric  acid  and  iodine.     When 
dis.solved  in  chloroform,  one  drop  of  concentrated  sulphuric  acid  causes  a  deep  red  color  {H.  Schiff). 

(5)  Among  the  other  organic  constituents:  Lecithin  (§23),  or  its  decom- 
position product,  neurin  (cholin),  and  glycero-phosphoric  acid  (into  which 
lecithin  may  be  artificially  transformed  by  boiling  with  baryta) ;  palmatin, 
stearin,  olein,  as  well  as  their  soda  soaps;  diastatic  ferment;  traces  of 
urea;  (in  ox  bile,  acetic  acid  and  propionic  acid,  united  with  glycerine  and 
metals,  Dogiei). 

(6)  Inorganic  constituents  of  bile  (0.6  to  i  per  cent.)  :  — 

They  are— sodic  and  pota.ssic  chloride,  calcic  and  magnesic  phosphate,  and  much  iron,  which  in 


ever,  lx.ing  almost  completely  absorbed  within  the  gall  bladder 


SECRETION    OF    BILE.  315 


The  mean  composition  of  human  bile  is ; 


Lecithin, 0.5  per  cent. 

Mucin  and  pigments,  .    I  to  3  " 

Ash 0.61      " 


Water, 82  to  90  per  cent. 

Bile  salts, 6  to  11       " 

Fat  and  soaps, 2       " 

Cholesterin, 0.4    " 

Further,  unchanged  fat  probably  always  passes  into  the  bile,  but  it  is  again  absorbed  therefrom 
(  Virchow).  The  amount  of  S  in  dry  dog's  bile  ^  2.8  to  3. 1  per  cent.,  the  N  =  7  to  10  per  cent. 
{Spiro) ;  the  sulphur  of  the  bile  is  not  oxidized  into  sulphuric  acid,  but  it  appears  as  a  sulphm-  com- 
pound in  the  urine  {Kunkel,  v.   Voit). 

178.  SECRETION   OF  BILE.— (i)  The  secretion  of  bile  is  not  a 

mere  filtration  of  substances  already  existing  in  the  blood  of  the  liver,  but  it  is  a 
chemical  production  of  the  characteristic  biliary  constituents,  accompanied  by 
oxidation,  within  the  hepatic  cells,  to  which  the  blood  of  the  gland  only  supplies 
the  raw  material.  The  liver  cells  themselves  undergo  histological  changes  during 
the  process  of  digestion.  It  is  secreted  continually;  but  part  is  stored  up  in  the 
gall  bladder,  and  is  poured  out  copiously  during  digestion.  The  higher  tempera- 
ture of  the  blood  of  the  hepatic  vein,  as  well  as  the  large  amount  of  CO2  in  the 
bile,  indicates  that  oxidations  occur  within  the  liver.  The  water  of  the  bile  is  not 
merely  filtered  through  the  blood  capillaries,  as  the  pressure  within  the  bile  ducts 
may  exceed  that  in  the  portal  vein. 

(2)  The  quantity  of  bile  was  estimated  by  v.  Wittich,  from  a  biliary  fistula, 
at  533  cubic  centimetres  in  twenty-four  hours  (some  bile  passed  into  the  intes- 
tine) ;  by  Westphalen,  at  453  to  566  grms.  [by  Murchison,  at  40  oz.]  ;  by  Joh.. 
Ranke,  on  a  biliary-pulmonary  fistula,  at  652  cubic  centimetres.  The  last 
observation  gives  14  grms.  (with  0.44  grms.  solids)  per  kilo,  of  man  in  twenty- 
four  hours. 

Analogous  values  for  animals  are — I  kilo,  dog,  32  grms.  (1.2  solids) ;  I  kilo,  rabbit,  137  grms.  (2.5. 
solids);  I  kilo,  guinea  pig,  176  grms.  (2.5  solids). 

(3)  The  excretion  of  bile  into  the  intestine  shows  two  maxima  during  one 
period  of  digestion;  the  first  from  3  to  5  hours,  and  the  second  from  13  to  15 
hours,  after  food.  The  cause  is  due  to  simultaneous  reflex  excitement  of  the 
hepatic  blood  vessels,  which  become  greatly  dilated. 

(4)  The  influence  of  food  is  very  marked.  The  largest  amount  is  secreted 
after  a  flesh  diet,  with  some  fat  added  ;  less  after  vegetable  food  ;  a  very  small 
amount  with  a  pure  fat  diet ;  it  stops  during  hunger.  Draughts  of  water  increase 
the  amount,  with  a  corresponding  relative  diminution  of  the  solid  constituents. 
[The  biliary  solids  are  increased  by  food,  reaching  their  maximum  about  one  hour 
after  feeding.] 

(5)  The  influence  of  blood  supply  is  variable  : — 

(a)  Secretion  is  greatly  favored  by  a  copious  and  rapid  blood  supply.  The  blood  pressiu-e  is  not 
the  prime  factor,  as  ligature  of  the  cava  above  the  diaphragm,  whereby  the  greatest  blood  pressure 
occurs  in  the  liver,  arrests  the  secretion. 

(l>)  Simultaneous  ligature  of  the  hepatic  artery  (diameter,  5^  mm.)  and  the  portal  vein  (diameter,. 
16  mm.)  abolishes  the  secretion  i^Rohrig).  These  two  vessels  supply  the  raw  material  for  the  secre- 
tion of  bile. 

(f)  If  the  hepatic  artery  be  ligatxu-ed,  the  portal  vein  alone  supports  the  secretion.  Ligature  of  the 
artery  or  one  of  its  branches  ultimately  causes  necrosis  of  the  parts  supplied  by  that  branch,  and 
eventually  of  the  entire  liver,  as  this  artery  is  the  nutrient  vessel  of  the  liver. 

{d)  If  the  branch  of  the  portal  vein  to  one  lobe  be  ligatured,  there  is  only  a  slight  secretion  in  that 
lobe,  so  that  the  bile  must  be  fonned  from  the  arterial  blood.  Complete  ligature  of  the  portal  veia 
rapidly  causes  death  (|  87).  Neither  ligature  of  the  hepatic  artery  by  itself,  nor  gradual  obliteration 
of  the  portal  vein  by  itself,  causes  cessation  of  the  secretion,  but  it  is  diminished.  That  sudden  ligature 
of  the  portal  vein  causes  cessation  is  due  to  the  fact  that,  in  addition  to  diminution  of  the  secretion,  the 
enormous  stagnation  of  blood  in  the  rootlets  of  the  portal  vein  in  the  abdominal  organs  makes  the  liver 
very  anaemic,  and  thus  prevents  it  from  secreting. 

(if)  If  the  blood  of  the  hepatic  artery  is  allowed  to  pass  into  the  portal  vein  (which  has  been  liga- 
tured on  the  peripheral  side),  secretion  continues  [Sckiff). 

(/)  Profuse  loss  of  blood  arrests  the  secretion  of  bile  before  the  muscular  and  nervous  apparatus- 
become  paralyzed.    A  more  copious  supply  of  blood  to  other  organs — e.g.,  to  the  muscles  of  the  trunk — 


310 


lULIAKV    1-ISTUIJE. 


durins  viRoroa.  exercise,  diminishes  the  secretion,  while  the  transfusion  of  large  quantities  of  blood 
incri-aU  It.  hut  if  iw  hi^h  n  pressure  is  caused  in  the  jwrtal  vein,  by  introducuig  blood  from  the  caro- 
tid of  anothiT  animal,  it  is  diminished.  •     i  i  i      . 

IP-)  Influence  of  Nerves.— All  conditions  which  cause  contraction  of  the  alxlommal  blood 
vcs-t-ls  f  ■'  simulation  of  the  an>a  \ieussenii.  of  the  inferior  cervical  ganglion,  of  the  hepatic 
ncr>c>.'of""thc  spljinchnics.  of  the  spinal  cord  (either  directly  by  stiychnia,  or  reflexly  through  stimu- 
lalion  of  senior)- ner%es).  affect  the  secretion;  and  so  do  all  conditions  which  cause  stagnation  or 
congestion  of  the  blood  in  the  hepsitic  vessels  (section  of  the  splanchnic  nerves,  diabetic  puncture, 
J  175).  ■•^-c''""  "f  '''*^  cer%ic.il  spinal  cord.  Paralysis  (ligature)  of  the  hepatic  nerves  causes  at  first 
an  increase  of  the  biliarj-  secretion. 

(*i  Portal  and  Hepatic  Veins.— With  regard  to  the  raw  m.atenal  supplied  to  the  liver  by  its 
bloo<l  vessel.-,  it  i>  imix.ilaiit  to  note  the  dilTerence  in  the  com]K)sition  of  the  blood  of  the  hepatic  and 
portal  veins.  The  bkxxl  of  the  hepatic  vein  contains  more  sugar  (?),  lecithin,  cholesterin  ^DrosJoff), 
and  blood  corjmscles,  but  less  albumin,  fibrin,  h.-emoglobin,  fat,  water,  and  salts. 

[(«|  ltTelm.inn  ol)servcd  that  the  flow  of  bile  from  a  person  with  a  biliary  fistula  was  arrested 
during  fever.] 

(6)  The  formation  of  bile  is  largely  dependent  upon  the  decomposition  of 
red  blood  corpuscles,  as  they  supply  the  material  necessary  for  the  formation 
of  some  of  its  constituents. 

Hence,  all  conditions  which  cause  solution  of  the  colored  blood  corpuscles  are  accompanied  by  an 
increased  fonnaiion  of  bile  ({!  iSo). 

(7)  Of  course  a  normal  condition  of  the  hepatic  cells  is  required  for  a  normal 
secretion  of  bile. 

Biliary  Fistulac. — Tlie  mechanism  of  the  biliarv*  secretion  is  .studied  in  animals  by  means  of 
biharj'  fi-stuKv.     Schwann  opened  the  belly  by  a  vertical  incision  a  little  to  the  right  of  the  ensiform 

process,  cut  into  the  fundus  of  the  gall  bladder, 
and  sewed  its  margins  to  the  edges  of  the  wound 
in  the  abdomen,  and  afterward  introduced  a  can- 
nula into  the  wound  (Fig.  197).  To  secure  that 
all  the  bile  is  discharged  externally,  tie  the  com- 
mon bile  duct  in  two  [Maces  and  divide  it  between 
the  two  ligatures.  After  a  fistula  is  fj-eshly  made 
the  secretion  falls.  This  depends  upon  the  re- 
moval of  the  bile  from  the  body.  If  bile  be 
supplied,  the  secretion  is  increased  Regenera- 
tion of  the  divided  bile  duct  may  occur  in  dogs. 
V.  Wittich  observed  a  bilian,-  fistula  in  man.  [A 
temporar}-  biliarj-  fistula  may  also  be  made.  The 
abdomen  is  opened  in  the  same  way  as  described 
above.  A  long  bent  gla.ss  cannula  is  introduced 
and  tied  into  the  common  bile  duct,  and  the  cystic 
duct  is  ligatured  or  clamped  (Fig.  197).  The 
tube  is  brought  out  through  the  wound  in  the 
al)domen. 
[Influence  of  the  Liver  on  Metabolism.— If  the  liver  be  excluded  from  the  circulation, 
important  changes  must  necessarily  occur  in  the  metabolism.  In  birds  (the  goose)  there  is  an 
anastomosis  l)etween  the  jx)rtal  system  of  the  liver  and  that  of  the  kidneys,  .so  that,  when  the  portal 
circulation  IS  interrupted  m  these  animals,  there  is  never  any  great  congestion  in  the  abdominal 
^■^"m"'  r  ,r  ^"*^  ^"^•'  g^"<^'"^"y  eight  to  ten  hours  after  the  operation,  the  uric  acid  in  the  urine 
rapidly  falls  to  a  minimum  {^  to  ^^  of  normal);  the  chief  constituent  of  the  urine  is  then  sarcolactic 
acid,  while  m  normal  unne  there  is  none ;  the  ammonia  is  increased  ( MinkowskiV  This  experiment 
goes  to  indic.ite  that  unc  acid  is  formed  in  the  liver.  Dog.-lf  the  liver  be  excluded  fiom  the  portal 
circulation  by  connecting  the  portal  vein  with  the  inferior  vena  cava,  and  ligaturing  the  h^atic 
arter>-.  a  dog  will  hve  m  the  former  case  three  to  six  days,  and  in  the  latter  one  to  two.  The  liver 
does  not  undergo  necrosis  nor  does  bile  cease  to  be  secreted.     The  liver  is  nourished  by  the  blood  in 

f^«/ST.  'n"'-1  P  /  fi"','"u'^"  7'"  '^'"S  P''^^^'^'y  ""-^^^  ^^  ^he  respiraton-  movements 
iSr/n..  X  fl.i  1  f  T  '  '^','"  ^"^^2'^  ^  ^onmov,  of  nitrogenous  balance,  some  drugs  which 
increase  the  flow  of  bile  (^.  g.,  salicylate  and  benzoate  of  soda,  colchicum,  perchloride  of  mercurv-   and 

wK  a  ^e,^"  Hi'r^t  f  j^^'^^^'^"  «/  ""'^^  •'  h^""'  ^e  Concludes  that  the  formation  of  urea  hi  the 
hver  bears  a  \er>-  direct  relationship  to  the  secretion  of  bile  (§  256)  ] 

179.  EXCRETION   OF   BILE.-[In   this    connection    we  must  keep  in 

ir„nnn  tb  1  "'  r'T'u  '''  Jhe  bile-secreting  mechanism  depend- 
ent upon   the  hver  cells,  ^vhlch  are  always  in  a  greater  or  less  degree  of  acti^vity  ; 


Schwann's  permanent  fistuLn,  and  a  temporary  fistula. 
.1^/,  .ibdominal  w.ill :  G.  I!.,  gall  bladder  ;  INT., 
intestine  ;  T.,  tube  in  temporary  fistida  [Stirling). 


EXCRETION    OF    BILE.  317 

(2)  the  bile-expelling  mechanism,  which  is  specially  active  at  certain  periods 
of  digestion  (§  178). 

Excretion  of  bile  is  due  to  (i)  the  continual  pressure  of  the  newly-formed 
bile  within  the  inter-lobular  bile  ducts  forcing  onward  the  bile  in  the  excretory 
ducts. 

(2)  The  interrupted  periodic  compression  of  the  liver  from  above,  by  the 
diaphragm,  at  every  inspiration.  Further,  every  inspiration  assists  the  flow  of 
blood  in  the  hepatic  veins,  and  every  respiratory  increase  of  pressure  within  the 
abdomen  favors  the  current  in  the  portal  vein. 

It  is  probable  that  the  diminution  of  the  secretion  of  bile,  which  occurs  after  bilateral  division  of  the 
vagi,  is  to  be  explained  in  this  way;  still,  it  is  to  be  remembered  that  the  vagus  sends  branches  to  the 
hepatic  plexus.  It  is  not  decided  whether  the  biliary  secretion  is  diminished  after  section  of  the 
phrenic  nerves  and  paralysis  of  the  abdominal  muscles. 

(3)  The  contraction  of  the  smooth  muscles  of  the  larger  bile  ducts  and  the  gall 
bladder.  Stimulation  of  the  spinal  cord,  from  which  the  motor  nerves  for  these 
structures  pass,  causes  acceleration  of  the  outflow,  which  is  afterward  followed  by 
a  diminished  outflow.  Under  normal  conditions,  this  stimulation  seems  to  occur 
reflexly,  and  is  caused  by  the  passage  of  the  ingesta  into  the  duodenum,  which,  at 
the  same  time,  excites  movement  of  this  part  of  the  intestine. 

(4)  Direct  stimulation  of  the  liver,  and  reflex  stimulation  of  the  spinal  cord, 
diminish  the  excretion  ;  while  extirpation  of  the  hepatic  plexus  and  injury  to  the 
floor  of  the  fourth  ventricle  do  not  exert  any  disturbing  influence. 

(5)  A  relatively  small  amount  of  resistance  causes  bile  to  stagnate  in  the  bile 
ducts. 

Secretion  Pressure. — A  manometer,  tied  into  the  gall  bladder  of  a  guinea  pig,  supports  a  column 
of  200  millimetres  of  water ;  and  secretion  can  take  place  under  this  pressure.  If  this  pressui-e  be 
increased,  or  too  long  sustained,  the  watery  bile  passes  from  the  liver  into  the  blood,  even  to  the 
amount  of  four  times  the  weight  of  the  liver,  thus  causing  solution  of  the  red  blood  corpuscles  by  the 
absorbed  bile ;  and  very  soon  thereafter  haemoglobin  appears  in  the  urine.  [This  fact  is  of  practical 
importance,  as  duodenitis  may  give  rise  to  symptoms  of  jaundice,  the  resistance  of  the  inflamed 
mucous  membrane  being  sufficient  to  arrest  the  outflow  of  bile.] 

Passage  of  Substances  into  the  Bile. —  Some  substances  which  enter  the  blood  pass  into  the 
bile;  especially  the  metals,  copper,  arsenic,  iron,  etc.;  potassium  iodide,  bromide,  and  sulphocyanide 
and  turpentine ;  to  a  less  degree,  cane  sugar  and  grape  sugar ;  sodium  sahcylate,  and  carbohc  acid. 
If  a  large  amount  of  water  be  injected  into  the  blood,  the  bile  becomes  albuminous ;  mercuric  and 
mercurous  chlorides  cause  an  increase  of  the  water  of  the  bile.  Sugar  has  been  found  in  the  bile  in 
diabetes ;  leucin  and  tyrosin  in  typhus,  lactic  acid  and  albumin  in  other  pathological  conditions  of  this 
fluid. 

180.  REABSORPTION  OF  BILE;  JAUNDICE.— I.  Absorption  Jaundice.— When 
resistance  is  offered  to  the  outflow  of  bile  into  the  intestine,  e.  g.,  by  a  plug  of  mucus,  or  a  gall  stone 
which  occludes  the  bile  duct,  or  where  a  tumor  or  pressure  from  without  makes  it  impervious — the 
bile  ducts  become  filled  with  bile  and  cause  an  enlargement  of  the  liver.  The  pressure  within  the 
bile  ducts  is  increased.  As  soon  as  the  pressure  has  reached  a  certain  amount,  which  it  soon  does 
when  the  bile  duct  is  occluded  (in  the  dog  275  mm.  of  a  column  of  bile),  reabsorption  of  bile  from 
the  distended  larger  bile  ducts  takes  place  into  the  lymphatics  (not  the  blood  vessels)  of  the  liver,  the 
bile  acids  pass  into  the  lymphatics  of  the  liver.  [The  lymphatics  can  be  seen  at  the  portal  fissure 
filled  with  yellow-colored  lymph.]  The  lymph  passes  into  the  thoracic  duct,  and  so  into  the  blood 
(yFleischl).  Even  when  the  pressure  is  very  low  within  the  portal  vein,  bile  may  pass  into  the  blood 
without  any  obstruction  to  the  bile  duct  being  present.  This  is  the  case  in  Icterus  neonatorum,  as 
after  ligature  of  the  umbilical  cord  no  more  blood  passes  through  the  umbilical  vein ;  further,  in  the 
icterus  of  hunger,  "  hunger  jaundice"  as  the  portal  vein  is  relatively  empty,  owing  to  the  feeble 
absorption  from  the  intestinal  canal  (C/.  Bernard). 

II.  Cholsemia  may  also  occur,  owing  to  the  excessive  production  of  bile  (hypercholia),  the  bile 
not  being  all  excreted  into  the  intestine,  so  that  part  of  it  is  reabsorbed.  This  takes  place  when  there 
is  solution  of  a  great  number  of  blood  corpsucles  (^  178,  6),  which  yield  material  for  the  formation  of 
bile.  Thick,  inspissated  bile  accumulates  in  the  bile  ducts,  so  that  stagnation,  with  subsequent 
reabsorption  of  the  bile,  takes  place.  The  tranfusion  of  heterogeneous  blood  obtained  by  dissolving 
colored  blood  corpuscles  acts  in  this  direction.  Icterus  is  a  common  phenomenon  after  too  copious 
transfiision  of  the  same  blood.  The  blood  corpuscles  are  dissolved  by  the  injection  into  the  blood  of 
heterogeneous  blood  serum,  by  the  injection  of  bile  acids  into  the  vessels,  and  by  other  salts,  by 


318  REABSORPTION    OF    BILE;    JAUNDICE. 

phosphoric  acid,  water,  chloral,  inhalation  of  chloroform  and  ether;  the  injection  of  dissolved 
Lvni. vlol-in  into  thf  artcrios  or  into  a  loop  of  the  small  intestine  acts  m  the  same  way. 

Icterus  Neonatorum.— WhtM).  owinj,'  to  compression  of  the  placenta  withm  the  uterus,  too  much 
bUxxl  IS  fi.rced  into  the  l-lootl  vessels  of  the  newly-horn  infant,  a  part  of  the  surplus  blood  durmg  the 
fir.t  few  days  becomes  dissolved,  part  of  the  hemoglobin  is  converted  nito  bilirubin,  thus  causing 
iauiulice  (  I'irihow,  I'io/ft). 

Absorption  Jaundice.— When  the  jaundice  is  caused  by  the  absorption  of 
bile  already  formed  in  the  liver,  it  is  called  hepatogenic  or  absorption  jaundice. 
The  following  are  the  symptoms  : — 

(1)  Hile  pij^nents  and  bile  .acids  pxss  into  the  tissues  of  the  body;  hence,  the  most  pronounced 
external  symptom  is  the  yellowish  tint  o\  jaundice.  The  skin  and  the  sclerotic  become  deeply  colored 
yellow.     In  pregn.incy  the  fietus  is  also  tinged. 

(2)  Hile  pigments  aiid  bile  acids  pass  into  the  urine  (not  into  the  saliva,  tears,  or  mucus)  (^  177). 
When  there  is  much  bile  pigment,  the  urine  is  colored  a  deep  yellowish  brown,  and  its  froth  is  citron 
yellow  ;  while  strijjs  of  gelatin  or  paper  dipped  into  it  also  become  colored.  Occasionally  bilirubin 
(=  h.x-matoidin)  crystals  occur  in  the  urine  (<i  266). 

(3)  The  faeces  are  "  clay  colored'''  (because  the  hydrobilirubin  of  the  bile  is  absent  from  the  fecal 
matter) — very  hard  (because  the  fluid  of  the  bile  does  not  pass  into  the  intestine) ;  contain  much  fat 
(in  globules  and  crj-stals).  because  the  fat  is  not  sufficiently  digested  in  the  intestine  without  bile,  so 
that  78  per  cent,  of  the  fat  taken  with  the  food  reappears  in  the  f.eces  {v.  Foil) ;  they  have  a  very 
disiigreeaHe  odor,  because  the  bile  normally  greatly  limits  the  putrefaction  in  the  intestine.  [V.  Voit 
finds  that  putrefaction  does  not  take  place  if  fats  be  withheld  from  the  food.]  The  evaluation  of  the 
fu-ces  occurs  slo;i>ly,  partly  owing  to  the  hardness  of  the  f.vces,  partly  because  of  the  absence  of  the 
]>eristaltic  movements  of  the  intestine,  owing  to  the  want  of  the  stimulating  action  of  the  bile. 

(4)  The  heart  beats  are  greatly  diminished,  e.g.,  to  40  per  minute.  This  is  due  to  the  action  of 
the  bile  salts,  which  at  first  slimul.ate  the  cardiac  ganglia,  and  then  weaken  them  Bile  salts  injected 
into  the  heart  produce  at  first  a  lemix)rar)"  acceleration  of  the  pulse,  and  afterward  slowing  (R'ohrig). 
The  same  occurs  when  they  are  injected  into  the  blood,  but  in  this  case  the  stage  of  excitement  is 
ver>-  short.  The  jihenomenon  is  not  affected  by  section  of  the  vagi.  It  is  probable,  that  when  the 
action  of  the  bile  salts  is  long  continued,  they  act  upon  the  heart  nuiscle.  In  addition  to  the  action 
on  the  heart,  there  is  slowing  of  the  respiration  and  diminution  of  temperature. 

(5)  That  the  nervous  system,  and  perhaps  also  the  muscles,  are  affected,  either  by  the  bile  salts 
or  by  the  accumulation  of  cholesterin  in  the  blood,  is  shown  by  the  very  general  relaxation,  sensation 
of  fatigue,  weakness,  drowsiness,  and  lastly,  deep  coma — sometimes  there  is  sleeplessness,  itchiness  of 
the  skin,  even  mania,  and  spasms.  Luwit,  after  injecting  bile  into  animals,  observed  phenomena 
referable  to  stimulation  of  the  respirator)-,  cardio-inhibitory,  and  vasomotor  nerve  centres. 

(6)  In  very  pronounced  jaundice  there  may  be  '' yello7v  vision,''  owing  to  the  impregnation  of  the 
retina  and  macula  lutea  with  the  bile  pigment. 

(7)  The  bile  acids  in  the  blood  dissolve  the  red  blood  corpuscles.  The  haemoglobin  is  changed 
into  new  bile  pigment,  and  the  globulin-like  Ixidy  of  the  haemoglobin  may  form  urinary  cylinders  or 
casts  in  the  urin.ary  tui)ules,  which  are  ultimately  washed  out  of  the  tubules  by  the  urine. 

[Influence  of  Drugs  on  the  Secretion  of  Bile. — On  animals  one  may  make  either  a  perma- 
nent or  a  temiHirary  fistula.  Tlie  latter  is  the  more  satisfactory  method,  and  the  experiments  are 
u^ually  m.ide  on  fasting  curarized  dogs.  .\  suitable  cannula  is  introduced  into  the  common  bile  duct 
'  '■'g-  '971.  the  animal  is  curarized,  artificial  respiration  being  kept  up,  while  the  drug  is  injected  into 
the  stom.ach  or  intestine.  Rohrig  used  this  method,  which  was  improved  by  Rutherford  and  Vignal. 
Rohrig  found  that  some  purgatives,  croton  oil,  colocynth,  jalap,  aloes,  rhubarb,  senna,  and  other 
.substances,  increased  the  secretion  of  bile.  Rutherford  and  Vignal  investigated  the  action  of  a  large 
niimber  of  drugs  on  the  bile-secreting  mechanism.  They  found  that  croton  oil  is  a  feeble  hepatic 
stimulant,  while  jxKlophyllin.  aloes,  colchicum,  euonj-min,  iridin,  sanguinarin,  ipecacuan,  colocynth, 
sodium  phosphate,  phytolaccin,  sodium  benzoate,  sodium  salicylate,  dilute  nitro-hydrochloric  acid 
ammonium  phos,)hate,  mercuric  chloride  (corrosive  sublimate),  are  all  powerful,  or  very  considerable, 
hepatic  stimulants  Some  substances  stimulate  the  intestinal  glands,  but  not  the  liver,  e.  r.,  magnesium 
sulphate,  castor  oil,  gamboge,  ammonium  chloride,  manganese  sulphate,  calomel.  Other  substances 
stimulate  the  liver  as  well  as  the  intestinal  glands,  although  not  to  the  same  extent,  e.  -.,  scammony 
(powerful  intestinal,  feeble  hepatic  stimulam);  colocynth  excites  both  powerflillv;  jalap,  sodium 
sulphate,  and  baptism,  act  with  considerable  power  lx)th  on  the  liver  and  the  intestinal  glands. 
Calabar  l.ean  stimulates  the  liver,  and  the  increased  secretion  caused  thereby  may  be  reduced  by 
sulphate  of  atropin.  although  the  latter  drug,  when  given  alone,  does  not  notably  affect  the  secretion 

was  nroHn?.H  'IT  1     "  TV  T    "  "\'^^'^^'  '''?^'^''''  '^^  ^"'^^^''°"-      ^"  ^"  ^^^^  ^'^ere  purgation 

T'^^rtZlJir  -A  ■'fA''T^''T'  T^  "'  niagnesium  sulphate,  gamboge,  and  castor  oil, 
ofZTZ.ll  Itf,  7'"r  1  ^"  ^"  ^"^h  e^lf  i-^ents  it  is  most  important  that  the  temf^erature 
t^^LrZ^Lti^  Yi.  .K  V^%^^^'-,^''°"  °f  bile  diminishes.  Paschkis's  results  on  dogs  differ 
considerablj  fi^om  those  of  Rutherford  Me  asserts  that  only  the  bile  acids  (salts)  of  all  the  substances 
he  mvestigated  excite  a  prompt  and  distinct  cholagogue  action.]  suosiances 


FUNCTIONS    OF   THE    BILE.  319 

[As  yet  we  cannot  say  definitely  whether  or  not  these  substances  stimulate  the  secretion  of  bile, 
by  exciting  the  mucous  membrane  of  the  small  intestine,  and  thereby  inducing  reflex  excitement  of 
the  liver.  Their  action  does  not  seem  to  be  due  to  increase  of  the  blood  stream  through  the  liver. 
More  probably,  as  Rutherford  suggests,  these  drugs  act  directly  on  the  hepatic  cells  or  their  nerves. 
Acetate  of  lead  directly  depresses  the  biliary  secretion,  while  some  substances  affect  it  indirectly.] 

[Cholesteraemia. — Flint  ascribes  great  importance  to  the  excretion  of  cholesterin  by  the  bile,  with 
reference  to  the  metabolism  of  the  nervous  system.  Cholesterin,  which  is  a  normal  ingredient  of 
nervous  tissue,  is  excreted  by  the  bile;  and  if  it  be  retained  in  the  blood  "  cholesteroemia,"  with  grave 
nervous  symptoms,  is  said  to  occur.  This,  however,  is  problematical,  and  the  phenomena  described 
are  probably  referable  to  the  retention  of  the  bile  acids  in  the  blood.] 

i8i.  FUNCTIONS  OF  THE  BILE.— [(i)  Bile  is  concerned  in  the 
digestion  of  certain  food  stuffs;  (2)  part  is  absorbed;   (3)  part  is  excreted.] 

(A)  Bile  plays  an  important  part  in  the  absorption  of  fats  : — 

(i)  It  eniulsionizes  neutral  fats,  whereby  the  fatty  granules  pass  more  readily 
through  or  between  the  cylindrical  epithelium  of  the  small  intestine  into  the 
lacteals.  It  does  not  decompose  neutral  fats  into  glycerine  and  a  fatty  acid,  as 
the  pancreas  does  (§  170,  III). 

When,  however,  fatty  acids  are  dissolved  in  the  bile,  the  bile  salts  are  decomposed,  the  bile  acids 
being  set  free,  while  the  soda  of  the  decomposed  bile  salts  readily  forms  a  soluble  soap  with  the  fatty 
acids.  These  soaps  are  soluble  in  the  bile,  and  increase  considerably  the  emulsifying  power  of  this 
fluid.  Bile  can  dissolve  fatty  acids  to  form  an  acid  fluid,  which  has  high  emulsionizing  properties 
i^Steiner).     Emulsification  is  influenced  by  a  i  per  cent,  solution  of  NaCl,  or  Na^SO^. 

(2)  As  fluid  fat  flows  more  easily  through  capillary  tubes  moistened  with  bile,  it 
is  concluded  that  when  the  pores  of  the  wall  of  the  small  intestine  are  moistened 
with  bile,  the  fatty  particles  pass  more  easily  through  them. 

(3)  Filtration  of  fat  takes  place  through  a  membrane  moistened  with  bile  or  bile 
salts  under  less  pressure  than  when  it  is  moistened  with  water  or  salt  solution  {y. 
Wistinghausen) . 

(4)  As  bile,  like  a  solution  of  soap,  has  a  certain  relation  to  watery  solutions, 
as  well  as  to  fats,  it  permits  diffusion  to  take  place  between  these  two  fluids,  as  the 
membrane  is  moistened  by  both  fluids. 

It  is  clear,  therefore,  that  the  bile  is  of  great  importance  in  the  absorption  of  fats.  This  is  strikingly 
illustrated  by  experiments  on  animals,  in  which  the  bile  is  entirely  discharged  externally  through  a 
fistula.  Dogs,  under  these  conditions,  absorbed  at  most  40  per  cent,  of  the  fat  taken  with  the  food 
[60  per  cent,  being  given  off  by  the  faeces,  while  a  normal  dog  absorbs  99  per  cent,  of  the  fat].  The 
chyle  of  such  animals  is  very  poor  in  fat,  is  not  white  but  transparent ;  the  f^ces,  however,  contain 
much  fat,  and  are  oily ;  the  animals  have  a  ravenous  appetite ;  the  tissues  of  the  body  contain  little 
fat,  even  when  the  nutrition  of  the  animals  has  not  been  much  interfered  with.  Persons  suff"ering 
from  disturbances  of  the  biliary  secretion,  or  from  liver  affections,  ought,  therefore,  to  abstain  from 
fatty  food.  [The  digestion  of  flesh  and  gelatin  is  not  interfered  with  in  dogs  by  the  removal  of  the 
bile  [v.  Voit).'] 

(B)  Fresh  bile  contains  a  diastatic  ferment,  which  transforms  starch  into 
sugar,  and  also  glycogen  into  sugar. 

(C)  Bile  excites  contractions  of  the  muscular  coats  of  the  intestine,  and 
contributes  thereby  to  absorption. 

(i)  The  bile  acids  act  as  a  stimulus  to  the  muscles  of  the  villi,  which  contract  from  time  to 
time,  so  that  the  contents  of  the  origins  of  the  lacteals  are  emptied  toward  the  larger  lymphatics,  and 
the  villi  are  thus  in  a  position  to  absorb  more.  [The  villi  act  like  numerous  small  pumps,  and  expel 
their  contents,  which  are  prevented  from  returning  by  the  presence  of  valves  in  the  larger  lymphatics.] 

(2)  The  musculature  of  the  intestine  itself  seems  to  be  excited,  pei'haps  thi-ough  the  agency  of 
the  plexus  myentericus.  In  animals  with  a  biliary  fistula,  and  in  which  the  bile  duct  is  obstructed, 
the  intestinal  peristalsis  is  greatly  diminished,  while  the  salts  of  the  bile  acids  administered  by  the 
mouth  causes  diarrhoea  and  vomiting.  As  contraction  of  the  intestine  aids  absorption,  bile  is  also 
necessary  in  this  way  for  the  absorption  of  the  dissolved  food  stuffs. 

(D)  The  presence  of  bile  seems  to  be  necessary  to  the  vital  activity  of  the  intes- 
tinal epithelium  in  its  supposed  function  of  being  concerned  in  the  absorption  of 
fatty  particles  (§  190). 

(E)  Bile  moistens  the  wall  of  the  intestines,  and  gives  to  the  faeces  their  normal 


320  FATE   OF   THE    BILE. 

amount  of  water,  so  that  they  can  be  readily  evacuated.  Anirnals  with  biliary 
fistula,  or  persons  with  obstruction  of  the  bile  ducts,  are  very  costive.  The  mucus 
aids  the  forward  nvnement  of  the  ingesta  through  the  intestinal  canal.  [Thus,  in 
a  certain  sense,  bile  is  a  natural pur^^aiii'e.'\ 

(F)  The  bile  diminishes  i)utrefactive  decomposition  of  the  intestinal  contents, 
esjKJcially  with  a  fatty  diet,  §  190.  [Thus,  it  is  an  antiseptic,  although  this  is 
doubted  by  v.  Voit.] 

(G)  When  the  strongly  acid  contents  of  the  stomach  pass  into  the  duodenum, 
the  glycocholic  acid  is  ])recipitated  by  the  gastric  acid,  and  carries  the  pepsin  with 
it  (Burkart).  Some  of  the  albumin,  which  has  been  simply  dissolved  (but  not 
peptone  or  propeptone),  is  also  precipitated,  by  the  taurocholic  acid  {Maly  and 
Emiih).  The  bile  salts  are  decomposed  by  the  acid  of  the  gastric  juice.  When 
the  mixture  is  rendered  alkaline  by  the  pancreatic  juice  and  the  alkali  derived 
from  the  decomposition  of  the  bile  salts,  the  pancreatic  juice  acts  energetically  in 
this  alkaline  medium  i^Molescholt). 

[Taurocholic  .ncid  .iml  its  soda  salts  precipitate  alliuniin,  i)ut  not  peptone;  glycocholic  acid  does 
not  precipitate  albumin,  so  that  in  the  intestine  the  peptone  is  separated  from  the  albumin  (and 
s)Titonini.  and  m.iy  therefore  be  more  readily  absorbed,  while  the  precipitate  adhering  to  the  intestinal 
wall  can  Ik;  further  digested  {Maly  ami  Emith).  Taurocholic  acid  behaves  in  the  same  way  toward 
gelatin  ]H-ptone.] 

Bilious  Vomit. — When  bile  passes  into  the  stomach,  as  in  vomitittg,  the  acid  of  the  gastric  juice 
unites  with  the  b.ises  of  the  bile  salts;  scnlium  chloride  and  free  bile  acids  are  formed,  and  the  acid 
reaction  is  thereby  somewhat  iliminished.  The  bile  acids  cannot  carrv'  on  gastric  digestion;  the 
neutralization  alx)  causes  a  precipitation  of  the  jjepsin  and  mucin.  As  soon,  however,  as  the  walls  of  the 
stonunch  secrete  more  acid,  the  pejjsin  is  redissolved.  The  bile  which  passes  into  the  stomach 
deranges  ga.stric  <ligestion.  by  shriveling  the  proteids,  which  can  only  be  peptonized  when  they  are 
swollen  up  (J).  295). 

182.  FATE  OF  THE  BILE.— Some  of  the  biliary  constituents  are  com- 
pletely evacuated  with  tlie  Heces,  while  others  are  reabsorbed  by  the  intestinal 
walls. 

(i)  Mucin  passes  imchanged  into  the  faeces. 

(2<  The  bile  pigments  are  reduced,  and  are  partly  excreted  with  the  faeces 
as  hydrobilirubin,  and  partly  as  the  identical  end-product  urobilin  by  the 
urine  (§  177,  3^). 

From  meconium  hydrobilirubin  is  absent,  while  crystalline  bilirubin  and  l)iliverdin,  and  an 
unknown  rol  oxidation  product  of  them,  are  present  [bi'le  acids,  even  taurocholic,  and  small  trace 
of  Litty  acids]  \Z-.-fifel\,  .so  that  it  gives  (Jmelin's  reaction.  Hence,  no  reduction— but  rather  oxida- 
tion—processes  occur  in  the  futal  intestine.  [Composition.— Dar\-  gives  72.7  per  cent,  water, 
23.6  mucus  and  ci)ithelium,  I  per  cent,  fat  and  chole.sterin,  and  3  per 'cent,  bile  pi<Tments  Zweifel 
gives  79.78  per  cent  water,  and  solids  20.22  per  cent.  It  does  not  contain  lecithin,  but  so  much 
bilirubm  that  nopi>e-Seyler  uses  it  as  a  good  source  whence  to  obtain  this  pigment  It  gives  a 
spectrum  of  a  Uxly  rilati-<l  to  urobilin.] 

(3)  Cholesterin  is  given  off  with  the  faeces. 

( 4 )  The  bile  salts  are  for  the  most  part  reabsorbed  by  the  walls  of  the  jejunum 
and  ileum  to  be  re-employed  in  the  animal's  economv.  Tappeiner  found  them 
in  the  chyle  of  the  thoracic  duct— minute  quantities  pass  normally  from  the  blood 
into  the  urine.  Only  a  very  small  amount  of  glycocholic  acid  appears  unchanged 
m  the  fneces.  The  taurocholic  acid,  as  far  as  it  is  not  absorbed,  is  easily  decom- 
posed in  the  intestine,  by  the  putrefactive  processes,  into  cholalic  acid  and  taurin  : 
the  former  of  the.se  is  found  in  the  f^e.  es,  but  the  taurin  at  least  seems  not  to  be 
constantly  present.  Part  of  the  cholalic  acid  is  absorbed,  and  may  unite  in  the 
liver  either  with  glycin  or  taurin  CJfvm).  ^ 

(5)  The  fa.-ces  contain  mere  traces  of  lecithin. 

r.  ^!!?''''i[.*'**,l!^*"*'°."T'^'  ^'•■:'^'  ''^"^  °^  '^^  "^"^'  in.ix,rtant  biliar^•  constituents  the  bile  acids 
u^n  the  digestion  of  the  fats  tSg  ^i:::^^^^:;^ ^:^  of  tUtalrt 


THE    INTESTINAL   JUICE. 


321 


such  dogs  are  to  maintain  their  weight,  they  must  eat  twice  as  much  food.  In  such  cases,  carbo- 
hydrates most  beneticially  replace  the  fats.  If  the  digestive  apparatus  is  otherwise  intact,  the  animals, 
on  account  of  their  voracity,  may  even  increase  in  weight,  but  the  flesh  and  not  the  fat  is  increased. 

Bile  partly  an  Excretion. — The  fact  that  bile  is  secreted  during  the  foetal 
period,  while  none  of  the  other  digestive  fluids  is,  proves  that  it  is  an  excretion. 

The  cholalic  acid  which  is  reabsorbed  by  the  intestinal  walls  passes  into  the  body  and  seems  ulti- 
mately to  be  burned  to  form  CO2  and  Yijd.  The  glycin  (with  hippuric  acid)  forms  urea,  as  the 
urea  is  increased  after  the  injection  of  glycin.  The  fate  of  taurin  is  unknown.  When  large  quanti- 
ties are  introduced  into  the  human  stomach,  it  reappears  in  the  urine  as  tauro-carbamic  acid,  along 
with  a  small  quantity  of  unchanged  tamin.     \\Tien 

injected  subcutaneously  into  a  rabbit,  nearly  all  of  Yvc.  198. 

it  reappears  in  the  urine. 

[Practical. — In  practice  it  is  important  to  re-  v      v       v      v        v     v 

member  that  bile  once  in  the  intestine  is  liable  to 
be  absorbed  unless  it  be  carried  down  the  intestine ; 
hence,  it  is  one  thing  to  give  a  drug  which  will 
excite  the  secretion  of  bile,  i.  e.,  a  hepatic  stimu- 
lant, and  another  to  have  the  bile  so  secreted 
expelled.  It  is  wise,  therefore,  to  give  a  drug 
which  will  do  both,  or  at  least  to  combine  a  hepatic 
stimulant  with  one  which  will  stimulate  the  muscu- 
lature of  the  intestine  as  well.  Active  exercise,  -^-i 
whereby  the  diaphragm  is  vigorously  called  into 
action  to  compress  the  liver,  will  aid  in  the  expul- 
sion of  the  bile  from  the  liver  [Brun/on).^  B.< 

183.  THE  INTESTINAL  JXIICE,— 
Length  of  Intestine. — The  human  intestine  is 
ten  times  longer  than  the  length  of  the  body,  as 
measiued  from  the  vertex  to  the  anus.  It  is  longer 
comparatively  than  that  of  the  omnivora.  Its  mini- 
mum length  is  507,  its  maximum  1194  centimetres 
[17  to  35  feet]  ;  its  capacity  is  relatively  greater  in 
children  i^Beneke).  ,_ 

The  succus  entericus  is  the  digestive 
fluid  secreted  by  the  numerous  glands  of 
the  intestinal  mucous  membrane.  The 
largest  amount  is  produced  by  Lieber- 
kiihn's  glands,  while  in  the  duodenum 
there  is  added  the  scanty  secretion  of  Brunner's  glands. 

Brunner's  glands  are  small,  branched,  tubular  glands,  lying  in  the  sub-mucosa  of  the  duodenum. 
Their  fine  ducts  run  inward,  pierce  the  mucous  membrane,  and  open  at  the  bases  of  the  villi  (Fig. 
198).  The  acini  are  lined  by  cylindrical  cells,  like  those  lining  the  pyloric  glands.  In  fact,  Brunner's 
glands  are  structurally  and  anatomically  identical  with  the  pyloric  glands  of  the  stomach.  During 
hunger,  the  cells  are  turbid  and  small,  while  during  digestion  they  are  large  and  clear.  The  glands 
receive  nerve  fibres  from  Meissner's  plexus  {Drasch). 

I.  The  Secretion  of  Brunner's  Glands. — The  granular  contents  of  the 
secretory  cells  of  these  glands,  which  occur  singly  in  man,  but  form  a  continuous 
layer  in  the  duodenum  of  the  sheep,  \)fi\6.t?,proteids,  consist  of  mucin  and  z.  ferment 
substance  of  unknown  constitution.  The  watery  extract  of  the  glands  causes  (i) 
Solution  of  proteids  at  the  temperature  of  the  body  {Krolow).  (2)  It  also  has  a 
diastatic  action.  It  converts  maltose  into  glucose  {Brown  and  Heron).  It  does 
not  appear  to  act  upon  fats. 

On  account  of  the  smallness  of  the  objects,  such  experiments  are  only  made  with  great  difficulty, 
and,  therefore,  there  is  a  considerable  uncertainty  with  regard  to  the  action  of  the  secretion. 

Lieberkiihn's  glands  are  simply  tubular  glands  resembling  the  finger  of  a  glove  [or  a  test-tube], 
which  lie  closely  packed,  vertically  near  each  other,  in  the  mucous  membrane  (Fig.  199) ;  they  are 
most  numerous  in  the  large  intestine,  owing  to  the  absence  of  villi  in  this  region.  They  consist  of  a 
structureless  membrana  propria  lined  by  a  single  layer  of  low  cylindrical  epithelium,  between  which 
numerous  goblet  cells  occur,  the  goblet  cells  being  fewer  in  the  small  intestine  and  much  more  numer- 
ous in  the  large  (Fig.  199).     The  glands  of  the  small  intestine  yield  a  thin  secretion,  while  those  of 


Mucous 
coat. 


Muscu- 

laris 

mucosae. 

Sub- 
.  mucous 
coat. 


Muscular 
coat. 


Serous  coat. 

Vertical  section  of  duodenum  (cat),  X  3°.  E,  epithelium  ; 
c  and  /,  circular  and  longitudinal  muscular  fibres  ; 
L.g,  Lieberkiihn's  glands;  B.g,  Brunner's  glands, 
g,  ganglion  cells  ;  v,  villi. 


322 


LIEI3ERKUHN  S    GLANDS. 


the  large  intestine  yield  a  large  amount  of  sticky  mucus  from  their  gol)lct  cells  (AVose  and  Heiden- 
kain).  [In  n  vertical  section  of  the  small  intestine  they  lie  at  the  base  of  the  villi  (Fig.  198).  In 
transverse  section  they  are  shown  in  Fig.  200.] 

II.  The  Secretion  of  Lieberkuhn's  Glands,  from  the  duodenum  onward, 
is  the  chief  source  of  the  intotinal  juice. 

Intestinal  Fistula. — The  intestinal  juice  is  obtained  by  making  a  Thiry's  Fistula  (1864).  A 
loop  of  the  intestine  of  a  clog  is  pulled  forw.ird  (Fig.  20I,  l),  and  a  piece  about  4  inches  in  length  is 
cut  out,  so  that  the  continuity  of  the  intestinal  tube  is  broken,  Init  the  mesentery  and  its  blood  vessels 
are  not  <livided.  ( )nc  end  of  this  tube  is  clo.sed,  and  the  other  end  is  left  open  and  stitched  to  the 
aUlominal  wall  (Fig.  201,  3).  The  two  ends  of  the  intestine  from  wliicli  this  piece  was  taken  are 
l>rought  together  with  sutures,  so  as  to  establish  the  continuity  of  the  intestinal  canal  (Fig.  201,  2). 
The  excised  piece  of  intestine  yields  a  secretion  which  is  uncontaminated  with  any  other  digestive 


Fir..  19Q. 


Cavity 
of  the 
gland. 


Fig.  200. 


—   Crypt. 

Glandular 
epithelium. 

I'lood  vessel. 


TransvcHc  section  of  Lieberkiihn's  follicles. 


Fig.  201. 


Abd 


Abd 


Abd 


Abd 


Lieberkahn's  gland  from  the  large  intestine  (dog). 


Scheme  of  Thiry's  Fistula,    i,  2,  3,  4,  Vella's  Fistula.    AA'are 
stitched  together  ;  Ait/,  Abdominal  wall  (Stirling). 


secretion  [Thiry's  method  is  N-x;ry  unsatisfactory,  as  judged  from  the  action  of  the  separated  loop  in 
[^juTd".!;  i"Smration:r  ^"^  °""'  '^  '^^  '""""  "'"'''"'  '"^"'"^  ^'™P''^'  '^°"^  "'^^  '  °^ 

rlTr^^  ^^""'f.  "'f'^y  "  ""''".  °P^"'"^  '"  '^^  intestine,  through  which  he  introduces  two  small 
collapsed  md.a-rubber  balls,  one  above  and  the  other  below  the  opening,  which  are  then  distended  by 
mflatton  unt.I  they  comp leely  block  a  certain  length  of  the  intis'ine.^  The  loop  thus  blocked  off 
havmg  l>een  previously  well  wa.shed  out,  is  allowed  to  become  filled  with  succus,  wh  ch  is  ecretedvfn 
the  apphcation  of  vanous  st.muh.  By  means  of  Bernard's  gastric  cannula  (2  165)  'nserted  ntrthe 
fistula  m  the  loop,  the  secretion  can  be  removed  when  desired  1  ^  msenea  mio  tne 

^t'^'"*'^  ^■".'""^^--^l^"  the  belly  of  a  dog,  and  pull  out  a  loop  (30  to  50  ctm  Ul  to  l^  feetl 

Ir^tin  SU  cTl  fenT  o^  tf  f  '  ^'°^^  ^"'  '^'°^^''  --^=^'''^h  the  cLSn'/y'^of  .h^reS  ol 
^Vh.^u       ■  r  •  ^  ^^^  '°°P  ""^  '"testme  into  the  wound  in  ihe  linea  alba  ( Fi^  201   4> 

a'ndtwtTpi^ir'eT       '"""^  ^"'^  '"^  '^  "  '^^^^  ^^^^^^^  ^"'^  "^^^-'  '^^'^'^"^  and  S  a^ip^e^; 


ACTIONS    OF    THE    INTESTINAL   JUICE.  323 

The  intestinal  juice  of  such  fistulse  flows  spontaneously  in  very  small  amount, 
and  is  increased  during  digestion ;  it  is  increased — especially  its  mucus — by 
mechanical,  chemical,  and  electrical  stimuli ;  at  the  same  time,  the  mucous  mem- 
brane becomes  red,  so  that  loo  centimetres  yield  13  to  18  grammes  of  this  juice 
in  an  hour  {Thiry).  The  juice  is  light  yellow,  opalescent,  thin,  strongly  alkaline, 
specific  gravity  loii,  evolves  CO2  when  an  acid  is  added;  it  contains  albumin, 
ferments,  and  mucin — especially  the  juice  of  the  large  intestine.  Its  composition 
is — water,  97,59;  proteids,  0.80;  other  organic  substances  ^  0.73 ;  salts,  0.88 
per  cent. ;  among  these,  sodium  carbonate,  0.32  to  0.34  per  cent. 

[The  intestinal  juice  obtained  by  Meade  Smith's  method  contained  only  0.39  per  cent,  of  organic 
matter,  and  in  this  respect  agreed  closely  with  the  juice  which  A.  Moreau  procured  by  dividing  the 
mesenteric  nerves  of  a  ligatured  loop  of  intestine.  The  secretion  of  the  large  intestine  is  much  more 
viscid  than  that  of  the  small  intestine,] 

Actions  of  Succus  Entericus. — It  is  most  active  in  the  dog,  and  in  other 
animals  it  is  more  or  less  inactive, 

(i)  It  is  less  diastatic  than  the  saliva  and  the  pancreatic  juice,  but  it  does  not 
form  maltose ;  while  the  juice  of  the  large  intestine  does  not  possess  this  property 
{Eichhorst). 

(2)  It  converts  maltose  into  grape  sugar.  It  seems,  therefore,  to  continue  the 
diastatic  action  of  saliva  (§  148)  and  pancreatic  juice  (§  170),  which  usually  form 
only  maltose. 

According  to  Bourquelot  this  action  is  due  to  the  intestinal  schizomycetes  and  not  to  the  intestinal 
juice  as  such,  the  saliva,  gastric  juice  or  invertin.  The  greater  part  of  the  maltose  appears,  however, 
to  be  absorbed  imchanged. 

(3)  Fibrin  is  slowly  (by  the  trypsin  and  pepsin — Kuhne)  peptoni-zed  {Thiry, 
Leube);  less  easily  albumin  {Masioff),  fresh  casein,  flesh  raw  or  cooked,  vegetable 
albumin  ;  probably  gelatin  also  is  changed  by  a  special  ferment  into  a  solution 
which  does  not  gelatinize  (^Eichhorst). 

(4)  Fats  are  only  partly  emulsionized  {Schijff^,2ind  afterward  decomposed  (  Vella). 

(5)  According  to  CI.  Bernard,  invertin  occurs  in  intestinal  juice  (this  ferment 
can  also  be  extracted  from  yeast).  It  causes  cane  sugar  (C12H22O11)  to  take  up 
water  (-f-  H^O),  and  converts  it  into  invert-sugar,  which  is  a  mixture  of  left- 
rotating  sugar  (laevulose,  CgHijOe)  and  of  grape  sugar  (dextrose,  CgHijOg).  Heat 
seems  to  be  absorbed  during  the  process. 

[Hoppe-Seyler  has  suggested  that  this  ferment  is  not  a  natural  product  of  the  body,  but  is  intro- 
duced from  without  with  the  food.  Matthew  Hay,  however,  finds  it  to  be  invariably  present  in  the 
small  intestine  of  the  foetus.  ] 

[Effect  of  Drugs. — The  subcutaneous  injection  of  pilocarpin  causes  the  mucous  membrane  of  a 
Vella's  fistula  to  be  congested,  when  a  strongly  alkaline,  opalescent,  watery,  and  shghtly  albuminous 
secretion  is  obtained.  This  secretion  produces  a  reducing  sugar,  converts  cane  sugar  into  invert-sugar, 
emulsifies  neutral  fats,  ultimately  spiriting  them  up,  peptonizes  proteids,  and  coagulates  milk,  even 
although  I  he  milk  be  alkaline.  The  juice  attacks  the  sarcous  substance  of  muscle  before  the  connective 
tissues — the  reverse  of  the  gastric  juice.  The  mucous  membrane  in  a  Vella's  fistula  does  not  atrophy. 
K.  B.  Lehmann  finds  that  the  succus  entericus  obtained  from  the  intestine  of  a  goat  by  a  Vella  fistula  has 
no  digestive  action.] 

The  Action  of  Nerves  on  the  secretion  of  the  intestinal  juice  ^ 

is  not  well  determined.  Section  or  stimulation  of  the  vagi  has  no 
apparent  effect;  while  extirpation  of  the  large  sympathetic  abdom- 
inal ganglia  causes  the  intestinal  canal  to  be  filled  with  a  watery  fluid, 
and  gives  rise  to  diarrhoea.  This  may  be  explained  by  the  paralysis  of 
the  vasomotor  nerves,  and  also  by  the  section  of  large  lymphatic  ves- 
sels during  the  operation,  whereby  absorption  is  interfered  with  and 
transudation  is  favored.  Moreau's  Experiment. — Moreau  placed 
four  ligatures  on  a  loop  of  intestine  at  equal  distances  fi-om  each  other 
(tig.  202).  The  ligatures  were  tied  so  that  three  loops  of  intestine 
were  shut  off.  The  nerves  (N)  to  the  middle  loop  were  divided,  and 
the  intestine  was  replaced  in  the  abdominal  cavity.  After  a  time.  Scheme  of  Moreau's  experiment 
a  very  small  amount  of  secretion,  or  none  at  all,  was  found  in  two  of 
the  ligatured  compartments  of  the  gut,  i.  e.,  in  those  with  the  nerves  and  blood  vessels  intact  (l,  3), 


324 


FERMENTATION    IN    THE    INTESTINE. 


hut  the  comiwrtineiil  (2)  whose  nerves  had  l>ecn  divided  contained  a  watery  secretion.  Perhaps  the 
secretion  which  iKCurs  after  section  of  the  inesenteiic  nerves  is  a  paralytic  secretion,  'llie  secretion 
of  the  intestinal  and  (,'astric  juices  is  diminished  in  man  in  certain  nervous  afiections  (hysteria,  hypo- 
chondria-si-,  and  various  cerebral  diseases) ;  while  in  other  conditions  these  .secretions  are  increased. 

Excretion  of  Drugs.— If  an  isolated  intestinal  fistula  he  made,  and  variousdrugs  administered,  the 
mucous  m.nii)rane  excretes  io<line,  bromine,  lithium,  sulphocyanides,  but  noi  potassium  ferrocyanide, 
arvnious  or  Imracic  acid,  or  iron  .salts. 

In  sucklings,  not  unfre<iuently  a  large  amount  of  acid  is  formed,  when  the  fungi  in  the  intestine 
.split  up  milk  sug.ir  or  grape  sugar  into  lactic  acid  (/.«</i^).  .Starch  changed  into  grape  .sugar  may 
undergo  the  same  abnormal  process;  hence,  infants  ought  not  to  be  fed  with  .starchy  food. 

[Fate  of  the  Ferments. — I.angley  is  of  opinion  that  the  digestive  ferments  are  destroyed  in  the 
intestinal  canal;  the  diastalic  fennent  of  saliva  is  destroyed  by  the  free  IICI  of  the  gastric  juice; 
pepsin  and  rennet  are  actetl  uixm  by  the  alkaline  salts  of  the  pancreatic  and  intestinal  juices,  and  by 
tr>i>sin;  while  the  dijistatic  and  i>eptic  ferments  of  the  pancre.as  disajjpear  under  the  intluence  of  the 
acid  ffrnuntalion  in  the  large  intestine.] 

184.  FERMENTATION  IN  THE  INTESTINE.— Those  processes 
whi<  h  are  to  be  regarded  as  fermentations  or  putrefactive  processes,  are  quite  dif- 
ferent from  tliose  caused  by  the  digestive  enzymes  or  ferments  just  considered. 
The  putrefactive  changes  are  connected  with  the  presence  of  lower  organisms, 
so-called  fermentation  or  putrefaction  producers ;  and  they  may  develop  in 
suitable  media  outside  the  body.  The  lowly  organisms  which  cause  the  intestinal 
fermentation  are  swallowed  with  the  food  and  drink,  and  also  with  the  saliva. 
When  they  are  introduced,  fermentation  and  putrefaction  begin,  and  gases  are 
ei'olvci. 

Intestinal  Gases. — During  the  whole  of  the  foetal  period,  until  birth, 
fermentation  cannot  occur;  hence  gases  are  never  present  in  the  intestine  of  the 
newly-born.  The  first  air  bubbles  pass  into  the  intestine  with  the  saliva  which  is 
swallowed,  even  before  food  has  been  taken.  The  germs  of  organisms  are  thus 
introduced  into  the  intestine,  and  give  rise  to  the  formation  of  gases.  The  evolu- 
tion of  intestinal  gases  goes  hand-in-hand  with  the  fermentations.  Air  is  also 
swallowed,  and  an  exchange  of  gases  takes  place  in  the  intestine,  so  that  the 
composition  of  the  intestinal  gases  depends  upon  various  conditions.  Kolbe  and 
Ruge  collected  the  gases  from  the  anus  of  a  man,  and  found  in  100  vols.  : — 


Food. 

CO,. 

H. 

CH4. 

N. 

HjS. 

Milk 

nesh,    .... 
Peas,     .... 

1 6.8 
12.4 
21.0 

43-3 
2.1 
4-0 

0.9 
275 
55-9 

38.3 

57-8 
18.9 

Quantity  not 
estimated. 

1.  Air  bubbles  are  swallowed  with  the  food.  The  O  is  rapidly  absorbed  in  the 
intestinal  tract,  so  that  in  the  lower  part  of  the  large  intestine,  even  traces 
of  O  are  absent.  In  exchange,  the  blood  vessels  in  the  intestinal  wall  give  off  CO, 
into  the  intestine,  so  that  part  of  the  CO^  in  the  intestine  is  driven  by  diffusion 
from  the  blood. 

2.  H,  CO-i,  NH3,  and  CH«  are  also  formed  from  the  intestinal  contents  by 
fermentation,  which  takes  place  even  in  the  small  intestine. 

Fungi.— The  chief  agents  in  the  prwluciion  of  fermentations,  ]nitrefaction  and  other  similar  decom- 
poMtions  are  undoubtedly  the  group  of  fungi  called  schizomycetes.  They  are  small  unicellular 
organisms  of  various  fonn.s— globular,  micrococcus  ;  short  rods,  bacterium';  long  rods,  bacillus  ; 
or  spiral  thread.s.  vibno,  spirillum,  spirochaeta  (Fig.  23).  The  mode  of  reproduction  is  by  division, 
and  they  may  either  remain  single  or  unite  to  form  colonies.  Each  organism  is  usually  capable  of  some 
degree  o  motion  1  hey  pro<iuce  profound  chemical  changes  in  the  fluids  or  media  in  which  they 
grow  and  multiply,  and  these  changes  depend  u,wn  the  vital  activity  of  their  protoplasm.  These 
minute  microscopic  organi.sms  take  certain  constituents  from  the  "  nutrient  fluids"  in  which  they  live, 
and  use  them  partly  for  building  up  their  own  tis-sues  and  partly  for  their  own  metabolism.  In  these 
FOces.ses,  some  of  the  suUtances  so  absorbed  and  a.ssimilated  undergo  chemical  changes,  mv^<,  ferments 
seem  thereby  to  l)e  produced,  which  in  their  turn  may  act  ujx^n  material  present  in  the  nutritive  fluid. 

1  hese  fungi  consist  of  a  capsule  enclosing  prolopla.smic  contents.    Many  of  them  are  provided  with 


FERMENTATION    OF    CARBOHYDRATES. 


325 


excessively  delicate  cilia,  by  means  of  whicli  they  move  about.  The  new  organisms,  produced  by  the 
division  of  pre-existing  ones,  sometimes  form  large  colonies  visible  to  the  naked  eye,  the  individual 
fungi  being  united  by  a  jelly-like  mass,  the  whole  constituting  zoogloea.  In  some  fungi,  reproduction 
takes  place  by  spores  ;  more  especially  when  the  nutrient  fluids  are  poor  in  nutritive  materials.  The 
bacteria  form  longer  rods  or  threads,  which  are  jointed,  and  in  each  joint  or  segment  small  (l— 2  fi), 
highly  refractive  globules  or  spores  are  developed  (Fig.  203,  7).  In  some  cases,  as  in  the  butpic  acid 
fermentation,  the  rods  become  fusifomi  before  spores  are  formed,  \^^len  the  envelope  of  the  mother 
cell  is  ruptured  or  destroyed,  the  spores  are  liberated,  and  if  they  fall  upon  or  into  a  suitable  medium, 
they  germinate  and  reproduce  organisms  similar  to  those  from  which  they  sprang.  The  process  of  spore 
production  is  illustrated  in  Fig.  203,  7,  8,  9,  and  in  i,  2,  3,  4  is  shown  the  process  of  germination 
in  the  butyric  acid  fungus.  The  spores  are  very  tenacious  of  life ;  they  may  be  dried,  when  they  resist 
death  for  a  veiy  long  time ;  some  of  them  are  killed  by  being  boiled.  Some  fungi  exhibit  their  vital 
activities  only  in  the  presence  of  O  (aerobes),  while  others  require  the  exclusion  of  O  (anaerobes, 
Pasteur).  According  to  the  products  of  their  action,  they  are  classified  as  follows :  Those  that  pro- 
duce fermentations  (zymogenic  schizomycetes)  ;  those  that  produce  pigments  (chromogenic) ; 
those  that  produce  disagreeable  odors,  as  dm-ing  putrefaction  (bromogenic) ;  and  those  that,  when 
introduced  into  the  living  tissues  of  other  organisms,  produce  pathological  conditions,  and  even  death 
(pathogenic).     All  these  different  kinds  occur  in  the  human  body. 

When  we  consider  that  numerous  fungi  are  introduced  into  the  intestinal  canal  with  the  food  and 
drink — that  the  temperature   and  other  conditions  within   this  tube  are  specially  favorable  for  their 

Fig.  203. 


V5r 


^.ot 


3  ^^ 


§4 
i 


A,  Bacterium  ace/i  in  the  form,  of  cocci  (i) ;  diplococci  (2);  short  rods  (3);  and  jointed  threads  (4,  5).  Bacillus 
butyricus  (i)  isolated  spore;  (2,3,4)  germinating  condition  of  the  spores;  (5,  6)  short  and  long  rods  ;  (7,8,9) 
formation  of  spores  within  a  cellular  fungus. 

development ;  that  there  also  they  meet  with  sufficient  pabulum  for  their  development  and  reproduction — 
we  cannot  wonder  that  a  rich  crop  of  these  organisms  is  met  with  in  the  intestine,  and  that  they  pro- 
duce there  numerous  fermentations. 

I.  Fermentation  of  Carbohydrates. — (i)Bacillus  acidi  lactici  consists  of 
biscuit-shaped  cells,  1.5-3  /^-  ^^  length,  arranged  in  groups  or  isolated.  They  split 
up  grape  sugar  into  lactic  acid ; 

I  grape  sugar  =  CgHiiOg  =  aCCgHgOa)  =  2  lactic  acid. 

Milk  sugar  (CijHjzOu)  can  be  split  up  by  the  same  ferment  causing  it  to  take  up 
H2O,  and  forming  2  molecules  of  grape  sugar,  2(C6Hi206),  which  are  again  split 
into  4  molecules  of  lactic  acid  4(C3H603). 

This  fungus  and  its  spores  occur  everywhere  in  the  atmosphere,  and  are  the  cause  of  the  spontaneous 
acidification  and  subsequent  coagulation  of  milk  (^  230). 

(2)  Bacillus  butyricus,  which  in  the  presence  of  starch  is  often  colored  blue 
by  iodine,  changes  lactic  acid  into  butyric  acid,  together  with  CO2  and  H  {Fraz- 
mowski). 

C^HgOs  =  1  butyric  acid. 
2(C3H602)  lactic  acid  =^  \  2(062)  =  2  carbon  dioxide. 

4H  ==  4  hydrogen. 


3l>6  FERMENTATION    OF    PROTEIDS. 

This  fungus  (Fig.  203,  B)  is  a  true  anxrohc,  and  grows  only  in  the  absence  of  O.  The  lactic  acid 
fungus  u-scs  O  very  largely,  and  is,  therefore,  its  natural  precursor.  The  butyric  acid  fermentation  is 
the  last  ch-ingc  undergone  by  many  carbohydrates,  especially  by  starch  and  inulin.  It  takes  place 
constantly  in  the  feces. 

(3)  Certain  micrococci  cause  alcohol  X.o  be  formed  from  carbohydrates.  The 
presence  of  yeast  may  cause  the  formation  of  alcohol  in  the  intestine,  and  in 
both  cases  also  from  milk  sugar,  which  first  becomes  changed  into  dextrose. 

(4)  Bacterium  aceti  (Fig.  203,  A)  converts  alcohol  into  acetic  acid  outside  the  body.  Alcohol 
(C,H,0)  4-  O  =  CjH^O  (Aldehyd)  +  II.p.  Acetic  acid  (QII^Oj)  is  formed  from  aldehyd  by 
oxidation.  .According  to  NSgeli,  the  same  fungus  causes  the  formation  of  a  small  amount  of  CO^  and 
H,0.  As  the  acetic  fermentation  is  arrested  at  35°  C,  this  fermentation  cannot  occur  in  the  intestine, 
and  the  acetic  acid,  which  is  constantly  found  in  the  faces,  must  be  derived  from  another  source. 
During  putrefaction  of  the  protcids,  with  exclusion  of  air,  acetic  acid  is  produced  {Nencki). 

(5)  Starch  and  cellulose  are  partly  dissolved  by  the  schizomycetes  (Bac. 
butyricus  and  Vibrio  rugula)  of  the  intestine.  If  cellulose  be  mixed  with  cloaca! 
mucus,  or  with  the  contents  of  the  intestine,  it  passes  into  a  saccharine  carbo- 
hydrate which  decomposes  into  equal  volumes  of  CO2  and  CH4  {^Hoppe-Seyler). 

(6)  P\mgi,  whose  nature  is  unknown,  can  partly  transform  starch  (?  and  cellu- 
lose) into  sugar. 

(7)  Others  produce  invertin.     Invertin  changes  cane  sugar  into  invert-sugar 

Fig.  204. 


Bacillut  tMbtilis.     1,  spore  ;  a,  3,  4,  its  germination ;  5,  6.  short  rods  ;  7,  jointed  thread,  with  the  formation  of  spores 
in  e.ich  segment ;  8,  short  rods,  some  of  them  containing  spores  ;  9,  spores  in  single  short  rods;  10,  fungus  with  a 


C§  183,  II,  5).      Cane  sugar,  Cj.H^^O.i  +  H,0  =  CeHi.Os  (Dextrose)  +  CeHj^Os 
(Lnevulose). 

II.  Fermentation  of  Fats  (§  251).  During  putrefaction,  organisms  of  an 
unknown  nature  cause  neutral  fats  to  take  up  water  and  split  into  glycerine  and 
their  corresponding  fatty  acid  (§  170).  Glycerine  is  capable  of  undergoing 
several  fermentations,  according  to  the  fungus  which  acts  upon  it  (§  251).  With 
a  neutral  reaction,  in  addition  to  succinic  acid,  a  number  of  fatty  acids,  H  and 
CO,,  are  formed. 

Fitz  found  that  the  hay  bacillus  (Bacillus  subtilis,  Fig.  204)  formed  alcohol  with  caproic,  butyric, 
and  acetic  acids;  in  other  cases,  especially  butylic  alcohol,  van  de  Velde  found  butyric,  lactic,  and 
traces  of  succinic  acid  with  CO5,  HjO,  N. 

The  fatty  acids,  especially  as  chalk  soaps,  form  an  excellent  material  for 
termentation  Calcium  formiate  mixed  with  cloacal  mucus  ferments  and  yields 
calcium  carbonate,  CO,  and   H  ;   calcium  acetate,  under  the  same  conditions. 


produces  calcium  carbonate,  CO.,  and  CH,  Among  the  oxy-acids,  we  are 
acnuainted  with  the  fermentations  of  lactic,  glycerinic,  malic,  tartaric,  and  citric 
acids. 

Accor^ng  to  Fitz^^^/.  ^«^  (in  combination  with  chalk)  produces  propionic  and  acetic  acids, 
CO,.  H,0.     Other  ferments  cause  the  formation  of  valerianic  acid.     Glycerinic  acid,  in  addition  to 


REACTIONS    FOR   INDOL.  327 

alcohol  and  succinic  acid,  yields  chiefly  acetic  acid ;  malic  acid  forms  succinic  and  acetic  acid.     The 
other  acids  above  enumerated  yield  somewhat  similar  products. 

III.  Fermentation  of  Proteids  (§  249). — The  undigested  proteids  and 
their  derivatives  appear  to  be  acted  upon  by  fungi.  Many  schizomycetes  (hay 
bacillus  and  Bac.  subtilis),  however,  can  produce  a  peptonizing  ferment.  We 
have  already  seen  that  pancreatic  digestion  acts  upon  the  proteids,  forming, 
among  other  products,  amido-acids,  leucin,  tyrosin,  and  other  bodies  (§  170, 
II).  Under  normal  conditions,  this  is  the  greatest  decomposition  produced  by 
the  pancreatic  juice.  The  putrefactive  fermentation  of  the  large  intestine  causes 
further  and  more  profound  decompositions.  Leucin  (CgHigNOj)  takes  up  two 
molecules  of  water  and  yields  valerianic  acid  (C5H10O2),  ammonia,  CO2  and 
2(112)  'i  glycin  behaves  in  a  similar  manner.  Tyrosin  (CgHuNOg)  is  decom- 
posed into  indol  (CgH^N),  which  is  constantly  present  in  the  intestine  along 
with  COjjHaO,!!.  If  O  be  present,  other  decompositions  take  place.  These 
putrefactive  products  are  absent  from  the  intestinal  canal  of  the  foetus  and  the 
newly-born.  During  the  putrefactive  decomposition  of  proteids,  CO2,  HjS,  H, 
and  CH4,  are  formed ;  the  same  result  is  obtained  by  boiling  them  with  alkalies. 
Gelatin,  under  the  same  conditions,  yields  much  leucin  and  ammonia,  CO2, 
acetic,  butyric,  and  valerianic  acids,  and  glycin.  Mucin  and  nuclein  undergo 
no  change.  Artificial  pancreatic  digestion  experiments  rapidly  tend  to  undergo 
putrefaction. 

The  substance  which  causes  the  peculiar  fecal  odor  is  produced  by  putrefaction,  but  its  nature  is 
not  known.  It  clings  so  firmly  to  indol  and  skatol  that  these  substances  were  formerly  regarded  as 
the  odorous  bodies,  but  when  they  are  prepared  pure  they  are  odorless  [Bayer). 

Among  the  solid  substances  in  the  large  intestine  formed  only  by  putrefaction  is 
indol  (CsHtN),  a  substance  which  is  also  formed  when  proteids  are  heated  with 
alkalies,  or  by  superheating  them  with  water  to  200°  C.  It  is  the  stage  preceding 
the  indican  in  the  urine.  If  the  products  of  the  digestion  of  the  proteids — the 
peptones — are  rapidly  absorbed,  there  is  only  a  slight  formation  of  indol ;  but 
when  absorption  is  slight,  and  putrefaction  of  the  products  of  pancreatic  diges- 
tion occurs,  much  indol  is  formed,  and  indican  appears  in  the  urine. 

Jaffe  found  much  indican  in  the  urine  in  strangulated  hernia,  and  when  the  small  intestine  was 
obstructed. 

Reactions  for  Indol. — Acidulate  strongly  with  HCl,  and  shake  vigorously  after  adding  a  few 
drops  of  turpentine.  If  there  be  an  intense  red  color,  the  pigment  is  removed  by  ether.  The  sub- 
stance which  is  formed  after  the  digestion  of  fibrin  by  trypsin,  and  which  gives  a  violet  color  with 
bromine  water  (§  170,  2),  can  be  removed  by  chloroform.  In  addition  to  the  last  pigment,  there  is  a 
second  one,  which  passes  over  during  distillation,  and  which  can  be  extracted  from  the  distillate  by 
ether.     Both  substances  seem  to  belong  to  the  indigo  group  [Krukenberg). 

A.  Bayer  prepared  indigo-blue  artificially  from  ortho-phenyl-propionic  acid,  by  boiling  it  with  dilute 
caustic  soda,  after  the  addition  of  a  little  grape  sugar.  He  obtained  indol  and  skatol  from  indigo- 
blue.  Hoppe-Seyler  found  that  on  feeding  rabbits  with  ortho-nitrophenyl -propionic  acid,  much 
indican  was  present  in  the  urine. 

Phenol  (CgHgO)  is  formed  during  putrefaction  in  the  intestine,  and  it  is  also 
formed  when  fibrin  and  pancreatic  juice  putrefy  outside  the  body,  while  Brieger 
found  it  constantly  in  the  faeces.  It  seems  to  be  increased  by  the  same  circum- 
stances that  increase  indol,  as  an  excess  of  indican  in  the  urine  is  accompanied  by 
an  increase  of  phenylsulphonic  acid  in  that  fluid  (§  262). 

From  putrefying  flesh  and  fibrin,  amido-phenylpropionic  acid  is  obtained,  as  a  decomposition  pro- 
duct of  tyrosin.  A  part  of  this  is  transformed  by  putrefactive  ferments  into  hydrocinnamic  acid 
(phenylpropionic  acid).  The  latter  is  completely  oxidized  in  the  body  into  benzoic  acid,  and  appears 
as  hippuric  acid  in  the  urine.  Thus  is  explained  the  formation  of  hippuric  acid  from  a  purely  albu- 
minous diet; 

Skatol  (C9H9N  =  methyl-indol)  is  a  constant  human  fecal  substance,  and  has 
been  prepared  artificially  by  Nencki  and  Secretan  from  egg  albumin,  by  allowing 


323  PROCESSES    IN    THE    LARGE    INTESTINE. 

it  to  putrefy  for  a  long  time  under  water.  It  also  appears  in  the  urine  as  a  sulphur 
compound.  The  excretin  of  human  fceces,  described  by  Marcet,  is  related  to 
cholcsterin,  but  its  history  and  constitution  are  unknown. 

According  to  Salkowski.  skntol  and  indol  arc  both  formed  from  a  common  substance  which  exists 
preformed  in  albumin,  and  which,  when  it  is  decomposed,  at  one  time  yields  more  indol,  at  another 
skatol,  nccordinj;  a.s  the  h>pothctical  "  indol  fungus,"   or  ''  skatol  fungus;'  is  the  more  abundant. 

It  is  of  the  Utmost  importance,  in  connection  with  the  processes  of  putrefaction, 
to  determine  whether  they  take  place  when  oxygen  is  excluded,  or  not.  When  O 
is  absent,  reductions  take  place  ;  oxy-acids  are  reduced  to  fatty  acids,  and  H,CH^ 
and  H,S  are  formed  :  while  the  H  may  produce  further  reductions.  If  O  be 
present,  the  nascent  H  separates  the  molecule  of  free  ordinary  oxygen  (=  O,) 
into  two  atoms  of  active  oxygen  (r=r  O).  Water  is  formed  on  the  one  hand, 
while  the  second  atom  of  O  is  a  powerful  oxidizing  agent  {Hoppe-Sey/er). 

It  is  remarkable  that  the  putrefactive  processes,  after  the  development  of  phenol,  indol,  skatol, 
crcsol.  phcnvlpropionic  and  phenylacctic  acids  are  subsequently  limited,  and  after  a  certain  concentra- 
tion is  rcacheii,  they  ccuse  altogether.  The  putrefactive  process  produces  antiseptic  substances  which 
kill  the  micro  orjjanisms,  so  we  may  assume  that  these  substances  limit  to  a  certain  extent  the  putrefac- 
tive processes  in  the  intestine. 

The  reaction  of  the  intestine  immediately  below  the  stomach  is  acid,  but  the 
pancreatic  and  intestinal  juices  cause  a  neutral  and  afterward  an  alkaline  reaction, 
which  obtains  along  the  whole  small  intestine.  In  the  large  intestine,  the  reaction 
is  generally  acid,  on  account  of  the  acid  fermentation  and  the  decomposition  of 
the  ingesta  and  the  fceces. 

185.  PROCESSES    IN    THE    LARGE    INTESTINE.— Within  the 

large  intestine,  the  fermentative  and  putrefactive  ])rocesses  are  certainly  more 
prominent  than  the  digestive  processes  proper,  as  only  a  very  small  amount  of  the 
intestinal  juice  is  found  in  it.  The  absorptive  function  of  the  large  intestine  is 
greater  than  its  secretory  function,  for  at  the  beginning  of  the  colon  its  contents 
are  thin  and  watery,  but  in  the  further  course  of  the  intestine  they  become  more 
solid.  Water  and  the  products  of  digestion  in  the  solution  are  not  the  only  sub- 
stances absorbed,  but  under  certain  circumstances,  unchanged  fluid  egg  albumin, 
milk  and  its  proteids,  flesh  juice,  solution  of  gelatin,  myosin  with  common  salt, 
may  also  be  absorbed.  Experiments  with  acid  albumin,  syntonin,  or  blood  serum 
gave  no  result.  Toxic  substances  are  certainly  absorbed  more  rapidly  than  from 
the  stornach.  [In  the  dog  the  secretion  of  the  large  intestine  has  no  digestive 
properties,  but  tats  are  absorbed  in  it.  Klug  and  Koreck  regard  its  Lieberkuhnian 
glands  not  as  secreting  but  as  absorbing  structures.]  The  fecal  matters  are 
formed  or  rather  shaped  in  the  lower  part  of  the  gut.  The  cKcum  of  many 
animals,  e. ,«,-.,  rabbit,  is  of  considerable  size,  and  in  it  fermentation  seems  to  occur 
with  considerable  energy,  giving  rise  to  an  acid  reaction.  In  man,  the  chief 
function  of  the  caecum  is  absorption,  as  is  shown  by  the  great  number  of  lymphat- 
ics m  Its  walls.  From  the  lower  part  of  the  small  intestine  and  the  csecum 
onward,  the  ingesta  assume  the  fecal  odor. 

The  amount  of  faeces  is  about  [5  oz.  or]  170  grms.  (60  to  250  grms.)  in 
twenty-four  hours ;  but  if  much  indigestible  food  be  taken,  it  may  be  as  much  as 
500  grms.  The  amount  is  less,  and  the  absolute  amount  of  solids  is  less,  after  a 
diet  of  flesh  and  albumin,  than  after  a  vegetable  diet.  The  fsces  are  rendered 
lighter  by  the  evolution  of  gases,  and  hence  they  float  in  water. 

The  consistence  depends  on  the  amount  of  water  present— usually  about  75 
per  cent  I  he  amount  of  water  depends  partly  on  the  food— pure  flesh  diet 
causes  relatively  dry  faeces,  while  substances  rich  in  sugar  yield  f^ces  with  a  rela- 
tively large  amount  of  water.  The  quantity  of  water  taken  has  no  effect  upon 
the  amount  of  water  in  the  faeces.  But  the  energy  of  the  peristalsis  has.  The 
more  energetic  the  peristalsis  is,  the  more  watery  the  faeces  are,  because  sufficient 


COMPOSITION    OF   THE    F^CES.  329 

time  is  not  allowed  for  absorption  of  the  fluid  from  the  ingesta.  Paralysis  of  the 
blood  and  lymph  vessels,  or  section  of  the  nerves,  leads  to  a  watery  condition  of 
the  faeces  (§  183"). 

The  reaction  is  often  acid,  in  consequence  of  lactic  acid  being  developed  from 
the  carbohydrates  of  the  food.  Numerous  other  acids  produced  by  putrefaction 
are  also  present  (§  184).  If  much  ammonia  be  formed  in  the  lower  part  of  the 
intestine,  a  neutral  or  even  alkaline  reaction  may  obtain.  A  copious  secretion  of 
mucus  favors  the  occurrence  of  a  neutral  reaction. 

The  odor,  which  is  stronger  after  a  flesh  diet  than  after  a  vegetable  diet,  is 
caused  by  some  fecal  products  of  putrefaction,  which  have  not  yet  been  isolated  ; 
also  by  volatile  fatty  acids  and  by  sulphuretted  hydrogen,  when  it  is  present. 

The  color  of  the  faeces  depends  upon  the  amount  of  altered  bile  pigments 
mixed  with  them,  whereby  a  bright  yellow  to  a  dark  brown  color  is  obtained. 

The  color  of  the  food  is  also  of  importance.  If  much  blood  be  present  in  the  food,  the  fseces  are 
almost  brownish- black,  from  hamatin  ;  green  vegetables  =  brownish-green,  from  chlorophyll ;  bones 
{dog)  =  white,  from  the  amount  of  lime  ;  preparations  of  iron  =^  black,  from  the  formation  of  sulphide 
of  iron. 

The  faeces  contain — 

(i)  The  unchanged  residue  of  animal  or  vegetable  tissues  used  as  food ;  hairs, 
horny  and  elastic  tissues ;  most  of  the  cellulose,  woody  fibres,  spiral  vessels  of 
vegetable  cells,  gums. 

(2)  Portions  of  digestible  substances,  especially  when  these  have  been  taken  in 
too  large  amount,  or  when  they  have  not  been  sufficiently  broken  up  by  chewing. 
Portions  of  muscular  fibres,  ham,  tendon,  cartilage,  particles  of  fat,  coagulated 
albumin — vegetable  cells  from  potatoes,  and  other  vegetables,  raw  starch,  etc. 

All  food  yields  a  certain  amount  of  residue — white  bread,  3.7  per  cent. ;  rice,  4. 1  per  cent. ;  flesh, 
4.7  per  cent. ;  potatoes,  9.4  per  cent. ;  cabbage,  14.9  per  cent.  ;  black  bread,  15  per  cent. ;  yellow 
turnip,  20.7  per  cent.  {Rubner). 

(3)  The  decomposition  products  of  the  bile  pigments,  which  do  not  now  give 
Gmelin's  reaction  ;  as  well  as  the  altered  bile  acids  (§  177,  2).  This  reaction, 
however,  may  be  obtained  in  pathological  stools,  especially  in  those  of  a  green 
color;  unaltered  bilirubin,  biliverdin,  glycocholic  and  taurocholic  acids  occur  in 
meconium  (§  182). 

[MacMunn  found  no  unchanged  bile  pigments  in  the  fseces.  A  substance  called  stercobilin  is 
obtained  from  the  fseces,  and  it  closely  resembles  what  has  been  called  "  febrile  "  urobiUn,  but  it  is 
certainly  different  from  normal  urobilin.] 

(4)  Unchanged  mucin  and  nuclein — the  latter  occasionally  after  a  diet  of  bread, 
together  with  partially  disintegrated  cylindrical  epithelium  from  the  intestinal 
canal,  and  occasionally  drops  of  oil.  Cholesterin  is  very  rare.  [Ten  grains  of  a 
substance,  stercorin,  said  to  be  a  modification  of  cholesterin,  occur  in  the  faeces, 
{Flint).'\  The  less  the  mucus  is  mixed  with  the  faeces,  the  lower  the  part  of  the 
intestine  from  which  it  was  derived  {JVofhnagel). 

(5)  After  a  milk  diet,  and  also  after  a  fatty  diet,  crystalline  needles  of  lime 
combined  with  fatty  acids  and  chalk  soaps  constantly  occur,  even  in  sucklings 
{Wegscheider).  Even  unchanged  masses  of  casein  and  fat  occur  during  the  milk 
cure.  Compounds  of  ammonia,  with  the  acids  mentioned  as  the  result  of  putre- 
faction (§  184,  III),  belong  to  the  fecal  matters  {Brieger). 

(6)  Among  inorganic  residues,  soluble  salts  rarely  occur  in  the  faeces  because 
they  diffuse  readily,  e.  g.,  common  salt,  and  the  other  alkaline  chlorides,  the  com- 
pounds of  phosphoric  acid,  and  some  of  those  of  sulphuric  acid.  The  insoluble 
compounds  of  which  ammoniaco-magnesic  or  triple  phosphate,  neutral  calcic 
phosphate,  yellow-colored  lime  salts,  calcium  carbonate,  and  magnesium  phos- 
phate are  the  chief,  form  70  per  cent,  of  the  ash.  Some  of  these  insoluble  sub- 
stances are   derived   from  the  food,  as  lime  from  bones,  and  in  part  they  are 


330 


COMPOSITION    OF   THE    F^CES. 


excreted  after  the  food  has  been  digested,  as  ashes  are  eliminated  from  food  which 
has  been  burned. 

Concretions  —The  excretion  of  inorganic  substances  is  sometimes  so  great,  that  they  form  incrus- 
UUons  around  other  fecal  matters.  L'sually  ammoniaco-magnesic  phosphate  occurs  in  large  crystals 
by  itself,  or  it  may  l>c  mixc<l  with  magnesium  phosphate. 

(7)  Micro-organisms. — A  considerable  portion  of  normal  fecal  matter  con- 
sists of  micrococci  and  micro-bacteria  ;  yeast  is  seldom  absent  {Frerichs,  Noih- 
nagel). 

To  i.solatc  the  individual  fungi.  Escherich  has  made  pure  cultivations  from  the  mtestmal  contents 
of  sucklings,  and  Hienstock  from  .idults.  In  the  intestine  of  sucklings  which  have  been  nourished 
entirely  on  their  mother's  milk,  the  Bacterium  Uutis  aerogenes  (Fig.  205,  2)  causes  the  lactic  acid 
fermentation  with  the  evolution  of  CO,  and  II,  in  the  upper  part  of  the  canal  where  some  milk  sugar 
is  still  unal>sorl)cd.  In  the  evacuations  is  the  characteristic  slender  Bacterium  coli  commune  (Fig. 
205,  I).     In  addition,  occasionally  there  are  other  Ijacilli,  cocci,  spores  of  yeast,  and  a  mould. 


Fig.  205. 


0 1  / 


6 


} 


Vk^ 


I,  Bacterium  coli  commune;  2,  bacterium  laclis  aerogenes  ;  3  and  4,  the  large  bacilli  of  Bienstock,  with  partial  endo- 
genous spore  formation  :  5,  the  various  stages  in  the  development  of  the  bacillus  which  causes  the  fermentation 
of  albumin. 

In  the  faeces  of  an  adult.  Bienstock  detected  two  large  forms  of  bacilli  (Fig.  205,  3,  4),  closely 
resembling  Bacillus  subtilis  in  form  and  size,  but  distinguished  from  it  only  by  the  form  of  its  pure 
cultivation,  by  the  mode  of  growth  of  its  spores,  and  by  the  absence  of  movements.  These  two  forms 
can  \tc  di.>itinguished  microscopically  by  the  mode  of  their  cultivation,  which  is  either  in  the  form  of  a 
grape  or  a  (1at  membrane.  These  two  do  not  excite  a  fermentative  action.  A  third  micrococcus-like, 
small,  ver)'  slowly  developing  bacillus  occurs  in  three-fourths  of  all  stools.  A  fourth  kind  ( absent  in 
sucklings)  is  the  specific  bacillus  (>,_  184,  III),  causing  the  decomposition  of  albumin,  resulting  in  the 
products  of  putrefaction  and  a  fecal  odor.  This  is  the  only  bacillus  that  excites  these  processes  in  the 
intestine;  but  it  does  not  decompose  casein  and  alkali  albumin.  In  Fig.  205,  5,  a-g,  the  stages  in  the 
development  of  this  bacillus  are  represented,  but  the  stages  from  c  and^  are  absent  in  the  faeces,  and 
are  found  only  in  artificial  cultivations. 

If  the  f.tces  are  simply  investigated  microscopically  and  without  special  precautions,  there  are  other 
fungi,  some  of  which  may  l)e  introduced  through  the  anus.  In  stools  that  contain  much  starch,  the 
bacillus  but)Ticus,  which  is  tinged  blue  with  iodine,  occurs  (^  184),  and  other  small  globular  or  rod- 
like fungi,  which  give  a  similar  reaction  {Nothnagel,  Uffelmann). 

The  changes  of  the  intestinal  contents  have  been  studied  on  persons  with  an  accidental  intestinal 
fistula,  or  an  artificial  anus. 

[The  follow  ing  scheme  from  Krukenberg  shows  graphically  the  reaction  of  the  contents  of  the  various 
parts  of  the  alimcntan,-  canal,  and  also  the  distribution  of  the  ferments.] 


.  \  / 


1    /■      \ 

•v..        ■" 

"•-..  J. 

•C^ 

MOUTH  i   (IS0PH*Gu3 

STOMACH 

SMALL    INTESTINE 
ALKtUHE 

URGE    INTESTItiE 
ALKALIHE 

Amylol/tic   ferment 

Hilk  coiiulat'ng  ferment 

Peptin 

Trypsin 

Bacttrit 


PATHOLOGICAL   VARIATIONS    OF    DIGESTION.  331 

i86.  PATHOLOGICAL  VARIATIONS.— A.  The  taking  of  food  may  be  interfered  with 
by  spasm  of  the  muscles  of  mastication  (usually  accompanied  by  general  spasms),  stricture  of  the  ceso- 
phagus,  by  cicatrices  after  swallowing  caustic  fluids  [e.g.,  caustic  potash,  mineral  acids),  or  by  the 
presence  of  a  tumor,  such  as  cancer.  Inflammation  of  all  kinds  in  the  mouth  or  pharynx  interferes  with 
the  taking  of  food.  Inability  to  swallow  occurs  as  part  of  the  general  phenomena  in  disease  of  the 
medulla  oblongata,  in  consequence  of  paralysis  of  the  motor  centre  (superior  olives)  for  the  facial,  vagus, 
and  hypoglossal  nerves,  and  also  for  the  afferent  or  sensory  fibres  of  the  glosso-phar^iigeal,  vagus,  and 
trigeminus.  Stimulation  or  abnormal  excitation  of  these  parts  causes  spasmodic  swallowing,  and  the 
disagreeable  feeling  of  a  constriction  in  the  neck  (globus  hystericus). 

B.  The  secretion  of  saliva  is  diminished  during  inflammation  of  the  salivary  glands ;  occlusion 
of  their  ducts  by  concretions  (salivary  calculi) ;  also  by  the  use  of  atropin,  daturin,  and  during  fever, 
whereby  the  secretory  (not  the  vasomotor)  fibres  of  the  chorda  appear  to  be  paralyzed  ( ^  145  ).  When 
the  fever  is  very  high,  no  saliva  is  secreted.  The  saliva  secreted  during  moderate  fever  is  turbid  and 
thick,  and  usually  acid.  As  the  fever  increases,  the  diastatic  action  of  the  saliva  diminishes.  The 
secretion  is  increased  by  stimulation  of  the  buccal  nerves  (inflammation,  ulceration,  trigeminal  neu- 
ralgia), so  that  the  saliva  is  secreted  in  great  quantity.  Mercmy-  and  jaborandi  cause  secretion  of  saliva, 
the  former  causing  stomatitis,  which  excites  the  secretion  of  saliva  reflexly.  Even  diseases  of  the  stomach 
accompanied  by  vomiting  cause  secretion  of  saliva.  A  very  thick,  tenacious,  sympathetic  saliva  occurs 
when  there  is  violent  stimulation  of  the  vascular  system  during  sexual  excitement,  and  also  during  cer- 
tain psychical  conditions.  The  reaction  of  the  saliva  is  acid  in  catarrh  of  the  mouth,  in  fever  in 
consequence  of  decomposition  of  the  buccal  epithelium,  and  in  diabetes  mellitus  in  consequence  of 
acid  fermentation  of  the  saliva  which  contains  sugar.  Hence,  diabetic  persons  often  suffer  fi-om 
carious  teeth.  Unless  the  mouth  of  an  infant  be  kept  scrupulously  clean,  the  saliva  is  apt  to  become 
acid. 

C.  Disturbances  in  the  activity  of  the  musculature  of  the  stomach  may  be  due  to  paralysis 
of  the  muscular  layers,  whereby  the  stomach  becomes  distended,  and  the  ingesta  remain  a  long 
time  in  it.  A  special  form  of  paralysis  of  the  stomach  is  due  to  non-closure  of  the  pylorus 
[Ebsiein].  This  may  be  due  to  disturbances  of  innervation  of  a  central  or  peripheral  nature,  or 
there  may  be  actual  paralysis  of  the  pyloric  sphincter,  or  anaesthesia  of  the  pyloric  mucous  mem- 
brane, which  acts  reflexly  upon  the  sphincter  muscle;  and  lastly,  it  may  be  due  to  the  reflex 
impulse  not  being  transferred  to  the  efferent  fibre  within  the  nerve  centre.  Abnormal  activity 
of  the  gastric  musculature  hastens  the  passage  of  the  ingesta  into  the  intestine;  vomiting  often 
occurs. 

D.  Gastric  digestion  is  delayed  by  violent  bodily  or  mental  exercise,  and  sometimes  it  is  arrested 
altogether.  Sudden  mental  excitement  may  have  the  same  effect.  These  efforts  are  very  probably 
caused  through  the  vasomotor  nei-ves  of  the  stomach.  Feeble  and  imperfect  digestion  may  be  of  a 
purely  nervous  nature  (Dyspepsia  nervosa — Letibe  ;  Nevirasthenia  gastrica — [Burkart).  An  excessive 
formation  of  acid  may  be  due  to  nervous  disturbance,  and  is  called  "nervous  gastroxynsis "  by  Ross- 
bach. 

[Action  of  Alcohol,  Tea,  etc.,  in  Digestion. — According  to  J.  W.  Fraser,  all  infused  beverages, 
tea,  coffee,  cocoa,  retard  the  peptic  digestion  of  proteids,  with  few  exceptions.  The  retarding  action  is 
less  with  coffee  than  with  tea.  The  tannic  acid  and  volatile  oil  seem  to  be  the  retarding  ingredients 
in  teas.  Distilled  Spirits — brandy,  whisky,  gin — have  but  a  trifling  retarding  effect  on  the  digestive 
processes ;  and  when  one  considers  their  action  on  the  secretory  glands,  it  follows  that  in  moderate 
dietetic  doses  they  promote  digestion.  Wines  are  highly  inimical  to  salivary  digestion,  but  this  is  due  to 
their  acidity ;  and  this  effect  can  be  removed  by  the  addition  of  an  alkali.  Wines  retard  peptic 
digestion,  the  sparkling  less  than  the  still  wines.  Tea  has  an  intensely  inhibitory  action  on  salivary 
digestion ;  in  fact  a  small  quantity  paralyzes  the  action  of  saliva,  while  coffee  has  only  a  slight  effect. 
This  action  of  tea  is  due  to  the  tannin.  Tea,  coffee,  and  cocoa  all  retard  peptic  digestion,  when  they 
form  20  per  cent,  of  the  digestive  mixture  (  W.  Roberts)  P^ 

Inflammatory  or  catarrhal  affections  of  the  stomach,  as  well  as  ulceration  and  new  formations, 
interfere  with  digestion,  and  the  same  result  is  caused  by  eating  too  much  food  which  is  difficult  of 
digestion,  or  taking  too  much  highly  spiced  sauce  or  alcohol.  In  the  case  of  a  dog  suffering  from 
chronic  gastric  catarrh,  Griitzner  observed  that  the  secretion  took  place  continuously,  and  that  the  gas- 
tric juice  contained  little  pepsin,  was  turbid,  sticky,  feebly  acid,  and  even  alkaline.  The  introduction 
of  food  did  not  alter  the  secretion,  so  that  in  this  condition  the  stomach  really  obtains  no  rest.  The 
chief  cells  of  the  gastric  glands  were  tiu-bid.  Hence,  in  gastric  catarrh,  we  ought  to  eat  frequently,  but 
take  little  at  a  time,  while  at  the  same  time  dilute  hydrochloric  acid  ought  to  be  administered  (0.4  per 
cent.).     Small  doses  of  common  salt  seem  to  aid  digestion. 

[Absence  of  HCl. — HCl  is  almost  always  absent  in  carcinoma  of  the  stomach  {van  de  Vetde), 
amyloid  degeneration  of  the  gastric  mucous  membrane  {Edinger),  and  sometimes  in  fever.  In  all 
these  cases  the  acid  reaction  is  due  to  lactic  or  butyric  acid.  The  absence  of  HCl  in  cancer  of  the 
stomach  is  an  important  diagnostic  and  prognostic  symptom.  It  is  not  absent  in  simple  dilatation  of 
the  stomach.  Test  the  contents  of  the  stomach  for  free  HCl  with  tropseolin  (red  colon,  methyl  violet 
(blue),,  and  with  ferric  chloride  and  carbolic  acid  ( Uffelmann).     ^V  P^"^  cent,  of  free  HCl  causes  the 


332  PATHOLOGICAL   VARIATIONS   OF   DIGESTION. 

aniclhvst  l.luc  of  ihe  last  to  »)CCome  steel  Rray.  %vhile  somewhat  more  discharges  the  color  altogether, 
r  In  tcMinc  for  the  nrcsc-nce  of  free  lactic  acid  in  the  gastric  contents  use  L  t  elmann  s  reaction  ( ^,  163). 
■Vhe  lactic  acid  is  casilv  eMracled  by  ether  from  the  gastric  contents  and  the  reaction  can  then  he 
,x-rfoniud  with  the  residue  obtained  after  evaiH.raling  the  ether.  A  solution  of  I  drop  of  the  liquor 
pcrchloride  in  50  c.  c.  of  water  is  made  yellow  l.y  lactic  acid.]  .    ,  ,     . 

Feeble  digestion  mav  U-  caused  either  by  imperfect  formation  of  acid  or  pepsin,  so  that  both 
sulMances  mav  W  a.lminiitered  in  such  a  condition.  [It  may  also  be  due  to dehcient  muscular  power 
in  the  wall  of  the  stomach.]  In  other  cases,  lactic,  butyric,  and  acetic  acids  are  formed,  owing  to  the 
presence  of  lowlv  organi.sms.  In  such  cases,  small  doses  of  salicylic  acid,  together  with  some  hydro- 
chloric acid  are  u.seful.  I'epsin  need  not  he  given  often,  as  it  is  rarely  absent,  even  from  the  diseased 
Rastric  mucous  memi)rane.   Albumin  has  been  found  in  the  gastric  juice  in  cases  of  gastric  catarrh  and 

cholera.  .  r    » 1     •     c-^ 

E.  Digestion  during  fever  and  Anaemia.— lieaumont  found  that  in  the  ca.se  of  Alexis  bt. 
Martin,  when  fever  occurre.l.  a  small  amount  of  gastric  juice  was  secreted;  the  mucous  membrane 
was  dr>-.  red.  and  irritable.  Dogs  sulTering  from  septicemic  fever,  or  rendered  anemic  by  great  loss 
of  blood,  secrete  gastric  juice  of  feeble  digestive  iwwer  and  containing  little  acid  {Manassein).  [In 
acute  diseases  accompanied  by  fever,  the  inner  cells  of  the  fundus  glands  of  the  human  stomach  may 
di.sappcar  (C.  h'upffer).']  Hoppe-Seyler  investigated  the  gastric  juice  of  a  typhus  patient  in  which 
van  de  Velde  found  no  free  acid.  Usually  no  free  hydrochloric  acid  is  found  in  cancer  of  the  stomach. 
The  ga-stric  juice  of  the  tv-jihus  patient  did  not  digest  artificially,  even  after  the  addition  of  hydrochloric 
acid.  The  diminution  of  acid,  under  these  circumstances,  favors  the  occurrence  of  a  neutral  reaction, 
so  that,  on  the  one  hand,  digestion  cannot  proceed,  and  on  the  other,  fermentative  processes  (lactic  and 
Imtyric  acid  fermentations  with  the  evolution  of  gases)  occur.  These  results  are  a,ssociated  with  the 
presence  of  micro-organisms  and  Sarcina  veutriciili  (GoocJsir).  Ufl'elmann  found  that  the  secretion 
of  a  j>eptone- forming  gastric  juice  cexsed  in  fever,  when  the  fever  is  severe  at  the  outset,  when  a  feeble 
condition  occurs,  or  when  the  temper.iture  is  very  high.  The  amount  of  juice  secreted  is  certainly 
diminished  during  fever.  The  excitability  of  the  mucous  membrane  is  increased,  so  that  vomiting 
readily  occurs.  The  increased  excitability  of  the  vasomotor  nerves  during  fever  is  disadvantageous 
for  the  secretion  of  the  digestive  fluids  \,Ueiiienhain').  Beaumont  observed  that  fluids  are  rapidly 
alisorlied  from  the  stomach  during  fever,  but  the  ab.sorption  of  peptones  is  diminished  on  account  of  the 
accompanying  catairhal  condition  of  the  stomach,  and  the  altered  functional  activity  of  the  muscular 
mucos,e  ( Leube). 

Many  salts,  when  given  in  lar^e  amount,  disturb  gastric  digestion,  e.  <^.,  the  sulphates.  While  the 
alkaloids,  morphia,  strychnia,  digitalin,  narcotin,  veratria  have  a  similar  action,  quinine  favors  it 
( IVolberg).  In  some  nervous  individuals  "  p>eristaltic  unrest  of  the  stomach,"  conjoined  with  a  dys- 
peptic condition,  occurs  (A'/^jwr?///).  [Professor  James  directs  attention  to  the  value  of  peptic  and 
pancreatic  salts,  which  are  preparations  of  common  salt  mixed  with  pepsin  and  the  ferments  of  the 
pancreas  res]icclively.] 

[Artificial  Digestion  is  affected  by  various  salts  according  to  their  nature  and  dilution.  The 
digestion  oi  fihrin  hy  pef'sin  goes  on  best  without  the  addition  of  salts,  being  diminished  by  magnesic 
sulphate,  .so<lic  carlxjnate,  and  sulphate.  The  digestion  of  fibrin  by  pancreatic  extract  is  accelerated 
by  .sodic  carlxinate  (  Ileid(nhain\,  and  retarded  by  MgSO,  and  Na2S04.  The  dia.static  action  of  the 
saliva  and  pancreas  on  starch  is  greatly  accelerated  by  XaCl  (2  per  cent.),  while  Na2C03,  Na2S04, 
and  Mg."^(  'i^  hinder  it(  Pfeiff'er).']  According  to  Schiitz,  artificial  gastric  digestion  is  retarded  by  a  2 
per  cent,  solution  of  alcohol,  and  also  by  a  solution  of  salicylic  acid  (.06  to  .1  per  cent.).  Buchner, 
however,  finds  that  lo  per  cent,  of  alcohol  does  not  affect  artificial  gastric  digestion,  while  above  20 
per  cent,  arrests  it.     Beer  hinders  digestion. 

F.  In  acute  disea.ses,  the  secretion  of  bile  is  affected  ;  it  becomes  less  in  amount  and  more  watery, 
».  e.,  it  contains  fewer  .specific  constituents.  If  the  liver  undergoes  great  structural  change,  the 
.secretion  may  l>e  arrested. 

G.  Gall  Stones. — When  decomposition  of  the  bile  occurs,  gall  stones  are  formed  in  the  gall 
Haddfr  or  in  the  bile  duds.  .Some  are  white,  and  consist  almost  entirely  of  stratified  layers  of  crystals 
of  cholesterin.  The  hro-a<n  forms  consist  of  bilirubin-lime,  and  calcium  carbonate,  often  mixed  with 
iron,  copjx-r,  and  manganese.  The  gall  stones  in  the  gall  bladder  become  facetted  by  rubbing  against 
each  other.  The  nucleus  of  the  white  stones  often  consists  of  chalk  and  bile-coloring' matters,  together 
with  nitrogenous  residues,  derived  from  shed  epithelium,  mucin,  bile  salts,  and  fats,  (iall  stones  may 
occlude  the  bile  duct  and  cause  cholemia.  When  a  small  .stone  becomes  impacted  in  a  duct,  it  gives 
nse  to  excessive  pain,  constituting  hepatic  colic,  and  may  even  cause  rupture  of  the  bile  duct'with  its 
sharp  edges. 

H.  Nothing  certain  has  been  determined  regarding  the  pancreatic  secretion  in  disease,  but  in 
lever  it  appears  to  be  diminished  in  amount  and  digestive  activity.  The  suppression  of  the  pancreatic 
secretion  [as  by  a  cancerous  tumor  of  the  head  of  the  pancreas],  is  often  accompanied  by  the  appear- 
ance of  fat.  m  the  form  of  globules  or  groups  of  crystals  in  the  feces. 

,  ?•  Constipation  is  a  most  important  derangement  of  the  digestive  tract.  It  may  be  caused  by— 
(I)  Condition^  which  obstruct  the  normal  channel,  e.  g.,  constriction  of  the  gut  from  stricture— in  the 


COMPARATIVE    PHYSIOLOGY   OF    DIGESTION.  333 

large  gut  after  dysentery,  tumors,  rotation  on  its  axis  of  a  loop  of  intestine  (volvulus),  or  invagination, 
occlusion  of  a  coil  of  gut  in  a  hernial  sac,  or  by  the  pressure  of  tumors  or  exudations  from  without,  or 
congenital  absence  of  the  anus.  (2)  Too  great  dryness  of  the  contents,  caused  by  too  little  water  in 
the  articles  of  diet,  diminution  of  the  amount  of  the  digestive  secretions,  e.  g.,  of  bile  in  icterus  ;  or  in 
consequence  of  much  fluid  being  given  off  by  other  organs,  as  after  copious  secretion  of  saliva,  milk, 
or  in  fever.  (3)  Variations  in  the  functional  activity  of  the  muscles  and  motor  nervous  apparatus  of 
the  gut  may  cause  constipation,  owing  to  imperfect  peristalsis.  This  condition  occurs  in  inflammations, 
degenerations,  chronic  catarrh,  and  diaphragmatic  inflammation.  Affections  of  the  spinal  cord,  and 
sometimes  also  of  the  brain,  are  usually  accompanied  by  slow  evacuation  of  the  intestine.  WTiether 
diminished  mental  activity  and  hypochondriasis  are  the  cause  of  or  are  caused  by  constipation,  is  not 
proved.  Spasmodic  contraction  of  a  part  of  the  intestine  may  cause  temporary  retention  of  the 
intestinal  contents,  and,  at  the  same  time,  give  rise  to  great  pain  or  colic ;  the  same  is  true  of  spasm  of 
the  anal  sphincter,  which  may  be  excited  reflexly  from  the  lower  part  of  the  gut.  The  fecal  masses 
in  constipation  are  usually  hard  and  diy,  owing  to  the  water  being  absorbed  ;  hence  they  form  large 
masses  or  scybala  within  the  large  intestine,  and  these  again  give  rise  to  new  resistance.  Among 
the  reagents  which  prevent  evacuation  of  the  bowels,  some  paralyze  the  motor  apparatus  temporarily, 
f.  ^.,  opium,  morphia;  some  diminish  the  secretion  of  the  intestinal  mucous  membrane,  and  cause 
constriction  of  the  blood  vessels,  as  tannic  acid,  vegetables  containing  tannin,  alum,  chalk,  lead  acetate, 
silver  nitrate,  bismuth  nitrate. 

J.  Increased  evacuation  of  the  intestinal  contents  is  usually  accompanied  by  a  watery  condition  of 
the  faeces,  constituting  diarrhoea.     The  causes  are : — 

1.  A  too  rapid  movement  of  the  contents  through  the  intestine,  chiefly  through  the  large  intestine, 
so  that  there  is  no  time  for  the  normal  amount  of  absorption  to  take  place.  The  increased  peristalsis 
depends  upon  stimulation  of  the  motor  nervous  apparatus  of  the  intestine,  usually  of  a  reflex  nature. 
Rapid  transit  of  the  contents  through  the  intestine  causes  the  evacuation  of  certain  substances  which 
cannot  be  digested  in  so  short  a  time. 

2.  The  stools  become  tliinner  from  the  presence  of  much  water,  mucus,  and  the  admixture  with  fat, 
and  by  eating  fruit  and  vegetables.  In  rare  cases,  when  the  evacuations  contain  much  mucin, 
Charcot's  crystals  occur  (Fig.  144,  c).  In  ulceration  of  the  intestine,  leucocytes  (pus)  are  present 
{Nothnagel). 

3.  Diarrhoea  may  occur  as  a  consequence  of  disturbance  of  the  diffusion  processes  through  the 
intestinal  walls,  as  in  affections  of  the  epithelium,  when  it  becomes  swollen  in  inflammatory  or  catarrhal 
conditions  of  the  intestinal  mucous  membrane.  [Irritation  over  the  abdomen,  as  from  the  subcutaneous 
injection  of  small  quantities  of  sahne  solutions,  causes  diarrhoea.] 

4.  It  may  also  be  due  to  increased  secretion  into  the  intestine,  as  in  capillary  diffusion,  when  magne- 
sium sulphate  in  the  intestine  attracts  water  from  the  blood. 

The  same  occvirs  in  cholera,  when  the  stools  are  copious  and  of  a  rice-water  character,  and  are 
loaded  with  epithelial  cells  from  the  viUi.  The  transudation  into  the  intestine  is  so  great  that  the  blood 
in  the  arteries  becomes  very  thick,  and  may  even  on  this  account  cease  to  circulate. 

Transudation  into  the  intestine  also  takes  place  as  a  consequence  of  paralysis  of  the  vaso- 
motor nerves  of  the  intestine.  This  is  perhaps  the  case  in  diarrhoea  following  upon  a  cold.  Certain 
substances  seem  directly  to  excite  the  secretory  organs  of  the  intestines  or  their  nerves,  such  as  the 
drastic  purgatives  (^  180).     Pilocarpin  injected  into  the  blood  causes  great  secretion  [Masloff). 

During  febrile  conditions,  the  secretion  of  the  intestinal  glands  seems  to  be  altered  quantitatively 
and  qualitatively,  with  simultaneous  alteration  of  the  functional  activity  of  the  musculature  and  the 
organs  of  absorption,  while  the  excitabihty  of  the  mucous  membrane  is  increased  (  Uffelmann).  It  is 
important  to  note  that  in  many  acute  febrile  diseases  the  amount  of  common  salt  in  the  urine  di- 
minishes, and  increases  again  as  the  fever  subsides. 

187.  COMPARATIVE. — Salivary  Glands. — Among  mammals,  the  herbivora  have  larger 
salivary  glands  than  the  camivora ;  while  midway  between  both  are  the  omnivora.  The  whale  has 
no  salivary  glands.  The  pinnipedia  have  a  small  parotid,  which  is  absent  in  echidna.  The  dog  and 
many  camivora  have  a  special  gland  lying  in  the  orbit,  the  orbital  or  zygomatic  gland.  In  birds  the 
salivary  glands  open  at  the  angle  of  the  mouth,  but  the  parotid  is  absent.  Among  reptiles  the 
parotid  of  some  species  is  so  changed  as  to  form  poison  glands  ;  the  tortoise  has  sub-lingual  glands  ; 
reptiles  have  labial  glands.  The  amphibia  and  fishes  have  merely  small  glands  scattered  over  the 
mouth.  The  salivary  glands  are  large  in  insects  ;  some  of  them  secrete  formic  acid.  The  salivary 
glands  are  well  developed  in  mollusks,  and  the  saUva  of  Dolium  galea  contains  more  than  3  per  cent, 
of  free  sulphuric  acid  (?).     The  cephalopods  have  double  glands. 

A  crop  is  not  present  in  any  mammal ;  the  stomach  is  either  simple,  as  in  man,  or,  as  in  many 
rodents,  it  is  divided  into  two  halves,  into  a  cardiac  and  a  pyloric  portion.  The  intestine  is  short  in 
flesh-eating  animals  and  long  in  herbivora.  The  stomach  of  ruminants  is  compound,  and  consists  of 
four  cavities.  The  first  and  largest  is  the  paunch  or  rumen,  then  the  reticulum.  In  these  two 
cavities,  especially  the  former,  the  ingesta  are  softened  and  undergo  fermentation.  They  are  then 
returned  to  the  mouth  by  the  action  of  the  voluntary  muscular  fibres,  which  reach  to  the  stomach. 
This  is  the  process  of  rumination.     The  ingesta   are  chewed  again  in  the  mouth,  and  are  again 


334  HISTORICAL   ACCOUNT   OF    DIGESTION. 

swallowed,  luit  this  time  they  enter  ihc  third  cavity  or  psalterium— (which  is  absent  in  the  camel)— 
and  thence  into  the  fourth  stomach  or  abomasum,  in  which  the  fermentative  digestion  takes  place. 
The  aixum  is  a  very  large  and  imi)orfant  digestive  organ  in  hcrl)ivora  and  in  most  rodents;  it  is 
small  in  man,  and  absent  in  camivora.  The  asophagus  in  grain-eating  birds  not  unfrequently  has  a 
blind  diverticulum  or  crop  for  softening  the  food.  In  the  crop  of  pigeons  during  the  lireeding  season, 
there  is  fonnal  a  jnculiar  secretion--"  i)igeon's  milk,"  which  is  used  to  feed  the  young  (/.  JJunler). 
The  stomach  consists  of  a  glandular /;<'7'c;;//-/V/////J  and  a  strong  vittscular  Uomach  \s\\\c\\  is  covered 
with  homy  q)ithelium  and  triturates  the  fo(xl.  There  are  usually  two  lluid  diverticula  on  the  small 
intestine  near  where  it  joins  the  large  gut.  In  fishes  the  intestinal  canal  is  generally  simple  ;  the 
stomach  is  merely  a  dilatation  of  the  tube  ;  and  at  the  pylorus  there  may  be  one,  but  usually  many, 
blind  glantlular  apjx-ndages  (tiie  apjx;ndices  pyloric.^).  They  are  generally  longitudinal  folds  in  the 
intestinal  mucous  membrane,  but  in  some  fishes  e.  g.,  the  shark,  there  is  a  spiral  valve.  [The  inver- 
sive  (cane  sugar)  ferment  is  wanting  in  the  herbivora,  as  the  cow,  horse,  and  sheep,  but  is  present  in 
the  dog  and  cat.  It  is  also  met  with  in  birds  and  reptiles,  and  in  many  of  the  invertebrates,  as  the 
ordinar)'  earth-worm  {M.  //(/i').] 

In  amphibia  and  reptiles  the  stomach  is  a  simple  dilatation;  the  gut  is  larger  in  vegetable  feeders 
than  in  tlt^-h  feeders.  The  liver  is  never  absent  in  vertebrates,  although  the  gall  bladder  frequently 
is.      The  pancreas  is  absent  in  some  fishes. 

Digestion  in  Plants. — The  observations  on  the  albumin  digesting  power  of  some  plants  are 
extremely  interesting  {^Canhy,  1869;  Ch.  Dartuin,  1875).  The  sundew  or  drosera  has  a  series  of 
tentacles  on  the  surface  of  its  leaves,  and  the  tentacles  are  provided  with  glands.  When  an  insect 
alights  ujxin  a  leaf,  it  is  suddenly  seized  by  the  tentacles ;  the  glands  pour  out  an  acid  juice  over  the 
prey,  which  is  gradually  digested,  all  except  the  chitinous  structures.  The  S;cretion,  as  well  as  the 
sut)se  [Ui-nt  absorption  of  the  products  of  digestion,  are  accomplished  by  the  activity  of  the  proto- 
plasm of  the  cells  of  the  leaves  The  digestive  juice  contains  a  pepsin-like  ferment  and  formic  acid. 
Similar  phenomena  are  manifested  by  the  Venus  flytrap  (Dioniva),  by  pinguicula,  as  well  as  by  the 
cavity  of  the  altered  leaves  of  nepenthes.  About  fifteen  species  of  these  "insectivorous"  or  carnivo- 
rous plants  are  known.  [Papain,  and  other  ferments  analogous  in  their  action  to  trypsin,  are  referred 
to  in  \  170] 

188.  HISTORICAL. — Digestion  in  the  Mouth. — The  older  observers  regarded  \\\t^  saliva 
as  a  solvent,  and  in  addition,  many  bad  qualities,  especially  in  starving  animals,  were  ascribed  to  it. 
This  arose  from  the  knowledge  of  the  saliva  of  mad  animals,  and  the  parotid  saliva  of  poisonous 
snakes.  The  .salivary  glands  have  been  known  for  a  long  time.  Clalen  ( 131-203  A.  D. )  was  acquainted 
with  Wharton's  duct, and  Aetius  (270  A.  D.)  with  the  submaxillar)'  and  sub-lingual  glands.  Hapcl  de 
la  Chenaye  (1 780)  obtainc<l  large  (|uantities  of  saliva  from  a  horse,  in  which  he  was  the  first  to  make 
a  salivary  fistula.  .Spallanzani  (1786)  asserted  that  food  mixed  with  saliva  was  more  easily  digested 
than  food  moi.stened  with  water.  Bamberger  and  Siebold  investigated  the  reaction,  consi-stence,  and 
specific  gravity  of  saliva,  and  found  in  it  mucus,  albumin,  common  salt,  calcium  and  sodium  phos- 
phates, berzelius  gave  the  name  ptyalin  to  the  characteristic  organic  constituent  of  saliva,  but  Leuchs 
( 1831)  was  the  fir^t  to  detect  its  diastatic  action. 

Gastric  Digestion. —  Digesiion  was  formerly  compared  to  "coction,"  whereby  solution  was 
effected.  According  to  (Jalen,  only  substances  that  have  been  dissolved  passed  through  the  pylorus 
into  the  intestine.  He  described  the  movements  of  the  stomach  and  the  peiistalsis  of  the  intestines. 
Aelian  gave  names  to  the  four  .stomachs  of  the  ruminants.  Vidius  (f  1567)  noticed  the  numerous 
small  apertures  of  the  gastric  glands.  Van  Helmont  (f  1644)  expressly  notices  the  acidity  of  the 
stomach.  Reaumur  (1752)  knew  that  a  juice  was  secreted  by  the  stomach,  which  effected  solution, 
and  with  w  hich  he  and  .Spallanzani  performed  experiments  on  digestion  outside  the  body.  Carminati 
(1785)  found  that  the  stomachs  of  carnivora  during  digestion  secreted  a  very  acid  juice.  Prout  (1824) 
discovered  the  hydrochloric  acid  of  the  gastric  juice,  Sprott  and  Boyd  (1836)  the  glands  of  the  gastric 
mucous  memi)rane,  while  Wasmann  and  Hischoff  noted  the  two  kinds  of  gastric  glands.  After  Beau- 
mont^l  1834)  hid^made  his  observations  upon  Alexis  St.  Martin,  who  had  a  gastric  fistula  caused  by  a 

.   ga.stric   fistulse 
min,  when  alter 

.  ^,  „  .  .    ,  .  o carefully,  gave  ,.  ...v, 

li^t  pepume.  .Schwann  isolated /^/««  (1836),  and  established  the  fact  of  its  activity  in  the  presence 
o(  hydrochloric  acid.  ^ 

Pancreas,  Bile  Intestinal  Digestion.— The  pancreas  was  known  to  the  Hippocratic  School; 
r\  /'5f'"''""(  '642)  demonstrated  its  duct  (fowl),  and  Wirsung  described  it  in  man.  Regner  de 
Graaf  (1664)  collected  the  pancreatic  juice  from  a  fi.stula,  and  Tiedemann  and  Gmelin  found  it  .0  be 
alkaline,  while  Lauret  and  Lassaigne  found  that  it  resembled  saliva.  Valentin  discovered  its  dias- 
^h!L*  '^'  VT  ''^«"»!s'oni«ng  power,  and  CI.  Bernard  (1846)  its  tryptic  and  fat  splitting  prop- 
erties. The  las^  mentioned  ftinction  was  referred  to  by  Purkinje  arul  Pappenhcim  (1836).  Aristotle 
ch.ir..cterized   the  bile  as  a   useless  secretion;  according  to   Era.sistratus   (304  B c);  fine   invisible 

Uo^nf  fh^r."'^^  :  '"  P  ''T  '^'  '"^''  '"^°  ^'^^  g^"  '^'^^der.     Aretaeus  ascribed  icterus  to  obsLc 
Uon  of  the  bile  duct.     Benedetti  (1493)  described  gall  stones.     According  to  Jasolinus  (1573),  the 


HISTORICAL   ACCOUNT   OF   DIGESTION.  335 

gall  bladder  is  emptied  by  its  own  contractions.  Sylvius  noticed  the  lymphatics  of  the  liver  (1640)  • 
Walaeus,  the  connective  tissue  of  the  so  called  capsule  of  Glisson  (1641).  Haller  indicated  the 
uses  of  bile  in  the  digestion  of  fats.  The  liver  cells  were  described  by  Henle,  Purkinje,  and 
Dutrochet  (1838).  Heynsius  discovered  the  urea  and  CI.  Bernard  (1853)  the  sugar  in  th-  liver,  and 
he  and  Hensen  (1857)  found  glycogen  in  the  liver.  Kieman  gave  a  more  exact  description  of  the 
hepatic  blood  vessels  (1834).  Beale  injected  the  lymphatics,  and  Gerlach  the  finest  bile  ducts. 
Schwann  (1844)  made  the  first  biliary  fistula;  Dem  rcay  particularly  referred  to  the  combination  of 
the  bile  acids  with  soda  (1838) ;  Strecker  discovered  the  soda  compounds  of  both  acids,  and  isolated 
them.  Celsus  mentions  nutrient  enemata  (3-5  A.D.).  Fallopius  (1561)  described  the  valvulse  con- 
niventes  and  vilh  of  the  intestinal  mucous  membrane,  and  the  nervous  plexus  of  the  mesentery.  The 
agminated  glands  or  patches  of  Peyer  were  known  to  Severinus  (1645). 


PHYSIOLOGY  OF  ABSORPTION. 


Fir,.  206. 


189.  THE  ORGANS  OF  ABSORPTION.— [As  most  substances  in  the 
state  in  which  they  arc  used  for  food  are  either  insoluble,  or  diffuse  but  imperfectly 
through  membranes,  the  whole  drift  of  the  complicated  digestive  processes  is  to 
render  these  substances  soluble  and  diffusible,  and  thus  fit  them  for  absorption ; 
while  most  of  the  fats  are  eniulsionized.] 

The  mucous  membrane  of  the  whole  intestinal  tract,  as  far  as  it  is  covered 
by  a  single  layer  of  columnar  epithelium,  i.e.,  from   the  cardiac   orifice  of  the 

stomach  to  the  anus — is  adapted  for  absorption. 
The  mouth  and  oesophagus,  lined  as  they  are 
by  stratified  squamous  epithelium,  are  much  less 
adapted  for  this  purpose.  Still,  poisoning  is 
caused  by  placing  potassium  cyanide  in  the 
mouth.  The  channels  of  absorption  in  the  in- 
testinal tract  are  (Fig.  206) — (i)  the  capil- 
laries [(//mV],  and  (2)  the  lacteals  \indirect\ 
of  the  mucous  membrane.  Almost  the  whole 
of  the  substances  absorbed  by  the  former  pass 
into  the  rootlets  of  the  portal  vein,  and  traverse 
the  liver,  while  those  that  enter  the  lacteals 
really  pass  into  lymphatics,  so  that  the  chyle 
Scheme  of  imotinai  A»)sorpiion.   LAC  lac-  passcs  through  the  thoracic  duct  and  is  poured 

teaU  :  T.  I).,  thoracic  duct :  P.V.  and  H. v.,    {_       •       ■  r        ii         i  i  i  ,  •         i 

portalandhepalic  veins;  INT.,  intestine.        by  it    intO    the    blood,    whcre    the    thoraClC    dUCt 

joins  the  subclavian  vein. 

Watery  solutions  of  salts,  grape  sugar,  peptone,  poisons,  and  in  a  still  higher 
degree  alcoholic  solutions  of  poisons,  are  absorbed  in  the  stomach.  The 
empty  stomach  absorbs  more  rapidly  than  one  filled  with  food  ;  gastric  catarrh 
delays  absorption.  After  a  copious  diet  of  milk,  fatty  granules  have  been  found 
in  the  protoplasm  of  the  goblet  cells ;  so  that  according  to  this  view,  the  goblet 
cells  have  a  double  function,  to  secrete  mucus  and  to  absorb  nutriments. 

The  greatest  area  of  absorption  is  undoubtedly  the  small  intestine,  especially 
its  upper  half,  owing  to  the  jiresence  of  the  valvulae  conniventes  and  the  villi. 

190.  STRUCTURE  OF  THE  SMALL  AND  LARGE  INTES- 
TINES.—[The  wall  of  the  small  intestine  consists  of  four  coats;  which, 
from  without  inward,  are  named  serous,  muscular,  sub-mucous,  and  mucous 
(Fig.  207).] 

(1)  The  serous  coat  has  the  same  structure  as  the  peritoneum,  /.  e.,  a  thin  basis  of  fibrous  tissue 
covered  on  it.s  .mtcr  Mirlace  by  endothehum. 

(2)  The  muscular  coat  consi.sts  of  a  thin  outer  longitudinal  and  an  inner  thicker  circular 
layer  ot  non  stni>e(l  nuiscul.-ir  fibres  (Fig.  207). 

(3)  The  sub  mucous  coat  consists  of  loose  connective  tissue  containing  large  blood  vessels  and 
nerves,  and  it  connects  the  muscular  with  the  mucous  coat. 

(4)  The  mucous  coat  is  the  most  internal  coat,  and  its  absorbing  surface  is  largely  increased  bv 
fordf^fTh"  y  conmventes  and  villi.  [The  valvule  conniventes  are  peramnent 
folds  of  the  mucous  membrane  of  the  small  intestine,  arranged  across  the  long  axis  of  the  g^t.  Thev 
pass  round  a  half  or  more  of  the  mner  surface  of  the  gut.     They  begin  a  little  below  the  commence- 

336 


STRUCTURE   OF    A   VILLUS. 


33 


ment  of  the  duodenum,  and  are  large  and  well  marked  in  the  duodemmi,  and  remain  so  as  far  as  the 
upper  half  of  the  jejunum,  where  they  begin  to  become  smaller,  and  finally  disappear  about  the  lower 
part  of  the  ileum.]  The  villi  are  characteristic  of  the  small  intestine,  and  are  confined  to  it;  they 
occur  everywhere  as  closely-set  projections  over  and  between  the  valvulse  conniventes  (Fig.  207). 
When  the  inner  surface  of  the  mucous  membrane  is  examined  in  water,  it  has  a  velvety  appearance 
owing  to  their  presence.  [They  vary  in  length  from  -jL  to  -J^  of  an  inch,  are  largest  and  most  nvmie- 
rous  in  the  upper  part  of  the  intestine,  duodenum,  and  jejunum,  where  absorption  is  most  active,  but 
they  are  less  abundant  in  the  ileum.  Their  total  number  has  been  calculated  at  four  millions  by 
Krause  ]      Each   villus   is    a    projection    of    the 


Fig.  207. 


Villi 

with  epi- 
thelium. 


entire  mucous  membrane,  so  that  it  contains  within 
itself  representatives  of  all  the  tissue  elements  of 
the  mucosa.  The  orifices  of  the  glands  of  Lieber- 
kiihn  open  between  the  bases  of  villi  (Fig.  207). 

Each  villus,  be  it  cylindrical  or  conical  in 
shape,  is  covered  by  a  single  layer  of  columnar 
epithelium,  whose  protoplasm  is  reticulated,  and 
contains  a  well-defined  nucleus  with  an  intra- 
nuclear plexus  of  fibrils.  The  enHs  of  the 
epithelial  cells  directed  toward  the  gut  are 
polygonal,  and  present  the  appearance  of  a  mosaic 
(Fig.  208,  D).  When  looked  at  fi-om  the  side, 
their  Iree  surface  is  seen  to  be  covered  with  a 
clear,  highly  refractive  disk  or  "  cuticula," 
which  is  marked  with  vertical  striae.  These  striae 
were  supp"sed  by  Kolliker  to  represent  pores  for 
the  absorption  of  fatty  particles,  1  ut  this  has  not 
been  confirmed,  while  Brettauer  and  Steinach 
regarded  them  as  produced  by  prisms  placed  side 
by  ^ide. 

According  to  v.  Thanhoffer,  however,  this 
clear  disk  is  comparable  to  the  thickened  flange 
around  the  bottom  of  a  vessel,  such  as  is  used  for 
collecting  gases.  On  this  suppositii  'U,  the  upper 
end  of  each  cell  is  open,  and  from  it  there  project 
pseudopodia-like  bundles  of  protopla.smic  pro- 
cesses (Fig.  208,  B)  These  processrs  are  sup- 
posed to  be  extended  beyond  the  margin  of  the 
cell,  and  again  rapidly  retracted,  and  in  so  acting 
they  are  said  to  carry  the  fatty  particles  into  the 
interior  of  the  cells,  much  as  the  pseudopodia  of 
an  amoeba  entangle  its  food.  [This  view  has  not 
been  confirmed  by  a  sufficient  number  of  ob- 
servers.] Between  the  epithelial  cells  are  the 
so-called  goblet  cells  (Fig.  208,  C).  [Each 
goblet  cell  is  more  or  less  like  a  chalice,  narrower 
above  and  below,  and  broad  in  the  middle,  with 
a  tapering  fixed  extremity.  The  outer  part  of 
these  cells  is  filled  with  a  clear  substance  or 
mucigen,  which,  on  the  addition  of  water,  yields 
mucus.  The  mucigen  lies  in  the  interva's  of  a 
fine  network  of  fibrils,  which  pervades  the  cell 

protoplasm,  while  the  protoplasm  containing  a  globular  or  triangular  nucleus,  is  pushed  into  the 
lower  part  of  the  cell.  Those  goi)let  cells  are  simply  altered  columnar  epithelial  cells,  which  secrete 
mucus  in  their  interior.  They  are  more  niunerous  under  certain  conditions.  Not  unfirequently  in  a 
section  of  the  mucous  membrane  of  the  gut,  after  it  is  siained  with  logwood,  we  may  see  a  deep  blue 
plug  of  mucus  partly  exuded  from  these  eel's.  When  looked  at  f  om  above  they  give  the  appearance 
seen  in  Fig.  208,  I).]  The  epithelial  cells  are  shed  in  enormous  numbers  in  cholera,  and  in 
poisoning  with  arsenic  and  muscaiin  {Bohiti). 

[The  epithelial  cells  covering  the  villus  are  placed  upon  a  layer  of  squamous  epithelium  (basement 
membrane) — the  sub-epithelial  membrane  of  Debove.  This  basement  membrane  is  said  to  be 
connected  by  processes  with  the  so-called  liranched  cells  of  the  adenoid  tissue  of  the  villus,  while  it 
also  sends  up  processes  between  the  epithelial  covering.] 

The  villus  itself  consists  of  a  basis  of  adenoid  tissue,  containing  in  its  centre  one  or  more  lacteals, 
closely  invested  with  bundles  of  longitudinal  smooth  muscular  fibres,  derived  fi-om  the  musrularis 
mucosae,  and  a  plexus  of  blood  vesse's.  The  adenoid  tissue  of  the  vil  us  consists  of  a  reticulum  of 
fibrils  with  endothelial  plates  at  its  nodes.     The  spaces  of  the  adenoid  tissue  form  a  spongy  network 


Longitudinal  section  of  the  small  intestine  of  a  dog  through 
a  Peyer's  patch. 


338 


Fic.  209. 


Capillaryi . 


Artery. 


Vein. 


Injected  blood  vessels  of  a  villus. 


of  inter-communicating  channels  con- 
taining stroma  cells  or  leucocytes 
(Fig.  208,  A,  e,  e).  These  leucocytes 
or  lymph  corpu.scles  have  been  seen 
to  contain  fatty  granules,  and  they  are 
perhaps  concerned  in  the  absorption 
of  fatty  particles. 

The  lymphatic  or  lacteal  lies  in 
the  axis  of  the  villus  (Fig.  210,  af). 
Some  regard  the  lacteal  merely  as  a 
space  in  the  centre  of  the  villus,  but 
more  probably  it  has  a  distinct  wall 
composed  of  endothelial  cells,  with 
apertiu-es  or  stomata  here  and  there 
between  the  cell  plates.  These 
stomata  place  the  interior  of  the  lacteal 
in  direct  communication  with  the 
spaces  of  the  adenoid  tissue.  Perhaps, 
white  blood  corpuscles  wander  out  of 
the  blood  vessels  of  the  villi  into  the 
spaces  of  the  adenoid  tissue  where 
they  become  loaded  with  fatty  gran- 
ules, and  pass  into  the  central  lacteal. 
Zuwarj'kin  and  Wiedersheim  suppose 
that  the  leucocytes  pass  from  the 
parenchyma  of  the  villus  toward  the 
epithelial  layer,  and  even  between  the 
epithelial  cells,  from  which  they  re- 
turn toward  the  axis  of  the.  villus, 
laden  with  .substances  which  they  have 
taken  into  their  interior  (^  192,  II). 


GLANDS    IN    THE    INTESTINE. 


339 


A  small  artery  placed  eccentrically  passes  into  each  villus  (Fig.  209).  In  man  it  begins  to  divide 
about  the  middle  of  the  villus,  but  in  animals  it  usually  runs  to  the  apex  before  it  divides.  The 
capillaries  resulting  fi-om  the  division  of  the  artery  form  a  fine  dense  network  placed  stiperficially , 
immediately  under  the  epithelium  of  the  surface.  The  blood  is  can-ied  out  of  a  villus  by  one  or  two 
veins  (Figs.  207,  209). 

Non-striped  muscular  fibres  are  present  in  villi.  They  are  arranged  longitudinally  in  several 
bundles  from  base  to  apex,  immediately  outside  the  central  lacteal.  When  they  contract  they  tend 
to  empty  the  lacteal.  A  few  muscular  fibres  are  placed  more  superficially,  and  run  in  a  more  trans- 
verse direction.  [The  longitudinal  bundles  of  non-striped  muscle  in  the  villi  are  connected  together 
by  oblique  strands;  while  the  longitudinal  bundles  shorten  the  villus,  the  oblique  fibres  keep  the 
lacteal  open;  thus  the  parenchyma  of  the  villus  is  also  compressed  transversely,  whereby  the 
products  of  absorption  are  forced  into  the  lacteal.  The  muscles  are  fixed  by  cement  to  the  sub- 
epithelial basal  membrane.  The  muscular  fibres  of  the  villi  are  direct  prolongations  of  the  muscularis 
mucosae.] 

Nerves  pass  into  the  villi  from  Meissner's  plexus  lying  in  the  sub-mucous  coat.  The  nerves  to  the 
vilU  are  said  to  have  small  granular  ganglionic  cells  in  their  course,  and  they  terminate  partly  in  the 
muscular  fibres  and  partly  in  the  arteries  of  the  villi. 

[On  making  a  vertical  section  of  the  mucous  membrane  of  the  small  intestine,  it  is  seen  to  consist 
of  a  network  of  adenoid  tissue  loaded  with  leucocytes.  This  tissue  forms  its  basis,  and  in  it  are  placed 
vertically,  side  by  side,  like  test-tubes  in  a  stand,  immense  numbers  of  simple  tubular  glands — the 
crypts  of  Lieberkiihn  (Fig.  207).]  [Kultschitzki  finds  that  the  connective-tissue  framework  of 
the  mucous  membrane  of  the  small  intestine  is  not  true  adenoid  tissue,  but  a  transition  form  between 
the  latter  and  loose  fibrous  tissue.]  Lieberkiihn's  glands  open  above  at  the  bases  of  the  villi,  while 
their  closed  lower  extremity  reaches  almost  to  the  muscularis  mucosae.  Each  tube  consists  of  a  base- 
ment membrane  lined  by  a  single  layer  of 


columnar  epithelium,  leaving  a  wide  lumen, 
the  cells  lining  them  being  continuous  with 
those  that  cover  the  mucous  membrane. 
Some  goblet  cells  are  often  found  between 
the  columnar  epithelium.  Immediately 
below  the  bases  of  the  follicles  of  Lieber- 
kiihn is  the  muscularis  mucosae,  consist- 
ing of  two  or  three  narrow  layers  of  non- 
striped  muscular  fibres  arranged  circularly 
and  longitudinally.  [It  is  continuous  with 
the  muscularis  mucosa?  of  the  stomach,  and 
extends  throughout  the  whole  intestine,  not 
as  a  continuous  layer,  but  as  a  close  net- 
work of  bundles  of  smooth  muscle.  It 
sends  fibres  upward  into  the  villi  (Fig.  212, 
e).-\ 

[Brunner's  Glands  are  compound  tubu- 
lar glands  lying  in  and  confined  to  the  sub- 
mucous coat  of  the  duodenum  (Fig.  198). 
Their  ducts  perforate  the  muscularis  mucosa 
to  open  on  the  surface.  They  seem  to  be 
the  homologues  of  the  pyloric  glands  of  the 
stomach.] 

[Solitary  Follicles  are  small  round  or 
oval  white  masses  of  adenoid  tissue  with 
their  deeper  parts  embedded  in  the  sub- 
mucosa,  and  their  apices  projecting  into  the 
mucosa  of  the  intestine.  They  begin  at  the 
pyloric  end  of  the  stomach  and  are  found 
throughout  the  whole  intestine.     They  con- 


FiG.  210. 


sist  of  small  masses  of  adenoid  tissue  loaded   Mucous  membrane  of  the  small  intestine  of  the  dog  ; 
with  leucocytes  (Fig.  214).      They   are  well  ?re   black,   and    the  blood    vessels   lighter. 


the  lacteals 
,   artery ;    b, 

supphed  with  blood  vessels  (|  1 97 ) ,  although  L^ebSi's'gllnds!  °^  ""P'""""'  ™  ''^"  ^'"' '  '^'  ^^"""^  =  '' 
no  lymphatic  vessels  enter  them.     They  are 

surrounded  by  lymphatics,  and,  in  fact,  they  may  be  said  to  hang  into  a  lymph  stream.  The  distribu- 
tion of  solitary  follicles  is  fairly  uniform  in  the  small  intestine ;  their  number  generally  increases  from 
the  stomach  to  the  large  intestine;  although  there  are  considerable  variatioris  in  different  individuals, 
there  seems  to  be  the  same  number  of  solitary  follicles  and  Peyer's  patches  in  the  infant  as  in  the  adult 
(^Passow).'\ 

[Peyer's  glands,  or  agminated  glands,  consist  of  groups  of  lymph  fohicles  like  the  foregoing 
(Figs.  207,  213).     The  masses  are  often  more  or  less  fused  together,  their  bases  lie  in  the  sub-mucosa, 


340 


peyer's  glands. 


while  their  summits  project  into  the  mucosa,  wliere  they  are  covered  merely  by  the  columnar  epithelium 
of  the  intestine.  The  iymi)h  corpuscles  often  pass  between  the  ejiithelial  cells.  Ihe  patches  so 
formed  have  their  long  axis  in  the  axis  of  the  intestine,  and  they  are  always  placed  opix)site  the  attach- 

YlC.  211. 
Villi  wllli  blood  vessels  injccicJ.     Solitary  follicle. 


Muscular 
coat. 


Traiiiverse  scciiuii  ol"  Juodenuni  of  a  rabbit  injected,  X  30. 


■■-■■A'.   Q     WftN 


ig' 


m^^i^^p-ssm^ 


^'i— 


Section  °f  =« -l;'^^;^/^'"'^'^  °\ 'h«=  7=',".J"t«stine  (human),     a.  lymph  follicle  covered  with  epithelium  (/,)  which  has 
lallen  from  the  villi,  c.  d,  Lieberkuhn  s  follicle  ;  e,  muscularis  mucosae  ;  /,  sub-mucous  tissue. 

ment  of  the  mesentery.  Like  the  solitary  gland.s.  they  are  well  supplied  with  blood  vessels,  while 
around  them  is  a  dense  plexus  of  lymphati.-s  or  lacteals.  They  are  most  abundant  in  the  low^r  part 
of  the  Ileum.      These  glands  are  specially  affected  in  tj-phoid  fever.] 


NERVES    OF    THE    INTESTINE. 


341 


Nerves  of  the  Intestine.— Throughout  the  whole  intestinal  tract  there  exists  the  plexus   of 
Auerbach,  lying  between  the  longitudinal  and  circular  muscular  coats  (Figs.  174,  175).      This 


Fig.  213. 


Diagram  of  a  vertical  section  of  the  mucous  membrane  of  the  small  intestine  of  a  dog,  showing  the  closed  follicles,  aa ; 

b,  muscularis  mucosse. 


Fig.  214. 


Epi- 
thelium. 


Mucous 
Membrane. 


Capillary. 


Solitary 
follicle. 


Circular 
fibres. 

Muscular 
coat. 

Longitudinal 
fibres. 


Sub- 

tnucous 

coat. 


Longitudinal  section  of  the  large  intestine. 


plexus  consists  of  non-medullated  nerves  with  groups  of  ganglionic  cells  at  the  nodes.    Fibres  are  given 
off  by  it  to  the  muscular  coats.     Connected  by  branches  with  the  foregoing,  and  lying  in  the  sub- 


342 


FORCES   CONCERNED    IN    ABSORPTION. 


mucoM.  b  the  plexus  of  Meissner,  which  is  much  finer,  the  meshes  being  wider,  the  nodes  smaller, 
but  nlM»  providol  with  j,'nngl'"'>'C  ceils.  It  supplies  the  muscular  fibres  and  arteries  of  the  mucosa, 
incluHinj;  tho^  of  the  villi.     It  al.so  sends  branches  to  I.ieberkiihn's  glands  (Fig.  176). 

[Structure  of  the  Large  Intestine. — It  has  four  coats,  like  those  of  the  small  intestine.  The 
serous  coat  has  the  same  >truct6re  as  that  of  the  small  intestine.  The  muscular  coat  has  external 
lomptuiiinitl  fibres  occurring  all  round  the  gut,  but  they  form  three  flat,  ribl  on-like  longitudinal  bands 
in  the  cecum  and  colon  (Fig.  214).  Inside  this  coat  are  the  circular  fibres.  The  sub-mucosa  is 
practically  the  >amc  as  that  of  the  iimaU  intestine.  The  mucosa  is  distinguished  by  negative 
character..  It  has  no  villi  and  no  I'cyer's  patches,  but  otherwise  it  resembles  structurally  the  small 
intotinc,  consisting  of  a  basis  of  adenoid  tissue  with  the  simple  tubular  glands  of  Lieberkiihn 
(Fig.  199V  The-se  glands  are  very  numerous  and  somewhat  longer  than  those  of  the  small  intestine, 
and  they  always  contain  far  more  goblet  cells — about  ten  times  as  many.  The  cells  lining  them  are 
devoid  of  a  clear  di.sk.  Solitary  glands  occur  throughout  the  entire  length  of  the  large  intestine. 
At  the  basis  of  I.ieberkiihn's  glands  is  the  muscularis  mucosae.  The  blood  vessels  and  nerves 
have  a  >imilar  arrangement  to  tho.se  in  the  .stomach.] 

[Blood  Vessels. — On  looking  down  on  an  opaque  injection  of  the  mucous  membrane  of  the 
stomach,  one  sees  a  dease  meshwork  of  polygonal  areas  of  unecjual  size,  with  depressions  here  and 
there.  The  orifices  are  the  orifices  of  the  gastric  glands,  each  surrounded  by  a  capillary.  A  some- 
what similar  appearance  is  .seen  in  an  opaque  injection  of  the  mucous  membrane  of  the  large  intestine, 
but  in  the  latter  the  meshwork  is  uniform,  all  the  orifices  (of  Lieberkiihn's  glands)  being  of  the  same 
size.  ] 

191.  ABSORPTION  OF  THE  DIGESTED  FOOD.— The  physical 
forces  concerned  are  endosmosis,  diffusion,  and  filtration. 

All  the  constituents  of  the  AkkI,  with  the  exception  of  the  fats,  which  in  part  are  changed  into  a 
fine  emulsion,  are  brought  into  a  .state  of  solution  by  the  digestive  proce.sses.  These  substances  pass 
through  the  walls  of  the  intestinal  tract,  either  into  the  blood  vessels  of  the  mucous  membrane  or  into 
the  beginning  of  the  Ij-mphatics.  In  this  passage  of  the  fluids  two  physical  processes  come  into  play 
— cntiosmoiii  and  diffusion,  as  well  as  Jillration. 

I.  Endosmosis  and  diffusion  occur  between  two  fluids  which  are  capable  of  forming  an  intimate 
mixture  with  each  other,  e.  ;'.,  hydrochloric  acid  and  water,  but  never  between  two  fluids  which  do 
not   form  a  jierfect  mixture,  such  as  oil  and  water.     If  two  fluids  capable  ot 
Fig,  215.  mixing  with  each  other,  but  of  different  compositions,  be  separated  from  each 

^  other  by  means  of  a  septum  with  physical  pores  (which  occur  even  in  a  homo- 

geneous membrane),  an  exchange  of  the  constituents  in  the  fluids  occurs  until 
both  fluids  have  the  same  composition.  This  exchange  of  fluids  is  termed 
endosmosis  or  diosmosis. 

Diffusion. — If  the  two  mixable  fluids  are  placed  in  a  vessel,  the  one  fluid 
over  the  other,  but  without  being  separated  by  a  porous  septum,  an  exchange 
of  the  particles  of  the  fluids  aLso  occurs,  until  the  whole  mixture  is  of  uniform 
comix)>ition.     This  process  is  called  diffusion. 

Conditions  Influencing  Diffusion.— Graham's  investigations  showed  that 
the  rapidity  of  difi'usion  is  influenced  by  (i)  The  nature  of  the  fluids  them- 
selves ;  acids  diffu.se  most  rapidly ;  the  alkaline  salts  more  slowly ;  and  most 
slowly,  fluid  albumin,  gelatin,  gum,  dextrin.  These  last  do  not  cr)'staUize,  and 
perhaps  do  not  form  true  solutions.  (2)  The  more  concentrated  the  solutions, 
the  greater  the  diffusion.  (3)  Heat  accelerates,  while  cold  retards,  the  process. 
(4)  If  a  .solution  of  a  body  which  diffuses  with  difficulty  be  mixed  with  an 
easily  diffusible  one,  the  former  diff'uses  with  still  greater  difficulty.  (5)  Dilute 
solutions  of  .several  substances  diffu.se  into  each  other  without  any  difficulty,  but 
if  concentrated  solutions  are  employed  the  process  is  retarded.  (6)  Double 
salts,  one  constituent  of  which  diffuses  more  readily  than  the  other,  may  be 
chemically  separated  by  diffusion. 

Endosmometer.— The  exchange  of  the  fluid  particles  takes  place  inde- 
pendenlly  of  the  hydrostatic  pressure.  An  endosmometer  (Fig.  215)  consists 
of  a  glass  cylinder  filled  with  distilled  water,  and  into  this  is  placed  a  flask,  J, 
without  a  lx)ttom,  instead  of  which  a  membrane,  w,  is  tied  on.  A  glass  tube, 
K,  IS  fixed  firmly,  l;y  means  of  a  cork,  into  the  neck  of  the  flask.  The  flask  is 
filled  up  to  the  lower  end  of  the  tube  with  a  concentrated  salt  .solution,  and  is 
•ru"  n^  [^  •  '"  '^^  cylindrical  vessel  until  both  fluids  are  on  the  same  level,  x. 
1  he  fluid  m  the  tube,  R,  soon  begins  to  rise,  because  water  passes  through  the 
membrane  into  the  concentrated  .solution  in  the  flask,  and  this  independently  of 
the  hydrostatic  pressure.  Particles  of  the  concentrated  salt  solution  pass  into 
continue  nntil  th.  fl  "1  ".u  !"  """"i  '"'^,^'th  the  water,  F.  These  outgoing  and  ingoing  currents 
Lwavs  stld  hLLr  ''  ^"  ""»5,  ""^'"  J  ^""^  °f  ""'f°""  composition,  whereby  The  fluid  in  R 
al*a)s  standi  higher  {e.g.,  at  v),  while  it  is  lowered  in  the  cylinder      The  circumstance  of  the  level 


f 


"^ 


Endosmometer. 


COLLOIDS.  343 

of  the  fluid  within  the  tube  being  so  high,  and  remaining  so,  is  due  to  the  fact  that  the  pores  in  the 
membrane  are  too  fine  to  allow  the  hydrostatic  pressure  to  act  through  them. 

Endosmotic  Equivalent. — Experiment  has  shown  that  equal  weights  of  different  soluble  sub- 
stances attract  different  amounts  of  distilled  water  through  the  membrane  i.  e.,  a  known  weight  of  a 
soluble  substance  (in  the  flask)  can  be  exchanged  by  endosmosis  for  a  definite  weight  of  water.  The 
term  "endosmotic  equivalent"  indicates  the  weight  of  distilled  water  that  passes  into  the  flask  of  the 
endosmometer,  in  exchange  for  a  known  weight  of  the  soluble  substance  [Jolly).  For  i  grm.  alcohol 
4.2  grms.  water  were  exchanged;  while  for  I  grm.  NaCl,  4.3  grms.  water  passed  into  the  endosmo- 
meter.    The  following  numbers  give  the  endosmotic  equivalent  of — 


Acid  potassium  sulphate,         .  =  2.3 

Common  salt,       .       .       .       .  =  4.3 

Sugar, =7.1 

Sodium  sulphate,        .       .       .  =11.6 


Magnesium  sulphate,  .  .  =11.7 

Potassium  sulphate,  .  .  =  12.0 

Sulphvuic  acid,  .      .  .  .  =     0.39 

Potassium  hydrate,  .  .  .  — 915  n 


The  amount  of  the  substance  which  passes  through  the  membrane  into  the  water  of  the  cylinder  is 
proportional  to  the  concentration  of  the  solution.  If  the  water  in  the  cylinder,  therefore,  be  repeatedly 
renewed,  the  endosmosis  takes  place  more  rapidly,  and  the  process  of  equilibration  is  accelerated. 
The  larger  the  pores  of  the  membrane,  and  the  smaller  the  molecules  of  the  substance  in  solution,  the 
more  rapid  is  the  endosmosis.  Hence,  the  rapidity  of  endosmosis  of  different  substances  varies,  e.  g,, 
the  rapidity  of  sugar,  sodium  sulphate,  common  salt,  and  urea  is  in  the  ratio  of  I  :  I.I  :  5  :  9.5. 

The  endosmotic  eijuivalent  is  710I  constant  for  each  substance.  It  is  influenced  by  (l)  The 
temperature,  which,  as  it  increases,  generally  increases  the  endosmotic  equivalent.  (2)  It  also  varies 
with  the  degree  of  concentration  of  the  osmotic  solutions,  being  greater  for  dilute  solutions  of  the 
substances. 

If  a  substance  other  than  water  be  placed  in  the  cylinder,  an  endosmotic  cuiTent  occurs  on  both 
sides  until  complete  equality  is  obtained.  In  this  case,  the  currents  in  opposite  directions  disturb  each 
other.  If  two  substances  be  dissolved  in  the  water  in  the  flask  at  the  same  time,  they  diffuse  into 
water  without  affecting  each  other.  (3)  It  also  varies  with  membranes  of  varying  porosity.  Common 
salt,  which  gives  an  endosmotic  equivalent  with  a  pig's  bladder  =  4.3,  gives  6.4  when  an  ox  bladder 
is  used;   2.9  with  a  swimming  bladder;   and  20.2  with  a  collodion  membrane. 

Colloids. — There  are  many  fluid  substances  which,  on  account  of  the  great  size  of  their  molecules, 
do  not  pass,  or  pass  only  with  difficulty,  through  the  pores  of  a  membrane  impregnated  with  gelatinous 
bodies,  which  diffuse  slowly.  These  substances  are  not  actually  in  a  true  state  of  solution,  but  exist 
in  a  very  dilute  condition  of  imbibition.  Such  substances  are  the  fluid  proteids,  starches,  dextrin, 
gum,  and  gelatin.  These  diffuse  when  no  septum  is  present,  but  diffuse  with  difficulty,  or  not  at  all, 
through  a  porous  septum.  Graham  called  these  substances  colloids,  because,  when  concentrated, 
they  present  a  glue-like  or  gelatinous  appearance ;  farther,  they  do  not  crystallize,  while  those  sub- 
stances which  diffuse  readily  are  crystalline,  and  are  called  crystalloids.  Crystallizable  substances 
may  be  separated  from  non-crystallizable  by  this  process,  which  Graham  called  dialysis.  Mineral 
salts  favor  the  passage  of  colloids  through  membranes. 

That  endosmosis  takes  place  in  the  intestinal  tract,  through  the  mucous  mem- 
brane and  the  delicate  membranes  of  the  blood  and  lymph  capillaries,  cannot  be 
denied.  On  the  one  side  of  the  membrane,  within  the  intestine,  are  relatively 
concentrated  solutions  of  highly  diffusible  salts,  peptones,  sugar  and  soaps,  and 
within  the  blood  vessels  are  the  colloids  which  are  scarcely  diffusible,  e.g.,  the 
proteids  of  blood  and  lymph. 

II.  Filtration  is  the  passage  of  fluids  through  the  coarse  intermolecular  pores  of  a  membrane 
owing  to  pressure.  The  greater  the  pressme,  and  the  larger  and  more  numerous  the  pores,  the 
more  rapid  does  the  fluid  pass  through  the  membrane ;  increase  of  temperature  also  accelerates  it. 
Those  substances  which  are  imbibed  by  the  membrane  filter  most  rapidly,  so  that  the  same  substance 
filters  through  different  membranes  with  varying  rapidity.  The  filtration  is  usually  slower,  the  greater 
the  concentration  of  the  fluid.  The  filter  has  the  property  of  retaining  some  of  the  substances  from 
the  solution  passing  through  it,  e.g.,  colloid  substances — or  water  (in  dilute  solutions  of  nitre).  In  the 
foi-mer  case  the  filtrate  is  more  dilute,  in  the  latter  more  concentrated,  than  before  filtration.  Other 
substances  filter  without  undergoing  any  change  of  concentration.  Many  membranes  behave  differently, 
according  to  which  surface  is  placed  next  the  fluid ;  thus  the  shell  membrane  of  an  egg  permits  filtra- 
tion only  from  without  inward  ;  [and  the  same  is  true  to  a  much  less  extent  with  filter  paper ;  the 
smooth  side  of  the  filter  paper  ought  always  to  be  placed  next  the  fluid  to  be  filtered.  The  intact  skin 
of  the  grape  prevents  the  entrance  of  fungi  into  the  fi-uit] .  There  is  a  similar  difference  with  the  gastric 
and  intestinal  mucous  membrane. 

[By  using  numerous  layers  of  filter  paper,  many  colloids  and  crystalloids  are  retained  in  the  filter,  e.g., 
hemoglobin,  albumin,  and  many  coloring  matters,  especially  aniline  colors,  the  last  being  arrested  by 
glass  wool   [Krysinski).'] 

[Filtration  of  Albumin. — Rimeberg  finds  that  the  amount  of  albumin  in  pathological  transu- 
dations varies  with  (i)  the  capillary  area,  being  least  in  cedema  of  the  subcutaneous  tissue.     (2)  The 


344  ABSORPTION    OF   SOLUBLE   CARBOHYDRATES. 

preencc  or  al>scncc  of  inflammatory  procestfs  in  the  vascular  wall,  non-inflammatory  pleuritic  eftu- 
lion  containinR  2  ix-r  cent.,  and  inflammatory  6  i>er  cent.,  of  albumm.  (3)  1  he  condi  ion  and  amount 
of  alhumi,,  m  iht  bloci.  The  amount  of  albumin  in  the  transudate  never  reaches,  although  it  some- 
time ai.pnmchi-s.  that  in  bloo<l.  In  ascites  in  tjeneral  dropsy  the  amount  is  03  to  .04  I^'^r  cent  (4) 
The  JJranon  of  the  transudation.  (5)  Perhaps  the  blood  pressure  and  the  condition  of  the 
circulation.] 

Filtration  of  the  soluble  substance  may  take  place  from  the  canal  of  the 
digestive  tract  when  :  (i)  The  intestine  contracts  and  thus  exerts  pressure  upon  its 
contents.  This  is  possible  when  the  tube  is  narrowed  at  two  points,  and  the 
musculature  between  these  two  points  contracts  upon  the  fluid  coiitents.  (2) 
Filtration,  under  negative  pressure,  may  be  caused  by  the  villi  {Briicke). 
When  the  villi  contract  energetically,  they  empty  their  contents  toward  the 
blood  and  Ivmph  vessels.  The  lacteal  remains  empty,  as  the  chyle  is  prevented 
from  passing  backward  into  the  origin  of  the  lacteal  within  the  villi,  owing  to  the 
presence  of  numerous  valves  in  the  lymphatics.  When  the  villi  relax,  they  are 
refilled  with  fluids  from  the  intestine. 

192.  ABSORPTION  BY   THE  INTESTINAL   WALL.— I.  True 

solutions  undoubtedly  pass  by  endosmosis  into  the  blood  vessels  and  lymphatics 
of  the  intestinal  walls,  but  numerous  facts  indicate  that  the  protoplasm  of  the  cells 
takes  an  active  part  in  the  process  of  absorption.  The  forces  concerned  have  not 
as  yet  been  proved  to  be  ])urcly  physical  and  chemical  in  their  nature. 

(i)  Inorganic  Substances. — Water  and  the  soluble  salts  necessary  for 
nutrition  are  easily  absorbed,  the  latter  especially  by  the  blood  and  lymph 
vessels.  When  saline  solutions  pass  by  endosmosis  into  the  vessels,  water  must 
pass  from  the  intestinal  vessels  into  the  intestine.  The  amount  of  water,  how- 
ever, is  small,  owing  to  the  small  endosmotic  equivalent  of  the  salts  to  be  absorbed. 
More  salts  are  absorbed  from  concentrated  than  from  dilute  solutions.  If  large 
quantities  of  salt,  with  a  high  endosmotic  equivalent,  e.g.,  magnesiun  or  sodium 
sulphate,  are  introduced  into  tlie  intestine,  these  salts  retain  the  water  necessary 
for  their  solution,  and  may  thus  cause  diarrhoea.  Conversely,  when  these  sub- 
stances are  injected  into  the  blood,  a  large  quantity  of  water  passes  from  the 
intestine  into  the  blood,  so  that  constipation  occurs,  owing  to  the  dryness  of  the 
intestinal  contents  {Aiidert). 

[M.  Hay  concludes  from  his  experiments  (§  161),  that  salts,  when  placed  in  the  intestines,  do  not 
alistmct  water  from  the  blood,  or  are  themselves  absorbed,  in  virtue  of  an  endosmotic  relation  being 
establishc<l  between  the  blood  and  the  saline  solution  in  the  intestines.  Absorption  is  probably  due 
to  the  hllration  and  diflusion.  or  processes  of  inhibition  other  than  endosmosis,  as  yet  little  understood. 
The  result  obtained  by  Aubert,  which  is  not  constant,  is  mostly  caused  by  the  great  diuresis  which  the 
injected  salt  excites.]  The  absorption  of  fluids  takes  place  best  at  a  medium  pressure  of  80  to  140 
c.cm.  of  water  within  the  intestine;  higher  pressure  compresses  the  blood  vessels  and  diminishes  the 
aljsorption.  During  digestion,  owing  to  the  dilatation  of  the  vessels,  absorption  is  more  rapid.  The 
fact  that  0.5  per  cent,  solution  of  NaCl  is  absorbed  better  than  water,  and  soda  solution  than  potash 
solution,  seems  to  show  that  physical  forces  are  not  the  only  factors  concerned. 

Numerous  inorg.inic  substances,  which  do  not  occur  in  the  body,  are  absorbed  by  endosmosis  from 
the  intestine,  <•.,;'.,  dilute  sulphuric  acid,  jwlassium  iodide,  chlorate  and  bromide,  and  many  other  salts. 

(2)  The  soluble  carbohydrates,  such  as  the  sugars,  of  which  the  chief 
representatives  are  dextrose  and  maltose,  with  a  relatively  high  endosmotic 
equivalent.  Cane  sugar  is  changed  by  a  special  ferment  into  invert-sugar  (§  183,  5). 
Absorption  appears  to  take  place  somewhat  slowly,  as  only  very  small  quantities 
of  grape  sugar  are  found  in  the  chyle  vessels,  or  the  portal  vein,  at  any  time. 
According  to  v.  Mering,  the  sugar  passes  from  the  intestine  into  the  rootlets  of  the 
portal  vein  ;  dextrin  also  occurs  in  the  portal  vein.  When  the  blood  of  the  portal 
vein  IS  boiled  with  dilute  sulphuric  acid,  the  amount  of  sugar  is  increased  The 
amount  of  sugar  absorbed  depends  upon  the  concentration  of  its  solution  in  the 
intestine ;  hence  the  amount  of  sugar  in  the  blood  is  increased  after  a  diet  con- 
taining much  of  this  substance,  so  that  it  may  appear  in  the  urine  ;  in  which  case 


ABSORPTION    OF    PEPTONES    AND    PROTEIDS.  345 

the  blood  must  contain  at  least  0.6  per  cent,  of  sugar.  A  small  amount  of  cane 
sugar  has  also  been  found  in  the  blood  (C/.  Bernard).  The  sugar  is  used  up  in 
the  bodily  metabolism  ;  some  of  it  is  perhaps  oxidized  in  the  muscles  (§  176). 

(3}  The  peptones  have  a  small  endosmotic  equivalent,  a  2  to  9  per  cent, 
solution  =  7  to  10.  Owing  to  their  great  diffusibility  they  are  readily  absorbed, 
and  they  are  the  chief  representatives  of  the  proteids  which  are  absorbed.  The 
amount  absorbed  depends  upon  the  concentration  of  their  solution  in  the  intestine. 
When  animals  are  fed  on  peptones  (with  the  necessary  fat  or  sugar),  they  serve  to 
maintain  the  body  weight.  [According  to  Plosz  and  Gyorgyai,  Drosdorff  and 
Schmidt-Mulheim,  peptones  occur  only  in  traces  in  the  blood  of  the  portal  vein. 
Neumeister,  however,  using  the  best  methods,  finds  that  although  peptones  are 
abundant  in  the  intestine,  not  a  trace  of  peptone  or  of  the  albumoses  is  found 
either  in  the  blood  or  lymph.  This  coincides  with  Hofmeister's  researches,  and 
is,  of  course,  opposed  to  the  results  of  the  above-named  observers.  As  no  peptones 
or  albumoses  have  been  found  in  the  blood,  and  as  they  can  compensate  for  the 
total  metabolism  of  the  proteids  within  the  body,  we  must  assume  that  they  are 
rapidly  converted  into  albuminous  bodies.]  Hofmeister  supposes  that  the  leuco- 
cytes absorb  the  peptones  and  act  as  their  carriers,  much  as  the  red  corpuscles  are 
oxygen  carriers.  They  carry  the  peptones  into  the  mucous  membrane  of  the 
stomach  and  small  intestine,  which  are  very  rich  in  peptone  at  the  fourth  hour  of 
digestion.  [The  number  of  leucocytes  is  greatly  increased  in  the  mucous  mem- 
brane, especially  in  the  stomach  and  upper  part  of  the  duodenum,  during  diges- 
tion, and  diminished  during  fasting  in  dogs  and  cats.  The  same  is  the  case  with 
the  lymph  follicles,  the  cells  of  which  are  formed  by  the  division  of  the  pre-exist- 
ing cells.]  It  is  asserted  by  Salvioli  that  the  mucous  membrane  possesses  the 
property  of  changing  peptone  into  albumin. 

[Injection  of  Peptone  into  Blood. — When  peptone  is  injected  into  the  blood  of  an  animal, 
within  twenty  minutes  thereafter  no  trace  of  the  peptone  is  to  be  found  in  the  blood,  although  it  has 
not  been  excreted  by  any  of  the  organs.  Peptones  so  injected  prevent  the  blood  of  the  dog  (not  of  the 
rabbit  or  pig)  from  coagulating.  In  large  quantity  they  are  fatal.  Fano  asserts  that  the  peptone  is 
taken  up  by  the  red  blood  corpuscles,  which  thus  become  of  greater  specific  gravity,  and  change  it 
into  globulin.  After  three  or  more  hours  the  corpuscles  return  the  globulin  to  the  blood,  so  that  the 
corpuscles  represent  a  reserve  store  of  proteid.  The  peptones  used  in  these  experiments  were  really 
a  mixture  of  peptones  and  albumoses.  Neumeister  finds  that  in  the  dog,  when  albumoses  are 
injected  into  the  blood  they  reappear  in  the  urine,  but  somewhere  in  the  body  they  undergo  hydra- 
tion in  the  sense  in  which  peptic  digestion  causes  hydration.  The  two  primary  albumoses  reappear 
almost  completely  as  deutero-albumose,  and  deutero-albumose,  when  introduced,  reappears  as  pep- 
tone. Peptone,  however,  reappears  unchanged.  In  rabbits,  albumose  reappears  vmchanged  in  the 
urine.] 

(4)  Unchanged  true  proteids  filter  with  great  difficulty,  and  much  albumin 
remains  upon  the  filter.  On  account  of  their  high  endosmotic  equivalent  they 
pass  with  extreme  slowness,  and  only  in  traces,  through  membranes.  Neverthe- 
less, it  has  been  conclusively  proved  that  unchanged  proteids  can  be  absorbed 
(yBrilcke),  e.  g.,  casein,  soluble  myosin,  alkali-albuminate,  albumin  mixed  with 
common  salt,  gelatin  (Vbi'f,  Bauer,  Eichhorsf).  They  are  absorbed  even  from 
the  large  intestine  {Czerny  and  Latschenberger),  although  the  human  large  intes- 
tine cannot  absorb  more  than  6  grms.  daily.  But  the  amount  of  unchanged 
proteids  absorbed  is  always  very  much  less  than  the  amount  of  peptone. 

Egg  albumin  without  common  salt,  syntonin,  serum  albumin,  and  fibrin  are  not  absorbed  {Eick- 
horst).  Landois  observed  in  the  case  of  a  young  man  who  took  the  whites  of  14  to  20  eggs  along 
with  NaCl,  that  albumin  was  given  off  by  the  m-ine  for  4  to  10  hours  thereafter.  The  amount  of 
albumin  given  off  rose  until  the  third  day,  and  ceased  on  the  fifth  day.  The  more  albumin  taken, 
the  sooner  the  albuminuria  appeared,  and  the  longer  it  lasted.  The  unchanged  egg  albumin  re- 
appeared in  the  urine.  If  egg  albumin  be  injected  into  the  blood,  part  of  it  reappears  in  the  urine 
(§  41,  2)   [Stokvis,  Lehmann). 

(5)  The  soluble  fat  soaps  represent  only  a  fraction  of  the  fats  of  the  food 
which  are  absorbed ;   the  greater  part  of  the  neutral  fats  being  absorbed  in  the 


346  ABSORPTION    OF    FATTY    PARTICLES. 

form  of  very  fine  particles— as  an  emulsion  (§  192,  II).  The  absorbed  soaps 
have  been  found  in  (he  ch\/e,  and  as  the  blood  of  the  portal  vein  contains  more 
soaps  dtirin-i  digestion  than  during  hunger,  it  has  been  assumed  that  the  soaps 
pass  into  tlic  intestinal  blood  capillaries.  The  investigations  of  Lenz,  Bidder, 
and  Schmidt,  render  it  probable  that  the  organism  can  absorb  only  a  limited 
amount  of  fat  within  a  given  i)eriod  ;  the  amount  perhaps  bears  a  relation  to  the 
amount  of  bile  and  pancreatic  juice.  The  maximum  per  kilo,  (cat)  was  0.6 
grm.  of  fat  jK-r  hour. 

Perhaps  the  soaps  reunite  with  glycerine  in  the  parenchyma  of  the  villi,  to  form 
neutral  fats,  as  IVrewoznikoff  and  Will  found  neutral  fats,  after  injecting  these 
two  ingredients  into  the  intestinal  canal,  while  Ewald  found  that  fat  was  formed 
when  soaps  and  glycerine  were  brought  into  contact  with  the  fresh  intestinal 
mucous  meml)rane.  Perhaps  this  is  the  explanation  of  the  observation  of  Bruch, 
who  found  fatty  particles  within  the  blood  vessels  of  the  villi.  No  fatty  acids 
are  found  in  blood,  or  chyle. 

Absorption  of  other  Substances. — Of  soluble  substances  which  are  introduced  into  the  intes- 
tinal canal,  sonic  arc  al>sorl)c(l  and  others  are  not.  The  following  are  absorbed:  alcohol,  part  of 
which  ap|)ears  in  the  urine  (not  in  the  ex])ired  air),  viz.,  that  p.irt  which  is  not  changed  into  COj  and 
H,0,  within  the  IkhIv ;  tartaric,  citric,  malic,  and  lactic  acids;  glycerine,  inulin ;  gum  and  vegetable 
mucin,  which  give  rise  to  the  formation  of  glycogen  in  the  liver. 

.\mong  coloring  matters,  aliiiarin  (from  madder),  alkannet,  indigo-sulphuric  acid,  and  its  soda 
salt  arc  absorbed;  h;emalin  is  jiartly  absorbed,  while  chlorophyll  is  not.  Metallic  salts  seem  to  be 
kept  ill  solution  l)y  proteids,  are  perhaps  absorbed  along  with  them,  and  are  partly  canied  by  the 
blood  of  the  portal  vein  to  the  liver  (ferric  sul])hate  has  been  found  in  chyle).  Numerous  poisons 
are  ver)-  ra])idly  absorl)ed,  e.  ^.,  hydrocyanic  acid  after  a  few  seconds ;  potassium  cyanide  has  been 
found  in  the  chyle.  [If  salts  (KI,  sulphocyanide  of  ammonium)  be  injected  into  a  ligatured  loop  of 
intestine  (dog,  cat,  rabbit),  these  substances  are  absorbed  both  by  the  blood  and  lymph  vessels,  and 
in  lx)th  nearly  simultaneously.]  Even  for  the  ab.soqotion  of  completely  fluid  substances,  endosmosis 
and  filtration  seem  to  be  scarcely  sufficient.  An  active  participation  of  the  protoplasm  of  the  cells 
seems  here  also — in  part  at  least — to  l)e  necessary,  else  it  is  diftiult  to  explain  how  very  slight  dis- 
turbances in  the  activity  of  these  cells,  e.  i^,  from  intestinal  catarrh,  cause  sudden  variations  of  absorp- 
tion, and  even  the  passage  of  fluids  into  the  intestine. 

If  al>sor]ilion  were  due  to  dilTusion  alone,  when  alcohol  is  injected  into  the  intestine,  water  ought 
to  pass  into  the  intestine,  but  this  does  not  occur.  Hrieger  found  that  the  injection  of  a  0.5  to  1  per 
cent,  solution  of  salts  into  a  ligatured  loop  of  intestine  did  not  cause  water  to  pass  into  the  intestine; 
but  it  appc.ind  wli.n  a  20  per  cent,  solution  was  injected. 

II.  Absorption  of  the  Smallest  Particles.— The  largest  amount  of  the 
fats  is  absorbed  in  the  form  of  a  milk-like  emulsion,  formed  by  the  action  of 
the  bile  and  the  pancreatic  juice,  and  consisting  of  excessively  small  granules  of 
uniform  size  (§170,  III;  §181).  The  fats  themselves  are  not  chemically 
changed,  but  remain  as  undecomposed  neutral  fats.  The  particles  seem  to  be 
surrounded  by  a  delicate  albuminous  envelope,  or  haptogen  membrane,  partly 
derived  from  the  pancreatic  juice  [probably  from  its  alkali-albuminate].  The 
villi  of  the  small  intestine  are  the  chief  organs  concerned  in  the  absorption  of  the 
fatty  emulsion,  but  the  epithelium  of  the  stomach  and  that  of  the  large  intestine 
also  take  a  part.  The  fatty  granules  are  recognized  in  the  villi  (i)  Within  the 
delicate  canals?  (§  190)  in  the  clear  band  of  the  epithelium  {Kolliker).  [It  is 
highly  doubtful  if  the  vertical  lines  seen  in  the  clear  disk  of  the  epithelium  of  the 
intestine  are  due  to  pores.]  (2)  The  protoplasm  of  the  epithelial  cells  is  loaded 
with  fatty  granules  of  various  sizes  during  the  time  of  absorption,  while  the  nuclei 
of  the  cells  remam  free,  although,  from  the  amount  of  fat  within  the  cells,  it  is 
often  difficult  to  distinguish  them.  (3)  The  granules  pass  into  the  spaces  of  the 
parenchyma  of  the  vill, ;  these  spaces  communicate  freely  with  each  other.  (4) 
I  he  origin  of  the  lacteal  in  the  axis  of  the  villus  is  found  to  be  filled  with  fatty 
granule.s.  The  amount  of  fat  in  the  chyle  of  a  dog,  after  a  fatty  meal,  is  8  to  10 
per  cent.,  while  the  fat  disappears  from  the  blood  within  thirty  hours 

With  regard  to  the  forces  concerned  in  the  absorption  of  fats,  v.  Wist- 
inghausen  proved,  that  when   a  porous  membrane   is  moistened   with  bile    the 


NUTRIENT   ENEMATA.  347 

passage  of  fatty  particles  through  it  is  thereby  facilitated,  but  this  fact  alOne  does 
not  explain  the  copious  and  rapid  absorption  of  fats.  It  is  possible  that  the  proto- 
plasm of  the  epithelial  cells  is  actively  concerned  in  the  process,  and  that  it  takes 
the  particles  into  its  interior.  Perhaps  a  fine  protoplasmic  process  is  thrown  out 
by  these  cells,  just  as  pseudopodia  are  thrown  out  and  retracted  by  lower  organ- 
isms. It  is  possible  that  absorption  may  take  place  through  the  open  mouths  of 
the  goblet  cells.  The  protoplasm  of  the  epithelial  cells  is  in  direct  communica- 
tion with  the  numerous  protoplasmic  lymph  cells  within  the  reticulum  of  the 
villi,  so  that  the  particles  may  pass  into  these,  and  from  them  through  the 
stomata  (?)  between  the  endothelial  cells  into  the  central  lacteal  of  the  villus. 
According  to  this  view,  the  absorption  of  fatty  particles,  and  perhaps  also  the 
absorption  of  true  proteids,  is  due  to  an  active  vital  process,  as  indicated  by  the 
observations  of  Briicke  and  v.  Thanhoffer.  This  view  is  supported  by  the  obser- 
vation of  Griinhagen,  that  the  absorption  of  fatty  particles  in  the  frog  is  most 
active  at  the  temperature  at  which  the  motor  phenomena  of  protoplasm  are  most 
lively.  That  it  is  due  to  simple  filtration  alone  is  not  a  satisfactory  explanation, 
for  the  amount  of  fatty  particles  in  the  chyle  is  independent  of  the  amount  of 
water  in  it.  If  absorption  were  chiefly  due  to  filtration,  we  would  expect  that 
there  would  most  probably  be  a  direct  relation  between  the  amount  of  water  and 
fat  {^Ludwig  and  Zawilsky).  [The  observations  of  Watney  have  led  him  to  sup- 
pose that  the  fatty  particles  do  not  pass  through  the  cell  protoplasm  to  reach  the 
lacteal,  but  that  they  pass  through  the  cement  substance  between  the  epithelial 
cells  covering  a  villus.  If  this  view  be  correct,  the  absorbing  surface  is  thereby 
greatly  diminished.  Zuwarykin  and  Schafer  suggest  that  the  leucocytes,  which 
have  been  observed  between  the  columnar  cells  of  the  villi  of  the  small  intestine, 
are  carriers  of  at  least  part  of  the  fat  from  the  lumen  of  the  gut  to  the  lacteal ; 
they  also,  perhaps,  alter  it  for  further  use  in  the  economy.  According  to  Zu- 
warykin, Peyer's  patches  in  the  rabbit  seem  to  be  especially  active  in  the  absorp- 
tion of  fat,  so  that  he  attaches  great  importance  to  the  leucocytes  of  the  adenoid 
tissue  in  the  absorption  of  fat.] 

[According  to  Griinhagen,  there  are  several  channels  for  the  absorption  of  fats,  but  they  are  different 
in  different  animals.  Some  are  absorbed  by  the  columnar  epithelium  cells  themselves,  and  some 
passes  between  them.] 

The  activity  of  the  cells  of  the  intestine  with  pseudopodial  processes  may  be  studied  in  the  intestinal 
canal  of  Distomum  hepaticum.  Sommer  has  figm-ed  these  pseudopodial  processes  actively  engaged 
in  the  absorption  of  particles  from  the  intestine. 

193.  INFLUENCE  OF  THE  NERVOUS  SYSTEM.— With  regard 
to  the  influence  of  the  nervous  system  upon  intestinal  absorption,  we  know  very 
little.  After  extirpation  of  the  semilunar  ganglion,  as  well  as  after  section  of  the 
mesenteric  nerves  {Moreau),  the  intestinal  contents  become  more  fluid,  and  are 
increased  in  amount  (§  183).  This  may  be  partly  due  to  diminished  absorption, 
v.  Thanhoffer  states  that  he  observed  the  protrusion  of  threads  from  the  epithelial 
cells  of  the  small  intestine  only  after  the  spinal  cord,  or  the  dorsal  nerves,  had 
been  divided  for  some  time. 

194.  "  NUTRIENT  ENEMATA."— In  cases  where  food  cannot  be  taken  by  the  mouth, 
e.g.,  in  stricture  of  the  oesophagus,  continued  vomiting,  etc.,  food  is  given  per  rectum.  As  the  digestive 
activity  of  the  large  intestine  is  very  slight,  fluid  food  ought  to  be  given  in  a  condition  ready  to  be 
absorbed,  and  this  is  best  done  by  introducing  it  into  the  rectum  through  a  tube  with  a  funnel  attached, 
and  allowing  the  food  to  pass  in  slowly  by  its  own  weight.  The  patient  must  endeavor  to  retain  the 
enema  as  long  as  possible.  When  the  fluid  is  slowly  and  gradually  introduced,  it  may  pass  above  the 
ileo-csecal  valve. 

Soliitions  of  grape  sugar,  and  perhaps  a  small  amount  of  soap  solution,  are  useful ;  and  among  nitro- 
genous substances  the  commercial  flesh-,  bread-,  or  milk  peptones  of  Sanders-Ezn,  Adamkiewicz,  in 
Germany,  and  Darby's  fluid  meat,  and  Carnrick's  beef  peptonoids  in  this  country,  are  to  be  recom- 
mended. The  amount  of  peptone  required  is  i  .1 1  grm.  per  kilo,  of  body  weight  (  Catilloii ) ;  less  useful 
are  buttermilk,  egg  albumin  with  common  salt.  Leube  uses  a  mixture  of  150  grms.  flesh  with  50 
grms.   pancreas   and   loo  grms.  water,  which  he  slowly  injects  into  the  rectum,  where  the  proteids 


348  CIIVI.E    VESSELS   AND    LYMPHATICS. 

•re  p«Moni/cd  and  aJ«orl«d.  [Peptonized  food  prepared  after  the  method  of  Roberts  is  very 
useful  ({172)  1  The  mrtho<l  of  nutrient  enemata  only  permits  imperfect  nutrition,  and  at  most 
only  V  of  the  proteids  ncces.sary  for  maintaining  the  metabolism  of  the  body  is  absorbed  {v.  VoU, 
Bautr). 

105.  CHYLE  VESSELS  AND  LYMPHATICS.— Lymphatics.— Within  the  tissues  of 
the  U^lv.  and  .-v.n  iti  those  tis>ues  which  do  not  contain  blood  vessels,  e.g.,  the  cornea,  or  in  those 
which  contain  few  I.UkxI  ve.ssels,  there  exi.sts  a  system  of  vessels  or  channels  which  contain  the  juices 
of  the  tivues,  an.l  within  these  vessels  the  tluid  always  moves  in  a  centripetal  direction.  These  canals 
■rise  within  the  ti.ssues  in  a  variety  of  ways,  and  unite  in  their  course  to  form  delicate  and  afterward 
thicker  IuIh-s,  w  ich  ultimately  terminate 'in  two  large  trunks  which  open  at  the  junction  of  the  jugu- 
lar and  sulKrlavian  veins;  that' on  the  left  side  is  the  thoracic  duct,  and  that  on  the  right,  the  right 
lymphatic  trunk. 

With  regard  to  the  lymph  and  its  movements  in  different  organs,  it  is  to  be 
noticed  that  this  occurs  in  different  ways  in  different  places,  (i)  In  many  tissues 
the  lymphatics  represent  the  nutrient  channels  by  which  the  fluid  that  transudes 
through  the  neighboring  vessels  is  distributed,  as  in  the  cornea  and  in  many  con- 
nective tissues.  (2)  In  many  tissues,  as  in  glands,  e.g.,  the  salivary  glands  and 
the  testis,  the  lymph  spaces  are  the  chief  reservoirs  for  fluid,  from  which  the 
cells  during  the  act  of  secretion  derive  the  fluid  necessary  for  that  process.  (3) 
The  lymphatics  have  the  general  function  of  collecting  the  fluid  which  saturates 
the  tissues,  and  carrying  it  bark  again  to  the  blood.  The  capillary  blood  system 
may  be  regarded  as  an  irrigation  system,  which  supplies  the  tissues  with  nutri- 
ent fluids,  while  the  lymphatic  system  may  be  regarded  as  a  drainage  apparatus, 
which  conducts  away  the  fluids  that  have  transuded  through  the  capillary  walls. 
Some  of  the  decomjjosition  products  of  the  tissues,  proofs  of  their  retrogressive 
metabolism,  become  mixed  with  the  lymph  stream,  so  that  the  lymphatics  are  at 
the  same  time  absorbing  vessels.  Substances  introduced  into  the  parenchyma 
of  the  ti.ssues  \x\  other  ways,  e.  g.,  by  subcutaneous  injection,  are  partly  absorbed 
by  the  lymphatics.  .\  study  of  these  conditions  shows  that  the  lymphatic  system 
represents  an  appendix  to  the  blood-vascular  system,  and  further  that  there 
can  be  no  lymph  system  when  tlie  blood  stream  is  completely  arrested ;  it  acts 
only  as  a  part  of  the  whole,  and  with  the  whole. 

Lacteals. — When  we  speak  of  the  lymphatics  proper  as  against  the  chyle 
vessels  or  lacteals,  we  do  so  from  anatomical  reasons,  because  the  important  and 
considerable  lyinphatic  channels  coming  from  the  whole  of  the  intestinal  tract 
are,  in  a  certain  sense,  a  fairly  independent  province  of  the  lymphatic  vascular 
area,  and  are  endowed  with  a  high  absorptive  activity,  which,  from  ancient 
times,  has  attracted  the  notice  of  observers.  The  contents  of  the  chyle  vessels 
or  lacteals  are  mixed  with  a  large  amount  of  fatty  granules,  giving  the  chyle  a 
white  color,  which  distinguishes  them  at  once  from  the  true  lymphatics  with 
their  clear,  watery  contents.  From  a  physiological  point  of  view,  however,  the  lac- 
teals must  be  classified  with  the  lymphatics,  for,  as  regards  their  structure  and 
function,  they  are  true  lymphatics,  and  their  contents  consist  of  true  lymph  mixed 
with  a  large  amount  of  absorbed  substances,  chiefly  fatty  granules.  [The  con- 
tents of  the  lacteals  are  white  only  during  digestion  ;  at  other  times  they  are  clear, 
like  lymph.]  ^ 

196.  ORIGIN  OF  THE  LYMPHATICS. -(i)  Origin  in  Spaces. -Within  the  con- 
nective t.s,sues  (connective  tissue  proper,  bone)  are  numerous  stellate,  irregular  or  branched  spaces, 
which  communicate  with  each  other  by  numerous  tubular  processes  (Fig  216  s\-  in  these  com- 
nletT SdTv  fh  .  u'  f  l'"'""-  '''""'r'"  "^  '^''"  "■'^^"'^-  'Th"*^  ^P^^^^'  however,  are  not  com- 
^c/wh  ^h  '  '•'V  '•,  '"  "!!"''"'  \"'''  ^"'^"^*^"  '^^  ^^>-  °f  the  cell  and  the  wall  of  the 
space,  w  hich  is  grea  er  or  less  according  to  the  condition  of  movement  of  the  protoplasmic  cell  These 
spaces  are  the  so-called  "juice  canals"  or  "Saft-canalchen,"  and  they  represent  the  origin  of  the 
lymphatic  vessels  (t;.  Reckhn.hausen).     As  they  communicate  with  neighboring  spaces     he  move 

W°of  Jh^Tells'r'JiSIln'n'"-  '''.?  -"%-'-h 'ie  in  the  spaces  exiibit  aLUd  movements. 
borne  01  these  cells  remain  permanently,  each  in  its  own  space,  within  which  however  it  mav 
change  Its  form-these  are  the  so-called  ••  fixed  connective-tiLsue  corpuscles,''  and  bone  iorTs^ 
clcs-while  others  merely  wander  or  pass  into  these  spaces,  and  are  called  "  wandering  ceUs," 


ORIGIN    OF   THE    LYMPHATICS. 


349 


or  "  leucocytes  ;  "  but  the  latter  are  merely  lymph  corpuscles,  or  colorless  blood  corpuscles  which 
have  passed  out  of  the  blood  vessels  into  the  origin  of  the  lymphatics.  These  cells  exhibit  amoe- 
boid movements.  These  spaces  communicate  with  the  small  tubular  lymphatics — the  so-called  lymph 
capillaries  (L).     The  spaces  lie  close  together 

where  they  pass  into   a  lymph  capillary  («).  Fig.  216. 

The  lymph  capillary,  which  is  usually  of  greater 
diameter  than  the  blood  capillary,  generally 
lies  in  the  middle  of  the  space  within  the 
capillary  arch  (B).  The  finest  lymphatics  are 
lined  by  a  layer  of  delicate,  nucleated,  endo- 
thelial cells  (1?,  e),  with  characteristic  sinous 
margins,  whose  characters  are  easily  revealed 
by  the  action  of  silver  nitrate  (Fig.  217,  L). 
This  substance  blackens  the  cement  substance 
which  holds  the  endothelial  cells  together. 
Between  the  endothelial  cells  are  small  holes, 
or  stomata,  by  means  of  which  the  lymph 
capillaries  communicate  (at  x)  with  the  juice 
canals. 

It  is  assumed  by  Arnold  that  the  blood  ves- 
sels communicate  with  the  juice  canals,  and 
that  fluid  passes  out  of  the  thin-walled  capil- 
laries through  their  stomata  into  these  spaces 
[\  65).  This  fluid  nourishes  the  tissues,  the 
tissues  take  up  the  substances  appi-opriate  to 
each,  while  the  effete  materials  pass  back  into 
the  spaces,  and  from  these  reach  the  lym- 
phatics, which  ultimately  discharge  them  into 
the  venous  blood. 

Whether  the  cells  within  these  spaces  are 
actively  concerned  in  the  pouring  out  of  the 
blood  plasma,  or  take  part  in  its  movement,  is 
matter  of  conjecture.  We  can  imagine  that  by 
contracting  their  body,  after  it  has  been  impregnated  with  fluid,  this  fluid  may  be  propelled  from 
space  to  space  toward  the  lymphatics.  The  leucocytes  wander  through  these  spaces  until  they  pass 
into  the  lymphatics.  Fine  particles 
which  are  contained  in  these  spaces — 
e.g.,  after  tattooing  the  skin,  and  even 
fatty  particles  after  inunction — are  ab- 
sorbed by  the  leucocytes  and  carried 
by  them  to  other  parts  of  the  body. 
[The  pigment  particles  used  to  tattoo 
the  finger  are  usually  found  within 
the  first  lymphatic  gland  at  the 
elbow.] 

The  migration  of  cellular 
elements  from  the  blood  ves- 
sels into  the  origin  of  the 
lymphatics  is  to  be  considered 
as  a  normal  process.  Granu- 
lar coloring  matter  passes  from 
the  blood  into  the  protoplas- 
mic body  of  the  cells  within 
the  lymph  spaces ;  and  only 
when  the  granular  pigment  is 
in  large  amount,  does  it  ap- 
pear as  a  granular  injection  in 
the  branches  of  the  juice 
spaces. 

(2)    Origin   within   villi i.  e.    of  Pleural  surface  of  the  central  tendon  of   the  diaphragm  of  the  rabbit 

thp  rhvlp  vp?s;p1  or  Inrtpal hns  been  stained  with  silver  nitrate.     L,  lymphatic  with  its  sinuous  endothe- 

tne  cnyle  vessel  or  laCteal — nas  Oeen  j^^^^  .  ^^  ^,^,1^  ^^  ^^^  connective  tissue  brought  into  view  by  the  silver 

described  (^  190).  nitrate. 


Origin  of  lymphatics  from  the  central  tendon  of  the  diaphragm 
stained  with  nitrate  of  silver,  s,  the  juice  canals,  commu- 
nicating at  X  with  the  lymphatics;  a,  origin  of  the  lym- 
phatics by  the  confluence  of  several  juice  canals. 


Fig.  217. 


350 


ORIGIN    OF   THE    LYMPHATICS. 


f  •?>  Origin  in  perivascular  spaces  (I'ij;;.  21S). — Tlie  smallest  blood  vessels  of  hone,  the  central 
I,,  ,  tn.  retina  ami  the  liver,  are  coiniilelely  surrounded  l)y  wide  lymphatic  tubes,  so  that  the 

1  are   completely  bathetl  by  a  lymph  stream.      In  the  brain   these   lymphatics  are  partly 

I  delicate   connective  tissue  fibres,  which  traverse   the   lym|)h  space  and  become  attached 

I,  I  the   include<l  bloo<l  vessel,      lij,'.   21.S,   li,  rejjresents   a  transverse   section  of  a  small 

1  :  ,  It,  from  the  brain;  /  is  the  divided  iK"riva.scular  space.     This  space  is  called  the  peri- 

vascular space  of  His,  but  in  addition  to  it  the  blood  vessels  of  the  brain  have  a  lymph  space 
wiihin  the  ndventitia  of  the  bloo<l  vessels  [l'iiiho7f-Kohin's  space).  It  is  partly  lined  by  well- 
detincl  endothelium.  Where  the  bkxxl  ve.s.sels  l)egin  to  increase  considerably  in  diameter,  they  pass 
thniui;li  the  wall  of  the  lymphatics,  and  the  two  ves.sels  afterward  take  separate  courses.  In  all 
I  1  '         (here  i>  a  |K-riva.scular  s|>ace,  the  passage  of  lymj^h  and  blood  coq)uscles  into  the  l}Tnph- 

:r  Iv  facilitated.     In  the  tortoise  the  large  blood  vessels  are  often  surrounded  with  perivas- 

Lu....  I  ...lUcs.     Kig.  21S,  A,  gives  a  re|)resentation  of  the  aorta  surrounded  by  a  perivascular  space 

which  rs  vi>il)le  to  the  unaided  eye.  In  nianunals  the  periva.scular  spaces  are  microscopic. 

(4)  Origin  in  the  form  of  interstitial  slits  within  organs. — Within  the  testis  the  lymphatics 
U-gin  simply  in  the  form  of  numerous  slits,  which  occur  between  the  coils  and  twists  of  the  seminal 
tubules.  They  take  the  form  of  elongated  spaces  Ixjunded  by  the  curved  cylindrical  surfaces  of  the 
tubules.  The  surfaces,  however,  are  covered  with  endothelium.  The  lymphatics  of  the  testis  get 
indejK-ndent  walls  after  they  leave  the  parenchj-ma  of  the  organ.     In  many  other  glands  the   gland 


Fl.:.  21S. 


Fig.  219. 


^^^ 


Perivaicular  lymphatics.      A.    aorta   of   tortoise;    B, 
artery  from  the  brain. 


Stomata  in  the  great  lymph  sac  (frog), 
half-closed ;  c,  closed. 


I  open ;  l>. 


sul,stancc  '«  similarly  surrounded  by  a  lymph  space.  The  blood  vessels  pour  the  Ivmph  into  these 
simcc.s.  and  from  them  the  secretiug  cells  obtain  the  materials  necessary  for  the  formation  of  their 
secretion.  ^ 

(5)  Origin  by  means  of  free  stomata  on  the  walls  of  the  larger  serous  cavities,  which 
(Fig.  2lr,  „,  CM,nmun.cate  freely  with  the  lymphatics.  The  investigation  of  the  serous  surfaces  is 
most  e.i>,ly  accomplished  on  the  septum  of  the  great  aklominal  lymph  sac  of  the  frog.  Silver  nitrate 
vZhl^L  '"'""7'"  f7<-;l'»l'vely  large  free  o,>enings  or  stomata  lying  between  The  endothelium. 
undrnroT;!, ','  TV  ■  '"'T'  e^'^'^a'i"?  "lis,  which  have  a  granular  appearance,  and 
the^  celK  h^'il?  '.'''•  '°  '^'  "'"  ^""  "''  "^''  ^'""^-"^  '•'=1'^"^'^  "PO"  "^^  degree  of  contraction  of 
iJeThe  ori;in  nf  .t'  f  °'"?.  T  >'  '^  °I>^"  '«'-  ^alfopen  (/,,.  or  completely  closed  (.).  These  stomata 
Stidl  nlaced  in  ,h^  '>"'P*^""":  The  serous  cavities  belong  therefore  to  the  lymphatic  system,  and 
preta'^trilrdiumTr.'  ""^"^'V^  P^^^  ["^^  'he  h-mphatics.  The  cavities  of  the  peritoneum, 
TaSLfth^r^;  r?'"^"'''^^  ^'""''""'^  space,  aqueous  chambers  of  the   eye,  and  the 

mSann  1.  fern,  d  tha.T'  '^L?^  '''""''  ^f  t^^  ""'^  '^^>'  '^•^"^^'"  '^  '^  '^^  '"^g-'-d^d  L  lymph, 
the  gc^^al  ;;iSm  ]     ""'  ''^^  ^"^^""^  '^^  ^'^'"^'^  '"  '"^^  ^-g  -^  -"ds  branches  beLJen 

the  tnrin"  Mnpha^rcs".  1^'Tn  Ih"},  "^'T"'  °?  "^^^  "'"'""  -'''«^-«^^.  ^vhich  are  regarded  as 
Stru^turV     Th  '^i'      !h^.^''0"chi,  na.sal  mucous  membrane,  trachea  and  larynx 


LYMPHATIC    GLANDS. 


851 


Fig.  220. 


197.  THE  LYMPH  GLANDS.— The  lymphatic  glands  belong  to  the 

lymph  apparatus.  They  are  incorrectly  termed  glands,  as  they  are  merely  much- 
branched  lacunar  labyrin- 
thine spaces  composed  of 
adenoid  tissue,  and  interca- 
lated in  the  course  of  the 
lymphatic  vessels.  There 
are  simple  and  compound 
lymph  glands.  /^) 

(i)  The  simple  lymph  glands,    ^^ 
or,  more  correctly,  lymph  follicles,      ylj 
are  small  rounded  bodies,  about  the         '■ 
size  of  a  pin  head.     They  consist 
of  a  mass  of  adenoid  tissue   (Fig. 
220,   A),   i.   e.,  of  a  very   delicate 
network  of  fine  reticular  fibres  with 
nuclei  at  their  points  of  intersection, 

and  in  the  spaces  of  the  meshwork  ^^^  ^^^^^  folliclelT  A.  a  small  follicle  highly  magnified,  showing  the 
lie  the  lymph  and  the  IjTnph  corpus-  adenoid   reticulum ;     B,    a  follicle   less    highly   magnified,   showing 

cles.     Near  the  siu-face,  the  tissue  is  injected  bloodvessels, 

somewhat  denser,  where  it  forms  a 

capsule,  which  is  not,  however,  a  true  capsule,  as  it  is  permeated  with  numerous  small  sponge-like 
spaces.  Small  lymphatics  come  directly  into  contact  with  these  lymph  folUcles,  and  often  cover  their 
surface  in  the  form  of  a  close  network.  The  surface  of  the  l}-mph  follicles  is  not  unfrequently  placed 
in  the  wall  of  a  lymph  vessel,  so  that  it  is  directly  bathed  by  the  lymph  stream.  Although  no  direct 
canal-like  opening  leads  from  the  follicle  into  the  lymphatic  stream  in  relation  with  it,  a  communica- 
tion must  exist,  and  this  is  obtained  by  the  numerous  spaces  in  the  folhcle  itself,  so  that  a  lymph 
follicle  is  a  true  l)Tnphatic  apparatus  whose  juices  and  lymph  corpuscles  can  pass  into  the  nearest 
lymphatic.  The  follicles  are  sun-ounded  by  a  network  of  blood  vessels  which  sends  loops  of  capilla- 
ries into  their  interior  (Fig.  220,  B).  We  may  assume  that  lymph  corpuscles  pass  fi-om  these  capil- 
laries into  the  folhcle. 

In  connection  with  these  follicles,  including  those  of  the  back  of  the  tongue,  the  solitary  glands  of 
the  intestine  and  the  adenoid  tissue  in  the  bronchial  tract,  the  tonsils,  and  Peyer's  patches,  it  is  import- 
ant to  remember  that  enormous  num- 
bers of  leucocytes  pass  out  between  ric  221. 
the    epithelial    cells   covering    these 
follicles.     The   extruded  leucocytes 
undergo  disintegration  subsequently. 

(2)  The  compound  lymph 
glands — the  lymphatic  glands — 
represent  a  collection  of  lymph  folli- 
cles, whose  form  is  somewhat  altered. 
Every  lymph'gland  is  covered  exter- 
nally with  a  connective-tissue  cap- 
sule (Fig.  221,  c),  which  contains 
numerous  non-  striped  muscular  fibres . 
From  its  inner  surface,  numerous 
septa  and  trabeculee  (/r.)  pass  into 
the  interior,  so  that  the  gland  sub- 
stance is  divided  into  a  large  number 
of  compartments.  These  com- 
partments in  the  cortical  portion  of 
the  gland  have  a  somewhat  rounded 
form,  and  constitute  the  alveoli,  while 
in  the  medullary  portion  they  have  a 
more  elongated  and  irregular  form. 
[On  making  a  section  of  a  lymph 
gland  we  can  readily  distinguish  the 
cortical  from  the  medullary  pro- 
tion  of  the  gland,]  All  the  com- 
partments are  of  equal  dignity,  and  they  all  communicate  with  each  other  by  means  of  openings,  so 
that  the  septa  bound  a  rich  network  of  spaces  within  the  gland,  which  communicate  on  all  sides  with 
each  other. 

These  spaces  are  traversed  by  therfollicular  threads  (Fig.  222,/,/).     These  represent  the  con- 


Diagrammatic  section  ot  a  lymphatic  gland,  a.  I.,  aflferent,  e.  I.,  efiferent 
.•^.  lymphatics;  C,  cortical  substance:  M,  reticular  cords  of  medulla; 
:,   /.  s.,  lymph  sinus  ;  c,  capsule,  with  trabeculse,  tr. 


852 


LYMPHATIC    GLANDS. 


lenU  of  the  spaces,  but  ore  smaller  than  the  spaces  in  which  they  lie,  and  do  not  come  into  contact 
anywhere  with  the  walls  of  the  spaces.  If  we  imagine  the  spaces  to  be  injected  with  a  mass,  which 
ultimately  shrinks  to  one-half  of  Us  original  volume,  we  obtain  a  conception  of  the  relation  of  these 
follicular'lhrcads  to  the  spaces  of  the  gland.  The  blood  vessels  of  the  gland  {i)  lie  within  these 
follicular  threads.  Thev  are  surrounded  by  a  tolerably  thick  crust  of  adenoid  tissue,  with  very  fine 
meshes  (.r,  x)  filled  with  lymph  corj^uscles,  and  with  its  surface  {0,0)  covered  by  the  cells  of  the 
adenoid  reticulum,  in  such  a  way  as  to  leave  free  communications  through  the  narrow  meshes. 

Between  the  surface  of  the  follicular  threads  and  the  inner  wall  of  all  the  spaces  of  the  gland, 
lies  the  lymph  channel  or  lymph  path  (B,  B),  which  is  traversed  by  a  reticulum  of  adenoid 
tissue,  containing  relatively  few  lymph  cor|)Uscles.  It  is  very  probable  that  these  lymph  paths  are 
lined  by  endothelium. 

The  vasa  afTcrentia  (Kig.  221,  <;./.),  of  which  there  are  usually  several,  expand  upon  the  surface 

Fi<"..  222. 


follicular  MnuxU  from  The  lymph  pa.h'        '     '    '     ^'°°'*  ''"'"''=  "•  "'  "="^^ovv.meshed   part  limiting  the 


To  -n  e  va'sa  effTen  ia  Is''*"  ''  '"^  ^""^  '^'1'  ^°"^^°'^  '"^^  '^'  ^^'^P'^  P^'^s  of  the  gland 
form  Hr.rui .  *^"'^"*'='  "*"^^  '^-^  '"'  """"^rous  than  the  afTerentia,  and  come  out  at  the  hilum, 
h^^    hTl         K  •  '  cavernous  dilatations  and  they  anastomose  near  the  gland  (.  /)      ThroLh 

el  :h  and'pats'rn^Th^lVm'h ''?r'  ^'^  °'  ''^  S'^"^"  '^^^  >ymph%rcoL;es^through  the 
t'he  3fferent'a':?:fferTn't  l>m,!hTelK'^'  "'"'  "^"""^  ^  ''"'  ^^  '^'^  '"'^^'^^^  '"^-P°-d  '-'  — 

Iy.^p"""hrouU'r|tanH?r'e,;ri:  ^'P,""''^  '""'^^  ^-^^'^"^  °f  ^P^"^'  '^e  movement  of  the 
n^it  hasv.ryhttle   loul^^^^^^^^^^^  '"^  '^'  ""'""°"^  resistances  which  occur  in  Us 


COMPOSITION    OF    LYMPH    AND    CHYLE.  353 

cytes  wander  out  into  the  follicular  threads.  The  movement  of  the  lymph  through  the  gland  is 
favored  by  the  muscular  action  of  the  capsule.  When  the  capsule  contracts  energetically,  it  must 
compress  the  gland  like  a  sponge,  and  the  direction  in  which  the  fluid  moves  is  regulated  by  the 
position  and  arrangement  of  the  valves. 

Chemistry. — In  addition  to  the  constituents  of  lymph,  the  following  chemical  substances  have 
been  found  in  lymphatic  glands :  leucin  and  xanthin. 

ig8.  PROPERTIES  OF  CHYLE  AND  LYMPH.— Chyle  and 
lymph  are  albuminous,  colorless,  clear  juices,  containing  lymph  corpuscles, 
which  are  identical  with  the  colorless  blood  corpuscles  (§  9).  In  some  places,  e.g., 
in  the  lymphatics  of  the  spleen,  especially  in  starving  animals,  and  in  the  thoracic 
duct,  a  few  colored  blood  corpuscles  have  been  found.  The  lymph  corpuscles  are 
supplied  to  the  lymph  and  chyle  from  the  lymphatic  glands  and  the  adenoid 
tissue.  As  to  their  source  see  §  200,  2.  They  also  pass  out  of  the  blood  vessels 
and  wander  into  the  lymphatics.  As  red  blood  corpuscles  have  also  been  seen  to 
pass  out  of  the  blood  vessels,  this  explains  the  occasional  presence  of  these  cor- 
puscles in  some  lymphatics ;  but  when  the  pressure  within  the  veins  is  high,  near 
the  central  orifice  of  the  thoracic  duct,  red  blood  corpuscles  may  pass  into  the 
thoracic  duct.  But  we  are  not  entitled  to  conclude  from  their  presence  that 
lymph  cells  form  red  blood  corpuscles.  In  addition,  the  chyle  contains 
numerous  fatty  granules,  each  surrounded  with  an  albuminous  envelope. 
[Thus  the  chyle,  in  addition  to  the  constituents  of  the  lymph,  contains,  especially 
during  digestion,  a  very  large  amount  of  fat,  in  the  form  of  the  finely  emul- 
sionized  fat  of  the  food,  which  gives  it  its  characteristic  white  or  milky  appearance. 
During  hunger,  the  fluid  in  the  lacteals  resembles  ordinary  lymph.  The  fine  fat 
granules  constitute  the  so-called  "molecular  basis"  of  the  chyle.] 

Composition  of  Lymph. — The  lymph  consists  of  lymph  plasma  with 
lymph  corpuscles  suspended  in  it.  The  corpuscles  or  leucocytes  are  described 
in  §  24.  The  lymph  plasma  contains  the  three  so-called  fibrin  factors,  derived 
very  probably  from  the  breaking  up  of  lymph  corpuscles  (§  29).  When  lymph  is 
withdrawn  from  the  body,  these  substances  cause  it  to  coagulate.  Coagulation 
occurs  slowly,  owing  to  the  formation  of  a  soft,  jelly-like,  small  "  lymph  clot," 
which  contains  most  of  the  lymph  corpuscles.  The  exuded  fluid  or  lymph 
serum  contains  alkali  albuminate  (precipitated  by  acids),  serum  albumin  (coagu- 
lated by  heat),  and  paraglobulin — the  two  latter  occurring  in  the  same  proportion 
as  in  blood  serum  ;  37  per  cent,  of  the  coagulable  proteids  is  paraglobulin. 

(i)  Chyle,  which  occurs  within  the  lacteals  of  the  intestinal  tract,  can  only  be 
obtained  in  very  small  amount  before  it  is  mixed  with  lymph,  and  hence  the  difii- 
culty  of  investigating  it.  A  few  lymph  corpuscles  occur  even  in  the  origin  of 
lacteals  within  the  villi,  but  their  number  increases  in  the  vessels  beyond  the 
intestine,  more  especially  after  the  chyle  has  passed  through  the  mesenteric  glands. 
The  amount  ot  solids,  which  undergoes  a  great  increase  during  digestion,  on 
the  contrary,  diminishes  when  chyle  mixes  with  lymph.  After  a  diet  rich  in 
fatty  matters,  the  chyle  contains  \wxi\xx^&x2\At  fatty  granules  (2-4  //.  in  size).  [This 
is  the  so-called  "molecular  basis"  of  the  chyle.]  The  amount  oi  fibrin  factors 
increases  with  the  increase  of  lymph  corpuscles,  as  they  are  formed  from  the  break- 
ing up  of  the  lymph-corpuscles  ;  a  diastatic  ferment  absorbed  from  the  intestine ; 
occasionally  sugar  (to  2  per  cent.);  after  much  starchy  food,  lactates ;  peptone 
in  the  leucocytes  (§  192,  I,  3),  and  traces  of  urea  and  leucin. 

The  Chyle  of  a  person  who  was  executed  contained  90.5  per  cent,  of  water. 

f  Fibrin, trace 

I  Albumin,    .          .          .          .          .  7.1 

1  Fats,            .          .         .          .          .  0.9 
Solids,     ...         .         .         •     9'5      1 

I  Extractives,          .         .         .         .  i.o 

[  Salts, 0.5 

23 


;554 


QUANTITY    OF    LYMPH    AND    CHYLE. 


Schmidt  found  the  following  inorganic  siil)-tances  in  looo  parts  of  chyle  :— 


Sodic  chloride, 

Stxla, 

Totash, 


584 
1.17 


Sul])huric  acid, 
rho-.|)horic  acitl, 
Ca'cic  pho-^ohaie. 


0.05 
0.05 
0.20 


\Iagnesic  phosphate,         0.05 
Iron,         .  trace. 

(Horse.) 


(2)  The  lymph  obtained  from  the  beginning  of  the  lymphatic  system  contains 
very  few  lymjih  corpuscles  ;  it  is  clear,  transparent,  and  colorless,  and  closely 
resembles  the  fluids  of  serous  cavities.  That  the  lymph  coming  from  different 
tissues  varies  somewhat,  is  highly  probable,  but  this  has  not  been  proved.  After 
lymph  has  passed  through  lymphatic  glands,  it  contains  more  corpuscles,  and  also 
more  solids,  especially  albumin  and  fat.  Ritter  counted  8200  lymph  corpuscles 
in  I  cubic  centimetre  of  the  lymph  of  a  dog. 

Pure  lymph  obtained  from  a  lymphatic  fistula  in  the  leg  of  a  man  has  an  alkaline 
reaction' and  a  saline  taste,  and  the  following  composition  :  — 


Pure  Lymph 
(HfHien  &'  Dahnhardt). 


Water, 98.63 

Solids 1.37 

hibrin o.ll 

AUiumin o  14 

Alkali-albuminate,     .    .       0.09 

Extractives, 

Urea,  Leucin,    ....       105 

Salts,      0.88 

70  vol.  per  cent,  of  absorbed 
CO,,  50  per  cent,  could  be 
pumped  out,  and  20  per  cent. 
i)V  the  addition  of  an  acid. 


Cercbro-spinal  Fluid 
( Hoppe-Seyler). 


?8-74 

1.25 

0.16 


The  cerebro-spinal  fluid  and  ab- 
dominal lymph  contain  a  kind 
of  sugar  (without  the  property  of 
rotating  polarized  light — Hoppe- 
SeyUr). 


Pericardial  Fluid 
(».  Gorup-Besanei). 


95  5' 
4.48 
0.08 
2.46 

1.26 


100  parts  of  the  ash  of  lymph  contained  the  following  substances  : — 


Sodium  chloride,  .    .    .  74  48 

Soda, 10.36 

Potash, 3.26 


Sulphuric  acid,  .  .  .  .  1.28 
Carbonic  acid,  ....  8.21 
Iron  oxide 0.06 


Lime, 0.98 

Magnesia 0.27 

Phosphoric  acid, .    ,    .  i  .09 

Just  as  in  blood,  potash  and  phosphoric  acid  are  most  abundant  in  the 
corpuscles;  while  soda  (chiefly  sodium  chloride)  is  most  abundant  in  the 
lymph  serum.  The  potash  and  phosphoric  acid  compounds  are  most 
abundant  in  cerebro-spinal  fluid,  according  to  C.  Schmidt.  The  amount  of 
\vater  in  the  lymph  rises  and  falls  with  that  of  the  blood.  Gases. — Dog's  lymph 
contains  much  CO. — more  than  40  vols,  per  cent.,  of  which  17  per  cent,  can  be 
pumped  out,  and  23  per  cent,  expelled  by  acids,  while  there  are  only  traces  of  O 
and  1.2  vols,  per  cent.  N  i^Liuiwig,  H amine rsteti). 

[The  cerebro-spinal  fluid  contains  a  substance  which  reduces  an  alkaline  solution  of  cupric 
hydrate.  The  jjotassic  are  in  excess  of  the  soda  salts,  while  the  fluid  of  the  meningoceles  and 
chronic  hydrocephalus  contains  proto-albumose,  some  serum  globulin,  no  serum  albumin,  but  the  last 
is    present   in    acute  hydrocephalus    fluid.      No  albumo.se  is  found  in  pericardial  or  pleuritic  fluids 

{HaUibiitt.n  V] 

199.  QUANTITY  OF  LYMPH  AND  CHYLE.— When  it  is  stated  that 
the  total  amount  of  the  lymph  and  chyle  passing  through  the  large  vessels  in 
twenty-four  hours  is  equal  to  the  amount  of  the  blood,  it  must  be  remembered  that 
this  is  merely  a  conjecture.  Of  this  amount  one-half  may  be  lymph  and  the  other 
half  chyle.  The  formation  of  lymph  in  the  tissues  takes  place  continually,  and 
without  interruption.  Nearly  6  kilos,  of  lymph  were  collected  in  twenty-four 
hours  from  a  lymphatic  fistula  in  the  arm  of  a  woman,  by  Gubler  and  Quevenne  ; 
70  to  100  grms.  were  collected  in  i'^  to  2  hours  from  the  large  lymph  trunk  in 
the  neck  of  a  young  horse.  The  following  conditions  affect  the  amount  of  chyle 
and  lymph  :  — 


ORIGIN    OF    LYMPH.  355 

(i)  The  amount  of  chyle  undergoes  very  considerable  increase  during 
digestion,  more  especially  after  a  full  meal,  so  that  the  lacteals  of  the  mesentery 
and  intestine  are  distended  with  white  or  milky  chyle.  During  hunger  the  lymph 
vessels  are  collapsed,  so  that  it  is  difficult  to  see  the  large  trunks. 

(2)  The  amount  of  lymph  increases  especially  with  the  activity  of  the 
organ  from  which  it  proceeds.  Active  or  passive  muscular  movements  greatly 
increase  its  amount.  Lesser  obtained  in  this  way  300  cubic  centimetres  of  lymph 
from  a  fasting  dog,  whereby  its  blood  became  so  inspissated  as  to  cause  death. 

(3)  All  conditions  which  increase  the  pressure  upon  the  juices  of  the  tissues 
increase  the  amount  of  lymph,  and  vice  versa.     These  conditions  are  :  — 

(fl)  An  increase  of  the  blood  pressure,  not  only  in  the  whole  vascular  system,  but  also  in  the 
vessels  of  the  corresponding  organ,  augments,  the  amount  of  lymph  and  vice  versa  {Ltidtvig,  Tomsa). 
This,  however,  is  doubtful,  as  has  been  shown  by  Paschutin  and  Emminghaus.  [In  order  to  increase 
the  amount  of  lymph  depending  upon  pressure  within  the  vessels,  what  must  happen  is  increased 
pressure  within  the  capillaries  and  veins.] 

((6)  Ligature  or  obstruction  of  the  efferent  veins  greatly  increases  the  amount  of  lymph  which 
flows  fi-ora  the  corresponding  parts  {^Bidder-,  Em7?iinghaus).  It  may  be  doubled  in  amount.  Tight 
bandages  cause  a  swelling  of  the  parts  on  the  peripheral  side  of  the  bandage,  owing  to  a  copious 
effusion  of  lymph  into  the  tissue  (congestive  oedema). 

(f)  An  increased  supply  of  arterial  blood  acts  in  the  same  way,  but  to  a  less  degree.  Paraly.-is 
of  the  vasomotor  nerves,  or  stimulation  of  vaso-dilator  fibres,  by  increasing  the  supply  of  blood 
increases  the  amount  of  lymph;  while  diminution  of  the  blood  supply,  owing  to  stimulation  of  vaso- 
motor fibres  or  other  causes,  diminishes  the  amount.  Even  after  ligature  of  both  carotids,  as  the 
head  is  still  supplied  with  blood  by  the  vertebrals,  the  lymph  stream  in  the  large  cervical  lymphatic 
does  not  cease. 

(4)  WTien  the  total  amount  of  the  blood  is  increased,  by  the  injection  of  blood  or  serum  into 
the  arteries,  much  fluid  passes  into  the  tissues  and  increases  the  formation  of  lymph. 

(5)  The  formation  of  Ijinph  still  goes  on  for  a  short  time  after  death,  and  after  complete  cessation 
of  the  aciion  of  the  heart,  but  only  to  a  slight  extent.  If  fresh  blood  be  caused  to  circulate  in  the 
body  of  an  animal,  while  it  is  still  warm,  more  lymph  flows  from  the  lyrrphatics.  It  appears  as  if  the 
tissues  obtained  plasma  from  the  blood  for  a  time  after  the  stoppage  of  the  circulation.  This  perhaps 
explains  the  circumstance  that  some  tissues,  e.  g.,  connective  tissues,  contain  more  fluid  after  death 
than  during  life,  while  the  blcod  vessels  have  given  out  a  considerable  amount  of  their  plasma  after 
death. 

(6)  The  amount  of  lymph  is  increased  under  the  influence  of  curara,  and  so  is  the  amount  of  soUds 
in  the  lymph  [Lesser).  A  large  amount  of  lymph  collects  in  the  IjTnph  sacs  [especially  the  sub- 
lingual] of  firogs  poisoned  with  curara,  which  is  partly  explained  by  the  fact  that  the  lymph  hearts  are 
paralyzed  by  curara.     The  amount  of  lymph  is  also  increased  in  inflamed  parts. 

200.  ORIGIN  OF  LYMPH.— (i)  Source  of  the  Lymph  Plasma.— 

The  lymph  plasma  may  be  regarded  as  fluid  which  has  been  pressed  through  the 
walls  of  the  blood  vessels  by  the  blood  pressure,  /.  e.,  by  filtration  into  the  tissues. 
The  salts  which  pass  most  readily  through  membranes,  go  through  nearly  in  the 
same  proportion  as  they  exist  in  blood  plasma — \.\\tfibriti  factors  to  about  two- 
thirds,  and  albumin  to  about  one-half  of  that  in  the  blood.  As  in  the  case  of 
other  filtration  processes,  the  amount  of  lymph  must  increase  with  increasing 
pressure. 

This  was  proved  by  Ludwig  and  Tomsa,  who  found  that  when  they  passed  blood  serum  under 
varying  pressures  through  the  blood  vessels  of  an  excised  testis,  the  amount  of  transuded  fluid  which 
flowed  from  the  lymphatics  varied  with  the  pressure.  This  "  artificial  lymph  "  had  a  composition 
similar  to  that  of  the  natural  lymph.  Even  the  amount  of  al  'umin  increased  with  increasing  pressure. 
The  lymph  plasma  is  mixed  in  the  different  tissues  with  the  decomposition  products,  the  results  of  the 
metabolism  of  the  tissues. 

When  the  muscles  act,  not  only  is  the  lymph  poured  out  more  rapidly,  but 
more  lymph  is  formed.  The  tendons  and  fascise  of  the  muscles  of  the  skeleton, 
which  are  provided  with  numerous  small  stomata,  absorb  the  lymph  from  the 
muscles.  By  the  alternate  contraction  and  relaxation  of  these  fibrous  structures, 
they  act  like  suction  pumps,  whereby  the  lymphatics  are  alternately  filled  and 
emptied,  while  the  lymph  is  propelled  onward.      Even  passive  movements 


356  MOVEMENT  OF  CHYLE  AND  LYMPH. 

act  in  the  same  way.  If  solutions  be  injected  under  the  fascia  lata,  they  may  be 
propelled  onward  to  the  thoracic  duct  by  passive  movements  of  the  limb  {Ludwig, 
Schu>eig^(^er-Sei(icl ). 

(2)  The  source  of  the  lymph  corpuscles  varies. — (i)  A  very  considerable 
number  of  lymph  corpuscles  are  derived  from  the  lymphatic  glands  ;  they  are 
washed  out  of  these  glands  into  the  vas  efferens  by  the  lymph  stream,  hence,  the 
lymph  always  contains  more  corpuscles  after  it  has  passed  through  a  lymph  gland. 
Small  isolated  lymph  follicles  permit  corpuscles  to  pass  through  their  limiting 
laver  into  the  lymph  stream.  (2)  Those  organs  whose  basis  consists  of  adenoid 
tissue,  and  in  whose  meshes  numerous  lymph  corpuscles  occur,  e.  g.,  the  mucous 
membrane  of  the  entire  intestinal  tract,  red  marrow  of  bone,  and  the  spleen 
(,§  103).  The  cells  reach  the  origin  of  the  lymph  stream  by  their  own  amoeboid 
movements.  (3)  As  lymph  corpuscles  are  returned  to  the  blood  stream,  where 
they  appear  as  colorless  blood  corpuscles,  so  they  again  pass  out  of  the  blood 
capillaries  into  the  tissues,  partly  owing  to  their  amoeboid  movements,  and  they 
are  partly  expelled  by  the  blood  pressure.  In  rare  cases  lymph  corpuscles  wander 
from  lymphatic  spaces  back  again  into  the  blood  vessels. 

Fine  particles  of  cinnabar  or  milk  globules  intro  luced  into  the  blood  soon  pa«s  into  the  lymphatics. 
The  extrusion  of  particles  is  gieater  during  venous  congestion  than  when  the  circulation  is  undisturbed, 
just  as  with  diapedesis  (?.  95)  ;  intlammatoiy  affections  of  the  vascular  wall  also  fa^or  their  passage. 
The  vessels  of  the  portal  system  are  especially  pervious. 

(4)  By  division  of  the  lymph  corpuscles,  and  also  by  proliferation  of  the 
fixed  connective-tissue  corpuscles.  This  process  certainly  occurs  during 
inflammation  of  many  organs.  This  has  been  proved  for  the  excised  cornea  kept 
in  a  moist  chamber  ;  the  nuclei  of  the  cornea  corpuscles  also  proliferate. 

That  the  connective-tissue  corpuscles  proliferate  is  shown  by  the  enormous  product'on  of  lymph 
corpuscles  in  acute  inflammations  (with  the  formation  of  pus),  e.  ^s;-,  in  extensive  erysipelas,  and  in- 
flammatory purulent  effusions  into  serous  cavities,  where  the  number  of  corpuscles  is  too  gieat  to  be 
explaine  1  by  the  wandering  of  blood  coqjuscles  out  of  the  blood  vessels. 

Decay  of  Lymph  Corpuscles. — The  lymph  corpuscles  disappear  partly 
where  the  lymphatics  arise.  The  presence  of  the  fibrin  factors  in  the  lymph — 
formed  as  they  are  from  the  breaking  up  of  lymph  corpuscles — seems  to  indicate 
this.  In  inflammation  of  connective  tissue,  in  addition  to  the  formation  of 
numerous  new  lymph  corpuscles,  a  considerable  number  seems  to  be  dissolved  ; 
hence  the  lymph,  and  also  the  blood,  in  this  case  contains  more  fibrin.  Lymph 
corpuscles  are  also  dissolved  within  the  blood  stream,  and  help  to  form  the  fibrin 
factors. 

201.  MOVEMENT  OF  CHYLE  AND  LYMPH.— The  ultimate 
cause  of  the  movement  of  the  chyle  and  lymph  depends  ui)on  the  difference  of 
the  pressure  at  the  origin  of  the  lymphatics,  and  the  pressure  where  the  thoracic 
duct  opens  into  the  venous  system. 

(i)  The  forces  which  are  active  at  the  origin  of  the  lymphatics  are  concerned 
in  moving  the  lymph,  but  these  must  vary  according  to  the  place  of  origin,  (a) 
The  lacteals  receive  the  first  impulse  toward  the  movements  of  their  contents — 
the  chyle — from  the  contraction  of  the  muscular  fibres  of  the  villi  (pp.  339, 
344).  When  these  contract  and  shorten,  the  axial  lacteal  is  compressed,  and  its 
contents  are  forced  in  a  centripetal  direction  toward  the  large  lymphatic  trunks. 
When  the  villi  relax,  the  numerous  valves  prevent  the  return  of  the  chyle  into  the 
villi,  {b)  Within  those  lymphatics  which  take  the  form  of  perivascular  spaces, 
every  time  the  contained  bloodvessel  is  dilated  the  surrounding  lymph  will  be 
pressed  onward,  (r)  In  the  case  of  the  pleural  lymphatics  with  open  mouths, 
every  inspiratory  movement  acts  like  a  suction  pump  upon  the  lymph,  and 
the  same  is  the  case  with  the  openings  or  stomata  of  the  lymphatics  on  the 
abdominal  side  of  the.  diaphragm,     {d)  In   the  case  of  those  vessels  which  begin 


MOVEMENT  OF  CHYLE  AND  LYMPH. 


357 


by  means  of  fine  juice  canals,  the  movement  of  the  lymph  must  largely  depend 
upon  the  tension  of  the  juices  of  the  parenchyma,  and  this  again  must 
depend  upon  the  tension  or  pressure  in  the  blood  capillaries,  so  that  the  blood 
pressure  acts  like  a  vis  a  tergo  in  the  rootlets  of  the  lymphatics. 

[In  some  organs  peculiar  pumping  arrangements  are  brought  into  action.  The  abdominal  sur- 
face of  the  central  tendon  of  the  diaphragm  is  provided  with  stomata,  or  open  communications 
between  the  peritoneal  cavity  and  the  lymphatics  in  the  substance  of  the  tendon.  Von  Recklinghausen 
found  that  milk  put  upon  the  peritoneal  surface  of  the  central  tendon  showed  little  eddies,  caused  by 
the  milk  globules  passing  through  the  stomata  and  entering  the  lyrphatics.  The  central  tendon 
consists  of  two  layers  of  fibrous  tissue  arranged  in  diflerent  directions  (Fig.  223,  b,  c).     ^\^len  the 


Fig.  22' 


Section  ot  central  tendon  of  diaphragm.     The  injected  lymph  spaces,  h  and  h,  are  black.      At  f  the  walls  of  the 

space  have  collapsed. 

diaphragm  moves  during  respiration,  these  layers  are  alternately  pressed  together  and  pulled  apart. 
Thus  the  spaces  are  alternately  dilated  and  contracted,  lymph  being  drawn  into  the  lymphatics 
through  the  stomata  (Fig.  223,  h^.  The  same  kind  of  pumping  mechanism  exists  over  the  costal 
pleura.  The  fascia  covering  the  muscles  is  another  similar  mechanism.  The  fascia  consists  of  two 
layers  of  fibrous  ti-sue,  with  intervening  lymphatics  (Fig.  224).  WTien  a  muscle  contracts,  lymph  is 
forced  out  fi-om  between  the  layers  of  the  fascia,  while  when  it  relaxes,  the  lymph  fi-om  the  muscle, 
carrying  with  it  some  of  the  waste  products  of  muscular  action,  passes  out  of  the  muscle  into  the 
fascia,  between  the  now  partially  separated  layers.] 

[Ludwig's  Experiment. — Tie  a  respiration  cannula  in  the  trachea  of  a  dead  rabbit ;  cut  across 
the  body  of  the  animal  immediately  below  the  diaphragm  ;  remove  the  viscera,  and  ligature  the 
vessels  passing  between  the  thorax  and  abdomen  ;  tie  the  thorax  to  an  iron  ring,  and  hang  it  up  with 
the  head  downward ;  pour  a  solution  of  Berlin  blue  upon  the  peritoneal  surface  of  the  diaphragm ; 

Fig.  224. 


Injected  lymph  spaces  (black)  from  the  fascia  lata  of  the  dog. 

connect  the  respiration  cannula  either  with  a  pair  of  bellows  or  an  apparatus  for  artificial  respiration, 
and  imitate  the  respiratory  movements.  After  a  few  minutes  the  lymphatics  are  filled  with  a  blue 
injection  showing  a  beautiful  plexus.] 

(2)  Within  the  lymph  trunks  themselves,  the  independent  contraction  of 
their  muscular  fibres  partly  aids  the  lymph  stream.  Heller  observed  in  the 
mesentery  of  the  guinea  pig  that  the  peristaltic  movement  of  the  lymphatic  wall 
passed  in  a  centripetal  direction.  The  numerous  valves  prevent  any  reflux. 
The  contraction  of  the  surrounding  muscles,  and  pressure  upon  the 
vessels  and  the  tissues,  aid  the  current.  If  the  outflow  of  blood  from  the  veins  is 
interfered   with,  lymph  flows  copiously  from  the  corresponding  tissues.     [If  a 


358 


MOVEMENT   OF   THE    LYMPH. 


cannula  be  tied  in  a  lymphatic  of  a  dog,  a  few  drops  of  lymph  flow  out  at  long 
intervals.  But  if  even  />assivc  movements  of  the  limb  be  made,  e.  g.,  simply 
flexing  and  extending  the  limb,  the  outflow  becomes  very  considerable  and 
continuous.] 

(3)  Tlie  lymph  glands,  which  occur  in  the  course  of  the  lymphatics,  offer 
very  considerable  resistance  to  the  lymph  stream,  which  must  pass  through  the 
lymph  paths,  whose  spaces  are  traversed  by  adenoid  tissue,  and  contain  a  few 
lymph  corpuscles.  But  this  is,  to  a  certain  extent,  compensated  for  by  the  non- 
striped  muscle  which  exists  in  the  capsule  and  trabecular  of  the  glands.  When 
they  contract  they  force  on  the  lymph,  while  the  valves  prevent  its  reflux.  En- 
larged lymphatic  glands  have  been  seen  to  contract  when  stimulated  electrically. 
[Botkin  has  stimulated  enlarged  lymphatic  glands  with  electricity  in  cases  of  leu- 
kaemia.] 

(4)  The  lymph  vessels  gradually  join  to  form  larger  vessels,  and  finally  end  in 
one  trunk.  Thus  the  sectional  area  diminishes,  so  that  the  velocity  of  the  cur- 
rent and  the  pressure  are  increased.  Nevertheless,  the  velocity  is  always  small  ; 
it  varied  from  230  to  300  millimetres  per  minute  in  the  large  lymphatic  in  the 
neck  of  a  horse,  a  fact  which  enables  us  to  conclude  that  the  movement  must  be 
very  slow  in  small  vessels.  The  lateral  pressure  at  the  same  place  was  10  to  20 
mm.,  and  in  the  dog  5  to  10  mm.  of  a  weak  solution  of  soda,  although  it  was  = 
12  mm.  Hg  in  the  thoracic  duct  of  a  horse. 

(5)  The  respiratory  movements  exercise  a  considerable  influence  upon  the 
lymph  stream  in  the  thoracic  duct,  and  in  the  right  lymphatic  duct ;  every  inspi- 
ration  fiivors  the  passage  of  the  venous 

f  "^-  2-5-  blood,  and  also  of  the  lymph  toward  the 

I    „^  heart,  whereby  the  tension  in  the  thoracic 

duct  may  even  become  negative.  [The 
diastolic  suction  of  the  heart,  by  diminish- 
ing the  pressure  in  the  subclavian  vein, 
also  favors  the  inflow  of  lymph  into  the 
thorax.] 

(6)  Lymph  hearts  exist  in  certain  cold- 
blooded animals.  The  frog  has  two  axillary 
hearts  (above  the  shoulder  near  the  vertebral  col- 
umn), and  two  sacral  hesxis,  one  on  each  side  of 
the  coccyx  near  the  anus  (Fig.  225,  L).  They 
beat,  but  not  synchronously,  about  sixty  times  per 
minute,  and  contain  10  cubic  centimetres  of  lymph. 
They  have  transversely  striped  muscular  iibrcs  in 
their  walls,  and  are  also  provided  with  ne7",<e  gan- 
glia. The  posterior  pair  pump  the  lymph  into  the 
branch  of  the  vena  iliaca  communicans,  and  the 
anterior  pair  into  the  vena  subscapularis.  Their 
pulsation  depends  partly,  but  not  exclusively,  upon 
the  spinal  cord,  for  if  the  cord  l)e  rapidly  destroyed,  they  may  cease  to  pulsate,  but  not  unfrequently 
Ihey  continue  to  pulsate  after  removal  of  the  cord.  [And  if  the  cord  be  destroyed  gradually,  they 
continue  to  Vjcat  [  Kabrliel).']  A  second  source  of  their  pulsatile  movements  is  to  be  sought  for  in 
Waldeyer's  ganglia.  Stimulation  of  the  skin,  intestine,  or  l)lood  heart  influences  them  reflcxly — 
partly  accelerating  and  partly  retarding  them  [most  frequently  arresting  them  in  diastole,  so  that 
there  seems  to  be  an  inhibitory  mechanism  in  the  cord,  but  it  is  not  affected  by  atropine  {Kabrhel)']. 
If  the  coccygeal  nerve,  which  connects  the  sacral  hearts  to  the  spinal  cord  be  divided,  these  effects  do 
not  occur.  Strychnia  accelerates  their  movements,  and  so  does  heating  of  the  .spinal  cord  ;  but  if 
the  cord  be  cooled,  they  are  retarded.  A  lymph  heart  arrested  by  being  exposed,  or  after  the  action 
of  muscarin,  can  be  caused  to  beat  by  filling  it  under  pressure,  but  this  is  not  the  case  when  the  arrest 
is  caused  by  destrucdon  of  its  nerves.  Antiarin  paralyzes  the  lymph  heart  and  the  blood  heart  at 
the  same  time,  while  r«;rt;a  paralyzes  the  former  alone.  In  other  amphibi ins  there  are  two  lymph 
hearts ;  in  the  o.strich  and  cassowary  and  some  swimming  birds,  and  in  the  embryo  chick,  I  or  2. 
They  occur  in  some  fishes,  e.  g  ,  near  the  caudal  vein  of  the  eel. 


Posterior  pair  of  lymph  hearts  (L)  of  the  frog. 


ABSORPTION    OF    PARENCHYMATOUS    EFFUSIONS.  359 

(7)  The  nervous  system  has  a  direct  effect  upon  the  lymph  stream,  on  account 
of  its  connection  with  the  muscles  of  the  lymphatics  and  lymph  glands,  and  with 
the  lymph  hearts  where  these  exist.  Kiihne  observed  that  the  cornea  corpuscles 
contracted  when  the  corneal  nerves  were  stimulated  [and  Hoffman  has  described 
the  termination  of  nerves  in  connective  tissue  corpuscles].  Goltz  also  observed 
that,  when  a  dilute  solution  of  common  salt  was  injected  under  the  skin  of  a  frog, 
it  was  rapidly  absorbed,  but  if  the  central  nervous  system  had  been  destroyed,  it 
was  not  absorbed. 

If  inflammation  be  produced  in  the  hind  legs  of  a  dog,  and  if  the  sciatic  nerve  be  divided  on  one 
side,  cedema  and  a  simultaneous  increase  of  the  lymph  stream  occur  on  that  side.  [A  combination  of 
congestion  and  inflammation  greatly  increases  the  lymph  stream,  and  this  is  still  more  the  case  when 
the  nerves  are  divided  at  the  same  time.] 

Ligature  the  leg  of  a  frog,  except  the  nerves,  so  as  to  arrest  the  circulation,  and  place  the  leg  in 
water  ;  it  swells  up  very  rapidly,  but  a  dead  limb  does  not  swell  up.  So  that  absorption  is  independ- 
ent of  the  continuance  of  the  circulation.  Section  of  the  sciatic  nerve,  or  destruction  of  the  spinal 
cord  (but  not  section  of  the  brain),  arrests  absorption. 

202.  ABSORPTION  OF  PARENCHYMATOUS  EFFUSIONS.— Fluids  which  pass 
from  the  blood  vessels  into  the  spaces  in  the  tissues,  or  those  injected  subcutaneously,  are  absorbed 
chiefly  by  the  blood  vessels,  but  also  by  the  lymphatics.  Small  particles,  as  after  tattooing  with  cinna- 
bar or  China  ink,  may  pass  from  the  tissue  spaces  into  the  lymphatics — and  so  do  blood  corpuscles 
from  extravasations  of  blood,  and  fat  granules  from  the  marrow  of  a  broken  bone.  If  all  the  lym- 
phatics of  a  part  are  ligatured,  absorption  takes  place  quite  as  rapidly  as  before ;  hence,  absorbed 
fluid  must  pass  through  the  thin  membranes  of  the  blood  vessels.  The  corresponding  experiment  of 
ligaturing  all  the  blood  vessels,  when  no  absorption  of  the  parenchymatous  juices  takes  place,  does  not 
prove  that  the  lymphatics  are  not  concerned  in  absorption,  for,  after  ligaturing  the  blood  vessels  of  a 
part,  of  course  the  formation  of  lymph,  and  also  the  lymph  stream,  must  cease.  When  fluids  are 
injected  under  the  skin,  absorption  takes  place  very  rapidly — more  rapidly  than  when  the  substance  is 
given  by  the  mouth.  The  subcutaneous  injection  of  drugs  is  extensively  used,  but  of  course  the 
substances  used  must  not  corrode,  irritate,  or  coagulate  the  tissues.  Some  substances  do  not  act  when 
given  by  the  mouth,  as  snake  poison,  poisons  from  dead  bodies,  or  putrid  things,  although  they  act 
rapidly  when  introduced  subcutaneously.  If  emulsin  be  given  by  the  mouth,  and  amygdalin  be 
injected  into  the  veins  of  an  animal,  hydrocyanic  acid  is  not  formed,  as  the  emulsin  seems  to  be 
destroyed  in  the  alimentary  canal.  If  the  emulsin,  however,  be  injected  into  the  blood,  and  the  amyg- 
dalin be  given  by  the  mouth,  the  animal  is  rapidly  poisoned,  owing  to  the  formation  of  hydrocyanic 
acid,  as  the  amygdalin  is  rapidly  absorbed  from  the  intestinal  canal.  The  amygdalin,  a  glucoside 
(C2oH.^,NOij),  is  acted  upon  by  fresh  emulsin  like  a  ferment ;  it  takes  up  2(H.^0)  and  yields  hydro- 
cyanic acid  (CHN),  -|-  oil  of  bitter  almonds  (C^H^O),  -|-  sugar  2(CgH,,,Og).  Serum  injected  subcu- 
taneously is  rapidly  absorbed ;  it  is  decomposed  within  the  blood  stream,  and  increases  the  amount  of 
urea.     Albuminous  solutions,  oil,  peptones,  and  sugars  are  also  absorbed. 

203.  CEDEMA,  DROPSY,  AND  SEROUS  EFFUSIONS.— [Dropsy.— As  aptly  illus- 
trated by  Lauder  Brunton,  the  lymph  spaces  may  be  represented  by  cisterns,  each  of  which  is  pro- 
vided with  supply  pipes — the  arteries  and  capillaries  ;  while  there  are  two  exit  pipes — the  veins  and 
lymphatics.  In  health,  the  balance  between  the  inflow  and  outflow  is  such  that  the  spaces  are  merely 
moistened  with  fluid.  When  a  cannula  is  placed  in  a  lymphatic  vessel  in  a  dog,  only  a  few  drops  of 
lymph  flow  out  at  long  intervals,  but  if  the  veins  of  the  limb  be  ligatured,  the  lymph  flows  much  more 
quickly.  This  is  in  part  due  to  the  increased  transudation  of  fluid  from  the  small  blood  vessels,  but 
it  may  also  be  due  to  fluid  passing  away  by  the  lymphatics  when  it  can  no  longer  be  carried  away  by 
the  veins.  We  cannot  say  what  is  the  relative  share  of  the  veins  and  the  lymphatics,  nor  in  the  above 
experiment  do  we  know  how  much  is  due  to  increased  transudation  or  diminished  absorption.  When 
there  is  an  undue  accumulation  of  fluid  more  or  less  hke  serum  in  the  lymph  spaces,  we  have  the  con- 
dition termed  dropsy.     When  there  is  general  dropsy  it  is  called  anasarca.] 

CEdema — ^If  the  efferent  veins  and  lymphatics  of  an  organ  be  ligatured,  or  if  resistance  be 
offered  to  the  outflow  of  their  contents,  congestion  and  a  copious  transudation  of  lymph  into  the 
tissue  take  place.  These  are  most  marked  in  the  skin  and  subcutaneous  cellular  tissue.  The  soft 
parts  swell  up,  without  pain  or  redness,  and  a  doughy  swelling,  wliich  pits  on  pressure  with  the 
hnger,  results.  These  are  the  signs  of  lymph  congestion,  which  is  called  cedema  when  the  fluid  is 
■watery  and  localized. 

Under  similar  circumstances  lymph  is  effused  in  the  serous  cavities.  [In  the  peritoneum  it  is 
ascites — thorax,  hydrothorax  —pericardium,  hydro-pericardium — cranium,  hydrocephalus — 
tunica  vaginalis,  hydrocele — joints,  hydrarthrosis,  etc.]  If,  at  the  same  time,  a  large  number  of 
colorless  blood  corpuscles  pass  out  of  the  blood  vessels  into  the  cavity,  the  fluid  becomes  more  and 
more  like  pus.  In  order  that  these  corpuscles  may  prolif>;rate,  a  considerable  percentage  of  allumin 
is  necessary.     When  the  pressure  within  the  serous  cavity  rises  above  that  in  the  smiU  blood  vessels, 


360  (EDEMA    AND    DROPSY. 

water  may  pass  into  the  blood.  These  sero-purulent  effusions  not  unfrequently  undergo  changes,  and 
yield  deconiposiiion  products,  such  as  leuciii.  tyrosin,  xantbin,  kreatin,  krealinin  (?),  uric  acid  (?), 
urea.  Endothelium  from  the  .senms  caviiy,  sus^ar  in  pleuritic  efl'usions  and  in  ademas  with  little 
albumin,  cholesterin  frequently  in  hydrocele  fluid,  and  succinic  acid  in  the  fluid  of  echinococci,  have 
all  been  found  in  these  efl'usions.  The  eflusion  of  hmph  may  arise  not  only  from  pressure  upon  the 
lymphatics,  l)ut  also  from  inflammation  and  thrombosis  of  the  lymphatics  themselves,  in  which  cases 
not  unfrec|uently  new  lymphatics  are  formed,  so  that  the  comnumication  is  reestablished.  Sometimes 
the  ductus  thoracicus  bursts,  and  lymph  is  poured  directly  into  the  abdomen  or  thorax.  [Ligature 
of  the  thoracic  duct  results  in  rupture  of  the  receptaculum  chyli  and  escape  of  chyle  and  lymph  into 
the  large  serous  cavities  (Z^«(/7i'/i,'-). 

When  dropsy  or  eflusion  of  fluids  occurs  into  serous  cavities,  there  is  always  a  greater  transudation 
of  fluid  through  the  blood  vessels.  The  abdominal  blood  vessels,  and  those  which  yield  a  watery 
effusion  under  normal  circumstances,  are  those  mo.st  liable  to  be  affected. 

Transudation  is  favored  by  (i)  Venous  congestion,  so  as  to  r.iise  the  blood  pressure,  in 
which  case  the  eflusion  usually  contains  little  albumin  and  few  lymjih  corpuscles,  while  the  colored 
corpuscles,  on  the  contrary,  are  more  numerous  the  greater  the  venous  obstruction.  Ranvier  pro- 
duced.oedema  artificially  l)y  ligaturing  the  vena  cava  in  a  dog,  and  at  the  same  time  dividing  the 
sciatic  nerve.  The  paralytic  dilatation  of  the  blood  vessels  thereby  produced  caused  an  increa5ed 
amount  of  blood  to  pass  to  the  limb,  while  the  blood  pressure  was  raised,  and  both  factors  favored 
the  transudation  of  fluid.  [Ranvier's  experiment  proves  that  mere  ligature  of  the  venous  trunk  of  a 
limb  by  itself  is  not  sufficient  to  cause  cedema.  The  ccdema  is  due  to  the  concomitant  paralysis  of 
the  vasomotor  nerves.  If  the  motor  roots  of  the  sciatic  nerve  alone  be  divided  along  with  ligature 
of  the  vena  cava,  no  oedema  occurs,  but  if  the  vasomotor  fibres  are  divided  at  the  same  time,  the 
limb  rapidly  becomes  oedematous.  There  is  such  an  increased  transudation  through  the  vascular 
walls  that  the  veins  and  h-mphatics  cannot  remove  it  with  sufficient  rapidity,  and  oedema  occurs. 
If  there  be  weakness  of  the  vasomotor  nerves,  slight  obstruction  is  sufficient  to  produce  oedema,] 
When  the  leg  veins  are  occluded  with  an  injection  of  gypsum,  cedema  occurs.  (2)  Some  unknown 
physical  changes  occur  in  the  protoplasm  of  the  endothelium  of  the  capillaries  and  blood  vessels, 
which  favor  the  transudation  of  albumin,  haemoglobin,  and  even  blood  corpuscles.  1  his  occurs  when 
abnormal  substmces  accumulate  in  the  blood — e.g.,  dissolved  haemoglobin — and  when  the  blood 
contains  little  O  or  albumin.  The  same  has  been  obsers-ed  after  exposure  to  too  high  temperatures, 
and  the  swelling  of  soft  pans  in  the  neighborhood  of  an  inflammator)-  focus  seems  due  to  the  transu- 
dation of  fluid  through  the  altered  vascular  wall.  It  is  probable  that  a  nervous  influence  may  affect 
particular  areas  through  its  act  on  on  the  blood  vessels  of  the  part  (it  may  be  upon  the  protoplasm 
of  the  blood  ca()illaries).  The  transudations  of  this  nature  usually  contain  much  albumin  and  many 
lymph  corpusc'es.  (^)  Wlien  the  blood  contains  a  very  large  amount  of  water,  the  tendency  to 
transudation  of  fluid  is  increa--ed.  After  a  time  it  may  produce  the  changes  indicated  in  (2).  and 
when  long  continued  may  increase  the  permeability  of  the  vascular  wall.  Watery  hTiiphatic  effusions 
from  watery  blood — "  cachectic  cedema" — occur  in  feeble  and  badly-nouri.shed  individuals.  [One 
of  the  commonest  foims  of  dropsy  is  the  slight  oedema  of  the  legs  in  anremic  persons,  in  whom  the 
heart  and  lungs  are  healthy.  Many  factors  are  involved — the  blood  pressure,  watery  condiiion  of 
the  blood,  the  condition  of  nutrition  of  the  capillaries,  and  probably  a  tendency  to  vasomotor  paresis 

[The  fluid  poured  out  varies  according  to  the  rapidity  with  which  this  occurs.  In  acute  inflam- 
mations eflusif  n  or  exudation  takes  place  rapidly,  and  the  fluid  contains  the  fibrin  factors,  so  that  it 
tends  to  coagulate  spontaneously.  There  is  every  gradation  between  the  non-coagulable  hydrocele 
fluid  and  the  coagulable  exudation  in  inflammation.  The  fluids  in  ditTerent  dropsies  vary  in  comj  o- 
sition,  and  some  have  more  cells  in  them,  depending  on  local  causes,  as  in  some  situations  absorption 
is  more  active  than  in  others.  The  pleural  fluid  contains  most  solids,  then  ascitic,  cerebro-spinal, 
and  lastly  that  in  the  subcutaneous  tissue.  Transudation  corresponds  to  the  process  of  filtration 
through  animal  membranes,  /.  e.,  the  transudation  contains  only  those  substances  already  present  in 
the  blood  plasma.  The  filtra'e  may  even  contain  more  salts  than  the  original  fluid,  as  is  often  the 
case  with  fluids  containing  cry-talloid  and  colloid  bodies.  .Senator  finds,  in  cases  of  oedema  of  the 
leg,  that  increase  of  the  venous  pressure  increases  the  proteids  in  the  transudation,  but  causes  no 
essential  change  in  the  amount  of  the  salts.] 

[(4)  Ostroumoff  found  that  stimulation  of  the  lingual  nerve  n'<t  only  causes  the  blood  vessels  ot 
the  tongue  to  dilati^,  but  that  the  corresponding  side  of  the  tongue  becomes  oedematous.  If  a  solution 
of  dilute  hydrochloric  acid  or  quinine  (^  145)  be  injected  into  the  duct  of  the  sub  maxillary  gland, 
and  the  chorda  tympani  stimulated,  there  is  no  secretion  of  saliva,  but  the  gland  becomes  oedematous. 
In  an  animal  poioned  with  atropin,  stimulation  of  the  chorda  causes  dilatation  of  the  blood  vessels, 
although  there  is  no  secretion  of  saliva,  neverthele-s  the  gland  does  not  become  oedematous  (//£'/^^'«- 
haiti).  As  Brunton  suggests,  this  experiment  points  to  some  action  of  atropin  on  the  blood  vessels 
which  has  hitherto  been  entireh-  overlooked.] 

204.  COMPARATIVE  PHYSIOLOGY. — In  the  frog  large  lymph  sacs,  lined  with  endo- 
thelium, exist  under  the  skin,  while  large  lymph  sacs  lie  in  relation  with  the  vertebral  column — one 
on  each  side — separated  from  the  abdominal  cavity  by  a  thin  membrane,  perforated  with  stomala. 


COMPARATIVE    AND    HISTORICAL.  361 

This  is  the  cysterna  lymphatica  magna  of  Panizza.  Some  amphibians  and  many  reptiles  have 
under  the  skin  large  lymph  spaces,  which  occupy  the  whole  of  the  dorsal  region  of  the  body.  All 
reptiles  and  the  tailed  amphibians  have  large  elongated  reservoirs  for  lymph  along  the  coiu-se  of  the 
aorta.  The  lymph  apparatus  of  the  tortoise  (Fig.  218)  is  very  extensive.  The  osseous  fishes 
have  in  the  Jateral  parts  of  their  backs  an  elongated  lymph  trunk,  which  reaches  from  the  tail  to  the 
anterior  fins,  and  is  connected  with  the  dilated  lymphatic  rootlets  in  the  base  of  the  tail  and  in  the 
fins.  The  largest  internal  lymph  sinus  is  in  the  region  of  the  oesophagus.  Many  birds  possess  a 
sinus-like  dilatation  or  lymph  space  in  the  region  of  the  tail.  The  lymph  spaces  communicate  with 
the  venous  system — with  valves  properly  arranged — usually  in  connection  with  the  upper  vena  cava. 
Lymph  hearts  have  already  been  referred  to  '(§  201,  6).  In  carnivora  the  lymph  glands  of  the 
mesentery  are  united  into  one  large  compact  mass,  the  so-called  "pancreas  Asellii." 

205.  HISTORICAL. — Although  the  Hippocratic  School  was  acquainted  with  the  lymph  glands 
from  their  becoming  swollen  from  time  to  time,  and  ahhough  Herophilus  and  Erasistratus  had  seen 
the  mesenteric  glands,  yet  Aselli  (1662)  was  the  first  who  accurately  described  the  lacteals  of  the 
mesentery  with  their  valves.  Pecquet  (1648)  discovered  the  receptaculum  chyli;  Rudbeck  and 
Thom.  Bartholinus  the  lymphatic  vessels  (1650-52);  Eustachius  (1563)  was  acquainted  with  the 
thoracic  duct,  which  Gassendus  (1654)  maintained  that  he  was  the  first  to  see;  Lister  noticed  that 
the  chyle  became  blue  when  indigo  was  injected  into  the  intestine  (1671);  Sommering  observed  the 
separation  of  fibrin  when  lymph  coagulated ;  Reuss  and  Eramert  discovered  the  lymph  corpuscles. 
The  chemical  investigations  date  from  the  first  quarter  of  this  century ;  they  were  carried  out  by 
Lassaigne,  Tiedemann,  Graelin,  and  others.  The  two  last-named  observers  noticed  that  the  white 
color  of  chyle  was  due  to  the  presence  of  fatty  granules. 


Physiology  of  animal  Heat. 


206.  SOURCES  OF  HEAT.— The  heat  of  the  body  is  an  uninterrupted 
evolution  of  kinetic  energy,  which  we  must  represent  to  ourselves  as  due  to  vibra- 
tions of  the  corporeal  atoms.  The  ultimate  source  of  the  heat  is  contained  in 
the  potential  energy  taken  into  the  body  with  the  food,  and  with  the  O  of  the  air 

absorbed  during  respiration.  The 
amount  of  heat  formed  depends 
upon  the  amount  of  energy  liberated. 
The  energy  of  the  food  stuffs  may 
be  called  "latent  heat,"  if  we 
assume  that  when  they  are  used  up 
in  the  body,  chiefly  by  a  process  of 
combustion,  kinetic  energy  is  liber- 
ated only  in  the  form  of  heat.  As  a 
matter  of  fact,  however,  mechanical 
energy  and  electrical  energy  are  de- 
veloped from  the  potential  energy. 
In  order  to  obtain  a  unit  measure  for 
the  energy  liberated,  it  is  advisable 
to  express  all  the  potential  energy  as 
heat  units. 

The  Calorimeter. — This  instru- 
ment enables  us  to  transform  the  po- 
tential energy  of  the  food  into  heat, 
and,  at  the  same  time,  to  measure 
the  number  of  heat  units  produced. 


l^nre  and  Silbermann  used  a  water 
calorimeter  (Fig.  226).  The  substance  to 
l)e  I  urned  is  placed  in  a  larije  cylindrical 
comliustion  chamber  (K),  suspended  in  a 
lart^e  cylindrical  vessel  (I,)  filled  with  water 
(7a),  so  that  the  combuslion  chamber  is  com- 
pletely surr<.unded  by  the  water.  Three 
tubes  open  into  the  upper  ])nrt  of  the  cham- 
b  r;  one  of  them  (O)  supplies  the  air  which 
is  necessary  for  combustion,  it  reaches  almost 
to  the  bottom  of  the  chamber;  the  second  {n) 
is  fixed  in  the  middle  of  the  lid,  and  is  closed  above  with  a  thick  glass  plate,  and  on  this  is  placed, 
at  an  angle,  a  small  mirror  [s],  which  enables  an  observer  to  look  into  the  chamber,  and  observe 
the  process  of  combustion  at  c.  The  third  tube  (d)  is  used  only  when  combustible  gases  are  to  be 
biuTied  in  the  chamber.  It  can  be  closed  by  means  of  a  stop-cock.  A  lead  tube  [e,  e),  with  many 
twists,  passes  from  the  upper  part  of  the  chaml'er  through  the  water,  and  finally  opens  at  f.  The 
gaseous  products  of  combustion  pass  out  through  this  tule,  and  in  doing  so  help  to  heat  the  water. 
The  cylindrical  vessel  with  the  water  is  closed  with  a  lid  which  transmits  the  four  tubes.  The  water 
cylinder  stands  on  four  feet  within  a  large  cylinder  (M),  which  is  filled  wi'.h  some  good  non-con- 
ductor of  heir,  and  this  again  is  placed  in  a  lars^e  vessel  filled  with  water  (W).  This  is  to  prevent 
any  heat  reaching  the  inner  cylinder  from  without.  A  weighed  quintiiy  of  the  substance  (r)  to  be 
investigated  is  placed  in  the  combustion  chamber.     When  combuslion  is  ended,  during  which  the 

362 


ter  calorimeter  of  Favre  and  Silbermann. 


CALORIMETRY. 


363 


inner  water  must  be  repeatedly  stirred,  the  temperatiire  of  the  water  is  ascertained  by  means  of  a 
delicate  thermometer.  If  the  increase  of  the  temperature  and  the  amount  of  water  are  known,  then 
it  is  easy  to  calculate  the  number  of  heat  units  produced  by  the  combustion  of  a  known  weight  of 
substmce  (see  Itiiroduciion), 

-  -     .  ,      ,  ,       r^^^  inner  cylinder  is  filled  with  ice  and  not  with  water, 


Fig.  227. 


The  ice  calorimeter  may  also  be  used 
and  ice  is  also  placed  in  the  outer  cylin- 
der t  :>  prevent  any  heat  from  without  from 
acting  upon  the  inner  ice.  The  heat 
given  off  from  the  combustion  chamber 
causes  a  certain  amount  of  the  ice  to 
melt,  and  the  water  thereby  produced  is 
collected  and  measured.  It  requires  79 
heat  units  to  melt  I  grm.  of  ice  to  I  grm. 
of  water  at  0°  C. 

[The  amount  of  heat  produced  by  a 
living  animal  is  similarly  measured. 
The  animal  (Fig.  227),  in  a  cage,  is 
placed  in  a  large  vessel,  which  is  placed 
wiihin  another  vessel,  and  the  inter-space 
filled  wiih  water.  The  whole  should  be 
enclosed  in  a  large  box  packed  wiih  fur, 
shavings,  feathers,  or  other  bad  conductor 
of  heat.  A  tube,  D,  opens  into  the  inner 
space,  and  from  it  there  is  an  exit  tube, 
D',  which  winds  many  times  in  the  water 
space  beneath.  Air  passes  in  through  D 
and  out  by  D''.  The  temperature  of  the 
water  is  ascertained  by  thermometers  T 
and  T^,  while  the  water  is  moved  by  a  stirrer  (S)  placed  between  the  two.] 

Just  as  in  a  calorimeter,  although  ??izich  more  slowly,  the  food  stuffs  within  our 
body  are  burned  up,  oxygen  being  supplied,  and  thus  potential  energy  is  trans- 
formed into  kinetic  energy,  which,  in  the  case  of  a  person  at  rest,  almost  com- 
pletely appears  in  the  form  of  heat. 

Heat  Units. — Favre,  Silbermann,  Frankland,  Rechenberg,  B.  Danilewskj,  and  others  have 
made  calorimetric  experiments  on  the  heat  produced  by  food.  According  to  Danilewsky,  I  gramme 
of  the  following  dry  substances  yields  heat  units  :  — 


Water  calorimeter  of  Dulong. 


Casein,  .  ,  . 
Fibrin,  .... 
Peptone,  .  .  . 
Glufin,  .  .  , 
Ox-blood,  .  . 
Ox-flesh,  .  .  . 
Vegetable  fibrin, 
Gluten,  .  .  . 
Legumin,  .  , 
Palmitin,  .    .    . 


5855 
5772 
4876 

5493 
5900 

572-1 
6231 
6141 
5573 


Olein,    .    . 

8958 

Stearin,     . 

9036 

Ox-fat,      . 

9686 

Glycerine, 

4179 

Starch, 

4479 

Dextrose, 

3939 

Maltose,    . 

4163 

Milk  sugar. 

4162 

Cane  sugar. 

4173 

Cow's  milk, 

5733 

Woman's  milk. 
Egg  yelk,     . 
Potatoes, 
Rye  bread, 
Wheat  bread 
Rice,     .    .    . 
Peas,     .    .    . 
Buckwheat, 
Mai2e,       .    . 


4837 
4479 
4234 
4471 
4351 


4288 
5188 


Alcohol,  .    .    . 

.  6980 

Urea,    .    .    .    . 

.  2537 

Muscle 

^ 

Extractives 

V4400 

(Liebig's) 

1 

Flesh  extract,  . 

.  3216 

Acetic  acid, 

.3318 

Butyric  acid,    . 

.  5647 

Palmitic  acid,  . 

.  9316 

As  albumin  is  only  oxidized  to  the  stage  of  urea,  we  must  deduct  the  heat  units  obtainable  from 
urea  horn  those  of  albumin,  and  as  I  pare  of  albumin  yields  in  round  numbers  about  j^  of  lurea,  we 
obtain  about  5100  calories  [  =  2170  kilogram -metres]  fir  I  grm.  of  albumin. 

Isodynamic  foods,  i,  e.,  those  that  produce  an  equal  amount  of  heat ;  loo  grms.  animal  albumin 
(afier  deducting  the  heat  units  of  urea)  =  52  fat=  II4  starch  =  129  dextrfise;  loo  grms.  fat  are 
isodynamij  with  243  dry  flesh  or  225  of  dry  syntonin  [Riibtier) ;  100  grms.  of  vegetable  albumin  ^ 
55  fat  =  121  starch  =  137  dextrose  [Dafii/eicisky).  Rubner  calculated  that  in  man,  with  a  mixed 
diet,  the  available  heat  units  for  I  grm.  of  albumin  ^=  4100 ;  i  grm.  fat  =  9300;  and  for  i  grm. 
carbohydrate  =  4100  calories. 

When  we  know  the  weight  of  any  of  the  above-named  substances  consumed  by 
a  man  in  twenty-four  hours,  a  simple  calculation  enables  us  to  determine  how 
many  heat  units  are  formed  in  the  body  by  oxidation,  i.  e.,  provided  the  substance 
is  completely  oxidized. 


364  CHEMICAL   SOURCES   OF    HEAT. 

[Several  sources  of  heat  production  or  thermogenesis  are  to  be  found 
in  all  tissues  wherever  oxidation  is  going  on.  The  metabolism  of  protoplasm  is 
always  associated  with  the  evolution  of  heat.] 

(i)  ///  the  transformation  of  the  chemical  constituents  of  the  food,  endoived  with 
a  large  amount  of  potential  energy,  into  such  substances  as  have  little  or  no  energy. 
The  organic  substances  used  as  food  consist  of  C,  H,  O,  N,  so  that  there  takes 
place  ((I)  Combustion  of  C  into  CO.^,  of  H  into  H,0,  whereby  heat  is  pro- 
duced ;  I  grm.  C  burned  to  produce  CO2  yields  8080  heat  units,  while  i  grm.  H 
oxidized  to  W-.O  yields  37,460  heat  units.  The  O  necessary  for  these  purposes  is 
absorbed  during  respiration,  so  that,  to  a  certain  extent  at  least,  the  amount  of 
heat  produced  may  be  estimated  from  the  amount  of  O  consumed.  The  same 
consumption  of  O  gives  rise  to  the  same  amount  of  heat  whether  it  is  used  to 
oxidize  H  or  C  {Ffliiger).  There  is  a  relation,  amounting  to  cause  and  effect, 
between  the  amount  of  heat  produced  in  the  body  and  the  O  consumed.  The 
cold-blooded  animals,  which  consume  little  O,  have  a  low  temperature  ;  among 
warm-blooded  animals,  i  kilo,  of  a  living  rabbit  takes  up  within  an  hour  0.914 
grm.  O,  and  its  body  is  heated  to  a  mean  of  38°  C.  i  kilo,  of  a  living  fowl  uses 
1. 186  grms.  O,  and  gives  a  mean  temperature  of  43.9°  C.  The  amount  of  heat 
produced  is  the  same  whether  the  combustion  occurs  slowly  or  quickly;  the 
rapidity  of  the  metabolism,  therefore,  affects  the  rapidity,  but  not  the  absolute 
amount  of  heat  production.  The  combustion  of  inorganic  substances  in  the 
body  e.g.,  of  the  sulphur  into  sulphuric  acid,  the  phosphorus  into  phosphoric 
acid,  is  another,  although  very  small,  source  of  heat. 

[The  muscles  form  about  the  half  of  the  whole  mass  of  the  body  and  the 
bones  nearly  the  other  half.  In  the  latter,  oxidation  does  not  go  on  actively,  so 
that  the  muscles  must  be  the  great  seats  of  heat  production  or  thermogenesis  in  the 
body.  This  view  is  supported  by  the  fact  that  the  blood  leaving  a  muscle  at  rest 
contains  more  CO,  than  the  blood  in  the  right  ventricle.  Muscular  exercise 
greatly  increases  the  metabolism  and  the  CO.,  excreted  (§  127),  but  at  the  same 
time,  there  is  a  great  increase  in  heat  production.  The  muscles,  therefore,  are 
the  great  thermogenic  tissues,  and  they  yield  \  of  the  heat  in  health.  The  sev- 
eral secreting  glands,  especially  the  liver,  and  the  alimentary  canal,  during 
digestion,  are  also  foci  of  heat  formation.] 

{b)  In  addition  to  the  processes  of  combustion  or  oxidation,  all  those  chemical 
processes  in  our  body,  by  which  the  amount  of  the  available  potential  energy 
which  is  present  is  diminished,  in  consequence  of  a  greater  satisfaction  of  atomic 
affinities,  lead  to  the  production  of  heat.  In  all  cases  where  the  atoms  assume 
more  stable  positions  with  their  affinities  satisfied,  chemical  energy  passes  into 
kinetic  thermal  energy,  as  in  the  alcoholic  fermentation  of  grape  sugar  and  other 
similar  processes. 

Heat  is  also  developed  during  the  following  chemical  processes  : — 

(a)  During  the  union  of  bases  with  acid's.  The  nature  of  the  base  determines  the  amount  of  heat 
produced,  while  ihe  nature  of  the  acid  is  without  eflect.  Only  in  those  cases  where  the  acid,  e.,i^., 
CO2,  is  unable  to  set  aside  the  alkaline  reaction,  the  amount  of  heat  produced  is  less.  The  forma- 
tion of  compounds  of  chlorine  ((f-.i,'.,  in  the  stomach)  produces  heat. 

(,3)  When  a  neutral  salt  is  changed  into  a  basic  one.  In  the  blood  the  su'phuric  and  jihosphoric 
acids  derived  from  the  combustion  of  S  and  P  are  united  with  the  alkalies  of  the  blood  to  form  bas-ic 
salts.  The  decomposition  of  the  carbonates  of  the  blood  by  lactic  and  phosphoric  acids  forms  a 
double  source  of  heat,  on  the  one  hand,  by  the  formation  uf  a  new  salt,  and  on  the  other,  by  the 
liberation  of  CO,,,  wh'ch  is  partly  absorbed  by  the  blood. 

())  The  combination  of  haemoglobin  with  O  (§  36). 

During  those  chemical  processes,  whereby  the  heat  of  the  body  is  produced, 
heat-absorbing  intermediate  compounds  are  not  unfrequently  formed.  Thus,  in 
order  that  the  final  stage  of  more  complete  saturation  of  the  affinities  be  reached, 


HOMOIOTHERMAL   AND    POIKILOTHERMAL   ANIMALS*  365 

intermediary  atomic  groups  are  formed,  whereby  heat  is  absorbed.  Heat  is  also 
absorbed  when  the  solid  aggregate  condition  is  dissolved' during  retrogressive  pro- 
cesses. But  these  intermediary  processes,  whereby  heat  is  lost,  are  very  small 
compared  with  the  amount  of  heat  liberated  when  the  end  products  are  formed. 
(2)  Certain  physical  processes  are  a  second  source  of  heat,  (a)  The 
transformation  of  the  kinetic  mechanical  energy  of  internal  organs, 
when  the  work  done  is  not  transferred  outside  the  body,  produces  heat.  Thus 
the  whole  of  the  kinetic  energy  of  the  heart  is  changed  into  heat,  owing  to  the 
resistance  opposed  to  the  blood  stream  (§  93).  The  same  is  true  of  the  mechan- 
ical energy  evolved  by  many  muscular  viscera.  The  torsion  of  the  costal  cartilages, 
the  friction  of  the  current  of  air  in  the  respiratory  organs,  and  the  ingesta  in  the 
digestive  tract,  all  yield  heat. 

An  excessively  minute  amount  of  the  mechanical  energy  of  the  heart  is  transferred  to  surrounding 
bodies  by  the  cardiac  impulse  and  the  superficial  pulse  beats,  but  this  is  infinitesimally  small. 
During  respiration,  when  the  respiratory  gases  and  other  substances  are  expired,  a  very  small  amount 
of  energy  disappears  externally,  which  does  not  become  changed  into  heat.  If  we  assume  that  the 
daily  work  of  the  circulation  exceeds  86,000  kilogram-metres,  the  heat  evolved  is  equal  to  204,000 
calories,  in  twenty-four  hours  (|  93),  which  is  sufficient  to  raise  the  temperature  of  a  person  of 
medium  size  2°  C. 

(J))  When,  owing  to  muscular  activity,  the  body  produces  work  which  is  trans- 
ferred to  external  objects,  e.g.,  when  a  man  ascends  a  tower  or  mountain,  or 
throws  a  heavy  weight,  a  portion  of  the  kinetic  energy  passes  into  heat,  owing  to 
friction  of  the  muscles,  tendons,  and  the  articular  surfaces,  as  well  as  to  the  shock 
and  pressure  of  the  ends  of  the  bones  against  each  other. 

(c)  The  electrical  currents  which  occur  in  muscles,  nerves,  and  glands  very 
probably  are  changed  into  heat.  The  chemical  processes  which  produce  heat 
evolve  electricity,  which  is  also  changed  into  heat.  This  source  of  heat,  however, 
is  very  small. 

{d)  Other  processes  are  the  formation  of  heat  from  the  absorption  of  CO^,  by  the  concentration  of 
water  as  it  passes  through  membranes,  in  imbibition,  and  the  formation  of  the  solids,  e.  g.,  of  chalk 
in  the  bones.  After  death,  and  in  some  pathological  processes  during  life,  the  coagulation  of  blood 
and  the  production  of  rigor  mortis  are  sources  of  heat. 

207.  HOMOIOTHERMAL  AND  POIKILOTHERMAL  ANI- 
MALS.— In  place  of  the  old  classification  of  animals  into  "cold-blooded" 
and  "warm-blooded,"  another  basis  of  classification  seems  desirable,  viz.,  the 
relation  of  the  temperature  of  the  body  to  the  temperature  of  the  surrounding 
medium.  Bergmann  introduced  the  word  homoiothermal  for  the  warm- 
blooded animals  (mammals  and  birds),  because  these  animals  can  maintain  a  very 
uniform  temperature,  even  although  the  surrounding  temperature  be  subject  to 
considerable  variations.  The  so-called  cold-blooded  animals  are  called  poikilo- 
thermal,  because  the  temperature  of  their  bodies  rises  or  falls,  within  wide  limits, 
with  the  heat  of  the  surrounding  medium. 

When  homoiothermal  animals  are  kept  for  a  long  time  in  a  cold  medium, 
their  heat  production  is  increased,  and  when  they  are  kept  for  a  long  time  in  a 
warm  medium  it  is  diminished. 

Fordyce  gave  a  proof  of  the  nearly  uniform  temperatiure  in  man.  A  man  remained  ten  minutes- 
in  an  oven  containing  very  dry  hot  air  (§  218),  and  yet  the  temperature  of  the  palm  of  his  hand, 
mouth,  and  urine  was  increased  only  a  few  tenths  of  a  degree.  Becquerel  and  Brechet  investigated 
the  temperature  of  the  human  biceps  (by  means  of  thermo-electric  needles),  when  the  arm  had  been 
one  hour  in  iced  water,  and  yet  the  temperature  of  the  muscular  tissue  was  cooled  only  0.2°  C.  The 
same  muscle  did  not  undergo  any  increase  in  temperature,  or  at  most  0.2°  C,  when  the  man's  arm 
was  placed  for  a  quarter  of  an  hour  in  water  at  42°  C. 

If  heat  be  rapidly  abstracted  (§  225)  or  rapidly  supplied  (§  221)  to  the  body, 
so  as  to  produce  rapid  variation  of  the  temperature,  life  is  endangered. 


366 


THERMOMETRY. 


Poikilothermal  animals  behave  very  differently ;  the  temperature  of  their 
bodies  generally  follows;  although  with  considerable  variations,  the  temperature 
of  the  surroundings.  When  the  temperature  of  the  surroundings  is  increased,  the 
amount  of  heat  produced  is  increased,  and  when  the  surrounding  temperature  falls, 
the  amount  of  heat  evolved  within  the  body  also  falls. 

The  following  table  shows  very  clearly  the  characters  of  poikilothermal  animals,  e.g.,  frogs, 
which  were  placed  in  air  and  water  of  varj'ing  temperatures.  They  were  immersed  up  to  the 
mouth.  The  temperature  was  measuied  by  means  of  a  thermometer  introduced  through  the  mouth 
into  the  stomach. 


In  Water. 

In  Air. 

Temperature  of  the 
Water. 

Temperature  of  Frog's 
Stomach. 

Temperature  of  the 
Air. 

Temperature   of  Frog's 
Stomach. 

41.0°  C. 

30.0 

20.6 

5-9 
2.8 

38.0°  C. 
29.6 
20.7 
8.0 

5-3 

40.4°  C. 
27.4 
16.4 
6.2 

5-9 

31  7°  C. 

19.7 

14.6 

7.6 

8.6 

Birds. 

Temp. 

Thalassidroma,    .    .    .     40.30 

ProctUaria, 40.80 

Goose, 41-70 

c  f  39-o8 

Sparrow, ^I^^^j^^ 

Pigeon,     .    .    .      41.80-42.50 

Turkey, 4270 

Guinea  fowl,    ....    43-90 

Duck  { 4^-9° 

^^^^ \  42.50 

Crow, 4117 


[Temperature  of  Different  Animals. 
Temp. 

Swallow, 44.03 

Gull, 37.8 

Mammals. 

Tiger, 37.20 

Horse,  ....     36.80-37.50 

Rat, 38.80 

Hare, 37-8o 

Cat, 38.30-38.90 

Guinea  pig 38  80 

f  37-40 

Dog, \  39-00 

(  39-60 


Temp, 

Panther, 3890 

Mouse, 41. 1 

Dolphin, 35.5 

(  37-30-40.00 
Sheep, .   .    .    .   -^  39.50-40.00 

(  40.00-40  50 

Ape,   . 35.50 

Guinea  pig,     .    .  35.76-38.00 
Rabbit,    .    .    .       37.50-38.00 

Ox, 37.50 

Ass, 3695 

{^Gavarret  dr'  Rosenthal).'\ 


Reptiles — Snakes,  io°-i2°,  but  higher  when  incubating.  Amphibians  and  fishes — o  5°-3°  above 
the  temperature  of  the  surroundings.  Arthropoda — o.i°-5.8°  above  the  surroundings.  Bees  in  a 
hive,  30'^-32°,  and  when  swarming,  40°.  The  followmg  animals  have  a  temperaiure  higher  than  the 
surrounding  temperature  :  Cephalopods,  0.57°;  mollusks,  0.46°  ;  echinoderms,  O  40 ;  medusre,  0.27°  ; 
polyps,  0.21°  C. 

208.  ESTIMATION  OF  TEMPERATURE. — By  using  thermometric  apparatus,  we  are 
enabled  to  obtain  information  regardint;  the  degree  of  heat  of  the  body  to  be  investigated.  For  this 
purpose  the  following  methods  are  employed  :  — 

A.  The  Thermometer. — Celsius  (i  701-1744)  divided  his  thermometer  into  100  parts,  and  each 
part  was  again  divided  into  10  parts,  sa  that  -^^°  C.  could  be  easily  read  off.  All  thermometers 
which  have  been  used  for  a  long  time  gi%'e  too  high  readings;  hence  they  should  be  compared, 
from  time  to  time,  with  a  normal  thermometer.  When  taking  the  temperature,  the  bulb  ought  to 
be  surrounded  for  fifteen  minutes,  and  during  the  last  five  minutes  the  mercury  column  ought  not 
to  vary.  A  very  sensitive  thermometer  will  indicate  the  temperature  after  seven  seconds  if  the 
urine  stream  be  directed  upon  its  bulb.  Minimal  and  maximal  thermometers  are  often  of  use  to 
the  physician. 

[Clinically,  one  of  the  thermometers  shown  in  Fig.  228  may  be  used.  They  are  self-registering 
maximum  thermometers,  z.  ^.,  a  portion  of  the  mercury  is  separated  from  the  mercurial  column, 
to  form  the  index,  the  top  of  which  indicates  the  temperature.  Before  being  used,  the  index 
must  be  well  below  the  normal  temperature.  Various  forms  of  surface  thermometers  have  been 
used.] 


THERMO-ELECTRIC    MEASUREMENT   OF    HEAT. 


367 


Walferdin's  metastatic  thermometer  (Fig.  229)  is  specially  useful  for  comparative  observation. 
The  tube  is  very  narrow  in  comparison  with  the  bulb,  and  in  order  that  the  stem  be  not  too  long,  it  is 
constructed  so  that  the 

Fig.  228. 


amount  of  mercury  can 
be  varied.  A  quantity 
of  mercury  is  taken,  so 
that  with  the  tempera- 
ture  expected  the 
thread  of  mercury  will 


Fig.  229. 


A,  Cassella's  "  infallible,"  B,  "  Ferris'  perfect,"  and  C,  Evans'  and  Wormull's 

thermometers. 


'standard"  clinical 


Stand  about  the  middle  of  the  stem.  A  small  bulb  at  the  upper  part  of  the  stem 
receives  the  excess  of  Hg.  Suppose  a  temperature  between  37°-40°  C.  is  to  be  meas- 
ured, the  bulb  is  first  heated  a  little  over  40°  C,  it  is  then  suddenly  cooled,  and  shaken 
at  the  same  time,  so  that  the  thread  of  mercury  is  thereby  suddenly  broken  above  40°. 
The  tube  is  so  narrow  that  1°  C.  is  equal  to  about  10  centimetres  of  the  length  of  the 
tube,  so  that  ^50°  ^-  '^  ^'■^^^  ^  millimetre  in  length.  The  scale  is  divided  empirically, 
but  the  value  ot  the  divisions  must  be  compared  with  a  normal  thermometer. 

Kronecker  and  Meyer  used  verj' small  maximal  "outflow  thermometers,"  and 
caused  them  to  pass  through  the  intestinal  canal,  or  through  large  blood  vessels.  The 
mercury  flows  out  of  the  short  open  tube,  and  of  course  more  flows  out,  the  higher 
the  temperature.  After  these  small  bulbs  have  passed  through  the  animal,  a  comparison 
is  instituted  with  a  normal  thermometer,  to  determine  at  what  temperature  the  mercury 
reaches  the  free  margin  of  the  tube. 

B.  Thermo-electric  Method. — This  method  enables  us  to  determine  the  tempera- 
ture accurately  and  rapidly  (Fig.  230,  I).  The  thermo-electric  galvanometer  of 
Meissner  and  Meyerstein  consists  of  a  circular  magnet  (w)  suspended  by  a  thread  of  silk 
(c),  to  which  a  small  mirror  (S)  is  attached.  A  large  stationary  bar  magnet  (M)  is 
placed  near  the  magnet  (w),  so  that  the  north  poles  («  and  iSi)  of  bclh  magnets  point  in 
the  same  direction,  and  it  is  so  arrarged  that  the  suspended  magnet  is  caustd  to  point 
to  the  north  by  a  minimal  action  of  M.  A  thick  copper  wire  {/>,^)  is  coiled  several 
times  round  m  (although  in  the  figure  it  is  represented  as  a  single  coil),  and  the  ends  of  the 
wire  are  soldered  to  two  thermo-elements,  each  composed  of  two  different  metals — iron 
and  German  silver,  the  two  similar  free  elements  being  united  by  a  wire  [d),  so  that  the 
two  thermo-elements  form  part  of  a  closed  circuit.  A  horizontal  scale  (K,  K)  is  placed 
at  a  distance  of  3  metres  from  the  mirror,  so  that  the  divisions  of  the  scale  are  seen  in 
the  mirror.  The  scale  itself  rests  upon  a  telescope  (F)  directed  toward  the  mirror.  The 
observer  (B),  who  looks  through  the  telescope,  can  see  the  divisions  of  the  scale  in  the 
mirror.  When  the  magnet,  and  with  it  the  mirror,  swing  out  of  the  magnetic  meridian, 
the  observer  notices  ctlier  divisions  of  the  scale  in  the  mirror.  When  one  of  the  thermo- 
elements IS  heated,  an  electrical  current  is  produced,  which  passes  from  the  iron  to  the 
German  silver  in  the  heated  couple,  and  causes  a  deviation  of  the  suspended  magnet. 
Suppose  a  person  were  swimming  in  the  direction  of  the  current  in  the  conducting  wire, 
then  the  north  pole  of  the  magnet  goes  to  the  north  [Ampere).  The  tangent  of  the 
angle  (j>,  through  which  the  freely  movable  magnet  is  diverted  by  a  galvanic  current,  from 
its  position  of  rest  or  zero,  in  the  magnetic  meridian,  is  the  same  as  the  galvanic  stream; 

G 
G  is  proportional  to  the  magnetic  energy  D,  i.  e.,  tang.  <p=  y..     If  G  is  to  remain  the 

same,  and  the  tang,  (p  to  be  as  large  as  possible,  the  magnetic  energy  must  be  diminished 
as  much  as  possible.  If  the  magnetism  of  the  suspended  magnet  be  indicated  by ;;;,  and 
that  of  the  earth  by  T,  the  magnetic  directing  energy  D  =  Tw,  so  that  D  can  be  distin- 
guished in  two  ways:  (l)  by  diminishing  the  magnetic  moment  of  the  suspended  mag- 
net, as  may  be  done  by  using  a  pair  of  astatic  needles,  such  as  are  used  in  Nobih's 
galvanometer;  (2)  and  also  by  weakening  the  magnetism  of  the  earth,  by  placing  an 
accessory  stationary  magnet  (Hauy's  rod)  in  the  same  direction,  and  near  the  suspended 
magnet.     An  important  arrangement  for  rapidly  getting  the  magnet  to  zero  is  the  dead- 


Walferdin's 
metastatic 
thermo- 
meter. 


368 


THERMO-ELECTRIC    NEEDLES. 


beat  arrangement  of  Gauss  (not  figured  in  the  scheme).  It  consists  of  a  thick  copper  cylinder,  on 
which  the  wire  of  the  coil  is  wound.  This  mass  of  copper  may  be  regarded  as  a  closed  multipli- 
cator  with  a  ver>'  large  transverse  section.  The  vibrating  magnet  induces  in  this  closed  circuit  a 
current  of  electricity,  whose  intensity  is  greatest  when  the  velocity  of  the  excursion  of  the  majrnet  is 
greatest,  and  which  takes  the  opposne  direction  as  soon  as  the  magnet  returns  toward  zero.  These 
induced  currents  cause  a  diminution  of  the  vibration  of  the  magnet  in  this  way,  that  the  arc  of  vibra- 
tion of  the  magnet  diminishes  very  rapidly,  almost  in  a  geometrical  progression.  The  induced 
damping  current  is  stronger,  the  less  the  resistance  in  the  closed  circuit,  and  in  the  damper  or  dead- 
beat  arrangement  itself,  the  greater  the  section  of  the  copper  ring.     This  damping  arrangement  limits 

Fir,.  230. 


i 


m 


Scheme  of  thermo-electric  arrangements  for  estimating  the  temperature. 


the  oscillations  of  the  magnet,  and  it  comes  to  rest  rapidly  and  promptly  after  3  or  4  small  vibrations, 
so  that  much  time  is  saved.  The  angle  of  deviation  is  so  small  that  the  angle  itself  may  be  taken 
instead  of  the  tangent. 

The  thermo-electric  needles  of  Dutrochet  (II)  may  be  placed  in  the  circuit.  They  consist  of 
iron  and  German  silver  soldered  at  their  points ;  or  the  needles  of  Becquerel  (III)  may  be  used.  They 
consist  of  the  same  metal  soldered  in  a  straight  line,  one  behind  the  other.  The  needles  must  always 
be  covered  by  a  varnish,  which  will  prevent  the  parenchymatous  juices  from  acting  upon  them,  and  so 
causing  a  current.  Before  the  experiment  we  must  determine  what  extent  of  excursion  on  the  scale  is 
obtained  with  a  certain  temperature.     In  order  to  determine  this,  a  delicate  thermometer  is  fixed 


TEMPERATURE    TOPOGRAPHY.  369 

to  each  of  the  thenno-couples,  and  both  are  placed  in  oil  baths,  which  differ  in  temperature say  by 

1°  C. — as  can  be  determined  by  the  themiometer.  \\Tien  the  current  is  closed,  the  excursion  on  the 
scale  will  indicate  i°  C.  Suppose  that  the  excursion  was  150  mm.,  then  each  mm.  of  the  scale  would 
be  equal  to  yi^"  C.  AATien  this  is  determined,  the  two  thermo-needles  may  be  placed  in  the  different 
tissues  or  organs  of  animals,  and,  of  coiu-se,  we  obtain  the  difference  of  temperature  in  these  places. 
Or  one  thermo-couple  may  be  placed  in  a  bath  of  constant  temperature  (near-ly  that  of  the  body),  in 
which  is  placed  a  delicate  thermometer,  while  the  other  needle  is  introduced  into  the  organ  to'  be 
investigated.  In  this  case,  we  obtain  the  difference  of  temperature  between  the  tissue  and  the  source 
of  the  constant  heat.  The  electric  current  passes  in  the  warmer  needle  from  the  iron  to  the  German 
silver,  and  thus  through  the  wires  of  the  apparatus.  For  small  differences  of  temperature,  such  as  occur  in 
the  body,  the  thermo-electric  energy  is  always  proportional  to  the  difference  of  temperature  of  the  two 
needles  or  couples.  In  place  of  a  single  pair  of  needles  several  may  be  used,  whereby  the  sensitiveness 
of  the  apparatus  is  gi-eatly  increased.  Helmholtz  found  that  by  using  sixteen  antimony-bismuth 
couples,  he  could  detect  an  increase  of  ^^ oW°  C.  Schiffer  prepared  a  simple  thennopile  (IV)  by 
soldering  together  alternately  four  pairs  of  wires  of  iron  (/)  and  German  silver  {a).  These  are  placed 
in  the  two  organs  (A  and  B)  which  are  to  be  investigated,  whereby  a  very  high  degree  of  exactness  is 
obtained. 

209.  TEMPERATURE  TOPOGRAPHY.— Although  the  blood,  in 
virtue  of  its  continual  motion  (completing,  as  it  does,  the  circulation  in  twenty- 
three  seconds),  must  exercise  a  very  considerable  influence  on  the  equilibration  of 
the  temperature  in  different  organs,  nevertheless,  a  completely  uniform  tempera- 
ture does  not  exist,  and  the  temperature  varies  in  different  parts  :  — 


Skin  (/.  Davy). 

Middle  of  the  sole  of  the  foot,  32.26°  C. 

Near  tendo-Achillis,    ....  33.85 

Anterior  surface  of  leg,  .    .    .  33.05 

Middle  of  calf, 33.85 

Bend  of  knee, 35-oo 


Middle  of  upper  arm, 35-40°  C. 

Inguinal  fold, 35 -80 

Near  cardiac  impulse, 34-40 

Face, 31 -oo 

Nose  and  tip  of  ear,    . 22.24 


In  the  closed  axilla,  36.49  (mean,  of  505  individuals)  ; — 36.5  to  37.25  (  Wimderlic/i)  ; — 36.89°  C. 
{Liebermeister).     The  skin  over  muscles  is  warmer  than  that  over  bone  [K'unkel). 

The  temperature  of  the  skin  of  the  head  is  higher  in  the  forehead  and  parietal  region  than  in  the 
occipital  region ;  the  skin  on  the  left  side  of  the  head  is  warmer  than  on  the  right.  Dyspnoea 
increases  the  temperature  of  the  skin. 

Method. — Liebemieister  determines  the  temperature  of  free  cutaneous  surfaces  thus :  The 
bulb  of  the  thermometer  is  heated  slightly  above  the  temperature  expected ;  after  the  mercury  begins 
to  fall,  the  bulb  is  placed  on  the  skin,  and  if  the  bulb  has  the  same  temperature  as  the  skin,  the 
mercury  remains  stationary.     This  experiment  must  be  repeated  several  times. 

2.  Cavities.  ' 

Mouth  under  the  tongue,    .    .     37.19°  C.    I    Vagina, 38.30°  C. 

Rectum, 38  01  |     Urine, 37.03 

Uterine  cavity  somewhat  warmer;  cervical  canal  of  the  uterus  somewhat   cooler. 

The  temperature  falls  in  the  stomach  during  digestion  (§  166,  i).  Cold 
injections  (11°  C.)  into  the  rectum  rapidly  lower  the  temperature  in  the  stomach 
1°  C.  (  Winternitz^. 

3.  The  temperature  of  the  blood  is,  as  a  mean,  39°  C.  The  venous  blood 
in  internal  viscera  is  warmer  than  the  arterial,  but  it  is  cooler  in  peripheral  parts  : — 

Blood  of  the  right  heart, t^%.^°  I  Blood  of  the  superior  vena  cava,    .    .    .    36.78° 

left  heart, 38.6  |  "         inferior  vena  cava,      .    .    .     38. II 

^orta, 38.7  "         crural  vein, 37-20 

hepatic  vein, 39.7  |  "                  {CI.  Bernard  and  v.  Liebig.) 

The  lower  temperature  of  the  blood  in  the  left  heart  may  be  explained  by  the  blood  becoming 
cooled  in  its  passage  through  the  lungs  during  respiration.  According  to  Heidenhain  and  Korner, 
the  right  heart  is  slightly  warmer  because  it  lies  in  relation  with  the  warm  liver,  while  the  left  heart 
IS  surrounded_  by  the  lung,  which  contains  air.  This  observation  is  disputed  by  others,  who  say  that 
the  left  heart  is  slightly  warmer  because  the  combustion  processes  are  more  active  in  arterial  blood,  and 
heat  is  evolved  during  the  formation  of  oxyhjemoglobin.  The  blood  in  the  veins  is  usually  cooler 
than  in  the  corresponding  arteries,  owing  to  the  superficial  position  of  the  former,  whereby  they  give 
off  heat  during  their  long  course;  thus  the  blood  of  the  jugular  vein  is  ^  to  2°  C.  lower  than  the 
blood  in  the  carotid  ;  the  crural  veiti  }(  to  1°  cooler  than  in  the  crtiral  artery.  Superficial  veins, 
more  especially  those  of  the  skin,  give  off  much  heat,  and  their  blood  is,  therefore,  somewhat  cooler. 
24 


370  TEMPERATURE    OF    ORGANS. 

The  warmest  blood  is  that  of  the  hepatic  vein,  39.7°  C,  partly  owing  to  the  great  chemical 
changes  which  occur  within  the  liver,  from  its  secretory  activity  (^  210,  a),  and  partly  to  its  protected 
situation. 

4.  The  individual  tissues  are  warmer  :  (i)  The  greater  the  transformation  of 
kinetic  energy  into  lieat,  i.e.,  the  greater  the  tissue  metabolism;  (2)  the  more 
blood  they  contain  ;  (3)  and  the  more  protected  their  situation.  According  to 
Heidenhain  and  Korner,  the  cerebrum  is  the  warmest  organ  in  the  body. 


Subcutaneous  tissue  (sheep),  .    .  37.35° 

Brain, 4025 

Liver, 41-25 

Lungs, 41  40 


Rectum 40.67°  C. 

Right  hearf, •     .    .   41.60 

Left  heart, 40.90 


Becquerel  and  Brechet  found  the  temperature  of  the  human  subcutaneous  tissue  to  be  2.1°  C.  lower 
than  that  of  the  neighboring  muscles.  The  horny  tissues  do  not  produce  heat,  and  their  low  tempera- 
ture is  due  to  the  conduction  of  heat  from  the  parts  on  which  they  grow.  The  temperature  of  the 
cornea  partly  depends  on  that  of  the  iris,  and  the  more  contracted  the  pupil  is,  the  more  heat  it 
receives  from  the  blood  vessels  of  the  iris. 

210.  CONDITIONS  AFFECTING  THE  TEMPERATURE  OF 
ORGANS. — The  temperature  of  the  individual  organs  is  by  no  means  constant ; 
it  is  influenced  by  many  conditions ;  among  these  are  the  following  : — 

(i)  T/ie  more  heat  produced  independently  within  a  part,  the  higher  is  its 
temperature.  As  the  amount  of  heat  produced  within  a  part  depends  upon  its 
metabolism,  therefore,  when  the  metabolism  is  increased,  the  amount  of  heat  pro- 
duced is  similarly  increased. 

(a)  Glands  produce  more  heat  during  the  act  of  secretion,  as  is  proved  by 
the  higher  temperature  of  their  secretion,  or  by  the  higher  temperature  of  the 
venous  blood  flowing  out  of  their  veins. 

Ludwig  found  that  when  he  stimulated  the  chorda  tympani,  the  saliva  of  the  submaxillary  gland 
was  1.5°  C.  wanner  than  the  blood  in  the  carotid,  which  supplied  the  gland  with  blood  (p.  258).  The 
blood  in  the  renal  vein  in  a  kidney  which  is  secreting  is  warmer  than  the  l)lood  in  the  renal  artery. 
The  secreting  liver  produces  much  heat  (i!  178).  CI.  Bernard  investigated  the  temperature  of  the 
blood  of  the  portal  and  hepatic  veins  during  hunger,  at  the  beginning  of  digestion,  and  when 
digestion  was  most  active,  and  he  found : — 

Temperature  of  jxjrtal  vein,  . 
"  hepatic  vein. 

Temperature  of  portal  vein,  . 

"  hepatic  vein. 

Temperature  of  jxjrtal  vein,. 

"  hepatic  vein. 

In  the  dog  a  moderate  diet,  chemical  or  mechanical  stimulation  of  the  gastric  mucous  membrane,  or 
even  the  sight  of  food,  raises  the  temperature  in  the  stomach  and  intestine. 

{b)  When  the  muscles  contract,  they  evolve  heat.  Davy  found  that  an 
active  muscle  became  0.7°  C.  warmer;  while  Becquerel,  by  means  of  a  thermo- 
galvanometer,  found  that  human  muscles,  when  kept  contracted  for  five  minutes, 
became  1°  C.  warmer  (§  302). 

This  is  one  of  the  reasons  why  the  temperature  may  rise  alx)ve  40°  during  rapid  running.  A 
temperature  obtained  by  energetic  muscular  action  usually  does  not  fall  to  the  nomial  until  after  resting 
for  lyz  hour.  The  low  temperature  of  paralyzed  limbs  depends  partly  upon  the  absence  of  the  mus- 
cular contractions. 

{c)  With  regard  to  the  effect  of  sensory  nerves  upon  the  temperature,  some 
of  the  chief  points  to  ascertain  are — whether  the  circulation  is  accelerated  or 
retarded  by  their  stimulation,  or  whether  the  respiration  is  increased  or  dimin- 
ished (§  214,  II,  3),  and  whether  the  muscles  of  the  skeleton  are  relaxed  or  con- 
tracted reflexly  (§  214,  I,  3).  In  the  former  case  the  temperature  of  the  interior 
and  rectum  is  increased  ;  in  the  latter,  diminished. 


37-8°  C. 

I 

After  4  days' 

r 

Blood  of  right  heart. 

38.4 

starvation. 

I 

38.8° 

(Hunger  period.) 

39-9 

1 

Beginning  of 

39-5 

digestion. 

39-7 

} 

Digestion  most 

( 

Blood   of  right    heart, 

41-3 

active. 

I 

during  digestion,  39.2°, 

ESTIMATION    OF    HEAT. 


371 


{d)  The  temperature  of  the  body  rises  during  mental  exertion.  Davy 
observed  an  increase  of  0.3°  C.  after  vigorous  mental  exertion. 

{e)  The  parenchymatous  fluids,  serous  fluids  and  lymph  produce  little  heat, 
owing  to  their  feeble  metabolism,  hence  they  have  the  same  temperature  as  their 
surroundings ;  the  epidermal  and  horny  tissues  do  not  produce  heat,  they  merely 
conduct  it  from  subjacent  structures. 

(2)  The  temperature  depends,  to  a  large  extent,  upon  the  amount  of  blood  in  an 
organ,  and  also  upon  the  rapidity  with  which  the  blood  is  renewed  hy  the  circula- 
tion. This  is  best  observed  in  the  difference  of  the  temperature  between  a  cold, 
pale,  bloodless  hand,  and  a  warm,  red,  congested  one. 

Becquerel  and  Brechet  found  that  the  temperature  of  the  human  biceps  fell  several  tenths  of  a  degree 
when  the  axillary  artery  was  compressed.  Ligature  of  the  crural  artery  and  vein  in  a  dog  causes  a 
fall  of  several  degrees.  If  the  extremities  be  kept  suspended  in  the  air,  they  become  bloodless  and 
cold. 

Liebermeister  has  pointed  out  a  difference  with  regard  to  the  external  and  internal  parts  of  the  body. 
The  external  parts  give  off  more  heat  than  they  produce,  so  that  they  become  cooler  the  more  slowly 
new  blood  flows  into  them,  and  warmer  the  greater  the  rapidity  of  the  blood  stream  through  them. 
Acceleration  of  the  blood  stream,  therefore,  causes  the  temperature  of  peripheral  parts  to  approximate 
more  and  more  to  the  temperature  of  internal  organs,  while  retardation  of  the  blood  stream  causes 
them  to  approach  the  temperature  of  the  surrounding  medium  Exactly  the  reverse  is  the  case  with 
internal  parts,  where  a  large  amount  of  heat  is  produced,  and  heat  is  given  up  almost  alone  to  the 
blood  which  flows  through  them.  Their  temperature  must  fall  when  the  blood  stream  through  them 
is  accelerated,  and  it  is  raised  when  the  blood  stream  is  retarded.  Hence  it  follows,  that  the  greater 
the  differettce  of  the  temperature  between  peripheral  and  iftternal  parts,  the  slower  finist  be  the 
velocity  of  the  circulation. 

(3)  If  the  position  of  an  organ  be  such,  or  if  other  conditions  cause  it  to 
give  off  heat  by  conduction  or  radiation,  then  its  temperature  falls. 

A  good  example  of  this  is  the  skin,  which  varies  greatly  in  temperature  according  to  the  tempera- 
ture of  the  surrounding  medium,  whether  it  is  covered  or  uncovered,  whether  it  is  dry  or  moist  with 
sweat  (which  abstracts  heat  when  it  evaporates).  When  much  cold  food  or  drink  is  taken,  the 
stomach  is  cooled,  and  when  ice-cold  air  is  breathed,  the  respiratory  passages  as  far  as  the 
bronchi  are  cooled. 

211.  ESTIMATION  OF  HEAT.— Calorimetry  is  the  method  of  deter- 
mining the  amount  of  heat  possessed  by  any  body,  or  what  amount  of  heat  it  is 
capable  of  producing.  The  unit  of  measurement  is  the  "  heat  unit,"  /.  e.,  the 
amount  of  heat  (or  potential  energy)  required  to  raise  the  temperature  of  i 
gramme  of  water  1°  C.  (see  Introduction). 

Experiment  has  shown  that  equal  quantifies  of  different  substances  require  very  unequal  amounts 
of  heat  to  raise  them  to  the  same  temperattire,  e.  g.,  i  kilo,  water  requires  nine  times  as  much  heat  as 
I  kilo,  iron  to  raise  it  to  the  same  temperature.  In  the  human  body,  therefore,  which  is  composed  of 
very  different  substances,  unequal  amounts  of  heat  will  be  required  to  raise  them  all  to  the  same  tem- 
perature. The  same  amount  of  heat  transferred  to  two  different  substances  will  raise  them  to  different 
temperatures.  Hence,  bodies  of  different  temperatures  may  contain  equal  amounts  of  heat.  ^  The 
amount  of  heat  required  to  raise  a  definite  quantity  {e.  g.,  I  grm.)  of  a  substance  to  a  certain  higher 
degree  {e.  g.,  1°  C.)  is  called  "  specific  heat."  The  specific  heat  of  water  (which  of  all  bodies  has 
the  highest  specific  heat)  is  taken  as  =  i.  By  "  heat  capacity  "  is  meant  that  property  of  bodies 
in  virtue  of  which  they  must  absorb  a  given  amount  of  heat  in  order  to  have  a  certain  temperature. 

Calorimetry  is  employed  : — To  determifte  the  specific  heat  of  the  differe?it  organs 
of  the  body. — Only  a  few  observations  have  been  made.  The  mean  specific 
heat  of  the  following  animal  parts  (water  =  i)  is : — 


Human  blood  =  1. 02     (?)  I  Human  muscle  =  0.741 

Arterial  blood  =  1.031  (?)  |  Ox  muscle  =  0.787 

Venous  blood  =  0.892  (?)  |  Compact  bone  =  0.3 

Cow's  milk  =  0.992  |  Spongy  bone  =  0.71 


Fat  tissue  =     0.712 

Striped  muscle  =     D.825 

Defibrinated  blood  =     0.927 

(y.  Rosenthal }j 


The  specific  heat  of  the  human  body,  as  a  whole,  is  about  that  of  an  equal 
volume  of  water  (?). 


372 


CALORIMETRY. 


I-IC.    2^1. 


Kopp's  Method. — The  solid  to  be  investigated  is  hroken  in  pieces  about  the  size  of  a  pea,  and 
placed  in  a  test-tube.  A,  with  thin  walls,  which  is  closed  above  with  a  cork,  from  which  a  co])])er  wire 

with  a  hook  on  it  projects  (I'ig.  231).  The 
test-tube  contains  a  certain  quaniily  of  fluid 
which  does  not  dissolve  the  sui)stance,  but 
which  lies  between  its  pieces  and  covers  it. 
It  is  weighed  three  times  to  ascertain  the 
weight  (i)  of  the  empty  glass,  (2)  after  it  is 
filled  with  the  solid  substance,  (3)  after  the 
fluid  is  added,  so  that  we  obtain  the  weight 
of  the  solid  substance,  w,  and  that  of  the 
fluid,  f.  The  test-tube  and  its  contents  are 
placed  in  a  mercttry  balh,  HH,  and  this 
again  in  an  oil  bath,  CC,  and  the  whole  is 
raised  to  a  high  temperature.  Into  BB  there 
is  introduced  a  fine  thermometer,  T,  When 
the  tube.  A,  has  reached  the  necessary  tem- 
perature (say  40°),  it  is  rapidly  placed  in  the 
water  of  the  accompanying  calorimeter  box, 
1)1).  The  water  in  this  box,  which  also 
contains  a  thermometer,  D,  is  kept  in  motion 
until  it  has  completely  absorbed  all  the  heat 
given  off"  by  A.  Let  T  represent  the  tem- 
perature to  which  A  and  its  contents  were 
raised  in  the  mercury  bath,  and  T,  the  tem- 
perature to  which  it  fell  in  the  calorimeter ;  let  s  be  the  specific  heat,  and  m  the  weight  of  the  solid 
sul)stance  in  the  test  tulie,  while  o  and  //  represent  the  specific  heat  of  the  weight  of  the  interstitial 
fluid  in  the  test-tube ;  and  lastly,  let  w  ecjual  the  amount  of  water  in  contact  with  A,  which  absorbs 
and  gives  oft"  heat ;  then  \V  represents  the  amount  of  heat  which  the  test-tube  and  its  contents  give  oft 
during  cooling. 

W  ={s  .viAriv  -\-  c  //)  (T-T,) . 

The  amount  of  heat,  Wj,  absorbed  by  the  calorimeter  is 

where  M  represents  the  amount  of  water  in  the  calorimeter,  /  the  original  temperature  of  the  water  in 
the  calorimeter,  and  /,  the  temperature  to  which  it  is  raised  by  placing  A  in  it.  If  W  and  Wj  are 
equal,  then 

,M(/,-0-(7£'  +  <T.//)(T-T,) 


iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii 


Kopp's  apparatus  for  estimating  specific  heat. 


the  specific  heat,  s  =  ' 


/«(T-Ti) 


J,  the 


If  a  fluid  substance  is  placed  in  the  test-tube,  and  its  weight  =  m,  and  its  specific  heat 
formula  for  the  specific  heat  ot  the  fluid  to  be  investigated  is 

M(/,-/)-7c;(T-T0 
m  (T-Tj)  • 

II.  Calorimetry  is  more  important  for  determining  the  amount  of  heat 
produced  in  a  given  time  by  the  body  as  a  whole,  or  by  its  individual  parts. 

Lavoisier  and  I>aplace  made  the  first  calorimetric  ob-servations  on  animals  in  1783,  by  means  of  an 
ice  calorimeter;  a  guinea  pig  melted  13  oz.  of  ice  in  ten  hours.  Crawford,  and  afterward  Dulong 
and  Despretz,  used  Rumford's  water  calorimeter,  which  is  similar  to  Favre  and  Silbermann's.  Small 
animals  are  placed  in  the  inner  thin-walled  copper  chamber  (K),  which  is  placed  in  a  water  bath 
surrounded  on  all  sides  by  some  non-conducting  material.  We  ref[uire  to  know  the  amount  of  water, 
and  its  original  temperature.  The  number  of  calories  is  obtained  from  the  increase  of  the  temjjerature 
at  the  end  of  the  experiment,  which  lasts  several  hours.  The  air  is  supplied  to  the  animal  through 
a  special  apparatus,  resembling  a  gasometer.      The  amount  of  CO.^  in  the  gases  evolved  is  estimated. 

According  to  Despretz,  a  bitch  forms  14,610  heat  units  per  hour — i.e.,  393,000 
in  twenty-four  hours.  Other  things  being  equal,  a  man  seven  times  heavier  than 
this  would  produce  in  twenty-four  hours  about  2,750,000  calories.  Senator  found 
that  a  dog  weighing  6330  grms.  produced  15,370  calories,  and  excreted  at  the  same 
time  367  grms.  CO2.  The  first  calorimetric  experiments  on  man  were  made  by 
Scharling  (1849).  Liebermeister  estimated  the  amount  of  heat  given  off  by  a  man 
placed  in  a  cold  bath,  which  was  surrounded  with  a  woolen  covering.     Leyden 


VARIATIONS    OF   TEMPERATURE.  373 

placed  a  lower  limb  in  the  calorimeter,  whereby  6000  grms.  water  were  raised  1° 
C.  in  an  hour.  If  we  assume  that  the  total  superficial  area  of  the  body  is  fifteen 
times  greater  than  that  of  the  leg,  the  human  body  would  produce  2,376,000 
calories  in  twenty-four  hours. 

212.  THERMAL  CONDUCTIVITY  OF  TISSUES.— The  thermal  conductivity  of 
animal  tissues  is  of  special  interest  in  connection  with  the  skin  and  subcutaneous  fatty  tissue.  The 
fatty  layer  under  the  skin,  more  especially  in  the  whale,  walrus,  and  seal,  forms  a  protective  covering, 
whereby  the  conduction  of  heat  fi-om  internal  organs  is  rendered  almost  impossible.  Investigations 
upon  this  subject,  however,  are  few.  Griess  attempted  to  estimate  the  thermal  conductivity  by  heat- 
ing one  part  of  the  tissue,  and  determining  when  and  in  what  direction  pieces  of  wax  placed  on  the 
tissue  to  be  investigated  began  to  melt.  He  investigated  the  stomach  of  the  sheep,  the  bladder,  skin, 
hoof,  horn,  and  bones  of  an  ox,  deer's  horn,  ivory,  mother-of-pearl,  shell  of  haliotis.  He  found  that 
fibrous  tissues  conducted  heat  more  readily  in  the  direction  of  their  fibres  than  at  right  angles  to  the 
course  of  the  fibres.  Hence,  the  figures  obtained  from  the  melted  wax  were  usually  elliptical. 
Landois  has  made  similar  observations,  and  he  finds  that  tissues  conduct  better  in  the  direction  of 
their  fibres.  After  bones,  blood  clot  was  the  best  conductor,  then  followed  spleen,  liver,  cartilage, 
tendon,  muscle,  elastic  tissue,  nail  and  hair,  bloodless  skin,  gastric  mucous  membrane,  washed  fibrin. 
It  is  specially  interesting  to  note  how  much  better  skin  containing  blood  in  its  blood  vessels  conducts 
than  does  bloodless  skin.  Hence  little  heat  is  given  off  from  a  bloodless  skin,  while  congested  skin 
conducts  and  gives  off  much  more  heat. 

Like  all  other  substances,  the  human  body  is  enlarged  by  heat.  A  man  weighing  60  kilos.,  and 
who=e  temperature  is  raised  from  37°  C.  to  40°  C,  is  enlarged  about  62  cubic  centimetres.  Con- 
nective tissue  (tendon)  is  extended  by  heat,  while  elastic  tissue  and  the  skin,  like  caoutchouc,  are 
contracted. 

213.  VARIATIONS  OF  THE  MEAN  TEMPERATURE.— (i) 
General  Climatic  and  Somatic  Influences. — In  the  tropics  the  mean  tem- 
perature of  the  body  is  about  ^°  C.  higher  than  in  temperate  climates,  where 
again  it  is  several  tenths  of  a  degree  warmer  than  in  cold  climates  ;  but  this  has 
recently  been  denied.  The  difference  is  comparatively  trivial,  when  we  remember 
that  a  man  is  subjected  to  a  variation  of  over  40°  C.  in  passing  from  the  equator 
to  the  poles.  Observations  on  more  than  4000  persons  show  that  when  a  person 
goes  from  a  warm  to  a  cold  climate,  his  temperature  is  but  slightly  diminished, 
but  when  he  goes  from  a  cold  to  a  warm  climate  his  temperature  rises  relatively 
considerably  more.  In  the  temperate  zone,  the  temperature  of  the  body  during  a 
cold  winter  is  usually  o.  1°  to  0.3°  C.  lower  than  it  is  on  a  warm  summer  day.  The 
elevation  of  a  place  above  sea  level  has  no  obvious  effect  on  the  temperature 
of  the  body.  There  seems  to  be  no  difference  in  different  races,  nor  in  the 
sexes,  other  conditions  being  the  same.  Persons  of  powerful  physique  and  con- 
stitution are  said  to  have  generally  a  slightly  higher  temperature  than  feeble, 
weak,  anaemic  persons. 

(2)  Influence  of  the  General  Metabolism. — As  the  formation  of  heat 
depends  upon  the  transformation  of  chemical  compounds,  whose  chief  final  products 
in  addition  to  HjO,  are  CO.2  and  urea,  the  amount  of  heat  formed  must  ^o  pari  passu 
with  the  amount  of  these  excreta.  The  more  rapid  metabolism  which  sets  in  after 
a  full  meal,  causes  a  rise  of  temperature  to  several  tenths  of  a  degree  ("  Digestion 
fever").  As  the  metabolism  is  much  diminished  during  hunger,  this  explains 
why  the  mean  temperature  in  a  fasting  man  is  'i>^.(i° ,  while  it  is  37.17°  on  ordinary 
d^ys  (§  237). 

Jiirgensen  also  found  that  the  temperature  fell  on  the  first  day  of  inanition  (although  there  was  a 
temporary  rise  on  the  second  day).  In  experiments  made  upon  starving  animals,  the  temperature  at 
first  fell  rapidly,  then  remained  constant  for  a  considerable  time,  while  during  the  last  days  it  fell  con- 
siderably. Schmidt  starved  a  cat — on  the  15th  day  the  temperature  was  38.6°;  on  the  i6th,  38.3°; 
17th,  37.64;  i8th,  35.8;  19th  (death)  =33.0°.  Chossat  found  that  starving  mammals  and  birds 
had  a  temperature  16°  C.  below  normal  on  the  day  of  their  death. 

(3)  A-ge  has  a  decided  effect  upon  the  temperature  of  the  body.  The  extent  of 
the  general  metabolism  is  in  part  an  index  of  the  heat  of  the  body  at  different  ages, 
but  it  is  possible  that  other,  as  yet  unknown,  influences  are  also  active. 


374 


VARIATIONS   OF   TEMPERATURE. 


Age. 

Mean  Temperature  at  the 
Ordinary  Temperature. 

Normal  Limits. 

Where  Measured. 

Xewly-born, 

37-45°  C. 

37-35-37-55°  C. 

Rectum. 

S-9    year, 

37-72 

36.87-37.62 

JMouth  and  Rectum. 

15-20     " 

37-37 

36. 1 2-38. 1 

Axilla. 

21-30     " 

37.22 

« 

25-30     " 

36-91 

" 

31-40     " 

37-1 

36-25-37-5 

« 

41-50     " 

36.87 

t< 

51-60     " 

36-83 

« 

80     « 

37-46 

Mouth. 

Newly-born  animals  exhibit  peculiarities  owing  to  the  sudden  change  in 
their  conditions  of  existence.  Immediately  after  birth,  the  infant  is  0.3°  warmer 
than  the  vagina  of  the  mother,  viz.,  37.86°.  A  short  time  after  birth,  the  tem- 
perature falls  0.9°,  while  twelve  to  twenty-four  hours  afterward  it  has  risen  to  the 
normal  temperature  of  an  infant,  which  is  37.45°.  Several  irregular  variations 
occur  during  the  first  weeks  of  life.  During  sleep,  the  temperature  of  an  infant 
falls  0.34°  to  0.56°,  while  continued  crying  may  raise  it  several  tenths  of  a  degree. 
Old  people,  on  account  of  their  feeble  metabolism,  produce  little  heat;  they 
become  cold  sooner,  and  hence  ought  to  wear  warm  clothing  to  keep  up  their 
temperature. 

(4)  Periodical  Daily  Variations. — In  the  course  of  twenty-four  hours  there 
are  regular  periodic  variations  in  the  mean  temperature,  and  these  occur  at  all 
ages.  As  a  general  rule,  the  temperature  continues  to  rise  during  the  day  (maximum 
at  5  to  8  P.M.),  while  it  continues  to  fall  during  the  night  (minimum  2  to  6  a.m.). 
The  mean  temperature  occurs  at  the  third  hour  after  breakfast. 


Fig.  232. 


Variations  of  the  daily  temperature  in  health  during  twenty-four  hours. 

after  Jiirgensen. 


L ,  after  Liebermeister  ;  J , 


The  mean  height  of  all  the  temperatures  taken  during  a  day  in  a  patient  is 
called  the  "daily  mean,"  and  according  to  Jaeger  it  is  37.13°  in  the  rectum  in 
health.  A  daily  mean  of  more  than  37.8°  is  a  "fever  temperature,"  while  a 
mean  under  37.0°  C.  is  regarded  as  a  "  collapse  temperature." 


VARIATIONS    OF   TEMPERATURE. 


375 


Time. 

Barensprung. 

J.  Davy. 

Hallman. 

Gierse. 

Jiirgensen. 

Jager. 

Morning,   5 

.     . 

36-7 

36.6 

36.9 

6 

36.68 

•     • 

36-7 

36.4 

37.1 

7 

36.94- 

36.63 

36.98 

36.7* 

36.5* 

37.5* 

8 

37-16* 

36.S0* 

37.08* 

36.8 

36.7 

37.4 

9 

36.89 

36-9 

36.8 

37-5 

10 

37.26 

io>^=  37-36 

37.23 

37-0 

37-0 

37-5 

II 

36.89 

37.2 

37-2 

37-3 

Mid-day,  12 

36.87 

.     . 

37-3* 

37-3* 

37.5* 

I 

36.83 

37.21 

37-13 

37-3 

37-3 

37-4 

2 

37-05 

37-50* 

37.4 

37.4^ 

37-5 

3 

37-15* 

37-43 

37.4* 

37-3* 

37-5 

4 

37-17 

37.4 

37-3 

37.5* 

5 

3748 

37.05* 

5^^=37.31 

37.43 

37-5 

37.5 

37  5 

6 

6>^  =  36.83 

37-29 

37-5 

37-6 

37-4 

7 

37.43 

7>^=  36.50* 

37-31* 

37-5* 

37-6* 

37.3 

8 

37-4 

37.7 

37.1* 

9 

37.02* 

.    . 

37-4 

37-5 

36.9 

10 

37-29 

37-3 

37.4 

36.8 

II 

36.85 

36.72 

36.70 

36.81 

37-2 

37.1 

36.8 

Night,       12 

.    . 

37-1 

36.9 

369 

I 

36.65 

36.44 

.    . 

37-0 

36.9 

36.9 

2 

369 

36-7 

36.8 

3 

36.8 

36-7 

36-7 

4 

36.31 

367 

36.7 

36.7 

As  the  variations  occur  when  a  person  is  starved  for  a  day — although  those  that  occur  at  the 
periods  at  which  food  ought  to  have  been  taken  are  less — it  is  obvious  that  the  variations  are  not  due 
entirely  to  the  taking  of  food.      [The*  indicates  taking  of  food.] 

The  daily  variation  in  the  frequency  of  the  pulse  often  coincides  with  variation  of  the  tempera- 
ture. Barensprung  found  that  the  mid-day  temperature  maximimi  slightly  preceded  the  pulse  maxi- 
mum (I  70,  3,  C). 

If  we  sleep  during  the  day,  and  do  all  our  daily  duties  during  the  night,  the 
above  described  typical  course  of  the  temperature  is  reversed.  With  regard  to 
the  effect  of  activity  or  rest,  it  appears  that  the  activity  of  the  muscles  during  the 
day  tends  to  increase  the  mean  temperature  slightly,  while  at  night  the  mean  tem- 
perature is  less  than  in  the  case  of  a  person  at  rest. 

The  peripheral  parts  of  the  body  exhibit  more  or  less  regular  variations  of  their  temperature.  In 
the  palm  of  the  hand,  the  progress  of  events  is  the  following  :  After  a  relatively  high  night  tempera- 
ture there  is  a  rapid  fall  at  6  A.  M.,  which  reaches  its  minimum  at  9  to  10  A.  M.  This  is  followed  by 
a  slow  rise,  which  reaches  a  high  maximum  after  dinner ;  it  falls  between  I  to  3  P.  M.,  and  after  two 
or  three  hours  reaches  a  minimum.  It  rises  from  6  to  8  P.  M.,  and  falls  again  toward  morning.  A 
rapid  fall  of  the  temperature  in  a  peripheral  part  corre.sponds  to  a  rise  of  temperature  in  internal  parts. 

(5)  Many  operations  upon  the  body  affect  the  temperature.  After  hemor- 
rhage the  temperature  falls  at  first,  but  it  rises  again  several  tenths  of  a  degree, 
and  is  usually  accompanied  by  a  shiver  or  slight  rigor  :  several  days  thereafter  it 
falls  to  normal,  and  may  even  fall  somewhat  below  it.  The  sudden  loss  of  a  large 
amount  of  blood  causes  a  fall  of  the  temperature  of  ^  to  2°  C.  Very  long-con- 
tinued hemorrhage  (dog)  causes  it  to  fall  to  31°  or  29°  C. 

This  is  obviously  due  to  the  diminution  of  the  processes  of  oxidation  in  the  ansemic  body,  and  to 
the  enfeebled  circulation.  Similar  conditions  causing  diminished  metabolism  effect  the  same  result. 
Continued  stimulation  of  the  peripheral  end  of  the  vagus,  so  that  the  heart's  action  is  enormously 
slowed,  diminishes  the  temperature  several  degrees  in  rabbits  {^Landois  and  Amnion). 

The  transfusion  of  a  considerable  quantity  of  blood  raises  the  temperature 
about  half  an  hour  after  the  operation.  This  gradually  passes  into  a  febrile  attack, 
which  disappears  within  several  hours.  When  blood  is  transfused  from  an  artery 
to  a  vein  of  the  same  animal,  a  similar  result  occurs  (§  102). 


376  REGULATION  OF  THE  TEMPERATURE. 

(6)  Many  poisons  diminish  the  temperature,  e.  g.^  chloroform  and  the  anaes- 
thetics, alcohol  (>;  235),  digitalis,  quinine,  aconitin,  niuscarin.  These  appear 
to  act  partly  by  rendering  the  tissues  /ess  liable  to  undergo  molecular  transforma- 
tions for  the  production  of  heat.  In  the  case  of  the  anaesthetics,  this  effect  per- 
haps occurs,  and  is  due  i)ossibly  to  a  semi-coagulation  of  the  nervous  substance 
(?).  They  may  also  act  partly  by  influencing  the  giving  off  of  heat  (§  214,  II). 
Other  i)oisons  increase  the  temperature  for  opposite  reasons. 

The  temperature  is  increased  bv  strychnin,  nicotin,  ])icrotoxin,  veratrin,  laudanin. 

{7)  Various  diseases  diminish  the  tcin[)erature,  which  may  be  due  either  to  lessened  production 
of  lieat  (dimiiuition  of  the  metabolism),  or  to  increased  expenditure  of  heat.  Loewenhardt  found 
that  in  paralytics  and  in  insane  persons,  several  weeks  before  their  death,  the  rectal  temperature  was 
30°  to  31°  C,  in  diabetes  30°  C,  or  less ;  the  lowest  temperature  observed  and  life  retained  in  a  drunk 
person  was  24°  C. 

The  temperature  is  increased  in  fe7'er,  and  the  highest  point  reached  just  before  death,  and 
recorded  by  Wunderlich,  was  44.65°  C.  (compare  \  220). 

214.  REGULATION  OF  THE  TEMPERATURE.— As  the  bodily 
temperature  of  man  and  similar  animals  is  nearly  constant,  notwithstanding 
great  variations  in  the  temperature  of  their  surroundings,  it  is  clear  that  some 
mechanism  must  exist  in  the  body,  whereby  the  heat  economy  is  constantly 
regulated.  This  may  be  brought  about  in  two  ways  ;  either  by  controlling 
the  transformation  of  potential  energy  into  heat,  or  by  affecting  the  amount  of 
heat  given  off  according  to  the  amount  produced,  or  to  the  action  of  external 
agencies. 

[The  constancy  or  thermostatic  condition  of  the  temperature  is  brought  about 
by  three  co-operant  factors,  the  thermogenic  or  heat  producing,  the  thermo- 
lytic  or  heat  discharging,  and  the  thermotaxic  or  mechanism  by  which  heat 
production  and  heat  loss  are  balanced,  and  it  is  obvious  that  the  last  must  be  in 
relation  with  the  other  two.  The  thermotaxic  mechanism  is  developed  last,  is 
least  pronounced  in  the  lower  vertebrata,  and  is  most  easily  liable  to  fail  under 
injury  or  disease  {Mac  A  lister). '\ 

I.  Regulatory  Arrangements  governing  the  production  of  Heat. — 
Liebermeister  estimated  the  amount  of  heat  produced  by  a  healthy  man  at  1.8 
calorie  per  minute.  It  is  highly  probably  that,  within  the  body,  there  exist 
mechanisms  which  determine  the  molecular  transformations  upon  which  the  evo- 
lution of  heat  depends.  This  is  accomplished  chiefly  in  a  reflex  manner.  The 
peripheral  ends  of  cutaneous  nerves  (by  thermal  stimulation),  or  the  nerves  of  the 
intestine  and  the  digestive  glands  (by  mechanical  or  chemical  stimulation  during 
digestion  or  inanition),  may  be  irritated,  whereby  impressions  are  conveyed  to 
th  -•  heat  centre,  which  sends  out  impulses  through  efferent  fibres  to  the  depots 
of  potential  energy,  either  to  increase  or  diminish  the  extent  of  the  transforma- 
tions occurring  in  them.  The  nerve  channels  herein  concerned  are  entirely  un- 
known.    Many  considerations,  however,  go  to  support  such  an  hypothesis  (§  377). 

[Thermotaxic  Mechanism,  Thermal  Nerves  and  Centres. — Just  as  the  respiration  and  the 
state  of  the  blood  vessels  are  regulated  from  a  central  focus,  so  the  question  arises,  does  the  same 
obtain  with  regard  to  temperature?  .Studying  this  question,  however,  it  must  be  borne  in  mind  that 
thermometric  observations  alone  are  not  sufficient ;  the  true  test  must  be  calorimetric.  Sir  Benjamin 
Brodie  observed  that  in  a  case  of  injury  of  the  spinal  cord  in  the  neck  the  temperature  in  the  thigh 
rose  very  high.  In  some  cases  the  temperature  falls.  Wood  has  shown  that  section  of  the  cord 
above  the  origin  of  the  splanchnics  leads  to  decided  increase  in  the  amount  of  heat  dissipated,  but 
to  a  decided  diminution  of  heat  production.  The  vasomotor  paralysis  has  much  to  do  in  these  cases 
with  the  loss  of  heat.  In  warm-blooded  animals,  exposed  to  a  high  temperature,  the  heat  production 
is  diminished,  but  when  they  are  exposed  to  a  low  temperature  it  is  increased.  If  a  warm-blooded 
animal's  medulla  oblongata  be  divided,  there  is  a  fall  of  temperature,  chiefly  due  to  its  vasomotor 
paralysis,  and  such  an  animal  behaves,  as  regards  the  effect  of  heat  and  cold,  exactly  like  a  poikilo- 
thermal  animal,  i.e.,  its  metabolism  and  heat  production  are  increased  by  cold  and  diminished  by 
heat.  If,  however,  the  incision  be  made  above  the  pons,  so  as  to  leave  the  vasomotor  centre  intact 
ill  the  dog,  there  is  a  rise  of  the  temperature  and  increased  heat  production  for  24  hours  afterward. 


.REGULATION  OF  THE  TEMPERATURE.  377 

This  suggests  the  idea  that  this  region  is  traversed  by  inhibitory  nerves,  so  that  when  they  are  cut  oft 
from  their  centres  situate  above,  the  augmentor  nerves  can  act  more  vigorously.  This  suggests  the 
existence  of  thermo-inhibitory  centres  situate  higher  up  in  the  brain.  If  an  animal  be  curarized, 
not  only  is  there  paralysis  of  voluntary  motor  acts,  but  on  stimulating  an  ordinary  motor  nerve,  not 
only  is  there  no  muscular  contraction,  but  there  is  no  rise  of  temperature  of  the  muscles  supplied 
by  that  nerve.  In  such  an  animal  the  temperature  rises  and  falls  with  the  temperature  of  the  sur- 
rounding medium.  Even  although  the  respirations  be  kept  constant  and  the  vasomotor  nerves 
intact,  the  thermogenic  activity  of  muscles,  therefore,  seems  to  be  dependent  on  their  innervation.] 

[Cerebral  Centres. — Apart  from  the  cortical  heat  centres  (^  377),  Ott,  Aronsohn,  Sachs,  Richet 
and  others  have  shown  that  if  a  needle  be  thrust  through  the  skull  and  brain,  so  as  to  injure  certain 
deeper-seated  parts,  there  is  a  rise  of  temperature  and  increased  heat  production  for  several  hours. 
The  experiment  may  be  repeated  several  times  in  the  same  rabbit.  Ott  gives  three  areas  which, 
when  so  injured,  cause  these  effects  :  (l)  a  part  of  the  brain  in  the  median  side  of  the  corpus  striatum, 
and  near  the  nodus  cursorius  ;  (2)  a  part  between  the  corpus  striatum  and  the  optic  thalamus ;  and 
(3)  the  anterior  end  of  the  optic  thalamus  itself.  From  the  effect  of  atropin,  Ott  suggests  the  existence 
of  spinal  centres  as  well.] 

The  following  phenomena  indicate  the  existence  of  mechanisms  regulating  the 
production  of  heat : — 

( 1 )  The  temporary  application  of  moderate  cold  raises  the  bodily  temperature,  while 
heat,  similarly  applied  to  the  external  surface,  lowers  it  (§§  222  and  224). 

(2)  Cooling  of  the  surroundings  increases  the  aiiiount  of  CO2  excreted,  by  in- 
creasing the  production  of  heat,  while  the  O  consumed  is  also  increased  simul- 
taneously; heating  the  surrounding  medium  diminishes  the  CO2  (§  127,  5). 

D.  Finkler  found,  from  experiments  upon  guinea  pigs,  that  the  production  of  heat  was  more  than 
doubled  when  the  surrounding  temperature  was  diminished  24°  C.  The  metabolism  of  the  guinea 
pig  is  increased  in  winter  23  per  cent,  as  compared  with  summer,  so  that  the  same  relation  obtains 
as  in  the  case  of  a  diminution  of  the  surrounding  temperature  of  short  duration. 

C.  Ludwig  and  Sanders-Ezn  found  that  in  a  rabbit  there  was  a  rapid  increase  in  the  amount  of 
CO.^  given  off,  when  the  surroundings  were  cooled  from  38°  to  6°  or  7°  C. ;  while  the  excretion  was 
diminished  when  the  surrounding  temperature  was  raised  from  4°-9°  to  35°-37°,  so  that  the  thermal 
stimulation,  due  to  the  temperature  of  the  surrounding  medium,  acted  upon  the  combustion  within 
the  body.  Pfliiger  found  that  a  rabbit  which  was  dipped  in  cold  water  used  more  O  and  excreted 
more  COj. 

If  the  cooling  action  was  so  great  as  to  reduce  the  bodily  temperature  to  30°,  the  exchange  of 
gases  diminished,  and  where  the  temperatiu-e  fell  to  20°,  the  exchange  of  gases  was  diminished 
one-half.  It  is  to  be  remembered,  however,  that  the  excretion  of  COj  does  not  go  hand  in  hand 
with  the  formation  of  COj.  If  mammals  be  placed  in  a  warm  bath  which  is  2°  to  3°  higher  than 
their  own  temperature,  the  excretion  of  COj  and  the  consumption  of  O  are  increased,  owing  to 
the  stimulation  of  their  metabolism,  while  the  excretion  of  urea  is  also  increased  in  animals  and  in 
man  (|  133,  5). 

(3)  Cold  acting  upon  the  skin  causes  involuntary  muscular  movements 
(shivering,  rigors),  and  also  voluntary  movements,  both  of  which  produce  heat. 

The  cold  excites  the  action  of  the  muscles,  which  is  connected  with  processes  of  oxidation 
{FJiilger).  After  poisoning  with  curara,  which  paralyzes  voluntary  motion,  this  regulation  of  the 
heat  falls  to  a  minimum  [Rohrig  and  Zuntz),  [while  the  bodily  temperature  rises  and  falls  with  a 
rise  or  fall  in  the  temperature  of  the  surrounding  medium]. 

(4)  Variations  in  the  temperature  of  the  surroundings  affect  the  appetite 
for  food ;  in  winter,  and  in  cold  regions,  the  sensation  for  hunger  and  the  appe- 
tite for  the  fats,  or  such  substances  as  yield  much  heat  when  they  are  oxidized,  are 
increased  ;  in  summer  and  in  hot  climates,  they  are  diminished.  Thus  the  mean 
temperature  of  the  surroundings,  to  a  certain  extent,  determines  the  amount  of 
the  heat-producing  substances  to  be  taken  in  the  food. 

II.  Regulatory  Mechanisms  governing  the  Excretion  of  Heat  or 
Thermolysis. — The  mean  amount  of  heat  given  off  by  the  human  skin  in 
twenty-four  hours,  by  a  man  weighing  82  kilos.,  is  2092  to  2592  calories,  i.e., 
1.36  to  1.60  per  minute. 

(i)  Heat  causes  dilatation  of  the  cutaneous  vessels  ;  the  skin  becomes 
red,  congested,  and  soft ;  it  contains  more  fluids,  and  becomes  a  better  conductor 
of  heat ;  the  epithelium  is  moistened,  and  sweat  appears  on  the  surface.     Thus 


378  REGULATION  OF  THE  TEMPERATURE. 

increased  excretion  of  heat  is  provided  for,  while  the  evaporation  of  the  sweat 
also  abstracts  heat. 

The  amount  of  heat  necessary  to  convert  into  vapor  i  grm.  of  water  at  ioo°  C,  is  equal  to  that 
re(iuired  to  heat  lo  grnis.  from  0°  to  53.67°  C.  The  sweat  as  secreted  is  at  the  temperature  of  the 
body  ;   if  it  were  completely  changed  into  vapor,  it  would  rerjuire  the  heat  necessary  to  raise  it  to  the 

boiling  point,  and  also  that  necessary  to  convert  it  into  vapor. 

Cold  causes  contraction  of  the  cutaneous  vessels  ;  the  skin  becomes 
l)ale,  less  soft,  poorer  in  juices,  and  collapsed  ;  the  epithelium  becomes  dry,  and 
does  not  permit  fluids  to  pass  through  it  to  be  evaporated,  .so  that  the  excretion  of 
heat  is  diminished.  The  excretion  of  heat  from  the  periphery,  and  the  transverse 
thermal  conduction  through  the  skin,  are  diminished  by  the  contraction  of  the 
vessels  and  muscles  of  the  skin,  and  by  the  expulsion  of  the  well-conducting  blood 
from  the  cutaneous  and  subcutaneous  vessels.  The  cooling  of  the  body  is  very 
much  affected,  owing  to  the  diminution  of  the  cutaneous  blood  stream,  just  as 
occurs  when  the  current  through  a  coil  or  worm  of  a  distillation  apparatus  is  greatly 
diminished.  If  the  blood  vessels  dilate,  the  temperature  of  the  surface  of  the  body 
rises,  the  difference  of  temperature  between  it  and  the  surrounding  cooler  medium 
is  increased,  and  thus  the  excretion  of  heat  is  increased.  Tomsa  has  shown  that 
the  fibres  of  the  skin  are  so  arranged  anatomically,  that  the  tension  of  the  fibres 
produced  by  the  erector  pili  muscles  causes  a  diminution  in  the  thickness  of  the 
skin,  this  result  being  brought  about  at  the  expense  of  the  easily  expelled  blood. 

By  the  systematic  application  of  stimuli,  e.g.,c.o\di  baths,  and  washing  with  cold  water,  the  muscles 
of  the  skin  and  its  blood  vessels  may  be  caused  to  contract,  and  become  so  vigorous  and  excitable, 
that  when  cold  is  suddenly  applied  to  the  body,  or  to  a  part  of  it,  the  excretion  of  heat  is  energeti- 
cally prevented,  so  that  cold  l)aths  and  washing  with  cold  water  are,  to  a  certain  extent,  "  gymnastics 
of  the  cutaneous  muscles,"  which,  under  the  above  circumstances,  protect  the  body  from  cold. 

(2)  Increased  temperature  causes  increased  heart  beats,  while  dimin- 
ished temperature  diminishes  the  number  of  contractions  of  the  heart 
(§  58,  II,  a).  The  relatively  warm  blood  is  pumped  by  the  action  of  the  heart 
from  the  internal  organs  of  the  body  to  the  surface  of  the  skin,  where  it  readily 
gives  off  heat.  The  more  frequently  the  same  volume  of  blood  passes  through 
the  skin — twenty-seven  heart  beats  being  necessary  for  the  complete  circuit  of  the 
blood — the  greater  will  be  the  amount  of  heat  given  off,  and  conversely.  Hence, 
the  frequency  of  the  heart  beat  is  in  direct  relation  to  the  rapidity  of  cooling. 
In  very  hot  air  (over  100°  C.)  the  pulse  rises  to  over  160  per  minute.  The  same 
is  true  in  fever  (§  70,  3  c).  Liebermeister  gives  the  following  numbers  in  an 
adult  :— 

Pulse  beats,  per  min.,  .    .    .    78.6         91.2         99.8         108.5         "'^         '37-5 
Temperature  in  C°.,    ...     37°  38°  39°  40°  41°  42° 

(3)  Increased  Temperature  Increases  the  Number  of  Respirations. 

— Under  ordinary  circumstances,  a  much  larger  volume  of  air  passes  through  the 
lungs  when  it  is  warmed  almost  to  the  temperature  of  the  body.  Further,  a 
certain  amount  of  watery  vapor  is  given  off  with  each  expiration,  which  must  be 
evaporated,  thus  abstracting  heat.  Energetic  respiration  aids  the  circulation,  so 
that  respiration  acts  indirectly  in  the  same  way  as  (2).  According  to  other 
observers,  the  increased  consumption  of  O  favors  the  combustion  in  the  body, 
whereby  the  increased  respiration  must  act  in  producing  an  amount  of  heat  greater 
than  normal  (§  127,  8).  This  excess  is  more  than  compensated  for  by  the  cooling 
factors  above  mentioned.  Forced  respiration  produces  cooling,  even  when  the 
air  breathed  is  heated  to  54°  C,  and  saturated  with  watery  vapor. 

(4)  Covering  of  the  Body. — Aniinals  become  clothed  in  winter  with  a  winter 
fur  or  covering,  while  in  summer  their  covering  is  lighter,  so  that  the  excretion  of 
heat  in  surroundings  of  different  temperatures  is  thereby  rendered  more  constant. 

Many  animals  which  live  in  very  cold  air  or  water  (whale)  are  protected  from 


HEAT   BALANCE.  379 

too  rapid  excretion  of  heat  by  a  thick  layer  of  fat  under  the  skin.     Man  provides 
for  a  similar  result  by  adopting  summer  and  winter  clothing, 

(5)  The  position  of  the  body  is  also  important;  pulling  the  parts  of  the  body 
together,  approximation  of  the  head  and  limbs,  keep  in  the  heat ;  spreading  out 
the  limbs,  erection  of  the  hairs,  pluming  the  feathers,  allow  more  heat  to  be 
evolved.  Tf  a  rabbit  be  kept  exposed  to  the  air  with  its  legs  extended  for  three 
hours,  the  rectal  temperature  will  fall  from  39°  C.  to  37°  C.  Man  may  influence 
his  temperature  by  remaining  in  a  warm  or  a  cold  room — by  taking  hot  or  cold 
drinks — hot  or  cold  baths — remaining  in  air  at  rest  or  air  in  motion,  e.g.,  by  using 
a  fan. 

CLOTHING. — Warm  Clothing  is  the  Equivalent  of  Food. — As  clothes  are  intended  to 
keep  in  the  heat  of  the  body,  and  heat  is  produced  by  the  combustion  and  oxidation  of  the  food,  we 
may  say  the  body  takes  in  heat  directly  in  the  food,  while  clothing  prevents  it  from  giving  off  too 
much  heat.     Summer  clothes  weigh  3  to  4  kilos.,  and  winter  ones  6  to  7  kilos. 

In  connection  with  clothes,  the  following  considerations  are  of  importance : — 

(1)  Their  capacity  for  condtiction. — Those  substances  which  conduct  heat  badly  keep  us  warmest. 
Hare  skin,  down,  beaver  skin,  raw  silk,  taffeta,  sheeps'  wool,  cotton  wool,  flax,  spun  silk,  are  given 
in  order,  from  the  worst  to  the  best  conductors.  (2)  The  capacity  for  radiatio7t. — Coarse  materials 
radiate  more  heat  than  smooth,  but  color  has  no  effect.  (3)  Relation  to  the  stints  rays. — Dark 
materials  absorb  more  heat  than  light- colored  ones.  (4)  Their  hygroscopic  properties  are  important, 
whether  they  can  absorb  much  moisture  from  the  skin  and  gradually  give  it  off  by  evaporation,  or 
the  reverse.  The  same  weight  of  wool  takes  up  twice  as  much  as  linen ;  hence  the  latter  gives  it 
off  in  evaporation  more  rapidly.  Flannel  next  the  skin  is  not  so  easily  moistened,  nor  does  it  so 
rapidly  become  cold  by  evaporation;  hence  it  protects  against  the  action  of  cold.  (5)  The  perme- 
ability for  air  is  of  importance,  but  does  not  stand  in  relation  with  the  heat-conducting  capacity, 
The  following  substances  are  arranged  in  order  from  the  most  to  the  least  permeable — flannel,  buck- 
skin, linen,  silk,  leather,  wax  cloth. 

215.  HEAT  BALANCE. — As  the  temperature  of  the  body  is  maintained 
within  narrow  limits,  the  amount  of  heat  taken  in  must  balance  the  heat  given  off, 
/.  e.,  exactly  the  same  amount  of  potential  energy  must  be  transformed  in  a  given 
time  into  heat,  as  heat  is  given  off  from  the  body.  An  adult  produces  as  much 
heat  in  half  an  hour  as  will  raise  the  temperature  of  his  body  1°  C.  If  no  heat 
were  given  off,  the  body  would  become  very  hot  in  a  short  time  ;  it  would  reach 
the  boiling  point  in  thirty-six  hours,  supposing  the  production  of  heat  continued 
uninterruptedly.  The  following  are  the  most  important  calculations  on  the  sub- 
ject : — 

A.  Helmholtz  was  the  first  to  estimate  numerically  the  amount  of  heat  produced  by  a  man :  — 
(i)   Heat  Income. — (tf)  A  healthy  adult,  weighing  82  kilos.,  expires  in  twenty- 
four  hours  878.4  grms.  COj  {^Scharling).     The  combustion  of  the  C 

therein  into  COj  produces 1,730,760  cal. 

if)  But  he  takes  in  more  O  than  reappears  in  the  COj;  the  excess  is  used  in 
oxidation  processes,  e.g.,  for  the  formation  of  HjO,  by  union  with  H, 
so  that  13,615  grms,  H  will  be  oxidized  by  the  excess  of  O,  which  gives  318,000    " 

2,049,360    " 
[c]  About  25  per  cent,  of  the  heat  must  be  referred  to  sources  other  than  com- 
bustion (Z'm/ow^),  so  that  the  total     =2,732,000    " 

2,732,000  calories  are  actually  sufficient  to  raise  the  temperature  of  an 
adult,  weighing  80  to  90  kilos.,  from  10°  to  38°  or  39°  C,  /.  e.,  to  a 
normal  temperature. 

(2)  Heat  Expenditure. — (a)  Heating  the  food  and  drink,  which 

have  a  mean  temperature  of  12°  C 70)I57  cal.  =    2.6  per  cent. 

[p)  Heating  the  air  respired  ^^  16,400  grms.  with  an  initial 

temperature  of  20°  C 70,032    "    =     2.6        " 

(  When-the  temperature  of  the  air  is  0°,  140,064  cal.  =  5.2 
per  cent.) 

(c)  Evaporation  of  656  grms.  water  by  the  lungs, 397,536    "    =  14.7        " 

(d)  The  remainder  given  off  by  radiation  and  evaporation  of 

water  by  the  skin, (7 j,^  per  cent,  to)  =81.1         " 


380  VARIATIONS    IN    HEAT    PRODUCTION. 

B.  Dulong. — (I)  Heat  Income. — Dulong  and  others  sought  to  estimate  the  amount  of  heat 
from  the  C  and  II  contained  in  tlie  food.  As  we  know  that  the  combustion  of  i  grm.  C  =^  S040 
heat  units,  and  I  grm.  II  ;=  34,460  heat  units,  it  would  be  easy  to  determine  the  amount  of  heat 
were  the  C  simply  converted  into  CO.,  and  the  H  into  II.^O.  l>ut  Dulong  omitted  the  II  in  the 
carbohydrates  {e.^'.,  grape  sugar  =  CgH^.O^")  as  producing  heat,  because  the  II  is  already  combined 
with  O,  or  at  least  is  the  proportion  in  which  it  exists  in  water.  This  assumption  is  hypothetical, 
for  the  atoms  of  C  in  a  carbohydrate  may  be  so  firmly  united  to  the  other  atoms,  that  before  oxidation 
can  take  place  their  relations  must  be  altered,  so  that  potential  energy  is  used  up,  /.  c\,  heat  must  be 
rendered  latent;  so  that  these  considerations  rendered  the  following  example  of  Dulong's  method 
given  by  Vierordt  very  problematical  : — 

An  adult  eats  in  twenty-four  hours,  120  grms.  proteids,  90  grms.  fat,  and  340  grms.  starch  (carbo- 
hydrates).    These  contain : — 

Proteids, 120  grms,  contain     64.18  C.  and    8.60  H. 

Fat, 90     "  "  70.20  "     10.26 

Starch 330     "  "         146.S2  .    . 


2S1.20 
The  urine  and  flvces  contain  still  unconsumed,  ....      29.8 


Remainder  to  be  burned, 251.4         "        12.56 

As  I  grm.  C.  =  S040  heat  units  and  I  grm.  H  =  34,460  heat  units,  we  have  the  following  calcu- 
lation : — 

251.4    X    8,040  =  2,031,312  (from  combustion  of  C). 
12.56X34,460=     432,818  ("  "  H), 

2,464,130  heat  units. 
(2)  Heat  Expenditure  : — 

Per  cent,  of 
Heat  units,     the  e.\creta. 

1.  1900  grms.  are  excreted  daily  by  the  urine  and  faeces,  and  they 

are  25°  warmer  than  the  food 47,500  1.9 

2.  13.000  grms,  air  are  heated  (from  12°  to  37°  C.)  (heat  capacity 

of  the  air  =  0.26), 184,500  3.38 

3.  330  grms.  water  are  evaporated  by  the  respiration  (i  grm.  =  582 

heat  units), 192,060  7.68 

4.  660  grms,  water  are  evaporated  from  the  skin, 384,120  15-37 


Total, 708,180 

Remainder  radiated  and  conducted  from  the  skin,     .    .    .     1,791,820  7167 


Total  amount  of  heat  units  given  off, 2,500,000         too. 00 

C.  Heat  Income. — Frankland  burned  the  food  directly  in  a  calorimeter,  and  found  that  i  grm. 
of  the  following  substances  yielded : — 

Albumin,  i  grm. 4998  heat  units. 

Grape  sugar,  i  grm., 3217         " 

Ox  fat,  I   grm., 9069         " 

The  albumin,  however,  is  only  oxidized  to  the  stage  of  urea,  hence  the  heat  units  of  urea  must 
be  deducted  from  499S,  which  gives  4263  heat  units  obtainable  from  I  grm.  albumin.  When  we 
know  the  number  of  grammes  consumed,  a  simple  multiplication  gives  the  number  of  heat  units. 

The  heat  units  will  vary,  of  course,  with  the  nature  of  the  food.     J.  Ranke  gives  the  following  : — 

With  animal  diet, 2,779,524  heat  units. 

"     food  free  from  N, 2,059,506         " 

"     mixed  diet, 2,200,000         " 

"     during  hunger, 2,012,816         " 

216.  VARIATIONS  IN  HEAT  PRODUCTION.— (i)  Influence  of  Bodily  Surface.— 

Rubner  found  that  the  production  of  heat  depended  more  upon  the  size  of  the  body  and  its  superfi- 
cial area  than  upon  the  body  weight.  Small  or  young  animals  have  a  relatively  larger  surface  than 
large  or  older  ones,  and  as  the  removal  of  the  heat  takes  place  chiefly  from  the  external  surface, 
animals  with  a  larger  surface  must  produce  more  heat.  Small  animals  used  relatively  more  O. 
Rubner's  investigations  on  dogs  of  different  size  gave  a  heat  production  of  1,143,000  calories  for 
every  square  metre  of  cutaneous  surface.  On  comparing  the  body  weight  with  the  cutaneous 
surface  in  different  animals,  he  found  that  for  every  i  kilo,  of  body  weight  there  was  in  the  rat 
1650,  rabbit  946,  man  2S7  square  centimetres  of  surface. 


RELATION  OF  HEAT  PRODUCTION  TO  WORK.  381 

(2)  Age  and  Sex. — The  heat  production  is  less  in  infancy  and  in  old  age,  and  it  is  less  in  pro- 
portion in  tlie  female  than  in  the  male. 

(3)  Daily  Variation. — The  heat  production  shows  variations  in  twenty-four  hours  corresponding 
■with  the  temperature  of  the  body  (|   213,  4). 

(4)  The  heat  production  is  greater  in  the  waking  condition,  during  physical  and  mental  exertion, 
and  during  digestion,  than  in  the  opposite  conditions. 

217.  RELATION    OF  HEAT  PRODUCTION    TO    WORK.— The 

potential  energy  supplied  to  the  body  may  be  transformed  into  heat  and  kinetic 
energy  (see  Introduction').  In  the  resting  condition,  almost  all  the  potential 
energy  is  changed  to  heat ;  the  workman,  however,  transforms  potential  energy 
into  work — mechanical  work — in  addition  to  heat.  These  two  may  be  compared 
by  using  an  equivalent  measurement,  thus,  i  heat  unit  (energy  required  to  raise  i 
gramme  of  water  1°  C.)  =  425.5  gramme-metres. 

Relation  of  Heat  to  Work. — The  following  example  may  serve  to  illustrate  the  relation 
between  heat  production  and  the  production  of  work  :  Suppose  a  small  steam  engine  to  be  placed 
within  a  capacious  calorimeter,  and  a  certain  quantity  of  coal  to  be  burned,  then  as  long  as  the 
engine  does  not  perform  any  mechanical  work,  heat  alone  is  produced  by  the  burning  of  the  coal. 
Let  this  amount  of  heat  be  estimated,  and  a  second  experiment  made  by  burning  the  same  amount 
of  coal,  but  allow  the  engine  to  do  a  certain  amount  of  work — say,  raise  a  weight — by  a  suitable 
arrangement.  This  work  must,  of  course,  be  accomplished  by  the  potential  energy  of  the  heating 
material.  At  the  end  of  this  experiment,  the  temperature  of  the  water  will  be  much  less  than  in 
the  first  experiment,  i.  e.,  fewer  heat  units  have  been  transferred  to  the  calorimeter  when  the  engine 
was  heated  than  when  it  did  no  work.  Comparative  experiments  of  this  nature  have  shown  that  in 
the  second  experiment,  the  useful  work  is  very  nearly  proportional  to  the  decrease  of  the  heat  [Hu-n). 

Compare  this  with  what  happens  within  the  body :  A  man  in  a  passive 
condition  forms  from  the  potential  energy  of  the  food  between  2^  to  2^ 
million  calories.  The  work  done  by  a  workman  is  reckoned  at  300,000  kilo- 
gramme-metres (§  300). 

If  the  organism  were  precisely  similar  to  a  machine,  a  smaller  amount  of  heat, 
corresponding  to  the  work  done,  would  be  formed  in  the  body.  As  a  matter  of 
fact,  the  organism  produces  less  heat  from  the  same  amount  of  potential  energy 
when  mechanical  work  is  done.  There  is  one  point  of  difference  between  a 
workman  and  a  working  machine.  The  workman  consumes  much  more  potential 
energy  in  the  same  time  than  a  passive  person ;  much  more  is  transformed  in  his 
body ;  and  hence  the  increased  consumption  is  not  only  covered,  but  even  over- 
compensated.  Hence,  the  workman  is  warmer  than  the  passive  person,  owing  to 
the  increased  muscular  activity  (§  210,  I,  ^).  Take  an  example  :  Hirn  remained 
passive,  and  absorbed  30  grms.  O  per  hour  in  a  calorimeter,  and  produced  155 
calories.  When  in  the  calorimeter  he  did  work  equal  to  27,450  kilogramme- 
metres,  which  was  transferred  beyond  it;  he  absorbed  132  grms.  O,  and  produced 
only  251  calories. 

In  estimating  the  work  done,  we  must  include  only  the  heat  equivalent  of  the  work  transferred 
beyond  the  body ;  lifting  weights,  pushing  anything,  throwing  a  weight,  and  lifting  the  body  are 
examples.  In  ordinary  walking  we  must  take  into  account  that  we  overcome  the  resistance  of  the 
air  and  the  activity  of  the  muscles. 

The  organism  is  superior  to  a  machine  in  as  far  as  it  can,  from  the  same  amount 
of  potential  energy,  produce  rnore  work  in  proportion  to  heat.  While  the  very 
best  steam  engine  gives  \  of  the  potential  energy  in  the  form  of  work,  and  f  as 
heat,  the  body  produces  ^  as  work  and  4  as  heat.  Chemical  energy  can  never  do 
work  alone,  in  a  living  or  dead  motor,  without  heat  being  formed  at  the  same 
time. 

218.  ACCOMMODATION  FOR  VARYING  TEMPERATURES. 

- — All  substances  which  possess  high  conductivity  for  heat,  when  brought  into 
contact  with  the  skin,  appear  to  be  very  much  colder  or  hotter  than  bad  conductors 
of  heat.  The  reason  of  this  is  that  these  bodies  abstract  far  more  heat,  or  conduct 
more  heat  than  other  bodies.     Thus  the  water  of  a  cool  bath,  being  a  better 


382  STORAGE    OF    HEAT. 

conductor  of  heat,  is  always  thought  to  be  colder  tlian  air  at  the  same  temperature. 
In  our  climate  it  appears  to  us  that — 

Air,  at  i8°  C.  is  moderately  warm;  I  Water,  at  i8°  C.  is  cold ; 

"     at  25°-2S°  C,  hot ;  I  "        from  i8°- 29°  C,  cool ; 

''     above  28°,  very  hot.  |  "  "     29°-30°  C,  warm ; 

"  "     37-5°  and  above,  hot. 

Warm  Media. — As  long  as  the  temperature  of  the  body  is  higher  than  that  of 
the  surrounding  medium,  heat  is  given  off,  and  that  the  more  rapidly  the  better 
the  conducting  power  of  the  surrounding  medium.  As  soon  as  the  temperature  of 
the  surrounding  medium  rises  higher  than  the  temperature  of  the  body,  the  latter 
absorbs  heat,  and  it  does  so  the  more  rapidly  the  better  the  conducting  power  of 
the  medium.  Hence,  hot  water  appears  to  be  warmer  than  air  at  the  same  tempera- 
ture. A  person  may  remain  eight  minutes  in  a  bath  at  45.5°  C.  (dangerous  to 
life  !  )  ;  the  hands  may  be  plunged  into  water  at  50.5°  C,  but  not  at  51.65°  C, 
while  at  60°  violent  pain  is  produced. 

A  person  may  remain  for  eight  minutes  in  hot  air  at  127°  C,  and  a  tempera- 
ture of  132°  C.  has  been  borne  for  ten  minutes,  and  yet  the  body  temperature 
rise  only  to  38.6°  or  38.9°.  This  depends  upon  the  air  being  a  bad  conductor, 
and  thus  it  gives  less  heat  to  the  body  than  water  would  do.  Further,  and  what 
is  more  important,  the  skin  becomes  covered  with  sweat,  which  evaporates  and 
abstracts  heat,  while  the  lungs  also  give  off  more  watery  vapor.  The  enormously 
increased  heart-beats — over  160 — and  the  dilated  blood  vessels,  enable  the  skin  to 
obtain  an  ample  supply  of  blood  for  the  formation  and  evaporation  of  sweat.  In 
proportion  as  the  secretion  diminishes,  the  body  becomes  unable  to  endure  a  hot 
atmosphere  ;  hence  it  is  that  in  air  containing  much  watery  vapor  a  person  cannot 
endure  nearly  so  high  a  temperature  as  in  dry  air,  so  that  heat  must  accumulate  in 
the  body.  In  a  Turkish  vapor  bath  of  53°  to  60°  C,  the  rectal  temperature  rises 
to  40.7°  or  41.6°  C.  A  person  may  work  continuously  in  air  at  31°  C.  which  is 
almost  saturated  with  moisture. 

If  a  person  be  placed  in  water  at  the  temperature  of  the  body,  the  normal 
temperature  rises  1°  C.  in  one  hour,  and  in  i^  hour  about  2°  C.  A  gradual 
increase  of  the  temperature  from  38.6°  to  40.2°  C.  causes  the  axillary  temperature 
to  rise  to  39.0'^  within  fifteen  minutes. 

219.  STORAGE  OF  HEAT. — As  the  uniform  temperature  of  the  body, 
under  normal  circumstances,  is  due  to  the  reciprocal  relation  between  the  amount 
of  heat  produced  and  the  amount  given  off,  it  is  clear  that  heat  must  be  stored 
up  in  the  body  when  the  evolution  of  heat  is  diminished.  The  skin  is  the 
chief  organ  regulating  the  evolution  of  heat ;  when  it  and  its  blood  vessels 
contract,  the  heat  evolved  is  diminished,  when  they  dilate  it  is  increased.  Heat 
may  be  stored  up  when — 

{a)  The  skin  is  extensively  stimulated,  whereby  the  cutaneous  vessels  are  temporarily  contracted. 
(/J)  Any  other  circumstances  prevent  heat  from  being  given  off  by  the  skin,  (c)  When  the  vaso- 
viotor  centre  is  excited,  causing  all  the  blood  vessels  of  the  ])ody— those  of  the  skin  included — to 
contract.  This  seems  to  be  the  cause  of  the  rise  of  temperature  after  transfusion  of  blood,  and  the 
rise  of  temperature  after  the  sudden  rewova/  of  water  from  the  body  seems  to  admit  of  a  similar 
explanation,  as  the  inspissated  blood  occupies  less  space,  and  the  contracted  vessels  of  the  skin  admit 
less  blood.  (</)  When  the  circulation  in  the  cutaneous  vessels  of  a  large  area  is  mechanically 
slowed,  or  when  the  smaller  vessels  are  plugged  by  the  injection  of  some  sticky  substance,  or  by  the 
transfusion  of  foreign  blood,  the  temperature  rises  (|  102). 

It  is  also  obvious  that  when  a  normal  amount  of  heat  is  given  off,  an  increased 
production  of  heat  must  raise  the  temperature.  The  rise  of  the  temperature  after 
muscular  or  mental  exertion,  and  during  digestion,  seems  to  be  caused  in  this  way. 
The  rise  which  occurs  several  hours  after  a  cold  bath  is  probably  due  to  the  reflex 
excitement  of  the  skin  causing  an  increased  production  {/iirgensen). 

When   the  temperature  of  the  body,  as  a  whole   is  raised  6°  C,  death   takes 


FEVER.  383 

place,  as  in  sunstroke.  It  seems  as  if  there  was  a  molecular  decomposition  of  the 
tissues  at  this  temperature ;  while,  if  a  slightly  lower  temperature  be  kept  up 
continuously,  fatty  degeneration  of  many  tissues  occurs  {Litten).  If  animals, 
which  have  been  exposed  artificially  to  a  temperature  of  over  42°  to  44°  C,  be 
transferred  to  a  cooler  atmosphere,  their  temperature  becomes  sub-normal  (36°  C), 
and  may  remain  so  for  several  days. 

220.  FEVER. — Fever  consists  in  a  "disorder  of  the  body  heaf''  and  at  the  same  time  there  is 
greatly  increased  tissue  metabolis7n  (especially  in  the  muscles).  Of  course  the  mechanism  regula- 
ting the  balance  of  formation  and  expenditure  of  heat  is  disturbed.  During  fever  the  body  is 
greatly  incapacitated  for  performing  mechanical  work.  It  is  evident,  therefore,  that  the  large  amount 
of  potential  energy  transformed  is  almost  all  converted  into  heat,  so  that  the  non-transformation  of 
the  energy  into  mechanical  work  is  another  important  factor.  We  may  take  intermittent  fever  or 
ague  as  a  type  of  fever,  in  which  violent  attacks  of  fever  of  several  hours'  duration  alternate  with 
periods  free  from  fever.    This  enables  us  to  analyze  the  symptoms.    The  symptoms  of  fever  are: — 

(i)  The  increased  temperature  of  the  body  (38°  to  39°  C,  slight;  from  39°  to  41°  C.  and 
upward,  severe).  The  high  temperature  occurs  not  only  in  cases  where  the  skin  is  red,  and  has  a 
hot  burning  feeling  (calor  mordax),  but  even  during  the  rigor  or  the  shivering  stage,  the  tempera- 
ture is  raised.  The  congested  red  skin  is  a  good  conductor  of  heat,  while  the  pale,  bloodless  skin 
conducts  badly;  hence  the  former  feels  hot  to  the  touch  (|  212). 

[The  following  table  in  °  C.  and  °  F.  indicates  generally  the  degree  of  fever : — 
F Collapse.  I       39°     C.  =  102.2°  F.   ) 


35°  C 

•=  95° 

36 

=  96.8 

36.S 

=  97-7 

37 

=  98.6 

37-5 

=  99-5 

38 

^=  100.4 

38.S 

=  101.3 

Low.  39.5         =  103. 1  / 


Sub-normal. 
Normal. 


Sub-febrile. 


Moderate  fever. 
High  fever. 


40  =  104 
40.5         =  104.9 

41  =  105.8  Hyperpyretic. 


Fi7tlayson.'\ 


(2)  The  increased  production  of  heat  is  proved  by  calorimetic  observations.  This  is,  in 
small  part,  due  to  the  increased  activity  of  the  circulation  being  changed  into  heat  (§  206,  2,  a), 
but  for  the  most  part  it  is  due  to  increased  combustion  within  tlie  body. 

(3)  The  increased  metabolism  gives  rise  to  the  "consuming"  or  "wasting"  character  of 
fever,  which  was  known  to  Hippocrates  and  Galen.  In  1852  v.  Barensprung  asserted  that  "all  the 
so-called  febrile  symptoms  show  that  the  metabolism  is  increased."  The  increase  of  the  metabol- 
ism is  shown  in  the  increased  excfetion  of  CO^  ;=  70  to  80  per  cent.,  while  more  O  is  consumed, 
although  the  respiratory  quotient  remains  the  same.  According  to  D.  Finkler,  the  COj  excreted 
shows  greater  variations  than  the  O  consumed.  The  excretion  of  tirea  is  increased  ^  to  |-.  In  dogs 
suffering  from  septic  fever,  Naunyn  observed  that  the  urea  began  to  increase  before  the  temperature 
rose,  '■'■  prefebrile  rise."  Part  of  the  urea,  however,  is  sometimes  retained  during  the  fever,  and 
appears  after  the  fever  is  over,  '■'■  epicritical  excretion  of  nrea^  The  uric  acid  is  also  increased ; 
the  nrine  pigmettt  (|  19),  derived  from  the  hfemoglobin,  may  be  increased  twenty  times,  while  the 
excretion  of  potash  may  be  sevenfold.  It  is  important  to  observe  that  the  oxidation  or  combustion 
processes  within  the  body  of  the  fever  patient  are  greatly  increased  when  he  is  placed  in  a  wartner 
atmosphere.  The  oxidation  processes  in  fever,  however,  are  also  increased  under  the  influence  of 
cooler  surroundings  (|  214, 1,  2),  but  the  increase  of  the  oxidation  in  a  warm  medium  is  very  much 
greater  than  in  the  cold  (Z?.  Finkler).  The  amount  of  COj  in  the  blood  is  diminished,  but  not  at 
once  after  the  onset  even  of  a  very  severe  fever  [Geppert). 

(4)  The  diminished  excretion  of  heat  varies  in  different  stages  of  a  fever.  We  distinguish 
several  stages  in  a  fever — (^a)  The  cold  stage,  when  the  loss  of  heat  is  greatly  diminished, 
owing  to  the  pale,  bloodless  skin,  but  at  the  same  time  the  heat  production  is  increased  li  to  2J- 
times.  The  sudden  and  considerable  rise  of  the  temperature  during  this  stage  shows  that  the  dimin- 
ished excretion  of  heat  is  not  the  only  cause  of  the  rise  of  the  temperature.  (^)  During  the  hot 
stage  the  heat  given  off  from  the  congested  red  skin  is  greatly  increased,  but  at  the  same  time 
more  heat  is  produced.  Liebermeister  assumes  that  a  rise  of  1,2,  3,  4°  C.  corresponds  to  an 
increased  production  of  heat  of  6,  12,  18,  24  per  cent.  (,:)  In  the  sweating  stage  the  excretion 
of  heat  through  the  red  moist  skin  and  evaporation  are  greatest,  more  than  two  or  three  times  the 
normal.  The  heat  production  is  either  increased,  normal,  or  sub-normal,  so  that  under  these  condi- 
tions the  temperature  may  also  be  sub-normal  (36°  C. ). 

(5)  The  heat-regulating  mechanism  is  injured. — A  warm  temperature  of  the  surroundings 
raises  the  temperature  of  the  fever  patient  more  than  it  does  that  of  a  non-febrile  person.  The 
depression  of  fhe  heat  production,  which  enables  normal  animals  to  maintain  their  normal  tempera- 
ture in  a  warm  medium  (^  214),  is  much  less  in  fever  (Z).  Finkler). 

The  accessory  phenomena  of  fever  are  very  important :  Increase  in  the  intensity  and  number 
of  the  heart  beats  (§  214,  II,  2)  and  respirations  (in  adults  40,  and  children  60  per  min.),  both  being 


884  ARTIFICIAL    INCREASE    OF   THE    BODILY   TEMPERATURE. 

compensatory  phenomena  of  the  increased  temperature;  further,  diminished  digestive  activity  and 
intestinal  movements  (?.  i86,  D) ;  disturbances  of  the  cerebral  activities;  of  secretion;  of  muscular 
activity;  slower  excretion,  <•..;,'.,  of  potassium  iodide  throuLjh  the  urine.  In  severe  fever,  molecular 
degenerations  of  the  tissues  are  very  common.  For  the  condition  of  the  blood  corpuscles  in  fever, 
see  'i  lo,  the  vascular  tension,  ^  69,  the  saliva,  ?  146,  digestion,  ^  186. 

Quinine,  the  most  important  febrifuge,  causes  a  decrease  of  the  temperature  by  limiting  the  pro- 
duction of  heat  ('i,  213,  6).  Toxic  doses  of  the  metallic  salts  act  in  the  same  way,  while  there  is  at 
the  same  time  diminished  formation  of  CO.,.  [Antipyretics  or  Febrifuges. — All  methods  which 
diminish  abnormal  temperature  belong  to  this  group.  As  the  constant  temperature  of  the  body 
depends  on  (i)  the  amount  of  heat  production,  and  (2)  the  loss  of  heat,  we  may  lower  the  tempera- 
ture either  in  the  one  way  or  the  other.  When  cold  water  is  applied  to  the  body,  it  abstracts  heat, 
/.  e.,  it  affects  the  results  of  fever,  so  that  Liebermeister  calls  such  methods  antithermic.  Hut  those 
remedies  which  diminish  the  actual  heat  production  are  true  antipyretic.  In  practice,  however, 
both  methods  are  usually  employed,  and  spoken  of  collectively  as  antijiyretics.] 

[Among  the  methods  which  are  used  to  abstract  heat  from  the  body,  are  the  application  of 
colder  fluids,  such  as  the  cold  bath,  affusion,  douche,  spray,  ice,  or  cold  mixtures,  etc.  A  person 
suffering  from  high  fever  reriuires  to  be  repeatedly  placed  in  a  cold  bath  to  produce  any  permanent 
reduction  of  the  tenijierature.  Some  remedies  act  by  favoring  the  radiation  of  heat,  by  dilating  the 
cutaneous  vessels  (alcohol),  while  others  excite  the  sweat  glands — i.e.,  are  siidorifics — so  that  the 
water  by  its  evaporation  removes  some  heat.  Among  the  drugs  which  influence  tissue  changes  and 
oxidation,  and  thereby  lessen  heat  production,  are  quinine,  salicylic  acid,  some  of  the  salicylates, 
digitali-:,  and  veratrin.  Bloodletting  was  formerly  used  to  diminish  abnormal  temperature.  Among 
the  newer  antipyretic  remedies  are  hydiochlorate  of  kairin  and  antipyiin,  both  of  which  belong  to 
the  aromatic  group  (derivatives  of  benzol),  which  includes  also  many  of  our  best  antiseptics.] 

221.  ARTIFICIAL  INCREASE  OF  THE  BODILY  TEMPER- 
ATURE.— If  mammals  are  kept  constanily  in  air  at  40°  C,  the  excretion  of 
heat  from  the  body  ceases,  so  that  the  heat  produced  is  stored  up.  At  first  the 
temperature  falls  somewhat  for  a  very  short  time,  but  soon  a  decided  increase 
occurs.  The  respirations  and  pulse  are  increased,  while  the  latter  becomes 
irregular  and  weaker.  The  O  absorbed  and  CO2  given  off  are  diminished 
after  six  to  eight  hours,  and  death  occurs  after  great  fatigue,  feebleness,  spasms, 
secretion  of  saliva,  and  loss  of  consciousness,  when  the  bodily  temperature  has 
been  increased  4°  or  at  most  6°  C.  Death  does  not  take  place  owing  to  rigidity 
of  the  muscles,  for  the  coagulation  of  the  myosin  of  mammals'  muscles  occurs  at 
49°  to  50°  C,  in  birds  at  53°  C,  and  in  frogs  at  40°  C.  If  mammals  are  suddenly 
placed  in  air  at  100°  C,  death  occurs  (in  15  to  20  min.)  very  rapidly,  and  with 
the  same  phenomena,  while  the  bodily  temperature  rises  4°  to  5°  C.  In  rabbits 
the  body  weight  diminishes  i  grm.  per  min.  Birds  bear  a  high  temperature  some- 
what longer;  they  die  when  their  blood  reaches  48°  to  50°  C. 

Even  man  may  remain  for  some  time  in  air  at  100-110-132°  C,  but  in  ten  to 
fifteen  minutes  there  is  danger  to  life.  The  skin  is  burning  to  the  touch,  and 
red;  a  copious  secretion  of  sweat  bursts  forth,  and  the  cutaneous  veins  are  fuller 
and  redder.  The  pulse  and  respirations  are  greatly  accelerated.  Violent  head- 
ache, vertigo,  feebleness,  and  stupefaction,  indicate  great  danger  to  life.  The 
rectal  temperature  is  only  1°  to  2°  C.  higher.  The  high  temperature  of  fever 
may  even  be  dangerous  to  human  life.  If  the  temperature  remains  for  any  length 
of  time  at  42.5°  C,  death  is  almost  certain  to  occur.  Coagulation  of  the  blood 
in  the  arteries  is  said  to  occur  at  42.6°  C.  If  the  artificial  heating  does  not  pro- 
duce death,  fatty  infiltration  and  degeneration  of  the  liver,  heart,  kidneys,  and 
muscles  begin  after  thirty-six  to  forty-eight  hours. 

Coldblooded  animals,  if  placed  in  hot  air  or  warm  water,  soon  have  their  temperature  raised 
6  to  10°  C.  The  highest  temperature  compatible  with  life  in  a  frog  must  be  below  40°  C,  as  the 
frog's  heart  and  muscles  begin  to  coagulate  at  this  temperature.  Death  is  preceded  by  a  stage 
resembling  death,  during  which  life  may  be  saved. 

Most  of  the  juicy  plants  die  in  half  an  hour  in  air  at  52°  C,  or  in  water  at  46°  C.  {Sachs). 
Dried  seeds  of  corn  may  still  germinate  after  long  exposure  to  air  at  120°  C.  Lowly  organized 
plants,  such  as  algK,  may  live  in  water  at  60°  C.  (Noppe-Seyter).  Several  bacteria  withstand  a 
boiling  temperature  ( Tyndall). 

222.  EMPLOYMENT  OF  HEAT. — Action  of  Heat.— The  short,  but  not  intense,  action 
of  heat  on  the  surface  causes,  in  the  first  place,  a  transient  slight  decrease  of  the  bodily  temperature. 


INCREASE    OF   TEMPERATURE    POST-MORTEM.  385 

partly  because  it  retards  reflexly  the  production  of  heat,  and  partly  because,  owing  to  the  dilatation 
of  the  cutaneous  vessels  and  tne  stretching  of  the  skin,  more  heat  is  given  off.  A  warm  bath  above 
the  temperature  of  the  blood  at  once  increases  the  bodily  temperature. 

Therapeutic  Uses. — The  application  of  heat  to  the  entire  body  is  used  where  the  bodily  tem- 
perature has  fallen,  or  is  likely  to  fall,  very  low,  as  in  the  algid  stage  of  cholera,  and  in  infants  born 
prematurely.  The  general  application  of  heat  is  obtained  by  use  of  warm  baths,  packing,  vapor 
baths,  and  the  copious  use  of  hot  drinks.  The  local  application  of  heat  is  obtained  by  the  use  of 
warm  wrappings,  partial  baths,  plunging  the  parts  in  warm  earth  or  sand,  or  p'acing  wounded  parts 
in  chambers  filled  with  heated  air.  After  removal  of  the  heating  agent,  care  must  be  taken  to 
prevent  the  great  escape  of  heat  due  to  the  dilatation  of  the  blood  vessels. 

223.  INCREASE  OF  TEMPERATURE  POST-MORTEM.— Phenomena.—  Heiden- 
hain  lound  that  in  a  dead  dog,  before  the  body  cooled,  there  was  a  constant  temporary  rise  of  the 
temperature,  which  slightly  exceeded  the  normal.  The  same  observation  had  been  occasionally 
made  on  human  bodies  immediately  alter  death,  especially  when  death  was  preceded  by  muscular 
spasms  [also  in  yellow  fever].  Thus,  Wunderlich  measured  the  temperature  fifty-seven  minutes 
after  death  in  #case  of  tetanus,  and  found  it  to  be  45. 375°  C. 

Causes. — (i)  A  iemporaiy  increased  production  of  heat  after  death,  due  chiefly  to  the  change  of 
the  semi-sohd  myosin  of  the  muscles  into  a  solid  form  (rigor  mortis).  As  the  muscle  coagulates, 
heat  is  produced.  All  conditions  which  cause  rapid  and  intense  coagulation  of  the  muscles — e.  g., 
spasms,  favor  a.post->!iorteni  rise  of  temperature  (see  ^  295) ;  a  rapid  coagu'ation  of  the  blood  has  a 
similar  result  (|  28,  5). 

(2)  Imme-liately  after  death  a  series  of  chemical  processes  occur  within  the  body,  whereby  heat  is 
produced.  Valentin  placed  a  dead  rabbit  in  a  chamber,  so  that  no  heat  could  be  given  off  from  the 
body,  and  he  found  that  the  internal  temperature  of  the  animal's  body  was  increased.  The  processes 
whicti  cause  a  rise  of  iem^traiVLxe post-tnortem  are  more  active  during  the  first  than  the  second  hour; 
and  the  higher  the  temperature  at  the  moment  of  death,  the  greater  is  the  amount  of  heat  evolved 
after  death. 

(3)  Another  cause  is  the  diminished  excretion  of  heat  post-mortem.  After  the  circulation  is 
abolished,  within  a  {^vr  minutes  little  heat  is  given  off  from  the  surface  of  the  body,  as  rapid  excretion 
imp'ies  that  the  cutaneous  vessels  must  be  continually  filled  with  warm  blood. 

224.  ACTION  OF  COLD  ON  THE  BODY.— Phenomena.— A  short, 
temporary,  slight  cooling  of  the  skin  (removing  one's  clothes  in  a  cool  room,  a 
cool  bath  for  a  short  time,  or  a  cool  douche)  causes  either  no  change  or  a  slight 
rise  in  the  bodily  temperature.  The  slight  rise,  when  it  occurs,  is  due  to  the 
stimulation  of  the  skin  causing  reflexly  a  more  rapid  molecular  transformation, 
and  therefore  a  greater  production  of  heat,  while  the  amount  of  heat  given  off  is 
diminished  owing  to  contraction  of  the  small  cutaneous  vessels  and  the  skin  itself 
(yLiebermeister).  The  continuous  and  intense  application  of  cold  causes  a  decrease 
of  the  temperature,  chiefly  by  conduction,  notwithstanding  that  at  the  same  time 
there  is  a  greater  production  of  heat.  After  a  cold  bath  the  temperature  may  be 
34°,  32°,  and  even  30°  C. 

As  an  after-effect  of  the  great  abstraction  of  heat,  the  temperature  of  the 
body  after  a  time  remains  lower  than  it  was  before  ("/r/wary  after-effect^''  — 
Liebermeister)  ;  thus  after  an  hour  it  was  0.22°  C.  in  the  rectum.  There  is  a 
*'  secondary  after-effect'''  which  occurs  after  the  first  after-effect  is  over,  when  the 
temperature  rises  {^Jilrgensen).  This  effect  begins  five  to  eight  hours  after  a  cold 
bath,  and  is  equal  to  -j-  0.2°  C.  in  the  rectum.  Hoppe-Seyler  found  that  some 
time  after  the  application  of  heat  there  was  a  corresponding  lowering  of  the 
temperature. 

Taking  Cold. — If  a  rabbit  be  taken  from  a  surrounding  temperatm-e  of  35°  C,  and  suddenly 
cooled,  it  shivers,  and  there  may  be  diarrhoea.  After  two  days  the  temperature  rises  1.5°  C,  and 
albuminuria  occurs.  There  are  microscopic  traces  of  interstitial  inflammation  in  the  kidneys,  liver, 
lungs,  heart,  and  nerve  sheaths,  the  dilated  arteries  of  the  liver  and  lung  contain  thrombi,  and  in  the 
neighborhood  of  the  veins  are  accumulations  of  leucocytes.  In  pregnant  animals  the  foetus  shows  the 
same  conditions.     Perhaps  the  greatly  cooled  blood  acts  as  an  irritant  causing  inflammation. 

Action  of  Frost.— The  continued  application  of  a  high  degree  of  cold  causes  at  first  contraction 
of  the  blood  vessels  of  the  skin  and  its  muscles,  so  that  it  becomes  pale.  If  continued  paralysis  of 
the  cutaneous  vessels  occurs,  the  skin  becomes  red,  owing  to  congestion  of  its  vessels.  As  the  passage 
of  fl-uids  through  the  capillaries  is  rendered  more  difficult  by  the  cold,  the  blood,  stagnates,  and  the 
skin  aisume?  a  livid  appearance,  as  the  0  is  almost  completely  used  up.     Thus  the  peripheral  circu- 

25 


386  ARTIFICIAL    LOWERING    OF   THE    TEMPERATORE. 

lation  is  slowed.  If  ihe  action  of  the  coM  be  still  more  intense,  the  peripheral  circulation  stops 
completely,  especially  in  the  thinnest  and  most  exj  osed  organs — ears,  nose,  toes,  and  tingers.  The 
sensorv  nerves  are  paralyzed,  so  that  tiiere  is  numbness  with  loss  of  sensibility,  and  the  parts  may 
even  be  frozen  through  and  through.  As  the  slowing  of  the  circulation  in  the  superficial  vessels 
gradually  aftccts  other  areas  of  the  circulation,  the  pulmonary  circulation  is  enfeeblerl,  and  diminished 
oxidation  of  the  blood  occurs,  nutwithstanding  the  greater  amount  of  O  in  the  cold  air,  so  that  the 
nerve  cttttres  are  affected.  Hence  arise  great  dislike  to  making  movements  or  any  muscular  effort, 
a  painful  sensation  of  fatigue,  a  peculiar  and  almost  irresistible  desire  to  sleep,  cerebral  inactivity, 
blunting  of  the  sense  organs,  and  lastly,  coma.  The  blood  freezes  at  — 3.9°  C,  while  the  juices  oi 
the  superficial  parts  freeze  sooner.  Too  rapid  movements  of  the  frost  bitten  parts  ought  to  be 
avoided  Rubbing  with  snow,  and  the  very  gradual  application  of  heat,  produce  the  best  results. 
Partial  death  of  a  part  is  not  unfrequenily  produced  by  the  prolonged  action  of  cold. 

225.  ARTIFICIAL  LOWERING  OF  THE  TEMPERATURE.— 

Phenomena. — The  artificial  cooling  ot  warm-blooded  animals,  by  placing 
them  in  cold  air  or  in  a  freezing  mixture,  gives  rise  to  a  series  of  oiiaracteristic 
phenomena.  If  the  animals  (rabbits)  are  cooled  so  that  the  temperature  (rectum) 
falls  to  1 8°,  they  suffer  great  depression,  without,  however,  the  voluntary  or  reflex 
movements  being  abolished.  The  pulse  falls  from  100  or  150  to  20  beats  per 
minute,  and  the  blood  pressure  falls  to  several  millimetres  of  Hg.  The  respira- 
tions are  few  and  shallow.  Suffocation  does  not  cause  spasms,  the  secretion  of 
urine  stops,  and  the  liver  is  congested.  The  animal  may  remain  for  twelve  hours 
in  this  condition,  and  when  the  muscles  and  nerves  show  signs  of  paralysis, 
coagulation  of  the  blood  occurs  after  numerous  blood  corpuscles  have  been 
destroyed.  The  retina  becomes  pale,  and  death  occurs  with  spasms  and  the 
signs  of  asphyxia  If  the  bodily  temperature  be  reduced  to  17°  and  under,  the 
voluntary  movements  cease  before  the  reflex  acts.  An  animal  cooled  to  18°  C, 
and  left  to  itself,  at  the  same  temperature  as  the  surrounding,  does  not  recover  of 
itself,  but  if  artificial  respiration  be  employed,  the  temperature  rises  10°  C.  If 
this  be  combined  with  the  application  of  external  warmth,  the  animals  may  recover 
completely,  even  when  they  have  been  apparently  dead  for  forty  minutes. 
Walther  cooled  adult  animals  to  9°  C,  and  recovered  them  by  artificial  respira- 
tion and  external  warmth ;  while  Horvath  cooled  young  animals  to  5°  C. 
Mammals,  which  are  born  blind,  and  birds  which  come  out  of  the  egg  devoid  of 
feathers,  cool  more  rapidly  than  others.  Morphia,  and  more  so,  alcohol,  ac- 
celerate the  cooling  of  mammals,  at  the  same  time  the  exchange  of  gases  falls 
considerably  ;  hence,  drunken  men  are  more  liable  to  die  when  exposed  to  cold. 
Artificial  Cold-blooded  Condition.— CI.  Bernard  made  the  important 
observation,  that  the  muscles  of  animals  that  had  been  cooled  remained  irritable 
for  a  long  time,  to  direct  stimuli  as  well  as  to  stimuli  applied  to  their  nerves  ;  and 
the  same  is  the  case  when  the  animals  are  asphyxiated  for  want  of  O.  An  '^artifi- 
cial cold-blooded  condition,'"  i.  <?.,  a  condition  in  which  warm-blooded  animals 
have  a  lower  temperature,  and  retain  muscular  and  nervous  excitability,  may  also 
be  caused  in  warm-blooded  animals,  by  dividing  the  cervical  spinal  cord  and 
keeping  up  artificial  respiration  ;  further,  by  moistening  the  peritoneum  with  a 
cool  solution  of  common  salt. 

Hibernation  presents  a  series  of  similar  phenomena.  Valentin  found  that  hibernating  animals 
become  h.nlf  awake  when  their  bodily  temperature  is  28°  C.  ;  at  18°  C.  they  are  in  a  somnolent  con- 
dition, at  6°  they  are  in  a  gentle  sleep,  and  at  1.6°  C.  in  a  deep  sleep.  The  heart  beats  and  the  blood 
pressure  fall,  the  former  to  8  to  10  per  minute.  The  respirator^-,  urinary,  and  intestinal  movements 
cease  completely,  and  the  cardio-pneumatic  movement  alone  sustains  the  slight  exchange  of  gases  in 
the  lun^s  {\  59).  They  cannot  endure  cooling  to  0°  (J.  ;  and  awake  before  the  temperature  falls  so 
lov,'.  Hibernating  animals  may  be  cooled  to  a  greater  degree  than  other  mammals ;  they  give  off  heat 
rapidly,  and  they  become  warm  again  rapidly,  and  even  spontaneously.  New-born  mammals  resemble 
hibernating  animals  more  closely  in  this  respect  than  do  adults. 

V..old-blooded  animals  may  be  cooled  to  0°.  Even  when  the  blood  has  been  frozen  and  ice 
formed  in  the  lymph  of  the  peritoneal  cavity,  frogs  may  recover.  In  this  condition  they  appear  to  be 
dead,  but  when  placed  in  a  wann  medium  they  soon  recover.  A  frog's  muscle  so  cooled  will  contract 
again.     The  germs  and  ova  of  lower   animals,  e,g.,  insects'  eggs,  survive  continued  frost ;  and  if  the 


EMPLOYMENT   OF    COLD.  387 

cold  be  moderate,  it  merely  retards  development.  Bacteria,  e.  g.,  Bacillus  anthracis,  survive  a  tempera- 
ture of —  130°  C. ;  yeast,  even —  100°  C. 

Varnishing  the  skin  causes  a  series  of  similar  phenomena.  The  varnished  skin  gives  off  a  large 
amount  of  heat  by  radiation,  and  sometimes  the  cutaneous  vessels  are  greatly  dilated.  Hence  the 
animals  cool  rapidly  and  die,  although  the  consumption  of  O  is  not  diminished.  If  cooling  be  pre- 
vented by  warming  them  and  keeping  them  in  warm  wool,  the  animals  live  for  a  longer  time.  The 
blood  post-T/iorle7>i  does  not  contain  any  poisonous  substances,  nor  even  are  any  materials  retained  in 
the  blood  which  can  cause  death,  for  if  the  blood  be  injected  into  other  animals,  these  remain  healthy. 

226.  EMPLOYMENT  OF  COLD.— Cold  may  be  applied  to  the  whole  or  part  of  the  surface 
of  the  body  in  the  following  conditions  : — 

[a]  By  placing  the  body  for  a  time  in  a  cold  bath,  to  abstract  as  much  heat  as  possible,  when  the 
bodily  temperature  in  fever  rises  so  high  as  to  be  dangerous  to  life.  This  result  is  best  accomplished 
and  lasts  longest  when  the  bath  is  gi-adually  cooled  from  a  moderate  temperature.  If  the  body  be 
placed  at  once  in  cold  water,  the  cutaneous  vessels  contract,  the  skin  becomes  bloodless,  and  thus 
obstacles  are  placed  in  the  way  of  the  excretion  of  heat.  A  bath  gradually  cooled  in  this  way  is  borne 
longer.  The  addition  of  stimulating  substances,  e.  g.,  salts,  which  cause  dilatation  of  the  cutaneous 
vessels,  facilitates  the  excretion  of  heat ;  even  salt  water  conducts  heat  better.  If  alcohol  be  given 
internally  at  the  same  time,  it  lowers  the  temperature. 

(/')  Cold  may  be  applied  locally  by  means  of  ice  in  a  bag,  which  causes  contraction  of  the  cutane- 
ous vessels  and  contraction  of  the  tissues  (as  in  inflammation),  while  at  the  same  time  heat  is  abstracted 
locally. 

(c)  Heat  may  be  abstracted  locally  by  the  rapid  evaporation  of  volatile  substances  (ether,  carbon 
disulphide),  which  causes  numbness  of  the  sensory  nerves.  The  introduction  of  media  of  low  tem- 
perature into  the  body,  respiring  cool  air,  taking  cold  drinks,  and  the  injection  of  cold  fluids  into  the 
intestine  act  locally,  and  also  produce  a  more  general  action.  In  applying  cold  it  is  important  to 
notice  that  the  initial  contraction  of  the  vessels  and  the  contraction  of  the  tissues  are  followed  by  a 
greater  dilatation  and  turgescence,  /.  e.,  by  a  healthy  reaction. 

227.  HEAT  OF  INFLAMED  PARTS.— "  Calor,"  or  heat,  is  reckoned  one  of  the  funda- 
mental phenomena  of  inflammation,  in  addition  to  rubor  (redness),  tumor  (swelling),  and  dolor 
(paid).  But  the  apparent  increase  in  the  heat  of  the  inflamed  parts  is  not  above  the  temperature  of 
the  blood.  Simon,  in  i860,  asserted  that  the  arterial  blood  flowing  to  an  inflamed  part  was  cooler 
than  the  part  itself,  but  this  has  been  contradicted.  The  outer  parts  of  the  skin  in  an  inflamed  part 
are  warmer  than  usual,  owing  to  the  dilatation  of  the  vessels  (rubor)  and  the  consequent  acceleration 
of  the  blood  stream  in  the  inflamed  part,  and  owing  to  the  swelling  (tumor)  from  the  presence  of 
good  heat-conducting  fluids  ;  but  the  heat  is  not  greater  than  the  heat  of  the  blood.  It  is  not  proved 
that  an  increased  amount  of  heat  is  produced  owing  to  increased  molecular  decompositions  within  an 
inflamed  part. 

228.  HISTORICAL  AND  COMPARATIVE. — According  to  Aristotle,  the  heart  prepares 
the  heat  within  itself,  and  sends  it  along  with  the  blood  to  all  parts  of  the  body.  This  doctrine  pre- 
vailed in  the  time  of  Hippocrates  and  Galen,  and  occurs  even  in  Cartesius  and  Bartholinus  (1667, 
"  flammula  cordis  ").  The  iatro-mechanical  school  i^Boerkave,  van  Swieteii)  ascribed  the  heat  to 
the  friction  of  the  blood  on  the  walls  of  the  vessels.  The  iatro-chemical  school,  on  the  other 
hand,  sought  the  source  of  heat  in  the  fermentations  that  arose  from  the  passage  of  the  absorbed  sub- 
stances into  the  blood  (7)an  Helinout,  Sylvius,  Ettinilller).  Lavoisier  (1777)  vvas  the  first  to  ascribe 
the  heat  to  the  combustion  of  carbon  in  the  lungs.  After  the  construction  of  the  thermometer  by 
Galileo,  Sanctorius  (1626)  made  the  first  thermometric  observations  on  sick  persons,  while  the  first 
calorimetric  observations  were  made  by  Lavoisier  and  Laplace.  Comparative  observations  are 
given  at  \  207,  and  also  under  Hibernation  (|  225). 


Physiology-Metabolic  Phenomena. 


By  the  term  metabolism  we  mean  those  phenomena  whereby  all — even  the 
most  lowly — living  organisms  are  capable  of  incorporating  the  substances  obtained 
from  their  food  into  their  tissues,  and  making  them  an  integral  part  of  their  own 
bodies.  This  part  of  the  process  is  known  as  assimilation.  Further,  the  organ- 
ism in  virtue  of  its  metabolism  forms  a  store  of  potential  energy,  which  it  can 
transform  into  kinetic  energy,  and  which,  in  the  higher  animals  at  least,  appears 
most  obvious  in  the  form  of  muscular  work  and  heat.  The  changes  of  the 
constituents  of  the  tissues,  by  which  these  transformations  of  the  potential 
energy  are  accompanied,  result  in  the  formation  of  excretory  products,  which 
is  another  part  of  the  process  of  metabolism.  The  normal  metabolism  requires 
the  supply  of  food  quantitatively  and  qualitatively  of  the  proper  kind,  the  laying 
up  of  this  food  within  the  body,  a  regular  chemical  transformation  of  the  tisbues, 
and  the  formation  of  the  effete  products  which  have  to  be  given  out  through  the 
excretory  organs.  [Synthetic  or  constructive  metabolism  is  spoken  of  as  anabolic, 
and  destructive  or  analytical  metabolism  as  katabolic,  metabolism.] 

229.  THE  MOST  IMPORTANT  SUBSTANCES  USED  AS 
FOOD. — Water. — When  we  remember  that  58.5  per  cent,  of  the  body  con- 
sists of  water,  that  water  is  being  continually  given  off  by  the  urine  and  faeces,  as 
well  as  through  the  skin  and  lungs,  that  the  processes  of  digestion  and  absorption 
require  water  for  the  solution  of  most  of  the  substances  used  as  food,  and  that 
numerous  substances  excreted  from  the  body  require  water  for  their  solution, 
especially  in  the  urine,  the  great  importance  of  water  and  its  continual  renewal 
within  the  organism  are  at  once  apparent.  As  put  by  Hoppe-Seyler,  all  organ- 
isms live  in  water,  and  even  in  running  water,  a  saying  which  ranks  with  tlie  old 
saying — "  Corpora  non  agunt  nisi  fluida." 

Water — as  far  as  it  is  not  a  con  tituent  of  all  fluid  foods — occurs  in  different  forms  as  drink:  (l) 
Rain  water,  which  most  closely  resembles  distilled  or  chemically  pure  water,  always  contains 
minute  quantities  of  CO.„  NH.,,  n'itious  and  nitric  acids.  (2)  Spring  water  usually  contains  much 
mineral  suljstance.  It  is  formtd  from  the  deposition  of  watery  vapor  or  rain  from  the  air,  which 
].ermeates  the  soil,  containing  much  CO.^;  the  CO.^  is  dissolved  by  the  water,  and  aids  in  dissolving 
the  alkalies,  alkaline  earths,  and  metals,"which  appear  in  solution  as  bicarbonates,  e.  g.,  of  lime  or 
iron  oxide.  The  water  is  removed  from  the  spring  by  proper  mechanical  appliances,  or  it 
bubbles  up  on  the  surface  in  the  form  of  a  "  spring  "  (3)  River  water  usually  contains  much 
less  mineral  matter  than  spring  water.  Spring  water  floating  on  the  surface  rapidly  gives  off  its 
CO.^,  whereby  many  substances — e.  g.,  lime — are  thrown  out  of  solution,  and  deposited  as  insoluble 
precipitates. 

Gases. — Spring  water  contains  little  O,  but  much  CO.^,  the  latter  giving  to  it  its  fresh  taste. 
Hence,  vegetable  organisms  flourish  in  spring  water,  while  animals  requiring,  as  they  do,  much  O, 
are  but  poorly  represented  in  such  water.  Water  flowing  freely  gives  up  CO.^,  and  absorbs  O  from 
the  air,  and  thus  affords  the  necessary  conditions  for  the  existence  of  fishes  and  other  marine 
animals.  River  water  contains  ^^  to  ^L  of  its  volume  of  absorbed  gases,  which  may  be  expelled  by 
l)oiling  or  freezing. 

Drinking  water  is  chiefly  obtained  from  springs.  River  water,  if  used  for  this  purpose,  must 
be  filtered  to  get  rid  of  mechanically  suspended  impurities.  For  household  purposes  a  charcoal 
fiher  may  be  usid,  as  the  charcoal  acts  as  a  disinfectant.  Alum  has  a  remarkable  action.  When 
added  to  give  a  dilu.io.i  containing  o.OOOl  per  cent.,  it  makes  turbid  water  clear. 

388 


WATER.  389 

Investigation  of  Drinking  Water. — Drinking  water,  even  in  a  thick  layer, 
ought  to  be  completely  colorless,  not  turbid,  and  without  odor.  Any  odor  is  best 
recognized  by  heating  it  to  50^^  C,  and  adding  a  little  caustic  soda.  It  ought 
not  to  be  too  hard,  i.  e.,  it  ought  not  to  contain  too  much  lime  (and  magnesia) 
salts. 

By  the  term  "degree  of  hardness"  of  a  water  is  meant  the  unit  amount  of  lime  (and  magnesia) 
in  100,000  parts  of  water;  a  water  of  20  degrees  of  hardness  contains  20  parts  of  lime  (calcium 
oxide)  combined  with  CO2,  sulphuric,  or  hydrochloric  acids  (the  small  amount  of  magnesia  may  he 
neglected).  A  good  drinking  water  ouL^ht  not  to  exceed  20  degrees  of  hardness.  The  hardness  is 
determined  by  titrating  the  water  with  a  standard  soap  solution,  the  result  being  the  formation  of  a 
scum  of  lime  soap  on  the  surface.  The  hardness  of  tmboiled  water  is  called  its  total  hardness, 
while  that  of  boiled  water  is  called  permanent  hardness.  Boiling  drives  off  the  COj,  and  pre- 
cipitates the  calcium  carbonate,  so  that  the  water  at  the  same  time  becomes  softer. 

The  presence  of  sulphuric  acid,  or  sulphates,  is  determined  by  the  water  becoming  tiubid  on 
adding  a  solution  of  barium  chloride  and  hydrochloric  acid. 

Chlorine  occurs  in  small  amount  in  pure  spring  water,  but  when  it  occurs  there  in  large  amount — 
apart  from  its  being  derived  from  saline  springs,  near  the  sea  or  manufactories — we  may  conclude 
that  the  water  is  contaminated  from  water  closets  or  dunghills,  so  that  the  estimation  of  chlorine  is 
of  importance.  For  this  piu-pose  use  a  solution.  A,  of  1 7  grms.  of  crystallized  silver  nitrate  in  i  litre 
of  distilled  water;  i  cubic  centimetre  of  this  solution  precipitates  3.55  milligrammes  of  chlorine  as 
silver  chloride.  Use  also  B,  a  cold  saturated  solution  of  neutral  potassium  chromate.  Take  50 
cubic  centimetres  of  the  water  to  be  investigated,  and  place  it  in  a  beaker,  add  to  it  2  to  3  drops  of 
B,  and  allow  the  fluid  A  to  run  into  it  from  a  burette  until  the  white  precipitate  first  formed  remains 
red,  even  after  the  fluid  has  been  stin-ed.  Multiply  the  number  of  cubic  centimetres  of  A  used  by 
7.1,  and  this  will  give  the  amount  of  chlorine  in  100,000  parts  of  the  water.  Example — 50  c.  cmtr. 
requires  2.9  c.  cmtr.  of  the  silver  solution,  so  that  100,000  parts  of  the  water  contain  2.9  X  7-1  -= 
20.59  parts  chlorine  [Kiibel  Tieniann).  Good  water  ought  not  to  contain  more  than  15  milli- 
grammes  of  chlorine  per  litre. 

The  presence  of  lime  may  be  ascertained  by  acidulating  50  cubic  centimetres  of  the  water  with 
HCl,  adding  ammonia  in  excess,  and  afterward  adding  ammonia  oxalate ;  the  white  precipitate  is 
lime  oxalate.  According  to  the  degree  of  turbidity,  we  judge  whether  the  water  is  "  soft"  (poor  in 
lime),  or  "hard"  (rich  in  lime). 

Magnesia  is  determined  by  taking  the  clear  fluid  of  the  above  operation,  after  removing  the  pre- 
cipitate of  lime,  and  adding  to  it  a  solution  of  sodium  phosphate  and  some  ammonia ;  the  crystalline 
precipitate  which  occurs  is  magnesia. 

The  more  feeble  all  these  reactions  which  indicate  the  presence  of  sulphuric  acid,  chlorine,  lime, 
and  magnesia,  are,  the  better  is  the  water.  In  addition,  good  water  ought  not  to  contain  more  than 
traces  of  nitrates,  nitrites,  or  compounds  of  ammonia,  as  their  presence  indicates  the  decomposhion 
of  nitrogenous  organic  substances. 

For  nitric  acid,  take  100  cubic  centimetres  of  water  acidulated  with  two  or  three  drops  of  con- 
centrated sulphuric  acid,  add  several  pieces  of  zinc  together  with  a  solution  of  potassium  iodide,  and 
starch  solution — a  blue  color  indicates  nitric  acid.  The  following  test  is  very  delicate  :  Add  to  half 
a  drop  of  water  in  a  capsule  two  drops  of  a  watery  solution  of  Brucinum  sulphuricum,  and  aftei-ward 
several  drops  of  concentrated  sulphuric  acid ;  a  rose-red  coloration  indicates  the  presence  of  nitric 
acid. 

The  presence  of  nitrous  acid  is  ascertained  by  the  blue  coloration  which  results  from  the  addition 
of  a  solution  of  potassium  iodide,  and  solution  of  starch,  after  the  water  has  been  acidulated  with 
sulphuric  acid. 

Compounds  of  ammonia  are  detected  by  Nessler's  reagent,  which  gives  a  yellow  or  reddish 
coloration  when  a  trace  of  ammonia  is  present  in  water;  while  a  large  amount  of  these  compounds 
gives  a  brown  precipitate  of  the  iodide  of  mercury  and  ammonia. 

The  contamination  of  water  by  decomposing  animal  substance  is  determined  by  the  amount 
of  N  it  contains.  In  most  cases  it  is  sufficient  to  determine  the  amount  of  nitj-ic  acid  present.  For 
this  purpose  we  require  (A)  a  solution  of  1.871  grms.  potassium  nitrate  in  I  litre  distiliel  water — I 
cubic  centimetre  contains  I  milligramme  nitric  acid;  (B)  a  dilute  solution  of  indigo,  which  is  prepared 
by  rubbing  together  one  part  of  pulverized  indigotin  with  six  parls  H^SO^,  and  allowing  the  deposit, 
to  subside,  when  the  blue  fluid  is  poured  into  forty  times  its  volume  of  distilled  water  and  filtered.- 
This  fluid  is  diluted  with  distilled  water  until  a  layer,  12  to  15  mm.  in  thickness,  begins  to  be  trans- 
parent. 

To  test  the  activity  of  B,  place  l  cubic  centimetre  of  A  in  24  cubic  centimetres  water,  add  some- 
common  salt  and  50  cubic  centimetres  concentrated  sulphuric  acid,  and  allow  B  to  flow  from  a 
burette  into  this  mixture  until  a  faint  green  color  is  obtained.  The  number  of  cubic  centimetres  of 
B  used  correspond  to  i  milligramme  of  nitric  acid. 

Twenty-five  cubic  centimetres  of  the  water  to  be  investigated  are  mixed  with  50  cubic  centimetres 
of  concentrated  H2SO4,  and  titrated  with  B  until  a  green  color  is  obtained.     This  process  must  be: 


390 


MAMMARY    GLANDS. 


Fig.  233. 


repeated,  and  on  the  second  occasion  the  solution  R  must  be  allowed  to  flow  in  at  once,  when  usually 
somewhat  more  indigo  solution  is  required  to  obtain  the  green  solution.  The  number  of  cubic  centi- 
metres of  B  (corresponding  to  the  strength  of  H,  as  determined  alx)ve)  indicates  the  amount  of  nitric 
acid  present  in  25  c.cmtr.  of  the  water  investigated.  As  much  as  10  milligiammcs  nitric  acid  have 
been  found  in  spring  water  [J/tirx,   TroiniiisJorff'). 

Sulphuretted  Hydrogen  is  recognized  by  its  d'^/^;-;  also  by  a  piece  of  blotting  paper  moi.siened 
with  alkaline  .solution  of  lead  becoming  brown  when  it  is  held  over  the  boiling  water.  If  it  occurs 
as  a  contpoutiti  in  the  water,  .sodium  nitro-prussitle  gives  a  reddish-violet  color 

It  is  of  the  greatest  importance  that  drinking  water  should  be  free  from  the  presence  of  organic 
matter  in  a  state  of  decomposition.  Organic  matter  in  a  state  of  dccom])osition,  and  the  organisms 
therewith  associated,  when  introduced  into  the  body,  may  give  rise  to  fatal  maladies,  e.  ^.,  cholera  and 
typhoid  fever.  This  is  the  case  when  the  water  supply  has  been  contaminated  from  water  which  ha.s 
percolated  from  water  closets,  privies  and  dung  jiits.  T/ie  presenre  of  ori;(7ttic  inatler  tuny  he  detecletl 
thus  (\)  A  considerable  amount  of  the  water  is  evaporatal  to  diyness  in  a  porcelain  vessel,  if  the 
residue  be  heated  again  a  Ijrown  or  black  color  indicates  the  presence  of  a  considerable  amount  of 
organic  matter;  and  if  it  contain  N,  there  is  an  odor  of  ammonia.  Clood  water  treated  in  this  way 
gives  only  a  light  brown  .stain.  The  presence  of  micro-organisms  may  be  determined  microscopic- 
ally after  evaporating  a  small  quantity  of  the  water  on  a  glass  slide.  (2)  The  addition  of  potassio- 
golii  chloride  to  the  water  gives  a  black  frothy  precipitate  after  long  .standing.  (3)  A  solution  of 
potassium  permtjit^anate,  added  to  the  water  in  a  covered  jar,  giadually  becomes  decolorized,  and  a 
brownish  precipitate  is  fomied. 

Water  containing  much  organic  matter  should  ue~c<er  be  used  as  drinking  water,  and  this  is  especially 
the  ca.se  when  there  is  an  epidemic  of  typhoid  fever,  cholera  or  dianlnea.  In  all  such  circumstances, 
the  water  (  ught  to  be  boiled  for  a  long  time,  whereiiy  the  organic  genns  are  killed.  The  insipid  taste 
of  the  water  after  boiling  may  be  corrected  by  adding  a  little  sugar  or  lime  juice. 

230.  THE  MAMMARY  GLANDS  AND  MILK.— Milk  Duct.— About  20  gabctoferous 
ducts  open  singly  upon  the  surface  of  the  nipple.     Each  of  these,  just  before  it  opens  on  the  surface, 

is  provided  with  an  oval  dilatation — the  sinus  lacteus.  When 
traced  into  the  gland,  the  galactoferous  ducts  divide  like  the  branches 
of  a  tree,  and  a  large  branch  of  the  duct  passes  to  each  lobe  of  the 
gland,  all  the  lobes  being  held  together  by  loose  connective  tissue. 
Only  during  lactation  do  all  the  fine  terminations  of  the  ducts  com- 
municate with  the  globular  glandular  acini.  Ever)-  gland  acinus 
consists  of  a  membrana  propria,  surrounded  e.\temally  with  a  net- 
work of  branched  connective-tissue  coqiuscles,  and  lined  internally 
with  a  somewhat  flattened  polyhedral  layer  of  nucleated  secretory 
Cv.'lls  (Fig.  233)  The  size  of  the  lumen  of  the  acini  depends  upon 
the  secre'ory  activity  of  the  glands;  when  it  is  large,  it  is  filled  with 
milk  containing  numero's  refr  ctivc  fatty  granules.  The  walls  of 
the  milk  d  icts  consist  of  fibrillar  connective  tissue,  some  fibres  are 
arranged  longitudinally,  l^ut  the  chief  mass  are  disposed  circularly, 
and  are  ]iermeated  externally  with  el.istic  fibres,  while  in  the  finer 
ducts  there  is  a  membrana  propria  continuous  with  that  of  the  gland 
acini.  The  duels  are  lined  by  cylindrical  epithelium. 
During  the  first  few  days  after  delivery,  the  brea.sts  secrete  a  small  amount  of  milk  of  greater 
consistence,  and  of  a  yellow  color — the  colostrum — in  which  large  cells  filled  with  fatty  granules 
occur — the  colostrum  corpuscles  (Fig.  235).  Sometimes  a  nucleus  is  ob.servable  within  them,  and 
rarely  they  exhibit  amithoid  movements  (Fig.  234,  r,  ^Z,  <•).  The  regular  secretion  of  milk  begins 
after  three  to  four  days.  It  was  fonnerly  .supposed  that  the  cells  of  the  acini  underwent  a  fatty  degen- 
eration, and  thus  produced  the  fatty  granules  of  the  milk.  It  is  more  pruliable,  from  recent  observa- 
tions, th.at  the  cells  of  the  acini  manufacture  the  fatty  granules,  and  their  protoplasm  eliminates  them, 
at  the  same  time  fonning  the  clear  fluid  p.art  of  the  milk. 

Changes  during  Secretion. — Pratsch  and  Heidenhain  found  that  the  secre- 
tory cells  in  the  non-secreting  gland  (Fig.  234,  I)  were  flat,  polyhedral  and 
uni-nucleated,  while  the  secreting  cells  (Fig.  234,  11)  often  contained  several 
nuclei,  were  more  albuminous,  higher,  and  cylindrical  in  form.  The  edge  of  the 
cell  directed  toward  the  lumen  of  the  acinus  undergoes  characteristic  changes 
during  secretion.  Fatty  granules  are  formed  in  this  part  of  the  cell,  and  are 
afterward  extruded.  The  decomposed  portion  of  the  cell  is  dissolved  in  the 
milk,  and  the  fatty  granules  become  free  as  milk  globules  (Fig.  234,  II,  a).  If 
nuclei  are  present  in  that  part  of  the  cell  which  is  broken  up,  they  also  pass  into 
the  milk  and  give  rise  to  the  presence  of  nuclein  in  the  secretion. 

Besides  the  milk  globules  and  colostrum  corpuscles,  Rauber  has  found  leucocytes  undergoing  fatty 


v§&'«r^»&v 


Acini  of  the  mammary  giand  of  a 
sheep  during  lactation.  «,  mem- 
brana propria  ;  b,  secretory  epi- 
thelium. 


STRUCTURE    OF    THE    MAMMA. 


391 


degeneration  and  single  pale  cells  (/).  Occasionally  milk  globules  are  found  with  traces  of  the  cell 
substance  adhering  to  their  surface  {/>). 

Formation  of  Milk. — Concerning  the  formation  of  the  individual  constituents  of  milk,  H. 
Thierfelder,  who  digested  fresh  mammary  glands  directly  after  death,  found  that  dming  the  digestion 
of  the  glands,  at  the  temperature  of  the  body,  a  reducing  substance,  probably  lactose,  was  formed 
by  a  process  of  fermentation.  The  mother  substance  (saccharogen)  is  soluble  in  water,  but  not  in 
alcohol  or  ether,  is  not  destroyed  by  boihng,  and  is  not  identical  with  glycogen  The  ferment  which 
forms  the  lactose  is  connected  with  the  gland  cells— it  does  not  pass  into  the  milk,  nor  into  a  watery 
extract  of  the  gland.  During  the  digestion  of  the  mammary  glands  at  the  temperature  of  the  body, 
casein  is  formed,  probably  from  serum  albumin,  by  a  process  of  fermentation.  This  ferment  occurs 
in  the  milk. 

The  nipple  and  its  areola  are  characterized  by  the  presence  of  pigment— more  abundant  during 
pregnancy— in  the  rete  Malpighii  of  the  skin,  and  by  large  papillse  in  the  cutis  vera.  Some  of  the 
papillae  contain  touch  corpuscles.  Numerous  non-striped  muscular  fibres  surround  the  milk  ducts  in 
the  deep  layers  of  the  skin  and  in  the  subcutaneous  tissue,  which  contains  no  fat.  These  muscular 
fibres  can  be  traced,  following  a  longitudinal  course,  to  the  terminati.'U  of  the  ducts  on  the  surface. 
The  small  o-/an^s  of  Alontiroinery,  which  occur  on  the  areola  during  lactation,  are  just  small  milk 
glands,  each  with  a  special  duct  opening  on  the  surface  of  the  elevation. 

Arteries  proceed  from  several  sources  to  supply  the  mamma,  but  their  branches  do  not  accompany 
the  milk  ducts ;  each  gland  acinus  is  surrounded  by  a  network  of  capillaries,  which  communicate 
with  those  of  adjoining  acini  by  small  arteries  and  veins.  The  veins  of  the  areola  are  arranged  in  a 
circle  (circulus  Halleri).  The  nerves  are  derived  from  the  supraclavicular,  and  the  II-IV-VI  inter- 
costals;  they  proceed  to  the  skin  over  the  gland,  to  the  very  sensitive  nipple,  to  the  blood  vessels  and 
non-striped  muscle  of  the  nipple,  and  to  the  gland  acini,  where  their  mode  of  termination  is  still 


Inactive  acinus  of  the  mamma      II.    During  the  secretion  of  milk — a,  i5,  milk  globnles ;  c,  d,  e, 
colostrum  corpuscles  ;  f,  pale  cells  (bitch). 


unknown.  Lymphatics  sm-round  the  alveoli,  and  they  are  often  full.  The  milk  appears  to  \>^ 
prepired  from  the  lymph  contained  in  the  lymphatics  suiTOunding  the  acini. 

The  comparative  anatomy  of  the  mamma. — The  rodents,  insectivora,  and  carnivora  have  lo  to 
12  teats,  while  some  of  them  have  only  4.  The  pachydermata  and  ruminantia  have  2  to  4  abdominal 
teats,  the  whale  has  2  near  the  vulva.  The  apes,  bats,  vegetable-feeding  whales,  elephants,  and 
sloths  have  2,  like  man.  In  the  marsupials  the  tubes  are  arranged  in  groups,  which  open  on  a  patch 
of  skin  devoid  of  hair  without  any  nipple.  The  young  animals  remain  within  the  mother's  pouch, 
and  the  milk  is  expelled  into  their  mouths  by  the  action  of  a  muscle — the  compressor  mammae. 

The  development  of  the  human  mamma  begins  in  both  sexes  during  the  third  month;  at  the 
fourth  and  fifth  months  a  few  simple  tubular  gland  ducts  are  arranged  radially  around  the  position  of 
the  future  nipple,  w  ich  is  devoid  of  hair.  In  the  new-born  child  the  ducts  are  branched  twice  or 
thrice,  and  are  provided  with  dilated  extremities,  the  future  acini.  Up  to  the  twelfth  year,  in  both 
sexes,  the  ducts  continue  to  divide  dendritically,  but  without  any  proper  acini  being  f  -rmed.  In  the 
girl  at  puberty,  the  ducts  branch  rapidly;  but  the  acini  are  formed  07ily  at  the  periphery  of  the 
gland;  durin;  pregnancy,  acini  are  also  formed  in  the  centre  of  the  gland,  while  the  connective 
tissue  at  the  same  time  becomes  somewhat  more  opened  out.  At  the  climacteric  period,  or  meno- 
pause, all  the  acini  and  numerous  fine  milk  ducts  degenerate.  In  the  adult  )uale,the  gland  remains 
in  the  non  developed  infantile  condition.  Accessory  or  supernumerary  glands  upon  the  breast  and 
abdomen  are  not  uncommon  ;  sometimes  the  mamma  occurs  in  the  axilla,  on  the  back,  over  the 
acromion  process,  or  on  the  leg.     A  slight  secretion  of  milk  in  a  newly-born  infant  is  normal. 

During  the  evacuation  of  the  milk  (500-1500  cubic  centimetres  daily"),  there  is  not  only  the 
mechanical  action  of  sucking-,  but  also  the  activity  of  the  gland  itself  (|  152).  This  consists  in  the 
erection  of  the  nipple,  whereby  its  non-striped  muscular  fibres  compress  the  sinuses  on  the  milk  duct<, 
and  empty  them,  so  that  the  milk  may  flow  out  in  streams.     The   gland   acini   are  also   excited  to 


392 


MILK    AND    ITS    PREPARATIONS. 


Fig.  235. 


secretion  reflexly  by  the  stimulation  of  tlie  sensory  nerves  of  the  nipple.  The  vessels  of  the  gland 
are  dilated,  and  there  is  a  copious  transudation  into  the  gland — the  transuded  fluid  being  manufac- 
tured into  milk  under  the  intlutnce  of  the  .secrttoiy  protopla.sm.  'Jlie  amount  of  .secrttion  depends 
upon  the  blood  pressure  (AV'7/ /-/;-).  During  .sucking,  not  only  is  the  milk  in  the  gland  extracted,  but 
new  milk  is  farmed,  owing  to  the  accelerated  .secretion.  Emotional  di  lurbances — anger,  fear,  etc. — 
arrest  the  secretion.  I  affont  found  that  stimulation  of  the  mammar}'  nerve  (ijitch)  caused  erection 
of  the  teat,  dilatation  of  the  vessels,  and  secretion  of  milk.  After  section  of  the  cerebro-spinal  nerves 
going  to  the  mamma,  Eckhard  observed  that  erection  of  the  teat  ceased,  although  the  secretion  of 
milk  in  a  goat  was  not  interrupted.  The  rarely  observed  galactorrhoea  is  perhaps  to  be  regarded 
as  a  parahtic  secretion  analogous  to  the  paralytic  secretion  of  saliva,  lleidenhain  and  Pratsch  found 
that  the  secretion  (bitch)  was  increased  by  injecting  strychnine  or  curara  after  section  of  the  nerves 
of  the  gland.  The  "milk  fever,"  which  accompanies  the  first  secretion  of  milk,  [probably  depends 
on  stimulation  of  the  vasomotor  nerves,  but  this  condition  must  be  studied  in  relation  with  the  otiier 
changes  which  occur  within  the  pehic  cavity  after  birth.  [Some  substances,  such  as  atropin,  aiTest 
the  secretion  of  milk.] 

231.  MILK  AND  ITS  PREPARATIONS.— Milk  represents  a  com- 
plete or  typical  food  in  which  are  present  all  the  constittients  necessary  fur 
maintaining  the  life  and  growth  of  the  body  of  an  infant  (§  236).  [If  an  adult 
were  to  live  on  milk  alone,  to  get  the  23  oz.  of  dry  solids  necessary,  he  would  have 
to  take  9  pints  of  milk  daily,  which  would  give  far  too  much  water,  fat,  and  pro- 
teids.]  To  every  10  parts  of  proteids  there  are  10  parts  tat  and  20  parts  sugar. 
Relatively  more  of  the  fat  than  the  albumin  of  the  milk  is  absorbed  {Ru/>ner)  ; 
while  a  part  of  both  is  excreted  in  the  faeces. 

Characters. — Milk  is  an  opaque,  bluish-white  fluid  with  a  sweetish  taste  and  a 
characteristic  odor,  probably  due  to  the   peculiar  volatile  substances  derived  from 

the  cutaneous  secretions  of  the  glands,  and 
it  has  a  specific  gravity  of  1026  to  1035. 
When  it  stands  for  a  tiine,  numerous  milk 
globules,  butter  globules,  or  cream,  collect 
on  its  surface,  under  which  there  is  a  bluish 
watery  fluid.  Human  milk  is  always  aika- 
line,  cow's  milk  may  be  alkaline,  acid,  or 
amphoteric  ;  while  the  milk  of  carnivora  is 
ahvavs  acid. 

Milk  Globules. — When  milk  is  examined 
microscopically,  it  is  seen  to  contain  numerous 
small,  highly  refractive  oil  globules,  floating 
in  a  clear  fluid — the  milk  plasma  (  Figs.  234, 
a,  b,  235);  while  colostrum  corpuscles  and 
epithelium  from  the  milk  ducts  are  not  so 
numerous.  The  white  color  and  opacity  of 
the  milk  are  due  to  the  presence  of  the  milk 
globules,  which  reflect  the  light ;  the  globules 
consist  of  a  fat,  or  butter,  and  are  said  by 
some  to  be  surrounded  with  a  very  thin  envelope  of  casein  or  haptogen  membrane. 

If  acetic  acid  be  added  to  a  microscopic  preparation  of  milk,  the  fatty  granules  run  together  to 
form  irregular  masses.  If  cow's  milk  be  shaken  with  caustic  potash,  the  casein  envelopes  are  dis- 
solved, and  if  ether  be  added,  the  milk  becomes  clear  and  transparent,  as  the  ether  dissolves  out  all 
the  fatty  particles  in  the  solution.  Ether  cannot  extract  the  fat  from  cow's  milk  until  acetic  acid  or 
caustic  potash  is  aided  to  liberate  the  fats  from  their  envelopes;  but  shaking  with  ether  is  .sufficient 
to  extract  the  fats  from  human  milk.  Some  observers  deny  thit  an  envelope  of  casein  exists,  and 
according  to  them  milk  is  a  simple  emulsion,  kept  emulsionized  owing  to  the  colloid  swollen-up  casein 
in  the  milk  plasma.  The  treatment  of  milk  with  pDtash  and  ether  makes  the  casein  unible  any 
longer  to  preserve  the  emulsion  i^Soxhlet). 

The  fats  of  the  milk  globules  are  the  triglycerides  of  stearic,  palmitic,  oleic 
(very  little),  myristic,  arachinic  (butinic),  capric,  caprylic,  caproic,  and  butyric 
acids,  with  traces  of  acetic  and  formic  acids  and  cholesterin. 


Microscopic  appearance  of  milk,  (M)  upper  half, 
anU  colostrum  ^C)  lower  half. 


FAT   AND    PLASMA    OF    MILK.  393 

Butter. — ^\Vhen  milk  is  beaten  or  stiiTed  for  a  long  time  (i.e.,  churned),  the  fat  of  the  milk 
glo'iules  is  ultimately  olitained  in  the  form  o^  butter,  owing  to  the  rupture  of  the  envelopes  of  casein. 
Butter  is  soluble  in  alcohol  and  ether,  and  it  is  clarified  by  heat  (60°  C),  or  by  washing  in  water  at 
40°  C.  When  allowed  to  stand  exposed  to  the  air,  it  first  becomes  sour,  owing  to  the  formation  of 
lactic  acid,  and  afterward  rancid,  owing  to  the  glycerme  of  the  neutral  fats  being  decomposed  by 
fungi  into  acrolein,  and  formic  acid,  while  the  volatile  fatty  acids  give  it  its  rancid  odor. 

The  milk  plasma,  obtained  by  filtration  through  a  clay  filter  or  membranes, 
is  a  clear,  slightly  opalescent  fluid,  and  contains  casein  (§  249,  III,  3),  some 
serum  albumin  (§  32),  peptone  (0,13  per  cent.),  nuclein,  and  a  trace  of 
diastatic  ferment  (in  human  milk). 

The  presence  of  other  peculiar  chemical  bodies,  e.g.,  lactoprotein,  globulin,  albumose,  galactin, 
etc.,  is  disputed  by  some  chemists. 

When  milk  is  boiled  the  albumin  coagulates,  while  the  surface  also  becomes 
covered  with  a  thin  scum  or  layer  of  casein,  which  has  become  insoluble  [the  rest 
of  the  milk  remaining  fluid]. 

Casein. — When  milk  is  filtered  through  fresh  animal  membranes  or  through  a  clay  filter,  the 
casein  does  not  pass  through.  Precipitation. — It  is  precipitated  by  adding  crystals  of  MgSO^  to 
saturation.  [If  to  milk  twice  its  volume  of  a  saturated  solution  of  NaCl  and  crystals  of  NaCl  be 
added,  and  tiie  whole  shaken  thoroughly,  casein  is  precipitated,  and  carries  down  with  it  fat,  so  that 
the  clear  filtrate  contains  the  lactose,  salts,  and  coagulable  proteids.] 

The  plasma  contains  milk  sugar  (§  252)  ;  a  carbohydrate  resembling  dextrin, 
(?  lactic  acid),  lecithin,  urea,  extractives,  kreatin,  sarkin  (potassic  sulphocyanide 
in  cow's  milk),  sodic  and  potassic  chlorides,  alkaline  phosphates,  calcium  and 
magnesium  sulphates,  alkaline  carbonates,  traces  of  iron,  fluorine,  and  silica,  CO2, 
N,  and  O. 

The  coagulation  of  milk  depends  upon  the  coagulation  of  its  casein.  In  milk,  casein  is  com- 
bined with  calcium  phosphate,  which  keeps  it  in  solution  ;  ac'ds  which  act  on  the  calcium  phosphate 
cause  coagulation  of  the  casein  (acetic  and  tartaric  acids  in  excess  redissolve  it).  All  acids  do  not 
coagulate  human  milk.  It  is  coa.julated  by  two  or  more  drops  of  hydrochloric  acid  (o.l  per  cent.) 
or  acetic  acid  (0.2  per  cent.).  The  spontaneous  coagulation  of  milk  after  it  has  stood  for  a  time, 
especially  in  a  warm  place,  is  due  to  the  production  of  lactic  acid,  which  is  formed  from  the  milk 
sugar  in  the  milk  by  the  action  of  bacillus  acidi  lactici  [which  is  introduced  from  without]  (^  184, 
I).  It  changes  the  neutral  alkaline  phosphate  into  the  acid  phosphate,  takes  the  casein  from  the 
calcium  phosphate,  and  precipitates  the  casein.     The  sugar  is  decomposed  into  lactic  acid  and  CO.^. 

Rennet  (§  250,  9,  d,  \  166,  II)  coagulates  milk  with  an  alkaline  reaction  (sweet  whey).  This 
ferment  decomposes  the  casein  into  the  precipitated  cheese  and  also  into  the  slightly  soluble  whey 
albumin,  so  that  the  coagulation  by  rennet  is  a  process  quite  distinct  from  the  coagulation  of  milk 
by  the  gaitric  and  pancreatic  juices,  [and  also  from  the  precipitation  produced  by  acids.  The 
presence  of  calcium  phosphate  seems  to  be  necessary  for  the  complete  action  of  the  rennet 
(  Ha  mniarstenY\. 

[Experiments. — Warm  a  little  milk  to  40°  C,  and  add  a  few  drops  of  commerciil  rennet,  setting 
aside  the  mixture  in  a  warm  plice;  a  solid  coagulum  is  then  formed,  and  by  and  by  the  whey 
separates  from  it.  If  the  milk  be  previously  diluted  with  water,  no  coagulum  is  formed  ;  and  if  the 
rennet  be  boiled  before,  it,  like  othtr  ferments,  is  destroyed.  A  solution  of  rennet  may  be  prepared 
by  extracting  the  fourth  stomach  of  the  calf  with  glycerine.  [When  the  milk  is  coagulated  we 
obtain  the  curd,  consisting  of  casein  with  some  milk  globules  entangled  in  it ;  tlie  whey  contains 
some  soluble  albumin  and  fat,  and  the  great  proportion  of  the  salts  and  milk  sugar,  together  with 
lactic  acid.] 

[A  milk-coagulating  ferment  is  found  in  certain  plants  (artichokes,  figs,  Carica  papaya),  and 
causes  milk  to  coagulate  in  neutral  or  alkaline  solutions.  It  is  also  found  in  the  small  intestine  of 
the  calf,  while  a  5  per  cent.  NaCl  solution  of  the  seeds  of  Withania  coagtilans  coagulates  milk 
in  an  alkaline  medium.] 

Boiling  (by  killing  all  the  lower  organisms),  sodium  bicarbonate  (xoW)'  ammonia,  salicylic  acid 
(WoT^'  glycerine,  and  ethereal  oil  of  mustard  prevent  the  spontaneous  coasjulation.  Fresh  milk 
makes  tincture  of  guaiacum  blue,  but  boiled  milk  does  not  do  so.  When  milk  is  exposed  to  the  air 
for  a  long  time,  if  gives  off"  CO2  and  absorbs  O  ;  the  fats  are  increased  (?  owing  to  the  development 
of  fungi  in  the  milk),  and  so  are  the  alcoholic  and  ethereal  extracts,  from  the  decomposition  of  the 
casein.  According  to  Schmidt- Miilheim,  some  of  the  casein  becomes  converted  into  peptone,  but 
this  occurs  only  in  unboiled  milk. 


394  TESTS    FOR    MILK. 

Composition. —  loo  parts  of  milk  contain — 

Human.                                             Cow.                   Goat.  Ass. 

Water 87.24  to  90.58                               86.23  86.S5  S9.0I 

Solids 9-42"   12.39                               13.77  13.52  10.99 

Casein 2.91  "     3.92  "I  .        .  .  f    3.2^  2  5?  ) 

Albumin, ^         ^      J- 1.90  to  2.36 1    3^3               ^  5.  |  3.57 

Butter, 267"     4.30  4.50  4.34  1.S5 

Milk  sugar, 3.15  "     6.09  4.93  3.78  \ 

Salts, 0.14"     0.28  0.61  0.65  /  505 

Human  milk  contains  less  albumin,  which  is  more  soluble  than  the  albumin  in  the  milk  of  animals. 

Colostrum  contains  much  serum-albumin,  and  very  little  casein,  while  all  the  other  substances, 
and  especially  the  fats,  are  more  abundant. 

Gases. — Pfliiger  and  Setschenow  found  in  100  vols,  of  milk  5.01  to  7.60  COj ;  0.09  to  0.32  O; 
0.70  to  1. 41  N,  according  to  volume.     Only  part  of  the  C(\  is  expelled  by  pho.sphoric  acid. 

Salts. — The /o/as/i  sa//s  {a.s  in  blood  and  muscle)  are  more  abundant  than  the  soda  compounds, 
while  there  is  a  considerable  amount  of  calcium  phosphate,  which  is  necessary  ior  forviin<^  the  bones 
of  the  infant.  Wddenstein  found  in  loo  parts  of  the  ash  of  human  milk — sodium  chloride,  10.73; 
potassium  chloride,  26.33  ;  potash,  21.44;  lime,  1S.7S  ;  magnesia,  0.S7  ;  phosphoric  acid,  19  ;  ferric 
phosphate,  0.21  ;  sulphuric  acid,  2.64  ;  silica,  traces.  The  amount  of  salts  present  is  affected  by  the 
salts  of  the  food. 

Conditions  Influencing  the  Composition. — The  oftener  the  breasts  are  emptied,  the  richer  the 
milk  becomes  in  casein.  The  last  milk  obtained  at  any  time  is  always  richer  in  butter,  as  it  comes 
from  the  most  distant  part  of  the  gland — viz.,  the  acini.  Some  substances  are  diminished  and  others 
increased  in  amount,  according  to  the  time  after  delivery.  The  following  are  increased  :  Until  the 
second  month  after  delivery,  casein  and  fat;  until  the  5th  month,  the  silts  (which  diminish  progres- 
sively from  this  time  onward);  from  the  Sth  to  the  loth  month,  the  sugar.  The  following  are 
diminished :  From  loth  to  24th  month,  casein  ;  from  5th  to  6th  and  loth  to  llth  month,  fat ;  during 
1st  month,  the  sugar ;   from  the  5th  month,  the  salts. 

The  greater  the  amount  of  milk  that  is  secreted  (woman),  the  more  casein  and  sugar,  and  the  less 
butter  it  contains.  The  milk  of  a  primiparais  less  watery.  Rich  feeding,  especially  proteids  (small 
amount  of  vegetable  food),  increases  the  amount  of  milk  and  the  casein,  sugar  and  fat  in  it ;  a  large 
amount  of  carbohydrates  (not  fats)  increases  the  amount  of  sugar. 

[Modifying  Conditions. — That  cow's  milk  is  influenced  by  the  pasture  and  food  is  well 
krown.  Turniji  as  food  gives  a  peculiar  odor,  taste,  and  flavor  to  the  milk,  and  so  do  the  fragrant 
grasses.  Thcmental  stale  of  the  nurse  influences  the  quantity  and  quality  of  the  milk.  Jaborandi  is  the 
nearest  approach  to  a  galactagogue,  but  its  action  is  temporary.  Atropin  is  a  true  anti-galactagogue. 
The  composition  of  the  milk  may  be  affected  by  using  fatty  food,  by  the  use  of  salts,  and  above  all 
by  the  diet  {Dolan).'] 

[Milk  may  be  a  vehicle  for  communicating  disease — by  direct  contamination,  from  the  water 
used  for  adulterating  it  or  cleansing  the  vessels  in  which  it  is  kept ;  by  the  milk  absorbing  deleterious 
gases;  by  the  secre:ion  being  altered  in  diseased  animals.]  Milk  ought  not  to  be  kept  in  zinc 
vessel-:,  owing  to  the  formation  of  zinc  lactate. 

Substitutes. — If  other  than  human  milk  has  to  be  used,  ass's  milk  most  closely  resembles  human 
milk.  Cow's  milk  is  best  when  it  contains  plenty  of  fatty  matters — it  must  be  diluted  with  its  own 
volume  of  water  at  first,  and  a  little  milk  sugar  added.  The  ca.sein  of  cow's  milk  differs  qualitatively 
from  that  of  human  milk ;  its  coagulated  flocculi  or  curd  are  much  coarser  than  the  fine  curd  of 
human  milk,  and  they  are  only  i,^  dissolved  by  the  digestive  juices,  while  human  milk  is  completely 
dissolved.     Cow's  milk  when  bjiled  is  less  digestible  than  unboiled. 

Tests  for  Milk. — The  amount  of  cream  is  estimated  by  placing  the  milk  for  twenty-four  hours 
in  a  tall  cylindrical  glass  graduated  into  a  hundred  parts,  or  creamometer;  the  cream  collects  on 
the  surface,  and  ought  to  form  from  10  to  24  vols,  per  cent.  [The  cream  is  generally  about  yf^.] 
The  specific  gravity  (fresh  cow's  milk,  1029  to  1034;  when  creamed,  1032  lo  1040)  is  estimated  with 
the  lactometer  at  15°  C.  The  sugar  is  estimated  by  titration  with  Fehling's  solution  \\  150,  II), 
but  in  this  cnse  I  cubic  centimetre  of  the  solution  corresponds  to  0.0067  g^rn  of  milk  sugar;  or  its 
amount  may  be  estimated  with  the  polariscopic  apparatus  (\  150).  The  proteids  are  precipitated 
and  the  fats  e.xtracted  with  ether.  The  fats  in  fresh  milk  form  about  3  per  cent.,  and  in  skimmed 
milk  i^  per  cent.  The  amount  of  water  in  relation  to  the  milk  globules  is  estimated  by  the  lacto- 
scope  or  the  diaphanometer  of  Donne  (modified  by  Vogel  and  Hoppe-Seyler),  which  consists  of 
a  glass  vessel  with  plane  parallel  sides  placed  I  centimetre  apart.  A  measured  quantity  of  milk  is 
taken,  and  water  is  added  to  it  from  a  burette  until  the  outline  of  a  candle  flame  placed  at  a  distance 
of  I  metre  can  be  distinctly  seen  through  the  diluted  milk.  This  is  done  in  a  dark  room  For  I 
cubic  centim-rti-e  of  g'^od  cow's  milk,  70  to  85  centimetres  water  are  required.  [Other  forms  of  licto- 
scope  are  used,  all  depending  on  the  same  principle  of  an  optical  te-^t,  viz.,  that  the  opacity  of  milk 
varies  with  and  is  proportional  to  the  amount  of  butter-fats  present,  i.e.,  the  oil  globules.  Bond  u=es 
a  shallow  cylindrical  vessel  with  the  bottom  covered  by  black  lines  on  a  white  surface.     A  measured 


PREPARATIONS    OF    MILK. 


395 


quantity  of  water  is  placed  in  this  vessel,  and  milk  is  added,  drop  by  drop,  until  the  parallel  lines  on 
the  pattern  at  the  bottom  of  the  dish  cease  to  be  visible.  On  counting  the  number  of  drops,  a  table 
accompanying  the  appliance  gives  the  percentage  of  fats.  This  method  gives  approximate  results. 
In  all  cases  it  is  well  to  use  fresh  milk.] 

Various  substances  pass  into  the  milk  when  they  are  administered  to  the  mother — many 
odoriferous  vegetable  bodies,  e.g.,  anise,  vermuth,  garlic,  etc.;  chloral,  rhubarb,  opium,  indigo,  salicylic 
acid,  iodine,  iron,  zinc,  mercury,  lead,  bismuth,  antimony.  In  osteomalacia  the  amount  of  lime  in  the 
milk  is  increased  i^Giissero^v).  Potassium  iodide  diminishes  the  secretion  of  milk  by  affecting  the 
secretory  function.  Among  abnormal  constituents  are — haemoglobin,  bile  pigments,  mucin,  blood 
corpuscles,  pus,  fibrin.  Numen  us  fungi  and  other  low  organisms  develop  in  evacuated  milk,  and  the 
rare  blue  milk  is  due  to  the  development  of  bacillus  cyanogeneum.  The  milk  serum  is  blue,  not  the 
fungus.  Blue  milk  is  unhealthy,  and  causes  diarrhoea.  There  are  fungi  which  make  milk  bluish- 
black  or  green.  Red  and  yellow  milk  are  produced  by  a  similar  action  of  cbromogenic  fungi  (§  184). 
The  fomiir  is  produced  by  Micrococcus  prodigiosus,  which  is  colorless.  The  color  seems  to  be  due 
to  fuchsin.  The  yellow  color  is  produced  by  bacillus  synxanihus.  Some  of  the  pigments  seem  to 
be  related  to  the  aniline  and  others  to  the  phenol  colonng  matters  [Iliippe). 

The  rennet-like  action  of  bacteria  is  a  widely  diffused  property  of  these  organisms;  they  coagu- 
late and  peptonize  casein  and  may  ultimately  produce  further  decompositions.  The  butyric  acid 
bacil  us  (I  184)  first  coagulates  casein,  then  peptonizes  it,  and  finally  splits  it  up,  with  the  evolution 
of  ammonia  [Hilppe) 

Milk  becomes  stringy  owing  to  the  action  of  cocci  which  form  a  stringy  substance  \_^  dextran, 
CjjHjqOjq  [Scheibler)'\,]\ist  as  beer  or  wine  undergoes  a  similar  or  ropy  change.  [The  milk  of  dis- 
eased animals  may  contain  or  transmit  directly  infectious  matter.]    - 

Preparations  of  Milk. — (i)  Condensed  milk — 80  grms.  cane  sugar  are  added  to  i  litre  of  milk; 
the  whole  is  evaporated  to  -1-;  and  while  hot  sealed  up  in  tin  cans.  For  children  one  teaspoonful  is 
dissolved  in  a  pint  of  cold  water,  and  then  boiled. 

(2)  Koumiss  is  prepared  by  the  Tartars  from  mare's  milk.  After  the.  addition  of  koumiss  and 
sour  milk,  the  whole  is  violently  stirred,  and  it  undergoes  the  alcoholic  fermentation,  whereby  the 
milk  sugar  is  first  changed  into  galactose,  and  then  into  alcohol;  so  that  koumiss  contains  2  to  3  per 
cent,  of  alcohol ;  while  the  casein  is  at  first  precipitated,  but  is  afterwards  partly  re-dissolved  and 
changed  into  acid  albumin  and  peptone.  Tartar  koumiss  seems  to  be  produced  by  the  action  of  a 
special  bacterium  (Diaspora  caucasia). 

(3)  Cheese  is  prepared  by  coagulating  milk  with  rennet,  allowing  the  whey  to  separate,  and 
adding  salt  to  the  curd.  When  kept  for  a  long  time  cheese  "ripens,"  the  casein  again  becomes 
soluble  in  water,  probably  fi-om  the  formation  of  soda  albuminate;  in  many  cases  it  becomes  semi- 
fluid, when  it  takes  the  characters  of  peptones.  When  further  decomposition  occm^s,  leucin  and 
tyrosin  are  formed.  The  fats  increase  at  the  expense  of  the  casein,  and  they  again  undergo  further 
change,  the  volatile  fatty  acids  giving  the  characteristic  odor.  The  formation  of  peptone,  leucin, 
tyrosin,  and  the  decomposition  of  fat  recall  the  digestive  processes.  [Cheese  is  coagulated  casein 
entanghng  more  or  less  fat.  so  that  the  richness  of  the  cheese  will  depend  upon  the  lind  of  milk  from 
which  it  is  made.  There  are,  in  this  sense,  three  kinds  of  cheese,  whole  milk,  skimmed  milk,  and 
cream  cheese,  the  last  being  represented  by  Stilton,  Roquefort,  Cheshire,  etc.  The  composition  is 
shown  in  the  following  table,  after  Bauer  : — 


Water. 

Nitrogenous 
Matter. 

Fat. 

Extractives. 

Ash. 

Cream  cheese,      .    . 
Whole  milk,    .    .    . 
Skim  milk,  .... 

35-75 
46.82 
48.02 

7.16 
27.62 
32.65 

30-43 

20.54 

8.41 

2-53 
2-97 
6.80 

4-13 
3-05 
4.12 

Cream  cheese,  especially  if  it  be  made  fi-om  goat's  milk,  acquires  a  very  high  odor  and  strong  flavor 
when  it  is  kept  and  "  ripens  "  ;  the  casein  is  partly  decomposed  to  yield  ammonia  and  ammonium 
sulphide,  while  the  fats  yield  butyric,  caproic,  and  other  acids  ] 

232.  EGGS  must  be  regarded  as  a  complete  food,  as  the  organism  of  the  young 
chick  is  developed  from  them.  The  yolk  contains  a  characteristic  proteid  body — 
vitellin  (§  249),  and  an  albu?ninate  in  the  envelopes  of  the  yellow  yolk  spheres — 
nuclein,  from  the  white  yolk  ;  fats  in  the  yellow  yolk  (palmitin,  olein),  cholesterin, 
much  lecithin  ;  and  as  its  decomposition  product,  glycerin-phosphoric  acid — grape 
sugar,  pigmefits  (lutein),  and  a  body  containing  iron  and  related  to  haemoglobin  ; 


396  FLESH    AND    ITS    TREPARATIONS. 

lastly,  salfs  qualitatively  the  same  as  in  blood — quantitatively  as  in  the  blood  cor- 
puscles— and  gases.  The  chief  constituent  of  the  white  of  egg  is  eg^  albumin 
(§  249),  together  with  a  small  amount  of  palmitin  and  olein  ])artly  saponified  with 
soda  ;  grape  sugar,  extractives  ;  lastly  salts,  qualitatively  resembling  those  of  blood, 
but  quantitatively  like  those  of  serum,  and  a  trace  of  fluorine.  Relatively  more 
of  the  nitrogenous  constituents  than  of  the  fatty  constituents  of  eggs  are  absorbed 
(^Rubncr). 

[The  shell  is  composed  chiefly  of  mineral  matter  (91  per  cent,  of  calcic  carbonate,  6  per  cent, 
of  calcic  phosphate,  and  3  per  cent,  of  organic  mitter.)     A   hen's  egg  weighs  about    i^/  oz.,  of 
which  the  shell  forms  about  y'^.     Note  the  amount  of  fats  in  the  yolk.] 
Composition  : — 

White  of  Egg.  Yolk.  White  of  Egg.  Yolk. 

Water, 84.8         51.5        !        Mineral  matter, 1.2         1.4 

Proteids 12.0         15.0  Pigment  extractives, 2.1 

Fats,  etc., 2.0        30.0 

233.  FLESH  AND  ITS  PREPARATIONS.— Flesh,  in  the  form  in 
which  it  is  eaten,  contains  in  addition  to  the  muscle  substance  proper,  more  or  less 
of  the  elements  of  fat,  connective  and  elastic  tissue  mixed  with  it  (§  293).  The 
following  results  refer  to  flesh  freed  as  much  as  possible  from  those  constituents. 
The  chief  proteid  constituent  of  the  contractile  muscular  substance  is  myosin  ; 
serum  albumin  occurs  in  the  fluid  of  the  fibres,  in  the  lymph  and  blood  of  muscle. 
The/^7/i-  are  for  the  most  part  derived  from  the  interfascicular  fat  cells,  while  lecithin 
and  choleslerin  come  from  the  nerves  of  the  muscles  ;  the  gelatin  is  derived  from 
the  connective  tissue  of  the  perimysium,  perineurium,  and  the  walls  of  blood 
vessels  and  tendons.  The  red  color  of  the  flesh  is  due  to  the  haemoglobin  present 
in  the  sarcous  substance,  but  in  some  muscles,  e.g.,  the  heart,  there  is  a  special 
pigment,  myohjematin  {MacMuun).  Elastin  occurs  in  the  sarcolemma,  neuri- 
lemma, and  in  the  elastic  fibres  of  the  perimysium  and  walls  of  the  vessels;  the 
sinall  amount  of  keratin  is  derived  from  the  endothelium  of  the  vessels.  The 
chief  muscular  substance,  the  result  of  the  retrogressive  metabolism  of  the  sarcous 
substance,  is /vva////  ( — 0.05  per  cent.);  kreatiiiin,  the  mcowsiSint.  inosinic  acid, 
then  lactic,  or  rather  sarcolactic  acid  (§  293).  Further,  taurin,  sarkin,  xanthin, 
uric  acid,  carnin,  inosit  (most  abundant  in  the  muscles  of  drunkards),  urea  (o.  i 
per  cent.)  dextrin  (in  horse  or  rabbit,  not  constant)  ;  grape  sugar,  but  this  is 
very  probably  derived  post-mortem  from  glycogen  (0.43  per  cent.),  which  occurs 
in  considerable  amount  in  foetal  muscles  ;  lastly  fatty  acids.  Among  the  salts, 
potash  and  phosphoric  acid  compounds  are  most  abundant  ;  magnesium  phosphate 
exceeds  calcium  phosphate  in  amount.  [The  composition  varies  somewhat  even 
in  different  muscles  of  the  sanie  animal.] 

In  IOC  parts  Flesh  there  are,  according  to  Schlossberger  and  v.  Bibra — 


Ox. 


}- 


Water I  77  5° 

Solids, I  22.50 

Soluble  album'n. 

Coloring  matter, 

Giutin, 1.30 

Alcoholic  extract,     .        1.50 

Fats,      

Insoluble  albumin. 
Blood  vessels,  etc.,       17.50 


Calf, 


78.20 
21.80 

2.60 

1.60 
1.40 

16.2 


Deer. 


7463 

25-37 

1.94 

0.50 

4-75 
1.30 


Pig. 

7830 
21.70 

2.40 

0.80 
1. 70 


16.81    i   16.81 


Man. 

74  45 
25-55 

1-93 

2.07 

3-7 1 
2.30 

•5-54 


Fowl. 


77-30 
22.7 

3o{ 

1.2 

1-4 


16.5 


Carp. 

7978 
20.22 

2.35 

i".98 

3-47 
I. II 


Frog. 


80.43 

19-57 
1.86 

2.'48 

3-46 

O.IO 


11.31  I  11.67 


FLESH    AND    ITS    PREPARATIONS. 
In  loo  parts  Ash  there  are — 


397 


Potash,    .... 

Soda, 

Magnesia,     .    .    . 

Chalk, 

Potassium,  .  .  . 
Sodium,  .... 
Chlorine,  .... 
Iron  oxide,  .  .  . 
Phosphoric  Acid, 
Sulphuric  " 

Silicic  " 

Carbonic  " 

Ammonia,     .    .    . 


Horse. 


3940 
4.86 
3.88 
1.80 


1.47 
I.O 

46.74 

o.  ;o 


Ox. 


35  94 

3-31 

1-73 
5-36 

4.86 
0.96 
34-36 
3-37 
2.07 
8.02 
0.15 


Calf. 


34-40 

235 

1-45 

1.99 


}      IO-59    { 


0.27 
48-13 

0.81 


Pis 


37-79 
4.02 
4.81 
7-54 

0.40 

0.62 

0-35 

44-47 


The  amount  of  fat  in  flesh  varies  very  much  according  to  the  condition  of  the  animal.  After 
removal  of  the  visible  fat,  human  flesh  contains  7.15  ;  ox,  11. 12;  calf,  104;  sheep,  3.9  ;  wild 
goose,  8.8;  fowl,  2.5  percent. 

The  amount  of  extractives  is  most  abundant  in  those  animals  which  exhibit  energetic  muscular 
action  ;  hence  it  is  largest  in  wild  animals.  The  extract  is  increased  after  vigorous  muscular  action, 
whereby  sarcolaclic  acid  is  developed,  and  the  flesh  becomes  more  tender  and  is  more  palatable. 
Some  of  the  extractives  excite  the  nervous  system,  e,g.^  kreatin  and  kreatinin  ;  and  others  give  to 
flesh  its  characteristic  agreeable  flavor  ["  osmasome,"]  but  this  is  also  partly  due  to  the  different  fats 
of  the  flesh,  and  is  best  developed  when  the  flesh  is  cooked.  The  extractives  in  100  parts  of  flesh 
are,  in  man  and  pigeon,  3 ;  deer  and  duck,  4  ;  swallow,  7  per  cent. 

Cooking  of  Flesh. — As  a  general  rule,  the  flesh  of  young  animals,  owing  to  the  sarcolemma, 
connective  tissue,  and  elastic  constituents  being  less  tough,  is  more  tender  and  more  easily  digested 
than  the  flesh  of  old  animals ;  after  flesh  has  been  kept  for  a  time  it  is  more  friable  and  tender, 
as  the  inosit  becomes  changed  mto  sarcolactic  acid  and  the  glycogen  into  sugar,  and  this  again  into 
lactic  acid,  whereby  the  elements  of  flesh  undergo  a  kind  of  maceration.  Finely  divided  flesh  is 
more  digestible  than  when  it  is  eaten  in  large  pieces.  In  cooking  meat,  the  best  ought  not  to  be  too 
intense,  and  ought  not  to  be  continued  too  long,  as  the  muscular  fibres  thereby  become  hard  and 
shrink  very  much.  Those  parts  are  most  digestible  which  are  obtained  from  the  centre  of  a  roast 
where  they  have  been  heated  to  60°  to  70°  C,  as  this  temperature  is  sufficient,  with  the  aid  of  the 
acids  of  the  flesh,  to  change  the  connective  tissue  into  gelatin,  whereby  the  fibres  are  loosentd,  so 
that  the  gastric  juice  readily  attacks  them.  In  roasting  beef,  apply  heat  suddenly  at  first,  to  coagu- 
late a  layer  on  the  surface,  which  prevents  the  escape  of  the  juice. 

Meat  Soup  is  best  prepared  by  cutting  the  flesh  into  pieces  and  placing  them  for  several  hours 
in  cold  water,  and  afterward  boiling.  Liebig  found  that  6  parts  per  100  of  ox  flesh  were  dissolved 
by  cold  water.  When  this  cold  extract  was  boiled,  2.95  parts  were  precipitated  as  coagulated 
albumin,  which  is  chiefly  removed  by  "  skimming,"  so  that  only  3.05  parts  remain  in  solution.  From 
100  parts  of  flesh  of  fowl,  8  parts  were  ^extracted,  and  of  these  4.7  was  coagulated  and  3.3  remained 
dissolved  in  the  soup.  By  boiling  for  a  very  long  time,  part  of  the  albumin  may  be  redissolved. 
The  dissolved  substances  are:  (i)  Inorganic  salts  of  the  meat,  of  which  82.27  per  cent,  pass  into 
the  soup;  the  earthy  phosphates  chiefly  remain  in  the  cooked  meat.  (2)  Kreatin,  kreatinin,  the 
inosinates  and  lactates  which  give  to  broth  or  beef  tea  their  stimulating  quahties,  and  a  small  amount 
of  aromatic  extractives.  (3)  Gelatin,  more  abundantly  extracted  from  the  flesh  of  young  animals. 
According  to  these  facts,  therefore,  flesh  broth  or  beef-tea  is  a  powerful  stimulant,  supplying  muscle 
with  re-,toratives,  but  is  not  a  food  in  the  ordinary  sense  of  the  term,  as  kreatin  in  general  leaves  the 
body  unchanged  {v.  Voii).  The  flesh,  especially  if  it  be  cooked  in  a  large  mass,  after  the  extrac- 
tion of  the  broth  is  still  available  as  a  food. 

Liebig's  Extract  of  Meat  is  an  extract  of  flesh  evaporated  to  a  thick  syrupy  consistence.  It 
contains  no  fat  or  gelatin,  and  is  chiefly  a  solution  of  the  extractives  and  salts  of  flesh. 

[Extract  of  Fish. — A  similar  extract  is  now  prepared  from  fish,  and  such  extract  has  no  fishy 
flavor,  but  presents  much  the  same  appearance,  odor,  and  properties  as  extract  of  flesh.] 

234.  VEGETABLE  FOODS.— The  nitrogenous  constituents  of  plants  are 
not  so  easily  .absorbed  as  animal  food  {Rubner).  Carbohydrates,  starch,  and 
sugar  are  very  completely  absorbed,  and  even  a  not  inconsiderable  proportion  of 
cellulose  may  be  digested.  The  more  fats  that  are  contained  in  the  vegetable 
food,  the  less  are  the  carbohydrates  digested  and  absorbed. 


398 


VEGETABLE    FOODS. 


I.  The  cereals  are  most  important  vegetable  foods;  they  contain  proteids, 
starch,  salts,  and  water  about  14  per  cent.  The  nitrogenous  body  glutin  is  most 
abundant  under  the  husk  (Fig.  236,  c).  The  use  of  whole  meal  containing  the 
outer  layers  of  the  grain  is  highly  nutritive,  but  bread  containing  much  bran  is 
somewhat  indigestible  (^Rubner).     Their  composition  is  the  following  : — 


100  Parts  of  the  Dry  Meal  contain                     ! 

100  Parts  of  Ash  contain 

Of 

Albumin. 

Starch.        i 

Red  Wheat. 

White  Wheat. 

Wheat, 

Rye, 

Barley, 

Maize, 

Rice, 

Buckwheat,     .    .    . 

16.52% 
II  92 
17.70 

1365 
7.40 
6.8-10.5 

56.25% 
60  91 
38.31 
77-74 
86.21 

6505 

27.87 

15-75 

1-93 
9.60 

1.36 

4936 

0.13 

1 
Potash,                           33.84 

Soda j 

Lime, 3.09 

Magnesia     ....          '3-54 
Iron  oxide  ....            031 
Phosphoric  Acid,          59.21 
Silica,       

•lU  Ot- 
is;  d, 


It  is  curious  to  observe  that  soda  is  absent  from  white  wheat,  its  place  being  taken  by  other  alkalies. 
Rye  contains  more  cellulose  and  dextrin  than  wheat,  but  less  sugar;  rye  bread  is  usually  less  porous 

[Oatmeal  contains  more  nitrogenous  substances  (gliadin  and  glutin-casein)  than  wheaten  Hour,  but 
owing  to  the  want  of  adhesive  properties  it  cannot  be  made  into  bread.  The  amount  of  fat  and  salts 
is  large.] 

In  the  preparation  of  bread  the  meal  is  kneaded  with  water  until  dough  is  formed,  and  to  it  is 

added  salt  and  yeast  (Saccharomycetes  cerevisire). 
Fig.  236.  When  j>laced  in  a  warm  oven,  the  proteids  of  the 

meal  begin  to  decompose  and  act  as  a  ferment  upon 
the  swoUen-up  starch,  which  becomes  in  part 
changed  into  sugar.  The  sugar  is  further  decom- 
posed into  CO.,  and  alcohol,  the  C(.).,  forms  bubbles, 
which  cause  the  bread  to  "  rise  "  and  thus  become 
spongy  and  porous.  The  alcohol  is  driven  oft"  by 
the  baking  (200°),  while  much  soluble  dextrin  is 
formed  in  the  cru.st  of  the  bread.  [But  CO.^  may 
be  set  free  within  the  dough  by  chemical  means, 
without  yeast  or  leaven,  thus  fonning  unfermente  1 
bread.  This  is  done  by  mixing  with  the  dough 
an  alkaline  carbonate  and  then  adding  an  acid. 
Uaking  jjowders  consist  of  carbonate  of  soda  and 
tartaric  acid.  In  I)aughlish"s  process  for  aerated 
bread,  the  CO.,  is  forced  into  water,  and  a  dough  is 
made  with  this  water  under  pressure,  and  when  the 
dough  is  heated,  the  CO.^  expands  and  forms  the  .spongy  bread.  Bread  as  an  article  of  food  is  defi- 
cient in  N,  while  it  is  poor  in  fats  and  some  salts.  Hence  the  necessity  for  using  some  form  of  fat 
with  it  (butter  or  bacon).] 

2.  The  pulses  contain  much  albumin,  especially  legumin  ;  together  with 
starch,  lecithin,  cholesterin,  and  9  to  19  per  cent,  water.  Peas  contain  18.02 
proteids,  and  34.81  starch  ;  beans  28.54,  and  37.50  ;  lentils,  29.31,  and  40,  and 
more  cellulose.  Owing  to  the  absence  of  glutin  they  do  not  form  dough,  and 
bread  cannot  be  prepared  from  them.  On  account  of  the  large  amount  of  pro- 
teids which  they  contain,  they  are  admirably  adapted  as  food  for  the  poorer 
classes. 

[3.  The  whole  group  of  farinaceous  sub.stances  used  as  "  pudding  stuffs,"  such  as  com-fiour, 
arrow-root,  rice,  hominy,  are  really  very  largely  composed  of  starchy  substances.] 

4.  Potatoes  contain  70  to  81  per  cent,  water.  In  the  fresh  juicy  cellular 
tissue,  which  has  an  acid  reaction,  from  the  presence  of  phosphoric,  malic,  and 
hydrochloric  acids,  there  is  16  to  23  per  cent,  of  starch,  2.5  soluble  albumin, 
globulin,  and  a  trace  of  asparagin.  The  envelopes  of  the  cells  swell  up  by  boil- 
ing, and  are  changed  into  sugar  and  gums  by  dilute  acids.  The  poisonous  solanin 


Microscopic  characters  of  wheat  (+  20o).  n,  c 
the  bran;  ^,  cells  of  thin  cuticle ;  c,  glutin  eel 
starch  cells. 


UTILIZATION    OF    FOOD. 


399 


occurs  in  the  sprouts.  In  loo  parts  oi potato  ash,  May  found  49.96  potash,  2.41 
sodium  chloride,  8. 11  potassium  chloride,  6.50  sulphuric  acid  derived  from  burned 
proteids,  7.17  silica. 

5.  In  fruits  the  chief  nutrient  ingredients  are  sugar  and  salts;  the  organic 
acids  give  them  their  characteristic  taste ;  the  gelatinizing  substance  is  the  soluble 
so-called  pectin  (Ca-^HigOaj),  which  can  be  prepared  artificially  by  boiling  the 
very  insoluble  pectose  of  unripe  fruits  and  mulberries. 

6.  Green  Vegetables  are  especially  rich  in  salts,  which  resemble  the  salts  of 
the  blood  ;  thus,  dry  salad  contains  23  per  cent,  of  salts,  which  closely  resemble 
the  salts  of  the  blood.  Of  much  less  importance  are  the  starch,  cell  substance, 
dextrin,  sugar,  and  the  small  amount  of  albumin  which  they  contain. 

[Vegetables  are  chiefly  useful  for  the  salts  they  contain,  while  many  of  them  are  antiscorbutic. 
Their  value  is  attested  by  the  serious  defects  of  nutrition,  such  as  scurvy,  which  result  when  they  are 
not  supplied  in  the  food.  In  Arctic  expeditions  and  in  the  navy,  lime  juice  is  served  out  as  an  anti- 
scorbutic] 

[Preserved  Vegetables. — The  dried  and  compressed  vegetables  of  Messrs.  Chollet  &  Company 
are  an  excellent  substitute  for  fresh  vegetables,  and  are  used  largely  in  naval  and  miUtary  expeditions.] 

[Utilization  of  Food. — As  regards  what  percentage  of  the  food  swallowed  is 
actually  absorbed,  we  know  that,  stated  broadly,  vegetable  food  is  assimilated  to  a 
much  less  extent  than  animal  food  in  man.  Fr.  Hofmann  gives  the  following 
table  as  showing  this  : — 


Weight  of  Food. 

Vegetable. 

Animal. 

Digested. 

Undigested. 

Digested. 

1 
Undigested. 

Of  100  parts  of  solids, 

"    100        "       albumin,      

"    100        "       fats  or  carbohydrates,     .    . 

75  5 
46.6 

903 

24.5 

53-4 
9-7 

899 
81.2 
96.9 

II. I 

18.8 

3-1] 

[The  following  table,  abridged  from  Parkes,  shows  the  composition  of  the   chief  articles  of  diet, 
and  is  also  used  for  calculating  diet  tables: — 


Articles. 


Water. 


Proteids. 


Beefsteak,    .... 

Fat  pork, 

Smoked  ham,  .  .  . 
White  fish,     .... 

Poultry, 

White  wheaten  bread, 
Wheat  flour,      .    .    . 

Biscuit, 

Rice, 

Oatmeal, 

Maize, 

Macaroni,  .... 
Arrow  root,  .... 
Peas  (dry),    .... 

Potatoes, 

Carrots, 

Cabbage, 

Butter, 

Egg  (tV  for  shell),   . 

Cheese, 

Milk  (S.  G.  1032), 
Cream,  .    .    .  " .    .    . 
Skimmed  milk,     .    . 
Sugar, 


74-4 

20.5 

390 

98 

27.8 

24.0 

78.0 

18.1 

74.0 

21.0 

40.0 

8.0 

15.0 

II.O 

8.0 

15-6 

1 0.0 

5.0 

15.0 

12.6 

13-5 

lO.O 

131 

9.0 

15.4 

0.8 

150 

22.0 

74.0 

2  0 

85.0 

1.6 

91.0 

1.8 

6.0 

03 

73-5 

13-5 

368 

33-5 

86.8 

4.0 

66.0 

2.7 

88.0 

4.0 

3-0 

3-5 
48.9 

365 
2.9 

3-^ 
1-5 
2.0 

1-3 

0.8 

5-6 
6.7 
03 

2.0 

0.16 

0.25 

5-0 
91.0 
1 1.6 

24-3 
3-7 

26.7 
1.8 


Carbo- 
hydrates. 


492 
70-3 

73-4 
83.2 
63.0 
64.5 
76.8 
83.3 
53-0 
21,0 

8.4 
5-8 


4.8 
2.8 

5-4 
96.5 


Salts. 


1.6 
2.3 

lO.I 
I.O 
1.2 

1-3 
1-7 
1-7 

0.5 

3-0 

I  4 

0.8 

0.27 

2.4 

1.0 

1.0 

0.7 

2.7 

1.0 

54 
0.7 
1.8 
0.8 
05] 


400  ACTION    OF    ALCOHOL. 

235.  CONDIMENTS,   COFFEE,  TEA,   ALCOHOL— Some  substances  are  used  along 

■with  food,  not  so  much  on  account  of  their  nutritive  properties  as  on  account  of  their  stimulating  effects 
and  agreeable  qualities,  which  are  exeited  partly  upon  the  organ  of  taste  and  partly  upon  the  nerv- 
ous system.     These  are  called  condiments. 

Coffee,  Tea,  and  Chocolate  are  prepared  as  infusions  of  certain  vegetables  [the  first  of  the 
roasted  berry,  the  second  of  the  leaves,  and  the  third  of  the  seeds]  Their  chief  active  ingredients 
are  respectively  caffein.  thein  (CgHj^N^O^  -f  H.^O),  and  theobromin  (C;HgN/3.^),  which  are 
regarded  as  alkaloids  of  the  vegetable  bases,  and  which  have  recently  been  prepared  aitificially  from 
xanthin  (£■.  Fischer).  [Guarana,  or  Brazilian  cocoa,  is  made  of  the  seeds  ground  into  a  ]iaste  in 
the  form  of  a  sausage.  Mate  or  Par.igiiay  tea  (the  leaves  of  a  species  of  holly)  is  used  in  South 
America,  and  so  aho  is  the  coca  of  the  Andes  (Erythroxylon  Coca).]  These  "alkaloids"  occur  as 
such  in  the  plants  containing  them;  they  behave  like  ammoni.i  ;  they  have  an  alka'ine  reaction, 
and  form  crv-staliine  salts  with  acids.  All  these  vegetAl)le  bases  act  upon  the  nervous  system;  some 
more  feebly  (as  the  above),  others  more  powerfully  (quinine) ;  some  stimulate  powerfully,  or  com- 
pletely paralyze  (morphia,  atropin,  strychnin,  curarin,  nicotin). 

Effects. — All  these  substances  act  on  the  nervous  system  ;  they  quicken 
thought,  accelerate  movement,  and  stir  one  to  greater  activity.  In  these  respects 
they  resemble  the  stimulating  extractives  of  beef  tea.  Coffee  contains  about  yi 
per  cent,  of  caffein,  part  of  which  only  is  liberated  by  the  act  of  roasting.  Tea 
has  6  per  cent,  of  thein  ;  while  green  tea  contains  i  per  cent,  ethereal  oil,  and 
black  tea  ]A  per  cent.  ;  in  green  tea  there  is  18  per  cent.,  in  black  15  per  cent, 
tannin;  green  tea  yields  about  46  per  cent.,  and  the  black  scarcely  30  per  cent, 
of  extract.  The  inorganic  salts  present  are  also  of  importance;  tea  contains 
3.03  per  cent,  of  salts,  and  among  these  are  soluble  compounds  of  iron,  manganese, 
and  soda  salts.  In  coffee,  which  yields  3  41  per  cent,  of  ash,  potash  salts  are 
most  abundant ;  in  all  three  substances  the  other  salts  which  occur  in  the  blood 
are  also  present. 

Alcoholic  drinks  owe  their  action  chiefly  to  the  alcohol  which  they  contain. 
Alcohol,  when  taken  into  the  body,  undergoes  certain  changes  and  produces 
certain  effects  :  (i)  About  95  per  cent,  of  it  is  oxidized  chiefly  into  CO^  and 
H.^0,  so  that  it  is  so  far  a  source  of  heat.  As  it  undergoes  this  change  very  readily 
when  taken  to  a  certain  extent,  it  may  act  as  a  substitute  for  the  consumption  of 
the  tissues  of  the  body,  especially  when  the  amount  of  food  is  insufficient. 
[Hammond  found  that  when  he  lived  on  an  insufficient  amount  of  food,  alcohol, 
if  given  in  a  certain  quantity,  supplied  the  place  of  the  deficiency  of  food,  and 
he  even  gained  in  weight.  If,  however  sufficient  food  was  taken,  alcohol  was 
unnecessary.  As  it  interferes  with  oxidation,  and  where  there  is  a  sufficient  amount 
of  other  food,  in  health,  it  is  unnecessary,  for  dietetic  reasons.]  Small  doses 
diminish  the  decomposition  of  tlie  proteids  to  the  extent  of  6  to  7  per  cent. 
Only  a  very  small  part  of  the  alcohol  is  excreted  in  the  urine  ;  the  odor  of  the 
breath  is  not  due  to  alcohol,  but  to  other  volatile  substances  mixed  with  it,  e.g., 
fusel  oil,  etc.  (2)  In  small  doses  it  excites,  while  in  large  doses  it  paralyzes  the 
nervous  system.  By  its  stimulating  qualities  it  excites  to  greater  action,  which, 
however,  is  followed  by  depression.  (3)  It  diminishes  the  sensation  of  hunger. 
(4)  It  excites  the  vascular  system,  accelerates  the  circulation,  so  that  the  muscles 
and  nerves  are  more  active,  owing  to  the  greater  supply  of  blood.  It  also  gives 
rise  to  a  subjective  feeling  of  warmth.  In  large  doses,  however,  it  paralyzes  the 
vessels,  so  that  they  dilate,  and  thus  much  heat  is  given  off  (§  213,  7  ;  §  227). 
The  action  of  the  heart  also  becomes  affected,  the  pulse  becomes  smaller,  feebler, 
and  more  rapid.  In  high  altitudes  the  action  of  alcohol  is  greatly  diminished, 
owing  to  the  diminished  atmospheric  pressure,  whereby  it  is  rapidly  given  off  from 
the  blood. 

Alcohol  in  small  doses  is  of  great  use  in  conditions  of  temporary  want,  and 
where  the  food  taken  is  insufficient  in  quantity.  When  alcohol  is  taken  regularly, 
more  especially  in  large  doses,  it  affects  the  nervous  system,  and  undermines  the 
physical  and  corporeal  faculties,  partly  from  the  action  of  the  impurities  which 
it  may  contain,  such  as  fusel  oil,  which  has  a  poisonous  effect  upon  the  nervous 


PREPARATION    OF    ALCOHOLIC    DRINKS. 


401 


system,  partly  by  the  direct  effects,  such  as  catarrh  and  inflammation  of  the 
digestive  organs,  which  it  produces,  and  lastly,  by  its  effect  upon  the  normal 
metabolism. 

[The  action  of  alcohol  in  lowering  the  temperature,  even  in  moderate  doses,  is  most  important. 
By  dilating  the  cutaneous  vessels,  it  thus  permits  of  the  radiating  of  much  heat  from  the  blood. 
When  the  action  of  alcohol  is  pushed  too  far,  and  especially  when  this  is  combined  with  the  action 
of  great  cold,  its  use  is  to  be  condemned.  Brunton  has  pointed  out  that,  as  regards  its  action  on  the 
nervous  system,  it  seems  to  induce  progressive  paralysis,  affecting  the  nervous  tissues  "in  the 
inverse  order  of  their  development,  the  highest  centres  being  affected  first  and  the  lowest  last."  The 
judgi7ient  is  affected  first,  although  the  imagination  and  "  emotions  may  be  more  than  usually  active." 
The  jHoior  centres  and  speech  are  affected,  then  the  cerebellum  is  influenced,  and  afterward  the 
cord,  while  by  and  by  the  centres  essential  to  life  are  paralyzed,  provided  the  dose  be  sufficiently  large.] 

Preparation. — Alcoholic  drinks  are  prepared  by  the  fermentation  of  various  carbohydrates, 
such  as  sugar  derived  from  starch.  The  alcoholic  fermentation,  such  as  occurs  in  the  manufacture 
of  beer,  is  caused  by  the  development  of  the  yeast  plant,  Saccharomycetes  cerevisiae  ;  while  in 
the  fermentation  of  the  grape  (wine),  S.  EUipsoideus  is  the  species  present  (Fig.  237).  The  yeast 
takes  the  substances  necessary  for  the  maintenance  of  its  organic  processes  directly  from  the  mixture 
of  the  sugar,  viz.,  carbohydrates,  proteids  and  salts,  especially  calcium  and  potassium  phosphates 
and  magnesium  sulphate.  These  substances  undergo  decomposition  within  the  cells  of  the  yeast 
plant,  which  multiply  dur- 
ing the  process,  and  there  Fig 
are  produced  alcohol  and 
CO,  (I  150),  together  with 
glycerine  (3.2  to  3.6  per 
cent.)  and  succinic  acid  0.6 
to  0.7  per  cent.).  Yeast  is 
either  added  intentionally  or 
it  reaches  the  mixture  from 
the  air,  which  always  con- 
tains its  spores.  When  yeast 
is  completely  excluded,  or  if 
it  be  killed  by  boiling  [or  if 

its  action  be  prevented  by  the  presence  of  some  germicide],  the  fermentation  does  not  occur, 
alcohohc  fermentation  is  due  to  the  activity  of  a  low  organism. 

In  the  preparation  of  brandy,  the  starch  of  the  grain  or  potatoes  is  first  changed  into  sugar  by  the 
action  of  diastase  or  maltin.  Yeast  is  added,  and  fermentation  thereby  produced  ;  the  mixture  is 
distilled  at  78.3°C.  The  fusel  oil  is  prevented  from  mixing  with  the  alcohol  by  passing  the  vapor 
through  heated  charcoal.     The  distillate  contains  50  to  55  per  cent,  of  alcohol. 

In  the  preparation  of  wine,  the  saccharine  juice  of  the  grape  —  the  must  —  after  being  ex- 
pressed from  the  grapes,  is  exposed  to  the  air  at  10°  to  15°  C,  and  the  yeast  cells,  which  are  float- 
ing about,  drop  into  it  and  excite  fermentation,  which  lasts  10  to  14  days,  when  the  yeast  sinks  to 
the  bottom.  The  clear  wine  is  drawn  off  into  casks,  where  it  becomes  turbid  by  undergoing  an 
after-fermentation,  until  the  sugar  is  converted  into  alcohol  and  COj,  which  is  accompanied  by  the 
deposition  of  some  yeast  and  tartar.  If  all  the  sugar  is  not  decomposed — which  occurs  when  there 
is  not  sufficient  nitrogenous  matter  present  to  nourish  the  yeast — a  sweet  whie  is  obtained.  Wine 
contains  89  to  90  per  cent,  water,  7  to  8  per  cent,  alcohol,  together  with  Eethylic,  propylic,  and 
butylic  alcohol.  The  red  color  of  some  wines  is  due  to  the  coloring  matter  of  the  skin  of  the  grapes, 
but  if  the  skins  be  removed  before  fermentation,  red  grapes  yield  white  wine.  When  wine  is  stored, 
it  develops  a  fine  flavor  or  bouquet,  The  characteristic  vinous  odor  is  due  to  cenanthic  ether. 
The  salts  of  wine  closely  resemble  the  salts  of  the  blood. 

In  the  preparation  of  beer  the  grain  is  moistened,  and  allowed  to  germinate,  when  the  temperature 
rises,  and  the  starch  (68  per  cent,  in  barley)  is  changed  into  sugar.  Thus  "malt"  is  formed, 
which  is  dried,  and  afterward  pulverized,  and  extracted  with  water  at  70°  to  75°,  the  watery  extract 
being  the  "wort."  Hops  are  added  to  wort,  and  the  whole  is  evaporated,  when  the  proteids  are 
coagulated.  Hops  give  beer  its  bitter  taste,  and  make  it  keep,  while  their  tannic  acid  precipitates 
any  starch  that  may  be  present,  and  clarifies  the  wort.  After  being  boiled,  it  is  cooled  rapidly 
(l2°  C.) ;  yeast  is  added,  and  fermentation  goes  on  rapidly  and  with  considerable  effervescence  at  10° 
to  14°.  Beer  contains  75  to  95  per  cent,  water ;  alcohol,  2  to  5  per  cent,  (porter  and  ale,  to  8  per 
cent.)  ;  COj,  o.l  to  0.8  per  cent. ;  sugar  2  to  8  per  cent. ;  gum,  dextrin,  2  to  10  per  cent. ;  the  hops 
yield  traces  of  protein,  fat,  lactic  acid,  ammonia  compounds,  the  salts  of  the  grain  and  of  the  hops. 
In  the  ash  there  is  a  great  preponderance  of  phosphoric  acid  and  potash,  both  of  which  are  of  great 
importance  for  the  -formation  of  blood.  In  100  parts  of  ash  there  are  40.8  potash,  20.0  phosphorus, 
magnesium  phosphate  20,  calcium  phosphate  2.6,  silica  16. 6  per  cent.  The  formation  of  blood, 
muscle,  and  other  tissues  from  the  consumption  of  beer  is  due  to  the  phosphoric  acid  and  potash, 
while  if  too  much  be  taken,  the  potash  produces  fatigue. 
26 


I,  Isolated   yeast   cells;    2,  3,  yeast   cells   budding;    4,  5,  so-called   endogenous 
formation  of  cells;    6,  sprouting  and  formation  of  buds. 

The 


402  EQUILIBRIUM    OF    THE    METABOLISiM. 

Condiments  are  taken  with  food,  partly  on  account  of  their  taste,  and  partly 
because  they  excite  secretion.  Common  salt,  in  a  certain  sense,  is  a  condiment. 
We  may  also  include  many  substances  of  unknown  constitution  which  act  upon 
the  gustatory  organs,  <?. ^tr-,  dextrin,  and  substances  in  the  crust  of  bread  and  in 
meat  which  has  been  roasted. 

236.  EQUILIBRIUM  OF  THE  METABOLISM.— By  this  term  is 
meant  tliat,  under  normal  pliysiological  conditions,  just  as  much  material  is 
absorbed  and  assimilated  from  the  food  as  is  removed  from  the  body  by  the 
excretory  organs  in  the  form  of  effete  or  end  products,  the  result  of  the  retrogres- 
sive tissue  changes.  The  income  must  always  balance  the  expenditure  ;  wherever 
a  tissue  is  used  up,  it  must  be  replaced  by  the  formation  of  new  tissue.  During 
the  period  of  growth,  the  increase  of  the  body  corresponds  to  a  certain  increase 
of  formation,  whereby  the  metabolism  of  the  growing  parts  of  the  body  is  2.5  to 
6.3  times  greater  than  that  of  the  parts  already  formed.  Conversely,  during  senile 
decay,  there  is  an  excess  of  expenditure  from  the  body. 

Methods. — The  normal  equilibrium  of  the  metabolism  of  the  body  is  investigated  (i)  By 
determining  chemically  that  the  sum  of  all  the  substances  passing  into  the  body  is  equal  to  the 
sum  of  all  the  substances  given  off  from  it.  Thus  the  C,  N,  H,  O,  salts  and  water  of  the  food, 
and  the  O  inspired,  must  be  ec|ual  to  the  C,  N.  M,  O,  salts  and  water  given  off  in  the  excreta 
(urine,  fxces,  air  expired,  water  excreted).  (2)  The  physiological  equilibrium  is  determined 
empirically  by  observing  that  the  body  retains  its  normal  weight  with  a  given  diet ;  so  that,  by 
simply  weighing  a  person,  a  physician  is  enabled  to  determine  exactly  the  state  of  convalescence 
of  his  patient.  The  tedious  process  of  making  an  elementary  analysis  of  the  metallic  sub- 
stances was  first  undertaken  in  the  Munich  School  by  v.  Bischoff,  v.  Voit,  v.  Pettenkofer,  and 
others. 

Circulation  of  C. — In  the  circulation  of  materials  the  total  amount  of  C  taken 
in  the  food,  if  the  metabolism  be  in  a  condition  of  physiological  equilibrium,  must 
be  equaled  by  the  C  in  the  CO.  given  off  by  the  lungs  and  skin  (90  per  cent.), 
together  with  the  relatively  small  amount  of  C  in  the  organic  excreta  of  the  urine 
and  faeces  (10  per  cent.). 

Circulation  of  N. — Nearly  all  the  iV  taken  in  with  the  food  is  excreted  within 
twenty-four  hours  in  the  form  of  urea.  A  very  small  amount  of  nitrogenous  mat- 
ter is  excreted  in  the  faeces,  while  the  other  nitrogenous  urinary  constituents  (uric 
acid,  kreatinin,  etc.)  represent  about  2  per  cent,  of  N.  A  trace  of  the  N  is  given 
off  by  the  breath  (§  124),  and  a  minute  proportion  in  combination,  in  the  epider- 
mal scales  (50  milligrammes  daily  in  the  hair  and  nails),  and  in  the  sweat. 

Deficit  of  N. — That  nearly  all  the  N  taken  in  the  food  reappears  in  the 
urine  and  faeces,  as  was  stated  by  v.  Voit  to  be  the  case  in  the  carnivora  and 
in  the  herbivora,  and  by  v.  Ranke  in  man,  is  contradicted  partly  by  old  and 
partly  by  new  observations,  which  go  to  show  that  the  whole  of  the  N  cannot 
be  recovered  from  these  excretions,  but  that  on  the  contrary  there  is  a  considerable 
deficit. 

According  to  Leo,  only  0.55  per  cent,  of  the  albumin  transformed  within  the  body  (assuming  15 
per  cent.  N  in  albumin)  gives  off  its  N  in  the  form  of  gaseous  N  (according  to  Seegen  and  Nowak, 
12  times  more).  In  every  exact  analysis  of  the  metabolism  of  X  this  gaseous  excretion  of  N  must 
be  taken  into  account. 

The  excretion  of  N  after  food  does  not  take  place  regularly  from  hour  to  hour,  but  it  increases 
at  once  and  distinctly,  reaches  its  maximum  in  five  to  six  hours,  and  then  gradually  falls.  The  same 
is  true  of  the  excretion  of  S  and  P ;  but  in  these  cases  the  maximum  of  excretion  is  reached  at  the 
fourth  hour.  When  fat  is  added  to  a  diet  of  flesh,  the  excretion  of  N  and  S  is  uniformly  distributed 
over  the  individual  hours  of  the  day  [v.   Voit  and  Feder). 

The  nitrogenous  constituents  in  the  body  during  metabolism  become  poorer  in  C,  and  richer 
in  N  and  O.  Thus  in  albumin  to  I  atom  of  N  there  are  4  atoms  C;  in  gelatin,  3^  C;  in 
glycocoll,  2  C;  in  kreatin,  i)/^  C;  in  uric  acid,  l^  C;  in  allantoin,  i  C ;  in  urea,  only  ^ 
atom  of  C. 

The  H  leaves  the  body  chiefly  in  the  form  of  water — a  part,  however,  is  in 
combination  in   other  excreta ;    the  O  is  chiefly  excreted  as  CO.,  and  water ;    a 


EQUILIBRIUM    OF   THE    METABOLISM.  403 

little  is  given  off  in  combination  in  other  excreta ;  \Arater  is  given  off  by  evapo- 
ration from  the  lungs  and  skin,  and  also  in  the  urine  and  faeces.  As  H  is  oxidized 
to  H2O,  more  water  is  excreted  than  is  taken  in.  Most  of  the  readily  soluble 
salts  are  given  off  by  the  urine ;  the  less  soluble  salts,  especially  those  of 
potash,  and  the  insoluble  salts,  in  the  faeces ;  while  others  are  given  off  in  the 
sweat.  Of  the  sulphur  of  albumin,  about  one-half  is  excreted  in  the  sulphur 
compounds  in  the  urine,  and  the  other  half  in-ihe  faeces  (taurm)  and  in  the  epi- 
dermal tissues. 

Every  organism  has  a  minimum  and  a  maximum  limit  of  metabolism, 
according  to  the  amount  of  work  done  by  the  body,  and  its  weight.  If  less  food 
be  given  than  is  necessary  to  maintain  the  former,  the  body  loses  weight ;  while, 
if  more  be  given  after  the  maximum  limit  is  reached,  the  food  so  given  is  not 
absorbed,  but  remains  as  a  floating  balance,  and  is  given  off  with  the  faeces.  When 
food  is  liberally  supplied  and  the  weight  increases,  of  course  the  minimum  limit 
rises;  hence,  during  the  process  of  "feeding"  or  "fattening,"  the  amount  of 
food  necessary  is  very  much  greater  than  in  poorly  fed  animals,  for  the  same 
increase  of  the  body  weight.  By  continuing  the  process,  a  condition  is  at  last 
reached  in  which  the  digestive  organs  are  just  sufficient  to  maintain  the  existing 
condition,  but  cannot  act  so  as  to  admit  of  new  additions  being  made  to  the  body 
weight  (v.  Bischoff,  v.   Voit,  v.  Pettenkofer). 

By  the  term  "  luxus  consumption"  is  meant  the  direct  combustion  or  oxi- 
dation of  the  superfluous  food  stuffs  absorbed  in  the  blood.  This,  however,  does 
not  exist;  on  the  contrary,  the  material  in  the  juices  is  always  being  used  for 
building  up  the  tissues.  The  albumin  found  in  the  fluids  which  everywhere 
permeate  the  tissues,  has  been  called  "circulating  albumin,"  and  according 
to  V.  Voit  it  undergoes  decomposition  sooner  than  the  organized  or  "organic 
albumin"  which  forms  an  integral  part  of  the  tissue.  According  to  v.  Voit,  in 
24  hours  I  per  cent,  of  the  organic  and  70  per  cent,  of  the  circulating  albumin  is 
used  up. 

[Liebig  taught  that  the  nitrogenous  metabolism  of  the  body  depended  on  a  corresponding 
decomposition  of  the  proteids  of  the  organs,  so  that  the  proteids  in  the  food  supphed  the  place  of 
the  proteids  of  the  organs  thus  used  up.  He  called  the  proteids  "plastic  foods  "  or  "tissue 
formers,"  while  he  regarded  the  fats  and  carbohydrates  as  "  respiratory  foods,"  as  he  sup- 
posed that  they  alone  were  concerned  in  the  evolution  of  heat.  As  a  matter  of  fact,  experiment 
proved  that  the  N  metabolism  is  to  a  large  extent  independent  of  the  proteids  of  the  food.  The 
luxus-consumption  theory  was  invented  to  explain  this.  It  simply  means,  that  proteids  taken  with 
the  food  not  only  replace  the  amount  of  proteids  which  have  been  decomposed  during  the  activity 
of  organs  and  tissues,  but  that  any  excess  is  imm,ediately  consumed  without  being  converted  into 
tissue,  and  thus  this  surplus  amount  giving  rise  to  heat,  by  being  oxidized,  to  a  certain  extent 
replaces  the  fats  and  carbohydrates.  But  Voit  showed  that  the  nitrogenous  metabolism  is  not  influ- 
enced by  the  activity  of  the  organism,  and  he  proved  that  in  ordinary  conditions  only  a  small 
amount  of  the  organic  albumin,  i.e.,  that  composing  tissues  and  organs,  undergoes  decomposition, 
while,  owing  to  the  action  of  the  cellular  elements  of  the  tissue,  a  large  amount  of  the  circulating 
albumin  is  split  up,  so  that  under  ordinary  conditions  the  organic  albumin  is  comparatively  stable. 
This  he  demonstrated  from  a  comparison  of  the  urea  excreted,  for  the  urea  may  be  taken  as  an  index 
of  the  N  metabolism  in  well  fed,  fasting,  and  starving  animals.  But  in  certain  pathological  con- 
ditions the  organic  albumin  may  undergo  rapid  change,  having  become  less  stable,  as  in  fevers,  and 
poisoning  with  phosphorus.] 

Quality  and  Quantity  of  the  Diet. — As  far  as  his  organization  is  concerned, 
man  belongs  to  the  omnivorous  animals,  i.  e.,  those  that  can  live  upon  a  mixed 
diet.  For  an  adequate  diet  man  requires  for  his  existence  and  to  maintain 
health  a  mixture  of  the  following  four  chief  groups  of  food  stuffs  along  with  the 
necessary  relishes ;  none  of  them  must  be  absent  from  the  food  for  any  length  of 
time.     They  are  : — 

I.  Water — for  an  adult  in  his  food  and  drink,  2700  to  2800  grms.  [70  to  90 
oz.]  daily  (§  229  and  §  247,  i). 

[Thirst. — The  needs  of  the  economy  for  water  are  expressed  by  the  sensation  of  thirst.  The 
sensation  of  heat  and  dryness  may  be  confined  to  the  tongue,  mouth  and  fauces,  and  indeed  may  be 


404 


COMPOSITION    UF    FOODS. 


excited  by  inhaling  dry  air.  This  local  thirst  maybe  allayed  by  swallowing  water  or  by  eating 
substances  which  excite  the  secretion  of  saliva.  More  frequently,  however,  the  sensation  is  the 
expression  of  a  general  condition  indicating  the  diminution  of  water  in  the  tissues;  or  it  may  be 
due  to  excess  of  saline  matters  in  the  blood.  In  some  diseases  this  sensation  is  very  intense,  (r.^^, 
diabetes.  If  water  be  injected  into  the  blood  vessels,  or  stomach,  both  the  general  and  local  thirst 
are  abolished,  even  although  no  water  enters  the  mouth.] 


Fig.  238. 
Animal  Foods. 


Beef. 


Pork. 


62 


Albiiminoitls.       N-free  org.  bodies.  Salts. 


55 


33' 


73 


p.U.7i    '3 


Fish. 


7fi 


111 


Egg. 


73,5 


IM 


Cow's 
milk. 


8fi 


Human 
milk. 


CI 


89 


Vegetable  Foods. 


iii " 


Wheaten 
bread 


Proteids.  Digestible.  Non-digestible.  Salts. 

N-free  organic  bodies. 


*1,3 


as!3G 


I 


Peas. 


n 


55,5 


Rice. 


Potatoes. 


19 


75 


l::^ 


White 
Turnip. 


90,5 


Cauli- 
flower. 


90 


0,2 


Beer,     f 


80 


IMM 


2.  Inorganic  substances  or  Salts  are  an  integral  part  of  all  tissues,  and 
without  them  the  tissues  cannot  be  formed.  They  occur  in  ordinary  food.  The 
addition  of  too  much  salt  increases  the  consumption  of  water,  and  this  in  turn 
increases  the  transformation  of  N  in  the  body.  If  an  animal  be  deprived  of  salts, 
nutrition  is  interfered  with ;  food  deprived  of  its  lime  affects  the  formation  of  the 
bones  ;  deprival  of  common  salt  causes  albuminuria  (247,  A,  III).  The  alkaline 
salts  serve  to  neutralize  the  sulphuric  acid  formed  by  the  oxidation  of  the  sulphur 


COMPOSITION    OF    FOODS.  405 

of  the  proteids.     Iron,  which  is  so  essential  for  the  formation  of  blood,  exists  in 
animals  and  plants  in  combination  with  complex  organic  bodies. 

Only  in  times  of  famine  is  man  driven  to  eat  large  quantities  of  inorganic  substances,  to  extract 
the  organic  matter  mixed  therewith.  A.  v.  Humboldt  states,  in  regard  to  the  inhabitants  of  the 
Orinoco,  that  they  eat  a  kind  of  earth  which  contains  innumerable  infusoria. 

3.  At  least  one  animal  or  vegetable  albuminous  body  or  proteid  (§§  248,  250). 
The  proteids  are  required  to  replace  the  used-up  nitrogenous  tissues,  e.g.,  for 
muscles.     They  contain  15.4  to  16.5  per  cent.  N. 

The  proteids  are  in  blood  =  20.56  per  cent.;  muscles,  19.9  per  cent.;  liver,  11.74  per  cent.; 
brain,  8.63  per  cent.;  blood  plasma,  7.5  per  cent.;  milk,  3.94  per  cent.;  lymph,  2.46  per  cent. 
According  to  Pfliiger  and  Bohland,  a  youth  of  full  stature,  and  62  kilos.  [136  lbs.]  weight,  decom- 
poses 89.9  grms.  of  albumin  daily. 

Asparagin,in  combination  with  gelatin,  can  replace  albumin  in  the  food  {  Wets ie),  while  asparagin 
alone  hmits  the  decomposition  of  albumin  in  herbivora  but  not  in  carnivora  (J^.  Alimk').  Ammoniacal 
salts,  glycocoll,  sarkosin,  and  benzamid  increase  with  the  amount  of  albumin  in  the  body. 

4.  At  least  one  fat  (§  251),  or  a  digestible  carbohydrate  (§  252).  These 
chiefly  serve  to  replace  the  transformed  fats  and  non-nitrogenous  constituents. 
Owing  to  the  large  amount  of  C  which  they  contain,  when  they  undergo  oxidation, 
they  form  the  chief  source  of  the  heat  of  the  body  (§  206).  Fats  and  carbohydrates 
may  replace  each  other  in  the  food,  and  in  inverse  proportion  too,  corresponding 
to  the  amount  of  C  which  each  contains.  As  far  as  the  mere  evolution  of  heat  is 
concerned^  100  parts  of  fat  =  256  of  grape  sugar  =  234  of  cane  sugar  =  221  of 
dry  starch  (^Rubnet-).     A  man  consumes  210  grms.  fat  daily. 

[5.  Every  proper  diet  ought  to  have  a  certain  degree  of  sapidity  or  flavor.  The  substances 
which  give  this  are  not  useful  in  the  evolution  of  energy  or  building  up  the  tissues,  but  they  stimulate 
the  nervous  system  and  excite  secretion.  They  are  called  "Genussmittel"  (means  of  enjoying  food) 
by  the  Germans,  but  we  have  no  exact  equivalent  for  this  word  in  English,  though  the  articles  them- 
selves are  included  under  our  expression  "  condiments."  These  substances  are  the  aromatic  matter 
in  roast  meat  (osmasome),  tea,  vinegar,  salt,  mustard,  pepper,  etc.] 

[Condition  of  Diet  for  Health. — In  an  adequate  diet,  not  only  (i)  should 
the  total  quantity  be  sufficient  and  not  more  than  sufficient,  but  (2)  the  constitu- 
ents should  exist  in  proper  proportions,  (3)  be  digestible,  and  (4)  the  whole  should 
be  in  good  condition,  wholesome,  and  not  adulterated  with  any  substance  preju- 
dicial to  health.] 

With  regard  to  the  relative  proportions  of  the  various  kinds  of  food  which 
ought  to  be  taken,  experience  has  shown  that  the  diet  best  suited  for  the  body 
must  contain  1  part  of  nitrogenous  foods  to  3^  or,  at  most,  4^  of  the  non-nitrogenous. 
Looking  at  ordinary  foods  from  this  point  of  view,  we  see  how  far  they  correspond 
to  this  requirement,  and  how  several  substances  may  be  combined  to  produce  a 
satisfactory  diet. 

Nit.  Non-Nit.!  Nit.  Non-Nit.  Nit.  Non-Nit. 

1.  Veal, 10  I       j  8.  Pork,    ...     10  30  \     14.  Barley  meal,  .  10  57 

2.  Hare's  flesh,  .    .  10  219.  Cow's  milk,    10  30  15.  White 

3.  Beef, 10  17       j  10.  Human  milk,    10  37  :                 potatoes,     .  10  86 

4.  Lentils,  ....  10  21       I  11.  W  beaten  16.  Blue     "  .10  115 

5.  Beans,    ....  10  22       j  flour,    .    .     10  46  1      17.  Rice,  ....  10  123 

6.  Peas, ID  23       i  12.  Oat  meal,      .10  50  18.  Buckwheat 

7.  Mutton,  ....  10  27       1  13.   Rye  meal,    .10  57  1                 meal,  ...  10  130 

An  examination  of  this  table  shows  that,  in  addition  to  human  milk,  wheat  flour  has  the  right 
proportion  of  nitrogenous  to  non-nitrogenous  substances.  A  man  who  tries  to  nourish  himself  on 
beef  alone,  commits  as  great  a  mistake  as  the  one  who  would  feed  himself  on  potatoes  alone. 
Experience  has  taught  people  that  man  may  live  upon  milk  and  eggs,  but  that  in  addition  to  flesh 
we  must  eat  bread  or  potatoes,  while  pulses  require  fat  or  bacon. 

The  diet  varies  with  the  climate  and  with  the  season  of  the  year.  As  the  organism  must 
produce  more  heat  in  cold  latitudes,  the  inhabitants  of  northern  climates  must  eat  more  non-nitro- 
genous foods,  such  as  fats  and  sugars  or  starches,  which,  on  account  of  the  large  amoimt  of  C  they 
contain,  are  admirably  adapted  for  producing  heat  (|  214,  I,  4). 

The  graphic  representation  of  the  composition  of  foods  (Fig.  238;  shows  the 


406 


DAILY    QUANTITY    OF    FOOD    REQUIRED. 


relative  proportions  of  the  most  important  food  stuffs,  and  how  they  vary  from 
the  standard  of  i  nitrogenous  to  3^3  or  4^4  non-nitrogenous. 

The  absolute  amount  of  food  stuffs  required  by  an  adult  in  twenty-four  hours 
depends  ui)on  a  variety  of  conditions.  As  the  food  represents  the  chemical 
reservoir  of  i)otential  energy,  from  which  the  kinetic  energy  (in  its  various  forms) 
and  the  heat  of  the  body  are  obtained,  the  absolute  amount  of  food  must  be 
increased  when  the  body  loses  more  heat,  as  in  winter,  and  when  more  muscular 
activity  (work)  is  accomjilished.  As  a  general  rule  an  adult  requires  daily  130 
grammes  proteids,  84  grammes  fats,  404  grammes  carbohydrates,  and 
30  grammes  salts. 

A  Healthy  Adult  requires  in  24  Hours,  of  water-free  solids — 


Food  in  Grammes. 


At  Rest. 
(Play/air.) 


Moderate  Work. 
(Moles  :hott.) 


Proteids, 70.87 

Fats, !  28.35 

Carbohydrates  (Sugar,  Starch,  etc . ) ,  3 1 o. 20 

Salts, 14.00 


130 
84 

404 
30 


Laborious  Work. 


(Play/air.) 


155.92 
70.87 

56750 
40.00 


(zi.  Pettenko/er 
andv.  Voit.) 


137 

117 

352 
40 


[When  we  record  these  numbers  in  ounces  we  get  the  following  results  as 
■water-free  solids  required  by  an  average  man  {Farkes)  : — 


Proteids, 

Fats, 

Carbohydrates,     .    .    . 
Salts, 

Total  water-free  food, 


At  Rest. 


2-5 
I.O 

12.0 

05 


Ordinary  Work. 


4.6 

30 

14.4 

1.0 


Laborious  Work. 


6     to    7 

3-5  10    4-5 
16     to  18 

1.2  to      1.5 


16.0 


23.0 


26.7  to  31.0 


During  ordinary  work  the  proportion  is  about :  — 

Proteids  i  :   fats  0.6  :  carbohydrates  3.0, 
/.  e.,  I  nitrogenous  to  3.6  non-nitrogenous.] 

[In  a  diet  for  ordinary  work  (23  oz.  of  dry  solids)  a  man  takes  about  y^  part 
of  his  own  weight  daily;  ordina?y  food,  however,  as  it  is  consumed,  contains 
between  50  and  60  per  cent  of  water  ;  if  we  add  this  proportion  of  water  to  the 
actually  dry  food,  we  get  48  to  60  oz.  of  ordinary  food  (exclusive  of  liquids). 
But  we  consume  50  to  80  oz.  of  water  in  some  liquid  form,  making  the  total 
amount  of  water  70  to  90  oz.  (^Farkes).'\ 

The  following  tables  show  the  elementary  composition  of  the  income  and 
expenditure : — 

An  Adult  doing  a  Moderate  Amount  of  Work  takes  in : — 


c. 

H. 

N. 

0. 

120  grammes  albumin, 
90         "           fats, 
330         "           starch, 

containing 

X 

64.18 

70.20 

146.82 

8.60 
10.26 
20.33 

18.88 

28.34 

9-54 

162.85 

a 

281.20 

>  3919 

18.88 

200.73 

DAILY    QUANTITY   OF    FOOD    REQUIRED. 


407 


Add    744.11  grm.  O  from  the  air  by  respiration. 
"     2818  "     H.fi. 

"         32  "     Inorganic  compounds  (salts). 

The  whole  is  equal  to  3^  kilos.  [7  lbs.],  /.  e.,  about  -^  of  the  body  weight;  so 
that  about  6  per  cent,  of  the  water,  about  6  per  cent,  of  the  fat,  about  i  percent, 
albumin,  and  about  0.4  per  cent,  of  the  salts  of  the  body  are  daily  transformed 
within  the  organism. 

An  Adult  doing  a  Moderate  Amount  of  Work  gives  off,  in  grammes : — 


By  respiration, 
Perspiration, 
Urine,    .    .    .    . 
Faeces,  .    .    .    . 


Water. 


330 
660 

1700 

128 


2818 


c. 


2.6 

9.8 

20.0 


281.2 


3-3 
30 


6.3 


15-8 
3-0 


651-15 
7.2 
II. I 
'  12.0 


681.45 


Add  to  this  (besides  2818  grammes  water  as  drink)  296  grammes  water  formed  in  the  body  by  the 
oxidation  of  H.  These  296  grammes  of  water  contain  34.89  grms.  H,  and  263.41  grms.  O;  26 
grms.  of  salts  are  given  off  in  the  urine,  and  6  by  the  faeces.  96.5  grms.  of  proteid  (=  1.46  grm. 
per  kilo.)  are  used  up  by  a  resting  adult  in  24  hours;  but  while  working  107.6  grms.  are  used. 
Nominally  2.3  times  as  much  fat  as  albumin  are  used  up. 

The  investigations  of  the  Munich  School  have  shown  that  the  following  numbers  represent  the 
minimum  amount  of  food  necessary  for  different  ages  : — 


Age. 


Child  until  i^  years,  .    . 
"     from  6  to  15  years, 
Man  (moderate  work),     . 
Woman,  " 

Old  man, 

Old  woman, 


Nitrogenous. 


20-36  grms. 
70-80 
1x8 
92 


Fat. 


30-45  grms. 
37-50      " 
56      " 

44  " 
68  " 
50     " 


Carbohydrates. 


60-90  grms. 
250-400  " 
500  " 
400  " 
350  " 
260     " 


Small  animals  have  a  more  lively  metabolism  than  large  ones.  In  small  animals  the  decomposi- 
tion of  albumin  per  unit  weight  of  body  is  greater  than  in  large  animals  [v.  Vuit).  Small  animals 
as  a  rule  consume  more  proteid  than  larger  ones,  because  they  generally  have  less  bodily  fat 
{^Ricbner'). 

Relation  of  N  to  C. — In  most  of  the  ordinary  articles  of  diet,  nitrogenous 
and  non-nitrogenous  substances  are  present,  but  in  very  varying  proportion,  in 
the  different  foods.  Man  requires  that  these  shall  be  in  the  proportion  of  i  :  3!- 
to  I  :  4|-.  If  food  be  taken  in  which  this  proportion  is  not  observed,  in  order  to 
obtain  the  necessary  amount  of  that  substance  which  is  contained  in  too  small  pro- 
portion in  his  food,  he  must  consume  far  too  much  food.  In  order  to  obtain  the 
130  grammes  of  proteids  necessary  a  person  must  use 


Cheese, 388  grms. 

Lentils,      491     " 

Peas,      582     " 


Beef, 614  grms. 

Eggs, 968     " 

Wheat  bread,   .    .    .  1444     " 


Rice,  .  .  . 
Rye  bread. 
Potatoes,    . 


2562  grms 
2875     " 
10,000     ' ' 


provided  he  were  to  take  only  one  of  these  substances  as  food ;  so  that  if  a  work- 
man were  to  live  on  potatoes  alone,  in  order  to  get  the  necessary  amount  of  N  he 
would  have  to  consume  an  altogether  excessive  amount  of  this  kind  of  food. 

To  obtain  the  448  grammes  of  carbohydrates,  or  the  equivalent  amount 
of  fat  necessary  to  support  him,  a  man  must  eat 


Rice, 572  grms. 

Wheat  bread,    .    .    .    625     " 
Lentils, 806     " 


Peas 819  grms. 

Eggs, 902     " 

Rye  bread,     ....    930     " 


Cheese, 201 1  grms. 

Potatoes,    ....    2039     " 
Beef, 2261     " 


408 


LOSS   OF   WEIGHT    DURING    STARVATION. 


SO  that  if  he  were  to  live  upon  cheese  or  flesh  alone,  he  would  require  to  eat  an 
enormous  amount  of  these  substances. 

In  the  case  of  herbivora,  the  pro])oriion  of  nitrogenous  to  non-nitrogenous  food  necessar)-  is  l  of 
the  former  to  8  or  9  parts  of  the  latter. 

237.  HUNGER  AND  STARVATION.— If  a  warm-blooded  animal 
be  deprived  of  all  food,  it  must,  in  order  to  maintain  the  temperature  of  its 
body  and  to  produce  the  necessary  amount  of  mechanical  work,  transform  and 
utilize  the  potential  energy  of  the  constituents  of  its  own  body.  The  result  is 
that  its  body  weight  diminishes  from  day  to  day,  until  death  occurs  from  star- 
vation. 

The  following  table,  from  Bidder  and  Schmidt,  shows  the  amounts  of  the  different  excreta  in  the 
case  of  a  starved  cat : — 


Day. 

Body 
weight. 

Water 
taken. 

Urine. 

Urea. 

Inorganic 

Substances 

in  Urine. 

Dry 
Faeces. 

Expired  C. 

Water  in 

Urine 

and  Faeces. 

I. 

2464 

98 

7-9 

1-3 

1.2 

139 

91.4 

2. 

2297 

II.5 

54 

5-3 

0.8 

1.2 

12.9 

50-5 

3- 

2210 

45 

4.2 

0.7 

I.I 

'3 

42.9 

4. 

2172 

68.2 

45 

3-8 

0.7 

I.I 

12.3 

43 

5- 

2129 

55 

4-7 

0.7 

1-7 

1 1.9 

54-1 

6. 

2024 

44 

4-3 

0.6 

0.6 

11.6 

41. 1 

7- 

1946 

40 

3-8 

0-5 

0.7 

II 

37-5 

8. 

1873 

42 

3-9 

0.6 

I.I 

10.6 

40 

9- 

I7S2 

15.2 

42 

4 

0.5 

1-7 

10.6 

41.4 

10. 

I717 

35 

3-3 

04 

1-3 

lo-s 

34 

II. 

1695 

4 

32 

2.9 

0-5 

I.I 

10.2 

30.9 

12. 

1634 

22.5 

30 

2.7 

0.4 

I.I 

10.3 

29.6 

13- 

1570 

71 

40 

3-4 

0.5 

0.4 

10. 1 

36.6 

14- 

1518 

3 

41 

3-4 

05 

03 

9-7 

38 

15- 

1434 

41 

2.9 

0.4 

0.3 

9-4 

38.4 

16. 

1389 

48 

3 

0.4 

0.2 

8.8 

45-5 

17- 

1335 

28 

1.6 

0.2 

0.3 

7.8 

26.6 

i8.t 

1267 

13 

0.7 

0.1 

0-3 

6.1 
190.7 

12.9 
734-4 

-II97 

131-5 

733 

65.8 

9.8 

157 

The  cat  lost  1197  grms.  in  weight  before  it  died,  and  this  amount  is  apportioned 
in  the  following  way:  204.43  grams.  (=17.01  per  cent.)  loss  of  albumin;  132.75 
grms.  (=  11.05  per  cent.)  loss  of  fat;  863.82  grms.  loss  of  water  (=  71.91  per 
cent,  of  the  total  body  weight). 

Methods. — In  order  to  investigate  the  condition  of  inanition  it  is  necessary  (i)  to  weigh  the 
animal  daily;  (2)  to  estimate  daily  all  the  C  and  N  given  off  from  the  body  in  the  faxes,  urine,  and 
expired  air.  The  N  and  C,  of  course,  can  only  be  obtained  from  the  decomposition  of  tissues  con- 
taining them. 

Among  the  general  phenomena  of  inanition,  it  is  found  that  strong,  well-nourished  dogs  die 
after  4  weeks,  man  after  21  to  24  days — (6  melancholies  who  took  water  died  after  51  days) ;  small 
mammals  and  birds  9  days,  and  frogs  9  months.  Vigorous  adults  die  when  they  lose  ^*j  of  their 
body  weight,  but  young  individuals  die  much  sooner  than  adults.  The  symptoms  are  obvious: 
The  mouth  is  drj',  the  walls  of  the  alimentary  canal  become  thin,  and  the  digestive  secretions  cease 
to  be  formed;  pulse  beats  and  respirations  are  fewer;  urine  ver)'  acid,  from  the  presence  of  an  in- 
creased amount  of  sulphuric  and  phosphoric  acids,  while  the  chlorine  compounds  rapidly  diminish 
and  almost  disappear.  The  blood  contains  less  water  and  the  plasma  less  albumin,  the  gall  bladder 
is  distended,  which  indicates  a  continuous  decomposition  of  blood  corpuscles  within  the  liver.  The 
liver  is  small  and  very  dark  colored,  the  muscles  are  very  brittle  and  dry,  so  that  there  is  great 
muscular  weakness,  and  death  occurs  with  the  signs  of  great  depression  and  coma. 

The  relations  of  the  metabolism  are  given  in  the  foregoing  table,  the  diminu- 
tion in  the  excretion  of  urea  is  much  greater  than  that  of  CO2,  which  is  due  to 


METABOLISM    ON    A    FLESH    DIET.  409 

a  larger  amount  of  fats  than  proteids  being  decomposed.  According  to  the 
calculation,  there  is  daily  a  tolerably  constant  amount  of  fat  used  up,  while,  as 
starvation  continues,  the  proteids  are  decomposed  in  much  smaller  amounts  from 
day  to  day,  although  the  drinking  of  water  accelerates  their  decomposition. 

Loss  of  ^A^eight  of  Organs. — It  is  of  importance  to  determine  to  what 
extent  the  individual  organs  and  tissues  lose  weight ;  some  undergo  simple  loss 
of  weight,  e.  g.,  the  bones,  the  fat  undergoes  very  considerable  and  rapid  decom- 
position, while  other  organs,  as  the  heart,  undergo  little  change,  because  they 
seem  to  be  able  to  nourish  themselves  from  the  transformation  products  of  other 
tissues. 

A  starving  cat,  according  to  v.  Voit,  lost — 

Per  cent.  Per  cent,  of                                                               Per  cent.  Per  cent,  of 

originally  the  total  loss  of                                                            originally  the  total  loss  of 

present.  body  weight.                                                                present.  body  weight. 

1.  Fat, 97  26.2  10.  Lungs, 17.7  0.3 

2.  Spleen, 66.7  0.6  11.  Pancreas, 17.0  o.i 

3.  Liver, 53.7  4.8  12.  Bones, 13.9  5.4 

4.  Testicles, 40.0  o.i            i    I3-  Central  Nervous  Sys- 


Per  cent, 
the  total  lo 
body  weig 
26.2 

of 

;sof 
ht. 

10. 

0.6 

II. 

4.8 

12. 

O.I 

13- 

42.2 

0.6 

14- 
15- 

tern 3.2  O.I 

Heart, 2.6  0.02 

Total  loss  of  the  rest 

of  the  body,     .    .    .  36.8  5.0 


5.  Muscles,      30.5 

6.  Blood, 27.0 

7.  Kidneys, 25.9 

8.  Skin, 20.6 

9.  Intestine, 18.0 

There  is  a  very  important  difference  according  as  the  animals  before  inanition 
have  been  fed  freely  on  flesh  and  fat  [/.  e.,  if  they  have  a  surplus  store  of  food 
within  themselves],  or  as  they  have  merely  had  a  subsistence  diet.  Well-fed  ani- 
mals lose  weight  much  more  rapidly  during  the  first  few  days  than  on  the  later 
days.  V.  Voit  thinks  that  the  albumin  derived  from  the  excess  of  food  occurs  in 
a  state  of  loose  combination  in  the  body  as  "  circulating"  or  " storage  albumin," 
so  that  during  hunger  it  must  decompose  more  rapidly  and  to  a  greater  extent 
than  the  "  organic  albumin,"  which  forms  an  integral  part  of  the  tissues  (  §  236). 
Further,  in  fat  individuals,  the  decomposition  of  fat  is  much  greater  than  in 
slender  persons. 

238.  METABOLISM  ON  A  PURELY  FLESH  DIET.— A  man  is 

not  able  to  maintain  his  metabolism  in  equilibrium  on  a  purely  flesh  diet;  if  he  were 
compelled  to  live  on  such  a  diet,  he  would  succumb.  The  reason  is  obvious.  In 
beef  the  proportion  of  nitrogenous  to  non-nitrogenous  elementary  constituents  of 
food  is  I  :  1.7  (p.  405).  A  healthy  person  excretes  280  grammes  [8  to  9  oz.]  01 
carbon  in  the  form  of  CO2,  in  the  expired  air,  and  in  the  urine  and  faeces.  If  a 
man  is  to  obtain  280  grammes  C.  from  a  flesh  diet  he  must  consume — digest  and 
assimilate — more  than  2  kilos.  [4.4  lbs.]  of  beef  in  twenty-four  hours.  But  our 
digestive  organs  are  unequal  to  this  task  for  any  length  of  time.  The  person  is 
soon  obliged  to  take  less  beef,  which  would  necessitate  the  using  of  his  own 
tissues,  at  first  the  fatty  parts  and  afterward  the  proteid  substances. 

A  carnivorous  animal  (dog),  whose  digestive  apparatus,  being  specially  adapted  for  the  diges- 
tion of  flesh,  has  a  short  intestine  and  powerfully  active  digestive  fluids,  can  only  maintain  its  meta- 
bolism in  a  state  of  equilibrium  when  fed  on  a  flesh  diet  free  from  fat,  provided  its  body  is  already 
well  supplied  with  fat,  and  is  muscular.  It  consumes  23-  to  2V  P^''^  ^^  the  weight  of  its  body  in  flesh, 
so  that  the  excretion  of  urea  increases  enormously.  If  it  eats  a  larger  amount,  it  may  "put  on  flesh," 
when,  of  course,  it  requires  to  eat  more  to  maintain  itself  in  this  condition,  until  the  limit  of  its  diges- 
tive capacity  is  reached.  If  a  well-nourished  dog  is  fed  on  less  than  ^-g  to  -^^  of  its  body  weight  of 
flesh,  it  uses  part  of  its  own  fat  and  muscle,  gradually  diminishes  in  weight,  and  ultimately  succumbs. 
Poorly  fed,  non-muscular  dogs  are  unable  from  the  very  beginning  to  maintain  their  metabolism  in 
equilibrium  for  any  length  of  time  on  a  purely  flesh  diet,  as  they  must  eat  so  large  a  quantity  of  flesh 
that  their  digestive  organs  cannot  digest  it.  The  herbivora  cannot  live  upon  flesh  food,  as  their 
digestive  apparatus  is  adapted  solely  for  the  digestion  of  vegetable  food. 

[The  proteid  metabolism  depends  (i)  on  the  amount  of  proteids  ingested, 


410  A    DIET   OF    FAT    OR    OF    CARBOHYDRATES. 

for  the  great  mass  of  these  becomes  changed  into  circulating  albumin  ;  (2)  upon 
the  previous  condition  of  nutrition  of  the  organism,  for  we  know  that  a  certain 
amount  of  proteid  may  produce  very  different  results  in  the  same  individual  when 
he  is  in  good  health,  and  when  he  has  suffered  from  some  exhausting  disease. 
(3)  The  use  of  other  foods,  e.  g.,  fats  and  carbohydrates.  If  a  certain  amount 
of  fat  be  added  to  a  diet  of  flesh,  much  less  flesh  is  required,  so  that  the  N  meta- 
bolism is  reduced  by  fat.  This  is  spoken  of  as  the  "albumin-sparing  action  " 
of  fats.] 

Exactly  the  same  result  occurs  with  other  forms  of  proteids,  as  with  flesh. 
It  has  been  proved  that  gelatin  may  to  a  certain  extent  replace  proteids  in  the 
food,  in  the  proportion  of  2  of  gelatin  to  i  of  albumin.  The  carnivora,  which  can 
maintain  their  metabolism  in  equilibrium  by  eating  a  large  amount  of  flesh,  can 
do  so  with  less  flesh  when  gelatin  is  added  to  their  food.  A  diet  of  gelatin  alone, 
which  produces  much  urea,  is  not  sufficient  for  this  purpose,  and  animals  soon  lose 
their  appetite  for  this  kind  of  food. 

[Gelatin. — Voithas  shown  that  gelatin  readily  undergoes  metabolism  in  the  body  and  forms  urea, 
and  if  a  small  quantity  be  taken,  it  is  completely  and  rapidly  metabolized.  When  administered  it 
acts  just  like  fats  and  carbohydrates,  as  an  "albumin  sparing"  substance.  It  seems  that  gelatin  is 
not  available  directly  for  the  growth  and  repair  of  tissues.]  Owing  to  the  great  solubility  of  gelatin, 
its  value  as  a  food  used  to  be  greatly  discussed.  The  addition  of  gelatin  in  the  form  of  calf 's-foot 
jelly  is  recommended  to  invalids.  [When  a  large  amount  of  gelatin  is  given  as  food,  owing  to  the 
large  and  rapid  excretion  of  urea,  the  latter  excites  diuresis.]  When  chondrin  is  given  along  with 
flesh  for  a  time,  grape  sugar  is  found  in  the  urine. 

[The  Metabolism  of  Peptones. — Most  of  the  proteids  absorbed  into  the 
blood  are  previously  converted  into  peptones  by  the  digestive  juices.  It  has  been 
asserted,  more  especially  by  Briicke,  that  some  albumin  is  absorbed  unchanged 
(§  192,  4),  and  that  only  this  is  capable  of  forming  organic  albumin,  while  the 
peptones,  after  undergoing  a  reconversion  into  albumin,  undergo  decomposition 
as  such.  This  view  is  opposed  by  many  observers,  who  maintain  that  peptones 
perform  all  the  functions  of  proteids,  so  that  peptones,  with  the  other  necessary 
constituents  of  an  adequate  diet,  suffice  to  maintain  a  proper  standard  of  health.] 

239.  A  DIET  OF  FAT  OR  OF  CARBOHYDRATES.  — If  fat 
alone  be  given  as  a  food,  the  animal  lives  but  a  short  time.  The  animal  so  fed 
excretes  even  less  urea  than  when  it  is  starving ;  so  that  the  consumption  of  fat 
limits  the  decomposition  of  the  animal's  own  proteids.  As  fat  is  an  easily  oxi- 
dized body,  it  yields  heat  chiefly,  and  becomes  sooner  oxidized  than  the  nitrogen- 
ous proteids  which  are  oxidized  with  more  difficulty.  If  the  amount  of  fat  taken 
be  very  large,  all  the  C  of  the  fat  does  not  reappear,  e.  g.,  in  the  CO2  of  the 
expired  air ;  so  that  the  body  must  acquire  fat,  while  at  the  same  time  it  decom- 
poses proteids.  The  animal  thus  becomes  poorer  in  proteids  and  richer  in  fats  at 
the  same  time. 

[The  metabolism  of  fats  is  not  dependent  on  the  amount  of  fats  taken  with 
the  food.  I.  It  is  largely  influenced  by  work,  /.  e.,  by  the  activity  of  the  tissues, 
and  in  fact  with  muscular  work  CO.,  is  excreted  in  greatly  increased  amount 
(§  127,  6).  2.  By  the  temperature  of  the  surroundings,  as  more  CO^  is  pro- 
duced in  the  cold  (§  214,  2),  and  far  more  fatty  foods  are  required  in  high  lati- 
tudes. In  their  action  on  the  organism,  proteids  and  fats  so  far  oppose  each 
other,  as  the  former  increase  the  waste,  and  therefore  oxidation,  while  the  latter 
diminish  it,  probably  by  affecting  the  metabolic  activity  of  the  cells  themselves 
(^Bauer).  As  a  matter  of  fact,  fat  animals  or  persons  bear  starvation  better  than 
spare  individuals.  In  the  latter,  the  small  store  of  fat  is  soon  used  up,  and  then 
the  albumin  is  rapidly  decomposed.  For  the  same  reason  corpulent  persons  are 
very  apt  to  become  still  more  so,  even  on  a  very  moderate  diet.] 

When  carbohydrates  alone  are  given,  they  must  first  be  converted  by  diges- 
tion into  sugar.     The  result  of  such  feeding  coincides  pretty  nearly  with  feeding 


ORIGIN    OF    FAT    IN    THE    BODY.  411 

with  fat  alone.  But  the  sugar  is  more  easily  burned  or  oxidized  within  the  body 
than  the  fat,  and  17  parts  of  carbohydrate  are  equal  to  to  parts  of  fat.  Thus 
the  diet  of  carbohydrates  limits  the  excretion  of  urea  more  readily  than  a  purely 
fat  diet.  The  animals  lose  flesh,  and  appear  even  to  use  up  part  of  their  own  fat. 
[The  metabolism  of  carbohydrates  also  serves  to  diminish  the  proteid 
metabolism,  as  they  are  rapidly  burned  up,  and  thus  "spare"  the  circulating 
albumin.  But  Pettenkofer  and  Voit  assert  that  they  are  rapidly  destroyed  in  the 
body,  even  when  given  in  large  amount,  so  that  they  differ  from  fats  in  this 
respect.  They  are  more  easily  oxidized  than  fats,  so  that  they  are  always  con- 
sumed first  in  a  diet  of  carbohydrates  and  fats.  By  being  consumed  they  protect 
the  proteids  and  fats  from  consumption.] 

The  direct  introduction  of  grape  and  cane  sugar  into  the  blood  does  not  increase  the  amount  of 
O  used,  but  the  amount  of  J^Oj  is  increased.  [The  doctrine  of  Liebig,  that  the  oxygen  taken  in  is 
a  measure  of  the  metabolic  processes,  is  refuted  by  these  and  other  experiments.  It  would  seem 
that  fat  is  not  directly  oxidized  by  O,  but  that  it  is  split  up  into  other  simpler  compounds  which  are 
slowly  and  gradually  oxidized ;  in  fact,  fat  may  lessen  the  amount  of  O  taken  in,  as  it  diminishes 
waste.] 

240.  FLESH  AND  FAT,  OR  FLESH  AND  CARBOHYDRATES. 

— An  amount  of  flesh  equal  to  ^V  to  -jio  of  the  weight  of  the  body  is  required  to 
nourish  a  dog,  which  is  fed  on  a  purdy  flesh  diet;  if  the  necessary  amount  of  fat 
or  carbohydrates  be  added  to  the  diet,  a  smaller  quantity  of  flesh  is  required  {v. 
Voit).  For  100  parts  of  fat  added  to  the  flesh  diet,  245  parts  of  dry  flesh  or  227 
of  syntonin  can  be  dispensed  with.  If  instead  of  fats  carbohydrates  are  added, 
then  100  parts  of  fat  =  230  to  250  of  the  latter  (^Rubner).  When  the  amount 
of  flesh  is  insufficient,  the  addition  of  fat  or  carbohydrates  to  the  food  always 
limits  the  decomposition  of  the  animal's  own  substance.  Lastly,  when  too  much 
flesh  is  given  along  with  these  substances,  the  weight  of  the  body  increases  more 
with  them  than  without  them.  Under  these  circumstances,  the  animal's  body 
puts  on  more  fat  than  flesh.  The  consumption  of  O  in  the  body  is  regulated 
by  the  mixture  of  flesh  and  non-nitrogenous  substances,  rising  and  falling  with 
the  amount  of  flesh  consumed.  It  is  remarkable  that  more  O  is  consumed  when 
a  given  amount  of  flesh  is  taken,  than  when  the  same  amount  of  flesh  is  taken 
with  the  addition  of  fat. 

It  seems  that,  instead  of  fat,  the  corresponding  amount  of  fatty  acids  has  the  same  effect  on  the 
metabolism.  [If  a  dog  be  fed  with  fatty  acids  and  a  sufficient  amount  of  proteid,  no  fatty  acids  are 
found  in  the  chyle,  while  fat  is  formed  synthetically,  the  glycerin  for  the  latter  probably  being  pro- 
duced in  the  body.]  They  are  absorbed  as  an  emulsion  just  like  the  fats.  When  so  absorbed,  they 
seem  to  be  reconverted  into  fats  in  their  passage  from  the  intestine  to  the  thoracic  duct  probably  by 
the  action  of  the  leucocytes  [J.  Munk,  IViil).  [Glycerin  in  small  doses  has  no  effect  on  the  meta- 
bolism of  proteid,  but  in  large  doses  it  increases  it.  It  is  consumed  in  the  body,  as  shown  by  experi- 
ments on  the  respiratory  products,  and  it  prevents  a  certain  amount  of  fat  from  being  used  up. 
About  20  per  cent,  is  excreted  in  the  urine  {Arnschink).'] 

241.  ORIGIN   OF   FAT    IN   THE    BODY.— I.  Fart  oi  tht  fat  of  the 

body  is  derived  directly  from  the  fat  of  the  food,  i.  e.,  it  is  absorbed  and  depos- 
ited in  the  tissues.  This  is  shown  by  the  fact  that,  with  a  diet  containing  a  small 
amount  of  albumin,  the  addition  of  more  fat  causes  a  deposition  of  a  larger 
aniount  of  fat  in  the  body  {v.  Voit,  Hofmami). 

[Hofmai:in  starved  a  fat  dog  for  30  days  until  all  its  fat  was  used  up.  He  fed  it  on  lard  and  a 
little  albumin  for  5  days  and  then  killed  it.  In  5  days  it  absorbed  1854  grms.  of  fat  and  254  grms. 
of  albumin.  It  added  to  its  body  1353  grms.  of  fat;  but  this  amount  could  not  be  formed  from  the 
proteids  of  the  food,  and  therefore  the  fat  must  have  come  from  the  fat  of  the  food.  Pettenkofer 
and  Voit  arrived  at -the  same  result  in  another  way.  They  fed  dogs  on  fish  and  much  fat,  and  by 
their  respiration  apparatus  e.slimated  the  gaseous  income  and  expenditure  {\  122).  All  the  N taken 
in  reappeared  in  the  excreta,  bid  not  all  the  C.  The  amount  of  C  retained  was  very  large,  there- 
fore a  non-nitrogenous  residue  must  have  been  laid  up  in  the  body,  and  it  could  only  be  fat,  as  this 
was  the   only  substance  found  in  large  amount  in  the  body.     They  estimated  the  possible  amoimt  of 


412  ORIGIN    OF    FAT    IN    THE    BODY. 

fat  that  could  be  formed  from  the  proteids,  and  found  that  the  amount  stored  up  was  far  greater  than 
this;  so  that  the  fat  of  the  food  must  have  been  stored  up  in  the  tissues.] 

Lebedefl"  found  that  dogs,  which  were  starved  for  a  month,  so  as  to  get  rid  of  all  their  own  fat,  on 
being  fed  with  linseed  oil,  or  mutton  suet  and  Hesh,  had  these  fats  restored  to  their  tissues.  These 
fats,  therefore,  must  have  been  absorbed  and  deposited.  J.  Munk  found  the  same  on  feeding  animals 
with  rape-seed  oil.  Fatty  acids  may  also  contribute  to  ihc  formation  of  fats,  as  glycerin  when 
formed  in  the  body  must  be  stored  up  during  metabolism  {J.  Munk). 

Fatty  acids  may  contribute  to  the  formation  of  fats  by  union  with  the  glycerin  of  the  body  during 
the  metabolism. 

II.  A  second  source  of  the  fats  is  albuminous  bodies.  In  the  case  of  the 
formation  of  fats  from  proteids,  which  may  yield  ii  per  cent,  of  fat  (according 
to  Henneberg  loo  parts  of  dry  albumin  can  form  51.5  parts  of  fat),  these  proteids 
split  up  into  a  non-nitrogenous  and  a  nitrogenous  atomic  compound.  The  former, 
during  a  diet  containing  much  albumin,  when  it  is  not  coptpletely  oxidized  into 
CO.^,  and  H2O,  is  the  substance  from  which  the  fat  is  formed — the  latter  leaves 
the  body  oxidized  chiefly  to  the  stage  of  urea. 

Examples. — That  fats  are  formed  from  proteids  is  shown  by  the  following:  I.  A  cow  which 
produces  i  lb.  of  butter  daily  does  not  take  nearly  this  amount  of  fatty  matter  in  its  food,  so  that 
the  fat  would  appear  to  be  formed  from  vegetable  proteids.  2.  Carnivora  giving  suck,  when  fed  on 
plenty  of  flesh  and  some  fat,  yield  milk  rich  in  fat.  3.  Dogs  fed  with  plenty  of  flesh  and  some  fat, 
add  more  fat  to  their  bodies  than  the  fat  contained  in  the  food.  4.  Fatty  degeneration,  e.g.,  of 
nerve  and  muscle,  is  due  to  a  decomposition  of  proteids.  5.  The  transformation  of  entire  bodies, 
e.g.,  such  as  have  lain  for  a  long  time  surrounded  with  water,  into  a  mass  consisting  almost  entirely 
of  palmitic  acid  or  adipocere  is  also  a  proof  of  the  transformation  of  part  of  the  proteids  into  fats. 
6.  Fungi  are  also  able  to  form  fat  from  albumin  during  their  growth.  [7.  In  starving  dogs,  Bauer 
estimated  the  N  and  CO.^  given  off,  and  O  taken  in,  and  then  slowly  poisoned  them  with  phosphorus, 
and  he  found  that  the  excretion  of  N  was  increased  twofold,  while  the  excretion  of  CO^  and  the 
absorption  of  O  were  diminished  one-half  Therefore  from  a  large  amount  of  nitrogenous  tissue,  a 
nitrogenous  body  and  a  small  amount  of  a  carbonaceous  compound  were  excreted,  while  a  large 
amount  of  a  non-nitrogenous  residue  was  retained  unconsumed.  There  was  fatty  degeneration  of 
all  the  organs,  the  fat  being  derived  from  the  non-nitrogenous  part  of  the  proteid.  The  same 
obtains  with  arsenic  and  antimony.] 

Fats  not  merely  absorbed. — Experiments  which  go  to  show  that  the  fat  of  animals,  during 
the  fattening  process,  is  not  absorbed  as  such,  from  the  food,  are  :  I.  Fattening  occurs  with  flesh 
and  soaps ;  it  is  most  improbable  that  the  soaps  are  transformed  into  neutral  fats  by  taking  up  gly- 
cerin and  giving  up  alkali.  2.  If  a  lean  dog  be  fed  with  flesh  and  palmitin-  and  stearin-^oda  soap, 
the  fat  of  its  body  contains,  in  addition  to  palmitin  and  stearin,  o/ein  fat,  so  that  the  last  must  be 
formed  by  the  organism  from  the  proteids  of  the  flesh.  Further,  Ssubotin  found  that,  when  a  lean 
dog  was  fed  on  lean  meat  and  spermaceti  fit,  a  very  small  amount  of  the  latter  was  found  in  the  fat 
of  the  animal.  Although  these  experiments  show  that  the  fat  of  the  body  must  be  formed  from  the 
decomposition  of  proteids,  they  do  not  prove  that  ail  the  fat  arises  in  this  way,  and  that  none  of  it 
is  absorbed  and  redeposited  (§  241,  I). 

III.  According  to  v.  Voit,  no  fat  is  formed  in  the  body  directly  from  carbo- 
hydrates, e.g.,  by  reduction.  As  fattening  occurs  on  a  diet  of  pure  flesh  with 
the  addition  of  carbohydrates,  it  is  assumed  that  the  carbohydrates  are  consumed 
or  oxidized  in  the  body,  and  that  thereby  a  non-nitrogenous  body  derived  from 
the  proteids  is  prevented  from  being  burned  up,  and  that  it  is  changed  into  fat, 
and  stored  up  as  such.  No  doubt  fat  is  formed  indirectly  in  the  blood  in  this  way 
(§  240). 

From  experiments  upon  fattening  animals,  however,  Lawes  and  Gilbert,  Leh- 
mann,  Heiden,  v.  Wolff,  and  others,  think  they  are  entitled  to  conclude  that  the 
carbohydrates  absorbed  are  directly  concerned  in  the  formation  of  fats,  a  view 
which  is  supported  by  Henneberg,  B.  Schulze,  and  Soxhlet.  According  to  Pasteur, 
glycerin  (the  basis  of  neutral  fats)  may  be  formed  from  carbohydrates. 

[Tscherwinsky  fed  two  similar  pigs  from  the  same  litter;  No.  I  weighed  7300  grms. ;  No.  II 
7290  grms.  No.  I  was  killed  and  its  fat  and  proteids  estimated.  No.  II  was  fed  for  four  months 
on  grain  and  then  killed,  the  grain  and  excreta  and  the  undigested  fat  and  proteids  were  aiialyzed, 
so  that  the  amount  of  fat  and  proteid  absorbed  in  four  months  was  estimated.  The  pig  then 
■weighed  24  kilos.,  it  was  killed  and  its  fat  and  proteids  estimated. 


CORPULENCE.  413 

No.  II  contained  2.50  kilos,  albumin  and  9.25  kilos,  fat. 
No.  I  "         0.96     "  "  o.( 

Assimilated,  1.56     "  " 

Taken  in  in  food,  7.49     '*  '• 

Difference,        — 5.93     "  "  +  7-90      "       " 

There  M'ere  therefore  7.90  kilos  of  fat  in  the  body  which  could  not  be  accounted  for  in  the  fat  of 
the  food.  The  5.93  kilos,  of  albumin  of  the  food  which  were  not  assimilated  as  albumin  could 
yield  only  a  small  part  of  the  7.90  kilos  of  fat,  so  that  at  least  5  kilos,  of  fat  must  have  been 
formed  from  carbohydrates.  Lawes  and  Gilbert  calculated  that  40  per  cent,  of  the  fat  in  pigs  was 
derived  from  carbohydrates.  How  the  carbohydrates  are  changed  into  fat  in  the  body  is  entirely 
unknown.] 

Formerly  it  was  believed  that  bees  could  prepare  wax  from  honey  alone ;  this  is  a  mistake — an 
equivalent  of  albumin  is  required  in  addition — the  necessary  amount  is  found  in  the  raw  honey  itself. 

242.  CORPULENCE  — The  addition  of  too  much  fat  to  the  body  is  a  pathological  phenome- 
non which  is  attended  with  disagreeable  consequences.  With  regard  to  the  causes  of  obesity, 
without  doubt  there  is  an  inherited  tendency  (in  ^;^  to  56  per  cent,  of  the  cases)  in  many  families 
— and  in  some  breeds  of  cattle,  to  lay  up  fat  in  the  body,  while  other  families  may  be  richly  supplied 
with  fat,  and  yet  remain  lean.  The  chief  cause,  however,  is  taking  too  much  food,  2.  e.,  more 
than  the  amount  requiied  for  the  normal  metabolism ;  corpulent  people,  in  order  to  maintain  their 
bodies,  must  eat  absolutely  and  relatively  more  than  persons  of  spare  habit,  under  analogous  condi- 
tions of  nutrition  (^  236). 

Conditions  favoring  Corpulence. — (i)  A  diet  rich  in /r(?/fza'j-,  with  a  corresponding  addition 
oi  fat  or  carbohydrates.  As  flesh  or  muscle  is  formed  from  proteids,  and  part  of  the  fat  of  the  body 
is  also  formed  from  albumin  ;  the  assumption  that  fats  and  carbohydrates  fatten,  or,  when  taken 
alone,  act  as  fattening  agents,  is  completely  without  foundation.  (2)  Diniinished  disintegration  of 
materials  within  the  body,  e.g.,  (a)  diminished  nniscitlar  activity  (much  sleep  and  little  exercise); 
((5)  abrogation  of  the  sexzial  fnnctio7is  (as  is  shown  by  the  rapid  fattening  of  castrated  animals,  as 
well  as  by  the  fact  that  some  women,  after  cessation  of  the  menses,  readily  become  corpulent) ;  (^) 
diviinished  mental  activity  (the  obesity  of  dementia),  phlegmatic  temperament.  On  the  contrary, 
vigorous  mental  work,  excitable  temperament,  care  and  sorrow,  counteract  the  deposit  of  fat;  (</) 
diminished  extent  of  the  respiratory  activity,  as  occurs  when  there  is  a  great  deposition  of  fat  in  the 
abdomen,  limiting  the  action  of  the  diaphragm  (breathlessness  of  corpulent  people),  whereby  the 
combustion  of  the  fatty  matters  which  become  deposited  in  the  body  is  limited;  (^e')  a  corpulent  per- 
son requires  to  use  relatively  less  heat-giving  substances  in  his  body,  partly  because  he  gives  off  rela- 
tively less  heat  from  his  compact  body,  than  is  done  by  a  slender,  long-bodied  individual,  and  partly 
because  the  thick  layer  of  fat  retards  the  conduction  of  heat  (|  214,  4).  Thus,  corresponding  to 
the  relatively  diminished  production  of  heat,  more  fat  may  be  stored  up ;  (/")  a  dimimition  of  the 
red  blood  corpuscles,  which  are  the  great  exciters  of  oxidation  in  the  body,  is  generally  followed  by 
an  increase  of  fat — fat  people,  as  a  rule,  are  fat  because  they  have  relatively  less  blood  (|  41) — 
women  with  fewer  red  blood  corpuscles  are  usually  fatter  than  men;  {g")  the  consumption  of  alcohol 
favors  the  conservation  of  fat  in  the  body,  the  alcohol  is  easily  oxidized,  and  thus  prevents  the  fat 
from  being  burned  up  {\  235). 

Disadvantages. — Besides  the  inconvenience  of  the  great  size  and  weight  of  the  body,  corpulent 
people  suffer  from  breathlessness — they  are  easily  fatigued,  are  liable  to  intertrigo  between  the  folds 
of  the  skin,  the  heart  becomes  loaded  with  fat,  and  they  not  unfrequenlly  are  subject  to  apoplexy. 

In  order  to  counteract  corpulence  we  ought  to  (l)  Reduce  ziniforinly  all  articles  of  diet.  The 
diet  and  body  ought  to  be  weighed  from  week  to  week,  and  as  long  as  there  is  no  diminution  in  the 
body  weight  the  amount  of  food  ought  to  be  gradually  and  uniformly  reduced  (notwithstanding  the 
appetite).  This  must  be  done  very  gradually  and  not  suddenly.  A  moderate  reduction  of  fat  and 
carbohydrates  in  a  normal  diet,  at  the  same  time  leads  to  a  diminution  of  the  fat  of  the  body  itself. 
Let  a  person  who  is  capable  of  muscular  exertion  take  156  grms.  proteid,  43  grms.  fat,  and  1 14 
grms.  carbohydrates;  but  in  those  where  congestions,  hydrsemia,  breathlessness  have  taken  place, 
take  170  grms.  proteid,  25  grms.  fat,  and  70  grms.  carbohydrates  {Oertel).  It  is  not  advisable  to 
limit  the  amount  of  fat  and  carbohydrates  alone,  as  is  done  in  the  Banting  cure  or  Bantingism. 
Apart  altogether  from  the  fact  that  fat  is  formed  from  proteids,  if  too  little  non-nitrogenous  food  be 
taken,  severe  disturbance  of  the  bodily  metabolism  is  apt  to  oocur.  (2)  It  is  advisable  during  the 
chief  meal  to  limit  the  consumption  of  fluids  of  all  sorts  (even  until  three-quarters  of  an  hour  there- 
after), and  thus  render  the  absorption  and  digestive  activity  of  the  intestine  less  active  (^Oertel). 
(3 )  The  muscular  activity  ought  to  be  greatly  developed  by  doing  plenty  of  muscular  work,  or 
taking  plenty  of  exercise,  both  physical  and  mental.  (4)  Favor  the  evolution  of  heat  by  taking 
cold  baths  of  considerable  duration,  and  afterward  rubbing  the  skin  strongly  so  as  to  cause  it  to 
become  red ;  further,  dress  lightly,  and  at  night  use  light  bed-clothing ;  tea  and  coffee  are  useful,  as 
they  excite  the  circulation.     (5)   Use  gentle  laxatives;  acid  fruits,  cider;  alkaline  carbonates   (of 


414  METABOLISM    OF   THE    TISSUES. 

Marienbad,  Carlsbad,  Vichy,  Neuenahr,  Ems,  etc.)  act  by  increasing  the  intestinal  evacuations  and 
diminishing  absorption.  (6)  If  from  accumulation  of  (at  there  is  danger  of  failure  of  the  heart's 
action,  Oertel  recoumiends  hill  climbing,  whereby  the  cardiac  muscle  is  exercised  and  strengthened. 
At  the  same  time  the  circulation  becomes  more  lively  and  the  metabolism  is  increased. 

[Oertel's  Method  goes  on  the  idea  of  strengthening  the  cardiac  musculature,  which  is  sought 
to  be  accomplished  by  (i)  limiting  the  amount  of  fluids  consumed,  and  (2)  carefully  regulated  mus- 
cular exertion.  The  amount  of  food  is  lirst  reduced  one-half,  and  the  water  to  a  stdl  lower  amount, 
while  the  nitrogenous  elements  in  food  are  increased,  the  non  nitrogenous  are  decreased.  The  per- 
sm  is  then  instructed  to  take  e.xercise  under  certain  medical  precautions,  first  on  level  ground,  and 
then  on  gradually  increasing  gradients.] 

Fatty  Degeneration. — The  process  of  fattening  consists  in  the  deposition  of  drops  of  fat  within 
the  fat  cells  of  the  panniculus  and  around  the  viscera,  as  well  as  in  the  marrow  of  Ijone  (lut  they 
are  never  deposited  in  the  subcutaneous  tissue  of  the  eyelids,  of  the  penis,  of  the  red  jxirt  of  the 
lips,  in  the  ears  and  nose).  This  is  quite  difierent  from  the  fatty  atrophy  or  fatty  degeneration 
which  occurs  in  the  form  of  fatty  globules  or  granules  in  albuminous  tissues,  e.^^.,  in  muscular  fibres 
(heart),  gland  cells  (liver,  kidney),  cartilage  cells,  lymph  and  pus  corpuscles,  as  well  as  in  nerve 
fibres  separated  from  their  nerve  centres.  The  fat  in  these  cases  is  derived  from  albumin,  much  in 
the  same  way  as  fat  is  formed  in  the  gland  cells  of  the  mammary  and  sebaceous  glands.  Marked 
fatty  degeneration  not  unfrequently  occurs  after  severe  fevers,  and  after  artificial  heating  of  the 
tissues;  when  a  too  small  amount  of  O  is  supplied  to  the  tissues,  as  occurs  in  cases  of  phosphorus 
poisoning  {Bauer) ;  in  drunkards;  after  poisoning  with  arsenic  and  other  substances,  and  after  some 
disturbances  of  the  circulation  and  innervation.  Some  organs  are  especially  prone  to  undergo  fatty 
degeneration  (luring  the  course  of  certain  diseases. 

243.  METABOLISM  OF  THE   TISSUES.— The   blood    stream  is 

the  chief  medium  whereby  new  material  is  supplied  to  the  tissues  and  the  effete 
products  removed  from  them.  The  lymph  which  passes  through  the  thin  capil- 
laries comes  into  actual  contact  with  the  tissue  elements.  Those  tissues  which  are 
devoid  of  blood  vessels  in  their  own  substance,  such  as  the  cornea  and  cartilage, 
receive  nutrient  fluid  or  lymph  from  the  adjacent  capillaries,  by  means  of  their 
cellular  elements,  which  act  as  juice-conducting  media.  Hence,  when  the  normal 
circulation  is  interfered  with,  by  atheroma  or  calcification  of  the  walls  of  the 
blood  vessels,  these  tissues  are  secondarily  affected  [this,  for  example,  is  the  case 
in  arcus  senilis  of  the  cornea,  due  to  a  fatty  degeneration  of  the  corneal  tissue, 
owing  to  some  affection  of  the  blood  vessels  on  which  the  cornea  depends  for  its 
nutrition].  Total  compression  or  ligature  of  all  the  blood  vessels  results  in 
necrosis  of  the  parts  supplied  by  the  ligatured  blood  vessels. 

Atrophies  caused  by  diminution  of  the  normal  supply  of  blood,  gradually,  in  the  course  of  time 
become  less  and  less  {^Samuel). 

Hence,  there  must  be  a  double  ciir7-ent  of  the  tissue  juices  ;  the  afferent  or 
supply  current,  which  supplies  the  new  material,  and  the  efferent  stream, 
which  removes  the  effete  products.  The  former  brings  to  the  tissues  the  proteids, 
fats,  carbohydrates,  and  salts  from  which  the  tissues  are  formed.  It  is  evident 
that  any  interruption  of  the  arterial  supply  to  the  tissues  will  diminish  this  supply. 

That  such  a  current  exists  is  proved  by  injecting  an  indifferent,  easily  recognizable  substance  into 
the  blood,  e.g.,  potassium  ferrocyanide,  when  its  presence  may  be  detected  in  the  tissnes,  to  which 
it  has  been  carried  by  the  outgoing  current. 

The  efferent  stream  carries  away  the  decomposition  products/r^w  the  various 
tissues,  more  especially  urea,  CO;,  H^O,  and  salts,  and  these  are  transferred  as 
quickly  as  possible  to  the  organs  through  which  they  are  excreted. 

That  such  a  current  exists  is  proved  by  injecting  such  a  substance  as  potassium  ferrocyanide  into 
the  tissues,  e.  g.,  subcutaneously,  when  its  presence  may  be  detected  in  the  urine  within  two  to  five 
minutes. 

If  the  current  from  the  tissues  to  the  blood  is  so  active  that  the  excretory  organs 
cannot  eliminate  all  the  effete  products  from  the  blood,  then  these  products  are 
found  in  the  tissues.  When  certain  poisons  are  injected  subcutaneously,  they  pass 
rapidly  into  the  blood  and  are  carried  in  great  quantity  to  other  tissues,  e.  g.,  to 
the  nervous  system,  on  which  they  act  wiih  fatal  effect,  before  they  are  eliminated 


METABOLISM    OF   THE   TISSUES.  415 

to  any  great  extent  from  the  blood  by  the  action  of  the  excretory  organs.  The 
effete  materials  are  carried  away  from  the  tissues  \>y  two  channels,  viz.,  by  the 
veins  and  by  the  lymphatics,  so  that  if  these  be  interfered  with,  the  metabolism 
of  the  tissues  must  also  suffer.  When  a  limb  is  ligatured  so  as  to  compress  the 
veins  and  the  lymphatics,  the  efferent  stream  stagnates  to  such  an  extent  that  con- 
siderable swelling  of  the  tissues  or  oedema  may  occur  (§  203).  The  action  of  the 
muscles  and  fascise  are  very  important  in  removing  these  effete  matters. 

H.  Nasse  found  that  the  blood  of  the  jugular  vein  is  0.225  per  1000  specifically  heavier  than  the 
blood  of  the  carotid,  and  contains  0.9  parts  per  1000  more  solids  ;  1000  cubic  centimetres  of  blood 
circulating  through  the  head  yield  about  5  cubic  centimetres  of  transudation  into  the  tissues. 

The  extent  and  intensity  of  the  metabolism  of  the  tissues  depend  upon  a 
variety  of  factors. 

1.  Upon  their  activity. — The  increased  activity  of  an  organ  is  indicated  by 
the  increased  amount  of  blood  going  to  it,  and  by  the  more  active  circulation 
through  it  (§  100).  When  an  organ  is  completely  inactive,  such  as  a  paralyzed 
muscle,  or  the  peripheral  end  of  a  divided  nerve,  the  amount  of  blood  and  the 
nutritive  exchange  of  fluid  diminish  within  these  parts.  The  parts  thus  thrown 
out  of  activity  become  pale,  relaxed,  and  ultimately  undergo  fatty  degeneration. 
The  increased  metabolism  of  an  organ  during  its  activity  has  been  proved  experi- 
mentally in  the  case  of  muscle,  and  [(§  263)  also  in  the  brain  {^Speck)\.  Langley 
and  Sewell  have  recently  observed  directly  the  metabolic  changes  within  suffi- 
ciently thin  lobules  of  glands  durmg  life.  The  cells  of  serous  glands  (§  143), 
and  those  of  mucous,  and  pepsin-forming  glands  (§  164),  during  quiescence, 
become  filled  with  coarse  granules,  which  are  dark  in  transmitted  light  and  white 
in  reflected  light,  which  granules  are  consumed  or  disappear  during  granular 
activity.  During  sleep,  when  most  organs  are  at  rest,  the  metabolism  is  limited, 
darkness  also  diminishes  it ;  while  light  excites  it,  obviously  owing  to  nervous 
influences.  The  variations  in  the  total  metabolism  of  the  body  are  reflected  in 
the  excretion  of  CO2  (§  127,  9)  and  urea  (§  257),  which  may  be  expressed  graph- 
ically in  the  form  of  a  curve  corresponding  with  the  activity  of  the  organism  ; 
this  curve  corresponds  very  closely  with  the  daily  variations  in  the  respirations, 
pulse,  and  temperature  (p.  374). 

2.  The  composition  of  the  blood  has  a  marked  effect  upon  the  current  on 
which  the  metabolism  of  the  tissues  depends.  Very  concentrated  blood,  which 
contains  a  small  amount  of  water,  as  after  profuse  sweating,  severe  diarrhoea, 
cholera,  makes  the  tissues  dry,  while  if  much  water  be  absorbed  into  the  blood, 
the  tissues  become  more  succulent  and  even  oedema  occur.  When  much  common 
salt  is  present  in  the  blood,  and  when  the  red  blood  corpuscles  contain  a  dimin- 
ished amount  of  O,  and  especially  if  the  latter  condition  be  accompanied  by 
muscular  exertion  causing  dyspnoea,  a  large  amount  of  albumin  is  decomposed, 
and  there  is  a  great  formation  of  urea.  Hence,  exposure  to  a  rarefied  atmosphere 
is  accompanied  by  increased  excretion  of  urea.  Certain  abnormal  conditions  of 
the  blood  produce  remarkable  results  ;  blood  charged  with  carbonic  oxide  cannot 
absorb  O  from  the  air,  and  does  not  remove  CO2  from  the  tissues  (§  16).  The 
presence  of  hydrocyanic  acid  in  the  blood  (§  16)  is  said  to  interrupt  at  once  the 
chemical  oxidation  processes  in  the  blood,  so  that  rapid  asphyxia,  owing  to  cessa- 
tion of  the  z;2/(?r;za/ respiration,  occurs.  Fermentation  is  interrupted  by  the  same 
substance  in  a  similar  way.  A  diniinutio7i  of  the  total  amount  of  the  blood  causes 
more  fluid  to  pass  from  the  tissues  into  the  blood,  but  the  absorption  of  sub- 
stances— such  as  poisons  or  pathological  effusions — from  the  tissues  or  intestines  is 
delayed.  If  the  substances  which  pass  from  the  tissues  into  the  blood  be  rapidly 
eliminated  from  it,  absorption  takes  place  more  rapidly. 

3.  The  blood  pressure,  when  it  is  greatly  increased,  causes  the  tissues  to  con- 
tain more  fluid,  while  the  blood  itself  becomes  more  concentrated,  to  the  extent 
of  3  to  5  per  1000.     We  may  convince  ourselves  that  blood  plasma  easily  passes 


416  REGENERATION    OF   ORGANS   AND   TISSUES. 

through  the  capillary  wall,  by  j)ressing  upon  the  efferent  vessel  coming  from  the 
chorium  deprived  of  its  epidermis,  e.  g.,  by  a  burn  or  a  blister,  when  the  surface 
of  the  wound  becomes  rapidly  suffused  with  plasma.  Diminution  of  the  blood 
pressure  produces  the  opposite  result.  The  oxidation  processes  in  the  body  are 
diminished  after  tlie  use  of  P,  Cu,  ether,  chloroform,  and  chloral. 

4.  Increased  temperature  of  the  tissues  (several  hours  daily)  does  not 
increase  the  breaking  up  of  albumin  and  fats.     (See  §§  220,  221,  225.) 

5.  The  influence  of  the  nervous  system  on  the  metabolism  is  twofold.  On 
the  one  hand,  it  acts  indirectly  through  its  effect  upon  the  blood  vessels,  by  caus- 
ing them  to  contract  or  dilate  through  the  agency  of  vasomotor  nerves, 
whereby  it  influences  the  amount  of  blood  supplied,  and  also  affects  the  blood 
pressure.  But  quite  independently  of  the  blood  vessels,  it  is  probable  that  certain 
special  nerves — the  so-called  trophic  nerves — influence  the  metal)olism  or  nutri- 
tion of  the  tissues  (§  342,  c).  That  nerves  do  influence  directly  the  transforma- 
tion of  matter  within  the  tissues  is  shown  by  the  secretion  of  saliva  resulting  from 
the  stimulation  of  certain  nerves,  after  cessation  of  the  circulation  (§  145),  and  by 
the  metabolism  during  the  contraction  of  bloodless  muscles.  Increased  respiration 
and  apnoea  are  not  followed  by  increased  oxidation  (^Pfliiger)  (§  127,  8). 

[Gaskell  has  raised  the  question  as  to  the  existence  of  katabolic  and  anabolic  nerves  controlling 
respectively  the  analytic  and  synthetic  metabolism  of  the  tissues.] 

244.  REGENERATION. — The  extent  to  which  lost  parts  are  replaced  varies  greatly  in  different 
organs.  Among  ilie  /o7ver  animals,  the  parts  of  organs  are  replaced  to  a  far  greater  extent  than 
among  wa-m-blooded  animals.  When  a  hydra  is  divided  into  two  parts,  each  part  forms  a  new  indi- 
vidual— nay,  if  the  body  of  the  animal  be  divided  into  several  parts  in  a  particular  way,  then  each  part 
gives  rise  to  a  new  individual  [Spallanzani).  The  Planarians  also  show  a  great  capability  of  repro- 
ducing lost  parts  {Bu^es).  Spiders  and  crabs  can  reproduce  lost  feeler~,  limbs,  and  claws  ;  snails, 
part  of  the  head,  feelers,  and  eyes,  provided  the  central  nervous  system  is  not  injured.  Many  fishes 
reproduce  fins,  even  the  tail  fin.  Salamanders  and  lizards  can  produce  an  entire  tail,  including  bones, 
muscles,  and  even  the  posterior  part  of  the  spinal  cord ;  while  the  trilon  rejiroduces  an  amputated 
limb,  the  lower  jaw,  and  the  eye.  This  reproduction  necessitates  that  a  small  stump  be  left,  while 
total  extirpation  of  the  parts  prevents  reproduction.  In  amphibians  and  reptiles  the  regeneration  of 
organs  and  tissues,  as  a  whole,  takes  place  after  the  type  of  the  embryonic  development,  and  the  same 
is  true  as  regards  the  histological  processes  which  occur  in  the  regenerated  tail  and  other  parts  of  the 
body  of  the  earth-worm. 

The  extent  to  which  regeneration  can  take  place  in  mammals  and  in  man  is 
very  slight,  and  even  in  these  cases  it  is  chiefly  confined  to  young  individuals.  A 
true  regeneration  occurs  in — 

1.  The  blood,  including  the  plasma,  the  colorless  and  colored  corpuscles.  (§  7 
and  §  41,) 

2.  The  epidermal  appendages  (§  283)  and  the  epithelium  of  the  mucous 
membranes  are  reproduced  by  a  proliferation  of  the  cells  of  the  deeper  layers  of 
the  epithelium,  with  simultaneous  division  of  their  nuclei.  Epithelial  cells  are 
reproduced  as  long  as  the  matrix  on  which  they  rest  and  the  lowest  layer  of  cells 
are  intact.  Wiien  these  are  destroyed  cell  regeneration  from  below  ceases,  and 
the  cells  at  the  margins  are  concerned  in  filling  up  the  deficiency.  Regeneration, 
therefore,  either  takes  place  from  below  or  from  the  margins  of  the  wound  in  the 
epithelial  covering ;  leucocytes  also  wander  into  the  part,  while  the  deepest  layer 
of  cells  forms  large  multi-nucleated  cells,  which  reproduce  by  division  polygonal 
flat  nucleated  cells.  [In  the  process  of  division  of  the  cells,  the  nucleus  plays  an 
important  part,  and  in  so  doing  it  shows  the  usual  karyokinetic  figures  (§  431).] 
The  nails  grow  from  the  root  forward ;  those  of  the  fingers  in  four  to  five 
months,  and  that  of  the  great  toe  in  about  twelve  months,  although  growth  is 
slower  in  the  case  of  fracture  of  the  bones.  The  matrix  is  co-extensive  with  the 
lunule,  and  if  it  be  destroyed  the  nail  is  not  reproduced  (§  284).  The  eyelashes 
are  changed  in  100  to  150  days,  the  other  hairs  of  the  body  somewhat  more  slowly. 
If  the  papilla  of  the  hair  follicle  be  destroyed,  the  hair  is  not  reproduced.     Cut- 


REGENERATION    OF    ORGANS   AND    TISSUES.  417 

ting  the  hair  favors  its  growth,  but  hair  which  has  been  cut  does  not  grow  longer 
than  uncut  hair.  After  hair  has  grown  to  a  certain  length,  it  falls  out.  The  hair 
never  grows  at  its  apex.  The  epithelial  cells  of  mucous  membranes  and  secre- 
tory glands  seem  to  undergo  a  regular  series  of  changes  and  renewal.  The  presence 
of  secretory  cells  in  the  milk  (§  231)  and  in  the  sebaceous  secretion  (§  285)  proves 
this  ;  the  spermatozoa  are  replaced  by  the  action  of  spermatoblasts.  In  ca- 
tarrhal conditions  of  mucous  membranes,  there  is  a  great  increase  in  the 
formation  and  excretion  of  new  epithelium,  while  many  cells  are  but  indifferently 
foroied  and  constitute  mucous  corpuscles.  The  crystalline  lens,  which  is  just 
modified  epithelium,  is  reorganized  like  epithelium  ;  its  matrix  is  the  anterior  wall 
of  its  capsule,  with  the  single  layer  of  cells  covering  it.  If  the  lens  be  removed 
and  this  layer  of  cells  retained,  these  cells  proliferate  and  elongate  to  form  lens 
fibres,  so  that  the  whole  cavity  of  the  empty  lens  capsule  is  refilled.  If  much 
water  be  withdrawn  from  the  body,  the  lens  fibres  become  turbid.  [A  turbid  or 
opaque  condition  of  the  lens  may  occur  in  diabetes,  or  after  the  transfusion  of 
strong  common  salt  or  sugar  solution  into  a  frog.] 

3.  The  blood  vessels  undergo  extensive  regeneration,  and  they  are  regene- 
rated in  the  same  way  as  they  are  formed  (§  7,  B).  Capillaries  are  always  the 
first  stage,  and  around  them  the  characteristic  coats  are  added  to  form  an  artery 
or  a  vein.  When  an  artery  is  injured  and  permanently  occluded,  as  a  general 
rule  the  part  of  the  vessel  up  to  the  nearest  collateral  branch  becomes  obliterated, 
whereby  the  derivatives  of  the  endothelial  lining,  the  connective-tissue  corpuscles 
of  the  wall,  and  the  leucocytes  change  into  spindle-shaped  cells,  and  form  a  kind 
of  cicatricial  tissue.  Blind  and  solid  outshoots  are  always  found  on  the  blood 
vessels  of  young  and  adult  animals,  and  are  a  sign  of  the  continual  degeneration 
and  regeneration  of  these  vessels.  Lymphatics  behave  in  the  same  way  as  blood 
vessels ;  after  removal  of  a  lymphatic  gland,  a  new  one  may  be  formed  {Bayer). 

4.  The  contractile  substance  of  muscle  may  undergo  regeneration  after  it 
has  become  partially  degenerated.  This  takes  place  after  amyloid  or  wax-like 
degeneration,  such  as  occurs  not  unfrequently  after  typhus  and  other  severe  fevers. 
This  is  chiefly  accomplished  by  an  increase  of  the  muscle  corpuscles.  After  being 
compressed,  the  muscular  nuclei  disappear,  and  at  the  same  time  the  contractile 
contents  degenerate.  After  several  days,  the  sarcolemma  contains  numerous  nuclei 
which  reproduce  new  muscular  nuclei  and  the  contractile  substance.  In  fibres 
injured  by  a  subcutaneous  wound,  Neumann  found  that,  after  five  to  seven  days, 
there  was  a  bud-like  elongation  of  the  cut  ends  of  the  filDres,  at  first  without  trans- 
verse striation,  but  with  striation  ultimately.  If  a  large  extent  of  a  muscle  be  removed, 
it  is  replaced  by  cicatricial  connective  tissue.  Non-striped  muscular  fibres  are  also 
reproduced  ;  the  nuclei  of  the  injured  fibres  divide  after  becoming  enlarged,  and 
exhibit  a  well-marked  intra-nuclear  plexus  of  fibrils.  The  nuclei  divide  into  two, 
and  from  each  of  these  a  new  fibre  is  formed,  probably  by  the  differentiation  of  the 
perinuclear  protoplasm. 

5.  After  a  nerve  is  divided,  the  two  ends  do  not  join  at  once  so  as  to  permit  the 
function  of  the  nerve  to  be  established.  On  the  contrary,  marked  changes  occur.  If 
a  piece  be  cut  out  of  a  nerve  tmnk,  the  peripheral  end  of  the  divided  nerve  de- 
generates, the  axial  cylinder  and  the  white  sulDstance  of  Schwann  disappear.  The 
inter\'al  is  filled  up  at  first  with  juicy  cellular  tissue.  The  subsequent  changes  are 
fully  described  in  §  325,  4.  There  seems  to  be  in  peripheral  nerves  a  continual 
disappearance  of  fibres  by  fatty  degeneration,  accompanied  by  a  consecutive  forma- 
tion of  new  fibres  (Si'gm.  Mayer).  The  regeneration  of  peripheral  ganglionic 
cells  is  unknown,  v.  Voit,  however,  observed  that  a  pigeon,  part  of  whose  brain 
was  removed,  had  within  five  months  reproduced  a  nervous  mass  within  the  skull, 
consisting  of  medullated  nerve  fibres  and  nerve  cells.  Eichhorst  and  Naunyn  found 
that  in  young  dogs,  whose  spinal  cord  was  divided  between  the  dorsal  and  lumbar 
regions,  there  was  an  anatomical  and  physiological  regeneration,  to  such  an  extent 

27 


418  REGENERATION    OF    BONE. 

that  voluntary  movements  could  be  executed  (§  338,  3).  Vaulair,  in  the  case  of 
frogs,  and  Masius  in  dogs,  found  that  mobility  or  motion  was  first  restored,  and 
afterward  sensibility.     Regeneration  of  the  spinal  ganglia  did  not  occur. 

6.  In  many  glands,  the  regeneration  of  their  cells  during  normal  activity  is  very 
active — sebaceous,  mucous,  Liebcrkiihnian,  uterine,  mauimary  glands  during  j^reg- 
nancy — in  others  less.  If  a  large  portion  of  a  secretory  gland  be  removed,  as  a 
general  rule,  it  is  not  reproduced.  A  gland,  if  injured,  and  if  sujjpuration  follows,  is 
not  regenerated.  But  the  bile  ducts  (^  173)  and  the  pancreatic  duct  may  be 
reproduced  (§  171).  According  to  PhiliiJiJcaux  and  Grilhni,  if  part  of  the  spleen 
be  removed  it  is  rejiroduced  (i;  103).  Tizzoni  and  Collucci  observed  the  formation  of 
new  liver  cells  and  bile  ducts  afier  injury  to  the  liver  (§  173),  and  Pisenti  makes  the 
same  statement  as  regards  the  kidney.  After  mechanical  injury  to  the  secretory 
cells  of  glands  (liver,  kidney,  salivary,  Meibomian;,  neighboring  cells  undergo  pro- 
liferation and  aid  in  the  restoration  of  the  cells. 

7.  Among  connective  tissues,  cartilage,  provided  its  perichondrium  be  not 
injured,  reproduces  itself  by  division  of  its  cartilage  cells ;  but  usually  when  a  part 
of  a  cartilage  is  removed,  it  is  replaced  by  connective  tissue. 

8.  When  a  tendon  is  divided,  proliferation  of  the  tendon  cells  occurs,  and  the 
cut  ends  are  united  by  connective  tissue. 

9.  The  reproduction  of  bone  takes  place  to  a  great  extent  under  certain  con- 
ditions. If  the  articular  end  be  removed  by  excision,  it  may  be  reproduced, 
although  there  is  a  considerable  degree  of  shortening.  Pieces  of  bone  which  have 
been  broken  off  or  sawn  off  heal  again,  and  become  united  with  the  original  bone. 
A  tooth  may  be  removed,  replanted  in  tlie  alveolus,  and  become  fixed  there.  If 
a  piece  of  periosteum  be  transplanted  to  another  region  of  the  body,  it  eventu- 
ally gives  rise  to  the  formation  of  new  bone  in  that  locality.  If  part  of  a  bone  be 
removed,  provided  the  periosteum  be  left,  new  bone  is  rapidly  reproduced  ;  hence, 
the  surgeon  takes  great  care  to  preserve  the  periosteum  intact  in  all  operations 
where  he  wishes  new  bone  to  be  reproduced.  Even  the  marrow  of  bone,  when 
it  is  transplanted,  gives  rise  to  the  formation  of  bone.  This  is  due  to  the  osteo- 
blasts adhering  to  the  osseous  tissue. 

In  fracture  of  a  long  bone,  the  periosteum  deposits  on  the  surface  of  the  ends  of  the  broken 
bones  a  ring  of  suljstance  which  forms  a  temporary  support,  the  external  callus.  At  first  this 
callus  is  jelly-like,  soft,  and  contains  many  corpuscles,  but  afterward  it  becomes  more  solid  and 
somewhat  like  cartilage.  A  similar  condition  occurs  within  the  bone,  where  an  internal  callus  is 
formed.  The  formation  of  this  temporary  callus  is  due  to  an  inflammatory  proliferation  of  the 
connective-tissue  corpuscles,  and  partly  to  the  osteoblasts  of  the  periosteum  and  marrow.  According 
to  Rigal  and  Vignal,  the  internal  callus  is  always  osseous,  and  is  derived  from  the  marrow  of  the 
bone.  The  outer  and  inner  callus  become  calcified  and  ultimately  ossified,  whereby  the  broken  ends 
are  reunited.  Toward  the  fortieth  day  a  thin  layer  of  bone  is  formed  (intermediary  callus) 
between  the  ends  of  the  bone.  Where  this  begins  to  be  definitely  ossified,  the  outer  and  inner  callus 
begin  to  be  absorbed,  and  ultimately  the  intermediary  callus  has  the  same  structure  as  the  rest  of  the 
bone. 

There  are  many  interesting  observations  connected  with  the  growth  and  metabolism  of  bones. 
I.  The  addition  of  a  very  small  amount  of  phosphorus  or  arsetiious  acid  to  the  food  causes  consid- 
erable thickening  of  the  bones.  This  seems  to  be  due  to  the  non-absorption  of  those  parts  of  the 
bones  which  are  usually  absorbed,  while  new  growth  is  continually  taking  place.  2.  When  food 
devoid  of  litne  sails  \%  gw&n  to  an  animal,  the  growth  of  the  bones  is  not  arrested,  but  the  bones 
become  thinner,  whereby  all  parts,  even  the  organic  basis  of  the  bone,  undergo  a  uniform  diminu- 
tion. 3.  Feeding  with  madder  makes  the  bones  red,  as  the  coloring  matter  is  deposited  with  the 
bone  salts  in  the  bone,  especially  in  the  growing  and  last  formed  parts.  In  birds  the  shell  of  the  egg 
becomes  colored.  4.  The  continued  use  of  lactic  acid  dissolves  the  bones.  The  ash  of  bone  is 
thereby  diminished.  If  lime  salts  be  withheld  at  the  .same  time,  the  effect  is  greatly  increased,  so 
that  the  bones  come  to  resemble  rachitic  bones.     (Development  of  Bone,  \  447-) 

When  a  lost  tissue  is  not  replaced  by  the  same  kind  of  tissue,  its  place  is  always 
taken  by  cicatricial  connective  tissue. 

A\Tien  this  is  the  case,  the  part  becomes  inflamed  and  swollen,  owing  to  an  exudation  of  plasma. 
The  blood  vessels  become  dilated  and  congested,  and,  notwithstanding  the  slower  circulation,  the 


INCREASE    IN    SIZE    AND    WEIGHT. 


419 


amount  of  blood  is  greater.  The  blood  vessels  are  increased,  owing  to  the  formation  of  new  ones. 
Colorless  blood  corpuscles  pass  out  of  the  vessels  and  reproduce  themselves,  and  many  of  them 
undergo  fatty  degeneration,  while  others  take  up  nutriment  and  become  converted  into  large  uni- 
nucleated  protoplasm  cells,  from  which  giant  cells  are  developed.  The  newly  formed  blood  vessels 
supply  all  these  elements  with  blood. 

245.  TRANSPLANTATION  OF  TISSUES.— The  nose,  ear,  and  even  a  finger,  after 
having  been  severed  from  the  body  by  a  clean  cut,  have,  under  certain  circumstances,  become  united 
to  the  part  from  which  they  were  removed.  The  skin  is  frequently  transplanted  by  surgeons,  as,  for 
example,  to  form  a  new  nose.  The  piece  of  skin  is  cut  from  the  forehead  or  arm,  to  which  it  is  left 
attached  by  a  bridge  of  skin,  is  then  stitched  to  the  part  which  it  is  desired  to  cover  in,  and  when  it 
has  become  attached  in  its  new  situation,  the  bridge  of  skin  is  severed.  Reverdin  cut  a  piece  of  skin 
into  pieces  about  the  size  of  a  pea  and  fixed  them  on  an  ulcerated  surface,  where  they,  as  it  were, 
took  root,  grew,  and  sent  off  from  their  margins  epithelial  outgrowths,  so  that  ultimately  the  whole 
surface  was  covered  with  epithelium.  [White  skin  transplanted  to  a  negro  ultimately  becomes  pig- 
mented, and  black  skin  transplanted  to  a  white  person  becomes  white.]  The  excised  sptcr  of  a  cock 
was  transplanted  and  fixed  in  the  comb  of  the  same  animal,  where  it  grew  [Jokit  Hunter).  P.  Bert 
cut  off  the  tail  and  legs  of  rats  and  transplanted  them  under  the  skin  of  the  back  of  other  rats,  where 
they  united  with  the  adjoining  parts.  Oilier  found  that,  when  periosteum  was  transplanted,  it  grew 
and  reproduced  bone  in  its  new  situation.  Even  blood  and  lymph  may  be  transfused  (Transfusion, 
\  102.)  [Small  portions  (1.5  mm.)  of  epiphyses,  costal  cartilage,  of  a  rabbit  or  kitten,  when  trans- 
planted quite  fresh  into  the  anterior  chamber  of  the  eye,  testis,  sub-maxillary  gland,  kidney,  and  under 
the  skin  of  a  rabbit,  attach  themselves  and  grow,  and  the  growth  is  more  rapid  the  more  vascular  the 
site  on  which  the  tissue  is  transplanted.  The  cartilage  is  not  essentially  different  from  hyaline  car- 
tilage, but  the  cells  are  fewer  in  the  centre,  while  the  matrix  tends  to  become  fibrous.  Small  pieces 
of  epiphyseal  cartilage  introduced  into  the  jugular  vein  were  found  as  cartilaginous  foci  in  the  lungs. 
Tissues  transplanted  from  embryonic  structures  grow  far  better  than  adult  tissues.  If  a  portion  of  the 
cornea  of  a  rabbit  be  transplanted  to  a  human  eye,  provided  Descemet's  membrane  be  clear,  it  will 
grow  and  remain  clear  (v.  HippeU).  A  rabbit's  nerve  has  been  transplanted  to  the  human  subject, 
but  without  success.] 

Many  of  these  results  seem  only  to  be  possible  between  individuals  of  the  same  species,  although 
Helferich  has  recently  f^und  that  a  piece  of  a  dog's  muscle,  when  substituted  for  human  muscle, 
united  to  the  adjoining  muscle,  and  became  functionally  active.  [J.  R.  Wolfe  has  transplanted  the 
conjunctiva  of  the  rabbit  to  the  human  eye.]  Most  tissues,  however,  do  not  admit  of  transplantation, 
e.g.,  glands  and  the  sense  organs.  They  may  be  removed  to  other  parts  of  the  body,  or  into  the  peri- 
toneal cavity,  without  exciting  any  inflammatory  reaction;  they,  in  fact,  behave  like  inert  foreign  matter. 

246.  INCREASE  IN  SIZE  AND  WEIGHT.— The  length  of  the  body,  which  at  birth 
is  usually  J-^  of  the  adult  body,  undergoes  the  greatest  elongation  at  an  early  period  :  in  the  first 
year,  20;  in  the  second,  10;  in  the  third,  about  7  centimetres;  while  from  five  to  sixteen  years  the 
annual  increase  is  about  5  j^  centimetres.  In  the  twentieth  year  the  increase  is  very  slight.  From 
fifty  onward  the  size  of  the  body  diminishes,  owing  to  the  intervertebral  disks  becoming  thinner,  and 
the  loss  may  be  6  to  7  centimetres  about  the  eightieth  year.  The  weight  of  the  body  (^^  of  an 
adult)  sinks  during  the  first  five  to  seven  days,  owing  to  the  evacuation  of  the  meconium  and  the 
small  amount  of  food  which  is  taken  at  first.     Only  on  the  tenth  day  is  the  weight  the  same  as  at  birth. 


Length  (Cmtr.). 

Weight  (Kilo.). 

Length  (Cmtr.). 

Weight 

(Kilo.). 

Age. 

Age. 

Man. 

Woman. 

Man. 

Woman. 

Man. 

Woman. 

Man. 

Woman. 

0 

49-6 

48.3 

3.20 

2.91 

15 

155.9 

147.5 

46.41 

41.30 

I 

69.6 

69.0 

10.00 

9-30 

16 

161.O 

150.0 

53.39 

44  44 

2 

79.6 

78.0 

12.00 

11.40 

17 

167.0 

154.4 

57.40 

49.08 

0 

86.0 

85.0 

13.21 

12.45 

18 

170.0 

156.2 

61.26 

53-10 

4 

93-2 

91.0 

15-07 

14.18 

19 

170.6 

63.32 

5 

99.0 

97.0 

16.70 

15-50 

20 

171. 1 

157.0 

65.00 

54-46 

6 

104.6 

103.2 

18.04 

16.74 

i      25 

172.2 

157.7 

68.29 

55.08 

7 

III. 2 

109.6 

20.16 

18.45 

i      30 

172.2 

157.9 

68.90 

55-14 

8 

I  I  7.0 

"3-9 

22.26 

19.82 

40 

171-3 

155.5 

68.81 

56.65 

9 

122.7 

120.0 

24.09 

22.44 

50 

167.4 

153.6 

67.45 

5S.45 

10 

128.2 

124.8 

26.12 

24.24 

60 

163.9 

I5I.6 

65.50 

56-73 

II 

132.7 

127.5 

27.85 

26.25 

70 

162.3 

151.4 

63-03 

53-72 

12 

135-9 

132.7 

31.08 

30-54 

80 

161.3 

150.6 

61.22 

51-52 

13 

140.3 

138.6 

35-32 

34.65 

90 

57-83 

49-34 

14 

148.7 

144.7 

40.50 

38.10 

(Chiefly  from  Q 

uetelet.) 

420  INXREASE    IN    SIZE    AND    WEIGHT. 

The  increase  of  weight  is  greater  in  the  same  time  than  the  increase  in  length.  Within  the  first 
year  a  child  trebles  its  weight.  The  greatest  weight  is  usually  reached  about  forty,  while  toward 
sixty  a  decrease  begins,  which  at  eighty  may  amount  even  to  6  kilos.  The  results  of  measurements, 
chiefly  by  Quetelt-t,  are  given  on  the  jireceding  page. 

Between  the  twelfth  and  fifteenth  ye.irs  the  weight  and  size  of  the  girl  are  greater  than  of  the  boy. 
Growth  is  most  active  in  the  last  months  of  foetal  life,  and  afterward  from  the  si.xth  to  the  n'nth 
year  until  the  thirteenth  to  the  sixteenth.  Tiie  full  stature  is  reached  about  tliiriy,  but  not  the 
greatest  weight. 


GENERAL  VIEW  OF  THE  CHEMICAL  CONSTITUENTS 
OF  THE  ORGANISM. 


247.  (A)  INORGANIC  CONSTITUENTS.— I.  Water  forms  58.5  per  cent,  of  the  whole 
body,  but  it  occurs  in  different  quantity  in  the  different  tissues.  The  kidneys  contain  the  most 
water,  82.7  per  cent. ;  bones,  22  per  cent. ;  teeth,  10  per  cent. ;  white  enamel  contains  the  least,  0.2 
per  cent,  ('i,  229).  According  to  some  observers,  peroxide  of  hydrogen  (^H^O.,)  is  also  present  in  the 
body. 

[Approximately,  water  forms  about  two-thirds  of  the  weight  of  the  body,  so  that  a  body  weighing 
.75  kilos.  (165  lbs.)  contains  .50  kilos,  (no  lbs.)  of  water.  The  following  table,  modified  from 
Beaunis,  shows  the  percentage  of  water  in  several  tissues  and  organs : — 

Solids. 

Tissue  or  Organ.         Water.      Solids,  i  Tissue  or  Organ.       Water.      Solids.  |  Tissue  or  Organ.         Water.    Solids. 


Enamel,    .  . 

Dentine,    .  . 

Bone,     .    .  . 

Fat,   .        .  . 
Elastic  tissue, 

Cartilage,  .  . 

Liver,    .    .  . 


lo.o 
48.6 
29.9 
49.6 
55-0 
69.3 


Blood,  ,  .  .  .  .  79  I 
b6  4 
89.1 
90.1 
92.8 


Bile, 

Milk,     .... 
Liquor  sanguinis. 
Chyle,   .... 


998 
90.0 

514 
70.1 
504 
45-0 
30.7 


20.9 
136 
10. 9 

9-9 

72 


Spinal  Cord,  . 
White  matter  ) 
of  brain,  J 
Skin,  .  .  . 
Brain,  .... 
Muscles,  .  . 
Spleen,    .    .    . 

Liqu 
Lymph,  .    .    . 
Serum,     .    .    . 
Gastric  juice,  . 
Inle-tinal  juice. 
Tears,  .... 


69.7 

70.0 

72.0 
75-0 
757 
75-8 


ds. 

95 
95 
97 
97 


30-3 
30.0 

28.0 
25.0 

24-3 
24.2 


4.2 

4-1 
2.7 

2.5 

1.8 


Thymus,  .  . 
Connective 

tissue,  .  . 
Kidney,  .  .  . 
Gray  matter  of 

brain, .  .  . 
Vitreous  humor 


77.0 
79.6 
82.7 
85.8 
98.7 


Aqueous  humor,    98  6 
Cerebro-spinal 
fluid,  .    .    . 

Saliva 99.5 

Sweat, 99.5 


98.8 


20  4 

17-3 
14.2 

13 

1.4 
1.2 

0-5 
05 


II.  Gases.— O,  -  ozone  {\  37)  -  H,  -  N  -  CO,  (|  38).  Marsh  gas  CH^  (|  124),  NH3  (|  30, 
I  124,  \  184),  H,S  (?  184). 

III.  Salts. — Sodium  chloride  [is  one  of  the  most  important  inorganic  substances  present  in 
the  body.  It  occurs  in  all  the  tissues  and  fluids  of  the  body,  and  plays  a  most  prominent  part  in 
connection  with  the  diffusion  of  fluids  through  membranes,  and  its  presence  is  necessary  for  the 
solution  of  the  globulins  (p.  424).  Sometimes  it  exists  in  a  state  of  combination  with  proteid  bodies, 
as  in  the  blood  plasma.  Common  salt  is  absolutely  necessary  for  one's  existence  ;  if  it  be  withdrawn 
entirely,  life  soon  comes  to  an  end.    About  15  grammes  are  given  off  in  the  twenty-four  hours,  chiefly 

■  by  the  urine.  Boussingault  showed  that  the  addition  of  common  salt  to  the  food  of  cattle  greatly 
improved  their  condition.] 

[Calcium  phosphate  (CajPoOg)  is  the  most  abundant  salt  in  the  body,  as  it  forms  more  than  one- 
half  of  our  bones;  but  it  also  occurs  in  dentine,  enamel,  and  to  a  much  less  extent  in  the  other 
solids  and  fluids  of  the  body.  Among  secretions,  milk  contains  relatively  the  largest  amount  (2.72 
per  cent.).  In  milk  it  is  necessary  for  forming  the  calcareous  matter  of  the  bones  of  the 
infant.  It  gives  bones  their  hardness  and  rigidity.  It  is  chiefly  derived  from  the  food,  and,  as 
only  a  small  quantity  is  given  off  in  the  excretions,  it  seems  not  to  undergo  rapid  removal  from  the 
body.] 

[Sodium  phosphate  {V'Hsi^O^j,  acid  sodium  phosphate  [ViiSi^O^i,  acid  potassium  phosphate 
[V^^^aO^.  The  sodium  phosphate  and  the  corresponding  potash  salt  give  most  of  the  fluids  of  the 
body  their  alkaline  reaction.  The  alkaline  reaction  of  the  blood  plasma  is  partly  due  to  alkaline 
phosphates,  which  are  chiefly  derived  from  the  food.  The  acid  sodium  phosphate  is  the  chief  cause 
of  the  acid  reaction  of  the  urine.  A  small  quantity  of  phosphoric  acid  is  formed  in  the  body  owing 
to  the  oxidation  of  lecithin,  which  contains  phosphorus.] 

[Sodium  carbonate  (Na^COg)  and  sodium  bicarbonate  (NaHCOg)  exist  in  small  quantities  in 
the  food,  and  are  formed  in  the  body  from  the  decomposition  of  the  salts  of  the  vegetable  acids. 

421 


422 


INORGANIC    CONSTITUENTS   OF   THE    BODY. 


They  occur  in  the  blood  plasma,  wiiere  they  play  an  important  part  in  carrying  the  CO.^  from  the 
tissues  to  the  liinc;?.] 

I  Sodium  and  potassium  sulphates  (NhjSO^  and  K^SO^)  exist  in  very  small  quantity  in  the 
bodv,  and  are  introduced  with  the  food,  but  part  is  formed  in  the  body  from  the  oxidation  of  organic 
bodies  containinj^  sulphur.] 

[Potassium  chloride  (  KCI)  is  pretty  widely  distiibuted,  and  occurs  specially  in  muscle,  colored 
blood  corpuscles,  and  milk.  Calcium  fluoride  (CaFl.^)  occurs  in  small  quantity  in  bones  and 
teeth.  Calcium  carbonate  (CaCO.,)  is  associated  with  calcium  phosphate  m  bone,  tooth,  and  in 
some  fluids,  but  it  occurs  in  relatively  much  smaller  amount.  It  is  Icept  in  solution  by  alkaline 
chlorides,  or  by  the  presence  of  free  carbonic  acid.  Ammonium  chloride  (NH^CI). — Minute 
traces  occur  in  the  gastric  juice  and  the  urine.  Magnesium  phosphate  (MgsI'O^)  occurs  along 
\sith  calcium  phosphate,  but  in  very  much  smaller  (juantity.] 


Table,  by  Beaunis,  of  the  relative  proportions  of  Salts. 


Heintz. 


Staffel. 


Bone. 


Muscle  of 
calf. 


Breed. 


Brain. 


Oidtmann. 


Liver. 


C.  Schmidt 


Lungs. 


Oidtmann. 


Spleen. 


Sodic  chloride, 

Potassic  chloride,  .    .    .    . 

Soda,   

Potash, 

Lime, 

Magnesia, . 

Ferric  oxide, 

Chlorine, 

Fluorine       

Phosphoric  acid  (free),  .    . 
Phosphoric  acid  (combined 

Sulpiiuric  acid, 

Carbon  dioxide, 

Silicic  acid, 

Ferric  phosphate,  .    .    .    . 


3758 
1.22 


1.66 


53  3J 

547 


10.59 

2-35 

3440 

1.99 

1.45 


48-13 
081 


4-74 

10.69 

3442 

o  72 

1.23 


9-'5 
39.02 

0.75 

0.12 
1.23 


14-51 
2523 
3.61 
0.20 
2.74 
2.58 


5018 
o  92 

0.27 


13.0 

195 
1-3 
1-9 
1-9 
3-2 


48.5 
1.4 


44-33 
9.60 
7.48 
0.49 
7.28 
0.54 


27.10 
254 

017 


Table,  by  Beaunis,  of  the  Mineral  Matter  in  Animal  Fluids. 


Verdeil. 

Weber. 

Weber. 

Dahn- 
hardt. 

Porter. 

Wilder- 
stein. 

Rose. 

Porter. 

Blood. 

Blood 
serum. 

Blood. 

Lymph. 

Urine. 

Bulk. 

Bile. 

Faeces. 

Sodic  chloride,     . 
Potassic  chloride. 

Soda,     

Potash,      .... 

Lime, 

Magnesia,     .    .    . 
Ferric  oxide,    .    . 
Phosphoric  acid,  . 
Suli)liuric  acid,    . 
Carbon  dioxide,  . 
Silicic  acid,  .    .    . 

58.81 

4-15 

11.97 

1.76 

1. 12 

8.37 

10.23 

1.67 

1.19 

72.88 
1293 

2-95 
2.28 
0.27 
0.26 

1-73 
2.10 
4.40 
0.20 

'7-36 

2987 

3-55 
22.36 

2.58 
0.53 

10.48 

10.64 

0.09 

2.17 

0.42 

74.48 

10-35 
325 
097 
0.26 
0.50 
I  09 

8.20 
1.27 

67.28 

1-33 

13-64 

I-«5 

1-34 
11.21 

4.06 

10.73 
26.33 

21-44 
18.78 
.0.87 

O.IO 
19.00 

2.64 

27.70 

36-73 
4.80 

1-43 
0-53 
0-33 

10.45 
6-39 

11.26 
0.36 

4-33 

5-07 

6.10 

26.40 

10.54 

2.50 

36.03 

313 

IV.  Free  Acids. — Hydrochloric  acid  (liCl)  [occurs  /ree  in  the  gastric  juice,  but  in  combina- 
tion with  the  alkalies  it  is  widely  distributed  as  chlorides].  Sulphuric  acid  (IL^SO^)  [is  said  to 
occur  free  in  the  saliva  of  certain  gasteropods,  as  Dolium  galea.  In  the  body  it  forms  sulphates, 
chiefly  in  combination  with  soda  and  potash]. 

V.  Bases. — Silicon  as  silicic  acid  (SiOj);  manganese,  iron,  the  last  forms  an  integral  con- 
stituent of  hasmoglobin  ;   copper  [?),  (^  174)- 


CHARACTERS    OF   THE    TROTEIDS.  423 

248.  (B)  ORGANIC  COMPOUNDS. — I.  The  Albuminous  or  Proteid  Substances. — 
(i)  True  Proteids  and  their  allies  are  composed  of  C,  H,  O,  N,  and  S,  and  are  derived  from 
plants  (see  hitrodiutioii).  [The  formation  of  albumin  from  the  elements  is  accomplished  only 
by  plants.  What  the  chemical  processes  are  is  quite  unknown.  We  only  know  that  the  N  is  in  the 
first  instance  obtained  from  the  nitric  acid  or  ammonia  of  the  soil.  The  former  is  probably  not  used 
directly  as  such,  but  serves,  perhaps,  for  the  formation  of  amides  or  amido  acids,  from  which,  by  the 
action  of  non-nitrogenous  bodies,  proteids  are  formed.] 

[According  to  Hoppe  Seyler  their  general  percentage  composition  is — 

O.         H.         N.  C.  S. 

From 20.9       6.9        15.2       51.5       0.3 

To 23.5  to  7.3  to  17.0  to  54.5  to  2.O.] 

They  exist  in  almost  all  animal  fluids  and  tissues  partly  in  the  fluid  form,  although  Briicke  maintains 
that  ihe  molecule  of  albumin  exists  in  a  condition  midway  between  a  state  of  imbibition  and  a  true 
solution — and  partly  in  a  more  concentrated  condition.  Besides  forming  the  chief  part  of  muscle, 
nerve  and  gland,  they  occur  in  nearly  all  the  fluids  of  the  body,  including  the  blood,  lymph,  and 
serous  fluids,  but  in  health  mere  traces  occur  in  the  sweat,  while  they  are  absent  from  the  biie  and 
the  urine.  Unboiled  white  of  egg  is  the  type.  In  the  alimentary  canal  they  are  changed  into 
peptones.  The  chief  products  derived  from  their  oxidation  within  the  body  are  CO,,  HjO,  and 
especially  urea,  which  contains  nearly  all  the  N  of  the  proteids. 

Constitution.— Their  chemical  constitution  is  quite  unknown.  The  N  seems  to  exist  in  two 
distinct  conditions,  partly  loosely  combined,  so  as  to  j'ield  ammonia  readily  when  they  are  decomposed, 
and  partly  in  a  more  fixed  condition.  According  to  Pfliiger,  part  of  the  N  in  living  proteia  bodies 
exists  in  the  form  of  cyanogen.  [Loew  supports  Pfliiger's  view  that  the  molecule  of  living  (active) 
albumin  ditTers  from  that  of  dead  albumin,  as  he  finds  that  the  living  protoplasm  of  certain  alg^ 
can  reduce  silver  in  very  dilute  alkaline  solutions,  which  dead  protoplasm  cannot  do.]  The  proteid 
molecule  is  very  large,  and  is  a  very  complex  one;  a  small  part  of  the  molecule  is  composed  of 
substances  from  the  group  of  aromatic  bodies  (which  become  conspicuous  during  putrefaction),  the 
larger  part  of  the  molecule  belongs  to  Xh^  fatty  bodies  ;  during  the  oxidation  of  albumin  fatty  acids 
especially  are  developed.  Carbohydrates  may  also  appear  as  decomposition  products.  For  the 
decompositions  during  digestion  see  \  170,  and  during  putrefaction  §  184.  The  proteids  form  a  large 
group  of  closely  related  substances,  all  of  w^hich  are  perhaps  modifications  of  the  same  body.  When 
we  remember  that  the  infant  manufactures  most  of  the  proteids  of  its  ever-growing  body  from  the 
casein  in  milk,  this  last  view  seems  not  improbable. 

Characters. — Proteids,  the  anhydrides  of  peptones  (|  166)  are  colloids  (§  19 1 ),  and  therefore  do 
not  diffuse  easily  through  animal  membraaes ;  they  are  amorphous  and  do  not  crystallize,  and 
hence  are  isolated  with  difficulty;  some  are  soluble,  others  are  msoluble  in  water  ;  insoluble  in  alcohol 
and  ether  ;  rotate  the  ray  of  polarized  light  to  the  left  ;  when  burned  they  give  the  odor  of  burned 
horn.  Various  metallic  salts  and  alcohol  precipitate  them  from  their  solution;  they  are  coagulated 
by  heat,  mineral  acids,  and  theprolonged  action  of  alcohol.  Cau.stic  alkalies  dissolve  them  (yellow), 
and  from  this  solution  they  are  precipitated  by  acids.  By  powerful  oxidizing  agents  they  yield 
carbamic  acid,  guanidin,  and  volatile  fatty  acids. 

Decomposition.  —  [The  number  and  varieties  of  these  products  are  exceedingly  great,  so  that  it 
is  not  easy  to  separate  the  several  products.  In  the  first  place,  there  is  great  difficulty  in  getting  in 
sufficient  quantity  a  perfectly  pure  proteid,  wherewith  to  institute  the  necessary  experiments.  The 
decomposition  products  of  albumin  when  acted  on  by  barium  hydrate  have  been  most  fully  investi- 
gated. The  action  of  concentrated  HCl,potassic  permanganate,  and  bromine  has  also  been  studied. 
The  action  of  the  animal  or  vegetable  digestive  ferments  is  very  important  (|  170),  and  especially 
that  of  bacteria  causing  putrefaction  (§  184).]  \'VTien  acted  upon  in  a  suitable  manner  by  acids  and 
alkalies,  they  give  rise  to  the  decomposition  products — leucin  (10  to  18  per  cent.),  tyrosin  (o  25  to  2 
per  cent.),  aspartic  acid,  glutamic  acid,  and  also  volatile  fatty  acids,  benzoic  and  hydrocyanic  acids, 
and  aldehydes  of  benzoic  and  fatty  acids;  also  indol  [Hlasiwetz,  Heberiiiami).  Similar  products 
are  formed  during  pancreat.c  digestion  [\  170)  and  during  putrefaction  (§  184).  [Although  it  is 
assumed  that  the  proteids  have  the  closest  relation  to  urea,  no  one,  so  far,  has  succeeded  in  preparing 
urea  by  the  direct  decomposition  of  albumin.  Both  by  the  action  of  acids  and  baiium  hydrate,  the 
splitting  up  into  simpler  compounds  does  not  take  place  at  once,  but  by  successive  stages,  on  to  the 
formation  of  different  bodies.  Proteids,  when  fully  decomposed,  either  by  acids  or  alkalies,  yield  as 
the  final  products  ammonia,  and  amido  acids;  by  alkalies  also  carbonic,  acetic,  and  oxalic  acids. 
The  amido  acids  contain  several  series  including  leucin,  tyrosin,  and  glutamic  acid.  But  all  proteids 
do  not  yield  these  three  bodies,  for  tyrosin  may  be  absent,  while  leucin,  so  far,  has  been  always  found. 
It  has  therefore  been  attempted  to  classify  proteids  into  those  that  yield  tyrosin  (i.e.,  aromatic  com- 
pounds) and  those  that  do  not.  Classes  I-VII,  p.  424,  yield  when  decomposed  aromatic  bodies 
(tyrosin,  indol,  phenol),  while  gelatin-yielding  bodies  and  spongin  yield  no  aromatic  bodies  ] 

General  Reactions. —  (i )  Xanthoproteic  Reaction. — Heated  with  strong  nitric  acid  they  give 
a  yellow,  the  addition  of  ammonia  gives  a  deep  orange  color. 

(2)  With  Millon's  reagent  they  give  a  precipitate,  and  when  heated  with  this  reagent  above 


424  NATIVE    ALBUMINS    AND    GLOBULINS. 

60°  C.  they  give  a  red  one,  probably  owing  to  the  formation  of  lyrosin.  [If  the  proteids  are  present 
in  large  amount,  a  red  precipitate  occurs,  but  if  mere  traces  are  present  only  the  fluid  becomes 
red.] 

(3)  The  addition  of  a  few  drops  of  a  dilute  solution  of  cupric  sulphate,  and  the  subsequent 
addition  of  caustic  potash  or  soda,  give  a  vicict  color,  which  flepcnds  on  boiling  ;  [the  same  color 
is  obtained  by  adding  a  few  drops  of  Fehling's  solution  (biuret  reaction)]. 

(4)  They  are  precipitated  afier  strong  acidulation  by  acetic  acid  and  by  potassium  ferrocyanide. 

(5)  When  boiled  with  concentrated  hydrochloric  acid,  they  give  a  violet- red  color  (Liebermann's 
reaction). 

(6)  Sulphuric  acid  containing  molybdic  acid  gives  a  blue  color  {Frohde). 

(7)  Their  solution  in  acetic  acid  is  colored  violet  with  concentrated  sulphuric  acid,  and  shows  the 
absorption  band  of  hydrobilirubin  (//^^/////(vVwVc). 

(8)  Iodine  is  a  good  microscopic  reagent,  which  strikes  a  brownish  yellow,  while  sulphuric  acid 
and  cane  sugar  give  a  purplish  violet  i^E.  Schnltze). 

[{9)  \Yhen  rendered  strongly  acid  with  acetic  acid  and  boiled  with  an  equal  volume  of  a  con- 
centrated solution  of  sodic  sulphate,  they  are  precipitated.  This  method  is  used  for  removing  proteids 
from  other  li(|uids,  as  it  does  not  interfere  with  the  presence  of  other  substances.  Saturation  with 
sodio-magnesic  sulphate  precipitates  the  proteids,  but  not  peptones,  and  the  same  is  the  case  with 
saturation  with  neutral  ammonia  sulphate  {\  249).] 

[(10)  The  precipitation  of  albumin  by  <;c?(/5  is  more  delicate  when  the  acid  is  dissolved  in  alcohol 
containing  10  per  cent,  of  ether  ;  the  precipitate  is  not  dissolved  by  an  excess  of  the  reagent.] 

[(II)  Most  of  them  are /rc-^z/Z/ftto/ by  strong  mineral  acids,  and  metaphosphoric  acid,  tannic  acid 
(in  an  acid  solution),  phcsphowolframic  and  phospho-molybdic  acids  (in  acid  solution);  potassio- 
mercuric  iodide  (in  acid  solutions);  many  metallic  salts,  e.g.,  of  Cu,  Pb,  Ag,  Hg;  chloral,  phenol, 
trichloracetic  acid,  picric  acid,  alcohol.  Taurocholic  acid  precipitates  albumin  and  syntonin,  but 
not  peptone  or  hemi-albumose  (§  275).] 

249.  THE  ANIMAL  PROTEIDS  AND  THEIR  CHARACTERS.— Class  I.— Native 
Albumins  occur  in  a  natural  condition  in  animal  solids  and  fluids.  They  are  soluble  in  water, 
and  are  not  precipitated  by  alkaline  carbonates,  NaCl,  or  by  very  little  dilute  acids.  Their  solutions 
are  coagulated  by  heating  at  65°  to  73°  C.  Dried  at  40°  C,  they  yield  a  clear,  yellow,  amber- 
colored,  friable  mass,  "  soluble  albumin,"  which  is  soluble  in  water. 

(i)  Serum  albumin  (^  32  and  \  41). — [Its  specific  rotatory  power  is — 56°.]  Almost  all  its  salts 
may  be  removed  fnmi  it  by  dialysis,  when  it  is  no  longer  coagulated  by  heat.  It  is  coagulated  by 
strong  alcohol ;  and  not  very  readily  precipitated  by  hydrochloric  acid,  whde  the  precipitate  so  formed 
is  easily  dissolved  on  adding  more  acid.  When  precipitated  it  is  readily  soluble  in  strong  nitric  acid. 
It  is  not  coagulated  when  shaken  up  with  ether.  The  addition  of  water  to  the  hydrochloric  solution 
precipitates  acid  albumin.     For  iis  presence  in  urine,  see  \  264. 

(2)  Egg  albumin. — \Mien  injected  into  the  blood  vessels  or  under  the  skin,  or  even  when  intro- 
duced in  large  (juantity  into  the  intestine,  part  of  it  appears  unchanged  in  the  urine  (§  192,  4,  and 
\  264).  When  shaken  with  ether  it  is  precipitated.  These  two  reactions  serve  to  distinguish  it 
from  (i).     The  specific  rotation  is  — 35-5°,  i-  e.,  for  yellow  light.     Amount  of  S,  1.6  per  cent. 

(Metalbumin  and  Paralbumin  have  been  found  by  Scherer  in  ropy  solutions  in  ovarian  cysts; 
they  are  only  panially  precipitated  by  heat.  The  precipitate  thrown  down  by  the  action  of  strong 
alcohol  is  soluble  in  water.) 

Class  II. — Globulins  are  native  proteids,  insoluble  in  distilled  water,  but  soluble  in  dilute 
neu  ral  saline  solutions,  i.e.,  neutral  solutions  of  the  alkalies  and  alkaline  earths,  e.g.,  NaCl, 
KCI,  NH^Cl,  MgSO^,  (but  not  Na.jCOg,  NajHPO^),  sodium  chloride  of  i  per  cent.,  and  in  mag- 
nesium sulphate.  These  soluions  are  coagulated  by  heat,  and  are  precipitated  by  the  addition  of  a 
large  quantity  of  water.  Most  of  them  oxe  precipitated  from  their  sodium  chloride  solution  by  the 
addition  of  crystals  of  sodium  chloride,  and  also  by  saturating  their  neutral  solution  at  jo°  7vith 
crystals  of  viagnesium  sulphate.  When  acted  upon  by  dilute  acids  they  yield  acid  albumin,  and  by 
dilute  alkalies,  alkali  albumin. 

(i)  Globulin  (Crystallin)  is  obtained  by  passing  a  stream  of  CO,  through  a  watery  extract  of  the 
crystalline  lens. 

(2)  Vitellin  is  the  chief  proteid  in  the  yolk  of  egg.  It  is  also  said  to  occur  in  the  chyle  (?)  and 
in  the  amniotic  fluid  (  Weyl).  Both  the  foregoing  are  not  precipitated  from  their  neutral  solutions  by 
saturation  with  sodium  chloride. 

(3)  Paraglobulin  or  Serum  globulin  [\  29),  and  in  urine  {\  264). 

.  (4)  Fibrinogen  {\  29). — In  the  clear  jelly-like  secretion  of  the  vesiculse  seminales  of  the  guinea 
pig,  there  is  a  globulin-like  body  closely  resembling  fibrinogen.  It  contains  29  per  cent,  of  albumin, 
with  scarcely  any  ash.  If  it  be  touched  with  a  trace  of  blood  serum,  without  mixing  them,  it  gradu- 
ally and  completely  forms  a  solid  mass  quite  like  fibrin. 

(5)  Myosin  is  the  chief  proteid  in  dead  muscle.  Its  coagulation  in  muscle  post-mortem  con- 
stituus  rigor  mortis.  If  muscle  be  repeatedly  washed,  and  afterward  treated  with  a  10  per  cent, 
solution  of  sodium  or  ammonium  chloride,  it  yields  a  viscid  fluid  which,  when  dropped  into  a  large 


ALBUMINATES    AND    OTHER    PROTEIDS.  425 

quantity  of  distilled  water,  gives  a  white  flocculent  precipitate  of  myosin.  It  is  also  precipitated 
from  its  NaCl  solution  by  crystals  of  NaCl.     For  Kiihne's  and  other  methods  see  ^  293. 

(6)   Globin  [Freyer),  the  proteid  residue  of  hsemogoblin  (§  18). 

Class  III. — Derived  Albumins  (Albuminates). — (i)  Acid  albumin  or  Syntonin. — When 
proteids  aie  dissolved  in  the  stronger  acids,  ^.^.,  hydrochloric,  they  become  changed  into  acid 
albumin«.  They  are  precipitated  from  solution  by  the  addition  of  many  salts,  sodic  chloride,  acetate 
or  phosphate,  or  by  neutralization  with  an  alkali,  e.  g.,  sodic  carbonate,  but  they  are  not  precipitated 
by  heat.  The  concentrated  solution  gelatinizes  in  the  cold,  and  is  redissolved  by  heat.  Syntonin, 
which  is  obtained  by  the  prolonged  action  of  dilute  hydrochloric  acid  (2  per  looo)  upon  minced 
muscles,  is  also  an  acid  albumin.  It  is  formed  also  in  the  stomach  during  digestion  (|  166,  I). 
According  to  Soyka,  the  alkali  and  acid  albumins  differ  from  each  other  only  in  so  far  as  the  pioteid 
in  the  one  case  is  united  with  the  base  (metal)  and  in  the  other  with  the  acid. 

(2)  Alkali  albumin.— If  egg  or  serum  albumin  be  acted  upon  for  some  time  by  dilute  alkalies, 
a  solution  of  alkali  albumin  is  obtained.  Strong  caustic  potash  acts  upon  white  of  egg,  and  yields 
a  thick  jelly,  Lieberkiihn's  jelly.  The  solution  is  not  precipitated  by  heat,  but  it  is  precipitated 
by  the  addition  of  an  acid.  [Although  alkali  albumin  is  precipitated  on  neutralization,  this  is  not 
the  case  in  the  presence  of  alkaline  phosphates,  e.  g.,  sodic  phosphate.] 

(3)  Casein  is  the  chief  proteid  in  milk  (^  231.)  It  is  precipitated  by  acids  and  by  rennet  at 
40°  C.  In  its  characters  it  is  closely  related  to  alkali  albuminate,  but  it  contains  more  N.  It 
contains  a  large  amount  of  phosphorus  (0.S3  per  cent.).  It  may  be  precipitated  from  milk  by 
diluting  it  with  sevei^al  times  its  volume  of  water  and  adding  dilute  acetic  acid,  or  by  adding  mag- 
nesium sulphate  crystals  to  milk  and  shaking  vigorously.  Ov^^ing  to  the  large  amount  of  phosphorus 
which  it  contains,  it  is  sometimes  referred  to  the  nucleo-albumins.  When  it  is  digested  with  dilute 
HCl  (o.  I  per  cent.)  and  pep.-in  at  the  temperature  of  the  body,  it  gradually  yields  nuclein. 

Class  IV. — Fibrin. — (§  27)  and  for  the  fibrin  factors  (^  29). 

Class  V. — Peptones. — For  peptones  and  propeptone  or  the  albumoses  (§  166,  I) ,  in  urine 
{I  264). 

Class  VI. — Lardacein  and  Other  Bodies. — There  fall  to  be  mentioned  the  "  yelk  plates," 
which  occur  in  the  yelk  :  Ichthin  (cartilaginous  fishes,  frog) ;  Ichthidin  (osseous  fishes) ;  Ichthulin 
(salmon) ;  Emydin  (tortoise) ;  also  the  indigestible  amyloid  substance  or  lardacein,  which 
occurs  chiefly  as  a  pathological  infiltration  into  various  organs,  as  the  liver,  spleen,  kidneys,  and 
blood  vessels.  It  gives  a  blue  with  iodine  and  sulphuric  acid  (like  cellulose),  and  a  mahogany 
brown  with  iodine.      It  is  difficult  to  change  it  into  an  albuminate  by  the  action  of  acids  and  alkalies. 

Class  VII. — Coagulatfed  Proteids. — When  any  native  albumins  or  globulins  are  coagulated, 
€,  g.,  at  70°  C,  they  yield  bodies  Avith  altered  characters,  insoluble  in  water  and  saline  solutions,  but 
soluble  ill  boiling  strong  acids  and  alkalies,  when  they  are  apt  to  split  up.  They  are  dissolved 
during  gastric  and  pancreatic  digestion  to  produce  peptones. 

Appendix  :  Vegetable  Proteid  Bodies. — Plants,  like  animals,  contain  proteid  bodies,  although 
in  less  amount.  They  occur  either  in  solution  in  the  juices  of  living  plants  or  in  the  solid  form. 
In  composition  and  reaction  they  resemble  animal  proteids. 

[The  characters  of  vegetable  proteids  have  a  great  resemblance  to  animal  proteids.  They  have 
frequently  been  obtained  in  a  crystalline  form,  «■.  ^.,  from  the  seeds  of  the  gourd  and  various 
oleaginous  seeds.  They  occur  in  greatest  bulk  in  the  seeds  of  plants,  aleurone  grains  being  for 
the  most  part  composed  of  them.  In  seeds,  globulins  and  "  vegetable  peptone  "  lorm  the  greater 
proportion  of  the  proteid  constituents.] 

[Globulins. — These  varieties  have  been  described  as  occurring  in  the  seeds  of  plants  :  vege- 
table myosin,  vitellin  and  paraglobulin  (^Marti7i).  They  have  practically  the  same  properties 
as  those  found  in  the  animal  kingdom  ;  vegetable  vitellin  has,  however,  not  been  sufficiently  studied. 
Paraglobulin  has  been  found  in  papaw  juice  {^Martin).  Myosin  occurs  in  the  seed  of  legumiiiosse, 
in  flour,  and  in  the  potato.] 

[Albumin. — The  existence  of  a  body  corresponding  to  egg  or  serum  albumin  in  the  vegetable 
kingdom  is  doubtful  [Ritthaiisen).     Such  a  body  has  been  described  in  papaw  juice  iyMartiti).'] 

[Vegetable  Peptone  ;  Albumoses. — A  true  peptone  has  not  yet  been  recognized  in  plants  : 
what  has  been  described  as  such  is  hemi-albumose  (  Vines).  Albumoses  have  been  found  in  the 
seeds  of  leguminosse,  in  flour,  and  in  papaw  juice.  In  the  last,  two  forms  occur,  called  respec- 
tively a-  and  /3-  phytalbumose.  The  former,  a-phytalbumose,  agrees  with  the  hemi-albumose 
described  by  Vines,  being  soluble  in  cold  and  boiling  water ;  giving  also  a  biuret  reaction,  and  a 
precipitate  by  saturation  with  sodium  chloride  only  in  an  acid  solution.  The  latter,  fi  phytalbumose, 
is  soluble  in  cold,  but  not  in  boiling,  distilled  water ;  hence  it  is  precipitated  by  heat.  It  is  also  readily 
thrown  down  by  saturation  wiih  sodium  chloride,  and  gives  a  faint  biuret  reaction  [A/artin).'] 

[Vegetable  Casein  is  said  to  occur  in  the  seeds  of  leguminosse  ;  and  it  is  slightly  soluble  in  water, 
but  readily  so  in  weak  alkalies  and  in  solutions  of  basic  calcic  phos-phate.  A  solution  of  this  body  is 
precipitated  by  acids  and  rennet.  Two  varieties  have  been  described — (a)  legumin,  in  peas,  beans, 
lentils;  acid  in  reaction,  soluble  in  weak  alkalies  and  very  dilute  HCl  or  acetic  acid;  (/3)  conglutin, 
a  very  similar  body  occurring  in  hops  and  almonds.     The  existence  of  vegetable  casein  is  denied. 


426  ALBUMINOIDS. 

Vines  slates  that  both  legumin  and  conglulin  are  artificial  products,  being  formed  from  the  globulins 
present  liv  ihe  dilute  alkali  used  in  exlraciicm  of  tiie  proieids.     This  is  denied  by  Rilthausen.] 

[Gluten  and  Glutin.  — Cluten  is  reaiily  prepared  from  flour  by  washing  and  kneading  it  in  a 
muslin  1  a^  under  a  htream  of  water.  So  prepared  it  is  yellowish  brov  n  in  color,  very  sticky,  and 
capable  of  being  drawn  out  into  long  shreils.  It  is  insoluble  in  water,  soluble  (but  not  completely) 
by  prolonged  action  in  dilute  acids  nnd  alkalies  (.2  per  cent.  K  HO  and  HCl).  The  prolonged  action 
of  alcohol  [So  to  S5  pir  cent.)  dissolves  part  of  the  substance  of  gluten,  leaving  a  residue,  called 
by  Liebig  plant  fibrin  and  by  Ritlhausen  gluten  casein.  The  alcohol  contains  gliadin  (glulin), 
gluten  fibrin,  and  mucedin.  Gluten  casein  is  readily  soluble  in  dilute  alkalies,  almost  insoluble 
in  dilute  acetic  aciil.  and  (|uue  insoluble  in  cold  and  bodm..;  waier ;  the  pro  iucts  of  its  decomposi- 
tion, by  heating  wi  h  H.,SO.,,  are  leucin,  tyrosin,  glutamic,  and  as|)araginic  acids.  The  three  liodies 
di-solved  from  glulin  by  alcohi  Idifier  chiefly  in  their  solubility  in  alcohol  and  water.  Gluten  fibrin, 
the  least  soluble,  is  c.»agulated  by  the  action  of  absolute  alcohol;  it  is  readily  soluble  in  dilute  aciHs 
and  alkalies,  being  precipitated  by  neutralization.  Gliadin  (glutin,  plant  gelatin)  may  be  prepared 
by  boilin.;  gluten  with  water  :  it  deposits  on  cooling  tiie  solution  Though  soluble  in  water  at  100° 
C.  at  fir.»t,  it  becomes  insoluble  by  the  prolonged  aclion  of  water  at  that  temperature.  It  is,  like 
gluten  fibrin,  soluble  in  dilute  acids  and  alkalies.  Mucedin  differs  from  gliadin  in  being  less  soluble 
in  strong  alcohol.  The  water  used  in  washing  the  flour  in  the  preparation  ol  gluten  contains  hemi- 
albumose  (  /  'hies)  and  a  globulin  ( IVeyl).  Rye  flour,  as  well  as  wheaten,  yields  gluten  under  similar 
ireatmeiu  with  water.] 

[Nitrogenous  Crystalline  Principles. — Leucin,  tyrosin,  asparagin,  and  glutamic  acid  have  been 
found  in  tlie  seeds  ol  plants.] 

250.  (2)  THE  ALBUMINOIDS. — These  substances  closely  resemble  true  proteids  in  their 
compojilion  and  origin,  and  are  amorphous  non-crystalline  colloids  ;  some  of  them  do  not  contain  S, 
but  the  most  of  them  have  not  been  prepared  free  from  ash.  Their  reactions  and  decomposition  pro- 
ducts closely  resemble  those  of  the  proteids;  some  of  them  i)roduce,  in  addition  to  leucin  and 
lyiosin,  glycin  and  alanin  (amidopropionic  acid).  They  occur  as  organized  constituents  of  the 
tissues  and  also  in  fluid  form.  It  is  unknown  whether  they  are  farmed  by  oxidation  from  proteid 
bodies  or  by  synthesis. 

1.  Mucin  is  the  characteristic  substance  present  in  mucus.  That  obtained  from  the  sub-maxil- 
lary gland  contains — C  52.31,  H  7.22,  N  11.84,028.63.  According  to  Hammarslen  it  contains 
S  1.79  and  N  13.5  per  cent.  It  dissolves  in  water,  making  it  sticky  or  slimy,  and  can  be  filtered. 
It  is  precipitated  by  acetic  acid  and  alcohol ;  and  the  alcohol  precipitate  is  again  soluble  in  water. 
It  is  not  precipitated  by  acetic  acid  and  ferrocyanide  of  potassium,  but  HNO.j  and  other  mineral 
aciiis  precipitate  it.  It  occurs  in  saliva  (^  146),  in  bile,  in  mucous  glands,  secretions  of  mucous 
membranes,  in  mucous  tissue,  in  synovia,  and  in  tendons.  Pathologically  it  occurs  not  unfrequently 
in  cysts;  in  the  animal  kmgdom,  especially  in  snails  and  in  the  skin  of  hololhurians.  It  yields 
lucin  and  7  ])er  cent,  of  tyrosin  when  it  is  decomposed  by  prolonged  boiling  wiih  sulphuric  acid. 
[  The  precipitate  called  mucin  has  not  always  the  same  characters,  and,  in  fact,  it  ditfers  according 
to  the  animal  from  which  it  is  obtained  {Landwe/ir.)'\ 

2.  Nuclein  [Miescher,  \  198) — (C  29,  H  49,  N  9,  P  3,  O  22) — contains  phosphoric  acid,  and  is 
slightly  soluble  in  water,  easily  in  ammonia,  alkaline  carbonates,  strong  HNO3;  it  gives  the  biuret 
I eaci ion  ;  no  reaction  with  Millon's  reagent ;  when  decomposed  it  yields  phosphorus.  It  occurs  in 
the  nuclei  of  pus  and  blood  corpuscles  \\  22),  in  spermatozoids,  yelk  spheres,  liver,  brain,  and  milk, 
veast.  fungi,  and  many  seeds.  It  has  resemblances  to  mucin,  and  is  perhaps  an  intermediate  jiroduct 
ijetween  albumin  and  lecithin  {Hoppe-Seyler).  It  is  prepared  by  the  artificial  digestion  of  )ius,  when 
it  remains  as  an  indigestible  residue  ;  acids  precipitate  it  from  an  alkaline  solution.  It  gives  a 
feeble  xanthoproteic  reaction;  after  the  prolonged  action  of  alkalies  and  acid,  substances  similar 
to  albumin  and  syntonin  are  formed.  Hypoxanthin  and  guanin  have  been  obtained  as  decomposition 
products  from  it  {A'assel). 

3.  Keratin  occurs  in  all  horny  and  epidermic  tissues  (epidermic  scales,  hairs,  nails,  feathers) — 
C  50.3-52.5,  H  6.4-7,  ^^  16.2-17,0  20.8-25,  S  0.7-5  P^""  ^^"f- — is  .soluble  in  boiling  cau.<itic  alkalies, 
but  swells  up  in  cold  concentrated  acetic  acid.  When  decomposed  by  H^SO^  it  yields  10  per  cent, 
leucin  and  3.6  per  cent  tyrosin.     Neuro-keratin  (^  321). 

4.  Fibroin  is  soluble  in  strong  alkalies  and  mineral  acids,  in  ammonio-sulphate  of  copper;  wlien 
boiled  with  H.^SO^  it  yields  5  per  cent.  tyro,sin,  leucin,  and  glycin.  It  is  the  chief  constituent  of  the 
cocoons  of  insects  anil  threads  of  spiders. 

5.  Spongin,  aUied  to  fibroin,  occurs  in  the  bath  sponge,  and  yields,  as  decomposition  products, 
leucin  and  glycin  (Slacie/er). 

6.  Elastin,the  fundamental  substance  in  elastic  tissue,  is  soluble  only  when  boiled  in  concentrated 
caus'ij  pot.ish — C  55-55.6,  H  7.1-7.7.  N  16.I-17.7,  O  19.2-21.1  per  cent.  It  yields  36  to  45  per 
cent,  of  leucin  and  ^'^  per  cent,  of  tjTosin. 

7.  Gelatin  (Glutin),  obtained  fi-om  connective  tissues  by  prolonged  boiling  with  water;  it 
gelatinizes  in  the  cold— C  52.2-50.7.  H  6.6-7.2,  N  17. 9-18. 8,  S  -r-  (J  23.5-25  (S  o  7  per  cent).  [The 
ordinary  coimective  tissues  are  supposed  to  contain  ihe  hypothetical  anhydride  collagen,  while  the 


FERMENTS.  427 

organic  basis  of  bone  is  called  ossein.]  It  rotates  the  ray  of  polarized  ligbt  strongly  to  the  left  = 
—  130°.  By  prolonged  boiling  and  digestion,  it  is  converted  into  a  peptone-like  body  (gelatin  pep- 
tone), which  does  not  gelatinize  (^.  161, 1).  [It  swells  up,  but  does  not  dissolve  in  cold  water;  when 
dissolved  in  warm  water,  and  tinged  with  Berlin  blue  or  carmine,  it  forms  the  usual  colored  mass 
which  is  employed  by  histologisis  for  making  fine  transparent  injections  of  blood  vessels.]  A  body 
resembling  gelatin  is  found  in  leuksemic  blood  and  in  the  juice  of  the  spleen  (^  103,  1).  When 
decomposed  with  sulphuric  acid  it  yields  glycin,  ammonia,  leucin,  but  no  tyj-osui.  [It  is  precipitated 
from  its  solution  by  alcohol,  mercuric  chloride,  metapbosphoric  acid,  phospho-wolframic  acid,  tauro- 
cholic  acid,  tannic  acid,  but  the  precipitate  with  the  last  does  not  occur  when  sails  are  absent.  It  is 
readily  soluble  in  dilute  acids,  even  in  acetic  acid.  When  boiled  with  Millon's  reagent,  it  is  not 
colored  red.  With  cupric  sulphate  and  caustic  soda  it  gives  a  violet  color  which,  on  boiling,  be- 
comes light  red.     It  gives  no  color  with  concentrated  H^SO^  and  acetic  acid.] 

8.  Chondrin  occurs  in  the  matrix  of  hyaline  cartilage  and  between  the  fibres  in  fibro-cartilage. 
It  is  obtained  from  hyaline  cartilage  and  the  cornea  by  boiling.  [Its  solutions  gelatinize  on  cooling.] 
It  occurs  also  in  the  mantle  of  mollusks— C  49.5-50.9,  H  6.6-7.1,  N  14.4-14.9,  S  -f-  O  27.2-29  (S 
0.4  per  cent.).  When  boiled  with  sulphuric  acid  it  yields  leucin;  with  hydrochloric  acid,  and  when 
digested,  chondro-glucose  (Jlleissner) ;  it  belongs  to  the  glucosides,  which  contain  N.  When  acted 
upon  by  oxidizing  reagents  it  is  converted  into  gelatin  [Branie).  The  substance,  which  yields 
chondrin  is  called  chondrogen,  which  is  perhaps  an  anhydride  of  chondrin.  The  following  pro- 
perties of  gelatin  and  chondrin  are  to  be  noted  :  Gelatin  is  precipitated  by  tannic  acid,  mercuric 
chloride,  chlorine  water,  platinic  chloride,  and  alcohol,  but  not  by  acids,  alum,  or  salts  of  silver, 
iron,  copper,  or  lead;  its  specific  rotation  is  =  — - 130°.  [Compare  these  precipitants  with  those  of 
albumin  ]  Chondrin  is  precipitated  by  acetic  acid  and  dilute  sulphuric  and  hydrochloric  acids,  by 
alum,  and  by  salts  of  silver,  iron,  and  lead ;  its  specific  rotation  =  —  213°. 

9  The  hydrolitic  ferments  have  recently  been  called  enzymes  by  W.  Kiihne,  in  order  to  dis- 
tinguish them  from  organized  ferments,  such  as  yeast.  The  enzymes,  hydrolytic  or  organic  ferments, 
act  only  in  the  presence  of  water.  They  act  upon  certain  bodies,  causing  them  to  take  up  a  mole- 
cule of  water.  They  all  decompose  hydric  peroxide  into  water  and  O.  They  are  most  active 
between  30°  to  35°  C,  and  are  destroyed  by  boiling,  but  when  dry  they  may  be  subjected  to  a 
temperature  of  100°  without  being  destroyed.  Their  solutions,  if  kept  for  a  long  time,  gradually 
lose  their  properties  and  undergo  more  or  less  decomposition. 

[a)  Sugar-forming  or  diastatic  ferment  occurs  in  saliva  (|  148), pancreatic  juice  (|  170),  intes- 
tinal juice  (I  183),  bile  (|  180),  blood  (|  22),  chyle  (|  1S9),  liver  (|  174),  in  human  milk  (|  231).  In- 
vertin  in  intestinal  juice  (|  183).  Almost  all  dead  tissues,  organic  fluids,  and  even  proteids,  although 
only  to  a  slight  degree,  may  act  diastatically.  Diastatic  ferments  are  very  generally  distributed  in 
the  vegetable  kingdoni. 

(b')  Proteolytic,  or  ferments  which  act  upon  proteids.— Pepsin  in  gastric  juice  and  in 
muscles  (|  166),  in  vetches,  myxomycetes  [Krukenbei-g),  trypsin  in  the  pancreatic  juice  (|  170),  a 
similar  ferment  in  the  intestinal  juice  {\  183),  and  urine  (^  264). 

[c)  Fat- decomposing  in  pancreatic  juice  (|  170),  in  the  stomach  (§  166). 

(</)  Milk-coagulating  in  the  stomach  (§  166),  pancreatic  juice  (§  170),  and  perhaps  also  in  the 
.  intestinal  juice  (?) — (  W.  Roberts). 

[The  importance  of  fermentative  processes  has  already  been  referred  to  in  detail  under 
"  Digestion."  Ferments  are  bodies  which  excite  chemical  changes  in  other  matter  with  which 
they  are  brought  into  contact.     They  are  divided  into  two  classes  : — 

(i)  Unorganized;  soluble  or  non-living. 
(2)   Organized,  or  living.] 

[(i)  The  Unorganized  Ferments  are  those  mentioned  in  the  following  table.  They  seem  to 
be  nitrogenous  bodies,  although  their  exact  composition  is  unknown,  and  it  is  doubtful  if  they  have 
ever  been  obtained  perfectly  pure.  They  are  present  in  many  secretions,  and  are  produced  within 
the  body  by  the  vital  activity  of  the  protoplasm  of  cells.  They  are  termed  soluble  because  they  are 
soluble  in  water,  glycerin,  and  some  other  substances  {\  148),  while  they  can  be  precipitated  by 
alcohol  and  some  other  reagents.  They  do  not  multiply  during  their  activity,  nor  is  their  activity 
prevented  by  a  certain  proportion  of  salicylic  acid.  They  are  not  affected  by  oxygen  subjected  to 
the  compression  of  many  atmospheres  (/".  Bert).  They  are  non-living.  Their  other  properties  are 
referred  to  above  ] 


428  FERMENTS. 

[The  unorganized  ferments  present  in  the  body,  and  their  actions  ( H^.  Roberts) 


Fluid  or  Tissues. 

Ferment. 

Actions. 

Saliva,  .    .    .    . 

I.  Ryalin  (§  148) 

Converts  starch  chiefly  into  maltose. 

Gastric  juice,    - 

1.  Pepsin, -1 

2.  Milk-curdling, 

3.  Lactic  acid  ferment,      .    .    . 

4.  Fat-splitting 

Converts  proteids  into  peptones  in  an  acid 
medium,  certain  by-products  being  fotmed 
(1  166). 

Curdles  casein  of  milk. 

Splits  up  milk  sugar  into  lactic  acid. 

Splits  up  fats  into  glycerin  and  fatty  acids. 

!               r 

j    Pancreatic 
1       juice, 

I 

1.  Diastatic  or  amylopsin,     .    . 

2.  Trj-psin, -j 

3.  Emulsive  (?), 

4.  Fat-splitting  or  steapsin,  .    . 

5.  Milk-curdling 

1 

Converts  starch  chiefly  into  maltose. 
Changes  proteids  into  peptones  in  an  alkaline 

medium,  certain  by-products  beini:  formed 

(§  170). 
Emulsifies  fats. 

Splits  fats  into  glycerin  and  fatty  acids. 
Curdles  casein  of  milk. 

c 

>    Intestinal 
i       juice. 

1.  Diastatic i 

2.  Proteolytic, 

3.  Invertin, 

4.  Milk-curdling, 

Does  not  form  maltose,  but  maltose  is  changed 

into  glucose  (^  183). 
Fibrin  into  peptone  (?). 
Changes  cane-  into  grape  sugar. 
(?  in  small  intestine). 

Blood 

Chyle 

Liver  (?),  .    .    . 
Milk,     .... 
Most  tissues  .    . 

V  Diastatic  ferments 

•    • 

Muscle,     .    .    . 
Urine,    .... 

V  Pepsin  and  other  ferments. 

Blood 

Fibrin-forming  ferment. 

[(2)  The  Organized  or  living  ferments  are  represented  by  yeast  (§  235).  Other  living  ferments 
belonging  to  the  schizomycetes,  occurring  in  the  intestinal  canal,  are  referred  to  in  ^  184.  Yeast 
causes  fermentation  by  splitting  up  sugar  into  CO,^  and  alcohol  (^  156),  but  this  result  only  occurs 
so  long  as  the  yeast  is  living.  Hence,  its  activity  is  coupled  with  the  vitality  of  the  cells  of  the 
yeast.  If  yeast  be  boiled,  or  if  it  be  mixed  with  carbolic  or  salicylic  acid,  or  chloroform,  all  of 
which  destroy  its  activity,  it  cannot  produce  the  alcoholic  fennentation.  As  yet  no  one  has  succeeded 
in  extracting  from  yeast  a  substance  which  will  excite  the  alcoholic  fermentation.  All  the  organized 
ferments  grow  and  multiply  during  their  activity  at  the  expense  of  the  substances  in  which  they 
occur.  Thus  the  alcoholic  fermentation  depends  upon  the  "  life  "  of  the  yeast.  They  are  said  to 
be  killed  by  oxygen  subjected  to  the  compression  of  many  atmospheres  {P.  Bert).  But  it  is  important 
to  note  that  Hoppe-Seyler  has  extracted  from  dea<t  yeast  (killed  by  ether)  an  unorganized  ferment 
which  can  change  cane  sugar  into  grape  sugar.] 

lo.  Haemoglobin,  the  coloring  matter  of  blood,  which,  in  addition  to  C,  H,  O,  N,  and  S,  con- 
tains iron,  may  be  taken  with  the  albuminoids  (g  11).     [Haemocyanin  (§  32).] 

(3)  Glucosides  cgntaining  Nitrogen. 

In  addition  to  chondrin,  the  following  glucosides  containing  nitrogen,  when  subjected  to  hydro- 
lytic  processes,  may  combine  with  water,  and  form  sugar  and  other  substances : — 

Cerebrin  (^  322)  =  Cj-HjjqN.^O.^^  [Geoghegan).  [Parens  has  shown  that  cerebrin  as  originally 
prepared  by  W.  Miiller  is  a  mixture  of  three  bodies,  viz.,  cerebrin,  homocerebrin,  and  en- 
cephalin.] 

Protagon — C  66.29,  H  10.69,  N  2.39,  P  1.068,  per  cent. — occurs  in  nerves,  and  contains  phos- 
phorus (j;  322). 

Chitin,  2(Cj.H2gN20jo),  is  a  glucoside  containing  nitrogen,  and  occurs  in  the  cutaneous  coverings 
of  arthropoda,  and  also  in  their  intestine  and  tracheae ;  it  is  soluble  in  concentrated  acids,  e.  g.. 


ORGANIC    ACIDS. 


429 


hydrochloric  or  nitric  acid,  but  insoluble  in  other  reagents.  According  to  Sandwick,  chitin  is  an 
amin  derivative  of  a  carbohydrate  with  the  general  formula  n(Cj2H2oOjQ).  The  hyalin  of  v^orms  is 
closely  related  to  chitin.  (Solanin,  amygdalin  (^  202),  and  salicin,  etc.,  are  glucosides  of  the  vege- 
table kingdom.) 

(4)  Coloring  Matters  containing  Nitrogen. 

Their  constitution  is  unknovirn,  and  they  occur  only  in  animals.  They  are  in  all  probability 
derivatives  of  haemoglobin.  They  are  (i)  hsematin  (§  18,  A),  myohaematin  (^  232,  §  292,  a), 
histohaematin  (§  103,  IV),  and  haematoidin  (§  20).  (2)  Bile  pigments  (|  177,  3).  (3) 
Urine  pigments  (except  Indican).  (4)  Melanin— C^^, 2,  H.,,  Ng  3,  O^g.g— or  the  black  pigment, 
which  occurs  partly  in  epithelium  (choroid,  retina,  iris,  and  in  the  deep  layers  of  epidermis  in 
colored  races)  and  partly  in  connective-tissue  corpuscles  (Lamina  fusca  of  the  choroid).  [Turacin 
occurs  in  the  red  feathers  of  Corythaix  Buffoni  or  Plantain  Eater.  Its  ash  contains  nearly  6  per 
cent,  of  copper  [Cku7-c/i).     The  reddish  spots  or  parts  of  feathers  burn  with  a  green  flame.] 

II.  Organic  Acids  free  from  Nitrogen. 

(i)  The  fatty  acids,  with  the  formula  CnH2n.iO(OH),  occur  in  the  body  partly  free  and  partly 
in  combination.  Free  volatile  fatty  acids  occur  in  decomposing  cutaneous  secretions  f sweat).  In 
combination,  acetic  acid  and  caproic  acid  occur  as  amido  compounds  in  glycin  (=  amido- acetic 
acid)  and  leucin  (^  amido-caproic  acid).  More  especially  do  they  occur  united  with  glycerin  to 
form  neutral  fats,  from  which  the  fatty  acid  is  again  set  free  by  pancreatic  digestion  (§  170,  III). 

(2)  The  acids  of  the  acrylic  acid  series,  with  the  formula  CqHj  30(H0),  are  represented  in  the 
body  by  one  acid  oleic  acid,  which  in  combination  with  glycerin  yields  the  neutral  fat  olein. 

251.  FATS. —  (i)  Neutral  fats  occur  very  abundantly  in  animals,  but  they  alsooccurin  all  plants: 
in  the  latter  more  especially  in  the  seeds  (nuts,  almonds,  cocoanut,  poppy),  more  rarely  in  the  peri- 
carp (olive)  or  in  the  root.  They  are  obtained  by  pressure,  melting,  or  by  extracting  them  with 
ether  or  boiling  alcohol.  They  [<?.  ^.,  tristearin,  C.^H^jgOg]  contain  much  less  O  than  the  carbo- 
hydrates, such  as  sugar  and  starch ;  they  give  a  greasy  spot  on  paper,  and  when  shaken  with  colloid 
substances,  such  as  albumin,  they  yield  an  emulsion.  When  treated  with  superheated  steam  or 
with  certain- ferments  (p.  301),  they  take  up  water  and  yield  glycerin  and  fatty  acids,  and  if 
the  latter  be  volatile  they  have  a  rancid  odor.  Treated  with  caustic  alkalies  they  also  take  up 
water,  and  are  decomposed  into  glycerin  and  fatty  acids  ;  the  fatty  acid  unites  with  the  alkali  and 
forms  a  soap,  while  glycerin  is  set  free.     The  soap  solution  dissolves  fats. 

Glycerin  is  a  triatomic  alcohol,  C3H-(OH)3,  and  unites  with  (l)  the  following  monobasic  fatty 
acids  (those  occurring  in  the  body  are  printed  in  italics)  : — 

Acids. 
[Marganc,     .    .  Cy^Yi^fi^ 
is  a  mixture  of 
13  and   14.] 

14.  Stearic,    ....  CjgHggOj 

15.  Arachinic,   .    .    .  C2oH^o02 

16.  Hyanic,  ....  Cj-H-gOj 

17.  Cerotinic,    .    .    ,  Cj^Hj^O,^ 

The  acids  form  a  homologous  series  with  the  formula  CaH2n.iO(OH).  With  every  CHj  added 
their  boiling  point  rises  19°.  Those  containing  most  carbon  are  solid,  and  non-volatile;  those  con- 
taining less  C  (up  to  and  including  10)  are  fluid  like  oil,  have  a  burning  acid  taste,  and  a  rancid 
odor.  The  earlier  members  of  the  series  may  be  obtained  by  oxidation  from  the  later,  by  CH^ 
being  removed,  while  CO.,  and  H^O  are  formed  ;  thus,  butyric  acid  is  obtained  from  propionic  acid. 
Nos.  13  and  14  are  found  in  human  and  animal  fat,  less  abundant  and  more  inconstant  are  12,  11,  6, 
8,  10,  4.  Some  occur  in  sweat  (|  287)  and  in  milk  (^  231).  Many  of  them  are  developed  during 
the  decomposition  of  albumin  and  gelatin.  Most  of  the  above  (except  15  to  17)  occur  in  the  con- 
tents of  the  large  intestine  (§  185). 

(2)  Glycerin  al=o  unites  with  the  monobasic  oleic  acid,  which  also  forms  a  series,  whose 
general  formula  is  CnH2n-,0(0H),  and  they  all  contain  2H  less  than  the  corresponding  members 
of  the  faUy  acid  series.  The  corresponding  fatty  acids  can  be  obtained  from  the  oleic  acid  series 
and  vice  versa.  Oleic  acid  (olein  elainic  acid),  CigH3^02,  is  the  only  one  found  in  the  organism  ; 
united  with  glycerin,  it  forms  the  fluid  fat,  olein.  The  fat  of  new-born  chfldren  contains  more 
glyceride  of  palmitic  and  stearic  acid  than  that  of  adults,  which  contains  more  glyceride  of  oleic 
acid.  Oleic  acid  also  occurs  united  with  alkalies  (in  soaps)  and  (like  some  fatty  acids)  in  the 
lecithins  (^  23).  If  lecithin  be  acted  on  with  barium  hydrate,  we  obtain  insoluble  stearic,  or  oleic, 
or  palmitic  acids  arid  barium  oleate,  together  with  dissolved  neurin  (§  322,  b)  and  baric  glycerin 
phosphate.  It  appears  as  if  there  were  several  lecithins,  of  which  the  most  abundant  are  the  one 
with  stearic  acid  and  that  with  palmitin  +  oleic  acid  radicle  [Diakonow).  Lecithin  occurs  in  the 
blood  corpuscles  (§  23),  semen  and  nerves,  while  neurin  is  constantly  present  in  fungi. 


I. 

2. 

Acids. 
Formic,    .    .    . 
Acetic,      .    .    . 

.  CH2O2 

7- 
8. 

Acids. 
QLnanthylic,    . 

Capry/ic,       .    . 

•  CgHieO 

3- 
4- 

5- 

Propionic,   .    . 
Butyric,  .    .    . 
[Isobutyric, 
Valerianic, 

•  CgHgOj 

.  C,H302] 

•  C5H,„02 

9- 
10. 
II. 
12. 

Pelargonic,  .    . 
Capric,    .    .    . 
Laurostearic, 

Myristic,     .    . 

•    CgHjgO, 

•  C12H2A 

6. 

Caproic,        .    . 

•   CgH,202 

13- 

Palmitic,  .    . 

C16H32O5 

430  ORGANIC    ACIDS    AND    ALCOHOLS. 

The  neutral  fats  [palmitin,  stearin  (both  solid),  and  olein  (Huid)].  tlie  glycerides  of  fatty  acids, 
and  of  oleic  acid,  arc  triple  etliers  of  triatomic  alcohol  glycerin.  With  the  neuiral  fats  may  be  asso- 
ciated glycerin  phosphoric  acid,  an  acid  glycerin  ether,  formed  by  the  union  of  glycerin  and 
pliosphoric  acid,  with  the  giving  off  of  a  molecule  of  water  (C^UgPOg) ;  it  is  a  decomposition  pro- 
duct of  lecithin  (^  23). 

(3")  The  glycolic  acids  (acids  of  the  lactic  acid  series)  have  the  formula  CnH.2n-20(OH).^. 
Thev  are  formed  by  oxidation  from  the  fatty  acid  series  by  substituting  OH  (hydroxyl)  for  one  atom 
of  \i  of  the  fatty  acids.  Conversely,  fatty  acids  may  be  obtained  from  the  glycolic  acids.  The  fol- 
lowing acids  of  this  series  occur  in  the  body  :  — 

(a)  Carbonic  Acid  (oxy  formic  acid),  CO(OM)2;  in  this  form,  however,  it  only  makes  salts. 
Free  carbonic  acid  or  cai'bon  dioxide  is  an  anhydride  of  the  same  ^  CO.,. 

(/')  Glycolic  Acid  (oxy-acetic  acid),  C._,H20(0H).,,  does  not  occur  free  in  the  body.  One  of  its 
coinjwunds,  glycin  (l;1vcoco11,  amido-acetic  acid,  or  gelatin  sugar),  occurs  as  a  conjugate  acid,  viz., 
as  glycocolic  acid  in  the  bile  (^  177,  2),  and  as  hippuric  acid  in  the  urine  {'i  260).  Clycin  exists  in 
complex  combination  in  the  gelatin. 

((■)  Lactic  Acid  (oxy-propionic  acid)  C3lI^O(OH)2,  occur  in  the  body  in  two  isomeric  forms — 
I.  'WxQ  ethylicienelactic  rtc/a',  which  occurs  in  two  modifications — as  the  right  rotatory  .frt/(<?/rtf//V 
/7c/</' (paralactic),  a  metabolic  product  of  muscle ;  and  as  the  ordinary  optically  inactive  product  of 
"  lactic  fermentation,"  which  occurs  in  gastric  juice,  in  sour  milk  (sauerkraut,  acid  cucuml)er),  and 
can  be  obtained  by  fermentation  from  sugar  (^  184).  2.  The  isomer,  ctliyUne-laciic  acid,  occurs  in 
the  watery  extract  of  muscles  (^  293). 

((/)  Leucic  Acid  (oxy  caproic  acid),  CgHjjO.,,  does  not  occur  as  such,  but  only  in  the  form  of 
one  of  its  derivatives,  leucin  (amidocaproic  acid),  as  a  product  of  the  metaljolism  in  many  tissues, 
and  is  fomied  during  pancreatic  digestion  (^  170,  II).  Leucic  acid  may  be  prepared  from  leucin, 
and  glycolic  acid  from  glycin,  by  the  action  of  nitrous  acid. 

(4)  Acids  of  the  Oxalic  Acid  or  Succinic  Acid  Series,  having  the  formula  C„H.,„.,0.,(0H)2, 
are  bi-basic  acids,  which  are  formed  as  completely  oxidized  products  by  the  c>xidation  of  fatty  acids 
and  glycolic  acid,  water  being  removed.  It  is  important  to  note  their  origin  from  substances  lich  in 
carbon,  c.g.^  fats,  carbohydrates,  and  proteids. 

(a)  Oxalic  Acid,  C.,0.,(OH),,  arises  from  the  oxidation  of  glycol,  glycin,  cellulose,  sugar,  starch, 
glycerin,  and  many  vegetable  acids —  it  occurs  in  the  urine  as  calcium  oxalate  (?  260). 

(h)  Succinic  Acid,  C^H,0.,(OH),,,  has  been  found  in  small  amount  in  animal  solids  and  fluids; 
spleen,  liver,  thymus,  thyroid  ;  in  the  fluids  of  echinococcus,  hydrocephalus,  and  hydrocele,  and 
more  abundantly  in  dog's  urine  after  fatty  and  flesh  food;  in  rabbit's  urine  after  feeding  with  yellow 
turnips.     It  is  also  formed  in  small  amount  during  alcoholic  fermentation  (§  150). 

(5)  Cholalic  Acid  in  the  bile  (?  177)  and  in  the  intestine  [\  182). 

(6)  Aromatic  Acids  contain  the  radicle  of  benzol.  Benzoic  acid  (=:  phenyl-formic  acid) 
occurs  in  urine  united  with  glycerin,  as  hippuric  acid  (|  260). 

III.  Alcohols. 
Alcohols  are  bodies  which  originate  from  carbohydrates,  in  which  the  radical  hydroxyl  (HO)  is 

H  ) 

substituted  for  one  or  more  atoms  of  H.  They  may  be  regarded  as  water,  it  >  0,  in  which  the  half 

'  C  H  1 

of  the  H  is  replaced  by  a  CH  compound.     Thus,  C^Hg  (ethyl  hydrogen)  passes  into      '^yfi  \  O 

(ethylic  alcohol).  PHI 

(rt)     Cholesterin,       ^^yx^  f  Oj 's  a  true  monatomic  alcohol,  and  occurs  in  blood,  yelk,  brain, 

bile  (§  177,  4),  and  generally  in  vegetable  cells,  and  it  is  the  only  solid  monatomic  alcohol  in  the 
body.'  rOH 

{b)  Glycerin,  CjHj-j  OH,  is  a  triatomic  alcohol.     It  occurs  in  neutral  fats  united  with  fatty  acids 
iOH 
and  oleic  acid  ;  it  is  formed  by  the  splitting  up  of  neutral  fats  during  pancreatic  digestion  (|  170, 
111),  and  during  the  alcoholic  fermentation  (iJ  150). 

{c)   Phenol    (=  phenylic  acid,  carbolic  acid,  oxybenzol)  (?  184,  III). 

{d)   Pyrokatechin   (=r  dioxybenzol)  (^  252). 

(f )  The  Sugars  are  closely  related  to  the  alcohols,  and  they  may  be  regarded  as  poly-atomic 
alcohols.  Their  constitution  is  unknown.  Together  with  a  series  of  closely  related  bodies  they 
form  the  great  group  of  the  carbohydrates,  some  of  which  occur  in  the  animal  body,  while  others 
are  widely  d.stributed  in  the  vegetable  kingdom. 

252.  THE  CARBOHYDRATES. — Occur  in  plants  and  animals,  and  received  their  name, 
because  in  addition  to  C  (at  least  6  atoms),  they  contain  H  and  (),  in  the  proportion  in  which  these 
occur  in  water.  They  are  all  solid,  chemically  indifferent,  and  without  odor.  They  have  either  a 
sweet  taste  (sugars),  or  can  be  readily  changed  into  sugars  by  the  action  of  dilute  acids;  they  rotate 
the  ray  of  polarized  light  either  to  the  right  or  left;  as  far  as  their  constitution  is  concerned,  they 
may  be  regarded  as  fatty  bodies,  as  hex-atomic  alcohols,  in  which  2H  are  wanting. 


CARBOHYDRATES.  431 

They  are  divided  into  the  following  groups  : — 

1.  Division.— Glucoses  (CgH,20g). — (i)  Grape  sugar  (glucose,  dextrose,  or  diabetic  sugar) 
occurs  in  minute  quantities  in  the  blood,  chyle,  muscle,  liver  i?),  urine,  and  in  large  amount  in  the 
urine  in  diabetes  mellitus  (|  175).  It  is  formed  by  the  action  of  diastalic  ferments  upon  other 
carbohydrates,  during  digestion.  In  the  vegetable  kingdom,  it  is  extensively  distributed  in  the 
sweet  juices  of  many  fruits  and  flowers  (and  thus  it  gets  into  honey).  It  is  formed  from  cane  sugar, 
maltose,  dextrin,  glycogen,  and  starch,  by  boiling  with  dilute  acids.  It  crystallizes  in  warty  masses 
with  one  molecule  of  water  of  crystallization;  unites  with  bases,  salts,  acids,  and  alcohols,  but  is 
easily  decomposed  by  bases;  it  reduces  many  metallic  oxides  (§  149).  Fresh  solutions  have  a 
rotatory  power  of  -j-  106°.  By  fermentation  with  yeast  it  splits  up  into  alcohol  and  COj  {I  150) ; 
.with  decomposing  proteids  it  splits  into  2  molecules  of  lactic  acid  (§  184,  I)  ;  the  lactic  acid  splits 
up  under  the  same  conditions  in  alkaline  solutions,  into  butyric  acid,  CO.^,  and  H.  For  the  quali- 
tative and  quantitative  estimation  of  glucose,  see  ^  149  and  g  150.  In  alcoholic  solution,  it  forms 
very  insoluble  compounds  with  chalk,  barium,  and  potassium,  and  it  also  forms  a  crystalline  com- 
pound with  common  salt  (Estimation,  |  150)- 

(2)  Galactose,  obtained  by  boiling  milk  sugar  (lactose)  with  dilute  mineral  acids;  it  crystallizes 
readily,  is  very  fermentable,  and  gives  all  the  reactions  of  glucose.  When  oxidized  with  nitric  acid 
it  becomes  transformed  into  mucic  acid.     Its  specific  rotatory  power  =  +  88.oS°. 

(3)  Laevulose  (left-fruit-,  invert-,  or  mucin  sugar)  occurs  as  a  colorless  syrup  in  the  acid  juices 
of  some  fruits  and  in  honey ;  is  non-crystallizable,  and  insoluble  in  alcohol ;  specific  rotatory  power 
=  —  io6°.  It  is  formed  normally  in  the  intestine  (^  183),  and  occurs  rarely  as  a  pathological 
product  in  urine. 

II.  Division. — This  contains  carbohydrates  with  the  formula  Q,H.„Oji,  and  its  members  may 
be  regarded  as  anhydrides  of  the  first  division— i.  Milk  sugar  or  lactose  occurs  only  in  milk, 
crystallizes  in  cakes  (with  I  molecule  of  water)  from  the  syrupy  concentrated  whey;  it  rotates 
polarized  light  to  the  right  =  +  59.3,  and  is  much  less  soluble  in  water  and  alcohol  than  grape 
sugar.  When  boiled  with  dilute  mineral  acids  it  passes  into  galactose,  and  can  be  directly  trans- 
formed into  lactic  acid  only  by  fermentation;  the  galactose,  however,  is  capable  of  undergoing  the 
alcoholic  fermentation  with  yeast  (Koumiss  preparation,  g  232).  For  its  quantitative  estimation 
(I  231).     Rare  in  urine  (§  267). 

2.  Maltose  (CjgHjP^^)  +  Hfi  {O' Sullivan)  has  i  molecule  of  water  less  than  grape  sugar 
(C12H24O12),  is  formed  during  the  action  of  a  diastatic  ferment,  such  as  saliva  upon  starch  (|  148); 
is  soluble  in  alcohol,  right-rotatory  power  =  +  150°;  it  is  crystalline,  while  its  reducing  power  is 
only  two-thirds  that  of  dextrose.  [The  ratio  of  the  reducing  power  of  maltose  to  that  of  glucose  is 
100  to  66.] 

(3.  Saccharose  (cane  sugar)  occurs  in  sugar  cane  and  some  plants,  it  does  not  reduce  a  solution 
of  copper,  is  insoluble  in  alcohol,  is  right-rotatory,  and  not  capable  of  fermentation.  When  boiled 
with  dilute  acids,  it  becomes  changed  into  a  mixture  of  easily  fermentable  glucose  (right-rotatory) 
and  laevulose  (invert  sugar,  \  183,  5,  and  §  184,  I,  6),  which  ferments  with  difficulty  and  is  left- 
rotatory  (^  183).     When  oxidized  with  nitric  acid,  it  passes  into  glucic  acid  and  oxalic  acid.) 

(4.  Meiitose,  from  Eucalyptus  manna;  Meleztose,  from  Larch  manna;  Trehalose  (Mycose), 
from  Ergot:  all  are  right-rotatory,  and  do  not  reduce  alkaline  cupric  solutions.) 

III.  Division. — This  contains  carbohydrates,  with  the  formula,  CgHjoOj,  which  may  be  regarded 
as  anhydrides  of  the  second  division. 

1.  Glycogen,  with  a  dextro-rotatory  power  of  211°,  does  not  reduce  cupric  oxide.  It  occurs  in 
the  liver  (^  174),  muscles,  many  embryonic  tissues,  the  embryonic  area  of  the  chick  {Ki'dz),  in 
normal  and  pathological  epithelium;  in  diabetic  persons  it  is  widely  distributed;  brain,  pancreas, 
and  cartilage;  and  in  the  spleen,  pancreas,  kidney,  ovum,  brain,  and  blood,  together  with  a  small 
amount  of  glucose  {Pavy).  It  also  occurs  in  the  oyster  and  some  of  the  moUusks  {Bizio),  and 
indeed  in  all  tissues  and  classes  of  the  animal  kingdom. 

2.  Dextrin  was  discovered  by  Limpricht  in  the  muscles  of  the  horse.  It  is  right-rotatory  =  -f- 
138°,  soluble  in  water,  and  forms  a  very  sticky  solution,  from  which  it  is  precipitated  by  alcohol  or 
acetic  acid ;  it  is  tinged  slightly  red  with  iodine.  It  is  formed  in  roasted  starch  (hence  it  occurs  in 
large  quantity  in  the  crust  of  bread — see  Bread,  |  234),  by  dilute  acids,  and  in  the  body  by  the 
action  of  ferments  (^  148).  It  is  formed  from  cellulose  by  the  action  of  dilute  sulphuric  acid.  It 
occurs  in  beer,  and  is  found  in  the  juices  of  most  plants. 

3.  Amylum  or  Starch  occurs  in  the  "mealy"  parts  of  many  plants,  is  formed  within  vegetable 
cells,  and  consists  of  concentric  layers  with  an  eccentric  nucleus  (Fig.  239).  The  diameter  and 
characters  of  starch  grains  vary  greatly  with  the  plant  from  which  they  are  derived.  At  72°  C.  it: 
swells  up  in  water  and  forms  a  mucilage  ;  in  the  cold,  iodine  colors  it  blue.  Starch  grains  always 
contain  more  or  less  cellulose  and  a  substance,  erythrogranulose,  which  is  colored  red  with  iodine 
(I  148).  It  &nd  glycogen  axe.  transformed  into  dextrose  by  certain  digestive  ferments  in  the  saliva, 
pancreatic,  and  intestinal  juices,  and  artificially  by  boiling  with  dilute  sulphuric  acid. 

(4.  Gum,  C^oH20*-'iO'  occurs  in  vegetable  juices  (especially  in  acacise  and  mimosje),  also  in  the 
salivary  glands,  mucous  tissue,  lungs,  and  urine;  is  partly  soluble  in  water  (arabin),  partly  swells. 


4o2  CARBOHYDRATES. 

up  like  mucin  (bassorin).  Alcohol  precipitates  it.  It  is  fermentable,  and  when  boiled  with  dilute 
acids  yields  a  reducing  sugar.) 

(5.  Inulin,  a  crystalline  powder  occurring  in  the  root  of  chicory,  dandelion,  and  specially  in  the 
bulbs  of  the  dahlia;  it  is  not  colored  blue  by  iodine.) 

(6.  Lichenin  occurs  in  the  intercellular  substance  of  Iceland  moss  (Cetraria  islandica)  and  algx; 
is  transformed  into  glucose  by  dilute  suii»huric  acid.) 

(7.  Paramylum  occurs  in  the  form  of  granules  resembling  starch,  in  the  infusoria,  Euglena 
viridis.^ 

(8.  Cellulose  occurs  in  the  cell  walls  of  all  plants  (in  the  exo-skeleton  of  arthropoda,  and  the 
skin  of  snakes);  soluble  only  in  ammonio-cupric  oxide  ;  rendered  blue  by  sulphuric  acid  and  iodine. 
Boiled  with  dilute  sulphuric  acid,  it  yields  dextrin  and  glucose.     Concentrated  nitric  acid  mixed 


«^ 


C-: 


a.  West  Indian  arrowroot ;  c,  Tahiti  arrowroot ;  d,  Potato  starch. 

with  sulphuric  acid  changes  it  (cotton)  into  nitro-cellulose  (gun  cotton),  C6H7(N0.2)305,  which 
dissolves  in  a  mixture  of  ether  and  alcohol  and  forms  collodion.) 

(9.  Tunicin  is  a  substance  resembling  cellulose,  and  occurs  in  the  integument  of  the  Tunicata  or 
Ascidians.) 

IV.  Division. — This  contains  the  carbohydrates  which  do  not  ferment. 

I.  Inosit  (phaseo-mannit,  muscle  sti'^ar)  occurs  in  muscle  [Sc/ierer],  lung,  liver,  spleen,  kidney, 
brain  of  ox,  human  kidney  ;  pathologically  in  urine  and  the  fluid  of  echinococcus.  In  the  vegetable 
kingdom,  in  beans  (leguminosse),  and  the  juice  of  the  grape.  It  is  an  isomer  of  grape  sugar; 
optically  it  is  inactive,  crystallizes  in  warts  with  2  molecules  of  water,  in  long  monoclinic  crystals; 
it  has  a  sweet  taste,  is  insoluble  in  water,  does  not  give  Trommer's  reaction,  is  cap.able  of  undergoing: 
only  lh.e  sarcolactic  acid  fermentation.  (Nearly  allied  are  Sorbin,  trom  sorbic  acid — Scyllit,  from 
the  intestnies  of  the  hag  fish  and  skate— and  Eukalyn,  arising  from  the  fermentation  of  melitose.) 

IV.  Derivatives  of  Ammonia  and  their  Compounds. 

The  ammonia  derivatives  are  obtained  from  the  proteids,  and  are  decomposition  products  of 
their  metabolism. 

(i)  Amines, /.  ^.,  compound  ammonias  which  can  be  obtained  from  ammonia  (Xllg),  or  from 
ammonium  hydroxide  (NH^  —  OH),  by  replacing  one  or  all  the  atoms  of  H  by  groups  of  carbo- 
hydrates (alcohol  radicals).  The  amine  derived  from  one  molecule  of  ammonia  is  called  mon- 
amine.     We  are  only  acquainted  with 

H  ^  CH,^ 

H    I      N  Methylamine  and  Tri-Methylamine.  CH^  \         N, 

CH,j  ChJ 

as  decomposition  products  of  cholin  (neurin)  and  of  kreatin.  Neurin  occurs  in  lecithin  in  a  very 
complex  combination  (see  Lecithin,  p.  429,  and  also  ^  23). 

(21  Amides,  i.  e.,  derivatives  of  acids,  which  have  exchanged  the  hydroxyl  (HO)  of  the  acids 
for  NH.,.  Urea,  CO(NH2)^,  the  bi-amid  of  CO,,  is  the  chief  end  product  of  the  metaboii.'^m  of  the 
nitrO;jenous  constituents  of  our  bodies  (see  Urine,  ^  256).  Carbon  dioxide  containing  water  = 
CO(OH).„  where  both  OH  are  replaced  by  NH,— thus  we  get  CO(NH.,).j,  urea. 

{3)  Amido  acids,  /.  e.,  nitrogenous  compounds,  which  show  partly  the  character  of  an  acid  and 
partly  that  of  a  weak  base,  in  which  the  atoms  of  H  of  the  acid  radical  are  replaced  by  NH^,  or  by 
the  substituted  ammonia  groups. 

{n)  Glycin  (or  amido-acetic  acid,  glycocoll,  gelatin  sugar,  ?  177,  2)  is  formed  by  boiling  gelatin 
with  dilute  sulphuric  acid.  It  has  a  sweet  taste  (gelatin  sugar),  behaves  as  a  weak  acid,  but  also 
unites  with  acids  as  an  amine  base.  It  occurs  as  glycin  +  benzoic  acid  =  hippuric  acid  in  urine 
(g   260);    and   also  as  glycin -|- cholalic   acid  =  glycocholic  acid  in  bile  (^   177).     {b)  Leucin 


HISTORICAL.  433 

— (^  170)  =  amido-caproic  acid.  (<r)  Serin — (  ^?  amido-lactic  acid)  obtained  from  silk  gelatin. 
(d)  Aspartic  acid — (amido-succinic  acid) ;  and.  [e)  Glutamic  acid,  obtained  by  the  splitting  up  of 
proteids  (§  170).  Other  amido  acids  are — {/)  Cystin  =  amido-lactic  acid,  in  which  O  is  replaced  by 
S  (I  268).  {g)  Taurin — (|  I77),  amido-ethyl-sulphonic  acid,  occurs  (except  in  certain  glands) 
chiefly  in  combination  with  cholalic  acid,  as  taurocholic  acid  in  bile.  Tyrosin  (parahydro-oxyphenyl- 
amido-propionic  acid),  an  amido  acid  of  unknown  constitution,  occurs  along  with  leucin  during  pan- 
creatic digestion  (|  170),  is  a  decomposition  product  of  proteids,  and  occurs  plentifully  in  the  urine  in 
acute  yellow  atrophy  of  the  liver  (|  269). 

To  the  amido  acids  are  related — («)  Kreatin  in  muscle,  brain,  blood,  urine,  regarded  as  methyl- 
lu-amido-acetic  acid  (C^HgNgOg).  It  has  been  prepared  artificially.  When  boiled  with  baryta 
water,  it  takes  up  HjO,  and  splits  into  urea — and  [d)  Sarkosin  (CgH-NOj),  methyl-amido-acetic 
acid.  When  boiled  with  water,  heated  with  strong  acids,  in  the  presence  of  putrefying  substances, 
kreatin  gives  oft"  water,  and  is  changed  into  kreatinin  (C_jH.N30).  This  strong  base  can  be 
rechanged  by  alkalies  into  kreatin. 

(4)  Ammonia  Derivatives  of  Unknown  Constitution. — Uric  acid  (^  258);  allantoin  (§  260), 
is  formed  by  the  oxidation  of  uric  acid  by  means  of  potassium  permanganate ;  cyanuric  acid  in 
dog's  urine  ;  inosinic  acid  in  muscle ;  guanin  in  traces  in  the  liver  and  pancreas,  in  guano,  the 
excrements  of  spiders,  in  the  skin  of  amphibia  and  reptiles,  in  the  silver  sheen  of  many  fishes  {A. 
Euuald  and  Krukenberg) ,{?^  283) ;  by  oxidation  it  yields  urea;  hypoxanthin  or  sarkin  occurs  along 
with  xanthin  in  many  organs  and  in  urine.  Kossel  prepared  hypoxanthin  from  nuclein  by  prolonged 
boiling  of  the  latter.  It  may  be  obtained  fi-om  fibrin  by  putrefaction,  by  gastric  and  pancreatic 
digestion,  and  by  dilute  acids  {Salomon,  H.  Krause,  Chittenden) ;  xanthin  is  prepared  by  oxidation 
from  hypoxanthin.  It  occurs  veiy  rarely  in  the  form  of  a  urinary  calculus.  Paraxanthin  in  urine 
and  a  similar  body  carnin  in  flesh  (|  233).  [Adenin  (C5H-N5),  discovered  by  Kossel  in  the 
pancreas,  yeast,  and  tea  leaves,  has  also  been  isolated  from  the  spleen,  l}'Tnphatic  glands,  and  kidney; 
it  appears  to  be  present  in  all  highly  cellular  animal  and  vegetable  tissues.  Like  the  allied  bases — 
xanthin  and  guanin,  it  is  a  derivative  of  the  nuclein  of  the  nuclei.] 

Aromatic  Substances. 
I.  Monatomic  phenols — {a)  Phenol  ( hydro xyl  of  benzol)  in  the  intestine  (|  184).  Phenyl 
sulphonic  acid  in  urine  (|  262).  i^b)  Kresol,  in  the  form  of  orthokresol  and  parakresol,  united 
with  sulphonic  acid,  occur  in  urine  (|  262).  2.  Diatomic  phenols — (a)  pyrokatechin  united 
with  sulphonic  acid  in  urine  (|  262).  3.  Aromatic  oxyacids — (a)  Hydroparacumaric  acid ;  (3) 
Paraoxyphenylacetic  acid  in  urine  (|  262).  4.  Indol  and  skatol  in  the  intestine  (|  184),  con- 
joined with  sulphonic  acid  in  urine  [\  262). 

253.  HISTORICAL. — According  to  Aristotle,  the  organism  requires  food  for  three  purposes — 
for  growth,  for  the  production  of  heat,  and  to  compensate  for  the  loss  of  the  bodily  excreta.  The 
formation  of  heat  takes  place  in  the  heart  by  a  process  of  concoction,  the  heat  so  formed  being  dis- 
tributed to  all  parts  of  the  body  by  means  of  the  blood,  while  respiration  is  regarded  as  an  act  whereby 
the  blood  is  cooled.  Galen  accepted  this  view  in  a  somewhat  modified  form;  according  to  him,  the 
metabolic  processes  may  be  compared  to  the  processes  going  on  in  a  lamp ;  the  blood  represents  the 
oil ;  the  heart,  the  wick ;  the  lungs,  the  fanning  apparatus.  According  to  the  view  of  the  iatro- 
chemical  school  {van  Helmoni'),  the  metabolic  processes  of  the  body  are  fermentations,  whereby  the 
food  is  mixed  with  the  juices  of  the  body.  Since  the  middle  of  the  seventeenth  century  [Boyle),  the 
knowledge  of  the  metabolic  processes  has  followed  the  development  of  chemistry.  A.  V.  Haller 
regarded  heat  as  due  to  chetnical  processes — the  food  continually  supplying  the  waste  which  is  ex- 
creted from  the  body.  After  the  discovery  of  oxygen  (1774,  by  Priestley  and  Scheele),  Lavoisier 
formulated  the  theory  of  combustion  in  the  lungs,  whereby  carbonic  acid  and  water  were  formed. 
Mitscherlich  compared  the  decomposition  processes  in  the  living  body  with  putrefactive  processes. 
Magendie  was  the  first  to  emphasize  the  difference  between  nitrogenous  and  non-nitrogenous  foods, 
and  he  showed  that  the  latter  alone  were  not  able  to  support  life.  Even  gelatin  alone  is  not  suffi- 
cient for  this  purpose.  The  greatest  advance  in  the  theory  of  nutrition  was  made  by  J.  v.  Liebig, 
who  laid  the  foundation  of  our  present  knowledge  of  this  subject.  According  to  Liebig,  foods  may 
be  divided  into  two  classes,  viz.,  the  "  plastic,''  suitable  for  the  construction  of  the  organism,  and 
the  "  respiratory"  for  the  maintenance  of  the  temperature  ;  to  the  former  class  he  referred  the  albu- 
minates or  proteids,  to  the  latter,  the  non-nitrogenous  carbohydrates  and  fats  (p.  403).  Among 
recent  observers,  the  Munich  School,  as  represented  by  v.  Bischoff,  v.  Pettenkofer,  and  V.  Voit,  has 
done  most  to  give  us  an  exact  knowledge  of  this  department  of  physiology. 


28 


The  Secretion  of  Urine. 


254.  STRUCTURE  OF  THE  KIDNEY.— [Capsule.— The  kidney  is  a  compound 
tubular  gland,  and  is  invested  l^y  a  thin,  tough,  fibrous  capsule,  easily  stripped  off  from  the  substance 
of  the  organ,  to  which  it  is  attached  by  fine  processes  of  connective  tissue  and  blood  vessels.] 

[Naked  Eye  Appearances. — ( )n  dividing  the  kidney  longitudinally  from  the  hiluni  to  its  outer 
border,  and  examining  the  cut  surface   with  the   naked  eye,  we  observe  the  parenchyma  of  the 


Boundary  layer  1    „ 

of  Medulla.     J  ^ 
Papillary       por-1 
tion    of    me-  >2' 
dulla.  j 

Transverse  section") 
of      tubules       in  V3 
boundary  layer.    ) 


Fat  of  renal  sinus.  4. 


FlC.    240. 


i"  Labyrinth. 
,      /  Medullary 
\      rays. 

MEDULLA. 


Transversely  "j 

coursing  medul-  !>- 
lary  rays.  ) 


Artery.  5. 


Artery.   5. 


(  Branch  of 
A     (      renal  artery. 


Longitudinal  section  through  the  kidney  ( Tyson,   after  Henle). 


kidney,  consisting  of 
composed  of  about  tw 
toward  and  embraced 
is  further  subdivided 
to  Klein,  the  relative 
papillary  portion,  4. 
aspect,  with  radiating 


an  outer  cortical  and  an  inner  medullary,  or  pyramidal  portion,  the  latter 
elve  conical  papilla;,  or  pyramids   of  Malpighi,  with   their  apices  directed 

bythecalices  of  the  pelvis  of  the  kidney  (Fig.  240).  The  medullary  portion 
into  the  boundary  layer  of  Ludwig  and  the  papillary  portion.     According 

proportions  of  these  three  parts  are — corte.x,  3.5  ;  boundary  layer,  2.5  ;  and 
The  cortex  has  a  light  brown  color,  and  when  torn  presents  a  slightly  granular 
lines  running  at  regular  distances.    The  granules  are  due  to  the  presence'of  the 

434 


STRUCTURE    OF   THE    KIDNEY. 


435 


Malpighian   corpuscles,  and  the  strise  to  the  medullary  rays.     The  boundary  zone  is  darker,  and 

often  purplish  in  color.     It  is  striated  with  clear  and  red  hnes  alternating  with  opaque  ones,  the 

former  being  blood  vessels  and  the  latter  uriniferous  tubules.     The  papillary    zone    is    nearly  white 

and  uniformly  striated,  the  striee  converging  to 

the   apex   of  the   pyramid.     The    medulla  is  Fig.  241. 

much  denser  and  less  friable  than  the  cortex, 

owing   to  the   presence  of  a   large  amount  of 

connective  tissue    between   the    tubules.     The 

bundles    of  straight  tubes  of  the  medulla  may 

be  traced   at  regular  intervals  running  outward 

into  the  cortex,  constituting  medullary  rays, 

which  become  smaller   as  they  pass  outward  in 

the  cortical  zone,  so   that  they  are   conical  and 

form  the   pyramids   of  Ferrein    (Fig.   241, 

PF).     The  portion  of  the  cortex  lying  between 

the  medullary  rays  is  known  as  the  labyrinth, 

from    the     complicated     arrangement    of    its 

tubules.] 

[Size,  Weight. — The  adult  kidney  is 
about  II  centimetres  (4.4  inches)  in  length,  5 
centimetres  (2  inches)  wide,  and  3  centimetres 
(i  inch)  in  thickness.  It  weighs  in  the  male 
1 13.5  to  170  grms.  (4  to  6  oz.),  in  the  female 
1 13.5  to  156  grms.  (4  to  $}4  oz.).  The  width 
of  the  cortex  is  usually  5  to  6  millimetres  (i  to 
iinch).] 

I.  The  uriniferous  tubules  all  rise  within 
the  labyrinth  of  the  cortex  by  means  of  a 
globular  enlargement,  200  to  300  /j,  [j^q  to 
j^j  inch]  in  diameter,  called  Bowman's 
capsule  (Figs.  242,  243).  After  pursuing  a 
complicated  course,  altering  their  direction, 
diameter,  and  structure,  and  being  joined  by 
other  tubules,  they  ultimately  form  large  collect- 
ing tubes,  which  terminate  by  minute  apertures, 
visible  with  the  aid  of  a  hand  lens,  on  the 
apices  of  the  papillae  projecting  into  the  calices 
of  the  kidney.  Each  urinary  tubule  is  com- 
posed of  a  homogeneous  membrana  propria, 
lined  by  epithelial  cells,  so  as  to  leave  a  lumen 
for  the  passage  of  the  urine  from  the  Malpighian 
corpuscles  to  the  pelvis  of  the  kidney.  The  diameter  and  direction  of  the  tubules  vary,  and  the 
epithelium  differs  in  its  characters  at  different  parts  of  the  tube,  while  the  lumen  also  undergoes 
alterations  in  its  diameter. 

Course  and  Structure  of  the  Tubules. — In  the  labyrinth  of  the  cortex,  tubules  arise  in  the 
spherical  enlargement  known  as  Bowman's  capsule  (Fig.  242,  i),  which  invests  (in  the  manner 
presently  to  be  described)  the  tuft  of  capillary  blood  vessels  called  a  glomerulus  or  Malpighian 
corpuscle.  By  means  of  a  short  and  narrow  neck  (2)  the  capsule  becomes  continuous  with  a  con- 
voluted tubule,  X  in  Fig.  243.  This  tubule  is  of  considerable  length,  forming  many  windings  in 
the  cortex  (Fig.  242,  3)  ;  the  first  part  of  it  is  45  /i  wide,  constituting  the  proximal  or  first  convo- 
luted tubule.  It  becomes  continuous  with  a  spiral  tubule  of  Schachowa  (4),  which  lies  in  a 
medullary  ray  where  it  pursues  a  slightly  wavy  or  spiral  course.  On  the  boundary  line  between  the 
cortical  and  boundary  zone,  the  spiral  tubule  suddenly  becomes  smaller  and  passes  into  the  descend- 
ing portion  of  Henle's  loop  (5),  which  is  14  //  in  breadth,  and  is  continued  downward  through 
the  boundary  zone  into  the  medulla,  where  it  forms  the  narrow  loop  of  Henle  (6),  which  runs 
backward  in  the  medullary  part  to  the  boundary  zone.  Here  it  becomes  wider  (20-26  /i),  and  as  it 
continues  its  undulating  course,  it  enters  a  medullary  ray,  where  it  constitutes  the  ascending 
looped  tube  (7),  which  becomes  narrower  in  the  cortex.  Leaving  the  medullary  ray  again,  it 
passes  into  the  labyrinth,  where  it  forms  a  tube  with  irregular  angular  outlines  —the  irregular 
tubule  (10),  which  is  continuous  with  (Fig.  243,  n,  n)  the  second  or  distal  convoluted  tubule 
(11),  which  resembles  the  proximal  tubule  of  the  same  name.  Its  diameter  is  40//.  A  short, 
narrow,  wavy  junctional  or  curved  collecting  tubule  (12)  connects  the  latter  with  one  of  the 
straight  collecting  tubes  (13)  of  a  medullary  ray.  As  the  collecting  tubule  proceeds  through 
the  boundary  zone,  it  receives  numerous  junctional  tubes,  and  when  it  reaches  the  boundary  zone,  it 
forms  one  of  the  collecting  tubes  (Fig.  243,  0),  which  unite  with  one  another  at  acute  angles  to 
form  the  larger  straight  excretory  tubes  or  ducts  of  Belhni  (15),  which  open  on  the  summit  of 


Papillary 
zone. 


Longitudinal  section  of  a  Malpighian  pyramid.  PF,  pyra- 
mids of  Ferrein;  R A,  branch  of  renal  artery;  RV, 
lumen  of  a  renal  vein  receiving  an  inter-lobular  vein  ; 
VR,  vasa  recta  ;  PA,  apex  of  a  renal  papilla :  b,  b, 
embrace  the  bases  of  the  renal  lobules. 


436 


STRUCTURE  OF  THE  TUBULES. 


the  Malpighian  pyramids  into  a  calyx  of  the  pelvis  of  the  kidney.  In  the  cortex  the  collecting 
tubules  are  45  //  in  diameter,  but  where  they  have  formed  an  excretory  tube  (O),  their  diameter  is 
200  to  300  // ;  24  to  So  of  these  tubes  ojien  on  the  apex  of  each  of  the  12  to  15  Malpii;hian  pyra- 
mids. In  the  lowest  and  broadest  part,  tlie  membrana  propria  is  strcni^lhened  l)y  the  presence  of  a 
thick  supportintj  framework  of  connective  tissue. 

Structure  of  the  Tubules. — [Itciow  the  neck,  tlie  tubules  arc  lined  everywhere  by  a  single 
layer  of  nucleated  epithelium.]  Bowman's  capsule,  which  is  about  .,1^,  inch  in  diameter  (I*'ig. 
244,  II),  consists  of  a  homogeneous  basement  memlirane  lined  internally  by  a  single  continuous 
layer  of  flattened  cells   [^•).     According  to    Kotli,   the   basement   membrane   itself  is  composed  of 


Fic. 


4.  Spiral  tube. 

13.  Straight  part  of  col- 
lecting tube. 

9.  Wavy  part  of  ascend- 
ing limb  of  Henle's 
loop. 

Inner  stratum  of  corte-v 
without  Malpighian 
corpuscles. 


7  and  8.  Ascending  limb 
of  Henle's  loop 
tube. 


Sub-cap.sular  layer 
without  Malpigh- 
ian corpuscles. 


First  part   of  col- 
lecting tube. 
Distal  convoluted 
tubule. 
CORTEX. 
Irregular  tubule. 


3.  Proximal  convo- 
luted tubule. 

9.  Wavy  part  of  as- 
cending limb. 

2.  Constriction  or 
neck. 

4.  Spiral  tubule. 
I.  Malpighian    tuft 

surrounded  b  y 
Bowman's  cap- 
sule. . 


8,  Spiral  part  of  as- 
cending limb  of 
Henle's  loop. 


B.  BOUNDARY 
ZONE. 

5.  Descending  limb 
of  Henle's  loop 
tube. 


6.  Henle's  loop. 


C.  P  API  LLAR  Y 
ZONE. 


Diagram  of  the  course  of  two  uriniferous  tubules  (Kieiit  and Noblc-Stnitli), 


endothelial  cells.  [In  the  fcetus  the  lining  cells  are  more  polyhedral.]  Within  the  capsule  lies  the 
glomerulus  or  tuft  of  blood  vessels.  The  cells  lining  the  capsule  are  reflected  over  and  between  the 
lobules  of  which  the  glomerulus  consists.  The  glomerulus  may  not  completely  fill  the  capsule,  so 
that,  according  to  the  activity  of  the  kidney,  there  may  be  a  larger  or  smaller  space  between  the 
glomerulus  and  the  capsule  into  which  the  filtered  urine  passes.  The  neck  is  lined  by  cubical  cells. 
These  cells,  in  some  animals,  e.  g.,  the  raljbit.  sheep,  mouse,  and  frog,  are  ciliated. 

The  proximal  convoluted  tubule  is  lined  by  characteristic  epithelium.     The  cells,  which  are 
short  or  polyhedral,  contain  a  turbid  or  cloudy  protoplasm  (Fig.  244,  III,  i  and  2),  which  not 


STRUCTURE  OF  THE  TUBULES. 


437 


Fig 


unfrequently  contains  oil  globules,  and  they  form  a  single  layer.  Each  cell  consists  of  two  parts; 
the  inner,  containing  the  spherical  nucleus,  is  next  the  lumen,  and  granular  (III,  2,g),  while  the 
outer  part,  next  the  membrana  propria,  appears  fibrillated,  or  "  redded,"  from  the  presence  of  rods 
or  fibrils  placed  vertically  to  the  basement  membrane  (Fig.  245).  These  appear  like  the  hairs  of  a 
brush  pressed  upon  a  plate  of  glass 
(III,  2).  The  cells  are  not  easily 
separated  from  each  other,  as  neigh- 
boring cells  interlock  by  means  of 
the  branched  ridges  on  their  sur- 
faces (III,  i) — {Heidetthain,  Scha- 
chowa).  The  lumen  is  well  de- 
fined, but  its  size  seems  to  depend 
upon  the  state  of  imbibition  of  the 
cells  bounding  it. 

The  spiral  tubule  has  similar 
epithelium  and  a  corresponding 
lumen,  although  the  epithelium 
becomes  lower  and  somewhat  al- 
tered in  its  characters  at  the  lower 
part  of  the  tube. 

The  descending  limb  of  Hen- 
le's  loop,  and  the  loop  itself 
with  a  relatively  wide  lumen,  are 
bounded  by  clear,  flattened,  epi- 
thelial cells,  with  a  bulging  nucleus 
(IV,  S) ;  the  cells  lying  on  one 
side  of  the  tube  being  so  placed 
that  the  bulging  part  of  the  bodies 
of  the  cells  is  opposite  the  thin 
part  of  the  cells  on  the  opposite 
side  of  the  tube.  [These  tubes 
might  be  mistaken  for  blood  capil- 
laries, but  in  addition  to  their  squa- 
irious  lining,  they  have  a  basement 
membrane,  which  capillaries  have 
not.]  In  the  ascending  limb, 
the  lumen  is  relatively  wide,  while 
its  epithelium  agrees  generally  with 
that  in  the  convoluted  tubule,  ex- 
cepting that  the  "rods"  are  shorter. 
Sometimes  the  cells  are  arranged 
in  an  "  imbricate  "  manner. 

In  the  irregular  tubule,  which 
has  a  very  small  lumen,  the  poly- 
hedral cells  lining  it  contain  oval 
nuclei,  and  are  shorter  than  those 
of  the  convoluted  tubules.  The 
cells,  again,  are  very  irregular  in 
size,  while  their  "  rodded  "  char- 
acter is  much  coarser  and  more 
defined  (Fig.  246). 

The  distal  convoluted  tubule 
closely  resembles  in  its  structure 
the  proximal  convoluted  tubule, 
and  is  lined  by  similar  cells.  The 
curved  collecting,  or  junctional 
tubule,  although  narrow,  has  a 
relatively  wide  lumen,  as  it  is 
lined  by  clear,  somewhat  flattened 
cells. 

The  collecting  tubes  have  a 
distinct  lumen,  and  are  lined  by 
clear',  somewhat  irregular,  cubical 
cells  (Fig.  244,  V),  which  in  the  larger  excretory  tubes  are  distinctly  columnar  (VI).  The  base- 
ment membrane  is  said  to  be  absent  in  the  larger  tubes.  [Klein  describes  a  thin,  delicate,  nucleated, 
centro-tubular  membrane  lining  the  surface  of  the  epithelium  next  the  lumen.] 


I,  Blood  vessels  and  uriniferous  tubules  of  the  kidney  (semi-diagrammatic) ; 
A,  capillaries  of  the  cortex^  B,  of  the  medulla;  a,  inter-lobular  artery ; 
I,  vas  afferens  ;  2,  vas  efferens  ;  r,  e,  vasa  recta,  c,  venae  rectse  ;  v,  v, 
inter-lobular  vein  ;  S,  origin  of  a  vena  stellata;  i,  i.  Bowman's  capsule 
and  glomerulus  ;  X,  X,  convoluted  tubules  ;  t,  f,  Henle's  loop  ;  n,  n, 
junctional  piece  ;  <?,  o,  collecting  tubes  ;  O,  excretory  tube. 


438 


BLOOD    VESSELS   OF   THE    CORTEX. 


II.  The  Blood  Vessels. — The  renal  artery  (Fig.  250)  divides  into  four  or  five  branches,  which 
pass  into  the  kidney  at  the  hilum.  These  branches,  surrounded  by  connective  tissue  continuous  with 
tiiat  of  the  capsule,  continue  to  divide,  and  pass  between  the  pajiilkv.  to  reach  the  bases  of  the 
pyramids  on  the  limits  between  the  cortical  and  boundary  zones,  where  tiiey  form  incomplete  arches. 
From  these  horizontal  trunks,  the  inter-lobular  arteries  (Fig.  243.  n)  run  vertically  and  singly  into 
the  cortex,  between  each  two  medullary  rays,  and  in  their  course  they  give  off  on  all  sides  the  short, 
undivided  vasa  afferentia  (l),  each  of  which  enters  a  Malpighian  capsule  at  the  opposite  pole  from 
which  the  urinary  tul)ule  is  given  off.  Within  the  capsule,  each  afferent  artery  breaks  up  into  capilla- 
ries arranged  in  lobules  and  supported  by  connective  tissue,  the  whole  forming  a  tuft  of  capillary  blood 

Fig.  244. 


II,  Bowman's  capsule  and  glomemliis.  a,  vas  afferens  ;  e,  vas  efferens  :  c.  capillar)'  network  of  the  cortex  ;  /t,  en- 
dothelium of  the  capsule:  /(.origin  of  a  convoluted  tuhule.  Ill,  "  rodded  "  cells  from  a  convoluted  tubule — 
2,  seen  from  the  side,  with  £■,  inner  granular  zone  ;  i,  from  the  surface.  IV,  cell  lining  Henle's  looped  tubule. 
V,  cells  of  a  collecting  tube.     VI,  section  of  an  excretory  tube. 

vessels,  or  a  glomerulus.  Each  glomerulus  is  covered  on  its  surface,  directed  toward  the  wall  of  the 
capsule  by  a  layer  of  flat,  nucleated,  epithelial  cells  (Fig.  229,  II),  which  also  dip  down  between  the 
capillaries.  A  vein,  the  vas  efferens  (2),  which  is  always  smaller  than  the  afferent  arteriole,  proceeds 
from  the  centre  of  the  glomerulus,  and  leaves  the  capsule  close  to  the  point  at  which  the  afferent  vessel 
enters  it  (Fig.  244,  II).  In  their  .structure  and  distribution  all  the  efferent  ves.sels  resemble  arteries,  as 
they  divide  into  branches  to  form  a  dense,  narrow-meshed  capillary  network  (Fig.  243,  A,  and 
Fig.  244,  II,  (t),  which  ramifies  over  and  between  the  convoluted  tubules.  Tiie  meshes  are  elongated 
around  the  tubules  of  the  medullary  rays,  and  more  polygonal  arounil   the  convoluted  tubules 


Fig.  245. 


Convoluted   tubule   (after   ammonium   chromate)   showing 
"  rodded  "  epithelium. 


I'li;.  246. 


Epithelium   ol    an   irregular  tubule   of    the 
kidney  of  a  dog. 


(Fig.  243).  Some  of  the  lowest  efferent  vessels  split  up  into  vasa  recta,  which  run  toward  the 
medulla.  The  interlobular  arteries  become  smaller  as  they  pass  toward  the  surface  of  the  kidney, 
and  some  of  their  terminal  capillaries  communicate  with  the  capillaries  of  the  external  capsule 
itself.  Venous  trunks  proceed  from  the  capillary  network,  to  terminate  in  the  inter-lobular  veins 
(V),  which  begin  close  under  the  capsule  l)y  venous  radicals  arranged  in  a  stellate  manner  (consti- 
tuting the  stellula;  Verheynii,  or  venae  stellatae),  and  accompany  the  corresponding  artery  to  the 
limit  between  the  cortex  and  lioundary  zone,  where  they  communicate  with  the  large  venous  trunks 
in  that  situation. 

The  blood  vessels  of  the  medulla  arise  from  the  vasa  recta  (Fig.  243,  r),  which  begin  on  the 
limit  of  the  cortex  and  medulla,  either  as  single,  direct,  muscular  branches  (r)  of  the  large  arterial 


LYMPHATICS,    NERVES,    CONNECTIVE    TISSUE. 


439 


trunks,  or  from  those  efferent  vessels  [e)  which  Ue  next  to  the  medulla.  The  latter  are  said  to  be 
devoid  of  muscle.  According  to  Huschke,  a  few  vasa  recta  are  formed  by  the  union  of  the  capil- 
laries of  the  medullary  rays.  All  the  vasa  recta  enter  the  boundary  layer,  where  they  split  up  into 
a  leash  or  pencil  of  small  arterioles,  which  pass  between  the  straight  tubules  toward  the  pelvis,  and 
form  in  their  course  a  capillary  network  with  elongated  meshes.  From  these  capillaries  there  arise 
venous  radicles,  which,  as  they  proceed  toward  the  limit  between  the  cortex  and  medulla,  form  the 
venae  rectae  (<:),  and  open  into  the  concave  side  of  the  venous  trunks  in  this  region.  At  the  apex 
of  the  papillae,  the  capillaries  of  the  medulla  form  connections  with  the  rosette-like  capillaries  sur- 
rounding the  excretory  ducts  (at  i). 

[The  circulation  through  the  vasa  recta  is  most  important.  The  cortical  system  of  blood  vessels 
communicates  with  the  medullary,  but  as  most  of  the  vasa  recta  are  derived  from  the  same  vessel  as 
the  interlobular  arteries,  it  is  evident  that  they  may  form  a  side  stream  through  which  much  of  the 
blood  may  pass  without  traversing  the  vessels  of  the  cortex.  Very  probably  the  "short  cut"  is  use- 
ful in  congestions  of  the  kidney.  The  amount  of  distention  of  these  vessels  also  will  influence 
the  size  of  the  tubules  lying  between  them.  There  are  two  other  channels  by  which  blood 
can  pass  through  the  renal  arteries  without  traversing  the  glomeruli  (l)  The  anastomoses 
between  the  terminal  twigs  of  the  renal  artery  and  the  subcapsular  venous  plexus;  (2)  small 
branches  given  off,  either  by  the  interlobular  arteries  or  by  the  afferent  vessels  before  entering  the 
glomeruli  [Brzinton).^ 

The  blood  vessels  of  the  external  capsule  are  derived  partly  from  the  terminal  twigs  of 
the  interlobular  arteries,  partly  from  branches  of  the  suprarenal,  phrenic,  and  lumbar  arteries,  which 
anastomose  with  each  other.  The  capillary  network  has  simple  meshes.  The  venous  radicles  pass 
partly  into  the  vena;  stellatae,  and  partly  into  the  veins  of  the  same  name  as  the  arteries.  The  con- 
nection of  the  area  of  the  renal  artery  with  the  other  arteries  of  the  capsule  explains  why,  after 
ligature  of  the  renal  artery  within  the  kidney,  the  blood  still  circulates  in  the  external  capsule  (C 
Liidwig,  M.  Herrmanit) ;  in  fact,  these  blood  vessels  still  supply  the  kidney  with  a  small  amount 
of  blood,  which  may  suffice  to  permit  a  slight  secretion  of  urine  to  take  place  [Litten,  Patitynski). 

III.  The  lymphatics  form  a  wide-meshed  plexus  in  the  capsule  of  the  kidney,  while  under  it 
they  form  large  spaces  {^Ueidetikaiti).  In  the  parenchyma  of  the  kidney,  the  lymphatics  are  said  to 
be  represented  by  large  slits  devoid  of  a  wall  in  the  tissues,  and  are  more  numerous  around  the 
convoluted  than  the  straight  tubules.  The  slits  pass  to  the  surface  of  the  kidney,  and  expand  under 
the  capsule.  When  the  lymphatics  are  greatly  distended,  they  tend  to  compress  the  uriniferous 
tubules  and  the  blood  vessels  (  C.  Ludwig  and  Zaivarykin  ).  According  to  Ryndowsky,  the  urini- 
ferous tubules  are  sun^ounded  by  true  lymphatics  with  an  endothelial  lining,  and  they  even  penetrate 
into  the  capsule  of  Bowman  along  with  the  vas  afferens.  [The  large  bloodvessels  are  also  sur- 
rounded by  lymphatics].  Large 
lymphatics,  provided  with  valves, 
pass  out  of  the  kidneys  at  the  hilum, 
while  others  emerge  through  the  cap- 
sule; both  sets  are  connected  with 
the  lymph  spaces  of  the  capsule  of 
the  kidney  {A.  Budge). 

IV.  The  nerves  form  small 
trunks  provided  with  ganglia,  and 
accompany  the  blood  vessels.  [They 
are  derived  from  the  renal  plexus 
and  the  lesser  splanchnic  nerve.] 
They  contain  meduUated  and  non- 
medullated  fibres,  and  the  latter  have 
been  traced  by  W.  Krause  as  far  as 
the  apices  of  the  papillae.  Their 
mode  of  termination  is  unknown. 
Physiologically,  we  are  certain  that 
they  contain  both  vasomotor  and  sen- 
sory fibres ;  perhaps  there  may  be 
also  vaso-dilator  and  secretory  fibres. 

V.  The  connective  tissue,  or 
interlobular  stroma,  forms  in  the 
papillae,  especially  at  their  apices, 
fibrous,  concentric  layers  of  consid- 
erable thickness  between  the  excre- 
tory tubules  (Fig.  247).  Further 
outward,  the  fibrillar  character  be- 
comes less  distinct,  while  at  the  same 

time  branched  connective- tissue  corpuscles  occur  in  greater  numbers.  In  the  cortex,  the  inter- 
stitial stroma  consists  almost  entirely  of  branched  corpuscles,  which  anastomose  with  each  other. 


Transverse  section  of  apex  of  Malpighian  pyramid,     a,  large  collecting 
tubes  ;  b,  c,  d,  tubules  of  Henle  ;  e,f,  blood  capillaries. 


440  THE    URINE. 

[There  is  also  a  small  quantity  of  delicate  fibrous  tissue  around  Kownian's  capsule,  and  along  the 
course  of  the  arteries.  The  connective  tissue  often  plays  an  important  role  in  pathological  condi- 
tions of  the  kidney,  as  interstitial  nephritis.]  The  outer  layers  of  the  capsule  of  the  kidney  are 
composed  of  dense  Ijuiuiles  of  fibrous  tissue,  while  the  deeper  layers  are  more  loose,  and  send 
processes  into  the  cortical  layers.  The  capsule  is  easily  strijiped  off.  None  of  the  secretory  sub- 
stance is  removed  with  it.  Under  the  capsule  in  the  human  kidney,  there  is  a  thin  plexus  of  non- 
Striped  muscular  fibres.  At  the  hilum  it  becomes  continuous  with  the  outer  fibrous  coat  of  the 
dilated  upper  end  of  the  ureter.  Smooth  muscular  fibres  also  occur  in  a  sphincter-like  arrangement 
round  the  apex  of  each  papilla,  while  others  ])roceed  from  the  pelvis  between  the  pyramids  along 
the  blood  vessels  (^Jardct).  The  fat  surrounding  the  kidney  is  united  to  the  latter  partly  by  blood 
vessels  and  partly  by  bands  of  connective  tissue.  [The  sul)capsular  layer  of  the  cortex,  and  a  thin 
layer  next  the  boundary  zone  (Fii^.  242,  </,  i?,),  are  devoid  of  Malpighian  corjiuscles.] 

[Development  of  a  Malpighian  Capsule. — The  upper  end  of  the  urinary  tubule  is  dilated 
and  closed,  and  into  it  there  grows  a  tuft  of  blood  vessels  ((/)  pushing  one  layer  of  the  tube  before 
it  {b'),  hence  the  capillaries  become  invested  by  it,  just  as  an  organ  is  surrounded  by  a  serous  sac,  so 
that  one  layer — the  reflected  one  {b) — of  the  tubule  is  closely  applied  to  the  blood  vessels,  while 
the  other  (c)  lies  loosely  over  it  with  a  space  between  the  two  (Fig.  248).] 

255.  THE  URINE. — Physical  Characters. — A  knowledge  of  the  com- 
position of  this  secretion  is  of  the  greatest  value  to  the  physician  and  surgeon. 

1.  The  quantity  of  urine  passed  by  an  adult  man  in  twenty-four  hours  is 
between  1000  and  1500  cubic  centimetres,  or  about  50  ozs.,  and  in  the  female 
900  to  1200  c.c.  The  minimum  is  secreted  between  2  to  4  a.  m.,  and  the  maxi- 
mum between  2  to  4  p.  m.  ( IVeigelin). 

The  amount  is  diminished  by  profuse  sweating,  diarrhoea,  thirst,  non-nitrogenous  food,  diminu- 
tion of  the  general  blood  pressure,  after  severe  hemorrhage,  and  in  some  diseases  of  the  kidneys. 
The  minimum,  which  may  be  normal,  is  400  to  500  c.c.  It  is  increased  by  increase  of  the  general 
blood  pressure,  or  of  the  pressure  within  the  area  of  the  renal  artery,  by  copious  drinking,  contrac- 
tion of  the  cutaneous  vessels  through  the  action  of  cold,  the  passage  of  a  large  amount  of  soluble 
substances  (urea,  salts,  and  sugar)  into  the  urine,  a  large  amount  of  nitrogenous  food,  as  well  as  by 
various  drugs,  such  as  digitalis,  alcohol,  squills.  After  taking  fluids  charged  with  CO.^,  the  amount 
of  urine  is  increased  during  the  following  hours  {Quincke). 

The  secretion  is  influenced  directly  by  the  nervous  system,  as  in  the  sudden  polyuria  following 
nervous  excitement,  such  as  hysteria  [when  the  person  usually  passes  a  large  amount  of  very  pale- 
colored  urine]  ;  after  an  epileptic  attack,  and  also  afcer  pleasureable  excitement  [Bftieke).  We  may 
have  polyuria  unaccompanied  by  the  presence  of  sugar  in  the  urine,  which  follows  injury  to  a  cer- 
tain part  of  the  floor  of  the  fourth  ventricle  {CI.  Bernard).  The  urine  is  measured  in  tall  gradu- 
ated cylindrical  vessels  (Fig.  249).  [In  estimating  the  quantity  of  urine  passed,  the  patient  must, 
of  course,  be  directed  always  to  empty  his  bladder  at  a  particular  hour,  and  collect  the  urine  passed 
during  the  next  twenty-four  hours.] 

2.  The  specific  gravity  varies,  as  a  mean,  between  1015  and  1025  ;  the  mini- 
mum, after  copious  draughts  of  water,  may  be  1002;  while  the  maximum,  after 
profuse  perspiration  and  great  thirst,  may  be  1040.  The  mean  specific  gravity  is 
about  1020.  In  newly- born  children,  the  specific  gravity  falls  very  considerably 
during  the  first  three  days,  which  is  due  to  the  amount  of  food  taken  {Martin  and 
Huge).  [The  specific  gravity  of  the  urine  in  infants  is  aljout  1003  to  1006.]  A 
healthy  adult  excretes  about  70  grms.  \_2y2  oz.]  daily  of  solids  by  the  urine,  or 
about  I  grm.  of  solids  per  i  kilo,  of  body  weight. 

The  specific  gravity  is  estimated  by  means  of  a  urinometer  (Fig.  250),  the  urine  being  at  the 
temperature  of  16°  C.  [The  urinometer,  when  placed  in  distilled  water,  ought  to  float  at  the 
mark  0°  or  zero,  which  is  conventionally  spoken  of  as  1000.  Place  the  urine  to  be  tested  in  a  tall 
cylindrical  glass,  of  such  width  that  the  urinometer,  when  placed  in  it,  may  float  freely  and  not 
touch  the  sides.  Take  care  that  no  air  bubbles  adhere  to  the  instrument.  When  reading  off  the 
mark  on  the  stem,  raise  the  vessel  to  the  eye  and  bring  the  eye  on  a  level  with  the  surface  of  the 
water,  noting  the  number  which  corresponds  to  this.  This  rule  is  adopted  because  the  water  rises 
on  the  stem  in  virtue  of  capillarity.  It  is  essential  that  a  sample  of  the  mixed  urine  of  the  twenty- 
four  hours  be  used  for  ascertaining  the  mean  specific  gravity.] 

Christison's  Formula. — To  estimate  the  amount  of  solids  in  the  urine.  This  may  be  done 
approximately  by  means  of  the  formula  of  Trapp  or  Haeser,  or,  as  it  is  called  in  this  country, 
"  Christison's  formula,"  viz.,  "  Multiply  the  two  last  figures  of  a  specific  gravity  expressed  in  four 
figures  by  2.33"  {Christison  and  Haeser),  or  by  2   {'Irapp),ox  2.2  {Loebisch).     This  gives  the 


THE   URINE. 


441 


amount  of  solids  in  every  looo  parts.     [Suppose   a  person  passes  1200  c.c.  urine  in  twenty-four 
hours,  and  the  specific  gravity  is  1022,  then 

22  X  2-33  =  51.26  grms.  in  1000  c.c. 

To  ascertain  the  amount  in  1200  c.c. 

51.26  X  1200 

1000  :  1200  :  :  51.26  :  X  = ^61.51.  grms.l 

-'  /^  1000  J      &        'J 

Direct  Estimation  of  Solids. — Place  15  c.c.  of  urine  in  a  capsule  of  known  weight,  and  evapo- 
rate it  over  a  water  bath,  afterward  completely  dry  the  residue  in  an  air  bath  at  100°  C,  and  then 
cool  it  over  concentrated  sulphuric  acid.  During  the  process  a  small  amount  of  urea  i.?  decomposed, 
so  that  the  value  obtained  is  slightly  too  small.  Of  course  the  specific  gravity  varies  with  the  amount 
of  water  in  the  urine.     The  most  concentrated  (highest  specific  gravity)  urine  is  the  morning  urine 


Fig.  250. 


JOOC 


104(1 


Development  of  a  glomerulus  and  Malpighian  capsule,     a,  capillary  ; 
b,  visceral ;  c,  parietal  layer  of  capsule. 


Fig.  249. 


"^P% 


\m 


Graduated  cylinder  and  flask  for  measuring  the  amount  of  urine. 


Urinometer. 


(Urina  noctis),  especially  after  being  retained  in'the  bladder,  e.g.,  in  prolonged  sleep  a  certain 
amount  of  water  is  absorbed,  so  that  the  vu-ine  becomes  more  concentrated.  The  most  dilute  urine 
is  secreted  after  copious  drinking  (Urina  potus).  Under  pathological  conditions,  as  in  diabetes 
mellitus  (§  175)-  Ae  urine  is,  at  the  same  time,  very  copious  (as  much  as  10,000  c.c),  and  very  con- 
centrated, while  the  specific  gravity  varies  from  1030  to  1060  [due  to  the  presence  of  a  large  amount 
of  grape  sugar].  In  fever  the  urine  is  concentrated,  and  small  in  amount.  In  polyuria,  due  to  cer- 
tain nervous  conditions,  the  urine  is  very  dilute  and  copious,  while  the  specific  gravity  may  be  as  low 
as  looi. 

3.  The  color  of  the  urine  depends  on  die  coloring  matters  present  in  it,  and 
varies  greatly,  but  the  differences  in  color  are  due  chiefly  to  variations  in  the  amount 
of  water.     Normally  it  has  a  pale  straw  color,  but  if  it  contains  more  water  than 


442 


THE    URINE. 


usual  it  has  a  very  j^ale  tint,  and  in  certain  cases  (as  in  the  sudden  polyuria  occur- 
ring after  an  attack  of  hysteria)  it  may  be  as  clear  as  water.  Concentrated  urine,  as 
after  meals,  or  the  first  urine  pas.sed  in  the  morning,  has  a  darker  color ;  it  is  a  dark 
yellow  or  brownish  red  ;  while  it  is  usually  dark  colored  in  fever. 

Fretal  urine,  and  also  the  urine  first  passed  after  birth,  are  as  clear  and  colorless  as  water.  The 
admixture  of  various  substances  with  the  urine  alters  its  color.  When  mixed  with  blood,  according 
to  the  degree  of  decomposition  of  the  hemoglobin,  the  urine  is  red  or  dark  brownish  red  [more  fre- 
quently it  is  5wr'/'_r],  especially  if  the  blood  comes  from  the  kidneys  and  the  urine  is  acid.  When 
mixed  with  bile  pigments,  it  is  of  a  deep  yellowish  brown,  with  an  intense  yellow  froth;  senna 
taken  internally  makes  it  intensely  red,  rhubarb  brownish  yellow,  and  carbolic  acid  black.  Urine 
undergoing  the  ammoniacai  fermentation  may  present  a  dirty  bluish  ajipearance,  owing  to  the  forma- 
tion of  indigo.  The  color  of  urine  is  estimated  by  Neubauer  and  Vogel  by  means  of  an  empirical 
"  color  scale." 

Urine,  but  especially  ammoniacai  urine,  exhibits  fluorescence,  which  disappears  on  the  addition 
of  an  acid,  and  reappears  after  the  addition  of  an  alkali. 

Normal  urine,  after  standing  for  several  hours,  deposits  a  fine  cloud  of  vesical  mucus  [like  deli- 
cate cotton  wool].  The  froth  of  normal  urine  is  white,  and  disaj^pears  pretty  rapidly,  wliile  that  on 
an  albuminous  urine  perists  much  longer.  The  urine  not  unfrequently  contains  some  epithelial 
cells  from  the  bladder  and  urethra. 


[Amounts  of  the  Several  Urinary 

Constituents  (Loebisch).                                \ 

[Amounts  of  the  Severai,  Urinary 
Constituents  Passed  in  24  Hours  {Parkes). 

Constituents. 

Man,  28  years  of  age, 
weight,  72  kilos,  observa- 
tions over  8  days 
(Kerner). 

Mean  of    ] 
analyses  in  ! 

different     j 
individuals  ' 

(yo£:el). 

i 

By  an  aver- 
CoNSTiTUENTS.            age  man  of 
66  kilos. 

Pen 

kilo,  of 
body- 
weight. 

In  24  hours. 

Min. 

Max. 

Mean. 

In  24  hours. 

c.c. 

Quantity, ,  1099 

Specific  gravity,     .    .     1015 

Water 

Solids, 

Urea, ^      32.00 

Uric  acid !        0.69 

Sodium  chloride,    .    .  |      15.00 
Phosphoric  acid,    .    .           3.00 
Sulphuric  acid,   ...           2.26 
Phosphorus,  Calcium,         0.25 
Magnesium  phosphate         0.67 
Total   quantity   of 

earthy  phosphates.   ;        0.92 

Ammonia 0.74 

Free  acid, 1.74 

c.c. 
2150 
1027 

43-4 
1-37 

19.20 
4.07 
2.84 
0.51 
1.29 

1.80 

I.OI 

2.20 

c.c. 
1491 

I02I 

38:x 

0.94 
16.8 
3:42 

2.48 
0.38 
0.97 

1-35 
0.83 
1-95 

c  c. 
1500 
1020 
1440 
60 
35 
0  75 
16.5 
3-5 

.':° 

1.2 

0  65 
3     ] 

Water, 

Total  solids,    .... 

Urea,. 

Uric  acid 

Hippuric  acid,    .    .    . 

1   Kreatinin, 

j  Pigment  and  other 
1      substances,  .... 

Sulphuric  acid,   .   .    . 

Phosphoric  acid,    .    . 
;  Chlorine, 

Ammonia, 

Potassium, 

Sodium, 

1  Calcium 

!  Magnesium, 

grms. 

1500.000 

72.000 

33180 

0.55s 

0.400 

0.910 

10.300 

2.012 

3.164 

7.000(8.12) 

0.770 

2.500 
1 I .090 

0.260 

0.207 

grms. 
23  000 
1.100 
0.500 
00084 
o.oc6o 
0.0140 

0.J510 
0.0305 
0  0486 
0.1260 

4.  Consistence. — Normal  urine,  like  water,  is  a  freely  mobile  fluid. 

Large  quantities  of  sugar,  albumin  or  mucus  make  it  less  mobile;  while  the  so-called  chylous 
urine  of  warm  climates  may  be  like  a  white  jelly. 

5.  The  taste  is  a  saline  bitter;  the  odor  is  characteristic  and  aromatic. 

Ammoniacai  urine  has  the  odor  of  ammonia.     Turpentine  taken  internally  gives  rise  to  the  odor . 
of  violets,  copaiba  and  cubebs  a  strongly  aromatic,  and   asparagus  an   unpleasant  odor.     Valerian, 
assafoetida,  and  castoreum  [but  not  camphor]  also  produce  a  characteristic  odor.     [The  odor  of  dia- 
betic urine  is  described  as  "sweet."] 

6.  The  reaction  of  normal  urine  is  acid,  owing  to  the  presence  of  acid  salts, 
chiefly  acid  sodic  phosphate,  which  seems  to  be  derived  from  basic  sodic  phos- 
phate, owing  to  the  uric  acid,  hippuric  acid,  sulphuric  acid,  and  CO^  taking  to 
themselves  part  of  the  soda,  so  that  the  phosphoric  acid  forms  an  acid  salt.  After 
a  diet  of  flesh,  acid  pota.ssic  phosphate  is  the  cause  of  the  acidity.     That  the  urine 


ORGANIC    CONSTITUENTS    OF    URINE UREA. 


443 


contains  no  free  acid  is  proved  by  the  fact  that  it  gives  no  precipitate  with  sodic 
hyposulphite  {v.  Voit,  Huppert'). 

The  acid  reaction  is  increased  after  the  use  of  FiG.  251. 

acids,  e.g.,  hydrochloric  and  phosphoric,  also  by 
ammoniacal  salts,  which  are  changed  within  the 
body  into  nitric  acid  ;  lastly,  after  prolonged  mus- 
cular exertion.  The  morning  urine  is  strongly 
acid. 

The  urine  becomes  less  acid  or  alkaline — 
(l)  By  the  use  of  caustic  alkalies,  alkaline  carbon- 
ates, or  alkaline  salts  of  the  vegetable  acids,  the 
last  being  oxidized  within  the  body  into  carbon- 
ates. (2)  By  the  presence  of  calcic,  or  magnesic 
carbonate.  (3)  By  admixture  with  alkaline  blood, 
or  pus.  (4)  By  removing  the  gastric  juice  through 
a  gastric  fistula  (p.  291,  Maly) ;  further,  from  one 
to  three  hours  after  a  meal.  [The  reaction  of 
urine  passed  during  digestion  may  be  neutral,  or 
even  alkaline.  This  is  due  either  to  the  formation 
of  acid  in  the  stomach  lyBettce  yoiies),  or  to  a  fixed 
alkali  derived  from  the  basic  alkaline  phosphates 
taken  with  the  food  [IV.  Roberts).']  (5)  The 
urine  is  rarely  alkaline  in  anosm.ia,  owing  to  a  defi- 
ciency of  phosphoric  and  sulphuric  acids.  [(6) 
The  nature  of  the  food — vegetable  food  makes 
it  alkaline.  (7)  By  profuse  sweating.  (8)  By 
absorption  of  alkaline  transudations  (blood,  se- 
rum).] 

[Method. — The  reaction  of  urine  is  tested  by 
means  of  litmus  paper.  Normal  urine  turns  blue 
litmus  paper  red,  and  does  not  affect  red  litmus. 
An  alkaline  urine  makes  red  litmus  paper  blue, 
while  a  neutral  urine  does  not  alter  either  blue  or 
red  litmus  paper.]  Sometimes  violet  litmus  paper 
is  used,  which  becomes  red  in  acid,  and  blue  in 
alkaline  urine. 

Estimation  of  the  Acidity. — This  is  done 
by  determining  the  amount  of  caustic  soda 
necessary  to  produce  a  neutral  reaction  in  loo 
c.c.  of  urine.  A  soda  solution,  containing  0.0031 
grm.  of  soda  in  each  c.c.  is  used;  i  c.c.  of  this 
solution  exactly  neutralizes  0.0063  grm.  oxalic 
acid.  To  the  100  c.c.  of  lu-ine  in  a  beaker, 
soda  solution  is  added,  drop  by  drop,  from  a 
graduated  burette  (Fig.  251),  until  violet  litmus 
paper  becomes  neither  red  nor  blue.  The  number 
of  c.c.  of  soda  solution  is  now  read  off  on  the 

burette,  and  as  each  c.c.  corresponds  to  0.0063  grm.  oxalic  acid,  we  can  easily  calculate  the  amount 
of  oxalic  acid  which  is  equivalent  to  the  degree  of  acidity  in  loo  c.c.  of  urine.  So  that  the  degree 
of  acidity  of  the  urine  is  expressed  by  the  equivalent  amount  of  oxalic  acid,  which  is  completely 
neutralized  by  the  same  amount  of  caustic  soda. 

Urine  of  Mammals. — The  urine  of  carnivora  is  pale,  passing  into  a  golden  yellow ;  its  specific 
gravity  is  high,  and  its  reaction  strongly  acid.  The  urine  of  herbivora  is  alkaline ;  it  shows  a  pre- 
cipitate of  earthy  carbonates  (hence,  it  effervesces  on  the  addition  of  an  acid),  and  of  basic  earthy- 
phosphates.  During  hunger,  the  urine  presents  the  character  of  that  of  carnivora,  as  the  animal  in 
this  case  practically  lives  upon  its  own  flesh  and  tissues. 

256.  I.  THE  ORGANIC  CONSTITUENTS  OF  URINE.— Urea, 

CO(NH2).2,  the  diamide  of  CO2,  or  carbamid,  is  the  chief  end  product  of  the 
oxidation  of  the  nitrogenous  constituents  of  the  body.  Its  composition  is  com- 
paratively simple  : .  i  carbonic  acid  -)-  2  ammonia  —  i  water.  It  crystallizes  in 
silky  four-sided  prisms  with  oblique  ends  (rhombic  system),  without  water  of 
crystallization  (Fig.  252,  1),  if  it  crystallizes  rapidly  it  fornis  delicate  white  needles. 
It  has  no  action  on  litmus,  is  odorless,  and  has  a  weak,  bitter,  cooling  taste,  like 


Graduated  Burette. 


444 


QUANTITY   OF    UREA. 


saltpetre;  is  readily  soluble  in  water  and  akoliol,  hut  insoluble  in  ether.  It  is  an 
isomer  of  ammonium  cyanate,  from  which  it  may  lie  prejiared  by  evaporation, 
whereby  the  atoms  rearrange  themselves  {IVohler,  1828).  It  can  be  prei)ared  arti- 
ficiall)-  in  many  other  ways. 

Decomposition. — When  heated  al)ove  120°,  it  gives  off  ammonia  vapor,  while  a  glassy  mass  of 

hiuret  and  cyanic  acid  is  left.     When  urine  undergoes  the  alkaline  fermentation   (i;  263),  or  when 

urea  is  treated  with  strong  mineral  acitls,  or  boiled  with  the  hydrates  of  the  alkalies,  or  superheated 

with  water  (240°  C),  it  takes  up  two  molecules  of  water  and  produces  ammonium  carbonate,  thus — 

C()(XI1.,).,  +  2H.,0  =  C()(NH,0)2. 

When  brought  into  relation  with  nitrous  acid,  it  splits  up  into  water,  CO.^,  and  \.  The  two  last 
decompositions  are  made  the  basis  of  methods  for  the  quantitative  estimation  of  urea  (^  257). 

Quantity. — In  normal  urine,  urea  occurs  to  the  extent  of  2.5  to  3.2  percent. 
An  adult  man  excretes  daily  from  30  to  40  grms.  [500  grains,  or  a  little  over  i  oz.]  ; 
women  less,  children  relatively  more ;  owing  to  the  relatively  greater  metabolism 
in  children,  the  unit  weight  of  body  produces  more  urea  than  the  unit  weight  of  'an 

Fu;.  252. 


I,  2,  Prisms  of  pure  urea ;  3,  rhomboidal  plates  ;  4,  hexagonal  tablets  ;  5,  6,  irregular  scales  and  plates 

of  urea  nitrate. 


adult,  in  the  proportion  of  1.7  :  1.  If  the  metabolism  of  the  body  is  in  a  condition 
of  equilibrium  (§  236),  the  urea  excreted  contains  almost  as  much  N  as  is  taken  in 
with  the  nitrogenous  constituents  of  the  food. 

Variations  in  the  Quantity. — The  amoimt  of  urea  increases  when  the 
amount  of  proteids  in  the  food  is  increased ;  and  also  when  there  is  a  more  rapid 
breaking  up  of  the  nitrogenous  tissues  of  the  body  itself.  As  this  breaking  up  is 
increased  by  diminution  of  O,  and  by  loss  of  blood,  so  these  conditions  also  increase 
the  urea  (§  41).  It  is  also  increased  by  drinking  large  draughts  of  water,  by  various 
salts,  by  frequent  urination,  and  by  exposure  to  compressed  air.  In  diabetic  persons, 
who  eat  very  large  (}uantities  of  food,  it  may  exceed  100  grms.  [over  3  oz.]  per  day; 
during  hunger  it  sinks  to  6.1  grms.  [90  grains]  per  day  During  inanition,  the 
maximum  amount  is  excreted  toward  mid-day,  and  the  minimum  in  the  morning. 
The  daily  amount  of  urea  varies  with  the  quantity  of  urine ;  three  to  five  hours  after 
a  meal,  the  formation  of  urea  is  at  a  maximum,  when  it  sinks  and  reaches  its 
minimum  during  the  night.  Muscular  exercise,  as  a  rule,  does  not  increase  it 
(v.  Voit,  Fick  and  Wislicetius — §  295),  but  only  when  deficiency  of  O,  causing 
dyspnoea,  occurs  at  the  same  time  {Oppenheim). 


COMPOUNDS   OF   UREA.  445 

Pathological. — In  acute  febrile  inflammations,  and  in  fevers  generally  (§  22,  3),  the  urea 
increases  until  the  crisis  is  reached,  and  afterward  it  diminishes.  After  the  fever  has  passed  off,  the 
amount  excreted  is  often  under  the  normal.  In  some  cases  of  high  fever,  although  the  amount  of 
urea  formed  is  increased,  it  may  not  be  excreted ;  there  is  a  retention  of  the  urea,  which,  later  on,  may 
lead  to  an  increased  excretion  (^Naunyn).  In  chronic  diseases,  the  amount  depends  largely  upon  the 
state  of  the  nutrition,  the  metabolism,  and  also  upon  the  degree  of  fever  present.  Degenerative  changes 
in  the  liver,  e.g.,  due  to  poisoning  with  phosphorus,  may  be  accompanied  by  diminished  excretion 
of  urea  and  increased  excretion  of  ammonia  (Stadelmann).  It  is  increased  in  man  by  morphia, 
narcotin,  narcein,  papaverin,  codein,  thebain  {^Fubini),  arsenic  i^Gdthgens),  compounds  of  antimony, 
and  small  doses  of  phosphorus  [Bauer),  which  favor  the  decomposition  of  proteids,  and  by  sub- 
stances which  increase  the  bile  formation  in  the  liver  (yV.  Faton).  Quinine,  which  "spares"  the 
proteids,  diminishes  it. 

Occurrence. — Urea  occurs  in  the  blood  (i  :  10,000),  lymph,  chyle  (2  :  1000),  liver,  lymph  glands, 
spleen,  lungs,  brain,  eye,  bile,  saliva,  amniotic  fluid,  and  pathologically  in  sweat,  e.g.,  in  cholera,  in 
the  vomit  and  sweat  of  ursemic  patients,  and  in  dropsical  fluids. 

Formation. — It  is  certain  that  it  is  the  chief  end  product  of  the  metabohsm  of 
the  proteids.  Less  oxidized  prodiacts  are  uric  acid,  guanin,  xanthin,  hypoxanthin, 
alloxan,  allantoin.  Uric  acid  administered  internally  appears  in  the  urine  as  urea ; 
alloxan  and  hypoxanthin  can  be  changed  directly  into  urea.  The  urea  excretion  is 
increased  by  the  administration  of  leucin,  glycin,  aspartic  acid,  or  ammonia  salts 
{Schulzen,  Nencki).  As  yet  it  has  not  been  definitely  determined  where  urea  is 
formed,  but  the  liver  and,  perhaps,  the  lymph  glands,  are  organs  where  it  is  pro- 
duced (§  178). 

In  birds,  the  liver  forms  uric  acid  from  ammonia.  The  liver  can  be  readily  excluded  from  the 
circulation  in  birds,  and  Minkowski  found  that  after  this  operation  the  uric  acid  was  diminished  and 
the  ammoniacal  salts  were  increased  (§  178). 

Antecedents. — -During  digestion,  the  proteids  are  converted  into  leucin,  tyrosin,  glycin,  and 
aspartic  acid.  If  the  aniido  acids,  glycin,  leucin,  or  aspartic  acid,  or  ammoniacal  salts,  be  given  to 
an  animal,  the  amount  of  urea  excreted  is  increased.  As  the  molecule  of  the  amido  acids  contains 
only  one  atom  of  N,  and  the  molecule  of  urea  contains  two  of  N,  it  is  probable  that  urea  may  be 
formed  synthetically  from  these  acids.  It  is  possible  that  the  amido  acids  meet  with  nitrogenous 
residues  in  the  juices  of  the  body,  e.  g.,  carbamic  acid  or  cyanic  acid.  The  union  of  these  may  pro- 
duce urea.  According  to  Salkowski,  feeding  with  these  substances  causes  the  breaking  up  of  the 
proper  proteids  of  the  body  so  as  to  provide  the  necessary  components.  Schmiedeberg  is  of  opinion 
that  urea  is  formed  in  the  body  from  ammonia  carbonate  by  the  removal  of  water;  and  v.  Schroder 
found  that,  when  he  passed  blood  containing  ammonia  carbonate  through  a  fresh  liver,  the  urea  in 
the  blood  was  greatly  increased  Drechsel  succeeded  in  producing  urea  at  ordinary  temperatures 
by  the  rapid  alternating  oxidation  and  reduction  of  a  watery  solution  of  ammonia  carbonate.  [We 
know  that  the  greater  part  of  the  urea  exists  in  the  blood,  and  that  the  renal  epithelium  removes  it 
from  the  blood.  Although  it  is  surmised  that  some  of  the  nitrogenous  bodies  named  above,  more 
especially  leucin,  and  perhaps  also  kreatin,  are  the  precursors  of  urea,  yet  we  cannot  say  definitely 
how  or  where  the  transformation  takes  place.  Perhaps  this  is  effected  in  the  liver,  and,  it  may  be, 
also  in  the  spleen  (§  193)-] 

Preparation. — Urea  may  be  prepared  from  dog's  urine  (especially  after  a  diet  of  flesh)  by 
evaporating  it  to  a  syrupy  consistence,  extracting  it  with  alcohol,  and  again  evaporating  the  filtrate 
to  a  syrupy  consistence.  The  ciystals  which  separate  are  washed  with  water  to  remove  any  extract- 
ives that  may  be  mixed  with  them,  and  dissolved  in  absolute  alcohol.  It  is  then  filtered,  and  allowed 
to  crystallize  slowly.  Or,  human  urine  may  be  evaporated  to  one-sixth  of  its  volume  and  cooled 
to  0°,  and  excess  of  strong  nitric  acid  added,  which  precipitates  urea  nitrate  mixed  with  coloring 
matter.  This  precipitate  is  pressed  in  blotting  paper,  then  dissolved  in  boiling  water  containing 
animal  charcoal,  and  filtered  while  hot.  When  it  cools,  colorless  crystals  of  urea  nitrate  separate 
(Fig.  252).  These  crystals  are  redissolved  in  warm  water,  and  barium  carbonate  added  until  effer- 
vescence ceases ;  urea  and  barium  carbonate  are  formed.  Evaporate  to  dryness,  extract  with  abso- 
lute alcohol,  filter,  and  allow  evaporation  to  take  place,  when  urea  separates. 

Compounds  of  Urea. — Urea  combines  with  acids,  bases,  and  salts.  The  fol- 
lowing are  the  most  important  combinations  :  — 

I.  Urea  nitrate  (CH^NjO,  HNO3)  ^^  easily  soluble  in  water,  and  not  so  soluble  in  water  con- 
taining nitric  acid,  it  forms  characteristic  rhombic  crystals  (Fig.  252,  3,  4,  5,  6).  Sometimes  the 
formation  of  these  crystals  is  used  to  determine  microscopically  the  presence  of  urea  in  a  fluid. 
If  a  fluid  is  suspected  to  contain  minute  traces  of  urea,  it  is  concentrated  and  a  drop  of  the  fluid  is 
put  on  a  microscopic  slide.    A  thread  is  placed  in  the  fluid,  and  the  whole  is  covered  with  a  cover- 


446 


QUANTITATIVE    ESTIMATION    OF    UREA. 


glass.     A  drop  of  concentrated  nitric  acid  is  allowed  to  flow  under  the  cover-glass,  and  after  a  time 
crystals  of  urea  nitrate  adhering  to  the  thread  may  be  detected  with  the  microscope. 

2.  Urea  oxalate  (€11^X20)2,  CjR^O^-f-  H.,0,  is  made  by  mixing  a  concentrated  solution  of  urea 
with  oxalic  acid.  The  crystals  form  groups  of  rhombic  tables,  often  of  irregular  shape.  It  is  only 
slightly  soluble  in  cold  water,  and  still  less  so  in  alcohol  (Fig.  253). 

3.  Urea  phosphate  (CH^NjO,  H3PO4),  forms  large,  glancing,  rhombic  crystals,  very  easily  solu- 
ble in  water.     It  is  obtained  by  evaporating  the  urine  of  pigs  fed  on  dough. 

4.  Sodic  chloride  —  urea  (CH^N.^O,  NaCl  -(-  ^^2^)  forms  rhombic,  shining  prisms,  which  are 
sometimes  deposited  in  evaporated  human  urine. 

5.  Urea  —-  mercuric  nitrate  is  obtained  as  a  white  cheesy  precipitate,  when  mercuric  nitrate 
is  added  to  a  solution  of  urea.  Liebig's  titration  method  for  urea  dejjcnds  on  this  reaction  (jJ  257, 
11). 

257.  QUALITATIVE  AND  QUANTITATIVE  ESTIMATION  OF  UREA.— I. 
The  qualitative  Estimation  of  Urea. — (i)  Jt  may  be  isolated  as  such.  If  (7/(5/^/«/«  be  present, 
add  to  the  fluid  three  or  four  times  its  volume  of  alcohol,  and,  after  several  hours,  filter.  Evaporate 
the  filtrate  over  a  water  bath,  and  dissolve  the  residue  in  a  few  drops  of  water. 

(2)  The  crystals  of  urea  nitrate  may  be  detected  microscopically  (Fig.  252). 

II.  Quantitative  Estimation. — (i)  Sodic  hypobromite  decomposes  urea  into  CO.,,  HjO,  and 
N.     On  this  reaction  depends  the  Knop-Hiifner  method  of  quantitative  estimation.     The  N  rises  in 


Fig.  253. 


fo^ 


Fig.  254. 


Perfect  crystals  of  oxalate  of  urea. 


Ureameter  of  Charteris. 


the  form  of  small  bubbles  in  the  mixed  fluid,  while  the  CO.^  is  absorbed  by  the  caustic  soda.     [The 
reaction  is  the  following : — 

NjH^CO  +  3NaBrO  =  3NaBr  +  CO,^  +  2H2O  -f  N. 
The  nitrogen  is  collected  and  estimated  in  a  graduated  tube,  and  the  amount  of  urea  calculated  from 
the  volume  of  nitrogen.     The  uric  acid  is  also  decomposed,  but  that  can  be  estimated  separately 
and   a  correction  made.     We  may  use  the  apparatus  of  Russell  and  West,  or  Dupre,  or  that  of 
Charteris  (Fig.  254).] 

[Ureameter. — Make  a  solution  of  hypobromiteof  soda  by  mixing  100  grammes  NaHOin  250  c.  c. 
of  water,  and  adding  25  c.  c.  of  bromine.  It  is  better  to  be  made  fresh,  as  it  decomposes  by  keeping. 
The  graduated  tube  is  placed  in  a  cylindrical  vessel,  filled  with  water,  and  depressed  until  the  zero  on 
the  tubes  coincides  with  the  level  of  the  water.  Introduce  15  c.  c.  of  the  hypobromite  solution  into  the 
pyramidal-shaped  bottle,  while  into  a  short  test-tube  are  placed  5  c.  c.  of  urine.  The  test-tube  with 
the  urine  is  introduced  into  the  bottle  by  means  of  a  pair  of  forceps  in  such  a  way  that  it  does  not 
spill.  Close  the  bottle  tightly  with  the  caoutchouc  stopper,  through  which  passes  a  glass  tube  to 
connect  it  with  the  graduated  burette.  Incline  the  bottle  so  as  to  allow  the  urme  to  mix  with  the 
hypobromite  solution  when  the  gases  are  given  off,  and  pass  into  the  collecting  tube,  which  is  gradu- 
ally raised  until  the  surfaces  of  the  liquids,  outside  and  in,  coincide.  Time  should  be  allowed  to 
permit   the  whole  apparatus  to   have  the  same   temperature.      Read  off  the  amount  of  gas  N 


URIC    ACID, 


447 


evolved,  for  the  CO2  is  absorbed  by  the  caustic  soda.  The  collecting  tube  is  usually  graduated 
beforehand,  so  that  each  division  of  the  tube  is  =  o.i  per  cent,  of  urea,  or  0.44  gr.  per  fluid  oz. 
Thus,  suppose  that  50  oz.  of  urine  are  passed  in  twenty- four  hours,  and  that  5  c.  c.  of  urine  evolve 
18  measures  of  N,  then  0.44  X  18  X  5°  =  39^  grs.  of  urea.  If,  however,  the  tube  be  graduated 
into  c.  c,  then  30.3  c.  c.  of  N  =  o.i  grm.  of  urea  at  the  ordinary  temperature  and  pressure.] 

III.  Volumetric  Method  {Liebig). — By  means  of  a  graduated  pipette  (Fig.  255)540  cubic 
centimetres  of  the  urine  are  placed  in  a  beaker;  add  20  cubic  centimetres  of  barium  mixture  to 
precipitate  the  sulphuric  and  phosphoric  acids.  The  barium  mixture  consists  of  i  vol. 
of  a  cold  saturated  solution  of  barium  nitrate  and  2  vols,  of  a  cold  saturated  solution  of  FiG.  255. 
♦barium  hydrate.  Filter  through  a  dry  filter,  and  take  15  cubic  centimetres  of  the 
filtrate,  -which  correspond  to  10  c.  c.  of  urine,  and  place  in  a  beaker.  Allow  a  titrated 
standard  solution  of  mercuric  nitrate  to  drop  from  a  burette  into  the  urine  until  a 
precipitate  no  longer  occurs.  The  mercuric  nitrate  is  made  of  such  a  strength  that  I 
cubic  centimetre  of  it  will  combine  with  lo  milligrammes  of  urea.  Test  a  drop  of  the 
mixture  from  time  to  time  in  a  watch  glass  or  piece  of  glass  blackened  on  its  under 
surface,  with  a  solution  of  sodic  carbonate,  which  is  called  the  indicator.  When- 
ever the  slightest  excess  of  mercuric  nitrate  is  added,  the  mixture  strikes  a  yellow  color 
with  the  soda.  The  standard  solution  must  be  added  drop  by  drop  until  this  result  is 
obtained.  Read  off  the  number  of  cubic  centimetres  of  the  standard  solution  used ;  as 
each  centimetre  corresponds  to  10  milligrammes  of  urea,  multiply  by  ten,  and  the 
amount  of  urea  in  10  cubic  centimetres  of  urine  is  obtained. 

This  method  does  not  give  quite  accurate  results  even  in  normal  urine.  To  urine 
containing  much  phosphates  is  added  an  equal  volume  of  the  barium  mixture.  Very 
acid  urines  may  require  several  volumes  to  be  added.  Urine  containing  albumin  or 
blood  must  be  boiled,  after  the  addition  of  a  few  drops  of  acetic  acid,  to  remove  the 
albumin.  The  sodic  chloride  in  the  urine  also  interferes  with  the  accuracy  of  the  pro- 
cess, as  on  adding  mercuric  nitrate  to  urine,  mercuric  chloride  and  sodic  nitrate  are 
formed,  so  that  the  urine  does  not  combine  until  the  sodic  chloride  is  decomposed. 
When  the  urine  contains,  as  is  usually  the  case,  i  to  i  ;-<  per  cent.  NaCl,  deduct  2  c.  c. 
from  the  number  of  c.  c.  of  the  S.S.  added  to  10  c.  c.  of  urine. 

Estimation  of  the  total  N  in  Urine. — Pflliger  and  Bohland  recommend  the 
following  modification  of  the  method  of  Kjeldahl.  Five  c.c.  of  a  m-ine  of  medium 
concentration  are  allowed  to  flow  from  a  burette  into  Erlenmeyer's  flask,  capable  of 
containing  about  300  c.c,  and  to  it  are  added  20  c.c.  of  concentrated  sulphuric  acid. 
The  whole  is  boiled  until  all  the  water  and  gases  ai-e  driven  off'.  The  fluid  at  first 
becomes  black  fi-om  the  action  of  the  sulphuric  acid,  but  when  it  has  become  of  brownish 
tone  lessen  the  heat  of  the  Bunsen  burner.  About  half  an  hour  suffices  to  heat  it,  when 
the  fluid  at  last  becomes  bright  yellow.  Allow  it  to  cool,  dilute  it  with  water  to  200  c.c., 
and  place  the  whole  in  a  flask,  add  80  c.c.  of  caustic  soda  (S.9.  1-3),  cork  the  flask  as 
quickly  as  possible,  and  distill  its  contents.  The  distillate  must  pass  over  into  sulphuric 
acid,  which  must  be  titrated  beforehand.  The  quantity  of  sulphuric  acid  not  combined 
with  ammonia  must  be  estimated  by  titration  with  caustic  soda. 

The  N  in  the  Urine  may  be  estimated  approximately  thus.     To  10  c.c.  of  the  urine 
add  from  a  burette  Liebig's  mercuric  niti-ate   solution,  and  test  the  mixture  in  a  black       Graduated 
glass  plate  with  dry  sodic  bicarbonate  until  a  yellow  speck  remains.      Multiply  the        Pipette, 
number  of  c.c.  of  the  burette  fluid  used  by  0.04  [P/lilger  and  Bohland). 

258.  URIC  ACID  =  CjHiN^Os  is  the  nitrogenous  substance  which,  next  to 
urea,  carries  off  most  of  the  N  from  the  body;  in  twenty-four  hours  0.5  grm.  (7 
to  10  grains)  ;  during  hunger,  0.24  grm.  (4  grains)  j  after  a  strongly  animal  diet, 
2. 1 1  grm.  (30  to  35  grains)  are  excreted.  The  proportion  of  urea  to  uric  acid  is 
45  :  I.  If  a  mammal  be  fed  with  uric  acid,  part  of  it  becomes  more  highly  oxidized 
into  urea,  while  the  oxalic  acid  in  the  urine  is  also  increased  (§  260)  ;  in  fowls, 
feeding  with  leucin,  glycin,  or  aspartic  acid  {v.  Knierieni),  or  ammonia  carbonate 
iSchroeder),  increases  the  amount  of  uric  acid.  When  urea  is  administered  to 
fowls,  it  is  reduced  chiefly  to  uric  acid. 

It  is  the  chief  nitrogeneous  product  in  the  urine  of  birds,  reptiles,  and  insects,  while  it  is  absent 
from  herbivorous  urine. 

Properties. — It  is  dibasic,  colorless,  and  crystallizes  in  various  forms  (Figs.  256 
and  257),  belonging  to  the  rhombic  system  (i).  When  the  angles  are  rounded,  the 
whetstone  form  (2)  is  produced,  and  if  the  long  surfaces  be  flattened,  six-sided  tables 
occur.  Not  unfrequently  diabetic  urine  deposits  spontaneously,  large,  yellow,  trans- 
parent rosettes  (6,  8).     If  20  c.c.   of  HCl,  or  acetic  acid,  be  added  to  i  htre  of 


448 


URIC    ACID. 


urine,  crystals  (9)  are  deposited,  like  cayenne  pepper,  on  the  surface  and  sides  of 
the  glass,  after  several  hours.  [The  HCl  decomposes  the  urates,  and  lil)erates  the 
acid,  which  does  not  crystallize  at  once,  owing  to  the  ])resence  of  the  ])hosphates  in 
the  urine.  Crystals  of  uric  acid  are  usually  yellowish  in  color  from  the  pigment  of 
the  urine,  and  they  are  soluble  in  caustic  potash.] 

Solubility. — It  is  tasteless  and  odorless  ;  reddens  litmus;  is  soluble  in  18,000  parts  of  cold  and 
in  15,000  of  boiling  water,  and  insoluble  in  alcohol  and  ether.  Ilorbaczewski  prepared  it  synthetic- 
ally by  melting  together  glycin,  or,  as  it  is  also  called,  glycocin,  and  urea.  It  is  freely  soluble  in 
alkaline  carbonates,  borates,  phosj)hites,  lactates,  and  acetates,  these  salts  at  the  same  time  removing 
a  part  of  the  base;  thus,  there  are  formed  acid  urates  and  acid  salts  from  the  neutral  salts.  It  is 
soluble  in  concentrated  sulphuric  acid,  from  which  it  may  be  precipitated  by  the  addition  of  water. 

Decomposition. — During  dry  distillation  it  decomposes  into  urea,  cyanuric  acid,  hydrocyanic 
acid,  and  ammonium  carbonate.  Superoxide  of  lead  converts  it  into  urea,  allantoin,  oxalic  acid, 
and  C(  ^.,_ ;  while  ozone  forms  the  same  substances,  with  the  addition  of  alloxan.  ^Vhen  it  is  reduced 
by  H  in  statu  nascenJi,  as  by  sodium  amalgam,  it  forms  xanthin  and  sarkin.  It  is  a  less  oxidized 
metabolic  product  than  urea,  but  it  is  by  no  means  proved  that  uric  acid  is  a  precursor  of  urea. 


Forms  of  uric  acid,     i.  Rhombic  plates  ;  2,  whetstone  forms;   3,  quadrate  forms;  4,  5,  prolonged   into  points  ;  6,  8, 
rosettes;  7,  pointed  bundles;  9,  barrel  forms  precipitated   by  adding  hydrocliloric  acid  to  urine. 

Occurrence. — Uric  acid  occurs  dissolved  in  the  urine  in  the  form  of  acid 
urates  of  soda  and  potash.  These  salts  occur  also  in  urinary  calculi,  gravel, 
and  in  gouty  de])Osits.  Ammcniium  urate  occurs  in  very  small  (piantity  in  a  deposit 
of  "  urates,"  but  is  formed  in  considerable  amount  when  urine  becomes  ammo- 
niacal  from  decomposition  (Fig.  261).  Free  uric  acid  occurs  in  normal  urine  only 
in  the  very  smallest  amount.  It  is  sometimes  deposited  after  a  time  (Fig.  260).  It 
frequently  forms  urinary  calculi  and  gravel. 

The  urine  of  newly-born  children  contains  much  uric  acid.  Uric  acid  and  its  salts  are  increased 
after  severe  muscular  exertion,  accompanied  by  perspiration,  in  catarrhal  and  rheumatic  fevers,  and 
such  conditions  as  are  accompanied  by  disturbance  of  the  respiration  ;  in  leukaemia  and  tumors  of 
the  spleen,  cirrhotic  liver,  and  generally  in  cases  of  catarrah  of  the  stomach  and  intestinal  tract,  fol- 
lowing the  excessive  use  of  alcohol.  [It  is  also  increased  during  ague  and  fevers,  and  perhaps  this 
has  some  relation  to  the  congestion  of  the  spleen  which  accompanies  these  conditions.]  It  is 
diminished  after  copious  draughts  of  water,  after  large  doses  of  quinine,  caffein,  potassic  iodide, 
common  salt,  sodic  and  lithic  carbonates,  sodic  sulphate,  inhalation  of  O,  slight  muscular  exertion. 
In  gout,  the  amount  excreted  in  the  urine  is  small.  In  chronic  tumors  of  the  spleen,  anaemia,  and 
chlorosis,  when  the  respiration  is  not  at  the  same  time  embarrassed,  it  is  also  diminished. 


ESTIMATION    OF    URIC    ACID.  449 

Urates. — Uric  acid  forms  salts — chiefly  acid  urates — with  several  bases,  which 
dissolve  with  difficulty  in  cold  water,  but  are  easily  soluble  in  warm  water.  Neutral 
urates  are  changed  by  CO2  into  acid  salts.  Hydrochloric  and  acetic  acids  break  up 
the  compounds,  and  crystals  of  uric  acid  separate. 

(i)  Acid  sodic  urate  usually  appears  as  a  brick-red  deposit  in  urine;  more  rarely  gray  or  white 
(lateritious  deposit),  tinged  with  uroerythrin,  in  catarrhal  conditions  of  the  digestive  organs,  and  in 
rheumatic  and  febrile  affections.  Microscopically,  it  is  completely  amorphous,  consisting  of  gran- 
ules,  sometimes  disposed  in  groups  (Fig.  260,  b) — sometimes  the  granules  have  spines  on  them.  The 
corresponding  potash  salt  occurs  not  unfrequently  under  the  same  conditions,  and  presents  the  same 
characters. 

(2)  Acid  ammonium  urate  (Fig.  261,  a)  always  occurs  as  a  sediment  in  ammoniacal  urine, 
either  with  (i),  or  mixed  with  free  uric  acid,  accompanied  by  a  triple  phosphate.  Microscopically,  it 
is  the  same  as  (i).  (l)  and  (2)  are  distinguished  by  the  sediment  dissohmig  when  the  tcrine  is 
heated.  If  a  drop  of  hydrochloric  acid  be  added  to  a  microscopic  preparation  of  the  sediment, 
crystals  of  uric  acid  separate. 

(3)  Acid  calcic  urate  occurs  sometimes  in  calculi,  and  is  a  white,  amorphous  powder,  slightly 
soluble  in  water.  When  heated  on  platinum  it  leaves  an  ash  of  calcium  carbonate.  Magnesium 
urate  rarely  occurs  in  urinary  calculi. 

259.  ESTIMATION  OF  URIC  ACID.— I.  Qualitative.— i.  Micro- 
scopic Characters. — The  appearances  presented  by  uric  acid  and  its  salts  under 
the  microscope.  It  is  deposited  from  urine  after  several  hours,  on  adding  acetic  or 
hydrochloric  acid. 

2.  Murexide  Test. — Gently  heat  a  urate  or  uric  acid  in  a  porcelain  vessel 
along  with  nitric  acid.  Decomposition  takes  place  and  the  color  changes  to  yellow. 
N  and  CO2  are  given  off ;  urea  and  alloxan  (C4H2N2O4)  remain.  Evaporate  slowly 
and  allow  the  yellowish-red  stain  to  cool ;  on  adding  a  drop  of  dilute  ammonia  a 
purplish-red  color  of  murexide  is  obtained,  it  becomes  blue  on  the  addition  of 
caustic  potash.  If  potash  or  soda  be  added  instead  of  ammonia,  a  violet  color  is 
obtained. 

3.  Schiff 's  Test. — Dissolve  uric  acid  or  a  urate  in  a  solution  of  an  alkaline  carbonate,  and  drop 
it  upon  blotting-paper  saturated  with  a  solution  of  silver  nitrate  ;  reduction  of  the  silver  takes  place 
at  once,  and  a  black  spot  is  formed. 

4.  On  boiling  a  solution  of  uric  acid  or  a  urate  in  an  alkali,  with  Fehling's  solution  (§  149,  2),  at 
first  white  urate  of  the  subo.xide  of  copper  is  deposited,  while  later,  red  copper  suboxide  is  formed. 

II.  Quantitative  Estimation. — Add  5  cubic  centimetres  of  concentrated  HCl  to  100  c.c.  of 
urine,  and  allow  it  to  stand  for  forty-eight  hours  in  the  dark,  when  the  uric  acid  is  precipitated  like 
fine  cayenne  pepper  crystals.  All  the  uric  acid  is  not  precipitated  by  the  HCl,  even  after  standing 
for  a  time.  [E.  A.  Cook  uses  sulphate  of  zinc  to  precipitate  the  uric  acid  as  urate  of  zinc.  Caustic 
soda  is  added  to  precipitate  the  phosphates,  and  then  to  the  clear  fluid  zinc  sulphate  solution,  which 
precipitates  urate  of  zinc  as  a  white  gelatinous  deposit.] 

Fokker-Salkowski  Method. — Make  200  c.c.  of  urine  strongly  alkaline  with  sodic  carbonate, 
and  after  an  hour  add  200  c.c.  of  a  concentrated  solution  of  ammonium  chloride,  whereby  acid  urate 
of  ammonium  is  precipitated.  After  forty-eight  hours  filter,  through  a  small  weighed  filter,  and  wash 
it  several  times.  Fill  the  filter  with  dilute  HCl  and  collect  the  filtrate.  Do  this  until  all  the  acid 
urate  is  dissolved.  From  the  total  filtrate  after  a  time  all  the  uric  acid  separates.  It  is  collected  in 
the  same  filter,  washed  with  water  and  alcohol  until  the  acid  reaction  disappears,  dried  at  ioo°  C. 
and  weighed.     To  the  weight  in  excess  of  the  filter  add  0.030  grm. 

260.  KREATININ   AND    OTHER    SUBSTANCES.  — Kreatinin, 

C4H9N3O2,  is  derived  from  the  kreatin  of  muscle  by  the  removal  of  a  molecule  of 
water,  and  partly  from  flesh  food.  The  quantity  excreted  daily  is  0.6  to  1.3 
gramme  (8  to  18  grains). 

It  is  diminished  in  progressive  muscular  atrophy,  tetanus,  anaemia,  marasmus,  chlorosis,  con- 
sumption, paralysis;  and  is  increased  in  typhus,  inflammation  of  the  lung;  it  is  absent  from  the 
urine  of  sucklings. 

Properties, — Kreatinin  is  alkaline,  easily  soluble  in  water  and  hot  alcohol.  It  forms  colorless, 
oblique  rhombic  columns;  unites  with  acids  and  salts,  silver  nitrate,  mercuric  chloride,  and  espe- 
cially with  zi7ic  chloride.  Kreatinin-zinc  chloride  (Fig.  257)  is  used  to  detect  its  presence. 
Weyl's  Test. — Add  to  urine  a  few  drops  of  a  slightly  brownish  solution  of  nitro-prusside  of  soda, 
and  then  weak  caustic  soda  solution,  producing  a  Burgundy-red  color,  which  soon  disappears. 
29 


150 


KREATININ    AND    OTHER    SUBSTANCES. 


When  heated  with  glacial  acetic  acid,  the  color  changes  to  green,  which  after  a  time  changes  to  blue 
iSalko'wski).  [The  blue  color — Berlin  lilue — is  due  to  the  formation  of  an  iron  salt,  ferrocyanide 
of  sodium,  from  the  decomposition  of  the  nitro-iirusside.  The  reaction  also  succeeds  with  formic 
acid instead  of  glacial  acetic  acid — if  some  time  be  allowed  to  elapse  after  Weyl's  reaction.] 

Xanthin  =  C^H^N,0.^  occurs  only  to  the  amount  of  i  gramme  in  300  kilos,  of  urine.  It  is  a 
substance  intermediate  between  sarkin  and  uric  acid,  (iuanin  and  hypoxantiiin  may  be  changed 
into  .xanthin;  in  contact  with  water  and  ferments  it  passes  into  utic  acid.  When  evaporated  with 
nitric  acid,  it  gives  a  yellow  stain,  which  becomes  yellowish-red  on  adding  potash,  and  violet-red  on 
applying  more  heat.  It  is  an  amorphous,  yellowish-white  powder,  fairly  soluble  in  boiling  water. 
It  has  also  been  found  in  traces  in  muscles,  brain,  liver,  spleen,  pancreas  and  thymus.  The  crystal- 
line body  paraxanthin  (dimethylxanthin)  and  the  amorphous  heteroxanthin  (methylxanthin)  occur 
in  traces  in  the  urine  [Salomon'). 

Sarkin  or  Hypoxanthin,  C^II^Np.— As  yet  this  substance  has  been  found  only  in  the  urine  of 
leukxmic  patients  [Jakuhasch),  and  it  has  been  prepared  in  the  form  of  needles  or  flattened  scales 
from  muscle,  spleen,  thymus,  brain,  bone,  liver  and  kidney.  In  normal  urine  a  l)ody  nearly  related 
to,  and  possibly  identical  with,  hypoxanthin  occurs  {E.  Salkoivski).  Hypoxanthin  closely  resem- 
bles xanthin,  and  can  be  changed  into  it  by  oxidation.  Nascent  hydrogen,  on  the  other  hand, 
reduces  uric  acid  to  xanthin  and  hypoxanthin.  When  evaporated  with  nitric  acid  it  gives  a  light 
yellow  stain,  which  becomes  deeper,  but  not  reddish-yellow,  on  adding  caustic  soda.  It  is  more 
easily  soluble  in  water  than  xanthin,  and  by  this  means  the  two  substances  can  be  separated  from 
each  other.     Guanin  is  insoluble  in  water. 


Fig.  257. 


'       If'}  ^-^ 


Oxalate  of  lime,  a,  b,  octahedra; 
c,  compound  forms  ;  d,  dumb 
bells. 


Krcatinin-zinc   chloride.      n,  balls   with  radiating  marks  ;    b, 
crj'stallized  from  water  ;  c,  from  alcohol. 

Oxaluric  acid  (C3H4X2O4)  occurs  in  very  small  qiianlity  combined  with  ammonia  in  urine. 
Physiologically,  it  is  interesting  on  account  of  its  relation  to  uric  acid.  It  is  a  white  powder  slightly 
soluble  in  water.     Ammonia  oxalurate  can  be  prepared  from  uric  acid. 

Oxalic  Acid  (C.H.O^)  occurs,  but  not  constantly,  to  the  amount  of  20  milli- 
grammes daily  as  oxalate  of  lime,  which  is  known  by  the  "envelope"  shai)e  of 
the  crystals  (Fig.  258);  insoluble  in  acetic  acid,  and  forming  transparent  octahedra. 
More  rarely  it  assumes  a  biscuit  or  sand-glass  form.  The  genetic  relation  of  oxalic 
acid  to  uric  acid  is  shown  by  the  fact  that  dogs  fed  with  uric  acid  excrete  much 
oxalate  of  lime.  Oxalic  acid  may  also  be  produced  by  the  oxidation  of  products 
derived  from  the  fatty  acid  series  (p.  430). 

Oxaluria.— The  eating  of  substances  containing  oxalate  of  lime  ( rhubarb)  increases  the  excre- 
tion. Increased  excretion  is  called  oxaluria;  it  is  regarded  as  a  sign  of  retarded  metaboli.sm  [Beneke), 
and  it  may  give  rise  to  the  formation  of  a  calculus.  In  oxaluria  the  uric  acid  is  also  often  increa.sed 
in  amount.  Perhaps,  in  the  first  instance,  there  is  an  increased  formation  of  uric  acid,  from  which 
oxalic  acid,  urea,  and  CO.^  may  be  formed.  The  amount  of  oxalic  acid  is  increased  after  the  use  of 
wine  and  sodic  bicarbonate. 


HIPPURIC    ACID. 


451 


Hippuric  Acid  =:  C9H9NO3  (Benzoylamidoacetic  acid)  occurs  in  large  amount 
in  the  urine  of  herbivora,  and  in  them  is  the  chief  end  product  of  the  metabohsm 
of  nitrogenous  substances;  in  human  urine  the  daily  quantity  is  small,  0.3  to  3.8 
grms.  (5  to  50  grains).  It  is  an  odorless  monobasic  acid  with  a  bitter  taste,  crys- 
tallizing in  colorless  four-sided  prisms  (Fig.  259).  Readily  soluble  in  alcohol,  and 
soluble  in  600  parts  of  water. 

[Crystals  of  hippuric  acid  when  heated  in  a  test-tube  are  decomposed,  and  a  sublimate  of  benzoic 
acid  and  amnionic  benzoate  condenses  on  the  upper  cool  part  of  the  tube,  while  there  is  an  odor  of 
new  hay,  and  oily  drops  remain  in  the  tube.] 

It  is  a  conjugated  acid,  and  is  formed  in  the  body  from  benzoic  acid,  or  some 
nearly  related  chemical  body,  such  as  the  cuticular  substance  of  plants,  or  from  oil 
of  bitter  almonds,  cinnamic  or  chinic  acid,  which  easily  pass  by  reduction  (chinic 
acid)  or  by  oxidation  (cinnamic  acid)  into  benzoic  acid  ;  glycin  uniting  with  it, 
with  the  formation  of  water — 


CjHgO^     4-     C2H5NO2 

Benzoic  acid      +  Glycin 


C9H9NO3     +     H,0 

Hippuric  acid       +        Water. 


[Formation. — When  benzoic  acid  is  introduced  into  the  alimentary  canal  of  an 
animal  (rabbit  or  dog),  it  appears  in  the  urine  as  hippuric  acid  ;  while  nitro-benzoic 
acid  appears  as  nitro-hippuric  acid.    As 

the   benzoic   acid    passes    through  the  Fig.  259. 

body,  it  becomes  conjugated  with  gly- 
cin or  glycocin,  chiefly  in  the  kidneys. 
The  hippuric  acid  in  the  urine  of  her- 
bivora is  chiefly  derived  from  some 
substance  with  a  benzoic  acid  residue 
present  in  the  cuticular  coverings  of 
the  food.  That  hippuric  acid,  in  part 
at  least,  is  formed  in  the  kidneys 
is  shown  by  the  following  considera- 
tions :  If  arterialized  blood,  containing 
benzoic  acid  and  glycin,  or  even  ben- 
zoic acid  alone,  be  passed  through  the 
blood  vessels  of  a  fresh,  living,  excised 
kidney,  hippuric  acid  is  found  in  the 
blood  after  it  is  perfused.  Even  after 
forty-eight  hours,  if  the  kidney  be  kept 
cool,  the  synthesis  takes  place.  If  the 
kidney  be  kept  too  long,  the  conjuga- 
tion does  not  take  place.  If  the  fresh  Hippuric  Acid. 
kidney  be  chopped  up,  and  kept  at  the 

temperature  of  the  body  with  benzoic  acid  and  glycin,  hippuric  acid  is  formed. 
Oxygen  seems  to  be  necessary  for  the  process,  for,  if  blood  or  serum  containing 
carbonic  oxide  be  used,  there  is  no  formation  of  hippuric  acid.] 

According  to  this  view,  it  is  derived  chiefly  from  the  food  of  herbivorous  animals,  and  hence  it  is 
absent  from  the  urine  of  sucking  calves,  as  well  as  after  feeding  with  grain  devoid  of  husk.  But  it 
is  also  formed  in  the  body  from  the  proteids.  In  the  dog,  the  fonnation  of  hippuric  acid  occurs  in 
the  kidney  {Schmiedeherg  atid  Bunge),  and  in  the  frog  also  outside  the  kidney.  Kiihne  and  Hall- 
wachs  thought  it  was  formed  in  the  liver,  and  Jaarsveld  and  Stockvis  in  the  kidney,  liver,  and  intes- 
tine. The  observation  of  Salomon  that,  after  excision  of  the  kidneys  in  rabbits,  and  injection  of 
benzoic  acid  into  the  blood,  hippuric  acid  was  found  in  the  muscles,  blood,  and  liver,  goes  to  show 
that  it  must  be  formed  in  other  organs  beside  the  kidneys.  The  power  of  changing  benzoic  acid 
introduced  into  the  human  body  into  hippuric  acid,  may  even  be  abolished  in  disease  of  the  kidney. 
Under  certain  circumstances  it  seems  that  hippuric  acid,  already  formed,  may  be  again  decomposed 
in  the  tissues. 

It  is  greatly  increased  after  eating  pears,  plums  and  cranberries ;  in  icterus,  some  liver  affections, 


452  COLORING    MATTERS    OF    URINE. 

and  in  diabetes.  When  boiled  with  strong  acid  or  allvalies,  or  with  putrid  substances,  it  takes  up 
IIjO  and  splits  into  benzoic  acid  and  glycin. 

Preparation. — Add  milk  of  lime  to  the  fresh  urine  of  horses  or  cows  to  form  calcic  hippurate. 
Filter,  evaporate  the  filtrate  to  a  small  bulk,  and  precipitate  the  hippuric  acid  with  excess  of 
hydrochloric  acid.  To  purify  the  hippuric  acid,  crystallize  it  several  times  from  a  hot  watery 
solution. 

Cyanuric  Acid. — Co^^u^'^P6+  ^^f^  occurs  in  the  urine  of  dogs  [J.  v.  Liebig). 

AUantoin,  C^HgNiO:,,  which  occurs  in  the  amniotic  fluid  of  the  cow,  is  found 
in  minute  traces  in  normal  urine  after  flesh  food,  and  is  more  abundant  during  the 
first  weeks  of  hfe,  and  during  pregnancy. 

After  large  doses  of  tannic  acid,  the  amount  is  increased  {SckoUin),  while  in  dogs  feeding  with 
uric  acid  also  increases  it  [Salkoivski). 

Properties. — It  forms  shining  prismatic  crystals;  from  the  urine  of  sucking  calves  it  crystallizes 
in  transparent  prisms.  It  is  decomposed  by  ferments  into  urea,  ammonium  oxalate,  and  carbonate,  and 
another  as  yet  unknown  body.  Preparation — [a)  the  urine  is  precipitated  with  basic  lead  acetate, 
the  lead  in  the  filtrate  is  removed  by  sulphuretted  hydrogen,  and  the  liltrate  itself  is  then  evaporated 
to  a  syrup,  from  which  the  crystals  separate,  after  standing  for  several  days.  They  are  then  washed 
with  water,  and  recr}stallized  from  the  water  [Salkowski). 

261.  COLORING    MATTERS  OF  THE  URINE.  — t.  Urobilin  is 

most  abundant  in  the  highly  colored  urine  of  fevers,  but  it  also  occurs  in  normal 
urine  {Jaffe).  It  is  identical  with  the  hydrobilirubin  of  Maly  (§  117,  3,  g).  It  is 
a  derivative  of  heematin,  which  also  yields  the  bile  pigments  (§  177).  It  gives  a 
red  or  reddish-yellow  color  to  urine,  which  becomes  yellow  on  the  addition  of 
ammonia. 

[MacMunn,  chiefly  from  spectroscopic  observations,  finds  that  two  entirely  different  substances 
have  been  included  under  the  name  of  "  urobilin,"  viz.,  that  of  normal  and  that  of  pathological 
urine,  and  that  hydrobilirubin  is  not  identical  with  either.  The  pathological  urobilin  seems  to  be 
closely  connected  with  stercobilin  {\  185).] 

Preparation. — Prepare  a  chloroform  extract  of  urine  containing  urobilin — add  iodine  to  the 
extract,  and  remove  the  iodine  by  shaking  the  mixture  with  dilute  caustic  potash,  which  forms  potas- 
sic  iodide.  This  potash  solution  becomes  yellow  or  brownish- yellow,  and  exhibits  beautiful  green 
Jluorescence  [Ge7-ha}\it). 

Urobilin  may  be  extracted  from  many  urines  by  ether  (Sal/cowski).  When  subjected  to  the  action 
of  reducing  agents,  e.g.,  sodium  amalgam,  a  colorless  product  is  obtained,  which  on  exposure  to  the 
air  absorbs  O,  and  becomes  re-transformed  into  urobilin.  This  colorless  body  is  identical  with  the 
chromogen  which  Jafife  found  in  urine. 

If  urine  is  treated  with  soda  or  potash,  the  characteristic  absorption  band  lying  between  b  and  F 
passes  nearer  to  b,  becomes  darker  and  more  sharply  defined.  According  to  lioppe-Seyler,  urobilin 
is  formed  in  urine  after  it  is  voided,  from  another  urobilin-forming  body  ( Jaffe's  chromogen)  absorb- 
ing oxygen.  If  urine  containing  urobilin  be  made  alkaline  with  ammonia,  and  zinc  chloride  be 
added,  it  exhibits  marked  fluorescence  ;  it  has  a  green  shimmer  by  reflected  light.  When  urobilin  is 
isolated,  it  fluoresces  without  the  addition  of  zinc  cldoride.  In  cases  of  jaundice  {>/,  180),  where 
Gmelin's  test  sometimes  fails  to  reveal  the  presence  of  bile  pigments,  urobilin  occurs.  This  "  urobilin- 
icterus"  {Gerhardt)  occurs  chiefly  after  the  absorption  of  large  extravasations  of  blood.  According 
to  Cazeneuve,  the  urobilin  is  increased  in  all  diseases  where  there  is  increased  disintegration  of 
blood  corpuscles. 

2.  Urochrome  (  Tkudickuvi)  is  regarded  as  the  chief  coloring  matter  of  urine.  It  may  be  iso- 
lated in  the  form  of  yellow  scales,  .soluble  in  water,  and  in  dilute  acids  and  alkalies.  The  watery 
solution  oxidizes,  and  when  exposed  to  air  becomes  red,  owing  to  the  formation  of  uroerythrin. 
When  acted  on  by  acids,  new  decomposition  products  are  formed,  e.g.,  uromelanin.  Uroerythrin 
gives  the  red  color  to  deposits  of  urates  (^  258). 

3.  A  brown  pigment  containing  iron  is  carried  down  with  uric  acid,  which  is  precipitated 
on  the  addition  of  hydrochloric  acid  (^258).  By  repeatedly  adding  sodic  urate  to  the  urine, 
and  precipitating  the  uric  acid  by  hydrochloric  acid,  a  considerable  amount  may  be  obtained 
{Kunkel). 

4.  Urine  boiled  with  HCl  yields  a  garnet-red  crystalline  pigment,  urorubin,  to  ether. 

In  cases  of  melanotic  tumors,  there  has  been  occasionally  observed  urine,  which  becomes  dark, 
owing  to  melanin  (^  250,  4),  or  to  a  coloring  matter  containing  iron  [Ktinkel). 

262.  INDIGO,  PHENOL,  KRESOL,  PYROKATECHIN,  AND 
SKATOL  FORMING  SUBSTANCES.  —  i.  Indican  [C,H,NSOJ,  or 
indigo-forming  substance  {Schunck),  is  derived   from  indol,  CsHyN,  the  basis  of 


INDICAN,    PHENOL   AND    PARAKRESOL.  453 

indigo,  which  is  formed  in  the  intestine  by  the  pancreatic  digestion  of  proteids 
(§  170,  II),  but  it  also  arises  as  a  putrefactive  product  (§184,  6).  Indol,  when 
united  with  the  radical  of  sulphuric  acid,  HSO3,  and  combined  with  potassium, 
forms  the  so-called  indigogen  or  indie  an  of  urine  (^Brieger,  Baumami).  This  sub- 
stance (C8H6NS04K=  potassium  indoxyl-sulphate)  forms  white  glancing  tablets  and 
plates ;  readily  soluble  in  water,  and  less  so  in  alcohol.  By  oxidation  it  forms  indigo- 
blue  ;  2  indican  +  03  =  CigHjoNaOa  (indigo  blue)  +  2HKSO4  (acid  potassic  sul- 
phate). It  is  more  abundant  in  the  urine  in  the  tropics,  and  it  is  absent  from  the 
urine  of  the  newly  born  {Senatot'). 

Tests. — (i)  Add  to  40  drops  of  urine  3  to  4  c.c.  of  strong  fuming  hydrochloric  acid,  and  2  to  3 
drops  of  nitric  acid.  Boil,  a  violet  red  color  (with  the  deposition  of  true  crystalline  indigo  blue 
(rhombic)  and  indigo  red  attest  its  presence.  Putrefaction  causes  a  similar  decomposition  in  indican; 
hence,  we  not  unfrequently  observe  a  bluish-red  pellicle  of  micioscopic  cr}-stals  of  indigo  blue,  or  even 
a  precipitate  of  the  same.  (2)  Mix  in  a  beaker  equal  quantities  of  urine  and  hydrochloric  acid,  and 
add  two  drops  of  solution  of  chlormated  lime;  the  mixture  at  first  becomes  clear,  then  blue  (Jaffe). 
Add  chloroform,  and  shake  the  mixture  vigorously  for  some  time;  the  chloroform  dissolves  the  blue 
coloring  matter,  which  is  obtained  as  a  deposit,  when  the  chloroform  evaporates  (^Senator,  Salkowski). 
(3)  Heat  to  70°  one  part  of  urine  with  two  parts  of  nitric  acid,  and  shake  up  with  chloroform;  the 
chloroform  dissolves  the  indigo  which  is  formed,  assumes  a  violet  color,  and  gives  an  absorption  band 
between  C  and  D,  slightly  nearer  D  {Hoppe-Seyler).  Quantity. — Jaffe  found  in  1500  c.c.  of  normal 
human  urine  4.5  to  19. 5  milligrammes  of  indigo  ;  horse's  urine  contains  23  times  as  much.  The  sub- 
cutaneous injection  of  indol  increases  the  indican  in  the  urine  {Jaffe).  E.  Ludwig  obtained  indican 
by  heating  hsematin  or  urobilin  with  a  caustic  alkali  and  zinc  dust.  It  has  also  been  found  in  the 
sweat  {Bizio). 

Pathological. — The  indican  in  the  urine  is  increased  when  much  indol  is  formed  in  the  intestine 
(^  172,  H),  e.g.,  in  typhus,  lead  colic,  trichinosis,  catarrh,  and  hemorrhage  of  the  stomach,  cholera, 
carcinoma  of  the  liver  and  stomach  ;  obstruction  of  the  bowel  or  ileus,  peritonitis,  and  diseases  of  the 
small  intestine. 

2.  Phenol,  CgHsO  (carbolic  acid,  §  252),  was  discovered  by  Stadeler  in  human 
urine  (more  abundant  in  horse's  urine).  It  does  not  occur  as  carbolic  acid,  but 
in  combination  with  a  substance  from  which  it  is  separated  by  distillation  with 
dilute  mineral  acids.  The  "phenol-forming  substance"  is,  according  to  Bau- 
mann,  "  phenolsulphonic  acid"  (C6H50,S03H),  which  in  urine  is  united  with 
potash. 

Phenol  is  derived  from  the  decomposition  of  proteids  by  pancreatic  digestion  (|  172,  II),  and  also 
from  putrefaciion  (|  184,  6),  the  mother  substance  being  tyrosin.  Hence  the  formation  of  phenol- 
sulphonic acid  is  analogous  to  the  formation  of  indican. 

If  in  the  employment  of  carbolic  acid  it  be  absorbed,  the  phenolsulphonic  acid  becomes  greatly 
increased  in  amount,  so  that  sulphm-ic  acid  must  be  united  with  it;  hence,  alkaline  sulphates  are 
decomposed  in  ihe  body,  so  that  the  latter  may  be  absent  from  the  urine  {Baumann).  Living  muscle 
or  liver,  when  digested  in  a  stream  of  air  for  several  hours  with  blood  to  which  phenol  and  sodic  sul- 
phate are  added,  yields  phenolsulphonic  acid  ;  while,  under  the  same  circumstances,  pyrokatechin  forms 
ethersulphonic  acid. 

Carboluria. — WTien  carbolic  acid  is  used  externally  or  internally,  and  it  is  absorbed,  it  causes 
a  deep,  dark  colored  urine,  due  to  the  oxidation  of  phenol  into  hydrochinon  (orthobioxybenzol 
=  CgHg02),  which  for  the  most  part  appears  in  the  urine  as  ethersulphonic  acid  [Batiniann  and 
others). 

3.  Parakresol  (hydroxyltoluol,  C^HgO),  with  its  isomers  ortho-  and  meta- 
kresol  (the  latter  in  traces),  is  more  abundant  in  urine  (^Bmimann,  Preusse).  It 
also  occurs  in  combination  with  sulphonic  acid. 

Test  for  phenol  (and  also  kresol) :  Distill  150  c.c.  urine  with  dilute  sulphuric  acid.  The  distil- 
late gives  a  brown  crystalline  deposit  of  tribromophenol  with  bromine  water,  as  well  as  a  red  color 
with  Millon's  reagent. 

Hydroxybenzol  (pyrokatechin,  hydrochinon)  is  obtained  from  lorine,  when  it  is  heated  for  a  long 
time  with  hydrochloric  acid. 

Resorcin,  which  is  an  isomer  of  hydrochinon,  when  administered  internally,  also  appeai-s  in 
the  lu-ine  as  ethersulphonic  acid.  Toluol  and  naphthalin  behave  similarly.  Benzol  is  oxidized  to 
phenol. 

4.  Pyrokatechin  =  CgHeOa  (metadihydroxylbenzol),    is  formed  along  with 


454  PYROKATECHIN  AND  SKATOL. 

hydrochinon  from  phenol,  and  is  an  isomer  of  the  former.  It  behaves  like  indol 
and  phenol,  for  when  united  with  sulphonic  acid,  it  yields  the  pyrokatechin-forming 
substance.  Small  quantities  sometimes  occur  in  human  urine ;  it  is  more  abun- 
dant in  the  urine  of  children  ;  it  becomes  darker  when  the  urine  putrefies. 

5.  Skatol,  which  is  crystalline,  and  is  formed  during  putrefaction  in  the  intes- 
tine, also  appears  in  the  urine  as  a  compound  of  sulphonic  acid  (§  252).  On 
feeding  a  dog  with  skatol,  Brieger  found  much  potassic  skatol-oxysulphate. 

Test. — Skatol  compounds  are  recognized  by  adding  dilute  nitric  acid,  which  causes  a  violet  color, 
or  fuming  nitric  acid,  which  precipitates  red  flakes  (.Vifncii).  Its  quantity  is  regulated  by  the  same 
conditions  as  indican. 

The  aromatic  oxyacids,  hydroparacumaric  acid,  and  paraoxyphenylacetic  acid  (the 
former  a  putrefactive  product  of  flesh,  the  latter  obtained  by  E.  and  H.  Salkowski  from  putrid  albu- 
min) occur  in  the  urine  [Baumann,  g  252).  Shake  the  urine  treated  with  a  mineral  acid  with  ether, 
evaporate  the  latter,  and  dissolve  the  residue  in  water.  If  aromatic  oxyacids  are  present,  they  give 
a  red  color  with  Millon's  reagent. 

Baumann  gives  the  following  series  of  bodies,  which  are  formed  from  tyrosin  by  decomposition 
and  oxidation ;  most  of  the  substances  are  formed  both  during  the  decomposition  of  albumin,  and 
also  in  the  intestine,  whence  they  pass  into  the  urine  :  Tyrosin,  C9HjjX03-f-  H.j^CjHjqOj  (hydro- 
paracumaric acid)  -^  NH,.  CgHjf,03t=  CgHj^O  (paraethylphenol,  not  yet  proved)  -4-  COj.  CgH,gO 
+  03=C5H-03  (paraoxyphenylacetic  acid)  —  H,0.  qHg03=C-Hj,0  (parakresol)  +  COj.  C^HgO 
-j-  03=  C.HgOj  (paraoxybenzoic  acid,  not  yet  proved)  —  H.^O.     C.H5O  =CgH50  phenol  +  COj. 

Potassium  sulphocyanide,  derived  from  the  saliva,  also  occurs  in  urine.  After  acidulation 
with  hydrochloric  acid,  its  presence  may  be  detected  by  the  ferric  chloride  test  (§  146 — Gscheidlen 
and  J.  Miink).     One  litre  of  human  urine  contains  0.02  to  0.08  gramme  combined  with  an  alkali. 

Succinic  Acid  (C^HgO^)  occurs  chiefly  after  a  diet  of  flesh  and  fat,  and  almost  disappears  after 
a  vegetable  diet.  It  is  a  decomposition  product  of  asparagin,  and  occurs  in  considerable  amount  in 
the  urine  after  eating  asparagus.  It  is  also  a  product  of  the  alcoholic  fermentation  (|  150),  and  as 
it  passes  out  of  the  body  unchanged,  it  occurs  in  the  urine  of  those  who  imbibe  spirituous  liquors. 
It  passes  unchanged  into  the  urine  (^Xetibauer). 

Lactic  acid  (C3H5O3)  is  a  constant  constituent  of  urine.  Other  observers  have  found  ferment- 
able lactic  acid  in  diabetic  urine  ;  sarcolactic  acid  after  poisoning  with  phosphorus  and  in  trichinosis. 
Occasionally  traces  of  volatile  fatty  acids  are  present.  Some  animal  gum  occurs  in  urine  (p. 
431),  and  Bechamp's  "  nephrozymose  "  consists  for  the  most  part  of  gum  {Landwehr).  This 
substance  is  precipitated  from  urine  by  adding  to  it  three  times  its  volume  of  90  per  cent,  alcohol. 
It  is  not  a  simple  body,  but  at  60'  to  70^  C.  it  transforms  starch  into  sugar  {v.  Vintschgau). 

Ferments. — Traces  of  diastatic,  peptic,  and  rennet  ferment  have  been  found,  especially  in 
urine  of  high  specific  gravity.     Tn.-psin  is  said  not  to  occur  normally  [Leo). 

Traces  of  sugar  (Brucke,  Bence  Jones),  to  the  amount  of  0.05  to  O.OI  per  cent.,  occur  in  normal 
urine.  After  the  ingestion  of  milk-,  cane-,  or  grape  sugar,  (50  grms.)  these  varieties  of  sugar  appear 
in  small  quantity  in  the  urine  {IVorm-Miiller — \  267,7). 

Kryptophanic  acid  (C3HJNO5),  according  to  Thudichum,  occurs  as  a  fi-ee  acid  in  urine,  but 
Landwehr  regards  it  as  an  animal  gum. 

Aceton  iCjHgO)  is  formed  when  normal  urine  is  oxidized  with  potassic  bichromate  and  sulphuric 
acid,  and  it  is  formed  from  a  reducing  substance  present  in  normal  urine  (apparently  derived  from 
the  graj)e  sugar  of  the  blood).  Aceton  occurs  in  traces  as  a  normal  urinary  constituent,  which  is 
increased  during  increased  decomposition  of  the  tissues,  e.g.,  carcinoma,  inanition.  It  has  also  been 
found  in  the  blood  in  fever  {v.  Jacksch).  Lieben's  Test. — Acidulate  half  a  litre  of  urine  with 
HQ  and  distill ;  when  treated  with  tincture  of  iodine  and  ammonia  there  is  a  turbidity  due  to 
iodoform. 

II.  THE  INORGANIC  CONSTITUENTS  OF  THE  URINE.— 

The  inorganic  constituents  are  either  taken  into  the  body  as  such  with  the  food 
and  pass  off  unchanged  in  the  urine,  or  they  are  formed  in  the  body,  owing  to  the 
sulphur  and  phosphorus  of  the  food  being  oxidized  and  the  products  uniting  with 
bases  to  form  salts.  The  quantity  of  salts  excreted  daily  in  the  urine  is  9  to  25 
grammes  [J^  to  3^  oz.]. 

I.  Sodic  chloride — to  the  amount  of  12  (10  to  13)  grammes  [180  grains] 
— is  excreted  daily.  It  is  increased,  after  a  meal,  by  muscular  exercise,  drinking 
of  water,  and  generally,  when  the  quantity  of  urine  is  increased,  by  the  free  use  of 
large  quantities  of  common  salt,  but  by  potash  salts  also ;  it  is  diminished  under 
the  opposite  conditions. 

In  disease  it  is  greatly  diminished ;  in  pneumonia  and  other  inflammations  accompanied  by 


PHOSPHORIC    AND    SULPHURIC    ACID.  455 

efhisions,  in  continued  diarrhoea  and  profuse  sweating,  constantly  in  albuminuria  and  in  dropsies.  [In 
cases  of  'pneumonia,  sodic  chloride  may  at  a  certain  stage  almost  disappear  from  the  urine,  and  it  is  a 
good  sign  when  the  chlorides  begin  to  reappear.]  In  other  chronic  diseases,  the  amount  of  NaCl 
excreted  runs  nearly  parallel  with  the  amount  of  urine  passed.  In  conditions  of  excitement  the 
amount  of  sodic  chloride  is  diminished,  and  potassic  chloride  increased ;  in  conditions  of  depression 
the  reverse  is  the  case  (Z£?;//3fr).  ,•  j 

Test. Add  to  the  urine  nitric  acid  and  then  nitrate  of  silver  solution,  which  gives  a  white  curdy 

precipitate  of  chloride  of  silver.  In  albuminous  urine  the  albumin  must  first  be  removed.  Micro- 
scopically look  for  the  step-like  forms  of  common  salt,  and  also  for  the  cr\-stals  of  sodic  chloride  and 
urea  (^  256,  4). 

2.  Phosphoric  acid  occurs  in  urine  as  acid  sodic  phosphate  and  acid 
calcic  and  magnesic  phosphates  to  the  amount  of  about  2  grammes  daily 
[30  grains]  ;  it  is  more  abundant  after  an  animal  than  after  a  vegetable  diet.  The 
amotmt  increases  after  a  midday  meal  until  evening,  and  falls  during  the  night 
until  next  day  at  noon.  It  is  partly  derived  from  the  alkaline  and  earthy  phos- 
phates of  the  food,  and  partly  as  a  decomposition  product  of  lecithin  and  nuclein. 
As  phosphorus  is  an  important  constituent  of  the  nervous  system,  the  relative 
increase  of  phosphoric  acid  is  due  to  increased  metabolism  of  the  nervous  sub- 
stance. 

Pathological.— In  fevers,  the  increased  excretion  of  potassic  phosphate  is  due  to  a  consumption  of 
blood  and  muscle  (?  220,  3.)     It  is  also  increased  in  inflammation  of  the  brain,  softening  of  the 
bones,  diabetes,  andoxaluria;  after  the  administration  of  lactic  acid,  morphia,  chloral,  or  chloroform 
It  is  diminished  during  pregnancy,  owing  to  the  formation  of  the  foetal  bones;   also  after  the  use  of 
ether  and  alcohol,  and  in  inflammation  of  the  kidney. 

[Tests.— To  urine  add  nitric  acid  and  solution  of  ammonium  molybdate  and  boil,  a  canaiy  yellow 
precipitate  of  ammonium  phosphomolybdate  indicates  the  presence  of  phosphoric  acid.  Or,  add  half 
Its  volume  of  caustic  potash  to  urine,  and  boil.  The  earthy  phosphates  are  precipitated,  but  not  the 
alkaline  phosphates.] 

Earthy  phosphates  are  precipitated  by  heat  in  some  pathological  urines. 
This  precipitate  is  distinguished  from  albumin,  which  is  also  precipitated  by  heat, 
by  being  soluble  in  nitric  acid,  which  precipitated  albumin  is  not.  [The  earthy 
phosphates  are  not  precipitated  until  near  the  boiling  point.] 

Quantitative.— The  amotint  of  phosphoric  acid  is  estimated  by  titration  with  a  standard  solution 
of  ttranium  acetate  ;  ferrocyanide  of  potassium  being  the  indicator.  The  indicator  gives  a  brownish 
red  color  when  there  is  an  excess  of  free  uranium  acetate.  _ 

In  addition  to  phosphoric  acid,  phosphorus  occurs  in  an  incompletely  oxidized  form  in  the  urine, 
e.g.,  glycerinphosphoric  acid  (>^  251,  2),  which  occurs  to  the  amount  of  15  milligrammes  m  a  litre 
of^urine;  it  is  increased  in  nervous  diseases  and  after  chlorotorm  narcosis. 

3.  Sulphuric  acid  occurs  in  the  urine,  the  greater  part  in  combination  with 
the  alkalies,  and  the  remainder  united  with  indol,  skatol,  and  pyrokatechm,  m  the 
form  of  aromatic  ethersulphonic  compounds,  the  ratio  being  i  :  0.1045.  All  condi- 
tions which  favor  the  formation  of  indol,  skatol,  or  pyrokatechm,  increase  the 
amount  of  combined  sulphuric  acid.  The  total  daily  amount  of  sulphuric  acid 
is  2.5  to  3.5  grammes  [37  to  52  grains].  It  is  increased  by  the  administration  of 
sulphur  i^Kraiisi).  The  sulphuric  acid  is  chiefly  derived  from  the  decomposition 
of  proteids,  and  hence  its  amount  runs  parallel  with  the  amount  of  urea  excreted. 
The  amount  of  alkaline  sulphates  in  the  food  is,  as  a  rule,  very  small. 

An  increased  excretion  of  sulphuric  acid  in  fevers  indicates  an  increased  metabolism  of  the  tissues 
of  the  body  In  renal  inflammation  it  has  been  observed  to  be  diminished,  and  in  eczema  it  is  greatly 
increased.  Feeding  with  taurin  (which  contains  sulphm-),  in  the  case  of  rabbits,  ( but  not  in  carnivora 
or  man),  increases  the  sulphuric  acid  in  the  urine  {^Salkowski).  According  to  Zulzer,  a  copious  secre- 
tion of  bile  lessens  the  relative  amount  of  sulphuric  acid  in  the  urine.  ,   ki     • 

Test.— Barium  chloride  gives  a  copious  white  heavy  precipitate  of  barium  sulphate,  insoluble  m 

°'ln  addition  to  sulphuric  acid,  sulphur  (i)  occurs  in  an  incompletely  oxidized  foi-m  in  the  urine 
(potassium  sulphocyanide,  cystin,  and  sulphur-bearing  compounds  derived  from  the  bile)  {Kiinkel,  v. 
Voit—l  177,  6).  Hvposulphnrous  acid,  as  an  alkaline  salt,  is  an  abnormal  constituent  in  typtius; 
and  so 'is  sulphuretted  hydrogen,  which  is  recognized  by  the  blackening  of  a  piece  of  paper  moist- 
ened with  lead  acetate  and  ammonia,  held  over  the  urine. 


456 


ACID    FERMENTATION    OF    URINE. 


4.  Excessively  minute  traces  of  silicic  acid  and  nitric  acid  derived  from  drink- 
ing water  have  been  found  in  urine.  Organic  acids,  e.g.,  citric  and  tartaric,  when 
taken  internallv,  increase  the  amount  of  carbonates  in  the  urine.  The  urine  may 
effervesce  on  the  addition  of  an  acid. 

The  sodium  in  the  urine  is  chiefly  combined  with  chlorine,  but  a  small  part  of 
it  is  united  with  phosi)horic  and  uric  acids;  potassium  (which  is  about  yi  of  the 
sodium)  is  chiefly  combined  with  chlorine.  In  fevers,  more  ])Otash  is  excreted  than 
soda,  and  during  convalescence,  the  reverse  is  the  case  ;  calcium  and  magnesium 
exist  in  normal  acid  urine  as  chlorides  or  acid  phosphates.  If  the  urine  is  neutral, 
neutral  calcium  phosphate  and  magnesium  phosphate  are  precipitated.  Kl)stein  found 
the  latter  in  alkaline  urine,  as  large,  clear,  four-sided  i)risms,  in  diseases  of  the  stomach. 
If  the  urine  is  alkaline,  calcium  carbonate  (Fig.  281)  and  tribasic  calcic  phosphate 
are  deposited  as  such,  while  the  magnesium  is  precipitated  in  the  form  of  ammonio- 
magnesium  phosphate,  or  triple  phosphate.  The  calcium  is  derived  from  the  food, 
and  depends  upon  the  amount  of  lime  salts  absorbed  from  the  intestine.  Free 
ammonia  is  said  to  occur  (0.72  gramme,  or  7  grains  daily)  in  perfectly  fresh  urine 
{Neuhauer,  Brilcke),  and  the  amount  is  greater  with  an  animal  than  with  a  vegetable 
diet  {Coranda).  The  amount  of  fixed  ammonia  is  increased  by  the  administration 
of  mineral  acids  (  ^^zZ/^r,  Schmiedeberg,  Gdthgens).  Iron  (i  to  1 1  milligrammes 
per  litre)  is  never  absent.  There  is  a  trace  of  hydric  peroxide  (Schonbein), 
which  is  detected  by  its  decolorizing  indigo  solution  on  the  addition  of  iron 
sulphate. 

Gases. — 24.4  c.c.  of  gas  was  obtained  from  one  litre  of  urine — 100  volumes  of  the  gases  pumped 
out  consisted  of  65.40  vol.  CO.,,  2.74  O,  13.86  N.  Afier  severe  muscular  action,  the  amount  of  COj 
may  be  doubled;  digestion  also  increases  it,  copious  dnnking  dimini.shes  it. 

263.  FERMENTATIONS    OF    URINE.  — Acid    Fermentation.— 

When  perfectly  fresh  urine  is  set  aside,  it  gradually  becomes  more  acid  from  day  to 
day.  This  is  called  the  "  acid  fermentation."  It  seems  to  be  due  to  the  devel- 
opment of  special  fungi  (Fig.    260,   a),  and  the  process  is  accompanied  by  the 

Fic.  260. 


^^^•i 


■4--  6 


Deposit  in  "acid  fermentation"  of  urine,  a,  fungus;  i, 
amorphous  sodium  urate ;  c,  uric  acid;  t/,  calcium  ox- 
alate. 


Deposit  in  ammoniacal  urine  (alkaline  fermentation). 
a,  acid  ammonium  urate  ;  d,  ammonio-magnesium 
phosphate;  (,  bacterium  ureae. 


deposition  of  uric  acid  (c),  acid  sodium  urate,  in  amorphous  grains  {b),  and  calcium 
oxalate  {d).  According  to  Scherer  the  fungus  and  the  mucus  from  the  bladder 
decompose  part  of  the  urinary  pigment  into  lactic  and  acetic  acids.  The  latter  sets 
free  uric  acid  from  neutral  sodium  urate,  so  that  free  uric  acid  and  sodium  urate 
must  be  formed.     Butyric  scad  formic  acids  have  been  found  as  abnormal  decompo- 


ALKALINE    FERMENTATION    OF    URINE.  457 

sition  products  of  other  urinary  constituents.  When  the  acid  fermentation  begins, 
the  urine  absorbs  oxygen  {Pasteur).  According  to  Briicke,  it  is  the  lactic  acid, 
formed  from  the  minute  traces  of  sugar  present  in  urine,  which  causes  the  acidity. 
According  to  Rohmann,  who  recognizes  the  acid  fermentation  as  an  exceptional 
phenomenon,  the  acids  are  formed  from  the  decomposition  of  sugar,  and  from 
alcohol  which  may  be  present  accidentally.  While  the  urine  is  still  acid,  it  becomes 
turbid  and  contains  nitrous  acid,  whose  source  is  entirely  unknown.  According  to 
V.  Voit  and  Hofmann,  phosphoric  acid  and  a  basic  salt  are  formed  from  acid  sodium 
phosphate,  whereby  part  of  the  uric  acid  is  displaced  from  sodium  urate,  thus  causing 
the  formation  of  an  acid  urate. 

Alkaline  Fermentation. — When  urine  is  exposed  for  a  still  longer  time,  more 
especially  in  a  warm  place,  it  becomes  neutral  and  ultimately  ammoniacal,  i.e., 
it  undergoes  the  alkaline  fermentation  (Fig.  261). 

This  condition  is  accompanied  by  the  formation  of  the  micrococcus  ureae 
(Fig.  262)  {Pasteur,  Cohn)  and  Bacterium  ureae  (Fig.  261),  which  causes  the  urea 
to  take  up  water  and  decompose  into  CO.^  and  ammonia. 

Urea  [C0(HN2).,  +  2(H20)  =  ammonium  carbonate  [(NHJ^COj]. 

The  property  of  decomposing  urea  belongs  to  many  different  kinds  of  bacteria,  including  even  the 
sarcina  of  the  lungs — whose  germs  seem  to  be  universally  diffused  in  the  air.  These  organisms  pro- 
duce a  soluble  ferment  {Musctilus),  which,  however,  only  passes  from  the  body  of  the  cells  into 
the  fluid  after  the  cell  or  organism  has  been  killed  by  alcohol  {Lea). 

The  presence  of  ammonia  causes  the  urine  to  become  turbid,  and  those  substances 
which  are  insoluble  in  an  alkaline  urine  are  precipitated — earthy  phosphates, 
consisting  of  the  amorphous  calcic  phosphate,  acid  ammonium  urate  (Fig. 
261,  a),  in  the  form  of  small,  dark  granules  covered  with  spines;  and,  lastly,  the 
large,  clear,  knife-rest  or  "  coffin  lid  "  form  of  ammonio-magnesic  phosphate, 
or  triple  phosphate  (Fig.  282).  [The  last  substance  does  not  exist  as  such  in 
normal  urine,  but  it  is  formed  when  ammonia  is  set  free  by  the  decomposition  of 
urea,  the  ammonia  uniting  with  the  magnesium  phosphate.  y\g   262 

Its  presence,  therefore,  always  indicates  ammoniacal  fer- 
mentation of  the  urine.]    In  cases  of  catarrh  or  inflam- 
mation of  the  bladder,  this  decomposition  may  take  1  ^""^ 
place  within  the  bladder,  when  the  urine  always  contains  \,^:P\^ 
pus  cells  (Fig.    267)  and    detached    epithelium.     When    j^^oG 
much  pus  is  present,  the  urine  contains  albumin.     Am- 
moniacal urine  forms  white  fumes  of  ammonium  chloride.  Micrococcus  urese. 
when  a  glass  rod  dipped  in  hydrochloric  acid  is  brought  near  it.      [When  ammonia 
is   added  to  normal  urine,    triple  phosphate  is   precipitated   in  a  feathery  form 
(Fig-  283).] 

[Significance  of  Triple  Phosphate. — If  urine  be  alkaline  when  it  is  passed,  and  the  alkalinity 
be  due  to  a  volatile  alkali,  i.e.,  to  NH.^,  then  decomposition  of  the  urine  has  taken  place,  and  this 
kind  of  urine  is  a  sure  sign  that  there  is  disease  of  the  genito-urinary  mucous  membrane.] 

264.  ALBUMIN  IN  URINE  OR  ALBUMINURIA.— Serum  albu- 
min is  the  most  important  abnormal  constituent  in  urine  which  engages  the 
attention  of  the  physician.  It  occurs  in  blood  (§  32),  and  its  characters  are 
described  in  §  249. 

Causes  of  Albuminuria. — i.  Serum  albumin  may  appear  in  urine  without  any  apparent  ana- 
tomical or  structural  change  of  the  renal  tissues.  This  condition  has  been  called  by  v.  Bamberger 
"  Hcematogenous  albutninuria.'''  It  occurs  but  rarely,  however,  and  sometimes  in  healthy  individ- 
uals when  there  is  an  excess  of  albumin  in  the  blood  plasma  {e.g.,  after  suppression  of  the  secretion 
of  milk),  and  after  too  free  Use  of  albuminous  food.  2.  As  a  result  of  increased  blood  pressure  in 
the  renal  vessels,  e.g.,  after  copious  drinking.  It  may  be  temporary,  or  it  may  be  persistent,  as  in 
cases  of  congestion  following  heart  disease,  emphysema,  chronic  pleuritic  effusions,  infiltrations  of  the 
lungs,  and  after  compression  of  the  chest,  causing  congestion  in  the  pulmonary  circuit,  which  extends 
even  into  the  renal  veins,  etc.  3.  After  section  or  paralysis  of  the  vasomotor  nerves  of  the  kidneys, 
which  causes  great  congestion  of  these  organs.  The  albuminuria,  which  accompanies  intense  and 
long-continued  abdominal  pain,  is  brought  about  owing  to  a  reflex  paralysis  of  the  renal  vessels. 


458  TESTS    FOR    ALBUMIN    IN    URINE. 

4.  After  violent  muscular  exercise.  [Senator  found  that  forced  marches  in  young  recruits  were  very 
frequently  followed  by  the  appearance  of  albumin  in  the  urine,  which  persisted  for  several  days.]  Con- 
vulsh'e  disorders,  e.^.,  epilepsy,  the  spasms  of  dyspnrea  after  strychnin  poisoninp;,  in  shock  of  the 
brain,  apojilexy,  spinal  paralysis,  and  violent  emotions ;  the  excessive  use  of  moqihia,  which,  perhaps, 
acts  on  the  vasomotor  centres.  5.  It  may  accompany  many  acute  febrile  diseases,  e.i^.,  the  exanthe- 
mata (scarlet  fever),  typhus,  pneumonia,  and  pyxmia.  In  these  cases,  it  may  l)e  due  to  the  increase 
of  temperature  paralyzing  the  vessels,  but  more  probably  the  secretory  apparatus  of  the  kidney  is  .so 
changed  (f^-,  cloudy  swelling  of  the  renal  epithelium)  that  the  albumin  can  pass  through  the  renal 
membrane.  6.  Certain  degenerations  and  inflammations  of  the  kidneys  at  several  of  their  stages. 
7.  Inflammation  or  suppuration  in  the  ureter  or  urinary  pa.ssages.  8.  Certain  chemical  substances 
which  irritate  the  renal  parenchyma,  e.(;.,  cantharides,  carbolic  acid.  9.  The  complete  withdrawal  of 
common  salt  from  the  food.  The  albumin  disappears  when  the  common  salt  is  given  again.  lO.  The 
epitheliuiit  may  be  in  such  a  condition  that  it  cannot  retain  the  alhttniin  within  the  vessels,  due  to 
imperfect  nourishment  and  functional  weakness  of  the  excretory  elements.  This  includes  the  albu- 
minuria of  ischi^mia,  and  that  after  hemorrhage,  in  anaemia,  scorbutus,  icterus,  diabetes.  [Grainger 
Stewart  finds  that  albuminuria  is  more  common  among  presumably  healthy  people  than  was  formerly 
supposed.] 

[Besides  being  derived  from  the  secreting  parenchyma  of  the  kidney,  albumin  may  be  present 
owing  to  admixture  with  the  secretions  from  any  part  of  the  urinary  tract,  including  the  vagina  and 
uterus  in  the  female.  In  some  cases  the  transudation  of  albumin  is  favored  by  changes  in  the 
capillary  walls,  the  albumin  being  forced  through  by  the  intravascular  pressure.  Sometimes  all)U- 
minuria  occurs  during  the  course  of  severe  typhoid  fever,  and  in  acute  fevers  generally,  where  the 
temperature  is  persistently  above  40°  C.  (104°  F.).  The  high  temperature  alters  the  filtering 
membrane  and  permits  the  filtration  of  albumin.] 

[Physiological  Albuminuria. — This  term  has  been  applied  to  that  condition  of  the  urine,  where 
traces  of  albumin  are  found  in  individuals  apparently  in  perfect  health.  Johnson  and  Pavy  cite 
such  cases,  while  Posner  asserts  that  all  urine — even  healthy  urine — contains  traces  of  proteids,  whose 
presence  is  ascertained  after  concentrating  the  urine.  It  is  safe  to  assume  that  normal  urine  should 
give  no  reaction  with  the  usual  tests  for  albumin.  Posner  precipitated  the  urine  with  alcohol,  washed 
the  precipitate,  dissolved  it  in  acetic  acid,  and  tested  it  with  the  ferrocyanide  test  for  albumin.  He 
finds  that  minute  traces  of  proteid  are  detected  by  the  following  modification  of  the  biuret  test : 
Make  the  urine  alkaline,  and  by  the  "  contact  method  "  bring  a  layer  of  very  dilute  cupric  sulphate 
over  it ;  when  the  two  fluids  touch,  a  reddish-violet  ring  is  obtained.] 

The  tests  for  albumin  in  urine  depend  upon  the  facts  that  it  is  coagulated 
by  heat  in  neutral  or  acid  sohitions,  and  it  is  precipitated  by  various  reagents. 

[(i)  Heller's  Test. — Place  10  c.c.  of  the  urine  in  a  test-glass,  and  pour  in  pure  colorless  HNO3 
so  as  to  run  down  the  side  of  the  glass,  forming  a  layer  beneath  the  urine.  A  white  zone  of  coagu- 
lated albumin  indicates  the  presence  of  albumin.  In  this  test  it  is  important  to  wait  a  certain  time 
for  the  development  of  the  reaction.  In  urines  of  high  specific  gravity,  a  haziness  due  to  acid  urates 
may  be  formed  above  where  the  two  fluids  meet,  but  its  upper  edge  is  not  circumscribed.  The  acid 
decomposes  the  neutral  urates  and  forms  a  more  insoluble  acid  salt.  This  cloud  of  acid  urates  is 
readily  dissolved  by  heat,  while  the  albumin  is  not;  the  latter  is  always  a  sharply-defined  zone 
between  the  two  fluids.  In  very  concentrated  urine  (rare),  nitric  acid  may  gradually  precipitate 
crystalline  urea  nitrate.  In  patients  taking  copaiba,  nitric  acid,  by  acting  on  the  resin,  causes  a 
slight  milkiness.] 

[(2)  Boiling  and  Nitric  Acid. — Place  10  c.c.  of  urine  in  a  test-tube  and  boil.  If  albumin  be 
present  in  small  quantity,  a  faint  haziness,  which  may  be  detected  in  a  proper  light,  will  be  produced. 
Add  10  to  12  drops  of  HNO,.  If  the  turbidity  disappears  it  is  due  to  phosphates,  while  if  any 
remain  it  is  due  to  albumin.  If  albumin  be  present  in  large  quantity,  a  copious  whitish  coagulum  is 
obtained.  Precautions. — (a)  In  all  cases,  if  the  urine  be  turbid,  filter  it  before  applying  any  test. 
{b)  How  to  boil. — Boil  the  upper  strata  of  the  liquid,  and  take  care,  if  any  coagulum  be  formed, 
that  it  does  not  adhere  to  the  side  of  the  lube,  else  the  tube  is  liable  to  break,  {c)  In  performing 
this  test  with  a  «^w/r<7/ solution,  note  when  the  precipitate  falls,  for  albumin  is  precipitated  about  70° 
C,  phosphates  not  till  about  the  boiling  point.  (</)  Amount  of  Acid — If  too  little  (2  or  3  drops) 
HNO3  be  added,  or  too  much  (30  or  40  drops),  we  may  fail  to  detect  albumin,  although  it  is  present.] 

(3)  Ferrocyanide  Test. — By  the  addition  of  acetic  acid  and  potassium  ferrocyanide.  [If  albu- 
min be  present,  a  white  flocculent  precipitate  separates  in  the  cold.  Dr.  Pavy  has  introduced 
pellets,  consisting  of  a  mixture  of  citric  acid  and  sodic  ferrocyanide.  All  that  is  required  is  to  add 
a  pellet  to  the  suspected  urine.  Oliver's  papers. — Dr.  Oliver  uses  papers,  one  saturated  with  citric 
acid  and  another  with  ferrocyanide  of  potassium.  The  two  papers  are  added  to  the  clear  filtered 
urine.  Other  precipitants  of  albumin,  such  as  small  pieces  of  paper  impregnated  with  potassio- 
mercuric  iodide,  are  used  by  Oliver.] 

(4)  Boiling  Acid  Urine. — If  the  urine  be  alkaline,  although  albumin  may  be  present,  it  is  not 
precipitated  by  heat  alone.  We  require  to  add  acetic  acid  until  a  slightly  acid  reaction  is  obtained. 
Boiling  may  give  a  precipitate  of  earthy  phosphates  in  an  alkaline  urine,  owing  perhaps  to  the  CO.^ 


TESTS    FOR   ALBUMIN    IN    URINE. 


459 


being  driven  off.  This  precipitate  might  be  mistaken  for  albumin,  but  on  adding  acetic  or  nitric 
acid,  the  earthy  precipitate  is  dissolved,  while  the  precipitate  of  albumin  is  not  dissolved.  In  testing 
for  albumin,  always  use  clear  urine.     If  it  is  turbid,  filter  it. 

[(5)  Metaphosphoric  acid  is  dissolved  in  water  just  before  it  is  to  be  used  and  added  to  clear 
urine  [Hindenlang).  Graham  pointed  out  that  metaphosphoric  acid  precipitated  albumin.  A  20  per 
cent,  solution  of  the  ordinary  glacial  phosphoric  acid  is  a  good  test  for  albumin,  but  it  also  precipi- 
tates peptones.  It,  however,  changes  into  ordinary  phosphoric  acid  by  keeping,  and  then  it  no 
longer  precipitates  albumin.] 

[(6)  Sodic  Sulphate  and  Acetic  Acid. — Acidulate  10  c.c.  of  urine  with  acetic  acid,  and  add 
Y(,  of  its  volume  of  a  concentrated  solution  of  sulphate  of  soda  or  magnesia.  On  heating,  if  albumin 
be  present,  a  distinct  cloudiness  is  obtained.] 

[(7)  In  picric  acid,  according  to  Dr.  Johnson,  we  have  a  more  delicate  test  for  minute  traces  of 
albumin  than  either  heat  or  nitric  acid,  or  than  both  these  tests  combined.  It  is  used  either  in  the 
form  of  crystals  or  powder,  or  as  a  satvuated  aqueous  solution.  Take  a  four-inch  column  of  urine  in 
a  test-tube,  hold  the  tube  in  a  slanting  direction,  and  pour  an  inch  of  the  picric  acid  solution  on  the 
surface  of  the  urine,  where  in  consequence  of  its  low  specific  gravity  (1005)  it  mixes  only  with  the 
upper  layer  of  the  urine.  It  coagulates  any  albumin  present.  The  precipitate  occurs  at  once,  and  is 
increased  by  heat,  while  the  urate  of  soda,  which  is  sometimes  precipitated,  is  soluble  on  heating.] 

[Dr.  Roberts  regards  any  test  for  albumin  which  requires  strong  acidulation  with  an  organic  acid, 
citric,  acetic,  or  lactic,  as  unsatisfactory,  since  it  precipitates  mucin.  For  this  reason  he  rejects  the 
tungstate,  mercuric  iodide,  and  potassic  ferrocyanide  tests.  Dr.  Roberts  regards  the  heat  test,  with 
the  addition  of  a  small  definite  quantity  of  acetic  acid,  as  the  best  test  for  the  detection  of  small 
quantities  of  albumin.] 

1.  Quantitative  Estimation  of  Albumin. — 100  c.c.  of  urine  are  boiled  in  a  capsule,  some  acetic 
acid  being  ultimately  added,  whereby  the  albumin  is  precipitated  in  flakes.  The  precipitate  is  collected 
on  a  weighed,  dried  ( 1 10°),  ash-free  filter,  and  repeatedly  washed  with  hot  water,  then 

with  alcohol,  and  dried  in  an  air  bath  at  1 10°.     The  weight  of  the  filter  is  deducted,       FiG.  263. 

and  finally  the  dried  filter  with  the  albumin  is  burned  in  a  weighed  platinum  capsule, 

and  the  weight  of  the  ash  also  deducted.      [This  method  is  not  available  for  the  busy 

practitioner  on  account  of  the  time  it  takes.    Practically,  it  is  sufficient  to  compare  firom 

day  to  day  the  proportion  that  the  precipitated  albumin  bears  to  the  bulk  of  the  urine 

tested.     A  graduated  tube  may  be  used,  so  that   after  the  prepipitate  has   subsided, 

the  physician  may  see  what  proportion  of  the  whole  the  precipitate  occupies.] 

Esbach's  Albumimeter  fFig.  263). — A  glass  cylinder  is  filled  witli  the  urine  up 
to  the  mark  U,  and  to  R  with  the  precipitant  (20  citric  acid,  10  picric  acid,  970  water). 
The  vessel  is  corked  and  then  shaken.  After  twenty- four  hours  the '  coagulated  albu- 
min subsides,  when  the  graduation  on  the  tube  indicates  the  number  of  grms.  of 
albumin  per  1000  c.c.  of  urine.     Very  albuminous  urine  must  be  previously  diluted. 

2.  Globulin  occurs  only  in  albuminous  urine,  and  is  frequently  present.  Its 
presence  is  ascertained  by  adding  powdered  magnesium  sulphate  in  excess  to  the 
urine;  when  it  is  present  it  is  precipitated  (^  32).  The  more  globulin  there  is  in  the 
presence  of  albumin,  the  more  difficult  it  is  to  precipitate  it.  [Sometimes,  when  an 
albuminous  urine  is  dropped  into  a  large  cylinder  of  water,  each  drop  as  it  sinks  is 
followed  by  a  milky  train,  and  when  a  sufficient  number  of  drops  has  been  added,  the 
water  becomes  opalescent,  the  opalescence  disappearing  on  adding  an  acid.  The 
globulin  is  kept  in  solution  by  common  salt  and  other  neutral  salts,  but  when  these  are 
largely  diluted,  the  globulin  is  precipitated  (^Iiohe7-ts).'\ 

3.  Peptone  occurs  in  some  specimens  of  albuminous  urine,  but  also  in  non- 
albuminous  urine.  Maixner  found  it  constantly  in  the  urine  in  all  cases  where  suppu- 
ration is  present,  and  even  in  phthisis,  constituting  pyogenic  peptonuria.  Peptone 
occurs  in  pus,  and  the  peptonuria  in  these  cases  is  a  sign  of  the  breaking  up  of  the 
pus  cells  (Hoftneister).  Also  when  many  leucocytes  are  broken  up  in  the  blood 
(haematogenic).  It  occurs  in  cases  where  there  is  great  disintegration  of  albuminous 
tissues,  e.g.,  in  cancer.  It  is  frequently  found  after  childbirth.  Ammonium  sulphate 
precipitates  all  proteids  except  peptones  (p.  294). 

Test. — Separate  the  albumin  byboiUng  and  the  addition  of  acetic  acid.  Treat  the 
filtrate  with  three  volumes  of  alcohol ;  this  precipitates  the  peptone,  which,  when 
dissolved  in  water,  gives  the  characteristic  reactions  for  peptone  (|  166,  I).  Esbach's  Albu- 

4.  Propeptone,  or  Hemialbumose,  occurs  very  rarely  e.g.,  in  osteomalacia  and         mimeter. 
intestinal  tuberculosis  [Bence  Jones).     The  urine  is  treated  to  saturation  with  NaCl 

and  a  large  quantity  of  acetic  acid  added,  and  filtered  while  hot,  to  separate  the  albumin  and 
globulin.  In  the  cold  filtrate  propeptone  forms  a  turbidity,  which  is  redissolved  by  heat.  The 
precipitate  thrown  down  by  HCl  and  HNO3  ^^  soluble  by  heat  i^Kuhne).  The  precipitate  is 
isolated  by  filtration,  and  dissolved  in  a  little  warm  water,  when  it  gives  with  HNO3  a  yellow  re- 
action; like  peptone  the  solution  gives  the  biuret  reaction  (p.  293). 

5.  Egg  albumin  appears  in  the  urine  when  much  egg  albumin  is  taken  in  the  food,  and  also 


460 


HEMATURIA    AND    H/EMOGLOBINURIA. 


when  it  is  injected  into  the  blood  vessels  (§  192,  4).  According  to  Semmola,  the  albumin  present 
in  the  urine  in  Bright's  disease  has  undergone  a  molecular  change  (similar  to  egg  albumin),  and 
hence  it  is  excreted. 

6.  Mucus  is  present  in  large  amount,  especially  in  catarrh  of  the  bladder.  It  contains  numerous 
mucus  corj^)uscles,  which  are  scarcely  distinguishable  from  pus  corpuscles.  They  contain  allmmin,  so 
that  urine  containing  much  mucus  is  albuminous  ;  mucin  is  not  precipitated  by  heat,  but  acetic  acid 
gives  a  flocculent  precipitate  in  clear  urine.  [.\Iinute  traces  of  mucin  occur  normally  in  urine.  If 
clear,  nomial  urine  be  set  aside  for  a  short  time,  a  flocculent  haziness,  like  a  cloud  of  cotton  wool,  is 
seen  floating  in  the  urine.  This  is  mucus  entangling  a  few  ejjithelial  cells  from  the  genito-urinary 
tract.  Mucin  Reaction. — .Vccording  to  W.  Roljcrts,  the  addition  of  a  concentrated  solution  of 
citric  acid  to  urine,  as  in  Heller's  test  (j;  264,  a),  where  the  two  fluids  meet,  causes  an  opalescent  zone 
gradually  to  be  formed  above  the  layer  of  acid.] 

265.  BLOOD  IN  URINE(HiEMATURIA)— HiEMOGLOBINURIA.— I.  Source  of 
the  Blood. — (l )  In  haematuria.  the  blood  may  come  from  any  part  of  the  urinary  apparatus,  I. 
In  hemorrhage  from  the  kidney,  the  amount  of  blood  is  usually  small  and  well  mi.\ed  with  the  urine. 
The  presence  of  "blood  cylinders,"  long  microscopic  blood  coagula,  casts  of  the  uriniferous  tubules, 
washed  out  of  them  by  the  urine,  is  characteristic  when  they  are  found  in  the  urine  ( Fig.  275).  The 
urine  usually  has  a  smoky  appearance.  [The  urine  slowly  dissolves  out  the  coloring  matter,  the 
stroma  of  the  corj3U.scles  after  a  time  being  deposited  as  a  brownish  sediment.     The  smoky  hue  occurs 


Fig.  264. 


Fig.  265. 


Fig.  266. 


Crenated  red  blood  corpuscles  in 
urine,  X  350. 


0  ^ 


Peculiar  changes  of 
the  red  blood  cor- 
puscles in  renal  hae- 
maturia. 


1^   @® 


»® 


®  m 


..*. 


Colored  and  {a)  colorless  blood 
corpuscles  of  various  forms. 


only  in  acid  urine  ;  if  the  urine  becomes  alkaline,  the  hue  becomes  brighter  red.]  The  blood  corpuscles 
show  pecuhar  changes  of  form  [they  become  crenated]  (Fig.  264),  and  exhibit  evidence  of  divi- 
sion,  due  to  the  action  of  urea  on  them  (?.  5).  Large  coagula  are  never  found  in  urine  mixed  with 
blood  derived  from  the  kidney.     2.   In  hemorrhage  from  the  ureter,  we  occasionally  find  worm-like 

masses  of  clotted  blood,  casts  of  the  canal  of  the  ureter.  3.  The 
relatively  largest  coagula  occur  in  hemorrhage  from  the  bladder. 
In  all  cases  where  blood  is  present,  we  must  examine  microscopically 
for  the  blood  corpuscles,  and  it  may  be  for  coagula  of  fibrin.  In 
acid  urine,  l)lood  corjjuscles,  but  never  arranged  in  rouleaux,  may  be 
found  after  two  to  three  days.  The  blood  coqDuscles  settle  as  a  red 
.sediment  at  the  bottom.  If  the  hemorrhage  is  copious  many  retain 
their  original  shape,  but  if  the  urine  is  very  concentrated,  they  may 
liecome  crenated. 

When  there  is  a  small  and  slow  hemorrhage  from  ruptured  small 
capillaries,  the  red  blood  corj^uscles  are  of  unequal  size,  many  %,  to 
^3  the  size  of  noiTnal,  while  the  pigment  has  become  brownish-yellow 
fFig.  265). 

If  a  hemoirhage  of  this  kind  be  accompanied  by  catarrhal  in- 
flammation  of  the  bladder,  there  is    found   between  the   red, 
numerous  shriveled  leucocytes  (Fig.  265),  which  in  freshly  passed 
urine   often  exhibit   lively  amoeboid  movements.     If  the   urine  be 
merous    lymph   corpuscles,  and    alkaline,  as  it  usually  IS,  crystals  of  triple  phosphate  also  occur, 
crystalsoftriplephosphate,  X350.        If  the  remains  of  the  red  blood  corpuscles  become  very  pale, 
their  presence  may  be   frequently  ascertained  by  adding  iodine  in  a 
solution  of  KI  (Fig.  265).     Blood  is  constantly  present  in  the  urine  during  menstruation. 

II.  Haemoglobinuria  is  quite  distinct   from   haematuria.     It  depends   upon   the    excretion   of 
haemoglobin  as  such    through  the  kidneys,  and  it  is  produced  when  haemoglobin  occurs  free 


Shriveled  blood  corpuscles  in  urine 
(catarrh  of  the  bladder),  with  nu 


TESTS    FOR    BLOOD    IN    URINE. 


461 


■within  the  blood  vessels,  as  in  cases  where  the  colored  blood  corpuscles  have  been  dissolved  inside 
the  bloodvessels  (hsemocytolysis).  It  occurs  when  foreign  blood  is  transfused,  ,?.^.,  when  lamb's 
blood  is  transfused  into  man.  The  foreign  blood  corpuscles  are  dissolved  in  the  blood  of  the  recipi- 
•ent,  and  the  haemoglobin  appears  in  the  urine  (|  102).  In  addition,  microscopic  "  cylinders,"  or 
"  casts,"  consisting  of  a  globulin-like  body  tinged  yellow  with  hsemoglobin,  may  likewise  be  found 
in  the  urine.  It  also  occurs  in  cases  of  severe  burns  (^  10,  3) ;  after  decomposition  of  the  blood  in 
pyaemia,  scorbutus,  purpura,  severe  typhus,  after  respiring  arseniuretted  hydrogen,  and  after  the 
passage  of  azobenzol,  naphthol,  pyrogallic  acid,  potassic  chlorate,  chloral,  phosphorus,  or  carbolic 
acid  into  the  circulation.  [The  injection  of  laky  blood,  water,  ether,  glycerin  [Adams),  or  toluy- 
lendiamin  [Afanassie^v),  also  causes  it,  and  in  such  cases  Afanassiew  asserts  that  the  Hb  passes  out 
through  the  glomeruli,  while  brown  degeneration  products  of  the  red  blood  corpuscles,  which  are 
dissolved  by  these  agents,  were  found  in  the  convoluted  tubules.]  These  substances  dissolve  the  red 
blood  corpuscles.  Sometimes  it  occurs  periodically  from  causes  and  conditions  as  yet  but  little 
xmderstood,  e.  ^.,  the  application  of  cold  to  the  skin. 

Tests  for  Blood  in  Urine. — i.  The  color  of  bloody  urine  shows  every  tint,  from  a  faint  red 
to  a  dark  blackish-brown,  according  to  the  amount  of  blood  present.     The  urine  is  often  turbid. 

2.  Urine  containing  blood  or  blood  pigment  contains  albumin. 

Fig.  268. 


Spectroscope  for  investigating  the  presence  of  haemoglobin  in  urine. 


3.  Heller's  Blood  Test. — Add  to  urine  half  its  volume  of  solution  of  caustic  potash,  and  heat 
gently.  The  earthy  phosphates  are  precipitated,  and  they  carry  the  haematin  with  them,  falling  as 
garnet-red  flocculi.     [This  is  not  a  reliable  test.] 

4  Haemin  Test. — The  colored  earthy  phosphates  may  be  collected  on  a  filter,  and  from  them 
liaemin  may  be  prepared  as  directed  in  ^  19. 

5.  Almen's  Test. — Add  to  urine,  freshly  prepared  tincture  of  guaiacum  and  ozonized  ether ;  a 
blue  color  indicates  the  presence  of  blood  (§  37). 

6.  Spectroscope  (see  ^  14).  Fig.  268  shows  the  arrangement  of  the  apparatus.  The  urine  is 
placed  in  a  glass  vessel,  D,  with  parallel  sides,  i  centimetre  apart  (haematinometer).  Light 
from  a  lamp,  E,  passes  through  the  fluid.  The  lamp,  F,  illuminates  the  scale  which  is  seen  by  the 
observer  through  the  telescope,  A.  [a)  Fresh  urine  containing  blood  gives  the  spectrum  of 
oxyhaemoglobin  (Fig.  17).  [b)  When  bloody  urine  is  expo-ed  for  some  time,  especially  in  a  warm 
place,  it  becomes  more  acid,  and  assumes  a  dark,  brownish  black  color.  The  haemoglobin  becomes 
changed  into  methaemoglobin  (|  15).  It  is  precipitated  by  lead  acetate,  which  does  not  precipi- 
tate oxyhsemoglobin  ;  the  spectrum  of  methaemoglobin  resembles  that  of  haematin  in  an  acid  solution 
(§  15,  Fig.  17).  The  spectra  may  be  combined,  (c)  The  microscopic  investigation  must  never 
be  omitted.     The  shape  of  the  corpuscles  may  vary  considerably  (Figs.  264  to  266). 


462  BILE    IN    URINE. 

266.  BILE  IN  URINE  (CHOLURIA).— The  physiological  conditions  which  cause  the  bile 
constituents  to  appear  in  the  mine  are  mentioned  in  part  at  ^  180. 

Haematogenic,  or  Anhepatogenic  Icterus  [Quincl-e),  occurs  when  bilirubin  (g  20)  is  formed  from 
extravasated  blood  by  the  action  of  the  connective-tissue  corpuscles,  so  that  bile  pigments,  in  addition 
to  coloring  the  tissues,  pass  into  the  urine. 

I.  Bile  Pigments. — Their  presence  is  ascertained  by  Gmelin-Heintz's  test.  C;rt'«  ( Biliver- 
din  I  is  the  characteristic  hue  in  the  play  of  colors  obtained  with  this  test,  which  is  fully  described  in 

'<i.  J77- 

Modifications  of  the  Test. — i.  If  icteric  urine  be  filtered  through  filtering  or  blotting  paper,  a 
drop  of  nitric  acid  containing  nitrous  acid,  when  applied  to  the  inner  surface  of  tlie  spread-out  filter, 
gives  a  yellowish-colored  ring  [Kosenlnich).  2.  In  order  that  the  reaction  may  not  take  place  too 
rapidly,  add  a  concentrated  solution  of  sodic  nitrate,  and  then  slowly  pour  in  sulphuric  acid  [Fieischl). 
3.  On  shaking  50  c.c.  of  icteric  urine  with  ID  c.c.  of  chloroform,  the  bilirubin  is  dissolved  by  the 
latter.  On  adding  bromide  water,  a  beautiful  ring  of  colors  is  obtained  {Alaly').  If  the  chloroform 
extract  be  treated  with  ozonized  turpentine  and  dilute  caustic  potash,  a  green  color,  due  to  biliverdin, 
occurs  in  the  watery  fluid  (  Geihardt). 

In  slight  degrees  of  jaundice,  urobilin  alone  may  be  found  (?  261,  i)  {Quincke). 

In  persistent  high  fever,  the  urine  contains  especially  biliprasin  (^HufperC).  If  it  contains  chole- 
telin  alone,  add  to  the  urine  some  hydrochloric  acid,  and  examine  it  with  the  spectroscope,  which 
gives  a  pale  absorption  band  between  b  and  F  (^  177,  '^^f^- 

Hsematoidin. — Sometimes  crystals  of  havialoiiiin  (^  20,  Fig.  14)  appear  in  the  urine,  es[3ecially 
when  blood  coqouscles  are  dissolved  within  the  blood  stream  ;  occasionally  in  scarlet  fever  and 
typhus,  and  sometimes  in  cases  of  periodic  hemoglobinuria.  The  breaking  up  of  old  blood  clots  in 
the  urinary  passages,  as  in  pyonephrosis  [Ebstein],  or  the  dissolution  of  necrotic  areas  {Hofmann 
and  Ullzmann)  produces  them,  and  similar  crystals  occur  in  analogous  cases  in  the  sputum  (^  138). 
In  jaundice  due  to  congestion  (^  180),  the  identical  crystalline  substance,  bilirubin,  is  found. 

II.  Bile  acids  occur  in  largest  amount  in  absorption  jaundice,  but  they  are  never  present  to  any 
extent.  The  test  is  described  at  \  177,  2,  the  cane-sugar  solution  consisting  of  c;  grm.  to  i  litre  of 
water.  If  the  urine  be  dilute,  it  is  advisable  to  concentrate  it  on  a  water  bath.  [It  is  rare  to  get  a 
satisfactory  result  with  Pettenkofer's  test  in  ordinary  icteric  urine.]  v.  Pettenkofer's  test  may  be 
used  with  the  alcoholic  extract  of  the  nearly  dry  residue,  but  no  albumin  must  be  present.  Dragen- 
dorff  found  0.8  gnn.  in  loo  litres  of  normal  urine. 

Strassburg's  Modification. — Dip  filter  paper  into  the  urine,  to  which  a  little  cane  sugar  has 
been  added  ;  dry  the  paper  and  apply  to  it  a  drop  of  sulphuric  acid.  A  violet-red  color  is  obtained 
after  a  short  time.     [Hay's  Reaction  (ij  177).] 

267.  SUGAR  IN  URINE  (GLYCOSURIAV— Diabetes  Mellitus.— The  excessively 
minute  trace  of  grape  sugar  or  dextrose,  which  is  constantly  [^resent  in  normal  urine,  sometimes 
becomes  greatly  increased  and  constitutes  the  conditions  of  diabetes  mellitus  and  glycosuria. 
The  physiological  conditions  which  determine  this  result  are  given  at  \  175.  In  this  condition,  the 
quantity  of  urine  is  greatly  increased,  it  may  reach  10  or  more  litres.  Slany  pints  may  be  passed 
daily.  [The  usual  abnormal  amount  of  sugar  is  from  i  to  8  per  cent.,  although  15  percent,  has  been 
found,  /.  e.,  found  from  5  to  50  grs.  per  fluid  oz.,  or  300  to  4000  grs.  in  twenty-foiu-  hours.]  The 
specific  gravity  is  also  increased  (1030  to  1040J.  [In  a  case  where  a  large  amount  of  urine  is 
passed  of  2.  pale  color  and  a  specific  gravity  above  1030,  always  suspect  sugar.]  A  diabetic  person 
gives  off  relatively  more  water  by  the  kidneys  and  less  by  the  skin  (and  lungs  ?)  than  a  healthy  person. 
The  color  is  very  pale  yellow,  although  the  amount  of  pigment  is  by  no  means  diminished — it  is  only 
diluted  [the  depth  of  the  color  being  inversely  as  the  quantity  passed].  The  amount  of  the  nitro- 
genous urinary  excreta  is  increased.  The  sugar  is  increased  by  a  diet  of  carbohydrates  and  dimin- 
ished by  an  albuminous  diet.  The  uric  acid  and  oxalate  of  lime  are  often  increased  at  the  commence- 
ment of  the  disease,  while  yeast  cells  are  constantly  present  after  the  urine  has  been  exposed  to  the 
air  for  some  time. 

Sugar  has  been  found  occasionally  after  poisoning  with  or  after  the  use  of  morphia,  CO,  chloral, 
chloroform,  curara;  after  the  injection  of  ether  and  amyl  nitrite  into  the  blood;  and  in  gout,  intermit- 
tent fever,  cholera,  cerebro- spinal  meningitis,  hepatic  cirrhosis,  and  cardiac  and  pulmonary  affections. 

[There  is  no  doubt  that  normal  healthy  human  urine  contains  a  reducing  agent,  which  reduc-s 
cupric  oxide  to  the  same  extent  as  if  the  urine  on  an  average  contained  6  grains  of  glucose  in  every 
10  fluid  ounces  of  urine,  or  1. 34  gnns.  per  litre.  As  this  sub.stance  does  not  cause  alcoholic  fermen- 
tation in  its  solutions,  its  identity  with  glucose  appears  to  be  doubtful.  The  most  active  reducing 
agent  is  probably  kreatinin  [G.  S.  Johnson).'\ 

Tests. — Any  of  the  tests  described  at  \  149  may  be  used,  but  the  urine  must  be  free  from  albumin. 
The  quantitative  estimation  by  fermentation  and  the  titration  methods  are  described  in  \  149.  [The 
tests  for  grape  sugar  described  in  \  149  are  (i)  Trommer's ;  {2)  Fehling's ;  (3)  Moore  &  Heller's; 
(4)  Bottger's  ;   (5)  Mulder  &  Xeubauer's  ;   (6)  Fermentation  test.] 

Worm-Miiller  recommends  the  following  modification  of  Fehling's  test :  Use  a  2.5  per  cent, 
solution  of  cupric  sulphate  solution,  and  another  of  10  parts  of  sodio-potassic  tartrate  in  loo  parts 
of  4  per  cent,  solution  of  soda.     Boil  5  c.cm.  of  urine  in  a  test-tube,  while  in  a  second  test-tube  is 


SUGAR    IN    URINE.  463 

boiled  I  to  3  c.cm.  of  the  copper  solution  and  2.5  c.cm.  of  the  potassio-tartrate  solution.  The  boil- 
ing of  both  iluids  is  stopped  simultaneously,  and  after  20  to  25  seconds  the  contents  of  one  test-tube 
are  added  to  those  of  the  other,  but  without  shaking  the  mixture,  the  reduction  taking  place  spon- 
taneously. 

8.  Nylander's  modification  of  Bottger's  test  is  also  good  (§  149). 

[9.  Picric  Acid  and  Potash  Test. — Braun  showed  that  grape  sugar,  when  boiled  with  picric 
acid  and  potash,  reduces  the  yellow  picric  acid  to  the  deep  red  picramic  acid,  the  depth  of  the  color 
depending  on  the  amount  of  sugar  present.  Dr.  Johnson  uses  this  test  for  detecting  the  presence  of 
sugar  in  urine,  and  also  for  estimating  the  amount  of  sugar  present,  the  depth  of  the  red  color 
obtained  in  boiling  being  compared  with  a  standard  dilution  of  ferric  acetate.  In  doing  the  test, 
use  I  drachm  of  urine,  y^  a  drachm  of  liquor  potassse,  and  10  minims  of  picric  acid  solution; 
make  up  to  2  drachms  with  distilled  water,  and  boil  the  mixture  for  one  minute.  This  test  indicates 
the  presence  of  0.6  grain  of  sugar  per  fluid  ounce  of  normal  urine.  Dr.  Johnson  claims  for  this  test 
that  it  possesses  all  the  advantages  of  the  other  tests,  while  it  is  not  affected  by  uric  acid  or  any 
other  normal  ingredient  of  urine;  neither  does  the  presence  of  albumin  interfere  with  the  action  of 
the  test  as  it  does  with  all  the  forms  of  copper  testing.] 

[10.  Indigo-carmine  Test. — A  blue  solution  of  this  substance,  when  boiled  with  diabetic  urine 
containing  sodic  carbonate,  changes  from  a  blue  to  a  violet,  purple,  red,  yellow,  and  finally,  straw- 
yellow  color.  After  cooling  and  exposure  to  the  air,  the  various  colors  are  obtained  in  the  reverse 
order  until  the  mixture  becomes  blue  again.  Dr.  Oliver  uses  this  test  in  the  form  of  test  papers. 
One  bibulous  paper  is  impregnated  with  the  indigo  carmine  and  the  other  with  sodic  carbonate. 
Drop  one  of  the  test  papers  and  a  sodic-carbonate  paper  into  a  test-tube  containing  i  j^  inches  of 
water,  heat  gently,  when  a  blue  solution  is  obtained.  x\dd  the  urine  slowly,  one  drop  at  a  time,  and 
boil  the  mixture,  observing  any  change  of  color  by  holding  the  tube  against  a  white  surface  below 
the  level  of  the  eye.  Uric  acid  and  urates,  which  reduce  Fehling's  solution,  do  not  affect  the  car- 
mine test,  nor  does  kreatinin,  although  it  reacts  with  the  picric  acid  test.] 

[Quantitative  Estimation. — {a)  Fermentation  Test  (|  150).  Take  4  oz.  (120  c.c.)  of  the 
urine  ;  add  a  lump  of  German  yeast,  about  the  size  of  a  walnut,  lightly  cork  the  bottle,  and  place 
it  aside  for  twenty-four  hours  in  a  moderately  warm  place,  e.  g.,  on  the  mantelpiece.  Take  the 
specific  gravity  before  and  after  the  fermentation.  Thus,  if  the  specific  gravity  be  1038  before  and 
1013  afterward,  the  difference  or  "density  lost"  is  25,  which  gives  25  grs.  of  sugar  per  fluid  oz. 
{Roberts).  If  it  be  desired  to  get  the  percentage,  multiply  the  density  lost  by  0.23,  thus  25  X^-^S 
=  5.69  in  100  parts.] 

\{b)  Volumetric  Analysis. — 10  c.c.  of  Fehling's  solution  =  .05  of  sugar. 

I.  Ascertain  the  quantity  of  urine  passed  in  twenty-four  hours.     2.  Filter  the  urine,  and  remove 

any  albumin  present  by  boiling  and  filtration.     3.   Dilute  ID  c.c.   of  Fehling's  solution  with  about 

twenty  times  its  volume  of  distilled  water,  and  place  it  in  a  white  porcelain  capsule  on  a  wire  gauze 

support  under  a  burette.     (It  is  diluted  because  any  change  of  color  is  more  easily  observed.)     4. 

Take  5  c.c.  of  the  urine,  and  95  c.c.  of  distilled  water,  and  place  the  diluted  urine  in  a  burette.     5. 

Gradually  boil  the  diluted  Fehling's  solution,  and  while  it  is  boiling  gradually  add  the  diluted  urine 

from  the  burette,  until  all  the  cuprous  oxide  is  precipitated  as  a  reddish  powder,  and  the  supernatant 

fluid  has  a  straw-yellow  color,  not  a  trace  of  blue  remaining.     Read  off  the  number  of  c.c.  of  dilute 

urine  employed.     Say  36  c.c.  were  used — that,  of  course,  represents  1.8  c.c  of  the  original  urine. 

Suppose  the  patient  passes  1550  c.c,  as   1.8  c.c.  of  urine  reduced  all  the  cupric  oxide  in  the  10  c.c. 

of  Fehling's  solution,  it  must  contain  .05  gramme  sugar,  hence, 

1550  X  -05 
1.8  :  1550  :  :  .05  :  —r =;  237.5  grammes  of  sugar  passed  in  24  hours.] 

[Preparation  of  Fehling's  Solution. — 34.64  grammes  of  pure  crystalline  cupric  sulphate  are 
powdered  and  dissolved  in  200  c.c.  of  distilled  water;  in  another  vessel  dissolve  173  grammes  of 
Rochelle  salts  in  480  c.c.  of  pure  caustic  soda,  specific  gravity  1.14.  Mix  the  two  solutions,  and 
dilute  the  deep  colored  fluid  which  results  to  i  litre.  N.B. — Fehling's  ought  not  to  be  kept  too 
long ;  it  is  apt  to  decompose,  and  should  therefore  be  preserved  from  the  light,  or  protected  with 
opaque  paper  pasted  on  the  bottle.  Some  other  substances  in  urine,  e.g.,  urates  and  uric  acid, 
reduce  cupric  oxide.] 

(<r)  According  to  Worm-Miiller,  the  polarization  method  is  almost  valueless  for  diabetic  urine. 

[Picro-Saccharimeter. — G.  Johnson  uses  a  stoppered  bottle  12  inches  long  and  |/  inch  wide, 
gi"aduated  in  -^-^  and  jig  (Fig.  269).  To  it  is  fixed  a  shorter  bottle  containing  the  standard  iron 
solution  for  comparison,  a  standard  solution,  composed  of  liquor  ferri  perchloride  '^],  liq.  ammon. 
acetatis  5;  iv,  glacial  acetic  acid  "J^  iv,  liq.  ammonise  ^j,  and  water  to  make  up  giv.  AH  B.  P.  prepa- 
rations give  a  color  identical  with  a  solution  containing  i  gr.  of  grape  sugar  per  oz.,  reduced  by 
picric  acid  and  afterward  diluted  four  times,  so  that  this  tint  =  yl  gr.  of  sugar  per  oz.  After 
reducing  the  sugar  with  the  picric  acid,  pour  into  the  tall  tube  the  dark  saccharine  liquid  pro- 
duced by  boiling  to  occupy  ten  divisions  of  the  tube,  and  add  distilled  water  cautiously  until 
the  color  approaches  that  of  the  standard;  read  off  the  level  of  the  fluid.  The  amount  of  sugar 
present  is  determined  from  the  amount  of  water  added.  In  making  the  test,  the  picric  acid  must 
be  added  in  proportion  to  the  amount  of  sugar  present.] 


464 


MILK    SUGAR    AND    OTHER    SUBSTANCES    IN    URINE. 


If  large  (luantities  of  dextrose  are  taken  in  the  food,  a  part  of  it  (and  more  in  diabetic  persons)  appears 
in  the  urine.  La.'vuiose,  when  taken  internally,  does  not  increase  the  amount  of  sugar  in  diabetes. 
The  free  use  of  starch  does  not  cause  glycosuria  in  health,  but  in  diabetes  it  increases  the  amount  ot 


Fig.  269. 


I'lc.  270. 


Inosit  cryst.illized  partly  from  alcohol  and  partly 
from  water  (after  Funke). 

sugar.  A  large  consumption  of  cane  or  milk  sugar  causes  the  passage  of 
small  quantities  of  both  of  these  sugars  into  the  urine  in  health,  while  in  dia- 
betes the  amount  of  dextrose  is  increa.sed  (^\l'orni-I\Iuller).  According  to 
Kiilz,  in  diabetic  persons  cane  sugar  splits  up  into  grape  and  fruit  sugar,  the 
latter  being  used  up  in  the  body,  the  former  partly  excreted ;  and  the  same  is 
the  case  with  milk  sugar. 

In  severe  cases  of  diabetes  mellitus,  Kiilz  found  the  left-rotatory  /3-oxy- 
butyric  acid  (the  next  highest  analogue  of  lactic  acid)  in  the  urine,  from  which 
acetic  acid  is  formed  by  oxidation  (^  175),  which  in  its  turn  readily  yields  COj 
and  aceton.  a-Crotonic  acid  is  formed  in  urine  by  the  removal  of  water  from 
oxybutyric  acid  in  the  urine  in  diabetes  [Stade/manii).  The  administration 
of  aceton  causes  albuminuria,  and  this  may  in  part  explain  in  some  cases  the 
Picro-sacch.irimeter  of    Complication  of  albuminuria  in  diabetes  [A/berfoni  and  Ptsenti). 

G  Johnson.  Aceton,  or  aceton-yielding  substance,  probably  aceto-acetic  acid,  is  some- 

times found  in  diabetic  urine.  It  has  a  peculiar  vinous  odor,  and  it  has  been 
detected  in  the  urine  during  fever.  CJerhardt  described  a  peculiar  substance  in  diabetic  urine,  which 
gave  a  deep  red  color  with  perchloride  of  iron.  This  substance  is  probably  diacetic  ether,  and  he 
considered  it  to  be  the  source  of  aceton ;  but  it  is  more  probably  derived  from  aceto-acetic  acid. 
Test  for  Aceton.  (i)  Perchloride  of  iron  =  Burgundy  red  color;  but  this  is  not  reliable.  (2) 
Lieben  suggested  an  iodofonn  lest.  Dissolve  20  grains  of  KI  in  a  fluid  drachm  of  liq.  potassK  and 
boil  the  fluid.  Pour  the  suspected  urine  on  the  surface,  when  a  ring  of  phosphates  is  deposited 
from  the  urine  by  the  hot  alkaline  solution.  If  aceton  be  present,  after  a  time  the  deposit  becomes 
yellow,  and  yellow  granules  of  iodoform  appear  and  sink  to  the  bottom  of  the  test-tube.  The  only 
other  substance  which  may  be  met  with  in  the  urine  giving  this  reaction  is  lactic  acid. 

Milk  sugar  is  sometimes  found  in  the  urine  of  women  who  are  nursing,  when  the  secretion  of 
milk  is  arrested,  absorption  taking  place  from  the  breasts  [Kirsten,  Spiegelberg).  Laevulose  is 
sometimes  found  in  diabetic  urine  \\  252). 

Dextrin  has  also  been  found  in  diabetic  urine.  Inosit,  or  muscle  sugar  (§  252),  is  sometimes 
found  in  diabetes,  in  polyuria,  and  albuminuria.  It  is  found  in  traces,  even  in  normal  urine. 
Occasionally,  after  the  pi<|ure  in  animals  (|  175),  inosit,  instead  of  grape  sugar,  appears  in  the 
urine  (Fig.  270).  In  testing  for  inosit,  remove  the  grape  sugar  by  fermentation,  and  the  albumin 
by  heat  after  the  addition  of  a  few  drops  of  acetic  acid  and  sodic  sulphate.  Some  of  the  filtrate  is 
evaporated  nearly  to  dryness  on  a  capsule.  To  the  residue  add  two  drops  of  mercuric  nitrate 
(Liebig's  titration  fluid  for  urea),  which  gives  a  yellow  precipitate.  When  this  colored  residue  is 
spread  out  and  carefully  heated,  a  dark  red  color,  which  disappears  on  cooling,  is  obtained  [Gallois, 
Kiilz).     [Inosit  gives  a  green  when  boiled  with  Fehling's  solution.] 

268.  CYSTIN. — This  left  rotatory  body,  CgHj.^NjS.^G^,  occurs  very  seldom  in  large  amount  in 
urine,  although  it  seems  to  be  a  constituent  of  normal  urine.  It  may  be  in  solution  or  in  the  form 
of  hexagonal  crystals  (Fig.  271,  A).     It  is  insoluble  in  water,  alcohol,  and  ether,  but  easily  soluble 


LEUCIN    AND    TYROSIN. 


465 


in  ammonia,  from  which  solution  it  may  be  crystallized.  According  to  Baumann  and  Preusse  there 
are  intermediate  products  of  the  metabolism,  from  which  are  furnished  the  materials  necessary  for 
the  formation  of  cystin.  During  normal  metabolism  these  materials  undergo  further  changes,  and 
the  sulphur  appears  oxidized  in  the  urine  as  sulphuric  acid.  In  rare  cases  these  oxidations  do  not 
take  place,  and  then  the  sulphur  appears  in  the  cystin  of  the  urine  [Stadthagen). 

269.  LEUCIN  =  CgHigNO,.  TYROSIN  =  CgHjiNOg.— Both  bodies  occur  in  the  urine  in 
acute  yellow  atrophy  of  the  liver,  and  in  poisoning  by  phosphorus.  (Their  formation  during 
pancreatic  digestion  has  been  referred  to  in  ^  170,  II.)  As  the  urea  excreted  is  usually  diminished 
at  the  same  time,  it  is  assumed  that,  in  these  diseases,  the  further  oxidation  of  the  derivatives  of  the 


Fig.  271. 


Fig.  272. 


A,  crystals  of  cystin  ;  B,  oxalate  of  lime  ;  c,  hour- 
glass forms  of  B. 


a,  a,  leucin  balls ;  b,  b,  tyrosin  sheaves ;  c,  double 
balls  of  ammonium  urate. 


proteids  is  interfered  with.  Leucin,  which  is  either  precipitated  spontaneously  or  obtained  after 
evaporating  an  alcoholic  extract  of  the  concentrated  urine,  occurs  in  the  form  of  yellowish-brown 
balls  (Fig.  272,  a,  a),  often  with  concentric  markings,  or  with  fine  spines  on  their  surface.  When 
heated,  it  sublimes  without  fusing. 

Tyrosin  forms  silky,  colorless  sheaves  of  needles  (Fig.  272,  b,  b).  When  boiled  with  mer- 
curic nitrate  and  nitric  acid  it  gives  a  red  color,  and  afterward  a  brownish-red  precipitate.  Piria's 
Test. — When  slightly  heated  with  a  few  drops  of  concentrated  sulphuric  acid,  it  dissolves  with  a 
temporary  deep  red  color.  On  diluting  with  water,  adding  barium  carbonate  until  it  is  neutralized, 
boiUng,  filtering,  and  adding  dilute  ferric  chloride,  a  violet  color  is  obtained  {Piria,  Stddeler). 

270.  DEPOSITS  IN  URINE. — Deposits  may  occur  in  normal  and  in 
pathological  urine,  and  they  may  be  either  "  organized  "  or  "  unorganized." 

I.  Organized  Deposits. 

A.  Blood:  red  and  white  blood  corpuscles  and  sometimes  fibrin  (Figs.  264-266). 

B.  Pus,  in  greater  or  less  amount  in  catarrh  or  inflammation  of  the  urinary  passages.  Pus  cells 
exactly  resemble  colorless  blood  corpuscles  (Figs.  9,  267).  Donne's  Test. — Pour  off  the  super- 
natant fluid  and  add  a  piece  of  caustic  potash  to  the  deposit ;  if  it  be  pus  it  becomes  gelatinous, 
ropy,  and  more  viscid  (alkali-albuminate).  Mucus,  when  so  acted  on,  becomes  more  fluid  and 
mixed  with  flocculi. 

C.  Epithelium  of  various  forms  occurs,  but  it  is  not  always  possible  to  say  whence  it  is 
derived. 

D.  Spermatozoa  may  be  present. 

E.  Lower  organisms  occur  in  the  urinary  passages  very  seldom,  but  they  may  be  present,  e.g., 
in  the  bladder,  when  germs  are  introduced  from  without  by  means  of  a  dirty  catheter.  [Before 
introducing  a  catheter  into  the  bladder  one  ought  always  to  make  sure  that  the  instrument  is 
perfectly  aseptic]  Micrococci  are  found  in  the  urine  in  certain  diseases,  e.g.,  diphtheria.  The 
following  forms  are  distinguished  : — 

30 


466 


TUBE    CASTS    IN    URINE. 


1.  Schizomycetes  (|   184).     Normal  human   urine  contains   neither   schizomycetes  nor  their 
spores.      In  pathological  conditions,   however,    fungi   may  pass   from   the  blood   into  the   urinary 


Fig.  273. 


tubules  and  thus  reach  the  urine  {Leiide),  During 
the  alkaline  fermentation  of  urme,  micrococci, 
rod-shaped  bacteria  or  bacilli  (Fig.  273)  appear. 
Sarcinse  belong  to  the  group  {\  186). 

2.  Saccharomycetes  (fermentation  fungi) :  {a) 
The  fungus  of  the  acid  urine  fermentation  (S. 
urinre)  consists  of  small  bladder- like  cells  arranged 
either  in  chains  or  in  groups  (Figs.  260,  n;  273, y). 
{b)  Veast  (S.  fermentum)  occurs  in  diabetic  urine, 
as  oval  cells  with  dotted  eccentrically-placed  nu- 
cleus (Fig.  237). 

3.  Phytomycetes  (moulds)  occur  in  putrid  urine 
(Fig.  273,  f).  They  are  without  clinical  signifi- 
cance. 

F.  Tube  Casts. — The  occurrence  of  tube  casts, 
i.  e.,  casts  of  the  uriniferous  tubules  {Ilenle,  1837),  is  of  great  importance  in  the  diagnosis  of  renal 
diseases.  If  these  structures  are  relatively  thick  and  straight,  they  probably  come  from  the  collect- 
ing tubules,  but  if  they  are  smaller  and  twisted,  they  probably  come  from  the  convoluted  tubules. 
There  are  various  forms  of  tube  casts:     i.  Epithelial  casts,  consisting  of  the  actual  cells  of  the 


Fungi   in  urine,     e,    mould  ;  f,  yeast ;    d,  g,   micro- 
cocci and  bacilli  ;  a,  b,  c,  uric  acid. 


Fig.  274. 


Fk;.  277. 


Leucocyte  cast.     Acid  sodic  urate  in 
cylinders. 


Fig.  278. 


Finely  granular  cast. 


Epitlie 


uriniferous  tubules.  They  indicate  that  there  is  no  very  great  change  going  on,  but  only  that,  as  in 
catarrhal  inflammation  of  any  mucous  membrane,  the  epithelium  is   in  process  of  desquamation. 

2.  Hyaline  casts  (Fig.  280)  are  quite  clear  and  homogeneous,  usually  long  and  small ;  sometimes 
they  are  "  finely  granular,"  from  the  presence  of  fat  or  other  particles.  They  are  best  seen  after 
the  addition  of  a  solution  of  iodine.  They  are  probably  formed  from  albumin,  which  passes  into 
the  uriniferous  tubules.  They  are  dissolved  in  alkaline  urine,  while  acid  urine  favors  their  formation. 
They  usually  occur  in  the  late  stages  of  renal  disease,  after  the  tubular  epithelium  has  been  shed. 

3.  Coarsely  granular  casts  (Fig.  279)  are  brownish-yellow,  opaque,  and  granular,  usually 
broader  than  2.  There  are  various  forms.  Not  unfrequently  there  are  fatty  granules,  and,  it 
may  be,  epithelial  cells  in  them.  4.  Amyloid  casts  occur  in  amyloid  degeneration  of  the  kidneys 
(Fig.  280).  They  are  refractive  and  completely  homogeneous,  and  give  a  blue  color  (amyloid 
reaction)  with  sulphuric  acid  and  iodine.  5.  Blood  casts  occur  in  capillary  hemorrhage  of  the 
kidney,  and  consist  of  coagulated  blood  entangling  blood  corpuscles  (Fig.  275).  When  tube  casts 
are  present,  the  urine  is  always  albiiininoits. 

Leucocyte  casts  occur  in  suppurating  conditions  of  the  urinary  tubules  (Fig.  280).     The  urates 
in  the  form  of  casts  (Fig.  277)  are  without  significance. 

II.  Unorganized  Deposits. 
Some  of  these  are  crystalline  and  others  are  amorphous,  and  they  have  been  referred  to  in 
treating  of  the  urinary  constituents. 


DETECTION    OF    URINARY   DEPOSITS, 


467 


271.  SCHEME  FOR  DETECTING  URINARY  DEPOSITS.— I.  In  acid  urine  there 
may  occur — 

I.  An  amorphous  granular  deposit: —  , -,•  v    • 

(rt)  Which  is  dissolved  by  heat  and  reappears  in  the  cold;   the  deposit  is  often  reddish  in 

color  =  urates  (Fig.  260). 
(3)  Which  is  not  dissolved  by  heat,  but  is  dissolved  by  acetic  acid,  but  without  effervescence  = 

probably  tribasic  calcic  phosphate. 
(c)  Small  bright  refractive  granules,  soluble  in  ether  =  fat  or  oil  granules  (?  41),  (Lipsmia). 
Fat  occurs  in  the  urine,  especially  when  the  round  worm,  Filaria  sanguinis  hommis,  is, 
present  in  the  blood  ;  sometimes,  along  with  sugar,  in  phthisis,  poisoning  with  phosphorus, 
yellow  fever,  pysemia,  after  long-continued  suppuration,  and  lastly,  after  the  injection  of 
fat  or  milk  into  the  blood  {'i  102).  It  occurs  also  in  fatty  degeneration  of  the  urinary 
apparatus,  admixture  with  pus  from  old  abscesses,  and  after  severe  injuries  to  bones.  In 
these  cases  attention  ought  to  be  directed  to  the  presence  of  cholesterin  and  lecithin. 
Very  rarely  is  the  fat  present  in  such  amount  in  the  urine  as  to  form  a  cream  on  the 
surface  (chyluria). 

Fig.  281. 


Fig.  279. 


Coarsely  granular  casts.  a.  Granules  of  calcic  carbonate  of  lime  ;  i,  c,  crystalline  neutral  calcic  phosphate. 

Fig.  282. 

'^  Fig.  28:;. 


Hyaline  casts,  a;  6,  with 
leucocytes ;  c,  with  renal 
epithelium. 


Ammonio-magnesic  phosphate. 


Imperfect  forms  of  the  same. 


2.  A  crystalline  deposit  may  be — 
{a)   Uric  acid  (Fig.  256). 

\b)  Calcium  oxalate  (Fig.  258) — octahedra  insoluble  in  acetic  acid. 
U]  Cystin  (Fig.  271). 
[d)  Leucin  and  tyrosin — very  rare  (Fig.  272). 

II.  In  alkaline  urine  there  may  occur —  ,  -a-  

I.  A    completely   amorphous    granular    deposit,   soluble  in  acids   without    effervescence  — 
tribasic  calcic  phosphate. 


468  URINARY    CALCULI. 

2.  SeJimenf,  crystalline,  or  with  a  characteristic  for  ni. 

(fl)  Triple  phosphate  (Figs  282,  283),  soluble  at  once  in  acids. 

(b)  Acid  ammonium  urate — dark-yellowish,  small  balls  often  beset  with  spines,  also  anior- 

pluHis  ^  I'it^.  2S4). 
(<•)    Calcium  carbonate — small  whitish  balls  or  biscuit-shaped  bodies.     Acids  dissolve  them 

with  elVeivescence  (Fig.  2S1). 
(</)  Leucin  and  tyrosin  (I'ig.  272) — very  rare. 

\e)   Neutral  calcic  phosphate  and  long  plates  of  tribasic  magnesic  phosphate  (Fig.  285). 
Organized  deposits  may  occur  both  in  alkaline  and  in  acid  urine;  pus  cells  are  more  abundant 
in  alkaline  urine,  and  so  are  the  lower  vegetable  organisms. 

272.  URINARY  CALCULI. — I'rinary  concretions  may  occur  in  granules  the  size  of  sand, 
or  in  masses  as  large  as  the  list.     According  to  their  size  they  are  spoken  of  as  sand,  gravel, 
stone,  or  calculi.     They  occur  in   the  pelvis  of  the   kidney,  ureters. 
Fig.  284.  bladder,  and  sinus  prostaticus. 

We  may  classify  them  as  follows  (^Ultzmann)  : — 
I.  Calculi  whose  nucleus  consists  of  the  sedimentary  deposits  that 
occur   in   acid    urine    (primary  formation  of   calculi).      They  are    all 

Fic.  285. 


%<$^^ 


P^    ^ 


Q 


Acid  ammonium  urate.  Basic  magnesic  phosphate. 

formed  in  the  kidney,  and  pass  into  the  bladder,  where  they  enlarge  by  the  deposition  of  matter 
on  their  surface. 

2.  Calculi  which  are  either  sedimentary  forms  from  alkaline  urine,  or  whose  nucleus  consists  of 
a  foreigti  body  (secondary  formation  of  calculi).     They  are  formed  in  the  bladder. 

The  primary  formation  of  calculi  begins  with  free  uric  acid  in  the  form  of  sheaves  (Fig.  256) 
which  form  a  nucleus,  with  concentric  layers  of  oxalate  of  lime.  The  secondary  formation  occurs 
in  neutral  urine  by  the  deposition  of  calcic  carbonate  and  crystalline  calcic  phosphate ;  in  alkaline 
urine,  by  the  deposition  of  acid  ammonium  urate,  triple  phosphate,  and  amorphous  calcic  phosphate. 

Chemical  Investigation. — Scrape  the  calculus,  burn  the  scrapings  on  platinum  foil  to  ascertain 
if  they  are  burned  or  not. 

I.  Combustible  concretions  can  consist  only  of  organic  substances. 

(a)  Apply  the  murexide  test  (g  259,  2),  and,  if  it  succeeds,  uric  acid  is  present.  Uric  acid 
calculi  are  very  common,  often  of  considerable  size,  smooth,  fairly  hard,  and  yellow  to  reddish- 
brown  in  color. 

(b)  If  another  portion,  on  being  boiled  with  caustic  potash,  gives  the  odor  of  ammonia  (or  when 
the  vapor  makes  damp  turmeric  paper  brown,  or  if  a  glass  rod  dipped  in  IICl  and  held  over  it  gives 
white  fumes  of  ammonium  chloride),  the  concretion  contains  ammonium  urate.  If  b  gives  no 
result,  pure  uric  acid  is  present.  Calculi  of  ammonium  urate  are  rare,  usually  small,  of  an  earthy 
consistence,  i.  e.,  soft  and  pale  yellow  or  whitish  in  color. 

(c)  If  the  xanthin  reaction  succeeds  (^  260),  this  substance  is  present  (rare).  Indigo  has  been 
found  on  one  occasion  in  a  calculus  {Ord). 

(d)  If,  after  solution  in  ammonia,  hexagonal  plates  (Fig.  271,  A)  are  found,  cystin  is  present. 

(e)  Concretions  of  coagulated  blood  or  fibrin,  without  any  crystals,  are  rare.  When  burned 
they  give  the  odor  of  singed  hair.  They  are  insoluble  in  water,  alcohol  and  ether;  but  are  soluble 
in  caustic  potash,  and  are  precipitated  therefrom  by  acids. 

(/")  Urostealith  is  applied  to  a  caoutchouc-like,  soft  elastic  substance,  and  is  very  rare.  When 
dry  it  is  brittle  and  hard,  brown  or  black.  When  warm  it  softens,  and  if  more  heat  be  applied  it 
melts.  It  is  soluble  in  ether,  and  the  residue  after  evaporation  becomes  violet  on  being  heated.  It 
is  soluble  in  warm  caustic  potash,  with  the  fonnation  of  a  soap. 

II.  If  the  concretions  are  only  partly  combustible,  thus  leaving  a  residue,  they  contain  organic 
and  inorganic  constituents. 

(a)  Pulverize  a  part  of  the  stone,  boil  it  in  water,  and  filter  while  hot.  The  urates  are  dissolved. 
To  test  if  the  uric  acid  is  united  with  soda,  potash,  lime,  or  magnesia,  the  filtrate  is  evaporated  and 
buraed.     The  ash  is  investigated  with  the  spectroscope  (§  14),  when  the  characteristic  bands  of 


THE    SECRETION    OF    URINE.  469 

sodium  or  potash  are  observed.  Magnesic  urate  and  calcic  urate  are  changed  into  carbonate  by 
burning.  To  separate  them,  dissolve  the  ash  in  dilute  hydrochloric  acid,  and  filter.  The  filtrate  is 
neutralized  with  ammonia,  and  again  redissolved  by  a  few  drops  of  acetic  acid.  The  addition  of 
ammonium  oxalate  precipitates  calcic  oxalate.  Filter,  and  add  to  the  filtrate  sodic  phospiiate  and 
ammonia,  when  the  magnesia  is  precipitated  as  ammonio-magnesic  phosphate. 

[b)  Calcic  oxalate  (especially  in  children,  either  as  small,  smooth,  pale  stones,  or  in  dark,  warty, 
hard  "mulberry  calculi")  is  not  affected  by  acetic  acid,  is  dissolved  by  mineral  acids  without  effer- 
vescence, and  again  precipitated  by  ammonia.  Heated  on  platinum  foil  it  chars  and  blackens,  then 
it  becomes  white,  owing  to  the  formation  of  calcic  carbonate,  which  effervesces  on  the  addition  of  an 
acid. 

[c)  Calcic  carbonate  (chiefly  in  whitish-gray,  earthy,  chalk-like  calculi,  somewhat  rare)  dissolves 
with  effervescence  in  hydrochloric  acid.  When  burned  it  first  becomes  black,  owing  to  admixture 
with  mucus,  and  then  white. 

{d)  Ammonio-magnesic  phosphate  and  basic  calcic  phosphate  usually  occur  together  in 
soft,  white,  earthy  stones,  which  occasionally  are  very  large.  These  stones  show  that  the  urine  has 
been  ammoniacal  for  a  very  long  time.  The  first  substance  when  heated  gives  the  odor  of  ammonia, 
which  is  more  distinct  when  heated  with  caustic  potash ;  is  soluble  in  acetic  acid  without  efferves- 
cence, and  is  again  precipitated  in  a  crysta'line  form  from  this  solution  on  the  addition  of  ammonia. 
When  heated  it  fuses  into  a  white  enamel-like  mass  [hence  it  is  called  "  fusible  calculus  "J.  Basic 
calcic  phosphate  does  not  effervesce  with  acids.  The  solution  in  hydrochloric  acid  is  precipitated 
by  ammonia.     When  ammonium  oxalate  is  added  to  the  acetic  acid  solution,  it  yields  calcic  oxalate. 

{e)  Neutral  calcic  phosphate  is  rare  in  calculi,  while  it  is  frequent  in  the  form  of  gravel. 
Physically  and  chemically,  these  concretions  resemble  the  earthy  phosphates,  only  they  do  not  contain 
magnesia. 

273.  THE  SECRETION  OF  URINE.— [The  functions  of  the  kidney 

are — 

1.  To  excrete  waste  products,  chiefly  nitrogenous  bodies  and  salts ; 

2 .  To  excrete  water  ; 

3.  And  perhaps  also  to  reabsorb  water  from  the  uriniferous  tubules,  after  it  has 
washed  out  the  waste  products  from  the  renal  epitheHum. 

The  chief  parts  of  the  organs  concerned  in  i,  are  the  epithelial  cells  of  the  con- 
voluted tubules ;  the  glomeruli  permit  water  and  some  solids  to  pass  through  them, 
while  the  constrictions  of  the  tubules  may  prevent  the  too  rapid  outflow  of  water, 
and  thus  enable  part  of  it  to  be  reabsorbed.] 

Theories. — The  two  chief  older  theories  regarding  the  secretion  of  urine  are  the 
following:  i.  According  to  Bowman  (^1842),  through  the  glomeruli  are  filtered 
only  the  water  and  some  of  the  highly  diffusible  and  soluble  salts  present  in  the 
blood,  while  the  specific  urinary  constituents  are  secreted  by  the  activity  of  the 
epithelium  of  the  urinary  tubules,  and  are  extracted  or  removed  from  the  epithelium 
by  the  water  flowing  along  the  tubules.  This  has  been  called  the  "vital"  theory. 
2.  C.  Ludwig  (1844)  assumes  that  very  dilute  urine  is  secreted  or  filtered  through 
the  glomerulus.  As  it  passes  along  the  urinary  tubules  it  becomes  more  concen- 
trated, owing  to  endosmosis.  It  gives  back  some  of  its  water  to  the  blood  and 
lymph  of  the  kidney,  thus  becoming  more  concentrated,  and  assuming  its  normal 
character.      [This  is  commonly  known  as  the  "  mechanical  "  theory.] 

The  secretion  of  urine  in  the  kidneys  does  not  depend  upon  definite  physical 
forces  only.  A  great  number  of  facts  force  us  to  conclude  that  the  vital  activity 
of  certain  secretory  cells  plays  a  foremost  part  in  the  process  of  secretion  (7?. 
Heidenhain^ . 

The  secretion  of  urine  embraces  (i)  The  \vater,  and  (2)  the  urinary  con- 
stituents therein  dissolved;  both  together  form  the  urinary  secretion.  The 
amount  of  urine  depends  chiefly  upon  the  amount  of  water  which  is  filtered 
through  or  secreted  by  the  glomeruli;  the  amount  of  solids  dissolved  in  the 
urine  determines  its  concentration. 

(A)  The  amount  of  urine,  which  is  secreted  chiefly  within  the  Malpighian 
capsules,  depends  prifnarily  upon  the  blood  pressure  in  the  area  of  the  refial  artery, 
and  follows,  therefore,  the  laws  of  filtration  (§  191,  II)  {Ludwig  and  Goll).  [In 
this  respect  the  secretion  of  urine  differs  markedly  from  that  of  saliva,  gastric  juice, 
or  bile.     We  may  state  it  more  accurately  thus,  that  the  amount  of  urine  depends 


470  GLOMERULAR    EPITHELIUM. 

very  closely  uj^on  the  differences  of  pressure  between  the  blood  in  the  glomeruli 
and  the  pressure  within  the  renal  tubules.  If  the  ureter  he  ligatured,  the  secretion 
of  urine  is  ultimately  arrested,  even  although  the  blood  pressure  be  high.  The 
secretion  may  also  be  arrested  by  ligature  of  the  renal  vein  ;  and  in  some  cases  of 
cardiac  or  i)ulmonary  disease  the  venous  congestion  thereby  produced  may  bring 
about  tlie  same  result.] 

Glomerular  Epithelium. — The  amount  of  urine  secreted  does  not  depend 
upon  the  hydrostatic  pressure  alone,  but  it  seems  that  the  e])ithelial  cells  covering 
the  glomerulus  also  particij^ate  actively  in  the  process  of  secretion.  Besides  the 
water,  a  certain  amount  of  the  salts  present  in  the  urine  is  excreted  through  the 
glomeruli.  The  serum  albuviin  of  the  blood,  however,  is  prevented  from  passing 
through.  With  regard  to  the  secretory  activity  of  these  cells,  the  quantity  of  water 
must  also  depend  upon  the  amount  of  the  urinary  constituents  and  water  present  in 
the  blood  {A.  Ifeidenhain). 

Only  when  the  vitahty  of  the  secretory  cells  is  intact,  is  there  independent  activity  of  these 
secretoiy  cells  [NeiJenkain).  When  the  renal  artery  is  closed  temporarily,  their  activity  is  paralyzed, 
so  that  the  kidneys  cease  to  secrete,  and  even  after  the  compression  is  removed  and  the  circulation  re- 
established, secretion  does  not  take  place  for  some  time  (^Overbeck). 

That  the  secretion  depends  in  part  upon  the  blood  pressure  is  proved  by 
the  following  considerations  :  — 

1.  Ificrease  of  the  total  contents  of  the  vascular  system,  so  as  to  increase  the  blood 
pressure,  increases  the  amount  of  water  which  filters  through  the  glomeruli.  The 
injection  of  water  into  the  blood  vessels,  or  drinking  copious  draughts  of  water,  acts 
partly  in  this  way.  If  the  blood  pressure  rises  above  a  certain  height,  albumin  may 
])ass  into  the  urine.  The  active  participation  of  the  cells  of  the  glomeruli  is  rendered 
probable  by  the  fact  that,  after  very  copious  drinking,  the  blood  pressure  is  not 
always  raised  {Fawlow)  ;  further,  after  copious  transfusion,  the  quantity  of  urine 
is  not  increased.  Conversely,  the  loss  of  water,  owing  to  profuse  sweating  or  diar- 
rhoea, copious  hemorrhage,  or  prolonged  thirst,  diminishes  the  secretion  of  the  urine, 

2.  Diminution  of  the  capacity  of  the  vascular  system,  provided  the  pressure  within 
the  renal  area  be  thereby  increased,  acts  in  a  similar  manner.  This  may  be  pro- 
duced by  contraction  of  the  cutaneous  vessels,  owing  to  the  action  of  cold,  stimula- 
tion of  the  vasomotor  centre,  or  large  vasomotor  nerves,  ligature,  or  compression  of 
large  arteries  (§  85,  e),  or  enveloping  the  extremities  in  tight  bandages.  All  these 
conditions  cause  an  increase  in  the  amount  of  urine,  and  of  course  the  opposite 
conditions  bring  about  a  diminution  of  urine,  e.  g.,  the  action  of  heat  on  the  skin 
causing  redness  and  dilatation  of  the  cutaneous  vessels,  weakening  of  the  vasomotor 
centre,  or  paralysis  of  a  large  number  of  vasomotor  nerves. 

3.  Increased' action  of  the  lieart,  whereby  the  tension  and  rapidity  of  the  blood  in 
the  arteries  are  increased  (§  85,  c'),  augments  the  amount  of  urine;  conversely, 
feeble  action  of  the  heart  (paralysis  of  motor  cardiac  nerves,  disease  of  the  cardiac 
musculature,  certain  valvular  lesions)  diminishes  the  amount.  Artificial  stimulation 
of  the  vagi  in  animals,  so  as  to  slow  the  action  of  the  heart,  and  thus  diminish  the 
mean  blood  pressure  from  130  to  100  mm.  Hg,  causes  a  diminution  in  the  amount 
of  urine  to  the  extent  of  one-fifth  {Goll,  CI.  Bernard)  ;  when  the  pressure  in  the 
aorta  falls  to  40  mm.  the  secretion  of  urine  ceases.  [If  the  medulla  oblongata  be 
divided  (dog),  there  is  an  immediate  fall  of  the  general\Aoo6.  pressure,  and  although, 
as  a  general  rule,  the  secretion  of  urine  is  arrested  when  the  pressure  falls  to  40  to 
50  mm.  Hg,  yet  secretion  has  been  observed  to  take  place  with  a  lower  pressure 
than  this.] 

4.  The  amount  of  urine  secreted  rises  or  falls  according  to  the  degree  of  fullness  of 
the  renal  artery  (^Ludwig,  Max  Hermann)  ;  even  when  this  artery  is  moderately 
constricted  in  animals,  there  is  a  decided  diminution  in  the  amount  of  urine. 

Pathological. — In  fever  the  renal  vessels  are  less  full,  and  there  is  consecutive  diminution  of  urine 
{Mefictetson).     It  is  most  important,  in  connection  with  certain  renal  diseases,  to  note  that  ligature  of 


ACTION    OF    DIURETICS.  471 

the  renal  artery,  even  when  it  is  obliterated  for  only  two  hours,  causes  necrosis  of  the  epithelium  of 
the  uriniferous  tubules.  When  the  arterial  ansemia  is  kept  up  for  a  long  time,  the  whole  renal  tissue 
dies  [Litten).  After  long-continued  ligation  of  the  renal  artery,  the  epithelium  of  the  glomeruli 
becomes  gi-eatly  changed  lyRibbert). 

5.  Most  diuretics  act  in  one  or  other  of  the  above  mentioned  ways. 

[Some  diuretics  act  by  increasing  the  ^^w^ra/ blood  pressure  (digitalis  and  the  action  of  cold  on  the 
skin),  others  may  increase  the  blood  pressure  locally  within  the  kidney,  and  this  they  may  do  in 
several  ways.  The  nitrites  are  said  to  paralyze  the  muscular  fibres  in  the  vasa  afiferentia,  and  thus 
raise  the  blood  pressure  within  the  glomeruli  But  some  also  act  on  the  secretory  epithelium,  such  as 
urea  and  caffein.  Brunton  recommends  the  combination  of  diuretics  in  appropriate  cases,  and  the 
diuretics  must  be  chosen  according  to  the  end  in  view — as  we  wish  to  remove  excess  of  fluids  from 
the  tissues  and  serous  cavities,  or  as  we  wish  to  remove  injurious  waste  products,  or  merely  to  dilute 
the  urine.] 

[6.  The  amount  of  urine  also  depends  upon  the  composition  of  the  blood.  Drink- 
ing a  large  quantity  of  water,  whereby  the  blood  becomes  more  watery,  increases 
the  amount  of  urine,  but  this  is  true  only  within  certain  limits.  It  is  not  merely 
the  increase  of  volume  of  the  blood  acting  mechanically  which  causes  this  increase, 
as  we  know  that  large  quantities  of  fluid  may  be  transfused  without  the  general 
blood  pressure  being  materially  raised  thereby.] 

[Heidenhain  argues,  that  it  is  not  so  much  the  presswe  of  the  blood  in  the 
glomeruli  as  its  velocity,  which  determines  the  process  of  the  secretion  of  water  in 
the  kidney.  He  contends  that,  while  increase  of  the  pressure  in  the  renal  artery 
causes  an  increased  flow  of  urine,  ligature  of  the  renal  vein,  whereby  the  pressure 
in  the  glomeruli  is  also  increased,  arrests  the  secretion  altogether.  In  both  cases 
the  pressure  is  increased  within  the  glomeruli,  and  the  two  cases  differ  essentially  in 
the  velocity  of  the  blood  current  through  the  glomeruli.] 

Pressure  in  the  Vas  Afferens. — The  pressure  in  each  vas  afferens  must  be 
relatively  great,  because  (i)  the  double  set  of  capillaries  in  the  kidney  offers  con- 
siderable resistance,  and  (2)  the  lumen  of  the  vas  efferens  is  narrower  than  that  of 
the  vas  afferens.  Hence,  owing  to  the  high  blood  pressure  in  the  capillaries  of  the 
renal  glomeruli,  filtration  must  take  place  from  the  blood  into  the  Malpighian 
capsules.  When  the  vasa  afferentia  are  dilated,  the  filtration  pressure  is  increased, 
while,  when  they  are  contracted,  the  secretion  is  lessened.  When  the  pressure 
becomes  so  diminished  as  to  retard  greatly  the  blood  stream  in  the  renal  vein,  the 
secretion  of  urine  begins  to  be  arrested.  Occlusion  of  the  renal  vein  com- 
pletely suppresses  the  secretion  {_H,  Meyer,  v.  Frerichs).  Ludwig  concluded  from 
this  observation,  that  the  filtration  or  excretion  of  fluid  could  not  take  place  through 
the  renal  capillaries /r^/<?r,  as,  owing  to  occlusion  of  the  renal  vein,  the  blood  pres- 
sure in  these  capillaries  must  rise,  which  ought  to  lead  to  increased  filtration.  Such 
an  experiment  points  to  the  conclusion  that  the  filtration  must  take  place  through 
the  capillaries  of  the  glomeruli.  The  venous  stasis  distends  the  vas  efferens,  which 
springs  from  the  centre  of  the  glomerulus,  and  compresses  the  capillary  loops  against 
the  wall  of  the  Malpighian  capsule,  so  that  filtration  cannot  take  place  through 
them.  It  is  not  decided  whether  any  fluid  is  given  off  through  the  convoluted 
urinary  tubules. 

Venous  congestion  in  the  kidneys  diminishes  the  quantity  of  urine  and  the  urea.  The  NaCl 
remains  constant,  but  pathological  albumin  is  increased  (^Senator  and  Munk). 

Pressure  in  Ureter. — As  the  blood  pressure  in  the  renal  artery  is  about  120  to  140  mm.  Hg,  and 
the  urine  in  the  ureter  is  moved  along  by  a  very  slight  propelling  force,  so  that  a  counter-pressure  of 
from  10  {Lobell)  to  40  mm.  of  Hg  is  sufficient  to  arrest  its  flow,  it  is  clear  that  the  blood  pressure  can 
also  act  as  a  vis  a  tergo  to  propel  the  urine  through  the  ureter.  The  pressure  in  the  lureter  is  meas- 
ured by  dividing  the  ureter  transversely  and  inserting  a  manometer  in  it. 

(B)  Secretory  Activity  of  the  Renal  Epithelium.— The  degree  of 
concentration  of  the  urine  depends  upon  the  quantity  of  the  dissolved  constitu- 
ents which  has  passed  from  the  blood  into  the  urine.  The  secretory  cells  of  the 
convoluted  tubules,  by  their  own  proper  vital  activity^  seem  to  be  able  to  take  up. 


472  nussbaum's  experiments. 

or  secrete,  some  at  least  of  these  substances  from  the  blood  {Bowman,  Heidenhain). 
The  watery  part  of  the  urine,  containing  only  easily  diffusible  salts,  as  it  flows  along 
the  tul)ules  from  the  glomeruli,  extracts  or  washes  out  these  substances  from  the 
secretor\-  epithelium  of  the  convoluted  tubules. 

Experiments. — i.  Sulphindigotate  of  soda  and  sodium  urate  when  injected 
into  the  blood,  pass  into  the  urine,  and  are  found  in  the  protoplasm  of  the  cells  of 
the  convoluted  tubules  [only  in  those  i)arts  lined  by  "  rodded  "  epithelium]  but  not 
in  the  Malpighian  capsules  {Heidenhain).  A  little  later  these  substances  are  found 
in  the  lumen  of  the  urinary  tubules,  from  which  they  are  washed  out  by  the  watery 
])art  of  the  urine  coming  from  the  glomeruli.  If,  however,  two  days  before  the 
injection  of  these  substances  into  the  blood,  the  cortical  part  of  the  kidney  contain- 
ing the  Malpighian  capsules  be  cauterized,  \_e.g.,  by  nitrate  of  silver],  or  sliced  off, 
the  blue  pigment  remains  within  the  convoluted  tubules.  It  cannot  be  carried  on- 
ward, as  the  water  which  should  carry  it  along  has  ceased  to  be  secreted,  owing  to 
the  destruction  of  the  glomeruli.  This  experiment  also  goes  to  show  that,  through 
i\\Q  glomeruli  the  watery  part  of  the  urine  is  chiefly  excreted,  while  through  the  con- 
voluted tubules  the  specific  urinary  constituents  are  excreted.  Uric  acid  salts,  injetted 
into  the  blood,  were  observed  by  Heidenhain  to  be  excreted  by  the  convoluted 
tubules.  Von  Wittich  had  previously  observed  that  in  birds,  crystals  of  uric  acid 
were  excreted  by  the  epithelium  of  the  convoluted  tubules.  [The  presence  of 
crystals  of  uric  acid  in  the  renal  epithelium  was  observed  by  Bowman,  and  used  as 
an  argument  to  support  his  theory.]  Nussbaum,  in  1878,  stated  that  urea  is  secreted 
by  the  urinary  tubules  and  not  by  the  glomeruli. 

The  same  is  true  for  the  bile  pii^ments,  for  the  iy-on  salts  of  the  vegetable  acids  when  injected 
subcutaneously,  and  for  ha;moglol)in.  After  injection  of  milk  into  the  blood  vessels,  numerous  fatty 
granules  occur  within  the  epithelium  of  the  urinary  tubules  [\  102). 

[Nussbaum's  Experiments. — In  the  frog  and  newt,  the  kidney  is  supplied 
with  blood  in  a  manner  different  from  that  obtaining  in  mammals.  The  glomeruli 
are  supjilied  by  branches  of  the  renal  artery.  The  tubules  are  supplied  by  the  renal- 
portal  vein.  The  vein  coming  from  the  posterior  extremities  divides  at  the  upper 
end  of  the  thigh  into  two  branches,  one  of  which  enters  the  kidney,  and  breaks  up 
to  form  a  capillary  plexus  which  surrounds  the  uriniferous  tubules,  but  this  plexus 
is  also  joined  by  the  efferent  vessels  of  the  glomeruli.  These  two  systems  are  partly 
independent  of  each  other.  After  ligaturing  the  renal  artery,  Nussbaum  asserted 
that  the  circulation  in  the  glomeruli  was  cut  off,  while  ligature  of  the  renal-portal 
vein  excluded  the  functional  activity  of  tubules.  By  injecting  a  substance  into 
the  blood,  after  ligaturing  either  the  artery  or  renal-i)ortal  vein,  and  observing 
whether  it  occurs  in  the  urine,  he  infers  that  it  is  given  off  either  by  the  glomeruli 
or  the  tubules.  Sugar,  peptones,  and  egg  albumin  rapidly  jjass  through  an  intact 
kidney,  but  if  the  renal  artery  be  tied  they  are  not  excreted.  Urea  when  injected 
into  the  circulation  is  excreted  after  the  artery  is  tied,  so  that  it  is  excreted  through 
the  tubules,  but  at  the  same  time  it  takes  with  it  a  considerable  quantity  of  water. 
Thus,  water  is  excreted  in  two  wa}-s  from  the  kidney,  by  the  glomeruli  and  also 
from  the  venous  plexus  aroimd  the  tubules  along  with  the  urea.  Indigo  carmine 
merely  passes  into  the  tubular  epithelium  of  the  convoluted  tubules,  btit  it  does  not 
cause  a  secretion  of  urine.  Albumin  passes  through  the  glomeruli,  but  only  after 
their  membranes  have  been  altered  in  some  way,  as  by  clamping  the  renal  artery  for 
a  time.] 

[Adami's  Experiments  on  the  kidney  of  the  frog  tend  to  show  that  Nussbaum's  conclusions 
are  not  justified,  for  Adami  found  that  if  the  renal  arteries  in  the  frog  be  ligatured,  within  a  few 
hours  a  collateral  circulation  is  established,  and  a  certain  amount  of  blood  flows  through  the  kidney. 
He  proved  this  by  injecting  into  the  blood,  carmine  or  painter's  vermilion,  in  a  state  of  fine  suspen- 
sion, and  after  ligature  of  the  renal  arteries,  he  found  it  in  many  of  the  glomeruli,  while  laky  blood 
similarly  injected  revealed  its  presence  as  menisci  of  lib  in  the  Malpighian  corpuscles.  Even 
secretion   of  some  urine  may  go   on  after  ligature   of  the  renal    arteries.     It    is  evident,  then,  that 


EXCRETION    OF    PIGMENTS.  473 

Nussbaum's  method  is  not  a  reliable  one  for  locating  the  parts  of  the  kidney  through 'which  certain 
substances  are  excreted.  Adami's  experiments  also  give  some  support  to  Heidenhain's  view,  that 
the  glomerular  epithelium  "  possesses  powers  of  a  selective  secretory  nature,"  for  he  finds  that  in 
frogs,  after  ligature  of  the  renal  arteries,  where,  of  course,  the  pressure  in  the  glomeruli  is  just  nearly 
that  in  the  veins,  and  in  the  dog  after  section  of  the  spinal  cord,  so  that  the  blood  pressure  has  fallen 
below  40  mm.  Hg,  whereby  the  secretion  of  urine  is  arrested,  the  injection  of  laky  blood  causes  Hb 
to  appear  in  the  capsules,  although  there  is  no  simultaneous  excretion  of  water.] 

Excretion  of  Pigments. — Only  during  very  copious  excretion  does  the  capsule  participate. 
After  the  introduction  of  a  large  amount  of  sodic  sulphindigotate,  and  when  the  experiment  has 
lasted  for  a  long  time,  the  epithelium  of  the  capsule  becomes  blue.  In  albuminuria,  the  abnormal 
excretion  of  lu-ine  takes  places  first  in  the  urinary  tubules,  and  aftersvard  in  the  capsules ;  Hb  is  partly 
found  in  the  capsules.     According  to  Nussbaum,  egg  albumin  passes  out  through  the  capsule. 

2.  Even  when  the  secretion  of  the  watery  part  of  the  urine  is  completely  arrested, 
either  by  ligature  of  the  ureter,  or  after  a  very  great  fall  of  the  blood  pressure  in  the 
renal  artery  [as  after  section  of  the  cervical  spinal  cord],  the  before-mentioned 
substances,  when  injected  into  the  blood,  are  found  in  the  cells  of  the  convoluted 
tubules.  The  injection  of  urea  under  these  circumstances  causes  renewed  secretion. 
These  facts  show  that,  independently  of  the  filtration  pressure,  the  secretory  activity 
of  these  cells  is  still  maintained. 

The  independent  vital  activity  of  the  secretory  cells  of  the  urinary  tubules,  which  as  yet  we 
are  unable  to  explain  on  purely  physical  grounds,  renders  it  probable  that  the  tubules  are  not  to  be 
compared  to  an  apparatus  provided  with  physical  membranes.  This  is  proved  by  the  following  experi- 
ment :  Abeles  caused  arterial  blood  to  circulate  through  freshly  excised  living  kidneys.  A  pale, 
urine-like  fluid  dropped  from  the  ureter.  On  adding  some  urea  or  sugar  to  the  blood,  the  secretion 
became  more  concentrated.  Thus,  the  excised  living  kidney  also  excretes  substances  in  a  more 
concentrated  form  than  those  supplied  to  it  in  the  diluted  blood  streaming  through  it.  J.  Munk 
obtained  similar  results  in  excised  kidneys  with  common  salt,  nitre,  caffein,  grape  sugar,  glycerin, 
with  increase  in  the  amount  of  urine  secreted.  The  addition  of  caffein  or  theobromin  to  the  perfused 
blood  increases  the  secretion,  exciting  the  secretory  cells  to  greater  activity  (v.  Schroeder). 

Salts  and  Gases. — The  vital  activity  explains  why  the  serum  albumin  of  the  blood  does  not 
pass  into  the  urine,  while  egg  albumin  and  dissolved  haemoglobin  readily  do  so.  Among  the  salts 
which  occiu"  in  the  blood  and  blood  corpuscles,  of  course  only  those  in  solution  can  pass  into  the 
urine.  Those  which  are  united  with  proteid  bodies,  or  are  fixed  in  the  cellular  elements,  cannot  pass  out, 
or  at  least  only  after  they  have  been  split  up.  Thus,  we  may  explain  the  difference  between  the  salts 
of  the  urine  and  those  of  the  blood.  Similarly,  the  urine  can  only  contain  the  absorbed  and  not  the 
chemically  united  gases. 

Ligature  of  the'  Ureter. — If  the  secretion  be  arrested  by  compression  or  by  ligature  of  the  ureter, 
the  lymph  spaces  of  the  kidney  become  filled  with  fluid,  which  may  pass  into  the  blood,  so  that  the 
organ  becomes  oedematous,  owing  to  the  passage  of  fluid  into  its  lymph  spaces.  The  secretion  under- 
goes a  change,  as,  first,  water  passes  back  into  the  blood,  then  the  sodic  chloride,  sulphuric,  and  phos- 
phoric acids  diminish,  and  lastly  the  urea  (C.  Ludwig,  Max  Her?nann).  Kreatinin  is  still  present 
in  considerable  amount.     There  is  no  longer  secretion  of  proper  urine  [Lobitl). 

Non-symmetrical  Renal  Activity. — It  is  remarkable  that  both  kidneys  do  not  secrete 
symmetrically — there  is  an  alternate  condition  of  hyperjemia  and  secretory  activity  on  opposite  sides 
(^  100).  One  kidney  secretes  a  more  watery  urine,  which  at  the  same  time  contains  more  NaCl  and 
urea.  Von  Wittich  observed  that  the  secretion  of  uric  acid  was  not  uniform  in  all  the  urinary  tubules 
of  the  same  bird.  Extirpation  of  one  kidney,  or  disease  of  one  kidney  in  man,  does  not  seem  to 
diminish  the  secretion  i^Rosenstehi).     The  remaining  kidney  becomes  more  active  and  larger. 

Reabsorption  in  the  Kidney. — In  discussing  the  secretion  of  the  kidney,  we  must  attach 
considerable  importance  to  the  variations  in  the  calibre  of  the  renal  tubules  in  their  course.  Perhaps 
in  the  narrowing  of  the  descending  part  of  the  looped  tubule  of  Henle  there  may  be  either  a 
reabsorption  of  water,  so  that  the  urine  becomes  more  concentrated,  or  there  may  be  absorption  even 
of  albumin,  which  may  perhaps  pass  through  the  glomeruli  in  small  amount.  [That  reabsorption 
of  fluid  takes  place  within  the  kidney  was  part  of  Ludwig' s  theory,  which  is  practically  a  process  of 
filtration  and  reabsorption.  Hiifiier  pointed  out  that  the  structure  of  the  kidneys  of  various  classes 
of  vertebrates  corresponded  closely  with  the  requirements  for  reabsorption  of  water.  The  experiments 
of  Ribbert  show  that  the  urine  actually  secreted  in  the  cortex  of  the  kidney  is  more  watery  than  that 
secreted  normally  by  the  entire  organ.  He  extirpated  the  medullary  portion  in  rabbits,  leaving  the 
cortical  part  intact,  and  in  this  way  collected  the  dilute  urine  from  the  Malpighian  corpuscles  before 
it  passed  through  Henle's  loops.] 

274.  FORMATION   OF    THE    URINARY  CONSTITUENTS.— 

The  question  has  often  been  discussed,  whether  all  the  urinary  constituents  are 
merely  excreted  through  the  kidneys,  /.  e.,  that  they  exist  preformed  in  the  blood; 


474  FORMATION    OF    THE    URINARY    CONSTITUENTS. 

or  whether  some  of  them  do  not  exist  preformed  in  the  blood,  but  are  formed 
within  the  kidneys,  as  a  result  of  the  activity  of  the  renal  epithelium. 

Urea  is  formed  Outside  the  Kidney. — Urea  exists  preformed  in  the 
blood,  from  which  it  is  separated  by  the  activity  of  the  kidney.  This  is  proved 
by  the  following  considerations  :  — 

1.  The  blood  contains  one  part  of  urea  in  3000  to  5000  parts,  but  the  renal  vein  contains  less 
urea  than  the  blood  of  the  corresponthng  artery. 

2.  After  extirpation  of  the  kidneys^^  or  nephrotomy,  or  after  ligature  of  the  renal  vessels,  tbe 
amount  of  urea  accumulates  in  the  blood,  and  increases  with  the  duration  of  the  experiment  to  j|^ 
to  tJj.  At  the  same  time  there  is  vomiting  and  diarrluea,  and  the  fluids  so  voided  contain  urea  ((/. 
Bernard).     Animals  die  in  from  one  to  three  days  after  the  operation. 

3.  After  ligature  of  the  ureters,  the  secretion  of  urine  is  soon  arrested.  Urea  accumulates  in 
the  blood,  but  not  to  a  greater  extent  than  after  nephrotomy.  It  is  possible,  however,  that  the 
kidneys,  like  other  organs,  may  form  a  small  amount  of  urea,  due  to  the  metabolism  of  their  o'vn 
tissues. 

[Urea  exists  in  the  blood;  whence  does  the  blood  derive  it?  It  can  only 
obtain  it  from  one  or  more  of  several  organs — (i)  muscle,  (2)  nervous  system, 
and  (3)  glands,  of  which  the  liver  is  the  most  prominent.  This  is  best  stated  by 
the  method  of  exclusion.] 

[i.  That  urea  is  not  formed  in  muscle  is  shown,  among  other  considerations,  by  the  fact  that  cnly 
a  trace  of  urea  occurs  in  muscle  (g  293),  and  that  the  amount  is  not  increased  by  exercise.  BlDod 
which  has  been  transfused  through  a  muscle,  or  the  blood  after  circulating  in  a  muscle  during 
violent  exercise,  does  not  contain  an  increase  of  urea,  nor  does  the  addition  of  ammonia  carbonat;  to 
blood  circulating  through  muscle  show  any  increase  of  urea.  Again,  muscular  exertion  does  not  (as 
a  rule)  increase  the  amount  of  urea  in  the  urine,  as  shown  by  the  experiments  of  Kick  and  Wislicenus 
(g  294),  Parkes,  and  others.  The  excretion  chiefly  increased  Ijy  muscular  exertion  is  the  pulmonary 
Cb^  {I  127).] 

[2.  From  what  we  know  of  the  nervous  system,  it  is  not  formed  there.  We  are  therefore  forced  to 
consider  the  evidence  as  to  the  liver,  as  the  organ,  or,  at  least,  the  chief  organ  in  which  it  is  formed. 
This  evidence  is  in  some  respects  contradictory,  but  it  is  partly  experimental  and  partly  clinical. 
Although  Hoppe  Seyler  denies  the  existence  of  urea  in  the  liver,  its  existence  there  was  proved  by 
Gscheidlen;  and  Cyon,  on  passing  blood  through  an  excised  liver  by  the  " perfusion "  method  of 
Ludwig,  found  that  blood,  after  being  passed  several  times  through  the  organ,  contained  an  increased 
amount  of  urea.  The  objection  to  these  experiments  is  that  Cyon's  method  of  estimating  the  urea 
was  unreliable.  But  von  Schroeder,  using  a  similar  method,  finds  that  if  blood  be  perfused  through 
the  liver  of  a  dog  in  full  digestion,  there  is  a  great  increase  in  the  amount  of  urea,  while  there  is 
none  in  the  liver  of  a  fasting  dog.  If  ammonia  carbonate  be  added  to  the  blood,  there  is  a  very 
much  greater  amount  of  urea  in  the  blood  of  the  hepatic  vein.  This  last  fact  is  confirmed  by  Salo- 
mon. The  experiments  of  Minkowski  on  the  liver  of  the  goose  (?  386)  show  that,  when  the  liver 
is  excluded  from  the  circulation,  lactic  acid  takes  the  place  of  uric  acid  in  this  bird.  Brouardel 
further  states,  that  if  the  region  of  the  liver  be  so  beaten  as  to  cause  congestion  of  that  organ,  there 
is  an  increase  of  the  urea  in  the  urine.] 

[The  clinical  evidence  points  strongly  to  the  formation  of  urea  in  the  liver.  Parkes  pointed  out 
that  in  hepatic  abscess,  during  the  early  congestive  stage,  the  urea  in  the  urine  is  increased,  while  it 
is  diminished  in  the  suppurative  stage,  when  the  hepatic  parenchyma  is  destroyed.  The  urea  is  also 
diminished  in  cancer  of  the  liver,  phthisis,  and  some  forms  of  hepatic  cirrhosis,  while  it  is  increased 
during  hepatic  congestion,  and  specially  so  in  some  cases  of  diabetes  mellitus.  The  most  striking  fact 
of  alTis  that,  in  acute  yellow  atrophy  of  the  liver,  the  urea  is  enormously  diminished  in  the 
urine,  and  may  even  disappear  from  it  while  its  place  is  taken  by  the  intermediate  products, 
leucin  and  tyrosin  [v.  Frenchs).  \\\  poisoning  by  phosphoras,  coincident  with  the  atrophy  of  the 
liver,  there  is  a  fall  in  the  urea  excretion.  Noel  Paton  finds  that  some  drugs  which  increase  the 
quantity  of  bile  in  dogs  in  a  state  of  N-equilibrium  {\  178),  <f.^.,  sodic  salicylate  and  benzoate, 
colchicum,  mercuric  chloride  and  eunonymin  also  increase  the  urea  in  the  urine,  he  therefore 
concludes  "that  the  formation  of  urea  in  the  liver  bears  a  very  direct  relationship  to  the  secretion  of 
bile  by  that  organ."] 

As  to  the  antecedents  of  urea  there  is  the  greatest  doubt  (§  256). 

Uric  Acid  is  formed  Outside  the  Kidneys. — i.  Birds'  blood  normally  contains  uric  acid 
{Meissner).  [The  liver  of  the  pigeon  contains  6  to  14  times  as  much  uric  acid  as  the  blood.]  Liga- 
ture of  the  ureters  or  renal  blood  vessels  {Pawlinoff),  or  gradual  destruction  of  the  renal  secretory 
parenchyma  by  the  subcutaneous  injection  of  neutral  potassium  chromate  {Ebstei?i),  is  follov^ed  by 
the  deposition  of  uric  acid  in  the  joints  and  tissues,  and  it  may  even  form  a  white  incrustation  on 


PASSAGE    OF    VARIOUS    SUBSTANCES    INTO    THE    URINE.  475 

the  serous  membranes.  The  brain  remains  free  [Zalesky,  Oppler).  Acid  urates  of  ammonia,  soda, 
and  magnes'ia  are  also  similarly  deposited.  Extirpation  of  a  snake's  kidneys  gives  the  same  result, 
but  to  a  less  degree. 

[Minkowski  found  that,  after  excluding  the  liver  from  the  circulation,  lactic  acid  took  the  place 
of  uric  acid  in  the  urine  (p.  474).  Some  uric  acid  still  appears  in  the  urine,  which  cannot  be  derived 
from  the  small  amount  in  the  iDlood,  so  that,  according  to  v.  Schroeder,  there  are  perhaps  other  foci  of 
formation  of  uric  acid.] 

[The  latter  experiment  points  to  the  formation  of  uric  acid  in  the  liver  in 
birds,  and  this  is  supposed  to  be  strengthened  by  the  appearance  of  tlie  deposition 
of  urates  in  the  urine  in  certain  disorders  of  digestion.]  Von  Schroeder  and 
Colasanti,  however,  as  the  result  of  their  experiments  upon  snakes,  come  to  the 
conclusion  that  there  is  no  special  organ  concerned  in  the  formation  of  uric  acid. 

Hippuric  acid  is  partly  formed  in  the  kidney,  for  the  blood  of  herbivora  does  not  contain  a 
\xa.CG.  of  it  i^Meissner  atid  Shepard).  In  rabbits,  perhaps  it  is  formed  synthetically,  in  other  tissues 
as  well  as  in  the  kidney.  If  blood  containing  sodic  benzoate  and  glycin  be  passed  through  the 
blood  vessels  of  a  fresh  kidney,  hippuric  acid  is  formed  (|  260)  {^Bunge,  Schmiedeberg,  Kocks). 
[The  other  evidence  is  given  in  |  260.] 

Kreatinin  has  intimate  relations  to  kreatin  of  muscle,  but  where  it  is  fonned  is  not  known.  If 
phenol  and  pyrokatechin  are  digested  along  with  fresh  renal  substance,  a  compound  of  sulphuric 
acid  similar  to  that  occurring  in  urine  is  formed  {\  262).  The  latter  substance,  however,  is  also 
formed  by  similarly  digesting  liver,  pancreas,  and  muscle.  It  is  concluded  from  these  experiments 
that  these  substances  are  formed  in  the  body  within  the  kidneys  and  the  other  organs  mentioned 
{Kochs). 

Chemistry  of  the  Kidney. — The  kidneys  contain  a  very  large  amount  of  water.  Besides  serum 
albumin,  globulin,  albumin  soluble  in  sodium  carbonate  {Gottwalt),  gelatin-yielding  substances,  fat  in 
the  epithelium,  elastic  substance  derived  from  the  membrana  propria  of  the  tubules,  the  kidneys  con- 
tain leucin,  xanthin,  hypoxanthin,  kreatin,  taurin,  inosit,  cystin  (the  last  in  no  other  tissue),  but  only 
in  very  small  amount.  The  occurrence  of  these  substances  points  to  a  lively  metabolism  in  the 
kidneys,  which  is  also  proved  by  the  liberal  supply  of  blood  they  receive. 

Blood  Vessels. — The  kidneys  receive  a  very  large  supply  of  blood,  and 
during  secretion  the  blood  of  the  renal  vein  is  bright  red.  [In  the  dog,  the 
diameter  of  the  renal  artery  may  be  diminished  to  .5  mm.  without  the  amount 
of  blood  flowing  through  the  kidney  being  thereby  greatly  interfered  with. 
Hence,  within  wide  limits,  the  amount  of  blood  is  independent  of  the  size  of  the 
arterial  lumen,  and  is  therefore  dependent  on  the  blood  pressure  in  the  aorta,  and 
the  resistance  to  the  blood  current  within  and  beyond  the  kidney  (^Heidenhahi).~\ 

The  reaction  of  the  kidneys  is  acid,  even  in  those  animals  whose  urine  is  alkaline.^  Perhaps  this 
fact  is  connected  with  the  retention  of  the  albumin  in  the  vessels. 

275.    PASSAGE    OF    VARIOUS    SUBSTANCES    INTO    THE    URINE.— i.  The 

following  substances  pass  unchanged  into  the  urine  :  Sulphate,  borate,  silicate,  nitrate,  and  carbon- 
ate of  the  alkalies;  alkaline  chlorides,  bromides,  iodides;  potassium  sulphocyanide  and  ferrocyanide ; 
bile  salts,  urea,  kreatinin;  cumaric,  oxalic,  camphoric,  pyrogallic,  and  carbolic  acids,  yiz.wy  alkaloids, 
e.g.,  morphia,  strychnia,  curara,  quinine,  caffein;  pigments,  sulphindigotate  of  soda,  carmine,  mad- 
der, logwood,  coloring  matter  of  cranberries,  cherries,  rhubarb;  santonin;  lastly,  salts  of  gold,  silver, 
mercury,  antimony,  arsenic,  bismuth,  iron  (but  not  lead),  although  the  greatest  pail  of  these  is 
excreted  by  the  bile  and  the  faeces. 

2.  Inorganic  acids  reappear  in  man  and  carnivora  as  neuti'al  salts  of  ammonia,  in  herbivora,  as 
neutral  salts  of  the  alkalies. 

3.  Certain  substances  which,  when  injected  in  small  amount,  seem  to  be  decomposed  in  the 
blood,  pass  in  part  into  the  urine,  when  they  occur  in  such  large  amount  in  the  blood  that  they  can- 
not be  completely  decomposed — sugar,  hemoglobin,  egg  albumin,  alkaline  salts  of  the  vegetable 
acids,  alcohol,  chloroform. 

4.  Many  substances  appear  in  an  oxidized  form  in  the  urine — moderate  quantities  of  organic 
alkaline  salts  as  alkaline  carbonates  (fVohler),  uric  acid  in  part  as  allantoin  i^Salkowski),  sulphides 
and  sulphites  of  soda,  in  part  as  sodium  sulphate,  potassium  sulphide  as  potassium  sulphate,  some 
oxyduls  as  oxides,  benzol  as  phenol  iyNaumyn  and  Schulzen). 

5.  Those  bodies  which  are  completely  decomposed,  as  glycerin,  resins,  give  rise  to  no  special  deriva- 
tives in  the  urine. 

6.  Many  substances  combine  and  appear  as  conjugated  compounds  in  the  urine,  e.  g.,  the  origin 
of  the  hippuric  acid*  by  conjugation  (|  260),  the  conjugation  of  sulphonic  acid  (§  262),  and  the  forma- 
tion of  urea  by  synthesis  from  carbamic  acid   and  ammonia  [Drechsel)  (§  256).     After  the  use  of 


476  INFLUENCE    OF    NERVES    AND    OTHER    CONDITIONS. 

camphor,  chloral,  or  butylchloral,  a  conjugated  compound  with  glycuronic  acid  (an  acid  nearly 
related  to  sugar)  appears  in  the  urine.  Taurin  and  sarcosin  unite  with  sulphaminic  acid.  When 
bromo]ihcnol  is  given,  it  unites  with  mercapturic  acid,  a  iiody  nearly  related  to  cystin  (<!  268). 

7.  Tannic  acid,  Cj^HjuO;,,  takes  up  Il./J,  and  is  decomposed  into  two  molecules  of  gallic  acid  = 
2  (C,Hs()5). 

8.  The  iodates  of  potash  and  soda  are  reduced  to  iodides;  malic  acid  (C^HgOj)  partly  to 
succinic  acid  (C^Hg04) ;  indigo-blue  (CigHjoN^O^)  takes  up  hydrogen  and  becomes  indigo-white 
(C,sH,,N.,().,). 

9.  Some  substances  do  not  pass  into  the  urine  at  all.  e.^^,,  oils,  insoluble  metallic  salts  and  metals. 

276.  INFLUENCE  OF  NERVES  AND  OTHER  CONDITIONS.— 

At  present  we  are  acHjuainted  merely  with  the  influence  of  the  vasomotor  nerves 
on  the  filtration  of  the  tirine  through  the  renal  vessels.  £ac/i  kidney  seems  to  be 
stipplied  with  vasomotor  nerves,  which  spring  from  //o/Zi  halves  of  the  spinal  cord 
{Nicoiaiiies).  As  a  general  rule,  dilatation  of  the  branches  of  the  renal  artery, 
chiefly  the  vasa  afferentia,  must  raise  the  pressure  within  the  glomeruli,  and  thus 
increase  the  amount  of  water  filtered  through  them.  The  more  the  dilatation  is 
confined  to  the  area  of  the  renal  artery  alone,  the  greater  is  the  amoiuit  of  the 
urine.  [As  yet  we  know  the  nervous  system  influences  the  secretion  of  urine  only 
in  so  far  as  it  modifies  the  pressure  and  velocity  of  the  blood  current  in  the 
kidney.  We  have  no  satisfactory  evidence  of  the  existence  of  direct  secretory 
nerves  in  the  kidney.] 

I.'  Renal  Plexus  and  its  Centre. — Section  of  the  nerves  of  the  renal  plexus 
— the  nerves  around  the  renal  artery — generally  causes  a  considerable  increase  in 
the  secretion  of  urine,  hydruria  or  polyuria  ;  sometimes,  on  account  of  the  great 
rise  of  the  pressure  within  the  glomeruli,  albumin  passes  into  the  urine,  and  there 
may  be  rupture  of  the  vessels  of  the  glomeruli,  leading  to  the  passage  of  blood  into 
the  urine.  The  nerve  centre  for  the  renal  nerves  lies  in  the  floor  of  the  fourth 
ventricle,  in  front  of  the  origin  of  the  vagus.  Injury  to  this  part  of  the  floor  of  the 
fourth  ventricle,  e.  g.,  by  puncture  (piqure),  may  increase  the  amount  of  urine 
(diabetes  insipidus),  which  is  sometimes  accompanied  by  the  simultaneous  appear- 
ance of  albumin  and  blood  in  the  urine  {CI.  Bernard).  Section  of  the  parts  which 
lie  directly  in  the  course  of  these  fibres,  as  they  pass  from  their  centre  to  the  kidney, 
produces  the  same  effects.  Close  to  this  centre  in  the  medulla,  lies  the  centre  for 
the  vasomotor  nerves  of  the  liver,  whose  injury  causes  diabetes  mellitus  (§  175). 
Eckhard  found  that  stimulation  of  the  vermiform  process  of  the  cerebellum  pro- 
duced hydruria.  In  man,  stimulation  of  these  parts  by  tumors  or  inflammation, 
etc.,  produces  similar  results. 

2.  Paralysis  of  Limited  Vascular  Areas. — If,  simultaneously  with  the 
paralysis  of  the  nerves  of  the  renal  artery,  the  nerves  of  a  neighboring  large  vascu- 
lar area  be  paralyzed,  necessarily  the  blood  pressure  in  the  renal  artery  area  will  not 
be  so  high,  as  more  blood  flows  into  the  other  paralyzed  provmce.  Under  these 
circumstances,  there  may  be  only  a  temporary,  or,  indeed,  no  increase  of  urine, 
provided  the  paralyzed  area  be  sufficiently  large.  There  is  a  moderate  increase  of 
urine  for  several  hours  after  section  of  the  splanchnic  nerve.  This  nerve  con- 
tains the  renal  vasomotor  nerves  (which,  in  part,  at  least,  leave  the  spinal  cord  at 
the  first  dorsal  nerve  and  pass  into  the  sympathetic  nerve),  but  it  also  contains  the 
vasomotor  nerves  for  the  large  area  of  the  intestinal  and  abdominal  viscera.  Stimu- 
lation of  this  nerve  has  the  opposite  effect  {CI.  Bernard,  Eckhara).  [The  polyuria 
thus  produced  is  not  so  great  as  after  section  of  the  renal  nerves,  because  the 
si)lanchnic  supplies  such  a  large  vascular  area,  that  much  blood  accumulates  in  that 
area,  and  also  because  all  the  renal  nerves  do  not  run  in  the  splanchnics.] 

3.  Paralysis  of  Large  Areas. — If,  simultaneously  with  paralysis  of  the  renal 
nerves,  the  great  majority  of  the  vasomotor  nerves  of  the  body  be  paralyzed  [as  by 
section  of  the  medulla  oblongata],  then,  owing  to  the  great  dilatation  of  all  these 
vessels,  the  blood  pressure  falls  at  once  throughout  the  arterial  system.  The  result 
of  this  may  be,  provided  the  pressure  is  sufificiently  low,  that  there  is  a  great  decrease, 


KENAL  ONCOGRAPH  AND  ONCOMETER. 


477 


or,  it  may  be,  entire  cessation  of  the  secretion  of  urine.  The  secretion  is  arrested 
when  the  cervical  cord  is  completely  divided,  down  even  as  far  as  the  seventh  cervi- 
cal vertebra  (^Eckhard').  The  polyuria  caused  by  injury  to  the  floor  of  the  fourth 
ventricle  at  once  disappears  when  the  spinal  cord  (even  down  to  the  twelfth  dorsal 
nerve)  is  divided. 

[4.  Other  Conditions. — As  already  stated,  section  of  the  renal  nerves  is  fol- 
lowed by  polyuria,  owing  to  the  increased  pressure  in  the  glomeruli,  but  this 
polyuria  may  be  increased  by  stimulating  the  spinal  cord  below  the  medulla 
oblongata,  because  the  contraction  of  the  blood  vessels  throughout  the  body  still 
further  raises  the  blood  pressure  within  the  glomeruli.  If,  however,  the  spinal 
cord  be  divided  below  the  medulla  oblongata — the  renal  nerve  being  also  divided 
— the  polyuria  ceases,  because  of  the  fall  of  the  general  blood  pressure  thereby 
produced.  Division  of  the  spinal  cord  in  the  dorsal  region  also  diminishes  or 
arrests  the  secretion  of  urine,  owing  to  the  fall  of  the  blood  pressure ;  but  animals 
recover  from  this  operation,  the  general  blood-pressure  rises,  and  with  it  the 
secretion  of  urine.  Stimulation  of  the  cord  below  the  medulla  arrests  the  secre- 
tion, as  it  causes  contraction  of  the  renal  arteries  along  with  the  other  arteries  of 
the  body.] 

[Volume  of  the  Kidney — Oncometer. — By  means  of  the  plethysmograph" 
(§  loi)  we  can  measure  the  variations  in  the  size  of  a  limb,  while  by  the  oncograph 


Fig.  286. — Oncometer.     K,  kidney;  the   thick  line  is  the  metallic  capsule ;  h,   hiiige;   I,  tube   for  filling  apparatus  ; 

T,  tube  to  connect  with  Ti  ;  a,  v,  u,  artery,  vein,  ureter  {Stirling,  after  Roy). 
Fig.  287.— Oncograph.     C,  ichamber  filled   with  oil,   communicating  by  Ti  with  T  ;    /,  piston  ;  /,  writing  lever 

(Stirling,  after  Roy). 

(oyxo?,  volume)  similar  variations  in  the  volume  of  the  spleen  are  measured  (§  103). 
Roy  and  Cohnheim  have  measured  the  variations  in  the  volume  of  the  kidney  by 
means  of  an  instrument  which  consists  of  two  parts,  one  termed  the  oncometer 
or  renal  plethysmometer,  in  which  the  organ  is  enclosed,  while  the  other  part 
is  the  registering  portion,  or  oncograph.  The  kidney  is  enclosed  in  a  kidney- 
shaped  metallic  capsule  (Fig.  286),  composed  of  two  halves  which  move  on  the 
hinge,  h,  to  introduce  the  organ.  The  renal  vessels  pass  out  at  a,  v.  The  kidney 
is  surrounded  with  a  thin  membrane,  and  between  this  membrane  and  the  inner 
surface  of  the  capsule  is  a  space  filled  with  warm  oil  through  the  tube,  I,  which  is 
closed  by  means  of  a  stop-cock  after  the  space  is  filled  with  oil.  The  tube,  T,  can 
be  made  to  communicate  with  another  tube,  Tj,  leading  into  a  metallic  chamber, 
C,  of  the  oncograph  (Fig.  287),  which  is  provided  with  a  movable  piston,  p, 
attached  by  a  thread  to  the  writing-lever,  /.  Any  increase  in  the  size  of  the  organ 
expels  oil  from  the  chamber,  O,  into  QI ,  and  thus  the  piston  is  raised,  while  a  dimi- 
nution in  the  size  of  the  kidney  diminishes  the  fluid  in  C,  and  the  lever  falls.  The 
actual  volume  of  the  living  kidney  depends  upon    the  state  of  distention  of  its 


478  EXPERIMENTS    WITH    THE    ONCOMETER. 

Structural  elements,  upon  the  amount  of  lymph  in  its  lymph  spaces,  but  chiefly  upon 
the  amount  of  blood  in  its  blood  vessels,  and  this  again  must  depend  ujjon  the 
condition  of  the  non-striped  muscles  in  the  renal  arteries.  When  the  vessels  dilate, 
the  kidnev  increases  in  size,  and  when  they  contract  it  contracts,  so  that  we  can 
register  on  the  same  revolving  cylinder  the  variations  of  the  volume  at  the  same  time 
that  we  record  the  general  arterial  blood  pressure.] 

[In  the  normal  circulation  through  the  kidney,  the  kidney  curve,  /.  <?.,  the 
curve  of  the  volume  of  the  kidney,  runs  parallel  with  the  blood-pressure  curve,  and 
shows  the  large  respiratory  undulations,  as  well  as  the  smaller  elevations  due  to  the 
systole  of  the  heart  (Fig.  2S8).  Usually,  when  the  blood  pressure  falls,  the  kidney 
curve  sinks,  and  when  the  blood  pressure  rises  the  volume  of  the  kidney  increases. 
When  the  blood-pressure  curve  is  complicated  by  Traube-Hering  waves  (§  85)  the 
opposite  effect  is  produced  on  the  kidney  cur\e  ;  the  highest  blood  pressure  corre- 
sponds to  the  smallest  size  of  the  kidne}-,  and  conversely.  This  is  due  to  the  fact 
that,  when  these  curves  occur,  all  the  small  arterioles,  including  those  in  the  kidney, 
are  contracted.  A  kidney  placed  in  an  oncometer  secretes  urine  like  a  kidney  under 
natural  conditions.] 

[Arrest  of  the  respiration  in  a  curarized  animal  produces  a  rapid  and  great 
diminution  of  the  volume  of  the  kidney,  caused  by  the  venous  blood  stimulating  the 
vasomotor  centres,  and  thus  contracting  the  small  arterioles,  including  those  of  the 

Fig.  288. 
B.  P 


B.  P.,  Blood-pressure  curve;    K.,  curve  of  the  volume  of  the  kidney;    T,  time  curve,  intervals  indicate  a  quarter  of 
a  minute  ;  A,  abscissa  (Stirling,  after  Roy). 

kidney.  This  result  occurs  whether  one  or  both  splanchnics  are  divided,  proving 
that  all  the  vasomotor  nerves  of  the  kidney  do  not  reach  it  through  the  splanchnics. 
When  all  the  renal  nerves  at  the  hilum  are  divided,  arrest  of  the  respiration  causes 
dilatation  of  the  organ,  which  condition  runs  parallel  with  the  rise  of  the  blood 
l)ressure.  Stimulation  of  a  sensory  nerve,  e.  g.,  the  central  end  of  the  sciatic  nerve, 
while  causing  an  increase  of  the  blood  pressure,  makes  the  kidney  shrink.] 

[In  poisoning  with  strychnin,  the  kidney  shrinks  while  the  blood  pressure  rises. 
Stimulation  of  the  central  or  j^eripheral  end  of  the  splanchnics,  divided  at  the 
diaphragm,  causes  contraction  of  the  renal  vessels  o{  both  sides;  the  former  is  a  re- 
flex, the  latter  a  direct  effect.  Stimulation  of  the  peripheral  end  of  one  si^lanchnic 
sometimes  affects  both  kidneys.  Stimulation  of  the  peripheral  end  of  the  renal 
nerves  always  causes  a  diminution  in  the  volume  of  the  kidney,  so  that  Cohnheim  and 
Roy  inferred  that,  although  there  was  evidence  of  the  existence  of  vasomotor  and 
sensory  nerves  to  the  kidney,  they  found  none  of  vaso-dilators.  Each  kidney 
acts  independently  of  the  other.  Sudden  compression  of  one  renal  artery  has  not 
the  slightest  effect  upon  the  blood  current  of  the  other  kidney.  If  a  kidney  be  ex- 
posed in  an  animal,  by  making  an  incision  in  the  lumbar  region,  on  stimulating  the 
medulla  oblongata  directly  with  electricity,  we  may  observe  the  kidney  itself  becom- 
ing paler,  the  pallor  appearing  in  a  great  many  small  spots  on  the  surface  of  the  organ, 
corresponding  to  the  distribution  of  the  interlobular  arteries.] 

[Cohnheim  showed  that  the  composition  of  the  blood  has  a  remarkable  effect 


UR/EMIA   AND    AMMONI^MIA.  479 

on  the  renal  circulation.  Some  substances  (water  and  urea  ),  when  injected  into  the 
blood,  cause  the  kidney  first  to  shrink  and  then  to  expand,  while  sodic  acetate  dilates 
the  kidney,  even  after  all  the  renal  nerves  are  divided — an  operation  which  is  very 
difficult  indeed.  Provided  all  the  renal  nerves  be  divided,  these  effects  would  indi- 
cate the  existence  of  some  local  intra-renal  vasomotor  mechanism  governing  the  renal 
blood  vessels.  The  general  blood  pressure  is  not  thereby  modified  ;  nor  need  we 
wonder  at  this,  as  ligature  of  one  renal  artery  does  not  increase  the  pressure  in  the 
aorta.] 

[The  reciprocal  relation  between  the  skin  and  the  kidneys  is  known  to  every 
one.  On  a  cold  day,  when  the  skin  is  pallid,  owing  to  contraction  of  the  cutaneous 
vessels,  the  amount  of  urine  secreted  is  great,  and  conversely,  in  summer  less  urine  is 
passed  than  in  winter.  Washing  the  skin  of  a  dog  for  two  minutes  with  ice-cold 
water  causes  a  great  contraction  of  the  kidney.] 

The  perfusion  of  blood  through  a  living  excised  kidney  is  materially 
influenced  by  the  substances  mixed  with  the  blood  perfused.  This  effect  may  in 
part  be  due  to  the  action  of  these  chemical  ingredients  upon  the  nuclei  of  the  endo- 
thelial lining  of  the  blood  vessels,  especially  the  capillaries,  or  the  effects  upon  the 
muscular  fibres  of  the  blood  vessels. 

[Strychnin  seems  to  cause  contraction  of  the  renal  vessels,  independently  of  its  action  on  the 
general  vasomotor  centre.  Brunton  and  Power  found  that  digitalis  caused  an  increase  of  the 
blood  pressure  (dog),  but  the  secretion  of  urine  was  either  at  the  same  time  diminished,  or  it  ceased 
altogether.  The  latter  result  was  due  to  contraction  of  the  renal  blood  vessels,  but  when  the  aortic 
blood  pressure  began  to  fall,  the  amount  of  urin?  secreted  rose  much  above  normal,  i.  e.,  when  the 
arteries  had  begun  to  relax.] 

During  fever,  the  renal  vessels  are  probably  contracted  in  consequence  of  the  stimulation  of  the 
renal  centre  by  the  abnormally  warm  blood  [Mendehon). 

The  repeated  respiration  of  CO  is  said  to  produce  polyuria,  perhaps  in  consequence  of  paralysis  of 
the  renal  vasomotor  centre. 

Action  of  the  Vagus. — According  to  CI.  Bernard,  stimulation  of  the  vagus  at  the  cardia  in- 
creases the  luinary  secretion,  while  at  the  same  time  the  blood  of  the  renal  vein  becomes  red.  This 
nerve  may  contain  vaso-dilator  nerve  fibres  corresponding  to  the  fibres  in  the  facial  nerve  for  the 
sahvary  glands  (|  145)- 

277.  URiEMIA — AMMONIiiEMIA. — Symptoms  of  Uraemia. — After  excision  of  the 
kidneys,  nephrotomy,  or  ligature  of  the  ureter ;  in  man,  also,  as  a  result  of  certain  diseased  con- 
ditions of  the  kidney,  leading  to  the  suppression  of  the  secretion  of  urine,  there  is  developed  a  series  of 
characteristic  symptoms  which  are  followed  by  death.  The  condition  is  called  urcemic  intoxication  or 
urcemia.  There  are  marked  cerebral  phenomena,  drowsiness,  and  deep  coma,  and  occasionally  local 
or  more  general  spas?ns.  Sometimes  there  is  delirium  ;  Cheyne-Stokes  phenomenon  is  often  observed 
{I  III,  II),  and  there  may  be  vomiting  and  diarrhoea,  while  in  the  fluids  voided,  as  well  as  in  the 
expired  air,  ammonia  may  sometimes  be  detected. 

The  cause  of  these  phenomena  has  been  ascribed  to  the  retention  in  the  blood  of  those  substances 
which  normally  are  excreted  by  the  urine,  but  as  yet  it  has  not  been  definitely  ascertained  which  of 
these  substances  cause  the  phenomena  : — 

1.  The  first  thought  is  to  ascribe  them  to  the  retention  of  the  urea.  v.  Voit  found  that  dogs  ex- 
hibited ur^emic  symptoms  if  they  were  fed  for  a  long  time  on  food  containing  urea  and  little  water. 
Meissner  found  that  in  nephrotomized  animals,  the  uraemic  symptoms  were  hastened  by  the  injection  of 
urea  into  the  blood.  The  injection  of  a  m.oderate  amount  of  urea  in  perfectly  healthy  animals  is  not 
followed  by  urremic  symptoms,  probably  because  the  urea  is  rapidly  excreted  by  the  kidneys ;  i  to  2 
grms.  [15  10  30  grains]  so  injected  produce  comatose  symptoms  in  rabbits. 

2.  The  injection  of  ammonium  carbonate  produces  symptoms  resembling  those  of  ursemia,  so 
that  V.  Frerichs  thought  that  the  urea  was  decomposed  in  the  blood,  yielding  ammonium 
carbonate — ammoniaemia.  Demjankow  observed  ursemic  phenomena  after  nephrotomy,  if  at  the 
time  he  injected  urea  ferment  into  the  blood  (|  263).  Feltz  and  Ritter  obtained  urzemic  symptoms  in 
dogs  by  injecting  salts  of  ammonia. 

3.  As  ligature  of  the  ureters  produces  a  comatose  condition  in  those  animals  which  excrete  chiefly 
uric  acid  in  the  luine — e.g.,  birds  and  snakes  [Zalesky) — it  is  possible  that  other  substances  may  pro- 
duce the  poisonous  symptoms.  The  injection  ofkreatinin  causes  feebleness  and  contraction  of  the 
muscles  in  dogs  {^Meissner).  Bernard,  Traube,  and  more  recently  Feltz  and  Ritter,  ascribe  the  syrap- 
toms  to  an  accumulation  of  the  neutral  potassium  salts  in  the  blood  {|  54).  The  injection  of  kreatin, 
succinic  acid  [Meissner),  mic  acid,  and  sodic  lu-ate  {Ranke),  is  without  effect.  Schottin  and  Oppler 
ascribe  the  results  to  an  accumulation  of  normal  or  abnormal  extractives.     It  is  possible  that  several 


480 


STRUCTURE    AND    FUNCTIONS    OF   THE    URETER. 


substances  and  their  decomposition  products  contribute  to  produce  the  result,  so  that  there  is  a  com- 
bined action  of  several  factors,  but  perhaps  the  retention  of  the  potash  salts  plays  the  most  important 
part. 

The  direct  application  of  some  ordinary  substances  (kreatinin,  kreatin,  acid  potassic  phosphate,  urates) 
to  the  surface  of  the  cerebrum  causes  all  the  symptoms  of  untmia.  Urea  is  inactive,  and  slightly  active 
are  ammonium  and  sodic  carl)onate,  leucin,  NaCl,  KCl  (Landois). 

[Alkaloids  in  Urine. —  Human  urine,  and  especially  febrile  urine,  when  injected  under  the  skin 
of  frogs  or  rabbits,  acts  as  a  jx)ison,  and  even  causes  death,  by  arresting  the  respiration.  The  alkaloids 
seem  to  be  formed  by  the  action  of  vegetable  organisms  in  the  intestine,  whence  they  arc  absorbed  into 
the  blood  and  pass  into  the  urine  (<!  Il6).  Urine  rendered  colorless  by  charcoal  loses  half  its  toxic 
power,  and  the  poisonous  substance  is  not  volatile,  and  even  resists  Ixjiling.  These  alkaloids  are 
increased  in  the  urine  in  typhoid  fever,  pneumonia,  but  not  in  diabetes.] 

Ammoniaemia. — When  urine  undergoes  the  alkaline  fermentation  within  the  bladder,  and 
ammonium  carbonate  is  formed,  the  ammonia  may  be  absorbed  and  produce  this  condition. 
The  breath  and  excretions  smell  strongly  of  ammonia ;  the  mouth,  pharynx,  and  .skin  are  very 
dry;  there  is  vomiting,  with  <liaiTh<ea  or  constipation,  while  ulcers  may  form  in  the  intestine. 
The  patient  rapidly  loses  fle.sh,  and  death  occurs  without  any  disturbance  of  the  mental  faculties. 

Uric  Acid  Diathesis. — NN'hen  too  much  nitrogenous  food,  too  much  of  any  alcoholic  fluid,  is  per- 
sistently used,  and  little  muscular  exercise  taken,  esiiecially  if  the  respirator)' organs  are  interfered  with, 
uric  acid  may  not  unfrequently  accumulate  in  the  blood  {Garrod).  It  may  be  deposited  in  the  joints 
and  their  ligaments,  especially  in  the  foot  and  hand,  giving  rise  to  painful  inflammation,  and  forming 
gout  stones  or  chalk  stones.  The  heart,  liver  and  kidneys  are  rarely  affected.  The  tissues  near  these 
deposits  undergo  necrosis. 

278.  STRUCTURE  AND  FUNCTIONS  OF  THE  URETER.  —  Mucous  Mem- 
brane.— The  pelvis  of  the  kidney  and  the  ureter  are  lined  by  a  mucous  membrane,  consisting  of  con- 
nective tissue,  and  covered  with   .several  layers  of  stratified  "transitional"  epithelium  (Fig.  290). 

Fig.  289. 


r-^.v 


'^  •s^-  ■*» 


Transverse  section  of  the  lower  part  of  human  ureter,  X  iS-     ^,  epithelium  ;  t,  tunica  propria  ;  s,  sub-mucosa  ;  /  and 

r,  longitudinal  and  circular  fibres. 


The  cells  are  of  various  shapes,  those  of  the  lowest  layer  being  usually  more  or  less  spherical  and 
small,  while  many  of  the  cells  in  the  upper  layers  are  irregular  in  shape,  often  with  long  processes 
passing  into  the  deeper  layers. 

Sub-mucosa. — Under  the  epithelium  there  is  a  layer  of  adenoid  tissue  [Hamburger,  Ckiari), 
which  may  contain  small  lymph  follicles  [embedded  in  loose  connective  tissue].  In  the  pelvis  of  the 
kidney  and  ureter  there  are  a  few  small  mucous  glands  lined  by  a  single  layer  of  columnar  epithelium 
[Unruh,  Egli). 

The  muscular  coat  consists  of  an  inner  somewhat  stronger  layer  of  longitudinal  non-striped 
fibres,  and  an  outer  circular  layer  (Fig.  289).  In  the  lowest  third  of  the  ureter  there  are  in  addition  a 
niunber  of  scattered  muscular  fibres.  All  these  layers  are  surrounded  and  supported  by  connective 
tissue.     The  outer  layers  of  the  connective  tissue  form  an  outer  coat  or  adventitia,  which  contains  the 


MOVEMENT   OF   THE    URINE. 


481 


large  vessels  and  nerves.  The  various  coats  of  the  ureter  can  be  followed  up  to  the  pelvis  of  the  kid- 
ney, and  to  its  caUces.  The  papillae  are  covered  only  by  the  mucous  membrane,  while  the  muscular 
layer  ceases  at  the  apex  of  the  pyramids,  where  they  are  disposed  circularly,  to  form  a  kind  of  sphincter 
muscle  for  each  papilla  [Jlenle). 

The  blood  vessels  supply  the  various  coats,  and  form  a  capillary  plexus  under  the  epithelium. 
The  nerves  are  not  veiy  numerous,  but  they  contain  medullated  (few)  and  non-meduUated  fibres, 
with  numerous  ganglia  scattered  in  their  course.  They  are  partly  motor,  and  supply  the  muscular 
layers,  and  some  pass  toward  the  epithelium,  and  are  sensory  and  excito-rejlex  in  function.  These 
nerves  are  excited  when  a  calculus  passes  along  the  ureter,  and  thus  give  rise  to  severe  pain.  The 
ureter  perforates  the  wall  of  the  bladder  obliquely.  The  inner  opening  is  a  narrow  slip  in  the 
mucous  membrane,  directed  downward  and  inward,  and  provided  with  a  pointed,  valve-like  process 
(Fig.  291). 

Movement  of  the  Urine.  —  The  urine  is  propelled  along  the  ureter  thus : 
(i)  The  secretion,   which  is  continually  being 

formed   under    a    high    pressure   in    the    kid-  ^'^'^-  ^9°- 

ney,  propels   the  urine   onward  in  front  of  it 
as  the  urnie  is  under  a  low  pressure  in  the  ureter 
(2)   Gravity  aids  the  passage  of  the  urine  when  K&'^it. 
the   person    is   in  the   erect  posture.     (3)  Tlie 
muscles  of  the  ureter  contract  rhythmically  and 
peristaltically,  and  so  propel  it  toward  the  blad- 
der.    This  movement  is  reflex,  and  is  due  to  the 
presence  of  the  urine  in  the  ureter.    Every  three- 
quarters  of  a  minute  several  drops  of  urine  pass 
into  the  bladder.     But  the  fibres  may  also  be 
excited  directly.     The  contraction  passes  along 
the  tube  at  the  rate  of  20  to  30  mm.  per  second, 
always  from  above  downward.     The  greater  the 
tension  of  the  ureter  due  to  the  urine,  the  more 

rapid  is  the  peristaltic  movement.  Transitional  epithelium  from  the  bladder.     Many 

r  r  of  tjie  large  cells  lie  upon  the  summit  of  the 

columnar  and  caudate  cells,  and  depressions 
Local    Stimulation. — On   applying   a  stimulus  to  the  are  seen  on  their  under  surface, 

ureter  dii^ectly,  the  contraction  passes  both  upward  and 

downward.  Engelmann  observed  that  the  movements  occur  in  parts  of  the  ureter  where  neither 
nerves  nor  ganglia  were  to  be  found,  and  he  concluded  that  the  movement  was  propagated  by 
"  muscular  conduction."  If  this  be  so,  then  an  impulse  may  be  propagated  from  one  non-striped 
muscular  cell  to  another  without  the  intervention  of  nerves  (see  Heart,  \  58,  I,  3). 

Prevention  of  Reflux. — The  urine  is  prevented  from  exerting  a  backward 
pressure  toward  the  kidneys:  (i)  The  urine  which  collects  in  the  pelvis  of  the  kid- 
ney is  under  a  high  pressure,  and  thus  tends  uniformly  to  compress  the  pyramids, 
so  that  the  urine  cannot  pass  into  the  minute  orifices  of  the  urinary  tubules. 
(2)  When  there  is  a  considerable  accumulation  of  urine  in  a  ureter,  e.  g.,  from  the 
presence  of  an  impacted  calculus  or  other  cause,  there  is  also  more  energetic 
peristalsis,  and,  at  the  same  time,  the  circular  muscular  fibres  round  the  apices  of 
pyramids  compress  the  pyramids  and  prevent  the  reflux  of  urine  through  the 
collecting  tubules.  The  urine  is  prevented  from  passing  back  from  the  bladder 
into  the  ureter,  the  wall  of  the  bladder  itself,  and  the  part  of  the  ureter  which 
passes  through  it,  are  compressed,  so  that  the  edges  of  the  slit-like  opening  of  the 
ureter  are  rendered  more  tense,  and  are  thus  approximated  toward  each  other  (Fig. 
291). 

.  279.  URINARY  BLADDER  AND  URETHRA.— Structure.— The  mucous  mem- 
brane of  the  bladder  resembles  that  of  the  ureter;  the  upper  layers  of  the  stratified  transitional 
epithelium  are  flattened.  It  is  obvious  that  the  form  of  the  cells  must  vary  with  the  state  of  distention 
or  contraction  of  the  bladder.  [The  mucous  membrane  and  muscular  coats  are  thicker  than  in  the 
ureter.  There  are  mucous  glands  in  the  mucous  membrane,  especially  near  the  neck  of  the  bladder.] 
Sub-mucous  Coat. — There  is  a  layer  of  delicate  fibrillar  connective  tissue  mixed  with  elastic 
fibres  between  the  mucous  and  muscular  layers. 

31 


482 


URINARY    BIADDER    AND    URETHRA. 


[The  serous  coat  is  continuous  with  and  has  the  same  structure  as  the  peritoneum,  and  it  covers 
only  the  posterior  and  upjier  half  of  the  organ.] 

Musculature. — The  non-striped  nuiscular  til)res  are  arranged  in  bvnidles  in  several  layers,  an 
external  hn^ittidina/  layer,  best  develojied  on  the  anterior  and  posterior  surfaces,  and  an  inner 
circular  layer.  [Between  these  two  is  an  ol'lii/ue  layer.]  There  are  other  bundles  of  niuscular 
fibres  arranged  in  different  directions.  Physiologically,  the  musculature  of  the  bladder  represents 
a  single  or  common  hollow  muscle,  whose  function  when  it  contracts  is  to  diminish  uniformly  the 
size  of  the  bladder,  and  thus  to  expel  its  contents  (^  306). 

The  blood  vessels  resemble  those  of  the  ureter.  The  nerves  form  a  jilexus,  and  are  placed  partly 
in  the  mucous  membrane  and  partly  in  the  muscular  coat,  anil,  like  all  the  extra-renal  parts  of  the 
urinary  apparatus,  are  provided  with  ganglia,  lying  in  the  muco'^a,  sub-mucosa,  and  connected  to 
each  other  by  fibres  {A/iiier).  (langlia  occur  in  the  course  of  the  motor  nerve  filires  in  the  bladder 
(IV.  Wolff).  Their  functions  are  motor,  sensory,  excito-motor,  and  vasomotor.  [Sympa- 
thetic nerve  ganglia  also  exist  underneath  the  serous  coat  (/^  Dttr~uin).'\ 

A  too  minute  dissection  of  the  several  layers  and  bundles  of  the  musculature  of  the  bladder  has 
given  rise  to  erroneous  inferences.  Thus,  we  speak  of  a  detrusor  urinae,  which,  however,  consists 
chiefly  of  fibres  running  on  the  anterior  and  jwsterior  surfaces,  from  the  vertex  to  the  fundus.  There 
does  not  seem  to  be  a  special  sphincter  vesicae  internus  ;  it  is  merely  a  thicker  circular  (6  to  12 
mm.)  layer  of  non-striped  muscle  which  surrounds  the  beginning  of  the  urethra,  and  which,  from  its 
shape,  helps  to  form  the  funnel-like  exit   of  the  bladder.     Numerous   muscular  bundles,  connected 


Fu;.  291. 


Lower  part  of  the  human  bladder  laid  open,  showing  clear  part,  or  trigone,  the  slit-like  openings  of  the  ureters,  the 
divided  ureters,  and  vesicula;  seminales  ;  the  sinus  prostaticus,  and  on  each  side  of  it  the  openings  of  the  ejacu- 
latory  ducts,  and  below  both  numerous  small  apertures  of  the  prostate  ducts. 

partly  with  the  longitudinal  and  partly  with  the  circular  fibres  of  the  bladder,  exist,  especially  in  the 
trigone,  between  the  orifice  of  the  ureters. 

In  the  female,  the  urethra  serves  merely  for  the  passage  of  urine.  The  mucous  membrane  consists 
of  connective  tissue  with  many  ela.stic  fibres,  and  provided  with  papill?e.  It  is  covered  by  stratified 
epithelium  and  contains  several  mucous  glands  [Littre).  Outside  this  is  a  layer  of  longitudinal, 
smooth,  muscular  fibres,  and  outside  this  again  a  layer  of  circular  fibres.  Many  elastic  fibres  exist  in 
all  the  layers,  which  are  traversed  by  numerous  wide  venous  channels. 

The  proper  sphincter  urethrae  is  a  transversely  striped  muscle  subject  to  the 
will,  and  consists  of  completely  circtilar  fibres  which  extend  downward  as  far  as  the 
middle  of  the  urethra,  and  partly  of  longitudinal  fibres,  which  extend  only  on 
the  posterior  surface  toward  the  base  of  the  bladder,  where  they  become  lost  between 
the  fibres  of  the  circular  layer. 

In  the  male  urethra,  the  epithelium  of  the  prostatic  part  is  the  same  as  that  in  the  bladder ;  in 
the  membranous  portion  it  is  stratified,  and  in  the  cavernous  part  the  .simple  cylindrical  form.  The 
mucous  membrane,  under  the  epithelium  itself,  is  beset  with  papilUe,  chiefly  in  the  posterior  part  of 
the  urethra,  and  contains  the  mucous  glands  of  Littre. 

Non-striped  muscle  occurs  in  the  prostatic  part  arranged  longitudinally,  chiefly  at  the  coUiculus 


ACCUMULATION    OF    URINE MICTURITION.  483 

seminalis ;  in  the  membranous  portion  the  direction  of  the  fibres  is  chiefly  circular,  with  a  few  longi- 
tudinal fibres  intercalated  ;  the  cavernous  part  has  a  few  circular  fibres  posteriorly,  but  anteriorly  the 
muscular  fibres  are  single  and  placed  obliquely  and  longitudinally. 

Closure  of  the  Bladder. — The  so-called  internal  vesical  sphincter  of  the 
anatomists,  which  consists  of  non-striped  muscle,  is  in  reality  an  integral  part  of 
the  muscular  coat  of  the  bladder  and  surrounds  the  orifice  of  the  urethra  as  far  down 
as  the  prostatic  portion,  just  above  the  coUiculus  seminalis.  It  is,  however,  not  the 
sphincter  muscle.  The  proper  sphincter  urethrse  (sph.  vesicae  externus)  lies 
below  the  latter.  It  is  a  completely  circular  muscle  disposed  around  the  urethra, 
close  above  the  entrance  of  the  urethra  into  the  septum  urogenitale  at  the  apex  of 
the  prostate,  where  it  exchanges  fibres  with  the  deep  transverse  muscle  of  the  peri- 
neum which  lies  under  it. 

Some  longitudinal  fibres,  which  run  along  the  upper  margin  of  the  prostate  from  the  bladder,  belong 
to  this  sphincter  muscle.  Single  transverse  bundles  passing  forward  from  the  surface  of  the  neck  of 
the  bladder,  the  transverse  bands  which  lie  within  the  prostate,  the  apex  of  the  colliculus  seminalis, 
and  a  strong  transverse  bundle  passing  in  front  of  the  origin  of  the  urethra  into  the  substance  of  the 
prostate — all  belong  to  the  sphincter  muscle  {/len/e).  In  the  male  urethra,  the  blood  vessels  ioxTn 
a.  rich  capillary  plexus  under  the  epithelium,  below  which  is  a  wide-meshed  lymphatic  plexus. 

[Tonus  of  Sphincter  Urethrae. — Open  the  abdomen  of  a  rabbit,  ligature  one  ureter,  tie  a  cannula 
in  the  other,  and  pour  water  into  the  bladder  until  it  runs  out  through  the  urethra,  which  is  usually 
under  a  pressure  of  i6  to  20  inches.  If  the  spinal  cord  be  divided  between  the  fifth  and  seventh 
lumbar  vertebra;,  a  column  of  6  inches  is  sufficient  to  overcome  the  resistance  of  the  sphincter,  while 
section  at  the  fourth  lumbar  vertebra  has  no  effect  on  the  height  of  the  pressure.  In  such  an  animal 
the  bladder  becomes  distended,  but  in  one  with  its  cord  divided  between  the  fifth  and  seventh  lumbar 
vertebrae,  there  is  incontinence  of  urine — in  the  former  case  because  the  excito-motor  impulses  are  cut 
off  from  the  centre  (5  to  7  vert.),  and  in  the  latter  because  the  tonus  of  the  sphincter  is  destroyed 
i^Kupressow).     This  tonus  is  denied  by  Landois  and  others.] 

280.    ACCUMULATION     OF     URINE— MICTURITION.— After 

emptying  the  bladder,  the  urine  slowly  collects  again,  the  bladder  being  thereby 
gradually  distended.  [A  healthy  bladder  may  be  said  to  be  full  when  it  contains 
20  oz.]  As  long  as  there  is  a  moderate  amount  of  urine  in  the  bladder,  the  elasticity 
of  the  elastic  fibres  surrounding  the  urethra,  and  that  of  the  sphincter  of  the  urethra 
(and  in  the  male  of  the  prostate),  suffice  to  retain  the  urine  in  the  bladder.  This  is 
shown  by  the  fact  that  the  urine  does  not  escape  from  the  bladder  after  death.  Ir 
the  bladder  be  greatly  distended  (1.5  to  1.8  litre),  so  that  its  apex  projects  above  the 
pubes,  the  sensory  nerves  in  its  walls  are  stimulated  and  cause  a  feeling  of  a  full 
bladder,  while  at  the  same  time  the  urethral  opening  is  dilated,  so  that  a  few  drops 
of  urine  pass  into  the  beginning  of  the  urethra.  Besides  the  subjective  feeling  of  a 
full  bladder,  this  tension  of  the  walls  of  the  bladder  causes  a  reflex  eifect,  so  that  the 
urinary  bladder  contracts  periodically  upon  its  fluid  contents,  and  so  do  the  sphincter 
of  the  urethra  and  the  muscular  fibres  of  the  urethra,  and  thus  the  urethra  is  closed 
against  the  passage  of  these  drops  of  urine.  As  long  as  the  pressure  within  the 
bladder  is  not  very  high,  the  reflex  activity  of  the  transversely  striped  sphincter  over- 
comes the  other  (as  during  sleep)  ;  but,  as  the  pressure  rises  and  the  distention 
increases,  the  contraction  of  the  walls  of  the  bladder  overcomes  the  closure  produced 
by  the  sphincter,  and  the  bladder  is  emptied,  as  occurs  normally  in  young  children. 
As  age  advances,  the  sphincter  urethrje  comes  under  the  control  of  the  will,  so 
that  it  can  be  contracted  voluntarily,  as  occurs  in  man  when  he  forcibly  contracts 
the  bulbo-cavernosus  muscle  to  retain  urine  in  the  bladder.  The  sphincter  ani 
usually  contracts  at  the  same  time.  The  reflex  activity  of  the  sphincter  may  also 
be  inhibited  voluntarily,  so  that  it  may  be  completely  relaxed.  This  is  the  condition 
when  the  bladder  is  emptied  voluntarily. 

Slight  movements,  confined  to  the  bladder,  occur  during  psychical  or  emotional  disturbances  {e.g., 
anger,  fear),  [the  bladder  may  be  emptied  involuntarily  during  a  fright],  after  stimulation  of  sensory 
nerves,  auditory  impressions,  restraining  the  respiration,  and  by  arrest  of  the  heart's  action.  There  are 
slight  periodic  variations  coincident  with  variations  in  the  blood  pressure.  The  contractions  of  the 
bladder  cease  after  deep  inspiration,  and  also  during  apncea  {Mosso  and  Pellacani).     The  excised 


484  EFFECT   OF    NERVES    ON    MICTURITION. 

bladder  of  the  frog,  and  even  portions  free  from  ganglia,  exhibit  rhythmical  contractions,  which  are 
increased  by  heat  {P/nh).  [Ashdown  found  in  dogs  that  the  bladder  exhibits  regular  rliythmical 
contractions,  which  were  intlucnced  by  the  degree  of  distention  of  the  bladder,  being  most  marked 
with  moderate  dilatation  and  least  when  the  bladder  was  feebly  or  over-distended.  The  contractions 
could  be  registered  by  means  of  a  water  manometer  communicating  wi.h  the  interior  of  the  bladder.] 

Nerves. — The  nerves  concerned  in  the  retention  and  evactiation  of  the  urine 
are:  i.  The  motor  nerves  of  the  sphincter  urethrae,  which  he  in  the  jnidendal 
nerve  (anterior  roots  of  the  third  and  fourth  sacral  nerves).  When  these  nerves  are 
divided,  as  soon  as  the  bladder  becomes  so  distended  as  to  dilate  the  urethral  oi)ening, 
the  urine  begins  to  trickle  away  (incontinence  of  urine).  2.  The  sensory  nerves 
of  the  urethra,  which  excite  these  reflexes,  leave  the  spinal  cord  by  the  i)osterior 
roots  of  the  third,  fourth  and  fifth  sacral  nerves.  Section  of  these  nerves  catises 
incontinence  of  urine.  The  centre  in  dogs  lies  opposite  the  fifth,  and  in  rabbits, 
opposite  the  seventh  lumbar  vertebra  (Budge).  3.  Fibres  pass  from  the  cerebrum 
— those  that  convey  voluntary  impulses  through  the  peduncles,  and  the  anterior 
columns  of  the  spinal  cord  (accord mg  to  Mosso  and  Pellacani,  through  the  posterior 
coliuiins  and  the  posterior  ])art  of  the  lateral  columns),  to  the  motor  fibres  of  the 
sphincter  urethrc^e.  4.  The  inhibitory  fibres  concerned  in  the  reflex  inhibition 
of  the  sphincter  urethrae,  take  the  same  course  (perhaps  from  the  optic  thalamus?) 
downward  through  the  cord  to  where  the  third,  fourth,  and  fifth  sacral  ner\es  leave 
it.  5.  Sensory  nerves  proceed  from  the  tirethra  and  bladder  to  the  brain,  but  their 
course  is  not  known.  Some  of  the  motor  and  sensory  fibres  lie  for  a  part  of  their 
course  in  the  sympathetic. 

Transverse  section  of  the  spinal  cord  above  where  the  nerves  leave  it,  is 
always  followed  in  the  first  instance  by  retention  of  tirine,  so  that  the  bladder  be- 
comes distended.  This  occurs  because  (i)  the  section  of  the  spinal  cord  increases 
the  reflex  activity  of  the  urethral  sphincter ;  and  (2),  because  the  inhibition  of  this 
reflex  can  no  longer  take  i)lace.  As  soon,  however,  as  the  bladder  becomes  so 
distended,  as  in  a  purely  mechanical  manner  to  cause  dilatation  of  the  urethral 
orifice,  then  the  urine  trickles  away,  but  the  amount  of  urine  which  trickles  out  in 
drops  is  small.  Thus  the  bladder  becomes  more  and  more  distended,  as  the  con- 
tinuously distended  walls  of  the  organ  yield  to  the  increased  tension,  so  that  the 
bladder  may  become  distended  to  an  enormous  extent.  The  urine  very  frequently 
becomes  ammoniacal,  accompanied  bv  catarrh  and  inflammation  of  the  bladder 

^^  '^3)-  '  .  ^  ^     ■ 

Voluntary  Micturition. — Observers  are  not  agreed  as  to  the  mechanism  con- 
cerned in  empt\  ing  the  l)ladder  when  it  is  only  partially  full.  It  is  stated  by  some 
that  a  voluntary  impulse  jjasses  from  the  brain  along  a  cerebral  peduncle,  and  the 
cord,  to  the  anterior  roots  of  the  3d  and  4th  sacral  nerves,  and  partly  through 
motor  fibres  from  the  2d  to  the  5th  lumbar  nerves  (especially  the  3d),  to  act 
directly  upon  the  smooth  muscular  fibres  of  the  bladder.  This  is  assumed,  because 
electrical  stimulation  of  any  part  of  this  nervous  channel  causes  contraction  of  the 
bladder.  This  view,  however,  does  not  seem  to  be  the  true  one.  It  is  to  be 
remembered  that  Budge  showed  that  the  sensory  nerves  of  the  wall  of  the  bladder 
are  contained  in  the  first,  second,  third,  and  fourth  sacral  nerves,  and  also  in  part 
in  the  course  of  the  hypogastric  plexus,  whence  they  ultimately  pass  by  the  rami 
communicantes  into  the  spinal  cord. 

According  to  Landois,  the  smooth  musculature  of  the  bladder  cannot  be  excited 
directly  by  a  voluntary  impulse,  but  it  is  always  caused  to  contract  reflexly.  If 
we  wish  to  micturate  when  the  urinary  bladder  contains  a  small  quantity  of  urine, 
we  first  excite  the  sensory  nerves  of  the  openmg  of  the  urethra,  either  by  causing 
contraction  or  relaxation  of  the  sphincter  urethra,  or  by  means  of  slight  abdoniinal 
pressure,  and  thus  force  a  little  urine  into  the  urethral  orifice.  This  sensory  stimu- 
lation causes  a  reflex  contraction  of  the  walls  of  the  urinary  bladder.  At  the  satne 
time,  this  condition  is  maintained  voluntarily,  by  the  action  of  the   intra-cranial 


ABSORPTION. 


485 


Fig.  292. 


reflex-inhibitory  centre  of  the  sphincter  urethrse.  The  centre  for  the  reflex 
stimulation  of  the  movements  of  the  walls  of  the  urinary  bladder  is  placed  some- 
what higher  in  the  spinal  cord  than  that  for  the  sphincter  urethrse.  In  dogs,  it  is 
opposite  the  4th  lumbar  vertebra  {^Gianuzzi,  Budge). 

[Two  centres  are  assumed  to  exist  in  the  cord,  Fig.  293,  one  the  automatic  (A.C.)  at  the  segment 
corresponding  to  the  2d,  3d,  and  4th  sacral  nerves,  which  maintains  the  tonic  action  of  the  sphincter ; 
the  other,  a  reflex  centre  (R.  C),  is  situated  higher,  and  through  it  the  detrusor  urinje  is  excited  to 
contraction.  Both  centres  are  connected  to  and  governed  or  controlled  by  a  cerebral  centre  (C). 
The  automatic  centre  is  connected  with  the  sphincter,  and  the  other  with  the  urine-expelling  fibres. 
They  are  also  connected  with  afferent  fibres  fi-om  the  bladder  and  elsewhere.  The  afferent  or  sensory 
fibres  are  also  connected  with  the  brain.  The  automatice  centi-e  maintains  the  closure  of  the  bladder, 
but  if  the  latter  be  distended,  different  impulses  proceeding  from  it  reach  the  spinal  centre,  and  it  may 
be  the  cerebrum.  The  impulses  reaching  the  automatic  centre  inhibit  its  action  and  those  to  the  reflex 
centre  excite  it,  so  that  the  detrusor  urinEe  contracts.  If  the  afferent  impulses  be  powerful,  a  desire 
to  urinate  is  excited,  and  voluntary  impulses  are  excited  which  act  upon  the  spinal  centres  as  the 
afferent  impulses  do,  and  thus  the  act  of  urination  is  more  easily  accomplished.] 

We  may  conceive  a  voluntary  impulse  to  pass  down  special  fibres  to  an  inhibitory  centre,  which 
may  either  act  directly  on  the  motor  centre,  or  possibly  may  send  branches  directly  to  the  sphincter 
muscles. 

Painful  stimulation  of  sensory  nerves  causes  reflex  contraction  of  the  bladder  and  evacuation  of  the 
urine  (in  children  during  teething).  Reflex  contraction  of  the  bladder  can  be  brought  about  in  cats,  by 
stimulation  of  the  inferior  mesenteric  ganglion.  After  section  of  all  the  nerves  going  to  the  bladder, 
hemorrhage  and  asphyxia  cause  contraction  by  a  direct  effect  upon  the  structures  in  the  wall  of  the 
bladder.  As  yet  no  one  has  succeeded  in  exciting  artificially  the  inhibitory  centre  in  the  brain  for 
the  sphincter  muscle  [Sokowin  and  Koivalesky). 

It  seems  probable  that,  as  in  the  case  of  the  anal  sphincter  (|  160),  there  is  not  a  continuous  tonic 
reflex  stimulation  of  the  sphincter  urethrse ;  the  reflex  is  excited  each  time  by  the  contents.  The 
sphincter  vesicse  of  the  anatomists,  which  consists  of  smooth  muscular  tissue,  does  not  seem  to  take 
part  in  closing  the  bladder.  Budge  and  Landois  found  that,  after  removal  of  the  transversely  striped 
sphincter  urethrse,  stimulation  of  the  smooth  sphincter  did  not  cause 
occlusion  of  the  bladder,  nor  could  L.  Rosenthal  or  v.  Wittich  con- 
vince themselves  of  the  presence  of  tonus  in  this  muscle.  Indeed, 
its  very  existence  is  questioned  by  Henle. 

Changes  of  the  Urine  in  the  Bladder. — When  the  urine  is  re- 
tained in  the  bladder  for  a  considerable  time,  according  to  Kaupp,  there 
is  an  increase  in  the  sodium  chloride  and  a  decrease  in  the  urea  and 
water.  Urine  which  remains  for  a  long  time  in  the  bladder  is  prone 
to  undergo  ammoniacal  decomposiiion. 

Absorption. — Many  observers  have  shown  that  the  mucous  mem- 
brane of  the  bladder  is  capable  of  absorbing  substances — potassium 
iodide  and  other  soluble  salts.  [Ashdown  has  shown  that  poisons, 
such  as  watery  solutions  of  strychnin,  cm'are,  eserin,  emulsions  of 
chloroform  and  ether,  are  absorbed  when  injected  into  the  bladder  of 
rabbits.  In  rabbits,  KI  injected  into  the  bladder  through  a  catether 
was  found  in  the  urine  obtained  from  the  divided  ureters.  Water  and 
urea  are  also  absorbed — the  latter  in  larger  proportion  than  the 
former.] 

As  the  vu-eters  enter  near  the  base  of  the  bladder,  the  last  secreted 
urine  is  always  lowest.  If  a  person  remain  perfectly  quiet,  strata  of 
urine  are  thus  formed,  and  the  urine  may  be  voided  so  as  to  prove 
tnis  {Edlefsen). 

The  pressure  within  the  bladder,  when  in  the  supine  position 
=  13  to  15  centimetres  of  water.  Increase  of  the  intra-abdominal 
pressure  (by  inspiration,  forced  expiration,  coughing,  bearing-down) 
increases  the  pressiure  within  the  bladder.  The  erect  posture  also 
increases  it,  owing  to  the  pressvu-e  of  the  viscera  from  above  i^Sckatz, 
Dubois).  [James  obtained  4  to  4.5  inches  Hg  as  the  highest  expul- 
sive power  of  the  bladder  including  the  abdominal  pressure,  volun- 
tary and  involuntary.  In  paraplegia,  where  there  is  merely  the 
expulsive  power  of  the  bladder,  he  found  20  to  30  inches  of  water.] 

[Hydronephrosis  occurs  when  the  ureters  and  pelvis  of  the 
kidney  become  dilated,  owing  to  partial  and  gradual  obstruction  of  the  outflow  of  urine  from  the 
ureters:  if  the  obstruction  become  complete,  there  is  cessation  of  the  urinary  secretion.  James  has 
shown  that  the  bladder  remains  contracted  for  several  seconds  after  ;t  is  emptied,  and  this  is  specially 


Scheme  of  micturition  :  A.C,  K.C., 
C.,  automatic,  reflex,  and  cere- 
bral centres  ;  B,  bladder;  S., 
sensory  centre  acted  on  by 
afferent  impulses. 


486  COMPARATIVE    AND    HISTORICAL. 

the  case  in  irritable  bladder;  so  that  this  coiulilioii  may  also  give  rise  to  liy<lroiie])hrosis  l)y  damming 
up  the  urine  in  the  ureters.] 

Rapidity  of  Micturition. — The  amount  of  urine  voided  at  first  is  small,  but  it  increases  with  the 
time,  and  toward  the  end  of  the  act  it  again  diminishes.  In  men,  the  last  drops  of  urine  are  ejected 
from  the  urethra  by  voluntary  contractions  of  the  bulbo-cavernosus  muscle.  Adult  dogs  increase  the 
stream  rliythmically  by  the  action  of  this  muscle. 

281.  RETENTION  AND  INCONTINENCE  OF  URINE.— Retention  of  urine  or 
ischuria  occurs:  I.  When  there  is  obstruction  of  the  urethra,  from  foreign  l>odies,  concretions, 
stricture,  swelling  of  the  prostate.  2.  Paralysis  or  exhaustion  of  the  musculature  of  the  bladder;  the 
latter  sometimes  occurs  after  delivery,  in  consequence  of  the  pres  ure  of  the  child  against  the  bladder. 
3.  After  section  of  the  spinal  cord  (p.  484).  4.  Where  the  voluntarj-  impulses  are  unaiile  to  act 
upon  the  inhibitor)'  apparatus  of  the  sphincter  urethrpe  reflex,  as  well  as  when  the  sphincter  urethrae 
reflex  is  increased. 

Incontinence  of  urine  (stillicidium  urinae)  occurs  in  consef|uence  of — i.  Paralysis  of  the 
sphincter  uretlira\  2.  Loss  of  sensibility  of  the  urethra,  which  of  course  abolishes  the  reflex  of  the 
sphincter.  3.  Trickling  of  the  urine  is  a  secondary  consequence  of  section  of  the  spinal  cord,  or  of 
its  degeneration. 

Strangury  is  an  excessive  reflex  contraction  of  the  walls  of  the  bladder  and  sphincter,  due  to 
stimulation  of  the  bladder  and  urethra;  it  is  observed  in  inflammation,  neuralgia  [and  after  the  use 
of  some  poisons,  e.  g.,  cantharides]. 

Enuresis  nocturna,  or  involuntary  emptying  of  the  bladder  at  night,  may  be  due  to  an  increased 
reflex  excitability  of  the  wall  of  the  bladder,  or  weakness  of  the  sphmcter. 

282.  COMPARATIVE  AND  HISTORICAL.— Among  vertebrates,  the  urinary  and 
genital  organs  are  frequently  combined,  except  in  the  osseous  fishes.  The  Wolffian  bodies  which  act 
as  organs  of  excretion  during  the  embryonic  period,  remain  throughout  life  in  fishes  and  amphibians 
and  continue  to  act  as  such.  Fishes. — The  tnyxinoids  (cyclostomata)  have  the  simplest  kidneys  ; 
on  each  side  is  a  long  ureter  with  a  series  of  short-stalked  glomeruli  with  capsules  arranged  along 
it.  Both  ureters  open  at  the  genital  pore.  In  the  other  fi.shes,  the  kidneys  lie  often  as  elongated 
compact  masses  along  both  sides  of  the  vertebral  column.  The  two  ureters  unite  to  form  a  urethra, 
which  always  opens  behind  the  anus,  either  united  with  the  opening  of  the  genital  organs,  or 
behind  this.  In  the  sturgeon  and  hag  fish,  the  anus  and  orifice  of  the  urethra  together  form  a 
cloaca.  Bladder-like  formations,  which,  however,  are  morphologically  homologous  with  the  urinary 
bladder  of  mammals,  occur  in  fishes,  either  on  each  ureter  (ray,  hag-fish),  or  where  both  join.  In 
amphibians,  the  vasa  efferentiaof  the  testicles  are  united  with  the  urinary  tubules;  the  duct  in  the 
frog  unites  with  the  one  on  the  other  side,  and  both  conjoined  ojiens  into  the  cloaca,  while  the 
capacious  urinary  bladder  opens  through  the  anterior  wall  of  the  cloaca.  From  reptiles  upward, 
the  kidney  is  no  longer  a  persistent  Wolffian  body,  but  a  new  organ.  In  reptiles,  it  is  usually  flat- 
tened and  elongated;  the  ureters  open  singly  into  the  cloaca.  .Saurians  and  tortoises  have  a  urinary 
bladder.  In  birds,  the  isolated  ureters  open  into  the  uro-genital  sinus,  which  opens  into  the  cloaca, 
internal  to  the  excretory  ducts  of  the  genital  apparatus.  The  urinary  bladder  is  always  absent.  In 
mammals,  the  kidneys  often  consist  of  many  lobules,  e.  g.,  dolphin,  ox. 

Among  invertebrates,  the  moUusca  have  excretory  organs  in  the  form  of  canals,  which  are 
provided  with  an  outer  and  an  inner  opening.  In  the  mussel,  this  canal  is  provided  with  a  sponge- 
like organ,  often  with  a  central  cavity,  and  consisting  of  ciliated  secretory  cells,  placed  at  the  base 
of  the  gills  (organ  of  Bojanus).  In  gasteropods,  with  analogous  organs,  uric  acid  has  been  found. 
Insects,  spiders,  and  centipedes  have  the  so-called  Malpighian  vessels,  which  are  excretory 
organs,  partly  for  uric  acid  and  partly  for  bile.  These  vessels  are  long  tubes,  which  open  into  the 
first  part  of  the  large  intestine.  In  crabs,  blind  tubes  connected  with  the  intestinal  tube,  perhaps 
have  the  same  functions.     The  vermes  also  have  renal  organs. 

Historical. — Aristotle  directed  attention  to  the  relatively  large  size  of  the  human  bladder — he 
named  the  ureters.  Massa  (1552)  found  lymphatics  in  the  kidney.  Eustachius  (f  1 580)  ligatured 
the  ureters  and  found  the  bladder  empty.  Cusanus  (1565)  investigated  the  color  and  weight  of  the 
urine.  Rousset  (1581)  described  the  muscular  nature  of  the  walls  of  the  bladder.  Vesling 
described  the  trigone  (1753).  The  first  important  chemical  investigations  on  the  urine  date  from 
the  time  of  van  Helmont  (1644).  He  isolated  the  solids  of  the  urine  and  found  among  them  com- 
mon salt ;  he  ascertained  the  higher  specific  gravity  of  fever  urine,  and  ascribed  the  origin  of  urinary 
calculi  to  the  solids  of  the  urine.  Scheele  (1766)  discovered  uric  acid  and  calcium  phosphate; 
Arand  and  Kunckel,  phosphorus;  Rouelle  (1773),  urea;  and  it  got  its  name  from  Fourcroy  and 
Vauquelin  (1799).  Berzelius  found  lactic  acid;  Seguin,  albumin  in  pathological  urine;  Liebig, 
hippuric  acid  ;  Heintz  and  v.  Pettenkofer,  kreatin  and  kreatinin ;  Wollaston  (1810),  cystin.  Marcet 
found  xanthin  ;  and  Lindbergson,  magnesic  carbonate. 


Functions  of  the  Skin. 


Fis.  293. 


283.  STRUCTURE  OF  THE  SKIN,  HAIRS,  AND   NAIL.— The 

skin  (3.3  to  2.7  mm.  thick;  specific  gravity,  1057)  consists  of — 
[i.  The  epidermis ; 

2.  The  chorium,  or  cutis  vera,  with  the  papillse  (Fig.  294).] 
The  epidermis  (0.08  to  0.12  mm.  thick)  consists  of  many  layers  of  stratified  epithelial  cells 
united  to  each  other  by  cement  substance  (Figs.  293,  294).  The  superficial  layers — stratum 
corneum — consist  of  several  layers  of  dry, 
horny,  non-nucleated  squames,  which  swell  up  in 
solution  of  caustic  soda  (Fig.  294,  E).  [It  is 
always  thickest  where  intermittent  pressure  is 
applied,  as  on  the  sole  of  the  foot  and  palm  of 
the  hand.]  The  next  layer  is  the  stratum 
lucidum,  which  is  clear  and  transparent  in  a 
section  of  skin,  hence  the  name,  and  consists  of 
compact  layers  of  clear  cells  with  vestiges  of 
nuclei.  Under  this  is  the  rete  mucosum  or 
rete  Malpighii  (Fig.  294,  d),  consisting  of  many 
layers  of  nucleated  protoplasmic  epithelial  cells 
which  contain  pigment  in  the  dark  races,  and  in 
the  skin  of  the  scrotum,  and  around  the  anus. 
[The  superficial  cells  are  more  fusiform  and  con- 
tain granules  which  stain  deeply  with  carmine. 
They  constitute,  3,  the  stratum  granulosum. 
In  these  cells  the  formation  of  keratin  is  about 
to  begin,  and  the  granules  have  been  called 
eleidin  granules  by  Ranvier.  They  are  chemi- 
cally on  the  way  to  be  transformed  into  keratin. 
All  corneous  structures  contain  similar  granules 
in  the  area  where  the  cells  are  becoming  corne- 
ous. Then  follow  several  layers  of  more  or 
less  polyhedral  cells,  softer  and  more  plastic  in 
their  nature,  and  exhibiting  the  characters  of  so- 
called  "  prickle  cells  "  (Fig.  294,  R).  [The 
spaces  between  the  fibrils  connecting  adjacent 
cells  are  lymph  spaces.]  The  deepest  layers  of 
cells  are  more  or  less  columnar,  and  the  cells 
are  placed  vertically  upon  the  papillse.  Granular 
leucocytes  or  wandering  cells  are  sometimes 
found  between  these  cells.  This,  the  fourth 
layer,  has  been  called  the  stratum  Malpighii. 
The  rete  Malpighii  dips  down  between  adjacent 
papillse  and  forms  interpapillary  processes.  Ac- 
cording to  Klein,  a  delicate  basement  mem- 
brane separates  the  epidermis  from  the  true  skin.]  The  superficial  layers  of  the  epidermis  are 
continually  being  thrown  oiif,  while  new  cells  are  continually  being  formed  in  the  deeper  layers  of 
the  skin  by  proliferation  of  the  cells  of  the  rete  Malpighii.  There  is  a  gradual  change  in  the  micro- 
scopic and  chemical  characters  of  the  cells  from  the  deepest  to  the  superficial  layers  of  the  epider- 
mis. [In  a  vertical  section  of  the  skin  stained  with  picro-carmine,  the  S.  granulosum  is  deeply 
stained  red,  and  is  thus  readily  distinguished  among  the  other  layers  of  the  epidermis.] 

(i)  Stratum  corneu7n,         \  p  t-iVlp 

(2)  Stratum  lucidum,  J 

(3)  Siratzim  granulomm,   j  Rete  Mucosum.] 

(4)  Stratum  Malpighii,       J 

487 


_Stratum 
corneum. 


Stratum 
lucidum. 


Stratum 
-granu- 
losum. 


_Stratum 
Malpighii. 


Vertical  section  of  the  human  epidermis  ;  the  nerve  fibrils, 
n,  b,  stained  with  gold  chloride. 


[Epidermis  (Fig.  293), 


488 


STRUCTURE    OF    THE    EPIDERMIS. 


No  pigment  is  formed  within  the  epidermis  itself  ;  when  it  is  present,  it  is  carried  by  leucocytes 
from  the  subcutaneous  tissue  {Kieh/,  Ehrmann,  Achy).  This  explains  how  it  is  that  a  piece  of 
white  skin,  transplanted  to  a  negro,  becomes  black  [Kari^'). 

The  chorium  (^Fig.  294,  I,  C)  is  beset  over  its  entire  surface  by  numerous  (0.5  to  O.I  mm.  high) 
papillae  (Fig.  294).  the  largest  being  upon  the  volar  surface  of  the  hand  and  foot,  on  the  nipple 
and  glans  penis.  Most  of  the  papill;i2  contain  a  looped  capillary  (^),  while  in  certain  regions  some 
of  th'em  contain   a  touch  corpuscle   (Fig.  295,  «).     The  papilla-  are  disposed  in  groups,  whose 


Fir,.  294. 


I,  Vertical  section  of  the  skin,  with  a  hair  and  sebaceous  gland,  T.  Epidermis  and  chorium  shortened— i,  outer ; 
2,  inner  fibrous  layer  of  the  hair  follicle  ;  3,  its  hyaline  layer ;  4.  outer  root  sheath ;  5,  Huxley's  layer  of  the  inner 
root  sheath  ;  6,  Henle's  layer  of  the  same;  /,  root  of  the  hair,  with  its  papilla;  A,  arrcctor  pili  muscle;  C, 
chorium;  a,  subcutaneous  fatty  tissue;  h,  epidermis  (horny  layer);  d,  rete  Malpighii  ;  ^,  blood  vessels  of 
papillje ;  t,  lymphatics  of  the  same  ;  h,  horny  or  corneous  substance ;  /,  medulla  or  pith  ;  k.  epidermis  or  cuticle 
of  hair;  K,  coil  of  sweat  gland  ;  E,  epidermal  scales  (seen  from  above  and  en/ace)  from  the  stratum  corneum  ; 
R,  prickle  cells  from  the  rete  Malpighii  ;  «,  superficial,  and  m,  deep  cells  from  the  nail ;  H,  hair  magnified;  e, 
cuticle  :  c,  medulla,  with  cells  ;  /,/,  fusiform  fibrous  cells  of  the  substance  of  the  hair  ;  x,  cells  of  Huxley's  layer ; 
/,  those  of  Henle's  layer ;  S,  transverse  section  of  a  sweat  gland  from  the  axilla ;  a,  smooth  muscular  fibres  sur- 
rounding it ;  /,  cells  from  a  sebaceous  gland,  some  of  them  containing  granules  of  oil. 

arrangement  varies  in  different  parts  of  the  body.  In  the  palm  of  the  hand  and  sole  of  the  foot 
they  occur  in  rows,  which  are  marked  out  by  the  existence  of  delicate  furrows  on  the  surface  visible 
to  the  naked  eye.  The  chorium  consists  of  a  dense  network  of  bundles  of  white  fibrous  tissue 
mixed  with  a  network  of  elastic  fibres,  which  are  more  delicate  in  the  papillne.  In  silversmiths  the 
elastic  fibres  are  blackened  by  the  partial  deposition  of  reduced  silver,  and  the  same  obtains  in 
those  who  take  silver  nitrate  in  such  quantity  as  to  produce  argyria.  The  connective  tissue  contains 
many  connective-tissue  corpuscles  and  numerous  leucocytes.     The  deeper  connecti\%  tissue  layers 


DEVELOPMENT   OF   THE    NAILS. 


489 


of  the  chorium  gradually  pass  into  the  subcutaneous  tissue,  where  they  form  a  trabecular  arrange- 
ment of  bundles,  leaving  between  them  elongated  rhomboidal  spaces  filled  for  the  most  part  with 
groups  of  fat  cells  (Fig.  294,  a,  a).  [In  microscopic  sections,  after  the  action  of  alcohol,  the  fat  cells 
not  unfrequently  contain  crystals  of  margarin.]  The  long  axis  of  the  rh'omb  corresponds  to  the 
greater  tension  of  the  skin  at  that  part  [C.  Langer').  In  some  situations  the  subcutaneous  tissue  is 
devoid  of  fat  [penis,  eyelids].  In  many  situations,  the  skin  is  fixed  by  solid  fibrous  bands  to  subja-- 
cent  structures,  as  fascise,  ligaments  or  bones  (tenacula  cutis)  ;  in  other  parts,  as  over  bony  promi- 
nences, bursa;  partially  lined  with  endothelium  and  filled  with  synovia-like  fluid,  occur. 

Smooth  muscular  fibres  occur  in  the  chorium  in  certain  situations  on  extensor  surfaces  {^Neu- 
mann) ;  nipple,  areola  mammae,  prepuce,  perinasum,  and  in  special  abundance  in  the  tunica  dartos 
of  the  scrotum. 

[Guanin  in  the  Skin. — The  skin  of  many  amphibians  and  reptiles  contains  brown  or  black  pig- 
ment granules,  and  other  granules  of  a  white,  silvery,  or  chalky  appearance.  Ewald  and  Krukenberg 
have  shown  that  the  latter  consists  of  guanin,  and  that  this  substance  is  very  widely  diffused  in  the  skin 
of  fishes,  amphibians,  and  reptiles.  Test :  Select  a  piece  of  skin  from  the  belly  of  a  frog ;  place  it 
in  a  porcelain  capsule  as  for  the  murexide  test ;  add  concentrated  nitric  acid,  and  heat  to  dryness,  when 
a  yellow  residue  is  obtained;  on  adding  a  drop  of  caustic  soda  a  red  color  is  struck.  The  yellow 
residue  gives  no  reaction  with  ammonia.  If  to  the  fluid  more  water  be  added,  and  it  be  then  heated, 
distributed  over  the  surface  of  the  capsule,  and  cooled  by  blowing  upon  it,  various  shades  of  purple 
and  violet  are  obtained.] 

The  nails  (specific  gravity  I.19)  consist  of  numerous  layers  of  solid,  horny,  homogeneous,  epidermal, 
or  nail  cells,  which  may  be  isolated  with  a  solution  of  caustic  alkali,  when  they  swell  up  and  exhibit 
the  remains  of  an  elongated  nucleus  (Fig.  294,  n,  m).    The  whole  under  surface  of  the  nail  rests  upon 
the  nail  bed;  the  lateral  and  posterior  edges  lie  in  a  deep  groove,  the  nail  groove  (Fig.  296,  e). 
The  chorium  under  the  nail  is  covered  through- 
out its   entire  extent  by  longitudinal  rows   of  FiG.  295. 
papillae  (Fig.  296,  d).     Above  this  there  lies, 
as  in  the  skin,  many  layers  of  prickle  cells  like 
those  in  the  rete  Malpighii  (Fig.  294,  a),  and 
above  this  again  is  the  substance  of  the  nail 
(Fig.   296,   a).     [The  stratum  granulosum  is 
rudimentary  in  the  nail  bed.    The  substance  of 
the  nail  represents  the  stratum  lucidum,  there 
being  no  stratum  corneum  (^K'lein).']    The  pos- 
terior part  of  the  nail  groove  and  the  half  moon, 
brighter  part  or  lunula,  form  the  root  of  the 
nail.     They  are,  at  the  same  time,  the  matrix, 
from  which  growth  of  the  nail  takes  place.    The  Papill»   of    the   skin,    epidermis    removed    blood   vessels 
1         ,.          °^.            -i.j        -ij-j                injected:   some  contain  a  Wagners  touch  corpuscle,  a, 
lunule  is  present  m  an  isolated  nail,  and  is  due         ^^^  others  a  capillary  loop. 
to  diminished  transparency  of  the    posterior 

part  of  the  nail,  owing  to  the  special  thickness  and  uniform  distribution  of  the  cells  of  the  rete 
Malpighii  [Toldt). 

Fig.  296. 


Transverse  section  of  one-half  of  a  nail,  a,  nail  substance:  b,  more  open  layer  of  cells  of  the  nail  bed;  c,  stratum 
Malpighii  of  the  nail  bed ;  d,  transversely  divided  papillse ;  e,  nail  groove ;  f,  horny  layer  of  e  projecting  over 
the  nail ;  g,  papillse  of  the  skin  on  the  back  of  the  finger. 

Growth  of  the  Nail. — According  to  Unna,  the  matrix  extends  to  the  front  part  of  the  lunule. 
The  nail  grows  continually  from  behind  forward,  and  is  formed  by  layers  secreted  or  formed  by  the 


490 


STRUCTURE   OF    A    HAIR    FOLLICLE. 


Fir..  297. 


matrix.  These  layeis  run  parallel  to  the  surface  of  the  matrix.  They  run  obliquely  from  above  and 
behind,  downward  and  forward,  through  the  thickness  of  the  substance  of  the  nail.  The  nail  is  of 
the  same  thickness  from  the  anterior  margin  of  the  lunule  forward  to  its  free  margin.  Thus  the  nail 
does  not  grow  in  thickiness  in  this  region.  In  the  course  of  a  year  the  fingers  produce  al)out  2  grms. 
of  nail  substance,  and  relatively  more  in  summer  than  in  winter. 

Development  — i.  From  the  second  to  the  eighth  month  of  fretal  life,  the  position  of  the  nail  is 
indicated  by  a  ]iaitial  but  marked  horny  condition  of  the  epidermis  on  the  back  of  the  first  phalanx, 
the  "  eponychium."  The  remainder  of  this  substance  is  represented  during  life  by  the  normally 
formed  epidermal  laver,  which  separates  the  future  nail  from  the  surface  of  the  furrow.  2.  The 
future  nail  is  formed  under  the  eponychium,  with  its  first  nail  cells  still  in  front  of  the  nail  groove; 
then  the  nail  grows  and  pushes  forward  toward  the  groove.  At  the  seventh  month,  the  nail  (itself 
covered  by  the  eponychium)  covers  the  whole  extent  of  the  nail  bed.  3.  When,  at  a  later  period,  the 
e[ionychium  splits  off,  the  nail  is  uncovered.  After  birth  the  papillae  are  formed  on  the  bed  of  the 
nail,  while  simultaneously  the  matrix  passes  backward  to  the  most  posterior  part  of  the  groove 
( Unna). 

Absence  of  Hairs. — The  whole  of  the  skin,  with  the  exception  of  the  palmar  surface  of  the 
hand,  sole  of  the  foot,  dorsal  surface  of  the  third  phalanx  of  the  fingers  and  toes,  outer  surface  of  the 
eyelids,  glans  penis,  inner  surface  of  the  prepuce,  and  part  of  the  labia  is  covered  with  hairs,  which 
may  be  strong  or  fine  (lanugo). 

A  Hair  (specific  gravity  1.26)  is  fixed  by  its  lower  extremity  (root)  in  a  depression  of  the  skin  or 
a  hair  follicle  (Fig.  294,  I,/)  which  passes  obliquely  through  the  thickness  of  the  skin,  sometimes 

as  far  as  the  subcutaneous  tissue.  The  structure  of  a  hair  follicle 
is  the  following :  I.  The  outer  fibrous  layer  (Figs.  294,  1,  293), 
composed  of  interwoven  bundles  of  connective  tissue,  arranged  for 
the  most  part  longitudinally,  and  provided  with  numerous  blood 
vessels  and  nerves.  [It  is  just  the  connective  tissue  of  the  sur- 
rounding chorium.]  2.  The  inner  fibrous  layer  (Figs.  294,  2, 
297)  consists  of  a  layer  of  fusiform  cells  (?  smooth  muscular  fibres) 
arranged  circularly.  [It  does  not  extend  throughout  the  whole 
length  of  the  follicle.]  3.  Inside  this  layer  is  a  transparent,  hya- 
line, glass-like  basement  membrane  (Figs.  292,  3,  297),  which 
ends  at  the  neck  of  the  hair  follicle ;  while  above  it  is  continued 
as  the  basement  membrane  which  exists  between  the  epideiTnis  and 
chorium.  In  addition  to  these  coverings,  a  hair  follicle  has  epi- 
thelial coverings  which  must  be  regarded  in  relation  to  the  layers 
of  the  epidennis.  Immediately  within  the  glass-like  membrane  is 
the  outer  root  sheath  (Figs.  294,  4,  297,  298),  which  consists 
of  so  many  layers  of  epithelial  cells  that  it  forms  a  conspicuous 
covering.  It  is,  in  fact,  a  direct  continuation  of  the  stratum 
Malpighii,  and  consists  of  many  layers  of  soft  cells,  the  cells  of  the 
outer  layer  being  cylindrical.  Toward  the  base  of  the  hair  follicle 
it  becomes  miTOwer,  and  is  united  to,  and  continues  with  the  cells 
of  the  root  of  the  hair  itself,  at  least  in  fully  developed  hairs.  The 
horny  layer  of  the  epidermis  continues  to  retain  its  properties  as  far 
down  as  the  orifice  of  the  sebaceous  follicle;  below  this  point, 
however,  it  is  continued  as  the  inner  root  sheath.  This  con- 
Transverse  section  of  a  hair  and  its  sists  of  (l)  a  single  layer  of  elongated,  flat,  homogeneous,  non- 
follicle,  a,  outer  fibrous  coat  with  nucleated  Cells  (Figs.  294,  6,  297,/ — Henlis  layer)  placed  next 
dis'XTajxt/ J.'irs^ikl^ayjl^;  and  wUhin  the  outer  root  sheath.  Within  this  lies  (2)  Huxle/s 
e,  outer, y;^,  inner,  root  sheath:/,  layer  (Figs.  294,  5,  297,  g),  consistmg  of  nucleated  elongated 
outer  layer  of  the  same  (Henle's  polygonal  cells  (Fig.  294,  X,  and  3),  while  the  cuticle  oivhe.  hair 
muxLV-s^'sireTth)''T,°c;uicle''7  follicle  is  Composed  of  cells  analogous  to  those  of  the  surface  of 
hair.  '  '  the  hair  itself.     Toward  the  bulb  of  the  hair  these  three  layers 

become  fused  together. 
[Coverings  of  a  hair  follicle  arranged  from  without  inward — 


./ — 


I.  Fibrous  layers. 


f  [a)  Longitudinally  aiTanged  fibrous  tissue. 
\  [b]  Circularly  arranged  spindle  cells. 


f  Henle's  layer. 
\  Huxley's  layer. 


2.  Glass-like  (hyaline)  membrane. 

!{a)  Outer  root  sheath. 
\b)  Inner  root  sheath, 
(c)  Cuticle  of  the  hair. 
4.  The  hair  itself.] 
The  arrector  pill  muscle  ( Fig.  294,  A)  is  a  fan-like  arrangement  of  a  layer  of  smooth  muscular 
fibres,  attached  below  to  the  side  of  a  hair  follicle  and  extending  toward  the  surface  of  the  chorium ;  as 
it  stretches  obhquely  upward,  it  subtends  the  obtuse  angle  formed  by  the  hair  follicle  and  the  surface  of 
the  skin  [or,  in  other  words,  it  forms  an  acute  angle  with  the  hair  follicle,  and  between  it  and  the 


DEVELOPMENT   AND    PROPERTIES    OF    HAIR. 


491 


Fig.  298. 


i M 


follicle  lies  the  sebaceous  gland].  When  these  muscles  contract,  they  raise  and  erect  the  hair  folli- 
cles, producing  the  condition  of  cutis  anserina  or  gooseskin.  As  the  sebaceous  gland  lies  in  the 
angle  between  the  muscle  and  the  hair  follicle,  contraction  of  the  muscle  compresses  the  gland  and 
favors  the  evacuation  of  the  sebaceous  secretion.  It  also  compresses  the  bloodvessels  of  the  papilla 
{^Unnd). 

The  hair  with  its  large  bulbous  extremity — hair  bulb — sits  upon  or  rather  embraces,  the  papilla. 
It  consists  of  (l)  the  7narrow  or  medulla  (Fig.  294,  ?),  which  is  absent  in  woolly  hah  and  in  the 
hairs  formed  during  the  first  year  of  life.  It  is  composed  of 
two  or  three  rows  of  cubical  cells  (H,  <r).  (2)  Outside  this 
lies  the  thicker  cortex  (/z),  which  consists  of  elongated,  rigid, 
homy,  fibrous  cells  (H,/, /),  while  in  and  between  these 
cells  he  the  pigment  granules  of  the  hair.  (3)  The  surface 
•of  the  hair  is  covered  with  a  cuticle  (/^),  and  consists  of 
imbricated  layers  of  non-nucleated  squames. 

Gray  Hair. — When  the  hair  becomes  gray,  as  in  old  age, 
this  is  due  to  defective  formation  of  pigment  in  the  cortical 
part.  The  silvery  appearance  of  white  hair  is  increased  when 
small  air  cavities  are  developed,  especially  in  the  medulla  and 
to  a  less  extent  in  the  cortex,  where  they  reflect  the  light. 
Landois  records  a  case  of  the  hair  becoming  suddenly  gray, 
in  a  man  whose  hair  became  gray  during  a  single  night,  in 
the  course  of  an  attack  of  delirium  tremens.  Numerous  hair 
spaces  were  found  throughout  the  entire  marrow  of  the  (blond) 
hairs,  while  the  hair  pigment  still  remained. 

[Blood  Pigment  in  Hairs. — The  feelers  of  albino  rab- 
bits contain  in  some  part  of  their  substances  blood  pigment 
{Sig  Mayer):\ 

Development  of  Hair. — According  to  Kolliker,  fiom 
the  1 2th  to  13th  week  of  intra-uterine  hfe,  sohd  finger  like 
processes  of  the  epidermis  are  pushed  down  into  the  chorium. 
The  process  becomes  flask-shaped,  while  the  central  cells  of 
the  cylinder  become  elongated  and  form  a  conical  body, 
arising,  as  it  were,  from  the  depth  of  the  recess.  It  soon 
differentiates  into  an  inner  darker  part,  which  becomes  the 
hair,  and  a  thinner,  clearer  layer  covering  the  former,  the 
inner  rooth  sheath.  The  outer  cells,  i.  e.,  those  lying  next 
the  wall  of  the  sac,  form  the  outer  root  sheath.  Outside  this, 
again,  the  fibrous  tissue  of  the  chorium  forms  a  rudimentary 
hair  follicle,  while  one  of  the  papillte  grows  up  against  it, 
indents  it,  and  becomes  embraced  by  the  bulb  of  the  hair. 
This  is  the  hair  papilla,  which  contains  a  loop  of  blood 
vessels.  The  cells  of  the  bulb  of  the  hair  proliferate  rapidly, 
and  thus  the  hair  grows  in  length.  The  point  of  the  hair  is 
thereby  gradually  pushed  upward,  pierces  the  inner  root 
sheath,  and  passes  obliquely  through  the  epidermis.  The 
hairs  appear  upon  the  forehead  at  the  19th  week ;  at  the  23d 
to  25th  week  the  lanugo  hairs  appear  free,  and  they  have  a 
characteristic  arrangement  on  different  parts  of  the  body. 

Physical  Properties. — Hair  has  very  considerable  elas- 
ticity (stretching  to  0.33  of  its  length),  considerable  cohesion 
(carrying  3  to  5  lbs.),  resists  putrefaction  for  a  long  time, 
and  is  highly  hygroscopic.  The  last  property  is  also  pos- 
sessed by  epidermal  scales,  as  is  proved  by  the  pains  that 
occur  in  old  wounds  and  scars  during  damp  weather. 

Growth  of  a  hair  occurs  by  proliferation  of  the  cells  on 
the  surface  of  the  hair  papilla,  these  cells  representing  the 
matrix  of  the  hair.  Layer  after  layer  is  formed,  and  gradu- 
ally the  hair  is  raised  higher  within  its  follicle. 

Change  of  the  Hair. — According  to  one  view,  when  the  hair  has  reached  its  full  length,  the 
process  of  formation  on  the  surface  of  the  hair  papilla  is  interrupted ;  the  root  of  the  hair  is  raised  from 
the  papilla,  becomes  horny,  remains  almost  devoid  of  pigment,  and  is  gradually  more  and  more  lifted 
upward  from  the  surface  of  the  papilla,  while  its  lower  bulbous  end  becomes  split  up  like  a  brush. 
The  lower  empty  part  of  the  hair  follicle  becomes  smaller,  while  on  the  old  papilla  a  new  formation 
of  a  hair  begins,  the  old  hair  at  the  same  time  falling  out  [Un7ta).  According  to  Stieda,  the  old 
papilla  disappears,  while  a  new  one  is  foraied  in  the  hair  folhcle,  and  from  it  th  e  new  hair  is  developed. 
According  to  Kolliker,  again,  both  processes  obtain. 


Section  of  a  hair  follicle  while  a  hair  is  being 
shed,  a,  outer  and  middle  sheaths  of 
hair  follicle  ;  b,  hyaline  membrane  ;  c, 
papilla,  with  a  capillary ;  d,  outer,  e, 
inner  root  sheath  ;/]  cuticle  of  the  latter  ; 
g,  cuticle  of  the  hair ;  h,  young  non- 
medullated  hair  ;  i,  tip  of  new  hair;  /, 
hair  knob  of  the  shed  hair,  with  k,  the 
remainder  of  the  cast-off  outer  root 
sheath. 


492 


THE    GLANDS   OF   THE    SKIN. 


284.  THE  GLANDS  OF  THE  SKIN.— The  sebaceous  glands  (Fig.  294,  I,  T)  are 
simple  acinous  gland.^i,  which  open  by  a  duct  into  the  hair  follicles  of  large  hairs  near  their  upper 
part;  in  the  case  of  small  hairs,  they  may  project  from  the  duct  of  the  gland  ( I'ig.  299).  In  some 
situations,  the  ducts  of  the  glands  open  free  ujwn  the  surface,  e.g.,  the  glands  of  labia  minora,  glans, 
prepuce  (Tyson's  glands),  and  the  red  margins  of  the  lips.  The  large.st  glands  occur  in  the  nose  and 
in  the  labia;  they  are  absent  only  from  the  vo!a  manus  and  planta  pedis.  The  oljlong  alveoli  of  the 
gland  consist  of  a  basement  membrane  lined  with  small  polyhedral  nucleated  granular  .secretory  cells 
(Fig.  294,  /).  Within  this  are  other  polyhedral  cells,  whose  sub.stance  contains  numeious  cil  globules ; 
the  cells  become  more  fatty  as  we  proceed  toward  the  centre  of  the  alveolus.  The  cells  lining  the 
duct  are  continuous  with  those  of  the  outer  root  sheath.  The  detritus  formed  by  the  fatty  metamor- 
phosis of  the  cells  constitutes  the  sebum  or  sebaceous  secretion.  [If  the  "oil  or  coccygeal  gland" 
of  a  duck  be  removed,  it  is  found  that,  when  the  animal  is  submerged,  it  takes  up  between  its  feathers 
aliout  the  same  amount  of  water  as  an  intact  duck ;  Init  it  retains  2  to  2^,4  times  as  mucli  water  in  its 
feat  hers  ( Ma.x  Joseph ) .  ] 

The  sweat  glands  (Fig.  294,  I,  k),  sometimes  called  sudoriparous  glands,  consist  of  a  long 
blind  tube,  whose  lower  end  is  arranged  in  the  furm  of  a  coil  placed  in  the  areolar  tissue  under  the 

skin,  while  the  somewhat  smaller  upper  end  or  excretory 
portion    winds    in   a    vertical,   slightly   wave-like   manner, 
Fk;.  299.  through  the  chorium,  and  in  a  corkscrew  or  spiral  manner 

through  the  epidermis,  where  it  opens  with  a  free,  somewhat 
trumpet-shaped,  mouth.  The  glands  are  very  numerous 
and  large  in  tiie  palm  of  the  hand,  sole  of  the  foot,  axilla, 
forehead,  and  around  the  nipple;  few  on  the  back  of  the 
trunk,  and  are  absent  on  the  glans,  prepuce,  and  margin  of 
the  lips.  The  circumanal  glands  and  the  ceruminous 
glands  of  the  external  auditory  meatus,  and  Moll's 
glands,  which  open  into  the  hair  follicles  of  the  eyelashes, 
are  modifications  of  the  sweat  glands. 

Each  gland  tube  consists  of  a  basement  membrane  lined 
l)y  cells;  the  excretory  part  or  sweat  canal  of  the  lube 
is  lined  by  several  layers  of  cubical  cells,  whose  surface  is 
covered  by  a  delicate  cuticular  layer,  a  small  central  lumen 
being  left.  Within  the  coil  the  structure  is  different.  The 
first  part  of  the  coil  resembles  the  above,  but  as  the  coil  is 
the  true  secretory  part  of  the  gland,  its  structure  differs 
from  the  sweat  canal.  This,  the  so-called  distal  portion  of 
the  tube,  is  lined  by  a  single  layer  of  moderately  tall,  clear, 
nucleated,  cylindrical  epithelium  (F^ig.  294,  S),  often  con- 
taining oil  globules.  Smootli  muscular  fibres  are  arranged 
longitudinally  along  the  tube  in  the  large  glands  (Fig.  294, 
S,  a).  There  is  a  distinct  lumen  present  in  the  tube.  As 
the  duct  pa.sses  through 'the  epidermis,  it  winds  its  way 
between  the  epidermal  cells  without  any  independent  mem- 
brane lining  it  [Heynold).  A  network  of  capillaries  sur- 
rounds the  coil.  Befoi-e  the  ar-teries  split  up  into  capillaries, 
they  fonn  a  true  rete  mirabile  around  the  coil  [Briicke). 
This  is  comparable  to  the  glomerulus  of  the  kidney,  which 
may  also  be  regarded  as  a  rete  mirabile.  Numerous  nerves 
pa.ss  to  form  a  plexus,  and  terminate  in  the  glands  (  Tomsa). 
The  total  number  of  sweat  glands  is  estimated  by 
Krause  at  2j^  millions,  which  gives  a  secretory  surface  of 
nearly  1800  square  metres.  These  glands  secrete  sweat. 
Nevertheless,  an  oily  or  fatty  substance  is  often  mixed  with 
tiie  sweat.  In  some  animals  (glands  in  the  sole  of  the  foot 
of  the  dog,  and  in  birds)  this  oily  secretion  is  very  marked. 
Numerous  lymphatics  occur  in  the  cutis,  some  arise  by  a  blind  end,  and  others  from  loops  within 
the  papilla  on  a  plane  lower  than  the  vascular  capillary.  [These  open  into  more  or  less  horizontal 
networks  of  tubular  lymphatics  in  the  cutis,  and  these  again  into  the  wide  lymphatics  of  the  subcu- 
taneous tissue,  which  are  well  provided  with  valves.]  Special  lymphatic  spaces  are  disposed  in 
relation  with  the  hair  follicles  and  their  glands  (Neumann),  [and  also  with  the  fat  [Klein).  The 
lymphatics  of  the  skin  are  readily  injected  with  Berlin  blue  by  the  puncture  method]. 

The  blood  vessels  of  the  skin  are  arranged  in  several  systems.  There  is  a  superficial  system, 
from  which  proceed  the  capillaries  for  the  papilli-e.  There  is  a  deeper  .system  of  vessels  which 
supplies  special  blood  vessels  to  (<?)  the  fatty  tis.sue ;  {b)  the  hair  follicles,  each  of  which  has  a 
special  vascular  arrangement  of  its  own,  and  in  connection  with  this  each  sebaceous  gland  receives  a 
special  artery;  (c)  an  artery  goes  also  to  each  coil  of  a  sweat  gland,  where  it  forms  a  dense  plexus  of 
capillaries  (  Tomsa). 


Sebaceous  gland,  with  a  lanugo  hair,  a, 
granular  epithelium  ;  b,  rete  Malpighii 
continuous  with  a  ;  c,  fatty  cells  and  free 
fat ;  d,  acini ;  e,  hair  follicle,  with  a  small 
hair.y. 


CUTANEOUS    respiration:    sebum — SWEAT.  493 

285.  THE  SKIN  AS  A  PROTECTIVE  COVERING.— The  sub- 
cutaneous fatty  tissue  fills  up  the  depressions  between  adjoining  parts  of  the 
body  and  covers  projecting  parts,  so  that  a  more  rounded  appearance  of  the  body 
is  thereby  obtained.  It  also  acts  as  a  soft  elastic  pad  and  protects  delicate  parts 
from  external  pressure  (sole  of  the  foot,  palm  of  the  hand),  and  it  often  surrounds 
and  protects  blood  vessels,  nerves,  etc.  It  is  a  bad  conductor  of  heat,  and  thus 
acts  as  one  of  the  factors  regulating  the  radiation  of  heat  (§  214,  II,  4),  and,  there- 
fore, the  temperature  of  the  body.  The  epidermis  and  cutis  vera  also  act  in  the 
same  manner  (§  212).  Klug  found  that  the  heat  conduction  is  less  through  the  skin 
and  subcutaneous  fatty  tissue  than  through  the  skin  alone ;  the  epidermis  conducts 
heat  less  easily  than  the  fat  and  the  chorium. 

The  solid,  elastic,  easily  movable  cutis  affords  a  good  pj'otection  against  external, 
mechanical  injuries  ;  while  the  dry,  impermeable,  homy  epidermis,  devoid  of  nerves 
and  blood  vessels,  affords  a  further  protection  against  the  absorption  of  poisons,  and 
at  the  same  time  it  is  capable  of  resisting,  to  a  certain  degree,  thermal  and  even 
chemical  actions.  A  thin  layer  of  fatty  matter  protects  the  free  surface  of  the  epi- 
dermis from  the  macerating  action  of  fluids,  and  from  the  disintegrating  action 
of  the  air.  The  epidermis  is  important  in  connection  with  t\\t  fluids  of  the  body. 
It  exerts  pressure  upon  the  cutaneous  capillaries,  and,  to  a  limited  extent,  prevents 
too  great  diffusion  of  fluid  from  the  cutaneous  vessels.  Parts  of  the  skin  devoid  of 
epidermis  are  red  and  always  moist.  When  dry,  the  epidermis  and  the  epidermal 
appendages  are  bad  conductors  of  electricity  (§  326).  Lastly,  the  existence  of 
uninjured  epidermis  prevents  adjoining  parts  from  growing  together. 

As  the  epidermis  is  but  slightly  extensile  it  is  stretched  over  the  folds  and  papillae  of  the  cutis  vera, 
which  becomes  level  vv^hen  the  skin  is  stretched,  and  the  papillse  may  even  disappear  with  strong 
tension  [LewmsH). 

286.  CUTANEOUS    RESPIRATION:    SEBUM— SWEAT.— The 

skin,  with  a  surface  of  more  than  i^  square  metre,  has  the  following  secretory 
functions :  — 

1.  The  respiratory  excretion  ; 

2.  The  secretion  of  sebaceous  matter  ;  and 

3.  The  secretion  of  sweat. 

[Besides  this  the  skin  is  protective,  contains  sense  organs,  is  largely  con- 
cerned in  regulating  the  temperature,  and  may  be  concerned  in  absorption.] 

I.  Respiration  by  the  skin  has  been  referred  to  (§  131).  The  organs  concerned  are  the  tubes 
of  the  sweat  glands,  moistened  as  they  are  with  fluids,  and  sun-ounded  by  a  rich  network  of  capillaries. 
It  is  uncertain  whether  or  not  the  skin  gives  off  a  small  amount  of  N  or  ammonia.  Rohrig  made 
experiments  upon  an  arm  placed  in  an  air-tight  metal  box.  According  to  him,  the  amount  of  COj 
and  H^O  excreted  is  subject  to  certain  daily  variations ;  it  is  increased  by  digestion,  increased 
temperature  of  the  surroundings,  the  application  of  cutaneous  stimuli,  and  by  impeding  the  pulmonary 
respiration.  The  exchange  of  gases  also  depends  upon  the  vascularity  of  certain  parts  of  the  skin, 
while  the  cutaneous  absorption  of  O  also  depends  upon  the  number  of  colored  corpuscles  in  the 
blood. 

In  frogs  and  other  amphibians,  with  a  thin,  always  moist  epidermis,  the  cutaneous  respiration  is 
more  considerable  than  in  warm-blooded  animals.  In  winter,  in  frogs,  the  skin  alone  yields  3^  of 
the  total  amount  of  CO2  excreted ;  in  summer,  %  of  the  same  [Bidder)  ;  thus,  in  these  animals  it  is 
a  more  important  respiratory  organ  than  the  lungs  themselves. 

Suppression  of  the  cutaneous  activity  by  varnishing  or  dipping  the  skin  in  oil,  causes  death 
by  asphyxia  (frogs)  sooner  than  ligature  of  the  lungs.  Varnishing  the  Skin. — When  the  skin  of 
a  warm-blooded  animal  is  covered  with  an  impermeable  varnish  [such  as  gelatin]  {Fourcault, 
Becqiierel^  Brechei),  death  occurs  after  a  time,  probably  owing  to  the  loss  of  too  much  heat.  The 
formation  of  crystalline  ammonio-magnesic  phosphate  in  the  cutaneous  tissue  of  such  animals 
[EdenJutizen)  is  not  sufficient  to  account  for  death,  nor  are  congestion  of  internal  organs  and  serous 
effusions  satisfactory  explanations.  The  retention  of  the  volatile  substances  (acids)  present  in  the 
sweat  is  not  sufficient.  Strong  animals  live  longer  than  feeble  ones ;  horses  die  after  several  days 
( Gerlacli) ;  they  shiver  and  lose  flesh.  The  larger  the  cutaneous  suface  left  unvarnished,  the  later 
does  death  take  place.  Rabbits  die  when  y^  of  their  surface  is  varnished.  When  the  entire  sur- 
face of  the   animal  is   varnished,  the   temperature   rapidly  rails  (to  19°),  the  pulse  and  respirations 


494  THE    SWEAT. 

vary;  usually  they  fall  when  the  varnishing  process  is  limited ;  increased  fiequency  ot  respiration 
has  been  observed  (?  225),  Pigs,  dogs,  horses,  when  one-half  of  the  body  is  varnished,  exhibit 
only  a  teniijorary  fall  of  the  temperature,  and  show  signs  of  weakness,  but  do  not  die  {Ellenbetger 
and  Ilofnuisler).  [In  extensive  burns  of  the  skin,  not  only  is  there  disintegration  of  the  colored 
blood  corpuscles  (v.  Lesser),  but  in  some  cases  ulcers  occur  in  the  duodenum.  The  cause  of  the 
ulceration,  however,  has  not  i:)een  ascertained  satisfactorily  [Curling).'\ 

2.  Sebaceous  Secretion. — The  fatty  matter  as  it  is  excreted  from  the  acini  of 
the  sebaceous  glands  is  fluid,  but  even  within  the  excretory  duct  of  the  gland  it 
stagnates  and  forms  a  white,  fat-like  mass,  which  may  sometimes  be  expressed  (at  the 
side  of  the  nose)  as  a  worm-like  white  body,  the  so-called  comedo.  The  sebaceous 
matter  keeps  the  skin  supple,  and  prevents  the  hair  from  becoming  too  dry.  Mi- 
croscopically the  secretion  is  seen  to  contain  innimierable  fatty  granules,  a  few 
gland  cells  filled  with  fat,  visible  after  the  addition  of  caustic  soda,  crystals  of 
cholesterin,  and  in  some  men  a  mic-.roscopic,  mite-like  animal  (Demodex  follicu- 
lorum). 

Chemical  Composition. — The  constituents  are  for  the  most  part  fatty;  chiefly  £>/<?/«  (fluid)  and 
tahnitin  (solid)  fat,  soa]is,  and  some  chole.sterin ;  a  small  amount  of  albumin  and  unknown  extrac- 
tives. Among  the  inorganic  constituents,  the  insoluble  earthy  phosphates  are  most  abundant ;  while 
the  alkaline  chlorides  and  phosphates  are  less  abundant. 

The  vernix  caseosa  which  covers  the  skin  of  a  new-born  child,  is  a  greasy  mixture  of  sebaceous 
matter  and  macerated  epidermal  cells  (containing  47.5  per  cent.  fat).  A  similar  product  is  the  smegma 
praeputialis  (52.S  per  cent,  fat),  in  which  an  ammonia  soap  is  present. 

The  cerumen  or  ear  wax  is  a  mixture  of  the  secretions  of  the  ceruminous  glands  of  the  ear 
(similar  in  structure  to  the  sweat  glands)  and  the  sebaceous  glands  of  the  auditory  canal.  Besides 
the  constituents  of  sebum,  it  contains  yellow  or  brownish  particles,  a  bitter,  yellow  extractive  substance 
derived  from  the  ceruminous  glands,  potash  soaps,  and  a  special  fat.  The  secretion  of  the  Meibo- 
mian glands  is  sebum. 

[Lanoline. — Liebreich  tinds  in  feathers,  hairs,  wool,  and  keratin  tissues  generally,  a  cholesterin 
fat,  which,  however,  is  not  a  true  fat,  although  it  saponifies,  but  an  ethereal  compound  of  certain  fatty 
acids  with  cholesterin.  In  commerce  it  is  obtained  from  wool,  and  is  known  Ijy  the  above  name;  it 
forms  an  admirable  basis  for  ointments,  and  it  is  very  readily  absorbed  by  the  skin.]  Thus,  the  fat-like 
substance  for  protecting  the  epidennis  is  partly  formed  along  with  keratin  in  the  epidermis  itself. 

3.  The  Sweat. — The  sweat  is  secreted  in  the  coil  of  the  sweat  glands.  As 
long  as  the  secretion  is  small  in  amount,  the  water  secreted  is  evaporated  at  once 
from  the  skin  along  with  the  volatile  constituents  of  sweat  ;  as  soon,  however,  as 
the  secretion  is  increased,  or  evaporation  is  ])re\-ented,  droi)s  of  sweat  appear  on  the 
surface  of  the  skin.  The  former  is  called  insensible  perspiration,  and  the  latter 
sensible  perspiration.  [Broadly,  the  quantity  is  about  2  lbs.  in  twenty-four 
hours.  ] 

The  sensible  perspiration  varies  greatly  ;  as  a  rule,  the  right  side  of  the  body  perspires  more  freely 
than  the  left.  The  palms  of  the  hands  secrete  most,  then  follow  the  soles  of  the  feet,  cheek,  breast, 
upper  arm,  and  forearm  [Peiper).  It  falls  from  morning  to  mid-day,  and  rises  again  toward  evening, 
reaching  its  maximum  before  midnight.  Much  moisture  and  cold  in  the  surrounding  atmosphere 
diminish  it,  and  so  does  diuresis.  In  children,  the  insensible  perspiration  is  relatively  great.  The 
drinking  of  water  favors  it,  alcohol  diminishes  it  (H.  Schtnid). 

Method. — Sweat  is  obtained  from  a  man  by  placing  him  in  a  metallic  vessel  in  a  warm  bath ;  the 
sweat  is  rapidly  secreted  and  collected  in  the  vessel.  In  this  way  P'avre  collected  2560  grammes  of 
sweat  m  lyi  hour.  An  arm  may  be  inclosed  in  a  cylindrical  vessel,  which  is  fixed  air  tight  round 
the  arm  with  an  elastic  bandage  [Scho/iin). 

Among  animals,  the  horse  .sweats,  so  does  the  ox,  but  to  a  less  extent;  the  vola  and  planta  of 
apes,  cats,  and  the  hedgehog  secrete  sweat ;  the  snout  of  the  pig  sweats  (?),  while  the  goat,  rabbit,  rat, 
mouse,  and  dog  are  said  not  to  sweat  [Luchsinger).  [The  skin  over  the  body  and  the  pad  on  the 
dog's  foot  contain  numerous  sweat  glands,  which  open  free  on  the  surface  of  the  pad  and  into  the 
hair  follicles  on  the  general  surface  of  the  skin  ( IV.  Siirlin<().'\ 

Microscopically. — The  sweat  contains  only  a  few  epidermal  scales  accidentally  mixed  with  it, 
and  fine  fatty  granules  from  the  sebaceous  glands. 

Chemical  Composition. — Its  reaction  is  alkaline,  although  it  frequently  is 
acid,  owing  to  the  admixture  of  fatty  acids  from  decomposed  sebum.  During 
profuse  secretion  it  becomes  neutral,  and  lastly  alkaline  again  {Triunpy  and  Luch- 
singer).     The  sweat  is  colorless,  slightly  turbid,  of  a  saltish  taste,  and  has  a  charac- 


INFLUENCE  OF  NERVES  ON  THE  SECRETION  OF  SWEAT.    495 

teristic  odor  varying  in  different  parts  of  the  body  ;  the  odor  is  due  to  the  presence 
of  volatile  fatty  acids.  The  constituents  are  water,  which  is  increased  by  copious 
draughts  of  that  fluid,  and  solids,  which  amount  to  1.180  per  cent.  (0.70  to  2.66 
percent. — Funke),  and  of  these  0.96  per  cent,  is  organic  and  0.33  inorganic. 
Among  the  organic  constituents  are  neutral  fats  (palmitin,  stearin),  also  present  in 
the  sweat  of  the  palm  of  the  hand,  which  contains  no  sebaceous  glands,  cholesterin, 
volatile  fatty  acids  (chiefly  formic,  acetic,  butyric,  propionic,  caproic,  capric  acids), 
varying  qualitatively  and  quantitatively  in  different  parts  of  the  body.  These  acids 
are  most  abundant  in  the  sweat  first  (acid)  secreted.  There  are  also  traces  of 
albumin  (similar  to  casein)  and  urea,  about  o.i  per  cent.  In  ursemic  conditions 
(anuria  in  cholera)  urea  has  been  found  crystallized  on  the  skin.  When  the  secretion 
of  sweat  is  greatly  increased,  the  amount  of  urea  in  the  urine  is  diminished,  both 
in  health  and  in  uraemia  {Leube^.  The  nature  of  the  reddish-yellow  pigment, 
which  is  extracted  from  the  residue  of  sweat  by  alcohol,  and  colored  green  by 
oxalic  acid,  is  unknown.  Among  inorganic  constituents,  those  that  are  easily 
soluble  are  more  abundant  than  those  that  are  soluble  with  difficulty,  in  the  pro- 
portion of  17  to  I  ;  sodium  chloride,  0.2  ;  potassium  chloride,  0.2  ;  sulphates,  o.oi 
per  1000,  together  with  traces  of  earthy  phosphates  and  sodium  phosphate.  Sweat 
contains  CO2  in  a  state  of  absorption  and  some  N.  When  decomposed  with  free 
access  of  air,  it  yields  ammonia  salts  {Gorup-B esanez) . 

Excretion  of  Substances. — Some  substances  when  introduced  into  the  body  reappear  in  the 
sweat — benzoic,  cinnaraic,  tartaric,  and  succinic  acids  are  readily  excreted ;  quinine  and  potassic  iodide 
with  more  difficulty.  Mercuric  chloride,  arsenious  and  arsenic  acids,  sodium  and  potassium  arseniate 
have  also  been  found.  After  taking  arseniate  of  iron,  arsenious  acid  has  been  found  in  the  sweat, 
and  iron  in  the  urine.  Mercury  iodide  reappears  as  a  chloride  in  the  sweat,  while  the  iodine  occurs 
in  the  saliva. 

Formation  of  Pigments. — The  leucocytes  furnish  the  material,  and  the  pig- 
ment is  deposited  in  granules  in  the  deeper  layers,  and,  to  a  less  extent,  in  the  upper 
layers,  of  the  rete  Malpighii.  This  occurs  in  the  folds  around  the  anus,  scrotum, 
nipple  [especially  during  pregnancy],  and  everywhere  in  the  colored  races.  There 
is  a  diffuse,  whitish-yellow  pigment  in  the  stratum  corneum,  which  becomes  darker 
in  old  age.  The  pigmentation  depends  on  chemical  processes,  reduction  taking 
place,  and  these  processes  are  aided  by  light.  Granular  pigment  lies  also  in  the 
layers  of  prickle  cells.  The  dark  coloration  of  the  skin  may  be  arrested  by  free  O 
[hydric  peroxide],  while  the  corneous  change  is  prevented  at  the  same  time  {Unna). 

Pathological. — To  this  belongs  the  formation  of  liver  spots  or  chloasma,  freckles,  and  the  pig- 
mentation of  Addison's  disease  [pigmentation  round  old  ulcers,  etc.]  (g  103,  IV).  [The  curious 
cases  of  pigmentation,  especially  in  neurotic  women  e.g.,  in  the  eyelids,  deserve  further  study  in 
relation  to  the  part  played  by  the  nervous  system  in  this  process.] 

287.  INFLUENCE  OF  NERVES  ON  THE  SECRETION  OF 
SWEAT. — The  secretion  of  the  skin,  which  averages  about  -^  of  the  body 
weight,  i.e.,  about  double  the  amount  of  water  excreted  by  the  lungs,  maybe 
increased  or  diminished.  The  liability  to  perspire  varies  much  in  different  individ- 
tials.  The  following  conditions  influence  the  secretion  :  i.  Increased  temper- 
ature of  the  surroundings  causes  the  skin  to  become  red,  while  there  is  a  profuse 
secretion  of  sweat  (§  214,  II,  i).  Cold,  as  well  as  a  temperature  of  the  skin  about 
50°  C,  arrests  the  secretion.  2.  A  very  watery  condition  of  the  blood,  ^.^.,  after 
copious  draughts  of  warm  water,  increases  the  secretion.  Increased  cardiac  ard 
vascular  activity,  whereby  the  blood  pressure  within  the  cutaneous  capillaries  is 
increased,  have  a  similar  effect ;  increased  sweating  follows  increased  muscular 
activity.  3.  Certain  drugs  favor  sweating,  e.g.,  pilocarpin.  Calabar  bean, 
strychnin,  picrotoxin,  muscarin,  nicotin,  camphor,  ammonia  compounds  ;  while 
others,  as  atropin  and  morphia,  in  large  doses,  diminish  or  paralyze  the  secretion. 
[Drugs  which  excite  copious  perspiration,  so  that  it  stands  as  beads  of  sweat  on  the 
skin,  are  called  sudorifics,  while  those  that  excite  the  secretion  gently  are  dia- 


496  INFLUENCE    OF    NERVES    ON    THE    SECRETION    OF    SWEAT. 

phoretics,  the  difference  being  one  of  degree.  Those  drugs  which  lessen  the 
secretion  are  called  antihydrotics.]  4.  It  is  important  to  notice  the  antagonism 
which  exists,  i)robal)ly  ujjon  medianical  grounds,  between  the  secretion  of  sweat, 
the  urinary  secretion,  and  the  evacuation  of  the  intestine.  Thus  copious  secretion 
of  urine  {e.g.,  in  diabetes)  and  watery  stools  coincide  with  dryness  of  the  skin. 
If  the  secretion  of  sweat  be  increased,  the  ])ercentage  of  salts,  urea,  and  albtmiin 
is  also  increased,  while  the  other  organic  substances  are  diminished.  The  more 
saturated  the  air  is  with  watery  vapor,  the  sooner  does  the  secretion  appear  in  drops 
upon  the  skin,  while  in  dry  air  or  air  in  motion,  owing  to  the  rapid  evaporation, 
the  formation  of  drops  of  sweat  is  prevented,  or  at  least  retarded.  [The  com- 
plementary relation  between  the  skin  and  kidneys  is  well  known.  In  summer, 
when  the  skin  is  active,  the  kidneys  separate  less  water ;  in  winter,  when  the 
.skin  is  less  active,  it  is  cold  and  comparatively  bloodless,  while  the  kidneys  excrete 
more  water,  so  that  the  action  of  these  two  organs  is  in  inverse  ratio.] 
The  influence  of  nerves  upon  the  secretion  of  sweat  is  very  marked. 

I.  Just  as  in  the  secretion  of  saliva  (§  145),  vasomotor  nerves  are  usually  in 
action  at  the  same  time  as  the  ])roper  secretory  nerves ;  the  vaso-dilator 
nerves  (sweating  with  a  red  congested  ^nV^w)  are  most  frequently  involved.  The  fact 
that  secretion  of  sweat  does  occasionally  take  place  when  the  skin  is  pale  (fear, 
death  agony)  shows  that,  when  the  vasomotor  nerves  are  excited,  so  as  to  constrict 
the  cutaneous  blood  vessels,  the  sweat-secretory  nerve  fibres  may  also  be  active. 

Under  certain  circumstances,  the  amount  of  blood  in  the  skin  seems  to  determine  the  occur- 
rence of  sweating;  thus,  Dupuy  found  that  section  of  the  cervical  sympathetic  caused  secretion  on 
that  side  of  the  neck  of  a  horse  ;  while  Nitzelnadel  found  that  percutaneous  electrical  stimulation  of 
the  cervical  sympathetic  in  min,  limited  the  sweating. 

[We  may  draw  a  parallel  between  the  secretion  of  saliva  and  that  of  sweat.  I>oth  are  formed 
in  glands  derived  from  the  outer  layer  of  the  embryo.  P>oth  secretions  are  formed  from  lymph 
supplied  by  the  blood  stream,  and  if  the  lymph  be  in  sufificient  quantity,  secretion  may  take  place 
when  there  is  no  circulation,  although  in  both  cases  secretion  is  most  lively  when  the  circulation  is 
most  active  and  the  secretory  nerves  of  both  are  excited  simultaneously  ;  both  glands  have  secretory 
nerves  distinct  from  the  nerves  of  the  blood  vessels;  both  glands  may  be  paralyzed  by  the  action 
of  the  nervous  system,  or  in  disease  (fever),  or  conversely,  both  are  paralyzed  by  atropine  and 
excited  by  other  drugs,  ^.  ,?■.,  pilocarpin.  In  the  gland  cells  of  both,  histological  changes  accom- 
pany the  secretory  act,  and  no  doubt  similar  electromotor  phenomena  occur  in  both  glands.] 

II.  Secretory  nerves,  altogether  independent  of  the  circulation,  control  the 
secretion  of  sweat.  Stimulation  of  these  nerves,  even  in  a  limb  which  has  been 
amputated  in  a  kitten,  causes  a  temporary  secretion  of  sweat,  /.  <?.,  after  complete 
arrest  of  the  circulation  (Go/tz,  Kendall  and  Luchsinger,  Ostroumow).  In  the 
intact  condition  of  the  body,  however,  profuse  perspiration,  at  all  events,  is  always 
associated  with  simultaneous  dilatation  of  the  blood  vessels  (just  as,  in  stimulation 
of  the  facial  nerve,  an  increased  secretion  of  saliva  is  associated  with  an  increased 
blood  stream — §  145,  A,  I).  The  secretory  nerves  and  those  for  the  blood  vessels 
seem  to  lie  in  the  same  nerve  trunks. 

The  secretory  nerves  for  the  hind  limbs  (cat)  lie  in  the  sciatic  nerve.  Luch- 
singer  found  that  stimulation  of  the  peripheral  end  of  this  nerve  caused  renewed 
secretion  of  sweat  for  a  period  of  half  an  hour,  provided  the  foot  was  always  wiped 
to  remove  the  sweat  already  formed.  If  a  kitten,  whose  sciatic  nerve  is  divided  on 
one  side,  be  placed  in  a  chamber  filled  with  heated  air,  all  the  three  intact  limbs 
soon  begin  to  sweat,  but  the  limb  whose  nerve  is  divided  does  not,  nor  does  it  do 
so  when  the  veins  of  the  limb  are  ligatured  so  as  to  produce  congestion  of  its 
blood  ve.ssels.  [The  cat  sweats  only  on  the  hairless  soles  of  the  feet.]  As  to  the 
course  of  the  secretory  fibres  to  the  sciatic  nerve,  some  j^ass  directly  from  the 
spinal  cord  (Vulpian),  some  pass  into  the  abdominal  sympathetic  {Luchsmger, 
Natvrocki,  Ostroumoiv),  through  the  rami  communicantes  and  the  anterior  spinal 
roots  from  the  upper  lumbar  and  lower  dorsal  spinal  cord  (9th  to  13th  dorsal 
vertebrae — cat),  where  the  sweat  centre  for  the  lower  limbs  is  situated. 


SWEAT   CENTRE.  497 

The  sweat  centre  may  be  excited  directly  :  (i)  By  a  highly  venous  condition 
of  the  blood,  as  during  dyspnoea,  e.  g.,  the  secretion  of  sweat  that  sometimes  pre- 
cedes death:  (2)  by  overheated  blood  (45°  C.)  streaming  through  the  centre;  (3) 
by  certain  poisons  (see  p.  495).  The  centre  maybe  also  excited  reflexly,  although 
the  results  are  variable,  e.  g.,  stimulation  of  the  crural  and  peroneal  nerves,  as  well 
as  the  central  end  of  the  opposite  sciatic  nerve,  excites  it.  [The  pungency  of 
mustard  in  the  mouth  may  excite  free  perspiration  on  the  face.] 

Anterior  Extremity. — The  secretory  fibres  lie  in  the  ulnar  and  median  nerves, 
for  the  fore  limbs  of  the  cat ;  most  of  them,  or  indeed  all  of  them  {Nawrocki), 
pass  into  the  thoracic  sympathetic  (Ggl.  stellatum),  and  part  (?)  run  in  the  nerve 
roots  direct  from  the  spinal  cord  {Licchsinger,  Vulpian,  Oit).  A  similar  SAveat 
centre  for  the  upper  limbs  lies  in  the  lower  part  of  the  cervical  spinal  cord. 
Stimulation  of  the  central  ends  of  the  brachial  plexus  causes  a  reflex  secretion  of 
sweat  upon  the  foot  of  the  other  side  (^Adamkiewicz).  At  the  same  time  the  hind 
feet  also  perspire. 

Pathological. — Degeneration  of  the  motor  ganglia  of  the  anterior  horns  of  the  spinal  cord 
causes  loss  of  the  secretion  of  sweat,  in  addition  to  paralysis  of  the  voluntary  muscles  of  the  trunk. 
The  perspiration  is  increased  in  paralyzed  as  well  as  in  oedematous  limbs.  In  nephritis,  there  are 
great  variations  in  the  amount  of  water  given  off  by  the  skin. 

Head. — The  secretory  fibres  for  this  part  (horse,  man,  snout  of  pig)  lie  in  the 
thoracic  sympathetic,  pass  into  the  ganglion  stellatum,  and  ascend  in  the  cervical 
sympathetic.  Percutaneous  electrical  stimulation  of  the  cervical  sympathetic  in 
man,  causes  sweating  of  that  side  of  the  face  and  of  the  arm  (J/.  Meyer).  In  the 
cephalic  portion  of  the  sympathetic,  some  of  the  fibres  pass  into,  or  become  applied 
to,  the  branches  of  the  trigeminus,  which  explains  why  stimulation  of  the  infra- 
orbital nerve  causes  secretion  of  sweat.  Some  fibres,  however,  arise  directly  from 
the  roots  of  the  trigeminus  (^Luchsinger),  and  the  facial  {Vulpian,  Adainkiewicz). 
Undoubtedly  the  cerebrum  has  a  direct  effect  either  upon  the  vasomotor  nerves 
(p.  496,  I)  or  upon  the  sweat-secretory  fibres  (II),  as  in  the  sweating  produced  by 
psychical  excitement  (pain,  fear,  etc.). 

Adamkiewicz  and  Senator  fovmd  that,  in  a  man  suffering  from  abscess  of  the  motor  region  of  the 
cortex  cerebri  for  the  arm,  there  were  spasms  and  perspiration  in  the  arm. 

Sweat  Centre. — 'According  to  Adamkiewicz,  the  medulla  oblongata  contains 
the  dominating  s^A^eat  centre  (§  373).  When  this  centre  is  stimulated  in  a 
cat,  all  the  four  feet  sweat,  even  three-quarters  of  an  hour  after  death  {Adam- 
kiewicz). 

III.  The  nerve  fibres  which  terminate  in  the  smooth  muscular  fibres  of  the  sweat 
glands  act  upon  the  excretion  of  the  secretion. 

[Changes  in  the  Cells  during  Secretion. — In  the  resting  glands  of  the  horse,  the  cylindrical 
cells  are  clear  with  the  nucleus  near  their  attached  ends,  but  after  free  perspiration  they  become 
granular,  and  their  nucleus  is  more  central  {lienaiii).'] 

If  the  sweat  nerves  be  divided  (cat),  injection  of  pilocarpin  Causes  a  secretion  of  sweat,  even  at 
the  end  of  three  days.  After  a  longer  period  than  six  days,  there  may  be  no  secretion  at  all.  This 
observation  coincides  with  the  phenomenon  of  dryness  of  the  skin  in  paralyzed  limbs.  Dieffenbach 
found  that  transplanted  portions  of  skin  first  began  to  sweat  when  their  sensibility  was  restored.  If 
a  motor  nerve  (tibial,  median,  facial)  of  a  man  be  stimulated,  sweat  appears  on  the  skin  over  the 
muscular  area  suppHed  by  the  nerve,  and  also  upon  the  corresponding  area  of  the  opposite  non- 
stimulated  side  of  the  body.  This  result  occurs  when  the  circulation  is  arrested  as  well  as  when  it 
is  active.  Sensory  and  thermal  stimulation  of  the  skin  always  cause  a  bilateral  reflex  secretion 
independently  of  the  circulation.  The  area  of  sweating  is  independent  of  the  part  of  the  skin 
stimulated. 

288.  PATHOLOGICAL  VARIATIONS. — i.  Anidrosis  or  diminution  of  the  secretion 
of  sweat  occurs  in  diabetes  and  the  cancerous  cachexia,  and  along  with  other  disturbances  of  nutri- 
tion of  the  skin  in  some  nervous  diseases,  e.  g.,  in  dementia  paral)tica;  in  some  limited  regions  of 
the  skin,  it  has  occurred  in  certain  tropho-neuroses,  e.  g.,  in  unilateral  atrophv  of  the  face  and  in 
paralyzed  parts.  In  many  of  these  cases  it  depends  upon  paralysis  of  the  corresponding  nerves  or 
their  spinal  sweat  centres. 
32 


498  CUTANEOUS   ABSORPTION. 

2.  Hyperidrosis,  or  increase  of  the  secretion  of  sweat,  occurs  in  easily  excitable  persons,  in 
Conse(iuencc  of  ihe  irritation  of  the  nerves  concerned  (§  288),  e.  <^.,  the  sweating  which  occurs  in 
debilitated  conditions  and  in  the  hysterical  (sometimes  on  the  head  and  hands),  and  the  so-called 
epi  eptoid  sweats  i^Eu/eitbttrg).  Sometimes  the  increase  is  confined  to  one  side  0/  the  /tend  (H. 
unlateralis).  This  condition  is  often  accompanied  with  other  nervous  phenomena,  partly  with  the 
symptoms  of  paralysis  of  the  cervical  sympathetic  (redness  of  the  face,  narrow  pupil),  partly  with 
symptoms  of  stimulation  of  the  sympathetic  (dilated  pupil,  exophthalmos).  It  may  occur  without 
these  phenomena,  and  is  due,  perhaps,  to  stimulation  of  the  proper  secretory  fibres  alone.  [Increased 
sweating  is  very  marked  in  certain  fevers,  both  during  their  course  and  at  the  crisis  in  some;  while 
the  sweat  is  not  only  copious  but  acid  in  acute  rheumatism.  The  "night  sweats"  of  phthisis  are 
very  marked  and  disagreeable.] 

3.  Paridrosis  or  qualitative  changes  in  the  secretion  of  sweat,  e.g.,  the  rare  case  of  "  sweating 
0/  blood"  (haematohidrosis),  is  sometimes  unilateral.  According  to  Ilebra,  in  .some  cases  this 
condition  represents  a  vicarious  form  of  men.struation.  It  is,  however,  usually  one  of  many  phe- 
nomena of  nervous  affections.  Bloody  sweat  sometimes  occurs  in  yellow  fever.  Bile  pigments  have 
been  found  in  the  sweat  in  jaundice;  blue  sweat  from  indigo  (Bizio),  from  pyocyanin  (the  rare  blue 
coloring  matter  of  pus),  or  from  phosphate  of  the  oxide  of  iron  {Osc.  Kolhnann)  is  extremely  rare. 
Such  colored  sweats  are  called  chromidrosis.  Numerous  micro-organisms  (which,  however,  are 
innocuous)  live  between  the  epidermal  scales  and  on  the  hairs,  two  varieties  of  Saccharomycetes;  in 
cutaneous  folds  Leptotlu'ix  epidermalis,  various  Schizomycetes,  and  five  kinds  of  Micrococci;  and 
between  the  toes — Bacterium  graveolens  [Bordoni-  Uffreduzzi),  which  causes  the  odor  of  the  sweat  of 
the  feet.  Microorganisms  are  also  the  cause  of  yellow,  blue,  and  red  sweat;  the  last  is  due  to 
Micrococcus  htematodes. 

Grape  sugar  occurs  in  the  sweat  in  diabetes  mellitus ;  uric  acid  and  cystin  very  rarely ;  and  in  the 
sweat  of  stinking  feet,  leucin,  tyrosin,  valerianic  acid,  and  ammonia.  Stinking  sweat  (bromidrosis) 
is  due  to  the  decomposition  of  the  sweat,  from  the  presence  of  a  special  microorganism  ( Bacterium 
foctidum — Thin).  In  the  sweating  stage  of  ague  butyrate  of  lime  has  been  found,  while  in  the 
sticky  sweat  of  acute  articular  rheumatism  there  is  more  albumin  {Anseh>iino),  and  the  same  is  the 
case  in  artificial  sweating  (Leuht') ;  lactic  acid  is  present  in  the  sweat  in  pueq:)eral  fever. 

The  sebaceous  secretion  is  sometimes  increased,  constituting  seborrhcea,  which  may  be  local  or 
general.  It  may  be  diminished  (Asteatosis  cutis).  The  sebaceous  glands  degenerate  in  old  people, 
and  hence  the  glancing  of  the  .skin  [Reviy).  If  the  ducts  of  the  glands  are  occluded  the  sebum 
accumulates.  Sometimes  the  duct  is  occluded  by  black  particles  or  ultramarine  (Unna)  from  the 
blue  used  in  coloring  the  linen.  When  pressed  out,  the  fatty  womi-shaped  secretion  is  called 
"  comedo." 

289.  CUTANEOUS  ABSORPTION— GALVANIC  CONDUCTION.— After  long  im- 
mersion in  water  the  superficial  layers  of  the  epidermis  become  moist  and  swell  up.  The  skin  is 
unable  to  absorb  any  substances,  either  salts  or  vegetable  poisons,  from  watery  solutions  of  these. 
TTiis  is  due  to  the  fat  normally  present  on  the  epidermis  and  in  the  pores  of  the  skin.  If  the  fat  be 
removed  from  the  skin  by  alcohol,  ether,  or  chloroform,  absorption  may  occur  in  a  few  minutes 
(Parisot).  According  to  Riihrig,  all  volatile  substances,  e.g.,  carbolic  acid  and  others,  which  act 
upon  and  corrode  the  epidermis,  are  capable  of  absorption.  While,  according  to  Juhl,  such  watery 
solutions  as  impinge  on  the  skin,  in  a  finely  divided  spray,  are  also  capable  of  absorption,  which  very 
probably  takes  place  through  the  interstices  of  the  epidermis. 

[Inunction. — When  ointments  are  rubbed  into  the  skin  so  as  to  press  the  substance  into  the 
pores,  absorption  occurs,  e.g.,  j)0tassium  iodide  in  an  ointment  so  rubbed  in  is  absorbed ;  so  is  mercu- 
rial ointment,  v.  Voit  found  globules  of  mercury  between  the  layers  of  the  epidermis,  and  even  in 
the  chorium  of  a  person  who  was  executed,  into  whose  skin  mercurial  ointment  had  been  previously 
rubbed.  The  mercury  globules,  in  cases  of  mercurial  inunction,  pass  into  the  hair  follicles  and  ducts 
of  the  glands,  where  they  are  affected  by  the  secretion  of  the  glands  and  transformed  into  a  compound 
capable  of  absorption.  An  abraded  or  inflamed  surface  (e.g.,  after  a  blister),  where  the  epidermis 
is  removed,  absorbs  very  rapidly,  just  like  the  surface  of  a  wound  (Endermic  method).] 

[Drugs  may  be  applied  locally  where  the  epidermis  is  intact — epidermic  method — as  when 
drugs  which  affect  the  sensory  nerves  of  a  part  are  painted  over  a  painful  area  to  diminish  the  pain. 
Another  method,  the  hypodermic,  now  largely  used,  is  that  of  injecting,  by  means  of  a  hypodermic 
syringe,  a  non-corrosive,  non-irritant  drug,  in  solution,  into  the  subcutaneous  tissue,  where  it  practi- 
cally passes  into  the  lymph  spaces  and  comes  into  direct  relation  with  the  lymph  and  bloodstream; 
absorption  takes  place  with  great  rapidity,  even  move  so  than  from  the  stomach.] 

Gases. — Under  normal  conditions,  minute  traces  of  O  are  absorbed  from  the  air  ;  hydrocyanic  acid, 
sulphuretted  hydrogen — CO,  CO.^,  the  vapor  of  chloroform  and  ether  may  be  absorbed  ( Chaussier, 
Gerlach,  Rohrig).  In  a  bath  containing  sulphuretted  hydrogen,  this  gas  is  absorbed,  while  CO^  is 
given  off  into  the  water  {Rohrig). 

Absorption  of  watery  solutions  takes  place  rapidly  through  the  skin  of  the  frog  {Gtittmann, 
W.  Stirling,  v.  IVitlich).  Even  after  the  circulation  is  excluded  and  the  central  nervous  system 
<Iestroyed,  much  water  is  absorbed  through  the  skin  of  the  frog,  but  not  to  such  an  extent  as  when 
the  circulation  is  intact  (Spina). 


COMPARATIVE HISTORICAL.  499 

Galvanic  Conduction  through  the  Skin. — If  the  two  electrodes  of  a  constant  current  be 
impregnated  with  a  watery  solution  of  certain  substances  and  applied  to  the  skin,  and  if  the  direction 
of  the  current  be  changed  from  time  to  time,  strychnin  may  be  caused  to  pass  through  the  skin  of  a 
rabbit  in  a  few  minutes,  and  that  in  sufficient  amount  to  kill  the  animal  i^H.  Munk).  In  man,  quinine 
and  potassium  iodide  have  been  introduced  into  the  body  in  this  way,  and  their  presence  detected  in 
the  urine.     This  process  is  called  the  cataphoric  action  of  the  constant  current  (§  328). 

290.  COMPARATIVE— HISTORICAL.— In  all  vertebrates,  the  skin  consists  of  chorium 
and  epidermis.  In  some  reptiles  the  epidermis  becomes  horny,  and  forms  large  plates  or  scales. 
Similar  structures  occur  in  the  edentata  among  mammals.  The  epidermal  appendages  assume 
various  forms,  such  as  hair,  nail,  spines,  bristles,  feathers,  claws,  hoof,  horns,  spurs,  etc.  The  scales  of 
some  fishes  are  partly  osseous  structures.  Many  glands  occur  in  the  skin ;  in  some  amphibia  they 
secrete  mucus,  in  others  the  secretion  is  poisonous.  Snakes  and  tortoises  are  devoid  of  cutaneous 
glands;  in  lizards  the  "  leg  glands"  extend  from  the  anus  to  the  bend  of  the  knee.  In  the  croco- 
dile, the  glands  open  under  the  margins  of  the  cutaneo-osseous  scales.  In  birds,  the  cutaneous 
glands  are  absent;  the  "  coccygeal  glands  "  form  an  oily  secretion  for  lubricating  the  feathers. 
[This  is  denied  by  O.  Liebreich,  as  he  finds  no  cholesterin  fats  in  their  secretion.]  The  civet  glands, 
at  the  anus  of  the  civet  cat,  the  preputial  glands  of  the  musk  deer,  the  glands  of  the  hare,  and  the 
pedal  glands  of  ruminants,  are  really  greatly  developed  sebaceous  glands.  In  some  invertebrata, 
the  skin,  consisting  of  epidermis  and  chorium,  is  intimately  united  with  the  subjacent  muscles,  form- 
ing a  musculo-cutaneous  tube  for  the  body  of  the  animal.  The  cephalopoda  have  chromatophores  in 
their  skin,  i.  e.,  round  or  irregular  spaces  filled  with  colored  granules.  Muscular  fibres  are  arranged 
radially  around  these  spaces,  so  that  when  these  muscles  contract  the  colored  surface  is  increased. 
The  change  of  color  in  these  animals  is  due  to  the  play  or  contraction  of  these  muscles  {Brilcke). 
Special  glands  are  concerned  in  the  production  of  the  shell  of  the  snail.  The  annulosa  are  covered 
with  a  chitinous  investment,  which  is  continued  for  a  certain  distance  along  the  digestive  tract  and  the 
tracheae.  It  is  thrown  off  when  the  animal  sheds  its  covering.  It  not  only  protects  the  animal,  bu 
it  forms  a  structure  for  the  attachment  of  muscles.  In  echinodermata,  the  cutaneous  covering  con- 
tains calcareous  masses ;  in  the  holothurians,  the  calcareous  structures  assume  the  form  of  calcareous 
spicules. 

Historical. — Hippocrates  (born  460  b.  c.)  and  Theophrastus  (born  371  b.  c.)  distinguished  the 
perspiration  from  the  sweat ;  and,  according  to  the  latter,  the  secretion  of  sweat  stands  in  a  certain 
antagonistic  relation  to  the  urinary  secretion  and  to  the  water  in  the  faeces.  According  to  Cassius 
Felix  (97  A.D.),  a  person  placed  in  a  bath  absorbs  water  through  the  skin;  Sanctorius  (1614)  meas- 
ured the  amount  of  sweat  given  off;  Alberti  (1581)  was  acquainted  with  the  hair  bulb;  Donatus 
(1588)  described  hair  becoming  gray  suddenly;  Riolan  (1626)  showed  that  the  color  of  the  skin  of 
the  negro  was  due  to  the  epidermis. 


Physiology  OF  the  Motor  apparatus. 


Fig.  ^oo. 


291.  [CILIARY  MOTION— PIGMENT  CELLS.]— [(>?)  Muscular 
Movement. — 15y  tar  the  greatest  number  of  the  movements  occurring  in  our 
bodies  is  accomplished  through  the  agency  of  muscular  fibre,  which,  when  it 
is  e.xcited  by  a  stimulus,  contracts,  i.e.,  it  forcibly  shortens,  and  thus  brings  its 
two  ends  nearer  together,  while  it  bulges  to  a  corresponding  extent  laterally.  In 
muscle,  the  contraction  takes  place  in  a  definite  direction.] 

\(^b)  Amoeboid  Movement. — Motion  is  also  exhibited  by  colorless  blood 
corpuscles,  lymph  corpuscles,  leucocytes,  and  some  other  corpuscles.  In  these 
structures  we  have  examples  of  amoeboid  movement  (^  9),  which  is  movement  in 
an  indefinite  direction.] 

\{c)  Ciliary  Movement. — There  is  also  a  peculiar  form  of  movement,  known 
as  ciliary  movonent.  There  is  a  gradual  transition  between  these  different  forms 
of  movement.  The  cilia  which  are  attached  to  the  ciliated  epithelium  are  the 
motor  agents  (Fig.  300).] 

[Ciliated  epithelium — where  found. — In  the  nasal  mucous  meml)rane,  except  the  olfactory- 
region;  the  cavities  accessory  to  the  nose;  the  upper  half  of  the  pharynx,  Eustachian  tube,  larynx, 

trachea,  and  bronchi;  in  the  uterus,  except 
the  lower  half  of  the  cervix ;  Fallopian 
tubes ;  vasa  efferentia  to  the  lower  end  of 
epididymis;  ventricles  of  brain  (child); 
and  the  central  canal  of  the  spinal  cord.] 

[The  cilia  are  flattened,  blade-like  or 
hair-like  appendages  attached  to  the  free 
end  of  the  cells.  They  are  about  ^5^5 
inch  in  length,  and  are  apparently  homo- 
geneous and  structureless.  They  are  planted 
upon  a  clear,  non-contractile  disk  on  the 
free  end  of  the  cell,  and  .some  observers 
state  that  they  pass  through  the  disk  to 
become  continuous  with  the  protoplasm  of 
the  cell,  or  with  the  plexus  of  fibrils  which 
pervades  the  protoplasm,  so  that  by  some 
observers  they  are  regarded  as  prolongations  of  the  intra-epithelial  plexus  of  fibrils.  They  are  spe- 
cially modified  parts  of  an  epithelial  cell,  and  are  contractile  and  elastic.  They  are  colorle.'-s, 
tolerably  strong,  not  colored  by  .staining  reagents,  and  are  possessed  of  considerable  rigidity  and 
flexibility.  They  are  always  connected  with  the  protoplasm  of  cells,  and  are  never  outgrowths  of 
the  solid  cell  membranes.  There  may  be  ten  to  twenty  cilia  distributed  uniformly  on  the  free  surface 
of  a  cell  (Fig.  300).] 

[In  the  large  ciliated  cells  in  the  intestine  of  some  mollusks  (mussel),  the  ci'ia  perforate  the 
clear  refractile  disk,  which  appears  to  consist  of  small  glolniles — basal  pieces — united  by  thtir 
edge,  so  that  a  cilium  seems  to  spring  from  each  of  these,  while  continueil  downward  into  the  pro- 
toplasm of  the  cell,  but  not  attached  to  the  nucleus,  there  is  a  single  varicose  fibril — rootlet,  and 
the  lea.sh  of  these  fibrils  passes  through  the  substance  of  the  cell  and  may  unite  toward  its  lower  tailed 
extremity  [Engehnann).'\ 

[Ciliary  motion  may  be  .studied  in  the  gill  of  a  mussel,  a  small  part  of  the  gill  being  teased  in 
sea  water  ;  or  the  hard  palate  of  a  frog,  newly  killed,  may  be  scraped  and  the  scraping  examined  in 
3^^  p.  c.  salt  solution.  ()n  analyzing  the  movement,  all  the  cilia  will  be  ol)served  to  execute  a  regular, 
periodic,  to-and-fro  rhythmical  movement  in  a  plane  usually  vertical  to  the  surface  of  the  cells,  the 
direction  of  the  movement  being  parallel  to  the  long  axis  of  the  organ.  The  appearance  presented 
by  the  movements  of  the  cilia  is  sometimes  described  as  a  lashing  movement,  or  hke  a  field  of  corn 

500 


Inner 
layer. 


FUNCTIONS    OF   CILIA.  501 

moved  by  the  wind.  Each  vibration  of  a  cihum  consists  of  a  rapid  forward  movement  or  flexion, 
the  tip  moving  more  than  the  base,  and  a  slower  backward  movement,  the  cihum  again  straightening 
itself.  The  forward  movement  is  about  twice  as  rapid  as  the  backward  movement.  The  amplitude 
of  the  movement  varies  according  to  the  kind  of  cell  and  other  conditions,  being  less  when  the  cells 
are  about  to  die,  but  it  is  the  same  for  all  the  cilia  attached  to  one  cell,  and  is  seldom  more  than  20° 
to  50°.  There  is  a  certain  periodicity  in  their  movement ;  in  the  frog  they  contract  about  twelve 
times  per  second.  The  result  of  the  rapid  forward  movement  is  that  the  surrounding  fluid,  and  any 
particles  it  may  contain,  are  moved  in  the  direction  in  which  the  cilia  bend.  All  the  cilia  of  adjoin- 
ing cells  do  not  move  at  once,  but  in  regular  succession,  the  movement  traveling  from  one  cell  to  the 
other,  but  how  this  co-ordination  is  brought  about  we  do  not  know.  At  least  it  is  quite  independent 
of  the  nervous  system,  as  cihary  movement  goes  on,  in  isolated  cells,  and  in  man  it  has  been  observed 
in  the  trachea  two  days  after  death.  Conditions  for  movement. — In  order  that  ciliary  move- 
ment may  go  on,  it  is  essential  that  (l)  the  ciHa  be  connected  with  part  of  a  cell;  (2)  moisture;  (3) 
oxygen  be  present;  and  (4)  the  temperature  be  within  certain  limits.] 

[A  ciliated  epithelial  cell  is  a  good  example  of  the  physiological  division  of  labor.  It  is 
derived  from  a  cell  which  originally  held  motor,  automatic,  and  nutritive  functions  all  combined 
in  one  mass  of  protoplasm,  but  in  the  fully  developed  cell,  the  nutritive  and  regulative  functions 
are  confined  to  the  protoplasm,  while  the  cilia  alone  are  contractile.  If  the  cilia  be  separated 
from  the  cell,  they  no  longer  move.  If,  however,  a  cell  be  divided  so  that  part  of  it  remains 
attached  to  the  cilia,  the  latter  still  move.  The  nucleus  is  not  essential  for  this  act.  It  would 
seem,  therefore,  that  though  the  ciha  are  contractile,  the  motor  impulse  probably  proceeds  from  the 
cell.  Each  cell  can  regulate  its  own  nutrition,  for  during  life  they  resist  the  entrance  of  certain 
colored  fluids.] 

[Effect  of  Reagents. — Gentle  heat  accelerates  the  number  and  intensity  of  the  movements, 
cold  retards  them.  A  temperature  of  45°  C.  causes  coagulation  of  their  proteids,  makes  them  per- 
manently rigid,  and  kills  them,  just  in  .the  same  way  as  it  acts  on  muscle,  causing  heat  stiffening 
(§  295,  i).  Weak  alkalies  may  cause  them  to  contract  after  their  movement  is  arrested  or  nearly 
so  (  Virchow),  and  any  current  of  fluid  in  fact  may  do  so.  Lister  showed  that  the  vapor  of  ether 
and  chloroform  arrests  the  movements  as  long  as  the  narcosis  lasts,  but  if  the  vapor  be  not  applied 
for  too  long  a  time,  the  cilia  may  begin  to  move  again.  The  prolonged  action  of  the  vapor  kills 
them.  As  yet  we  do  not  know  any  specific  poison  for  cilia — atropin,  veratrin,  and  curara  acting  like 
other  substances  with  the  same  endosmotic  equivalent  {^Engelmann).'\ 

[Functions  of  Cilia. — The  moving  cilia  propel  fluids  or  particles  along  the 
passages  which  they  line.  By  carrying  secretions  along  the  tubes  which  they  line 
toward  where  these  tubes  open  on  the  surface,  they  aid  in  excretion.  In  the 
respiratory  passages,  they  carry  outward  along  the  bronchi  and  trachea,  the  mucus 
formed  by  the  mucous  glands  in  these  regions.  When  the  mucus  reaches  the 
larynx  it  is  either  swallowed  or  coughed  up.  That  the  cilia  carry  particles  upward 
in  a  spiral  direction  in  the  trachea  has  been  proved  by  actual  laryngoscopic  inves- 
tigation, and  also  by  excising  a  trachea  and  sprinkling  a  colored  powder  on  its 
mucous  membrane,  when  the  colored  particles  (Berlin  blue  or  charcoal)  are  slowly 
carried  toward  the  upper  end  of  the  trachea.  In  bronchitis  the  ciliated  epithe- 
lium is  shed,  and  hence  the  mucus  tends  to  accumulate  in  the  bronchi.  They 
remove  mucus  from  cavities  accessory  to  the  nose,  and  from  the  tympanum,  while 
the  ova  are  carried  partly  by  their  agency  from  the  ovary  along  the  Fallopian  tube 
to  the  uterus.  In  some  of  the  lower  animals  they  act  as  organs  of  locomotion, 
and  in  others  as  adjuvants  to  respiration,  by  creating  currents  of  water  in  the 
region  of  the  organs  of  respiration.] 

[The  Force  of  Ciliary  Movement. — Wyman  and  Bowditch  found  that  the  amount  of  work 
that  can  be  done  by  cilia  is  very  considerable.  The  work  was  estimated  by  the  weight  which  a 
measured  surface  of  the  mucous  membrane  of  the  frog's  hard  palate  was  able  to  carry  up  an  incHned 
plane  of  a  definite  slope  in  a  given  time.] 

[Pigment  cells  belong  to  the  group  of  contractile  tissues,  and  are  well  developed  in  the  frog, 
and  many  other  animals  where  their  characters  have  been  carefully  studied.  They  are  generally 
regarded  as  comparable  to  branched  connective-tissue  corpuscles,  loaded  with  pigmented  granules  of 
melanin.  The  pigment  granules  may  be  diffused  in  the  cell,  or  aggregated  around  the  nucleus ;  in 
the  former  case,  the  skin  of  the  frog  appears  dark  in  color,  in  the  latter,  it  is  but  slightly  pigmented 
(Fig.  301).  Tlie  question  has  been  raised  whether  they  are  actual  cells  or  merely  spaces,  branched, 
and  containing  a  fluid  with  granules  in  suspension.  In  any  case,  they  undergo  marked  changes  of 
shape  under  various  influences.  If  the  motor  nerve  to  one  leg  of  a  frog  be  divided,  the  skin  of  the 
leg  on  that  side  becomes  gradually  darker  in  color  than  the  intact  leg.  A  similar  result  is  seen  in 
the  curara  experiment,  when  all  parts  are  ligatured  except  the  nerve.     Local  applications  affect  the 


502 


STRUCTURE    AND    ARRANGEMENT   OF    MUSCLES. 


Fic 


state  of  dift'usion  of  the  pigment,  as  v.  Witiich  found  tliat  turpentine  or  electricity  caused  the  cells  of 
the  tree  frog  to  contract,  and  the  same  effect  is  produced  by  light.  In  Rana  temporaria  local  irrita- 
tion has  little  effect,  but  light,  on  the  contrary,  h.is,  although  the  effect  of  light  seems  to  be  brought 
about  through  the  eye,  probably  by  a  retlex  mechanism  [Lister).  A  pale-colored  frog,  put  in  a  dark 
place,  assumes,  after  a  time,  a  ditTerent  color,  as  the  pigment  is  diffused  in  the  dark ;  but  if  it  be 
exposed  to  a  bright  light  it  soon  becomes  pale  again.      The  same  phenomenon  may  be  seen  on 

studying  the  web  of  a  frog's  leg  under 
the  microscope.  The-marked  variations 
of  color — within  a  certain  range — in 
the  chameleon  is  due  to  the  condition 
of  the  pigment  cells  in  its  skin,  covered 
as  they  are  by  epidermis,  containing  a 
thin  stratum  of  air  [BriicA'e).  When  it 
is  poisoned  with  strychnin,  its  whole 
body  turns  pale;  if  it  be  ill,  its  body 
becomes  spotted  in  a  dendritic  fashion, 
and  if  its  cutaneous  nerves  be  divided, 
tlie  area  supplied  by  the  nerve  changes 
to  black.  The  condition  of  its  skin, 
therefore,  is  readily  affected  by  the  con- 
dition of  its  nervous  system,  for  psy- 
chical excitement  also  alters  its  color. 
If  the  sympathetic  nerve  in  the  neck  of 
a  turbot  be  divided,  the  skin  on  the 
,  ,  dorsal  part  of  the  head  becomes  black. 

Pigment  cells  from  the  web  of  frog  s  foot;  <i,  cell  with  pigment  granules  ,.  ;.  ,,otr.Hoiis  that  the  rnlnr  of  fishp>i 
diffused;  l>,  granules  more  concentrated;  c,  more  concentrated."  IS  notorious  mat  tlie  Color  01  nsnes 
still ;  d,  cells  with  guanin  granules  (Stirling).  IS  adapted  to  the  Color  of  their  environ- 

ment. If  the  nerve  proceeding  from 
the  stellate  ganglion  in  the  mantle  of  a  cuttle-fish  be  divided,  the  skin  on  one-half  of  the  body 
becomes  pale.] 

[Guanin  in  Cells.  —  Besides  the  pigment  cells  in  the  web  of  a  frog's  foot 
(especially  in  Rana  temporaria)  there  are  other  cells  which  contain  granules  of 
guanin  (Fig.  301,  d).  If  the  web  of  a  frog's  foot  be  mounted  in  Canada  balsam 
and  examined  microscopically  between  crossed  Nicol's  prisms,  each  guanin  cell 
is  seen  to  contain  numerous  very  strongly  doubly  refractive  granules  of  guanin 
^§  283).] 

292.  STRUCTURE  AND  ARRANGEMENT  OF  MUSCLES.— 
[Muscular  Tissue  is  endowed  with  contractility,  so  that  when  it  is  acted  upon 
by  certain  forms  of  energy  or  stimuli,  it  contracts.  There  are  two  varieties  of  this 
tissue — 

(i)   Striped,  striated  (or  voluntary); 

(2)   Non-striped,  smooth,  organic  (or  involuntary). 

Some  muscles  are  completely  under  the  control  of  the  will,  and  are  hence  called 
"voluntary,"  and  others  are  not  directly  subject  to  the  control  of  the  will,  and 
are  hence  called  "involuntary;"  the  former  are  for  the  most  part  striped,  and 
the  latter  non-striped;  but  the  heart  muscle,  although  striped,  is  an  involuntary 
muscle.] 

I.  Striped  Muscles. — The  surface  of  a  muscle  is  covered  with  a  connective-tissue  envelope  or 
perimysium  externum,  from  which  septa,  carrying  blood  vessels  and  nerves,  the  perimysium 
internum,  pass  into  the  substance  of  the  muscle,  so  as  to  divide  it  into  bundles  of  fibres  or  fasciculi, 
which  are  fine  in  the  eye  muscles  and  coarse  in  the  glutei.  In  each  such  compartment  or  mesh  there 
lie  a  number  of  tyiiisctilar  fibres  arranged  more  or  less  ]5arallel  to  each  other.  [The  fibres  are  held 
together  by  delicate  connective  tissue  or  endomysium,  which  sunounds  groups  of  the  fibres;  each 
fibre  being,  as  it  were,  separated  from  its  neighbor  by  delicate  fibrillar  connective  tissue.]  Each 
muscular  fibre  is  surrounded  with  a  rich  plexus  of  capillaries  [which  form  an  elongated  meshwork, 
lying  between  adjacent  fibres,  but  never  penetrating  the  fibres,  which,  however,  they  cross  (Fig. 
307).  In  a  contracted  muscle,  the  cap  llaries  may  be  slightly  sinuous  in  their  course,  Ijut  when  a 
muscle  is  on  the  stretch,  these  curves  disappear.  The  capillaries  lie  in  the  endomysium,  and  near 
them  are  lymphatics']^.  Each  muscular  fibre  receives  a  nerve  fibre.  [Where  found. — Striped 
muscular  fibres  occur  in  the  skeletal  muscles,  heart,  diaphragm,  pharynx,  upper  part  of  ccsophagu.s, 
muscles  of  the  middle  ear  and  pinna,  the  true  sphincter  of  the  urethra,  and  external  anal  sphincter.] 


STRUCTURE    AND    ARRANGEMENT   OF    MUSCLES. 


503 


A  muscular  fibre  (Fig.  302,  i)  is  a  more  or  less  cylindrical  or  polygonal  fibre,  11  to  67  //  {^^^ 
to  g^o  in.]  in  diameter,  and  never  longer  than  3  to  4  centimetres  [i  to  i^  in.].  Within  short  mus- 
cles, e.£:,  stapedius,  tensor  tympani,  or  the  short  muscles  of  a  frog,  the  fibres  are  as  long  as  the  muscle 
itself;  within  longer  muscles,  however,  the  individual  fibres  are  pointed,  and  are  united  obliquely  by 
cement  substance  with  a  similar  beveled  or  pointed  end  of  another  fibre  lying  in  the  same  direction. 
Muscular  fibres  may  be  isolated  by  maceration  in  nitric  acid  with  excess  of  potassic  chlorate,  or  by  a 
36  per  cent,  solution  of  caustic  potash. 

[Each  muscular  fibre  consists  of  the  following  parts  : — 

1.  Sarcolemma,  an  elastic  sheath,  with  transverse  partitions,  stretching  across  the  fibre  at 

regular  intervals — the  iiiet}ibrane  of  Kraitse  ; 

2.  The  included  sarcous  substance  ; 

3.  The  nuclei  or  muscle  corpuscles.] 


Fig.  302. 


Histology  of  muscular  tissue,  i,  Diagram  of  part  of  a  striped  muscular  fibre;  S,  sarcolemma  ;  Q,  transverse  stripes  ; 
F,  fibrillse ;  K,  the  muscle  nuclei ;  N,  a  nerve  fibre  entering  it  with  a,  its  axis  cylinder  and  Kijhne's  motorial  end 
plate,  e,  seen  in  profile;  2,  transverse  section  of  part  of  a  muscular  fibre,  showing  Cohnheim's  areas,  c ;  3,  iso- 
lated muscular  fibrillae;  4,  part  of  an  insect's  muscle  greatly  magnified  ;  a,  Krause-Amici's  line  limiting  the  mus- 
cular cases  ;  ^,  the  doubly  refractive  substance;  c,  Hensen's  disk;  ^,  the  singly  refractive  subsiance;  5,  fibres 
cleaving  transverselj'  into  disks  ;  6,  muscular  fibre  from  the  heart  of  a  frog;  7,  development  of  a  striped  muscle 
from  a  human  fcetus  at  the  third  month;  8,  9,  muscular  fibres  of  the  heart;  c,  capillaries  ;  3,  connective-tissue 
corpuscles  ;   10,  smooth  muscular  fibres;  11,  transverse  section  of  smooth  muscular  fibres. 


Sarcolemma. — Each  muscular  fibre  is  completely  enclosed  by  a  thin,  colorless,  structureless,  trans- 
parent elastic  sheath  (Fig.  302,  i,  S),  which,  chemically,  is  midway  between  connective  and  elastic 
tissue,  and  within  it  is  the  contractile  substance  of  the  muscle,  [^^^len  a  muscular  fibre  is  being 
digested  by  trypsin,  Chittenden  observed,  at  the  beginning,  the  sarcolemma  raised  from  its  sarcous 
contents  as  a  folded  tube,  but  it  is  ultimately  digested  by  trypsin.  It  is  thus  distinguished  from  the 
collagen  substance  of  connective  tissue,  which  is  not  digested  by  trypsin.  It  is  not  dissolved  by  boil- 
ing, and  it  resists  the  action  of  acids  and  dilute  alkalies,  while  it  is  dissolved  by  concentrated  alkalies. 
Thus,  it  differs  from  elastic  fibres,  and" on  the  whole,  chemically,  it  seems  to  be  most  closely  related  to 
the  membrana  propria  of  glands.  It  has  much  more  cohesion  than  the  sarcous  substance  which 
it  encloses,  so  that  sometimes,  when  teasing  fresh  muscular  tissue  under  the  microscope,  one   may 


o04 


STKUCIURE    OF    A    MUSCULAR    FIBRILLA. 


]"IG.    ^O^. 


observe  the  sarcous  substance  torn  across,  with  the  unniplured  sarcoleninia  stretching  between  the 
ends  of  the  mptured  sarcous  substance.  If  muscular  fibres  be  teased  in  distilled  water,  sometimes 
tine  clear  blebs  are  seen  along  the  course  of  the  fil)re,  due  to  the  sarcolemma  being  raised  by  the  lluid 
ciitTusing  under  it.  The  sarcous  substance,  imt  not  the  sarcolemnn,  may  be  torn  across  by  plunging  a 
muscle  in  water  at  55°  C,  and  kee|)ing   it  there  for  some  time  (Rnnvier).^ 

Sarcous  Substance. — The  sarcous  substance  is  marked  transversely  by  alternate  light  and  dim 
l.iyers,  bands,  stripes  or  disks  (Kig.  302,  I,  Q),  so  that  each  fibre  is  saidto  be  "transversely 
striped."  [The  stripes  do  not  occur  in  the  sarcolemma,  but  are  confined  to  the  sarcous  substance, 
and  they  involve  its  whole  thickness.] 

[The  animals  most  suited  for  studying  the  structure  of  the  sarcous  substance  are  some  of  the 
insects.  The  muscles  of  the  water  beetle,  Dytiscus  marginalis,  and  the  Ilydrophilus  piceus  are  well 
.suited  for  this  purpose.  So  is  the  crab's  mu.scle.  In  examining  a  living  muscle  microscopically,  no 
fluid  e.\cept  the  muscle  juice  should  be  added  to  the  preparation,  and  very  high  powers  of  the  micro- 
scope are  required  to  make  out  the  finer  details.] 

Bowman's  Disks. — If  a  mu.scular  fibre  be  subjected  to  the  action  of  hydrochloric  acid  (1  per 
looo),  or  if  it  be  digested  by  gastric  juice,  or  if  it  be  frozen,  it  tends  to  cleave  transversely  into  disks 
{Bowinan),  which  are  artificial  products,  and  resemble  a  pile  of  coins  which  has  been  knocked  over 
(Fig.  302.  5). 

Fibrillae. — Under  certain  circum.stances,  a  fibre  may  t\\\\h\i  longitudinal  striaiion.  This  is  due 
to  the  fact  that  it  may  be  split  up  longitudinally  into  an  immense  number  of  ( I  to  1. 7  fi  in  diameter) 

fine,  contractile  threads,  the  primitive  fibrillae  (Fig.  302,  i,  F), 
placed  side  by  side,  each  of  which  is  also  transversely  striped,  and 
they  are  so  united  to  each  other  by  semi  fluid  cement  substance, 
that  the  transverse  markings  of  all  the  fibrilhv  lie  at  the  same  level. 
Several  of  these  fibrils  are  united  together  owing  to  the  mutual 
pre.s.sure,  and  prismatic  in  form,  so  that  when  a  transverse  section 
of  a  perfectly  fresh  muscular  fibre  is  observed  after  it  is  frozen,  the 
end  of  each  fibre  is  mapped  out  into  a  number  of  small  polygonal 
areas  called  Cohnheim's  areas  (Fig.  302,  2).  [Each  bundle 
of  fibrils  or  j)olygonal  area  represents  what  KoUiker  called  a 
"  Muscle  Column."] 

F'ibrillx-  are  easily  obtained  from  insects'  muscles,  while  those 
from  a  mammal's  muscle  are  readily  i.solated  by  the  action  of  dilute 
alcohol,  Midler's  fluid  [or,  best  of  all,  -^  per  cent,  solution  of 
chromic  acid]  (Fig.  302,  3). 

[In  studying  the  structure  of  muscle,  it  is  well  to  remember 
that  there  are  consideral)le  differences  between  the  muscles  of 
Vertebrates  and  those  of  .\rlhropoda.] 

[When  a  living  unaltered  vertebrate  muscular  fibre  is  ex- 
amined microscopically,  in  its  own  juice,  we  observe  the  alternate 
dim  and  light  transverse  disks.  Amici,  Krause,  and  Dobie  showed 
that  a  fine  dark  line  runs  across  the  light  disk,  and  divides  it  into 
two  (Fig.  303).  Amici  resolved  it  into  a  row  of  granules,  and 
by  others  (e.  g.,  Krause)  it  is  regarded  as  due  to  the  e.xi.stence  of 
a  membrane — hence  it  is  called  Krause's  membrane, — which 
runs  transversely  across  the  fibre,  being  attached  all  round  to  the 
sarcolemma,  thus  dividing  each  fibre  into  a  series  of  comparl- 
tnents  placed  end  to  end.  Hensen  described  a  disk  or  stripe  in 
the  centre  of  the  dim  disk.] 
[On  Krause's  theory,  each  muscular  compartment  contains  (i)  a  broad  dim  disk,  which  is 
the  <r<);//;(?(V/7c' part  of  the  sarcous  substance.  It  is  doubly  refractive  (anisotropous ),  and  is  com- 
jxjsed  of  Bowman's  sarcous  elements.  (2)  On  each  end  of  this  disk,  and  between  it  and  Krause's 
membranes,  is  a  narrower,  clear,  homogeneous,  and  but  singly  refractile  (isotropous),  soft  or  fluid 
substance,  which  forms  the  lateral  disk  of  Engelmann.  In  some  insects  it  contains  a  row  of  refractive 
granules,  constituting  the  granular  layer  of  Flogel.  If  a  muscular  fibre  be  .stretched  and  stained 
with  logwood,  the  central  patt  of  the  dim  disk  appears  lighter  in  color  than  the  two  ends  of  the  same 
disk.  This  has  been  described  as  a  separate  disk,  and  is  called  the  median  disk  of  Hensen  (Fig. 
302,  4,  <-).] 

[In  an  unaltered  fibre,  the  dim  broad  stripe  may  appear  homogeneous,  but  after  a  time  it  cleaves 
throughout  its  entire  extent,  in  the  long  axis  of  the  fibre,  into  a  number  of  prismatic  elements  or  fibres, 
the  sarcous  elements  of  Bowman  (F'ig.  302).  These  at  first  are  prismatic,  but  as  they  solidify 
they  shrink  and  seem  to  squeeze  out  of  them  a  fluid,  becoming  at  the  same  time  more  constricted  in 
the  centre.  This  separation  into  bundles  of  fibrils  with  an  interstitial  matter  gives  rise  to  the  appear- 
ance seen  on  transverse  section  of  a  frozen  muscle,  and  known' as  Cohnheim's  areas  (F"ig.  302,  2,  c). 
In  all  probability  the  cleavage  also  extends  through  the  lateral  disks,  and  thus  fibrils  are  formed  by 
longitudinal  cleavage  of  the  fibre.] 


Human  muscular  fibre. 


DISKS    AND    NUCLEI    IN    A    MUSCULAR    FIBRE. 


505 


[Muscles  of  Arthropoda. — Engelmann  showed  that  the  muscles  of  these  animals  have  a  large 
number  of  disks.  In  a  muscle  of  an  animal  killed  by  being  plunged  into  alcohol,  according  to  the 
position  of  the  lens  of  the  microscope,  one  sees  : — 

1.  The  broad  dim  disk,  composed  of  two  darker  lateral  portions  or  disks,  and  a  lighter  disk — that 
of  Hensen,  between  them.  In  Fig.  304  the  whole  disk  is  marked  Q,  and  Hensen's  disk  is  dis- 
tinguished as  h. 

2.  On  both  sides  of  this  is  a  small,  clear,  slightly  refractive  stripe,  J,  corresponding  to  one  of  Engel- 
mann's  isotropous  stripes. 

3.  On  both  sides  there  follows  symmetrically  a  dark,  strongly  refractive  stripe,  N,  corresponding 
to  Engelmann's  accessory  stripe  and  Flogel's  granular  layer. 

4.  Then  on  both  sides  there  is  a  clear,  feebly  refractive  disk,  E. 

5.  Beyond  E  is  a  small,  dark,  highly  refractive  stripe,  Z — usually  the  darkest — corresponding  to 
the  Amici-Krause  line.] 

[From  Z,  the  stripes  are  repeated  in  the  inverse  order  to  Q,  then  in  the  same  order  to  Z,  and  so  on. 
This  is  the  appearance  with  a  low  position  of  the  lens.  Many  muscles  do  not  show  all  these  stripes ; 
thus  h  is  often  absent.] 

[If  the  lens  of  the  microscope  be  ra'sed,  to  get  a  more  superficial  view  of  the  fibre,  the  distribution 
of  the  light  is  reversed  (Fig.  304,  II),  as  all  strongly  refi-active  sections  become  light,  and  all  feebly 
refractive  appear  darker,  while  with  a  deep  position  of  the  lens,  the  reverse  is  the  case.] 

[Experiment  shows  that  the  dim  disk  rapidly  swells  up  in  dilute  acids,  and  also  that  the  dim  disks 
(Q),the  accessory  disks  (N),  and  the  Amici-Krause  Hne  (Z),  stain  more  deeply  with  logwood  than 
the  other  disks,  and  h  less  than  the  rest  of  Q.] 

[If  a  muscle  which  has  been  some  time  in  alcjhol  be  examined  as  to  its  longitudinal  striation, 


Insect's  muscle  ;  I,  with  a  high  position  of  the  lens, 
and  II,  with  a  deeper  position. 


Fig.  305. 
Jf-^^-^i!!!!!!!!!!!!!"!!""'"""'// 

^"-"^.iiiiiiiiijiiiiiliiiililiiiifii^;,  ^ 

illlill iiiiiiiii... 

iljijljijijiiiijiimiiiiiiiiij^ 

n!iiijii|i|iiijiiijiiiiiliiiii|^\  ^ 

lliil 

lllllillllllillllllllllliiiiii  ;^ 
,- ^a   X 

iilii , 

fiuiiiiiiiiiuiiiiiiuuuiju'^ 

Muscular   fibre  of   Carabus 
cancellatus. 


it  will  be  seen  to  consist  of  rods  with  light  intervals  between  them  (Fig.  305).  The  rods  are  thicker 
at  their  ends,  and  thinner  and  lighter  at  their  middle.  RoUett  regards  the  clear  intervals  between 
these  rods  as  consisting  of  sarcoplasma,  a  body  closely  related  to  protoplasm,  and  the  rods  as 
bundles  of  fibrillse  or  "  muscle  columns."] 

[If  a  muscle  be  acted  upon  by  certain  acids  the  relative  appearance  of  the  muscle  columns  and 
the  sarcoplasma  is  altered  ;  and  the  latter  may  appear  in  these  and  in  gold  preparations  as  a  plexus 
of  fibrils  with  regular  longitudinal  and  transverse  meshes  [MeUand,  Marshall,  Fig.  306).] 

[Muscle  Rods. — Schafer  describes  the  appearance  differently  :  Double  rows  of  granules  are 
seen  lying  in  or  at  the  boundaries  of  the  hght  streaks  (disks),  and  very  fine  longitudinal  lines  may  be 
detected  running  through  the  dark  streak  (dim  disk)  and  uniting  the  minute  granules.  These  fine 
lines,  with  their  enlarged  extremities,  are  "  muscle  rods."  They  are  most  conspicuous  in  insects. 
During  the  contraction  of  a  living  muscular  fibre,  Schafer  describes  the  "  reversal  of  the  stripes  " 
[I  297)  as  follows:  "  When  the  fibres  contract,  the  light  stripes  are  seen,  as  the  fibre  shortens  and 
thickens,  to  become  dark,  an  apparent  reversal  being  thereby  produced  in  the  striae.  This  reversal  is 
due  to  the  enlargement  of  the  rows  of  dark  dots  and  the  formation  by  their  juxtaposition  and  blend- 
ing of  dark  disks,  while  the  muscular  substances  between  these  disks  has  by  contrast  a  bright  appear- 
ance." With  polarized  light  in  a  living  muscular  fibre,  all  the  sarcous  substance,  except  the 
muscle  rod,  is  doubly  refractive  or  anisotropous,  so  that  it  appears  bright  on  a  dark  field  when  the 
Nicol's  prisms  are  crossed,  while  under  the  same  conditions  contracted  muscle  and  dead  muscle  show 
alternate  dark  and  light  bands  (Sckdfe?-).'] 

The  nuclei  or  muscle  corpuscles  are  found  immediately  under  the  sarcolemma  in  all  mammals 
and  their  long  axis  lies  in  the  long  axis  of  the  fibre  (8  to  13  //  long,  3  to  4  //  broad). 


506 


TENDON    AND    BLOOD    VESSELS    OF    A    MUSCLE. 


[In  the  muscles  of  the  frop,  reptiles  and  some  other  animals,  e.<;^.,  the  red  muscles  of  the  rabbit 
and  hare  and  in  some  muscles  of  birds,  ihey  lie  in  the  substance  of  the  fibre  surrounded  by  a  small 
amount  of  protoplasm.]  When  they  occur  immediately  under  the  sarcolemma  they  are  more  or  less 
flattened,  and  lie  embedded  in  a  small  amount  of  protoplasm  (Fig.  302,  I  and  2,  K).  They  contain 
one  or  two  nucleoli,  and  it  is  said  that  the  protoplasm  .sends  out  fine  proces.ses  which  unite  with 
similar  processes  from  adjoining  corpuscles,  so  that,  according  to  this  view,  a  branched  protoplasmic 
network  exists  under  the  sarcolemma.  [Each  nucleus  has  a  reticulated  appearance  due  to  the 
presence  of  a  plexus  of  fibrils,  consisting  of  chromatin  ;  in  its  meshes  lies  an  achromatic  substance. 
The  nuclei  are  specially  large  in  Otiorrhynchus  iilanatus,  one  of  the  beetles.  Mitotic  figures  indicat- 
ing division  of  the  nuclei  have  lieen  observed.  The  nuclei  are  not  seen  in  a  perfectly  fresh  mu.scle, 
because,  vmtil  they  have  undergone  some  change,  their  refractive  index  is  the  same  as  that  of  the 
sarcous  substance.]  They  become  specially  evident  after  the  addition  of  acetic  acid,  llistogenetically, 
they  are  the  remainder  of  the  cells  from  which  the  muscular  fibres  were  developed  (Fig.  302,  7). 
According  to  ^L  Schultze,  the  sarcous  substance  is  an  intercellular  substance  difterentiated  and  formed 
by  their  activity.  Perhaps  they  are  the  centres  of  nutrition  for  the  muscular  fibres.  In  amphibians, 
birds,  fishes  and  reptiles,  they  lie  in  the  axis  of  the  fibres  between  the  fibrils. 

It  is  said  that  the  protoplasm  of  the  muscle  corpuscles  forms  a  tine  network  throughout  the  whole 


Fig.  306. 


Fic.  307. 


12 


Network  in  a  muscular  fibre. 


Relation  of  a  tendon,  S, 
to  its  muscular  fibre. 


Injected   blood   vessels    of   a  human    muscle. 
a,  small  artery  ;  b,  vein  ;  ^.capillaries.  X  250. 


muscular  fibre,  the  transverse  branches  taking  the  course  of  the  lines  of  Krause  or  Dobie,  and  the 
longitudinal  branches  running  in  the  interstices  between  Cohnheim's  area  [Relzius,  Bremer,  Melland, 
Fig.  306). 

Relation  to  Tendons. — According  to  Toldt,  the  delicate  connective-tissue  elements  which  cover 
the  several  muscular  fibres  pass  from  the  ends  of  the  latter  directly  into  the  connective-tissue 
elements  of  the  tendon.  The  end  of  the  muscular  fibre  is  peihaps  united  to  the  smooth  surface  or 
hollow  end  of  the  tendon  by  means  of  a  special  cement  ( IVeismann — Fig.  307,  S).  In  arthropoda, 
the  sarcolemma  passes  directly  into  and  becomes  continuous  with  the  tendon  (Leydig).  The  tendon 
itself  consists  of  longitudinally  arranged  bundles  of  \vhite  fibrous  tissue  with  cells — tendon  cells — 
embracing  them.  There  is  a  loose  capsule  or  sheath  of  connective  tissue — the  peritendineum  of 
Kollman — surrounding  the  whole  and  carrying  the  blood  vessels,  lymphatics,  and  nerves.  The 
tendons  move  in  the  tendon  sheaths,  which  are  moistened  by  a  mucous  fluid.  In  most  situations, 
muscular  fibres  are  attached  by  means  of  tendons  to  some  fixed  point,  but  in  other  situations  (face) 
the  ends  terminate  between  the  connective-tissue  elements  of  the  skin. 

[Blood  Vessels.— Muscles,  being,  very  active  organs,  are  richly  supplied  with  blood.  The  blood 
supply  of  a  muscle  differs  from  some  organs  in  not  constituting  an  actual  vascular  unit,  supplied  only 
by  one  artery-  and  one  vein,  thus  being  unlike  the  kidney,  spleen,  etc.     Each  muscle  usually  receives 


NERVES    OF    A    MUSCLE. 


507 


several  branches  from  difterent  arteries,  and  branches  enter  it  at  certain  distances  along  its  whole 
length.  The  artery  and  vein  usually  lie  together  in  the  connective  tissue  of  the  perimysium,  while 
the  capillaries  lie  in  the  endomysium.  The  capillaries  lie  between  the  muscular  fibres,  but  outside 
the  sarcolemma,  where  they  form  an  elongated  rich  plexus  with  numerous  transverse  branches 
(Fig.  308).  The  lymph  to  nourish  the  sarcous  substance  must  traverse  the  sarcolemma  to  reach  the 
former.  In  the  red  muscles  of  the  rabbit  {e.g.,  semitendinosus)  the  capillaries  are  more  wavy, 
while  on  the  transverse  branches  of  some  of  the  capillaries,  and  on  the  veins,  there  are  small,  oval, 
saccular  dilatations,  which  act  as  reservoirs  for  blood  (Ranvier).~\ 

[Lymphatics. — We  know  very  little  of  the  lymphatics  of  muscle,  although  the  lymphatics  of 
tendon  and  fascia  have  been  carefully  studied  by  Ludwig  and  Schweigger-Seidel.  There  are 
lymphatics  in  the  endomysium  of  the  heart,  which  are  continuous  with  those  under  the  pericardium. 
This  subject  still  requires  further  investigation.  Compare  the  lymphatics  of  the  fascia  lata  of  the  dog 
(Fig.  227,  §  201).] 

Entrance  of  the  Nerve. — The  trunk  of  the  motor  nerve,  as  a  rule,  enters  the  muscle  at  its  geo- 
metrical centre  (^Schwalbe) ;  hence,  the  point  of  entrance  in  muscles  with  long,  parallel,  or  spindle- 
shaped  fibres  lies  near  its  middle.  If  the  muscle  with  parallel  fibres  is  more  thaa  2  to  8  centimetres 
[1-3  inches]  in  length,  several  branches  enter  its  middle.  In  triangular  muscles,  the  point  of  entrance 
of  the  nerve  is  displaced  more  toward  the  strong  tendinous  point  of  convergence  of  the  muscular 
fibres.  A  nerve  fibre  usually  enters  a  muscle  at  the  point  where  there  is  the  least  displacement  of  the 
muscular  substance  during  contraction. 

Motor  Nerve. — Every  muscle  fibre  receives  a  motor  nerve  fibre  (Fig.  302,  i, 
N).  Each  nerve  does  not  contain  originally  as  many  motor  nerve  fibres  as  there 
are     muscular     fibres    in     the 

muscle  it  enters ;  in  the  human  '  ^  "' 

eye  muscles  there  are  only  3 
nerve  fibres  to  7  muscular  fibres  ; 
in  other  muscles  (dog),  i  nerve 
fibre  to  40  or  80  {Tergast). 
Hence,  when  a  nerve  enters  a 
muscle  it  must  divide,  which  oc- 
curs dichotomously  [at  Ran  vier's 
nodes],  the  structure  undergoing 
no  change  until  there  are  exactly 
as  many  nerve  fibres  as  muscular 
fibres.  In  warm-blooded  ani- 
mals each  muscular  fibre  has 
only  one,  while  cold-blooded 
animals  have  several  points  of 
insertion  of  the  nerve  fibre 
{Sandmann),  A  nerve  fibre  enters  each  muscular  fibre,  and  where  it  enters  it  forms 
an  eminence  {Doyere,  1840),  the   "  motorial  end  plate  "  (Fig.  302,  i,  e,  309, 

31°'  3^1)-  ..     .,      • 

[The  elaborate  investigations  of  K.  Mays  on  the  exact  distribution  ot  nerve 
fibres  in  the  muscles  of  the  frog  have  conclusively  proved — apart  from  experimental 
reasons — that  parts  of  muscles  receive  no  nerve  fibres  at  all,  large  portions  being 
free  from  nerves.  This  has  been  proved  for  all  cla.sses  of  vertebrates  except  osseous 
fishes.] 

[The  mode  of  termination  of  a  motor  nerve  in  a  muscular  fibre  is  not  the  same  in  all  animals,  but 
in  every  case  it  pierces  the  sarcolemma,  and  its  ultimate  distribution  has  a  disdnct  hypolemmal 
character.  The  Doyere's  eminence  is  present  in  most  mammals  and  reptiles,  but  in  amphibians  and 
birds,  the  ending  is  flat  on  the  muscle  fibre.  Most  of  the  results  known  to  us  have  been  worked  out 
by  Kiihne.  The  nerve  endings,  then,  are  confined  to  very  small  spots  or  areas  on  the  muscular 
fibres,  termed  by  Kiihne  "fields  of  innervation."  Most  nerve  fibres  have  only  one  such  field, 
but  very  long  fibres  may  have,  at  most,  eight.  One  or  more  medullated  nerve  fibres  pass — as  pre- 
terminal or  epilemmal  fibres— from  the  point  of  division  of  the  nerve  fibre  to  the  muscular  fibre,  to 
pass  into  the  nerve  endings.  The  nerve-endings  consist  of  divisions  of  the  axial  cylinder,  which  are 
distributed  over  the  sarcous  substance  without  (so  far  as  is  known)  forming  any  direct  connection 
with  it.  The  endings,  however,  lie  in  direct  contact  with  it.  This  branched  arrangement  of  the 
axis  cylinder  under  the  sarcolemma,  Kiihne  has  called  a  "  motor  spray  "  ("  motorisches  Geweih  "),  and 
the  mode  of  distribution  of  the  branches  varies  in  different  classes  of  animals.     In  the  frog  (Fig.  310), 


Nerve.  — terror-: 


Muscular  fibres  with  motorial  end  plates. 


508 


NERVES   OF    A    MUSCLE. 


tailed  amphibians,  and  birds,  the  hyix)lemmal  branches  of  the  axis  cyHnder  form  bayonet  like  and 
branched  endings.  In  the  lizard,  snakes  and  mammals,  the  branches  are  often  curved  or  twisted, 
and  possessed  of  lobes,  and  as  the  division  is  very  variable,  there  is  eveiy  form  from  a  siin])!e  hook- 
like bend  to  a  highly  arborescent  termination.] 

[Where  a  motor  nerve  enters  a  muscular  fibre  at  the  eminence  of  Doy6re,  the  sheath  of  the  nerve 
fibre,  known  as  the  perineural  or  Henle's  .sheath  (<;  321),  becomes  continuous  with  the  sarcolenmia. 
The  eminence  itself  consists  of  a  mass  of  protoplasm — or  sarcoplasm — called  by  Kiihne  sarcoglia — 
which  contains  granules  and  nuclei,  the  latter  with  a  membrane  and  peculiar  nucleoli ;  the  nuclei 
themselves  are  the  fundamental  or  basal  nuclei  of  the  sarcoglia.  The  outer  surface  of  the  eminence 
is  covered  by  a  membrane  called  telolemma  by  Kiihne.  but  which  in  reality  consists  of  two  mem- 
branes, an  outer  one,  the  epilemma,  continuous  with  the  perineural  or  Henle's  sheath,  and  an  inner 
one,  the  endolemma,  the  continuation  of  the  sheath  of  Schwann  of  the  nerve  fibre,  both  ultimately 
being  connected  with  the  sarcolemma.  As  the  nerve  pierces  the  muscular  fil)re,  it  loses  its  niyeline, 
and  «ith  it  disappears  the  keratin  sheath  or  axilemma  of  the  axis  cylinder,  so  that  the  spray-like  ending 
is  accompanied  only  by  the  telolemma  (Fig.  31 1).  The  telolemma  contains  nuclei  which  are  derived 
from  Henle's  sheath  (A"/7//«<').] 

Fig.  -^io. 


Fig.  311. 


Motor  nerve  ending  in  the  frog 
(Kuhne).  a,  t'rofile  view  of 
entrance  of  the  nerve  ;  b, 

b,  nuclei  of  the  branches 
of  the  axial  cylinder;  c,c, 

c,  nuclei  of  Henle's  sheath; 
e,  muscle  nuclei. 


a  A  « 


Motor  nerve  ending  in  lizards,  mammals,  and  man.  Schematic 
after  Kiihne.  A,  axis  cylinder ;  A'A',  terminal  branches  of  A; 
a, a,  myelin  of  nerves  ;  b,  perineural  or  Henle's  sheath,  and  its 
nuclei  (c)  ;  d,  nuclei  of  telolemma;  B,  bed  ;  D,  large  granule  in 
B;  C,  nuclei  of  the  bed  ;  E,  muscle  nuclei;  F,  contractile  sub- 
stance 


[In  some  animals,  such  as  the  lizard,  in  order  to  see  the  nerve  terminations,  il  is  sufficient  to  stain 
portions  of  fresh  muscles  with  Delafield's  logwood.] 

[Nerve  ending.s,  then,  are  sublemmar,  and  the  terminations  of  the  nerves  never 
penetrate  into  the  depth  of  the  muscular  fibre,  but  come  into  direct  contact  with  the 
contractile  prism  or  cylinder  moistened  by  the  fluids  of  the  muscle.  In  many 
cases  the  striped  substance  is  separated  from  the  blunt  nerve  endings  by  some  of 
the  sarcoglia,  which  in  some  cases  penetrate  and  traverse  the  other  constituent  of 
the  fibre.  The  latter  Kiihne  has  called  "  rhabdia."  The  antler-like  division  of 
the  axis  cylinder  or  spray,  in  contact  with  the  muscular  substance,  serves  to  con- 
duct the  excitation  from  the  former  to  the  latter,  but  excitation  of  the  muscular 
substance  is  never  transmitted  in  the  reverse  order  to  the  nerve  ending  {Kuhne}.'] 

Each  muscular  fibre  of  the  cray  fish  is  supplied  by  two  nerve  fibrils  arising  from  separate  axis 
cylinders  i^Biedermann). 

Sensory  fibres  also  occur  in  muscles,  and  they  are  the  channels  for  muscular 


RED    AND    PALE    MUSCLES,  509 

sensibility.  They  seem  to  be  distributed  on  the  outer  surface  of  the  sarcolemma, 
where  they  form  a  branched  plexus  and  wind  round  the  muscular  fibres  {Arndf, 
Sachs)  ;  but,  according  to  Tschirjew,  the  sensory  nerves  traverse  the  substance  of 
the  muscle,  and  after  dividing  dichotomously,  end  only  in  the  aponeurosis,  either 
suddenly  or  by  means  of  a  small  swelling — a  view  confirmed  by  Rauber.  The 
existence  of  sensory  nerves  in  muscles  is  also  proved  by  the  fact  that  stimulation 
of  the  central  end  of  a  motor  nerve,  e.g.,  the  phrenic,  causes  increase  of  the 
blood  pressure  and  dilatation  of  the  pupil  {Asp,  Kowalewsky,  Nawrocki),  as  well 
as  by  the  fact  that  when  they  are  inflamed  they  are  painful.  They  of  course  do 
not  degenerate  after  section  of  the  anterior  root  of  the  spinal  nerves. 

Red  and  Pale  Muscles. — In  many  fishes  (skate,  plaice,  herring,  mackerel)  (  W.  Stirliitg),  birds, 
and  mammals  (rabbits),  there  are  two  kinds  of  striped  muscle  {^Kraitse),  differing  in  color,  histological 
structure  [Ranvier),  and  physiological  properties  [K'?-oiieckcr  and  Stirling).  Some  are  "  red,"  e.g., 
the  soleus  and  semitendinosus  of  the  rabbit,  and  others  "pale,"  e.g.,  the  adductor  magnus.  In  the 
pale  muscles  the  transverse  striation  is  less  regular,  and  their  nuclei  fewer  than  in  the  red  muscles 
(Jianvier) ;  they  contain  less  glycogen  and  myosin.  [W.  Stirling  finds  that  the  red  muscles  in  many 
fishes,  e.g.,  the  mackerel,  contain  granules  of  oil,  and  present  all  the  appearance  of  muscle  in  a  state 
of  fatty  degeneration,  while  the  pale  muscles,  lying  side  by  side,  contain  no  fatty  granules.] 

Julius  Arnold  found  in  human  muscles  an  extensive  distribution  of  pale  fibres  among  the  red  ones, 
and  indeed  in  the  same  muscle  in  the  fi'Og  and  mammals,  red  and  pale  fibres  occur  together,  in  fact  this 
is  the  case  in  almost  every  muscle  [Gn'itzner). 

[Spectrum. — The  red  color  of  the  ordinary  skeletal  muscle  is  due  to  haemoglobin  in  the  sarcous 
substance  (^Kiihne).  This  is  proved  by  the  fact  that  the  color  is  retained  after  all  the  blood  is  washed 
out  of  the  vessels,  when  a  thin  muscle  still  shows  the  absorption  bands  of  hemoglobin  when  examined 
with  the  spectroscope.] 

[Myo-haematin. — MacMunn  points  out  that  although  most  voluntary  muscles  owe  their  color  to 
haemoglobin,  it  is  accompanied  by  myo-hcematin  in  most  cases,  and  sometimes  entirely  replaced  by 
it.  Myo-li£ematin  is  found  in  the  heart  of  vertebrates,  in  the  papillary  muscles  of  the  human  heart, 
and  in  abundance  in  the  pectoral  muscles  of  pigeons,  and  in  some  muscles  of  vertebrates  and  inverte- 
brates, d-.^e-)  certain  beetles  (Hydrophilus,  Dytiscus),  the  common  fly,  and  other  insects,  spiders,  crusta- 
ceans, and  mollusks.] 

Muscular  Fibres  of  the  Heart. — The  mammalian  cardiac  muscle  has  certain  peculiarities 
already  mentioned  (I  43)  :  (i)  It  is  striped,  but  it  is  involuntary ;  (2)  it  has  no  sarcolemma;  (3)  its 
fibres  branch  and  anastomose  ;  (4)  the  transverse  striation  is  not  so  distinct,  and  it  is  sometimes  striated 
longitudinally;  (5)  the  nucleus  is  placed  in  the  centre  of  each  cell  (see  \  43).  [The  cardiac  muscle, 
viewed  from  a  physiological  point  of  view,  stands  midway  between  striped  and  unstriped  muscle.  Its 
contraction  occurs  slowly  and  lasts  for  a  long  time  (p.  127),  while,  although  it  is  transversely  striped,  it 
is  involuntary.] 

[Purkinje's  Fibres. — These  fibres,  which  form  a  plexus  of  grayish  fibres  under  the  endocardium 
of  the  heart  of  ruminants,  have  been  described  already  (Fig.  28) ;  the  cells  have,  as  it  were,  advanced 
only  to  a  certain  stage  of  development  (|  46).] 

Development. — Each  muscular  fibre  is  developed  from  a  uni-nucleated  cell  of  the  mesoblast,  which 
elongates  into  the  form  of  a  spindle.  As  the  cell  elongates,  the  nuclei  multiply.  The  superficial 
or  parietal  part  of  the  cell  substance  shows  transverse  markings  (Fig.  302,  7),  while  the  nuclei  with  a 
small  amount  of  protoplasm  are  continuous  along  the  axis  of  the  fibre,  where  they  remain  in  some 
animals,  but  in  man  they  pass  to  the  surface  where  they  come  to  lie  under  the  sarcolemma.  The 
muscles  of  the  young  are  smaller  and  have  fewer  fibres  than  those  of  adults  {Budge).  In  developing 
muscle,  the  number  of  fibres  is  increased  by  the  proliferation  of  the  muscle  corpuscles,  which  form 
new  fibres. 

Striped  muscle,  besides  occiurring  in  the  corresponding  organs  of  vertebrata,  occurs  in  the  iris  and 
choroid  of  birds.  The  arthi'opoda  have  only  striped  muscle,  the  mollusks,  worms,  and  echinoderms 
chiefly  smooth  muscles  ;  m  the  latter  are  muscles  with  double  oblique  striation  [Sckwalbe).  According 
to  Paneth,  in  old  individuals  separate  cells  with  aggregation  of  contractile  substance — so-called  Sar- 
coplasts — unite  to  form  new  muscular  fibres.  Sig.  Mayer  regards  these  structures  as  retrogi-essive 
structures,  and  he  calls  them  Sarcolytes  (^  103,  II). 

2.  Non-striped  Muscle. — [Distribution. — It  occurs  very  widely  distributed  in  the  body,  in  the 
muscular  coat  of  the  lower  half  of  the  human  oesophagus,  stomach,  small  and  large  intestine,  muscu- 
laris  mucosfe  of  the  intestinal  tract,  in  the  arteries,  veins,  and  lymphatics,  posterior  part  of  the  trachea, 
bronchi,  infundibula  of  the  lung,  muscular  coat  of  the  ureter,  bladder,  urethra,  vas  deferens,  vesiculse 
seminales,  and  prostate ;  corpora  cavernosa  and  spongiosa  penis,  ovary,  Fallopian  tube,  uterus,  skin, 
ciliary  muscle,  iris,  upper  eyelid,  spleen  and  capsule  of  lymphatic  glands,  tunica  dartos  of  the  scrotum, 
gall  bladder,  in  ducts  of  glands,  and  in  some  other  situations.] 

Structure. — Smooth  muscular  fibres  consist  of  fusiform  or  spindle-shaped  elongated  cells,  with 
their  ends  either  tapering  to  fine  points  or  divided  (Fig.  312).     These  contractile  fibre  cells  may  be 


510 


NON-STRIPED    MUSCLE. 


isolated  l>y  steeping  a  piece  of  the  tissue  in  a  30  per  cent,  solution  of  caustic  potash,  or  a  strong  solution 
of  nitric  acid.  They  are  45  to  30  //  [^^^  to  y\,,  in.]  in  Icn^nh,  and  4  to  10  11  [scVn  '°  2Z7i6  '"•]  '" 
breadth.  Each  cell  contains  a  solid  oval  elongated  nucleus,  which  may  contain  one  or  more  nucleoli. 
It  is  brought  into  view  by  the  action  of  dilute  acetic  acid,  or  by  staining  reagents.  The  mass  of  the 
cell  appears  more  or  less  homogeneous  [and  is  surrounded  by  a  thin  elastic  envelope].  In  some 
places  it  shows  longitudinal  tii)rillation.  [Method. — This  fibrillation  is  revealed  more  distinctly  thus  : 
Place  the  mesentery  of  a  newt  (K'/fin)  or  the  bladder  of  the  salamandra  niaculata  (I-'lemtninif)  in  a 
5  per  cent,  solution  of  ammonium  chromate,  and  afterward  stain  it  w  ith  picro  carmine.  Each  cell 
consists  of  a  thin  elastic  sheath  ( sarcolemma  of  Krause)  enclosing  a  bundle  of  fibrils  ( I")  which  run 
in  a  longitudinal  direction  within  the  fibre  ( P'ig.  313).  They  are  continuous  at  the  poles  of  the  nucleus 
with  the  plexus  of  fibrils  which  lies  within  the  nucleus,  and,  according  to  Klein,  they  are  the  con- 
tractile part,  and  when  they  contract  the  sheath  becomes  shriveled  transversely  and  exhil)ils  what 
looks  like  thickenings  (S).  These  fibrils  have  been  observed  by  Flemming  in  the  cells  while  livitig. 
Sometimes  the  cells  are  branched,  while  in  the  frog's  bladder  they  are  triradiate.] 

[Arrangement. — Sometimes  the  fibres  occur  singly,  but  usually  they  are  arranged  in  groups,  forming 
lamelhie,  sheets,  or  bundles,  or  in  a  plexiform  manner,  the  bundles  being  surrounded  by  connective 
tissue.]  A  very  delicate  elastic  cement  substance  unites  the  individual  cells  to  each  other.  [This 
cement  may  be  demonstrated  by  the  action  of  nitrate  of  silver.  In  transverse  section  (Fig.  312,  II) 
ihey  appear  oval  or  polygonal,  with  the  delicate  homogeneous   cement  between  them  ;    but,  as  the 


Fir..  313. 


Fic.  312. 


Fig 


Smooth  muscular  fibres  (10) ; 
(11)  transverse  section. 


Smooth  muscular  fibre  from  the 
mesentery  of  a  newt  (ammo- 
nium chromate).  N,  nucleus  ; 
F,  fibrils;  S,  markings  in  the 
sheath. 


Termination  of  nerve  in  non-striped  muscle. 


fibres  are  cut  at  various  levels,  the  areas  are  unequal  in  size,  and  all  of  them,  of  course,  are  not  divided 
at  the  position  of  the  nucleus.] 

They  vary  in  length  from  yj^  to  ij^tj  of  an  inch ;  those  in  the  middle  coat  of  the  arteries  are  short, 
while  they  are  long  in  the  intestinal  tract,  and  especially  in  the  pregnant  uterus.  According  to 
Engelmann,  the  separation  of  the  smooth  muscular  substance  into  its  individual  spindle-like  elements 
is  a  post-mortem  change  of  the  tissue.  Sometimes  transverse  thickenings  are  seen,  which  are  not 
due  to  transverse  striaiion,  but  to  a  partial  contraction.     Occasionally  they  have  a  tendinous  insertion. 

Blood  Vessels. — Non-striped  muscle  is  richly  supplied  with  blood  vessels,  and  the  capillaries 
form  elongated  meshes  between  the  fibres  [although  it  is  not  so  vascular  as  striped  muscle].  Lym- 
phatics also  occur  between  the  fibres, 

Motor  Nerves. — According  to  J.  Arnold,  they  consist  of  medullated  and  non-medullated  fibres 
[derived  from  the  sympathetic  system]  which  form  a  plexus — ground  plexus — partly  provided  with 
ganglionic  cells,  and  lying  in  the  connective  tissue  of  the  jjerimysium.  [The  fibres  are  surrounded 
with  an  endothelial  sheath.]  Small  branches  [com]X)sed  of  bundles  of  fibrils]  are  given  off  from  this 
plexus,  forming  the  intermediary  plexus  with  angular  nuclei  at  the  nodal  points.  It  lies  either 
immediately  upon  the  musculature  or  in  the  connective  tissue  between  the  individual  bundles.  From 
the  intermedial y  plexus,  the  finest  fibrillas  (^0.3  to  0.5  //)  pa.ss  off,  either  singly  or  in  groups,  and  re- 
unite to  form  the  intermuscular  plexus  (Fig.  314,  d),  which  lies  in  the  cement  substance  between 


PHYSICAL   AND    CHEMICAL   PROPERTIES    OF    MUSCLE.  511 

the  muscle  cells,  to  end,  according  to  Frankenhauser,  in  the  nucleoli  of  the  nucleus,  or  in  the  neigh- 
borhood of  the  nucleus  [Liisiig).  According  to  J.  Arnold,  the  fibrils  traverse  the  fibre  and  the 
nucleus,  so  that  the  fibres  appear  to  be  strung  upon  a  fibril  passing  through  their  nuclei.  According 
to  Lowit,  the  fibrils  reach  only  the  interstitial  substance,  while  Gscheidlen  also  observed  that  the  finest 
terminal  fibrils,  one  of  vs'hich  goes  to  each  muscular  fibre,  ran  along  the  margins  of  the  lat'er  (Fig. 
314).  The  course  of  these  fibrils  can  only  be  traced  after  the  action  of  gold  chloride.  [Ranvier 
has  traced  their  terminations  in  the  stomach  of  the  leech.] 

Nerves  of  Tendon. — Within  the  tendons  of  the  frog,  there  is  a  plexus  of  medullated  nerve 
fibres,  from  which  brash-like  divided  fibres  proceed,  which  ultimately  end  with  a  point  in  nucleated 
plates,  the  nerve  flakes  of  Rollett.  According  to  Sachs,  bodies  like  end  bulbs  occur-  in  tendons, 
while  Rauber  found  Vater's  corpuscles  in  their  sheaths;  Golgi  found,  in  addition,  spindle- 
shaped  terminal  corpuscles,  which  he  regards  as  a  specific  apparatus  for  estimating  tension. 

293.  PHYSICAL  AND  CHEMICAL  PROPERTIES  OF  MUS- 
CLE.— I. The  consistence  of  the  sarcous  substance  is  the  same  as  that  of  living 
protoplasm,  e:  g.,  of  lymph  cells;  it  is  semi-solid,  /.  e.,  it  is  not  fluid  to  such  a 
degree  as  to  flow  like  a  fluid,  nor  is  it  so  solid  that,  when  its  parts  are  separated, 
these  parts  are  unable  to  come  together  to  form  a  continuous  whole.  The  con- 
sistence may  be  compared  to  a  jelly  at  the  moment  when  it  is  dissolved  {e.  g.,  by 
heat).     The  power  of  imbibition  is  increased  in  a  contracted  muscle  {Ranke). 

Proofs. — The  following  facts  corroborate  the  views  expressed  above :  [a)  The  analogy  between 
the  function  of  the  sarcous  substance  and  the  conti-aciile  protoplasm  of  cells  (^  9).  (^)  The  so-called 
Porret's  phenomenon,  which  consists  in  this,  that  when  a  galvanic  current  is  conducted  through 
the  living,  fresh,  sarcous  substance,  the  contents  of  the  muscular  fibre  exhibit  a  streaming  movement 
fi-om  the  positive  to  the  negative  pole  (as  in  all  other  fluids),  so  that  the  fibre  swells  at  the  negative 
pole  yKilkne).  [c)  By  the  fact  that  wave  movements  have  been  observed  to  pass  along  the  muscular 
fibre,  [d)  Direct  observation  has  shown  that  a  small  parasitic  round  worm  (Myoryctes  Weismanni) 
moved  freely  in  the  sarcous  substance  within  the  sarcolemma,  while  the  semi-solid  mass  closed  up  in 
the  tract  behind  it  [Kilhne,  Ebertli). 

2.  Polarized  Light. — The  contractile  substance  doubly  refracts  fight,  and  is  said  to  be  aniso- 
tropous,  while  the  ground  substance  causes  single  refraction,  and  is  isotropous.  According  to 
Briicke,  muscle  behaves  like  a  doubly  refractive,  positively  uniaxial  body,  whose  optical  axis  lies  in 
the  long  axis  of  the  fibre.  When  a  muscular  fibre  is  examined  under  the  polarization  microscope, 
the  doubly  refractive  substance  is  recognized  by  its  appearing  bright  in  the  dark  field  of  the  micro- 
scope when  the  Nicols  are  crossed  (|  297).  During  contraction  of  the  muscular  fibre,  the  contractile 
part  of  the  fibre  becomes  narrower,  and  at  the  same  time  broader,  while  the  optical  constants  do  not 
thereby  undergo  any  change.  Hence,  Briicke  concludes  that  the  contractile  disks  are  not  simple 
bodies  like  crystals,  but  must  consist  of  a  whole  series  of  small,  doubly  refractive  elements  arranged 
in  groups,  which  change  their  position  during  contraction  and  relaxation.  These  small  elements 
Briicke  called  disdiaclasts.  According  to  Schipiloff,  Danielewsky,  and  O.  Nasse,  the  contractile 
anisotropous  substance  consists  of  myosin,  which  occurs  in  a  crystalline  condition  and  represents  the 
disdiaclasts.  According  to  Engelmann,  however,  all  contractile  elements  are  doubly  refractive,  and 
the  direction  of  contraction  always  coincides  with  the  optical  axis. 

The  investigations  of  v.  Ebner  have  shown  that  during  the  process  of  growth  of  the  tissue,  ietision 
is  produced — the  tension  of  bodies  subjected  to  imbibition — which  results  in  double  refi-action,  and  so 
gives  rise  to  the  condition  called  anisotropous.  During  a  sustained  contraction,  the  index  of  refrac- 
tion of  the  muscular  fibre  increases  iExner).  * 

[Reaction. — If  a  transverse  section  of  a  living  excised  muscle  be  pressed  upon  a  strip  of  blue 
litmus  paper,  the  latter  may  assume  a  reddish  tinge,  and  if  upon  a  red  litmus  paper  the  latter  may 
assume  a  bluish  tinge,  but  it  will  not  alter  violet  litmus  paper.  This  is  the  amphochromatic  or 
amphoteric  reaction,  indicating  that  the  muscle  is  neutral.  It  may,  however,  give  only  an  alkaline 
reaction.  A  living  muscle  plunged  into  boilmg  water  still  retains  its  neutral  or  alkaline  reaction ; 
but  a  muscle,  which  has  been  tetanized,  or  is  in  rigor  mortis,  is  decidedly  acid.] 

The  chemical  composition  of  muscle  undergoes  a  great  change  after  death, 
owing  to  the  spontaneous  coagulation  of  a  proteid  within  the  muscular  fibres.  As 
frog's  muscles  may  be  frozen  and  thawed,  and  still  remain  contractile,  they 
cannot,  therefore,  be  greatly  changed  by  the  process  of  freezing.  Kiihne  bled 
frogs,  cooled  their  muscles  to  10°  or  7°  C.,  pounding  them  in  an  iced  mortar,  and 
expressed  their  juice  through  linen.  The  juice  so  expressed,  when  filtered  in  the 
cold,  forms  a  neutral  or  alkaline,  slightly  yellowish,  opalescent  fluid,  the  so-called 
"muscle  plasma."  Like  blood  plasnaa,  it  coagulates  spontaneously;  at  first 
it  is  like  a  uniform  soft  jelly,  but  soon  becomes  opaque ;   doubly  refractive  fibres 


512  CHEMICAL   COMPOSITION    OF    MUSCLE    SERUM. 

and  specks,  similar  to  the  fibrin  of  blood,  ap|)ear  in  the  jelly,  and  as  these  begin 
to  contract,  they  squeeze  out  of  the  jelly  an  <7r/V/ "  muscle  serum."  [Halli- 
burton finds  that  the  muscles  of  warm-blooded  animals  yield  a  similar  muscle 
plasma.]  Cold  prevents  or  delays  the  coagulation  of  the  muscle  plasma;  above 
o°,  coagulation  occurs  very  slowly,  and  the  rapidity  of  coagulation  increases 
rapidly  as  the  temperature  rises,  while  coagulation  takes  place  very  rapidly  at  40° 
C.  in  cold-blooded  animals,  or  at  48°  to  50°  C.  in  warm-blooded  animals.  The 
addition  of  distilled  water  or  an  acid  to  muscle  plasma  causes  coagulation  at  once. 
The  coagulated  proteid,  most  al)undant  in  muscle,  and  which  arises  from  the 
doubly  refractive  substance,  is  called  "  myosin  "  (  //'.  Kuhne). 

Myosin. — It  is  a  globulin  (\  245),  and  is  s-olubie  in  strong  (10  per  cent.)  solution  of  common 
salt,  and  is  again  precipitated  from  such  a  solution  by  dilution  with  water,  or  by  the  addition  of  very 
small  quantities  of  acids  (o. I  to  0.2  per  cent,  lactic  or  hydrochloric  acid).  It  is  soluble  in  dilute 
alkalies  or  slightly  stronger  acids  (0.5  per  cent,  lactic  or  hydrochloric  acid),  and  also  in  13  per  cent, 
ammonium  chloride  solution.  [The  more  myosin  is  freed  from  salts  (especially  of  calcium)  by 
washing,  the  more  insoluble  does  it  become,  both  in  saline  solutions  and  weak  hydrochloric  acid. 
When  once  precipitated  from  its  solution,  it  can  be  redissolved,  reprecipitated,  and  again  undergo 
coagulation  a  second  or  even  a  third  time  i^Hallilnirloii).'\  Like  tibrin,  myosin  rapidly  decomposes 
hvdric  peroxide.  When  treated  with  dilute  hydrochloric  acid  and  heat,  it  is  very  rapidly  changed 
i' to  svntonin  ( ii  245).  Myosin  may  be  extracted  from  muscle  by  a  10  1015  per  cent,  solution  of 
XII^Cl,  and  if  it  be  heated  to  65°,  it  is  precipitated  again  (Danielc~usky).  Danielewsky  succeeded 
in  partly  changing  syntonin  into  myosin  by  the  action  of  milk  of  lime  and  ammonium  chloride. 
Myosin  occurs  in  other  animal  structures  (cornea),  nay,  even  in  some  vegetables  {O.  Nasse). 

Muscle  serum,  according  to  Kiihne,  still  contains  three  proteids  (2.3  to  3  per 
cent.),  viz.  :  i.  Alkali  albuminate,  which  is  precipitated  on  adding  an  acid, 
even  at  20°  to  24°  C.  2.  Ordinary  serum  albumin,  1.4  to  1.7  per  cent.  (§  32, 
a),  which  coagulates  at  73°  C.     3.   An  albuminate  which  coagulates  at  47°  C. 

[Halliburton  finds,  however,  the  following  proteids  in  muscle  plasma:  — 


'^TJlfaf'^ 

Saturation  with  NaCl  or  NajSO^. 

1 

Paramyosinogen, j          47°  C. 

Myosinogen, 56° 

Myoglobulin, 63° 

Albumin, 73° 

Causes  precipitation.  \  Proteids  which  go  to 
"                 "            J       form  muscle  clot. 

^      .                 1        Proteids  of  the 
i^     1                 I         muscle  serum. 

Myoalbumose, Not  \. 

Although  the  first  two  go  to  form  the  clot  of  muscle  or  myosin,  paramyosinogen  is 
not  essential  for  coagulation.  Besides  these  bodies  there  are  haemoglobin  and 
also  myo-hsematin,  which  is  not  identical  with  the  blood  pigment.  It  can  be  ex- 
tracted by  ether  from  muscle  (<?.  g.,  the  breast  muscle  of  a  pigeon),  whereby  the 
ether  becomes  red.  It  can  exist  in  an  oxidized  and  reduced  condition  (AfacMunn).'] 
The  other  chemical  constituents  of  muscle  have  been  referred  to  in  treating  of 
flesh  (§  233).  I.  Muscle  ferments. — Briicke  found  traces  of  pepsin  and  pep- 
tone in  muscle  juice  [the  latter  is  denied  by  Halliburton]  ;  Piotrowsky,  a  trace  of 
a  diastatic  ferment.  [When  muscle  becomes  acid,  as  in  rigor  mortis,  the  pepsin 
at  a  suitable  temperature  (35°  to  40°  C.)  acts  on  the  proteids,  and  albumoses  and 
peptones  are  formed.  Halliburton  found  a  myosin  ferment  which  has  the  char- 
acters of  an  albumose.  2.  In  addition  to  volatile  fafty  acids  (formic,  acetic, 
butyric),  there  are  two  isomeric  forms  of  iac/ic  acid  (C.-jH603)  present  in  muscle 
with  an  acid  reaction  :  (a)  Ethylidenc-lactic  acid,  in  the  modification  known  as 
right-rotatory  sarcolactic  or  para/actic  diCxd,  which  occurs  only  in  muscles,  and  some 
other  animal  structures.  (A)  Ethylene-lactic  acid  in  small  amount  (§  251,  3,  c').  It 
Avas  formerly  assumed  that  lactic  acid  is  formed  by  fermentation  from  the  carbohy- 
drates of  the  muscle  (glycogen,  dextrin,  sugar),  and  Maly  has  observed  that  para- 
lactic  acid  is  occasionally  formed  when  these  bodies  undergo  fermentation.  Accord- 


METABOLISM    IN    MUSCLE.  513 

ing  to  Bohm,  however,  the  glycogen  of  muscle  does  not  pass  into  lactic  acid,  as 
during  rigor  mortis,  if  putrefaction  be  prevented,  the  amount  of  glycogen  does  not 
diminish.  If  muscle  be  suddenly  boiled  or  treated  with  strong  alcohol,  the  ferment 
is  destroyed,  and  hence  the  acidification  of  the  muscular  tissue  is  prevented  (^Du 
Bois-Reymond^.  Add  potassium  phosphate  also  contributes  to  the  acid  reaction. 
3.  Carnin  (CTHgN^Og)  which  is  changed  by  bromine  or  nitric  acid  into  sarkin, 
occurs  to  the  extent  of  i  per  cent,  in  Liebig's  extract  of  meat  {Weidel).  4.  Urea, 
o.oi  per  cent.  (^Hay craft).  [There  is  much  urea  in  the  muscles  of  the  skate.]  5. 
Glycogen  occurs  to  the  amount  of  over  i  per  cent,  after  copious  flesh  feeding,  and 
to  0.5  per  cent,  during  fasting.  It  is  stored  up  in  the  muscles,  as  well  as  in  the 
liver,  during  digestion,  but  it  disappears  during  hunger.  It  is  perhaps  formed  in 
the  muscles  from  proteids  (§  174,  2).  6.  Lecithin,  derived  in  part  from  the  motor 
nerve  endings  (§  23  and  §  251).  7.  The  gases  are  CO,  (15  to  18  vol.  per  cent. ), 
partly  absorbed,  partly  chemically  united  ;  some  absorbed  N,  but  no  O,  although 
muscle  continually  absorbs  O  from  the  blood  passing  through  it  (Z.  Hei-mann). 
The  muscles  contain  a  substance  whose  decomposition  yields  CO2.  When  muscles 
are  exercised,  this  substance  is  used  up,  so  that  severely  fatigued  muscles  yield  less 
CO2  (Stinzing).      [All  muscles  have  not  the  same  chemical  composition.] 

294.  METABOLISM  IN  MUSCLE.— [In  living  muscle  we  have  to  study 
the  transformations  of  energy,  and  the  chemical  changes  on  which  these  depend. 
But  as  we  cannot  examine  the  chemical  changes  which  occur  during  a  contraction, 
we  are  confined  to  a  study  of  (i)  the  composition  of  a  muscle  before  and  after 
contraction,  and  (2)  the  effect  of  contraction  on  the  medium  surrounding  or  pass- 
ing through  a  muscle.  We  may  observe  the  effect  produced  by  a  muscle  upon  air 
or  other  gases  to  which  an  excised  muscle  is  exposed,  or  we  may  investigate  the 
changes  which  the  blood  undergoes  in  passing  through  a  muscle,  and  if  the  muscle 
be  still  in  situ,  the  effect  upon  the  general  excreta.  These  methods  may  be  applied 
to  muscle  in  various  conditions,  passive  or  active,  dead  or  dying,  to  excised  muscles 
or  those  still  under  normal  circumstances.] 

I.  A  passive  muscle  continually  absorbs  a  certain  amount  of  O  from  the 
blood  flowing  through  its  capillaries,  and  returns  a  certain  amount  of  CO2  to  the 
blood  stream.  The  amount  of  CO.  given  off"  is  less  than  corresponds  to  the 
amount  of  O  absorbed.  Excised  muscles  freed  from  blood  exhibit  an  analogous 
but  diminished  gaseous  exchange.  As  an  excised  muscle  remains  longer  excitable 
in  O  or  in  air  than  in  an  atmosphere  free  from  O,  or  in  indifferent  gases,  we  must 
conclude  that  the  above-named  gaseous  exchange  is  connected  with  the  normal 
metabolism,  and  is  a  condition  on  which  the  life  and  activity  of  the  muscle  depend. 
[Resting  living  muscles  also  exhale  COj.] 

If  a  living  muscle  be  excised,  and  if  blood  be  perfused  through  its  blood  vessels,  the  amount  of 
O  used  up  is,  within  pretty  wide  limits,  almost  independent  of  temperature  ;  if  the  variations  of  tem- 
perature be  great,  it  rises  and  falls  with  the  temperature.  The  CO,  given  off  by  muscular  tissue  (less 
than  the  O  used  up)  falls  when  the  muscle  is  cooled,  but  it  is  not  increased  when  the  muscle  is  sub- 
sequently  warmed  i^Rubner). 

This  exchange  of  gases  must  be  distinguished  from  the  putrefactive  phenomena  due  to  the  devel- 
opment of  living  organisms  in  the  muscle.  These  putrefactive  phenomena  are  also  connected  ^sith 
the  consumption  of  O  and  the  excretion  of  CO,,  and  occur  soon  after  death  (Z.  Hermann). 

II.  In  an  active  muscle  the  blood  vessels  are  always  dilated  {Ludwig 
and  Sczelkow,  Gaskell) — a  condition  pointing  to  a  more  lively  material  exchange 
in  the  organ.  [The  dilatation  of  the  blood  vessels  can  be  observed  microscopically 
in  the  contracting  mylo-hyoid  muscle  of  the  frog.]  Hence,  the  active  muscle  is 
distinguished  from  the  passive  one  by  a  series  of  chemical  transformations. 

I.  Reaction. — The  neutral  or  feebly  alkaline  reaction  of  a  passive  muscle  (also 
of  the  non-striped  variety)  passes  into  an  acid  reaction  during  the  activity  of  the 
muscle,  owing  to  the  formation  of  paralactic  acid  (Du  Bois-Reymond,  1859)  ;  the 
degree   of  acidity  increases  up   to  a  certain   extent,  according   to  the  amount   of 


514  METABOLISM    IN    MUSCLE. 

work  performed  by  the  muscle  {R.  Heidenhaiti).  The  acidification  is  due,  accord- 
ing to  Weyl  and  Ztitler,  to  the  phosphoric  acid  produced  by  the  decomposition  of 
lecithin  and  (?  nuclein). 

It  is  doulitful  if  the  acidity  is  due  to  lactic  acid,  as  Warren  and  Astaschewsky  find  that  there  is  less 
lactic  acid  in  the  active  than  in  the  passive  muscle.  Marcuse,  however,  supports  the  lactic  acid 
theory,  while  Moleschott  and  Batiisiiiii,  agree  that  the  passive  muscle  contains  acid,  but  the  fatigued 
muscle  contains  more,  especially  of  phosphoric  acid  and  CO^. 

2.  Production  of  CO.. — An  active  muscle  excretes  considerably  more  CO,  than 
a  passive  one  :  {a)  active  muscular  exertion  on  the  part  of  a  man  or  of  animals 
increases  the  amount  of  CO.,  given  off  by  the  lungs  (§  127);  {b)  venous  blood 
flowing  from  a  tetanized  muscle  of  a  limb  contains  more  CO^,  more  CO^  being 
formed  than  corresponds  to  the  O  which  has  simultaneously  been  absorbed  {^Lud- 
wig  and  Sczelkoui).  The  same  result  is  obtained  when  blood  is  passed  through  an 
excised  muscle  artificially  ;  (0  an  excised  muscle  caused  to  contract  excretes  more 
CO.J.      (Compare  §  36S. ) 

3.  Consumption  of  Oxygen. — An  active  muscle  uses  up  more  O — (a)  when 
more  muscular  work  is  done,  the  body  absorbs  much  more  O  (§  217) — even  4  to 
5  times  as  much  {Eegnault  and  Reiset)  \  (/>)  venous  blood  flowing  from  an  active 
muscle  of  a  limb  contains  less  O  {Ludwig,  Sczclkow,  andAl.  Schmidt).  Neverthe- 
less, the  increase  of  O  used  up  by  the  active  muscle  is  not  so  great  as  the  amount 
of  CO,  given  off"  {v.  Pettenkofer  and  v.  Voit).  The  increase  of  O  used  up  may  be 
ascertained  even  during  the  period  of  rest  directly  following  the  period  of  activity, 
and  the  same  is  the  case  with  the  CO.,  excreted  (ik  Frey). 

As  yet,  it  is  not  possible  to  prove  by  gasometric  methods,  that  O  is  used  up  in 
an  excised  muscle  free  from  blood.  Indeed,  the  presence  of  O  does  not  seem 
to  be  absolutely  necessary  for  the  activity  of  muscle  during  short  periods,  as  an 
excised  muscle  may  continue  to  contract  in  a  vacuum,  or  in  a  mixture  of  gases 
free  from  O,  and  no  O  can  be  obtained  from  muscular  tissue  (Z.  Hermann).  A 
frog's  muscles  rob  easily  reducible  substances  of  their  O  ;  they  discharge  the  color 
of  a  solution  of  indigo  ;  muscles  which  have  rested  for  a  time,  acting  less  energeti- 
cally than  those  which  have  been  kept  in  a  state  of  continued  activity  {Griitzner, 
Gscheid/en~). 

4.  Glycogen. — The  amount  of  glycogen  (0.43  per  cent,  in  the  muscles  of  a 
frog  or  rabbit)  and  grape  sugar  is  diminished  in  an  active  muscle  {O.  JVasse, 
Weiss),  but  muscles  devoid  of  glycogen  do  not  lose  their  excitability  and  con- 
tractility. Hence,  glycogen  is  certainly  not  the  direct  source  of  the  energy  in  an 
active  muscle.  Perhaps  it  is  to  be  sought  for  in  an  as  yet  unknown  decomposition 
product  of  glycogen  i^Ltichsinger).  [There  is  more  glycogen  in  the  red  than  in 
the  pale  muscles  of  a  rabbit.] 

5.  Extractives. — An  active  muscle  contains  less  extractive  substances  soluble 
in  water,  but  more  extractives  soluble  in  alcohol  {v.  Helmhoitz,  1845)  '>  ^"^  ^^so 
contains  less  of  the  substances  which  form  CO,  {Ranke)  ;  less  fatty  acids  {^Sczelkow); 
less  kreatin  and  kreatinin  (v.   Voit). 

6.  During  contraction,  the  amount  of  water  in  the  muscular  tissue  increases, 
while  that  of  the  blood  is  correspondingly  diminished  (/.  Ranke).  The  solid 
substances  of  the  blood  are  increased,  while  they  (albumin)  are  diminished  in  the 
lymph  {Fa no). 

7.  Urea. — The  amount  of  urea  excreted  from  the  body  is  not  materially  in- 
creased during  muscular  exertion  {v.  Voit,  Fick  and  Wislicenus).  According  to 
Parkes,  however,  although  the  excretion  of  urea  is  not  increased  immediately,  yet 
after  i  to  i)^  day  there  is  a  slight  increase.  The  amount  of  work  done  cannot 
be  determined  from  the  amount  of  albumin  which  is  changed  into  urea. 

[Relation  of  Muscular  Work  to  Urea. — Ed.  Smiih,  Parkes,  and  others  have  made  numerous 
investigations  on  this  subject.     Fick  and  Wislicenus  (1S66)  ascended  the  Faulhorn,  and  for  seventeen 


METABOLISM    IN    MUSCLE.  515 

hours  before  and  for  six  hours  after  the  ascent  no  proteid  food  was  taken — the  diet  consisting  of  cakes 
made  of  fat,  sugar,  and  starch.     The  urine  was  collected  in  three  periods,  as  follows  : — 


Pick. 

Wisliceiius. 

1.  Urea  of  II  hours  before  the  ascent,  .    . 

2.  "             8      "      during          "           .    . 

3.  "            6      "      after             "          .    . 

238.55  grs. 

221.05  grs. 

103.46       "       \rQ..r 

A  hearty  meal  was  taken  after  this  period,  and  the  urine  of  the  next  eleven  hours  after  the  period 
of  rest  contained  159.15  grains  of  urea  [Pick),  and  176.71  (^Wislicentis).  All  the  experiments  go  to 
show  that  the  amount  of  urea  excreted  in  the  urine  is  far  more  dependent  upon  the  nitrogen  ingested, 
i.  e.,  the  nature  of  the  food,  than  upon  ihe  decomposition  of  the  muscular  substance.  A  vegetable 
diet  diminishes,  while  an  animal  diet  greatly  increases,  the  amount  of  urea  in  the  urine.  North's 
researches  confirm  those  of  Parkes,  but  he  finds  that  the  disturbance  produced  by  severe  muscular 
labor  is  considerable.  The  elimination  of  phosphates  is  not  effected,  while  the  sulphates  in  the 
urine  are  increased.] 

During  the  activity  of  a  muscle,  all  the  groups  of  the  chemical  substances 
present  in  muscle  undergo  more  rapid  transformations  {/.  Ranke).  It  is  still  a 
matter  of  doubt,  therefore,  whether  we  may  assume  that  the  kinetic  energy  of  a 
muscle  is  chiefly  due  to  the  transformation  of  the  chemical  energy  of  the  carbohy- 
drates which  are  decomposed  or  used  up  in  the  process  of  contraction.  As  yet 
we  do  not  know  whether  the  glycogen  is  supplied  by  the  blood  stream  to  the 
muscles,  perhaps  from  the  liver,  or  whether  it  is  formed  within  the  muscles  them- 
selves from  some  unknown  derivative  of  the  proteids.  The  normal  circulation  is 
certainly  one  of  the  conditions  for  the  formation  of  glycogen  in  muscle,  as  glyco- 
gen diminishes  after  ligature  of  the  blood  vtssth  {Chandelon) .  A  muscle  in  which 
the  blood  circulates  freely  is  capable  of  doing  more  work  than  one  devoid  of 
blood,  and  even  in  the  intact  body,  more  blood  is  always  supplied  to  the  con- 
tracted muscles. 

[Source  of  Muscular  Energy. — The  experiment  of  Fick  and  Wislicenus 
definitely  proved  that  the  proteids  are  not  the  exclusive,  or  by  any  means  the 
chief  source  of  muscular  energy.  As  it  is  conclusively  proved  that  during 
muscular  work  there  is  a  great  increase  in  the  amount  of  O  absorbed,  and  CO2 
given  off,  it  is  evident  that  the  non-nitrogenous  substances  of  the  food  must  be 
the  chief  sources  of  this  energy.  We  turn  naturally  to  the  carbohydrates,  and  as 
the  latter  are  chiefly  stored  up  m  the  form  of  glycogen  in  the  muscles,  it  is  assumed 
that  gl\cogen  is  the  chief  source  of  the  energy.  Glycogen  in  muscle  diminishes 
during  muscular  work,  and  is  stored  up  during  rest  {Bernard).  Kiilz  also  found 
that  in  dogs  the  glycogen  disappears  from  the  liver  during  work,  and  Voit  found 
that  the  muscle  glycogen  disappears  before  that  in  the  liver.  It  appears,  there- 
fore, that  the  carbohydrates  are  a  source  of  muscular  energy.  But  they,  again,  are 
not  the  only  source.  It  is  highly  probable  that  glycogen  can  be  formed  from 
proteids,  and  it  is  allowable,  therefore,  to  assume  that  proleids  may  also  serve  as  a 
source  of  muscular  energy.  If  this  be  not  so,  it  is  difificult  to  understand  how 
carnivora  can  be  fed  and  maintained  in  good  health  for  long  periods  on  lean  flesh. 
The  fats  are  probably  also  another  source.  Hence,  it  would  appear  that  all  three 
of  the  chief  groups  of  food  stuffs — carbohydrates,  proteids,  and  fats — may  serve 
as  the  source  of  muscular  energy ;  but  that,  so  long  as  non-nitrogenous  elements 
are  supplied  in  the  food  in  sufficient  quantity,  or  are  stored  up  in  the  body,  the 
muscles  do  their  work  chiefly  on  these.  After  they  are  used  up,  the  proteids  are, 
as  it  were,  called  up.] 

295.  RIGOR  MORTIS. — Cause. — Excised  striped,  or  smooth  muscles, 
and  also  the  inuscles  of  an  intact  body,  at  a  certain  time  after  death,  pass  into  a 
condition  of  rigidity — cadaveric  rigidity  or  rigor  mortis.       When  all  the 


516  CAUSE    OF    RIGOR    MORTIS. 

muscles  of  a  corpse  are  tlnis  affected,  the  whole  cadaver  becomes  completely  stiff 
or  rigid.  The  cause  of  this  phenomenon  depends  upon  the  spontaneous  coagu- 
lation of  a  proteid,  viz.,  the  myosin  of  the  muscular  fibres  (Kiihne).  Under 
certain  circumstances,  the  coagulation  of  the  other  proteids  of  the  muscle  may 
increase  the  rigidity.  During  the  process  of  coagulation,  an  acid  is  formed,  heat 
is  set  free  {v.  Walther,  Fick — §  223),  owing  to  the  passage  of  the  fluid  myosin  into 
the  solid  condition,  and  also  to  the  simultaneous  and  subsequently  increased 
density  of  tlie  tissue. 

Properties  of  a  Muscle  in  Rigor  Mortis. — It  is  shorter,  thicker,  and  some- 
what denser  {SchmiileTi'itscli)  ;  stiff,  compact,  and  solid  ;  turbid  and  opaque  (owing 
to  the  coagulation  of  the  myosin)  ;  incompletely  elastic,  less  extensible,  and  more 
easily  torn  or  ruptured  ;  it  is  completely  inexcitable  to  stimuli ;  the  muscular 
electrical  current  is  abolished  (or  there  is  a  slight  current  in  the  opposite  direc- 
tion) ;  its  reaction  is  acuf,  owing  to  the  formation  of  both  forms  of  lactic  acid 
(§  293),  glycero-phosphoric  acid  {Diakanow)  ;  while  it  also  develops  free  CO.. 
When  an  incision  is  made  into  a  rigid  muscle,  a  fluid,  the  muscle  serum,  appears 
spontaneously  in  the  wound  (§  293). 

The  first  formed  lactic  acid  converts  the  salts  of  the  muscle  into  acid  salts ;  thus,  potassium  lactate 
and  acid  potassium  phosphate  are  formed  from  jxatassium  phosphate.  The  lactic  acid,  which  i> 
formed  thereafter,  remains  free  and  ununited  in  the  muscle. 

Amount  of  Glycogen. — The  newest  observations  of  Hohm  are  against  the  view  that,  during  rigor 
mortis,  a  ]jarlial  or  complete  transformation  of  the  glycogen  into  sugar  and  then  into  lactic  acid  takes 
place.  During  digestion,  a  temporarj-  storage  of  glycogen  occurs  in  the  muscles  as  well  as  in  the 
liver,  so  that  about  as  much  is  found  in  the  muscles  as  in  the  liver.  There  is  no  diminution  of  the 
glycogen  when  rigidity  takes  place,  provided  putrefaction  be  prevented ;  so  that  the  lactic  acid  of 
rigid  muscles  cannot  be  formed  from  glycogen,  but  more  probably  it  is  formed  from  the  decomposition 
of  the  albuminates  [Deiiiant,  Boliiii'). 

The  amount  of  acid  does  not  vary,  whether  the  rigidity  occurs  rapidly  or  slowly  [J.  Ranke) ; 
when  acidification  begins,  the  rigidity  becomes  more  marked,  owing  to  the  coagulation  of  the  alkali- 
albuminate  of  the  muscle.  Less  CO.^  is  formed  from  a  rigid  muscle,  the  more  CO.^  it  has  given  off 
previously,  during  muscular  exertion.  A  rigid  muscle  gives  ofi"  N,  and  absorbs  O.  In  a -cadaveric 
rigid  muscle,  fibrin  ferment  is  present  (^Al.  Schmidt  and  others).  It  seems  to  be  a  product  of  pro- 
toplasm, and  is  never  absent  where  this  occurs  {Rauschenbach).  [The  myosin  ferment  seems  not  to 
be  identical  with  the  fibrin  ferment  (p.  512).] 

[Rigor  Mortis  and  Coagulation  of  Blood. — Thus,  there  is  a  marked 
analogy  between  the  coagulation  of  the  blood  and  that  of  muscle.  In  both  ca.ses, 
a  fluid  body  yields  a  solid  body,  fibrin  from  blood,  and  myosin  from  muscle  ;  the 
coagulation  of  blood  is  prevented  by  neutral  salts,  and  so  is  the  coagulation  of 
myosin  ;  dilution  of  the  salted  plasma  produces  coagulation  in  both  cases  ;  and 
perhaps  the  coagulation  in  both  is  due  to  the  action  of  a  ferment,  the  one  the 
fibrin  ferment,  the  other  the  myosin  ferment.  There  are,  however,  points  of 
difference,  for  myosin  can  be  dissolved,  reprecipitated,  and  coagulated  several 
times,  while  fibrin  does  not  undergo  recoagulation  ;  the  formation  of  myosin  from 
myosinogen,  again,  is  accompanied  by  the  development  of  an  acid,  whereas  that 
of  fibrin  from  fibrinogen  is  not :  further,  the  formation  of  myosin  is  not  accom- 
panied by  the  formation  of  another  globulin,  whereas  that  of  fibrin  from  fibrino- 
gen is.] 

Stages  of  Rigidity. — Two  stages  are  recognizable  in  cadaveric  muscles  :  In 
the  first  stage,  the  muscle  is  rigid,  but  still  excitable  ;  in  this  stage  the  myosin 
seems  to  be  in  a  jelly-like  condition.  Restitution  is  still  possible  during  this  stage. 
In  the  second  stage,  the  rigidity  is  well  pronounced,  with  all  the  phenomena 
above  mentioned. 

The  onset  of  the  rigidity  varies  in  man  from  ten  minutes  to  seven  hours  [but  as 
a  rule  it  is  complete  within  four  to  six  hours  after  death.  The  muscles  of  the  jaws 
are  first  affected,  then  those  of  the  neck  and  trunk,  afterward  (as  a  rule)  the  lower 
limbs,  and  finally  the  upper  limbs].  Its  duration  is  equally  variable — one  to  six 
days.     After  the  cadaveric  rigidity  has  disappeared,  the  muscles,  owing  to  further 


STAGES    OF    CADAVERIC    RIGIDITY.  517 

decompositions  and  an  alkaline  reaction,  become  soft,  and  the  rigidity  disappears 
i^Nysteii).  The  onset  of  the  rigidity  is  always  preceded  by  a  loss  of  nervous 
activity.  Hence,  the  muscles  of  the  head  and  neck  are  first  affected,  and  the  other 
muscles  in  a  descending  series  (§  352).  Disappearance  of  the  rigidity  occurs  first 
in  the  muscles  first  affected  {Nysteii).  Great  muscular  activity  before  death  {e.  g., 
spasms  of  tetanus,  cholera,  strychnin,  or  opium  poisoning)  causes  rapid  and  intense 
rigidity  ;  hence,  the  heart  becomes  rigid  relatively  rapidly,  and  strongly.  Hunted 
animals  may  become  affected  within  a  few  minutes  after  death.  Usually  the  rigidity 
lasts  longer  the  later  it  occurs.  Rigidity  does  not  occur  in  a  foetus  before  the 
seventh  month.  A  frog's  muscle  cooled  to  0°  C.  does  not  begin  to  exhibit  cada- 
veric rigidity  for  four  to  seven  days. 

Stenson's  Experiment. — The  amount  of  blood  in  a  muscle  has  a  marked 
effect  upon  the  onset  of  the  rigidity.  Ligature  of  the  muscular  arteries  causes  at 
first  in  all  mammals  an  increase  of  the  muscular  excitability,  and  then  a  rapid  fall 
of  the  excitability  {SchmiileivitscK) ;  thereafter  stiffness  occurs,  the  one  stage 
following  closely  upon  the  other  {Swammej'dam,  Nic.  Stenson,  1667).  [If  the 
ligature  be  removed  in  the  first  stage,  the  muscle  recovers,  but  in  the  later  stages 
the  rigidity  is  permanent.]  If  the  artery  going  to  a  muscle  be  ligatured,  Stannius 
observed  that  the  excitability  of  the  motor  nerves  disappeared  after  an  hour, 
that  of  the  muscular  substance  after  four  to  five  hours,  and  then  cadaveric  rigidity 
set  in. 

Pathological. — \\nien  the  blood  vessels  of  a  muscle  are  occkided,  by  coagulation  taking  place 
within  them,  rigidity  of  the  muscles  is  produced  (§  102).  True  cadaveric  rigidity  may  be  produced 
by  too  tight  bandaging;  the  muscles  are  paralyzed,  rigid,  and  break  up  into  flakes,  while  the  contents 
of  the  fibre  are  afterward  absorbed  (/?.  Volkinanii).  Occlusion  of  the  blood  vessels  of  muscles  by 
infarcts,  especially  in  persons  with  atheromatous  arteries,  may  even  cause  necrosis  of  the  muscles 
implicated  i^Finch,  Girandeati). 

If  the  circulation  be  re-established  during  the  first  stage  of  the  rigidity,  the 
muscle  soon  recovers  its  excitability  (^Stannius).  When  the  second  stage  has  set 
in,  restitution  is  impossible  {Kuhne).  In  cold-blooded  animals,  cadaveric  rigidity 
does  not  occur  for  several  days  after  ligaturing  the  blood  vessels.  Brown-Sequard, 
by  injecting  fresh  oxygenated  blood  into  the  blood  vessels,  succeeded  in  restoring 
the  excitability  of  the  muscles  of  a  human  cadaver  four  hours  after  death,  /.  e., 
during  the  first  stage  of  cadaveric  rigidity.  Ludwig  and  Al.  Schmidt  found  that 
the  onset  of  cadaveric  rigidity  was  greatly  retarded  in  excised  muscles,  when  arterial 
blood  was  passed  through  their  blood  vessels.  Blood  deprived  of  its  O  did  not 
produce  this  effect.  Cadaveric  rigidity  occurs  relatively  early  after  severe  hemor- 
rhage. If  a  weak  alkaline  fluid  be  perfused  through  the  blood  vessels  of  the  dead 
muscles  of  a  frog,  cadaveric  rigidity  is  prevented  {SchipilofT). 

Section  of  Nerves. — Preliminary  section  of  the  motor  nerves  causes  a 
later  onset  of  the  rigidity  in  the  corresponding  muscles  (^Brown-Sequard,  Hemeke). 
[The  same  result  occurs  after  a  hemi-section  of  the  spinal  cord  or  after  removal  of 
one  cerebral  hemisphere  {Bierfreund).'\  In  fishes,  whose  medulla  oblongata  is 
suddenly  destroyed,  cadaveric  rigidity  occurs  much  more  slowly  than  in  those 
animals  that  die  slowly  (^Blane). 

[Other  Influences. — Rigidity  begins  much  later  in  the  red  (11  to  15  hours)  than  in  pale  muscles 
(l  to  3  hours  post-mortem)  ;  the  rigor  is  complete  in  the  white  muscles  in  10  to  14  hours,  in  the  red 
in  52  to  58  hours.  The  extent  of  shortening  due  to  the  rigor  is  2  to  2j4  times  as  great  as  in  the 
white.  In  both  muscles  the  resolution  of  the  rigor  begins  12  to  15  hours  after  the  completion  of  the 
rigidity,  so  that  the  red  muscles  are  not  completely  rigid  before  the  other  muscles  appear  to  have  passed 
from  a  state  of  rigidity.  Temperature  has  a  marked  effect,  but  it  acts  more  on  the  resolution  than  on 
the  onset  of  the  rigor.  At  60°  C.  the  onset  begins  almost  at  once,  and  is  complete  in  a  few  minutes 
[Bierfreund).     Ether  and  chloroform  injected  into  the  blood  vessels  cause  almost  instantaneous  rigor 

Rigidity  may  be  produced  artificially  by  various  reagents  : — 

I.  Heat  ["  Heat  stiffening"]  causes  the  myosin  to  coagulate  at  40°  C.  in 


518  EFFECT   OF    HEAT,  WATER    AND    ACIDS    ON    MUSCLE. 

cold-blooded  animals,  in  birds  about  53°  C.  and  in  mammals  at  48°  to  50°  C. 
The  protoplasm  of  plants  and  animals,  e.  g.,  of  the  amccba,  is  coagulated  by  heat, 
giving  rise  to  heat  rigor. 

Schmulewitsch  found  that  the  longer  a  muscle  had  been  excised  from  the  body,  the  greater  was  the 
heat  re(|uired  to  produce  stilTening.  Meat  stiffening  differs  from  cadaveric  rigidity  thus :  a  13  per 
cent,  solution  of  ammonium  chloride  dissolves  out  the  m>  osin  from  a  cadaveric  rigid  muscle,  but  not 
from  one  rendered  rigid  by  heat  {Schi/>i/off).  If  the  ligid  cadaveric  muscles  of  a  frog  be  heated, 
another  proteid  coagulates  at  45°,  and  Ixstly  at  75°  the  seium  albumin  itself.  Hence,  both  processes 
together  make  the  muscle  more  rigid  (§  295). 

2.  When  a  muscle  is  saturated  with  distilled  water,  it  produces  "water 
stiffening  " — an  acid  reaction  being  developed  at  the  same  time. 

Muscles  rendered  stiff  by  water  still  exhibit  electro-motive  phenomena,  while  muscles  rendered 
rigid  by  other  me.ans  do  not  {Biedfrinnnu).  If  the  upper  limb  of  a  frog  be  ligatured,  deprived  of 
its  skin,  and  dipped  in  warm  water,  it  becomes  rigid.  If  the  ligature  1)C  removed  and  ihe  circulation 
reestablished,  the  rigidity  may  be  partially  set  aside.  If  there  be  well-marked  rigidity,  it  can  only  be 
set  aside  by  placing  the  limb  in  a  10  per  cent,  solution  of  common  salt,  which  dissolves  the  coagulum 
of  myosin  [Preyer). 

3.  Acids,  even  CO,,  ra])idly  produce  "acid  stiffening,"  which  is  probably 
different  from  ordinary  stiffening,  as  such  muscles  do  not  evolve  any  free  CO., 
(Z.  Hermann).  The  injection  of  o.  i  to  0.2  per  cent,  solutions  of  lactic  or 
hydrochloric  acid  into  the  muscles  of  a  frog  produces  stiffening  at  once,  which 
may  be  set  aside  by  injecting  0.5  per  cent,  solution  of  an  acid,  or  by  a  solution 
of  soda,  or  by  15  per  cent,  solution  of  ammonium  chloride.  The  acids  form  a 
compound  with  myosin  {Schipi/off). 

4.  Freezing  and  thawing  a  part  alternately,  rapidly  produce  stiffening ;  and 
it  is  aided  by  mechanical  injuries. 

Poisons. — Rigor  mortis  is  favored  by  quinine,  caffein,  digitalin  [a  concentrated  solution  of  caffein 
or  digitalin,  applied  to  the  muscle  of  a  fro/,  produces  rigor  mortis],  veratrin,  hydrocyanic  acid,  ether, 
chloroform,  the  oil  of  mustard,,  fennel,  and  aniseed;  direct  contact  of  muscular  tissue  with  potassium 
sulphocyanide  [Fiernard,  SetschenDw),  ammonia,  alcohol,  and  metallic  salts. 

Position  of  the  Body. — The  aUitude  of  the  body  during  cadaveric  rigidity  is  generally  that 
occupied  at  death ;  the  jiosition  of  the  limbs  is  the  result  of  the  varying  tensions  of  the  different 
muscles.  During  the  occurrence  of  rigor  mortis,  a  limb,  or  more  frequently  the  arm  and  fingers,  may 
move  {Somnier).  Thus,  if  stiffening  occurs  rapidly  and  firmly  in  certain  groups  of  muscles,  this 
may  produce  movements,  as  is  sometimes  seen  in  cholera.  If  cadaveric  rigidity  occurs  very  rapidly, 
the  body  may  occupy  the  same  position  which  it  did  at  the  moment  of  death,  as  sometimes  happens 
on  the  battle  field.  In  these  cases  it  does  not  seem  that  a  contracted  condition  of  the  muscle  passes 
at  once' into  rigor  mortis;  but  between  these  two  conditions,  according  to  Brucke,  there  is  always  a 
very  short  relaxation. 

Muscles  which  have  been  i:)lunged  into  boiling  water  do  not  undergo  rigor  mortis,  neither  do 
they  become  acid  (Du  Bois- Kevmond),  nor  evolve  free  CO,^  (A.  Hermami). 

Work  done  during  Rigidity.— A  muscle  in  the  act  of  becoming  stiff  will  lift  a  weight,  but  the 
height  to  which  it  is  lifted  is  greater  with  small  weights,  less  with  heavier  weights,  than  when  a 
living  muscle  is  stimulated  with  a  maximal  stimulus. 

Analogy  between  Contraction  and  Rigidity. — L.  Hermann  has  drawn 
attention  to  the  analogy  which  exists  between  a  muscle  in  a  state  of  contraction 
and  one  in  a  state  of  cadaveric  rigidity — both  evolve  CO.^  and  the  other  acids 
from  the  same  source;  [both  acts  take  place  without  the  consumption  of  O]. 
The  form  of  the  contracted  and  of  the  stiffened  muscles  is  shorter  and  thicker; 
both  are  denser,  le.ss  elastic,  and  evolve  heat ;  in  both  cases,  the  muscular  contents 
behave  negatively  as  regards  their  electro-motive  force,  in  reference  to  the  unaltered, 
living,  resting  substance.  Hence,  he  is  inclined  to  regard  a  muscular  contraction 
as  a  temporary,  physiological,  rapidly  disappearing  rigor.  Rigor  mortis  is  in  a 
certain  sense  the  last  flickering  act  of  a  living  muscle  [and  he  regards  contraction 
as  partial  death  of  a  muscle.  But  this  is  no  explanation,  and  moreover  there  are 
important  points  of  difference.  We  have  no  proof  of  a  coagulum  being  formed 
during  contraction,  while  the  extensibility  is  increased  during  contraction  and 
much  diminished  during  rigor.] 


MUSCULAR    EXCITABILITY.  519 

Disappearance  of  Rigidity. — When  rigor  mortis  passes  off,  there  is  a  con- 
siderable amount  of  acid  formed  in  the  muscle,  which  dissolves  the  coagulated 
myosin.  After  a  time  putrefaction  sets  in,  accompanied  by  the  presence  of 
microorganisms  and  the  evolution  of  ammonia  and  putrefactive  gases  (H.^S,  N,  CO2 
— §  184).  [Hermann  and  Bierfreund  attach  much  importance  to  the  resolution 
of  rigor  mortis  independently  of  putrefaction.] 

According  to  Onimus,  the  loss  of  excitability  which  precedes  the  onset  of  rigor  mortis  occurs 
in  the  following  order  in  man:  left  ventricle,  stomach,  intestine  (55  minutes);  urinary  bladder, 
right  ventricle  (60  min.) ;  iris  (105  min.)  ;  muscles  of  face  and  tongue  (180  min.)  ;  the  extensors 
of  the  extremities  (ab  jut  one  hour  before  the  flexors) ;  the  muscles  of  the  trunk  (five  to  six  hours). 
The  oesophagus  remains  excitable  for  a  long  time  (§  325). 

296.  MUSCULAR  EXCITABILITY.— By  the  term  excitability  or 
irritability  of  a  muscle,  is  meant  that  property  of  a  muscle  in  virtue  of  which  it 
responds  to  stimuli,  at  the  same  time  becoming  shorter  and  correspondingly  thicker. 
The  condition  of  excitement  is  the  active  condition  of  a  muscle  produced  by  the 
application  of  stimuli,  and  is  usually  indicated  by  the  act  of  contraction.  Stimuli 
are  simply  various  forms  of  energy,  and  they  throw  the  muscle  into  a  state  of 
excitement,  while  at  the  moment  of  activity  the  chemical  energy  of  the  muscle  is 
transformed  into  work  and  heat,  so  that  stimuli  act  as  "liberating"  or  "dis- 
charging forces."  [These  "  discharging  forces  "  may  themselves  be  very  feeble, 
but  they  are  capable  of  causing  the  manifestation  of  the  transformation  of  a  large 
amount  of  energy.]  The  normal  temperature  of  the  body  is  most  favorable  for 
maintaining  the  normal  muscular  excitability  ;  the  excitability  varies  as  the  tem- 
perature rises  or  falls. 

As  long  as  the  bloodstream  within  a  muscle  is  uninterrupted,  the  first  effect 
of  stimulation  of  a  muscle  is  to  increase  its  energizing  power,  partly  because  the 
circulation  is  more  lively  and  the  blood  vessels  are  dilated,  but  after  a  time,  the 
energizing  power  is  diminished.  Even  in  excised  muscles,  especially  when  the 
large  nerve  trunks  have  already  lost  their  excitability,  the  excitability  is  increased 
after  a  stimulus,  so  that  the  application  of  a  series  of  stimuli  of  the  same  strength 
causes  a  series  of  contractions  which  are  greater  than  at  first  (  Wundt).  Hence, 
we  account  for  the  fact  that,  although  the  first  feeble  stimulus  may  be  unable  to 
discharge  a  contraction,  the  second  may,  because  the  first  one  has  increased  the 
muscular  excitability  (^Fick). 

Effects  of  Cold. — If  the  muscles  of  a  frog  or  tortoise  be  kept  in  a  cool  place,  they  may  remain 
excitable  for  ten  days,  while  the  muscles  of  warm-blooded  animals  cease  to  be  excitable  after  one  and 
a  half  to  two  and  a  half  hours.  (For  the  heart,  see  ^  55.)  A  muscle,  when  stimulated  directly, 
always  remains  excitable  for  a  longer  time  when  its  motor  nerve  is  already  dead. 

[Independent  Muscular  Excitability. — Since  the  time  of  Albrecht  v. 
Haller,  and  R.  Whytt,  physiologists  have  ascribed  to  muscle  a  condition  of  exci- 
tability which  is  entirely  independent  of  the  existence  of  motor  nerves,  but  is 
dependent  on  certain  constituents  of  the  sarcous  substance.  Excitability,  or  the 
property  of  responding  to  a  stimulus,  is  a  widely  distributed  function  of  protoplasm 
or  its  modifications.  A  colorless  blood  corpuscle  or  an  amoeba  is  excitable,  and 
so  are  secretory  and  nerve  cells.  In  the  first  case,  the  application  of  a  stimulus 
results  in  motion  in  an  indefinite  direction,  in  the  second  in  the  formation  of  a 
secretion,  and  in  the  third  in  the  discharge  of  nerve  energy.  In  the  case  of  muscle,  a 
stimulus  causes  movement  in  a  definite  direction,  called  a  contraction,  and  depend- 
ing on  the  contractility  of  the  sarcous  substance.  There  are  many  considerations 
which  show  that  excitability  is  iiidependent  of  the  nervous  system,  although  in  the 
higher  animals,  nerves  are  the  usual  medium  through  which  the  excitability  is 
brought  into  action.     Plants,  however,  are  excitable,  and  they  contain  no  nerves.] 

Numerous  experiments  attest  the  ' '  independent  excitability  ' '  of  muscles  :  i . 
There  are  chemical  stimuli,  which  do  not  cause  movement  when  applied  to  motor 
nerves,  but  do  so  when  they  are  applied  directly  to  muscle  ;  ammonia,  lime-water, 


520  ACTION    OF   CURARA. 

carbolic  acid.  2.  The  ends  of  the  sartorius  of  the  frog,  in  which  no  nerve 
terminations  are  observable  by  means  of  the  microscope,  contract  when  they  are 
stimulated  directly  {A'ii/i/ic).  3.  Ciirara  paralyzes  the  extremities  of  the  motor 
nerves,  while  the  muscles  themselves  remain  excitable  (C/.  Bernard,  Ko/liker). 
The  action  of  cold,  or  arrest  of  the  blood  supply  in  an  animal,  abolishes  the 
excitability  of  the  nerves,  but  not  of  the  muscles  at  the  same  time.  4.  After 
section  of  its  nerve,  a  muscle  still  remains  excitable,  even  after  the  nerves  have 
undergone  fatty  degeneration  {Brown-Seqiiard,  Bidder).  5.  Sometimes  electrical 
stimuli  act  only  upon  the  nerves,  and  not  upon  the  muscle  itself  {Briicke).  [6. 
The  foetal  heart  contracts  rhythmically  before  any  nervous  structures  are  discover- 
able in  it.] 

[The  Action  of  Curara. —  Curara,  woorali,  urari,  or  Indian  arrow  poison  of  South  America,  is 
the  inspissated  juice  of  the  Strychnos  crevauxi.  A  watery  extract  of  the  drug,  when  injected  under 
the  skin  or  into  the  blood  of  an  animal,  acts  chiefly  upon  the  motor  nerve  endings,  and  does  not 
affect  the  muscular  contractility.  An  active  substance,  curarin,  has  been  isolated  from  it  (p.  523). 
Poison  a  frog  by  injecting  a  few  milligrammes  into  the  dorsal  lymph  sac.  In  a  few  minutes  after  the 
poison  is  absorbed,  the  animal  ceases  to  support  itself  on  its  fore-limbs;  it  lies  flat  on  the  table,  its 
limbs  are  paralyzed,  and  so  are  the  respiratory  movements  in  the  throat.  When  completely  under 
the  action  of  the  poison,  the  frog  lies  in  any  position,  limp  and  motionless,  neither  exhibiting  volun- 
tar}-nor  reflex  movements.  If  the  brain  be  destroyed  and  the  skin  removed,  on  faradizing  the  sciatic 
nerve,  no  contraction  of  the  muscles  of  the  hind  limb  occurs;  but  if  the  electrical  stimulus  be  applied 
directly  to  the  muscles,  they  contract,  thus  proving  that  curara  poisons  the  motor  connections  and 
not  the  muscles.  If  the  dose  be  not  too  large,  the  heart  still  continues  to  beat,  and  the  vasomotor 
nerves  remain  active.] 

[Methods. — (i)  Local  Application. — Bernard  took  two  nerve-muscle  prepa- 
rations, put  some  solution  of  curara  into  two  watch  glasses,  and  dipped  the  nerve 
into  one  glass  and  the  muscle  of  the  other  preparation  into  the  other  glass.  The 
curara  penetrated  into  both  preparations,  and  he  found,  on  stimulating  the  nerve 
which  had  been  steeped  in  curara,  that  its  muscle  still  contracted,  so  that  the  curara 
had  not  acted  on  the  motor  nerve  fibres  ;  while  stimulation  of  the  nerve  of  the  other 
preparation  produced  no  contraction,  although  the  corresponding  muscle  contracted. 
In  the  latter  case,  the  curara  had  penetrated  into  the  muscle  and  affected  the  intra- 
muscular portions  of  the  nerve.] 

[(2j  But  it  is  the  terminal  or  intra-muscular  portions  of  the  nerves,  not  the 
nerve  trunk,  which  are  paralyzed.  Ligature  the  sciatic  artery,  or,  better  still,  tie 
all  the  parts  of  the  hind  limb  of  a  frog,  except  the  sciatic  nerve,  at  the  upjjer  part 
of  a  thigh  (Fig.  315).  Inject  curara  into  the  dorsal  lymph  sac.  The  poisoned 
blood  will,  of  course,  circulate  in  every  part  of  the  body  except  the  ligatured  limb. 
The  shaded  parts  are  traversed  by  the  poison.  The  animal  can  still,  at  a  certain 
stage  of  the  poisoning,  pull  up  the  non-poisoned  limb,  while  it  cannot  move  the 
jX)isoned  one.  At  this  time,  although  poisoned  blood  has  circulated  in  the  sacral 
and  intra-abdominal  parts  of  the  nerves,  yet  they  are  not  paralyzed,  so  that  the  poi- 
son does  not  act  on  this  part  of  the  trunk  of  the  nerve.  But  we  can  show  that  it 
does  not  act  on  any  part  of  the  extra-muscular  trunk  of  the  nerve.  This  is  done  by 
ligaturing  the  arteries  going  to  the  gastrocnemius  muscle,  and  then  poisoning  the 
animal.  On  stimulating  the  nerve  on  the  ligatured  side,  the  gastrocnemius  of  that 
side  contracts,  although  the  whole  length  of  the  nerve  trunk  was  supplied  by  poi- 
soned blood.  Therefore,  it  is  the  intra-muscular  tenninations  of  the  nerves  which 
are  acted  on.] 

[By  means  of  the  following  arrangement  we  may  prove  that  the  terminal  parts 
of  the  nerve  are  paralyzed.  Ligature  the  sciatic  artery  of  one  leg  of  a  frog,  and 
then  inject  curara  into  a  lymph  sac.  After  the  animal  is  fully  poisoned,  expose 
the  sciatic  nerve  in  both  legs,  leaving  all  the  muscles  below  the  knee  joint ;  then 
clean  and  divide  the  femur  at  its  middle.  Pin  a  straw  flag  to  each  limb,  and  fix 
both  femora  in  a  clamp,  with  the  gastrocnemii  uppermost,  as  in  Fig.  316.  Place 
the  two  nerves,  N,  on  electrodes  attached  to  two  wires  coming  from  a  commutator, 


ACTION    OF    CURARA. 


521 


C  (Fig.  316).  From  the  opposite  binding  screws  of  tlie  commutator  two  wires 
pass  to  the  gastrocnemii.  The  other  two  binding  screws  of  the  commutator  are 
connected  with  the  secondary  coil  of  an  induction  machine  (§  330).  The  bridge 
of  the  commutator  can  be  turned  so  as  to  pass  the  current  either  through  both 
muscles  or  both  nerves — the  latter  is  the  case  in  the  diagram  (H).  When  both 
nerves  are  stimulated,  only  the  non-poisoned  leg  (NP)  contracts.  Reverse  the 
commutator,  and  pass  the  current  through  both  muscles,  when  both  contract. '\ 

[Rosenthal's  Modification. — Pull  the  secondary  coil  far  away  from  the  primary,  and  pass  the 
current  through  both  muscles.  Gradually  approximate  the  secondary  to  the  primary  coil,  and  in 
doing  so  it  will  be  found  that  the  non-poisoned  leg  contracts  first,  but  on  continuing  to  push  up  the 
secondary  coil,  both  limbs  contract.  Thus,  the  poisoned  limb  does  not  respond  to  so  feeble  a  faradic 
stimulus  as  the  non-poisoned  one,  a  result  which  is  not  due  to  the  action  of  the  curara  on  the  excita- 
bility of  the  muscle.  The  non -poisoned  limb  responds  to  a  feebler  stimulus  because  its  motor  nerve 
terminations  are  not  paralyzed,  while  the  poisoned  leg  does  not  do  so,  because  the  motor  terminations 
are  paralyzed.     A  feebler  induced  shock  suffices  to  cause  a  muscle  to  contract  when  it  is  applied  to 


Frog  with  sciatic  artery  liga- 
tured. S.P.,  spinal  cord 
with  afferent  and  efferent 
nerves;  P.,  poisoned, 
N.P.,  non-poisoned  leg; 
M,  gastrocnemius  mus- 
cles. 


Scheme  of  the  curara  experiment.  B,  bat- 
tery; I,  primary;  II,  secondary  spiral; 
N,  nerves;  F,  cl^mp ;  NP,  non-poisoned 
leg  ;  P,  poisoned  leg  ;  C,  commutator ; 
K,  key. 


the  nerve  than  when  it  is  applied  to  the  muscle  itself  directly.  In  large  doses,  curara  also  affects  the 
spinal  cord  (p.  523).] 

[On  what  structures  does  curara  act  ? — These  experiments  prove  that  cvu-ara  does  not  paralyze 
the  motor  nerve  trunks,  nor  the  muscular  fibres,  and  that  it  acts  on  the  motor  terminations  within 
the  muscles,  but  they  do  not  enable  us  to  state  the  precise  part  of  the  nerve  ending  so  affected.  It 
may  act  on  (l)  the  nerve  just  before  it  pierces  the  sarcolemma,  (2)  the  sub-lemmar  axis  cylinder,  (3) 
the  end  plates,  (4)  the  terminal  branches  or  spray.  Kiihne  and  Pollitzer  have  made  it  probable  that, 
even  when  a  muscle  is  thoroughly  impregnated  with  curara,  some  of  the  nervous  apparatus  is  unaf- 
fected. The  sartorius  is  most  excitable  where  there  are  most  nerves  (Fig.  318),  and  even  in  a  muscle 
profoundly  poisoned  with  ciu-ara,  the  distribution  of  excitability  varies  with  the  number  of  nerves  m 
the  several  parts  of  the  muscle  (Fig.  317)  just  as  in  a  normal  muscle,  with  this  difference,  that  the 
excitability  of  all  the  parts  of  the  muscle  containing  nerves  is  less  than  normal.  That  this  variation 
in  excitability  is  due  to  nervous  structures,  is  shown  by  using  a  polarizing  anelectrotonic_  cmrent 
(§  335)>  which  depresses  the  excitability  of  nerve  fibres,  and  then  this  difference  of  excitability  dis- 
appears, the  curve  of  excitability  running  parallel  with  the  abscissa,  so  that  the  difference  does  not 
seem  to  be  due  to  purely  muscular  causes.] 

[Pollitzer,  speculating   as  to  which  part  of  the  terminal  nerve  is  affected,  supposes  that  all  parts 


522 


MUSCULAR    AND    CHEMICAL    STIMULL 


beyond  the  last  node  of  Ranvier  retain  their  functions,  and  he  supposes  that  it  is  not  the  axis  cylinders 
themselves,  hut  the  cement  at  the  noHes,  on  which  the  drug  exerts  its  specific  action.] 

Neuro-Muscular  Cells. — Even  in  (he  lower  animals,  <•.  .(,"•.,  Hydra  and  Mcihis.v,  there  are  uni- 
cellular structures  called  "  )iiui}0  mtisrular  cells"  in  which  the  nervous  and  muscular  substances  are 
represented  in  the  same  cell  i^Kleitienbeii;  and  Eimer^.  [The  outer  part  of  these  cells  is  adapted 
for  the  action  of  stimuli,  and  corresponds  to  the  nervous  recejitive  organ,  while  the  inner  deeper  part 
is  contractile,  and  is  the  representative  of  the  muscular  part.] 

Muscular  Stimuli. — Various  stimuli  cause  a  muscle  to  contract,  either  by 
acting  upon  its  motor  nerve,  or  upon  the  muscular  substance  itself  (^  324).  [The 
former  is  called  indirect  stimulation,  the  latter  direct  stimulation.] 

1.  Under  ordinary  circumstances,  the  normal  stimulus  exciting  a  muscle  to 
contract  is  the  nerve  impulse  which  passes  along  a  nerve,  but  its  exact  nature 
is  unknown. 

2.  Chemical  Stimuli. — All  chemical  substances  which  alter  the  chemical 
composition  of  a  muscle  with  sufficient  rapidity,  act  as  7nuscular  stimuli.  Mineral 
acids  (HCl  o.i  per  cent.),  acetic  and  oxalic  acids,  the  salts  of  iron,  zinc,  copper, 


Fig.  317. 


Fig.  31S. 


Curve  showing  the  excitability  in  the  sar- 
torius  of  a  frog  in  a  normal  and  curarized 
muscle. 


Distnlnitioii  of  nerves  in  the  sartorius 
of  a  frog  and  the  curve  of  e.\ci  la- 
bility in  different  parts  of  the 
muscle,  i.e.,  the  excitability  is 
greatest  where  there  are  most 
nerve  endings. 


silver,  and  lead,  bile,  all  act  in  weak  solutions  as  muscular  stimuli ;  they  act  upon 
the  motor  nerve  only  when  they  are  more  concentrated.  Lactic  acid  and  glycerin, 
when  concentrated,  excite  only  the  nerve;  when  dilute,  only  the  muscle.  [The 
lower  end  of  the  sartorius,  which  contains  no  nerves,  may  be  dipped  into  glycerin, 
and  it  will  not  contract,  but  if  it  be  dipped  deeper  to  where  there  are  nerve 
endings,  it  will  contract  at  once.]  Neutral  alkaline  salts  act  equally  upon  nerve 
and  muscle ;  alcohol  and  ether  act  on  both  very  feebly.  When  water  is  injected 
into  the  blood  vessels,  it  causes  fibrillar  muscular  contractions  {v.  JVitfich),  while 
a  0.6  per  cent,  solution  of  NaCl  may  be  passed  through  a  muscle  for  days  without 
causing  contraction  {KoUiker,  O.  Nasse).  [Carslaw,  under  Ludwig's  direction, 
however,  found  that  solutions  containing  0.5  to  0.2  percent.  NaCl,  when  perfused 
through  the  muscles  of  a  frog,  excite  many  short,  powerful  attacks  of  tetanus, 
separated  from  each  other  by  periods  of  rest.  Solutions  containing  0.5  to  0.7  per 
cent.  NaCl,  /.  e.,  so-called  "indifferent  fluids"  or  "  normal  saline,"  are  not  without 


THERMAL,   MECHANICAL   AND    ELECTRICAL    STIMULI.  523 

influence,  but  of  all  known  saline  solutions,  they  injure  a  nerve-muscle  preparation 
least.  Solutions  of  i  to  2  per  cent,  rapidly  kill  the  muscle.]  Acids,  alkalies,  and 
extract  of  flesh  diminish  the  muscular  excitability,  while  the  muscular  stimuli, 
in  small  doses,  increase.it  {Rafike).  Gases  and  vapors  stimulate  muscle;  they 
cause  either  a  simple  contraction  (^.  g.,  HCl),  or  at  once  permanent  contraction 
or  contracture  {e.  g.,  CI).  Long  exposure  to  the  gas  causes  rigidity.  The  vapor 
of  bisulphide  of  carbon  stimulates  only  the  nerves,  while  most  vapors  {e.  g.,  HCl) 
kill  without  exciting  them  {^Killme  and  Jani). 

Method. — In  making  experiments  upon  tlie  chemical  stimulation  of  muscle,  it  is  inadvisable  to 
dip  the  transverse  section  of  the  muscle  into  the  solution  of  the  chemical  reagent  {^Hei-uig).  The 
chemical  stimulus  ought  to  be  applied  in  solution  to  a  limited  portion  of  the  uninjured  surface  of  the 
mnscle ;  after  a  few  seconds,  we  obtain  a  contraction  or  fibrillar  twitchings  of  the  superficial  muscular 
layers  (^Hering). 

[Rhythmical  Contraction. — While  rhythmical  contractions  are  very  marked  in  smooth  muscle, 
(especially  if  it  is  stretched  or  subjected  to  considerable  internal  pressure,  as  in  the  hollow  viscera), 
e.  g.,  the  intestine,  uterus,  ureter,  blood  vessels,  and  also  in  the  striped  but  involuntary  cardiac  mus- 
culature (I  58),  they  are  not,  as  a  rule,  very  common  in  striped  voluntary  muscle.  Chemical  stimuli 
are  particularly  effective  in  producing  them.]  If  the  sartorius  of  a  curarized  frog  be  dipped  into  a 
solution  composed  of  5  grms.  NaCl,  2  grms.  alkaline  sodium  phosphate,  and  0.5  gnn.  sodium  car- 
bonate in  I  litre  of  water,  at  10°  C,  the  muscle  contracts  rhythmically,  and  may  do  so  for  several 
days,  especially  with  a  low  temperature  {Bieder7)iann).  This  recalls  the  rhythmical  contraction  of 
the  heart.  [Kiihne  found  a  similar  result.  The  rhythm  is  arrested  by  lactic  acid  and  restored  by 
an  alkaline  solution  of  NaCl.]  Rhythmical  movements  may  also  be  induced  in  the  sartorius  (frog), 
by  the  combined  action  of  a  dilute  solution  of  sodic  carbonate  and  an  ascending  constant  electrical 
current.     Compare  also  the  action  of  a  constant  current  on  the  heart  (^  58). 

3.  Thermal  Stimuli. — If  an  excised  frog's  muscle  be  rapidly  heated  to  28°  C, 
a  gradually  increasing  contraction  occurs,  which,  at  30°  C,  is  more  pronounced, 
reaching  its  maximum  at  45°  C.  If  the  temperature  be  raised,  "  heat  stiffening  " 
rapidly  ensues.  The  smooth  muscles  of  warm-blooded  animals  also  contract  when 
they  are  warmed,  but  those  of  cold-blooded  animals  are  elongated  by  heat  {Griin- 
hagen').  If  a  frog's  muscle  be  cooled  to  0°,  it  is  very  excitable  to  mechanical 
stimuli  (^Griinhagen) ;  it  is  even  excited  by  a  temperature  under  0°  i^Eckhard). 

CI.  Bernard  observed  that  the  muscles  of  animals,  artificially  cooled,  remained  excitable  many  hours 
after  death  {\  225).     Heat  causes  the  excitability  to  disappear  rapidly,  but  increases  it  temporarily. 

4.  Mechanical  Stimuli. — Every  kind  of  sudden  mechanical  stimulus,  pro- 
vided it  be  applied  with  sufficient  rapidity  to  a  muscle  (and  also  to  a  nerve),  causes 
a  contraction.  If  stimuli  of  sufficient  intensity  be  repeated  with  sufficient  rapidity, 
tetanus  is  produced.  Strong  local  stimulation  causes  a  wheal-like,  long-continued 
contraction  at  the  part  stimulated  (§  297,  3,  a).  Moderate  tension  of  a  muscle 
increases  its  excitability. 

5.  Electrical  Stimuli  will  be  referred  to  when  treating  of  the  stimulation  of 
nerve  (§  324). 

Other  Actions  of  Curara. — When  it  is  injected  into  a  frog,  either  into  the  blood  or  subcuta- 
neously,  it  causes  at  first  paralysis  of  the  intra-nmscutar  ends  of  the  motor  nei-ves  (p.  520),  while  the 
muscles  themselves  remain  excitable.  The  sensory  nerves,  the  central  nervous  system,  viscera,  heart, 
intestine,  and  the  blood  vessels  are  not  affected  at  first  (C/.  Bernard,  Kolliker).  [If  the  skin  be 
stimulated,  the  frog  pulls  up  the  ligatured  leg  reflexly,  although  the  other  leg  remains  quiescent ; 
this  shows  that  the  sensory  nerve  and  nerve  centres  are  still  intact ;  but  when  the  action  of  the 
drug  is  fully  developed,  no  amount  of  stimulation  of  the  skin  or  the  posterior  roots  of  the  nerves 
will  give  rise  to  a  reflex  act,  although  the  motor  nerve  of  the  ligatiu-ed  limb  is  known  to  be  excitable ; 
hence,  it  is  probable  that  the  nerve  centres  in  the  cord  themselves  are  ultimately  affected.  If  the 
dose  be  very  large,  the  heart  and  blood  vessels  are  affected]  In  warm-blooded  animals,  death 
takes  place  by  asphyxia,  owing  to  paralysis  of  the  diaphragm,  but  of  course  there  are  no  spasms. 
In  frogs,  where  the  skin  is  the  most  important  respiratory  organ,  if  a  suitable  dose  be  injected  sub- 
cutaneously,  the  animal  may  remain  motionless  for  days  and  yet  recover,  the  poison  being  elimi- 
nated by  the  urine  [Kiihne).  If  the  dose  be  large,  the  inhibitory  fibres  of  the  vagus  may  be 
paralyzed.  In  electrical  fishes,  the  sensory  nerves,  and  in  frogs,  the  lymph  hearts  are  paralyzed. 
A  dose  sufficient  to  kill  a  frog,  when  injected  imder  its  skin,  will  not  do  so  if  administered  by  the 
mouth,  because  the  poison  seems  to  be  eliminated  as  rapidly  by  the  kidneys  as  it  is  absorbed  from  the 
gastric  mucous  membrane.     For  the  same  reason  the  flesh  of  an  animal  killed  by  curara  is  not  poi- 


524  CHANGES    IN    A    MUSCLE    DURING    CONTRACTION. 

sonous  when  eaten.  If,  however,  the  ureters  be  lied,  the  jwison  collects  in  the  blood,  and  poisoning 
takes  ]ilace  (/,.  Hfniiann).  [In  this  case  the  mammal  may  exhibit  convulsions.  NVhy  ?  Curara 
jiaraly/cs  the  respiratory  nerves,  so  that  as|)liyxia  is  ]>roducc(l  from  the  venosity  of  the  blood.  It 
atTects  the  respiratory  nerve  endings  before  those  in  the  muscles  generally,  so  that  when  the  venous 
blood  stimulates  the  nerve  centres,  the  partially  affected  muscles  respond  by  convulsions.  Other 
narcotics  may  excite  convulsions  indirectly  by  inducing  a  venous  condition  of  the  blood,  while  the 
motor  centres,  nerves,  and  muscles  are  still  unaffected.]  Large  doses,  however,  poiion  uninjured 
animals  even  when  given  by  the  nioulh.  The  nerves  and  muscles  of  poisoned  animals  exhibit  con- 
siderable electro-motive  force.      [  For  the  effect  of  curara  on  lymph  formation  see  (i;  199,  6).] 

Atropin  appears  to  be  a  specific  poison  for  smooth  muscular  tissue,  but  ditferent  muscles  are 
differently  affected  {Szpi/i>ii7nit,  Luchsiii^er).  [This  is  doubtl'ul.  A  small  c|uantity  of  atropin  seems 
to  affect  the  motor  nerves  of  smooth  muscle  in  the  same  way  that  curara  does  those  of  stripel  muscle; 
we  must  remember,  however,  that  there  are  no  end  plates  proper  in  the  former,  so  that  the  link  between 
the  nerve  fibrils  and  the  contractile  substance  is  probably  different  in  the  two  cases.  It  is  well  known 
that  the  amount  of  striped  and  smooth  muscle  varies  in  the  a-sophagus  in  different  animals.  S/.pdmaim 
and  Luchsinger  found  that,  after  the  action  of  airopin,  stimulation  of  the  peripheral  end  of  the  vagus 
will  still  cause  contraction  of  the  stri|)ed  muscvUar  fibres  in  the  oesophagus,  but  not  of  the  smooth 
fibres,  although  both  forms  of  muscular  tissue  respond  to  direct  stimulation.] 

After  section  of  the  motor  nerve  of  a  muscle,  the  excitability  undergoes  remarkable  changes; 
after  three  to  four  days  the  excital)ilily  of  the  paraly/.ed  muscle  is  diminished,  both  for  direct  and 
indirect  stimuli  (p.  522) ;  this  condition  is  followed  by  a  stage,  during  which  a  constant  current  is  more 
active  than  normal,  while  induced  currents  are  scarcely  or  not  at  all  effective  (i;  339,  I ).  The  excita- 
bility to  mechanical  stimuli  is  also  increased.  The  increased  excitability  occurs  until  about  the  seventh 
week ;  it  gradually  diminishes  until  it  is  abolished  toward  the  sixth  to  the  seventh  month.  Fatty 
degeneration  begins  in  the  second  week  after  section  of  the  motor  nerve,  and  goes  on  until  there  is 
complete  nuiscular  atrophy.  Immediately  after  section  of  the  sciatic  nerve,  Schmulewitsch  found  that 
the  excital)ility  of  the  muscles  sujiplied  by  it  was  increased. 

297.  CHANGES  IN  A  MUSCLE  DURING  CONTRACTION.— 
I.  Macroscopic  Phenomena. —  i.  When  a  muscle  contracts,  it  becomes  shorter 
and  at  tlie  same  time  correspondingly  thicker. 

The  degree  of  contraction,  which  in  very  excitable  frogs  may  be  65  to  85  per  cent.  (72  per 
cent,  mean)  of  the  total  lengih  of  the  muscle,  depends  upon  various  conditions  :  [a)  Up  to  a  certain 
point,  increasing  the  strength  of  the  stimulus  causes  a  greater  degree  of  contraction;  (b)  as  the 
muscular  fatigue  increases,  /.  c,  after  continued  vigorous  exertion,  the  stimulus  remaining  the 
same,  the  extent  of  contraction  is  diminished  ;  {c)  the  temperature  of  the  surroundings  has  a  certain 
effect.  The  extent  of  the  contraction  is  increased  in  a  frog's  nuiscle — the  strength  of  stimulus  and 
degree  of  fatigue  remaining  the  same — when  it  is  heated  to  '^2>°  C.  If  the  temperature  be  increased 
above  this  point,  the  degree  of  contraction  is  diminished  {SclimulewitscK). 

2.  The  volume  of  a  contracted  muscle  is  slightly  diminished  {S'loammerdam, 
t  1680).  Hence,  the  specific  gravity  of  a  contracted  muscle  is  slightly  increased, 
the  ratio  to  the  non-contracted  muscle  being  1062  :  1061  {Valentin);  the  diminu- 
tion in  volume  is,  however,  onlv  ysViT'  although  this  has  recentlv  been  denied  by 
J.  Ewald. 

Methods. — {a')  Erman  placed  jjortions  of  the  body  of  a  live  eel  in  a  glass  vessel  tilled  with  an 
indifferent  fluid.  A  narrow  tube  communicated  with  the  glass  vessel,  and  the  fluid  rose  in  the  tube 
to  a  certain  level.  As  soon  as  the  muscles  of  the  eel  were  caused  to  contract,  the  fluid  in  the  index 
tube  sank.  (3)  Landois  demonstrates  the  decrease  in  volume  by  means  of  a  manometric  flame.  The 
cylindrical  vessel  containing  the  muscle  is  provided  with  two  electrodes  fixed  into  it  in  an  air-tight 
manner.  The  interior  of  the  vessel  communicates  with  the  gas  supply,  while  there  is  a  small,  narrow 
exit  tube  for  the  gas,  which  is  lighted.  Every  time  the  muscle  contracts,  the  flame  diminishes.  The 
same  experiment  may  lie  performed  with  a  contracting  heart. 

3.  Total  and  Partial  Contraction. — Normally,  all  stimuli  applied  to  a 
muscle  or  its  motor  nerve  cause  contraction  in  all  its  muscular  fibres.  Thus,  the 
muscle  conducts  the  state  of  e.xcitement  to  all  its  parts.  Under  certain  circumstances, 
however,  this  is  not  the  case,  viz.  :  {a)  When  the  muscle  is  greatly  fatigued,  or  when 
it  is  about  to  die,  violent  mechanical  stimuli,  as  a  vigorous  tap  with  the  finger  or  a 
percussion  hammer  fand  also  chemical  or  electrical  stimuli),  cause  a  localized  con- 
traction of  the  muscular  fibres.  This  is  Schiff' s  "  idio-muscular  contraction." 
The  same  phenomenon  is  exhibited  by  the  muscles  of  a  healthy  man,  when  the  blunt 
edge  of  an  instnmient  is  drawn  transversely  over  the  direction  of  the  muscular  fibres. 
ib)  Under   certain    as    yet    but   imperfectly   known    conditions,  a   muscle   exhibits 


TOTAL   AND    PARTIAL    MUSCULAR    CONTRACTION. 


525 


so-called  fibrillar  contractions,  /.  e.,  short  contractions  occur  alternately  in 
different  bundles  of  muscular  fibres.  This  is  the  case  in  the  muscles  of  the  tongue, 
after  section  of  the  hypoglossal  nerve ;  and  in  the  muscles  of  the  face,  after  section 
of  the  facial  nerve. 

[In  some  phthisical  patients  there  is  marked  muscular  excitability,  so  that  if  the  pectoral  muscle  be 
percussed,  a  local  contraction — idio-muscular — occurs,  either  confined  to  the  spot,  or  two  waves  may 
proceed  outward  and  return  to  the  spot  struck.] 

Cause  of  Fibrillar  Contraction. — According  to  Bleuler  and  Lehmann,  section  of  the  hypo- 
glossal nerve  in  rabbits  is  followed  by  fibrillar  contractions  after  sixty  to  eighty  hours;  these  contrac- 
tions may  continue  for  months,  even  when  the  divided  nerve  has  healed  and  is  stimulated  above  the 
cicatrix  so  as  to  produce  movements  in  the  con-esponding  half  of  the  tongue.  Stimulation  of  the 
lingual  nerve  increases  the  fibrillar  contractions  or  an-ests  them.  This  nerve  contains  vaso-dilator 
fibres  derived  from  the  chorda  tympani.  Schiff  is  of  opinion  that  the  increased  blood  stream  through 
the  organ  is  the  cause  of  the  contractions.  Sig.  Mayer  found  that,  by  compressing  the  carotids  and 
subclavian,  and  again  removing  the  pressure  so  as  to  petmit  free  circulation,  the  muscles  of  the  face 
contracted.  Section  of  the  motor  nerves  of  the  face  did  not  abolish  the  phenomenon,  but  compression 
of  the  arteries  did.  The  cause  of  the  phenomenon,  therefore,  seems  to  lie  within  the  muscles  them- 
selves. This  phenomenon  may  be  compared  to  \}a& paralytic  secretion  of  saliva  and  pancreatic  juice 
which  follows  section  of  the  nerves  going  to  these  glands  (pp.  258,  303).  Similar  fibrillar  contractions 
occur  in  man  under  pathological  conditions,  but  they  may  also  occur  without  any  signs  of  pathological 
disturbance.  [Fibrillar  contractions,  due  to  a  central  cause,  occur  in  monkeys  after  excision  of  the 
thyroid  gland  (|  103,  III).  Some  drugs  cause  fibrillar  contractions,  e.g.,  aconitin,  guanidin,  nicotin, 
pilocarpin,  but  physostigmin  produces  them  in  warm-blooded  animals  (not  in  frogs).  According  to 
Brunton  these  drugs  probably  act  by  irritating  the  motor  nerve  endings,  as  the  contractions  are 
gradually  abolished  by  curara.] 

II.  Microscopic  Phenomena. — i.  Single  muscular yf^^r///^  exhibit  the  same 
phenomena  as  an  entire  muscle,  in  that  they  contract  and  become  thicker.  2.  There 
is  great  difficulty  in  observing  the  changes  that  occur  in  the  individual  parts  of  a 
muscular  fibre  during  the  act  of  contraction.  This  much  is  certain,  that  the  muscular 
elements  become  shorter  and  broader  during  contraction,  and  that  the  transverse 
striae  approach  nearer  to  each  other  (^Bowman,  1840).  3.  There  is  great  difference 
of  opinion  as  to  the  behavior  of  the  doubly  refractive  (anisotropous)  and  the  singly 
refractive  media. 

Engelmann's  View. — Fig.  319,  i,  on  the  left  represents  a  passive  muscular  element — from  c  to 
d  is  the  doubly  refractive  contractile  substance,  with  the  median  disk,  a,  b,  in  it;  h  and^  are  the 
lateral  disks.     Besides  these,  in  each  of 


Fig.  319. 


the  singly  refractive  disks  there  is  a  clear 
disk — "  secondaiy  disk  "y  and  d',  which 
is  only  slightly  doubly  refractive.  This 
occurs  only  in  the  muscles  of  insects. 
Fig.  I,  on  the  right,  shows  the  same  ele- 
ment in  polarized  light,  whereby  the  mid- 
dle area  of  the  element,  as  far  as  the 
contractile  substance  proper  extends,  is, 
owing  to  its  double  refi-action,  bright ; 
while  the  other  part  of  the  muscular  ele- 
ment, owing  to  its  being  singly  refractive, 
is  black.  Fig.  319,  2,  is  the  transition 
stage,  and  3  the  proper  stage  of  contrac- 
tion of  the  muscular  element.  In  both 
cases,  the  figures  on  the  left  are  viewed 
in  ordinary  light,  and  on  the  right,  in 
polarized  light.  During  contracion  (Fig. 
319,  3),  the  singly  refractive  disk  becomes 
as  a  whole  more  refractive,  the  doubly 
refractive  less  so.  Consequently,  a  fibre 
at  a  certain  degree  of  contraction  (2), 
when  viewed  in  ordinary  light,  may 
appear  homogeneous  and  but  slightly 
striped  transversely  =  the  hofnogeneotts  or  transition  stage.  Duiing  a  greater  degree  of  contraction 
(3),  veiy  dark  transverse  stripes  reappear,  corresponding  to  the  singly  refractive  disks.  At  every  stage 
of  the  contraction,  as  well  as  in  the  transition  stage,  the  singly  and  doubly  refractive  disks  are  shai-ply 
defined,  and  are  recognized  by  the  polariscope  as  regular  alternating  layers  (in  i,  2,  and  3  on  the 


The  microscopic  appearances  during  a  muscular  contraction  in  the 
individual  elements  of  the  fibrillse.  i,  2,  3  (after  Engeliitann) ; 
4,  s  (after  Merkel). 


526 


MUSCULAR    CONTRACTION    AND    MYOGRAPHS. 


right).  These  do  not  change  places  during  the  contraction.  The  height  of  both  disks  is  diminished 
during  contraction,  but  the  singly  refractive  do  so  more  rapidly  than  the  doubly  refractive  disks.  The 
total  volume  of  each  element  does  mjt  undergo  any  appreciable  alteration  in  volume  during  the 
contraction.  Hence,  the  doubly  refractive  disks  increase  in  volume  at  the  expense  of  the  singly 
refractive.  From  this  it  is  concluded  that,  during  the  contraction,  tluid  passes  from  tlie  singly 
refractive  into  the  doubly  refractive  disks;  the  former  shrink,  the  latter  swell. 

Merkel's  view  is  partially  difTerent.  In  Fig.  319,  4,  are  two  muscular  elements  at  rest;  in  (5), 
two  in  a  slate  of  contraction,  after  Merkel.  The  gray  punctuated  areas  are  the  doubly  refractive 
substance,  c,  the  median  disk.  According  to  Merkel,  during  contraction  the  dark  substance  lying 
in  the  middle  of  the  element  changes  its  position — either  in  part  or  as  a  whole;  it  leaves  the  middle 
of  the  element  (the  two  surfaces  of  Hensen's  median  disks.  4,  r),  and  places  itself  at  the  lateral 
disks,  5  at  i"  and  d,  while  the  clear  substance  leaves  the  lateral  disk,  4,  e  and  d,  and  ap|ilies  itself  to 
both  surfaces  of  the  median  disk,  5,  c.  The  clear  substance  of  the  isotropuus  disks  is  fluid,  and  plays  a 
more  passive  role;  duiing  contraction  it  is  in  part  absorbed  by  the  dark  substance  which  thus  swells 
up.  This  mutual  excliange  of  place  of  the  substances  is  accompanied  by  an  intermediate  "stage 
of  t/isso////to>t,"  in  which  the  whole  contents  of  the  element  appear  equally  homogeneous,  in  which, 
therefore,  the  fluid  singly  refractive  sulistance  has  uniformly  penetrated  the  doubly  refractive  sub- 
stance.    At  this  moment  only  the  lateral  disks  are  still  visible. 

[If  a  living  portion  of  an  insect's  muscle  be  examined  in  its  own  juice,  contraction  waves  may  be 
seen  to  pass  over  the  fibres.  When  a  contraction  wave  pas?es  over  part  of  the  fibres,  the  disks  become 
shorter  and  broader  ;  at  the  same  time,  in  the  fully  contracted  part,  tlie  dim  disk  appears  lighter  than 
the  centre  of  the  light  disk.  There  is  said  to  be  a  "  reversal  of  the  stripes  "  from  what  obtains  in 
a  passive  muscle.  Before  this  stage  is  reached,  there  is  an  intermediate  stage  where  the  two  bands 
are  almost  uniform  in  appearance.] 

Methods. — These  phenomena  are  best  observed  by  "  fixing"  the  difTerent  stages  of  rest  or  con- 
traction, by  suddenly  plunging  the  muscular  fibrilkx;  of  insect's  muscles  into  alcohol  or  osmic  acid, 
which  coaL;ulales  the  muscle  substance.  The  actual  contraction  may  be  observed  under  the  micro- 
scope in  the  transparent  parts  of  the  larvse  of  insects. 

Spectrum. — A  thin  muscle,  e.g.,  the  sartorius  of  the  frog,  when  placed  directly  behind  a  narrow 
slit  running  at  right  angles  to  the  C(  urse  of  the  fibres,  yields  a  diffraction  spectrum.  When  the 
muscle  contracts,  as  by  mechanical  stimulation,  the  spectrum  broadens,  a  proof  that  the  interspaces 
of  the  transverse  stripes  become  narrower  {^Ranvier). 

298.  MUSCULAR  CONTRACTION.— Methods.— In  order  to  deter- 
mine the  duration  of  each  phase  of  a  muscuhir  contraction,  myographs  of  vari- 
ous forms  are  used. 


Fig. 


Scheme  of  v.  Helmholtz's  myograph, 
clamp,  K:   F,  writing  style;    P 


V.  Helmholtz's  Myograph  is  shown  in 
Fig.  320.  A  muscle,  >I — say  the  gastrocne- 
mius of  a  frog  attached  to  the  femur — is  fixed 
by  the  femur  in  a  clamp,  K ;  its  lower  end  is 
attached  to  a  movable  lever  carrying  a  scale 
pan  and  weight,  W' ,  the  weight  being  varied  at 
pleasure.  When  the  muscle  contracts,  neces- 
sarily it  raises  the  lever.  At  the  free  end  of 
the  lever  is  a  movable  style,  F,  which  inscribes 
its  movements  on  a  revolving  cylinder  caused 
to  rotate  at  a  uniform  rate  by  means  of  clock- 
work. The  cylinder  is  covered  with  smoked 
enameled  paper  in  the  flame  of  a  turpentine 
lamp.  When  the  muscle  contracts,  it  inscribes 
a  curve — the  "  muscle  curve,"  or  "  myo- 
gram." The  abscissa  of  the  curve  indicates 
the  duration  of  the  contraction,  but  of  course 
the  rate  at  which  the  cylinder  is  moving  must 
be  known.  The  ordinates  represent  the 
height  of  contraction  at  any  particular  part  of 
the  curve. 

The  muscle  curve  may  be  inscribed  upon  a 


muscle  fixed  in  »  „^  ...uo 

weight  or  counterpoise         » -^  —"-^v-"-  v.u..v,  .nu^   .^v,   inov,.! 
for  the  lever;  W,  scale  pan  for  weights;  S,  S,  supports  for  smoked  glass  plate  attached    to   one   limb  of  a 
the  lever.  vibrating  tuning  fork.     Such  a  curve  registers 

the  time  units  in  all  its  parts.  Suppose  each 
vibration  of  the  tuning  fork  =001613  second,  then  the  duration  of  any  part  of  such  a  curve  is 
obtained  by  counting  the  number  of  vibrations  and  multplying  by  0.01613  second. 

[Pick's  Pendulum  Myograph. — A  board  fixed  to  the  wall  carries  a  heavy  iron  pendulum,  P, 
whose  axis,  A,  A,  moves  on  friction  rollers  (Fig.  321).     At  the  lower  swinging  end  are  two  glass 


PENDULUM    MYOGRAPH. 


527 


plates,  G  and  G^,  fixed  to  a  bearer,  T.  The  plates  can  be  adjusted  by  means  of  the  screw,  s,  so  that 
several  curves  can  be  written  one  above  the  other.  The  plate,  G'',  on  the  posterior  surface  is  merely 
a  compensator,  so  that,  when  G  is  elevated,  G^  is  lowered,  and  thus  the  duration  of  the  oscillation  is 
not  altered.  The  spring  catches,  H,  H,  which  can  be  turned  inward  or  outward,  are  used  to  fix 
the  pendulum  by  the  teeth,  a,  a,  when  it  is  drawn  to  one  side.  The  pendulum  is  drawn  to  one  side 
and  fixed,  a,  in  H,  so  that  when  H  is  pulled  down,  it  is  liberated  and  swings  to  the  other  side,  where 
it  is  caught  by  H  at  the  opposite  side.  In  the  improved  form,  the  catches,  H,  are  made  to  slide  along 
a  rod  like  the  arc  of  a  circle,  so  that  the  length  of  the  swing  can  be  varied.  As  the  pendulum 
swings  from  one  side  to  the  other,  the  projecting  points,  a,  a,  knock  over  the  contact  key,  b,  and 


Pick's  pendulum  myograph,  as  improved  by  v.  Helmholtz  (Jj  natural  size),  side  and  front  view. 


the  current  is  opened  and  a  shock  transmitted  to  the  muscle.  The  writing  lever  to  which  the 
muscle  is  attached  is  usually  a  heavy  one,  and  a  style  writes  upon  the  smoked  surface  of  the  glass. 
Of  course,  when  the  pendulum  swings,  it  moves  with  imequal  velocities  at  different  parts  of  its 
course.] 

[When  using  the  pendulum  myograph  to  study  a  muscular  contraction,  arrange  it  as  in  Fig.  322. 
The  fi-og's  muscle  is  attached  to  a  writing  lever,  which  is  very  like  the  lever  in  Fig.  321,  while  the 
style  inscribes  its  movements  on  the  blackened  plate.] 

[The  pendulum  is  fixed  in  the  catch,  C,  as  shown  in  the  figure ;  the  key,  K^,  is  closed  and  placed 


528 


MYOGRAM    UK    MUSCLE    CURVE. 


primary  circuit,  while  two  wires  from  the  secondary  coil  of  an  induction  machine  are  attached 
muscle.     When  the  pendulum  swings,  the  projecting  tooth,  S,  knocks  over  the  contact  at  K', 


in  the 

to  the  muscle.      When  ttie  penc 

and  breaks  the  primary  circuit,  when  a  shock  is  instantly  transmitted  through  the   muscle. 


Before 


Fu;. 


stimulating,  allow  the  pendulum  to  swing  to  obtain  an  abscissa.  The  time  is  recorded  by  a  vibrating 
tuning  fork,  of  known  rate  of  vibration,  connected  with  a  1  )uprc's  electric  chronograph.  I)upr6's 
chronograph  is  merely  a  small  electro-magnet  with  a  fine  writing  style  attached,  which  vibrates  when 
it  is  introduced  in  an  electrical  circuit,  in  which  is  placed  a  vibrating  tuning  fork.  The  signal  vibrates 
just  as  often  as  the  tuning  fori;.] 

[Du  Bois'  Spring  Myograph. — It  consists  of  a  glass  plate  fixed  in  a  frame,  and  moving  on  two 
polished  steel  wires,  stretched  between  the  supports  A  and  B  (Fig.  323).  Ai  h  is  a  spring  which, 
when  it  is  compressed  between  the  upright,  15,  and  the  knob,  h,  drives  the  glass  plate  from  H  to  A. 
As  the  plate  moves  from  one  side  to  the  other,  a  small  tooth,  d,  on  its  under  surface,  opens  the  key, 
//,  and  thus  a  shock  is  transmitted  to  the  muscle.  The  arrangement  otherwise  is  the  same  as  for  the 
pendulum  myograph.  The  smoked  glass  plate  is  liberated  by  the  projecting  finger  plate  attached  to 
the  upright.  A.] 

[Marey's  Simple  Myograph. — The  gastrocnemius  is  attached  to  a  horizontal  lever,  which 
inscribes  its  movements  on  a  revolving  cylinder.  This  form  of  myograph,  when  provided  with  two 
levers,  is  very  useful  for  comparing  the  action  of  a  poison  on  one  limb,  the  other  being  unpoisoned.] 

[Pfliiger's  stationary  form  is  simply  a  Ilelmholtz's  myograph  (Fig.  320)  arranged  to  record 
its  movements  on  a  stationary  glass  plate,  so  that  the  muscle  merely  makes  a  vertical  line  or 
ordinate  instead  of  a  curve;  it  thus  merely  indicates  the  height  or  extent  of  the  contraction,  not 
its  duration.] 

A  rapidly  rotating  disk    was    used   by  Valentin    and    Rosenthal   for   registering   the    muscle 

curve,  while  Harless  used  a  plate  which  was  allowed 
to  fall  rapidly,  the  so  called  "  Fallmyograph." 
In  all  these  experiments  it  is  necessary  to  indicate 
at  the  same  time  the  moment  of  stimulation. 

Contraction  Curve  of  Human  Mus- 
cle.— In  man,  another  principle  is  adopted, 
viz.,  to  measure  the  increase  in  thickness 
during  the  contraction,  either  by  means  of 
a  lever  or  a  compressible  tambour,  such 
as  is  used  in  Brondgeest's  pansphygmo- 
graph  (Fig.  36).  [The  thickening  of  the 
adductor  muscles  of  the  thumb  may  be  reg- 
istered by  ineans  of  Marey's  pince  myo- 
graphique.] 

I.  Simple  Contraction. — If  a  single 
shock  or  stimulus  of  ?nofnentary  duration  be 
applied  to  a  muscle,  a  "simple  muscular 
contraction ' '  [or  shortly,  a  contraction  or 
twitch]  is  the  result,  /.  <?.,  the  muscle  rap- 
idly shortens  and  quickly  returns  again  to 
its  original  relaxed  condition. 

Myogram   or  Muscle    Curve. — Sup- 


Scheme  of  the   arrangement  of  the  pendulum  myo- 
graph,    B,    battery;     I,   primary,  II,  secondary 


spiral  of  the  induction  machine;    S,  tooth;  K',  poSC  a  siuglc  StimuluS  be  applied   tO  a  mUSclC 
key;  C.C,  catches;   K',  in  the  corner,  scheme  of     ..11.  1  ■     1  ..  "i"     „     i„    „         ...k;„U 

K';K,  key  in  primary  circuit.  attached    to    a   light   Writing    Icver,   which 

is    not    "overweighted"   with    any  weight 
attached  to  it,  then,  when  the  muscle  contracts,  the  following  events  take  place: — 
[(i)  A  period  or  stage  of  latent  stimulation  (Figs.  324,  325). 

(2)  A  period  of  increasing  energy  or  contraction. 

(3)  A  period  of  decreasing  energy  or  more  rapid  relaxation. 

(4)  A  period  of  slow  relaxation,  or  the  elastic  after  vibration.] 
The  muscle  curve  proper  is  composed  of  2,  3,  and  4. 

I.  The  latent  period  (Fig.  324,  a,  li)  consists  in  this,  that  the  muscle  does 
not  begin  to  contract  precisely  at  the  moment  the  stimulus  is  applied  to  it,  but  the 
contraction  occurs  somewhat  later,  i.  e.,  a  short,  but  measurable  interval,  elapses 
between  the  application  of  a  momentary  stimulus  and  the  contraction  {v.  Helm- 
holtz).     If  the  entire  muscle  be  stimulated  by  a  momentary  stimulus,  e.g.,  a  single 


LATENT   PERIOD    OF   A    MUSCLE    CURVE. 


529 


break  induction  shock,  the  duration  of  the  latent  period  is  about  o.oi  second. 
In  smooth  muscle,  the  latent  period  may  last  for  several  seconds. 

[Although  no  change  be  visible  in  a  muscle  during  the  latent  period,  neverthe- 
less we  have  proof  that  some  change  does  take  place  within  the  muscle  substance. 


Fig. 


Spring  myograph  or  "shooter." 

for  we  know  that  the  electrical  current  of  the  muscle  is  diminished  during  this 
period,  or  we  have  what  is  known  as  the  negative  variation  of  the  muscle  cur- 
rent {Bernstein — §  333)-] 

In  man,  the  latent  period  varies  between  0.004  and  o.oi  second.  If  the  experiment  be  so 
arranged  that  the  muscle  can  contract  as  soon  as  the  stimulus  is  apphed  to  it,  i.  e.,  before  time  is  lost 
in  making  the  muscle  tense ;  or  to  put 

it  otherwise,  if  the  muscle  has  not  "to  FiG.  324. 

take  in  slack,"  as  it  were,  the  latent 
period  may  fall  below  0.004  second 
{Gad).  If  the  muscle  be  still  attached 
to  the  body,  protected  as  much  as  pos- 
sible from  external  influences  and  prop- 
erly supplied  with  blood,  the  latent 
period  may  be  reduced  to  0.0033  or 
even  0.0025. 

Modifying  Influences. — Thelatent 
period    is    shortened    by    an    increased    Muscle  curve  produced  by  a  single  induction  shock  applied  to  a  mus- 
Strength  of  the   stimulus   and   by  heat ;  i'^;  ""'A  abscissa  ;  a-c,  ordinate  ;  a  b,  period  of  latent  stimulation  ; 

,.,°  J...  ,.  ,    .     ■'         .     '  o  a,  period  of  increasmg  energy;  a  ?,  period  of  decreasing  energy  ; 

while  fatigue,  cooling,  and  increasing  ef.  elastic  after  vibrations. 
weight  lengthen  it  [Lauterbach,  Men- 
delssohn, Yeo,  Cash).  The  latent  period  of  a  break  contraction  is  longer  than  that  of  a  make 
contraction.  The  red  muscles  have  a  longer  latent  period  than  the  white.  Before  the  muscle 
contracts  as  a  whole,  the  individual  fibres  within  it  must  have  contracted.  We  must,  therefore,  con- 
clude that  the  latency  of  the  individual  muscular  elements  is  shorter  than  that  of  the  entire  muscle 
{Gad,  Tigerstedt). 

2.  The  contraction  or  stage  of  increasing  energy,  /.  e.,  from  the 
moment  the  muscle  begins  to  shorten  until  it  reaches  its  greatest  degree  of  con- 
traction (^  d).  At  first  the  muscle  contracts  slowly,  then  more  rapidly,  and  again 
more  slowly,  so  that  the  ascending  limb  of  the  curve  has  somewhat  the  form  of 
an  /.  The  stage  lasts  0.03  to  0,4  second.  It  is  shorter  when  the  contraction 
34 


530 


METHOD    OF    MEASURING    A    MYOGRAM. 


is  shorter  (weak  stimulus),  and  the  less  the  weight  the  muscle  has  to  lift.  It 
also  varies  with  the  excitability  of  the  muscle,  being  shorter  in  a  fresh,  non- 
fatigued  muscle. 

3.  Elongation  or  stage  of  decreasing  energy. — After  the  muscle  has 
contracted  up  to  its  maximum  for  any  particular  stimulus,  it  begins  to  relax — at 
first  slowly,  then  rapidly — and  lastly  more  slowly,  so  that  an  inverse  of  an  /  is 
obtained  {d  e).  This  stage  is  usually  of  shorter  duration  than  2.  The  duration 
varies  with  the  strength  of  the  stimulus,  being  shorter  than  2  with  a  weak  stimulus, 
and  longer  with  a  strong  stimulus.  It  also  depends  upon  the  extent  to  which  the 
muscle  is  loaded  during  contraction. 

4.  The  fourth  stage  has  received  various  names — stage  of  elastic  after 
vibration  [residual  contraction  or  contraction  remainder  {Hermann). 
The  after  vibrations  (<'/),  which  disappear  gradually,  depend  upon  the  elasticity 
of  the  muscle.  The  duration  of  this  stage  is  longest  with  a  powerful  contraction, 
and  when  the  weight  attached  to  the  muscle  is  small]. 

If  the  stimulus  be  applied  to  the  motor  nerve  instead  of  to  the  muscle  itself, 
the  contraction  is  greater  {Ffiiiger),  and  lasts  longer  (  Wundt)  the  nearer  to  the 
spinal  cord  the  stimulus  is  applied  to  the  nerve. 

[In  studying  a  muscle  curve,  the  more  or  less  vertical  character  of  the  ascent 


250  DV. 


Pendulum  myograph  curve  of  a  frog's  gastrocnemius.  S,  point  of  stimulation  ;  A,  latent  period;  B,  period  of 
shortening,  and  C,  of  relaxation.  250  DV.,  tuning  fork  vibrating  250  double  vibrations  per  sec.  The  dotted 
vertical  lines  are  ordinates  {Stirling). 


will  indicate  the  rapidity  of  the  contraction,  the  height  above  the  base  line  its 
extent,  the  length  of  the  curve  the  duration,  and  the  line  of  descent  the  rate  of 
its  extensibility.  The  form  of  the  muscle  curve  will  vary  with  the  kind  of  myo- 
graph used  ;  if  it  be  stationary,  then  the  muscle  will  merely  record  a  vertical 
line  ;  if  the  recording  surface  move  quickly,  the  two  parts  of  the  curve  will  form 
an  acute  angle  (Fig.  327)  ;  and  if  it  move  with  great  rapidity,  they  will  have 
the  form  of  Fig.  325,  that  obtained  with  a  pendulum  myograph.  A  vibrating 
tuning  fork  records  time  directly  under  the  tracing,  whereby  the  duration  of  each 
part  of  the  curve  is  readily  determined.] 

[In  measuring  the  myogram,  all  that  is  required  is  to  know  the  moment  at  which  the  stimulus 
was  appHed,  and  to  note  when  the  curve  begins  to  leave  the  base  line  or  abscissa.  Raise  a  vertical 
line  or  ordinate  from  each  of  these  points,  and  the  interval  between  these  lines,  as  measured  by  the 
chronograph,  indicates  the  time  (Fig.  325).] 

[The  time  relations  of  a  simple  muscular  contraction  caused  by  a  single 
induction  shock  may  be  studied  by  means  of  the  following  arrangement : 
Attach  a  frog's  gastrocnemius  to  a  lever,  as  in  Fig.  326,  and  through  the  frog's 
•  muscle  place  two  wires  from  the  secondary  coil  of  an  induction  machine.  A 
scale  pan  with  a  weight  is  attached  to  the  lever.  On  the  same  support  adjust  an 
electro-magnet  with  a  writing  style  in  the  primary  circuit,  and  in  this  circuit 
also,  place  a  key  (K)  to  make  and  break  the  current.  Fix  also  a  Dupre's  chrono- 
graph to  the  same  support,  and  make  it  vibrate  by  connecting  it  in  circuit  with 


OVERWEIGHTED    MUSCLES. 


531 


a  tuning  fork  of  known  rate  of  vibration,  and  driven  by  a  galvanic  battery.  See 
that  the  points  of  all  three  levers  write  exactly  over  each  other  on  the  revolving 
cylinder.  The  upper  lever  registers  the  contraction,  the  electro-magnet  the  moment 
the  stimulus  is  applied  to  the  muscle,  and  the  electrical  chronograph  the  time.] 


Fig.  326. 


Fig.  327, 


Frog's  muscle  stimulated  alternately  by  a  single  break  (B) 
and  make  shock  (M).  The  lower  curve  shows  the  same, 
but  with  the  muscle  fatigued. 

[Single  make  (closing)  or  break  (open- 
ing) induction  shocks.  A  muscle  or 
nerve  may  be  stimulated  either  with  a 
"make"  or  "break"  induction  shock,  but 
it  is  important  to  notice  that  the  break  shock 
is  stronger  than  the  make.  In  Fig.  327,  B 
shows  the  effect  produced  by  a  single  break 
induction  shock,  and  M  that  of  a  single 
make  shock.] 

Overweighted  Muscles. — The  foregoing  remarks  apply  to  curves  obtained  by  a  light  lever  con- 
nected with  the  muscle.  If  the  muscle  lever  be  "  overweighted"  or  overloaded,  i.  <?.,  if  the  lever 
be  loaded  so  that  when  the  muscle  contracts  it  has  to  lift  these  weights,  the  course  of  the  curve 
varies  according  to  the  weight  to  be  Ufted.  It  is  necessary,  however,  to  support  the  lever  in  the 
intervals  when  the  muscle  is  at  rest.  As  the  weights  are  increased,  the  occurrence  of  the  contraction 
is  delayed.  This  is  due  to  the  fact  that  the  muscle,  at  the  moment  of  stimulation,  must  accumulate 
as  much  energy  as  is  necessary  to  hft  the  weight.  The  greater  the  weight,  the  longer  is  the  time 
before  it  is  raised.  Lastly,  the  muscle  may  be  so  "  loaded,"  or  "  overloaded,"  that  it  cannot  contract 
at  all;  this  is  the  Hmit  of  the  muscular  or  mechanical  energy  of  the  muscle  {v.  Helmholtz). 


Arrangement  for  estimating  the  time  relations 
during  contraction  of  a  muscle  produced 
by  a  faradic  shock.  B,  battery  ;  K,  key 
in  primary  circuit ;  I,  primary,  II,  second- 
ary spiral ;  /,  muscle  lever  ;  e ,  electro- 
magnet in  primary  circuit ;  t,  electric  sig- 
nal ;  St,  support ;  RC,  revolving  cylinder 
(after  Rutherford). 


Fig.  328. 


I,  Contraction  of  s.  fatigued  frog's  muscle  writing  its  contraction  on  a  vibrating  plate  attached  to  a  tumng  fork. 
Each  vibration  =  0.01613  second;  a  3,  =  latent  period ;  ^  c,  stage  of  increasing  energy;  c  d,  oi  decreasing 
energy.  II,  The  most  rapid  writing  movements  of  the  right  hand  inscribed  on  a  vibrating  plate.  Ill,  The 
most  rapid  trembling  tetanic  movements  of  the  right  forearm  inscribed  on  the  same  plate. 

Fatigue. — If  a  muscle  be  caused  to  contract  so  frequently  that  it  becomes 
^'fatigued,'"  the  latent  period  is  longer,  the  curve  is  not  so  high,  because  the 
muscular  contraction  is  less,  and  the  abscissa  is  longer,  /.  e.,  the  contraction  is 


532  CONTRACTION    REMAINDER. 

slower  and  lasts  longer  (Fig.  328).  Cooling  a  muscle  has  the  same  effect.  Solt- 
mann  finds  that  the  fresh  muscles  of  nciv-born  animals  behave  in  a  similar  manner. 
The  myogram  has  a  flat  apex  and  considerable  elongation  in  the  descending  limb 
of  tlie  curve. 

Constant  Current. — If  the  motor  nerve  of  a  muscle  be  stimulated  by  a  make 
or  break  shock  of  a  constant  current,  the  resulting  muscular  contraction  corres- 
ponds exactly  to  that  already  described.  If,  however,  the  current  be  made  or 
broken  with  the  muscle  itself  directly  in  the  circuit,  during  the  make  shock,  there 
is  a  certain  degree  of  contraction  which  lasts  for  a  time,  so  that  the  curve  assumes 

the  form  of  Fig.  329,  where 
^'^-  ^"9-  S  represents  the  moment  of 

closing  or  making  the  cur- 
rent,   and  O    the    moment 
of  opening    or  breaking  it 
(§  336,  D). 

Effect  on  a  muscle  of  closing  and  opening  a  constant  current.     S,  closing  ;  1  he  investigations  Ol   Lasn  and 

O,  opening  shock  (JKawf^/).  Kronecker  show  that  individual 

muscles  have  a  special  form  of 
muscle  curve  ;  the  omohyoid  of  the  tortoise  contracts  more  rapidly  than  the  pectoralis.  Similar  dif- 
ferences occur  in  the  muscles  of  frogs  and  mammals.  The  flexors  of  the  frog  contract  more  rapidly 
than  the  extensors  [Griitzner).  Sometimes  within  one  and  the  same  muscle  there  are  "  red  "  (rich 
in  glycogen)  and  "  pale"  fibres  (^  292).  The  red  fibres  contract  more  slowly,  are  less  excitable, 
and  less  easily  fatigued  [Griitzner).  The  muscles  of  flying  insects  contract  very  rapidly,  even  more 
than  100  times  per  second. 

Poisons. — Very  small  doses  of  curara  or  quinine  increase  the  height  of  the  contraction  (excited 
by  stimulation  of  the  motor  nerve),  while  larger  doses  diminish  it,  and  finally  abolish  it  altogether. 
Guanidin  has  a  similar  action  in  larger  doses, but  the  ma.ximum  of  contraction  lasts  for  a  longer 
time.  Suitable  doses  of  veratrin  also  increase  the  contractions,  but  the  stage  of  relaxation  is  greatly 
strengthened  [Rossback  and  Clostermeyer^.  Veratrin,  anliarin,  and  digitalin,  in  large  doses,  act 
upon  the  sarcous  substance  in  such  a  way  that  the  contractions  become  very  prolonged,  not  unlike  a 
condition  of  prolonged  tetanus  {Har/ess,  1862).  The  latent  period  of  muscles  poisoned  with  veratrin 
and  strychnin  is  shortened  at  first,  and  afterward  lengthened.  The  gastrocnemius  of  a  frog  supplied 
by  blood  containing  soda  contracts  more  rapidly  (6^ r///c«<fr).  Kunkel  is  of  opinion  that  muscular 
poisons  act  by  controlling  the  imbibition  of  water  by  the  sarcous  substance.  As  mu.scular  contraction 
depends  on  imbibidon  (^  297,  II),  the  form  of  the  contraction  of  the  poisoned  muscle  will  depend 
upon  the  altered  condition  of  imbibition  produced  by  the  drug. 

[Veratrin. — If  a  frog  be  poisoned  with  veratrin,  and  then  be  made  to  spring,  it  does  so  rapidly, 
but  when  it  alights  again  the  hind  legs  are  extended,  and  they  are  only  drawn  up  after  a  time.  Thus, 
rapid  and  powerful  contraction,  with  slow  and  prolonged  relaxation,  are  the  character  of  the  move- 
ments. In  a  muscle  poisoned  "with  veratrin,  the  ascent  is  quick  enough,  but  it  remains  contracted 
for  a  long  time,  so  that  this  condition  has  been  called  "  contracture."  A  single  stimulation  may 
cause  a  contraction  lasting  five  to  fifteen  seconds,  according  to  circumstances  (Fig.  330).  Brunton 
and  Cash  find  that  cold  has  a  marked  effect  on  the  action  of  veratrin — in  fact,  its  eftect  may  be 
permanently  destroyed  by  exposure  to  extremes  of  heat  or  cold.  The  muscle  curve  of  a  brainless 
frog  cooled  artificially,  and  then  poisoned  by  veratrin,  occasionally  gives  no  indication  of  the  action 
of  the  poison  until  its  temperature  is  raised,  and  this  is  not  due  to  non- absorption  of  poison.  Cold, 
therefore,  abolishes  or  lessens  the  contracture  peculiar  to  a  veratrin  curve.  Similar  results  are 
obtained  with  salts  of  barium,  and  to  a  less  degree  by  those  of  strontium  and  calcium  {Brunton 
and  Casky\ 

Smooth  Muscles. — The  muscle  curve  of  smooth  or  non-striped  muscles  is 
similar  to  that  of  the  striped  muscles,  but  the  duration  of  the  contraction  is  visibly 
much  longer,  and  there  are  other  points  of  difference.  Some  muscles  stand 
midway  between  these  two,  at  least  as  far  as  the  duration  of  their  contractions 
is  concerned. 

The  "red"  muscles  of  rabbits,  the  muscles  of  the  tortoise,  the  adductors  of  the  common  mussel, 
and  the  heart,  all  react  in  a  similar  manner. 

Contraction  Remainder. — A  contracted  muscle  assumes  its  original  length 
only  when  it  is  extended  by  sufficient  traction,  e.  g,  by  means  of  a  weight. 
Otherwise,  the  muscle    may  remain  partially  shortened   for  a  long  time.     This 


EFFECT   OF   SUCCESSIVE   STIMULI. 


533 


condition  has  been  called  "contracture"  {Tiegef),  or,  better,  contraction 
remainder  {Hemianti).  This  condition  is  most  marked  in  muscles  that  have 
been  previously  subjected  to  strong,  direct  stimulation,  and  are  greatly  fatigued, 
which  are  distinctly  acid,  and  ready  to  pass  into  rigor  mortis,  or  in  muscles 
excised  from  animals  poisoned  with  veratrin  (Fig.  330). 

Rapidity  of  Muscular  Contraction. — In  man,  single  muscular  movements 
can  be  executed  with  great  rapidity.  The  time  relations  of  such  movements  can 
be  ascertained  by  inscribing  the  movements  upon  a  smoked  glass  plate  attached  to 
a  tuning  fork.  Fig.  328,  II,  represents  the  most  rapid  voluntary  movements  that 
Landois  could  execute,  as,  e.  g.,  in  writing  the  letters  n,  n,  and  every  contraction  is 
equal  to  about  3.5  vibrations  (i  vibration  =  0.01613  second)  =  0.0564  second. 
In  III,  the  right  arm  was  tetanized,  in  which  case  2  to  2.5  vibrations  occur  = 
0.0323  to  0.0403  second. 

V.  Kries  found  that  a  simple  muscular  twitch,  caused  by  a  single  induction 
shock,  is  shorter  than  a  momentary  voluntary  single  movement.  If  the  thickening 
caused  by  a  single  voluntary  contraction  of  a  muscle  be  registered  directly,  the 
curve  shows  that  the  contraction  within  the  muscle  lasts  longer  than  the  duration 
of  the  movement  produced  in  the  passive  motor  apparatus  itself.  This  paradoxical 
phenomenon  is  due  to  the  fact  that,  shortly  after  the  primary  voluntary  muscular 

Fig.  330. 


Lower  curve  is  the  normal  muscle  curve  (frog),  upper  one  of  the  same  muscle  with  veratrin  {Stirling). 


contraction,  there  is  a  contraction  of  the  antagonistic  muscles,  whereby  a  part  of 
the  intended  movement  is,  as  it  were,  cut  off.  During  the  most  rapid  voluntary 
movement  in  human  muscles,  v.  Kries  found  that  4  stimuli  per  second  were  active, 
so  that  a  voluntary  contraction  is  really  a  short  tetanus. 

Pathological. — In  secondary  degeneration  of  the  spinal  cord  after  apoplexy,  atrophic  muscular 
anchylosis  of  the  limbs,  muscular  atrophy,  progressive  ataxia,  and  paralysis  agitans  of  long  standing, 
the  latent  period  is  lengthened;  while  it  is  shortened  \xi  the  contracture  of  senile  chorea  and  spastic 
tabes  [Mendelssohn').  The  whole  curve  is  lengthened  in  jaundice  and  diabetes  {Edinger).  In 
cerebral  hemiplegia,  during  the  stage  of  contracture,  the  muscle  curve  resembles  the  curve  of  a 
muscle  poisoned  with  veratrin,  and  the  same  is  the  case  in  spastic  spinal  paralysis  and  amyotrophic 
lateral  sclerosis;  in  pseudo-hypertrophy  of  the  muscles  the  ascent  is  short  and  the  descent  very 
elongated.  In  muscular  atrophy,  after  cerebral  hemiplegia,  and  in  tabes,  the  latent  period  increases, 
while  the  height  of  the  curve  diminishes.  In  chorea,  the  curve  is  short  [Reaction  of  Degeneration, 
§  339).  In  rare  cases  in  man,  it  has  been  observed  that  the  execution  of  spontaneous  movements 
results  in  a  very  prolonged  contraction  (Thomsen's  disease).  In  such  cases  the  muscular  fibres 
are  very  broad,  and  the  nuclei  increased  [Erh). 

II.  Action  of  Two  Successive  Stimuli.  Let  two  momentary  stimuli  be 
applied  successively  to  a  muscle  :  (A)  If  each  stimulus  or  shock  be  of  itself 
sufficient  to  cause  a  maximal  contraction,  i.  e.,  the  greatest  possible  contraction 
which  the  muscle  can  accomplish,  then  the  effect  will  vary  according  to  the  time 
which  elapses  between   the  application  of  the  two  stimuli,     (jx)  If  the  second 


534 


TETANUS   OF    MUSCLE. 


X,  two  successive  sub-maximal  contractions  ;  II,  successive  contractions  produced 
by  stimulating  a  muscle  with  12  induction  shocks  per  second;  III,  curve 
produced  with  very  rapid  induction  shocks  (complete  tetanus). 


Stimulus  is  applied  to  the  muscle  after  the  relaxation  of  the  muscle  following  upon 
the  first  stimulus,  we  obtain  merely  two  maximal  contractions,  {b)  If,  however, 
the  second  stimulus  be  api)lied  to  the  muscle  during  the  time  that  the  effect  of  the 
first  is  present,  /.  e.,  while  the  muscle  is  in  the  phase  of  contraction  or  of  relaxa- 
tion ;  in  this  case  the  second  stimulus  causes  a  new  maximal  contraction,  according 
to  the  time  of  the  particular  phase  of  the  contraction.  (<r)  When,  lastly,  the 
second  stimulus  follows  the  first  so  rapidly  that  both  occur  during  the  latent  period, 
we  obtain  only  one  maximal  contraction  {v.  Helmholtz).     It  is  to  be  specially  noted 

that  a  single  maximal 
^'"'-  ^^^-  stimulus  never  excites 

the  same  degree  of 
shortening  as  tetanic 
stimulation  (III),  but 
only  about  yi  of  the 
height  of  the  contrac- 
tion in  tetanus. 

(B)  If  the  stimuli 
be  not  maximal,  but 
only  such  as  cause  a 
medium  or  sub-max- 
imal contraction,  the 
effects  of  both  stimuli 
are  superposed,  or  there 
is  a  summation  of 
the  contractions  (Fig. 
331).  It  is  of  no  consequence  at  what  particular  phase  of  the  primary  contraction 
the  second  shock  is  applied.  In  all  cases,  the  second  stimulus  causes  a  contraction, 
just  as  if  the  phase  of  contraction  caused  by  the  first  shock  was  the  natural  passive 
form  of  the  muscle,  /.  e.,  the  new  contraction  (/;,  c)  starts  from  that  point  as  from 
an  abscissa  (Fig.  331,  I,  b').  Thus,  under  favorable  conditions,  the  contraction  may 
be  twice  as  great  as  that  caused  by  the  first  stimulus.  The  most  favorable  time  for 
the  application  of  the  second  stimulus  is  ^V  second  after  the  application  of  the 
first  {Sewall).  The  effects  of  both  stimuli  are  obtained  even  when  the  second 
stimulus  is  applied  during  the  latent  period  {ik  Helmholtz). 

III.  Tetanus — Summation  of  Stimuli. — If  stimuli,  each  capable  of  causing 
a  contraction,  and  following  each  other  with  medium  rapidity,  be  applied  to  a 
muscle,  the  muscle  has  not  sufficient  time  to  elongate  or  relax  in  the  intervals  of 
stimulation.  Therefore,  according  to  the  rapidity  of  the  successive  stimuli,  it 
remains  in  a  condition  of  continued  vibratory  contraction,  or  in  a  state  of  tetanus. 
Tetanus  is,  however,  not  a  continuous  uniform  condition  of  contraction,  but  it  is  a 
discontinuous  condition  or  form  of  the  muscle,  depending  upon  the  summation 
or  accumulation  of  contractions.  If  the  stimuli  are  applied  with  moderate  rapidity, 
the  individual  contractions  appear  in  the  curve  (Fig.  331,  II);  if  they  occur 
rapidly,  and  thus  become  superposed  and  fused,  the  curve  appears  continuous  and 
unbroken  by  elevations  and  depressions  (Fig.  331,  III).  As  a  fatigued  muscle 
contracts  slowly,  it  is  evident  that  .such  a  muscle  will  become  tetanic  by  a  smaller 
number  of  stimuli  per  second  than  will  suffice  for  a  fresh  muscle  {Marey).  All 
muscular  movements  of  long  duration  occurring  in  our  bodies  are  probably  tetanic 
in  their  nature  (Ed.   IVeder). 

[Summation  of  Stimuli. — If  a  stimulus,  insufficient  in  itself  to  cause  con- 
traction of  a  muscle,  be  repeatedly  applied  to  a  muscle  in  proper  tempo  and  of 
sufficient  strength,  at  first  a  slight  and  then  a  stronger  or  maximal  contraction 
may  be  produced.  This  process  of  summation  occurs  also  in  nervous  tissue 
(§  360).] 


SUMMATION    OF    STIMULI. 


535 


[Staircase  or  "  Treppe."  Bowditch  showed  that  the  cardiac  contractions  exhibited  a  "  stair- 
case "  character,  i.e.,  the  height  of  the  second  beat  is  greater  than  that  of  the  first ;  and  the  third  than 
that  of  the  second  (p.  126).     The  same 

occurs  in  the  case  of  the  muscles  of  the  Fig.  332. 

frog   ( Tiegel,  Minot)  and   in  mammals  Minimal.  Maximal.  Sub-maximal.  Maximal. 

{^Rossbach).  Bohr  showed  that  the 
successive  ascending  apices  in  a  teta- 
nus curve  have  really  a  staircase  char- 
acter, and  that  its  exact  form  is  that  of 
a  hyperbola.  Bohr  found  that  (i)  this 
form — the  muscle  not  being  fatigued — 
is  independent  of  the  strength  and  fre- 
quency of  the  stimuli.  (2)  The  height  Four  groups  of  contractions  ;  interval  of  simulation  2  seconds,  and  5 
of  the   series  of  contractions  in  tetanus  minutes'  pause  between  two  groups  {Buckmaster). 

is  independent  of  the  frequency  of  the 

stimuli,  increase  of  frequency  merely  causing  the  staircase  to  reach  its  maximum   more  rapidly.     (3) 
The  height  of  the  staircase  increases — within  certain  limits — with  the  strength  of  the  stimulus.    Buck- 
master  has  confirmed  this  for  sim- 
ple contractions,  but  as  shown  in 

Fig.   332,  when  the  stimuli    are  Y\G.  333. 

minimal  or  sub-maximal,  there  is 

usually  no  staircase  character  of  I* 

the    contractions,    but     maximal 
Stimuli  always  cause  it.] 

A  continued  voluntary 
contraction  in  man,  con- 
sists of  a  series  of  single 
contractions  rapidly  follow- 
ing each  other.  Every 
such  movement,  on  being 
carefully  analyzed,  consists 
of  intermittent  vibrations, 
which  reach  their  maxi- 
mum when  a  person  shivers 
{Ed.  JVeder).—lBaxt  found 
that  the   simplest   possible 

voluntary  contractions,  e.  g.,  striking  with  the  index  finger,  occupies  on  an  aver- 
age nearly  twice  as  long  a  time  as  a  similar  movement  discharged  by  a  single 
induction  shock.] 

The  number  of  single  impulses  sent  to  our  muscles  during  a  voluntary 
movement  is  tolerably  variable,  during  a  slow  contraction  =  8  to  12,  and  during  a 
rapid  contraction  =  18  to  20  impulses  per  second.  Fig.  333,  I,  represents  a  myo- 
gram of  a  sustained  contraction  of  the  flexor  brevis  pollicis  and  abductor  pollicis, 
recorded  on  a  vibrating  plate.  The  wave-like  elevations  indicate  the  single 
impulses,  each  tooth  =  0.01613  second.  II  is  a  similar  curve  registered  by  the 
extensor  digiti  tertii  {Landots).  [Schafer  finds  that  a  prolonged  voluntary  con- 
traction in  man  is  an  incomplete  tetanus  produced  by  8  to  13  successive  nervous 
impulses  per  second.     About  10  per  second  may  be  taken  as  the  average.] 

The  requisite  degree  of  shortening  is  obtained  by  the  summation  of  single  stimuli  applied  to  the 
slowly  contracting  muscle,  until  the  desired  degree  of  shortening  is  obtained.  In  estimating  exactly 
the  amount  of  movement,  we  generally  oppose  some  resistance  by  contracting  antagonistic  muscles, 
as  is  shown  by  observations  on  spare  individuals  [Brilcke). 

The  tetanic  contractions,  which  occur  normally  in  an  intact  body,  are  proved  to  consist  of 
a  series  of  successive  contractions,  because  they  can  give  rise  to  secondajy  tetanus  (|  332,)  which 
may  also  be  caused  by  muscles  thrown  into  tetanus  by  strychnin  poisoning  {Loven).  The  muscle 
sound  cannot  be  regarded  as  a  proof  of  the  oscillator}^  movement  in  tetanus  [as  HelmhoUz  has  showa 
that  this  sound  coincides  with  the  resonance  sound  of  the  ear  [Hering  and  Friedrich)']. ^ 

If  a  muscle  be  connected  with  a  telephone,  whose  wires  are  brought  into  connection  with  two 
needles,  one  placed  in  the  tendon,  and  the  other  in  the  substance  of  the  muscle,  we  hear  a  sound 
when  the  muscle  is  thrown  into  tetanus,  which  proves  that  periodic  vibratory  processes,  i.  e.,  succes- 


I,  vibration  obtained  from  the  flexor  brevis  pollicis;  II,  from  the  extensor 
digiti  tertii. 


536 


SUMMATION    OF   STIMULI. 


sive  contractions,  occur  in  the  muscle  {Bernstein  and  Schonlein').  The  sound  is  most  distinct  when 
the  tetanizing  Neef 's  hammer  of  an  induction  machine  vibrates  about  50  times  per  second  (  Wedenski 
and  Kronecker\. 

The  number  of  stimuli  requisite  to  produc*  tetanus  varies  in  different  animals,  and  in  different 
muscles  of  the  same  animal.  About  15  stimuli  per  second  are  required  to  produce  tetanus  in  the 
muscles  of  the  frog  (hyoglossus  only  10,  gastrocnemius  27) ;  very  feeble  stimuli  (more  than  20  per 
second)  cause  tetanus  [Kronecker) ;  the  muscles  of  the  tortoise  become  tetanic  with  2  to  3  shocks 
per  second;  the  red  muscles  of  the  rabbit  by  10,  the  pale  by  over  20  [K'ronecker  and  Stirling) ; 
muscles  of  birds  not  even  with  70  [Marey);  muscles  of  insects  330  to  340  per  second  [Alarey). 
Tetanic  stimulation  of  the  muscles  of  the  crayfish  (Astacus)  and  also  in  hydrophilus,  may  cause 
rhythmical  contractions  {Richet),  or  rhythmically  interrupted  tetanus  (Schonlein). 

Curarized  muscles  sometimes  pass  into  tetanus  on  the  application  of  a  momentary  stimulus  [AUhne, 
Hering\. 

O.  Soltmann  found  that  the  pale  muscles  of  new-born  rabbits  were  rendered  tetanic  with  16 
stimuli  per  second,  so  that  tetanus  was  produced   in  them  with  the  same  number  of  shocks  as  in 

fatigued  adult  muscles.    This  may 
Fit;.  334.  serve  partly  to  explain  the  facility 

with  which  spasms  occur  in  new- 
I'Oin  animals. 

[The  red  and  pale  muscles 
of  a  rabbit,  as  already  shown, 
differ  structurally,  and  also  in 
regard  to  their  blood  supply  (p. 
507).  They  also  differ  physio- 
logically and  chemically  (p. 
509 1.  When  both  muscles  are 
caused  to  contract,  by  stimulating 
the  sciatic  nerve  with  a  single 
induction  shock,  the  curves  ob- 
tained are  shown  in  Fig.  334;  the 
lower  one  from  the  pale,  and  the 
upper  from  the  red  muscle.  The 
latent  period  is  longer,  while  the 
duration  of  a  simple  contraction 
Four  stimuli  per  second  cause  an 


Curves  obtained  from  red  (upper)  and  pale  (lower)  muscles  of  a  rabbit,  by 
stimulating  the  sciatic  nerve  with  a  single  induction  shock.  The  low- 
est line  indicates  time,  and  is  divided  into  ^Jj  second  {Kronecker  and 
Stirling).  * 


of  a  red  muscle  is  three  times  longer  than  that  of  a  pale  muscle 

incomplete  tetanus,  and  10  per  second  a  nearly  complete  tetanus  in  the  red  muscles  of  a  rabbit, 
while  the  pale  muscles  require  20  to  30  stimuli  per  second  to  be  completely  tetanized.  Fig.  335 
shows  the  results  produced  by  induction  shocks  applied  to  both  muscles  at  intervals  of  ^  second.] 

The  extent  of  shortening  in  a  tetanically  contracted  muscle,  within  certain  limits,  is  dependent 
upon  the  strength  of  the  individual  stimuli — but  not  upon  their  frequency.  The  contraction 
remainder  after  tetanus  is  greater  the  stronger  the  stimuli,  the  longer  they  are  applied,  and  the  feebler 
the  muscle  used  {Bohr).  For  an  unweighted  muscle,  the  height  of  a  contraction  and  that  of  tetanus 
are  the  same  (v.  Frey).  Only  when  a  muscle  is  weighted  is  the  height  of  a  single  contraction  less 
than  by  a  tetanic  contraction.  Sometimes  a  stimulus  applied  to  a  muscle  immediately  after  tetanus 
produces  a  greater  effect  than  it  did  before  the  tetanus  [Rossbach,  Bohr). 


Fig.  335. 


Make  and  break  induction  shocks  of  300  units,  applied  at  intervals  of  a  ^  second  to  the  pale  (lower)  and  red  (upper) 
muscles  of  a  rabbit.     The  lowest  line  marks  %  second  {Kronecker  and  Stirling). 

Duration  of  Tetanus. — A  tetanized  muscle  cannot  remain  contracted  to  the  same  extent  for  an 
indefinite  period,  even  if  the  stimuli  are  kept  constant.  It  gradually  begins  to  elongate,  at  first  some- 
what rapidly,  and  then  more  slowly,  owing  to  the  occurrence  of  fatigue.  If  the  tetanic  stimulation 
is  arrested,  the  muscle  does  not  regain  its  original  position  and  shape  at  once,  but  a  contraction 
remainder  exists  for  a  certain  time,  this  being  mo^ee^'ident  after  stimulation  with  induction  shocks. 


RAPIDITY   OF   TRANSMISSION    OF   A   CONTRACTION. 


537 


IV.  If  very  rapid  induction  shocks  (22410  360  per  second)  be  applied  to 
a  muscle,  the  tetanus  after  a  so-called  "initial  contraction"  {^Bernstein)  may 
cease  {Harless,  Heidenhaiti).  This  occurs  most  readily  when  the  nerves  are 
cooled.  Kronecker  and  Stirling,  however,  found  that  stimuli  following  each  other 
at  greater  rapidity  than  24,000  per  second  produced  tetanus. 

[Tone  inductorium  of  Kronecker  and  Stirling. — This  apparatus  (Fig.  336),  consists  of  a  rod 
of  iron,  d,  fixed  in  an  iron  upright  at  a.  The  primary,  s^,  and  secondary  spiral,  s^^,  rest  on  wooden 
supports,  which  can  be  pushed  over  both  ends  of  the  rod.  One  end  of  the  rod  hes  between  leather 
rollers,/"  and  g,  which  can  be  made  to  rub  on  the  rod  by  moving  the  toothed  wheels,  h  In  this  way 
a  tone  is  produced  by  the  longitudinal  vibrations  of  the  rod,  the  number  of  vibrations  being  pro- 
portional to  the  length  of  the  rod,  so  that  by  means  of  this  instrument  we  can  produce  from  1000  to 
24,000  alternating  induction  shocks  per  second.] 

Fig.  336. 


Tone  inductorium  of  Kronecker  and  Stirling,    d,  iron  rod,  clamped  at  a  ;  j„  primary ,  j„,  secondary  spiral,  with  a  key, 
k;  leather  rollers,/" and ^,  driven  by  wheels,  h. 


Fick  has  recently  investigated  the  changes — tension — undergone  by  a  muscle  when  it  is  stimulated, 
and  when  its  length  remains  constant,  and  he  calls  this  process  an  "  isometrical  muscular  act." 
He  finds  that  a  voluntary  contraction  in  an  isometrical  act  in  man  causes  a  higher  tension  than  a  con- 
traction excited  electrically.  In  the  frog,  the  tension  is  nearly  twice  as  great  during  tetanus  as  during 
a  single  maximal  muscular  contraction  ;  in  human  muscles,  it  may  be  ten  times  as  great. 

299.  RAPIDITY  OF  TRANSMISSION  OF  A  CONTRACTION. 

— I.  If  a  long  muscle  be  stimulated  at  one  end,  a  contraction  occurs  at  that 
point,  and  is  rapidly  propagated  in  a  wave-like  manner  through  the  whole  length 
of  the  muscle,  until  it  reaches  its  other  end.  The  condition  of  excitement  or 
molecular  disturbance  is  communicated  to  each  successive  part  of  the  muscle, 
in  virtue  of  a  special  conductive  capacity  of  the  muscle.  The  mean  velocity  of 
the  contraction  wave  is  3  to  4  metres  per  second  in  the  frog  (^Bernstein,  3.869 
metres)  ;  rabbit,  4  to  5  metres  {Berns/ein  and  Sterner)  ;  lobster  i  metre  {Fredericq 
and  van  de  Valde)  ]  in  smooth  muscle  and  in  the  heart,  only  10  to  15  milli- 
metres per  second  (§  58,  4).  These  results  have  reference  only  to  excised  muscles, 
the  velocity  of  transmission  being  much  greater  in  the  voluntary  muscles  of  a 
living  man,  viz.,  10  to  13  metres  {Hermann ,  §  334,  II). 

Methods. — Aeby  placed  writing  levers  upon  both  ends  of  a  muscle,  the  levers  resting  transversely 
to  the  direction  of  the  muscular  fibres.  The  muscle  was  stimulated,  and  both  levers  registered  their 
movements,  the  one  directly  over  the  other  on  a  revolving  cylinder.  On  stimulating  one  end  of 
the  muscle,  the  lever  nearest  to  this  point  is  raised  by  the  contraction-wave,  and  a  little  later  the  other 
lever.  When  we  know  the  rate  at  which  the  cylinder  is  moving,  and  the  distance  between  the  two 
elevations,  it  is  easy  to  calculate  the  rapidity  of  transmission  of  the  contraction  wave. 


538     EFFECT  OF  VARIOUS  CONDITIONS  ON  MUSCULAR  CONTRACTION. 

Duration  and  "Wave  Length. — The  time,  corresponding  to  the  length  of 
the  abscissa  of  the  muscle  curve  inscribed  by  each  writing  lever,  is  equal  to  the 
duration  of  the  contraction  of  this  part  of  the  muscle  (according  to  Bernstein, 
0.053  ^o  0.098  second).  If  this  value  be  multiplied  by  the  rapidity  of  transmis- 
sion of  the  muscular  contraction  wave,  we  obtain  the  wave  length  of  the  contrac- 
tion wave  (=  206  to  380  millimetres). 

Modifying  Influences. — Cold  (Fig.  337).  fatigue,  approaching  death,  and 
many  poisons  [veratrin,  KCy]  diminish  the  velocity  and  the  height  of  the  con- 
traction wave,  while  the  strength  of  the  stimulus  and  the  extent  to  which  the 
muscle  is  loaded  are  without  any  effect  upon  the  velocity  of  the  wave  {Aeby).  In 
excised  muscles,  the  size  of  the  wave  diminishes  as  it  passes  along  the  muscle,  but 
this  is  not  the  case  in  the  muscles  of  living  men  and  animals.  The  contraction 
wave  never  passes  from  one  muscular  fibre  to  a  neighboring  fibre. 

[F"ig.  337  shows  the  effect  of  cold  on  the  muscles  of  a  rabbit,  in  delaying  the  contraction  wave. 
There  is  a  longer  distance  between  I  and  2  in  the  lower  than  in  tlie  upper  curves.] 

2.  If  a  long  muscle  be  stimulated  locally  near  its  middle,  a  contraction  wave 
is  propagated  toward  both  ends  of  the  muscle.  If  several  points  be  stimulated 
simultaneously,  a  wave  movement  sets  out  from  each,  the  waves  passing  over  each 
other  in  their  course  {Schiff). 

3.  If  a  stimulus  be  applied  to  the  motor  nerve  of  a  muscle,  an  impulse  is 

Fic;.  337. 


Upper  two  curves,  2  and  i,  obtained  from  a  rabbit's  muscle  by  the  above  ai Tinyement ;  the    lower  two  curves  from 
the  same  muscle,  when  it  was  cooled  by  ice. 


communicated  to  every  muscular  fibre ;  a  contraction  wave  begins  at  the  end  organ 
[motorial  end  plate],  and  must  be  propagated  in  both  directions  along  the  mus- 
cular fibres,  whose  length  is  only  3  to  4  centimetres.  As  the  length  of  the  motor 
fibres  from  the  nerve  trunk  to  where  they  terminate  in  the  motorial  end  plate  is 
unequal,  contraction  of  all  the  muscular  fibres  cannot  take  place  absolutely  at  the 
same  moment,  as  the  nerve  impulse  takes  a  certain  time  to  travel  along  a  nerve. 
Nevertheless,  the  difference  is  so  small  that,  when  a  muscle  is  caused  to  contract 
by  stimulation  of  its  motor  nerve,  practically  the  whole  muscle  appears  to  contract 
simultaneously  and  at  once. 

4.  A  complete,  u7iiform,  momentary  contraction  of  all  the  fibres  oi  a  muscle  can 
only  take  place  when  all  the  fibres  are  excited  at  the  same  moment.^  This  occurs 
when  the  electrodes  are  placed  at  both  ends  of  the  muscle,  and  an  electrical 
stimulus  of  momentary  duration  passes  through  the  whole  length  of  the  muscle. 

300.  MUSCULAR  WORK. — Muscles  are  most  perfect  machines,  not  only 
because  they  make  the  most  thorough  use  of  the  substances  on  which  their  activity 
depends  (§  217),  but  they  are  distinguished  from  all  machines  of  human  manufac- 
ture by  the  fact  that,  by  frequent  exercise  they  become  stronger,  and  are  thereby 
capable  of  accomplishing  more  work  {^Du  Bois-Rey7nond^. 

The  amount  of  work  (W)  which  a  muscle  can  perform  is  equal  to  the  product 


MUSCULAR   WORK. 


539 


of  the  weight  lifted  (/)  and  the  height  to  which  it  is  lifted  (Ji),  i.  e.,Y^=iph 
(^Introduction).  Hence,  it  follows  that  when  a  muscle  is  not  loaded  (where/  =  o), 
then  w  must  be  =  o,  i.  e.,  no  work  is  performed.  If,  again,  it  be  overloaded  with 
too  great  a  load,  so  that  it  is  unable  to  contract  (/i^o),  here  also  the  work  is  nil. 
Between  these  two  extremes  an  active  muscle  is  capable  of  doing  a  certain  amount 
of  "work." 

I.  Work  with  Maximal  Stimulation. — When  the  strongest  possible,  or 
maximal  stimulus  is  applied — /.  e.,  when  the  strength  of  the  stimulus  is  such  as 
to  cause  a  muscle  to  contract  to  the  greatest  possible  extent  of  which  it  is  capable, 
the  amount  of  work  done  increases  more  and  more  as  the  weight  is  increased,  but 
only  up  to  a  certain  maximum.  If  the  weight  be  gradually  increased,  so  that  it  is 
lifted  to  a  less  height,  the  amount  of  work  diminishes  more  and  more,  and  gradu- 
ally falls  to  be  =  o,  when  the  weight  is  not  lifted  at  all. 

Example  of  the  work  done  by  a  frog's  muscle  {£d.  Weber) : — 


Weight  lilted  in  Grammes. 

Height  in  Millimetres. 

Work  done  in  Gramme-Millimetres. 

5 

15 
25 
30 

27.6 
25-1 
11-45 

7-3 

138 

286 
220 

[Suppose  a  muscle  be  loaded  with  a  certain  number  of  grammes,  and  then  caused  to  contract,  we 
get  a  certain  height  of  contraction.  Fig.  338  shows  the  result  of  an  experiment  of  this  kind.  The 
vertical  Unes   represent  the  height   to  which  the  weights  (in 

grammes)  noted  under  them  were  raised,  so  that,  as  a  rule,  as  Fig.  338. 

the  weight  increases  the  height  to  which  it  is  raised  decreases.] 

Laws  of  Muscular  Work. — i.  A  muscle  can 
lift  a  greater  load  the  larger  its  transverse  section, 
/.  <?.,  the  more  fibres  it  contains  arranged  parallel  to 
each  other. 

2.  The  longer  the  muscle,  the  higher  it  can  lift  a 
weight. 

3.  When  a  muscle  begins  to  contract,  it  can  lift 
the  largest  load  ;  as  the  contraction  proceeds,  it  can 
only  lift  a  less  and  less  load,  and  when  it  is  at  its 
maximum  of  shortening,  only  relatively  very  light 
loads. 

4.  By  the  term  "  absolute  muscular  force  " 
is  meant,  according  to  Ed.  Weber,  just  the  weight 
which  a  muscle  undergoing  maximal  stimulation  is 
no  longer  able  to  lift  (the  muscle  being  in  its  normal 
resting  phase),  and  without  the  muscle  at  the  moment  of  stimulation  being  elongated 
by  the  weight. 

Comparative. — Comparing  the  absolute  muscular  force  of  diiferent  muscles,  even  in  different 
animals,  it  is  usual  to  calculate  it  with  reference  to  that  of  a  square  centimetre.  The  mean  transverse 
section  of  a  muscle  is  obtained  by  dividing  its  volume  by  its  length.  The  volume  is  equal  to  the 
absolute  weight  of  the  muscles  divided  by  its  specific  gravity  =  1058.  The  absolute  muscular  force 
for  I  [J  centimetre  of  a  frog's  muscle  =  2.8  to  3  kilos.  [6.6  lbs.]  [J.  Rosenthal');  for  I  Q  centi- 
metre of  human  muscle  =;  7  to  8  {Henke  and  ICttorz),  or  tven  9  to  10  kilos.  [20  to  23  lbs.]  (^Korster, 
Haughton).  Insects  can  perform  an  extraordinaiy  amount  of  work — an  insect  can  drag  along 
sixty-seven  times  its  body  weight ;  a  horse  scarcely  three  times  its  own  weight. 

5.  During  tetanus,  when  a  weight  is  kept  suspended,  no  work  is  done  as  long 
as  the  weight  is  suspended,  but  of  course  work  is  done  in  the  act  of  lifting  the 
load.  To  produce  tetanus,  successive  stimuli  are  required,  the  muscular  metabol- 
ism is  increased,  and  fatigue  rapidly  occurs.     The  potential  energy  in  this  case  is 


250 

grammes. 
Height  to  which  each  of  the  weights  is 
raised. 


540  TESTING    INDIVIDUAL   MUSCLES. 

converted  into  heat  (§  302).  When  a  muscle  is  stimulated  with  a  maximal  stimulus, 
it  cannot  lift  so  great  a  weight  with  ^«<f  contraction  as  when  it  is  stimulated  tetani- 
cally  {Hermann).  The  energy  evolved,  even  during  tetanus,  is  greater  the  more 
frequent  the  stimulation,  at  least  up  to  100  stimuli  per  second  {Bernstein). 

II.  Medium  Stimuli. — If  a  muscle  be  caused  to  contract  by  stimuli  oi moder- 
ate strength,  i.  e.,  such  as  do  not  cause  a  maximal  contraction,  there  are  two  possi- 
bilities :  Either  the  feeble  stimulus  is  kept  constant  while  the  load  is  varied,  in 
which  case  the  amount  of  work  done  follows  the  same  law  as  obtains  for  maximal 
stimulation  ;  or,  the  load  may  be  kept  the  same,  while  the  strength  of  the  stimulus 
is  varied.  In  the  latter  case,  Fick  observed  that  the  height  to  which  the  load  was 
lifted  increased  in  a  direct  ratio  with  the  strength  of  the  stimulus. 

The  stimulus  which  causes  a  muscle  to  contract  must  reach  a  certain  strength  or  intensity  before  it 
becomes  effective,  i.  e.,  the  "  liminal  intensity  "  of  the  stimulus,  but  this  is  independent  of  the 
weight  apphed  to  the  muscle.  With  minimal  stimuli,  a  small  weight  is  raised  higher  than  a  large 
one,  but  as  the  stimulus  is  increased,  the  contractions  also  increase  in  a  larger  ratio  with  an  increased 
load  {v.  Kries). 

The  blood  stream  within  the  muscles  of  an  intact  body  is  increased  during 
muscular  activity.  The  blood  vessels  of  the  muscle  dilate,  so  that  the  amount 
of  blood  flowing  through  them  is  increased  {Ludwig  and  Sczelkoiv).  At  the  time 
that  the  motor  fibres  are  excited,  so  also  are  the  vaso-dilator  fibres,  which  lie  in 
the  same  nervous  channels  (§  294,  II).  [Gaskell  found  that  faradization  of  the 
nerve  of  the  mylo-hyoid  muscle  of  the  frog  not  only  caused  tetanus  of  the  muscle, 
but  also  dilatation  of  its  blood  vessels.] 

Testing  Individual  Muscles. — In  estimating  the  absolute  force  of  the  individual  muscles 
or  groups  of  muscles  in  man,  we  must  always  pay  particular  attention  to  the  physical  relations,  i.e., 

to   the  arrangement  of  the  levers,  direction  of  the 
Fig.  339.  traction,  degree  of  shortening,  etc.  (^  306.)     Dyna- 

mometer.— The  absolute  force  of  certain  groups 
of  muscles  is  very  conveniently  and  practically 
ascertained  by  means  of  a  dynamometer  (Fig.  339). 
This  instrument  is  very  useful  for  testing  the  differ- 
ence between  the  power  of  the  two  arms  in  cases  of 
paralysis.  The  patient  grasps  the  instrument  in  his 
liand  and  an  index  registers  the  force  exerted.  Que- 
telet  has  estimated  the  force  of  certain  muscles — the 
pressure  of  both  hands  of  a  man  to  be  =  70  kilos.; 
while  by  pulling  he  can  move  double  this  weight. 
Dynamometer  of  Mathieu.  The  force  of  the  female  hand  is  one-third  less.     A 

man  can  carry  more  than  double  his  own  weight ;  a 
woman  about  the  half  of  this.  Boys  can  carry  about  one-third  more  than  girls.  [Very  convenient 
dynamometers  are  made  by  Salter,  of  Birmingham,  both  for  testing  the  strength  of  pull  and  squeeze ; 
in  testing  the  former,  the  instrument  is  held  as  an  archer  holds  his  bow  when  in  the  act  of  drawing 
it,  and  the  strength  of  pull  is  given  by  an  index  ;  in  the  latter  another  form  of  the  instrument  is  used. 
Large  numbers  of  observations  were  made  by  means  of  these  instruments  by  Francis  Galton  at 
the  Health  Exhibition.  1SS5.] 

Amount  of  Work  Daily. — In  estimating  the  work  done  by  a  man,  we  have  to  consider,  not 
only  the  amount  of  work  done  at  any  one  moment,  but  how  often,  time  after  time,  he  can  succeed  in 
doing  work.  The  mean  value  of  the  daily  work  of  a  man  working  eight  hours  a  day  is  lO  (10.5 
to  II  at  most)  kilogramme-metres  per  second,  i.  <?.,  a  daily  amount  of  work  =  288,000  (300,000) 
kilogramme-metres. 

[Ergostat. — Sometimes  it  is  desirable  that  patients — especially  those  who  suffer  from  excessive 
corpulence — should  do  a  certain  amount  of  work  daily ;  this  can  be  carried  out  by  Gaertner's  Ergostat, 
which  resembles  a  winch,  driven  by  a  handle.  The  pressure  upon  the  wheel  can  be  regulated  by 
means  of  a  strap,  lever,  and  weights,  and  according  to  the  weight  and  number  of  revolutions  of  the 
wheel,  can  the  amount  of  mechanical  work  be  accurately  regulated.  This  fnstrument  is  recom- 
mended for  therapeutical  purposes.] 

Modifying  Conditions. — Many  substances,  after  being  introduced  into  the  body,  diminish,  and 
ultimately  paralyze  the  production  of  work — mercury,  digitalin,  helleborin.  potash  salts,  etc.  Others 
increase  the  muscular  activity —  veratrin  [Rossbach),  glycogen  [caffein  and  allied  alkaloids], 
muscarin  {King  and  Fr.  Hogyes),  kreatin  and  h)-poxanthin ;  extract  of  meat  rapidly  restores  the 
muscles  after  fatigue  {Koberl).     [Those  drugs  which  excite  muscular  tissue  restore  it  after  fatigue. 


THE   ELASTICITY   OF    MUSCLE. 


541 


Kreatin  is  a  waste  product  of  muscle,  and  beef-tea  and  Liebig's  extract  of  meat  perhaps  owe  their 
restorative  qualities  partly  to  these  extractives.] 

301.  THE  ELASTICITY  OF  MUSCLE.— Physical.— Everj^  elastic  body  has  its  "natural 
shape,"  /.  e.,  its  shape  when  no  external  force  (tension  or  pressure)  acts  upon  it  so  as  to  distort  it. 
Thus,  the  passive  muscle  has  a  "  natural  form."  If,  however,  a  muscle  be  extended  in  the  course  of 
its  fibres,  the  parts  of  the  muscle  are  evidently  pulled  asunder.  If  the  stretching  be  carried  only  to  a 
certain  degree,  the  muscle,  in  virtue  of  its  elasticity,  will  regain  its  natural  form.  Such  a  body  is  said 
to  possess  "  complete  elasticity,"  i.  e.,  after  being  stretched  it  regains  exactly  its  original  shape. 
By  the  term  "amount  of  elasticity"  (inoduhis)  is  meant  the  weight  (expressed  in  kilogrammes) 
necessary  to  extend  an  elastic  body  I  Q  millimetre  in  diameter,  its  own  length,  without  the  body  break- 
ing. Of  course  many  bodies  are  ruptured  before  this  occurs.  For  a  passive  muscle  it  is  =:  0.2734 
(  Wimdi),  [that  of  bone  ^  2264  (  Wertheiiii),  tendon  =  1.6693,  nerve  =  3.0905,  the  arterial  walls  = 
0.0726  (  Wundty].  Thus,  the  amount  of  elasticity  of  a  passive  muscle  is  small,  as  it  requires  only  a 
slight  stretching  force  to  extend  it  to  its  own  length.  It  has,  therefore,  no  gi-eat  amount  of  elasticity. 
The  term  "  coefficient  of  elasticity"  is  applied  to  the  fraction  of  the  length  of  an  elastic  body, 
to  which  it  is  elongated  by  the  unit  of  weight  applied  to  stretch  it.  It  is  large  in  a  passive  muscle. 
If  the  tension  be  sufficiently  great,  the  elastic  body  ruptures  at  last.  The  "  carrying  capacity''^  of 
muscular  tissue,  until  it  ruptures,  is  in  the  following  latios  for  youth,  middle,  and  old  age,  nearly 
7:3:2.  [Instead  of  the  word  "elasticity,"  Brunton  suggests  the  use  of  extensibility  and 
retractibility,  terms  suggested  by  Marey,  the  one  referable  to  the  elongation  on  the  application  of  a 
weight,  and  the  other  to  the  shortening  after  its  removal.] 

Curve  of  Elasticity. — In  inorganic  elastic  bodies,  the  line  of  elongation,  or 
the  extension,  is  directly  proportional  to  the  t xt ending  weight ;  in  organic  bodies, 
and,  therefore,  in  muscle,  this  is  not  the  case,  as  the  weight  is  continually  increased 
by  equal  increments — the  muscle  is  less  extended  than  at  the  beginning,  so  that  the 
extension  is  not propo?'tional  to  the  weight.     If  equal  weights  be  added  to  a  scale 


Fig.  340. 


Fig.  341. 


Fig.  342. 


Curve  of  elasticity 
from  an  inorganic 
body  (india-rub- 
ber). 


Curve  of  elasticity  from 
the  sartorius  of  a 
frog,  obtained  by 
adding  equal  incre- 
ments of  weight  at 
A,  B,  C,  etc. 


Curve  of  elasticity  produced  by  con- 
tinuous extension  and  recoil  of  a 
frog's  muscle ;  o  x,  abscissa 
before,  x'  after  extension. 


pan  attached  to  a  piece  of  india-rubber,  with  a  writing  lever  connected  with  it,  and 
writing  its  movements  on  a  plate  of  glass  that  can  be  moved  with  the  hand,  we 
get  such  a  curve  as  in  Fig.  340,  while,  if  the  same  be  done  with  the  sartorius  of  a 
frog,  we  get  a  result  similar  to  Fig.  341.  A  straight  line  joins  the  apices  of  the 
former,  while  the  curve  of  elasticity  is  a  hyperbola,  or  something  near  it,  in  the 
latter  case. 

Elastic  After-effect. — At  the  same  time,  after  the  first  elongation,  correspond- 
ing to  the  extending  weight,  is  reached,  the  muscle  may  remain  for  days,  and  even 
weeks,  somewhat  elongated.  This  is  called  the  ^^  elastic  after-effect^^  (§65). 
[Marey  attached  a  lever  to  a  frog's  muscle,  and  allowed  the  latter  to  record  its 
movements  on  a  slowly  revolving  cylinder.  To  the  lever  was  fixed  a  vessel  into 
which  mercury  slowly  flowed.  This  extended  the  muscle,  and  when  it  had  ceased 
to  elongate,  the  mercury  was  allowed  slowly  to  run  out  again.  The  curve  obtained 
is  shown  in  Fig.  342.  The  abscissae,  0  x  and  od ,  indicate  the  position  of  the 
writing  style  before  and  after  the  experiment,  and  we  observe  that  od  is  lower  than 
o  X,  so  that  the  recoil  is  imperfect.     There  has  been  an  actual  elongation  of  the 


542 


ELASTIC    AFTER-EFFECT. 


muscle,  so  that  the  limit  of  its  elasticity  is  exceeded.  Although  a  frog's  gastroc- 
nemius may  be  loaded  with  1500  grammes  without  rupturing  it,  100  grammes  will 
prevent  its  regaining  its  original  length.] 

Method. — In  order  to  test  the  elasticity  of  .1  muscle,  fix  it  to  a  support  provided  with  a 
graduated  scale,  and  to  the  lower  end  of  the  muscle  attach  a  scale  pan,  in  which  are  placed  various 
weights,  measuring  on  each  occasion  the  corresponding  elongation  of  the  muscle  thereby  obtained 
{Ed.  IVeber).  In  order  to  obtain  the  curve  of  elongation  or  extensibility  take  as  abscissa:  the 
successive  units  of  weight  added,  and  the  elongation  corresponding  to  each  weight  as  ordinates. 
Example  from  the  hyoglossus  of  the  frog  : — 


Weight  in  Grammes. 

Length  of  the  Muscle 
in  Millimetres. 

Extension. 

In  Millimetres. 

Percentage. 

03 

1-3 

2-3 

3-3 
4-3 
5-3 

24.9 
30.0 
323 

33-4 
34-2 
34-6 

51 
2-3 
I.I 

0.8 
0.4 

20 
7 

3 

2 

I 

The  elasticity  of  passive  muscle  is  small,  but  very  complete,  and  is  com- 
parable to  that  of  a  caoutchouc  fibre.  Small  weights  greatly  elongate  the  muscle. 
If  the  weights  be  uniformly  increased,  there  is  not  a  uniform  elongation  ;  with  equal 
increments  of  weight,  the  greater  the  load,  the  increase  in  elongation  always  becomes 
less;  or,  to  express  it  in  another  way,  the  amount  of  elasticity  of  the  passive  muscle 
increases  with  its  increased  extension  {Etl.   Weber). 

In  inorganic  bodies,  the  curve  of  extension  is  a  straight  line,  but  in 
organic  bodies,  it  more  closely  resembles  a  hyperbola  {IVcrtheim).  The 
elasticity  of  a  passive/a/'/^i'^  muscle  does  not  differ  essentially  from  that  of  a  non- 
fatigued  muscle. 

Muscles  in  the  living  body,  and  still  in  connection  with  their  nerves  and  blood  vessels,  are  more 
extensible  than  excised  ones.  Muscles,  when  quite  fresh,  are  elongated  (within  certain  small  limits 
as  regards  the  weight)  at  first  with  a  uniformly  increasing  weight,  to  an  extent  proportional  to  the 
latter,  just  as  with  an  inorganic  body.  When  heavy  weights  are  used,  we  must  be  careful  to  take 
into  consideration  the  "  elastic  after-effect"  (?  65). 

The  volume  of  a  stretched  muscle  is  slightly  less  than  an  unstretched  one,  similar  to  the  con- 
tracted (^  297,  2)  and  stiffened  muscle  (^  295). 

Dead  muscles  and  muscles  in  rigor  mortis  have  greater  elasticity,  i.e.,  they  require  a  heavier 
weight  to  stretch  them  than  fresh  muscles;  but,  on  the  other  hand,  the  elasticity  of  dead  muscles  is 
less  complete,  i.e.,  after  they  are  stretched,  they  only  recover  their  original  form  within  certain  limits. 

Elasticity  of  Intact  Muscles. — Normally,  within  the  body,  the  muscles  are 
stretched  to  a  very  slight  extent,  as  can  be  shown  by  the  slight  degree  of  retraction 
which  occurs  when  the  insertion  of  a  muscle  is  divided.  This  slight  degree  of 
extension,  or  stretching,  is  important.  If  this  were  not  so,  when  a  muscle  is  about 
to  contract,  and  before  it  could  act  upon  a  bone  as  a  lever,  it  would  have  to  "  take 
in  so  much  slack."  The  elasticity  of  muscles  is  manifested  during  the  contrac- 
tion of  antagonistic  muscles.  The  position  of  a  passive  limb  depends  upon  the 
resultant  of  the  elastic  tension  of  the  different  muscle  groups. 

The  elasticity  of  an  active  muscle  is  less  than  that  of  a  passive  muscle, 
/.  e.,  it  is  elongated  by  the  same  weight  to  a  greater  extent  than  a  passive  muscle. 
For  this  reason,  the  active  muscle,  as  can  be  shown  in  an  excised  contracted 
muscle,  is  softer ;  the  apparently  great  hardness  manifested  by  stretched  contracted 
muscles  depends  upon  their  tension.  When  the  active  muscle  becomes  fatigued. 
its  elasticity  is  diminished  {%  304). 

Method. — Ed.  ^Yeber  took  the  hyoglossus  muscle  of  a  frog  and  suspended  it  vertically,  noticirig 
its  length  when  it  was  passive.     It  was  then  tetanized  with  indnction  shocks  and  its  height  again 


USES    OF   ELASTICITY.  543 

noted.  One  after  the  other  heavier  weights  were  attached  to  it,  and  the  length  of  the  passive  and 
tetanized  muscle  observed  for  each  weight.  The  extent  to  which  the  active  loaded  muscle  shortened 
from  the  position  of  the  passive  loaded  muscle  he  called  the  "  height  of  the  lift  "  (or  "  Hubhohe"). 
The  latter  becomes  less  as  the  weight  increases,  and  lastly,  the  tetanized  muscle  may  be  so  loaded 
that  it  cannot  contract,  i.  e.,  the  height  of  the  Uft  is  :=  o. 

Weber's  Paradox. — The  case  may  occur  where,  when  a  muscle  is  so  loaded  that  it  cannot  con- 
tract when  it  is  stimulated,  it  may  even  elongate.  According  to  Wundt,  even  in  this  condition  the 
elasticity  is  not  changed.  [The  usual  explanation  given  is  that,  as  the  elasticity  of  a  muscle  is  dimin- 
ished during  contraction,  it  is  more  extended  with  the  same  weight  in  the  contracted  as  compared 
with  the  passive  or  uncontracted  state,  so  that  a  heavily-weighted  muscle,  when  stimulated,  may 
elongate  instead  of  shorten.]  According  to  Wundt,  however,  as  stated,  there  is  no  change  in  the 
elasticity  of  the  muscle.  In  these  experiments,  the  length  of  the  active  loaded  muscle  is  equal  to  the 
length  of  the  passive  muscle  when  similarly  loaded,  minus  the  "height  of  the  lift." 

Poisons. — Potash  causes  shortening  of  a  muscle  with  simultaneous  increase  of  its  elasticity. 
Digitalin  produces  other  changes  with  increased  elasticity.  Physostigmin  increases  it,  while  veratrin 
diminishesit,  and  interferes  with  its  completeness  i^Rossbach  andv.Anrep),a.nd.  tannin  makes  a  muscle 
less  extensible,  but  more  elastic  [Lewin).  Ligature  of  the  blood  vessels  produces  at  first  a  decrease, 
and  then  an  increase,  of  the  elasticity;  section  of  the  motor  nerve  diminishes  the  elasticity  {v.  Anrep) ; 
heat  increases  it. 

Eduard  Weber  concluded  from  his  experiments  that  a  muscle  assumes  two  forms,  the  active  and 
the  passive  form.  Each  of  these  corresponds  to  a  special  natural  form.  The  passive  muscle  is  longer 
and  thinner — the  active  is  shorter  and  thicker  in  form.  The  passive  as  well  as  the  active  muscle 
strives  to  retain  its  form.  If  the  passive  muscle  be  set  into  activity,  the  passive  rapidly  changes  into 
the  active  form,  in  virtue  of  its  elastic  force.  The  latter  is  the  energy  which  causes  muscular  work. 
Schwann  compared  the  force  of  an  active  muscle  to  a  long,  elastic,  tense  spiral  spring.  Both  can 
lift  the  gi-eatest  weight,  only  from  that  form  in  which  they  are  most  stretched.  The  more  they 
shorten,  the  less  the  weight  which  they  can  lift. 

[Uses  of  Elasticity. — As  already  pointed  out,  all  muscles  are  slightly  on  the 
stretch,  so  that  no  time  is  lost  nor  energy  wasted,  in  "  taking  in  slack,"  as  it  were; 
but  the  elasticity  also  lessens  the  shock  of  the  contraction,  so  that  it  is  developed 
gradually,  and  muscles  are  not  liable  to  be  torn  from  their  attachments.  The 
muscular  energy  is  transmitted  to  the  mass  to  be  moved  through  an  elastic  and 
easily  extensible  body  (muscle),  whereby  the  shock  due  to  the  contraction  is 
lessened,  but,  as  Marey  has  shown,  the  amount  of  work  is  thereby  considerably 
increased.] 

[Tonicity  of  Muscle  (§  362) — Sensibility  of  Muscle. — That  muscles  contain  sensory  fibres 
is  certain  (^  430).  Section  of  inflamed  muscles  is  painful,  and  during  muscular  cramp  intense  pain 
is  felt.  Sachs  discharged  a  reflex  action  by  stimulating  the  central  end  of  an  intra-muscular  nerve 
filament  in  a  frog,  while  stimulation  of  the  central  end  of  the  phrenic  nerve  raises  the  blood  pressure 
(^Muscular  Sense,  ^  430).] 

302.    FORMATION  OF    HEAT   IN    AN    ACTIVE    MUSCLE.— 

After  Bunzen,  in  1805  (§  209,  i,  ^),  showed  that  during  muscular  activity  heat  is 
evolved,  v.  Helmholtz  proved  that  an  excised  frog's  muscle,  when  tetanized  for  two 
to  three  minutes,  exhibited  an  increase  of  its  temperature  of  0.14°  to  0.18°  C. 
R.  Heidenhain  succeeded  in  showing  an  increase  of  0.001°  to  0.005°  C.  for  each 
single  contraction.     The  heart  is  warmer  during  every  systole  (^Marey). 

[Method. — The  rise  in  temperatm-e  of  a  frog's  muscle  may  be  estimated  by  placing  the  two 
gastrocnemii  of  a  frog's  muscle  on  the  two  junctions  of  a  thermo-electric  pile,  connected  with  a  heat 
galvanometer.  Of  course,  when  the  two  muscles  are  at  the  same  temperature,  the  needle  of  the 
galvanometer  is  stationary;  but,  if  one  muscle  is  made  to  contract,  or  is  tetanized,  then  an  electrical 
current  is  set  up  which  deflects  the  needle  {\  208,  B).  Lujankow  has,  by  means  of  a  delicate  ther- 
mometer placed  between  the  thigh  muscles  of  a  dog,  estimated  the  rise  of  temperature  under  diff'erent 
conditions  of  the  muscle,  while  the  latter  was  still  in  situ  and  intact.] 

The  following  facts  have  been  ascertained  with  regard  to  the  development  of 
heat : — 

I.   Relation  to  ^A^ork. — It  bears  a  relation  to  the  amount  of  work. 

(a)  If  a  muscle  during  contraction  carries  a  weight  which  extends  it  again 
during  rest,  no  work  is  transferred  beyond  the  muscle  (§  300).  In  this  case  all 
the  chemical  potential  energy  during  this  movement  is  converted  into  heat. 
Under  these  circumstances,  the  amount  of  heat  evolved  runs  parallel  with  the 


544  HEAT   FORMATION    IN    AN    ACTIVE    MUSCLE. 

amount  of  work  done,  /.  e.,  it  increases  as  the  load  and  the  height  increase  up  to  a 
maximum  point,  and  afterward  diminishes  as  the  load  is  increased.  The  heat  maxi- 
mum is  reached  with  a  less  load  sooner  than  the  work  maximum  {Ilcidenhain). 

(b)  If,  when  the  muscle  is  at  the  height  of  its  contraction,  the  load  be  removed, 
then  the  muscle  has  produced  work  referable  to  something  outside  itself;  in  this 
case  the  amount  of  heat  produced  is  less  {A.  Fick).  The  amount  of  work  pro- 
duced, and  the  diminished  amount  of  heat  formed,  when  taken  together,  repre- 
sent the  same  amount  of  energy,  corresponding  to  the  law  of  the  conservation  of 
energy. 

(c)  If  the  same  amount  of  work  is  performed  in  one  case  by  many  but  small 
contractions,  and  in  another  by  fewer  but  larger  contractions,  then,  in  the  latter 
case,  the  amount  of  heat  is  greater  {Neidenhain  and  Nawalichhi).  This  shows 
that  larger  contractions  are  accompanied  by  a  relatively  greater  metabolism  of  the 
muscular  substance  than  small  contractions,  which  is  in  harmony  with  practical 
experience  ;  thus  the  ascent  of  a  tower  with  steep  high  steps  causes  fatigue  more 
rapidly  (metabolism  greater)  than  the  ascent  of  a  more  gentle  slope  with  lower 
steps. 

(d)  If  the  weighted  muscle  executes  a  series  of  contractions  one  after  the  other, 
and  at  the  same  time  does  work,  then  the  amount  of  heat  it  produces  is  greater 
than  when  it  is  tetanic,  and  keeps  a  weight  suspended.  Thus,  the  transition  of  the 
muscle  into  a  shortened  form  causes  a  greater  production  of  heat  than  the  mainten- 
ance of  this  form. 

2.  Relation  to  Tension. — The  amount  of  heat  evolved  depends  upon  the 
tension  of  the  muscle ;  it  also  increases  as  the  muscular  tension  increases  {Heiden- 
hain).  If  the  ends  of  a  muscle  be  so  fixed  that  it  cannot  contract,  the  maximum 
of  heat  is  obtained  {Beclard),  and  this  the  more  quickly  the  more  rapidly  the 
stimuli  follow  each  other  {Fick).  Such  a  condition  occurs  durmg  tetanus,  in 
which  condition  the  violently  contracted  muscles  oppose  each  other,  and  very 
high  temperatures  have  been  registered  by  Wunderlich  (§  213,  7),  while  the  same 
is  true  of  animals  that  are  tetanized  {Ley'den).  Dogs  kept  in  a  state  of  tetanus  by 
electrical  stimulation  die,  because  their  temperature  rises  so  high  (44°  to  45°  C.) 
that  life  no  longer  can  be  maintained  {Richet).  In  addition  to  the  formation  of 
heat,  there  is  a  considerable  amount  of  acid,  and  of  alcoholic  extractives  produced 
in  the  muscular  tissue. 

3.  Relation  to  Stretching. — Heat  is  also  evolved  during  the  elongation  or 
relaxation  of  a  contracted  muscle,  e.  g.,  by  causing  a  muscle  to  contract  without 
the  addition  of  any  weight,  and  loading  it  when  it  begins  to  relax,  whereby  heat 
is  produced  {Steiner,  Schmi/lewitsch,  and  IVesterman).  If  weights  be  attached  to  a 
muscle  by  means  of  an  inextensible  medium,  and  the  weights  be  allowed  to  fall 
from  a  height  so  as  to  give  a  jerk  to  the  muscle,  then  an  amount  of  heat  equivalent 
to  the  work  done  by  the  drop,  is  set  free  in  the  muscle  {Fick  and  Danilewsky). 

4.  The  formation  of  heat  diminishes  as  the  muscular  fatigue  increases. 

5.  In  a  muscle  duly  supplied  with  blood,  the  production  of  heat  (as  well  as  the 
mechanical  work)  is  far  more  active  than  in  a  muscle  whose  blood  vessels  are 
ligatured  or  its  blood  stream  cut  off.  Recovery  takes  place  more  rapidly  and 
completely  after  fatigue,  while,  at  the  same  time,  there  is  a  new  increase  in  the 
production  of  heat  {Meade  Smitli). 

The  amount  of  work  and  heat  in  a  muscle  must  always  correspond  to  the  transformation  of  an 
equivalent  amount  of  chemical  energy.  A  greater  part  of  this  energy  is  manifested  as  work,  the 
greater  the  resistance  that  is  offered  to  the  muscular  contraction.  When  the  resistance  is  great,  j4^  of  the 
chemical  energy  may  be  manifested  as  work,  but  when  it  is  small,  only  a  small  part  of  it  is  so  converted. 

It  was  stated  that  a  nerve  in  action  is  ^^°  C.  warmer  (  Valentin),  but  this  is  denied  by  v.  Helm- 
holtz  and  Heidenhain. 

In  man,  if  the  muscles  be  stimulated  with  electricity  or  contracted  voluntarily,  the  production  of 
heat  may  be  detected  through  the  skin  {v.  Ziemsseit).  The  venous. blood  flowing  from  an  actively 
contracting  muscle  is  0.6°  C.  warmer  than  the  arterial  blood  {Meade  Smith). 


THE    MUSCLE    SOUND.  545 

303.  THE  MUSCLE  SOUND.— When  a  muscle  contracts,  and  is  at  the 
same  time  kept  in  a  state  of  tension  by  the  application  of  sufficient  resistance,  it 
emits  a  distinct  sound  or  tone  with  a  semi-musical  quality,  depending  upon  the 
intermittent  variations  of  tension  occurring  within  it  {Wollaston). 

Methods. — The  muscle  sound  may  be  heard  by  placing  the  ear  over  the  tetanically  contracted  and 
tense  biceps  of  another  person  ;  or  we  may  insert  the  tips  of  our  index  fingers  into  our  ears,  and  forci- 
bly contract  the  muscles  of  our  arm ;  or  the  sound  of  the  muscles  that  close  the  jaw  may  be  heard  by 
forcibly  contracting  them,  especially  at  night  when  all  is  still,  and  when  the  outer  ears  are  closed,  v. 
Helmholtz  found  that  this  tone  coincides  with  the  resonance  tone  of  the  ear,  and  he  thought  that  the. 
vibrations  of  the  muscles  caused  this  resonance  tone.  The  sound  of  an  isolated  frog's  muscle  may  be 
heard  by  placing  one  end  of  a  rod  in  the  ear,  the  other  ear  being  closed.  To  the  other  end  of  the 
rod  is  attached  a  loaded  frog's  muscle  kept  in  a  tetanic  condition.  The  pitch  of  the  note,  i.  e  ,  the 
number  of  vibrations,  may  be  estimated  by  comparing  the  muscle  sound  with  that  produced  by  elastic 
springs  vibrating  at  a  known  rate. 

When  a  muscle  contracts  voluntarily,  z.  e.,  through  the  will,  it  makes  19.5 
vibrations  per  second.  [Schafer  and  others  give  the  number  as  10  successive 
nervous  impulses  per  second,  p.  535.]  We  do  not  hear  this  very  low  tone,  owing 
to  the  number  of  vibrations  per  second  being  too  few,  but  what  we  actually  hear 
is  the  ^rs^  over-tone,  with  double  the  number  of  vibrations.  The  muscle  sound 
has  19.5  vibrations,  when  the  muscles  of  an  animal  are  caused  to  contract,  by 
stimulating  its  spinal  cord  (v.  Hebnholtz),  and  also  when  the  motor  nerve  trunk  is 
excited  by  chemical  means  (^Bernstein).  If,  however,  tetanizing  induction  shocks 
be  applied  to  a  muscle,  then  the  number  of  vibrations  of  the  muscle  sound  cor- 
responds exactly  with  the  number  of  vibrations  of  the  vibrating  spring  or  hammer 
of  the  induction  apparatus.  Thus,  the  tone  may  be  raised  or  lowered  by  altering 
the  tension  of  the  spring. 

Loven  found  that  the  muscle  sound  was  loudest  when  the  weakest  currents  capable  of  producing 
tetanus  were  employed.  The  sound  corresponded  to  the  number  of  vibrations  of  the  octave  just  below 
it  in  the  scale.  With  stronger  currents  the  muscle  sound  disappears,  but  it  reappears  with  the  same 
number  of  vibrations  as  that  of  the  interrupter  of  the  induction  apparatus,  if  still  stronger  cvurents 
are  used. 

If  the  induction  shocks  be  applied  to  the  nerve,  the  sound  is  not  so  loud,  but 
it  has  the  same  number  of  vibrations  as  the  interrupter.  With  rapid  induction 
shocks,  tones  caused  by  704  {Loveii)  and  1000  vibrations  per  second  have  been 
produced  {Bernstein). 

The  first  heart  sound  is  partly  muscular  (§  53). 

A  single  induction  shock  is  said  to  cause  the  muscle  sound  in  a  contracting  muscle.  If  this  be  so, 
it  is  doubtful  if  the  muscle  sound  can  be  regarded  as  a  sign  that  tetanus  is  due  to  a  series  of  single 
variations  of  the  muscle  {\  298,  III). 

304.  FATIGUE  AND  RECOVERY  OF  MUSCLE.— Fatigue.— By 

the  term  fatigue  is  meant  that  condition  of  diminished  capacity  for  work  which  is 
produced  in  a  muscle  by  prolonged  activity.  This  condition  is  accompanied  in  the 
living  person  with  a  peculiar  feeling  of  lassitude,  which  is  referred  to  the  muscles. 
A  fatigued  muscle  rapidly  recovers  in  a  living  animal,  but  an  excised  muscle 
recovers  only  to  a  slight  extent  {Ed.   Weber,  Valentin). 

[Waller  recognizes  a  certain  resemblance  between  experimental  fatigue  and  the  natural  decline  of 
excitabihty  at  death,  in  disease,  and  in  poisoning.] 

The  cause  of  fatigue  is  probably  partly  due  to  the  accumulation  of  decomposition 
products — "  fatigue  stuffs  " — in  the  muscular  tissue,  these  products  being  formed 
within  the  muscle  itself  during  its  activity.  They  zx&  phosphoric  acid,  either  free 
or  in  the  form  of  acid  phosphates,  acid  potassium  phosphate  (§  294),  glycerin-phos- 
phoric acid  (?)  and  CO2.  If  these  substances  be  removed  from  a  muscle,  by  pass- 
ing through  its  blood  vessels  an  indifferent  solution  of  common  salt  (0.6  percent.), 
or  a  weak  solution  of  sodium  carbonate  [or  a  dilute  solution  of  permanganate  of 
potash  {Krone ckery^,  the  muscle  again  becomes  capable  of  energizing  {J.  Ranke, 
35 


546 


FATIGUE    OF    MUSCLES. 


1863).  The  using  up  of  O  by  an  active  muscle  favors  fatigue  (v.  Pettenkofer  and 
V.  Voit).  The  transfusion  of  arterial  /'/ood  (not  of  venous — Bichaf)  removes  the 
{dXxgMt  (Ranke,  Krofifckcr),  probably  by  replacing  the  substances  that  have  been 
used  up  in  the  muscle.  Conversely,  an  actively  energizing  muscle  may  be  rapidly 
fatigued  by  injecting  into  its  blood  vessels  a  dilute  solution  of  phosphoric  acid,  of 
acid  potassium  i)hosphate,  or  dissolved  extract  of  meat  {Kemmerich).  A  muscle 
fatigued  in  this  way  absorbs  less  O,  and  when  so  fatigued,  it  evolves  only  a  small 
amount  of  acids  and  CO.^.  The  conditions  which  lead  up  to  fatigue  are  connected 
with  considerable  metabolism  in  the  muscular  tissue. 

rZabludowski  found  that  if  a  frog's  muscles  be  systematically  stimulated  by  maximum  induction 
shocks  until  they  cease  to  contract,  massage  or  kneading  them  rapidly  restored  their  excitability, 
while  simple  rest  had  little  efiect.  Massage  acts  on  the  nerves,  but  chiefly  by  favoring  the  blood  and 
lymph  streams  which  wash  out  the  waste  products  from  the  muscle.  A  similar  result  obtains  in  man, 
so  that  the  ancient  Roman  practice  of  "  rubbing"  after  a  bath  and  after  exercise  was  one  conducive 
to  restoration  of  the  power  of  the  muscles.] 

Modifying  Conditions. — In  order  to  obtain  the  same  amount  of  work  from  a 
fatigued  muscle,  a  much  more  powerful  stimulus  must  be  applied  to  it  than  to  a  fresh 
one.  A  fatigued  muscle  is  incapable  of  lifting  a  considerable  load,  so  that  its 
absolute  muscular  force  is  diminished.  If,  during  the  course  of  an  experiment,  an 
excised  muscle  be  loaded  with  the  same  weight,  and  if  the  muscle  be  stimulated  at 
regular  intervals  with  maximal  stimuli  (strong  induction  shocks),  contraction  after 
contraction  gradually  and  regularly  diminishes  in  height,  the  decrease  being  a 
constant  fraction  of  the  total  shortening.  Thus  the  fatigue  curve  is  represented  by 
a  straight  line  [/.  e.,  a  straight  line  will  touch  the  apices  of  all  the  contractions]. 
The  more  rapidly  the  contractions  succeed  each  other,  the  greater  is  the  fall  in  the 
height  of  the  contraction  [/.  e.,  if  the  interval  between  the  contractions  be  short, 
the  fatigue  curve  falls  rapidly  toward  the  abscissa],  and  conversely.  After  a  cer- 
tain number  of  contractions,  an  excised  muscle  becomes  exhausted. 

This  result  occurs  whether  the  stimuli  are  applied  at  short  or  long  mtervals 
(AVw/^fr/^^r),  and  a  similar  result  is  obtained  with  sub-maximal  stimuli  (7/V^<?/). 
A  fatigued  muscle  contracts  more  slowly  than  a  fresh  one,  while  the  latent  period 
is  also  longer  during  fatigue  (p.  529).  The  fatigued  muscle  is  said  to  be  inore 
extensible  {Danders  and  van  Ma/isvelt).  If  a  muscle  be  so  loaded  that,  when  it 
contracts,  it  cannot  lift  the  load,  fatigue  occurs  even  to  a  greater  extent  than  when 
the  load  is  such  that  the  muscle  can  lift  it  {Leber).  The  metabolism  and  the  for- 
mation of  acid  are  greater  in  a  contracted  muscle  kept  on  the  stretch,  than  in  a 
contracted  muscle  allowed  to  shorten  {Heidenhain).  If  a  muscle  contract,  but  be 
not  reciuired  to  lift  any  load,  it  becomes  fatigued  only  very  gradually.     If  a  muscle 

be  loaded  only  during  contraction. 
Fig.  343.  and    not    during    relaxation,    it    is 

fatigued  more  slowly  than  when  it  is 
loaded  during  both  phases ;  and  the 
same  is  true  when  a  muscle  has  to  lift 
its  load  only  during  the  course  of  its 
contraction,  instead  of  at  the  begin- 
ning of  the  contraction.  Loads  may 
be  suspended  to  perfectly  passive 
muscles  without  fatiguing  them  {Har- 
less,  Leber'). 

[Signs  of  Fatigue  (Fig.  343)--- 
In    the  record  of  the  series  of  con- 
tractions:   (i)   the  contractions  be- 
come  more    prolonged  ;     (2)    they 
decrease  in  height ;  (3)  the  latent  period  becomes  longer ;  (4)  if  maximal  shocks 
be  used,  the  beginning  of  the  series  exhibits  a  "staircase"  character  of  its  con- 
tractions, just  like  the  heart  [§  57).] 


Fatigue  curve  of  a  frog's  muscle.  The  sciatic  nerve  was 
stimvilated  with  maximal  induction  shocks  and  every 
fifteenth  contraction  recorded  {Stirling). 


FATIGUE    AND    RECOVERY   OF    MUSCLES. 


547 


[While  an  excised  frog's  muscle  is  fairly  rapidly  exhausted  by  single  opening  induction  shocks, 
at  intervals  of  one  second,  human  muscle  in  its  normal  relations  may  be  almost  indefinitely  so 
treated,  and  there  is  no  change  in  the  record  or  any  sensation  of  fatigue.  Waller  regards  this  as 
favoring  the  viev?  that  the  "  fatigue  consequent  upon  prolonged  muscular  exertion  is  normally  central 
rather  than  peripheral."  Such  results,  however,  do  not  harmonize  with  those  of  Zabludowski  on  the 
kneading  of  muscles,  or  massage.     Probably  there  are  two  factors,  one  central,  the  other  peripheral.] 

Blood  Supply. — If  the  arteries  of  a  mammal  be  ligatured,  stimulation  of  the  motor  nerves  produces 
complete  fatigue  after  120  to  240  contractions  (in  two  to  four  minutes),  but  direct  muscular  stimulation 
still  causes  the  muscles  to  contract.  In  both  cases  the  fatigue  curve  is  in  the  form  of  a  straight  line. 
If  the  blood  supply  to  a  mammalian  muscle  be  normal,  on  stimulating  the  motor  nerve,  the  muscular 
contractions  at  first  increase  in  height  and  then  fall,  their  apices  forming  a  straight  line  [Rossback  and 
Harteneck).  In  persons  who  have  used  their  muscles  until  fatigue  sets  in,  it  is  found  that  at  the 
beginning  the  nerves  and  muscles  react  better  to  galvanic  and  faradic  stimulation,  but  afterward 
always  to  a  less  degree  [Orschanski).  According  to  v.  Kries,  a  muscle  tetanized  and  fatigued  with 
maximal  stimuli  behaves  like  a  fresh  muscle  tetanized  with  sub-maximal  stimuli ;  both  show  an 
incomplete  transition  fi-om  the  passive  to  the  active  condition. 

[Relation  of  End  Plates. — Muscle  is  fatigued  far  more  rapidly  than  nerve,  and  the  fatigue 
begins  in  the  muscle  and  not  in  the  nerve,  and  it  seems  to  be  the  weakest  link  in  the  chain  between 
nerve,  and  muscle  which  is  affected  during  excessive  action,  viz.,  the  motor  end  plate  (  Waller).  In 
a  nerve  its  conductivity  is  sooner  affected  by  fatigue  than  its  direct  excitability.  Waller  finds  that 
after  death  "  the  excitability  of  a  nerve  persists  when  its  action  upon  muscle  has  ceased,  such  muscle 
being  still  excitable  by  direct  stimulation."  Some  link  in  the  chain  is  obviously  affected,  and  it  is 
perhaps  the  end  plates.] 

[Action  of  Drugs  on  Fatigue. — Waller  finds,  in  a  frog  poisoned  with  veratrin,  that  if  the  muscles 
be  stimulated  electrically,  the  characteristic  elongation  of  the  descent  (^  298)  gradually  disappears. 


Fig.  344. 


Curves  obtained  by  direct  stimulation  of  the  gastrocnemius  of  a  frog  poisoned  with  strychnin,  the  sciatic  nerve 
divided  on  one  side  (upper  curve)  and  not  on  the  other  (lower  or  fatigue  curve). 

but  reappears  after  a  period  of  rest.  In  this  respect,  strychnin  in  its  action  on  the  spinal  cord  behaves 
precisely  the  same  as  veratrin  on  muscle,  viz.,  its  effect  is  dissipated  by  action  and  restored  by  rest.] 
Curara  and  the  ptomaines  cause  an  irregular  course  of  the  fatigue  curve  (Cz^ar^j;-/^?  a«if  iJ/cii'j-o). 
[If  strychnin  be  injected  into  a  frog,  and  the  sciatic  nerve  on  one  side  be  divided  after  the  strychnin 
tetanus  has  lasted  for  a  time,  the  leg  muscles  of  the  side  with  the  nerve  undivided  exhibit  signs  of 
fatigue,  as  shown  by  direct  stimulation  of  the  muscles  of  both  legs,  when  a  curve  similar  to  Fig.  344 
is  obtained.  The  higher  one  is  the  non-fatigued,  the  lower  that  of  the  side  with  the  nerve  undivided 
(  Waller).'] 

Recovery  from  the  condition  of  fatigue  is  promoted  by  passing  a  constant 
electrical  curj-ent  through  the  entire  length  of  the  muscle  {Heideiihaiti),  also  by 
injecting  fresh  arterial  blood  into  its  blood  vessel,  or  by  very  small  doses  of  vera- 
trin [or  permanganate  of  potash],  and  by  rest. 

If  the  muscle  of  an  intact  animal  be  stimulated  continuously  (fourteen  days  or  so),  until  complete 
fatigue  occurs,  the  muscular  fibres  become  granular  and  exhibit  a  wax-like  degeneration.  The 
transverse  striation  is  still  visible  as  long  as  the  sarcous  substance  is  in  large  masses,  but  as  soon  as  it 
breaks  up  into  small  pieces  the  transverse  striation  disappears  completely  (6>.  Roth). 

305.    MECHANISM    OF   THE    BONES   AND  JOINTS.— Bones 

exhibit   in   the  inner   architecture  of   their   spongiosa  an   arrangement   of  their 
lamellae  and  spicules  which  represents  the  static  results  of  those  forces — pressure 


648 


MECHANISM    OF   THE    BONES    AND   JOINTS. 


and  traction — wliich  act  on  the  developing  bone  (Structure  of  Bone,  §  447). 
They  are  so  arranged  that,  with  the  minimum  of  material,  they  afford  the  greatest 
resistance  as  a  supporting  structure  or  framework  (//.  <'.  Meyer,  Culmann,  Jul. 
Wolffs. 

I.  The  joints  permit  the  freest  movements  of  one  bone  upon  another  [such  as  exist  between  the 
extremities  of  the  bones  of  the  limbs.  In  other  cases,  sutures  arc  formed,  which,  while  permitting 
no  movement,  allow  the  contents  of  the  cavity  which  they  surround  to  enlarge,  as  in  the  case  of  the 
cranium].  The  articular  end  of  a  fresh  bone  is  covered  with  a  thin  layer  or  plate  of  hyaline  carti- 
latje,  which  in  virtue  of  its  elasticity  moderates  any  shocks  or  impulses  communicated  to  the  bones. 
The  surface  of  the  articular  cartilage  is  perfectly  smooth,  and  facilitates  an  ea.sy  gliding  movement 
of  the  one  surface  upon  the  other.  At  the  outer  boundary  Ime  of  the  cartilage,  there  is  fixed  the 
capsule  of  the  joint,  which  encloses  the  articular  ends  of  the  bones  like  a  sac.  The  inner  .surface  of 
the  capsule  is  lined  by  a  synovial  membrane,  which  secretes  the  sticky,  semi  lluid  synovia,  moisten- 
ing the  joint.  The  outer  surface  of  the  capsule  is  provided  at  various  parts  with  bands  of  fibrous 
tissue,  some  of  which  strengthen  it,  while  others  restrain  or  limit  the  movement  of  the  joint.  Some 
osseous  processes  limit  the  movements  of  particular  joints,  e.  g.,  the  coronoid  process  of  the  ulna, 
which  permits  the  forearm  to  be  flexed  on  the  upper  arm  only  to  a  certain  extent ;  the  olecranon, 
which  prevents  over-extension  at  the  elbow  joint.  The  joint  surfaces  are  kept  in  apposition  (i)  by 
the  adhesion  of  the  synovia-covered,  smooth,  articular  surface;  (2)  by  the  capsule  and  its  fibrous 
bands;  and  (3)  by  the  elastic  tension  and  contraction  of  the  muscles. 

[Structure  of  Articular  Cartilage. — The  thin  layer  of  hyaline  encrusting  cartilage  is  fixed  by 
an  irregular  surface  upon  the  corresponding  surface  of  the  head  of  the  bone  (Kig.  345).  In  a  ver- 
tical section  through  the  articular  cartilage  of  a  bone  which  has  been  softened  in  chromic  or  other 
suitable  acid,  we  observe  that  the  cartilage  cells  are  flattened  near  the  free  surface  of  the  cartilage, 
and  their  long  axes  are  parallel  to  the  surface  of  the  joint ;  lower  down,  the  cells  are  arranged  in 
irregular  groups,  and  further  down  still,  nearer  the  bone,  in  columns  or  rows,  whose  long  axis  is  in 
the  long  axis  of  the  bone.  These  rows  are  produced  by  transverse  cleavage  of  preexistmg  cells.  In 
the  upper  two-thirds,  or  thereby,  the  matrix  of  the  cartilage  is  hyaline,  but  in  the  lower  third,  near 

the  bone,  the  matrix  is  granular  and  sometimes  fibrillated.     This 
Fig.  345.  is  the  calcified  zone,  which  is  impregnated  with  lime  salts,  and 

sharply  defined  by  a  nearly  straight  line  from  the  hyaline  zone 
above  it,  and  by  a  very  bold  wavy  line  from  the  osseous  head  of 
the  bone.] 

Synovial  Membrane. — Synovial  membrane  consists  of  bun- 
dles of  delicate  connective  tissue  mixed  with  elastic  tissue,  while 
on  its  inner  surface  it  is  provided  with  folds,  some  of  which  con- 
tain fat,  and  others  blood  vessels  (synovial  villi).  The  inner 
surface  is  lined  with  endothelium.  The  intracapsular  liga- 
Hyaline  ments  and  cartilages  are  not  covered  by  the  synovial  membrane, 
cartilage,  j^qj.  ^^g  jj^gy  Covered  by  endothelium.  The  synovia  is  a  color- 
less, stringy,  alkaline  fluid,  with  a  chemical  composition  closely 
allied  to  that  of  transudations,  with  this  difierence,  that  it  con- 
tains much  mucin,  together  with  albumin  and  traces  of  fat. 
Excessive  movement  diminishes  its  amount,  makes  it  more  inspis- 
sated, and  increases  the  mucin,  but  diminishes  the  salts. 


Bone. 


Vertical  section  of  articular  cartila 
{.Stirling.) 


Calcified 
cartilage. 


Joints  may  be  divided  into  several  classes,  accord- 
ing to  the  kind  of  movement  which  they  permit : — 


I .  Joints  -vith  movement  around  one  axis :  (a)  The  Gin- 
glymus,  or  Hinge  Joint. — The  one  articular  surface  represents 
a  portion  of  a  cylinder  or  sphere,  to  which  the  other  surface  is 
adapted  by  a  corresponding  depression,  so  that,  when  flexion  or 
extension  of  the  joint  takes  place,  it  moves  only  on  one  axis  of 
the  cylinder  or  sphere.  The  joints  of  the  fingers  and  toes  are 
hinge  joints  of  this  description.  Lateral  ligaments,  which  pre- 
vent a  lateral  displacement  of  the  articular  surfaces,  are  always 
present. 

The  Screw-hinge  Joint  is  a  modification  of  the  simple  hinge 
form  {Langer,  I/en/:e),  e.  g.,  the  humero-ulnar  articulation. 
Strictly  speaking,  simple  flexion  and  extension  do  not  take  place 
at  the  elbow  joint,  but  the  ulna  moves  on  the  cupitellum  of  the  humerus  like  a  nut  on  a  bolt ;  in  the 
right  humerus,  the  screw  is  a  right  spiral,  in  the  left,  a  left  spiral.  The  ankle  joint  is  another  exam- 
ple ;  the  nut  or  female  screw  is  the  tibial  surface,  the  right  joint  is  hke  a  left-handed  screw,  the  left 
the  reverse,     {d)  The  Pivot  Joint  (rotatoria),  with  a  cylindrical  surface,  e.g.,  the  joint  between 


MECHANISM    OF   THE    BONES   AND    JOINTS.  549 

the  atlas  and  the  axis,  the  axis  of  rotation  being  around  the  odontoid  process  of  the  axis.  In  the 
acts  of  pronation  and  supination  of  the  forearm  at  the  elbow  joint,  the  axis  of  rotation  is  from 
the  middle  of  the  cotyloid  cavity  of  the  head  of  the  radius  to  the  styloid  process  of  the  ulna.  The 
other  joints  which  assist  in  these  movements  are  above  the  joint,  between  the  circumferential  part  of 
the  head  of  the  radius  and  the  sigmoid  cavity  of  the  ulna,  and  belozv  the  joint,  between  the  sigmoid 
cavity  of  the  radius  which  moves  over  the  rounded  lower  end  of  the  ulna. 

2.  Joints  with  movements  around  two  axes. — {a)  Such  joints  have  two  unequally  curved  surfaces 
which  intersect  each  other,  but  which  lie  in  the  same  direction,  e.  g.,  the  atlanto-occipital  joint,  or  the 
wrist  joint,  at  which  lateral  movements,  as  well  as  flexion  and  extension,  take  place.  [U)  Joints  with 
curved  surfaces,  which  intersect  each  other,  but  which  do  not  lie  in  the  same  direction.  To  this 
group  belong  the  saddle- shaped  articulations,  whose  surface  is  concave  in  one  direction,  but  convex 
in  the  other,  f.^.,  the  joint  between  the  metacarpal  bone  of  the  thumb  and  the  trapezium.  The 
chief  movements  are  (l)  flexion  and  extension,  (2)  abduction  and  adduction.  Further,  to  a  limited 
degree,  movement  is  possible  in  all  other  directions;  and,  lastly,  a  pyramidal  movement  can  be 
described  by  the  thumb. 

3.  Joints  ivith  inovement  on  a  spiral  articular  surface  [spiral  joints)),  e.g.,  the  knee  joint 
{Goodsir).  The  condyle  of  the  femur,  curved  from  before  backward,  in  the  antero-posterior  sec- 
tion of  its  articular  surface,  represents  a  spiral  [Ed.  Weber),  whose  centre  lies  nearer  the  posterior 
part  of  the  condyle,  and  whose  radius  vector  increases  from  behind,  downward  and  foi"vvard.  Flexion 
and  extension  are  the  chief  movements.  The  strong  lateral  ligaments  arise  from  the  condyles  of  the 
femur  corresponding  to  the  centre  of  the  spiral,  and  are  inserted  into  the  head  of  the  fibula  and  inter- 
nal condyle  of  the  tibia.  \Vhen  the  knee  joint  is  strongly  flexed,  the  lateral  ligaments  are  relaxed — 
they  become  tense  as  the  extension  increases;  and  when  the  knee  joint  is  fully  extended,  they  act 
quite  like  tense  bands  which  secure  the  lateral  fixation  of  the  joint.  Corresponding  to  the  spiral  form 
of  the  articular  surface,  flexion  and  extension  do  not  take  place  around  otie  axis,  but  the  axis  moves 
continually  with  the  point  of  contact;  the  axis  moves  also  in  a  spiral  direction.  The  greatest  flexion 
and  extension  cover  an  angle  of  about  145°.  The  anterior  crucial  ligament  is  more  tense  during 
extension,  and  acts  as  a  check  ligament  for  too  great  extension,  while  the  posterior  ismore  tense  during 
flexion,  and  is  a  check  ligament  for  too  great  flexion.  The  movements  of  extension  and  flexion  at  the 
knee  are  further  complicated  by  the  fact  that  the  joint  has  a  screw-like  movement,  in  that  during  the 
greater  extension  the  leg  moves  outward.  Hence,  the  thigh,  when  the  leg  is  fixed,  must  be  rotated 
outward  during  flexion.  Pronation  and  supination  take  place  during  the  greatest  flexion  to  the  extent 
of  41°  {Albert)  at  the  knee  joint,  while  with  the  greatest  extension  it  is  nil.  It  occurs  because 
the  external  condyle  of  the  tibia  rotates  on  the  internal.  In  all  positions  during  flexion  the 
crucial  ligaments  are  fairly  and  uniformly  tense,  whereby  the  articular  surfaces  are  against  each 
other.  Owing  to  their  arrangement,  during  increasing  tension  of  the  anterior  ligament  (exten- 
sion), the  condyles  of  the  femur  must  roll  more  on  to  the  anterior  part  of  the  articular  surface  of 
the  tibia,  while  by  increasing  tension  of  the  posterior  ligament  (flexion),  they  must  pass  more 
backward. 

4.  Joints  zvith  the  axis  of  rotation  round  one  fixed  point. — These  are  the  freely  movable 
arthrodial  joints.  The  movements  can  take  place  around  innumerable  axes,  which  all  intersect 
each  other  in  the  centre  of  rotation.  One  articular  surface  is  nearly  spherical;  the  other  is 
cup-shaped.  The  shoulder  and  hip  joints  are  typical  "  ball-and-socket  joints."  We  may 
represent  the  movements  as  taking  place  around  three  axes,  intersecting  each  other  at  right 
angles.  The  movements  which  can  be  performed  at  these  joints  maybe  grouped  as :  (l)  pendu- 
lum-like movements  in  any  plane,  (2)  rotation  round  the  long  axis  of  the  limb,  and  (3)  circum- 
scribing movements  [circumduction],  such  as  are  made  round  the  .circumference  of  a  sphere; 
the  centre  is  in  the  point  of  rotation  of  the  joint,  while  the  circumference  is  described  by  the  limb 
itself 

Limited  arthrodial  joints  are  ball  joints  with  limited  movements,  and  where  rotation  on  the 
long  axis  is  wanting,  e.g.,  the  metacarpo-phalangeal  joints. 

5.  Rigid  joints  or  amphiarthroses  are  characterized  by  the  fact  that  movement  may  occur  in 
all  directions,  but  only  to  a  very  limited  extent,  in  consequence  of  the  tough  and  unyielding  external 
ligaments.  Both  articular  surfaces  are  usually  about  the  same  size,  and  are  nearly  plane  smfaces, 
e.g.,  the  articulations  of  the  carpal  and  the  tarsal  bones. 

II.  Symphyses,  synchondroses,  and  syndesmoses  unite  bones  without  the  formation  of  a 
proper  articular  cavity,  are  movable  in  all  directions,  but  only  to  the  slightest  extent.  Physiologically 
they  are  closely  related  to  amphiarthrodial  joints. 

III.  Sutures  unite  bones  without  permitting  any  movement.  The  physiological  importance  of 
the  suture  is  that  the  bones  can  still  grow  at  their  edges,  which  thus  renders  possible  the  distention 
of  the  cavity  enclosed  by  the  bones  [Herm.  v.  Meyer). 

.  306.  ARRANGEMENT  AND  USES  OF  MUSCLES.— The  muscles 
form  45  percent,  of  the  total  mass  of  the  body,  those  of  the  right  side  being 
heavier  than  those  on  the  left.  Muscles  may  be  arranged  in  the  following  groups, 
as  far  as  their  mechanical  actions  are  concerned  : — 


550  SPHINCTER    AND    OTHER    MUSCLES. 

A,  Muscles  without  a  definite  origin  and  insertion :  — 

1.  The  hollow  muscles  surrounding  globular,  oval,  or  irregular  cavities, 
such  as  the  urinary  bladder,  gall  bladder,  uterus,  and  heart ;  or  the  walls  of 
more  or  less  cylindrical  canals  (intestinal  tract,  muscular  gland  ducts,  ureters, 
Fallopian  tubes,  vasa  deferentia,  blood  vessels,  lymphatics).  In  all  these  cases 
the  muscular  fibres  are  arranged  in  several  layers,  e.g.,  in  a  longitudinal  and  a 
circular  layer,  and  sometimes  also  in  an  oblique  layer.  All  these  layers  act 
together  and  thus  diminish  the  cavity.  It  is  inadmissible  to  ascribe  different 
mechanical  effects  to  the  different  layers,  e.g.,  that  the  circular  fibres  of  the 
intestine  narrow  it,  while  the  longitudinal  dilate  it.  Both  sets  of  fibres  rather 
seem  to  act  simultaneously,  and  diminish  the  cavity  by  making  it  narrower  and 
shorter  at  the  same  time.  The  only  case  where  muscular  fibres  may  act  in 
partially  dilating  the  cavity  is  when,  owing  to  pressure  from  without,  or  from 
partial  contraction  of  some  fibres,  a  fold,  projecting  into  the  lumen,  has  been 
formed.  When  the  fibres,  necessarily  stretching  across  the  depression  thereby 
produced,  contract,  they  must  tend  to  undo  it,  /.  e.,  enlarge  the  cavity.  The 
various  layers  are  all  innervated  from  the  same  motor  source,  which  supports  the 
view  of  their  conjoint  action. 

2.  The  sphincters  surround  an  opening  or  a  short  canal,  and  by  their 
action  they  either  constrict  or  close  it,  e.g.,  sphincter  pupill?e,  palpebrarum,  oris, 
pylori,  ani,  cunni,  urethrae, 

B.  Muscles  with  a  definite  origin  and  insertion  :  — 

1.  The  origin  is  completely  fixed  when  the  muscle  is  in  action.  The 
course  of  the  muscular  fibres,  as  they  pass  to  where  they  are  inserted,  permits 
of  the  insertion  being  approximated  in  a  straight  line  toward  their  origin 
during  contraction,  e.  g.,  the  attollens,  attrahens,  and  retrahentes  of  the  outer 
ear,  and  the  rhomboidei.  Some  of  these  muscles  are  inserted  into  soft  parts 
which  necessarily  must  follow  the  line  of  traction,  e.g.,  the  azygos  uvulae, 
levator  palati  mollis,  and  most  of  the  muscles  which  arise  from  bone  and  are 
inserted  into  the  skin,  such  as  the  muscles  of  the  face,  styloglossus,  stylopharyn- 
geus,  etc. 

2.  Both  Origin  and  Insertion  movable. — In  this  case  the  movements  of 
both  points  are  inversely  as  the  resistance  to  be  overcome.  The  resistance  is  often 
voluntary,  which  may  be  increased  either  at  the  origin  or  insertion  of  the  muscle. 
Thus,  the  sterno-cleido-mastoid  may  act  either  as  a  depressor  of  the  head  or  as  an 
elevator  of  the  chest ;  the  pectoralis  minor  may  act  as  an  abductor  and  depressor 
of  the  shoulder,  or  as  an  elevator  of  the  3d  to  5  th  ribs  (when  the  shoulder  girdle 
is  fixed). 

3.  Angular  Course. — INIany  muscles  having  a  fixed  origin  are  diverted  from 
their  straight  course  ;  either  their  fibres  or  their  tendons  may  be  defi/  out  of  the 
straight  course.  Sometimes  the  curving  is  slight,  as  in  the  occipito-frontalis 
and  levator  palpebrae  superioris,  or  the  tendon  may  form  an  angle  round  some 
bony  process,  whereby  the  muscular  traction  acts  in  quite  a  different  direction, 
/.  e.,  as  if  the  muscle  acted  directly  from  this  process  upon  its  point  of  insertion, 
e.g.,  the  obliquus  oculi  superior,  tensor  tympani,  tensor  veli  palatini,  obturator 
internus. 

4.  Many  of  the  muscles  of  the  extremities  act  upon  the  long  bones  as  upon 
levers  :  («)  Some  act  upon  a  lever  with  one  arm,  in  which  case  the  insertion 
of  the  muscle  (power)  and  the  weight  lie  upon  one  side  of  the  fulcrum  or  point  of 
support,  c.  g. ,  biceps,  deltoid.  The  insertion  (or  power)  often  lies  very  close  to  the 
fulcrum.  In  such  a  case,  the  i-apidity  of  the  movement  at  the  end  of  the  lever  is 
greatly  increased,  but  force  is  lost  [/.  e.,  what  is  gained  in  rapidity  is  lost  in 
power].  This  arrangement  has  this  advantage,  that,  owing  to  the  slight  contrac- 
tion of  the  muscle,  little  energy  is  involved,  which  would  be  the  case  had  the 
muscular  contraction  been  more  considerable  (§  300,  I,  3).     (J))  The  muscles  act 


VARIOUS  KINDS  OF  LEVERS  ACTED  ON  BY  MUSCLES. 


551 


upon  the  bones  as  upon  a  lever  with  two  arms,  in  which  case  the  power  (insertion 

of  the  muscle)  lies  on  the  other  side  of  the  fulcrum  opposite  to  the  weight,  e.g., 

the  triceps  and  muscles  of  the  calf.     In  both  cases,  the  muscular  force  necessary 

to  overcome  the  resistance  is  estimated  by  the  principles 

of  the  lever :    equilibrium  is  established  when  the  static  yig.  346. 

moments  (==  product  of  the  power  in  its  vertical  distance 

from  the  fulcrum)  are  equal ;  or  when  the  power  and  weight  #  F  ^ 

are  inversely  proportional,  as  their  vertical  distance  from  w  a  p   ^^' 

the  fulcrum.  . 


[The  Bony  Lever. — All  the  three  orders  of  levers  are  met  with  in 
the  body.  Indeed,  in  the  elbow  joint  all  the  three  orders  are  represented. 
The  annexed  scheme  shows  the  relative  positions  of  P,  W,  and  F  (Fig. 
346).     The  first  order  represented  by  such  a  movement  as  nodding  the 


W 


(2) 


(3) 


head,  the  second  by  raising  the  body  on  the  tiptoes  by  the  muscles  of  the  \v  p 

calf,  and  the  third  by  the  action  of  the  biceps  in  raising  the  forearm. 

At  the  elbow  joint  the  first  order  is  illustrated  by  extending  the  flexed      The  three  orders  of  levers. 

forearm  on  the  upper  arm,  as  in  striking  a  blow  on  the  table,  where  the 

triceps  attached  to  the  olecranon  is  the  power,  the  trochlea  the  fulcrum,  and  the  hand  the  weight. 

If  the  hand  rest  on  the  table  and  the  body  be  raised  on  it,  then  the  hand  is  the  fulcrum,  while  the 

triceps  is  the  power  raising  the  humerus  and  the  parts  resting  on  it  (W).     The  third  order  has  already 

been  referred  to,  e.g.,  flexing  the  forearm.] 

Direction  of  Action  — It  is  most  important  to  observe  the  direction  in  which  the  muscular  force 
and  weight  act  upon  the  lever  arm.  Thus,  the  direction  may  be  vertical  to  the  lever  in  one  position, 
while  after  flexion  it  may  act  obliquely  upon  the  lever.  The  static  moment  of  a  power  acting 
obliquely  on  the  lever  arm  is  obtained  by  multiplying  the  power  with  the  power  acting  in  a  direction 
vertical  to  the  point  of  rotation. 

Examples. — In  Fig.  347,  I,  B  x  represents  the  humerus,  and  x  Z  the  radius;  Aji',  the  direc- 
tion of  the  traction  of  the  biceps.  If  the  biceps  acts  at  a  right  angle  only,  as  by  lifting  horizon- 
tally a  weight  (P)  lying  on  the  forearm  or  in  the  hand,  then  the  power  of  the  biceps  (=  A)  is 
obtained  from  the  formula,  A  y  x  ='?  x  Z,  i.  e.,  A  ^=  (F  x  Z)  :  y  x.     It  is  evident  that,  when  the 


Scheme  of  the  action  of  the  muscles  on  bones. 


radius  is  depressed  to  the  position  x  C,  the  result  is  different ;  then  the  force  of  the  biceps  =  Aj  = 
(PjW  x)  :  0  X.  In  Fig.  347,  II,  TF  is  the  tibia,  F,  the  ankle  joint,  MC,  the  foot  in  a  horizontal 
position.  The  power  of  the  muscles  of  the  calf  (^  a)  necessary  to  equalize  a  force,/,  directed 
from  below  against  the  anterior  part  of  the  foot,  would  be  a  :=  (/  AI  F)  :  F  C.  If  the  foot  be 
altered  to  the  position  R  S,  the  force  of  the  muscles  of  the  calf  would  then  be  a-^  =  (/^  M  F) :  F  C. 

In  muscles  also,  which,  like  the  coraco-brachialis,  are  stretched  over  the  angle 
of  a  hinge,  the  same  result  obtains. 


552  SYNERGETIC    AND    ANTAGONISTIC    MUSCLES. 

In  Fig.  347,  III,  II  E  is  the  humerus,  E,  ihe  elbow  joint,  E  R,  the  radius,  B  R.  the  coracobrachi- 
alis.  Its  moment  in  tliis  position  is  =  A,  a  E.  When  the  radius  is  raised  to  E  R,,  then  it  is  =  A, 
a  E.  \Ve  must  notice,  however,  that  B  R,  <;  B  R.  Hence,  the  absolute  muscular  force  must  be 
less  in  the  flexed  position,  because  ever>-  muscle,  as  it  becomes  shorter,  Ufts  less  weight.  What  is 
lost  in  power  is  gained  by  the  elongation  of  the  lever  arm. 

5.  Many  muscles  have  a  double  action  ;  when  contracted  in  the  ordinary 
way  they  execute  a  combined  movement,  e.g.,  the  biceps  is  a  flexor  and  supinator 
of  the  forearm.  If  one  of  these  movements  be  prevented  by  the  action  of  other 
muscles,  the  muscle  takes  no  part  in  the  execution  of  the  other  movement. 

If  the  forearm  be  strongly  pronated  and  flexed  in  this  position,  the  biceps  takes  no  part  therein; 
or,  when  the  elbow  joint  is  rigidly  supinated,  only  the  supinator  brevis  acts,  not  the  biceps.  The 
muscles  of  mastication  are  another  example.  The  masseter  elevates  the  lower  jaw,  and  at  the  same 
time  pulls  it  forward.  If  the  depressed  jaw,  however,  be  strongly  pulled  backward  when  the  jaw 
is  raised,  the  masseter  is  not  concerned.  The  temporal  muscle  raises  the  jaw,  and  at  the  same  time 
pulls  it  backward.  If  the  depressed  jaw  be  raised  after  being  pushed  forward,  then  the  temporal  is 
not  concerned  in  its  elevation. 

6.  Muscles  acting  on  two  or  more  joints  are  those  which,  in  their 
course  from  their  origin  to  their  insertion,  pass  over  two  or  more  joints.  Either 
the  tendons  may  deviate  from  a  straight  course,  e.g.,  the  extensors  and  flexors  of 
the  fingers  and  toes,  as  when  the  latter  are  flexed  ;  or  the  direction  is  always 
straight,  e.  g.,  the  gastrocnemius.  The  muscles  of  this  group  present  the  following 
points  of  interest:  (a)  The  phenomenon  of  so-called  "active  insufficiency." 
If  the  position  of  the  joints  over  which  the  muscle  passes  be  so  altered  that  its 
origin  and  insertion  come  too  near  each  other,  the  muscle  may  require  to  contract 
so  much  before  it  can  act  on  the  bones  attached  to  it,  that  it  cannot  contract 
actively  any  further  than  to  the  extent  of  the  shortening  from  which  it  begins  to 
be  active;  e.g.,  when  the  knee  joint  is  bent,  the  gastrocnemius  can  no  longer 
produce  plantar  flexion  of  the  foot,  but  the  traction  on  the  tendo-Achilles  is  pro- 
duced by  the  soleus.  (/>)  "  Passive  insufficiency"  is  shown  by  many-jointed 
muscles  under  the  following  circumstances :  In  certain  positions  of  the  joint,  a 
muscle  may  be  so  stretched  that  it  may  act  like  a  rigid  strap,  and  thus  limit  or 
prevent  the  action  of  other  muscles,  e.g.,  the  gastrocnemius  is  too  short  to  permit 
complete  dorsal  flexion  of  the  foot  when  the  knee  is  extended.  The  long  flexors 
of  the  leg,  arising  from  the  tuber  ischii,  are  too  short  to  permit  complete  exten- 
sion of  the  knee  joint  when  the  hip  joint  is  flexed  at  an  acute  angle.  The  extensor 
tendons  of  the  fingers  are  too  short  to  permit  of  complete  flexion  of  the  joints  of 
the  fingers  when  the  hand  is  completely  flexed. 

7.  Synergetic  muscles  are  those  which  together  subserve  a  certain  kind  of 
movement,  e.g.,  the  flexors  of  the  leg,  the  muscles  of  the  calf,  and  others.  The 
abdominal  muscles  act  along  with  the  diaphragm  in  diminishing  the  abdomen 
during  straining,  while  the  muscles  of  inspiration  or  expiration,  even  the  different 
origins  of  one  muscle,  or  the  two  bellies  of  a  biventral  muscle,  may  be  regarded 
from  the  same  point  of  view. 

Antagonistic  muscles  are  those  which,  during  their  action,  have  exactly  the 
opposite  eff'ect  of  other  muscles,  e.g.,  flexors  and  extensors— pronators  and  supi- 
nators— adductors  and  abductors — elevators  and  depressors — sphincters  and  dila- 
tors— inspiratory  and  expiratory. 

When  it  is  necessary  to  bring  the  full  power  of  our  muscles  into  action,  we 
quite  involuntarily  bring  them  beforehand  into  a  condition  of  the  greatest  tension, 
as  a  muscle  in  this  condition  is  in  the  most  favorable  position  for  doing  work 
(§  300,  I,  3).  Conversely,  when  we  execute  delicate  movements  requiring  little 
energy,  we  select  a  position  in  which  the  corresponding  muscle  is  already 
shortened. 

All  the  fasciae  of  the  body  are  connected  with  muscles,  which,  when  they  contract,  alter  the  tension 
of  the  former,  so  that  they  are,  in  a  certain  sense,  aponeuroses  or  tendons  of  the  latter  (K.  Bardelebett). 
[For  the  importance  of  muscular  movements  and  those  of  fascioe  in  connection  with  the  movements 
of  the  lymph,  see  \  201.] 


GYMNASTICS,  MASSAGE   AND    CHANGES    IN    MUSCLE.  553 

307.  GYMNASTICS;     MOTOR    PATHOLOGICAL   VARIATIONS.— Gymnastic 

exercise  is  most  important  for  the  proper  development  of  the  muscles  and  motor  power,  and  it  ought 
to  be  commenced  in  both  sexes  at  an  early  age.  Systematic  muscular  activity  increases  the  volume 
of  the  muscles,  and  enables  them  tQ  do  more  work.  The  amount  of  blood  is  increased  with 
increase  in  the  muscular  development,  while  at  the  same  time  the  bones  and  ligaments  become 
more  resistant.  As  the  circulation  is  more  lively  in  an  active  muscle,  gymnastics  favor  the  circulation, 
and  ought  to  be  practiced,  especially  by  persons  of  sedentary  habits,  who  are  apt  to  suffer  from  con- 
gestion of  blood  in  abdominal  organs  {e.g.,  haemorrhoids),  as  it  favors  the  movement  of  the  tissue 
juices  [^  201].  An  active  muscle  also  uses  more  O  and  produces  more  CO.,,  so  that  respiration  is 
also  excited.  The  total  increase  of  the  metabolism  gives  rise  to  the  feeling  of  well-being  and  vigor, 
diminishes  abnormal  irritability,  and  dispels  the  tendency  to  fatigue.  The  whole  body  becomes  firmer, 
and  specifically  heavier  {Jager). 

By  Ling's,  or  the  Swedish  system,  a  systematic  attempt  is  made  to  strengthen  certain  weak 
muscles,  or  groups  of  muscles,  whose  weakness  might  lead  to  the  production  of  deformities.  These 
muscles  are  exercised  systematically  by  opposing  to  them  resistances,  which  must  either  be  overcome, 
or  against  which  the  patient  must  strive  by  muscular  action. 

Massage,  which  consists  in  kneading,  pressing,  or  rubbing  the  muscles,  favors  the  blood  stream; 
hence,  this  system  maybe  advantageously  used  for  such  muscles  as  are  so  weakened  by  disease  that  an 
independent  treatment  by  means  of  gymnastics  cannot  be  adopted.  [The  importance  of  massage  as 
a  restorative  practice  in  getting  rid  of  the  waste  products  of  muscular  activity  has  been  already  referred 
to  (I  304).] 

Disturbances  of  the  normal  movements  may  partly  affect  the  passive  motor  organs  {e.g.,  the 
bones,  joints,  ligaments,  and  aponeuroses),  or  the  active  organs  (muscles  with  their  tendons,  and 
motor  nerves). 

Passive  Organs. — Fractures,  caries  and  necrosis,  and  inflammation  of  the  bones,  which  make 
movements  painful,  influence  or  even  make  movement  impossible.  Similarly,  dislocations,  relaxation 
of  the  ligaments,  arthritis,  or  anchylosis  interfere  with  movement.  Also  curvature  of  bones,  hyper- 
ostosis or  exostosis;  lateral  curvature  of  the  vertebral  column  (Scoliosis),  backward  angular  curva- 
ture (Kyphosis),  or  forward  curvature  (Lordosis).  The  latter  interfere  with  respiration.  In  the 
lower  extremities,  which  have  to  carry  the  weight  of  the  body,  genu  valgum,  may  occur  in  flabby, 
tall,  rapidly-growing  individuals,  especially  in  some  trades,  e.g.,  in  bakers.  The  opposite  form,  genu 
varum,  is  generally  a  result  of  rickets.  Flat  foot  depends  upon  a  depression  of  the  arch  of  the 
foot,  which  then  no  longer  rests  upon  its  three  points  of  support.  Its  causes  seem  to  be 
similar  to  those  of  genu  valgum.  The  ligaments  of  the  small  tarsal  joints  are  stretched,  and  the  long 
axis  of  the  foot  is  usually  directed  outward ;  the  inner  margin  of  the  foot  is  more  turned  to  the  ground, 
while  pain  in  the  foot  and  malleoli  make  walking  and  standing  impossible.  Club  foot  (Talipes 
varus),  in  which  the  inner  margin  of  the  foot  is  raised,  and  the  point  of  the  toes  is  directed  inward 
and  downward,  depends  upon  imperfect  development  during  foetal  life.  All  children  are  born  with 
a  certain  very  slight  degree  of  bending  of  the  foot  in  this  direction.  Talipes  equinus,  in  which  the 
toes,  and  T.  calcaneus,  in  which  the  heel  touches  the  ground,  usually  depend  upon  contracture  of 
the  muscles  causing  these  positions  of  the  foot,  or  upon  paralysis  of  the  antagonistic  muscles. 

Rickets  and  Osteomalacia. — If  the  earthy  salts  be  withheld  from  the  food,  the  bones  gradually 
undergo  a  change ;  they  become  thin,  translucent,  and  may  even  bend  under  pressure.  In  certain 
persistent  defects  of  nutrition,  the  lime  and  other  salts  of  the  food  are  not  absorbed,  giving  rise  to 
rachitis,  or  rickets,  in  children.  If  fully  formed  bones  lose  their  lime  salts  to  the  extent  of  ^  to  j^ 
(halisterisis),  they  become  brittle  and  soft  (osteomalacia).  This  occurs  to  a  limited  extent  in 
old  age. 

Muscles. — The  normal  nutrition  of  muscle  is  intimately  dependent  on  a  proper  supply  of 
sodium  chloride  and  potash  salts  in  the  food,  as  these  form  integral  parts  of  the  muscular  tissue 
{ICemmerich ,  Foj-ester).  Besides  the  atrophic  changes  which  occm:  in  the  muscles  when  these  sub- 
stances are  withheld,  there  are  disturbances  of  the  central  nervous  system  and  digestive  apparatus, 
and  the  animals  ultimately  die.  The  condition  of  the  muscles  during  inanition  is  given  in  §  237.  If 
muscles  and  bones  be  kept  inactive,  they  tend  to  atrophy  (|  244).  In  atrophic  muscles,  and  in  cases 
of  anchylosis,  there  is  an  enormous  increase,  or  "  atrophic  proliferation,"  of  the  muscle  corpuscles, 
which  takes  place  at  the  expense  of  the  contractile  contents  {Cohnkeim).  A  certain  degree  of  mus- 
cular atrophy  takes  place  in  old  age.  The  uterus,  after  delivery,  undergoes  a  great  decrease  in  size 
and  weight — from  1000  to  350  grammes — due  chiefly  to  the  diminished  blood  supply  to  the  organ. 
In  chronic  lead  poisojzing,  the  extensors  and  interossei  chiefly  undergo  atrophy.  Atrophy  and 
degeneration  of  the  muscles  are  followed  by  shortening  and  thinning  of  the  bones  to  which  the  muscles 
are  attached. 

Section  and  paralysis  of  the  motor  nerves  cause  palsy  of  the  muscle,  thus  rendering  them 
inactive,  and  they  ultimately  degenerate.  Atrophy  also  occurs  after  inflammation  or  softening  of  the 
multipolar  nerve  cells  in  the  anterior  horn  of  the  gray  matter  of  the  spinal  cord,  or  the  motor  nuclei 
(facial,  spinal  accessory,  and  hypoglossal  of  Stilling  in  the  medulla  oblongata),  in  the  muscles  con- 
nected with  these  parts.  Rapid  atrophy  takes  place  in  certain  forms  of  spinal  paralysis  and  in  acute 
bulbar  paralysis  (paralysis  of  the  medulla  oblongata),  and  in  a  chronic  form  in  progressive  muscular 


554  STANDING. 

atrophy,  ami  progressive  bulbar  paralysis.  The  muscles  and  their  nerves  become  small  and  soft.  The 
muscles  show  many  nuclei,  the  sarcous  substance  becomes  fatty,  and  ultimately  disappears.  Accord- 
ing to  Charcot,  these  areas  are  at  the  same  time  the  trophic  centres  for  the  nerves  j)roceeding  from 
them,  as  well  as  for  the  muscles  belonging  to  them.  According  to  Friedreich,  the  primary  lesi  ,n 
in  progressive  muscular  atrophy  is  in  the  muscles,  and  is  due  to  a  primar)-  interstitial  inflammation 
of  the  muscle,  resulting  in  atrophy  and  degenerative  changes,  while  the  nerve  centres  are  aflected 
secondarily,  just  .is  after  amputation  of  a  limb,  the  corresponding  part  of  the  spinal  cord  degenerates. 
In  pseudo-hypertrophic  muscular  atrophy  the  muscular  fibres  atrophy  completely,  with  copi- 
ous development  of  fat  and  connective  tissue  between  the  fibres,  without  the  nerves  or  spinal  cord 
undergoing  degeneration.  The  muscular  substance  may  also  undergo  amvloid  or  7i>ax-like  degen- 
eration, whereby  the  amyloid  substance  infilirates  the  tissue  ({;  249,  VI).  Sometimes  atrophic  mus- 
cles have  a  deep  brown  color,  due  to  a  change  of  the  haemoglobin  of  the  muscle.  When  muscles  are 
much  used,  they  hypertrophy,  as  the  heart  in  certain  cases  of  valvular  lesion  or  obstruction  {\  40), 
the  bladder,  and  intestine.  [In  true  hypertrophy  there  is  an  increased  number  or  increase  in  the 
size  of  its  tissue  elements,  throughout  the  entire  tissue  or  organ,  without  any  deposit  of  a  foreign 
body.  Perhaps,  in  hypertrophy  of  the  bladder,  the  thickened  muscular  coat  not  only  serves  to 
overcome  resistance,  but  it  offers  greater  resistance  to  bursting  under  the  increased  intra-vesical 
pressure.  Mere  enlargement  is  not  hypertrophy,  for  this  may  be  brought  about  by  foreign  elements. 
In  atrophy  there  is  a  diminution  in  size  or  bulk,  even  when  the  Ijlood  stream  is  kept  up,  the  decrease 
being  due  to  pressure.  An  atrophied  organ  may  be  even  enlarged,  as  seen  in  pseudo  hypertrophic 
paralysis,  where  the  muscles  are  larger,  owing  to  the  interstititial  growth  of  fatty  and  connective  tissue, 
while  the  true  muscular  tissue  is  diminished  and  truly  atrophied.] 

308.  STANDING. — The  act  of  standing  is  accomplished  by  muscular 
action,  and  is  the  vertical  position  of  eciuilibrium  of  the  body,  in  which  a  line 
drawn  from  the  centre  of  gravity  of  the  body  falls  within  the  area  of  both  feet 
placed  upon  the  ground.  In  the  military  attitude,  the  muscles  act  in  two  direc- 
tions— (i)  to  fix  the  jointed  body,  as  it  were,  into  one  unbending  column  ;  and 
(2)  in  case  of  a  variation  of  the  equilibrium,  to  compensate  by  muscular  action 
for  the  disturbance  of  the  equilibrium. 

The  following  individual  motor  acts  occur  in  standing : — 

1.  Fixation  of  the  head  upon  the  vertebral  column.  The  occiput  may  be  moved  in  various 
directions  upon  the  atlas,  as  in  the  acts  of  nodding.  As  the  long  arm  of  the  lever  lies  in  front  of  the 
atlas,  necessarily  when  the  muscles  of  the  back  of  the  neck  relax,  as  in  sleep  or  death,  the  chin  falls 
upon  the  breast.  The  strong  neck  muscles,  which  pull  from  the  vertel)ral  column  upon  the  occiput, 
fix  the  head  in  a  firm  position  on  the  vertebral  column.  The  chief  rotatory  movement  of  the  head 
on  a  vertical  axis  occurs  round  the  odontoid  process  of  the  axis.  The  artirular  surfaces  on  the 
pedicles,  and  part  of  the  bodies  of  the  ist  and  2d  vertebra^  are  convex  toward  each  other  in  the 
middle,  becoming  somewhat  lower  in  front  and  behind,  so  that  the  head  is  highest  in  the  erect  posture. 
Hence,  when  the  head  is  greatly  rotated,  compression  ofthe  medulla  oblongata  is  prevented  (Henke). 
In  standing,  these  muscles  do  not  require  to  be  fixed  by  muscular  action,  as  no  rotation  can  take 
place  when  the  neck  muscles  are  at  rest. 

2.  Fixed  Vertebral  Column. — The  vertebral  column  itself  must  be  fixed,  especially  where  it  is 
most  mobile,  i.e.,  in  the  cervical  and  lumbar  regions.  This  is  brought  about  by  the  strong  muscles 
situate  in  these  regions,  e.g.,  the  cervical  spinal  muscles,  Extensor  dorsi  comniiinis  and  Quadratus 
lumbortttn. 

Mobility  of  the  Vertebrae. — The  least  movable  vertebrae  are  the  3d  to  the  6th  dorsal ;  the  sacrum 
is  quite  immovable.  For  a  certain  length  of  the  column,  the  mobility  depends  on  [a)  the  number 
and  height  of  the  inter-articular  (ibro-cartilages.  They  are  most  numerous  in  the  neck,  thickest  in  the 
lumbar  region,  and  relatively  also  in  the  lower  cervical  region.  They  permit  movement  to  take 
place  in  every  direction.  Collectively  the  inter-articular  disks  form  one-fourth  of  the  height  of  the 
whole  vertebral  column.  They  are  compressed  somewhat  by  the  pressure  of  the  body;  hence,  the 
body  is  longest  in  the  morning  and  after  lying  in  the  horizontal  position.  The  smaller  periphery  of 
the  bodies  of  the  cervical  vertebrae  favors  the  mobility  of  these  vertebni;  compared  with  the  larger 
lower  ones,  {b)  The  position  ofthe  processes  also  influences  greatly  the  mobility.  The  strongly  de- 
pressed spines  ofthe  dorsal  region  hinder  hyper-extension.  The  articular  processes  on  the  cervical 
vertebrae  are  so  placed  that  their  surfaces  look  obliquely  from  before  and  upward,  backward,  and 
downward  ;  this  permits  relatively  free  movement,  rotation,  lateral  and  nodding  movements.  In 
the  dorsal  region,  the  articular  surfaces  are  directed  vertically  and  directly  to  the  front,  the  lower 
directly  backward ;  in  the  lumbar  region,  the  position  of  the  articular  processes  is  almost  completely 
vertical  and  antero-posterior.  In  bending  backward,  as  far  as  possible,  the  most  mobile  parts  of  the 
column  are  the  lower  cervical  vertebrae,  the  lith  dorsal  to  the  2d  lumbar  and  the  lower  two  lumbar 
vertebn^  {E.  H.  Weber). 

3.  The  centre  of  gravity  of  the  head,  trunk,  and  arms  when  fixed  as  above,  lies  in  front  of  the 
loth  dorsal  vertebra.     It  lies  further  forward,  in  a  horizontal  plane,  passing  through  the  xiphoid  pro- 


WALKING,  RUNNING   AND    SPRINGING.  555 

cess,  the  greater  the  distention  of  the  abdomen  by  food,  fat,  or  pregnancy.  A  line  drawn  vertically 
downward  from  the  centre  of  gravity  passes  behind  the  line  uniting  both  hip  joints.  Hence,  the  trunk 
would  fall  backward  on  the  hip  joint,  were  it  not  prevented  partly  by  ligaments  and  partly  by  muscles. 
The  former  are  represented  by  the  ileo-femoral  band  and  the  anterior  tense  layer  of  the  fascia  lata. 
As  ligaments  alone,  however,  never  resist  permanent  traction,  they  are  aided,  especially  by  the  ileo- 
psoas  muscle  inserted  into  the  small  trochanter,  and  in  part,  also,  by  the  rectus  femoris.  Lateral  move- 
ment at  the  hip  joint,  whereby  the  one  limb  must  be  abducted  and  the  other  adducted,  is  prevented 
especially  by  the  large  mass  of  the  glutei.  When  the  leg  is  extended,  the  ileo-femoral  ligament,  aided 
by  the  fascia  lata,  prevents  adduction. 

4.  The  rigid  part  of  the  body,  head,  and  trunk,  with  the  arms  and  legs,  whose  centre  of  gravity  lies 
lower  and  only  a  little  in  front,  so  that  the  vertical  line  drawn  downward  intersects  a  line  connecting 
the  posterior  surfaces  of  the  knee  joints,  must  now  be  fixed  at  the  knee  joint.  Falling  backward  is 
prevented  by  a  slight  action  of  the  quadriceps  femoris,  aided  by  the  tension  of  the  fascia  lata.  In- 
directly it  is  aided  also  by  the  ileo-femoral  ligament.  Lateral  movement  of  the  knee  is  prevented  by 
the  disposition  of  the  strong  lateral  ligaments.  Rotation  cannot  take  place  at  the  knee  joint  in 
the  extended  position  (|  305,  I,  3). 

5.  A  line  drawn  downward  from  the  centre  of  gravity  of  the  whole  body,  which  lies  in  the  pro- 
montory, falls  slightly  in  front  of  a  line  between  the  two  ankle  joints.  Hence,  the  body  would  fall 
forward  on  the  latter  joint.  This  is  prevented  especially  by  the  muscles  of  the  calf,  aided  by  the 
muscles  of  the  deep  layer  of  the  leg  (tibialis  posticus,  flexors  of  the  toes,  peroneous  longus  et  brevis). 

Other  Factors. — {n)  As  the  long  axis  of  the  foot  forms  with  the  leg  an  angle  of  50°,  falling 
forward  can  only  occur  after  the  feet  are  in  a  position  more  nearly  parallel  with  their  long  axis,  (b) 
The  form  of  the  articular  surfaces  helps,  as  the  anterior  broad  part  of  the  astragalus  must  be  pressed 
between  the  two  malleoli.     The  latter  mechanism  cannot  be  of  much  importance. 

6.  The  metatarsus  and  phalanges  are  united  by  tense  ligaments  to  form  the  arch  of  the  foot,  which 
touches  the  ground  at  three  points — tuber  calcanei  (heel),  the  head  of  the  first  metatarsal  bone  (ball  of 
the  great  toe),  and  of  the  fifth  toe.  Between  the  latter  two  points,  the  heads  of  the  metatarsal  bones 
also  form  points  of  supports.  The  weight  of  the  body  is  transmitted  to  the  highe.stpart  of  the  arch  of 
the  foot,  the  caput  tali.  The  arching  of  the  foot  is  fixed  only  by  ligaments.  The  toes  play  no  part  in 
standing,  although,  when  moved  by  their  muscles,  they  greatly  aid  the  balancing  of  the  body.  The 
maintenance  of  the  erect  attitude  fatigues  one  more  rapidly  than  walking. 

309.  SITTING. — Sitting  is  that  position  of  equilibrium  whereby  the  body  is  supported  on  the 
tubera  ischii,  on  which  a  to  and  fro  movement  may  take  place  {^H.  v.  Mever').  The  head  and  trunk 
together  are  made  rigid  to  form  an  immovable  column,  as  in  standing.  We  may  distinguish:  (l)  the 
forward  posture,  in  which  the  line  of  gravity  passes  in  fi-ont  of  the  tubera  ischii ;  the  body  being  sup- 
ported either  against  a  fixed  object,  e.g.,  by  means  of  the  arm  on  a  table,  or  against  the  upper  surface 
of  the  thigh.  (2)  The  backward  posture,  in  which  the  hne  of  gravity  falls  behind  the  tubera.  A 
person  is  prevented  from  falling  backward  either  by  leaning  on  a  support,  or  by  the  counter-weight  of 
the  legs  kept  extended  by  muscular  action,  whereby  the  sacrum  forms  an  additional  point  of  support, 
while  the  trunk  is  fixed  on  the  thigh  by  the  ileo-psoas  and  rectus  femoris,  the  leg  being  kept  extended 
by  the  extensor  quadriceps.  Usually  the  centre  of  gravity  is  so  placed  that  the  heel  also  acts  as  a 
point  of  support.  The  latter  sitting  posture  is  of  course  not  suited  for  resting  the  muscles  of  the 
lower  limbs.  (3)  When  "  sitting  erect  "  the  line  of  gravity  falls  between  the  tubera  themselves. 
The  muscles  of  the  legs  are  relaxed,  the  rigid  trunk  only  requires  to  be  balanced  by  slight  muscular 
action.     Usually  the  balancing  of  the  head  is  sufficient  to  maintain  the  equilibrium. 

310.  WALKING,  RUNNING,  AND  SPRINGING.— By  the  term 
•walking  is  understood  progression  in  a  forward  horizontal  direction  with  the 
least  possible  muscular  exertion,  due  to  the  alternate  activity  of  the  two  legs. 

Methods. — The  Brothers  Weber  were  the  first  to  analyze  the  various  positions  of  the  body  in 
walking,  running,  and  springing,  and  they  represented  them  in  a  continuous  series,  which  represents 
the  successive  phases  of  locomotion.  These  phases  may  be  examined  with  the  zoetrope  (|  398, 
3.)  Marey  estimated  the  ti»ie  relations  of  the  individual  acts,  by  transferring  the  movements,  by 
means  of  his  air  tambours,  to  a  recording  surface.  Recently,  by  means  of  a  revolving  camera,  he  has 
succeeded  in  photographing,  in  instantaneous  pictures  (yoVo  second),  the  whole  series  of  acts.  Of 
course  this  series,  when  placed  in  the  zoetrope,  represents  the  natural  movements.  Figs.  349,  350, 
351  represent  these  acts. 

In  walking,  the  legs  are  active  alternately;  while  one — the  ''supporting"  or 
"active"  leg — carries  the  trunk,  the  other  is  ''inactive"  or  "passive."  Each 
leg  is  alternately  in  an  active  and  a  passive  phase.  Walking  may  be  divided  into 
the  following  movements: — 

I.  Act  (Fig.  348,  2). — The  active  leg  is  vertical,  slightly  flexed  at  the  knee,  and  it  alone  supports 
the  centre  of  gravity  of  the  body.     The  passive  leg  is  completely  extended,  and  touches  the  ground 


556 


WALKING,  RUNNING    AND    SPRINGING. 


onlv  with  the  tip  of  the  great  toe  {z).     This  position  of  the  leg;  correspondstoarifjht-angled  triangle, 
in  wliich  the  active  leg  and  the  ground  fonn  two  sides,  while  the  passive  leg  is  the  hypothenuse. 

II.  Act. — For  the  forward  movement  of  the  trunk,  the  active  leg  is  inclined  slightly  from  its 
vertical  position  (cathctiis)  to  an  ohlique  and  more  forward  (hypothenuse)  position  ( 3V  In  order  that 
the  trunk  may  remain  at  the  same  height,  it  is  necessary  that  the  active  leg  he  lengthened.  This  is 
accomplished  by  completely  extending  the  knee  (3,  4,  5),  as  well   as  by  lifting  the  heel  from  the 


Phases  of  walking.     The  thick  lines  represent  the  active,  the  thin  the  passive  leg:   /(,  the  hip  joint;  i-. 
f,  b,  ankle ;  c,  d,  heel  ;  m,  e,  ball  of  the  tarso-metatarsal  joint ;  2,  g,  point  of  great  toe. 


knee  ; 


ground  (4,  5),  so  that  the  foot  rests  on  the  balls  or  the  heads  of  the  metatarsal  bones,  and,  lastly,  by 
elevating  it  on  the  point  of  the  great  toe  (2,  thin  line).  During  the  extension  and  forward  move- 
ment of  the  active  leg,  the  tips  of  the  toes  of  the  passive  leg  have  left  tl>€  ground  (3).  It  is  slightly 
flexed  at  the  knee  joint  (owing  to  the  shortening),  it  performs  a"  pendulum-like  movement"  (4,  5), 
whereby  its  foot  is  moved  as  far  in  front  of  the  active  leg  as  it  was  formerly  beliind  it.  The  foot  is 
then  placed  fiat  upon  the  ground  (l,  2,  thick  lines)  ;  the  centre  of  gravity  is  now  transferred  to  this 

Fig.  349. 


— 1 — - — \ ^ 1 ^ — 1 1 

0 

(>.:',(> 

1 

1.5iJ 

2 

2.50 

3   Metrn^ 

Phases  of  slow  walking.  Instantaneous  photograph  (^farey),  only  the  side  directed  to  the  observer  is  shown. 
From  the  vertical  position  of  the  right,  active  leg  ;  (I),  all  the  phases  of  this  leg  are  represented  in  six  pictures 
(I  to  Vl),  while  after  VI  the  vertical  position  is  regained.  The  Ar.-ibic  numerals  indicate  the  simultaneous  posi- 
tion of  the  corresponding  left  leg  ;  thus  i  =  I,  2  =  II,  etc.,  so  that  during  the  position  IV  of  the  right  leg,  at 
the  same  time  the  left  leg  has  the  position  as  i. 


active  leg,  which,  at  the  same  time,  is  slightly  flexed  at  the  knee,  and  placed  vertically.     The  first  act 
is  then  repeated. 

Simultaneous  Movements  of  the  Trunk. — During  vj^alking,  the  trunk  performs  certain 
characteristic  movements.  (l)  It  leans  every  time  toward  the  active  leg,  owing  to  the  traction  of 
the  glutei  and  the  tensor  fascice  lat.-e,  so  that  the  centre  of  gravity  is  moved,  which  in  short,  heavy 
persons  with  a  broad  pelvis  leads  to  their  "  waddling"  gait.  (2)  The  trunk,  especially  during  rapid 
walking,  is  inclined  slightly  forward  to  overcome  the  resistance  of  the  air.     (3)  During  the  "  pendulum- 


WALKING,  RUNNING   AND    SPRINGING.  557 

like  action,"  the  trunk  rotates  slightly  on  the  head  of  the  active  femur.  This  rotation  is  compensated, 
especially  in  rapid  walking,  by  the  arm  of  the  same  side  as  the  oscillating  leg  swinging  in  the  opposite 
direction,  while  that  on  the  other  side  at  the  same  time  swings  in  the  same  direction  as  the  oscillating 
limb. 

Modifying  Conditions:  i.  The  Duration  of  the  Step. — As  the  rapidity  of  the  vibration  of  a 
pendulum  (leg)  depends  upon  its  length,  it  is  evident  that  each  individual,  according  to  the  length  of 
his  legs,  must  have  a  certain  natural  rate  of  walking.  The  '■'■duration  of  a  step'''  depends  also  upon 
the  time  during  which  both  feet  touch  the  ground  simultaneously,  w'hich,  of  course,  can  be  altered 
voluntarily.  When  "walking  rapidly"  the  time  ^  O,  i.  e.,  at  the  same  moment  in  which  the  active 
leg  reaches  the  ground,  the  passive  leg  is  raised.  2.  The  length  of  the  step  is  usually  about  6  to  7 
decimetres  [23  to  27  inches],  and  it  must  be  greater,  the  more  the  length  of  the  hypothenuse  of  the 
passive  leg  exceeds  the  cathetus  of  the  active  one.  Hence,  during  a  long  step,  the  active  leg  is  greatly 
shortened  (by  flexion  of  the  knes),  so  that  the  trunk  is  pulled  downward.  Similarly,  long  legs  can 
make  longer  steps. 

According  to  Marey  and  others,  the  pendulum  movement  of  the  passive  leg  is  not  a  true 
pendulum  movement,  because  its  movement,  owing  to  muscular  action,  is  of  more  uniform  rapidity. 
During  the  pendulum  movement  of  the  whole  limb,  the  leg  vibrates  by  itself  at  the  knee  joint  i^Lucce, 
H.  Vierordl). 

Fixation  of  the  Femur. — ^According  to  Ed.  and  W.  Weber,  the  head  of  the  femur  of  the  passive 
leg  is  fixed  in  its  socket  chiefly  by  the  atmospheric  pressure,  so  that  no  muscular  action  is  necessary 
for  carrying  the  whole  limb.     If  all  the  muscles  and  the  capsule  be  divided,  the  head  of  the  femur 

Fig.  350. 


2.75      3  Mf.tm 


Instantaneous  photograph  of  a  rvmne^r  {Marey).     Ten  pictures  per  second.     The  abscissa  indicates 
the  length  of  the  step  in  metres. 

Still  remains  in  the  cotyloid  cavity.  Rose  refers  this  condition  not  to  the  action  of  the  atmospheric 
pressure,  but  to  two  adhesion  surfaces  united  by  means  of  synovia.  The  experiments  of  Aeby  show 
that  not  only  the  weight  of  the  limb  is  supported  by  the  atmospheric  pressure,  but  that  the  latter  can 
support  several  times  this  weight.  When  traction  is  exerted  on  the  limb,  the  margins  of  the  cotyloid 
ligament  of  the  cotyloid  cavity  are  apphed  like  a  valve  tightly  to  the  margin  of  the  cartilage  of  the 
head  of  the  femur.  According  to  the  Brothers  Weber,  the  leg  falls  from  its  socket  as  soon  as  air  is 
admitted  by  making  a  perforation  into  the  articular  cavity. 

Work  done  during  Walking. — Marey  and  Demery  estimate  the  amount  done  by  a  man 
weighing  64  kilos.  [10  stones],  when  walking  slowly,  as  =  6  kilogramme-metres  per  second;  rapid 
running  :=  56  kilogramme-metres.  The  work  done  is  due  to  the  raising  of  the  entire  body  and  extremi- 
ties, to  the  velocity  communicated  to  the  body,  as  well  as  to  the  maintenance  of  the  centre  of  gravity. 

In  springing  or  leaping,  the  body  is  rapidly  projected  upward  by  the  greatest  possible  and  most 
rapid  contraction  of  the  muscles,  while  at  the  same  time  the  centre  of  gravity  is  maintained  by  other 
muscular  acts  (Fig.  351). 

The  pressure  upon  the  sole  of  the  foot  in  "walking  is  distributed  in  the  following  manner :  The 
supporting  leg  always  presses  more  strongly  on  the  ground  than  the  other;  the  longer  the  step  the 
greater  the  pressure.  The  heel  receives  the  maximum  amount  of  pressure  sooner  than  the  point  of 
the  foot  {Car let). 

Running  is  distinguished  from  rapid  walking  by  tlie  fact  that,  at  a  particular 
moment  both  legs  do  not  touch  the  ground,  so  that  the  body  is  raised  in  the  air. 


558 


WALKING,  RUNNING    AND    SPRINGING. 


The  active  leg,  as  it  is  forciby  extended  from  a  flexed  position,  gives  the  l)ody  the 
necessary  impetus  (Fig.  350). 

Pathological. — V.iriations  of  the  walking  movements  depend  primarily  upon  diseases  of  bones, 
ligaments,  muscles,  and  tendons,  and  also  U]X)n  affections  of  the  motor  nerves.  The  effect  of  sensory 
nerves  and  the  reflex  mechanism  of  the  spinal  cord,  and  also  of  the  muscular  sense  on  walking,  are 
stated  in  {-i;  355,  360,  430. 

311.  COMPARATIVE. — The  absolute  muscular  force  in  animals  is  not,  as  a  rule,  much 
different  from  that  in  man.  The  great  motor  power  exerted  by  animals  results  from  the  thickness 
and  number  of  the  muscles,  as  well  as  from  the  different  arrangement  of  the  levers  and  the  action  of 
muscles  on  them.  Insects  particularly  exert  a  large  amount  of  force;  some  insects  can  drag  a  body 
sixty-seven  times  their  own  weight;  a  horse  scarcely  its  own  weight.  A  man  pressing  upon  a  dyna- 
mometer with  one  hand  exerts  pressure  -=  0.70  times  his  own  weight,  while  a  dog  lifting  its  lower 
jaw  exerts  8.3  times.  A  crab  by  closing  its  pincers  28.5  times.  A  mussel  on  closing  its  shell  382 
times  its  body  weight  {Plateau). 

In  mammals  standing  is  much  more  easy,  as  they  have  four  supporting  surfaces.  The  springing 
animals  have  a  sitting  attitude,  while  the  tail  is  often  used  as  a  support  (kangaroo,  squirrel).  In 
birds,  there  is  a  mechanical  arrangement  by  which,  while  perching,  the  tendons  are  flexed;  hence, 

Fig.  351. 


High  leap.  Instantaneous  photograph  (Marey).  The  pictures  partly  overlap  each  other,  as  soon  as  the  velocity  of 
the  forward  movement  on  the  descent  diminishes  after  springing.  In  the  left-hand  corner  is  the  dial  plate,  the 
radius  of  which  moved  one  division  in  -^  second.     The  abscissa  indicates  the  distance  in  metres. 


a  bird  while  sleeping  can  still  retain  its  hold  (Cuvier).  In  the  stork  and  crane,  which  stand  for  a 
long  time  on  one  leg,  this  act  is  unaccompanied  by  muscular  action,  as  the  tibia  is  fixed  by  means  of 
a  process  which  fits  into  a  depression  of  the  articular  surface  of  the  femur. 

In  walking,  we  distinguish  in  mammals  the  step  (le  pas) — the  four  feet  are  generally  moved  in 
four  tempo,  and  usually  diagonally,  ^.i,i-.,  in  the  horse  right  fore,  left  hind;  left  fore,  right  hind. 
[The  camel  is  an  exception — it  moves  the  fore  and  hind  limbs  simultaneously  on  each  side.]  In 
trotting  this  movement  is  accelerated;  the  two  limbs  in  a  diagonal  direction  lift  together,  so  that 
only  two  hoof  sounds  are  heard  while  at  the  same  time,  the  body  is  raised  more  in  the  air.  During 
the  interval  between  two  hoof  beats  the  body  is  free  in  the  air,  all  the  limbs  having  left  the  ground. 
Strictly  speaking,  the  fore  limb  leaves  the  ground  slightly  .sooner  than  the  hind  one.  The  gallop. — 
When  a  (right)  galloping  horse  moves  in  the  air,  the  upper  part  of  its  body  is  fairly  horizontal;  when 
it  touches  the  ground,  the  left  hind  foot  is  the  first  to  touch  the  ground.  Shortly  thereafter,  the  left 
fore  and  right  hind  foot  touch  the  ground,  while  the  right  fore  leg  has  not  yet  reached  the  ground 
and  is  directed  forward.  The  upper  part  of  the  body  still  retains  its  horizontal  <lirection.  When, 
however,  a  few  moments  thereafter,  the  left  hind  leg  again  leaves  the  ground,  it  is  higher  than  the 
fore  leg — simultaneously  the  right  fore  leg  is  thrown  forward  and  lower,  while  the  right  hind  and 
left  fore  leg  are  stretched  to  the  extreme.  Immediately  thereafter  these  limbs  leave  the  ground,  while 
the  hind  limb  so  far  overtakes  the  fore  limb  that  it  comes  to  lie  higher  than  the  latter.  The  body, 
therefore,  is  projected  forward  and  downward  until  the  right  fore  limb,  which  alone  touches  the 


ACT   OF    SWIMMING.  559 

ground,  actively  contracts  and  again  raises  the  body  from  the  ground.  When  this  happens,  the  horse 
again  floats  in  the  air,  its  body  being  directed  horizontally.  The  long  axis  of  the  horse's  body  in 
galloping  is  placed  obliquely  to  the  direction  of  movement,  and  forming  a  right  angle.  In  forced 
galloping  (la  carriere),  which  is  really  a  springing  movement,  the  right  hind  leg  and  left  fore  leg  do 
not  touch  the  ground  at  the  same  time,  but  the  former  does  so  sooner.  The  amble  is  a  modification 
of  the  step,  which  consists  in  this,  that  both  feet  on  the  same  side  move  at  the  same  time  or  shortly 
after  each  other  (camel,  giraffe,  elephant).  Marey  attached  compressible  ampullse  under  the  hoof  of 
a  horse,  connecting  them  with  registering  apparatus,  and  thus  accurately  registered  the  time  relation 
of  each  act.  Muybridge  photographed  the  actions  of  a  horse  and  the  different  phases  of  the  move- 
ment. 

In  snakes  the  rudder-like  elevation  and  depression  of  the  ribs  cause  the  progression  of  the 
body. 

Swimming  is  an  acquired  art  in  man.  The  specific  gravity  of  the  body  is  slightly  greater  than 
that  of  ordinary  water,  but  slightly  lighter  than  that  of  sea  water.  When  lying  quietly  on  the 
back,  so  that  only  the  mouth  and  nose  are  at  last  above  the  water,  very  slight  movements  of  the 
hands  are  necessary  to  keep  a  person  firom  sinking.  In  this  position,  progression  can  be  accomplished 
by  extending  and  adducting  the  legs,  while  the  movement  is  accelerated  by  rudder-like  movements 
of  the  arms.  Swimming  belly  downward  is  more  difificult,  because  the  head,  being  held  above  the 
water,  makes  the  body  specifically  heavier.  The  forward  movement  and  the  act  of  supporting  the 
body  in  the  water  consist  of  three  acts: — First,  horizontal,  rudder-like  movements  of  the  extended 
arms  from  before  backward,  until  they  reach  the  horizontal  position  (forward  movement);  second, 
pressure  of  the  arms  downward,  with  subsequent  adduction  of  the  elbow -joint  to  the  body  (elevation 
of  the  body),  together  with  retraction  of  the  extended  legs;  third,  projection  of  the  arms,  now 
brought  together,  and  at  the  same  time  extension  and  adduction  of  the  legs  obliquely  backward  and 
downward,  thus  causing  elevation  of  the  body  as  well  as  a  forward  movement.  Too  rapid  move- 
ments cause  fatigue,  while  the  respirations  must  be  carefully  regulated.  Many  land  mammals, 
whose  body  is  specifically  lighter  than  water,  can  swim,  especially  with  the  aid  of  their  hind  limbs, 
while  at  the  same  time,  all  the  legs  being  directed  downward,  and  being  specifically  the  heaviest  part 
of  the  body,  keep  the  trunk  in  the  normal  position.  Fishes  chiefly  use  their  tail  fin  as  a  motor 
organ,  which  is  moved  by  powerful  lateral  muscles.  When  the  tail  is  suddenly  extended,  it  presses 
upon  the  water  and  displaces  it.  Some  fish,  as  the  salmon,  can  lift  their  body  out  of  the  water  by  a 
blow  of  their  tail  fin.  The  dorsal  and  anal  fins  enable  the  animal  to  preserve  the  erect  position. 
The  pectoral  and  abdominal  fins  corresponding  to  the  extremities  execute  slight  movements,  especially 
upward  and  downward,  which  are  greater  during  sleep.  The  swimming  bladder  is  the  homologue 
of  the  lung,  and  is  used  for  hydrostatic  purposes  in  some  fishes,  and  as  an  auxiliary  respiratory 
organ  in  others,  I?,  jr.,  the  dipnoi  (|  140).  It  is  absent  or  rudimentary  in  the  cyclostomata.  In 
swimming  birds,  the  body  is  specifically  very  much  lighter  than  the  water,  while  their  feathers  are 
lubricated  by  the  oily  secretion  of  the  coccygeal  glands  (\  291).     Their  feet  are  usually  webbed. 

Flight. — Bats  and  their  allies  are  the  only  flying  mammals.  The  bones  of  the  upper  limb  and 
phalanges  are  greatly  elongated,  and  between  these  and  the  elongated  hind  limb  (except  the  foot) 
there  is  stretched  a  thin  membrane.  The  membrane  is  moved  by  the  powerful  pectoral  muscles. 
The  flying  squirrel  has  only  a  duplicature  of  the  skin  stretched  between  the  large  bones  of  the 
extremities,  which  serves  as  a  parachute  when  the  animals  spring.  In  birds  the  body  is  specifically 
light;  numerous  air  sacs  in  the  chest  and  belly  communicate  with  the  lungs,  and  with  the  cavities  of 
most  of  the  bones  (^  140).  The  modified  upper  extremities  are  supported  by  the  coracoid  bone 
and  the  united  clavicles  or  furculum,  and  are  moved  by  the  powerful  pectoral  muscles  attached  to 
the  keeled  sternum.  Marey,  by  means  of  his  revolving  photographic  camera,  has  analyzed  all  the 
phases  of  flight  in  a  bird. 

[Werner  has  studied  the  movements  of  the  fingers  and  correlated  these  movements  with 
changes  in  the  nerve  centres  in  certain  diseased  conditions,  e.  »-.,  chorea.  An  india-rubber  tube  is 
attached  to  each  finger,  and  this  "  motor"  part  of  the  apparatus  is  connected  with  a  Marey's  tambour. 
The  several  finger  tubes  are  fixed  to  an  arrangement  not  unlike  a  cricketer's  glove,  so  that  voluntary 
or  involuntary  movements  of  the  fingers  can  be  registered  and  studied.] 

312.  VOICE  AND  SPEECH,  PHYSICAL  CONSIDERATIONS. 

— The  blast  of  expired  air — and  under  certain  circumstances,  the  inspiratory 
blast  also — is  employed  to  throw  the  tense  vocal  cords  into  a  state  of  regular  vibra- 
tion, whereby  a  sound  is  produced.     The  sound  so  produced  is  the  human  voice. 

The  true  vocal  cords  are  really  elastic  membranous  reeds.  If  a  blast  of  air  be  forcibly  driven 
upward  through  the  partially  closed  glottis,  the  vocal  cords  are  pushed  asunder,  as  the  elastic  tension 
of  the  air  overcomes  the  resistance  of  the  cords.  After  the  escape  of  air  fi-om  below,  the  cords 
rapidly  return  to  their  former  position,  and  are  again  pushed  asunder,  and  caused  to  vibrate. 

I.  Thus,  when  a  membrane  vibrates,  the  ah  must  be  alternately  condensed  and  rarefied.  The 
condensation  and  rarefaction  are  the  chief  cause  of  the  tone  or  note  (as  in  the  siren),  not  so  much 
the  membranes  themselves  (v.  Hebnholtz). 


560  ARRANGEMENT  OF  THE  LARYNX. 

2.  The  air  tube  or  "  porte  vente,"  conducting  the  air  to  the  memliranes  in  man  is  the  lower 
portion  of  the  larjnx,  the  trachea,  and  the  whole  hronchial  system  ;  the  bellows  are  represented  by 
the  chest  and  lungs,  wliich  are  forcibly  diminished  in  size  by  the  expiratory  muscles. 

3.  The  cavities  which  lie  above  the  membranes  constitute  "  resonators,"  and  consist  of  the  upper 
part  of  the  lary-nx,  ])harynx,  and  also  of  the  cavities  of  the  nose  and  mouth,  arrani^ed,  as  it  were,  in 
two  stories,  the  one  over  the  other,  which  can  be  closed  alternately. 

The  pitch  of  the  tone  produced  by  a  membranous  apparatus  depends  upon  the  following 
factors  : — 

(a)  On  tlie  leii:^th  of  the  elastic  menbranes  or  plates.  The  jiitch  i?  inversely  proportional  to  the 
length  of  the  elastic  membrane,  /.  <•..  the  sliorter  tlie  membrane  the  higher  the  pitch,  or  the  greater 
the  number  of  vibrations  per  second.  Hence,  the  pitcli  of  a  child's  vocal  cords  (shorter)  is  higher 
than  that  of  an  adult. 

(/^)  The  pitch  of  the  tone  is  directly  proportional  to  the  square  root  of  the  amount  of  the  elasticity 
of  the  elastic  membrane.  In  membranous  reeds,  and  also  with  silk,  it  is  directly  proportional  to  the 
square  root  of  the  extending  weight,  which  in  the  case  of  the  larynx  is  the  force  of  the  muscles 
rendering  the  cords  tense. 

(c)  The  tone  of  membranous  reeds  is  not  only  strengthened  by  a  more p07verful  blast,  as  the 
amplitude  of  the  vibrations  is  increased,  but  the  pitch  of  the  tone  may  also  be  raised  at  the  same 
time,  because,  owing  to  the  great  amplitude  of  the  vibration,  the  mean  tension  of  the  elastic  mem- 
brane is  increased. 

(a*)  The  su]:ira-laryngeal  cavities,  which  act  as  resonators,  are  also  inflated  when  the  larynx  is  in 
action,  so  that  the  tone  produced  by  these  cavities  is  added  to  and  blended  with  the  sound  of  the 
elastic  membranes,  whereby  certain  partial  tones  of  the  latter  are  strengthened  (^  415)-  '^^^  char- 
acteristic timbre  of  the  voice  largely  depends  upon  the  form  of  the  resonators. 

{A  When  vocalizing,  the  strongest  resonance  takes  place  in  the  air  tubes^  as  they  contain 
compressed  air.  It  causes  the  vocal  fremitus  which  is  audible  on  placing  the  ear  over  the  chest 
(§117.6). 

(/)  Narrowing  or  dilating  the  glottis  has  no  effect  on  the  {)itch  of  the  tone,  only  with  a  wide 
glottis  much  more  air  must  be  driven  through  it,  which,  of  course,  grea'ly  increases  the  work  of  the 
thorax. 

313.  ARRANGEMENT  OF  THE  LARYNX.— I.  Cartilages  and 
Ligaments. — The  fundamental  part  of  the  larynx  consists  of  the  cricoid  carti- 
lage, whose  small,  narrow  portion  is  directed  forward  and  the  broad  plate  back- 
ward. The  thyroid  cartilage  articulates  by  its  inferior  cornu  with  the  posterior 
lateral  portion  of  the  cricoid.  This  permits  of  the  thyroid  cartilage  rotating 
upon  a  horizontal  axis  directed  through  both  of  the  articular  surfaces,  so  that  the 
upper  margin  of  the  thyroid  passes  forward  and  downward,  while  the  joint  is  so 
constructed  as  to  permit  also  of  a  slight  upward,  downward,  forward,  and  back- 
ward movement  of  the  thyroid  upon  the  cricoid  cartilage.  The  triangular  aryte- 
noid cartilages  articulate  at  some  distance  from  the  middle  line,  with  oval, 
saddle-like,  articular  surfaces  placed  upon  the  upper  margin  of  the  plate  of  the 
cricoid  cartilage.  The  articular  surfaces  permit  two  kinds  of  movements  on  the 
part  of  the  arytenoid  cartilages ;  first,  rotation  on  their  base  around  their  verti- 
cal long  axis,  whereby  either  the  anterior  angle  or  processus  vocalis,  which  is 
directed  forward,  is  rotated  outward  ;  while  the  processus  muscularis,  which  is 
directed  outward  and  projects  over  the  margin  of  the  cricoid  cartilage,  is  rotated 
backward  and  inward,  or  conversely.  Further,  the  arytenoids  may  be  slightly 
displaced  upon  their  bases  either  outward  or  inward. 

The  true  vocal  cords,  or  thyro-arytenoid  ligaments,  are  in  man  about  15 
millimetres,  and  in  woman  11  millimetres  in  length,  and  consist  of  numerous 
elastic  fibres.  They  arise  close  to  each  other  from  near  the  middle  of  the  inner 
angle  of  the  thyroid  cartilage,  and  are  inserted,  each  into  the  anterior  angle  or 
processus  vocalis  of  the  arytenoid  cartilages.  The  ventricles  of  Morgagni  per- 
mit free  vibration  of  the  true  vocal  cords,  and  separate  them  from  the  upper  or  false 
cords,  which  consist  of  folds  of  mucous  membrane.  The  false  vocal  cords  are 
not  concerned  in  phonation,  but  the  secretion  of  their  numerous  mucous  glands 
moistens  the  true  vocal  cords. 

The  obliquely  directed  under-surface  of  the  vocal  cords  causes  the  cords  to  come  together  very 
easily  when  the  glottis  is  narrow  during  respiration  (e.g.,  in  sobbing),  while  the  closure  may  be 
made  more  secure  by  respiration.     The  opposite  is  the  condition  of  the  false  vocal  cords,  which, 


ACTION    OF   THE    LARYNGEAL    MUSCLES. 


561 


when  they  touch,  are  easily  separated  during  inspiration;  while  during  expiration,  owing  to  the 
dilatation  of  the  ventricles  of  Morgagni,  they  easily  come  together  and  close  (^Wyllie,  L.  Brunton 
and  Cask). 

II.  Action  of  the  Laryngeal  Muscles. — These  muscles  have  a  double  func- 
tion :  I.  One  connected  with  respiration,  in  as  far  as  the  glottis  is  widened  and 
narrowed  alternately  during  respiration  ;  further,  Avhen  the  glottis  is  firmly  closed 
by  these  muscles,  the  entrance  of  foreign  substances  into  the  larynx  is  prevented. 
The  glottis  is  closed  immediately  before  the  act  of  coughing  (§  120).  2.  The 
laryngeal  muscles  give  the  vocal  cords  the  proper  tension  and  other  conditions 
for  phonation. 

Fig.  353. 
Fig.  352. 


tmdC 


Larynx  from  the  front,  with  the  ligaments  and  the  inser- 
tions of  the  muscles.  O.h.,  Os  hyoideum ;  C.tk., 
Cart,  thyreoidea ;  Corp.  trit.,  Corpus  triticeum ; 
C.C.,  Cart,  cricoidea;  C.tr.,  Cart,  tracheales  ;  Lig: 
thyr.-hyoid.  med.,  Ligamentum  thyreo-hyoideum 
medium;  Lig.  th.-h.  lat.,  Ligam.  thyreo-hyoideum 
laterale ;  Lig.  eric.  thyr.  med.,  Ligam.  crico- 
thyreoideum  medium;  Lig.  eric. -track.,  Ligam. 
crico— tracheale  ;  M.  St.-h.,  Muse,  sterno-hyoideus; 
M.  th.-hyoid..  Muse,  thyreo-hyoideus ;  M.  st.-ih.. 
Muse,  sterno-thyreoideus  ;  M.  cr.-th..  Muse,  crico- 
thyreoideus. 


Larynx  from  behind  after  removal  of  the  mus- 
cies.  E,,  Epiglottis  cushion  (W.)  ;  L.  ar.- 
ep.,  Lig.  ary-epiglotticum ;  M.m.,  Mem- 
brana  mucosa;  C.W.,  Cart.  Wrisbergii; 
C.S.,  Cart.  Santorini;  C.  aryt.,  Cart. 
aryta^noidea;  Cc,  Cart,  cricoidea  ; />.?«., 
Processus  muscularis  of  Cart,  arj  taen  ;  L. 
er.-ar.,  Ligam.  crico-arytsean  ;  C.s.,  Cornu 
superius  ;  C.z".,  Cornu  inferius  Cart,  thyre- 
oidea. L.  ce.-cr.  p.  i.,  Lig.  kerato-cricoi- 
deum.  post,  inf.;  C./r.,  Cart,  tracheales; 
P.m.tr.,  Pars  membranacea  trachese. 


I.  The  glottis  is  dilated  by  the  action  of  the  posterior  crico-arytenoid 
muscles.  When  they  contract  they  pull  both  processus  musculares  of  the  arytenoid 
cartilages  backward,  downward,  and  toward  the  middle  line  (Fig.  356),  so  that  the 
processus  vocales  (I,  I)  must  go  apart  and  upward  (II,  II).  Thus,  between  the 
vocal  cords  (glottis  vocalis),  as  well  as  between  the  inner  margins  of  the  aryte- 
noid cartilages,  a  large  triangular  space  is  formed  (glottis  respiratoria),  and 
these  spaces  are  so  arranged  that  their  bases  come  together,  so  that  the  aperture 
between  the  cords  and  the  arytenoid  cartilages  has  a  rhomboidal  form.  Fig.  356 
shows  the  action  of  the  muscles.  The  vocal  cords,  represented  by  lines  converging 
in  front,  arise  from  the  anterior  angle  of  the  arytenoid  cartilages  (I,  I).  When 
36 


662 


ACTION    OF   THE    LARYNGEAL    MUSCLES. 


these  cartilages  are  rotated  into  the  position  (II,  II),  the  cords  take  the  position 
indicated  by  the  dotted  lines.  The  widening  of  the  respiratory  portion  of  the 
glottis  between  the  arytenoid  cartilages  is  also  indicated  in  the  diagram. 

Pathological. — When  these  muscles  are  paralyzed,  the  wideninjr  of  the  glottis  does  not  take 
place,  and  there  may  be  severe  dyspnoea  during  inspiration,  although  the  voice  is  unaffected  {A'iei^g/, 
L.  Weber^.  In  a  larynx  just  excised,  the  dilators  are  the  first  to  lose  their  excitability  (Semon  and 
Horsley). 

2.  The  entrance  to  the  glottis  is  constricted  by  the  arytenoid  muscle 
(transverse),  which  extends  transversely  between  both  outer  surfaces  of  the  aryte- 


Fir..  354. 


Fig.  355. 


Larynx  from  behind  with  its  muscles.  £., 
Epiglottis,  with  the  cushion  (W.);  C.W., 
Cart.  Wrisbergii  ;  C.S.,  Cart.  Santorini  ; 
C.c,  Cart,  cricoidea.  Cornu  sup. — Cornu 
inf.,  Cart,  thyreoideae;  Af.  ar.  tr..  Muse, 
arytanoideus  transversus ;  Ahn.  ar.  obi., 
Musculi  arytEenoidei  obliqui  ;  M.  cr.-aryt. 
post.,  Miisculus  crico-arytEenoideus  post- 
icus; /Virj  car^..  Pars  cartilaginea  ;  Pars 
memb..  Pars  membranacea  tracheae. 


Nerves  of  the  larynx.  O.h.  Os  hyoideum  ; 
C.th.,  Cart,  thyreoidea ;  Cc,  Cart,  cricoi- 
dea; 7r.,  Trachea  ;  M.  ih.-ar.,'M..  thyreo- 
arytaenoideus  yJ/,  cr.-ar.  p.,  M.  crico- 
arytaenoideus  posticus  ;  M.  cr.-ar.  I.,  M. 
crico-arytsen.  lateralis  ;  M.  cr.-th.,  M.  crico- 
thyreoideus  ;  N.lar.  si4p.  v.,  N.  laryngeus 
sup.  ;  R.I,,  Ramus  internus  ;  R.E.,  Ramus 
ext.  ;  N.  lar,  rec.  v.,  N.  laryngeus  recur- 
rens  ;  R.I.N.L.R.,  Ramus  int.;  R.E.N. L.R., 
Ramus  ext.  nervi  laryngei  recurrentis  vagi. 


noids  along  their  whole  length  (Fig.  357)-  On  the  posterior  surface  of  this  muscle 
is  placed  the  cross  bundles  (Fig.  354)  of  the  thyro-aryei^iglotticus  (or  arytsenoidei 
obliqui)  ;  they  act  like  the  foregoing.  The  action  of  these  muscles  is  indicated  in 
Fig.  357;  the  arrows  point  to  the  line  of  traction. 

Pathological. — Paraly.sis  of  this  muscle  enfeebles  the  voice  and  makes  it  hoarse,  as  much  air 
escapes  between  the  arytenoid  cartilages  during  phonation. 

3.  In  order  that  the  vocal  cords  be  approximated  to  each  other,  which 
occurs  during  phonation,  the  processus  vocales  of  the  arytenoid  cartilages  must  be 
closely  apposed,  whereby  they  must   be   rotated   inward  and   downward.     This 


ACTION    OF   THE    LARYNGEAL   MUSCLES. 


563 


result  is  brought  about  by  the  processus  musculares  being  moved  in  a  forward  and 
upward  direction  by  the  thyro-arytenoid  muscles.  These  muscles  are  applied 
to,  and  in  fact  are  imbedded   in,  the  substance  of  the  elastic  vocal  cords,  and 


Fig.  356. 


Fig.  357. 


Schematic  horizontal  section  of  the  larynx.  I,  Position 
of  the  horizontally  divided  arytenoid  cartilages  dur- 
ing respiration  ;  from  their  anterior  processes  run 
the  converging  vocal  cords.  The  arrows  show  the 
line  of  traction  of  the  posterior  crico-arytenoid 
muscles;  II,  II,  the  position  of  the  arytenoid  mus- 
cles as  a  result  of  this  action. 


Schematic  horizontal  section  of  the  larynx,  to  illustrate 
the  action  of  the  arytenoid  77iuscle.  I,  I,  position  of 
the  arytenoid  cartilages  during  quiet  respiration.  The 
arrows  indicate  the  direction  of  the  contraction  of 
the  muscle  ;  II,  II,  the  position  of  the  arytenoid  car- 
tilages after  the  arytenoideus  contracts. 


their  fibres  reach  to  the  external  surface  of  the  arytenoid  cartilages.     When  they 

contract,  they  rotate  these  cartilages  so  that  the  processus  vocales  must  rotate 

inward.     The  glottis  vocalis  is  thereby  narrowed  to  a  mere  slit  (Fig.  358),  while 

the  glottis  respiratoria  remains  as  a 

broad     triangular    opening.      The  Fig.  358. 

action  of  these  muscles  is  indicated 

in  Fig.  358. 

The  lateral  crico-arytenoid 
muscle  is  inserted  into  the  anterior 
margin  of  the  articular  surface  of 
the  arytenoid  cartilage ;  hence,  it 
can  only  pull  the  cartilage  forward ; 
but  some  have  supposed  that  it  can 
also  rotate  the  arytenoid  cartilage 
in  a  manner  similar  to  the  thyro- 
arytenoid (?),  with  this  difference, 
that  the  processus  vocales  do  not 
come  so  close  to  each  other. 

Pathological. — Paralysis  of  both  thyro- 
arytenoid muscles  causes  loss  of  voice. 

4.  The  vocal  cords  are  ren- 


Scheme  of  the  closure  of  the  glottis  by  the  thyro-arytenoid 
muscles.  II,  II,  position  of  the  arytenoid  cartilages  dur- 
ing quiet  respiration.  The  arrows  indicate  the  direction  of 
the  muscular  traction.  I,  I,  position  of  the  arytenoid  car- 
tilages after  the  muscles  contract. 


dered   tense    by   their  points   of 

attachment    being    removed    from 

each  other  by  the  action  of  muscles. 

The  chief  agents  in  this  action  are  the  crico-thyroid  muscles,  which  pull  the 

thyroid   cartilage    forward   and   downward.     At   the   same   time,    however,    the 


564  RELAXATION  OF  THE  VOCAL  CORDS. 

posterior  crico-arytenoids  must  pull  the  arytenoid  cartilages  slightly  backward, 
and  also  keep  them  fixed. 

The  geniohyoid  and  thyro-hyoid,  when  they  contract,  pull  the  thyroid  upward  and  forward 
toward  the  cliin,  and  also  tend  to  increase  the  tension  of  the  vocal  cords  [C.  Mayer,  Griitzner). 

Pathological. — Paralysis  of  the  crico  thyroid  causes  the  voice  to  l)ecome  harsh  and  deep,  owing 
to  the  voc.ll  cords  not  being  sutViciently  tense. 

Position  during  Phonation. — The  tension  of  the  vocal  cords  brought 
about  in  this  way  is  not  of  itself  sufficient  for  phonation.  The  triangular 
aperture  of  the  glottis  respiratoria  between  the  arytenoid  cartilages,  produced 
by  the  unaided  action  of  the  internal  thyro-arytenoid  muscles  (see  3)  must  be 
closed  by  the  action  of  the  transverse  and  oblique  arytenoid  muscles.  The 
vocal  cords  themselves  must  have  a  concave  margin,  which  is  obtained  through 
the  action  of  the  crico-thyroids  and  posterior  crico-arytenoids,  so  that  the  glottis 
vocalis  presents  the  appearance  of  a  myrtle  leaf  {Henle),  while  the  rima  glottidis 
has  the  form  of  a  linear  slit  (Fig.  362).  The  contraction  of  the  internal 
thyro-arytenoid  converts  the  concave  margin  of  the  vocal  cords  into  a  straight 
margin.  This  muscle  adjusts  the  delicate  variations  of  tension  of  the  vocal 
cords  themselves,  causing  more  especially  such  variations  as  are  necessary  for 
the  production  of  tones  of  slightly  different  pitch.  As  these  muscles  come  close 
to  the  margin  of  the  cords,  and  are  securely  woven,  as  it  were,  among  the 
elastic  fibres  of  which  the  cords  consist,  they  are  specially  adapted  for  the  above- 
mentioned  purpose.  When  the  muscles  contract,  they  give  the  necessary  resistance 
to  the  cords,  thus  favoring  their  vibration.  As  some  of  the  muscular  fibres  end 
in  the  elastic  fibres  of  the  cords,  these  fibres,  when  they  contract,  can  render  cer- 
tain parts  of  the  cords  more  tense  than  others,  and  thus  favor  the  modifications  in 
the  formation  of  the  tones.  The  coarser  variations  in  the  tension  of  the  vocal 
cords  are  produced  by  the  separation  of  the  thyroid  from  the  arytenoid  cartilages, 
while  ih^Jiner  variations  of  tension  are  produced  by  the  thyro-arytenoid  muscles. 
The  value  of  the  elastic  tissue  of  the  cords  does  not  depend  so  much  upon  its 
extensibility,  as  upon  its  property  of  shortening  without  forming  folds  and  creases. 

Pathological. — In  paralysis  of  these  muscles,  the  voice  can  only  be  produced  by  forcible  expira- 
tion, as  much  air  escapes  through  the  glottis  ;  the  tones  are  at  the  same  time  deep  and  impure.  Paraly- 
sis of  the  muscle  of  one  side  causes  flapping  of  the  vocal  cord  on  that  side  [Gerhardt). 

5.  The  relaxation  of  the  vocal  cords  occurs  spontaneously  when  the 
stretching  forces  cease  to  act ;  the  elasticity  of  the  displaced  thyroid  and  arytenoid 
cartilages  comes  into  play,  and  restores  them  to  their  original  position.  The  vocal 
cords  are  also  relaxed  by  the  action  of  the  thyro-arytenoid  and  lateral  crico- 
arytenoid muscles. 

It  is  evident,  from  the  above  statements,  that  tension  of  the  vocal  cords 
and  narrowing  of  the  glottis  are  necessary  for  phonation.  The  tension  is 
produced  by  the  crico-thyroids  and  posterior  crico-arytenoids  ;  the  narrowing  of 
the  glottis  respiratoria  by  the  arytenoids,  transverse  and  oblique,  the  glottis  vocalis 
being  narrowed  by  the  thyro-arytenoids  and  (?  lateral  crico-arytenoids),  the  former 
muscles  causing  the  cords  themselves  to  become  tense. 

Nerves  (§352,5). — The  crico-thyroid  is  supplied  by  the  superior  laryngeal 
branch  of  the  vagus,  which  at  the  same  time  is  the  sensory  nerve  of  the  mucous 
membrane  of  the  larynx.  All  the  other  intrinsic  muscles  of  the  larynx  are  supplied 
by  the  inferior  laryngeal. 

The  mucous  membrane  of  the  larynx  is  richly  supplied  with  elastic  fibres,  and  so  is  the  sub- 
mucosa.  The  sub-mucosa  is  more  lax  near  the  entrance  to  the  glottis  and  in  the  ventricles  of  Mor- 
gagni,  which  explains  the  enormous  swelling  that  sometimes  occurs  in  these  parts  in  oedema 
glottidis.  A  thin,  clear,  limiting  membrane  lies  under  the  epithelium.  The  epithelium  is  stratified, 
cylindrical,  and  ciliated  with  intervening  goblet  cells.  On  the  true  vocal  cords  and  the  anterior  sur- 
face of  the  epiglottis,  however,  this  is  replaced  by  stratified  squamous  epithelium,  which  covers  the 
small  papillse  of  the  mucous  membrane.     Numerous  branched  mucous  glands  occur  over  the  car- 


LARYNGOSCOPY. 


565 


tilages  of  Wrisberg,  the  cushion  of  the  epiglottis,  and  in  the  ventricles  of  Morgagni ;  in  other  situa- 
tions, as  on  the  posterior  surface  of  the  larynx,  the  glands  are  more  scattered.  The  blood  vessels 
form  a  dense  capillary  plexus  under  the  membrana  propria  of  the  mucous  membrane ;  under  this 
however,  there  are  other  two  strata  of  blood  vessels.  The  lymphatics  form  a  superficial,  narrow 
meshwork  under  the  blood  capillaries,  with  a  deeper,  coarser  plexus.  The  medullated  nerves 
have  ganglia  in  their  branches,  but  their  mode  of  termination  is  unknown.  [W.  Stirling  has 
described  a  rich  sub- epithelial  plexus  of  medullated  nerve  fibres  on  the  anterior  surface  of  the  epi- 
glottis, while  he  finds  that  there  are  ganglionic  cells  in  the  course  of  the  superior  laryngeal  nerve.] 

Cartilages. — The  thyroid,  cricoid,  and  nearly  the  whole  of  the  arytenoid  cartilages  consist  of 
hyaline  cartilage.  The  two  former  are  prone  to  ossify.  The  apex  and  processus  vocalis  of  the 
arytenoid  cartilages  consist  oi yellozv  fibro-cartilage,  and  so  do  all  the  other  cartilages  of  the  larynx. 

The  larynx  grows  until  about  the  sixth  year,  when  it  rests  for  a  time,  but  it  becomes  again  much 
larger  at  puberty  (?  434). 

Fig.  359. 


Vertical  section  through  the  head  and  neck,  to  the  first  dorsal  vertebra,  a,  position  of  the  laryngoscope  on 
observing  the  posterior  part  of  the  glottis,  arytenoid  cartilages,  and  upper  surface  of  the  posterior  wall  of  the 
larynx ;  b,  its  position  on  observing  the  anterior  angle  of  the  glottis.     Large,  a,  and  b,  small  laryngoscopic 


314.  LARYNGOSCOPY. — Historical. — After  Bozzini  (1807)  gave  the  first  impulse  toward 
the  investigation  of  the  internal  cavities  of  the  body,  by  illuminating  them  with  the  aid  of  mirrors, 
Babington  (1829)  actually  observed  the  glottis  in  this  way.  The  famous  singer,  Manuel  Garcia 
(1854),  made  investigations  both  on  himself  and  other  singers,  regarding  the  movements  of  the 
vocal  cords,  during  respiration  and  phonation.  The  examination  of  the  larynx  by  means  of  the 
laryngoscope  was  rendered  practicable  chiefly  by  Tiirck  (1857)  and  Czermak,  the  latter  observer 
being  the  first  to  use  the  light  of  a  lamp  for  the  illumination  of  the  larynx.  Rhinoscopy  was  actu- 
ally first  practiced  by  Baumes  (1838),  but  Czermak  was  the  first  person  who  investigated  this  subject 
systematically. 


56G 


lilK    LARYNGOSCOPE. 


The  Laryngoscope  consists  of  a  small  miiror  fixed  to  a  long  handle,  at  an  anyle  of  125°  to 
130°  (Fig.  359,  a,  6).  When  the  mouth  is  opened,  and  the  tongue  drawn  forward,  the  mirror  is 
introduced,  as  is  shown  in  Fig.  360.  The  position  of  the  mirror  must  be  varied,  according  to  the 
portion  of  the  larA'nx  we  wish  to  examine ;  in  some  cases,  the  soft  palate  has  to  be  raised  by  the  back 
of  the  mirror,  as  in  the  position  d.  A  picture  of  the  part  of  the  larynx  examined  is  formed  in  the 
small  mirror,  tiie  rays  of  light  passing  in  the  direction  indicated  l)y  the  dotted  lines  from  the  mirror; 
they  are  retlected  at  the  same  angle  through  the  mouth  into  the  eye  of  the  observer,  who  must  place 
himself  in  tlie  direction  of  the  reflected  rays. 

The  illumination  of  the  larynx  is  accomplished  either  by  means  of  direct  sunlight  or  by  light 
from  an  artificial  source,  e.^--.,  an   ordinary  lamp,  an  oxyhydrogen  limelight,  or  the  electric  light. 


Method  of  examining  the  larynx. 

The  beam  of  light  impinges  upon  a  concave  mirror  ol  15  to  20  centimetres  focus,  and  10  centimetres 
in  width,  and  from  its  surface  the  concentrated  beam  of  light  is  reflected  through  the  mouth  of  the 
patient,  and  directed  upon  the  small  mirror  held  in  the  back  part  of  the  throat.  The  beam  of  light 
is  reflected  at  the  same  angle  toward  the  larynx  by  the  small  throat  mirror,  so  that  the  larynx  is 
brightly  illuminated.  The  observer  has  now  to  direct  his  eye  in  the  same  direction  as  the  illumina- 
ting rays,  which  can  be  accomplished  by  having  a  hole  in  the  centre  of  the  concave  mirror,  through 
which  the  observer  looks.  I'ractically,  however,  this  is  unnecessary  ;  all  that  is  necessary  is  to  fix 
the  concave  mirror  to  the  forehead  by  means  of  a  broad  elastic  band,  so  that  the  observer,  by  looking 

just  under  the  margin  of  the  concave  mirror,  can  see  the 
picture  of  the  larynx  in  the  small  throat  mirror  (Fig.  360). 
In  order  to  examine  the  larj'nx,  place  the  patient  imme- 
diately in  front  of  you,  and  cause  him  to  open  his  mouth 
and  protrude  his  tongue.  A  lamp  is  placed  at  the  side  of 
the  head  of  the  patient,  and  light  from  this  source  is 
reflected  from  the  concave  miiTor  on  the  observer's  fore- 
head, and  concentrated  upon  the  larj'ngoscopic  mirror 
introduced  into  the  back  part  of  the  throat  of  the  patient 
(Fig.  360). 

Oertel  was  able  by  means  of  a  rapid  intermittent  illu- 
mination of  the  larynx  through  a  stroboscopic  disk,  to 
tudy  the  movements  of  the  vocal  cords  directly  with  the 
eye.  Simanowsky  put  a  photographic  camera  in  the  po- 
sition of  the  eye  and  photogi-aphed  the  movements  of  the 
vocal  cords  of  an  artificial  larynx.  [Brown  and  Behnke 
have  photographed  the  human  vocal  cords.] 

Laryngeal  Electrodes. —  v.  Ziemssen  introduces 
glot~tis;  A. jy., true  vocal  cords ;. 5. iJ/.,  sinus  long  narrow  electrodes  into  the  larynx,  to  stimulate  the 
Morgagni,z.z/..r.,  false  vocal  cords;  /'.,po-  muscles  and  Study  their  actions.  Rossbach  finds  that  the 
wy^^'^^il:^:^^^^^'    --cles  and  nerves  of  the  interior  of  the  larynx  may  be 

stimulated  by  stimulatmg  the  skin,  t.  e.,  percutaneously. 
Those  methods  are  used  both  for  physiological  and  therapeutical  purposes. 


The  larynx,  as  seen  with  the  laryngoscope, 
tongue;  A".,  epiglottis  ;    K,  valleculla 


LARYNGOSCOPIC    IMAGE. 


567 


Picture  of  the  Larynx. — Fig.  361  shows  the  following  structures:  L.,  the 
root  of  the  tongue,  with  the  ligamentum  glosso-epiglotticum  continued  from  its 
middle;  on  each  side  of  the  latter  are  V.  V.,  the  so-called  valleculce.  The  epi- 
glottis (-5'.)  appears  like  an  arched  upper  lip ;  under  it,  during  normal  respiration, 
are  the  lancet-shaped  glottis  {J?.)  and  on  each  side  of  it  the  true  vocal  cords  (Z.z;.). 
The  length  of  the  vocal  cord  in  a  child  is  6  to  8  mm.,  in  the  female  10  to  15  mm. 
when  they  are  relaxed,  and  15  to  20  mm.  when  tense.  In  man,  the  lengths  under 
the  same  conditions  are  15  to  20  mm.  and  20  to  25  mm.  The  breadth  varies 
from  2  to  5  mm.  On  the  external  side  of  each  vocal  cord  is  the  entrance  to  the 
sinus  of  Morgagni  {S.  M.'),  represented  as  a  dark  line.  Further  upward  and 
more  external  are  (Z.  v.  s.)  the  upper  or  false  vocal  cords.  [The  upper  or  false 
vocal  cords  are  red,  the  lower  or  true,  white.]     On  each  side  of  P.  are  {S.  S.), 


Fig.  364. 


Fig.  362. 


Position  of  the  vocal  cords  on  uttering 
a  high  note. 


Fig.  363. 


View  of  the  rings  and  bifurcation  of 
trachea. 


Position  of  the  laryngoscopic  mirror  in  rhinoscopy. 


the  apices  of  the  cartilages  of  Santorini,  placed  upon  the  apices  of  the  arytenoid 
cartilages,  while  immediately  behind  is  the  wall  of  the  pharynx,  P.  In  the 
aryteno-epiglottidean  fold  are  (VV.  W.)  the  cartilages  of  Wrisberg,  while  outside 
these  are  the  depressions  (  S.p.^  constituting  the  sinus  piriformes. 

During  normal  respiration,  the  glottis  has  the  form  of  a  lancet-shaped  slit 
between  the  bright,  yellowish-white,  vocal  cords  (Fig.  362).  If  a  deep  inspira- 
tion be  taken,  the  glottis  is  considerably  widened  (Fig.  363),  and  if  the  mirror 
be  favorably  adjusted  we  may  see  the  rings  of  the  trachea,  and  even  the  bifurcation 
of  the  trachea. 

If  a  high  note  be  uttered,  the  glottis  is  contracted  to  a  very  narrow  slit 
(Fig.  362). 


568 


CONDITIONS    INFLUENCING    THE    LARYNGEAL   SOUNDS. 


Composite  rhinoscopic  view.  S.n.,  Septum  nari- 
um  ;  C.i.,  Cm.,  C.s.,  lower,  middle,  and  upper 
turbinated  bones;  T,  Eustachian  tube;  II'., 
tubular  eminence  ;  R.,  groove  of  Rosenmiiller  ; 


Rhinoscopy. — Tf  a.  small  mirror,  fixed  to  a  handle  at   an  angle  of  lOO°  to   llO°,  be  introduced 

into  the  jiharynx,  as  shown  in  V\g.  364,  and  if  the  mir- 
Fig.  365.  ror  be    directed    iifnoard,  certain    structures    are  with 

^^ ^.^;^---  -  _^^ -_  difficulty  rendered  visible  (Fig.  365).     In  the  middle 

is  the  septum  narium  {S.  «.),  and  on  each  side  of  it 
the  long  oval  large  jiosterior  nares  (C^.),  below  this  the 
soft />a/ate  {P. >n.),  \s\\.h  the  pendant  uvula  {U.).  In 
the  posterior  nares  are  the  posterior  extremities  of  the 
lower  (6".?.),  middle  {C.»i.),  and  uppev /ur/>iuiUeJ iones 
(C.S.).  At  the  upper  part,  a  jwrtion  of  the  roof  of  the 
l^harynx  (O.J?.)  is  seen,  with  the  arched  masses  of 
adenoid  tissue  lying  between  the  openings  of  the  Eusta- 
chian tubes  (  T.  7\),  and  called  by  Luschka  the///«^'«- 
geal  tonsils.  External  to  the  openings  of  the  Eustachian 
tube  is  the  tubular  eminence  {IV.),  and  outside  this  is 
the  gi-oove  of  Rosenmiiller  {^. )• 

Experiments  on  the  Larynx. — Ferrein  (g  741) 
and  Job.  Miiller  made  experiments  upon  the  excised 
larynx.  A  tracheal  tube  was  tied  into  the  excised 
human  larynx,  and  air  was  blown  through  it,  the  pres- 
sure being  measured  by  means  of  a  mercurial  mano- 
meter, while  various  arrangements  were  adopted  for 
fvuTa' ^"'^^  ^^''^'^  ■  '^•■^•''■°"''°'"P^">'"''-  ^■'    putting  the  vocal  cords  on  the  stretch  and  for  opening 

or  closing  the  glottis. 

315.  CONDITIONS  INFLUENCING  THE  LARYNGEAL 
SOUNDS. — The  pitch  of  the  note  emitted  by  the  larynx  depends  upon  — 

1.  The  Tension  of  the  Vocal  Cords,  /.  e.,  upon  the  degree  of  contraction 
of  the  crico-thyroid  and  posterior  crico-arytenoid  muscles,  and  also  of  the  internal 
thyro-arytenoids  (§  313,  II,  4). 

2.  The  Length  of  the  Vocal  Cords. — (a)  Children  and  females  with  short 
vocal  cords  produce  high  notes.  (/)  If  the  arytenoid  cartilages  are  pressed 
together  by  the  action  of  the  arytenoid  muscles  (transverse  and  oblique),  so  that 
the  vocal  cords  alone  can  vibrate,  while  their  intercartilaginous  portions  lying 
between  the  processus  vocales  do  not,  the  tone  thereby  produced  is  higher 
(Gara'a).  In  the  production  of  low  notes,  the  vocal  cords,  as  well  as  the  margins 
of  the  arytenoid  cartilages,  vibrate.  At  the  same  time  the  space  above  the  entrance 
to  the  glottis  is  enlarged  and  the  larynx  becomes  more  prominent,  (c)  Every 
individual  has  a  certain  medium  pitch  of  his  voice,  which  corresponds  to  the 
smallest  possible  tension  of  the  intrinsic  muscles  of  the  larynx. 

3.  The  Strength  of  the  Blast. — That  the  strength  of  the  blast  from  below 
raises  the  ])itch  of  the  tones  of  the  human  larynx  is  shown  by  the  fact,  that  tones 
of  the  highest  pitch  can  only  be  uttered  by  powerful  expiratory  efforts.  With 
tones  of  medium  pitch,  the  ])ressure  of  the  air  in  the  trachea  is  160  mm.,  with  /lig/i 
])itch  200  mm.,  and  with  very  high  notes  945  mm.,  and  in  whispering  t^o  mm.,  of 
water  {Cagfiiard-Latour).  These  results  were  obtained  in  a  case  of  tracheal 
fistula. 

Accessory  Phenomena. — The  following  as  yet  but  partially  exjslained  phenomena  are  observed 
in  connection  with  the  jjroduction  of  high  notes :  (a)  As  the  pitch  of  the  note  rises,  the  larynx  is 
elevated,  partly  because  the  muscles  raising  it  are  active,  partly  because  the  increased  intra-tracheal 
pressure  so  lengthens  the  trachea,  that  the  larynx  is  thereby  raised ;  the  uvula  is  raised  more  and 
more  (Labus).  {b)  The  upper  vocal  cords  approximate  to  each  other  more  and  more,  without,  how- 
ever, coming  into  contact,  or  participating  in  the  vibrations,  (c)  The  epiglottis  inclines  more  and 
more  backward  over  the  glottis. 

4.  The  falsetto  voice  with  its  soft  timbre  and  the  absence  of  resonance  or 
pectoral  fremitus  in  the  air  tubes  is  particularly  interesting.  Oertel  observed  that, 
during  the  falsetto  voice,  the  vocal  cords  vibrated  so  as  to  form  nodes  across  them, 
but  sometimes  there  was  only  one  node,  so  that  the  free  margin  of  the  cord  and 
the  basal  margin  vibrated,  being  separated  from  each  other  by  a  nodal  line  (par- 


RANGE    OF   THE    VOICE. 


569 


allel  to  the  margins  of  the  vocal  cord).  During  a  high  falsetto  note,  there  may  be 
three  such  nodal  lines  parallel  to  each  other.  The  nodal  lines  are  produced 
probably  by  a  partial  contraction  of  the  fibres  of  the  thyro-arytenoid  muscle 
(p.  563),  while  at  the  same  time  the  vocal  cords  must  be  reduced  to  as  thin  plates 
as  possible  by  the  action  of  the  crico-thyroid,  posterior  arytenoid,  thyro-  and 
genio-hyoid  muscles  {Oeriel).  The  form  of  the  glottis  is  elliptical,  while  with 
the  chest  voice  the  vocal  cords  are  limited  by  straight  surfaces ;  the  air  also  passes 
more  freely  through  the  larynx. 

Oertel  also  found  that  during  the  falsetto  voice  the  epiglottis  is  erect.  The  apices  of  the  aryte- 
noid cartilages  are  slightly  inclined  backward,  the  whole  larynx  is  larger  from  before  backward,  and 
narrower  from  side  to  side,  the  aryepiglottidean  folds  are  tense  with  sharp  margins,  and  the  entrance 
to  the  ventricles  of  Morgagni  is  narrowed.  The  vocal  cords  are  narrower,  the  processus  vocales 
toach  each  other.  The  rotation  of  the  arytenoid  cartilages  necessary  for  this  is  brought  about  by  the 
action  of  the  crico- arytenoid  alone,  while  the  thyro-aiytenoid  is  to  be  regarded  only  as  an  accessory 
aid.  The  pitch  of  the  note  is  increased  solely  by  increased  tension  of  the  vocal  cords.  In  addition, 
there  are  a  number  of  transverse  and  longitudinal  partial  vibrations.  During  the  chest  voice,  a 
smaller  part  of  the  margin  vibrates  than  in  the  falsetto  voice,  so  that  in  the  production  of  the  latter 
we  are  conscious  of  less  muscular  exertion  in  the  larynx.  The  uvula  is  raised  to  the  horizontal 
position. 

Production  of  Voice. — In  order  that  voice  be  produced,  the  following  condi- 
tions are  necessary:  (i)  The  necessary  amount  of  air  is  collected  in  the  chest ; 
(2)  the  larynx  and  its  parts  are  fixed  in  the  proper  position  \  (3)  air  is  then  forced 
by  an  expiratory  effort  either  through  the  linear  chink  of  the  clossed  glottis,  so 
that  the  latter  is  forced  open,  or  at  first  some  air  is  allowed  to  pass  through  the 
glottis  without  producing  a  sound,  but  as  the  blast  of  air  is  strengthened  the  vocal 
cords  are  thrown  into  vibration. 

316.  RANGE  OF  THE  VOICE.— The  range  of  the  human  voice  for 
chest  notes  is  given  in  the  following  scheme  :  — 


256 


Soprano. 


171 


Alto. 


684 


EFGAB        cdefgab        c' d' e' f^  s:'a^b/ 


1024 


:tz= 


c//(i//e//f  ^'g^/a^'  \i"'ii'" 


80 


Bass. 


342 


128 


Tenor. 


512 


The  accompanying  figures  indicate  the  number  of  vibrations  per  second  in  the  corresponding  tone. 
It  is  evident  that  from  c'  to  f  is  common  to  all  voices,  nevertheless,  they  have  a  different  timbre. 
The  lowest  note  or  tone,  which,  however,  is  only  occasionally  sung  by  bass  singers,  is  the  contra-F, 
with  42  vibrations — the  highest  note  of  the  soprano  voice  is  a'" ,  with  1708  vibrations. 

Timbre. — The  voice  of  every  individual  has  a  peculiar  quality,  clang,  or  timbre, 
which  depends  upon  the  shape  of  all  the  cavities  connected  with  the  larynx.  In 
the  production  of  nasal  tones,  the  air  in  the  nose  is  caused  to  vibrate  strongly,  so 
that  the  entrance  to  the  nares  must  necessarily  be  open. 

317.  SPEECH — THE  VOWELS. — The  motor  processes  connected  with 
the  production  of  speech  occur  in  the  resonating  cavities,  the  pharynx, 
mouth,  and  nose,  and  are  directed  toward  the  production  of  musical  tones  and 
noises. 


570  THE    FORMATION    OF   VOWELS. 

Whispering  and  Audible  Speech. — When  sounds  or  noises  are  produced 
in  the  resonating  chambers,  the  larynx  being  passive,  the  vox  clandestina,  or 
whispering  is  produced  ;  when  the  vocal  cords,  however,  vibrate  at  the  same 
time,  "  audible  speech  "  is  produced.  [Whispering,  therefore,  is  si)eech  with- 
out voice.]  Whispering  may  be  fairly  loud,  but  it  recjuires  great  exertion,  /.  e.,  a 
great  expiratory  blast  for  its  production  ;  hence  it  is  very  fatiguing.  It  may  be 
performed  both  with  inspiration  and  expiration,  while  audible  speech  is  but  tem- 
porary and  indistinct,  if  it  is  produced  during  inspiration.  Whispering  is  caused 
by  the  sound  produced  by  the  air  passing  over  the  obtuse  margins  of  the  cords. 
During  the  production  of  audible  soimds,  however,  the  sharp  margins  of  the  vocal 
cords  are  directed  toward  the  air  by  the  position  of  the  processus  vocales. 

During  speech  the  soft  palate  is  in  action ;  at  each  word  it  is  raised,  while  at  the  same  time, 
Passavant's  transverse  band  is  formed  in  the  pharynx  (§  156).  The  soft  palate  is  raised  highest 
when  u  and  i  are  sounded,  then  with  0  and  e,  and  least  with  a.  When  sounding  m  and  n  it  does 
not  move;  it  is  high  (like  n)  during  the  utterance  of  the  explosives.  With  1,  s,  and  especially  with 
the  guttural  r,  it  exhibits  a  trembling  movement  [Gentzen,  Falkson). 

Speech  is  composed  of  vowels  and  consonants. 

A.  Vowels  (analysis  and  artificial  formation,  §  415). — A.  During  whisper- 
ing, a  vowel  is  the  musical  tone  produced,  either  during  expiration  or  inspiration, 
by  the  inflated  characteristic  form  of  the  mouth,  which  not  only  has  a  definite 
pitch,  but  also  a  particular  and  characteristic  timbre.  The  characteristic  form  of 
the  mouth  may  be  called  ^^  vowel  cavity. '' 

I.  The  pitch  of  the  vowels  may  be  estimated  musically.  It  is  remarkable  that  the  funda- 
mental tone  of  the  "  vowel  cavity"  is  nearly  constant  at  different  ages  and  in  the  sexes.  The 
different  capacities  of  the  mouth  can  be  compensated  for  by  different  sizes  of  the  oral  aperture. 
The  pitch  of  the  vowel  cavity  may  be  estimated  by  placing  a  number  of  vibrating  tuning  forks  of 
different  pitch  in  front  of  the  mouth,  and  testing  them  until  we  find  the  one  which  corresponds 
with  the  fundamental  tone  of  the  vowel  cavity.  This  is  known  by  the  fact  that  the  tone  of  the 
tuning-fork  is  intensified  by  the  resonance  of  the  air  in  the  mouth,  or  the  vibrations  may  be  trans- 
ferred to  a  vibrating  membrane  and  recorded  on  a  smoked  surface,  as  in  the  phonautograph  of 
Bonders. 

According  to  Konig,  the  fundamental  tones  of  the  vowel  cavity  are  for 

U  =  b,  O  =  b',  A  =  b",  E  =  \J",  I  =  b"". 

If  the  vowels  be  whispered  in  this  series,  we  find  at  once  that  their  pitch  rises. 
The  fundamental  tone  in  the  production  of  a  vowel  may  vary  within  certain  limits. 
This  may  be  shown  by  giving  the  mouth  the  characteristic  position  and  then  per- 
cussing the  cheeks  {Aiierbach)  ;  the  sound  emitted  is  that  of  the  vowel,  wliose 
pitch  will  vary  according  to  the  position  of  the  mouth. 

When  sounding  A,  the  mouth  has  the  form  of  a  funnel  widening  in  front  (Fig.  366,  A).  The 
tongue  lies  in  the  floor  of  the  mouth,  and  the  lips  are  wide  open.  The  soft  palate  is  moderately 
raised  [Czermak).  It  is  more  elevated  successively  with  O,  E,  U,  I.  The  hyoid  bone  appears  as 
if  at  rest,  but  the  larynx  is  slightly  raised.     It  is  higher  than  with  U,  but  lower  than  with  I. 

If  we  sound  A  to  I,  the  larynx  and  the  hyoid  bone  retain  their  relative  position,  but  both  are 
raised.  In  passing  from  A  to  U,  the  larynx  is  depressed  as  far  as  possible.  The  hyoid  bone  passes 
slightly  forward  {Briic/ie).  When  sounding  A,  the  space  between  the  larynx,  posterior  wall  of  the 
pharynx,  soft  palate,  and  the  root  of  the  tongue,  is  only  moderately  wide ;  it  becomes  wider  with  E, 
and  especially  with  I  (I'ur/cinje),  but  it  is  smallest  with  U. 

When  sounding  U  (Fig.  366),  the  form  of  the  cavity  of  the  mouth  is  like  that  of  a  capacious 
flask  with  a  short,  narrow  neck.  The  whole  resonance  apparatus  is  then  longest.  The  lips  are 
protruded  as  far  as  possible,  are  arranged  in  folds  and  closed,  leaving  only  a  small  opening.  The 
larynx  is  depressed  as  far  as  possible,  while  the  root  of  the  tongue  is  approximated  to  the  posterior 
margin  of  the  palatine  arch. 

When  sounding  O,  the  mouth,  as  in  U,  is  like  a  wide-bellied  flask  with  a  short  neck,  but  the 
latter  is  shorter  and  wider  as  the  lips  are  nearer  to  the  teeth.  The  larynx  is  slightly  higher  than 
with  U,  while  the  resonance  chambers  also  are  shorter  (Fig.  366). 

When  sounding  I,  the  cavity  of  the  mouth,  at  the  posterior  part,  is  in  the  form  of  a  small-bellied 
flask  with  a  long  narrow  neck,  of  which  the  belly  has  the  fundamental  tone,  f,  the  neck  that  of  d^''. 
The  resonating  chambers  are  shortest,  as  the  larynx  is  raised  as  much  as  possible,  while  the  mouth, 


DIPHTHONGS    AND    NASAL   TIMBRE    OF   VOWELS. 


571 


owing  to  the  retraction  of  the  lips,  is  bounded  in  front  by  the  teeth.  The  cavity  between  the  hard 
palate  and  the  back  of  the  tongue  is  exceedingly  narrow,  there  being  only  a  median  narrow  slit. 
Hence,  the  air  can  only  enter  with  a  clear  piping  noise,  which  sets  even  the  vertex  of  the  skull  in 
vibration,  and  when  the  ears  are  stopped  the  sounds  seem  very  shrill.  When  the  larynx  is  depressed 
and  the  lips  protruded,  as  for  sounding  U,  I  cannot  be  sounded. 

When  sounding  E,  which  stands  next  to  I,  the  cavity  has  also  the  form  of  a  flask  with  a  small 
belly  (fundamental  tone,  F),  and  with  a  long,  narrow  neck  (fundamental  tone,  \>'"').  The  neck  is 
wider,  so  that  it  does  not  give  rise  to  a  piping  noise.  The  larynx  is  slightly  lower  than  for  I,  but 
not  so  high  as  for  A. 

Fundamentally,  there  are  only  three pri77tary  vowels — I,  A,  U,  the  others  and  the  so-called  diph- 
thongs standing  between  them  \Brucke). 

Diphthongs  occur  when,  during  vocalization,  we  pass  from  the  position  of  one 
vowel  into  that  of  another.  Distinct  diphthongs  are  sounded  only  on  passing 
from  one  vowel  with  the  mouth  wide  open  to  one  with  the  mouth  narrow ;  during 
the  converse  process,  the  vowels  appear  to  our  ear  to  be  separate  (^Brilcke). 

II.  Timbre  or  Clang  Tint. — Besides  its  pitch,  every  vowel  has  a  special 
timbre,  quality,  or  clang  tint. 

The  vocal  timbre  of  U  (whispering)  has,  in  addition  to  its  fundamental  tone,  b,  a  deep  piping 
timbre.  The  timbre  depends  upon  the  number  and  pitch  of  the  partials  or  overtones  of  the  vowel 
sound  {\  415). 

Fig.  ^66. 


Section  of  the  parts  concerned  in  phonation.     Z,  tongue ;  /,  soft  palate;  .f,  epiglottis  ;  ^.glottis;   ,4,  hyoid  bone;   i, 
thyroid,  2,  3,  cricoid,  4,  arytenoid  cartilage. 


Nasal  Timbre. — The  timbre  is  modified  in  a  special  manner  when  the  vowels  are  spoken  with  a 
"  nasal"  twang,  which  is  largely  the  case  in  the  French  language.  The  nasal  timbre  is  produced 
by  the  soft  palate  not  cutting  off  the  nasal  cavity  completely,  which  happens  every  time  z.  pure  vowel 
is  sounded,  so  that  the  air  in  the  nasal  cavity  is  thrown  into  sympathetic  vibration.  When  a  vowel 
is  spoken  with  a  nasal  timbre,  air  passes  out  of  the  nose  and  mouth  simultaneously,  while  with  a 
pure  vowel  sound,  it  passes  out  only  through  the  mouth. 

When  sounding  a  pure  vowel  (non-nasal),  the  shutting  off  of  the  nasal  cavity  from  the  mouth  is 
so  complete,  that  it  requires  an  artificial  pressure  of  30  to  100  mm.  of  mercury  to  overcome  it 
\^Hartman7i). 

The  vowels,  a,  a  (se),  6  (ce),  o,  e,  are  used  with  a  nasal  timbre — a  nasal  i  does  not  occur  in  any 
language.  Certainly  it  is  very  difficult  to  sound  it  thus,  because  when  sounding  i,  the  mouth  is  so 
narrow  that  when  the  passage  to  the  nose  is  open,  the  air  passes  almost  completely  through  the 
latter,  while  the  small  amount  passing  through  the  mouth  scarcely  suffices  to  produce  a  sound. 

In  sounding  vowels,  we  must  observe  if  they  are  sounded  through  a  previously  closed  glottis,  as 
is  done  in  the  German  language  in  all  words  beginning  with  a  vowel  (spiritus  lenis).  The  glottis, 
however,  may  be  previously  opened  with  a  preliminary  breath,  followed  by  the  vowel  sound;  we 
obtain  the  aspirate  vowel  (spiritus  asper  of  the  Greeks). 

B.  If  the  vowels  are  sounded  in  an  audible  tone,  /.  «?.,  along  with  the  sound 
from  the  larynx,  the  fundamental  tone  of  the  vocal  cavity  strengthens  in  a  charac- 
teristic manner  the  corresponding  partial  tones  present  in  the  laryngeal  sound 
{Wheatstone,  v.  Helmholtz). 


572  CLASSIFICATION    OF   CONSONANTS. 

318.  CONSONANTS.— The  consonants  are  noises  which  are  produced  at 
certain  parts  of  the  resonance  chamber.  [As  their  name  denotes,  they  can  only 
be  sounded  in  conjunction  with  a  vowel.] 

ClassiBcation. — The  most  obvious  classification  is  according  to  (I)  Their  acoustic  properties,  so 
that  they  are  divided  into  (i)  liquid  consonants,  i.  e.,  such  as  are  appreciable  without  a  vowel  (m, 
n,  1,  r,  s) ;  (2)  viutes,  including  all  the  others,  which  cannot  be  distinctly  heard  without  an  accom. 
panying  vowel.  (II)  According  to  their  mechanistn  of  fonnation,  as  well  as  the  type  of  the  organ 
of  speech,  by  whicli  ihey  are  produced.     They  are  divided  into — 

1.  Explosives. — Their  enunciation  is  accompanied  by  a  kind  of  bursting  open  of  an  obstacle, 
or  an  explosion,  occasioned  by  the  confined  and  compressed  air  which  causes  a  stronger  or  weaker 
noise  ;  or,  conversely,  the  current  of  air  is  suddenly  interrupted,  while,  at  the  same  lime,  the  nasal 
cavities  are  cut  off  by  the  soft  palate. 

2.  Aspirates,  in  which  one  part  of  the  canal  is  constricted  or  stopped,  so  that  the  air  rushes  out 
through  the  constriction,  causing  a  faint  whistling  noise.  (The  nasal  cavity  is  cut  off.)  In  uttering 
T,  which  is  closely  related  to  the  aspirates,  but  differs  from  them  in  that  the  narrow  passage  for  the 
rush  of  air  is  not  in  the  middle,  but  at  both  sides  of  the  middle  of  the  closed  part.  (The  nasal 
cavity  is  shut  off.) 

3.  Vibratives,  which  are  produced  by  air  being  forced  through  a  narrow  portion  of  the  canal,  so 
that  the  margins  of  the  narrow  tube  are  set  in  vibration.     (The  nasal  cavity  is  shut  off.) 

4.  Resonants  (also  called  nasals  or  semi-vowels).  The  nasal  cavity  is  completely  free,  while  the 
vocal  canal  is  completely  closed  in  the  front  part  of  the  oral  channel.  According  to  the  position  of 
the  obstruction  in  the  oral  cavity,  the  air  in  a  larger  or  smaller  portion  of  the  mouth  is  thrown  into 
sympathetic  vibration. 

We  may  also  classify  them  according  to  the  position  in  7vhich  ihey  are  produced 
— the  "  articulation  positions  "  of  Briicke.     These  are  : — 

A.  Between  both  lips  ;  B,  between  the  tongue  and  the  hard  palate  ;  C,  between 
the  tongue  and  the  soft  palate ;  D,  between  the  true  vocal  cords. 

A.    Consonants  of  the  First  Articulation  Position. 

1.  Explosive  Labials. — b,  the  voice  is  sounded  before  the  slight  explosion  occurs;  p,  the  voice 
is  sounded  after  the  much  stronger  explosion  has  taken  place  {A'empeleft).  [The  former  is  spoken 
of  as  "  voiced  "  and  the  latter  as  "  breathed."] 

2.  Aspirate  Labials. — f,  between  the  upper  incisor  teeth  and  the  lower  lip  (labio-dental).  It  is 
absent  in  all  true  .Slavic  words  {Pttrkine) ;  v,  between  both  lips  (labial) ;  w  is  formed  when  the 
mouth  is  in  the  position  for  f,  but  instead  of  merely  forcing  in  the  air,  the  voice  is  sounded  at  the 
same  time.  Really  there  are  two  different  w — one  corresponding  to  tlie  labial  f,  as  in  wiirde,  and 
the  labiodental,  e.  g.,  quelle  (Briicke). 

3.  Vibrative  Labials. — The  burring  sound,  emitted  by  grooms,  but  not  used  in  civilized 
language. 

4.  Resonant  Labials. — m  is  formed  essentially  by  sounding  the  voice  whereby  the  air,  in  the 
mouth  and  nose,  is  thrown  into  sympathetic  vibration  ["  voiced  "]. 

jB.    Consonants  of  the  Second  Articulation  Position. 

1.  The  explosives,  when  enunciated  sharply  and  witliout  the  voice,  are  T  hard  (also  dt  and 
th);  when  they  are' feeble  and  produced  along  with  simultaneous  laryngeal  sounds  (voice),  we  have 
D  soft. 

2.  The  aspirates  embrace  S,  including  s  sharp,  written  s  s  or  s  z,  which  is  produced  without 
any  audible  laryngeal  vibration  ;  or  soft,  which  requires  the  voice.  Then,  also,  there  are  modifica- 
tions according  to  the  position  where  the  noises  are  produced.  The  shaip  aspirates  include  Sch, 
and  the  hard  English  Th  ;  to  the  soft  belong  the  French  J  soft,  and  the  English  Th  soft.  L,  which 
occurs  in  many  modifications,  appears  here,  e.g.,  the  L  soft  of  the  French.  L  may  be  sounded  soft 
with  the  voice,  or  sharp  without  it. 

3.  The  vibrative,  or  R,  which  is  generally  voiced,  but  it  can  be  formed  without  the  larynx. 
The  resonants  are  N  sounds,  which  also  occur  in  several  modifications. 

C.    Consonants  of  the  Third  Articulation  Position. 

1.  The  explosives  are  the  K  sounds,  which  are  hard  and  breathed  and  not  voiced;  G  sounds, 
which  are  voiced. 

2.  The  aspirates,  when  hard  and  breathed  but  not  voiced,  the  Ch,  and  when  sounded  softly  and 
not  voiced,  J  is  formed. 

3.  The  vibrative  is  the  palatal  R,  which  is  produced  by  vibration  of  the  uvula  [Briicke). 

4.  The  resonant  is  the  palatal  N. 


PATHOLOGICAL   VARIATIONS    OF   VOICE    AND    SPEECH.  573 

D.    Consonants  of  the  Fourth  Articulation  Position. 
t.  An  explosive  sound  does  not  occur  when  the  glottis  is  forced  open,  if  a  vowel  is  loudly- 
sounded  with  the  glottis  previously  closed.     If  this  occurs  during  whispering,  a  feeble  short  noise, 
due  to  the  sudden  opening  of  the  glottis,  may  be  heard. 

2.  The  aspirates  of  the  glottis  are  the  H  sounds,  which  are  produced  when  the  glottis  is  moder- 
ately wide. 

3.  A  glottis  vibrative  occurs  in  the  so-called  laryngeal  R  of  lower  Saxon  {^Brilcke). 

4.  A  laryngeal  resonant  cannot  exist. 

The  combination  of  different  consonants  is  accomplished  by  the  successive  movements  necessary 
for  each  being  rapidly  executed.  Compound  consonants,  however,  are  such  as  are  formed  when  the 
oral  parts  are  adjusted  simultaneously  for  two  different  consonants,  so  that  a  mixed  sound  is  formed 
from  two.     Examples:  Sch — tsch,  tz,  ts — Ps  (1/') — Ks  (XS). 

319.  PATHOLOGICAL  VARIATIONS  OF  VOICE  AND  SPEECH.— Aphonia.— 

Paralysis  of  the  motor  nerves  (vagus)  of  the  larynx  by  injury,  or  the  pressure  of  tumors,  causes 
aphonia  or  loss  of  voice  [Galen).  In  aneurism  of  the  aortic  arch,  the  left  recurrent  nerve  may 
be  paralyzed  from  pressure.  The  laryngeal  nerves  may  be  temporarily  paralyzed  by  rheumatism, 
over-exertion,  and  hysteria,  or  by  serous  effusions  into  the  laryngeal  muscles.  If  the  tensors  are 
paralyzed,  monotonia  is  the  chief  result :  the  disturbances  of  respiration  in  paralysis  of  the  larynx 
are  important.  As  long  as  the  respiration  is  tranquil,  there  may  be  no  disturbance,  but  as  soon  as 
increased  respiration  occurs,  great  dyspnoea  sets  in,  owing  to  the  inability  of  the  glottis  to  dilate. 

If  only  one  vocal  cord  is  paralyzed,  the  voice  becomes  impure  and  falsetto-like,  while  we  may 
feel  from  without  that  there  is  less  vibration  on  the  paralyzed  side  [Gerhardt)^  Sometimes  the 
vocal  cords  are  only  so  far  paralyzed  that  they  do  not  move  during  phonation,  but  do  so  during  forced 
respiration  and  during  coughing  (phonetic  paralysis). 

Diphthongia. — Incomplete  unilateral  paralysis  of  the  recurrent  nerve  is  sometimes  followed  by 
a  double  tone,  owing  to  the  unequal  tension  of  the  two  vocal  cords.  According  to  Tiirck  and 
Schnitzler,  however,  the  double  tone  occurs  when  the  two  vocal  cords  touch  at  some  part  of  their 
course  [e.g.,  from  the  presence  of  a  tumor.  Fig.  367),  so  that  the  glottis  is  divided  into  two  unequal 
portions,  each  of  which  produces  its  own  sound. 

Hoarseness  is  caused  by  mucus  upon  the  vocal  cords,  by  roughness,  swelling,  or  laxness  of  the 
cords.  If,  while  speaking,  the  cords  are  approximated,  and  suddenly  touch  each  other,  the  "speech 
is  broken,"  owing  to  the  formation  of  nodal  points  (^  352).  Disease  of  the  pharynx,  naso-pharyngeal 
cavity,  and  uvula  may  produce  a  change  in  the  voice  reflexly. 

Paralysis  of  the  soft  palate  (as  well  as  congenital  perforation  or  cleft  palate)  causes  a  nasal 
timbre  of  all  vowels;  the  former  renders  difficult  the  normal  formation  of  consonants  of  the  third 
articulation  position ;  resonance  is  imperfect,  while  the  explosives  are  weak,  owing  to  the  escape  of 
the  air  through  the  nose. 

Paralysis  of  the  tongue  weakens  I;  E  and  A  (^)  are  less 
easily  pronounced,  while  the  formation  of  consonants  of  the 
second  and  third  articulation  position  is  affected.  The  term 
aphthongia  is  applied  to  a  condition  in  which  every  attempt  to 
speak  is  followed  by  spasmodic  movements  of  the  tongue 
{^Fleury'). 

In  paralysis  of  the  lips  [facial  nerve),  and  in  hare-lip, 
regard  must  be  had  to  the  fonnation  of  consonants  of  the  first 
articulation  position.  When  the  nose  is  closed,  the  speech  has  a 
characteristic  sound.     The  normal  formation  of  resonants  is  of 

course  at  an  end.     After  excision  of  the  larynx,  a  metal  reed,  

enclosed  in  a  tube,  and  acting  like  an  artificial  larynx,  is  introduced  t;^^^,^  ^^  the^cal  cords  causing 
between  the  trachea  and  the  cavity  of  the  mouth  [Czerny).  double  tone  from  the  larynx. 

Stammering  is  a  disturbance  of  the  formation  of  sounds. 
[Stammering  is  due  to  long-continued  spasmodic  contraction  of  the  diaphragm,  just  as  hiccough  is 
(^  120),  and,  therefore,  it  is  essentially  a  spasmodic  inspiradon.  As  speech  depends  upon  the 
expiratory  blast,  the  spasm  prevents  expiration.  It  may  be  brought  about  by  mental  excitement  or 
emotional  conditions.  Hence,  the  treatment  of  stammering  is  to  regulate  the  respirations.  In  stutter- 
ing, which  is  defective  speech  due  to  inability  to  form  the  proper  sounds,  the  breathing  is  normal.] 

320.  COMPARATIVE — HISTORICAL. — Speech  may  be  classified  with  the  "  expression 
of  the  emotions"  [Darwin).  Psychical  excitement  causes  in  man  characteristic  movements,  in 
which  certain  groups  of  muscles  are  always  concerned,  e.g.,  laughing,  weeping,  the  facial  expression 
in  anger,  pain,  shame,  etc.  These  movements  afford  a  means  whereby  one  creature  can  communicate 
with  another.  Primarily  in  their  origin,  the  movements  of  expression  are  reflex  motor  phenomena; 
when  they  are  produced  for  purposes  of  explanation,  they  are  voluntary  imitations  of  this  reflex. 
Besides  the  emotional  movements,  impressions  upon  the  sense  organs  produce  characteristic  reflex 
movements,  which  may  be  used  for  purposes  of  expression  [Geiger),e.  g.,  stroking  or  painful  stimula- 
tion of  the  skin,  movements  after  smelling  pleasant  or  unpleasant  or  disagreeable  odors,  the  action  of 
sound  and  light,  and  the  perception  of  all  kinds  of  objects. 


574  COMPARATIVE    AND    HISTORICAL. 

The  expression  of  the  emotions  occurs  in  its  simjilest  form  in  what  is  Icnown  as  expression  by 
means  of  signs  or  pantomime  or  mimicry.  Another  means  is  the  imitation  of  sounds  by  the 
organ  of  speech,  constituting  onainatopoesy,  e.g.,  the  hissing  of  a  stream,  the  roll  of  thunder,  the 
tumult  of  a  storm,  whistling,  etc.  The  expression  of  speech  is,  of  course,  dependent  upon  the  jiro- 
cess  of  ideation  and  perception. 

The  occurrence  of  different  sounds  in  different  languages  is  very  interesting.  Some  languages 
{e.  ^.,  of  the  Hurons)  have  no  labials ;  in  some  .South  Sea  Islands,  no  laryngeal  sounds  are  spoken; 
/  is  absent  in  Sanscrit  and  Finnish  ;  the  sliort  e,  o,  and  the  soft  sibilants  in  Sanscrit ;  d,  in  Chinese 
and  Mexican;  s,  in  many  Polynesian  languages;   r,  in  Chinese,  etc. 

Voice  in  Animals. — Animals,  more  especially  the  higher  forms,  can  express  their  emotions  by 
facial  and  other  gestures.  The  vocal  organs  of  mammals  .ire  es.sentially  the  .same  as  tho.se  of  man. 
Special  resonance  organs  occur  in  the  orang-outang,  mandril,  macacus,  and  mycetes  monkeys,  in  the 
form  of  large  cheek  pouches,  which  can  be  inflated  with  air,  and  open  between  the  larynx  and  the 
hyoid  bone. 

Birds  have  an  upper  (larynx)  and  a  lower  larynx  (syrinx) ;  the  latter  is  placed  at  the  bifurcation 
of  the  trachea,  and  is  the  true  vocal  organ.  Two  folds  of  mucous  membrane  (three  in  singing  birds) 
project  into  each  bronchus,  and  are  rendered  tense  by  muscles,  and  are  thus  adapted  to  serve  for  the 
production  of  voice. 

.\mong  reptiles,  the  tortoises  produce  merely  a  sniffing  sound,  which  in  the  Emys  has  a  peculiar 
piping  character.  The  blind  snakes  are  voiceless,  the  chameleon  and  the  lizards  have  a  very  feeble 
voice  ;  the  cajnnan  and  crocodile  emit  a  feeble  roaring  sound,  which  is  lost  in  some  adults  owing  to 
changes  in  the  larynx.  The  snakes  have  no  special  vocal  organs,  but  by  forcing  out  air  from  their 
capacious  lung,  they  make  a  peculiar  hissing  sound,  which  in  some  species  is  loud.  Among  amphi- 
bians, the  frog  has  a  larynx  provided  with  muscles.  The  sound  emitted  without  any  muscular 
action  is  a  deep  intermittent  tone,  while  more  forcible  expiration,  with  contraction  of  the  laryngeal 
constrictors,  causes  a  clearer  continuous  sound.  The  male,  in  Rana  esculenta,  has  at  each  side  of 
the  angle  of  the  mouth  a  sound  bag,  which  can  be  inflated  with  air  and  acts  as  a  resonance  chamber. 
The  "  croaking  "  of  the  male  frog  is  quite  characteristic.  In  Pipa,  the  larynx  is  provided  with  two 
cartilaginous  rods,  which  are  thrown  into  vibration  by  the  blast  of  air,  and  act  like  vibrating  rods  or 
the  limbs  of  a  tuning  fork.  Some  fishes  emit  sounds,  either  by  rubbing  together  the  upper  and 
lower  pharyngeal  bones,  or  by  the  expulsion  of  air  from  the  swimming  bladder,  mouth,  or  anus. 

Some  insects  cause  sounds  partly  by  forcing  the  expired  air  through  their  stigmata  provided  with 
muscular  reeds,  which  are  thus  thrown  into  vibration  (bees  and  many  diptera).  The  wings,  owing 
to  the  rapid  contraction  of  their  muscles,  may  also  cause  sounds  (flies,  cockroach,  liees).  The 
Sphinx  atropos  (death-head  moth)  forces  air  from  its  sucking  stomach.  In  others,  sounds  are  pro- 
duced by  rubbing  their  legs  on  the  wing  cases  (Acridium),  or  the  wing  cases  on  each  other  (Gryllus, 
locust),  or  on  the  thorax  (Cerambyx),  on  the  leg  (Geotrupes),  on  the  abdomen  or  the  margin  of  the 
wing  (Nekrophorus).  In  CicadacicC,  membranes  are  pulled  upon  by  muscles,  and  are  tlms  caused 
to  vibrate.  Friction  sounds  are  produced  between  the  cephalo-thorax  and  the  abdomen  in  some 
spiders  (Theridium),  and  in  some  crabs  (Palinurus).  Some  moUusca  (Pecten)  emit  a  sound  on 
separating  their  shells. 

Historical. — The  Hippocratic  School  was  aware  of  the  fact  that  division  of  trachea  abolished 
the  voice,  and  that  the  epiglottis  prevented  the  entrance  of  food  into  the  larynx.  Aristotle  made 
numerous  observations  on  the  voice  of  animals.  The  true  cause  of  the  voice  escaped  him  as  well  as 
Galen.  Galen  observed  complete  loss  of  voice  after  double  pneumothorax,  after  section  of  the 
intercostal  muscles  or  their  nerves,  as  well  as  after  destruction  of  part  of  the  spinal  cord,  even 
although  the  diaphragm  still  contracted.  He  gave  the  cartilages  of  the  larynx  the  names  that  still 
distinguish  them;  he  knew  some  of  the  laryngeal  muscles,  and  asserted  that  voice  was  produced 
only  when  the  glottis  was  narrowed.  He  compared  the  larynx  to  a  flute.  The  weakening  of  the 
voice,  in  feeble  conditions,  especially  after  loss  of  blood,  was  known  to  the  ancients.  Dodart  (ijcxj) 
was  the  first  to  explain  voice  as  due  to  the  vibration  of  the  vocal  cords  by  the  air  passing  between 
them. 

The  production  of  vocal  sounds  attracted  much  attention  among  the  ancient  Asiatics  and  Arabians 
— less  among  the  Greeks.  Pietro  Ponce  (11584)  was  the  first  to  advocate  instruction  in  the  art  of 
speaking  in  cases  of  dumbness.  Bacon  (1638)  studied  the  shape  of  the  mouth  for  the  pronunciation 
of  the  various  sounds.  Kratzenstein  (1781)  made  an  artificial  apparatus  for  the  production  of  vowel 
sounds,  by  placing  resonators  of  various  forms  over  vibrating  reeds.  Von  Kempelen  (1769  to  1791) 
constructed  the  first  speaking  machine.  Rob.  Willis  (1828)  found  that  an  ela.stic  vibrating  spring 
gives  the  vowels  in  the  series — U,  O,  A,  E,  I — according  to  the  depth  or  height  of  its  tone  ;  further, 
that  by  lengthening  or  shortening  an  artificial  resonator  on  an  artificial  vocal  apparatus,  the  vowels 
may  be  obtained  in  the  same  series.  The  newest  and  most  important  investigations  on  speech  are  by 
Wheatstone,  v.  Helmholtz,  Bonders,  Brucke,  etc.,  and  are  mentioned  in  the  context.  Hensen  suc- 
ceeded in  showing  exactly  the  pitch  of  vocal  tone,  thus  :  The  tone  is  sung  against  a  Konig's  capsule 
with  a  gas  flame.  Opposite  the  flame  is  placed  a  tuning  fork  vibrating  horizontally,  and  in  front 
of  one  of  its  limbs  is  a  mirror,  in  which  the  image  of  the  flame  is  reflected.  When  the  vocal  tone  is  of 
the  same  number  of  vibrations  as  the  tuning  fork,  the  flame  in  the  mirror  shows  one  elevation,  if 
double,  i.e.,  the  octave,  2,  and  with  the  double  octave,  4  elevations. 


General  Physiology  of  the  Nerves 
AND  Electro-Physiology. 


321.  STRUCTURE  OF  THE  NERVE  ELEMENTS.— Thenervous 
elements  present  two  distinct  forms  :  — 

I.  Nerve  Fibres.  {  m  ^^-'^fl'ff  ^^'^-  II.  Nerve  Cells,  j  Of  radons  forms 
[  Medullated.  (      and  functions. 

An  aggregation  of  nerve  cells  constitutes  a  nerve  ganglion.  The yf<^r^j- repre- 
sent a  conducti?ig  apparatus,  and  serve  to  place  tlie  central  nervous  organs  in 
connection  with  peripheral  end  organs.  The  nerve  cells,  however,  besides  trans- 
mitting impulses,  act  as  physiological  cenlres  for  automatic  or  reflex  movements, 
and  also  for  the  sensory,  perceptive,  trophic,  and  secretory  functions. 

I.   (i)  The  non-medullated  nerve  fibres  occur  in  several  forms: — 

1.  Primitive  Fibrils. — The  simplest  form  of  nerve  fibre,  which  is  visible  with  a  magnifying 
power  of  500  to  800  diameters  linear,  consists  of  primitive  nerve  fibrils.  They  are  very  delicate 
fibres  (Fig.  368,  i),  often  with  small  varicose  swellings  here  and  there  in  their  course,  which,  how- 
ever, are  due  to  ch.a.ng&s pos(-mo7'tent.  They  are  stained  of  a  brown  or  purplish  color  by  the  gold 
chloride  method,  and  they  occur  when  a  nerve  fibre  is  near  its  termination,  being  formed  by  the 
splitting  up  of  the  axis  cylinder  of  the  nerve  fibre,  e.  g.,  in  the  terminations  of  the  corneal  nerves, 
the  optic  nerve  layer  in  the  retina,  the  terminations  of  the  olfactory  fibres,  and  in  a  plexiform 
arrangement  in  non-striped  muscle  (p.  510).  Similar  fine  fibrils  occur  in  the  gray  matter  of  the  brain 
and  spinal  cord,  and  in  the  finely  divided  processes  of  nerve  cells. 

2.  Naked  or  simple  axial  cylinders  (Fig.  368,  2),  which  represent  bundles  of  primitive  fibrils 
held  together  by  a  slightly  granular  cement,  so  that  they  exhibit  very  delicate  longitudinal  striation 
with  fine  granules  scattered  in  their  course.  The  best  example  is  the  axial  cylinder  process  of  nerve 
cells  (Fig.  368,  I,  z).  [The  thickness  of  the  axis  cylinder  depends  upon  the  number  of  fibrils 
entering  into  its  composition.] 

3.  Axis  cylinders  surrounded  with  Schwann's  sheath,  or  Remak's  fibres  (3.8  to  6.8  fi  broad), 
the  latter  name  being  given  to  them  from  their  discoverer  (Fig.  368,  3).  [These  fibres  are  also 
called  pale  or  non-medullated,  and  from  their  abundance  in  the  sympathetic  nervous  system, 
sympathetic. '\  They  consist  of  a  sheath,  corresponding  to  Schwann's  sheath  [neurilemma,  or 
primitive  sheath,  which  encloses  an  axial  cylinder;  while  lying  here  and  there  under  the  sheath,  and 
between  it  and  the  axial  cylinder  are  nerve  corpuscles.  These  fibres  are  always  fibrillated  longitudi- 
nally]. The  sheath  is  delicate,  structureless,  and  elastic.  Dilute  acids  clear  the  fibrils  without 
causing  them  to  swell  up,  while  gold  chloride  makes  them  brownish-red.  They  are  widely 
distributed  in  the  sympathetic  nerves,  \^e.g.,  splenic],  and  in  the  branches  of  the  olfactory  nerves. 
All  nerves  in  the  embryo,  as  well  as  the  nerves  of  many  invertebrata,  are  of  this  kind.  [Accord- 
ing to  Ranvier,  these  fibres  do  not  possess  a  sheath,  but  the  nuclei  are  merely  applied  to  the  surface, 
or  slightly  embedded  in  the  superficial  parts  of  the  fibre,  so  that  they  belong  to  the  fibre  itself  These 
fibres  also  branch  and  form  an  anastomosing  network  (Fig.  370).  This  the  medullated  fibres 
never  do.  These  fibres,  when  acted  on  by  silver  nitrate,  never  show  any  crosses.  The  branched 
forms  occur  in  the  ordinary  nerves  of  distribution,  and  they  are  numerous  in  the  vagus,  but  the  olfac- 
tory nerves  have  a  distinct  sheath  which  is  nucleated.] 

(2)  Medullated  fibres  occur  also  in  several  forms : — 

4.  Axis  cylinders,  or  nerve  fibrils,  covered  only  by  a  medullary  sheath,  or  white  substance 
of  Schwann,  are  met  with  in  the  white  and  gray  matter  of  the  central  nervous  system,  in  the  optic 
and  auditory  nerves.  These  medullated  nerve  fibres,  without  any  netirilemma,  often  show  after 
death,  varicose  swellings  in  their  course  [due  to  the  accumulation  of  fluid  between  the  medulla  of 
myelin  and  the  axis  cylinder.]  Hence  they  are  called  varicose  fibres.  [The  varicose  appearance 
is  easily  produced  by  squeezing  a  small  piece  of  the  white  matter  of  the  spinal  cord  between  a  slide 

575 


570 


STRUCTURE    OF    NERVE    FIBRES. 


and  a  cover  glass.  Nitrate  of  silver  does  not  reveal  any  crosses,  and  there  are  no  nodes  of  Ranvier. 
When  acted  upon  by  coagulating  reagents,  ^.  ,;•-.,  chromic  acid,  the  medullary  sheath  appears  lami- 
nated, so  that  on  transverse  section,  when  the  axis  cylinder  is  stained,  it  is  surrounded  by  concentric 
circles  (Fig.  .>69). 

5.  Meduliated  Nerve  Fibres  with  Schwann's  Sheath  (Fig.  36S,  5,  6).— These  are  the  most 

Fig.  368. 


1,  Primitive  fibrillae  ;  2,  axis  cylinder;  3,  Remak's  fibres  ;  4,  meduUaf^d  varicose  fibre  ;  5,  6,  meduliated  fibre,  with 
Schwann's  sheath  :  c,  neurilemma ;  t,  t,  Ranvier's  nodes ;  b,  white  substance  of  Schwann  ;  d,  cells  of  the  en- 
doneurium  ;  a,  axis  cylinder  ;  x,  myelin  drops;  7,  transverse  section  of  nerve  fibres  ;  8,  nerve  fibre  acted  on  with 
silver  nitrate  and  showing  Fromann's  lines.  I,  multipolar  nerve  cell  from  the  spinal  cord  ;  z,  axial  cylinder  pro- 
cess ;  ^.protoplasmic  processes— to  the  right  of  it  a  bipolar  cell.  II,  peripheral  ganglionic  cell,  with  a  con- 
nective-tissue capsule.     Ill,  ganglionic  cell,  with  o,  a  spiral,  and  n,  straight  process  ;  m,  sheath. 

complex  nerve  fibres,  and  are  lo  to  22.6  }i  [77^50  *o  sA  0  inch]  broad.  They  are  most  numerous  in, 
and  in  fact  they  make  up  the  great  mass  of,  the  cerebro-spinal  nerves,  although  they  are  also  present  in 
the  sympathetic  nerves.  [WTien  examined  in  the  fresh  and  living  condition  m  siiu,  they  appear  refrac- 
tive and  homogeneous  [Ranvier,  Stirling) ;  but  if  acted  upon  by  reagents,  they  are  not  only  refractive, 
but  exhibit  a  double  contour,  the  margins  being  dark  and  well  defined.]      Each  fibre  consists  of — 


STRUCTURE    OF    NERVE    FIBRES.  577 

[i.  Schwann's  sheath,  neurilemma,  or  primitive  sheath ; 

2.  White  substance  of  Schwann,  medullary  sheath,  or  myelin  ; 

3.  Axis  cylinder  composed  of  fibrils  and  surrounded  by  a  sheath  called  the  axilemma  ; 

4.  Nerve  corpuscles.] 

A.  The  axis  cylinder,  which  occupies  ^  to  i  of  the  breadth  of  the  fibre,  is  the  essential  part 
of  the  nerve,  and  lies  in  the  centre  of  the  fibre  like  the  wick  in  the  centre  of  a  candle  (Fig.  368,  6, 
a).  Its  usual  shape  is  cylindrical,  but  sometimes  it  is  flattened  or  placed  eccentrically — [this  is  most 
probably  due  to  the  hardening  process  employed].  It  is  composed  oi  fibrils  [united  by  cement  or 
stroma;  they  become  more  obvious  near  the  terminations  of  the  nerve,  or  after  the  action  of 
reagents,  which  sometimes  cause  the  fibrils  to  appear  beaded.  It  is  quite  transparent,  and  stains 
deeply  with  carmine  or  logwood],  while  during  life,  its  consistence  is  semi-fluid.  According  to 
Kupffer,  a  fluid — "  neuroplasma  " — lies  between  the  fibrils  [while,  according  to  other  observers, 
the  whole  cylinder  is  enclosed  in  an  elastic  sheath  peculiar  to  itself  and  composed  of  neuro-keratin. 
This  sheath  is  called  by  Kiihne,  the  axilemma.  Each  axis  cylinder  is  an  enormously  long  process 
of  a  ganglionic  cell]. 

Fromann's  Lines. — Chloroform  and  collodion  render  it  visible,  while  it  is  most  easily  isolated 
as  a  solid  rod,  by  the  action  of  nitric  acid  with  excess  of  potassium  chlorate.  When  acted  on 
by  silver  nitrate,  Fromann  observed  transverse  markings  on  it,  but  their  significance  is  unknown 
(Fig.  368,  8). 

B.  The  white  substance  of  Schwann,  medullary  sheath  or  myelin,  surrounds  the  axis 
cylinder,  like  an  insulating  medium  around  an  electric  wire.  In  the  perfectly  fresh  condition  it  is 
quite  homogeneous,  highly  glistening,  bright,  and  refractive  ;  its  consistence  is  fluid,  so  that  it  oozes 
out  of  the  cut  ends  of  the  fibres  in  spherical  drops  (Fig.  368,  x)  [myelin  drops,  which  are  always 
marked  by  concentric  lines,  are  highly  refractive,  and  best  seen  when  a  fresh  nerve  is  teased  in  salt 
solution].  After  death,  or  after  the  action  of  reagents,  it  shiinks  slightly  from  the  sheath,  so  that 
the  fibres  have  a  double  contour,  while  the  substance  itself  breaks  up  into  smaller  or  larger  droplets, 
due  not  to  coagulation  [Pertik],  but,  according  to  Toldt,  to  a  process  like  emulsification,  the  drops 
pressing  against  each  other.  Thus  the  fibre  is  broken  up  into  masses,  so  that  it  has  a  characteristic 
appearance  (Fig.  368,  6).  It  contains  a  large  amount  of  cerebrin  and  lecithin,  which  swell  up  to 
form  myelin-like  forms  in  warm  water.  It  also  contains  fatty  matter,  so  that  these  fibres  are  black- 
ened by  osmic  acid  [while  boiling  ether  extracts  cholesterin  from  them].  Chloroform,  ether,  and 
benzin,  by  dissolving  the  fatty  and  some  other  constituents  of  the  fibres,  make  them  very  trans- 
parent.    [Some  observers  describe  a  fluid  lying  between  the  medulla  and  the  axis  cylinder.] 

C.  The  Sheath  of  Schwann  or  the  neurilemma,  lies  immediately  outside  of  and  invests  the  white 
sheath  (Fig.  368,  6,  c'),  and  is  a  delicate  structureless  membrane,  comparable  to  the  sarcolemma  of  a 
muscular  fibre. 

D.  Nerve  Corpuscles. — At  fairly  wide  intervals  under  the  neurilemma,  and  lying  in  depressions 
between  it  and  the  medullary  sheath,  are  the  nucleated  nerve  corpuscles,  which  are  readily  stained 
by  pigments  (Fig.  371).  [They  may  be  compared  to  the  muscle  corpuscles,  the  nuclei  being  sur- 
rounded by  a  small  amount  of  protoplasm  which  sometimes  contains  pigment.  They  are  not  so 
numerous  as  in  muscle.]  [Adamkiewicz  describes  nerve  corpuscles,  or  "  demilunes  "  under  the 
neurilemma,  quite  distinct  from  the  ordinary  nerve  corpuscles.  They  are  stained  yellow  by  safranin, 
while  the  ordinary  nerve  corpuscles  are  stained  by  methylanilin.] 

Ranvier's  Nodes  or  Constrictions. — The  neurilemma  forms  in  broad  fibres  at  longer,  and  in 
narrower  ones  at  shorter  intervals,  the  nodes  ox  constrictions  of  Ranvier  (Fig.  368,  6,  t,  t ;  Fig.  37I; 
Fig.  372, /yj.  They  are  constrictions  which  occur  at  regular  intervals  along  a  nerve  fibre;  at  them 
the  white  substance  of  Schwann  is  interrupted,  so  that  the  sheath  of  Schwann  lies  upon  the  axis 
cylinder  [or  its  elastic  sheath]  at  the  nodes.  The  part  of  the  nerve  lying  between  any  two  nodes  is 
called  an  inter-annular  or  inter-nodal  segynent,  and  each  such  segment  contains  one  or  more  nuclei, 
so  that  some  observers  look  upon  the  whole  segment  as  equivalent  to  one  cell. 

The  function  of  the  nodes  seems  to  be  to  permit  the  diffusion  of  plasma  through  the  outer 
sheath  into  the  axis  cylinder,  while  the  decomposition  products  are  similarly  given  off.  [A  coloring 
matter  like  picro-carmine  diffuses  into  the  fibre  only  at  the  nodes,  and  stains  the  axis  cylinder  red, 
although  it  does  not  diffuse  through  the  white  substance  of  Schwann.] 

Incisures  (of  Schmidt  and  Lantermann). — Each  inter- annular  segment  in  a  stretched  nerve  shows, 
running  across  the  white  substance,  a  number  of  oblique  lines,  which  are  called  incisures  (Figs.  372, 
373).  They  indicate  that  the  segment  is  built  up  of  a  series  of  conical  sections,  each  of  which  is 
beveled  at  its  ends,  and  the  bevels  are  arranged  in  an  imbricate  manner,  the  one  over  the  other, 
while  the  slight  interval  between  them  appears  as  an  incisure.  Each  such  section  of  the  white 
matter  is  called  a  cylinder  cone  {^Kiihnt). 

Neuro-Keratin  Sheath. — According  to  Ewald  and  Kiihne,  the  axis  cylinder,  as  well  as  the  white 
subtance  of  Schwann,  is  covered  with  an  excessively  delicate  sheath,  consisting  of  netiro-keratin, 
and  the  two  sheaths  are  connected  by  numerous  transverse  and  oblique  fibrils,  which  permeate  the 
white  substance.      [The  myelin  seems  to  lie  in  the  interstices  of  this  meshwork.] 

[Rod-like  Structures  in  Myelin. — If  a  nerve  be  hardened  in  ammonium  ckromate  {or picric 
acid),  M'Carthy  has  shown  that  the  myelin    exhibits  rod-hke  structures,  radiating  from  the  axis 

37 


578 


STRUCTURE    OF    NERVE    FIBRES, 


Fig.  369. 


Fir..  371. 


I^'iG.  373- 


a— 


Node  of  jj  Fig.  372. 

Ranvier 


Primitive        „    _ 

Sheath.  JV1 


A 


MeduUated       nerve 
White  fibres     blackened 

Sub-  by     osmic      acid, 

stance  of     /s,  R  a  n  v  i  e  r  '  s 
Schwann,    node:       s  c  h  , 
Schwann's  sheath. 


-P 


"-iii 

s- 


Node  of 
Ranvier. 


\k 


MeduUated  nerve  fibres  with  osmic 
acid.  a,  axis  cylinder;  s, 
sheath  of  Schwann  :  n,  nucleus  ; 
/,/,  granular  substance  at  the 
poles  of  the  nucleus ;  >-,  r, 
Ranvier's  nodes  where  the 
medullary  sheath  is  interrupted 
and  the  axis  cylinder  appears  ; 
i,  i,  incisures  of  Schmidt, 


Remak's  fibre  from  vagus  of  dog. 
6,  fibrils  ;  «,  nucleus  ;  /,  proto- 
plasm surrounding  it. 


MeduUated  nerve 
fibre  of  a  rab- 
bit acted  on  by 
osmic  acid,  X 
400, 


STRUCTURE   OF   NERVE    FIBRES. 


579 


Fig.  374. 


cylinder  outward,  which  are  stained  with  logwood  and  carmine.     The  rods  are  probably  not  distinct 
from  each  other,  but  are  perhaps  part  of  the  neuro- keratin  network  already  described.] 

Action  of  Nitrate  of  Silver. — When  a  small  nerve,  e.g.,  the  intercostal  nerve  of  a  mouse,  is 
acted  on  by  silver  nitrate,  it  is  seen  to  be  covered  by  an  endothelial  sheath  composed  of  flattened 
endothelial  cells  (Fig.  374),  while  the  nerve  fibres  themselves  exhibit  crosses  along  their  course. 
These  crosses  are  due  to  the  penetration  of  the  silver  solution  at 
the  nodes,  where  it  stains  the  cement  substance  and  also  part  of  the 
axis  cylinder,  so  that  the  latter  sometimes  exhibits  transverse  mark- 
ings called  Fromann's  lines  (Fig.  368,  8).] 

[New  Methods. — Much  progress  has  recently  been  made  in 
tracing  the  course  of  medullated  nerve  fibres  by  the  aciion  of  new 
staining  reagents ;  thus  acid  fuchsin  stains  the  myelin  deeply,  leav- 
ing the  other  parts  unstained,  at  least  it  can  be  so  manipulated  as 
to  yield  this  result.  Weigert's  Method  and  its  modifications 
have  yielded  most  important  results,  and  proved  that  medullated 
nerve  fibres  exist  in  many  parts  of  the  central  nervous  system  where 
they  cannot  be  seen  in  the  ordinary  way.  The  nerve  tissue  is 
hardened  in  a  solution  of  a  chromium  salt,  and  placed  in  a  half- 
saturated  solution  of  cupric  acetate;  it  is  then  stained  with  logwood, 
and  afterward  the  elements  are  differentiated  by  steeping  the  sections 
in  a  solution  of  ferricyanide  of  potash  and  borax.  The  myehn  is 
colored  a  logwood  tint.] 

In  the  spinal  nerves,  those  fibres  are  thickest  which  have  the 
longest  course  before  they  reach  their  end  organ  [Schivalbe),  while 
those  ganglion  cells  are  largest  which  send  out  the  longest  nerve 
fibres  {Pierret).  [Gaskell  finds  that  the  longest  nerves  are  not 
necessarily  the  thickest,  for  the  visceral  nerves  in  the  vagus  are 
small  nerves,  and  yet  run  a  very  long  course.] 

Division  of  Nerves. — Nerve  fibres  run  in  the  nerve  trunks 
without  dividing;  but  when  they  approach  their  termination  they  intercostal  nerve  of  a  mouse  (single 
often  divide  dichotoraously  [at  anode],  giving  rise  to  two  similar  fasciculus  of  nerve  fibres)  stained 
fibres,  but  there  may  be  several  branches  at  a  node  (Fig.  376,  /).  with  silver  nitrate.  Endothelial 
n^i      J.--  .  ,  it-j  IT  sheath  stained,  and  some  nodes  of 

[The  divisions  are  numerous  in  motor  nerves  to  striped  muscles.]         Ranvier  indicated  by  crosses. 
In  the  electrical  nerves  of  the  malapterurus  and  gymnotus,  there 

is  a  gr^at  accumulation  of  Schwann's  sheaths  round  a  nerve,  so  that  a  nerve  fibre  is  as  thick  as  a 
sewing  needle.     Such  a  fibre,  when  it  divides,  breaks  up  into  a  bundle  of  smaller  fibres. 

Fig 


^^-^%:#^^i' 


Trans,  section  of  a  nerve  (median),     ep,  epineurium;  ^e,  perineurium;  ed,  endoneurium. 

[Nerve  Sheaths. — A  nerve  trunk  consists  of  bundles  of  nerve  fibres.  The  bundles  are  held 
together  by  a  common  connective-tissue  sheath  (Fig.  375,  ep),  the  epineurium  which  contains  the 
larger  blood  vessels,  lymphatics,  and  sometimes  fat  and  plasma  cells.     Each  bundle  is  surrounded 


580 


STRUCTURE    OF    NERVE    FIBRES. 


with  its  own  sheath  or  perineurium  (/c),  which  consists  of  lamellated  connective  tissue  disjx>sed 
circularly,  and  between  the  lamelLv  are  lymph  spaces  lined  by  flattened  endothelial  plates.  These 
lymph  spaces  may  be  injected  from  and  communicate  with  the  lymphatics  [Axel  Key  and  Ketzius).'\ 
The  nerve  tibres  within  any  bundle  are  held  together  by  delicate  connective  tissue,  which  penetrates 
between  the  adjoininjj  tibres,  constituting  the  endoneurium  (cv/).  It  consists  of  delicate  fibres 
with  branched  connective-tissue  corpuscles  (Fig.  36S.  6,  d),  ami  in  it  lie  the  capillaries,  which  are  not 
very  numerous,  and  are  arranged  to  form  elongated  open  meshes. 

[Henle's  Sheath. — When  a  nerve  is  traced  to  its  distribution,  it  branches  and  becomes  smaller, 
until  it  may  consist  only  of  a  few  bundles  or  even  a  single  bundle  of  nerve  fibres.  As  the  bundle 
branches,  it  has  to  give  off  part  of  its  lamellated  sheath  or  ])erineurium  to  each  branch,  so  that,  as 
we  pass  to  the  periphery,  the  smaller  bundles  are  surrounded  by  few  lamelhi;.  In  a  bundle  contain- 
ing only  a  few  fibres,  this  sheath  may  be  much  reduced,  or  m.iy  consist  only  of  thin,  flattened,  con- 
nective-tissue corpuscles  with  a  few  fibres.  A  .sheath  surrounding  a  few  nerve  fibres  is  called  Henle's 
Shealh  by  Ranvier.] 

[Nervi  Nervorum. — Marshall  and  v.  Ilorsley  have  shown  that  the  nerve  sheaths  are  provided 
with  special  nerve  fibres,  in  virtue  of  which  they  are  endowed  with  sensibility.] 

Development. — At  first  nerve  fibres  consist  only  of  fibrils,  i.e.,  of  axis  cylinders,  which  become 
covered  with  connective  substance,  and  ultimately  the  white  substance  of  Schwann  is  developed  in 
some  of  them.     The  growth  in  length  of  the  fibres  takes  place  by 
elongation  of  the  individual  "  mter-annular "  segments,  and  also  by 
the  new  formation  of  these  (  Vii^nal^. 

II.  Ganglionic  or  Nerve  Cells. — i.  Multipolar  nerve  cells 
(Fig.  368,  I)  occur  partly  as  large  cells  (loo  //),  and  are  visible  to  the 
unaided  eye  as  in  the  anterior  horn  of  the  .spinal  cord,  and  in  a  differ- 
ent form  in  the  cerel)ellum,  and  partly  in  a  smaller  form  (20  to  10  ^i) 
in  the  posterior  horns  of  the  spinal  cord,  many  parts  of  the  cerebrum 
and  cerebellum,  and  in  the  retina.  They  may  be  spherical,  ovoid, 
pyramidal  [cerebrum],  pear-  or  flask-shaped  [cerebellum],  and  are 
provided  with  numerous  branched  processes  which  give  the  cells 
a  characteristic  appearance.  [Deiters  isolated  such  cells  from  the 
anterior  horn  of  the  gray  matter  of  the  .spinal  cord,  so  that  this  special 
form  of  cell  is  sometimes  called  "  Deiters'  cell  "  (Fig.  368,  I).]  They 
are  devoid  of  a  cell  envelope,  are  of  soft  consistence,  and  exhibit  a 
fibrillated  structure,  which  may  extend  even  into  the  processes.  Fine 
granules  lie  scattered  throughout  the .  cell  substance  between  the 
fibrils.  Not  unfrequently  yellow  or  brown  granules  of  pigment  are 
also  found,  either  collected  at  certain  parts  in  the  ceM  or  scattered 
throughout  it.  The  relatively  large  nucleus  consists  of  a  clear  envel- 
ope enclosing  a  resistant  substance.  It  does  not  appear  to  have  a 
membrane  in  youth  [Schzvallie).  Within  the  nucleus  lies  the  nucleolus, 
which  in  the  recent  condition  is  angular,  provided  with  processes  and 
capable  of  motion,  but  after  death  is  highly  refractive  and  spherical. 
There  is  always  one  unbranched  process,  constituting  the  axial 
cylinder  process  (I,  :)  which  remains  unbranched,  but  it  soon  be- 
comes covered  with  the  substance  of  Schwann,  and  the  other  sheaths 
of  a  medullated  nerve,  so  that  it  becomes  the  axial  cylinder  of  a 
nerve  fibre.  [Thus  a  nerve  fibre  is  merely  an  excessively  long,  un- 
branched process  of  a  nerve  cell  pushed  outward  toward  the  peri- 
phery.] It  is  not  definitely  ascertained  that  the  cerebral  cells  have 
such  processes.  All  the  other  processes  divide  very  frequently  until 
they  form  a  branched,  root -like,  complex  arrangement  of  the  finest 
primitive  fibriks.  These  are  called  protoplasmic  processes  (I, _)/). 
By  means  of  these  processes,  adjoining  cells  are  brought  into  commu- 
nication with  each  other,  so  that  impulses  can  be  conducted  from  one 
cell  to  another.  Further,  many  of  these  fibrils  approximate  to  each 
other  and  join  together  to  form  axis  cylinders  of  other  nerve  fibres, 
[v.  Thanhofler  states  that  he  has  traced  the  axis-cylinder  process 
to  the  nucleus  and  nucleolus.] 

2.  Bipolar  cells  are  best  developed  in  fishes,  e.g.,  in  the  .spinal 
ganglia  of  the  skate,  and  in  the  (lasserian  ganglion  of  the  pike. 
They  appear  to  be  nucleated,  fusiform  enlargements  of  the  axis 
cylinder  (Fig.  36S,  on  the  right  of  I).  The  white  substance  often  stops  short  on  each  side  of  the 
enlargement,  but  sometimes  the  white  substance  and  the  sheath  of  Schwaim  pass  over  the  enlargement 
3.  Nerve  cells  with  connective-tissue  capsules  occur  in  the  peripheral  ganglia  of  man 
(Fig.  368,  II),  e.g.,  in  the  spinal  ganglia.  The  soft  body  of  the  cell,  which  is  provided  with  several 
processes,  is  covered  by  a  thick,  tough  capsule  composed  of  several  layers  of  connective-tissue  cor- 


Cell  from  the  Gasserian  ganglion. 
«,  nuclei  of  the  sheath  ;  t,  fihre 
dividing  at  a  node  of  Ranvier. 


CHEMISTRY  OF  NERVOUS  MATTER.  581 

puscles ;  while  the  inner  surface  of  the  composite  capsule  is  lined  by  a  layer  of  delicate  endothelial 
cells  (Fig.  376).  The  body  of  the  cells  in  the  spinal  ganglia  is  traversed  by  a  network  of  fine 
fibrils  i^Memming).     The  capsule  is  continuous  with  the  sheath  of  the  nerve  fibre. 

Rawitz  and  G.  Retzius  find  that  the  cells  of  the  spinal  ganglia  are  unipolar,  the  outgoing  fibre 
taking  a  half-turn  within  the  capsule  before  it  leaves  the  cell  (Fig.  376).  Retzius  [and  Ranvier] 
observed  the  process  to  divide  like  a  T.  Perhaps  this  division  corresponds  to  the  two  processes  of 
a  bipolar  cell.  The  jugular  ganglion  and  plexus  gangliiformis  vagi  in  man  contain  only  unipolar 
cells,  so  that,  in  this  respect,  they  may  be  compared  to  spinal  ganglia.  The  same  is  the  case  in  the 
Gasserian  ganglion  ;  while  the  ciliary,  spheno-palatine,  otic,  and  submaxillary  ganglia  structurally 
resemble  the  ganglia  of  the  sympathetic. 

4.  Ganglionic  cells  with  spiral  fibres  occur  chiefly  in  the  abdominal  sympathetic  of  the  frog 
{Beale,J.  Arnold).  The  body  of  the  cell  is  usually  pyriform  in  shape,  and  from  it  proceeds  a 
straight  unbranched  process  (Fig.  368,  III,  «),  which  ultimately  becomes  the  axis  cylinder  of  a 
nerve.  A  spiral  fibre  springs  from  the  cell  (?  a  network),  emerges  from  it,  and  curves  in  a  spiral 
direction  round  the  former  [o).  The  whole  cell  is  surrounded  by  a  nucleated  capsule  (w).  We 
know  nothing  of  the  significance  of  the  different  fibres. 

322.  CHEMICAL  AND  MECHANICAL  PROPERTIES  OF 
NERVOUS  SUBSTANCE.— I.  Proteids.— Albumin  occurs  chiefly  in  the 
axis  cylinder  and  in  the  substance  of  the  ganglionic  cells.  Some  of  this  proteid 
substance  presents  characters  not  unlike  those  of  myosin  (§  293).  Dilute  solution 
of  common  salt  extracts  a  proteid  from  nervous  matter,  which  is  precipitated  by 
the  addition  of  much  water  and  also  by  a  concentrated  solution  of  common  salt 
{Feirowsky).  Potash  albumin  and  a  globulin-like  sicbstance  are  also  present. 
Nuclein  occurs  especially  in  the  gray  matter  (§  250,  2),  while  neuro-keratin, 
a  body  containing  much  sulphur  and  closely  related  to  keratin,  occurs  in  the  cor- 
neous sheath  of  nerve  fibres  (p.  577).  If  gray  nervous  matter  be  subjected  to 
artificial  digestion  with  trypsin,  both  of  these  substances  remain  undigested 
{Kiihne  and  Ew aid).  Pure  neuro-keratin  is  obtained  by  treating  the  residue  with 
caustic  potash.  The  sheath  of  Schwann  does  not  yield  gelatin,  but  a  substance 
closely  related  to  elastin  (§  250,  6),  from  which  it  differs,  however,  in  being  more 
soluble  in  alkalies.     The  connective  tissue  of  nerves  yields  gelatin. 

2.  Fats  and  other  allied  substances  soluble  in  ether,  more  especially  in  the  white 
matter:   {a)  Cerebrin,  free  from  phosphorus  (§  250,  3). 

Cerebrin  is  a  white  powder  composed  of  spherical  granules  soluble  in  hot  alcohol  and  ether,  but 
insoluble  in  cold  water.  It  is  decomposed  at  80°  C.,  and  its  solutions  are  neutral.  When  boiled 
for  a  long  time  with  acids,  it  splits  up  into  a  left-rotatory  body  like  sugar  and  another  unknown  pro- 
duct. Preparation. — Rub  up  the  brain  into  a  thin  fluid  with  baryta  water.  Extract  the  separated 
coagulum  with  boiling  alcohol.  The  extract  is  fi-equently  treated  with  cold  ether  to  remove  the 
cholesterin  {W.  Milller).  Parkus  separated  from  cerebrin  its  homologue,  homocerebrin,  which  is 
slightly  more  soluble  in  alcohol,  and  the  clyster-like  body,  encephalin,  which  is  soluble  in  hot 
water. 

{b')  Lecithin  and  its  decomposition  products — glycero-phosphoric  acid  and 
oleo-phosphoric  acid  (§  251). 

Neurin  (or  Cholin  =  C5H15NO2)  is  a  strongly  alkaline,  colorless  fluid,  forming  crystalline  salts 
with  acids.  It  is  soluble  in  water  and  alcohol,  and  has  been  formed  synthetically  from  glycol  and 
trimethylamin.     Lecithin  is  a  salt  of  the  base  neurin. 

{c)  Protagon,  which  contains  N  and  P,  is  similar  to  cerebrin,  and  is,  accord- 
ing to  its  discoverer,  the  chief  constituent  of  the  brain  {^Liebreich'). 

According  to  Hoppe-Seyler  and  Diaconow,  it  is  a  mixture  of  lecithin  and  cerebrin.  [The  inves- 
tigations of  Gamgee  and  Blankenhorn  have  shown,  however,  that  protagon  is  a  definite  chemical 
body.  They  find  that,  instead  of  being  unstable,  it  is  a  very  stable  body.]  It  is  a  glucoside,  and 
crystalline,  and  can  be  extracted  from  the  brain  by  warm  alcohol,  and  when  boiled  with  baryta 
yields  the  decomposition  products  of  lecithin. 

3.  The  following  substances  are  extracted  by  water:  Xanthin  and  hypoxanthin  {Sckerer),  kreatin 
{Lerck),  inosit  ( W.  Milller),  ordmary  lactic  acid  {Gsfkeidlen),  acetic  and  foi-mic  acids,  uric  acid  (?), 
and  volatile  fatty  acids;  leucin  (in  disease),  urea  (in  ursemia),  and  a  substance  like  starch  in  the 
human  brain  {Jaffe).  All  these  substances  are  for  the  most  part  products  of  the  regressive  metabol- 
ism of  the  tissues. 


582 


METABOLISM    OF    NERVES. 


Reaction. — Nervous  substance,  when  passive,  is  neutral  or  feebly  alkaline  in 
reaction,  while  active  (?  and  dead)  it  is  acid  {Fttnke).  The  gray  matter  of  the 
brain,  when  quite  fresh,  is  alkaline  {LiebreicJi),  but  death  rapidly  causes  it  to 
become  acid  ^Gscheidlen). 

The  reaction  of  nerve  fibres  varies  during  life.  After  introducing  methyl  blue  into  the  body  of 
a  living  animal,  Klirlich  found  that  the  axis  cylinder  became  blue,  ;.  <?.,  in  those  nerves  which  have 
an  alkaline  reaction  (cortex  cerebri,  cardiac,  sensory,  motor  (non-striped),  gustatory  and  olfactory 
fibres),  while  the  termination  of  motor  (^voluntary)  nerves  remained  uncolored.  The  latter  he 
regards  as  acid. 

The  nerves  after  death  have  a  more  solid  consistence,  so  that  in  all  probability 
some  coagulation  or  change,  comparable  to  the  stiffening  of  muscle,  occurs  in 
them  after  death,  while  at  the  same  time  a  free  acid  is  liberated  (§  295).  If  a 
fresh  brain  be  rapidly  "broiled  "  at  100°  C,  it,  like  a  muscle  similarly  treated, 
remains  alkaline  (§  295). 


Chemical  Composition. 


Water, 

Solids, 

The  solids  consist  of — 
Albumins  and  glutin,     .    .    . 

Lecithin, 

Cholesterin  and  fats,      .    .    . 

Cerebrin, 

Substances  insoluble  in  ether. 
Salts 


Gray  Matter. 

White  Matter. 

81.6  per  cent. 

68.4  per  cent. 

18.4 

31.6        « 

55-4       " 

24.7 

17.2 

9.9 

18.7        " 

52.1         " 

o.S        " 

9-5        " 

6.7        " 

3-3       " 

1.5 

0.5        " 

1 00.0 

1 00.0 

In  100  parts  of  ash,  Breed  found  potash  32,  soda  il,  magnesia  2,  lime  0.7,  XaCl  5,  iron  phos- 
phate 1.2,  fixed  phosphoric  acid  39,  sulphuric  acid  o.i,  silicic  acid  0.4. 

[Ptomaines  (\  166)  are  obtained  from  putrefying  brain.  They  have  an  effect  on  the  motor  nerves 
like  curara,  but  in  much  less  degree,  while  the  phenomena  last  for  a  much  shorter  time  [Guareschi 
and  iMosso).'] 

Mechanical  Properties. — One  of  the  most  remarkable  mechanical  properties 
of  nerve  fibres  is  the  absence  of  elastic  tension  according  to  the  varying  positions 
of  the  body.  Divided  nerves  do  not  retract ;  such  nerves  exhibit  delicate,  micro- 
scopic, transverse  folds  [like  watered  silk],  or  Fontana's  transverse  markings. 

The  cohesion  of  a  nerve  is  very  considerable.  When  a  limb  is  forcibly  torn 
from  the  body,  as  sometimes  happens  from  its  becoming  entangled  in  machinery, 
the  nerve  not  unfrequently  remains  unsevered,  while  the  other  soft  parts  are  rup- 
tured. [Tillaux  found  that  a  weight  of  no  to  120  lbs.  was  required  to  rupture 
the  sciatic  nerve  at  the  popliteal  space,  while  to  break  the  median  or  ulnar  nerve 
of  a  fresh  body,  a  force  equal  to  40  to  50  lbs.  was  required.  The  toughness  and 
elasticity  of  nerves  are  often  well  shown  in  cases  of  injury  or  gunshot  wounds. 
The  median  or  ulnar  nerve  will  gain  15  to  20  centimetres  (6  to  8  inches)  before 
breaking.  Weir  Mitchell  has  shown  that  a  healthy  nerve  will  bear  a  very  consid- 
erable amount  of  pressure  and  handling,  and,  in  fact,  the  method  of  nerve  stretch- 
ing depends  upon  this  property  of  a  nerve  trunk.] 

323.  METABOLISM  OF  NERVES.— Influence  of  Blood  Supply. 

— We  know  very  little  regarding  the  metabolic  processes  that  occur  in  nerve  tissue. 
Some  extractives  are  obtained  from  nerve  tissue,  and  they  may,  perhaps,  be 
regarded  as  decomposition  products  (p.  581).  It  has  not  been  proved  satisfac- 
torily that  during  the  activity  of  nerves  there  is  an  exchange  of  O  and  CO.^. 
That  there  is  an  exchange  of  materials  within  the  nerves  is  proved  by  the  fact  that, 
after  compression  of  the  blood  vessels  of  the  nerves,  the  excitability  of  the 


MECHANICAL    STIMULI    AND    NERVE    STRETCHING.  583 

nerves  falls,  and  is  restored  again  when  the  circulation  is  reestablished.  Com- 
pression of  the  abdominal  aorta  causes  paralysis  and  numbness  of  the  lower  half 
of  the  body,  while  occlusion  of  the  cerebral  vessels  causes  almost  instantaneously 
cessation  of  the  cerebral  functions.  The  metabolism  of  the  central  ner^'ous 
organs  is  much  more  aciive  than  that  of  the  nerves  themselves.  [If  the  abdomi- 
nal aorta  of  a  rabbit  be  compressed  for  a  few  minutes,  the  hind  limbs  are  quickly 
paralyzed,  the  animal  crawls  forward  on  its  forelegs,  drawing  the  hind  limbs  in  an 
extended  position  after  it.]     The  ganglia  form  much  lymph. 

324.    EXCITABILITY    OF   THE    NERVES— STIMULI.— Nerves 

possess  the  property  of  being  thro^^^a  into  a  state  of  excitement  by  stimuli,  and  are, 
therefore,  said  to  be  excitable  or  irritable.  The  stimuli  may  be  applied  to,  and 
may  act  upon,  any  part  of  the  nerve.  [The  following  are  the  various  kinds  of  stimuli, 
/.  e.,  modes  of  motion,  which  act  upon  nerves]  : — 

I.  Mechanical  stimuli  act  upon  nerves  when  they  are  applied  with  sufticient 
rapidity  to  produce  a  change  in  the  form  of  the  nerve  particles,  e.  g.,  2.  blow,  pres- 
sure, pinching,  tension,  puncture,  and  section.  In  the  case  of  sensory  nerves, 
when  they  are  stimulated,  pain  is  produced,  as  is  felt  when  a  limb  "  sleeps,"  or  when 
pressure  is  exerted  upon  the  ulnar  nerve  at  the  bend  of  the  elbow.  When  a  motor 
nerve  is  stimulated,  motion  results  in  the  muscle  attached  to  the  nerve.  If  the 
continuity  of  the  nerve  fibres  be  destroyed,  or,  what  is  the  same  thing,  if  the  con- 
tinuity of  the  axial  cylinder  be  interrupted  by  the  mechanical  stimulus,  the  co7i- 
duction  of  the  impulse  across  the  injured  part  is  interrupted.  If  the  molecular 
arrangements  of  the  nerves  be  permanently  deranged,  e.  g.,  by  a  violent  shock,  the 
excitability  of  the  nerves  may  be  thereby  extinguished. 

A  slight  blow  applied  to  the  radial  nerve  in  the  forearm,  or  to  the  axillary  nerves  in  the  supra- 
clavicular groove,  is  followed  by  a  contraction  of  the  muscles  supplied  by  these  ner\'es.  Under 
pathological  conditions,  the  excitability  of  a  nerve  for  mechanical  stimuli  may  be  increased 
enormously. 

Tigerstedt  ascertained  that  the  minimal  mechanical  stimulus  is  represented  by  900  milligramme- 
millimetres,  and  the  Diaximum  by  7000  to  8000.  Strong  stimuli  cause  fatigue,  but  the  fatigue  does 
not  extend  beyond  the  part  stimulated.  A  nerve  when  stimulated  mechanically  does  not  become  acid. 
Slight  pressure  without  tension  increases  the  excitability,  which  diminishes  after  a  short  time.  The 
mechanical  work  produced  by  an  excited  muscle  in  consequence  of  a  stimulus  was  loo  times  greater 
than  the  mechanical  energy  of  the  mechanical  nerve  stimulus. 

Continued  pressure  upon  a  mixed  nerve  paralyzes  the  motor  sooner  than  the 
sensory  fibres.  If  the  stimulus  be  applied  very  gradually,  the  nerv'e  may  be 
rendered  inexcitable  without  manifesting  any  signs  of  its  being  stimulated  (i^f^/z/^/^fsr, 
1758).  Paralysis,  due  to  continuous  pressure  gradually  applied,  may  occur  in 
the  region  supplied  by  the  brachial  nerves ;  the  left  recurrent  laryngeal  nerve 
also  may  be  similarly  paralyzed  from  the  pressure  of  an  aneurism  of  the  arch  of 
the  aorta. 

By  increasing  the  pressure  on  a  nerve  by  using  a  gradually  increasing  weight,  there  is  at  first  an 
increase  and  then  a  decrease  of  the  excitability.  Pressure  on  a  mixed  nerve  abolishes  reflex  con- 
duction sooner  than  motor  conduction  {Ki-oneckar  aiid  Zederbauin). 

Nerve  stretching  is  employed  for  therapeutical  purposes.  If  a  nerve  be  exposed  and  stretched, 
or  if  it  be  made  sufficiently  tense,  the  nerve  is  stimulated.  Slight  tension  increases  the  reflex  excita- 
bility [Sckleic/i],  while  violent  extension  produces  a  temporary  diminution  or  abolition  of  the 
excitability  (  Valentin).  The  centripetal  or  sensory  fibres  of  the  sciatic  nerve  are  sooner  paralyzed 
thereby  than  the  centrifugal  or  motor  [Conrad).  During  the  process  of  extension,  mechanical 
changes  are  produced,  either  in  the  nerve  itself  or  in  its  end  organs,  causing  an  alteration  of  the 
excitability,  but  it  may  also  affect  the  central  organs.  The  paralysis,  which  sometimes  occurs  after 
forcible  stretching,  usually  rapidly  disappears.  Therefore,  when  a  nerve  is  in  an  excessively  excita- 
ble condition,  or  when  this  is  due  to  an  inflammatory  fixation  or  constriction  of  the  nerve  at  some 
part  of  its  course,  nerve  stretching  may  be  useful,  partly  by  diminishing  the  excitability,  partly  by 
breaking  up  the  inflammatory  adhesions.  In  cases  where  stimulation  of  an  aflerent  ner\-e  gives  rise 
to  epileptic  or  teta7iic  spas??is,  nerve  stretching  may  be  useful  by  diminishing  the  excitability  at  the 
periphery,  in  addition  to  the  other  effects  already  described.  It  has  also  been  employed  in  some 
spinal  affections,  which  may  not  as  yet  have  resulted  in  marked  degenerative  changes. 


584  THERMAL    AND    CHEMICAL    STIMULL 

For  physiological  purposes,  a  nerve  may  be  stimulated  mechanically  by  means  of  Heidenhain's 
tetanomotor,  which  is  simply  an  ivory  hammer  attached  to  the  prolonged  spring  of  a  Neefs 
hammer  of  an  induction  machine.  [A  more  delicate  form  of  this  instrument  was  used  by  Tiger- 
stedt  (^  335)-]  1  he  rapid  vibration  of  the  hammer  communicates  a  series  of  mechanical  shocks  to 
the  nerve  upon  which  it  is  caused  to  beat.  Rhythmic  extension  of  a  nerve  causes  contractions  and 
even  tetanus. 

2.  Thermal  Stimuli. — If  a  frog's  nerve  be  heated  to  45°  C,  its  excitability  is 
first  increased  and  then  diminished.  The  higher  the  temperature,  the  greater  is  the 
excitability,  and  the  shorter  its  duration  (^Afanasieff).  If  a  nerve  be  heated  to 
50°  C.  for  a  short  time,  its  e.xcitabihty  and  conductivity  are  aboHshed.  The  frog's 
nerve  alone  regains  its  excitability  on  being  cooled  {Pickford).  If  the  tem]jerature 
be  raised  to  65°  C,  the  e.xcital)ility  is  abolished  without  the  occurrence  of  a  con- 
traction, while  its  medulla  is  broken  up  {Eckhard').  Sudden  cooling  of  a  nerve  to 
5°  C.  acts  as  a  stimulus,  causing  contraction  in  a  muscle,  while  sudden  heating  to 
40°  or  45°  C.  i)roduces  the  same  result.  If  the  temperature  be  increased  still  more, 
instead  of  a  single  contraction  a  tetanic  condition  is  produced.  All  such  rapid 
variations  of  temperature  quickly  exhaust  the  nerve  and  kill  it.  If  a  nerve  be  frozen 
gradually,  it  retains  its  excitability  on  being  thawed.  The  excitability  lasts  long  in 
a  cooled  nerwe.  ;  in  fact,  it  is  increased  in  a  motor  nerve,  but  the  contractions  are 
not  so  high  and  more  prolonged,  while  the  conduction  in  the  nerve  takes  place 
more  slowly.  Among  mammalian  nerves,  the  afferent  and  vaso-dilator  nerves  at 
45°  to  50°  C.  exhibit  the  results  of  stimulation,  while  the  others  only  show  a  change 
in  their  excitability.  When  cooled  to  +  5°  C,  the  excitability  of  all  the  fibres  is 
diminished  {Griifzner). 

3.  Chemical  Stimuli  excite  nerves  when  they  act  with  a  certain  rapidity,  and 
thereby  alter  the  condition  of  the  nerve  (p.  522).  Most  chemical  stimuli  act  by 
first  increasing  the  nervous  excitability,  and  then  diminishing  or  paralyzing  it. 
Chemical  stimuli,  as  a  rule,  have  less  effect  upon  \.\\t  sensory  than  upon  motor  fibres 
{Eckhard).  According  to  Griitzner,  the  inactivity  of  chemical  stimuli,  so  often 
observed  when  they  are  applied  to  sensory  nerves,  depends  in  great  part  upon  the 
non-simultaneous  stimulation  of  all  the  nerve  fibres.  Among  chemical  stimuli 
are  (a)  rapid  abstraction  0/ water  by  dry  air,  blotting  paper,  exposure  in  a  cham- 
ber containing  sulphuric  acid,  or  by  the  action  of  solutions  which  absorb  fluids, 
e.  g.,  concentrated  solutions  of  neutral  alkaline  salts  (NaCl,  excites  only  motor 
fibres  in  mammals— G^/'/V/sw^r),  sugar,  urea,  concentrated  glycerin  (and  ?  some 
metallic  saltsj.  The  subsequent  addition  of  water  may  abolish  the  contractions, 
while  the  nerve  may  still  remain  excitable.  The  abstraction  of  water  first  increases 
and  afterward  diminishes  the  excitability.  The  itnbibition  of  water  diminishes  the 
excitability,  {b)  Free  alkalies,  mineral  acids  (not  phosphoric),  many  organic  acids 
(acetic,  oxalic,  tartaric,  lactic),  and  most  salts  of  the  heavy  metals.  While  the 
acids  act  as  stimuli,  only  when  they  are  somewhat  concentrated,  the  caustic  alkalies 
act  in  solutions  of  0.8  to  o.i  per  cent.  {Ki'ihne).  Neutral  potash  salts,  in  a  con- 
centrated form,  rapidly  kill  a  nerve,  but  they  do  not  excite  it  nearly  so  strongly  as 
the  soda  compounds.  Dilute  solutions  of  the  neutral  potash  salts  first  increase  and 
afterward  diminish  it  {Ranke),  as  can  be  shown  by  stimulation  with  an  induction 
shock  {Biedermann).  (c)  Various  substances,  e.g.,  dilute  alcohol,  ether,  chloro- 
form, bile,  bile  salts,  and  sugar.  These  substances  usually  excite  contractions,  and 
afterward  rapidly  kill  the  nerve.  Ammonia,  lime  water,  some  metallic  salts,  carbon 
bisulphide,  and  ethereal  oils  kill  the  nerve  without  exciting  it — at  least  without  pro- 
ducing any  contraction  in  a  frog's  nerve-muscle  preparation.  [The  nerve  of  a  nerve- 
muscle  preparation  may  be  dipped  into  ammonia,  but  no  contraction  resirits,  while 
the  slightest  traces  of  ammonia  applied  to  a  muscle  cause  contraction.]  Carbolic 
acid  does  the  same,  although  when  applied  directly  to  the  spinal  cord  it  produces 
spasms.  These  substances  excite  the  muscles  when  they  are  directly  applied  to 
them.     Tannic  acid  does  not  act  as  a  stimulus  either  to  nerve  or  muscle.     As  a 


PHYSIOLOGICAL   AND    ELECTRICAL   STIMULI.  585 

general  rule,  the  stimulating  solutions  must  be  more  concentrated  vAitn  applied  to  a 
nerve  than  to  muscle,  in  order  that  a  contraction  may  be  produced. 

[Methods. — If  a  nerve-muscle  preparation  of  a  frog's  limb  be  made,  and  a  straw  flag  (p.  520) 
attached  to  the  toes  while  the  femur  is  fixed  in  a  clamp,  and  its  nerve  be  then  dipped  in  a  saturated 
solution  of  common  salt,  the  toes  soon  begin  to  twitch,  and  by  and  by  the  whole  limb  becomes  tetanic, 
and  thus  keeps  the  straw  flag  extended.  The  effect  of  fluid  on  a  muscle  or  nerve  is  easily  tested  by 
fixing  the  muscle  in  a  clamp,  while  a  drop  of  the  fluid  is  placed  on  a  greased  surface,  which  gives  it 
a  convex  form.  The  end  of  the  muscle  or  nerve  is  then  brought  into  contact  with  the  cupola  of  the 
•drop  [ICuhne)^] 

4.  The  Physiological  or  normal  stimulus  excites  the  nerves  in  the  normal 
intact  body.  Its  nature  is  entirely  unknown.  The  "  nerve  motion  "  thereby  set 
up  travels  either  in  a  "centrifugal"  or  outgoing  direction  from  the  central 
nervous  system,  giving  rise  to  motion,  inhibition  of  motion,  or  secretion ;  or  in  a 
*' centripetal "  or  ingoing  direction  from  the  ^.'ptci^c  end  organs  oi  tht  nerves 
of  the  special  senses  or  the  sensory  nerves.  In  the  latter  case,  the  impulse  reaches 
the  central  organs,  where  it  may  excite  sensation  or  perception,  or  it  may  be 
transferred  to  the  motor  areas  and  be  conducted  in  a  centrifugal  direction,  con- 
stituting a  "reflex"  stimulation  (§  360).  A  single  physiological  nerve  impulse 
travels  more  slowly  than  that  excited  by  the  momentary  application  of  an  induction 
shock  (^Loven,  v.  Kries).  It  is  not  a  uniform  process  excited  by  varying  intensity 
and  greater  or  less  frequency  of  stimulation,  but  it  is  essentially  a  process  varying 
considerably  in  duration,  and  it  may  even  last  as  long  as  y^  second  {v.  Kries). 

5.  Electrical  Stimuli. — [The  following  forms  of  electrical  stimuli  may  be 
used : — 

(i)  A  constant  current,  which  may  be  made  or  broken  (§  328). 

(2)  Induction  shocks,  either  make  or  break  shocks  (§  329), 

(3)  An  interrupted  current  (§  329).] 

The  electrical  current  acts  most  powerfully  upon  the  nerves  at  the  moment  when 
it  is  applied,  and  at  the  moment  when  it  ceases  (§  336)  ;  in  a  similar  way,  any 
increase  or  decrease  in  the  strength  of  a  constant  current  acts  as  a  stimulus.  If  an 
electrical  current  be  applied  to  a  nerve,  and  its  strength  be  very  gradually  increased 
or  diminished,  then  the  visible  signs  of  stimulation  of  the  nerve  are  very  slight. 
As  a  general  rule,  the  stimulation  is  more  energetic  the  more  rapid  the  variations 
of  the  strength  of  the  current  applied  to  the  nerve,  /.  e.,  the  more  suddenly  the 
intensity  of  the  stimulating  current  is  increased  or  diminished  {du  Bois-Reytnond'). 

An  electrical  current  mUst  have  a  certain  strength  or  liminal  intensity  before 
it  is  effective.  By  uniformly  increasing  the  strength  of  the  current,  the  size  of  the 
contraction  increases  rapidly  at  first,  then  more  slowly  (^Tigerstedi  and  Willhard'). 
■  An  electrical  current,  in  order  to  stimulate  a  nerve,  must  have  a  certain  dura- 
tion, it  must  act  at  least  during  0.0015  second  {Fick,  1863);  even  with  currents 
of  slightly  longer  duration,  the  opening  shock  may  have  no  effect.  If  the  duration 
of  the  closing  shock  of  a  constant  current  be  so  arranged  that  it  is  just  too  short  to 
be  active,  then  it  merely  requires  to  last  1.3  to  2  times  longer  to  produce  the  most 
complete  effect  (^Grunhagen). 

The  electrical  current  is  most  active  when  it  flows  in  the  long  axis  of  the  nerve; 
it  is  inactive  when  applied  vertically  to  the  axis  of  the  ntx^Q  {Galvani).  Similarly, 
muscles  are  incomparably  less  excited  by  transverse  than  by  longitudinal  currents 
(  Giuffre) . 

The  greater  the  length  of  nerve  traversed  by  the  current,  the  less  the  stimulus 
that  is  required  {P/aff). 

Constant  Current. — If  the  constant  current  be  used  as  a  nervous  stimulus,  the 
stimulating  effect  on  the  sensory  nerves  is  most  marked  at  the  moment  of  making 
and  breaking  the  current ;  during  the  time  the  current  passes,  only  slight  excite- 
ment is  perceived,  but,  even  under  these  circumstances,  very  strong  currents  may 
cause  very  considerable,  and  even  unbearable,  sensations.     If  a  constant  current  be 


586  UNEQUAL    EXCITABILITY. 

applied  to  a  motor  nerve,  the  greatest  effect  is  produced  when  the  current  is 
made  or  closed  [closing  or  make  contraction],  and  when  it  is  broken  or  opened 
[opening  or  break  contraction].  lUu  uliile  the  current  is  passing,  the  stimu- 
lation does  not  cease  complete]}-,  tor,  with  a  certain  strength  of  stimulus,  the  muscle 
remains  in  a  state  of  tetanus  (galvanotonus  or  "  closing  tetanus  ")  {Pfliiger). 
For  the  same  effect  on  muscles,  see  p.  532.  With  strong  currents  this  tetanus  does 
not  appear,  chiefly  because  the  current  diminishes  the  excitability  of  the  nerves, 
and  thusdevelojxs  resistance,  which  prevents  the  stimulus  from  reaching  the  muscle. 
According  to  Hermann,  a  descending  current  applied  to  the  nerve,  at  a  distance 
from  the  muscles,  causes  this  tetanus  more  readily,  while  an  ascending  current  causes 
it  more  readily  when  the  current  is  closed  near  the  muscle.  The  constant  current 
is  said  by  Griitzner  to  have  no  effect  on  vasomotor  and  secretory  fibres. 

Over-maximal  Contraction. — By  gradually  increasing  the  strength  of  the  electrical  stimulus 
applied  to  a  motor  nerve,  l-'ick  observed  that  the  muscular  contractions  (height  of  the  lift)  at  first 
increased  proportionally  to  the  increase  of  the  stimulus,  until  a  maximal  contraction  was  obtained. 
If  the  strength  of  the  stimulus  be  increased  still  further,  another  increase  of  the  contraction  above  the 
first-reached  maximum  is  obtained.  This  is  called  an  "over-maximal  contraction."  Occa- 
sionally between  the  first  maximum  and  the  second  there  is  a  diminution,  or  indeed  absence  of,  or 
gap  or  hiatus,  in  the  contractions.  The  cause  of  this  lies  in  the  positive  pole,  which  with  a  certain 
strength  of  current  is  sufficient  to  prevent  the  further  transmission  of  the  excitement  (^  335).  On 
continuing  to  increase  the  induction  current,  ultimately  a  stage  is  reached  where  the  stimulation  at  the 
negative  pole  again  becomes  stronger  than  the  inhibition  at  the  positive,  and  this  overcomes  the 
latter.  The  contractions  before  the  gap  are  caused  by  the  occurrence  of  the  induction  current  (their 
latent  period  is  short) ;  the  contractions  (long  latent  period,  like  that  after  all  opening  shocks — 
/Frt/A'r),  after  the  gap,  are  caused  by  the  disappearance  of  the  induction  current,  i.e.,  by  polarization; 
this  is  added  to  the  stimulation  proceeding  from  the  negative  pole,  which  after  the  gap  overcomes  the 
inhibition  at  the  positive  pole,  and  excites  the  over-maximal  contractions  ( Zi^g-^rj/^^/'/'  and  IVillhard). 

Tetanus. — If  single  shocks  of  short  duration  be  rapidly  applied  after  each  other 
to  a  nerve,  tetanus  in  the  corresponding  muscle  is  produced  (>^  298,  III). 

A  motor  nerve  has  a  greater  specific  excitability  for  electrical  stimuli  than  the 
muscle  substance.  This  is  proved  by  the  fact  that,  a  feebler  stimultis  suffices  to 
excite  a  muscle  when  applied  to  the  nerve  than  when  it  is  applied  to  the  mtiscle 
directly,  as  occurs  when  the  terminations  of  the  motor  nerves  are  paralyzed  by 
curara  (^Rosenthal). 

Soltmann  found  that  the  excitability  of  the  motor  nerves  of  new-born  animals 
for  electrical  stimuli  is  less  than  in  adults.  The  excitability  increases  until  the  5th 
to  loth  month. 

Unequal  Excitability. — Under  certain  circumstances,  the  nearer  the  part  of 
the  motor  nerve  stimulated  lies  to  the  central  nervous  system,  the  greater  is  the 
effect  produced  (contraction)  ;  [or  what  is  the  same  thing,  the  further  the  point  of 
a  nerve  which  is  stimulated  is  from  the  muscle,  the  stimulus  being  the  same,  the 
greater  is  the  contraction.  This  led  Pfliiger  to  his  "avalanche  theory,"  ;.  e.,  that 
the  "  nerve  motion  "  increases  in  the  nerve  as  it  passes  toward  the  muscles.  This 
effect  is  explained,  however,  by  the  unequal  excitability  of  different  parts  of  the 
sanie  nerve].  According  to  Fleischl,  all  parts  of  the  nerve  are  equally  excitable 
for  chemical  stimuli.  Further,  it  is  said  that  the  higher  placed  parts  of  a  nerve  are 
more  excitable  only  when  the  stimulating  current  passes  in  a  descending  direction ; 
the  reverse  is  the  case  when  the  current  ascends  (Hermann).  On  stimulating  a 
sensory  nerve,  Rutherford  and  Hallsten  found  that  the  reflex  contraction  was 
greater  the  nearer  the  stimulated  point  was  to  the  central  nervous  system. 

Unequal  Excitability  in  the  same  Nerve. — Nerve  fibres,  even  when  func- 
tionally the  same  and  included  in  the  same  nerve  trimk,  are  not  all  equally  excitable. 
Thus,  feeble  stimulation  of  the  sciatic  nerve  of  a  frog  catises  contraction  of  the  flexor 
muscles,  while  it  requires  a  stronger  stimulus  to  prodtice  contraction  of  the  extensors 
{Ritter,  1805,  Rollett).     According  to  Ritter,  the  nerves  for  the  flexors  die  first. 

Direct  stimulation  of  the  muscles  in  curarized  animals  shows  that  the  flexors  contract  with  a 
feebler  stimulus  (but  also  fatigue  sooner)  than  the   extensors;  the  pale  muscles  of  the  rabbit  are 


UNIPOLAR    STIMULATION    AND    NORMAL   NUTRITION.  587 

also  more  excitable  than  the  red.  As  a  rule,  poisons  affect  the  flexors  sooner  than  the  extensors. 
In  some  muscles  some  pale  fibres  are  present,  and  they  are  more  excitable  than  the  red 
[Grilizner)  (^  298).  If  a  frog's  nerve-muscle  preparation  be  exposed  to  the  action  of  ether, 
on  strong  stimulation  of  the  sciatic  nerve,  flexion  occurs  (^Griltzner,  Bowditch),  but  if  the  current 
be  made  stronger,  extension  takes  place.  During  deep  ether-narcosis,  strong  stimulation  of  the 
recurrent  nerve  causes  dilatation,  and  with  slight  narcosis,  narrowing  of  the  glottis  takes  place  ; 
dilatation  occurs  on  slight  stimulation  {^Bowditch).  The  adductor  muscle  of  the  claw  of  a  crayfish 
is  relaxed  under  a  weak  stimulus,  but  it  contracts  when  a  strong  stimulus  is  applied  to  it.  The 
reverse  is  the  case  with  the  muscle  which  opens  the  claw  [Biedermann). 

Unipolar  Stimulation. — Hone  electrode  of  an  induction  apparatus  be  applied 
to  a  nerve,  it  may  act  as  a  stimulus.  Du  Bois-Reymond  has  called  this  "unipolar 
induction  action."  It  is  due  to  the  movement  of  the  electrical  current  to  and 
from  the  free  ends  of  the  open  induction  current  at  the  moment  of  induction. 
[Unipolar  induction  is  more  apt  to  occur  with  the  opening  than  the  closing  shock, 
because  the  former  is  more  intense.] 

Upon  muscle,  electrical  stimuli  act  quite  as  they  do  upon  nerves.  Electrical 
currents  of  very  short  duration  have  no  effect  upon  muscles  whose  nerves  are 
paralyzed  by  curara  {Briicke),  and  the  same  is  true  of  greatly  fatigued  muscles,  or 
muscles  about  to  die  or  greatly  weakened  by  diseased  conditions  (§  399). 

325.  DIMINUTION  OF  THE  EXCITABILITY— DEGENERA- 
TION AND  REGENERATION  OF  NERVES.— i.  Normal  Nutri- 
tion.— The  continuance  of  the  normal  excitability  in  the  nerves  of  the  body 
depends  upon  the  maintenance  of  the  normal  nutrition  of  the  nerves  themselves 
and  a  due  supply  of  blood.  Insufficient  nutrition  causes,  in  the  first  instance, 
increased  excitability,  and  if  the  condition  be  continued  the  excitability  is 
diminished  (§  339,  I). 

When  the  physician  meets  with  the  signs  of  increased  excitability  of  the  nerves,  under  bad  or 
abnormal  conditions  of  nutrition,  this  is  to  be  regarded  as  the  beginning  of  the  stage  of  decrease 
of  the  nerve  energy.     Invigorating  measures  are  required. 

If  the  terminal  nervous  apparatus  be  subjected  to  a  temporary  disturbance  of  its 
nutrition,  the  return  of  the  normal  nutritive  process  is  heralded  by  a  more  or  less 
marked  stage  of  excitement.  The  more  excitable  the  nervous  apparatus,  the 
shorter  must  be  the  duration  of  the  disturbance  of  nutrition,  e.g.,  cutting  off 
the  arterial  blood  supply  or  interfering  with  the  respiration. 

2.  Fatigue. — Continued  excessive  stimulation  of  a  nerve,  without  sufficient 
intervals  of  repose,  causes  fatigue  of  the  nerve,  and  by  exhaustion  rapidly 
diminishes  the  excitability.  A  nerve  is  more  slowly  fatigued  than  a  muscle 
{^Bernstein),  but  it  recovers  more  slowly  (§  304).  [Nerves  of  cold-blooded  animals 
(  Widenskii)  and  mammals  {BowditcJi)  may  be  tetanized  for  hours  without  becoming 
fatigued.] 

[To  show  that  a  muscle  is  much  more  rapidly  fatigued  than  a  nerve,  Bernstein  arranged  two 
nerve-muscle  preparations  so  that  both  nerves  were  tetanized  simultaneously,  but  through  one  of 
the  nerves,  a  polarizing  constant  current  was  passed  by  means  of  non-polarizable  electrodes  (^  327), 
so  that  the  condition  of  anelectrotonus  (|  335)  was  set  up  in  this  nerve,  and  thus  "blocked"  the 
propagation  of  impulses  to  the  corresponding  muscle.  Only  one  muscle,  therefore,  was  tetanized. 
Both  nerves  were  continuously  stimulated  until  fatigue  of  the  contracting  muscle  took  place,  and  on 
breaking  the  polarizing  current  applied  to  the  other  nerve,  the  corresponding  muscle  at  once  became 
tetanic.  Now,  as  both  nerves  were  equally  stimulated,  and  the  muscle  in  connection  with  one  nerve 
was  fatigued,  while  the  other  muscle  at  once  contracted,  it  is  evident  that  a  muscle  is  much  more 
rapidly  fatigued  than  a  motor  nerve.  In  sensory  nerves,  fatigue  and  recovery  are  analogous  to  the 
corresponding  processes  in  motor  nerves  {^Bernstein). '\ 

Recovery. — When  a  nerve  recovers,  at  first  it  does  so  slowly,  then  more  rapidly, 
and  afterward  again  more  slowly.  If  recovery  does  not  occur  within  half  an  hour 
after  a  frog's  nerve  has  been  subjected  to  very  long  and  intense  stimulation,  it  will 
not  take  place  at  all. 

3.  Continued  inaction  of  a  nerve  diminishes,  and  may  ultimately  abolish 
the  excitability. 


588 


DEGENERATION    OF   NERVE    FIBRES. 


Thus,  the  central  ends  of  divided  sensory  nenes,  after  amputation  of  a  limb,  lose  their  excita- 
bility, although  the  nerves  are  still  connected  with  the  central  nervous  system,  because  the  end 
organs  through  which  they  were  normally  excited  have  been  removed. 

Fio.  377. 


Degeneration  and   regeneration  of  nerves.     A,  subdivision  of  the  myelin;  B,  further  disintegration  thereti 
(osmic  acid  staining)  ;  C,  interruption  of  the  axial  cylinder,  which  is  surrounded  with  the  broken-iip  ,j 
myelin;  D,  accumulation  of  nuclei,  with  the  remainder  of  the  myelin  in  a  spindle-shaped  fibre  ;   E,  a  ^ 
new  nerve  fibre,  with  a  new  sheath   of  Schwann,  sn,  within  the  old  sheath  of  Schwann,  sa;  F,  a  ncwj 
nerve  fibre  passing  in  a  cur\'ed  course  through  an  old  nerve  fibre  sheath. 


Fig.  378 


Diagram  of  the  roots  of  a  spinal  nerve,  showing  the  effect  of  section  (the  black  parts  represent  the  degenerated  parts). 
A,  section  of  the  nerve  trunk  beyond  the  ganglion;  B,  of  the  anterior  root,  and  C,  of  the  posterior;  D,  excision 
of  the  ganglion;  a,  anterior,/,  posterior  root;  ^,  ganglion. 

4.  Separation  from  their  Nerve  Centres. — The  nerve  fibres  remain  in  a 
condition  of  normal  nutrition,  only  when  they  are  directly  connected  with  their 
centre,  which  governs  the  nutritive  processes  within  the  nerve.  If  a  nerve 
within  the  body  be  separated  from  its  "  nutritive  centre  " — either  by  section 


TRAUMATIC  AND  FATTY  DEGENERATION.  589 

of  the  nerve  or  compressing  it — within  a  short  time  it  loses  its  excitability,  and 
XhQ peripheral  &r\6.  undergoes  fatty  degeneration,  which  begins  in  four  to  six  days 
in  warm-blooded  animals,  and  after  a  long  time  in  cold-blooded  ones  {/oh.  Millie?'^. 
See  also  the  changes  of  the  excitability  during  this  condition,  the  so-called 
"  Reaction  of  degeneration  "  (§  339).  If  the  sefisory  nerve  fibres  of  the  root 
of  a  spinal  nerve  be  divided  on  the  central  side  of  the  ganglion,  the  fibres  on  the 
peripheral  side  do  not  degenerate,  for  the  ganglion  is  the  trophic  or  nutritive 
centre  for  the  sensory  nerves ;  but  the  fibres  still  in  connection  with  the  cord 
degenerate  (  Waller^. 

[Wallerian  Law  of  Degeneration. — If  a  spinal  nerve  be  divided,  the 
peripheral  part  of  the  nerve  and  its  branches,  including  the  sensory  and  motor 
fibres,  degenerate  completely  (Fig.  378,  A),  while  the  central  parts  of  the  nerve 
remain  unaltered.  If  the  anterior  root  of  a  spinal  nerve  alone  be  divided  before 
it  joins  the  posterior  root,  all  the  peripheral  nerve  fibres  connected  with  the 
anterior  root  degenerate  (Fig.  378,  B),  so  that  in  the  nerve  of  distribution  only 
the  motor  fibres  degenerate.  The  portion  of  the  nerve  root  which  remains 
attached  to  the  cord  does  not  degenerate.  If  tht  posterior  root  alone  be  divided, 
between  the  spinal  cord  and  the  ganglion,  the  effect  is  reversed,  the  part  of  the 
nerve  root  lying  between  the  section  and  the  spinal  cord  degenerates,  while  the 
part  of  the  nerve  connected  with  the  ganglion  does  not  degenerate  (Fig.  378,  C). 
The  central  fibres  degenerate  because  they  are  separated  from  the  ganglion.  If 
the  ganglion  be  excised,  or  if  separated,  as  in  Fig.  378,  D,  both  the  central  and 
peripheral  parts  of  the  posterior  root  degenerate.  These  experiments  of  Waller 
show  that  the  fibres  of  the  anterior  and  posterior  roots  are  governed  by  different 
centres  of  nutrition  or  "trophic  centres."  As  the  anterior  root  degenerates 
when  it  is  separated  from  the  cord,  and  the  posterior  when  it  is  separated  from  its 
own  ganglion,  it  is  assumed  that  the  trophic  centre  for  the  fibres  of  the  anterior 
root  lies  in  the  multipolar  nerve  cells  of  the  anterior  horn  of  the  gray  matter  of 
the  spinal  cord,  while  that  for  the  fibres  of  the  posterior  root  lies  in  the  cells  of 
the  ganglion  placed  on  it.  The  nature  of  this  supposed  trophic  influence  is 
entirely  unknown.] 

Traumatic  and  Fatty  Degeneration. — Both  ends  of  the  nerve  at  this  point  of  section  imme- 
diately begin  to  undergo  "  traumatic  degeneration."  (In  the  frog  on  the  1st  and  2d  day.) 
After  a  time  neither  the  myehn  nor  axis  cylinder  is  distinguishable  {^Schiff').  According  to  Engel- 
mann,  this  condition  extends  only  to  the  nearest  node  of  Ranvier,  and  afterward  the  so-called  "  fatty 
degeneration"  begins.  The  process  of  '■^ fatty"  degeneration  begins  simultaneously  in  the  whole 
peripheral  portion;  the  white  substance  of  Schwann  breaks  up  into  masses  (Fig.  377,  A),  just  as  it 
does  after  death,  in  microscopic  preparations ;  afterward,  the  myelin  forms  globules  and  round 
masses  (B),  the  axial  cylinder  is  compressed  or  constricted,  and  is  ultimately  broken  across  (C)  in 
many  places  (7th  day).  The  nerve  fitire  seems  to  break  up  into  two  substances — one  fatty,  the  other 
proteid  in  constitution,  the  fat  being  absorbed  (.S".  A'layer).  The  nuclei  of  Schwann's  sheath  swell 
up  and  proliferate  (D — until  the  loth  day).  According  to  Ranvier,  the  nuclei  of  the  inter-annular 
segments  and  their  surrounding  protoplasm  proliferate,  and  ultimately  interrupt  the  continuity'  of  the 
axis  cylinder  and  the  myelin.  They  then  undergo  considerable  development  with  simultaneous  dis- 
appearance of  the  medulla  and  axis  cylinder,  or  at  least  fatty  substances  formed  by  their  degeneration, 
so  that  the  nerve  fibres  look  like  fibres  of  connective  tissue.  [According  to  this  view,  the  process  is 
in  part  an  active  one,  due  to  the  growth  of  the  nerve  corpuscles  breaking  up  the  contents  of  the 
neurilemma,  which  then  ultimately  undergo  chemical  degenerative  changes.]  According  to  Ranvier, 
Tizzoni,  and  others,  leucocytes  wander  into  tlie  cut  ends  of  the  nerves,  and  also  at  Ranvier's  nodes, 
insinuating  themselves  into  the  nerve  fibres,  where  they  take  myelin  into  their  bodies,  and  subject  it 
to  certain  changes.  [These  cells  are  best  revealed  by  the  action  of  osmic  acid,  which  blackens  any 
myehn  particles  in  their  interior.]  Degeneration  also  takes  place  in  the  motorial  end  plates,  begin- 
ning first  in  the  non-meduUated  branches,  then  in  the  terminal  fibrils,  and  lastly  in  the  nerve  truaks 
( Gessle}-) . 

Regeneration  of  Nerves. — In  order  that  regeneration  of  a  divided  nerve  may  take  place 
{Cridckshank,  1795),  the  divided  ends  of  the  nerve  must  be  brought  into  contact  (|  244).  In  man 
this  is  done  by  means  of  sutures.  About  the  middle  of  the  fourth  week,  small  clear  bands  appear 
within  the  neurilemma,  winding  between  the  nuclei  and  the  remains  of  the  myelin  (E).  They  soon 
become  wider,  and  receive   myelin  with  incisures,  and  nodes,  and  a   sheath  of  Schwann  (2d  to  3d 


590  TROPHIC    CENTRES    AND    MODIFYING    CONDITIONS. 

month — F),  The  regeneration  process  takes  place  in  each  inter-annular  segment,  while  the  individual 
segments  unite  end  to  end  at  the  nodes  of  Kanvier  (§  321,  I,  5).  On  this  view,  each  nerve  segment 
of  the  fibre  corresponds  to  a  "  cell  unit"  (A'.  A'eur/iann,  Eichhorst').  The  same  process  occurs  in 
nerves  ligatured  in  their  course.  Sereral  new  fibres  may  be  formed  within  one  old  nerve  sheath. 
The  divided  axis  cylinders  of  the  crntrit/  end  of  the  nerve  begin  to  grow  about  the  I4ih  day,  until 
they  meet  the  newly  ft)nned  ones,  with  which  they  unite. 

[Primary  and  Secondary  Nerve  Suture. — Numerous  experiments  on  anim.ils  and  man  have 
established  the  fact  that,  immediate  or  primary  suture  of  a  nerve,  after  it  is  divided,  either 
accidentally,  or  intentionally,  hastens  reunion  and  regeneration,  and  accelerates  the  restoration  of 
function.  Secondary  suture,  i.  e.,  bringing  the  ends  together  long  after  the  nerve  has  been 
divided,  has  been  jiracticed  with  success.  Surgeons  have  recorded  cases  where  the  function  was 
restored  after  dividon  had  taken  place  for  3  to  16  months,  and  even  longer,  and  in  most  cases  the 
sensibility  was  restored  first,  the  average  time  being  2  to  4  weeks.  Motion  is  recovered  much 
later.  The  ends  of  the  nerve  should  be  stitched  to  each  other  with  catgut,  the  muscles  at  the  same 
time  being  kept  from  becoming  atrophied  by  electrical  stimulation  and  the  systematic  use  of  massage 
(?  307).  After  suture  of  a  nerve,  conductivity  is  restored  in  the  ral)bit  in  40  days,  on  the  31st  in 
dogs,  and  25th  in  fowls,  but  after  simple  division  without  suture,  not  until  the  60th  day  in  the  rabbit. 
Transplantation  of  nerve  does  not  succeed  {Johnson).'] 

Union  of  Nerves. — The  central  end  of  a  divided  motor  nerve  may  unite  with  the  peripheral  end 
of  another,  and  still  conduct  impulses  {/\ava).  [It  is  stated  that  sensory  fibres  will  reunite  with 
sensory  fibres,  and  motor  fibres  with  motor  fibres,  and  the  regenerated  nerve  will,  in  the  former  case, 
conduct  sensory  impulses,  and  the  latter  motor  impulses.  There  is  very  considerable  diversity  of 
opinion,  however,  as  to  the  regeneration  or  union  of  sensory  with  motor  fibres.  Paul  Bert  made  the 
following  experiment :  He  stitched  the  tail  of  a  rat  into  the  animal's  back,  and  after  union  had  taken 
place,  he  cut  the  tail  from  the  body  at  the  root,  so  that  the  tail,  as  it  were,  grew  out  of  the  animal's 
back,  broad  end  upjiermost.  On  irritating  the  end  of  the  tail,  which  was  formerly  the  root,  the 
animal  gave  signs  of  pain.  This  experiment  was  devised  by  Bert  to  try  to  show  that  nerve  fibres 
can  conduct  impulses  in  both  directions.  One  of  two  things  must  have  occurred.  Either  the  motor 
fibres,  which  normally  carried  impulses  down  the  tail,  now  convey  them  in  the  opposite  direction, 
and  convey  them  to  sensory  fibres  with  which  they  have  united  ;  or  the  sensory  fibres,  which  normally 
conducted  impulses  from  the  tip  upward,  now  carrying  them  in  the  opposite  direction.  If  the 
former  were  actually  what  happened,  it  would  show  that  nerve  fibres  of  different  function  do  unite 
(?  349).  Reichert  asserts  that  he  has  succeeded  in  uniting  the  hypoglossal  with  the  vagus  in  the  dog. 
According  to  Gessler  the  end  plate  is  the  first  to  regenerate.] 

Trophic  Centres. — The  regeneration  of  the  nerves  seems  to  take  place  under 
the  influence  of  the  nerve  centres,  which  act  as  their  nutritive,  or  trophic  centres. 
Nerves  permanently  separated  from  these  centres  never  regenerate. 

During  the  regeneration  of  a  mixed  nerve,  sensibility  is  restored  first,  subse- 
quently voluntary  motion,  and  lastly  the  movements  of  the  muscles,  when  their 
motor  nerves  are  stimulated  directly  {Schiff,  Erb,  v.  Ziemssen). 

Wallerian  Method  of  Investigation. — As  \.\it  peripheral  er\A^  of  a  nerve  undergoes  degenera- 
tion after  section,  we  use  this  method  for  determining  the  course  of  nerve  fibres  in  a  complex  arrange- 
ment of  nerves.  The  course  of  special  nerve  fibres  may  be  ascertained  by  tracing  the  degeneration 
tract  {IValler).  If  after  section,  reunion  or  regeneration  of  a  motor  nerve  does  not  take  place,  the 
muscle  supplied  by  this  nerve  ultimately  undergoes  fatty  degeneration. 

5.  Modifying  Conditions. — Under  the  action  of  various  operations,  e.  g., 
compresshigdi  nerve  [so  as  not  absolutely  to  sever  the  physiological  continuity],  it 
has  been  found  that  voluntary  impulses  or  stimuli  applied  above  the  compressed 
spot,  give  rise  to  impulses  which  are  conducted  through  the  nene,  and  in  the  case 
of  a  motor  nerve,  cause  contraction  of  the  muscles,  while  the  excitability  of  the 
parts  below  the  injured  spot  is  greatly  diminished  {Sclu'ff).  In  a  similar  manner,  it 
is  found  that  the  nerves  of  animals  poisoned  with  COj,  curara  orconiin,  sometimes 
even  the  nerves  of  paralyzed  limbs  in  man,  are  not  excitable  to  direct  stimuli, 
while  they  are  capable  of  conducting  impressions  coming  from  the  central  nervous 
system  {Duchenne).  The  injured  part  of  the  nerve,  therefore,  loses  its  excitability 
sooner  than  its  power  of  conducting  an  impulse. 

6.  Certain  poisons,  such  as  veratrin,  at  first  increase  the  excitability  of  the 
nerves,  and  afterward  abolish  it ;  with  some  other  poisons,  the  abolition  of  the 
excitability  passes  off  very  rapidly,  e.g.,  curara.  Conium,  cynoglossum,  iodide 
of  methylstrychnin,  and  iodide  of  jethylstrychnin  have  a  similar  action. 


RITTER-VALLI    LAW   AND    ELECTRO-PHYSIOLOGY.  591 

If  the  nerve  or  muscle  of  a  frog  be  placed  in  a  solution  of  the  poison,  we  obtain  a  different  effect 
from  that  which  results  when  the  poison  is  injected  into  the  body  of  the  animal.  Atropin  diminishes 
the  excitability  of  a  nerve-muscle  preparation  of  the  frog  without  causing  any  previous  increase,  while 
alcohol,  ether,  and  chloroform  increase  and  then  diminish  the  excitabihty  i^Mqmtnseti). 

7.  Ritter-Valli  Law. — If  a  nerve  be  separated  from  its  centre,  or  if  the 
centre  die,  the  excitability  of  the  nerve  is  increased ;  the  increase  begins  at  the 
central  end,  and  travels  toward  the  periphery — the  excitability  then  falls  until  it 
disappears  entirely.  This  process  takes  place  more  rapidly  in  the  central  than  in 
the  peripheral  part  of  the  nerve,  so  that  the  peripheral  end  of  a  nerve  separated 
from  its  centre  remains  excitable  for  a  longer  time  than  the  central  end. 

The  rapidity  of  the  transmission  of  impulses  in  a  nerve  is  increased  when  the  excitability  is 
increased,  but  it  is  lessened  when  the  excitability  is  diminished.  In  the  latter  condition,  an  electrical 
stimulus  must  last  longer  in  order  to  be  effective ;  hence  rapid  induction  shocks  may  not  produce 
any  effect. 

The  law  of  contraction  also  undergoes  some  modification  in  the  different  stages  of  the  changes  of 
excitabihty  (|  336,  II). 

8.  Excitable  Points. — Many  nerves  are  more  excitable  at  certain  parts  of  their 
course  than  at  others,  and  the  excitability  may  last  longer  at  these  parts.  One  of 
these  parts  is  the  upper  third  of  the  sciatic  nerve  of  a  frog,  just  where  a  branch  is 
given  off  {Budge'). 

The  motor  and  sensory  fibres  of  the  upper  third  of  the  sciatic  nerve  of  a  frog  are  more  excitable 
for  all  stimuli  than  the  lower  parts  {^Gri'ttzner  and  Elpon).  Whether  this  arises  from  injury  during 
preparation  (a  branch  is  given  off  there),  or  is  due  to  anatomical  conditions,  eg.,  more  connective 
tissue  and  more  nodes  in  the  lower  part  of  the  sciatic,  is  undetermined  i^Clara  Halperson). 

This  increased  excitability  may  be  due  to  injur}'  to  the  nerve  in  preparing  it  for  experiment.  After 
section  or  compression  of  a  nerve,  all  electrical  currents  employed  to  stimulate  the  nerve  are  far  more 
active  when  the  direction  of  the  current  passes  away  from  the  point  of  injury,  than  when  they  pass 
in  the  opposite  direction.  This  is  due  to  the  fact,  that  the  current  produced  in  the  nerve  after  the 
lesion  is  added  to  the  stimulation  current  (|  331,  5).  Even  in  intact  nerves — sciatic  of  a  frog — where 
the  nerve  ends  at  the  periphery  or  at  the  centre,  or  where  large  branches  are  given  off,  there  are 
points  which  behave  in  the  same  way  as  those  points  where  a  lesion  has  taken  place  {^Grutzner  and 
Moschner') . 

Death  of  a  Nerve. — In  a  dead  nerve  the  excitability  is  entirely  abolished, 
death  taking  place  according  to  the  Ritter-Valli  Law,  from  the  centre  toward  the 
periphery.  The  reaction  of  a  dead  nerve  has  been  found  by  some  observers  to 
he  acid  (§  322). 

The  functions  of  the  brain  cease  immediately  death  takes  place,  while  the  vital  functions  of  the 
spinal  cord,  especially  of  the  white  matter,  last  for  a  short  time;  the  large  nerve  trunks  gradually 
die,  then  the  nerves  of  the  extensor  muscles,  those  of  the  flexors  after  three  to  four  hours ;  while  the 
sympathetic  fibres  retain  their  excitability  longest,  those  of  the  intestine  even  for  ten  hours  [Onimns). 
Compare  §  295.  The  nerves  of  a  dead  frog  may  remain  excitable  for  several  days,  provided  the 
animal  be  kept  in  a  cool  place. 

Electro-Physiology. — Before  beginning  the  study  of  electro-physiology,  the 
student  ought  to  read  and  study  carefully  the  following  short  preliminary  remarks 
on  the  physics  of  this  question : — 

326.  PHYSICAL— THE  GALVANIC  CURRENT— RHEOCORD.  —  i.  Electro- 
motive Force. — If  two  of  the  under-mentioned  bodies  be  brought  into  direct  contact,  in  one  of  them 
positive  electricity,  and,  in  the  other,  negative  electricity  can  be  detected.  The  cause  of  this  phe- 
nomenon is  the  electro-motive  force.  The  electro-motive  substances  may  be  arranged  in  a  series  of 
the  first  class,  so  that  if  the  first-mentioned  substance  be  brought  into  contact  with  any  of  the  other 
bodies,  the  first  substance  is  negatively,  the  last  positively,  electrified.  This  series  is  :  carbon,  plati- 
num, gold,  silver,  copper,  iron,  tin,  lead,  zinc  +  . 

The  amount  of  the  electro-motive  force  produced  by  the  contact  of  two  of  these  bodies  is  greater, 
the  further  the  bodies  are  apart  in  the  series.  The  contact  of  the  bodies  may  take  place  at  one  or 
more  points.  If  several  of  the  bodies  of  this  series  be  arranged  in  a  pile,  the  electrical  tension  thereby 
produced  is  just  as  great  as  if  the  two  extreme  bodies  were  brought  into  contact,  the  intermediate 
ones  being  left  out. 

2.  The  nature  of  the  two  electricities  is  readily  determined  by  placing  one  of  the  bodies  of  the 
series  in  contact  with  a  fluid.     If  zinc  be  placed  in  pure   or  acidulated  water,  the  zinc  is  -|-  (posi- 


592  ohm's  law,  strength  and  density  of  galvanic  currents. 

live)  and  the  water  —  (negative).  If  copper  be  taken  instead  of  zinc,  the  copper  is  -f  but  the 
fluid  — .  Experiment  shows  that  those  metals,  in  contact  with  fluid,  are  negatively  electrified  most 
strongly  which  are  most  acted  on  chemically  by  the  fluid  in  whicli  they  are  placed.  Each  such  com- 
bination affords  a  constant  difference  of  tension  or  potential.  The  tension  [or  jiower  of  overcoming 
resistance]  of  the  amount  of  electricity  obtained  from  both  bodies  depends  upon  the  size  of  the  sur- 
faces in  contact.  The  fluids,  i-.  j,--.,  the  solutions  of  acids,  alkalies,  or  salts,  are  called  exciters  of 
electricity  of  the  second  class.  They  do  not  form  among  themselves  a  definite  series  with  different 
tensions.  When  placed  in  these  fluids,  the  metals  lying  next  the  -)-  end  of  the  above  scries,  espe- 
cially zinc,  are  most  strongly  electrified  negatively,  and  to  a  less  extent  those  lying  nearer  the  —  end 
of  the  series. 

3.  Galvanic  Battery. — If  two  different  exciters  of  the  first  class  be  placed  in  fluid,  without  the 
bodies  coming  into  contact,  e.g.,  zinc  and  copper,  the  projecting  end  of  the  (negative)  zinc  shows 
free  negative  electricity,  while  the  free  end  of  the  (jxjsitive)  copper  shows  free  positive  electricity. 
Such  a  combination  of  two  electro- motors  of  the  first  class  with  an  electromotor  of  the  second  class 
is  called  z.  galvanic  bailery.  As  long  as  the  two  metals  in  this  fluid  are  kept  se[)arate,  the  circuit  is 
said  to  be  broken  or  open,  but  as  soon  as  the  free  projecting  ends  of  the  metals  are  connected  outside 
the  fluid,  e.  g.,  by  a  copper  wire,  the  circuit  or  current  is  tnaiieox  closed,  and  a  galvanic  or  constant 
current  of  electricity  is  obtained.  The  galvanic  current  has  resistance  to  encounter  in  its  course, 
which  is  called  "  coHt/iic/ion  resislance"  (W).  It  is  directly  proportional  (l)  to  the  length  (/)  of 
the  circuit ;  (2)  and  with  the  same  length  of  circuit,  inversely  as  the  section  (r/)  of  the  same ;  and 
(3)  it  also  depends  on  the  molecular  properties  of  the  conducting  material  {specific  conduction 
resistance  ^  s),  so  that  the  conduction  resistance,  W^  (5.  /)  :  q.  The  resistance  to  conduction 
increases  with  the  increase  of  the  temperature  of  the  metals,  but  diminishes  under  similar  conditions 
with  fluids. 

Ohm's  Law. — The  strength  of  a  galvanic  current  (S),  or  the  amount  of  electricity  passing  through 
the  closed  circuit,  is  proportional  to  the  electro-molive  force  (E) — or  the  electrical  tension,  but 
inversely  proportional  to  the  total  resistance  to  conduction  (L) — 

So  that  S  =  E  :  L  (Ohm's  Law,  1827). 

The  total  resistance  to  conduction,  however,  in  a  closed  circuit  is  composed  of  (i)  the  resistance 
outside  the  battery  ("  extraordinary  resistance") ;  and  (2)  the  resistance  within  the  battery  itself 
("essential  resistance").  The  specific  resistance  to  conduction  is  very  variable  in  different  sub- 
stances; it  is  relatively  small  in  metals  {e.  g.,  for  copper^  i,  iron  =  6.4,  Gennan  silver  =  12), 
but  very  great  in  fluids  {e.g.,  for  a  concentrated  solution  of  common  salt  6,515,000,  for  a  concen- 
trated solution  of  copper  sulphate  10,963,600). 

Conduction  in  Animal  Tissues. — It  is  also  very  great  in  animal  tissues,  almost  a  million 
times  greater  than  in  metals.  When  a  constant  current  is  applied  to  the  skin  so  as  to  traverse  the 
body,  the  resistance  diminishes  because  of  the  conduction  of  water  in  the  epidermis  under  the  action 
of  the  constant  current  (|  290),  and  the  congestion  of  the  cutaneous  blood  vessels  in  consequence 
of  the  stimulation.  But  the  resistance  varies  in  different  parts  of  the  skin,  the  least  being  in  the 
palm  of  the  hand  and  sole  of  the  foot.  The  chief  seat  of  the  resistance  is  the  epidermis,  for  after 
its  removal  by  means  of  a  bli.ster,  the  resistance  is  greatly  diminished.  Dead  tissue,  as  a  rule,  is  a 
worse  conductor  than  living  tissues  {Jolly').  When  the  current  is  passed  transversely  to  the  direc- 
tion of  the  fibres  of  a  muscle,  the  resistance  is  nearly  nine  times  as  great  as  when  the  current  passes 
in  the  direction  of  the  fibres — a  condition  which  disappears  in  rigor  mortis  {Hermann).  In  nerves, 
the  resistance  longitudinally  is  two  and  a  half  million  times  greater  than  in  mercury,  transversely 
about  twelve  million  times  greater  {Hermann).  Tetanus  and  rigor  mortis  diminish  the  resistance 
in  muscle  {Du  Bois-Keymond). 

Deductions. — It  follows  from  Ohm's  law  that — I.  If  there  is  very  great  resistance  to  the  current 
outside  the  battery  [?'.  e.,  between  the  electrodes],  as  is  the  case  when  a  nerve  or  a  muscle  lies  on  the 
electrodes,  the  strength  of  the  current  can  only  be  increased  by  increasing  the  number  of  the  electro- 
motive elements.  II.  When,  however,  the  extraordinary  resistance  is  very  small  compared  with 
that  within  the  battery  itself,  the  strength  of  the  current  cannot  be  increased  by  increasing  the 
number  of  the  elements,  l)ut  only  by  increasing  the  surfaces  of  the  plates  in  the  battery. 

Strength  and  Density. — We  must  carefully  distinguish  the  strength  (intensity)  of  the  current 
from  its  density.  As  the  same  amount  of  electricity  always  flows  through  any  given  transverse 
section  of  the  circuit,  then,  if  the  size  of  the  transverse  section  of  the  circuit  varies,  the  electricity 
must  be  of  greater  density  in  the  narrower  parts,  and  it  is  evident  that  the  density  will  be  less  where 
the  transverse  section  is  greater.  Let  S  =  the  strength  of  the  current,  and  q  the  transverse  section 
of  the  given  part  of  the  circuit,  then  the  density  {d)  at  the  latter  part  is  ^  =  S  :  ^. 

If  the  galvanic  current  passing  from  the  positive  pole  of  a  battery  is  divided  into  two  or  more 
streams,  which  are  again  reunited  at  the  other  pole,  then  the  sum  of  the  strength  of  all  the  streams 
is  equal  to  the  strength  of  the  undivided  stream.  If,  however,  the  difterent  streams  are  different  as 
regards  length,  section  and  material,  then  the  strength  of  the  current  passing  in  each  of  the  streams 
is  inversely  proportional  to  the  resistance  to  the  conduction. 

Du  Bois-Reymond's  Rheocord. — This  instrument,  constructed  on  the  principle  of  the 
"secondary"  or  "  short  circuit,"  enables  us  to  graduate  the  strength  of  a  galvanic  current  to  any 


RHEOCORD GALVANOMETER. 


593 


required  degree,  for  the  stimulation  of  nerve  and  muscle.     From  the  two  poles  (Fig.  379,  a,  b)  of  a 

constant  battery,  there  are  two   conducting  wires  {a,  c  and  d,  b),  which  go  to  the  nerve  of  a  frog's 

nerve-muscle  preparation  (F).     The  portion  of  nerve  (c,  d^  introduced  into  this  circuit  {a,  c,  d,  b) 

ofiers  very  great  resistance.     The  second  stream  or  secondary  circuit  (a  A,  b  B)  conducted  from  a 

and  b  passes  through  a  thick  brass  plate  (A,  B),  consisting  of  seven  pieces  of  brass  (l  to  7)  placed 

end  to  end,  but  not  in  contact.     They  can  all,  with  the  exception  of  i   and  2,  be  made   to   form  a 

continuous  conductor  by  placing  in  the  spaces  between  them  the  brass  plugs  (Sj  to  S5).     Evidently, 

with  the  arrangement  shown  in  Fig.  379,  only  a  minimal  part  of  the  current  will  pass  through  the 

nerve  {c,  a),  owing  to  the  very  great  resistance  in  it,  while  by  far  the  gi-eatest  part  will  pass  through 

the  good  conducting  medium  of  brass  (A,  L,  B).     If  new  resistance  be  introduced  into  this  circuit, 

then  the  a,  c,  d,  b  stream  will  be  strengthened.     This  resistance  can  be  introduced  into  the  latter 

circuit  by  means  of  the  thin  wires  marked  \  a,\b,  I  <;-,  II,  V,  X.     Suppose  all  the  brass  plugs  from 

Sj  to  Sg  to  be  removed,  then  the  current  entering  at  A  must 

traverse  the  whole  system  of  thin  wires.     Thus,  there  is  more 

resistance  to  the  passage  of  this  current,  so  that  the  current 

through  the  nerve  must  be  strengthened.     If  only  one  brass 

plug  be  taken  out,  then  the  current  passes  through  only  the 

corresponding  length  of  wire.     The  resistances  offered  by  the 

different  lengths  of  wire  from   I  a   to  X  are  so  arranged  that 

\  a,\  b   and  I  c  each  represents  a  unit  of  resistance ;    II, 

double ;  V,  five  times ;  and  X,  ten  times  the  resistance.     The 

length  of  wire,  I  a,  can  also  be  shortened  by  the  movable 

bridge  (L)  [composed  of  a  small  tube  filled  with  mercury, 

through  which  the  wires  pass],  the  scale  [x,  y)  indicating  the 

length  of  the  resistance  wires.     It  is  evident  that,  by  means  of 

the  bridge,  and  by  the  method  of  using  the  brass  plugs,  the 

apparatus  can  be  graduated  to  yield  very  variable  currents  for 

stimulating  nerve  or  muscle.     When  the  bridge  (L)  is  pushed 

hard  up  to  i  and  2,  the  current  passes  directly  from  A  to  B, 

and  not  through  the  thin  wires  (I  a). 

The  rheostat  is  another  instrument  used  to  vary  the  resist- 
ance of  a  galvanic  current  ( IVheatstone). 

327.  ACTION  OF  THE  GALVANIC  CURRENT 
ON  A  MAGNETIC  NEEDLE— GALVANOME- 
TER.— In  1820,  Oerstedt,  of  Copenhagen,  found  that  a 
magnetic  needle,  suspended  in  the  magnetic  meridian,  was 
deflected  by  a  constant  current  of  electricity  passed  along  a 
wire  parallel  to  it.  [The  side  to  which  the  north  pole  is 
deflected  depends  upon  the  direction  of  the  current,  and 
whether  it  passes  above  or  below  the  needle.] 

Ampere's  Rule. — Ampere  has  given  a  simple  rule  for 
determining  the  direction.  If  an  observer  be  placed  parallel 
to  and  facing  the  needle,  and  if  the  current  be  passing  from 
his  feet  to  his  head,  then  the  north  pole  of  the  needle  will 
always  be  deflected  to  the  left,  and  the  south  pole  in  the  oppo- 
site direction.  The  effect  exerted  by  the  constant  current  acts 
always  in  a  direction  toward  the  so-called  electro-magnetic 
plane.  The  latter  is  the  plane  passing  through  the  north 
pole  of  the  needle,  and  two  points  in  the  straight  wire  running  parallel  with  the  needle.  The  force 
of  the  constant  current,  which  causes  the  deflection  of  the  magnetic  needle,  is  proportional  to  the 
sine  of  the  angle  between  the  electro-magnetic  plane  and  the  plane  of  vibration  of  the  needle. 

Multiplicator. — The  deflection  of  the  needle  caused  by  the  constant  current  may  be  increased  by 
coiling  the  conducting  wire  many  times  in  the  same  direction  on  a  rectangular  frame,  or  merely 
around  and  in  the  same  direction  as  the  needle  [provided  that  each  tmn  of  the  wire  be  properly 
insulated  from  the  other].  An  instrument  constructed  on  this  principle  is  called  a  multiplicator  or 
multiplier.  The  greater  the  number  of  turns  of  the  wire,  the  greater  is  the  angle  of  deflection  of  the 
needle,  although  the  deflection  is  not  directly  proportional,  as  the  several  turns  or  coils  are  not  at 
the  same  distance  from,  or  in  the  same  position  as,  the  needle.  By  means  of  the  multiplier  we  may 
detect  the  presence  [and  also  the  amount  and  direction]  of  feeble  currents.  [The  instrument  is  now 
termed  a  galvanometer.]  Experience  has  shown  that,  when  great  resistance  (as  in  animal  tis- 
sues) is  opposed  to  the  weak  galvanic  currents,  we  must  use  a  very  large  number  of  turns  of  thin 
wire  round  the  needle.  If,  however,  the  resistance  in  the  circuit  is  butsmall,  ^.^.,in  thermo-electrical 
arrangements,  a  few  turns  of  a  thick  wire  round  the  needle  are  sufficient.  The  multiplier  may  be 
made  more  sensitive  by  weakening  the  magnetic  directive  force  of  the  needle,  which  keeps  it  pointing 
to  the  north. 

38 


Scheme  of  du  Bois-Reymond's  rheocord. 


594 


GALVANOMETER. 


Galvanometer  and  Astatic  Needles. — In  the  multiplier  of  Schweigger,  used  for  physiological 
purposes,  the  tendency  of  the  needle  to  point  to  the  north  is  greatly  weakened  by  using  the  astatic 
needles  of  Nobili.  [A  multiplier  or  galvanometer  with  a  single  magnetic  needle  always  requires 
comparatively  strong  currents  to  deflect  the  needle.  Tlie  needle  is  continually  acted  upon  by  the 
directive  magnetic  influence  of  the  earth,  which  tends  to  keep  it  in  the  magnetic  meredian,  and,  as 
soon  as  it  is  moved  out  of  the  magnetic  meridian,  the  directive  action  of  the  earth  tends  to  bring  it 
back.  Hence,  such  a  simple  form  of  galvanometer  is  not  sufticiently  sensitive  for  detecting  feeble 
currents.  In  1827,  Nobili  devised  an  astatic  combination  of  needles,  whereby  the  action  of  the 
earth's  magnetism  was  diminished.]  Two  similar  magnetic  needles  are  united  by  a  solid  light  piece 
of  horn  [or  tortoise  shell],  and  are  so  arranged  that  the  north  pole  of  the  one  is  placed  over  or 
opposite  to  the  south  pole  of  the  other  (Fig.  380).  [If  both  needles  are  equally  magnetized,  then  the 
earth's  influence  on  the  needle  is  neutralized,  so  that  the  needles  no  longer  adjust  themselves  to  the 
magnetic  meridian;  hence,  such  a  system  is  called  astatic.]  As  it  is  impossible  to  make  both  needles 

of  absolutely  equal  magnetic  strength,  one 
needle  is  always  stronger  than  the  other.  The 
difference,  however,  must  not  be  so  great  that 
the  stronger  needle  points  to  the  north,  but 
only  that  the  freely  suspended  system  of  needles 
forms  a  certain  angle  with  the  magnetic  me- 
ridian, into  which  position  the  system  always 
swings  after  it  is  deflected  from  this  position. 
This  angular  deviation  of  the  astatic  system 
toward  the  magnetic  meridian  is  called  the 
"  free  deviation."  The  more  perfectly  an  astatic 
condition  is  reached,  the  nearer  does  the  angle 
formed  by  the  direction  of  the  free  deviation 
with  the  magnetic  meridian  become  a  right 
angle.  The  greater,  therefore,  the  astatic  con- 
dition, the  fewer  vibrations  will  the  astatic 
system  make  in  a  given  time,  after  it  has  been 
deflected  from  its  position.  The  duration  of 
each  single  vibration  is  also  very  great.  [Hence, 
when  using  a  galvanometer,  and  adjusting  its 
needle  to  zero,  if  the  magnets  dance  about  or 
move  quickly,  then  the  system  is  not  sensitive, 
but  a  sensitive  condition  of  the  needles  is  in- 
dicated by  a  sio'w  period  of  oscillation.] 

In  making  a  galvanometer,  the  turns  of  the 
wire  must  have  the  same  direction  as  the 
needles.  In  Nobili's  galvanometer,  as  im- 
proved by  du  Bois-Reymond,  the  upper  needle 
swings  above  a  card  divided  into  degrees  (Fig. 
380),  on  which  the  e-xtent  of  its  deflection  may 
be  read  off.  Even  the  purest  copper  wire  used 
for  the  coils  round  the  needles  always  contains 
a  trace  of  iron,  which  exerts  an  influence  upon 
the  needles.  Hence,  a  small  fixed  directive 
or  compensatory  magnet  (r)  is  placed  near  one  of  the  poles  of  the  upper  needle  to  compensate  for  the 
action  of  the  iron  on  the  needles. 


y  p 

Scheme  of  the  galvanometer.  N,  N,  astatic  needles  sus- 
pended by  the  silk  fibre,  G ;  P,  P,  non-polarizable 
electrodes,  containing  zinc  sulphate  solution,  j,  and  pads 
of  blotting  paper,  b,  covered  with  clay,  t,  t,  on  which 
the  muscle,  M,  is  placed;  II  and  111,  arrangement  of 
the  muscle  on  the  electrodes;  IV,  non-polarizable  elec- 
trodes ;  Z,  zinc  wire  ;  K,  cork  ;  «,  zinc  sulphate  solu- 
tion ;  t,  t,  clay  points. 


328.  ELECTROLYSIS,  POLARIZATION,  BATTERIES.— Electrolysis.— Every  gal- 
vanic current  which  traverses  a  fluid  conductor  causes  decomposition  or  electrolysis  of  the  fluid. 
The  decomposition  products,  called  "  ions,"  accumulate  at  the  poles  (electrodes)  in  the  fluid, 
the  positive  pole  (-J-)  being  called  the  anode  [aid,  up,  oJof,  a  way],  the  negative  pole  ( — )  the 
cathode  (Ka-a,  down,  b^oq,  a  way).  The  anions  accumulate  at  the  anode  and  the  kations  at  the 
cathode. 

Transition  Resistance. — When  the  decomposition  products  accumulate  upon  the  electrodes,  by 
their  presence  they  either  increase  or  diminish  the  resistance  to  the  electrical  current.  This  is  called 
transition  resistance.  If  the  resistance  within  the  battery  is  thereby  increased,  the  transition  resist- 
ance is  said  to  ht positive;  if  diminished,  negative. 

Galvanic  Polarization. — The  ions  accumulated  on  the  electrodes  may  also  vary  the  strength 
of  the  current,  by  developing  between  the  anions  and  kations  a  new  galvanic  current,  just  as  occurs 
between  two  different  bodies  connected  by  a  fluid  medium.  The  phenomenon  is  called  galvanic 
polarization.  Thus,  when  water  is  decomposed,  the  electrodes  being  of  platinum,  the  oxygen 
(negative)  accumulates  at  the  +  pole,  and  the  hydrogen  (positive)  at  the  —  pole.  Usually  the  polari- 
zation current  has  a  direction  opposite  to  the  original  current ;  hence,  we  speak  of  negative polariza- 


ELECTROLYSIS,   POLARIZATION,  BATTERIES. 


595 


tion.     When  the  two  currents  have  the  i2ixa&  ^\x^c'C\ox\, positive  polarization  o\i\.2!Yas.     Of  course , 
transition  resistance  and  polarization  may  occur  together  during  electrolysis. 

Test. — Polarization,  when  present,  may  be  so  slight  as  not  to  be  visible  to  the  eye,  but  it  may  be 
detected  thus  :  After  a  time  exclude  the  primary  source  of  the  current,  especially  the  element  con- 
nected with  the  electrodes,  and  place  the  free  projecting  end  of  the  electrodes  in  connection  with  a 
galvanometer,  which  will  at  once  indicate,  by  the  deflection  of  its  needle,  the  presence  of  even  the 
slightest  polarization. 

Secondary  Decompositions. — The  ions  excreted  during  electrolysis  cause,  especiallj'  at  their 
moment  of  formation,  secondary  decompositions.  With  platinum  electrodes  in  a  solution  of  common 
salt,  chlorine  accumulates  at  the  anode  and  sodium  at  the  cathode,  but  the  latter  at  once  decomposes 
the  water,  and  uses  the  oxygen  of  the  water  to  oxidize  itself,  while  the  hydrogen  is  deposited  seconda- 
rily upon  the  cathode.  The  amount  of  polarization  increases,  although  only  to  a  slight  extent,  with 
the  strength  of  the  current,  while  it  is  nearly  proportional  to  the  increase  of  the  temperature.  The 
attempts  to  get  rid  of  polarization,  which  obviously  must 
very  soon  alter  the  strength  of  the  galvanic  current,  have 
led  to  the  discovery  of  two  important  arrangements,  viz., 
the  construction  of  constant  galvanic  batteries,  and 
non-polarizable  electrodes  {du  Bois-Reymond). 

Constant  Batteries,  Elements,  or  Cells. — A  per- 
fectly constant  element  produces  a  constant  current,  i.  e., 
one  remaining  of  equal  strength,  by  the  ions  produced  by  the 
electrodes  being  got  rid  of  the  moment  they  are  formed,  so 
that  they  cannot  give  rise  to  polarization.  For  this  purpose, 
each  of  the  substances  from  the  tension  series  used  is  placed 
in  a  special  fluid  (§  326),  both  fluids  being  separated  by  a 
porous  septum  (porcelain  cylinder). 

Grove's  cell  has  two  metals  and  two  fluids  (Fig.  381). 
The  zinc  is  in  the  form  of  a  roll  placed  in  dilute  sulphuric 
acid  [i  acid  to  7  of  water,  which  is  contained  in  a  glass, 
porcelain,  or  ebonite  vessel].  The  platinum  is  in  contact 
with  strong  nitric  acid  [which  is  contained  in  a  porous  cell 
placed  inside  the  roll  of  zinc].  The  O,  formed  by  the 
electrolysis  and  deposited  on  the  zinc  plate,  forms  zinc 
oxide,  which  is  at  once  dissolved  by  the  sulphuric  acid. 
The  hydrogen  on  the  platinum  unites  at  once  with  the 
nitric  acid,  which  gives  up  O  and  forms  nitrous  acid  and 
water,  thus — 


[H2  -f  HNO3  =  HNO2  +  H2O.] 
[Platinum  is  the  -\-  pole,  and  zinc  the  —  .] 


Large  Grove's  cell. 


[Grove's  battery  is  very  powerful,  but  the  nitrous  fumes 
are  very  disagreeable  and  irritating ;  hence  these  elements 
should  be  kept  in  a  special  well-ventilated  recess  in  the  laboratory,  in  an  evaporating  chamber, 
or  under  glass.     The  fumes  also  attack  instruments.] 

Bunsen's  cell  is  similar  to  Grove's,  only  a  piece  of  compressed  carbon  is  substituted  for  the 
platinum  in  contact  with  the  nitric  acid. 

[The  carbon  is  the  -f-  pole,  the  zinc_the  —  .] 

[Daniell's  cell  consists  of  an  outer  vessel  of  glass  or  earthenware,  and  sometimes  of  metallic 
copper,  filled  with  a  saturated  solution  of  cupric  sulphate  (Fig.  382).  A  roll  of  copper,  perforated 
with  a  few  holes,  is  placed  in  the  copper  solution,  and  in  order  that  the  latter  be  kept  saturated,  and 
to  supply  the  place  of  the  copper  used  up  by  the  battery  when  in  action,  there  is  a  small  shelf  on  the 
copper  roll,  on  which  are  placed  crystals  of  cupric  sulphate.  A  porous  earthenware  vessel  containing 
zinc  in  contact  with  dilute  sulphuric  acid  (i  :  7)  is  placed  within  the  copper  cylinder.  When  the 
circuit  is  completed,  the  zinc  is  acted  on,  zinc  sulphate  being  formed,  and  hydrogen  liberated.  The 
hydrogen  in  statu  nascendi  passes  through  the  porous  cell,  reduces  the  cupric  sulphate  to  metallic 
copper,  which  is  precipitated  on  the  copper  cylinder,  so  that  the  latter  is  always  kept  bright  and 
clean.  The  liberated  sulphuric  acid  replaces  that  in  contact  with  the  zinc.  Owing  to  the  absence 
of  polarization,  the  Daniell  is  one  of  the  most  constant  batteries,  and  is  generally  taken  as  the 
standard  of  comparison.] 

[The  copper  is  the  -j-  pole,  zinc  the  —  .] 

[Smee's  cell  contains  only  one  fluid,  viz.,  dilute  sulphuric  acid  (l  :  7),  in  which  the  two  metals^ 
zinc  and  platinum,  or  zinc  and  platinized  silver,  are  placed. 

The  platinum  is  the  -j-  pole,  and  zinc  the  —  .] 
[Grennet's  or  the  Bichromate  cell  consists  of  one  plate  of  zinc  and  two  plates  of  compressed 


596         DANIELL,    SMEE,    GRENNET,    AND    LECLANCH^'S    ELEMENT. 

carbon  in  a  fluid,  containiuij  bichromate  of  potash,  sulphuric  acid,  and  water.  The  fluid  consists  of 
I  part  of  potassium  bichromate  dissolved  in  8  parts  of  water,  to  which  one  part  of  sulphuric  acid  is 
added.  Measure  by  'weight.  The  cell  consists  of  a  wide-mouthed  glass  bottle  (Fig.  383)  ;  the 
carbons  remain  in  the  fluid,  while  the  zinc  can  be  raised  or  depressed.  ^\  hen  not  in  action,  the 
zinc,  which  is  attached  to  a  rod  (B),  is  lifted  out  of  the  fluid.  It  is  not  a  very  constant  battery. 
When  in  action,  the  zinc  is  acted  on  by  the  sulphuric  acid,  hydrogen  being  liberated,  which  reduces 
the  bichromate  of  potash. 

The  carbon  is  the  -|-  pole,  and  the  zinc  the  —  .] 

Fig.  382. 


— ^UUUUtJ^ 


Fig.  384. 


Daniell's  Cell. 

Fig.  383. 


Leclanche's  cell.  A,  outer  vessel ;  T,  porous  cylinder,  containing  K, 
carbon  ;  B,  binding  screw  ;  Z,  zinc  ;  C,  binding  screw  of  negative 
pole. 


Grennet's  cell.  A,  glass  vessel  ;  K,  K,  car- 
bon ;  Z,  zinc;  D,  E,  binding  screws  for 
the  wires  ;  B,  rod  to  raise  the  zinc  from 
the  fluid  ;  C,  screw  to  fix  B.| 


[Leclanche's  cell  (Fig.  384)  consists  of  an  outer  glass  vessel  containing  zinc  in  a  solution  of 
ammonium  chloride,  while  the  porous  cell  contains  compressed  carbon  in  a  fluid  mixture  of  black 
oxide  of  manganese  and  carbon.  It  is  most  frequently  used  for  electric  bells,  as  its  feeble  current 
lasts  for  a  long  time. 

The  carbon  is  the  -(-  pol^j  ^"^  the  zinc  the  —  .] 

Non-polarizable  Electrodes. — If  a  constant  current  be  applied  to  moist  animal  tissues,  e.  g., 
nerve  or  muscle,  by  means  of  ordinary  electrodes  composed  either  of  copper  or  platinum,  of  course 


REFLECTING    GALVANOMETER   AND    SHUNT. 


597 


electrolysis  must  occur,  and  in  consequence  thereof  polarization  takes  place.  In  order  to  avoid  this, 
non-polarizable  electrodes  (Figs.  380,  385)  are  used.  Such  electrodes  are  made  by  taking  two  pieces 
of  carefully  amalgamated,  pure,  zinc  wire  (z,  s),  and  dipping  these  in  a  saturated  solution  of  zinc 
sulphate  contained  in  tubes  (a,  a),  whose  lower  ends  are  closed  by  means  of  modeler's  clay  (/,  /), 
moistened  with  0.6  per  cent,  normal  saline  solution.  The  contact  of  the  tissues  with  these  elec- 
trodes does  not  give  rise  to  polarity.  [The  brush  electrodes  of  v.  Fleischl  are  very  serviceable 
(Fig.  386).  The  lower  end  of  the  glass  tube  is  plugged  with  a  camel-hair  pencil,  moistened  with 
modeler's  clay,  otherwise  the  arrangement  is  the  same  as  shown  in  Fig.  380,  IV.] 

Arrangement  for  the  Muscle  or  Nerve  Current. — In  order  to  investigate  the  electrical  cur- 
rents of  nerve  or  muscle,  the  tissue  must  be  placed  on  non-polarizable  electrodes,  which  may  either 
be  one  of  the  forms  described  above,  or  the  original  form  used  by  du  Bois-Reymond.  (Fig.|38o). 
The  last  consists  of  two  zinc  troughs  (j>,  p)  thoroughly  amalgamated  inside,  insulated  on  vulcanite, 


Fig.  385. 


Fig.  387. 


Non-polarizable  electrode  of  du  Bois-Reymond.     Z,  zinc  ;  H,  movable 
support ;  C,  clay  point — the  whole  on  a  universal  joint. 


Fig.  386. 


Brush  electrodes  of  v.  Fleischl. 


jmson's  reflecting  galvanometer. 
u,  upper,  /,  lower  coil ;  s,  s,  level- 
ing screws  ;  }fi,  magnet  on  a  brass 
support,  6. 


and  filled  with  a  saturated  solution  of  zinc  sulphate  {s,  s).  In  each  trough  is  placed  a  thick  pad  or 
cushion  of  white  blotting  paper  {i>,  b)  saturated  with  the  same  fluid  [deriving  cushions].  [The 
cushion  consists  of  many  layers,  almost  sufficient  to  fill  the  trough,  and  they  are  kept  together  by  a 
thread.  To  prevent  the  action  of  the  zinc  sulphate  upon  the  tissue,  each  cushion  is  covered  with  a 
thin  layer  of  modeler's  clay  [t,  t),  moistened  with  0.6  per  cent,  saline  solution,  which  is  a  good 
conductor  [clay  guard].  The  clay  guard  prevents  the  action  of  the  solution  upon  the  tissue. 
Connected  with  the  electrodes  are  a  pair  of  binding  screws,  whereby  the  apparatus  is  connected 
with  the  galvanometer  (Fig.  380). 

[Reflecting  Galvanometer. — The  form  of  galvanometer,  used  in  this  country  for  physiological 
purposes,  is  that  of  Sir  William  Thomson  (Fig.  387).  In  Germany,  Weidemann's  form  is  more 
commonly  used.  In  Thomson's  instrument,  the  astatic  needles  are  very  light,  and  connected  to 
each  other  by  a  piece  of  aluminium,  and  each  set  of  needles  is  surrounded  by  a  separate  coil  of  wire, 


598 


REFLECTING    GALVANOMETER    AND    SHUNT. 


Lamp  and 


for  'I'hoiiison's  gal 
kanometer. 


Shunt  for  galvanometer. 


the  lower  coil  (/)  winding  in  a  direction  opposite  to  that  of  the  upper  (tt).  A  small,  round,  light, 
slightly  concave  mirror  is  fixed  to  the  upper  set  of  needles.  The  needles  are  suspended  by  a 
delicate  silk  til^ril,  and  they  can  be  raised  or  lowered  as  required  by  means  of  a  small  milled  head. 
When  the  milled  head  is  raised,  the  system  of  needles  swings  freely.     The  coils  are  protected  by  a 

glass  shade,  and  the  whole  stands  on  a 
F'k^..   "^SS.  Fig.   389.  vulcanite  base,  which  is  leveled  ijy  three 

screws  (s,  s).  On  a  brass  rod  (6)  is  a 
feeble  magnet  (w),  which  is  used  to  give 
an  artificial  meridian.  The  magnet  (m) 
can  be  raised  or  lowered  by  means  of  a 
milled  head.] 

[Lamp  and  Scale. — When  the  instru- 
iiunt  is  to  be  used,  place  it  so  that  the 
coils  face  east  and  west.  At  3  feet  dis- 
tant from  the  front  of  the  galvanometer, 
facing  west,  is  placed  the  lamp  and  scale 
(Fig.  388).  There  is  a  small  vertical 
slit  in  front  of  the  lamp,  and  the  image  of 
this  slit  is  projected  on  the  mirror  attached 
to  the  upper  needles,  and  by  it  is  reflected 
on  to  the  paper  scale  fixed  just  above  the 
slit.  The  spot  of  light  is  focused  at 
zero  by  means  of  the  magnet,  w.  The 
needles  are  most  sensitive  when  the  oscil- 
lations occur  slowly.  The  sensitiveness  of  the  needles  can  be  regulated  by  means  of  the  magnet. 
In  every  case  the  in.strument  must  be  (juite  level,  and  for  this  purpose  there  is  a  small  spirit-level  in 
the  base  of  the  galvanometer.] 

[Shunt. — As  the  galvanometer  is  very  delicate,  it  is  convenient  to  have  a  .shunt  to  regulate  to  a 
certain  extent  the  amount  of  electricity  transmitted  through  the  galvanometer.  The  shunt  (F"ig.  389) 
consists  of  a  brass  box  containing  coils  of  German  silver  wire,  and  is  constructed  on  the  same  prin- 
ciple as  resi-Stance  coils  or  the  rheocord  (^  326).  On  the  upper  surface  of  the  box  are  several  plates 
of  brass  separated  from  each  other,  like  tho^e  of  the  rheocord,  but  which  can  be  united  by  brass 
plugs.  The  two  wires  coming  from  the  electrodes  are  connected  with  the  two  binding  screws,  and 
from  the  latter  two  wires  are  led  to  the  outer  two  binding  screws  of  the  galvanometer.  V>y  placing 
a  plug  between  the  brass  plates  attached  to  the  two  binding  screws  in  the  figure,  the  current  is  short 
circuited.  On  removing  both  plugs,  the  whole  of  the  current  mu.st  pass  through  the  galvanometer. 
If  ofie  plug  be  placed  between  the  central  disk  of  brass  and  the  plate  marked  i  (the  other  being  left 
out),  then  J^  of  the  cun-ent  goes  through  the  galvanometer  and  -^^  to  the  electrodes.  If  the  plug  be 
placed  as  shown  in  the  figure  opposite  -Jtj,  then  ^J^  part  of  the  current  goes  to  the  galvanometer, 
while  j'j^^  are  short  circuited.  If  the  plug  be  placed  opposite  ^Ig,  only  yjjVff  P''*'"'  8°^^  through  the 
galvanometer.] 

Internal  Polarization  of  Moist  Bodies. — Nerves  and  muscular  fibres,  the  juicy  parts  of  vege- 
tables and  animals,  fibrin,  and  other  similar  bodies  possessing  a  porous  structure  filled  with  fluid, 
exhibit  the  [ihenomena  of  polarization  when  subjected  to  strong  currents — a  condition  termed  internal 
polarization  of  moist  bodies  by  du  Bois-Reymond.  It  is  assumed  that  the  solid  parts  in  the  interior 
of  these  bodies  which  are  better  conductors,  produce  electrolysis  of  the  adjoining  fluid,  just  like 
metals  in  contact  with  fluid.  The  ions  produced  by  the  decomposition  of  the  internal  fluids  give 
rise  to  differences  of  potential,  and  thus  cause  internal  polarization  (^  33i)- 

Cataphoric  Action. — If  the  two  electrodes  from  a  galvanic  battery  be  placed  in  the  two  com- 
partments of  a  fluid,  separated  from  each  other  by  a  porous  septum,  we  observe  that  the  fluid  particles 
pass  in  the  direction  of  the  galvanic  current,  from  the  -(-  to  the  —  pole,  so  that  after  some  time,  the 
fluid  in  the  one-half  of  the  vessel  increases,  while  it  diminishes  in  the  other.  The  phenomena  of 
direct  transference  were  called  by  du  Bois-Reymond  the  cataphoric  action  of  the  constant  current. 
The  introduction  of  dissolved  substances  through  the  skin  by  means  of  a  constant  current  depends 
upon  this  action  (^  290),  and  so  does  the  so-called  Porret's  phenomenon  in  living  muscle  (g  293, 
I,^). 

External  Secondary. Resistance. — This  condition  also  depends  on  cataphoric  action.  If  the 
copper  electrodes  of  a  constant  battery  be  placed  in  a  vessel  filled  with  a  solution  of  cupric  sulphate, 
and  from  each  electrode  there  project  a  cushion  saturated  with  this  fluid,  then,  on  placing  a  piece  of 
muscle,  cartilage,  vegetable  tissue,  or  even  a  prismatic  strip  of  coagulated  albumin  across  these 
cushions,  we  observe  that,  very  soon  after  the  circuit  is  closed,  there  is  a  considerable  variation  of 
the  current.  If  the  direction  of  the  current  be  reversed,  it  first  becomes  stronger,  but  afterward 
diminishes.  By  constantly  altering  the  direction  of  the  current  we  cause  the  same  changes  in  the 
intensity.  If  a  prismatic  strip  of  coagulated  albumin  be  used  for  the  experiment,  we  observe  that, 
simultaneously  with  the  enfeeblement  of  the  current  in  the  neighborhood  of  the  +  pole,  the  albumin 
loses  water  and  becomes  more  shriveled,  while  at  the  —  pole  the  albumin  is  swollen  up  and  contains 


INDUCED    OR    FARADIC    ELECTRICITY.  599 

more  water.  If  the  direction  of  the  current  be  altered,  the  phenomena  are  also  changed.  The 
shriveling  and  removal  of  water  in  the  albumin  at  the  positive  pole  must  be  the  cause  of  the  resist- 
ance in  the  circuit,  which  explains  the  enfeeblement  of  the  galvanic  current.  This  phenomenon  is 
called  "external  secondary  resistance"  [die  Bois-Reymo7id). 

329.  INDUCTION— EXTRA  CURRENT— MAGNETIC  INDUCTION.— Induction 

of  the  Extra  Current. — If  a  galvanic  element  is  closed  by  means  of  a  short  arc  of  wire,  at  the 
moment  the  circuit  is  again  opened  or  broken,  a  slight  spark  is  observed.  If,  however,  the  circuit 
is  made  or  closed  by  means  of  a  very  long  wire  rolled  in  a  coil,  then  on  breaking  the  circuit  there 
is  a  strong  spark.  If  the  wires  be  connected  with  two  electrodes,  so  that  a  person  can  hold  one 
in  each  hand,  the  current  at  the  moment  it  is  opened  must  pass  through  the  person's  body,  then 
there  is  a  violent  shock  communicated  to  the  hand.  This  phenomenon  is  due  to  a  current  induced 
in  the  long  spiral  of  wire  which  Faraday  called  the  extra  current.  It  is  caused  thus :  When  the 
circuit  is  closed  by  means  of  the  spiral  wire,  the  galvanic  current  passing  along  it  excites  an  elec- 
tric current  in  the  adjoining  coils  of  the  same  spiral.  At  the  moment  of  closing  or  making  the  cir- 
cuit in  the  spiral,  the  induced  current  is  in  the  opposite  direction  to  the  galvanic  current  in  the 
circuit ;  hence  its  strength  is  lessened,  and  it  causes  no  shock.  At  the  moment  of  opening,  how- 
ever, the  induced  current  has  the  same  direction  as  the  galvanic  stream,  and  hence  its  action  is 
strengthened. 

Magnetization  of  Iron. — If  a  rod  of  soft  iron  be  placed  into  the  cavity  of  a  spiral  of  copper 
wire,  then  the  soft  iron  remains  magnetic  as  long  as  a  galvanic  current  circulates  in  the 
spiral.  If  one  end  of  the  iron  rod  be  directed  toward  the  observer,  and  the  other  away  from 
him,  and  if,  further,  the  positive  current  traverse  the  spiral  in  the  same  direction  as  the  hands 
of  a  clock,  then  the  end  of  the  magnet  directed  toward  the  person  is  the  negative  pole  of  the 
magnet.  The  power  of  the  magnet  depends  upon  the  number  of  spiral  windings,  and  on  the 
thickness  of  the  iron  bar.  As  soon  as  the  current  is  opened,  the  magnetism  of  the  iron  rod  dis- 
appears. 

Induced  or  Faradic  Current. — If  a  very  long,  insulated  wire  be  coiled  into  the  form  of  a  spiral 
roll,  which  we  may  call  the  secondary  spiral,  and  if  a  similar  spiral,  the  primary  spiral,  be  placed 
near  the  former,  and  the  ends  of  the  wire  of  the  primary  spiral  be  connected  with  the  poles  of  a  con- 
stant battery,  every  time  the  current  in  the  primary  circuit  is  made  (closed),  or  broken  (opened),  a 
current  takes  place,  or,  as  it  is  said,  is  induced  in  the  secondary  spiral.  If  the  primary  circuit 
be  kept  closed,  and  if  the  secondary  spiral  be  brought  nearer  to,  or  removed  further  from,  the  primary 
spiral,  a  current  is  also  induced  in  the  secondary  spiral  [Faraday,  1832).  The  current  in  the  sec- 
ondary circuit  is  called  the  induced  or  Faradic  current.  When  the  primary  circuit  is  closed,  or 
when  the  two  spirals  are  brought  nearer  to  each  other,  the  current  in  the  secondary  spiral  has  a  direction 
opposite  to  that  in  the  primary  spiral,  while  the  current  produced  by  opening  the  primary  circuit,  or 
by  removing  the  spirals  further  apart,  has  the  same  direction  as  the  primary.  During  the  time  the 
primary  circuit  is  closed,  or  when  both  spirals  remain  at  the  same  distance  from  each  other,  there  is  no 
current  in  the  secondary  spiral. 

Difference  betvireen  the  Opening  [break]  and  Closing  [make]  Shocks. — The  opening 
and  closing  shocks  in  the  secondary  spiral  are  distinguished  from  each  other  in  the  following  respects 
(Fig.  390)  :  The  amount  of  electricity  is  the  same,  during  the  opening,  as  during  the  closing  shock; 
but  during  the  opening  shock  the  electricity  rapidly  reaches  its  maximum  of  intensity  and  lasts  but 
a  short  time,  while  during  the  closing  shock  it  gradually  increases,  but  does  not  reach  the  high 
maximum,  and  this  occurs  more  slowly.  [In  Fig.  390,  Pj  and  Sq  are  the  abscissae  of  the  primary 
(inducing)  and  induced  currents  respectively.  The  vertical  lines  or  ordinates  re'preseni  the  intensity 
of  the  current,  while  the  length  of  the  abscissa  indicates  its  duration.  Curve  I  indicates  the  course 
of  the  primary  current,  and  2,  that  in  the  secondary  spiral  (induced)  when  the  current  is  closed,  v;\i\\& 
at  I  the  primary  current  is  suddenly  opened,  when  it  gives  rise  to  the  induced  current,  4,  in  the 
secondary  spiral.]  The  cause  of  the  difference  is  the  following:  When  the  primary  circuit  is  closed, 
there  is  developed  in  it  the  extra  current,  which  is  opposite  in  direction  to  the  primary  current. 
Hence,  it  opposes  considerable  resistance  to  the  complete  development  of  the  strength  of  the  primary 
current,  so  that  the  current  induced  in  the  secondary  spiral  must  also  develop  slowly.  But  when  the 
primary  spiral  is  opened,  the  extra  current  in  the  latter  has  the  same  direction  as  the  primary  current 
— there  is  no  extra  resistance.  The  rapid  and  intense  action  of  the  opening  induction  shock  is  of 
great  physiological  importance. 

Break  or  Opening  Shock. — [On  applying  a  single  induction  shock  to  a  nerve  or  a  muscle,  the 
effect  is  greater  with  the  break  or  opening  shock.  If  the  secondary  spiral  be  separated  from  the  pri- 
mary, so  that  the  induced  currents  are  not  sufficient  to  cause  contraction  of  a  muscle  when  applied 
to  its  motor  nerve,  then,  on  gradually  approximating  the  secondary  to  the  primary  spiral,  the  break 
or  opening  shock  will  cause  a  contraction  before  the  closing  one  does  so.] 

Helmholtz's  Modification. — Under  certain  circumstances,  it  is  desirable  to  equalize  the  make 
and  break  shocks.  This  may  be  done  by  greatly  weakening  the  extra  current,  which  may  be  accom- 
plished by  making  the  primary  spiral  of  only  a  few  coils  of  wire.  v.  Helmholtz  accomplishes  the 
same  result  by  introducing  a  secondary   circuit  into  the   primary  current.     By  this   arrangement 


600 


UNIPOLAR   INDUCTION. 


the  current  in  tlie  primary  spiral  never  completely  disapjiears,  but  by  alternately  making  and 
breaking  this  secondary  circuit  where  the  resistance  is  much  less,  it  is  ahernately  weakened  and 
strengthened. 

[In  Fig.  391  a  wire  is  introduced  between  a  and  /",  while  the  binding  screw,/,  is  separated  from 
the  platinum  contact,  c,  of  Neefs  hammer,  but,  at  the  same  time,  the  screw,  ti,  is  raised  so  that  it 
touches  Neefs  hammer.  The  current  passes  from  the  battery,  K,  through  tiie  pillar,  a,  to/ in  the 
direction  of  the  arrow,  through  the  primary  spiral,  P,  to  the  coil  of  soft  wire,  r',  and  back  to  the  bat- 
tery, through  h  and  e.  But  .j,''  is  magnetized  thereljy,  and  when  it  is  so,  it  attracts  c  and  makes  it 
touch  the  screw,  d.  Thus  a  sccondaiT  circuit,  or  short  circuit,  is  formed  through  a,  l>,  c,  d,  e,  which 
weakens  the  current  passing  through  the  electro  magnet,  ,?•,  so  that  the  elastic  metallic  spring  flies 
up  again  and  the  current  through  the  primary  spiral  is  long-circuited,  and  thus  the  process  is 
repeated.  In  Fig.  390  the  lines  i  and  7  indicate  the  course  of  the  current  in  the  primary  circuit  at 
closing  (a),  and  opening  (e).  It  must  be  remembered  that  in  this  arrangement  there  is  always  a 
current  passing  through  the  primary  spiral,  P  (Fig.  391).  The  dotted  lines,  6  and  8,  above  and 
below  Sg,  represent  the  course  of  the  opening  [a)  and  closing  shocks  (c)  in  the  secondary  spiral. 
Even  with  this  arrangement  the  opening  is  still  slightly  stronger  than  the  closing  shock.]  The  two 
shocks,  however,  may  be  completely  equalized  by  placing  a  resistance  coil  or  rheostat  in  the  short 
circuit,  which  increases  the  resistance,  and  thus  increases  the  current  through  the  primary  spiral  when 
the  short  circuit  is  closed. 


Fig.  390. 


Scheme  of  the  induced  currents.  Pj,  abscissa  of 
the  primary,  and  Sq,  of  the  secondary  cur- 
rent ;  A,  beginning,  and  E,  end  of  the  inducing 
current;  i,  curve  of  the  primary  current  weak- 
ened by  the  extra  current;  3,  where  the  pri- 
mary current  is  opened;  2  and  4,  correspond- 
ing currents  induced  in  the  secondary  spiral ; 
P5,  height,  i.  e.,  the  strength  of  tlie  constant 
inducing  current ;  5  and  7,  the  curve  of  the  in- 
ducing current  when  it  is  opened  and  closed 
during  Helmholtz's  modification  ;  6  and  8,  the 
corresponding  currents  induced  in  the  second- 
ary circuit. 


Fig.  391. 


Helmholtz's  modification  of  Neefs  hammer. 
As  long  as  c  is  not  in  contact  with  d,gh 
remains  magnetic  ;  thus  c  is  attracted  to  d 
and  a  secondary  circuit,  «,  b,  c,  d,  e,  is 
formed  ;  c  then  springs  back  again,  and 
thus  the  process  goes  on.  A  new  wire  is 
introduced  to  connect  a  withyi  K,  bat- 
tery. 


Unipolar  Induction. — ^Vhen  there  is  a  very  rapid  current  in  the  primary  spiral,  not  only  is  there 
a  current  induced  in  the  secondary  spiral,  when  its  free  ends  are  closedi^-.o".,  by  being  connected  with 
an  animal  tissue,  but  there  is  also  a  current  when  one  wire  is  attached  to  a  binding  screw  connected 
with  one  end  of  the  wire  of  the  secondary  spiral  (p.  587).  A  muscle  of  a  frog's  leg,  when  connected 
with  this  wire,  contracts,  and  this  is  called  a  unipolar  induced  contraction.  It  usually  occurs  when 
the  primary  circuit  is  opened.  The  occurrence  of  these  contractions  is  favored  when  the  other  end 
of  the  spiral  is  placed  in  connection  with  the  ground,  and  when  the  frog's  muscle  preparation  is  not 
completely  insulated. 

Magneto-Induction. — If  a  magnet  be  brought  near  to,  or  thrust  into  the  interior  of,  a  coil  of 
wire,  it  excites  a  current,  and  also  when  a  piece  of  soft  iron  is  suddenly  rendered  magnetic  or  sud- 
denly demagnetized.  The  direction  of  the  current  so  induced  in  the  spiral  is  exactly  the  same  as 
that  with  Faradic  electricity,  i.e.,  the  occurrence  of  the  magnetism,  on  approximating  the  spiral  to  a 
magnet,  excites  an  induced  current  in  a  direction  opposite  to  that  supposed  to  circulate  in  the  mag- 
net. Conversely,  the  demagnetization,  or  the  removal  of  the  spiral  from  the  magnet,  causes  a  cur- 
rent in  the  same  direction. 

Acoustic  Tetanus. — If  a  magnet  be  rapidly  moved  to  and  fro  near  a  spiral,  which  can  easily  be 
done  by  fixing  a  vibratory  magnetic  rod  at  one  end  and  allowing  the  other  end  to  swing  freely  near 


DU   BOIS-REYMOND  S    INDUCTORIUM. 


601 


the  spiral,  then  the  pitch  of  the  note  of  the  vibrating  rod  gives  us  the  rapidity  of  the  induction 
shocks.  If  a  frog's  nerve-muscle  preparation  be  stimulated,  we  get  what  Grossmann  called  "acoustic 
tetanus." 

330.  DU  BOIS-REYMOND'S  INDUCTORIUM— MAGNETO-INDUCTION  AP- 
PARATUS.— The  inductoriumof  du  Bois-Reymond,  which  is  used  for  physiological  purposes, 
is  a  modification  of  the  magneto-electromotor  apparatus  of  Wagner  and  Neef.  A  scheme  of  the 
apparatus  is  given  in  Fig.  392.  D  represents  the  galvanic  battery.  The  wire  from  the  positive  pole, 
a,  passes  to  a  metallic  column,  S,  which  has  a  horizontal  vibrating  spring,  F,  attached  to  its  upper 
end.  To  the  outer  end  of  the  spring  a  square  piece  of  iron,  e,  is  attached.  The  middle  point  of 
the  upper  surface  of  the  spring  [covered  with  a  little  piece  of  platinum]  is  in  contact  with  a  movable 
screw,  b,  A  moderately  thick  copper  wire,  c,  passes  from  the  screw,  b,  to  the  primary  spiral  or 
coil,  X,  X,  which  contains  in  its  interior  a  number  of  pieces  of  soft  iron  wire,  i,  i,  covered  with  an 
insulating  varnish.  The  copper  wire  which  surrounds  the  primary  spiral  is  covered  with  silk.  The 
wire,  d,  is  continued  from  the  primary  spiral  to  a  horseshoe  piece  of  soft  iron,  H,  around  which  it  is 
coiled  spirally,  and  from  thence  it  proceeds,  at/",  back  to  the  negative  pole  of  the  battery,  g.  When 
the  current  in  this  circuit — called  the  primary  circuit — is  closed,  the  following  effects  are  produced : 
The  horseshoe,  H,  becomes  magnetic,  in  consequence  of  which  it  attracts  the  movable  spring  or 
Neef's  hammer,  e,  whereby  the  contact  of  the  spring,  F,  with  the  screw,  b,  is  broken.  Thus  the 
current  is  broken,  the  horseshoe  is  demagnetized,  the  spring,  e,  is  liberated,  and,  being  elastic,  it 


Fig.  392. 
I 


v 

c  _ 

> 

W 

flTf 

r/^ 

41^ 

jljL 

iJJLi|_l_ 

i  !>  Ill 

wft 

'^VV.\ 

L>V\ 

iiirV\.\ 

I,  Scheme  of  du  Bois-Reymond's  sledge  induction  machine.  D,  galvanic  battery  :  a,  wire  from  -f  pole,  (^)  —  pole  ; 
S,  brass  upright ;  F,  elastic  spring  ;  i,  binding  screw  ;  c,  wire  round  primary  spiral  (jr,  jc),  containing  {i,  i)  soft 
iron  wire;  K,  K,  secondary  spiral,  with  board  (/,/)  on  which  it  can  be  moved;  H,  soft  iron  magnetized  by 
current  (^,y")  passing  round  it.  II,  key  for  secondary  circuit;  as  shown  it  is  short-circuited.  Ill,  electrodes 
{r,  r),  with  a  key  (K)  for  breaking  the  circuit. 


springs  upward  again  to  its  original  position  in  contact  with  b,  and  thus  the  current  is  reestablished. 
The  new  contact  causes  H  to  be  remagnetized,  so  that  it  must  alternately  rapidly  attract  and  liberate 
the  spring,  e,  whereby  the  primary  current  is  rapidly  made  and  broken  between  F  and  b. 

A  secondary  spiral  or  coil  (K,  K)  is  placed  in  the  same  direction  as  the  primary  {x,  x),  but 
having  no  connection  with  it.  It  moves  in  grooves  upon  a  long  piece  of  wood  (/,/).  The  second- 
ary spiral  consists  of  a  hollow  cylinder  of  wood  covered  with  numerous  coils  of  thin,  silk-covered 
wire.  The  secondary  spiral,  moving  in  slots,  can  be  approximated  to  or  even  pushed  entirely  over 
the  primary  spiral,  or  can  be  removed  from  it  to  any  distance  desired. 

[Fig.  393  shows  the  actual  arrangement  of  du  Bois-Reymond's  inductorium.  The  primary 
coil  (R'')  consists  of  about  150  coils  of  thick  insulated  copper  wire,  the  wire  being  thick  to  offer 
slight  resistence  to  the  galvanic  current.  The  secondary  coil  (R^^)  consists  of  6000  turns  of  thin 
insulated  copper  wire  arranged  on  a  wooden  bobbin;  the  whole  spiral  can  be  moved  along  the  board 
(B)  to  which  a  millimetre  scale  (I)  is  attached,  so  that  the  distance  of  the  secondary  from  the 
primary  spiral  may  be  ascertained.  At  the  left  of  the  apparatus  is  Wagner's  hammer,  as  adapted 
by  Neef,  which  is  just  an  automatic  arrangement  for  opening  and  breaking  the  primary  circuit.  WTien 
Neef's  hammer  is  used,  the  wires  from  the  battery  are  connected  as  in  the  figure  ;  but  when  single 
shocks  are  required,  the  wires  from  the  battery  are  connected  with  a  key,  and  this  again  with  the 


602 


MAGNETO-INDUCTION. 


Fi<-..  394. 


two  terminals  of  the  primary  spiral,  S''  and  S'^'.  In  the  improved  form  of  this  apparatus  (Fig. 
394)  the  secondary  spiral  is  equipoised  over  a  pulley  with  a  back  weight,  so  that  it  can  move  easily  in 
a  vertical  direction  to  and  from  the  primary  spiral.  A.  de  Walteville  has  used  a  form  similar  to  this 
for  a  long  time.] 

According  to  the  law  of  induction  (§  329),  when  the  primary  circuit  is  closed,  a  current  is  induced 
in  the  secondary  circuit  in  a  direction  the  reverse  oi  that  in  the  primary,  while,  when  it  is  opened, 
the  induced  current  has  the  same  direction.  Further,  according  to  the  laws  of  magneto  induction,  the 
magnetization  of  the  iron  rods  {/,  /)  within  the  primary  spiral  (.r,  .r),  causes  a  reverse  current  in  the 
secondary  spiral  (K,  K),  while  the  demagnetization  of  the  iron  rods,  on  opening  the  pi imary  circuit 
causes  an  induced  current  in  the  same  direction.  Thus,  we  ex- 
plain the  much  more  powerful  action  of  the  opening  or  break 
shock  as  compared  with  the  closing  or  make  shock  (p.  53')- 
[The  direction  of  the  in.iucing  current  remains  the  same,  while 
the  induced  currents  are  constantly  reversed.] 

The  magneto-induction  (R)  apparatus  of  Pi.xii,  as  improved 
by  Stohrer,  consists  of  a  very  powerful  horseshoe  steel  mag- 
net (Fig.  395).  Opposite  its  two  poles  (N  and  S)  is  a  horse- 
shoe-shaped jMece  of  iron  (H),  which  rotates  on  a  horizontal  axis 
(a,  V).  On  the  ends  of  the  horseshoe  are  fixed  wooden  bobbins 
(f, </),  with  an  insulated  wire  coiled  round  them.     When  the 

Fig.  393. 


Induction  apparatus  of  du  Eois-Keymond.     R',  primary,  K",  secondary 
spiral ;  B,  board  on  which  R"  moves  ;  I,  scale;    H ,  wires  from  bat- 
tery ;   P',   P",  pillars;  H,  Neefs   hammer;   B',   electro-magnet;    S', 
binding  screw  touching   the  steel   spring  (H);    S"  and  S"',  binding    New  form  of  du  Bois-Reymond's  induc- 
screws  to  which  to  attach  wires  where  Neefs  hammer  is  not  required.  torium. 

horseshoe  is  at  rest,  as  in  the  figure,  it  becomes  magnetized  by  the  .steel  magnet,  while  in  the  wires 
of  both  bobbins  {c  and  a')  an  electric  current  is  developed  every  tine  the  horseshoe  is  demagnetized, 
and  again  magnetized.  When  the  bobbins  rotate  in  front  of  the  magnet,  as  each  coil  approaches  one 
pole,  a  current  is  induced,  and  similarly  when  it  is  carried  past  the  pole  of  the  magnet,  so  that  four 
currents  are  induced  in  each  coil  by  a  single  rotation.  By  means  of  Stohrer's  commutator  (w,  «) 
attached  to  the  spindle  («,  b'),  and  the  divided  metal  plates  (y,  2)  which  pass  to  the  electrodes,  the 
two  currents  induced  in  the  bobbins  are  obtained  in  the  same  direction. 

Keys,  or  arrangements  for  opening  or  closing  a  circuit,  are  of  great  use.  Fig.  392,  II,  shows  a 
scheme  of  the  friction  key  of  du  Bois-Reymond,  introduced  into  the  secondary  circuit.  It  consists 
of  two  brass  bars  (z  and^')  fixed  to  a  plate  of  ebonite,  and  as  long  as  the  key  is  down  on  the  metal 
bridge  {y,  r,  z)  it  is  ^^  short-circuited,^^  i.  e.,  the  conduction  is  so  good  through  the  thick  brass  bars 
that  none  of  the  current  goes  through  the  wires  leading  from  the  left  of  the  key.  When  the  bridge 
(r)  is  lifted  the  current  is  open.  [Fig.  396  shows  the  form  of  the  key,  v  being  a  screw  wherewith 
to  clamp  it  to  the  table.]  Similarly  the  key  electrodes  (III)  may  be  used,  the  current  being  made  as 
soon  as  the  spring  connecting  plate  (^)  is  raised  by  pressing  upon  k.  This  instrument  is  opened  by 
the  hand;  a,  b  are  the  wires  from  the  battery  or  induction  machine  ;  r,  r,  those  going  to  the  tissue; 
G,  the  handle  of  the  instrument. 

[Plug  Key. — Other  forms  of  keys  are  in  use,  e.g.,  Fig.  397,  the  plug  key,  the  two  brass  plates 
to  which  the  wires  are  attached  being  fixed  on  a  plate  of  ebonite.  The  brass  plug  is  used  to  connect 
the  two  brass  plates.  All  these  are  dry  contacts,  but  sometimes  a  fluid  contact  is  used  as  in  the 
mercury  key,  which  merely  consists  of  a  block  of  wood  with  a  cup  of  mercury  in  its  centre.     The 


VARIOUS   FORMS   OF   KEYS. 


603 


ends  of  the  wires  from  the  battery  dip  into  the  mercury ;  when  both  wires  dip  into  the  mercury  the 
circuit  is  made,  and  when  one  is  out  it  is  broken.] 

[Capillary  Contact  Key. — Where  an  ordinary  mercury  key  is  used  to  open  and  close  the  pri- 
mary circuit,  the  layer  of  oxide  formed  on  the  surface  by  the  opening  spark  disturbs  the  conduction 
after  a  short  time ;  hence,  it  is  advisable  to  wash  the  surface  of  the  mercury  with  a  dilute  solution  of 


Fig.  395. 


Magneto-induction  apparatus,  with  Stohrer's  commutator. 


Du  Bois-Reymond's  friction  key. 


alcohol  and  water  ( W.  Stirlmg).  A  handy  form  of  "  capillary  contact"  is  shown  in  Fig.  398,  such 
as  was  used  by  Kroneclcer  and  StirHng  in  their  experiments  on  the  heart.  "  A  glass  T  tube  is  pro- 
vided at  the  crossing  point  with  a  small  opening  [a).  The  vertical  tube  (b')  is  bent  in  the  form  of  a 
U,  and  filled  so  full  with  mercury  that  the  convex  surface  of  the  latter  projects  within  the  lumen  of 


Fig.  397. 


Fir.  398, 


Plug  Key. 


Capillary  contact,  e,  vibrating  platinum  style  adjustable  by/"  and 
^anddippinginto  mercury  ata;  3,  bent  tube  filled  with  mercury, 
into  which  dips  a  wire  {d) ;  a,  opening  in  cross  tube  (c). 

the  transverse  tube  [c).  One  end  of  c  is  connected  with  a  Mariotte's  flask  containing  diluted  alcohol, 
and  the  supply  of  the  latter  can  be  regulated  by  means  of  a  stop-cock.  The  fluid  flows  over  the 
apex  of  the  mercury  and  keeps  it  clean.  The  vibrating  platinum  style  {e)  is  attached  to  the  end  of 
a  rod  which  in  turn  is  connected  with  the  positive  pole  of  the  battery,  while  the  platinum  wire  (d) 
is  connected  with  the  negative  pole  of  the  "  battery."] 


604 


ELECTRICAL   CURRENTS    IN    NERVE    AND    MUSCLE. 


[331.  ELECTRICAL  CURRENTS  in  PASSIVE  MUSCLE  and  NERVE— SKIN 
CURRENTS. — Methods. — In  order  to  inve.sligatc  the  laws  of  the  muscle  current,  we  must  use  a 
muscle  composed  of  jiarallel  rii)res,  and  with  a  simple  arrangement  of  its  tihrcs  in  the  form  of  a  prism 
or  cylinder  (Fig.  ^y),  I  and  II).  The  sartorius  muscle  of  the  frog  sui>i)lies  these  conditions.  In 
such  a  muscle,  we  distinguish  the  surface  or  the  natural  longitudinal  section,  its  tendinous 
ends  or  the  natural  transverse  section  ;  furtlier,  when  the  latter  is  ciivide<l  transversely  to  the 
long  axis,  the  artificial  transverse  section  (Fig.  399,  I,  c,  df,  lastly,  the  term  equator  {a,  l>-in,  n) 
is  applied  to  a  line  so  drawn  as  exactly  to  divide  tlie  length  of  the  muscle  into  halves.  .\s  the  cur- 
rents are  very  feel^le,  it  is  necessary  to  use  a  galvanometer  with  a  periodic  damped  magnet  (Figs.  380, 
I,  and  3S7),  or  a  tangent  mirror  boussole  similar  to  that  used  for  thermo-electric  purposes  (  Fig.  230). 
The  wires  leading  from  the  tissue  are  connected  with  non-polari/able  electrodes  (Fig.  380,  1',  P). 

The  capillary  electrometer  of  Lippmann  may  be  used  for  detecting  the  current  (Fig.  400).  A 
thread  of  mercury  enclosed  in  a  capillary  tube  and  touching  a  conducting  fluid,  e.  g.,  dilute  sulphuric 
acid,  is  displaced  by  the  constant  current,  in  consequence  of  the  polarization  taking  place  at  the  point 
of  contact  altering  the  constancy  of  the  capillarity  of  the  mercur}'.  The  displacement  of  the  mer- 
cury which  the  observer  (B)  detects  by  the  aid  of  the  microscope  (M)  is  in  the  direction  of  the 
positive  current.     R  is  a  capillary  glass  tube,  filled  from  above  with  mercury,  and  from  below  with 


Fii;.  400, 


Scheme  of  the  muscle  current. 


Capillary  electrometer.  R. 
mercury  in  tube  ;  capillary 
tube  ;  s,  sulphuric  acid  ; 
y,  Hg ;  B,  observer;  M, 
microscope. 


dilute  sulphuric  acid.  Its  lower  narrow  end  opens  into  a  wide  glass  tube,  provided  below  with  a 
platinum  wire  fused  into  it  and  filled  with  Hg  (17),  and  this  again  is  covered  with  dilute  sulphuric 
acid  {s).  The  wires  are  connected  with  non-polarizable  electrodes  applied  to  the  +  and  —  surfaces  of 
the  muscle.  On  closing  the  circuit,  the  thread  of  mercury  passes  downward  from  c  in  the  direction 
of  the  arrow. 

Compensation. — The  strength  of  the  current  in  animal  tissues  is  best  measured  by  the  com- 
pensation method  of  Poggendorf  and  du  Bois-Reymond.  .\  current  of  known  strength,  or  which 
can  be  accurately  graduated,  is  passed  in  an  opposite  direction  through  the  same  galvanometer  or 
boussole,  until  the  current  from  the  animal  tissue  is  just  neutralized  or  compensated.  [When  this 
occurs,  the  needle  deflected  by  the  tissue  current  returns  to  zero.  The  principle  is  exactly  the  same 
as  that  of  weighing  a  body  in  terms  of  some  standard  weights  placed  in  the  opposite  scale  pan  of 
the  balance.] 

[Hermann  calls  the  current  obtained  from  an  injured  muscle,  /.  e.,  one  on  which 
an  artificial  transverse  or  other  section  has  been  made,  a  demarcation  current, 
while  the  currents  obtained  when  such  a  muscle  contracts,  he  calls  action  cur- 


ELECTRICAL    CURRENTS    IN    NERVE   AND    MUSCLE.  605 

rents.     This  section  deals  with  demarcation  currents,  or  the  muscle  current  of 
du  Bois-Reymond.] 

1.  Perfectly  fresh  uninjured  muscles  yield  no  current,  and  the  same  is  true 
of  dead  muscle  (Z.  Hermann,  1867). 

2.  Strong  electrical  currents  are  observed  when  the  traftsverse  section  of  a  muscle 
is  placed  on  one  of  the  cushions  of  the  non-polarizable  electrodes  (Fig.  380, 1,  M), 
while  the  surface  is  in  connection  with  the  other  {Nobili,  Matteucci,  du  Bois- 
Reymond^.  The  direction  of  the  current  is  from  the  (positive)  longitudinal 
section  to  the  (negative)  transverse  section  in  the  conducting  wires  (z".  e. ,  within 
the  muscle  itself  from  the  transverse  to  the  longitudinal  section  (Figs.  380,  I,  and 
399,  I).  This  current  is  stronger  the  nearer  one  electrode  is  to  the  equator,  and 
the  other  to  the  centre  of  the  transverse  section  ;  while  the  strength  diminishes, 
the  nearer  the  one  electrode  is  to  the  end  of  the  surface,  and  the  other  to  the 
margin  of  the  transverse  section. 

Smooth  muscles  also  yield  similar  currents  between  their  transverse  and  longitudinal  surfaces 
{I  334,  11). 

3.  Weak  electrical  currents  are  obtained  when  {a')  two  points  at  unequal  dis- 
tances from  the  equator  are  connected  ;  the  current  then  passes  from  the  point 
nearer  the  equator  (  +  )  to  the  point  lying  further  from  it  (  —  ),  but  of  course 
this  direction  is  reversed  within  the  muscle  itself  (Fig.  399,  II,  ke  and  ie).  (d) 
Similarly  weak  currents  are  obtained  by  connecting  points  of  the  transverse  sec- 
tion at  unequal  distances  from  the  centre,  in  which  case  the  current  outside  the 
muscle  passes  from  the  point  lying  nearer  the  edge  of  the  muscle  to  that  nearer 
the  centre  of  the  transverse  section  (Fig.  399,  II,  /,  c). 

4.  When  two  points  on  the  surface  are  equidistant  from  the  equator  (Fig. 
399,  I,  X,  y,  V,  z, — II,  r,  e^,  or  two  equidistant  from  the  centre  of  the  transverse 
section  (II,  c)  are  connected,  no  current  is  obtained.  [Because  the  points  are 
iso-electrical,  that  is  of  equal  potentiality.] 

5.  If  the  transverse  section  of  the  muscle  be  oblique  (Fig.  399,  III),  so  that 
the  muscle  forms  a  rhomb,  the  conditions  obtaining  under  III  are  disturbed. 
The  point  lying  nearer  to  the  obtuse  angle  of  the  transverse  section  or  surface  is 
positive  to  the  one  lying  near  to  the  acute  angle.  The  equator  is  oblique  {a,  c). 
These  currents  are  called  '■'■deviation  currents  or  inclination  currents'''  by  du  Bois- 
Reymond,  and  their  course  is  indicated  by  the  lines  1,2,  and  3. 

The  electromotive  force  of  a  strong  muscle  current  (frog)  is  equal  to  0.05  to  0.08  of  a 
Daniell's  element;  while  the  strongest  deviation  current  maybe  o.l  Daniell.  The  muscles  of  a 
curarized  animal  at  first  yield  stronger  currents ;  fatigue  of  the  muscle  diminishes  the  strength  of  the 
current  (^Roeber),vi\\As.  it  is  completely  abolished  when  the  muscle  dies.  i%(7/z>zo- a  muscle  increases 
the  current;  but  above  40°  C.  it  is  diminished  i^Steiner).  Cooling  diminishes  the  electromotive 
force.  The  warmed  livitig  muscular  and  nervous  substance  is  positive  to  the  cooler  portions  {^Her- 
mann) ;  while,  if  the  dead  tissues  be  heated,  they  behave  practically  as  indifferent  bodies  as  regards 
the  tissues  that  are  not  heated. 

6.  The  passive  nerve  behaves  like  muscle,  as  far  as  2,  3,  and  4  are  concerned. 

The  electromotive  force  of  the  strongest  nerve  current,  according  to  du  Bois-Reymond,  is 
0.02  of  a  Daniell.  Heating  a  nerve  from  15°  to  25°  C.  increases  the  nerve  current,  while  high  tem- 
peratures diminish  it  [Sieiner) 

7.  If  the  two  transversely  divided  ends  of  an  excised  nerve,  or  two  points  on 
the  surface  equidistant  from  the  equator,  be  tested,  a  current — the  axial  current 
— flows  in  the  nerve  fibre  in  the  opposite  direction  to  the  direction  of  the  normal 
impulse  in  the  nerve;  so  that  in  centrifugal  nerves  it  flows  in  a  centripetal  direc- 
tion, and  in  centripetal  nerves  in  a  centrifugal  direction  (^Mendelssohn  and 
Christiani) . 

The  electromotive  force  increases  with  the  length  of  the  nerve  and  with  the  area  of  its  transverse 
section.  Fatigue  {e.  g-,  tetanic  stimulation)  weakens  it,  especially  in  motor  nerves,  and  to  a  less 
extent  in  centripetal  nerves. 


606 


SELF-STIMULATION    OF    THE    MUSCLE. 


[Nerve-muscle  Preparation. — This  term  has  been  used  on  several  occasions. 

It  is  simply  the  sciatic  nerve  with  the  gastrocnemius  of  the  frog  attached  to  it 
(Fig.  401).  The  sciatic  nerve  is  dissected  out  entire  from  the 
vertebral  column  to  the  knee  ;  the  muscles  of  the  thigh  sepa- 
rated from  the  femur,  and  the  latter  divided  about  its  middle, 
so  that  the  preparation  can  be  fixed  in  a  clamp  by  the  remain- 
ing portion  of  the  femur;  while  the  tendon  of  the  gastrocne- 
mius is  divided  near  to  the  foot.  If  a  straw  flag  is  to  be 
attached  to  the  foot,  do  not  divide  the  tendo-Achillcs.] 

Rheoscopic  Limb. — The  existence  of  a  muscle  current 
may  be  proved  without  the  aid  of  a  galvanometer  :  i. 
By  means  of  a  sensitive  nerve-muscle  preparation  of  a  frog,  or 
the  so-called  ^''physiological  rheoscope.^'  Place  a  moist  con- 
ductor on  the  transverse  and  another  on  the  longitudinal  sur- 
face of  the  gastrocnemius  of  a  frog.  On  placing  the  sciatic 
nerve  of  a  nerve-muscle  preparation  of  a  frog  on  these  con- 
ductors, so  as  to  bridge  over  or  connect  their  two  surfaces, 
contraction  of  the  muscle  connected  with  the  nerve  occurs  at 

Nerve-muscle  preparation  oucc  )  and  the  samc  occurs  whcn  the  nerve  is  removed. 

of  a  frog.   F,  femur;       Make  a  transvcrse  section  of  the  gastrocnemius  muscle  of  a 

S,  sciatic    nerve;     I,  •  .  1       11  1  •      • 

tendo-Achiiies.  frog  s  ncrve-muscle  preparation,  and  allow  the  sciatic  nerve  to 

fall  upon  this  transverse  section  ;  the  limb  will  contract  as  the 

muscle  current  from  the  longitudinal  to  the  transverse  surface  now  traverses  the 

nerve  {Galvani,  Al.  v.  Humboldt).     These  experiments  have  long  been  known  as 

"  contraction  without  metals." 

[Use  a  nerve-muscle  preparation,  or,  as  it  is  called,  a  physiological  limb.  Hold  the  preparation  by 
the  femur,  and  allow  its  own  nerve  to  fnll  upon  the  gastrocnemius,  and  the  muscle  will  contract,  but 
it  is  better  to  allow  the  nerve  to  fall  suddenly  u]3on  the  cross  section  of  the  muscle.  The  nerve  then 
completes  the  circuit  between  the  longitudinal  and  transverse  section  of  the  muscle,  so  that  it  is 
stimulated  by  the  current  from  the  latter,  the  nerve  is  stimulated,  and  through  it  the  muscle.  That 
it  is  so,  is  proved  by  tying  a  thread  round  the  nerve  near  the  muscle,  when  the  latter  no  longer 
contracts.] 

2.  Self-stimulation  of  the  Muscle. — We  may  use  the  muscle  current  o{  an 
isolated  muscle  to  stimulate  the  latter  directly  and  cause  it  to  contract.  If  the 
transverse  and  longitudinal  surfaces  of  a  curarized  frog's  nerve-muscle  preparation 
be  placed  on  non-polarizable  electrodes,  and  the  circuit  be  closed  by  dipping  the 
wires  coming  from  the  electrodes  in  mercury,  then  the  muscle  contracts.  Simi- 
larly a  nerve  may  be  stimulated  with 
Fig.  402.  its   own     demarcation    current    (</« 

Bois-Reymond  and  others).  If  the 
lower  end  of  a  muscle  with  its  trans- 
verse section  be  dipped  into  normal 
saline  solution  (0.6  per  cent.  NaCl), 
which  is  quite  an  indifferent  fluid,  this 
fluid  forms  an  accessory  circuit  between 
the  transverse  and  adjoining  longitudi- 
nal surface  of  the  muscle,  so  that  the 
muscle  contracts.  Other  indifferent 
fluids  used  in  the  same  way  produce  a 
similar  result. 

[Kiihne's  Experiment  (Fig.  402). 
— The  demarcation  current  of  the 
nerve  of  a  nerve-muscle  preparation  may  be  used  as  the  stimulus  to  that  nerve 
on  completing  the  circuit.  On  an  earthenware  bowl  (B)  is  fixed  a  glass 
plate  (G),  and  thin  rolls  of  modeler's  clay  (P  P'j  are  bent  over  G.     A  nerve- 


Kiihne's  nerve  demarcation-current  experiment. 


ELECTRICAL    CURRENTS    OF   ACTIVE    MUSCLE.  607 

muscle  preparation  is  placed  with  its  nerve  (N)  on  the  clay,  touching  the  latter 
with  its  transverse  and  longitudinal  surfaces.  On  dipping  the  clay  into  a  vessel 
containing  normal  saline  (C),  the  muscle  contracts,  and  on  withdrawing  the 
normal  saline,  it  again  contracts.  In  this  case  the  nerve  is  stimulated  by  the 
completion  of  the  circuit  of  its  own  demarcation  current.] 

3.  Electrolysis. — If  the  muscle  current  be  conducted  through  starch  mixed 
with  potas sic  iodide,  then  the  iodine  is  deposited  at  the  -j-  pole,  where  it  makes  the 
starch  blue. 

Frog  Current. — It  is  asserted  that  the  total  current  in  the  body  is  the  sum  of  the  electrical  cur- 
rents of  the  several  muscles  and  nerves  which,  in  a  frog  deprived  of  its  skin,  pass  from  the  tip  of  the 
toes  toward  the  trunk,  and  in  the  trunk  from  the  anus  to  the  head.  This  is  the  "  cor7-ente  propria 
delta  rana"  of  Leopoldo  Nobili  (1827),  or  the  "frog  currenf^  of  du  Bois-Reymond.  In  mam- 
mals, the  corresponding  current  passes  in  the  opposite  direction. 

After  death,  the  currents  disappear  sooner  than  the  excitability  (  Valentin)  ;  they  remain  longer 
in  the  muscle  than  the  nerves,  and  in  the  latter  they  disappear  sooner  in  the  central  portions.  If  the 
nerve  current  after  a  time  become  feeble,  it  may  be  strengthened  by  making  a  new  transverse  section 
of  the  nerve.  A  motor  nerve  completely  paralyzed  by  curara  gives  a  current  [Funke),  and  so  does 
a  nerve  beginning  to  undergo  degeneration,  even  two  weeks  after  it  has  lost  its  excitability.  Muscles 
in  a  state  of  rigor  mortis  give  currents  in  the  opposite  direction,  owing  to  inequalities,  which  take 
place  during  decomposition.     The  nerve  current  is  reversed  by  the  act  on  of  boiling  water  or  drying. 

Currents  from  Skin  and  Mucous  Membranes. — In  the  skin  of  the  frog 
the  outer  surface  is  +,  the  inner  is  —  {du  Bois-Reymond),  and  the  same  is  true  of 
the  mucous  membrane  of  the  intestinal  tract  {Rosenthal'),  the  cornea  {Grunhagen), 
as  well  as  the  non-glandular  skin  of  fishes  {He7-mann'),  and  mollusks  {Oehler). 
Currents  are  also  manifested  by  glands. 

332.  CURRENTS  OF  STIMULATED  MUSCLE  AND  NERVE 
—ACTION  CURRENTS.— I.  Negative  Variation  of  the  Muscle  Cur- 
rent.— :If  a  muscle,  which  yields  a  strong  electrical  current,  be  thrown  into  a 
state  of  tetanic  contraction  by  stimulating  its  motor  nerve,  then,  when  the  muscle 
contracts,  there  is  a  diminution  of  the  muscle  current,  and  occasionally  the 
needle  of  the  galvanometer  may  swing  almost  to  zero.  This  is  the  "  negative 
variation  of  the  muscle  current"  {du  Bois-Reymond).  It  is  larger,  the  greater 
the  primary  deflection  of  the  galvanometer  needle  and  the  more  energetic  the 
contraction. 

After  tetanus,  the  muscle  current  is  weaker  than  it  was  before.  If  the  muscle  was  so  placed  upon 
the  electrodes  that  the  current  was  "  feeble,"  equally  during  tetanus  there  is  a  diminution  of  this  cur- 
rent. In  the  inactive  arrangement,  the  contraction  of  the  muscle  has  no  effect  on  the  needle.  If  the 
muscle  be  prevented  from  shortening,  as  by  keeping  it  tense,  the  negative  variation  still  takes  place. 

2.  Current  during  Tetanus. — An  excised  frog's  muscle  tetanized  through  its 
nerve  shows  electromotive  force — the  so-called  '*  action  current."  In  a  tetan- 
ized frog's  gastrocnemius,  there  is  a  descending  current.  In  completely  uninjured 
human  muscles,  however,  thrown  into  tetanus  by  acting  on  their  nerves,  there  is 
no  such  current  {L.  Hermann)  ;  similarly,  in  ^uite  uninjured  frog's  muscles,  as 
well  as  when  these  muscles  are  directly  and  completely  tetanized,  there  is  no  current. 

3.  Current  during  the  Contraction  Wave. — If  one  end  of  a  muscle  be 
directly  excited  with  a  momentary  stimulus,  so  that  the  contraction  wave  (§  299) 
rapidly  passes  along  the  whole  length  of  the  muscular  fibres,  then  each  part  of  the 
muscle,  successively  and  immediately  before  it  contracts,  shows  the  negative  varia- 
tion. Thus,  the  "  contraction  wave''''  is  preceded  by  a  "  negative  wave  "  of  the 
muscle  current,  the  latter  occurring  during  the  latent  period.  Both  waves  have  the 
same  velocity,  about  3  metres  per  second.  The  negative  wave,  which  first  increases 
and  then  diminishes,  lasts  at  each  point  only  0.003  second  {Bernstei?i). 

4.  During  a  Single  Contraction. — A  single  contraction  also  shows  a  muscle 
current.  [The  electrical  variation  takes  place  during  the  latent  period  of  the 
muscular  contraction,  so  that  it  precedes  the  latter.  The  variation  begins  .01"  to 
.04"  after  excitation,  while  the  contraction  does  not  begin  until  .ii"  to  .t,^    {Wal- 


608 


ELECTRICAL   CURRENTS   OF    ACTIVE    MUSCLE. 


ler).  A  frog's  muscle  may  be  made  to  record  its  contraction,  and  simultaneously 
the  variation  of  the  electrical  current,  as  ascertained  by  the  capillary  electrometer, 
may  be  photographed  (Fig.  403),  and  the  same  may  be  done  in  the  case  of  the 

heart  (Fig.  404).    The  capillary  electrometer  may 
Fig.  403.  \\\\.\i  advantage  be  employed  to  measure  this  time 

^^^^^^^^^^^^^^^       difference,    the    electrical    and     the    mechanical 
^^    B*S^S*S^S*S^3*        events  being  simultaneously  recorded.] 

The  diphasic  variation — 1st  phase  middle  negative  to  end  ; 
2d  phase  and  negative  to  middle  begins  about  .01 ''  before  the 
commencement  of  muscular  contraction  (  Waller). 

The  variation  is  diphasic — 1st  phase  base  negative  to  apex  ; 
2d  phase  apex  negative  to  base  (  Waller^.  The  first  phase 
begins  ■^^"  before  the  commencement  of  contraction. 

One  of  the  best  objects  for  this  ])urpose  is  the 
contracting  heart,  which  is  placed  upon  the  non- 
])olarizable  electrodes  connected  with  a  sensitive 
galvanometer.  Each  beat  of  the  heart  causes  a 
deflection  of  the  needle,  which  occurs  before  the 
contraction  of  the  cardiac  muscle  {K'dlliker  and 
H.  Milller).  The  electrical  disturbance  in  the 
muscle  causing  the  negative  variation  always  pre- 
cedes the  actual  contraction  {v.  Helmholtz,  1845). 
Still  it  lasts  throughout  the  whole  duration  of  the 
contraction  {Lee).  When  the  completely  uninjured 
frog's  gastrocnemius  contracts  by  stimulating  the 
nerve,  there  is  at  first  a  descending  and  then  an 
ascending  current  {Sig.  Mayer,  §  334,  II). 

More  exact  observations  on  the  electrical  processes  of  the  pulsating  heart  show  that  complicated 
phenomena  occur.  The  apex  of  the  dog's  heart  i-;  negative  to  the  base  during  systole.  In  many 
cases  this  [is  preceded,  and   in  some   it  is  followed,  by  an   opposite  condition  [Fredericq),  i.  e.,  a 


Frog.  Gastrocnemius  led  off  to  electro- 
meter from  the  middle   of  the  muscle 

BSTand  from  the  tendon.  Contraction  ex- 
cited by  a  single  break  induction  shock 
applied  to  the  sciatic  nerve,  e,  elec- 
trometer ;    j«,    muscle  ;    t,  time  in  ^ 

t  sec.  (muscle  to  H0SO4 ;  tendon  to 
Hg)    {.Waller). 


Frog's  heart.     Spontaneous   contraction,     e,  e,   electrometer ;  h,  h.  heart's  contraction  ;  t,  t,  time   in  ^  sec.  (apex 

to  HabOi,  base  to  Hg)  ( Waller). 


diphasic  variation.  If  the  heart  be  arrested  in  diastole  by  stimulation  of  the  vagus  (^  369),  there 
is  a  positive  variation  of  the  muscle  current  [Gaskell,  Fano).  \Valler  has  demonstrated  a  true 
electrical  variation  of  the  human  intact  heart. 

[Heart. — Gaskell  has  shown  that,  when  the  vagus  of  a  tortoise  is  stimulated  so 
as  to  arrest  its  heart  in  diastole,  the  action  of  the  inhibitory  nerve  is  accompanied 


SECONDARY    CONTRACTION.  609 

by  a  positive  electrical  variation  of  the  heart  current,  while  stimulation  of  the 
sympathetic  (augmentor)  nerve  causes  an  electrical  variation  of  the  same  sign  as 
that  caused  by  a  contraction  in  the  non-beating  tissue  of  the  ventricle  of  the  toad. 
In  both  cases,  the  respective  nerves  can  produce  their  electrical  effect  after  the 
heart  has  been  brought  to  standstill  by  the  application  of  muscarin  to  the  sinus. 
These  experiments  are  of  the  utmost  importance  in  connection  with  the  theory 
of  the  action  of  these  nerves  on  the  heart  (§  370),  and  the  mode  of  action  of 
poisons  on  the  heart  itself.] 

Secondary  Contraction. — A  nerve-muscle  preparation  may  be  used  to  de- 
monstrate the  electrical  changes  that  occur  during  a  single  contraction.  If  the 
sciatic  nerve.  A,  of  such  a  preparation  be  placed  upon  another  muscle,  B,  as  in 
Fig.  405,  then  every  time  the  latter,  B,  contracts,  the  frog's  muscle.  A,  connected 
with  the  nerve  also  contracts. 

If  the  nerve  of  a  frog's  nerve-muscle  preparation  be  placed  on  a  contracting 
mammalian  heart,  then  a  contraction  of  the  muscle  occurs  with  every  beat  of  the 
heart  {^Matteucci,   1842).     The  diaphragm,   even  after 
section  of  the  phrenic  nerve,   especially  the   left,  also  Fig.  405. 

contracts  during  the  heart  beat  {Schiff^.     This  is  the 
"  secondary  contraction  "  of  Galvani. 

Secondary  Tetanus. — Similarly,  if  a  nerve  of  a 
nerve-muscle  preparation  be  placed  on  a  muscle  which 
is  tetanized,  then  the  former  also  contracts,  showing 
"secondary  tetanus"  {du  Bois-Reymond).  The  latter 
experiment  is  regarded  as  a  proof  that,  during  the  pro- 
cess of  negative  variation  in  the  muscle,  many  successive 
variations  of  the  current  must  take  place,  as  only  rapid 
variations  of  this  kind  can  produce  tetanus  by  acting  on 
a  nerve — continuous  vibrations  being  unable  to  do  so. 

Usually,  there  is  no  secondary  tetanus  in  a  frog's  nerve-muscle 

preparation  when  it  is  laid  upon  a  muscle  which  is  tetanized  volun-     o      'j  •         ™,        .    . 

f     .r  ,  1         •      1      ^-        T  i_  •        •  -1  1     •         becondary  contraction.     The  sciatic 

tarily,   or   by  chemical    stimuh,    or    by   poisonmg  with    strychnin  nerve  of  A  lies  on  B;  E  elec- 

iyHering,  Kuhne) ;  still,  Loven  has   observed   secondary  strychnin  trodes   applied   to    the   sciatic 

tetanus  composed  of  six  to  nine  shocks  per  second.      Observations  nerve  of  B. 

with  a  sensitive  galvanometer,  or  Lippmann's  capillary  electrometer 

(Fig.  400),  show  that  the  spasms  of  strychnin  poisoning,  as  well  as  a  voluntary  contraction,  are  dis- 
continuous processes  [Loven,  p.  485). 

Biedermann  observed  that  striped  muscle,  under  the  influence  of  the  vapor  of  ether,  passes  into  a 
condition  in  which  it  shows  no  obvious  change  of  form  or  movement  when  it  is  stimulated,  while  at 
the  spot  stimulated,  there  are  galvanometric  variations  of  the  same  strength  as  occurred  during  stimu- 
lation before  the  action  of  the  ether.  Owing  to  the  abolition  of  the  power  of  conductivity,  they  can 
only  manifest  themselves  locally. 

[Secondary  Contraction  from  Muscle  to  Muscle  {Kiihne). — If  5  mm.  of 
one  end  of  the  sartorius  of  acurarized  frog  be  laid  upon  a  corresponding  5  mm.  of 
the  other  sartorius,  so  that  both  muscles  are  in  line,  and  if  the  surfaces  of  contact 
be  pressed  together,  either  by  an  ebonite  press  or  other  means,  on  stimulating  the 
free  end  of  one  of  the  muscles — either  electrically,  mechanically,  or  chemically — 
the  other  muscle  also  contracts,  and  if  the  first  one  be  tetanized,  the  second  one 
also  is  thrown  into  tetanus.  The  experiment  may  be  repeated  with  five  or  six 
muscles  in  line.  The  conduction  is  interrupted  at  once  by  ligature  of  the  muscle. 
The  second  muscle  contracts,  because  it  is  stimulated  directly  by  the  action  cur- 
rents of  the  contracting  muscular  fibres.  The  effect  is  prevented  by  introducing, 
between  the  overlapping  ends  of  the  muscle,  a  thin  plate  of  gutta  percha,  tinfoil, 
or  any  insulator.  This  experiment  of  Kiihne's  shows  us  how  important  a  role 
electrical  phenomena  play  in  connection  with  muscular  contraction.  Secondary 
contraction  from  nerve  has  long  been  known.] 

Negative  Variation  in  Nerve. — If  a  nerve  be  placed  with  its  transverse 
39 


010 


CURRENT    IN    THE    SPINAL    CORD. 


section  on  one  non-polarizable  electrode,  and  its  longitudinal  surface  on  the  other, 
and  if  it  be  stimulated  electrically,  chemically,  or  mechanically,  the  nerve  current 
is  also  diminished  (<///  Bois-jReymond).  This  negative  variation  is  i)ropagated 
toward  />oih  ends  of  a  nerve,  and  is  composed  of  very  rapid,  successive,  periodic 
interruptions  of  the  original  current,  just  as  in  a  contracted  muscle  {Bernstein). 
Hering  succeeded  in  obtaining  from  a  nerve,  as  from  a  muscle,  a  secondary  con- 
traction or  secondary  tetanus.  The  amount  of  the  negative  variation  depends  upon 
the  extent  of  the  jirimary  deflection,  also  upon  the  degree  of  nervous  excitability, 
and  on  the  strength  of  the  stimulus  employed.  The  negative  variation  occurs  on 
stimulating  with  tetanic  as  well  as  with  single  shocks.  The  negative  variation 
is  not  observed  in  completely  uninjured  nerves. 

Hering  found  that  the  negative  variation  of  the  nerve  current  caused  by  tetanic  stimulation  is  fol- 
lowed by  ^positive  variation,  which  occurs  immediately  after  the  former,  /.  e.,  it  is  diphasic.  It 
increases  to  a  certain  degree  with  the  duration  of  the  stimulation,  as  well  as  with  the  strength  of  the 
stimulus,  and  with  the  drying  of  the  nerve  {Hemi).     {Effect  of  Eh-ctrotoiiiis,  §  335,  I). 

EiG.  406. 


Scheme  of  Bernstein's  diflferential  rheotome  ;  N  «,  nerve  :  J.  induction  machine;  G,  galvanometer,  .r,,)*,  deflection 
of  needle  ;  E,  batter)'  and  prim.yy  circuit  with  C  fer  opening  it  at  o  ;  c,  for  closing  galvanometer  circuit  ;  z  z, 
electrodes  in  galvanometer  circuit  ;  S,  motor. 


Negative  Variation  of  the  Spinal  Cord. — This  is  the  same  as  in  nerves  generally.  If  a  current 
be  conducted  from  the  transverse  and  longitudinal  surfacesof  the  upper  part  of  the  medulla  oblongata, 
we  observe  spontaneous,  intermittent,  ne'^atii'e  variations,  perhaps  due  to  the  intermittent  excitement 
of  the  nerve  centres,  more  especially  of  the  respiratory  centre.  Similar  variations  are  obtained 
reflexly  by  single  stimuli  applied  to  the  sciatic  nerve,  while  strong  stimulation  by  common  salt  or 
induction  shocks  inhibits  them. 

Velocity. — The  process  of  negative  variation  is  propagated  at  a  measurable  velocity  along  the 
nerve,  most  rapidly  at  15°  to  25°  C.  (Steiner),  and  at  the  same  rate  as  the  velocity  of  the  nervous 
impulse  itself,  about  27  to  28  metres  per  second.  The  duration  of  a  single  variation  (of  which 
the  process  of  negative  variation  is  composed)  is  only  0.0005  'o  0.0008  second,  while  the  wave  length 
in  the  nerve  is  calculated  by  Bernstein  at  18  mm. 

Differential  Rheotome. — J.  Btrnstein  estimated  the  velocity  of  the  negative  variation  in  a  nerve 
by  means  of  a  differential  rheotome  thus  (Fig.  406)  :  A  long  stretch  of  a  nerve  (N  n)  is  so  arranged 
that  at  one  end  of  it  (N)  its  transverse  and  longitudinal  surfaces  are  connected  with  a  galvanometer 
(G),  while  at  the  other  end  (w)  are  placed  the  electrodes  of  an  induction  machine  (J).  A  disk  (B) 
rapidly  rotating  on  its  vertical  axis  (A)  has  an  arrangement  (C)  at  one  point  of  its  circumference,  by 
means  of  which  the  current  of  the  primary  circuit  (E)  is  rapidly  opened  and  closed  during  each 
revolution.  This  causes,  with  each  rotation  of  the  disk,  an  opening  and  a  closing  shock  to  be  applied 
to  the  end  of  the  nerve.     At  the  diametrically  opposite  part  of  the  circumference  is  an  arrangement 


ELECTRICAL    CURRENTS   DURING    ELECTROTONUS. 


611 


(c)  by  which  the  galvanometer  circuit  is  closed  and  opened  during  each  revolution.  Thus,  the  stimu- 
lation and  the  closing  of  the  galvanometer  circuit  occur  at  the  same  moment.  On  rapidly  rotating 
the  disk,  the  galvanometer  indicates  a  strong  nerve  current,  an  excursion  of  the  magnetic  needle  to 
J.  At  the  moment  of  stimulation,  the  negative  variation  has  not  yet  reached  the  other  end  of  the 
nerve.  If,  however,  the  arrangement  which  closes  the  galvanometer  circuit  be  so  displaced  (to  o) 
along  the  circumference,  that  the  galvanometer  circuit  is  closed  somewhat  /a^er  than  the  nerve  is 
stimulated,  then  the  current  is  weakened  by  the  negative  variation  (the  needle  passing  backward  to 
jr).  When  we  know  the  velocity  of  rotation  of  the  disk,  it  is  easy  to  calculate  the  rate  at  which  the 
impulse  causing  the  negative  variation  passes  along  a  given  distance  of  nerve  from  N  to  ;z. 

The  negative  variation  is  absent  in  degenerated  nerves  as  soon  as  they  lose  their  excitability. 

Retinal  and  Eye  Currents. — If  a  freshly-excised  eyeball  be  placed  on  the  non-polarizable 
electrodes  connected  with  a  galvanometer,  and  if  light  fall  upon  the  eye,  then  the  normal  eye  current 
from  the  cornea  (+)  to  the  transverse  section  of  the  optic  nerve  ( — )  is  at  first  increased.  Yellow 
light  is  most  powerful,  and  less  so  the  other  colors  [Hobngren,  AP Kendrick  and  Dewar).  The 
inner  surface  of  t\ie  passive  retina  is  positive  to  the  posterior.  When  the  retina  is  illuminated  there 
is  a  double  variation,  a  negative  variation  with  a  preliminary  positive  increase  ;  while,  when  the  light 
ceases,  there  is  a  simple  positive  variation.  Retinse,  in  which  the  visual  purple  has  disappeared 
owing  to  the  action  of  light,  show  smaller  variations  [Kilkne  and  Steiner). 

Stimulation  of  the  secretory  nerves  of  the  ^/a«(/z//ar  membranes,  besides  causing  secretion, 
affects  the  current  of  rest  [Roeber).  This  secretion  current  passes  in  the  same  direction  in  the 
skin  of  the  frog  and  warm-blooded  animals  as  the  current  of  rest,  although  in  the  frog  it  is  occasion- 
ally in  the  opposite  direction  {Hermann).  If  the  current  be  conducted  uniformly  from  both  hind 
feet  of  a  cat,  on  stimulating  the  sciatic  nerve  of  one  side,  not  only  is  there  a  secretion  of  sweat 
(g  288),  but  a  secretion  current  is  developed  [Lticksinger  and  Hermann).  If  two  symmetrical 
parts  of  the  skin  in  the  leg  or  arm  of  a  man  be  similarly  tested,  and  the  muscle  of  one  side  be  con- 
tracted, a  similar  current  is  developed.  Destruction  or  atrophy  of  the  glands  abolishes  both  the 
power  of  secretion  and  the  secretion  current.  There  is  no  secretion  current  from  skin  covered  with 
hairs,  but  devoid  of  glands  {Bubnoff).  [The  secretion  current  from  the  sub-maxillary  gland  is 
referred  to  in  ^  145  [Bayliss  and  Bradford)^ 

333.   ELECTROTONIC  CURRENTS   IN   NERVE   AND   MUS- 
CLE.—[When  a  constant    current    called   the   "polarizing   current"  is 
passed  through  a  stretch  of  nerve,  the  nerve  is  thrown  into  a  peculiar  condition, 
called  the  -''electrotonic  condition,"  or  briefly  electrotonus.    In  this  condition, 
the  vital  properties  of  the  nerve  are  modified,  i.  e. — 
(i)  Its  electromotivity  (§  333). 
(2)  Its  excitability  (§  335). 
The  former  is  considered  in  this  section,  and  the 
latter  in  a  subsequent  section.] 

1.  Positive  Phase  of  Electrotonus. — If  a 
nerve  be  so  arranged  upon  the  electrodes  (Fig.  407, 
I)  that  its  transverse  section  lies  on  one,  and  its  lon- 
gitudinal on  the  other  electrode,  then  the  galvano- 
meter indicates  a  strong  current.  If  now  a  constant 
current  be  transmitted  through  the  end  of  the  nerve 
projecting  beyond  the  electrodes  (the  so-called  "Z^- 
larizing^^  end  of  the  nerve),  and  if  the  direction  of 
this  current  coincide  with  that  in  the  nerve,  then  the 
magnetic  needle  gives  a  greater  deflection,  indicating 
an  increase  of  the  nerve  current — "the  positive 
phase  of  electrotonus."  The  increase  is  greater 
the  longer  the  stretch  of  nerve  traversed  by  the 
current,  the  stronger  the  galvanic  current,  and  the 
less  the  distance  between  the  part  of  the  nerve 
traversed  by  the  constant  current  and  that  on  the 
electrodes. 

2.  Negative  Phase  of   Electrotonus. — If  in 

the  same  length  of  nerve  the  constant  current  passes  in  the  opposite  direction 
to  the  nerve  current  (Fig.  407,  II),  there  is  a  diminution  of  the  electromotive 
force  of  the  latter — "negative  phase  of  electrotonus." 


Fig.  407. 


Nerve  current  in  electrotonus. 
vanomeler  ;  b,  electrodes ; 
slant  current. 


612  MUSCLE    CURRENT    DURING    ELECIROTONUS. 

3.  Equator. — If  two  points  of  the  nerve  equidistant  from  the  equator  be 
placed  on  the  electrodes  (III),  there  is  no  deflection  of  the  galvanometer  needle 
(p.  605,  4).  If  a  constant  current  be  passed  through  one  free  projecting  end  of 
the  nerve,  then  the  galvanometer  indicates  an  electromotive  effect  in  the  same 
direction  as  the  constant  current. 

Electrotonus. — These  experiments  show  that  a  constant  current  causes  a 
change  of  the  electromotive  force  of  the  part  of  the  nerve  directly  traversed  by 
the  constant  current,  /'.  e.,  in  the  intra-polar  area,  and  also  in  the  part  of  the 
nerve  outside  the  electrodes,  /.  <?.,  in  the  extra-polar  area.  This  condition  is 
called  electrotonus  {du  Bois-Reymoiui,  1843). 

The  electrotonic  current  is  strongest  not  far  from  the  electrodes,  and  it  may  be  twenty-five  times  as 
strong  as  the  nerve  current  of  rest  (<1  331,  5) ;  it  is  greater  on  the  anode  than  on  the  cathode  side; 
it  undergoes  a  negative  variation  hke  the  resting  nerve  current  during  tetanus;  it  occurs  at  once 
on  closing  the  constant  current,  although  it  diminishes  uninterruptedly  at  the  cathode  {du  Bois- 
Reymond).  On  the  contrary,  between  the  electrodes,  besides  the  polarizing  current  itself,  there  is 
no  obvious  electrotonic  increase  of  the  current  to  be  observed  {I/tTiiiann).  These  phenomena  take 
place  only  as  long  as  the  nerve  is  excitable.  If  the  nerve  be  ligatured  in  the  projecting  part  in  the 
galvanometer  circuit,  the  phenomena  cease  in  the  ligatured  part.  The  above  described  galvanic 
electrotonic  changes  of  the  extra-polar  part  are  absent  in  non-medullated  nerve  fibres,  while, 
on  the  contrary,  the  physiological  electrotonus  is  present.  The  physiological  electrotonus  of  medul- 
lated  nerves  can  be  set  aside  by  treating  meduUated  nerves  with  ether,  while  the  physical  phenomena 
remain  {Biedermann). 

The  negative  variation  (^  332)  occurs  more  rapidly  than  the  electrotonic  increase  of  the  current, 
so  that  the  former  is  over  before  the  electromotive  increase  occurs.  The  velocity  of  the  electro- 
tonic change  in  the  current  is  less  than  the  rapidity  of  propagation  of  the  excitement  in  the  nerves — 
being  only  8  to  10  metres  per  second  (  Tsrhirjew,  Bernstein). 

"  The  secondary  contraction  from  a  nerve  "  depends  upon  the  electrotonic  state.  If  the 
sciatic  nerve  of  a  frog's  nerve-muscle  preparation  be  placed  on  an  excised  nerve,  and  if  a  constant 
current  be  passed  through  the  free  end  of  the  latter — non-electrical  stimuli  being  inactive — the  mus- 
cles contract.  This  occurs  because  the  electrotonizing  current  in  the  excised  nerve  stimulates  the 
nerve  lying  on  it.  By  rapidly  closing  and  opening  the  current,  we  obtain  "secondary  tetanus  from 
a  nen'e''''  (p.  609). 

[Paradoxical  Contraction. — Exactly  the  same  occurs  when  the  current  is 
applied  to  one  of  the  two  branches  into  which  the  sciatic  nerve  of  the  frog  divides. 
The  sciatic  nerve  of  the  frog  divides  at  the  lower  end  of  the  thigh  into  \\\q.  peroneal 
and  tibial  branches.  If  the  sciatic  nerve  be  divided  above,  and  the  peroneal 
branch  be  also  divided  and  stimulated  with  interrupted  induction  shocks,  the 
muscles  supplied  by  the  tibial  branch  will  contract.  There  is  no  contraction  of 
the  muscle  if  the  peroneal  nerve  be  ligatured.] 

Polarizing  After-Currents. — When  the  constant  current  is  opened,  there  are  after-currents 
depending  upon  internal  polarization  (J.  328).  In  living  nerves,  muscle,  and  electrical  organs  this 
internal  polarization  current,  when  a  strong  primary  current  of  very  short  duration  is  used,  is  always 
positive,  i.e.,  has  the  same  direction  as  the  primary  current.  Prolonged  duration  of  the  primary 
current  ultimately  causes  negative  polarization.  Between  these  two  is  a  stage  when  there  is  no  polari- 
zation. Positive  polarization  is  especially  strong  in  nerves  when  the  primary  current  has  the  direc- 
tion of  the  impulse  in  the  nerve ;  in  muscle,  when  the  primary  current  is  directed  from  the  point  of 
entrance  of  the  nerve  into  the  muscle  toward  the  end  of  the  muscle  {I  334,  II). 

4.  Muscle  Current  during  Electrotonus. — The  constant  current  also 
produces  an  electrotonic  condition  in  muscle;  a  constant  current  in  the  same 
direction  increases  the  muscle  current,  while  one  in  an  opposite  direction  weakens 
it,  but  the  action  is  relatively  feeble. 

[Electrotonic  Phenomena  in  Conductors. — Matteucci  found  that  a  metallic  wire  surrounded 
by  a  moist  conductor,  when  traversed  by  a  galvanic  current,  exhibits  currents  possessing  the  properties 
of  electrotonic  currents  of  nerves.  He  also  found  that  the  currents  ceased  if  the  wire  was  of  zinc 
and  the  envelope  a  saturated  solution  of  zinc  sulphate.  This  shows  that  these  currents  were  due  to 
polarization  between  the  core  and  the  fluid.  Hermann  finds  that  the  currents  only  obtain  when  a 
polarizable  core  is  present.  A  straw  without  joints,  if  filled  with  a  saturated  solution  of  c>ommon 
salt,  or  the  tentacles  of  a  lobster  when  moistened  with  saline  solution,  and  traversed  by  a  constant 
current,  exhibit  similar  electrotonic  currents  {Hering).'] 


THEORIES    OF    MUSCLE    AND    NERVE    CURRENTS.  613 

334.  THEORIES  OF   MUSCLE  AND   NERVE   CURRENTS.— 

I.  Molecular  or  pre-existence  Theory.- — To  explain  the  currents  in  muscle 
and  nerve,  du  Bois-Reymond  proposed  the  so-called  molecular  theory.  Accord- 
ing to  this  theory,  a  nerve  or  muscle  fibre  is  composed  of  a  series  of  small  electro- 
motive molecules  arranged  one  behind  the  other,  and  surrounded'by  a  conducting 
indifferent  fluid.  The  molecules  are  supposed  to  have  a  positive  equatorial  zone 
directed  toward  the  surface,  and  two  negative  polar  surfaces  directed  toward  the 
transverse  section.  Every  fresh  transverse  section  exposes  new  negative  surfaces, 
and  every  artificial  longitudinal  section  new  positive  areas. 

This  scheme  explains  the  strong  currents — when  the  +  longitudinal  surface  is  connected  with  the 
—  transverse  surface,  a  current  is  obtained  from  the  former  to  the  latter — but  it  does  not  explain  the 
feeble  currents.  To  explain  their  occurrence  we  must  assume  that,  on  the  one  hand,  the  electro- 
motive force  of  the  molecules  is  weakened  with  varying  rapidity  at  unequal  distances  from  the  equator; 
on  the  other,  at  unequal  distances  from  the  transverse  section.  Then,  of  course,  differences  of 
electrical  tension  obtain  between  the  stronger  and  the  feebler  molecules. 

Parelectronomy. — But  the  natural  transverse  section  of  a  muscle,  i.  e.,  the  end  of  the  tendon,  is 
not  negative,  but  more  or  less  positive  electrically.  To  explain  this  condition,  du  Bois-Reymond 
assumes  that  on  the  end  of  the  tendon  there  is  a  layer  of  electropositive  muscle  substance.  He 
supposes  that  each  of  the  peripolar  elements  of  muscle  consists  of  two  bipolar  elements,  and  that  a 
layer  of  this  half  element  lies  at  the  end  of  the  tendon,  so  that  its  positive  side  is  turned  toward  the 
free  surface  of  the  tendon.  This  layer  he  calls  the  "  parelectronomic  layer."  It  is  never  com- 
pletely absent.  Sometimes  it  is  so  marked  as  to  make  the  end  of  the  tendon  -\-  in  relation  to  the 
surface.     Cauterization  destroys  it.      [It  is  supposed  to  be  favored  by  cold.] 

The  negative  variation  is  explained  by  supposing  that,  during  the  action  of  a  muscle  and  nerve, 
the  electromotive  force  of  all  the  molecules  is  diminished.  During  partial  contraction  of  a  muscle, 
the  contracted  part  assumes  more  the  characters  of  an  indifferent  conductor,  which  now  becomes 
connected  with  the  negative  zone  of  the  passive  contents  of  the  muscular  fibres. 

The  electrotonic  currents  beyond  the  electrodes  in  nerves  must  be  explained.  To  explain  the 
electrotonic  condition,  it  is  assumed  that  the  bipolar  molecules  are  capable  of  rotation.  The  polarizing 
current  acts  upon  the  direction  of  the  molecules,  so  that  they  turn  their  negative  surfaces  toward  the 
anode,  and  their  positive  surfaces  to  the  cathode,  whereby  the  molecules  of  the  intra-polar  region  have 
the  arrangement  of  a  Volta's  pile.  In  the  part  of  the  nerve  outside  the  electrodes,  the  further  removed 
it  is,  the  less  precisely  are  the  molecules  airanged.  Hence,  the  swing  of  the  needle  is  less,  the  further 
the  extra-polar  portion  is  from  the  electrodes. 

II.  Difference  or  Alteration  Theory. — The  difference  theory  was  proposed 
by  L.  Hermann,  and,  according  to  him,  the  four  following  considerations  are 
sufficient  to  explain  the  occurrence  of  the  galvanic  phenomena  in  living  tissues ;  (i) 
Protoplasm,  by  undergoing  partial  death  in  its  continuity,  whether  by  injury  or  by 
(horny  or  mucous)  metamorphosis,  becomes  negative  toward  the  uninjured  part. 
(2)  Protoplasm,  by  being  partially  excited  in  its  continuity,  becomes  negative  to 
the  uninjured  part.  (3)  Protoplasm,  when  partially  heated  in  its  continuity, 
becomes  positive,  and  by  cooling  negative,  to  the  unchanged  part.  (4)  Proto- 
plasm is  ?,txong\y polarizable  on  its  surface  (muscle,  nerve),  the  polarization  con- 
stants diminishing  Avith  excitement  and  in  the  process  of  dying. 

Streamless  Fresh  Muscles. — It  seems  that  passive,  uninjured,  and  abso- 
lutely fresh  nerves,  and  muscles,  are  completely  devoid  of  a  current,  e.g.,  the 
heart  (^Engelmanti),  also  the  musculature  of  fishes  while  still  covered  by  the  skin. 

[According  to  Hermann,  the  currents  obtained  from  muscle  are  due  to  injury  of 
the  muscle  substance,  whereby  a  difference  of  potential  is  set  up,  the  injured  part 
being  negative  to  the  uninjured.  In  fact,  it  is  impossible  to  isolate  a  muscle  with- 
out injuring  it,  owing  to  its  connections.  Frogs  exhibit  skin  currents  after  the 
skin  is  destroyed ;  the  muscles  still  exhibit  currents,  but  Hermann  explains  this  by 
the  action  of  the  irritant,  used  to  destroy  the  skin,  also  affecting  the  muscle.  In 
fishes,  however,  there  are  no  skin  currents,  and  if  they  be  curarized,  absolutely  no 
current  is  obtained  from  their  uninjured  muscles  {Hermann).  The  heart  also  when 
passive  and  uninjured  gives  no  current,  although  it  exhibits  an  action  current  when 
it  contracts,  and  every  injured  part  in  it  possesses  a  negative  electrical  potential 
with  reference  to  the  rest.] 


614  ACTION    CURRENTS. 

L.  Hermann  also  finds  that  the  muscle  current  is  always  developed  after  a  time,  which  is  very 
short,  when  a  new  transverse  section  is  made.  [By  means  of  his  "  Fall-rheotom,"  an  arrangement 
wherein'  a  weigiit,  covered  with  shagreen,  injured  a  muscle,  and  at  the  same  time,  closed  and  opened 
a  galvanometer  circuit,  Hermann  was  able  to  show  that  the  current — demarcation  current — took  a 
certain  time  to  develop.  Had  it  been  preexistent,  as  supposed  by  du  Bois-Reymond,  this  ought  not 
to  have  lieen  the  case.] 

Demarcation  Current. — Eveiy  injury  of  a  muscle  or  nene  causes  at  the  ])oint  of  injury  {demar- 
cation siirfiic()  a  dying  sulistance,  which  behaves  negatively  to  the  positive  intact  substance.  The 
current  thus  produced  is  called  by  Hermann  the  'Uiemarcation  current."  If  individual  parts  of  a 
muscle  be  moistened  with  potash  salts  or  muscle  juice,  they  become  negatively  electrical ;  if  these 
substances  be  removed  the.se  parts  cease  to  be  negative  {Bieder/nann). 

It  appears  that  all  living  jjrotoiilasmic  substance  has  a  special  property,  whereby  injury  of  a  part  of 
it  makes  it,  when  dying,  negative,  while  the  intact  parts  remain  jxisitively  electrical.  Thus,  all 
transverse  sections  of  living  parts  of  plants  are  negative  to  their  surface  {Buff) ;  and  the  same  occurs 
in  animal  parts,  e.g.,  glands  and  bones.  Engelmann  made  the  remarkable  observation  that  the  heart 
and  smooth  muscle  again  lose  the  negative  condition  of  their  transverse  section,  when  the  muscle  cells 
are  completely  dead,  as  far  as  the  cement  substance  of  the  nearest  cells;  in  nerves,  when  the  divided 
portion  dies,  as  far  as  the  first  node  of  Ranvier.  When  all  these  organs  are  again  completely  si  ream- 
less,  then  the  absolutely  dead  substance  behaves  essentially  as  an  indifferent  moi.st  conductor.  Muscles 
divided  subcutaneously  and  healed  do  not  exhibit  a  negative  reaction  of  the  surface  of  their  section. 

All  these  considerations  go  to  show  that  the  pre'existence  of  a  current  in  living, 
uninjured  tissues  can  no  longer  be  maintained. 

Theoretical. — Grunhagen  and  L.  Hennann  explain  the  electrotonic  currents  as  lieing  due  to 
internal  polarization  in  the  nerve  fibre  between  the  conducting  core  of  the  nerve  and  the  enclosing 
sheaths.  Matteucci  found  that,  when  a  wire  is  surrounded  with  a  moist  conductor,  and  the  covering 
placed  in  connection  with  the  electrodes  of  a  constant  current,  currents  similar  to  the  electrotonic 
currents  in  nerves,  and  due  to  polarization,  are  developed.  If  either  the  wire  or  the  moist  covering 
be  interrupted  at  any  part,  then  the  polarization  current  does  not  extend  beyond  the  rupture  (p.  6l2). 
The  polarization  developed  on  the  surface  of  the  wire  by  its  transition  resistance  causes  the  conducted 
current  to  extend  much  beyond  the  electrodes. 

Muscles  and  nerves  consist  of  fibres  surrounded  by  indifterent  conductors.  As  soon  as  a  constant 
current  is  closed  on  their  surface,  internal  polarization  is  developed,  which  produces  the  electrotonic 
variation ;  it  disappears  again  on  opening  or  breaking  the  current.  Polarization  is  detected  by  the 
fact  that,  in  living  nerve,  the  galvanic  resistance  to  conduction  across  a  fibre  is  about  five  times,  and 
in  muscles  about  seven  times  greater  than  in  the  longitudinal  direction. 

Action  Currents. — The  term  "action  current  "  is  applied  by  L.  Hermann  to  the  currents  obtained 
during  the  activity  of  a  muscle  or  nerve.  When  a  single  stimulation  wave  (contraction)  passes 
along  muscular  fibres,  which  are  connected  at  two  points  with  a  galvanometer,  then  that  ]X)int  through 
which  the  wave  is  just  passing  is  negative  to  the  other.  Occasionally,  in  excised  muscles,  local  con- 
tractions occvu",  and  these  points  are  negative  to  the  other  passive  parts  of  the  muscle  (Biedermann). 
In  order,  therefore,  to  explain  the  currents  obtained  from  a  frog's  leg  during  tetanus,  we  mu.st  assume 
that  the  end  of  the  fibre  which  is  negative  participates  less  in  the  excitement  than  the  middle  of  the 
fibre.     But  this  is  the  case  only  in  dying  or  fatigued  muscles. 

According  to  <!  336,  I),  the  direct  application  of  a  constant  current  to  a  muscle  causes  contraction 
first  at  the  cathode,  when  the  current  is  closed,  and  when  it  is  oj^ened,  at  the  anode.  This  is 
explained  by  assuming  that,  during  the  closing  contraction,  the  muscle  is  negative  at  the  cathode, 
while  with  the  ojjening  contraction  the  negative  condition  is  at  the  anode. 

If  a  muscle  be  thrown  into  contraction  by  stimulating  its  nerve,  then  the  wave  of  excitement 
travels  from  the  entrance  of  the  nerve  to  both  ends  of  the  muscle,  which  also  behave  negatively 
to  the  passive  parts  of  the  muscle.  According  to  the  point  at  which  the  nerve  enters  the  muscle, 
the  ascending  or  descending  wave  of  excitement  will  reach  the  end  (origin  or  insertion)  of  the 
muscle  sooner  than  the  other.  On  placing  such  a  muscle  in  the  galvanometer  circuit,  then  at  first 
that  end  of  the  muscle  will  be  negative  which  lies  nearest  to  the  point  of  entrance  of  the  nerve  {e.g.., 
the  upper  end  of  the  gastrocnemius),  and  afterward  the  lower  end.  Thus,  there  appears  rapidly 
after  each  other,  at  first  a  descending,  and  then  an  ascending,  current  in  the  galvanometer  circuit, 
of  course  reversed  within  the  muscle  itself  (.S'zV-  ^I(^yer)  (§  332,  4). 

The  same  occurs  in  the  muscles  of  the  human  forearm.  When  these  were  caused  to  contract 
through  their  nerves,  at  first  the  point  of  entrance  of  the  nerve  (10  cm.  above  the  elbow  joint)  was 
negative,  and  then  followed  the  ends  of  the  muscles  when  the  contraction  wave,  with  a  velocity  of 
10  to  13  metres  per  second,  reached  them  (Z.  Hermann)  (^  399,  i). 

If  a  completely  uninjured,  streamless  muscle  be  made  to  zo\\\xz.c\.  directly  and  in  /(^/o,  then  neither 
during  a  single  contraction,  nor  in  tetanus,  is  there  a  current,  because  the  whole  of  the  muscle  passes 
at  the  same  moment  into  a  condition  of  contraction. 

Nerve  Currents. — Hermann  also  supposes  that  the  contents  of  dying  or  active  nerves  behave 
negatively  to  the  passive  normal  portions. 


VARIATIONS    OF   THE    EXCITABILITY   DURING    ELECTROTONUS.      615 

Imbibition  Currents. — When  water  flows  through  capillary  spaces,  this  is  accompanied  by  an 
electrical  movement  in  the  same  direction  [Quincke,  Zollner).  Similarly,  the  forward  movement  of 
water  in  the  capillary  interspaces  of  non-living  parts  (pores  of  a  porcelain  plate)  is  also  connected 
with  electrical  movements,  which  have  the  same  direction  as  the  current  of  water.  The  same  effect 
occurs  in  the  movement  of  water,  which  results  in  that  condition  known  as  imbibition  of  a  body. 
We  must  remember,  that  at  the  demarcation  surface  of  an  injured  nerve  or  muscle,  imbibition  takes 
place ;  that  also  at  the  contracted  parts  of  a  muscle  imbibition  of  fluid  occurs  (|  227,  II) ;  and  that 
during  secretion  there  is  a  movement  of  the  fluid  particles. 

In  plants,  electrical  phenomena  have  been  observed  during  the  passive  bending  of  vegetable 
plants  (leaves  or  stalks),  as  well  as  during  the  active  movements  which  are  associated  with  the 
bending  of  certain  parts,  e.g.,  as  in  the  mimosa  and  dionsea  {^Biirdon- Sanderson).  These  phenomena 
are  perhaps  explicable  by  the  movement  of  water  which  must  take  place  in  the  interior  of  the 
vegetable  parts  {^A.  G.  Kunket).  The  root  cap  of  a  sprouting  plant  is  negative  to  the  seed  coverings 
[Hermatin) ;  the  cotyledons  positive  to  the  other  parts  of  the  seedling  [MuHer-Hettlingen).  In  the 
incubated  hen's  egg,  the  embryo  is  -|-  j  the  yelk  —  {IIer?nann  atid  v.  Gendre). 

335.  ELECTROTONIC  ALTERATION  OF  THE  EXCITA- 
BIJLITY. — Cause  of  Electrotonus. — If  a  certain  stretch  of  a  living  nerve  be 
traversed  by  a  constant  electrical  {^'^ polarizing^ ^)  current,  it  passes  into  a  condi- 
tion of  altered  excitability  {Ritter,  1802,  and  others),  which  du  Bois-Reymond 
called  the  electrotonic  condition,  or  simply  electrotonus.  This  condition  of  altered 
excitability  extends  not  only  over  the  part  actually  traversed  by  the  current, 
intra-polar  portion,  but  it  is  communicated  to  the  entire  nerve,  i.e.,  to  the 
extra-polar  portions.  Pfliiger  (1859)  discovered  the  following  laws  of  electro- 
tonus:— 

At  the  positive  pole  or  anode  (Fig.  408,  J.)  the  excitability  is  diminished — 
this  is  the  region  of  anelectrotonus  ;  at  the  negative  pole  or  cathode  {K)  it  is 
increased — this  is  the  region  of  cathelectrotonus.  The  changes  of  excitability 
are  most  marked  in  the  regions  of  the  poles  themselves. 

Indifferent  Point. — In  the  intra-polar  region  a  point  must  exist  where  the 
anelectrotonic  and  cathelectrotonic  regions  meet,  where  therefore  the  excitability 
is  unchanged;  this  is  called  the  indifference  or  neutral  point.  This  point 
lies  nearer  the  anode  (/)  with  a  weak  current,  but  with  a  strong  current  nearer 
the  cathode  (i^^ ;  hence,  in  the  first  case,  almost  the  whole  intra-polar  portion  is 
more  excitable  ;  in  the  latter,  less  excitable.  [Expressed  otherwise,  a  weak  current 
increases  the  area  over  which  the  negative  pole  prevails,  while  the  reverse  is  the 
case  with  a  strong  current.  Or  in  the  intra-polar  region,  the  diminution  of  excita- 
bility extends  as  the  strength  of  the  current  increases,  or  to  put  it  otherwise,  with 
an  increasing  strength  of  current,  the  indifferent  point  moves  from  the  positive  to 
the  negative  pole.]  Very  strong  currents  greatly  diminish  the  conductivity  at  the 
anode,  and  indeed  may  make  the  nerve  completely  incapable  of  conduction  at  this 
part. 

At  the  cathode  also,  but  only  after  the  polarizing  current  has  passed  for  some  time  through  the 
nerve  (Werigo),  the  excitability  is  diminished,  and  the  nerve  in  this  area  is  rendered  incapable  of 
conduction  [Griin/iagen). 

Extra-polar  Region. — The  extra-polar  area,  or  that  lying  outside  the  electrodes, 
is  greater,  the  stronger  the  current.  Further,  with  the  weakest  currents,  the  extra- 
polar  anelectrotonic  area  is  greater  than  the  extra-polar  cathelectrotonic.  With 
strong  currents  this  relation  is  reversed. 

Fig.  408  shows  the  excitability  of  a  nerve  [JV,  n)  traversed  by  a  constant  current  in  the  direction 
of  the  arrow.  The  curve  shows  the  degree  of  increased  excitability  in  the  neighborhood  of  the 
cathode  [IC)  as  an  elevation  above  the  nerve,  diminution  at  the  anode  {A)  as  a  depression.  The 
curve  m,  0,  i//,p,  r,  shows  the  degree  of  excitability  with  a  strong  current;  e,f,  ij,  h,  y^,.with  a 
medium  current ;  lastly,  a,  b,  i,  c,  d,  with  a  weak  current. 

The  electrotonic  effect  increases  with  the  length  of  the  nerve  traversed  by  the  current.  The 
changes  of  the  excitability  in  electrotonus  occur  instantly  when  the  circuit  is  closed,  while 
anelectrotonus  develops  and  extends  more  slowly.  Cold  diminishes  electrotonus  iyHermann  and  v. 
Gendre^. 


616 


PROOF   OF    ELECTROTONUS   IN    MOTOR    NERVES. 


When  the  polarizing  current  is  opened  or  broken,  at  first  there  is  a  reversal  of 
tlie  relations  of  the  excitability,  and  then  there  follows  a  transition  to  the  normal 


Fig.  408. 


Scheme  of  the  electrotonic  excitability. 

condition  of  excitability  of  the  passive  nerve  {Ffliiger').  At  the  very  first 
moment  of  closing,  Wundt  observed  that  the  excitability  of  the  whole  nerve  was 
increased. 

I.   Proof  of  Electrotonus   in  Motor  Nerves. — To  test  the  laws  of  electrotonus,  take  a  frog's 
nerve-nuiscle  preparation   (Fig.  401).     A  constant  current  (p.   592)    is 
Fig.  409.  applied  to  a  limited  part  of  the  nerve  by  means  of  non-polarizable  elec- 

trodes. A  stimulus,  electrical,  chemical  (saturated  solution  of  common 
salt"),  or  mechanical,  is  applied  either  in  the  region  of  the  anode  or  cathode ; 
and  we  observe  whether  the  contraction  which  results  is  greater  when  the 
polarizing  current  is  opened  or  closed.  We  shall  consider  the  following 
cases  (Fig.  409). 

(a)  Descending  extra-polar  anelectrotonus.     With  a  descending 
\  current  we  have  to  test  the   excitability  of  the  e.xtra-polar  region  at  the 

n)j)  )  anode.  If  the  stimulus  (common  salt)  applied  at  R  (while  the  circuit 
t(  was  open)  causes  in  this  case  (A)  moderately  strong  contractions  in  the 
limb,  then  these  at  once  become  weaker,  or  disappear  as  soon  as  the 
constant  current  is  transmitted  through  the  nerve.  After  the  circuit  is 
opened,  the  contractions  produced  by  the  salt  again  occur  of  the  original 
strength. 

(b)  Descending  extra-polar  cathelectrotonus  (A).  The  stimulus 
(salt)  is  at  R,,  and  the  contractions  thereby  produced  are  Tiionc^iucreased 
after  closing  the  polarizing  current.  On  opening  it  they  are  again 
weakened. 

(c)  Ascending  extra-polar  anelectrotonus  (15).  The  salt  lies  at  r, ; 
the  moderately  strong  contractions  excited  by  the  salt  before  the  current 
is  made,  become  feebler  after  the  current  is  made. 

(d)  Ascending  extra-polar  cathelectrotonus  (B).     The  salt  lies 
Method  of  testing  the  excita- at  r.     In  this  case  we  must  distinguish  according  to  the  strength  of  the 

bility  in  electrotonus.    R,  polarizing  Current:      (i)  When  the  current  is  very  weak,  \\h\ch  can  be 

^'.?'Ui'J\r^i'mI',h,''i'1c''^rot)tained  with  the  aid  of  the  rheocord  (Fig.  379),  on  closing  the  polar- 

mon    salt  (stimulus)  is   ap-  ..  .  ^.^-"■^".  ,11, 

plied.  izing  current,  there  is  an   increase  of  the  contraction  produced  by  salt. 

(2)   If,  however,  the  current  is  stronger,  the  contractions  become  either 

smaller  or  cease.     This  is  due   to  the  fact  that  with  strong  currents  the  conductivity  of  the  nodes  is 

diminished  or  even  abolished  (p.  615).      Although  the  salt  acts  on  the  excitaljle  ner\'e,  there  is  no 

contraction  of  the  muscle,  as  the  conduction  of  an  impulse  is  prevented  by  the  resistance  in  the 

nerve. 

The  law  of  electrotonus  may  also  be  demonstrated  on  a  completely  isolated  nerve.  The 
end  of  the  nerve  is  properly  disposed  upon  electrodes  connected  with  a  galvanometer,  so  as  to  olitain 
a  strong  current.  If  the  nerve,  when  the  constant  current  is  closed,  is  stimulated  in  the  anelectro- 
tonic  area,  e.g.,  by  an  induction  shock,  then  the  negative  variation  is  weaker  than  when  the  polar- 
izing circuit  was  open.  Conversely,  it  is  stronger  when  it  is  stimulated  in  the  cathelectrotonic  area. 
The  currents  from  the  extra-polar  areas  of  a  nerve  in  a  condition  of  electrotonus,  exhibit  the  negative 
variation  when  the  nerve  is  stimulated  (^Bernstein). 


PROOF  OF  ELECTROTONUS  IN  SENSORY  AND  INHIBITORY  NERVES.   617 

[Tigerstedt,  instead  of  employing  an  electrical  or  chemical  stimulus  to  excite  the  electrotonic 
nerve,  used  an  apparatus  like  Heidenhain's  tetanometer,  whereby  the  nerve  was  beaten  gently  with 
a  small  ivory  hammer.     He  fully  confirms  PflUger's  results.] 

Proof  in  Man. — In  performing  this  experiment  it  is  important  to  remember  the  distribution  of 
the  current  in  the  body.  If  both  electrodes,  for  example,  be  placed  over  the  course  of  the  ulnar 
nerve  (Fig.  410),  the  currents  entering  the  nerve  at  the  anode  (-f-  a  a)  must  diminish  the  excitability; 
only  above  and  below  the  anode  (at  c  c)  the  positive  cm-rent  emerges  from  the  nerve  and  excites 
cathelectrotonus  at  these  points.  Similarly,  where  the  cathode  is  applied  ( —  c  c)  there  is  increased 
excitability,  but  in  higher  and  lower  parts  of  the  nerve,  where  (at  a  a)  the  positive  current  (coming 
from  -}-)  enters  the  nerve,  the  excitability  is  diminished  (anelectrotonus)  (v.  Helmholtz,  Erb).  If 
we  desire  to  stimulate  in  the  neighborhood  of  an  electrode,  then  we  cannot  act  upon  that  part  of  the 
nerve  whose  excitability  is  influenced  by  the  electrode.  In  order,  therefore,  to  stimulate  directly  the 
same  point  on  which  the  electrode  acts,  it  is  necessar>'  to  apply  the  stimulus  at  the  same  time  by  the 
electrode  itself,  e.g.,  either  mechanically  or  by  conducting  the  stimulating  cm-rent  through  the 
polarizing  current  (  Waller  and  de  Watteville). 

II.  Proof  of  Electrotonus  in  Sensory  Nerves. — Isolate  the  sciatic  nerve  of  a  decapitated 
frog.  When  this  nerve  is  stimulated  in  its  course  with  a  satm-ated  solution  of  common  salt,  reflex 
movements  are  excited  in  the  other  leg,  the  spinal  cord  being  intact.  These  disappear  as  soon  as  a 
constant  current  is  applied  to  the  nerve,  provided  the  salt  lies  in  the  anelectrotonic  area  {PJluger 
and  Ziirhelle,  Hallsten). 

III.  Proof  of  Electrotonus  in  Inhibitory  Nerves. — To  show  this,  proceed  thus  :  On  causing 
dyspnoea  in  a  rabbit,  the  number  of  heart  beats  is  diminished,  owing  to  the  action  of  the  dyspnoeic 
blood  on  the  cardio-inhibitory  centre  in  the  medulla  oblongata.     If,  after  dividing  the  vagus  on  one 

Fig.  410. 


Scheme  of  the  distribution  of  an  electrical  current  in  the  nerve  on  galvanizing  the  ulnar  nerve. 


side,  a  constant  descending  current  be  passed  through  the  other  intact  vagus,  the  number  of  pulse 
beats  is  again  decreased  (descending  extra-polar  anelectrotonus).  If,  however,  the  current  through 
the  nerve  be  an  ascending  one,  then  with  tveak  currents  the  number  of  heart  beats  increases  still 
more  (ascending  extra-polar  cathelectrotonus).  Hence,  the  action  of  inhibitory  nerves  in  electrotonus 
is  the  opposite  of  that  in  motor  nerves. 

During  the  electrotonus  of  muscle,  the  excitability  of  the  intfa-polar  portion  is 
altered.  The  delay  in  the  conduction  is  confined  to  this  area  alone  {v.  Bezold) — 
compare  §  337,  i. 

336.  ELECTROTONUS— LAW  OF   CONTRACTION.— Opening 

and  Closing  Shocks. — A  nerve  is  stimulated  both  at  the  moment  of  the  occur- 
rence and  that  of  disappearance  of  electrotonus  {i.  e.,  by  closing  and  opening  the 
current — Ritter)  :  (i)  When  the  current  is  closed,  the  stimulation  occurs  only  at 
the  cathode,  z.  e.,  at  the  moment  when  the  electrotonus  takes  place.  (2)  When 
the  current  is  opened,  stimulation  occurs  only  at  the  anode,  /-  e.,  at  the  moment 
when  the  electrotonus  disappears.  [This  is  Pfliiger's  well-known  principle — "A 
given  tract  of  nerve  is  stimulated  by  the  appearance  of  cathelectrotonus  and  the  dis- 
appearance of  anelectrotonus — not,  however,  by  the  disappearance  of  cathelectrotonus 
nor  by  the  appearance  of  anelectrotonus. ' '     From  this  principle  can  be  deduced  the 


618 


THE    LAW    OF    CONTRACTION. 


law  of  contraction.]     (3)  The  stimulation  at  the  occurrence  of  cathelectrotonus  is 
stronger  than  that  at  the  disappearance  of  anelectrotonus  (^Pflih^er). 

Hitter's  Opening  Tetanus. —  That  stimulation  occurs  only  at  the  anode,  when  the  current  is 
opened,  was  j^roved  by  Ptiiiger  by  means  of  "  Kilter's  opening  tet.nnus."  Hitter's  tetanus  consists  in 
this,  that  when  a  constant  current  is  passed  for  a  long  time  through  a  long  stretch  of  nerve,  on  open- 
ing the  current,  tetanus  lasting  for  a  considerable  time  results.  If  the  current  was  a  descending  one, 
then  this  tetanus  ceases  at  once  after  section  of  the  intra-polar  area,  a  proof  that  the  tetanus  resulted 
from  the  now  separated  anode.  If  the  current  was  an  ascending  one,  section  of  the  nerve  has  no 
efl'ect  on  the  tetanus. 

Ptiiiger  and  v.  Bezold  found  a  further  \)\ool  that  the  closing  or  make  contraction  proceeds  from  the 
cathode,  and  the  opening  or  break  contraction  from  the  anode,  by  showing  that  with  a  descending 
current,  the  closing  contraction  in  the  muscle,  at  the  moment  of  closing  occurred  earlier,  while  the 
opening  contraction  at  the  moment  of  opening  occurred  later  ;  and,  conversely,  with  an  ascending 
current  the  closing  contraction  occurred  later,  and  the  opening  contraction  sooner.  The  difference 
in  time  corresponds  to  the  time  required  for  the  propagation  of  the  pulse  in  the  intra-jx>lar  region 
(?  337V  If  a  lai-ge  part  of  the  intra-polar  region  in  a  frog's  nerve  be  rendered  ine.xcitable  by  apply- 
ing ammonia  to  it,  then  only  the  electrode  next  the  muscle  stimulates,  /.  e.,  always  on  closing  or 
making  a  descending  current  and  on  opening  or  breaking  an  ascending  one  {Biedermann). 

A.  The  la'w  of  contraction  is  valid  for  all  kinds  of  nerves — I.  The  contrac- 
tion occurring  at  tlie  closing  or  opening  of  a  constant  current  varies  with  (a)  the 
direction  (P/af),  and  {b)  the  strength  of  the  current  {Heidenhain). 

(i)  Very  feeble  currents,  in  conformity  with  the  third  of  the  above  state- 
ments, cause  only  a  closing  contraction,  both  with  an  ascending  and  a  descend- 
ing current.  The  disappearance  of  electrotonus  is  so  feeble  a  stimulus  as  not  to 
excite  the  nerve. 

(2)  Medium  currents  cause  opening  or  closing  contractions  both  with  an 
ascending  and  descending  current. 

(3)  Very  strong  currents  cause  only  a  closing  contraction  with  a  descending 
current ;  the  opening  shock  does  not  occur,  because,  with  very  strong  currents, 
almost  the  whole  of  the  intra-polar  portion  of  the  electrotonic  nerve  is  incapable 
of  conducting  an  impulse  (p.  615),  Ascending  currents  cause  only  an  opening 
contraction  for  the  same  reason.  With  a  certain  strength  of  current,  the  muscle 
remains  tetanic  while  the  current  is  closed  {"  c/osing  tetanus'^). 

[The  law  of  contraction  is  formulated  :   R  =  rest ;  C  =  contraction.] 


Strength  of  Current. 

Ascending.                                                 Descending. 

On  Closing.              On  Opening. 

On  Closing. 

On  Opening. 

Weak,      

C 
C 

R 

R 
C 
C 

C 
C 

c 

R 

c 

R 

Medium,       

Strong, 

II.  In  a  dying  nerve,  losing  its  excitability,  according  to  the  Ritter-^'alli  law 
(§  325,  7),  the  law  of  contraction  is  modified.  In  the  stage  of  increased  excita- 
bility, weak  currents  cause  only  closing  contractions  with  both  directions  of  the 
current.  In  the  following  stage,  when  the  excitability  begins  to  diminish,  weak 
currents  cause  opening  and  closing  contractions  with  both  currents.  Lastly,  when 
the  excitability  is  very  greatly  diminished,  the  descending  current  is  followed  only  by 
a  closing  contraction,  and  the  ascending  by  an  opening  contraction  {Ritter,  1829). 

III.  As  the  various  changes  in  excitability  occur  in  a  centrifugal  direction  along 
the  nerve,  we  may  detect  the  various  stages  simultaneously  at  different  parts  along 
the  course  of  the  nerve.  According  to  Valentin  and  Fick,  the  living  intact  nerve 
shows  only  a  closing  contraction  with  both  directions  of  the  current,  and  opening 
contractions  only  with  very  strong  currents. 

Fleischl's  Law  of  Contraction. — v.  Fleischl  and  Strieker  have  stated  a  different  law,  in 
respect  to  the  fact,  that  the  excitability  varies  at  certain  points  in  the  course  of  a  nerve.  The  sciatic 
nerve  is  divided  into  three  areas :    (i)  Stretches  from  the  muscle  to  the  place  where  the  branches  for 


THE    LAW    OF    COXTR.\CTION.  619 

the  thigh  muscles  are  given  off;  (2)  from  here  to  the  intervertebral  ganglion ;  (3)  from  here  into  the 
spinal  cord.  Each  of  these  three  areas  consists  of  two  parts  ("  upper  and  lower  pole ""),  which  adjoin 
each  other  at  an  equator.  In  each  upper  pole,  the  excitability  of  the  nerve  is  greater  for  descending 
currents,  and  in  each  lower  pole  for  ascending  ones.  At  each  equator  the  excitability  of  the  nerve 
is  the  same  for  ascending  and  descending  currents.  The  diflference  in  the  activity,  due  to  the  direc- 
tion of  the  current,  is  greater  for  each  stretch  of  nerve  the  greater  this  stretch  is  distant  from  the 
equator.  The  excitability  is  less  at  those  points  of  the  nerve  where  the  three  areas  join  each  other. 
Eckhard  observed  that,  on  opening  an  ascending  medium  current  applied  to  the  hypoglossal  ner^'e 
of  a  rabbit,  one-half  of  the  tongue  exhibited  a  tj  embling  movement  instead  of  a  contraction,  while 
on  closing  a  descending  ciurrent,  the  same  result  occurred  (|  297,  3).  According  to  Pfliiger,  the 
molecules  of  the  passive  nerve  are  in  a  certain  state  of  medium  mobility.  In  cathelectrotonus  the 
mobility  of  the  molecules  is  increased,  in  anelectrotonus  diminished. 

B.  The  law  for  inhibitory  nerves  is  similar.  ^Sloleschott,  v.  Bezoldj  and 
Bonders  have  found  similar  results  for  the  vagus,  \vith  this  difference,  that, 
instead  of  the  contraction  of  a  muscle,  there  is  inhibition  of  the  heart. 

C.  For  sensory  nerves  also  the  result  is  the  same,  but  we  must  remember  that 
the  perceptive  organ  lies  at  the  central  end  of  the  nerve,  while  in  a  motor  nerve 
it  is  at  the  periphery  (muscle).  Pfliiger  studied  the  effect  of  closing  and  opening 
a  current  on  sensory  nerves  by  observing  the  reflex  movement  which  resulted. 
Weak  currents  cause  only  closing  contractions  :  medium  currents  both  opening  and 
closing  contractions  :  j//-*?//^  descending  currents  only  opening  contractions;  and 
ascending  only  closing  contractions.  Weak  currents  applied  to  the  human  skin 
cause  a  sensation  with  both  directions  of  the  current  only  at  closing  ;  strong 
descending  currents  a  sensation  only  at  opening;  strong  ascending  currents  a 
sensation  only  at  closing  (Marianini,  Matteucci).  When  the  current  is  closed, 
there  is  prickly  feeling,  which  increases  with  the  strength  of  the  current  (^Volfa). 
Analogous  phenomena  have  been  observed  in  the  sense  organs  1  sensations  of 
light  and  sound  by  Volta  and  Ritter). 

D.  In  muscle,  the  law  of  contraction  is  proved  thus:  by  fixing  one  end  of 
the  muscle,  keeping  it  tense,  so  that  it  cannot  shorten,  and  opening  and  closing 
the  current  at  this  end.  The  end  of  the  muscle  which  is  free  to  move,  shows  the 
same  law  of  contraction  as  if  the  motor  ner%-e  were  stimulated  (z'.  Bezold).  On 
closing  the  current,  the  contraction  begins  at  the  cathode  ;  on  opening,  at  the 
anode  (^Engelmann).  E.  Hering  and  Biedermann  showed  more  clearly  that  both 
the  closing  and  opening  contractions  are  purely  polar  effects  ;  when  a  weak  current 
applied  to  a  muscle  is  closed,  the  first  effect  is  a  small  contraction  limited  to  the 
cathodic  surface  of  the  muscle.  Increase  of  the  current  causes  increased  contraction 
which  extends  to  the  anode,  but  which  is  weaker  there  than  at  the  cathode  ;  at  the 
same  time,  the  muscle  remains  contracted  d-uring  the  time  the  current  is  closed.  On 
opening,  the  contraction  begins  at  the  anode;  even  after  opening, the  muscle  for  a  time 
may  remain  contracted,  which  ceases  on  closing  the  current  in  the  same  direction. 

By  killing  the  end  of  a  muscle  in  various  ways,  the  excitability  is  diminished  near  this  part. 
Hence,  at  such  a  place  the  polar  action  is  feeble  {van  Loon  and  Engebnantt,  Biedermann). 
Touching  a  part  with  extract  of  flesh,  potash,  or  alcohol  diminishes  locally  the  polar  action,  while 
soda  salts  and  veratrin  increase  it  {Biedermann^. 

Closing  Continued  Contraction. — The  moderate  continued  contraction,  which  is  sometimes 
observed  in  a  muscle  while  the  current  is  closed  (Fig.  329,  O),  depends  upon  the  abnormal  pro- 
longation of  the  closing  contraction  at  the  cathode  when  a  strong  stimulus  is  used,  or  during  the 
stage  of  dying,  or  in  cooled  winter  frogs ;  sometimes  the  opening  of  the  current  is  accompanied  by 
a  similar  contraction  proceeding  from  the  anode  Biedermann).  This  tetanus  is  also  due  to  the 
summation  of  a  series  of  simple  contractions  (5.  298,  TIT).  By  acting  on  a  muscle  with  a  2  per 
cent,  saline  solution  containing  sodic  carbonate,  the  duration  of  the  contraction  is  increased  consider- 
ably, and  occasionally  the  muscle  shortens  rhythmically  1  'i_  296')  \  Biedennann). 

If  the  whole  muscle  is  placed  in  the  circuit,  the  closing  contraction  is  strongest 
with  both  directions  of  the  current;  during  the  time  the  current  is  closed,  a  con- 
tinued contraction  is  strongest  when  the  current  is  ascending  (JVundt). 

Inhibitory  Action. — The  constant  current,  when  applied  to  a  muscle  in  a 
condition  of  continued  and  sustained  contraction,  has  exactly  the  opposite  effect 


620  ritter's  opening  tetanus. 

to  that  on  a  relaxed  muscle.  If  a  constant  current  be  applied  by  means  of  non- 
polarizable  electrodes  to  a  muscle  in  a  state  of  continued  contraction,  e.  g.,  after 
poisoning  with  veratrin  or  through  the  contracted  ventricle,  when  the  current  is 
closed,  there  is  a  relaxation  beginning  at  the  anode  and  extending  to  the  other 
parts;  on  opening  the  current  applied  to  muscle  in  continued  contraction,  the 
relaxation  procedes  from  the  cathode. 

Corresponding  to  this  remarkable  phenomenon,  Biedermann  found  as  regards  the  currents  in  the 
muscle  substance  following  the  ordinary  law,  that  every  contracted  part  is  negative  to  every  passive 
section  of  the  muscle.  Perhaps  the  experiment  of  Pawlow,  who  found  nerve  fibres  in  the  adductor 
muscle  of  the  mussel,  whose  stimulation  caused  relaxation  of  the  muscular  contraction,  may  throw 
some  light  on  this  question. 

Ritter's  Opening  Tetanus. — If  a  nerve  or  muscle  be  traversed  by  a  constant 
current  for  some  time,  we  often  obtain  a  prolonged  tetanus,  after  opening  the 
current  ( Ritter's  opening  tetanus,  1798).  It  is  set  aside  by  closing  the  original 
current,  while  closing  a  current  in  the  opposite  direction  increases  it  ("  Volta's 
alternative").  The  continued  passage  of  the  current  increases  the  excitability 
for  the  opening  of  the  current  in  the  same  direction,  and  for  the  closing  of  the 
reverse  current ;  conversely,  it  diminishes  it  for  the  closing  of  the  current  in  the 
same  direction,  and  for  the  opening  of  the  reverse  current  \Voltd). 

According  to  Griitzner  and  Ti^erstedt,  the  cause  of  the  opening  contraction  is  partly  due  to  the 
occurrence  of  polarizing  after  currents  (§  333),  and  according  to  Hermann  to  a  diminution  of  the 
anodic  positive  polarization. 

Engelmann  andGriinhagen  explain  the  occurrence  of  opening  and  closing  tetanus,  thus,  as  due  to 
latent  stimulations,  drying,  variations  of  the  temperature  of  the  prepared  nerve,  which  of  themselves 
are  too  feeble  to  cause  tetanus,  but  which  become  effective  if  an  increased  excitability  obtains  at  the 
cathode  after  closure,  and  at  the  anode  after  opening  the  current. 

Biedermann  showed  that,  under  certain  conditions,  two  successive  opening  contractions  can  be 
obtained  in  a  frog's  nerve-muscle  preparation,  the  second  and  later  one  corresponding  to  Ritter's 
tetanus.  The  first  of  these  contractions  is  due  to  the  disappearance  of  anelectrotonus  in  Pfliiger's 
sense;  the  second  is  explained,  like  Ritter's  opening  tetanus,  in  Engelmann  an  1  Griinhagen's  sense. 

Simultaneous  action  of  the  constant  current  and  the  nerve  current. — Action  of  two 
currents.  In  a  nerve-muscle  preparation  used  to  j^rove  the  law  of  contraction,  of  course  a  demar- 
cation current  is  developed  in  the  nerve  {\  334,  II).  If  an  artificial  weak  stimulating  current  be 
applied  to  such  a  nerve,  we  obtain  an  inteference  effect  due  to  these  two  currents ;  closing  a  weak 
constant  current  causes  a  contraction,  which,  however,  is  not  properly  a  closing  contraction,  but 
depends  upon  the  opening  (or  derivation)  of  a  branch  of  the  demarcation  current;  conversely,  the 
opening  of  a  weak  constant  current  may  excite  a  contraction,  which  is  really  due  to  the  closing  of 
a  side  branch  of  the  nerve  current,  in  a  secondar)^  circuit  through  the  electrodes  [Ilerin^,  Bieder- 
mann, Griitzner'). 

If  two  induction  shocks  be  simultaneously  applied  to  a  motor  nerve,  two  cases  are  possible. 
Either  the  one  shock  is  so  feeble  that  the  nerve  is  not  thereby  sufficiently  excited  to  cause  a  contrac- 
tion, while  the  other  shock  causes  only  a  feeble  contraction.  In  this  case,  the  sub-maximal  shock 
plays  the  part  of  a  weak  constant  current,  and  the  size  of  the  contraction  depends  only  upon  whether 
the  effective  stimulus  was  applied  in  the  area  of  the  anode  or  the  cathode  of  the  sub-maximal  shock 
{Seroall,  Griinkagen,  IVerigo).  If,  however,  unequal,  strong  induction  shocks,  each  of  which  is 
effective — but  separated  from  each  other  on  account  of  the  electrotonic  action — be  applied  to  a 
nerve,  then  the  result  is  as  if  the  stronger  alone  was  active.  The  feebler  wave  of  excitation  passes 
completely  into  the  stronger  one  [Griin/iajen.  IVtvigo). 

337.  TRANSMISSION  OF  NERVOUS  IMPULSES.— i.  If  a  motor 
nerve  be  stimulated  at  its  central  end  (i)  a  condition  of  excitation  is  set  up, 
and  (2)  an  impulse  is  transmitted  along  the  nerve  to  the  muscle  with  a  certain 
velocity.  The  latter  depends  on  the  former  and  represents  the  function  of  con- 
ductivity. The  velocity  is  about  271^  metres  [about  90  feet]  per  second 
{v.  Hi'/mho/tz),  and  for  the  human  motor  nerves  33.9  [too  to  120  feet  per  second] 
(i).  Helinholtz  and Baxt). 

The  velocity  is  less  in  the  visceral  nerves,  e.g.,  in  the  pharyngeal  branches  of  the  vagus  8.2 
metres  [26  feet]  lC/ianveau\ ;  in  the  motor  nerves  of  the  lobster  6  metres  [18  feet]  {^Fredericq  and 
van  de  Velde). 

Modifying  Conditions. — The  velocity  is  influenced  by  various  conditions: 
Temperature. — It  is  lessened  considerably  by  cold  {v.  Helmholtz),  but  both  high 


NERVE    IMPULSE    IN    SENSORY   NERVES    AND    REACTION    TIME.      621 


and  low  temperatures  of  the  nerve  (above  or  below  15°  to  25°  C.)  lessen  it  {Steiner 
and  Trojtzky)  ;  also  airara,  the  electrotonic  condition  {v.  Bezold)  ;  or  only  anelectro- 
tonus,  while  cathelectrotonus  increases  it  (  Rutherford,  Wundt).  It  varies  also  with 
the  length  of  the  conducting  nerve,  but  it  increases  with  the  strength  of  the  stimulus 
(v.  Hdmholtz  and  Baxi),  although  not  at  first  (v.  Vintschgaii). 

Methods. — l.  v.  Helmholtz  (1850)  estimated  the  velocity  of  the  nerve  impulse  in  a  frog's  motor 
nerve  after  the  method  of  Pouillet.  The  method  depends  upon  the  fact  that  the  needle  of  a  gal- 
vanometer is  deflected  by  a  current  of 

very  short  duration,  the  extent  of  the  FiG.  411. 

deflection  being  proportional  to  the 
duration  and  strength  of  the  current. 
The  apparatus  is  so  arranged  that  the 
"time-marking  current"  is  closed  at 
the  moment  the  nerve  is  stimulated, 
and  opened  again  when  the  muscle 
contracts.  If  the  nerve  attached  to  a 
muscle  be  now  stimulated  at  the  further 
point  from  the  muscle,  and  a  second 
time  near  its  entrance  to  the  muscle, 
then  in  the  latter  case  the  time  between 
the  appUcation  of  the  stimulus  and  the 
beginning  of  the  contraction  of  the 
muscle,  /.  e.,  the  deflection  of  the  gal- 
vanometer, will  be  less  than  in  the 
former  case,  as  the  impulse  has  to 
traverse  the  whole  length  of  the  nerve 
to  reach  the  muscle.  The  difference 
between  the  two  times  is  the  time  re- 
quired by  the  impulse  to  traverse  a 
given  distance  of  nerve.  Fig.  41 1 
shows  in  a  diagrammatic  manner  the 
arrangement  of  the  experiment.  The 
galvanojneter,  G,  is  placed  in  the  time- 
marking  circuit  (open  at  first),  a,  b 
(element),  c  (piece  of  platinum  on  a 
key,  W),  introduced  into  the  time- 
marking  circuit,  d,  e,f,  h.  The  circuit  is  made  by  closing  the  key,  S,  when  d  depresses  the  platinum 
plate  of  the  key,  W.  At  once  when  the  current  is  closed,  the  magnetic  needle  is  deflected,  and  its 
extent  noted.  At  the  same  moment  in  which  the  current  between  c  and  d  is  closed,  the  primary 
circuit    of    the    induction    machine   is 


W      k 

V.  Helmholtz's  method  of  estimating  the  velocity  of  a  nerve  pulse. 


opened,  the  circuit  being  z,  k,  I  (ele- 
ment), 771,0  (primary spiral),/.  There- 
by an  opefiifig  shock  is  induced  in  the 
secondary  spiral,  R,  which  stimulates 
the  nerve  of  the  frog's  leg  at  n.  Thus, 
the  closing  of  the  galvanometer  circuit 
exactly  coincides  with  the  stimulation 
of  the  nerve.  The  impulse  is  propa- 
gated through  the  nerve  to  the  muscle, 
M,  and  the  latter  contracts  when  the 
impulse  reaches  it,  at  the  same  time 
opening  the  time- measuring  circuit  at 
the  double  contact,  e  and  f,  by  raising 
the  lever,  H,  which  rotates  on  x.  At 
the  moment  of  opening,  the  further  de- 
flection of  the  magnetic  needle  ceases. 
The  contact  at  f  is  made  by  a  pointed 
cupola  of  mercury.  When  the  lever,  H, 
falls  after  the  contact  of  the  muscle,  so 


Fig.  412. 


that    the    point,   e,   comes    into    contact  Scheme  for  measuring  the  velocity  of  nerve  ener^^^    /;  clamp  for 
r  '     '  femur;  ?«,  muscle  ;  N,  nerve;  a;,  near,  6,  removed  irom,  C  com- 

mutator ;   II,  secondary  ;   I,  primary  spiral  of  induction  machine  ; 
B,  battery ;  1,2,  key  ;  3,  tooth  on  the  smoked  plate,  P. 


with  the  underlying  5o/zV  plate,  y,  the 
contact  at  f  still  remains  open,  i.e., 
through  the  galvanometer  circuit.  If 
the  nerve  be  stimulated  with  the  opening  shock,  first  at  n,  and  then  at  N,  the  deflection  of  the  needle 


022        METHOD   OF    ESTIMATING    RAPIDITY    OF    A    NERVE    IMPULSE. 

is  greater  in  the  former  tlian  in  the  latter  case.     From  the  difierence  we  calculate  the  time  for  the 
conduction  of  the  impulse  in  the  stretch  of  the  nerve  between  n  and  N. 

[2.  A  simpler  method  is  that  shown  in  the  scheme,  Fig.  412.  Use  a  pendulum 
or  spring  myograph  (Fig.  323^  and  suspend  in  a  suitable  manner  a  frog's  gas- 
trocnemius ( w),  with  a  long  portion  of  the  sciatic  nerve  (N)  dissected  out,  by  fixing 
the  femur  in  a  clamp  (/),  while  the  tendo-Achilles  is  fixed  to  a  lever,  which 
inscribes  its  movements  on  the  smoked  glass  plate  (P)  of  the  myograph  ;  place  the 
key  of  the  myograph  (2)  in  the  circuit  with  the  battery  (H),  and  the  primary  cir- 
cuit of  the  induction  machine  (I).  To  the  secondary  coil  (II)  attach  two  wires, 
and  connect  them  with  a  zomvc\M\.2Xox  7vi thou t  cross  bars  (C).  Connect  the  other 
binding  screws  of  the  commutator  with  two  pairs  of  wires,  arranged  so  that  one 
pair  can  stimulate  the  nerve  near  the  muscle  {a),  and  the  other  at  a  distance  from 
it  (d^).  When  the  glass  plate  flies  from  one  side  to  the  other,  the  tooth  (3)  on  its 
framework  opens  the  key  (2)  in  the  primary  circuit ;  and  if  the  commutator  be  in 
the  position  indicated,  then  the  induced  current  will  stimulate  the  nerve  at  a,  and 
a  curve  will  be  obtained  on  the  glass  plate.  Rearrange  the  pendulum  as  before, 
but  turn  the  handle  of  the  commutator,  and  allow  the  glass  plate  to  fly  again. 
This  time  the  induced  current  will  stimulate  the  nerve  at  b,  and  a  second  con- 
traction, a  Utile  later  than  the  first  one,  will  be  obtained.  Register  the  velocity  of 
the  glass  plate  by  means  of  a  timing  fork,  and  the  curve  obtained  will  be  something 
like  Fig.  413,  although  this  curve  was  obtained  on  a  c}  Under  traveling  at  a  uniform 

Fig.  413. 


I,  curve  obtained  on  stimulating  a  nerve  (man)  near  the  muscle  ;  2,  when  the  stimulus  was  applied  to  the  nerve  at  a 
distance  from  the  muscle  ;  D,  vibrations  of  a  tuning  fork  (250  per  second). 


rate.  The  difference  between  the  beginning  of  the  a  and  b  curves  indicates  the 
time  that  the  nerve  impulse  took  to  travel  from  b  to  a.  This  time  is  measured  by 
the  tuning  fork,  and  if  the  distance  between  the  points  a  and  b  is  known,  then  the 
calculation  is  a  simple  one.  Suppose  the  stretch  of  nerve  between  a  and  <^  to  be  2 
inches,  and  the  time  required  by  the  impulse  to  travel  from  ^  to  ^  to  be  -^^  second, 
then  we  have  the  simple  calculation — 2  inches  :  12  inches  ::  -^^'  :  -^' ,  or  80 
feet  per  second.  In  Fig.  413  the  experiment  was  made  on  man  ;  the  curve  i  was 
obtained  by  stimulating  the  nerve  near  the  muscle,  and  2  when  the  nerve  was 
stimulated  at  a  distance  of  30  centimetres.  The  interval  between  the  vertical  lines 
corresponds  to  y^^  second,  /.  e.,  the  time  required  by  the  nerve  impulse  to  pa«s 
along  30  centimetres  of  nerve,  which  is  ecjual  to  a  velocity  of  30  metres  (90  feet) 
per  second.] 

In  man,  v.  Helmholtz  and  Baxt  estimated  the  velocity  of  the  impulse  in  the  median  nerve  by 
causing  the  muscles  of  the  ball  of  the  thum.b  to  write  oft'  their  contractions  on  a  rapidly  revolving 
cylinder.  [In  this  case  the  "  pince  myographique  "  of  Marey  may  be  used  (^  708).  The  ends  of 
the  pince  are  applied  so  as  to  embrace  the  ball  of  the  thumb,  so  that  when  the  muscles  contract,  the 
increase  in  thickness  of  the  muscles  expands  the  pince,  which  acts  on  a  Marey's  tambour,  by  which 
the  movement  is  transmitted  to  another  tambour  provided  with  a  writing  style,  and  inscribing  its 
movements  upon  a  rapidly  moving  surface,  either  rotatory  or  swinging.]  The  nerve  is  stimulated  at 
one  time  in  the  axilla  and  again  at  the  wrist.  Two  curves  are  obtained,  which,  of  course,  do  not 
begin  at  the  same  time.     The  difference  in  time  between  the  beginning  of  the  two  curves  is  the  time 


NERVE    IMPULSE    IN    SENSORY    NERVES   AND    REACTION   TIME.      623 

taken  by  the  impulse  to  traverse  the  above-mentioned  length  of  nerve.  [The  time  is  easily  ascer- 
tained by  causing  a  tuning  fork  of  a  known  rate  of  vibration  to  write  its  movements  under  the 
curves.] 

3.  In  the  sensory  nerves  of  man,  the  velocity  of  the  impulse  is  probably 
about  the  same  as  in  motor  nerves.  The  rates  given  vary  between  94  to  30  metres 
[280  to  90  feet]  per  second  (v.  Helmholtz). 

Method. — Two  points  are  chosen  as  far  apart  as  possible,  and  at  unequal  distances  from  the  brain, 
and  they  are  successively  excited  by  a  momentaiy  stimulus,  e.  g.,  an  opening  niduction  shock  applied 
successively  to  the  tip  of  the  ear  and  the  great  toe.  The  moment  of  the  application  of  the  stimulus 
is  indicated  on  the  registering  surface.  The  person  experimented  on  is  provided  with  a  key  attached 
to  an  electric  arrangement,  by  which  he  can  mark  on  the  registering  surface  the  moment  he  feels  the 
sensation  in  each  case. 

Reaction  Time. — The  time  which  elapses  between  the  application  of  the  stimulus  and  the  reac- 
tion is  called  the  "  reactiott  timer  It  is  made  up  of  the  time  necessaiy  for  conduction  in  the  sensory 
nerve,  that  for  the  process  of  perception  in  the  brain,  for  the  conduction  in  the  motor  nerves  to  the 
muscles,  by  which  the  signs  on  the  registering  surface  were  made,  and  lastly  by  the  latent  period  (p. 
528).     The  reaction  time  is  usually  about  0.125  ^'^  0-2  second  (\  374). 

Pathological. — The  conduction  in  the  cutaneous  nerves  is  sometimes  greatly  delayed,  in  altera- 
tions of  the  cutaneous  sensibihty,  in  certain  diseases  of  the  spinal  cord  (^  364).  The  sensation  itself 
may  be  unchanged.  Sometimes  only  the  conduction  for  painful  impressions  is  retarded,  so  that  a 
painful  impression  on  the  skin  is  first  perceived  as  a  tactile  sensation,  and  afterward  as  pain,  or  con- 
versely. When  the  interval  of  time  between  these  two  sensations  is  long,  then  there  is  a  distinctly 
double  sensation  i^Naunyn).  It  is  rarely  that  voluntar}'  movements  are  executed  much  more  slowly 
from  causes  depending  on  the  motor  nerves,  but  occasionally  the  time  between  the  voluntary  impulse 
and  the  contraction  is  lengthened,  but  there  may  be  in  addition  slower  or  longer  continued  contrac- 
tion of  the  muscle.  In  tabes  dorsalis  or  locomotor  ataxia,  the  discharge  of  rejlex  movements'\% 
delayed;  it  is  slower  with  thermal  stimuli  (60°)  than  with  cold  ones  (0.52°  C,  Ewald). 

338.  DOUBLE    CONDUCTION    IN    NERVES.— Conductivity  is 

that  property  of  a  living  nerve  in  virtue  of  which,  on  the  application  of  a  stimulus, 
it  transmits  an  hnpulse.  [The  nature  of  a  nerve  impulse  is  entirely  unknown ;  we 
may  conveniently  term  the  process  nerve  motion,  but  there  is  some  reason  to 
believe  that  nerve  energy  is  transmitted  by  some  sort  of  molecular  vibration.]  The 
conductivity  is  destroyed  by  all  influences  or  conditions  which  injure  the  nerve  in  its 
continuity  (section,  ligature,  compression,  destruction  by  chemical  agents)  ;  or  which 
abolish  the  excitability  at  any  part  of  its  course  (absolute  deprival  of  blood  ;  certain 
poisons,  e.  g.,  curara  for  motor  nerves;  also  strong  anelectrotonus,  §  335). 

Law  of  Isolated  Conduction. — Conduction  always  takes  place  only  in  the 
continuity  of  fibres,  the  impulse  never  being  transferred  to  adjoining  nerve  fibres. 

Double  Conduction.  — Although  apparently  conduction  in  motor  nerves  takes 
place  only  in  a  c ent7'ifuga I  dLixtction  toward  the  muscles,  and  in  sensory  nerves  in  a 
centripetal  di^ixtoXxoxi,  i.  e.,  toward  the  centre;  nevertheless,  experiment  has  proved 
that  a  nerve  conducts  an  impulse  in  both  directions,  just  as  in  a  non-living  conduc- 
tor. If  a  pure  motor  or  sensory  nerve  be  stimulated  in  its  course,  an  impulse  is 
propagated  at  the  same  time  in  a  centrifugal  and  in  a  centripetal  direction.  This  is 
the  phenomenon  of  ^'double  conduction.''^ 

Proofs. — I.  If  a  nerve  be  stimulated,  its  electro-motive  properties  are 
affected  both  above  and  below  the  point  of  stimulation  (see  Negative  Variation  in 
Nerves,  §  332). 

2.  Electrical  Nerves. — If  the  posterior  free  end  of  the  electrical  centrifugal 
nerves  of  the  malapterurus  be  stimulated,  the  branches  given  off  above  the  point  of 
stimulation  are  also  excited,  so  that  the  whole  electrical  organ  discharges  its  elec- 
tricity (^Babuchin,  Ma7ttey). 

3.  Kuhne's  Experiments. — The  sartorius  of  the  frog  has  no  nerve  fibres 
at  its  upper  and  lower  ends.  If  the  lower  end  be  cut  off,  and  if  the  lower  third  of 
the  muscle  be  suspended  and  divided  vertically,  on  stimulating  mechanically  one 
apex  of  the  muscle,  then  the  impulse  passes  in  the  motor  nerves  centripetally  to  the 
place  where  the  nerve  fibre  bifurcates  in  the  muscle,  and  from  thence  centrifugally 
into  the  other  or  non-stimulated  apex,  and  causes  it  to  contract. 


624 


PROOFS   OF    DOUBLE    CONDUCTION    IN    NERVES. 


Fir..  414. 


[The  Gracilis  of  the  frog  is  divided  into  a  larger  and  smaller  portion  (L)  by  a 
tendinous  inscription  ( K)  running  across  it  (Fig.  414).  The  nerve  (N)  enters  at 
the  hilum  in  the  larger  portion.  ])ifurcates,  and  gives  a  branch  (/') 
to  the  smaller  portion  and  another  to  the  larger  portion  of  the 
muscle.  Let  the  muscle  be  cut  as  shown  in  Fig.  414,  avoiding 
injury  to  the  nerves,  so  that  only  the  nerve  twig  {k)  connects 
the  larger  and  smaller  portions  of  the  muscle.  If  the  tongue  or 
tip  of  muscle  (Z)  with  its  nerves  be  stimulated,  contraction 
occurs  both  in  L  and  M,  which  is  due  to  centripetal  conduction 
in  the  motor  nerve.  The  nerve  fibres  divide  dichotomously 
above  where  the  nerves  are  given  off  to  the  portions  L  and  M.] 

[If  the  inscription  be  left,  and  the  lower  tip  of  the  muscle 
(which  is  devoid  of  nerves)  be  stimulated,  only  the  lower  and 
not  the  ujiper  part  twitches  ;  but  if  a  part  of  the  muscle  con- 
taining nerves  common  to  both  parts  be  stimulated,  then  both 
parts  of  the  muscle  contract.  This  also  proves  that  j)ure  muscu- 
lar excitation  does  not  travel  backward  from  the  muscle  to  the  nerves.  How  this 
comes  about,  we  are  entirely  ignorant.] 

The  following  experiments  used  to  be  cited  as  proofs,  but  they  do  not  stand  the 
test  of  criticism. 

4.  Union  of  Motor  and  Sensory  Nerves. — Tf  the  hypoglossal  and  Ungual  nerves  be  divided 
in  a  dog,  and  if  the  peripheral  end  of  the  hypoglossal  be  stitched,  so  as  to  unite  with  the  central  end 

of  the  lingual  (^Bidder),  then,  several 


Kuhne's  Gracilis  ex- 
periment. 


Fig.  415. 


Fig.  416. 


Fk;.  417. 


months  after  the  union  and  restitution 
of  the  nerves,  stimulation  of  the  cen- 
tral end  of  the  lingual  causes  con- 
traction in  the  corresponding  half  of 
the  tongue.  Hence,  it  has  been  as- 
sumed that  the  lingual,  which  is  the 
sensoyy  nerve  of  the  tongue,  must 
conduct  the  impulse  in  a  peripheral 
direction  to  the  end  of  the  hypoglos- 
sal. This  experiment  is  not  conclu- 
sive, as  the  trunk  of  the  lingual 
receives  high  up  the  centrifugal  fibres 
from  the  seventh,  viz.,  the  chorda 
tympani,  which  may  unite  with  those 
of  the  hjpoglossal.  Further,  if  the 
chorda  be  divided  and  allowed  to 
degenerate  before  the  above  described 
experiment  is  made,  then  no  contrac- 
tions occur  on  .stimulating  the  lingual 
above  the  point  of  union  {\  349). 

5.  Bert's  Experiment.  —  Paul 
Bert  removed  the  skin  from  the  tip  of 
the  tail  of  a  rat,  and  stitched  it  into 
the  skin  of  the  back  of  the  animal, 
where  it  united  with  the  tissues. 
After  the  first  union  had  taken  place, 
the  tail  was  then  divided  at  its  base, 
so  that  the  tail,  as  it  were,  grew  out  of 
the  skin  on  the  back  of  the  animal.  On 
stimulating  the  tail,  the  animal  exhib- 
ited signs  of  sensation.  For  the  expla- 
nation of  this  experiment,  see  ^  325. 

339.  ELECTRO-THERAPEUTICS— REACTION  OF  DEGENERATION.— Elec- 
tricity is  frequently  employed  for  therapeutical  puqDOses,  the  rapidly  interrupted  current  of  the 
induction  machine,  or  Faradic  current,  being  frequently  used  (especially  since  Duchenne,  1847),  the 
W(7^«^/(?-^/if(-/r/ftf/ apparatus,  and  the  i?jr/ra-«<r;Y«/ apparatus.  The  constant  or  galvanic  current  ig 
also  used,  especially  since  Remak's  time,  1855  (?  330). 

I.  In  paralysis,  Faradic  currents  are  applied,  either  to  the  muscles  themselves  (^Duchenne),  or 


Double  sponge  rheophore.         Disk  rheophore.       Metallic  brush. 


THERAPEUTICAL   USES   OF    ELECTRICITY RHEOPHORES. 


625 


the  points  of  entrance  of  the  motor  nerves,  by  means  of  suitable  electrodes,  or  rheophores  covered 
with  sponge,  etc.,  and  moistened  (v.  Zie?nssen). 

[Rheophores. — Many  different  forms  are  used,  according  to  the  organ  or  part  to  be  stimulated. 


Fig.  418. 

N.  i-adialis. 
M.  tiracliiaL  intern. 
M.  supiiiator  iong. 
M.  radial,  ext.  long. 


M.  radiaV  est.  'brev. 
M.  extena.  digit,  communis. 

M.  extens.  digit,  min. 
M.  extens.  indicia. 


M.  abdact.  poUic.  long. 

M.  extens.  poUic.  brev. 
M.  extens.  poll.  loni 


M.  triceps  (cuput  6xt.) 
M.  triceps 
(caput  long) 
M.  deltoideus 
(post.  half). 

(N.  axillaris). 


M.  abduct,  digit,  min.  (N.  ulnaria.) 


Mm.  inteross.  dorsal.  I,  II,  III,  et  IV. 
(N.  ulnaria.) 

Motor  points  of  the  radial  nerve  and  the  muscles  supplied  by  it ;  dorsal  surface. 


Fig.  419. 


M.  deltoideus  (ant.  half)  N.  axillaris, 
N.  musculo-outaneus. 
M.  biceps  brachii. 

M.  brach.  anticus. 


M.  abductor  pjUic.  brer. 
M.  flex,  digitor.  commun.  profund     j      jj  ^pponens  poUicis. 
il.  flex,  carpi  radialis. 

M.  flex,  digitor.  sublim. 

8Ubl 


M.  flex.  polL  brev. 

M.  abductor  pollic.  brev. 
Mm.  lumbricalea 
1  et  II. 


M.  opponens  digit,  ijiio. 
M.  flexor  digit,  min. 
M.  abductor  digit  min. 
M.  1  almaris  brev. 

N.  ulnaria.  M.  flexor  carpi  ulnaria.  N.  ulnaris. 

Motor  points  of  the  median  and  ulnar  nerves,  with  the  muscles  supplied  by  them. 


or  the  effect  desired.     When  electricity  is  applied  to  the  skin  to  remove  anaesthesia,  hyperaesthesia, 
or  altered  sensibility,  and  we  desire  to  limit  the  effect  to  the  skin  alone,  then  the  rheophores  are 
applied  dry,  and  are  usually  made  of  metal.     If,  however,  deeper-seated  structures,  as  muscles  or 
40 


626 


EFFECT   OF   THE    CONSTANT   CURRENT. 


nerve  trunks,  are  to  be  affected,  the  skin  must  be  well  moistened  and  softened  by  sponging  with 
warm  water,  while  the  rheophores  are  fitted  with  sponges  moistened  with  common  salt  and  water, 
which  diminishes  the  resistance  of  the  skin  to  the  passage  of  electricity  (Figs.  415-417).] 

In  faradizing  the  paralyzed  muscle,  the  object  is  to  cause  artificial  movements  in  it,  and  thus  pre 
vent  the  degeneration  which  it  would  otherwise  undergo,  merely  from  inaction.  If,  in  addition  to 
the  motor  nerves,  its  trophic  nerves  are  also  paralyzed,  then  a  muscle  atrophies,  notwithstanding 
the  faradization  {\  325,  4).  The  use  of  the  induced  current  also  improves  a  paralyzed  muscle,  as  it 
increases  the  blood  stream  through  it,  while  it  atTects  the  metabolism  of  the  muscle  reflexly.  In 
addition,  weak  currents  may  restore  the  excitability  of  enfeebled  nerves  yv.  BezolJ,  Engelmann). 

The  Figs.  41 S,  419,  420,  421  indicate  the  positions  of  the  motor  points  of  the  extremities,  where, 


Fig.  420. 


I  f 

>i    I 

3 

2      I 
O 


N  obturator. 
M.  pectineus. 

M.  adductor  magnus. 

M.  adduct.longus. 


N.  peroneus, 

M.  tibial,  antic. 
M.  e.xten.  dig.com.  long. 

M.  peroneus  longus. 

M.  peroneus bre vis. 

M.  extens.  hallucis  long. 


M.  extens.  digit,  comm 
brevis. 


N.  cruralis. 

M.  tensor  fasciae  latse 
(Nn.  glut.  sup.). 


M.  quadriceps  femoris 
(general  centre). 

M.  rectus  femoris. 
M.  cruralis. 

M.  vastus  externus. 

M.  vastus  internus.  I 

M.  gastrocnem.  extern 
M.  soleus. 


M.  flexor  hallucis  long. 
M.  abductor digiti.  min. 


Mm.  interossei  dorsales. 

Motor  points  of  the  peroneal  and  tibial  nerves  on  the  front  of  the  leg ;  the  peroneal  on  the  left,  the  tibial  on  the 

right  (after  Eichhorst). 


by  Stimulating  at  the  entrance  of  the  nerve,  each  muscle  may  be  caused  to  contract  singly.     In  \  349 
the  motor  points  of  the  face,  and  in  \  347  those  of  the  neck,  are  indicated. 

The  constant  current  may  be  employed  as  a  stimulus,  when  it  is  closed  and  opened,  in  the  form 
of  an  internipteJ  currtxw.,  by  altering  its  direction  and  increasing  or  diminishing  its  intensity,  but  it 
also  causes  upoiur  action.  On  ciosini^  the  current,  the  nerve  at  the  cathode  is  stimulated  ;  similarly, 
on  opening  the  current,  at  the  anode  {\  336).  Thus,  when  the  current  is  closed,  the  excitability  of 
the  nerve  is  increased  at  the  cathode  (^335),  which  may  act  favorably  upon  the  nerve.  Increased 
excitability  in  eiectrotonus  at  the  anode,  although  feebler,  has  been  observed  during  percutaneous 
galvanization  in  man.  This  is  especially  the  case  by  repeatedly  reversing  the  current,  .sometimes  also 
by  opening  and  closing,  or  even  with   a  uniform    current.      If  the  increase  of  the    excitability  is 


REACTION    OF   DEGENERATION. 


627 


obtained,  then  the  direction  of  the  current  increases  the  excitability  on  closing  the  reverse  current 
and  on  opening  the  one  in  the  same  direction. 

Restorative  Effect. — Further,  in  using  the  constant  current,  we  have  to  consider  its  restorative 
effects,  especially  when  it  is  ascending.  R.  Heidenhain  found  that  feeble  and  fatigued  muscles 
recover  after  the  passage  of  a  constant  current  through  them. 

Lastly,  the  constant  current  may  be  useful  from  its  catalytic  or  cataphoric  action  (§  328).  The 
effect  is  directly  upon  the  tissue  elements.  It  may  also  act  directly  or  reflexly  upon  the  blood  and 
lymph  vessels. 

Faradization  in  Paralysis. — If  the  primary  cause  of  the  paralysis  is  in  the  muscles  themselves 
then  the  induced  current  is  generally  applied  directly  to  the  muscles  themselves  by  means  of  sponge 
electrodes  (Fig.  415);  while,  if  the  motor  nerves  are  the  primary  seat,  then  the  electrodes  are 
applied  over  them.  The  current  used  must  be  only  of  ve>y  moderate  strength ;  strong  tetanic 
contractions  are  injurious,  and  so  is  too  prolonged  application  i^Eulenburg). 


Fig.  421. 


M.  biceps  fern.  (cap.  long.) 
(grt.  sciat.). 


M.  biceps  fern.  (cap.  brev.) 
(grt.  sciat.). 


N.  peroneus. 


M.  gluteus  maxiraus  (great 
sciatic). 


N.  ischiadicus. 

M.  adduct.  magnus  (n.obt.). 

M.  semitendinosus  (grt. 

(sciat.). 
M.  semimembranosus 
(grt.  sciat.). 


N.  tibialis. 

M.  gastrocnem.  (cap.  extr.). 
M.  gastrocnem.  (cap.  int.). 

M.  soleus. 


M.  flex.  dig.  comra.  long. 
M.  flexor  hallucis  longus. 

N.  tibialis. 


Motor  points  of  the  sciatic  nerve  and  its  branches ;  the  peroneal  and  tibial  nerves. 

The  galvanic  current  may  also  be  applied  to  the  muscles  or  to  their  motor  nerves,  or  to  the 
centres  of  the  latter,  or  to  both  muscle  and  nerve  simultaneously.  As  a  rule,  the  cathode  is  placed 
nearer  the  centre,  as  it  increases  the  excitability.  When  the  electrode  is  moved  along  the  course  of 
the  nerve,  or  when  the  strength  of  the  current  is  varied,  the  action  is  favored.  If  the  seat  of  the 
lesion  is  in  the  central  nervous  system,  then  the  electrodes  are  apphed  along  the  vertebral  column, 
or  on  the  vertebral  column  and  the  course  of  the  nerves  at  the  same  time,  or  one  on  the  head  and 
the  other  on  a  point  as  near  as  possible  to  the  supposed  seat  of  the  lesion.  The  current  must  rot  be 
too  strong  nor  applied  too  long. 

Induced  v.  Constant  Current :  Reaction  of  Degeneration. — Paralyzed  nerves  and  muscles 
behave  quite  differently  as  regards  the  induced  {x2j^\d\y  interrupted)  and  the  constant  current.  This 
is  called  the  "  reaction  of  degeneration."  We  must  remember  the  physiological  fact  that  a  dying 
nerve  attached  to  a  muscle  (|  325),  and  also  the  muscles  of  a  curarized  animal,  react  much  less 
strongly  to  rapidly   interrupted  currents  than  fresh  non-curarized  muscles.     Baierlacher,  in  1859, 


028  REACTION    OF    DEGENERATION. 

found  that,  in  a  case  of  facial  paralysis,  the  facial  muscles  contracted  but  feebly  to  the  induced 
current,  but  very  energetically  on  the  constant  current  being  used.  The  excitability  for  the  constant 
current  may  be  abnormally  increased,  but  may  disappear  on  recovery  taking  place.  According  to 
Neumann,  it  is  the  longer  duration  of  the  constant  current  as  opjwsed  to  the  momentary  closing  and 
opening  of  the  induced  current  which  makes  the  contraction  of  the  muscle  possible.  If  thp  constant 
current  be  broken  as  rapidly  as  the  Faradic  current  is  broken,  then  the  constant  current  does  not 
cause  contraction.  Conversely,  the  induced  current  may  be  rendered  efiective  by  causing  it  to  last 
longer.  We  may  also  keep  the  primary  circuit  of  the  induction  machine  closed,  and  move  the 
secondary  spiral  to  and  fro  along  the  slots.  Thus  we  obtain  slow  gradations  of  the  induced  current 
which  act  energetically  upon  curarized  muscles  ( Briicie).  Hence,  in  stimulating  a  muscle  or  nerve, 
we  have  to  consider  not  only  the  strength,  but  also  the  duration,  of  the  current,  just  as  the  deflection 
of  tiie  magnetic  needle  depends  ujxjn  these  two  factors. 

[Galvanic  excitability  is  the  tenn  applied  to  the  condition  of  a  nerve  or  muscle,  whereby  it 
responds  to  the  opening  or  closing  of  a  continuous  current.  The  effects  difl'er  according  as  the 
current  is  opened  or  closed,  and  according  to  its  strength.  As  a  rule,  the  cathode  causes  a  con- 
traction chiefly  at  closure,  the  anode  at  opening  the  current,  while  the  cathode  is  the  stronger 
stimulus.  With  a  7t>fi7/:  current,  the  cathode  produces  a  simple  contraction  on  closing  the  current, 
but  no  contraction  from  the  anode.  With  a  medium  cun^ent,  we  get  with  the  cathode  a  strong 
closing  contraction  but  no  opening  contraction,  while  the  anode  excites  feeble  opening  and  closing 
contractions.  With  a  strong  current,  we  get  with  the  cathode  a  tetanic  contraction  at  closure,  and 
a  perceptible  contraction  at  opening,  while  with  the  anode  there  is  contraction  both  at  opening  and 
closing.] 

[The  law  of  contraction  is  usually  expressed  by  the  following  formula  {Erb) :  An  =  anode, 
Ca  =  cathode,  C  =  contraction,  c  =  feeble  contraction,  C  ;=  strong  contraction,  S  =  closure  of 
current,  O  =  opening  of  current,  Te  =  tetanic  contraction — so  that,  expressing  the  above  statements 
briefly,  we  have — 

Weak  currents  produce  Ca  S  C ; 

Medium   "  "        Ca  S  C'',  An  S  c,  An  O  c; 

Strong      "  "        Ca  S  Te,  An  S  C,  An  O  C,  Ca  Oc.} 

[Typical  Reaction  of  Degeneration. — When  the  reaction  of  the  nerve  and 
muscle  to  electrical  stimulation  is  altered  both  qualitatively  and  quantitatively, 
we  have  the  reaction  of  degeneration,  which  is  characterized  essentially  by  the 
following  conditions]  :  The  excitability  of  the  muscles  is  diminished  or  abolished 
for  the  Faradic  current,  while  it  is  increased  for  the  galvanic  current  from  the  3d  to 
58th  day  ;  it  again  diminishes,  however,  with  variations,  from  the  7 2d  to  80th  day  ; 
the  anode  closing  contraction  is  stronger  than  the  cathode  closing  contraction. 
The  contractions  in  the  affected  muscles  occur  slowly  in  a  peristaltic  manner,  and 
are  local,  in  contrast  with  the  rapid  contraction  of  normal  muscle.  The  diminution 
of  the  excitability  of  the  nenies  is  similar  for  the  galvanic  and  Faradic  currents. 
If  the  reaction  of  the  nerves  be  normal,  while  the  muscle  during  direct  stimulation 
with  the  constant  current  exhibits  the  reaction  of  degeneration,  we  speak  of 
"  partial  reaction  of  degeneration,"  which  is  constantly  present  in  progressive 
muscular  atrophy  {EH?). 

[The  "reaction  of  degeneration"  may  occur  before  there  is  actual  paralysis, as  in  lead  poison- 
ing. When  it  occurs  we  have  to  deal  with  some  affection  of  the  nerve  fibres,  or  of  the  trophic  nerve 
cells.  When  it  is  established,  (i)  stimulation  of  the  nerve  with  Faradic  and  galvanic  electricity  does 
not  cause  contraction  of  the  muscle ;  (2)  direct  Faradic  stimulation  of  the  muscles  does  not  cause 
contraction ;  (3)  the  galvanic  current  usually  excites  contraction  more  readily  than  in  a  normal 
muscle,  so  that  the  muscle  responds  to  much  feebler  currents  than  act  on  healthy  muscles,  but  the 
contraction  is  longer  and  more  of  a  tonic  character,  and  shows  a  tendency  to  become  tetanic.  The 
electrical  excitability  is  generally  unaffected  in  paralysis  of  cerebral  origin,  and  in  some  forms  of 
spinal  paralysis,  as  primary  lateral  sclerosis  and  transverse  myelitis,  but  the  "  reaction  of  degeneration  " 
occurs  in  traumatic  paralysis,  due  to  injury  of  the  nerve  trunks,  neuritis,  rheumatic  facial  paralysis, 
lead  palsy,  and  in  affections  of  the  nerve  cells  in  the  anterior  cornu  of  the  gray  matter  of  the  spinal 
cord.]  In  rare  cases  the  contraction  of  the  muscles,  caused  by  applying  a  Faradic  current  to  the 
nerve,  follows  a  slow  peristaltic-like  course — "■Faradic  reaction  0/ degeneration'''  [E.  Reviak,  Erb). 

II.  In  Various  Forms  of  Spasm  (spasms,contracture,  muscular  tremor)  the  constant  current 
is  most  effective  [Re'nak).  liy  the  action  of  anelectrotonus,  a  pathological  increase  of  the  excita- 
bility is  subdued.  Hence,  the  anode  ought  to  be  applied  to  the  part  with  increased  excitability,  and 
if  it  be  a  case  of  reflex  spasm,  to  the  points  which  are  the  origin  or  seat  of  the  increased  excitability. 
Weak  currents  of  uniform  intensity  are  most  effective.  The  constant  current  may  also  be  useful 
from  its  cataphoric  action,  whereby  it  favors  the  removal  of  irritants  from  the  seat  of  the  irritation. 


APPLICATIONS    OF    ELECTRICITY    IN    DISEASE.  629 

Further,  the  constant  current  increases  the  voluntary  control  over  the  affected  muscles.  In  spasms 
of  central  origin,  the  constant  current  may  be  applied  to  the  central  organ  itself.  Faradization  is 
used  in  spasmodic  affections  to  increase  the  vigor  of  enfeebled  antagonistic  muscles.  Muscles  in  a 
condition  of  contracture  are  said  to  become  more  extensible  under  the  influence  of  the  Faradic 
current  [Eeinak),  as  a  normal  muscle  is  more  excitable  during  active  contraction  (^  301). 

In  Cutaneous  Anaesthesia,  the  Faradic  current  applied  to  the  skin  by  means  of  hair-brush 
electrodes  is  frequently  used  (Fig.  417).  When  using  the  constant  current,  the  cathode  must  be 
applied  to  the  parts  with  diminished  sensibility.  The  constant  current  alone  is  applied  to  the  central 
seat  of  the  lesion,  and  care  must  be  taken  to  what  extent  the  occurrence  of  cathelectrotonus  in  the 
centre  affects  the  occurrence  of  sensation. 

III.  In  Hyperaesthesia  and  Neuralgias,  Faradic  currents  are  applied  with  the  object  of  over- 
stimulating  the  hypersensitive  parts,  and  thus  to  benumb  them.  Besides  these  powerful  currents, 
weak  currents  act  rejiexly  and  accelerate  the  blood  stream,  increase  the  heart's  action,  and  constrict 
the  blood  vessels,  while  strong  c\y\:x^w\.%  cause  the  opposite  effects  (C.  7Vaz<wa««).  Both  maybe 
useful.  In  employing  the  constant  current  in  neuralgia  [-Re?nak),  one  object  is  by  exciting  anelec- 
trotonus  in  the  hypersensitive  nerves,  to  cause  a  diminution  of  the  excitability.  According  to  the 
nature  of  the  case,  the  anode  is  placed  either  on  the  nerve  trunk,  or  even  on  the  centre  itself,  and 
the  cathode  on  an  indifferent  part  of  the  body.  The  catalytic  and  cataphoric  effects  also  are  most 
important,  for  by  means  of  them,  especially  in  recent  rheumatic  neuralgias,  the  irritating  inflamma- 
tory products  are  distributed  and  conducted  away  from  the  part.  A  descending  current  is  trans- 
mitted continuously  for  a  time  through  the  nerve  trunk,  and  in  recent  cases  its  effects  are  sometimes 
very  striking.  Lastly,  of  course,  the  constant  current  may  be  used  as  a  cutaneous  stimulus,  while 
the  Faradic  current  also  acts  reflexly  on  the  cardiac  and  vascular  activity. 

Recently,  Charcot  and  Ballet  have  used  the  electric  spark  from  an  electrical  machine  in  cases  of 
anaesthesia,  facial  paralysis,  and  paralysis  agitans.  In  some  cases  of  spinal  paralysis,  muscles  can  be 
made  to  contract  with  the  electric  spark,  which  do  not  contract  to  a  Faradic  current.  [Electricity 
is  sometimes  used  to  distinguish  real  from  feigned  disease,  or  to  distinguish  death  from  a  condition 
of  trance.] 

Galvano-Cautery. — The  electrical  current  is  used  for  thermal  purposes,  as  in  the  galvano- 
cautery. 

Galvano-Puncture. — The  electrolytic  properties  of  electrical  currents  are  employed  to  cause 
coagulation  in  aneurisms  or  varix.  [If  the  electrodes  from  a  constant  battery  in  action  be  inserted 
in  an  anemrismal  sac,  after  a  time  the  fibrin  of  the  blood  is  deposited  in  the  sac,  whereby  the  cavity 
of  the  aneurism  is  gradually  filled  up.  A  galvanic  current  passed  through  defibrinated  blood 
causes  the  formation  of  a  coagulum  of  proteid  matter  at  the  positive  pole  and  bubbles  of  gas  at  the 
negative.] 

340.  ELECTRICAL  CHARGING  OF  THE  BODY.— Saussure  investigated  by  means 
of  the  electroscope  the  "  charge  "  of  a  person  standing  on  an  insulated  stool.  The  phenomena 
observed  by  him,  which  were  always  inconstant,  were  due  to  ih^  friction  of  the  clothes  upon  the  skin. 
Gardini,  Hemmer,  Ahrens  (1817),  and  Nasse  regarded  the  body  as  normally  charged  vf\\h positive 
electricity,  while  Sjosten  and  others  regarded  it  as  7iegatively  charged.  Most  probably  all 
these  phenomena  are  due  to  friction,  and  are  modified  effects  of  the  air  in  contact  with  the 
heterogeneous  clothing  i^Hankel).  A  strong  charge  resulting  in  an  actual  spark  has  frequently 
been  described.  Cardanus  (1553)  obtained  sparks  from  the  tips  of  the  hair  of  the  head.  Accord- 
ing to  Horsford  (1837),  long  sparks  were  obtained  from  the  tips  of  the  fingers  of  a  nervous 
woman  in  Oxford,  when  she  stood  upon  an  insulated  carpet.  Sparks  have  often  been  observed  on 
combing  the  hair  or  stroking  the  back  of  a  cat  in  the  dark.  Freshly  voided  urine  is  negatively 
electrical  ( Vasalli-Eandi,  Volta) ;  so  is  the  freshly  formed  web  of  a  spider,  while  the  blood  is 
positive. 

341.  COMPARATIVE— HISTORICAL.— Electrical  Fishes.— Some  of  the  most  interest- 
ing phenomena  connected  with  animal  electricity  are  obtained  in  electrical  fishes,  of  which  there 
are  about  fifty  species,  including  the  electrical  eel,  or  Gymnotus  electricus,  of  the  lagoons  of  the 
region  of  the  Orinoco  in  South  America — it  may  measure  over  7  feet  in  length — the  Torpedo  77iar- 
morata  and  some  allied  species,  30  to  70  centimetres  [l  to  2^  feet),  in  the  Adriatic  and  Mediter- 
ranean, the  Malapteru7-us  electricus  of  the  Nile,  and  the  Mor77iyrus  also  of  the  same  river.  By 
means  of  special  electrical  organs  {Redi,  1666),  these  animals  can  in  part  voluntarily  (gymnotus 
and  malapterurus),  and  in  part  reflexly  (torpedo),  give  a  very  powerful  electrical  shock.  The  elec- 
trical organ  consists  of  "  compartments  "  of  various  forms,  separated  from  each  other  by  connective 
tissue,  and  filled  with  a  jelly  like  substance,  which  the  nerves  enter  on  one  surface  and  ramify  to 
produce  a  plexus.  From  this  plexus  there  proceed  branches  of  the  axial  cylinder,  which  end  in  a 
nucleated  plate,  the  "  electrical  plate  "  [Billha7-z,  M.  Schulze).  When  the  "  electrical  nerves  " 
proceeding  to  the  organ  are  stimulated,  an  electrical  discharge  is  the  result. 

In  Gymnotus,  the  electrical  organ  consists  of  several  rows  of  columns  arranged  along  both  sides 
of  the  spinal  column  of  the  animal,  under  the  skin  as  far  as  the  tail.  It  receives  on  the  anterior 
surface  several  branches  from  the  intercostal  nerves.     Be-ides  this  large  organ  there  is  a  smaller  one 


630 


COMPARATIVE HISTORICAL. 


lying  on  both  sides  alx)ve  the  anal  tins.     Here  the  plates  are  vertical,  and  the  direction  of  the  elec- 
trical current  in  the  fish  is  ascending,  so  that  of  course  it  is  descending  in  the  surrounding  water 

[/''araiiiiv,  dn  Bois-Reyniond). 

In  Malapterurus,  the  organ  surrounds  the  body  like  a  mantle,  and  receives  only  one  nerve-fibre 
(p.  579),  whose  axis  cylinder  arises  near  the  medulla  oblongata  from  one  gigantic  ganglionic  cell 
{Billharz),  and  is  composed  of  proto]3lasmic  pr  cesses  {Fritsc/i).  The  plates  are  also  vt-rlical,  and 
receive  their  nerves  from  the  posterior  surface.  The  direction  of  the  current  is  descending  in  the  fish 
durii'g  the  discharge  [dii  Bois-ReymonJ). 

In  ihe  Torpedo,  the  organ  lies  imme.iialely  under  the  skin  laterally  on  each  side  of  the  head, 
reaching  as  far  as  the  pectoral  fins  It  receives  several  nerves  which  arise  from  the  lobus  clectricus, 
between  the  corpora  quadrigemina  and  the  medulla  oblongata  The  plates,  which  do  not  increa.se  in 
number  with  the  growth  of  the  animal  {Dclle  Chinje,  Bubuchin),  lie  horizontally,  while  the  nerve 
fibres  enter  them  on  their  dorsal  surfaces,  the  current  in  the  fish  being  from  the  abdominal  to  the 
dorsal  surface  (Gahuiui). 

It  is  extremely  probable  that  the  electric  organs  are  modified  muscles,  in  which  the  nerve  termi- 
nations are  highly  developed,  the  electrical  j)lates  corre.sjx>nding  to  the  motorial  end  jjlates  of  the 
muscular  fibres,  the  contraciile  sutistance  having  disappeared,  .so  that  during  phy>iological  activity 
the  chemical  energy  is  changed  into  electricity  alone,  while  there  is  no  •'  work  "  done.  This  view  is 
supported  by  the  observation  of  Baljuchin,  that  during  development  the  organs  are  originally  formed 
like  musclts ;  further,  that  the  organs  when  at  rest  are  neutral,  but  when  active  or  dead,  acid  ;  and 
lastly,  they  contain  a  substance  related  to  myosin  which  coagulates  after  death  (^  295 — IVeyl). 
Ihe  organs  manifest  fatigue;  they  have  a  "latent  period"  of  0016  second,  while  one  shock  of  the 
organ  (comparable  to  the  current  in  an  active  muscle)  lasts  0-07  second.  About  twenty-five  of  these 
shocks  go  to  make  a  discharge,  which  lasts  about  0-23  second.  The  discharge,  like  tetanus,  is  a 
discontinuous  jjrocess  {Marey).  Mechanical,  chemical,  thermal,  and  electrical  stimuli  cause  a  dis- 
charge; a  single  induction  shock  is  not  effective  (Jfrtf//.?).  During  the  electrical  discharge  the  current 
traverses  the  muscles  of  the  animal  itself;  the  latter  co.itract  in  the  toqiedo,  while  they  do  not  do  so 
in  the  gyninotus  and  malapterurus  during  the  discharge  (S/einer).  A  torpedo  can  give  about  fifty 
shocks  per  minute  ;  it  then  becomes  fatigued,  and  requires  some  time  to  recover  itself.  It  may  only 
partially  discharge  its  organ  [Al.  v.  Humboldt,  Sachs).  Cooling  makes  the  organ  less  active,  while 
heating  it  to  22  C.  makes  it  more  so.  The  organ  becomes  tetanic  with  strychnin  [Becquerel],  while 
curara  paralyzes  it  {Sachs).  Stimulation  of  the  electrical  organ  of  the  torpedo  causes  a  discharge 
(Malleitcci) ;  cold  retards  it,  while  section  of  the  electrical  nerves  paralyzes  the  organ.  The  electri- 
cal fishes  themselves  are  but  slightly  affected  by  very  .strong  induction  .shocks  transmitted  through  the 
water  in  which  they  are  swimming  [du  Bois-Reyinond).  The  substance  of  the  electrical  organs  is 
singly  refractive;  excised  ])ortions  give  a  current  during  rest,  which  has  the  same  direction  as  the 
shock;  tetanus  of  the  organ  weakens  the  current  [Sachs,  dti  Buis-Keymond).  Perhaps  the  electrical 
organ  of  malapterurus  is  evolved  from  modified  cutaneous  glands  {Frilsch). 

Historical. — Richer  (1672)  made  the  first  communication  about  the  gymnotus.  Walsh  (1772) 
made  investigations  on  the  torpedo,  on  its  discharge,  and  its  power  of  communicating  a  shock.  J. 
Davy  magnetized  particles  of  .steel,  caused  a  deflection  of  the  magnetic  needle,  and  obtained  electro- 
lysis with  the  electrical  discharge.  Becquerel,  Brechet,  and  Matteucci  studied  \h&  direction  o{  \!af: 
discharge.  Al.  v.  Humboldt  described  the  habits  and  actions  of  the  gymnotus  of  South  America. 
Hausen  (1743)  and  de  Sauvages  (1744)  supposed  that  electricity  was  the  active  force  in  nerves. 
The  actual  investigations  into  animal  electricity  began  with  G.  Aloisio  (lalvani  (1791),  who  observed 
that  frogs'  legs  connected  with  an  electrical  machine  contracted,  and  also  when  they  were  toucher! 
with  two  difterent  metals.  He  believed  that  nerves  and  muscles  generated  electricity.  Alessandro 
Volta  ascribed  the  second  experiment  to  the  electrical  current  proiuced  by  the  contact  of  dissimilar 
metals,  and  therefore  outside  the  tissues  of  the  frog.  The  contraction  without  metals  described  by 
Oalvani  was  confirmed  by  Alex.  V.  Humboldt  (1798).  PfafT  ( 1 793 )  first  observed  the  efiect  of  the 
direction  of  the  current  upon  the  contraction  of  a  frog's  leg  obtained  by  stimulating  its  nerve. 
Bunzen  made  a  galvanic  pile  of  frogs'  legs.  The  whole  subject  entered  on  a  new  phase  with  the 
construction  of  the  galvanometer  and  since  the  introduction  of  the  classical  methods  devised  by 
du  Bois-Reymond,  i.e.,  from  1843  onward. 


Physiology  t°h'k  peripheral  Nerves. 


342.  FUNCTIONAL  CLASSIFICATION  OF  NERVE  FIBRES. 

— As  nerve  fibres,  on  being  stimulated,  are  capable  of  conducting  impulses  in 
both  directions  (§  338),  it  is  obvious  that  the  physiological  position  of  a  nerve 
fibre  must  depend  essentially  upon  its  relations  to  the  peripheral  end  organ  on 
the  one  hand,  and  its  central  connection  on  the  other.  Thus,  each  nerve  is 
distributed  to  a  special  area  within  which,  under  normal  circumstances,  in  the 
intact  body,  it  performs  its  functions.  This  function  of  the  individual  nerves, 
determined  by  their  anatomical  connections,  is  called  their  "  specific  energy." 

I.  Centrifugal  or  Efferent  Nerves. — (a)  Motor. — Those  nerve  fibres 
whose  peripheral  end  organ  consists  of  a  muscle,  the  central  ends  of  the  fibres 
being  connected  with  nerve  cells  : — 

1.  Motor  fibres  of  striped  muscle  (^^  292  to  320). 

2.  Motor  nerves  of  the  heart  (^  57). 

3.  Motor  nerves  of  smooth  muscle,  1?.^.,  the  intestine  (^  171).  The  vasomotor  nerves  are 
specially  treated  of  in  |  371. 

(b)  Secretory. — Those  nerve  fibres  whose  peripheral  end  organ  consists  of  a 
secretory  cell,  the  central  ends  of  the  fibres  being  connected  with  nerve  cells. 

Examples  of  secretory  nerves  are  the  secretory  nerves  for  saliva  (^  145)  and  those  for  sweating 
(§  289,  II).  It  is  to  be  remembered,  however,  that  these  fibres  not  unfrequently  lie  in  the  same 
sheath  with  other  nerve  fibres,  so  that  stimulation  of  a  nerve  may  give  rise  to  several  results, 
according  to  the  kind  of  nerve  fibres  present  in  the  nerve.  Thus,  the  secretory  and  vasomotor 
nerves  of  glands  maybe  excited  simultaneously. 

(c)  Trophic. — The  end  organs  of  these  nerve  fibres  lie  in  the  tissues  them- 
selves, and  are  as  yet  unknown.  These  nerves  are  called  trophic,  because  they  are 
supposed  to  govern  or  control  the  normal  metabolism  of  the  tissues. 

In  some  tissues,  we  know  of  a  direct  connection  of  their  elements  with  nerve  fibres,  which  may 
influence  their  nutrition.  Nerves  are  connected  with  the  corneal  corpuscles  (^  201,  7),  with  the 
pigment  cells  of  the  frog's  skin  (^,^r;«a««),  the  connective -tissue  corpuscles  of  the  serous  membrane 
of  the  stomach  of  the  frog,  and  the  cells  around  the  stomataof  lymphatic  surfaces  (^  196,  5)  [£.  F. 
Hoffmann). 

Trophic  Influence  of  Nerves. — The  trophic  functions  of  certain  nerves  are  referred  to  as 
follows :  On  the  influence  of  the  trigeminus  on  the  eye,  the  mucous  membrane  of  the  mouth  and 
nose,  the  face  (§  347);  the  influence  of  the  vagus  on  the  lungs  (|  352) ;  motor  nerves  on  muscle 
(?  307) ;  nerve  centres  on  nerve  fibres  (^  325,  4) ;  certain  central  organs  upon  certain  viscera 

{I  379)- 

Section  of  certain  nerves  influences  the  growth  of  the  bones.  H.  Nasse  found  that,  after  sec- 
tion of  their  nerves,  the  bones  showed  an  absolute  diminution  of  all  their  individual  constituents, 
while  there  was  an  increase  of  the  fat.  Section  of  the  spermatic  nerve  is  followed  by  degeneration 
of  the  testicle  [Nelaton,  Obolensky).  After  extirpation  of  their  secretory  nerves,  there  is  degenera- 
tion of  the  sub-maxillary  glands  (p.  258).  Section  of  the  nerves  of  the  cock's  comb  inter- 
feres with  the  nutrition  of  that  organ  [Legros,  Schiff).  After  section  of  the  2d  cervical  nerve  in 
rabbits  and  cats,  the  hair  falls  ofl"  the  ear  on  that  side  [Joseph).  Section  of  the  cervical  sympa- 
thetic nerve  in  young,  groaning  animals  is  followed  by  a  more  rapid  growth  of  the  ear  upon  that  side 
[Bidder,  Stirling,  Strieker),  also  of  the  hair  on  that  side  [Schiff,  Stirling^  ;  while  it  is  said  that 
the  corresponding  half  of  the  brain  is  smaller,  which,  perhaps,  is  due  to  the  pressure  from  the  dilated 
blood  vessels  [Brown-Sequard], 

631 


632  TROPHIC    NERVES    AND    TROPHO-NEUROSES. 

Blood  Vessels. — Lewaschew  found  tliat  prolonged,  uninterrupted  stimulation  of  the  sciatic 
nerve  of  dogs,  by  means  of  chemical  stimuli  [threads  dii)ped  in  sulphuric  acid],  caused  hypertrophy 
of  the  lower  limb  and  foot,  together  with  the  formanon  of  aneurismal  dilatations  upon  the  blood 
vessels. 

Skin  and  Cutaneous  Appendages. — In  man,  stimulation  or  paralysisof  nerves,  or  degeneration 
of  tlie  gr.iy  mailer  of  the  spinal  con),  is  not  un frequently  followed  by  changes  in  the  pigmentation  of 
the  skin,  in  llie  nails,  in  the  hair  and  its  mode  of  growth  and  color  (Jtirisch).  [Injury  to  the  brain, 
as  by  a  fall,  sometimes  results  in  paralysis  of  the  hair  follicles,  so  that,  after  such  an  injur)-,  the  hair 
is  lost  over  nearly  the  whole  of  the  body.]  Sometimes  there  may  be  eruptions  u|)on  the  skin, 
apparantly  traumatic  in  their  origin  (r'.  BarenspniUi^  ).  .Sometimes  there  is  a  tendency  to  decubitus 
{\  379),  and  in  some  rare  cases  of  tabes,  there  is  a  peculiar  degeneration  of  the  joints  (Charcot's 
disease).      The  changes  which  take  place  in  a  nerve  separated  from  its  centre  are  described  in  §  325. 

[Tropho-neuroses. — Some  of  the  chief  data  on  which  the  existence  of  trophic  nerves  is  assumed 
are  indicated  alxive.  There  are  many  pathological  conditions  referable  to  diseases  or  injuries  of 
nerves.] 

[Muscles. — As  is  well  known,  paralysis  of  a  motor  nerve  leads  to  simple  atrophy  of  the  corres- 
ponding muscle,  provided  it  be  not  exercised;  but  when  the  motor  ganglionic  cells  of  the  anterior 
horn  of  gray  matter,  or  the  corresponding  cells  in  the  crus,  pons,  and  medulla,  are  paralyzed,  there 
is  an  active  condition  of  atrophy  with  proliferation  of  the  muscular  nuclei.  Progressive  muscular 
atrophy,  or  wasting  palsy,  is  another  trophic  change  in  muscle,  whereby  either  individual  muscles, 
or  groups  of  muscles,  are  one  after  the  other  paralyzed  and  become  atrophied.  In  pseudo-hyper- 
trophic  paralysis,  there  is  cirrhosis  or  increased  development  of  the  connective  tissue,  with  a 
diminution  of  the  true  muscular  elements,  so  that  although  the  muscles  increase  in  ijulk  their  power 
is  diminished.] 

Cutaneous  Trophic  Affections. — Among  these  may  be  mentioned  the  occurrence  of  red 
patches  or  er)'thema,  urticaria  or  nettle-rash,  some  forms  of  lichen,  eczema,  the  bulla;  or  blebs  of 
pemphigus,  and  some  forms  of  ichthyosis,  each  of  which  may  occur  in  limited  areas  after  injury  to  a 
nerve  or  its  spinal  or  cerebral  centre.  The  relation  between  the  cutaneous  eruption  and  the  distribu- 
tion of  a  nerve  is  sometimes  ver)'  marked  in  herpes  zoster,  which  fre(|uently  follows  the  distribution 
of  the  intercostal  and  supraorbital  nerves.  Glossy  skin  (Paget,  lVei>-  Mitchell)  is  a  condition 
depending  upon  impaired  nutrition  and  circulation,  and  due  to  injuries  of  nerves.  The  skin  is  smooth 
and  glossy  in  the  area  of  distribution  of  certain  nerves,  while  the  wrinkles  and  folds  have  disappeared. 
In  myxcedema,  the  subcutaneous  tissue  and  other  organs  are  infiltrated  with,  while  the  blood  con- 
tains, mucin.  The  subcutaneous  tissue  is  swollen,  and  the  patient  looks  as  if  suffering  from  renal 
dropsy.  There  is  marked  alteration  of  the  cerebral  faculties,  and  a  condition  resembling  a 
"  cretinoid  state  '"  occurs  after  the  excision  of  the  thyroid  gland.  Victor  Ilorsley  has  shown  that  a 
similar  condition  occurs  in  monkeys  after  excision  of  the  thyroid  gland  (^  103,  III).  [Laycock 
described  a  condition  of  nervous  cedema  which  occurs  in  some  cases  of  hemiplegia,  and  apparently 
it  is  independent  of  renal  or  cardiac  disease.] 

[There  are  alterations  in  the  color  of  the  skin  depending  on  nervous  affections,  including  localized 
leucoderma,  where  circumscribed  patches  of  the  skin  are  devoid  of  pigment.  The  pigmentation 
of  the  skin  in  Addison's  disease  or  bronzed  skin,  which  occurs  in  some  cases  of  disease  of  the 
suprarenal  capsules,  may  be  partly  nervous  in  its  origin,  more  especially  when  we  consider  the 
remarkable  pigmentation  that  occurs  around  the  nipple  and  some  other  parts  of  the  body  during 
pregnancy,  and  in  some  uterine  and  ovarian  affections. 

In  anaesthetic  leprosy,  the  anaesthesia  is  due  to  the  disease  of  the  nervous  structure,  which 
results  in  disturbance  of  motion  and  nutrition.  Among  other  remarkable  changes  in  the  skin, 
perhaps  due  to  trophic  conditions,  are  those  of  symmetrical  and  local  gangrene,  and  acute  decubi- 
tus or  bed  sores.] 

[Bed  Sores. — Besides  the  simple  chronic  form,  which  results  from  over  pressure,  bad  nursing, 
and  inattention  to  cleanliness,  combined  with  some  defect  of  the  nervous  conditions,  there  is  another 
form,  acute  decubitus,  which  is*  due  directly  to  nerve  influence  [Charcot).  The  latter  usually 
appears  within  a  few  hours  or  days  of  the  cerebral  or  spinal  lesion,  and  the  whole  cycle  of  changes 
— from  the  appearance  of  the  erythematous  dusky  patch  to  inflammation,  ulceration,  and  gangrene  of 
the  buttock — is  completed  in  a  few  days.  An  acute  bed  sore  may  form  when  every  attention  is  paid 
to  the  avoidance  of  pressure  and  other  unfavorable  conditions.  When  it  depends  on  cerebral 
affections,  it  begins  and  develops  rapidly  in  the  centre  of  the  gluteal  region  on  the  paralyzed  side, 
but  when  it  is  due  to  disease  of  the  spinal  cord  it  forms  more  in  the  middle  line  in  the  sacral  region ; 
while  in  unilateral  spinal  lesions  it  occurs  not  on  the  paralyzed,  but  on  the  anjesthetic  side,  a  fact 
which  seems  to  show  that  the  trophic,  like  the  sensory  fibres,  decussate  in  the  cord  {Ross).'\ 

[There  are  other  forms  due  to  nervous  disease,  including  symmetrical  gangrene  and  local 
asphyxia  of  the  terminal  parts  of  the  body,  such  as  toes,  nose,  and  external  ear,  caused  perhaps  by 
spasm  of  the  small  arterioles  (Raynaud's  disease) ;  and  the  still  more  curious  condition  of  per- 
forating ulcer  of  the  foot.  Hemorrhage  of  nervous  origin  sometimes  occurs  in  the  skin,  including 
those  that  occur  in  locomotor  ataxia  after  severe  attacks  of  pain,  and  haematoma  aurium,  or  the 
insane  ear,  which  is  specially  common  in  general  paralytics.] 


INHIBITORY    AND    AFFERENT   NERVES.  633 

(d)  [Inhibitory  nerves  are  those  nerves  which  modify,  inhibit,  or  suppress  a 
motor  or  secretory  act  already  in  progress.] 

Take  as  an  example  the  effect  of  the  vagus  upon  the  action  of  the  heart.  Stimulation  of  the 
peripheral  end  of  the  vagus  causes  the  heart  to  stand  still  in  diastole  (§  85) ;  see  also  the  effect  of  the 
splanchnic  upon  the  intestinal  movements  (^,  161).  The  vaso-dilator  nerves,  or  those  whose  stimu- 
lation is  followed  by  dilatation  of  the  blood  vessels  of  the  area  which  they  supply,  are  referred  to 
especially  in  ^  237. 

[There  is  the  greatest  uncertainty  as  to  the  nature  and  mode  of  action  of  inhibitory  nerves, 
but  take  as  a  type  the  vagus,  which  depresses  the  function  of  the  heart,  as  shown  by  the  slower 
rhythm,  diminution  of  the  contractions,  relaxation  of  the  muscular  tissue,  lowering  of  the  excitability 
and  conduction.  These  phenomena  are  not  due  to  exhaustion.  Gaskell  points  out  that  the 
action  is  beneficial  in  its  after  effects,  so  that  this  nerve,  although  it  causes  diminished  activity, 
is  followed  by  repair  of  function  ;  hence,  he  groups  it  as  anabolic  nerve,  the  outward  symp- 
toms of  cessation  of  function  indicating  that  constructive  chemical  changes  are  going  on  in  the 
tissue.] 

(e)  Thermic  and  electrical  nerves  have  also  been  surmised  to  exist. 

[Gaskell  classifies  the  efferent  nerves  differently.  Beside  motor  nerves  to  striped  muscle,  he 
groups  them  as  follows  : — - 

1.  Nerves  to  vascular  muscles. 

(a)  Vasomotor,  i.  e.,  vaso-constrictor,  accelerators  and  augmentors-of  the  heart. 
(^)    Vaso-inhibitory,  i.  e.,  vaso- dilators  and  inhibitors  of  the  heart. 

2.  Nerves  of  the  visceral  muscles. 

{a)    Visce7'o-motor. 

(b)  Viscero-inhibitory. 

3.  Glandular  nerves.] 

[Other  terms  are  applied  to  nerves  with  reference  to  the  chemical  changes 
they  excite  in  a  tissue  in  which  they  terminate.  The  ordinary  metabolism  is  the 
resultant  of  two  processes — one  constructive,  the  other  destructive,  or  of  assimila- 
tion and  dissimilation  respectively.  The  former  process  is  anabolism,  the  latter 
katabolism.  A  motor  nerve  excites  chemical  destructive  changes  in  a  muscle,  and 
is  so  far  the  katabolic  nerve  of  that  tissue ;  in  the  same  way  the  sympathetic 
to  the  heart,  by  causing  more  rapid  contraction,  is  also  a  katabolic  nerve,  while  the 
vagus,  as  it  arrests  the  heart's  action,  and  brings  about  a. constructive  metabolism 
of  the  cardiac  tissue,  is  an  anabolic  nerve  (^Gaskell>).'\ 

II,  Centripetal  or  Afferent  Nerves. — (a)  Sensory  Nerves  (sensory  in 
the  narrower  sense),  which  by  means  of  special  end 

organs  conduct  sensory  impulses  to  the  central  nervous  Fig.  422. 

system. 

(b)  Nerves  of  Special  Sense. 

(c)  Reflex  or  Excito-motor  Nerves. — When  the 
periphery  of  one  of  these  nerves  is  stimulated,  an  im- 
pulse is  set  up  which  is  conducted  by  them  to  a  nerve 
centre,  from  whence  it  is  transferred  to  a  centrifugal  or 
efferent  fibre,  and  the  mechanism  (I,  a,  b,  c,  d)  in  con- 
nection with  the  peripheral  end  of  this  efferent  fibre  is 
set  in  action  ;  thus,  there  are — Reflex  motor,  Reflex 
secretory,  and  Reflex  inhibitory  fibres.  [Fig.  422 
shows  the  simplest  mechanism  necessary  for  a  reflex  Scheme  of  a  reflex  motor  act.  s, 
motor  act.  The  impulse  starts  from  the  skin,  S,  travels  nerve  ceU;  ^yf  efferent  fibre.  ' 
up  the  nerve,  af,  to  the  nerve  centre  or  nerve  cell,  N, 

situate  in  the  spinal  cord,  where  it  is  modified  and  transferred  to  the  outgoing 
fibre,  <?/",  and  conveyed  by  it  to  the  muscle,  M.] 

III.  Inter-central  Nerves. — These  fibres  serve  to  connect  ganglionic  centres 
with  each  other,  as,  for  example,  in  co-ordinated  movements,  and  in  extensive 
reflex  acts. 


634  OLFACTORY    AND    OITIC    NERVE. 

THE    CRANIAL    NERVES. 

343.  I.  NERVUS  OLFACTORIUS. — Anatomical. — The  three-sided  prismatic  tractus 
olfactorius,  Iving  in  a  i;roovc  011  the  under  surface  of  the  frontal  lohe,  arises  by  means  of  an  inner, 
outer,  and  middle  root,  from  the  tuber  olfactorium  ( liij.  42S,  I).  The  tractus  swells  out  u])on  the  crib- 
rifonii  plate  of  the  ethmoid  bone,  and  becomes  the  bulbus  olfactorius,  which  is  the  analogue  of  the 
special  portion  of  the  l)rain,  existing  in  dilTerent  mammals  witii  a  well-developed  sense  of  smell  [Gra- 
iiolet).  From  twelve  to  fifteen  olfactory  fdaments  jiass  througli  tlie  foramina  in  the  cribriform  plate 
of  the  ethmoid  bone.  At  lirst  they  lie  between  the  periosteum  and  the  mucous  membrane,  but  in 
the  lower  third  of  their  course  they  enter  the  mucous  membrane  of  the  regio  olfactoria.  The  bulb 
consists  of  white  matter  below,  and  above  of  gray  matter  mi.xed  with  small  spindle-shaped  ganglionic 
cells.  Ilenle  describes  six,  and  Meyncrt  eight,  layers  of  nervous  matter  seen  on  transverse  section. 
[The  centre  for  smell  lies  in  the  tip  of  the  uncinate  gyrus  on  the  inner  surface  of  the  cerebral 
hemisphere  (/vrr/V/).]  According  to  Gudden,  removal  of  the  olfactory  bulb  is  followed  by  atrophy 
of  the  gyrus  uncinatus  on  the  same  side.  According  to  Hill,  the  three  roots  of  the  olfactory  bulb 
stream  backward,  the  inner  one  is  small,  the  middle  one  is  a  thick  bundle,  which  grooves  the 
head  of  the  caudate  nucleus,  curves  inward  to  the  anterior  commissure,  and  crosses  viA  this  com- 
missure, where  it  decussates,  and  passes  to  the  extremity  of  the  temporo-sphenoidal  lobe.  The 
outer  roots  pass  transversely  into  the  pyriform  lobe,  thence  77V?  the  fornix,  corpora  albicantia,  the 
bundle  of  Vic(|  d'Axyr  into  the  anterior  end  of  the  optic  thalamus.  Hill  also  points  out  that  the 
elements  contained  in  the  olfactory  bulb  are  identical  with  those  contained  in  the  four  outer  layers 
of  the  retina.  Flechsig  traces  its  origin  (i)  to  the  gyrus  fornicatus,  (2)  through  the  lamina  perforata 
anterior  to  the  internal  ca])sule  (sensory  part),  and  to  the  gyrus  uncinatus  (sensory  area  of  the  cere- 
brum) (^378,  IV).  Proliably  the  fibres  at  their  origin  cro.ss  to  the  cerebrum.  There  is  a  con- 
nection between  the  olfactory  bulbs  in  the  anterior  commissure.  [Each  nerve  is  related  to  both 
hemispheres.] 

Function. — It  is  the  only  nerve  of  smell.  Physiologically,  it  is  excited  only 
by  gaseous,  odorous  bodies — {Sense  of  Smell,  §  420).  Stimulation  of  the  nerve,  by 
any  other  form  of  stimulus,  in  any  part  of  its  course,  causes  a  sensation  of  smell. 
[It  also  conveys  those  impressions  which  we  call  flavors,  but  in  this  case  the  sen- 
sation is  combined  with  impressions  from  the  organs  of  taste.  In  this  case  also 
the  stimulus  reaches  the  nerve  by  the  posterior  nares.]  Congenital  absence  or 
section  of  both  olfactory  nerves  abolishes  the  sense  of  smell  (easily  performed  on 
young  animals — Biffi). 

Pathological. — The  term  hyperosmia  is  applied  to  cases  where  the  sense  of  smell  is  exces- 
sively and  abnormally  acute,  as  in  some  hysterical  persons,  and  in  cases  where  there  is  a  purely 
subjective  sen.se  of  smell,  as  in  some  insane  persons.  The  latter  is  perhaps  due  to  an  abnormal 
stimulation  of  the  cortical  centre  (§  378,  IV).  Hyposmia  and  anosmia  (/.«'.,  diminution  and 
abolition  of  the  sense  of  smell)  may  be  due  to  mechanical  causes,  or  to  over-stimulation.  Strych- 
nin sometimes  increases,  while  morphia  diminishes,  the  sense  of  smell.  [Method  of  Testing, 
^421.] 

344.  II.  NERVUS  OPTICUS. — Anatomical. — The  tractus  opticus  (Fig.  428,  II)  arises 
from  the  anterior  corpora  quadrigemina,  the  corpus  geniculatum  externum,  and  the  thalamus  opticus 
(P'ig.  428),  as  well  as  from  the  gray  matter  which  lines  the  third  ventricle  {Tartuferi).  A  broad 
bundle  of  fibres  passes  from  the  origin  of  the  optic  tract  to  the  cortical  visual  centre,  at  the  apex 
of  the  occipital  lobe  on  the  same  side  (  Wernicke — \  379,  IV).  Fibres  pass  from  the  cerebellum 
through  the  crura. 

The  optic  tract  bends  round  the  pedunculus  cerebri,  where  it  unites  with  its  fellow  of  the 
opposite  side  to  form  the  chiasma,  and  from  the  opposite  side  of  this  the  two  optic  nerves 
spring. 

[Connections  of  Optic  Tract. — There  is  very  considerable  diflficulty  in  ascertaining  the  exact 
origin  of  all  the  fibres  of  the  optic  tract.  Although  as  yet  the  statement  of  Gratiolet  is  not  proved 
that  the  optic  tract  is  directly  connected  with  every  part  of  the  cerebral  hemisphere  in  man,  from  the 
frontal  to  the  occipital  lobe,  still  the  researches  of  D.  J.  Hamilton  have  shown  that  its  connections 
are  very  extensive.  It  is  certain  that  some  of  them  are  ganglionic,  i.  e.,  connected  with  the  ganglia 
at  the  base  of  the  brain,  while  others  are  cortical,  and  form  connections  with  the  cortex  cerebri.  The 
ganglionic  fibres  arise  from  the  corpora  geniculata,  pulvinar,  and  anterior  corpora  quadrigemina, 
and  probably  also  from  the  substance  of  the  thalamus.  The  cortical  fibres  join  the  ganglionic  to 
form  the  optic  tract.  According  to  D.  J.  Hamilton,  the  connection  with  the  cortex  in  the  fi-ontal 
region  is  brought  about  by  "  Meynert's  commissure  "  The  latter  arises  directly  from  the  lenticular 
nucleus  loop,  decussates  in  the  lamina  cinerea,  and  passes  into  the  optic  nerve  of  the  opposite  side. 
The  lendcular  nucleus  loop  is  formed  below  the  lenticular  nucleus  by  the  junction  of  the  stria; 
medullares ;  the  striae  medullares  form  part  of  the  fibres  of  the  internal  capsule,  and  the  inner  cap- 


OPTIC   RADIATION    AND    CHIASMA. 


635 


sule  is  largely  composed  of  fibres  descending  from  the  cortex.  Hamilton  also  asserts  that  other  cor- 
tical connections  join  the  tract  as  it  winds  round  the  pedunculus  cerebri,  and  they  include  (a)  a  large 
mass  of  fibres  coming  from  the  motor  areas  of  the  opposite  cerebral  hemisphere,  crossing  in  the  cor- 
pus callosum,  entering  the  outer  capsule,  and  joining  the  tract  directly;  {d)  fibres  uniting  it  to  the 
temporo-sphenoidal  lobe  of  the  same  side,  especially  the  first  and  second  temporo-sphenoidal  convo- 
lutions; (<r)  fibres  to  the  gyrus  hippocampi  of  the  same  side;  (a')  a  large  leash  of  fibres  forming 
the  "  optic  radiation "  of  Gratiolet,  which  connect  it  directly  with  the  tip  of  the  occipital 
lobe.  There  are  probably  also  indirect  connections  with  the  occipital  region  through  some  of  the 
basal  ganglia.  Although  some  observers  do  not  admit  the  connections  with  the  frontal  and 
sphenoidal  lobes,  all  are  agreed  as  to  its  connection  with  the  occipital  by  means  of  the  "  optic  radia- 
tion."] 

[The  optic  radiation  of  Gratiolet  is  a  wide  strand  of  fibres  expanding  and  terminating  in  the 
occipital  lobes.  It  is  composed  of,  or,  stated  otherwise,  gives  branches  to  (a)  the  optic  tract 
directly,  {b)  the  corpus  geniculatum  internum  and  externum,  (<:)  to  the  pulvinar  and  substance  of 
the  thalamus,  (^)  a  direct  sensitive  band  (Meynert's  "  Sensitive  band  ")   to  the  posterior  third  of 


Fig.  424. 


Fig.  423. 


Scheme  of  the  semi-decussation  of  the  optic 
nerves.    L.A.,  left  eye  ;  R.A.,  right  eye. 


Diagram  of  the  relation  of  the  field  of  vision, 
retina,  and  optic  tracts.  RF,  LF,  right 
and  left  fields  of  vision — the  asterisk  is  at 
the  fixing  point;  RR,  LR,  right  and  left 
retina — the  asterisk  is  at  the  macula 
lutea;  /.A.,  r.A.,  left  half  and  right  half 
of  each  retina,  receiving  rays  from  the 
opposite  half  of  the  field  ;  RN,  LN,  right 
and  left  optic  nerves  ;  Ch,  chiasma  ;  RT, 
LT,  right  and  left  optic  tracts ;  below, 
the  halves  of  the  fields  from  which  im- 
pressions pass  by  each  optic  tract  are 
superimposed  (Gowers). 


the  posterior  limb  of  the  inner  capsule,  {e)  fibres  which  run  between  the  island  of  Reil  and  the  tip 
of  the  occipital  lobe  {^D.J.  Hamilton).'\ 

Chiasma. — The  extent  of  the  decussation  of  the  optic  fibres  in  the  chiasma  is 
subject  to  variations.  As  a  rule,  rather  more  than  half  of  the  fibres  of  one  tract 
cross  to  the  optic  nerve  of  the  opposite  side  (Fig.  423),  so  that  the  left  optic  tract 
sends  fibres  to  the  left  half  of  both  eyes,  while  the  right  tract  supplies  the  right 
half  of  both  eyes  (§  378,  IV).  [Thus,  the  corresponding  regions  of  each  retina 
are  brought  into  relation  with  one  hemisphere.  The  fibres  which  cross  are  from 
the  nasal  half  of  each  retina  (Fig.  424).] 

Hence,  in  man,  destruction  of  one  optic  tract  (and  its  central  continuation  in  the  occipital  lobe  of 
the  cerebrum)  produces  "  equilateral  or  homonymous  hemianopia."  In  the  cat  there  is  a  semi- 
decussation ;  hence,  in  this  animal  extirpation  of  one  eyeball  causes  atrophy  and  degeneration  of  half 
of  the  nerve  fibres  in  both  optic  tracts  {Guddett).  Baumgarten  and  Mohr  have  observed  a  similar 
result  in  man.     A  sagittal  section  of  the  chiasma  in  the  cat  produces  partial  blindness  of  both  eyes 


636 


HEMIANOPIA    AND    HEMIANOPSIA. 


(.Vica/i).  According  to  (iudden,  the  fibres  which  decussate  are  more  numerous  than  those  which 
do  not,  although  J.  Stilling  maintains  that  they  are  only  slightly  more  numerous.  According  to  J. 
Stilling,  the  decussating  fibres  lie  in  the  central  axis  of  the  nerve,  while  those  which  do  not  decussate 
form  a  layer  around  the  former. 

Other  observers  maintain  that  there  is  complete  decussation  of  all  the  fibres  in  the  chiasma. 
Hence,  section  of  one  oplic  nerve  causes  dilatation  of  the  pupil  and  blindness  on  the  same  side, 
w'hile  section  of  one  optic  tract  causes  dilatation  of  the  pupil  and  blindness  of  the  opposite  eye 
{A'nol/).  In  osseous  fishes,  both  optic  nerves  are  isolated  and  merely  cross  over  each  other,  while 
in  the  cyclostomata  they  do  not  cross  at  all.  [Total  decussation  occurs  in  those  animals  where  the 
eyes  do  not  act  together.] 

Injury  of  the  external  geniculate  body  and  section  of  the  anterior  brachium  have  the  same  effect 
as  section  of  the  optic  tract  of  the  same  side  (§  359 — Bechterew). 

In  very  rare  cases  the  decussation  is  absent  in  man,  so  that  the  right  tract  passes  directly  into  the 
right  eyeball,  and  the  left  into  the  left  eyeball  (  Vesalitis,  Caldani),  the  sight  not  being  interfered 
with. 

It  is  quite  certain  that  the  individual  fibres  do  not  divide  in  the  chiasma.  Two  commissures,  the 
inferior  commissur'.  {GnJden)  and  Meynert's  commissure,  unite  both  optic  tracts  further  back. 

A  special  commissure  (C.  inferior)  extends  in  a  curved  form  across  the  posterior  angle  of  the 
chiasma  [GuiMeu).  It  does  not  degenerate  after  enucleation  of  the  eyeballs,  so  that  it  is  regarded 
as  an  inter-central  connection.  After  excision  of  an  eye,  there  is  central  degeneration  of  the  fibres 
of  the  optic  nerve  entering  the  eyeball  {Gudden),  and  in  man  about  the  half  of  the  fibres  in  the 
corresponding  optic  tract  (Baumgarten,  Alokr).  After  section  of  both  optic  nerves,  or  enucleation 
of  both  eyeballs,  there  is  a  degeneration,  proceeding  centrally,  of  the  whole  optic  tract.  The  de- 
generation extends  to  the  origins  in  the  corpora 
(juadrigemina,  corpora  geniculata,  and  pulvinar,  but 
not  into  the  conducting  paths  leading  to  the  cortical 
visual  centre  [v.  Alonakow)  (^.  37S,  IV,  I). 

[Hemianopia  and  Hemianopsia. — When  one 
optic  tract  is  interfered  with  or  divided,  there  is  inter- 
ference with  or  loss  of  sight  in  the  lateral  halves  of 
both  retinte,  the  blind  part  being  separated  from  the 
other  half  of  the  field  of  vision  by  a  vertical  line. 
Wlien  it  is  spoken  of  as  paralysis  of  one-half  of  the 
retina,  the  term  hemiopia,  or  preferably  hemian- 
opia, is  applied  to  it;  when  with  reference  to  the 
field  of  vision,  the  term  hemianopsia  is  used  (see 
Eye^.  Suppose  the  left  optic  tract  to  be  divided  or 
pressed  upon  by  a  tumor  at  K  (Fig.  425),  then  the 
outer  half  of  the  left  and  the  inner  half  of  the  right 
eye  are  blind,  causing  right  lateral  hemianopsia,  i.  e., 
the  two  halves  are  affected  which  correspond  in 
ordinar)'  vision,  so  that  the  condition  is  sjx)ken  of  as 
homonymous  hemianopsia.  Suppose  the  lesion 
to  be  at  T  (Fig.  425),  then  there  is  paralysis  of  the 
inner  halves  of  both  eyes,  causing  double  temporal 
hemianopsia.  When  there  are  two  lesions  at  NN, 
which  is  very  rare,  the  outer  halves  of  both  retinzE  are 
paralyzed,  so  that  there  is  double  nasal  hemianopsia. 
In  order  to  explain  some  of  the  eye  symptoms  that 
occasionally  occur  in  cerebral  disease,  Charcot  has 
eye,  and'coming^ogeth'eVTnThe^'left  iiemrsphere  supposed  that  Some  of  the  fibres  which  pass  from  the 
(LOG);  LOG,  K,  lesion  of  the  left  optic  tract  external  geniculate  body  to  the  visual  centres  in  the 
r^:^^^^^^S:^^:^d-^  ^^^j^^  .'^^e  cross  beWnd  the  corpora  quadrigemina, 
opia  (right  eye):  T,  lesion  producing  temporal  and  this  IS  represented  m  the  diagram  as  occurring  at 
hemianopsia ;  NN,  lesion  producing  nasal  hemi-  TQ,  in  the  Corpora  quadrigemina.  On  this  view,  all 
anopsia.  ^j^^  occipital  Cortical  fibres  fronj  one  eye  would  ulti- 

mately pass  to  the  cortex  of  the  occipital  lobe  of  the 
opposite  hemisphere.  This  view,  however,  by  no  means  explains  all  the  facts,  for  in  cases  of 
homonymous  hemianopsia  the  point  of  central  vision  on  both  sides,  /.  <?.,  both  maculfe  lutea:  are 
always  unaffected,  so  that  it  is  assumed  that  each  macula  lutea  is  connected  with  both  hemispheres. 
The  second  crossing  suggested  by  Charcot  probably  does  not  occur.  Affections  of  the  optic  nerve, 
^.  _^.,  between  the  eyeball  and  the  chiasma,  z.  ^.,  in  the  orbit,  optic  foramen,  or  within  the  .skull, 
affect  one  eye  only;  of  the  middle  of  the  chiasma,  cause  temporal  hemiopia;  of  the  oplic  tract, 
between  the  cliiasma  and  occipital  cortex,  hemiopia,  which  is  always  symmetrical  {Go7vers).'\ 

Fig.  424,  reduced  from  that  of  Gowers,  shows  the  relation  of  tJie  fields  of  vision  of  the  retina,  optic 
tracts,  and  the  cerebral  optic  centre. 


Diagram  of  the  decussation  of  the  optic  tracts  T, 
semi-decussation  in  the  chiasma  ;  TQ,  decussa- 
tion of  fibres  behind  the  ext.  geniculate  bodies 
(CG) ;  a'b,  fibres  which  do  not  decussate  in  the 
chiasma;  b'a,  fibres  proceeding  from  the  right 


FUNCTIONS  OF  THE  THIRD  CRANIAL  NERVE.         637 

Function. — The  optic  nerve  is  the  nerve  of  sight ;  physiologically,  it  is 
excited  only  by  the  transference  of  the  vibrations  of  the  ether  to  the  rods  and 
cones  of  the  retina  (§  s^S)'  Every  other  form  of  stimulus,  when  applied  to  the 
nerve  in  its  course  or  at  its  centre,  causes  the  sensation  of  light.  Section  or 
degeneration  of  the  nerve  is  followed  by  blindness.  Stimulation  of  the  optic 
nerve  causes  a  reflex  contraction  of  the  pupils,  the  efferent  nerve  being  the  oculo- 
motorius  or  third  cranial  nerve.  If  the  stimulus  be  very  strong,  the  eyelids  are 
closed  and  there  is  a  secretion  of  tears.  The  influence  of  light  upon  the  general 
metabolism  is  stated  at  §  127,  9. 

As  the  optic  nerve  has  special  and  independent  connections  with  the  so-called 
visual  cefitre  (§  378,  IV),  as  well  as  with  the  centre  for  narrowing  the  pupil  (§  345), 
it  is  evident  that,  under  pathological  circumstances,  there  may  be,  on  the  one 
hand,  blindness  with  retention  of  the  action  of  the  iris,  and  on  the  other  loss  of 
the  movements  of  the  iris,  the  sense  of  vision  being  retained  (  Wernicke^. 

Pathological. — Stimulation  of  almost  the  whole  of  the  nervous  apparatus  may  cause  excessive 
sensibility  of  the  visual  apparatus  (hyperaesthesia  optica),  or  even  visual  impressions  of  the  most 
varied  kinds  (photopsia,  chromatopsia),  which  in  cases  of  stimulation  of  the  visual  centre  may 
become  actual  visual  hallucinations  (§  378,  IV).  Material  change  in,  and  inflammation  of,  the  ner- 
vous apparatus  are  often  followed  by  a  nervous  weakness  of  vision  (amblyopia),  or  even  by  blind- 
ness (amaurosis).  Both  conditions,  however,  may  be  the  signs  of  disturbances  of  other  organs,  i.  e., 
they  are  "  sympathetic  "  signs,  due  it  may  be  to  changes  in  the  movement  of  the  blood  stream,  depend- 
ing upon  stimulation  of  the  vasomotor  nerves.  The  discovery  of  the  partial  origin  of  the  optic  nerve 
from  the  spinal  cord  explains  the  occurrence  of  amblyopia  with  partial  atrophy  of  the  optic  nerve,  in 
disease  of  the  spinal  cord,  especially  in  tabes.  Many  poisons,  such  as  lead  and  alcohol,  disturb 
vision.  There  are  remarkable  intermittent  forms  of  amaurosis  known  as  day  blindness  or  heme- 
ralopia,  which  occurs  in  some  diseases  of  the  liver  and  is  sometimes  associated  with  incipient  cataract. 
[The  person  can  see  better  in  a  dim  light  than  during  the  day  or  in  a  bright  light.  In  night  blindness 
or  nyctalopia,  the  person  cannot  see  at  night  or  in  a  dim  light,  while  vision  is  good  during  the  day 
or  in  a  bright  light.  It  depends  upon  disorder  of  the  eye  itself,  and  is  usually  associated  with  imper- 
fect conditions  of  nutrition.] 

345.  III.  NERVUS  OCUI-OMOTORIUS.— Anatomical.— It  springs  from  the  oculo- 
motorius  nucleus  (united  with  that  of  the  trochlearis),  which  is  a  direct  continuation  of  the  ante- 
rior horn  of  the  spinal  cord,  and  lies  unner  the  aqueduct  of  Sylvius  (Fig.  428).  [The  motor  nucleus 
(Fig.  427)  gives  origin  to  three  sets  of  fibres,  for  (l)  the  most  of  the  muscles  of  the  eyeballs,  (2)  the 
sphincter  pupillss,  ( 3)  ciliary  muscle.  The  nucleus  of  the  third  and  fourth  nerves  is  also  connected 
with  that  of  the  sixth  under  the  iter,  so  that  all  the  nerves  to  the  ocular  muscles  are  thus  co-related 
at  thefr  centres.] 

The  origin  is  connected  with  the  corpora  quadrigemina,  to  which  the  intra-ocular  fibres  may  be 
traced,  and  also  with  the  opposite  half  of  the  brain  to  the  angular  gyrus  (|  378,  I)  through  the 
pedunculus  cerebri  Beyond  the  pons,  it  appears  on  the  inner  side  of  the  cerebral  peduncle,  between 
the  superior  cerebellar  and  posterior  cerebral  arteries  (Fig.  428,  III). 

Function. — It  contains — (i)  the  voluntary  motor  fibres  for  all  the  external 
muscles  of  the  eyeballs — except  the  external  rectus  and  superior  oblique — and  for 
the  levator  palpebras  superioris.  The  coordination  of  the  movements  of  both 
eyeballs,  however,  is  independent  of  the  will.  (2)  The  fibres  for  the  sphincter 
pupillce,  which  are  excited  reflexly  from  the  retina.  (3)  The  voluntary  fibres  for 
the  muscle  of  accommodation,  the  tensor  choroidese  or  ciliary  muscle.  The  intra- 
bulbar  fibres  of  2  and  3  proceed  from  the  branch  for  the  inferior  oblique  muscle, 
as  the  short  root  of  the  ciliary  ganglion  (Fig.  429).  They  reach  the  eyeball 
through  the  short  ciliary  nerves  of  the  ganglion,  v.  Trautvetter  and  others 
observed  that  stimulation  of  the  nerve  caused  changes  in  the  eye  similar  to  those 
which  accompany  near  vision.  The  three  centres  for  the  muscle  of  accommoda- 
tion, the  sphincter  pupillge,  and  the  internal  rectus  muscle,  lie  directly  in  relation 
with  each  other,  in  the  most  posterior  part  of  the  floor  of  the  third  ventricle 
{Hens en  and  Volckers). 

The  centre  for  the  reflex  stimulation  of  the  sphincter  fibres  by  light  was  said 
to  be  in  the  corpora  quadrigemina,  but  newer  researches  locate  it  in  the  medulla 
oblongata  (§§  379,  392).     The  narrowing  of  the  pupil,  which  accompanies  the 


638 


FUNCTIONS   OF   THE    THIRD    CRANIAL    NERVE. 


act  of  accommodation  for  a  near  object,  is  to  be  regarded  as  an  associated  move- 
ment (§  392,  5). 

Anastomoses. — In  man,  the  nerve  anastomoses  on  the  sinus  cavernosus  with  the  ophthalmic 
branch  of  tlie  trigeminus,  whereby  it  receives  sensory  fibres  for  the  muscles  to  which  it  is  distributed 
( I'ti/e-n/i/i,  Ai/irwiU-),  whh  the  sympathetic  through  the  carotid  plexus,  and  (?)  indirectly  through 
the  alxlucens,  whereby  it  receives  vasomotor  fibres  (?). 

Varieties. — In  some  rare  cases,  the  pupillary  fibres  for  the  sphincter  run  in  the  alxlucens 
{A  till  >n  a  A),  or  even  in  the  trigeminus  {Schiff,  v.  Griife). 

Atropin  paralyzes  the  intra-bulbar  fibres  of  the  oculomotorius,  while  Calabar 
bean  stimulates  them  (or  paralyzes  the  sympathetic,  or  both — compare  §  392). 

Stimulation  of  the  nerve,  which  causes  contraction  of  the  pupil,  is  best  demonstrated  on  the  decapi- 
tated and  opened  head  of  a  bird.  The  pu])il  is  dilated  in  paralysis  of  the  oculomotorius,  in  asphyxia, 
sudden  cerebral  anremia  {^e.  g.,  by  ligature  of  the  carotids,  or  beheading),  sudden  venous  congestion, 
and  at  deatli. 

Pathological. — Complete  paralysis  of  the  oculomotorius  is  followed  by  (i)  drooping  of  the 
upper  eyelid  (ptosis  paralytica) ;  (2)  immobility  of  the  eyeball ;  (3)  squinting  (strabismus)  outward 
and  downward,  and  consequently  there  is  double  vision  (diplopia) ;  (4)  slight  protnision  of  the  eye- 
ball, because  the  action  of  the  superior  oblique  muscle  in  pulling  the  eyeball  forward  is  no  longer 
compensated  by  the  action  of  three  paralyzed  recti  muscles.  In  animals  provided  with  a  retractor 
bulbi  muscle,  the  protrusion  of  the  eyeball  is  more  pronounced;  (5)  moderate  dilatation  of  the  pupil 
(mydriasis  paralytica);  (6)  the  pupil  does  not  contract  to  light;  (7)  inability  to  accommodate  for 
a  near  object.  It  is  to  be  noted,  however,  that  the  paralysis  may  be  confined  to  individual  branches 
of  the  ner\'e,  /.  e.,  there  may  be  incomplete  paralysis. 

[Squinting. — In  paralysis  of  the  superior  rectus,  the  eye  cannot  be  moved  upward,  and  espe- 

FiG.  426. 


ty'vfty"vX/''vtyU 


Internal  External  Superior  Inferior  Inferior  Superior 

rectus.  rectus.  rectus.  oblique.  rectus.  oljlique. 

The  black  cress  r!presents  the  true  image,  the  light  cross  the  false  image.  The  left  eye  is  represented  as  affected  in 
all  cases  (Bristmv). 

cially  upward  and  outward.  There  is  diplopia  on  looking  upward,  the  false  image  being  above  the 
true,  and  turned  to  the  right  when  the  left  eye  is  affected  (Fig.  426,  3).  Inferior  Rectus. — Defect 
of  downward,  and  especially  downward  and  outward  movement,  the  eye  being  directed  upward  and 
outward.  Diplopia  with  crossed  images,  the  false  one  is  below  the  true  image  and  placed  obliquely, 
being  turned  to  the  left  when  the  left  eye  is  affected.  Diplopia  is  most  troublesome  when  the  object 
is  below  the  line  of  vision  (Fig.  426,  5).  Internal  Rectus. — Defective  inward  movement,  diver- 
gent stjuint,  and  diplopia,  the  images  being  on  the  same  plane,  the  false  one  to  the  patient's  right 
when  the  left  eye  is  affected.  The  head  is  turned  to  the  healtliy  side,  when  looking  at  an  object, 
while  there  is  secondary  deviation  of  the  healthy  eye  outward  (Fig.  426,  i).  Inferior  oblique  is 
rare,  the  eye  is  turned  slightly  downward  and  inward,  and  defective  movement  upward.  Diplopia 
with  the  false  image  above  the  true  one,  especially  on  looking  upward;  the  false  image  is  obHque, 
and  directed  to  the  patient's  left  when  the  left  eye  is  affected  (Fig.  426,  4).] 

Stimulation  of  the  branch  supplying  the  levator  palpebnx;  in  man  causes  lagophthalmus 
spasticus,  while  stimulation  of  the  other  motor  fibres  causes  a  corresponding  strabismus  spasticus. 
The  latter  form  of  scjuinting  may  be  caused  also  refie.xly — e.g.,  in  teething,  or  in  cases  of  diarrhoea 
in  children;  [the  presence  of  worms  or  other  source  of  irritation  in  the  intestines  of  children  is  a 
frequent  cause  of  squinting].  Clonic  spasms  occur  in  both  eyes,  and  also  as  involuntary  movements 
of  the  eyeballs  constituting  nystagmus,  which  m.^y  be  produced  by  stimulation  of  the  corpora  quad- 
rigemina,  as  well  as  by  other  means.  Tonic  contraction  of  the  sphincter  pupilla;  is  called  myosis 
spastica,  and  clonic  contraction,  hippus.  .Spasm  of  the  muscle  of  accommodation  (ciliary  muscle) 
is  sometimes  observed ;  owing  to  the  imperfect  judgment  of  distance,  this  condition  is  not  unfre- 
<iuently  associated  with  macropia. 

[Conjugate  Deviation. — Some  movements  are  produced  by  non-corresponding  muscles;  thus, 
on  looking  to  the  right,  we  use  the  right  external  rectus  and  left  internal  rectus,  and  the  same  is  the 
case  in  turning  the  head  to  tiie  right,  e.  g.,  the  inferior  oblique,  some  muscles  of  the  right  side  act 
along  with  the  left  sterno-mastoid.     In  hemiplegia,  the  muscles  on  one  side  are  paralyzed,  so  that  the 


FUNCTIONS  OF  THE  FOURTH  CRANIAL  NERVE. 


639 


head  and  often  the  eyes  are  turned  away  from  the  paralyzed  side,  i.  e.,  to  the  side  of  the  brain  on 
which  the  lesion  occurs.  This  is  called  "  conjugate  deviation  "  of  the  eyes,  with  rotation  of  the 
head  and  neck.  If  the  right  external  rectus  be  paralyzed  from  an  affection  of  the  sixth  nerve,  on 
telling  the  patient  to  look  to  the  right  it  will  be  found  that  the  left  eye  will  squint  more  inward  even 
than  the  right  eye,  i.  e.,  owing  to  the  strong  voluntary  effort,  the  muscle,  the  left  internal  rectus  which 
usually  acts  along  with  the  right  external  rectus,  contracts  vigorously,  and  so  we  get  secondary 
deviation  of  the  sound  eye.  Similar  results  occur  in  connection  with  paralysis  of  the  other 
ocular  muscles.] 

Fig.  427. 


Coii.irium  or  pineal  glnnd. 

Brachiam  conjunctiv-um  anticum. 


Brachinm  cocjunclivunj 
posticum. 


Corpus    f^^^- 
quadii-  •; 


Corpus  geniculatam 
/  laediale- 


Pedunculus  cerebn. 


ad  corpora  quadri- 
gremina,  or 

superior  cerebellar 

peduncle. 


MiJdie  cerebellar 
peduncle. 


^  -  ad  medullam  oblon- 

gratani,  or  inferior 
iijrr  cerebellar 

yjl  peduncle. 


Accessorias  nucleu3 


Obex 
Clava 


Funiculus  cuneatus 
(Part  of  reatiform  body). 


Funiculus  gracilis 
(Posterior  pyramid). 


Medulla  oblongata,  with  the  corpora  quadrigemina.  The  numbers  IV^XII  indicate  the  superficial  origins  of  the 
cranial  nerves,  while  those  (3-12)  indicate  their  deep  origin,  i.  e.,  the  position  of  their  central  nuclei ;  t,  funicu- 
lus teres. 


346.  IV.NERVUS  TROCHLEARIS.— Anatomical.— It  arises  from  the  valve  ofVieussens- 
i.  e.,  behind  \.\\t  fourth  ventricle,  but  its  fibres  pass  to  the  oculomotorious  ivovaXhe  trock/earis  nucleiisi 
which  is  to  a  certain  extent  a  continuation  of  the  anterior  horn  of  the  spinal  cord  (Fig.  427).  It 
passes  to  the  lower  margin  of  the  corpora  quadrigemina,  pierces  the  roof  of  the  aqueduct  of  Sylvius, 
then  into  the  velum  medullare  superius,  and  after  decussating  with  the  root  of  the  opposite  side 
behind  the  iter,  it  pierces  the  crus  at  the  superior  and  external  border  (Fig.  428).  Its  fibres  cross 
between  its  nucleus  and  its  distribution.  It  has  also  an  origin  from  the  locus  coeruleus.  The  root  of 
the  nerve  receives  some  fibres  from  the  nucleus  of  the  abducens  of  the  opposite  side.  Physiologically, 
there  is  a  necessity  for  a  connection  between  the  centre  and  the  cortical  motor  centre  for  the  eye  muscles. 


640 


THE    NERVUS   TRIGEMINUS, 


Function. — It  is  the  voluntary  motor  nerve  of  the  superior  ol)li(|ue  muscle.  (In 
coordinated  movements,  however,  it  is  involuntary.) 


l-ic.  428. 


d  ja 


Part  of  the  base  of  the  brain,  with  the  origins  of  the  cranial  nerves  ; 
the  convohitions  of  the  island  of  Reil  on  the  right  side,  but  re- 
moved on  the  left.  I',  olfactory  tract  cut  short;  II,  left  optic 
nerve;  II',  right  optic  tract;  77/,  cut  surface  of  the  left  optic 
thalamus;  C,  central  lobe,  or  island  of  Reil;  Sy,  fissure  of 
Sylvius  ;  XX,  the  locus  perforatus  anticus  ;  e,  the  external,  and 
J,  the  internal  corpus  geniculatuni ;  /j,  hypophysis  cerebri;  ic, 
tuber  cinereum,  with  the  infundibulum  ;  a,  points  to  one  of  the 
corpora  albicantia  ;  P,  the  cerebral  peduncle  ;  _/",  the  fillet ;  III, 
left  oculomotor  nerve;  X,the  locus  perforatus  posticus;  PV, 
pons  Varolii  ;  V.  the  greater  part  of  the  fifth  nerve  ;  -f,  the  les- 
ser root  (on  the  right  side  this  mark  is  placed  on  the  Gasserian 
ganglion  and  points  to  the  lesser  root);  i,  ophthalmic  division 
of  the  fifth;  VII  a,  facial,  VII  6,  auditory;  VIII,  vagus; 
VIII  a,  glosso-pharyngeal  :  VIII  6,  spinal  accessory;  IX, 
hypoglossal;  J?,  flocculus  ;  //t,  horizontal  fissure  of  the  cerebel- 
lum iCe);  a»i,  amygdala ; /a.  anterior  pyramid;  o,  olivary 
body;  e,  restiform  body;  d,  anterior  median  fissure;  c/,  the 
lateral  column  of  the  spinal  cord  ;  CI,  the  sub-occipital  or  first 
cervical  nerve. 


Anastomoses.  —  Its  connections 
with  the  plexus  caroticus  sympathici, 
and  with  the  first  branch  of  the  tri- 
geminus, have  the  same  significance  as 
similar  branches  of  the  oculomotorius. 

Pathological.  —  Paralysis  of  the 
trochlearis  nerve  causes  a  very  slight  loss 
of  the  mobility  of  the  eyeball  outward 
and  downward.  There  is  slight  squint- 
ing inward  and  upward,  with  diplopia, 
or  double  vision.  The  images  are  placed 
obliquely  over  each  other  [the  false 
image  being  the  lower,  and  directed  to 
the  ])atient's  right  when  the  left  eye  is 
affected  (I'ig.  426,  6)]  ;  they  approach 
each  other  when  the  head  is  turned 
toward  the  sound  side,  and  are  sepa- 
rated when  the  head  is  turned  toward 
the  other  side.  The  patient  at  first 
directs  his  head  forward  ;  later  he  rotates 
it  round  a  vertical  axis  toward  the  .sound 
side.  In  rotating  his  head  (whereby  the 
sound  eye  may  retain  the  primary  posi- 
tion), the  eye  rotates  with  it.  Spasm 
of  the  trochlearis  causes  squinting  out- 
ward  and  downward. 

347.  V.  NERVUS  TRIGEMI- 
NUS.—  Anatomical. —  The  trigemi- 
nus (Fig.  429,  5),  arises  like  a  spinal 
nerve  by  two  roots  (Fig.  428,  V). 
The  smaller,  anterior,  motor  root  pro- 
ceeds from  the  "  motor  trigeminal 
nucleus  "  (5),  which  is  provided  with 
many  multipolar  nerve  cells,  and  lies  in 
the  floor  of  the  medulla  oblongata,  not 
far  from  the  middle  line.  Fibres  con- 
nect this  nucleus  with  the  cortical  motor 
centres  on  the  opposite  side  of  the  cere- 
brum. Besides  this  the  "  descending 
root "  also  supplies  motor  fibres.  It 
extends  laterally  from  the  corpora  quad- 
rigemina  along  the  aqueduct  of  Sylvius 
downward  to  the  exit  of  the  nerve 
[Henle,  Fo}-el).  The  large  posterior 
sensory  root  receives  fibres :  ( i )  From 
the  small  cells  of  the  "  sensory  tri- 
geminal nucleus"  which  lies  at  the 
level  of  the  pons,  and  is  the  ana- 
logue of  the  posterior  horn  of  the  gray 
matter  of  the  s])inal  cord.  (2)  I'rom 
the  gray  matter  of  the  posterior  horn  of 
the  spinal  cord,  downward  as  far  as 
the  second  cervical  vertebra.  These 
fibres  run  into  the  posterior  column  of 
the  cord  and  then  appear  as  the  "  as- 
cending root  "  in  the  trigeminus.  (3) 
Some  fibres  come  from  the  cerebellum, 


through  the  crura  cerebeUi.  The  ori- 
gins of  the  sensory  root  anastomose  with  the  motor  nuclei  of  all  the  nerves  arising  from  the  medulla 
oblongata,  with  the  exception  of  the  abducens.  This  explains  the  vast  number  of  reflex  relations 
of  the  fifth  nerve.  The  thick  trunk  appears  on  each  side  of  the  pons  (Fig.  428),  when  its  posterior 
root  (perhaps  in  connection  with  some   fibres  from  the  anterior)  forms  the  Gasserian  ganglion, 


THE    OPHTHALMIC    BRANCH    OF   THE    FIFTH.  641 

upon  the  tip  of  the  petrous  part  of  the  temporal  bone   (Fig.  429).     Fibres  from  the  sympathetic 
proceed  from  the  plexus  cavemosus  to  the  ganglion.     The  nerve  divides  into  three  large  branches. 

I.  The  ophthalmic  division  (Fig.  429,  d~)  receives  syitipaihetic  fibres  {vaso- 
motor nerves)  from  the  plexus  cavernosus ;  it  passes  through  the  superior  orbital 
fissure  [sphenoidal]  into  the  orbit.     Its  branches  are  : — 

1.  The  small  recurrent  nerve  which  gives  sensory  branches  to  the  tentorium 
cerebelli.  Fibres — the  vasomotor  nerves  for  the  dura  mater — proceed  along  with 
it  from  the  carotid  plexus  of  the  sympathetic. 

2.  The  lachrymal  nerve  gives  off  {a)  Sensory  branches  to  the  conjunctiva,  the 
upper  eyelid,  and  the  neighboring  part  of  the  skin  over  the  temple  (Fig.  429,  a)  \ 
{b)  true  sensory  fibres  to  the  lachrymal  gland  (?).  Stimulation  of  this  nerve  is 
said  to  cause  a  secretion  of  tears,  while  its  section  prevents  the  reflex  secretion 
excited  through  the  sensory  nerves  of  the  eye.  After  a  time,  section  of  the  nerve 
is  followed  by  a  paralytic  secretion  of  tears  {Herzenstein  and  Wolferz),  although  the 
statement  is  contested  by  Reich.  The  secretion  of  tears  may  be  excited  reflexly, 
by  strong  stimulation  of  the  retina  by  light,  by  stimulation  of  the  first  and  second 
branches  of  the  trigeminus,  and  through  all  the  sensory  cranial  nerves  (^Demt- 
schenko)  (§  356,  A,  6). 

3.  The  frontal  (/)  gives  off  the  supra-trochlear,  which  supplies  sensory 
fibres  to  the  upper  eyelids,  brow,  glabella,  and  those  which  excite  the  secretion 
of  tears  reflexly  ;  and  by  its  supra-orbital  branch  (b),  analogous  branches  to  the 
upper  eyelid,  skin  of  the  forehead,  and  the  adjoining  skin  over  the  temple  as  far  as 
the  vertex. 

4.  The  naso-ciliary  nerve  {nc),  by  its  infra-trochlear  branch  supplies  fibres, 
similar  to  those  of  3,  to  the  conjunctiva,  caruncula,  and  saccus  lacrimalis,  the  upper 
eyelid,  brow,  and  root  of  the  nose.  Its  ethmoidal  branch  supplies  the  tip  and  alse 
of  the  nose,  outside  and  inside,  with  sensory  branches,  as  well  as  the  upper  part  of 
the  septum  and  the  turbinated  bones  with  sensory  fibres,  which  can  act  as  afferent 
nerves  in  the  reflex  secretion  of  tears ;  while  it  is  probable  that  vasomotor  fibres 
are  supplied  to  these  parts  through  the  same  channel.  (These  fibres  may  be  derived 
from  the  anastomosis  with  the  sympathetic  (?).)  The  naso-cihary  nerve  gives  off 
the  long  root  (/)  of  the  ciliary  ganglion  (<;),  and  i  to  3  long  ciliary  nerves. 

The  ciliary  ganglion  (Fig.  429,  c),  which,  according  to  Schwalbe,  perhaps 
belongs  rather  to  the  third  than  the  fifth  nerve,  has  three  roots  (a)  the  short 
or  oculomotorius  (3 — see  §  345)  ;  (<5)  the  long  (/),  from  the  naso-ciliary;  and  {c) 
the  sympathetic  (j-)  sometimes  united  with  b,  from  the  carotid  plexus.  The 
short  ciliary  nerves  {/),  six  to  ten  in  number,  proceed  from  the  ganglion,  along 
with  the  long  ciliary  nerves,  to  near  the  entrance  of  the  optic  nerve,  where  they 
perforate  the  sclerotic  coat  and  run  forward  between  it  and  the  choroid. 

Ciliary  Nerves. — Physiologically,  these  nerves  contain:  — 

1.  The  motor  fibres  for  the  sphincter  pupillae  and  the  tensor  choroidese 
from  the   root  of  the  oculomotorius  (§  345,  2,  3). 

2.  Sensory  fibres  for  the  cornea,  which  are  distributed  as  excessively  fine  fibrils 
between  the  epithelium  of  the  conjunctiva  bulbi ;  they  perforate  the  sclerotic.  These 
fibres  cause  a  reflex  secretion  of  tears  (N.  lacrimalis)  and  closure  of  the  eyelids 
(N.  facialis).  Sensory  fibres  are  supplied  to  the  iris  (pain  in  iritis  and  in  operations 
on  the  iris),  the  choroid  (painful  tension  when  the  ciliary  muscle  is  strained),  and 
the  sclerotic. 

3.  Vasomotor  nerves  for  the  blood  vessels  of  the  iris,  choroid,  and  retina. 
They  arise  in  part  from  the  sympathetic  root,  and  the  anastomosis  of  the 
sympathetic  with  the  ophthalmic  division  of  the  trigeminus  (  Wegner).  The  iris 
and  retina  receive  most  of  their  vasomotor  nerves  from  the  trigeminus  itself 
{Rogow),  and  few  from  the  sympathetic ;  according  to  Klein  and  Svetlin,  the 
retinal  vessels  are  not  influenced  either  by  stimulation  or  division  of  the  sympathetic. 

41 


642 


BRANCHES    AND    CONNECTIONS   OF    THE   TRIGEMINUS. 


Fig.  429. 


Semi-diagrammatic  representation  of  the  nerves  of  the  eyeball,  the  connections  of  the  trigeminus  and  its  ganglia, 
together  with  the  facial  and  glosso-pharyngeal  nerves.  3,  Branch  to  the  inferior  oblique  muscle  from  the 
oculomotorius,  with  the  thick,  short  root,  to  the  ciliary  ganglion  (c) ;  /■,  ciliary  nerves  ;  /,  long  root  to  the  ganglion 
from  the  naso-ciliary  («c) ;  s,  sympathetic  root  from  the  sympathetic  plexus  (Sy)  surrounding  the  internal 
carotid  (G);  </,  first  or  ophthalmic  division  of  the  trigeminus  (5),  with  the  naso-ciliary  («f),  and  the  terminal 
branches  of  the  lachrymal  {a),  supra-orbital ;  (6),  and  frontal  {/)  ;  e,  second  or  superior  maxillary  division  of  the 
trigeminus  ;  R,  infra-orbital ;  «,  spheno-palatine  (Meckel's)  ganglion  with  its  roots  ;  y,  from  the  facial,  and  z',  from 
the  sympathetic;  N,  the  nasal  branches,  and //,,  the  palatine  branches  of  the  ganglion;  ^,  third  or  inferior 
maxillary  division  of  the  trigeminus;  k,  lingual;  i  i,  chorda  tympani  ;  m,  otic  ganglion,  with  the  roots  from  the 
tympanic  plexus,  the  carotid  plexus,  and  from  the  3d  branch,  and  with  its  branches  to  the  auriculo-temporal  (A), 
and  to  the  chorda  (i  i)  ;  L,  sub-maxillary  ganglion  with  its  roots  from  the  tympanico-lingual,  and  the  sympathetic 
plexus  on  the  external  arterj'  (^).  7.  Facial  nerve— y,  its  great  superficial  petrosal  branch  :  a,  gang,  geniculatum ; 
P,  branch  to  the  tympanic  plexus  ;  y,  branch  to  the  stapedius ;  &,  anastomotic  twig  to  the  auricular  branch  of  the 
vagus;  //,  chorda  tympani;  S,  stylo-mastoid  foramen.  9.  Glosso-pharyngeal — A,  its  tympanic  branch;  tt,  and 
e,  connections  with  the  facial;  U,  terminations  of  the  gustatory  fibres  of  9  in  the  circumvallate  papillae;  Sy, 
sympathetic  with  Gg,  s,  the  superior  cervical  ganglion  ;  /,  //,  ///,  /K,  the  four  upper  cervical  nerves ;  P,  parotid, 
M,  sub-raaxillary  gland. 


BRANCHES   AND    CONNECTIONS    OF   THE   TRIGEMINUS.  643 

4.  Motor  fibres  for  the  dilator  pupillse,  which  for  the  most  part  are  derived 
from  the  sytnpathetic  {Petit,  1727),  through  the  sympathetic  root  of  the  ganglion, 
and  the  anastomosis  of  the  sympathetic  with  the  trigeminus  {Balogh,  Oehl). 
Some  observers  deny  altogether  the  existence  of  a  dilator  pupillse  muscle  (§  384). 
The  ophthalmic  division  contains  independent  fibres  for  the  dilatation  of  the  pupil 
(Sc/iif),  which  arise  in  the  medulla  oblongata  and  proceed  directly  into  the  oph- 
thalmic (?  or  arise  from  the  Gasserian  ganglion — Oehl'). 

It  is  not  conclusively  determined  whether  in  man  dilator  fibres  also  proceed  through  the  sympa- 
thetic root  of  the  ciliary  ganglion,  and  reach  the  iris  through  the  ciliary  nerves.  In  the  dog  and  cat 
these  fibres  do  not  pass  through  the  ciliary  ganglion,  but  go  directly  along  the  optic  nerve  to  the  eye 
{^Hensen  and  Volckers)  through  the  Gasserian  ganglion,  to  its  ophthalmic  branch  and  through  the 
long  ciliary  nerves  [Jegoroiv).  In  birds,  the  dilator  fibres  run  only  in  the  fifth  [Zeglinski).  For  the 
centre  (|  367,  8). 

After  section  of  the  trigeminus,  the  pupil  becomes  contracted  after  a  short 
period  of  dilatation  (rabbit,  frog),  but  this  effect  is  not  permanent.  After  excision 
of  the  superior  cervical  ganglion  of  the  sympathetic,  the  power  of  dilatation  of  the 
pupil  is  not  completely  abolished.  The  narrowing  of  the  pupil  which  follows  sec- 
tion of  the  trigeminus  in  the  rabbit,  and  which  rarely  lasts  more  than  half  an 
hour,  may  be  regarded  as  due  to  a  reflex  stimulation  of  the  oculomotorius  fibres  of 
the  sphincter,  in  consequence  of  the  painful  stimulation  caused  by  section  of  the 
trigeminus. 

Stimulation  of  the  Sympathetic. — Either  in  the  neck,  or  in  its  course  to  the  eye,  when  the 
peripheral  end  of  the  cervical  sympathetic  is  stimulated,  besides  the  effect  on  the  blood  vessels,  there 
is  dilatation  of  the  pupil,  as  well  as  contraction  of  the  sviooth  muscular  pibres  in  the  orbit  and  eye- 
lids. The  membrana  orbitalis,  which,  separates  the  orbit  from  the  temporal  fossa  in  animals,  con- 
tains numerous  smooth  muscular  fibres  {^muscular  orbitalis).  The  corresponding  membrane  of  the 
nferior  orbital  fissure  [spheno-maxillary  fissure]  in  man  has  a  layer  of  smooth  muscle,  one  milli- 
metre thick,  and  arranged  for  the  most  part  longitudinally.  Both  eyelids  contain  smooth  muscular 
fibres  which  serve  to  close  them ;  in  the  upper  lid  they  lie  as  if  they  were  a  continuation  of  the 
levator  palpebras  superioris;  in  the  lower  lid  they  close  under  the  conjunctiva.  Tenants  capsule  also 
contains  smooth  muscular  fibres.  The  sympathetic  nerve  supplies  all  these  muscles  [Heinr.  iMilller) 
— (the  orbital  muscle  is  partly  supplied  firom  the  spheno-palatine  ganglion) ;  in  animals,  the  retractor 
of  the  third  eyelid  at  the  inner  angle  of  the  eye  is  similarly  supplied.  Hence,  stimulation  of  the  syi7i- 
pathetic  causes  dilatation  of  the  pupil  and  of  the  palpebral  fissure,  with  protrusion  of  the  eyeball. 
This  result  may  be  caused  reflexly  by  strong  stimulation  of  sensory  nerves.  Strong  stimulation  of 
the  nerves  of  the  sexual  organs  is  followed  by  similar  phenomena  in  the  eye.  The  dilatation  of  the 
pupil,  which  occurs  m  children  affected  with  intestinal  worms,  is  perhaps  an  analogous  phenomenon. 
The  pupil  is  dilated  when  the  spinal  cord  is  stimulated  (at  the  origin  of  the  sympathetic),  as  in 
tetanus. 

Section  of  the  sympathetic,  besides  other  effects,  causes  narrowing  of  the  fissure  between 
the  eyelids,  the  eyeball  sinks  in  its  socket  (and  in  animals,  the  third  eyelid  is  relaxed  and  pro- 
truded). In  dogs,  section  causes  internal  squint,  as  the  external  rectus  receives  some  motor 
fibres  from  the  sympathetic.  (Origin  of  these  fibres  from  the  cilio-spinal  region.  Spinal  Cord, 
\  362,  I.) 

5.  It  is  probable  that  trophic  fibres  occur  in  the  trigeminus,  and  pass  through 
the  ciliary  nerves  to  reach  the  eye.  If  the  trigeminus  be  divided  within  the  cra- 
nium, after  six  to  eight  days,  inflammation,  necrosis  of  the  cornea,  and  ultimately 
complete  destruction  of  the  eyeball,  take  place,  constituting  panophthalmia 
{Fodera,  1823  ;  Magendie'). 

Trophic  Fibres.— In  weighing  the  evidence  for  and  against  the  existence  of  trophic  fibres,  we  must 
bear  in  mind  the  following  considerations:  i.  Section  of  the  trigeminus  makes  the  whole  eye 
insensible  ;  the  animal  is  therefore  unconscious  of  direct  injury  to  its  eye,  and  cannot  therefore  remove 
any  offending  body.  Dust  or  mucus,  which  may  adhere  to  the  eye,  is  no  longer  removed  by  the 
reflex  closing  of  the  eyelids ;  while,  owing  to  the  absence  of  the  reflex,  the  eye  is  more  open  and  is 
therefore  subject  to  more  injuries;  the  reflex  secretion  of  tears  is  also  arrested.  Snellen  (1857) 
fixed  the  ear  of  a  rabbit  in  front  of  its  eye  so  as  to  protect  the  latter  and  shield  it  from  injuries,  and 
he  found  that  the  inflammation  and  other  events  occurred  at  a  later  date,  v/hile,  according  to  Meiss- 
ner  and  Biittner,  if  the  eye  be  protected  by  means  of  a  complete  capsule,  the  inflammation  does  not 
occur  at  all.     There  can  be  no  doubt  that  the  loss  of  the  sensibility  of  the  eye  favors  the  occurrence 


644  TROPHIC    NERVES    IN    THE   TRIGEMINUS. 

of  inflammalion.  But  Meissner,  Biittner,  and  SchifF  observed  that  inflammation  of  the  eye  occurred 
when  the  trophic  (most  internal)  fibres  alone  were  divided,  the  eye  at  the  same  time  retaining  its 
sensibility;  this  would  seem  to  indicate  the  existence  of  trophic  fibres,  but  Cohnheim  and  Senfileben 
dispute  the  statement.  Conversely,  the  sensibility  of  the  eye  may  be  abolished  by  partial  section  of 
the  nerve,  yet  the  eye  does  not  become  inflamed  i^Schiff).  Ranvier,  who  denies  the  existence  of 
trophic  nerves,  made  a  circular  incision  round  the  margin  of  the  cornea  through  its  superficial  layers, 
so  as  to  divide  all  the  cortical  nerves.  Insensibility  of  the  cornea  was  thereby  ])roduced,  but  never 
keratitis.  Further,  in  man  and  animals,  when  they  are  unalile  to  close  their  eyelids,  there  is  redness 
with  secretion  of  tears,  or  slight  dryness  and  opacity  of  the  surface  of  the  eyeball  (xerosis),  but 
never  the  inflammation  already  described  (Sumiwl).  2.  We  must  also  take  into  consideration  the 
following :  Section  of  the  trigeminus  paralyzes  the  vasomotor  nerves  in  the  interior  of  the  eyeball, 
which  must  undoubtedly  cause  a  disturbance  in  the  intra-ocular  circulation.  According  to  Jesner  and 
Griinhagen,  the  trigeminus  also  contains  vaso-dilator  fibres,  whose  stimulation  is  followed  by 
increased  flow  of  blood  to  the  eye,  with  consecutive  excretion  of  the  fibrin  factors  and  increase  in 
the  amount  of  albumin  of  the  aqueous  humor.  3.  After  section  of  the  nerve,  the  intra-ocular 
tension  is  diminished  (while  stimulation  of  the  nerve  is  followed  by  increase  of  the  intra-ocular 
pressure)  {^Hippell,  Griinhagen).  This  diminution  of  the  normal  tension  necessarily  must  alter  the 
normal  relation  of  the  filling  of  the  blood  and  lymph  vessels,  and  also  the  movement  of  the  fluids, 
upon  which  the  normal  nutrition  is  largely  dependent.  4.  Kiihne  observed  that  stimulation  of  the 
corneal  nerves  was  followed  by  contraction  of  the  so-called  corneal  corpuscles.  Perhaps  the  move- 
ments of  these  corpuscles  may  influence  the  normal  movement  of  the  lymph  in  the  canalicular  system 
ol  the  cornea  (§  384) ;  these  movements,  however,  would  seem  to  depend  upon  the  nervous  system, 
so  that  its  destruction  is  likely  to  produce  disturbance  of  nutrition. 

[There  are  three  conditions  on  which  the  changes  may  depend:  (l)  mere  loss  of  sensibility, 
which  alone  is  not  sufhcient  to  explain  the  jjhenomena;  (2)  vasomotor  disturbance,  which  is 
excluded  by  the  above  facts,  and  also  by  the  other  consideration  that,  if  the  fifth  nerve  be  divided 
and  the  superior  cervical  ganglion  excised  simultaneously,  ophthalmia  does  not  occur,  and,  in  fact, 
excision  of  this  sympathetic  ganglion  may  modify  the  results  of  section  of  the  flfth  [Sinitzin). 
Thus  we  are  forced  to  (3)  the  theory  of  trophic  tit)res,  whose  centre  is  the  Gasserian  ganglion.] 

Pathological. — In  cases  of  anaesthesia  of  the  trigeminus'in  man,  and,  more  rarely,  in  severe  irri- 
tation of  this  nerve,  inflammation  of  the  conjunctiva,  ulceration  and  perforation  of  the  cornea,  and 
finally  panophthalmia,  have  been  observed  [Charles  Bell).  This  condition  has  been  called  ophthal- 
mia neuro-paralytica.  Samuel  found  that  a  similar  result  was  produced  by  electrical  stimulation  of 
the  Gasserian  ganglion  in  animals. 

There  are  other  aftections  of  the  eye  depending  upon  disease  of  the  vasomotor  nerves,  which 
are  quite  different  from  the  foregoing,  as  they  never  lead  to  degenerative  changes.  Such  is  ophthal- 
mia intermittens  (due  to  malaria),  a  unilateral,  intermittent,  excessive  filling  of  the  blood  vessels 
of  the  eye,  accompanied  by  the  secretion  of  tears,  photophobia,  often  accompanied  by  iritis  and  effu- 
sion of  pus  into  the  chambers  of  the  eye.  This  condition  is  regarded  as  a  vaso-neurotic  affection  of  the 
ocular  blood  vessels  by  Eulenburg.  Pathological  observations,  as  well  as  experiments  upon  animals, 
have  shown  that  there  is  an  intimate  physiological  connection  between  the  vascular  areas  of  both 
eyes,  so  that  affections  of  the  vascular  area  of  one  eye  are  apt  to  induce  similar  disturbances  of  the 
opposite  eye.  This  serves  to  explain  the  fact  that  inflammatory  processes  in  the  interior  of  one  eye- 
ball are  apt  to  produce  a  similar  condition  in  the  other  eye.  This  is  the  so-called  "  sympathetic 
ophthalmia."  Thus  stimulation  of  the  ciliary  nerves,  or  the  fifth  on  one  side,  causes  dilatation  of 
the  blood  vessels  not  only  on  its  own  side,  but  also  on  the  other  side  as  well  [Jesner  ami  Griin- 
hagen). The  pathological  condition  of  glaucoma  simplex,  where  the  intra-ocular  tension  is  greatly 
increased,  is  ascribed  by  Bonders  to  irritation  of  the  trigeminus.  [Increased  intra-ocular  tension 
may  be  produced  by  irritation  of  the  secretory  fibres  contained  in  the  fifth  nerve  [Danders),  by  stimu- 
lating the  nucleus  of  the  trigeminus  in  the  medulla  oblongata  [Ilippell  and  Griinhagen),  and  also 
reflexly  by  irritation  of  the  peripheral  branches  of  the  fifth,  as  by  nicotin  placed  in  the  eye.  It  is  pos- 
sible, however,  that  some  forms  of  glaucoma  are  produced  by  diminished  removal  of  the  arjueous 
humor  from  the  eye.]  Unilateral  secretion  of  tears,  due  to  irritation  of  the  ophthalmic  division  of  the 
fifth,  has  been  repeatedly  observed,  but  unilateral  cessation  of  tears,  due  to  paralytic  conditions,  very 
rarely. 

II.  Superior  Maxillary  Division  (Fig.  429,  <?). — It  gives  off — 

1.  The  delicate  recurrent  nerve,  a  sensory  branch  to  the  dura  mater,  which 
accompanies  the  vasomotor  nerves,  derived  from  the  superior  cervical  gan- 
glion of  the  sympathetic,  and  is  distributed  to  the  area  of  the  middle  meningeal 
artery. 

2.  The  subcutaneous  malar  or  orbital  {0)  supplies  by  its  tem])oral  and  orbital 
branches  sensibility  to  the  lateral  angle  of  the  eye  and  the  adjoining  area  of  skin 
of  the  temple  and  cheek.  Certain  fibres  are  said  to  be  the  true  secretory  nerves 
for  tears.      Compare  X.  lacrimalis,  p.  641. 


Meckel's  ganglion  and  its  connections.  645 

3.  The  dental,  anterior,  posterior,  and  median,  and  with  them  the  anterior  fibres 
from  the  infra-orbital  nerve,  supply  sensory  fibres  to  the  teeth  in  the  upper  jaw, 
the  gum,  periosteum,  and  the  cavities  of  the  jaw  (p.  642).  The  vasomotor  nerves 
of  all  these  parts  are  supplied  from  the  upper  cervical  ganglion  of  the  sympathetic. 

4.  The  infra-orbital  (R),  after  its  exit  from  the  infra-orbital  foramen,  supplies 
sensory  nerves  to  the  lower  eyelid,  the  bridge  and  sides  of  the  nose,  and  the 
upper  lip  as  far  as  the  angle  of  the  mouth.  The  accompanying  artery  receives  its 
vasomotor  fibres  from  the  superior  cervical  ganglion  of  the  sympathetic.  For  the 
sweat-secreting  fibres  which  occur  in  it  (pig)  see  §  288. 

The  spheno-palatine  ganglion  (Meckel's — ;/)  forms  connections  with  the 
second  division.  To  it  pass  two  short  sensory  root  fibres  from  the  second  division 
itself,  which  are  called  spheno-palatme.  Motor  fibres  enter  the  ganglion  from 
behind,  through  the  large  superficial  petrosal  branch  of  the  facial  (/)  ;  and  gray 
vasomotor  fibres  (z;)  from  the  sympathetic  plexus  on  the  carotid  (the  deep  large 
petrosal  nerve).  The  motor  and  vasomotor  fibres  from  the  Vidian  nerve,  which 
reach  the  ganglion  through  the  canal  of  the  same  name. 

Branches  of  the  Ganglion. — (i)  The  sensory  fibres  (N)  which  sGpply  the 
roof,  lateral  walls,  and  septum  of  the  nose  (posterior  and  superior  nasal)  ;  the  ter- 
minal fibres  of  the  tiaso-palatine  pass  through  the  canalis  incisivus  to  the  hard 
palate,  behind  the  incisor  teeth.  The  sensory  inferior  and  posterior  nasals  for  the 
lower  and  middle  turbinated  bones,  and  both  lower  nasal  ducts,  are  derived  from 
the  a7iterior  palatine  branch  of  the  ganglion,  which  descends  in  the  palato-maxillary 
canal.  Lastly,  the  sensory  branches  for  the  hard  (/)  and  soft  palate  (/i),  and  the 
tonsils  arise  from  the  posterior  palatine  nerve.  All  the  sensory  fibres  of  the  nose 
(see  also  the  Ethmoidal  ne7've),  when  stimulated,  cause  the  reflex  act  of  sneezing 
(§  120).  Preparatory  to  the  act  of  sneezing,  there  is  always  a  peculiar  feeling  of 
tickling  in  the  nose,  which  is  perhaps  due  to  dilatation  of  the  nasal  blood  vessels. 
This  dilatation  is  rapidly  caused  by  cold,  more  especially  when  it  is  applied  directly 
to  the  skin.  The  dilatation  of  the  vessels  is  followed  by  an  increased  secretion  of 
watery  fluid  from  the  nasal  mucous  membrane.  Stimulation  of  the  nasal  nerves 
also  causes  a  reflex  secretion  of  tears,  and  it  may  also  cause  standstill  of  the  res- 
piratory movements  in  the  expiratory  phase  (^Hering  and  Kratschner^ — (compare 
Respiratory  centre,  §  368).  (2)  The  motor  branches  descend  in  the  posterior 
palatine  nerve  through  the  small  palatine  canal,  and  give  oif  {Ji)  motor  branches  to 
the  elevator  of  the  soft  palate  and  azygos  uvulse  {Nuhi)  The  sensory  fibres  for 
these  muscles  are  supplied  by  the  trigeminus.  According  to  Politzer,  spasmodic 
contraction  of  these  muscles  occasionally  causes  crackling  noises  in  the  ears.  (3) 
The  vasomotor  nerves  of  this  entire  area  arise  from  the  sympathetic  root,  /.  e. ,  from 
the  upper  cervical  ganglion.  (4)  The  root  of  the  trigeminus  supplies  the  secretory 
nerves  of  the  mucous  glands  of  the  nasal  mucous  membrane.  Stimulation  excites 
secretion,  while  section  of  the  trigeminus  diminishes  it  with  simultaneous  atrophic 
degeneration  of  the  mucous  membrane.  Thus,  trophic  functions  for  the  mucosa 
have  been  ascribed  to  the  trigeminus  [Aschenbrandt'). 

Stimulation  of  the  Ganglion. — Feeble  electrical  stimulation  of  the  exposed  ganglion  causes  a 
copious  secretion  of  mucus  and  an  increase  of  the  temperature  in  the  nose  [Prevost),  with  dilation 
of  the  vessels  [Aschenbrandi).  [Meckel's  ganglion  has  been  excised  in  certain  cases  of  neuralgia 
{Walshani).'\ 

III.  Inferior  Maxillary  (g). — It  contains  all  the  motor  fibres  of  the  fifth, 
along  with  a  number  of  sensory  fibres  ;  it  gives  off  — 

1.  The  recurrent,  which  springs  by  itself  from  the  sensory  root,  enters  the 
skull  through  the  foramen  spinosum,  and,  along  with  the  nerve  of  the  same  name 
from  the  II  division,  supplies  sensory  fibres  to  the  dura  mater.  Fibres  proceed 
from  it  through  the  petroso-squamosal  fissure  to  the  mucous  membrane  of  the  cells 
of  the  mastoid  process. 

2.  Motor  fibres  for  the  muscles  of  mastication,  viz.,  the  masseteric,   the  two 


646  INFERIOR    MAXILLARY   DIVISION. 

deep  temporal  nerves,  and  the  internal  and  external  pterygoid  nerves.  The  sensory 
fibres  for  the  muscles  are  supplied  by  the  sensory  fibres. 

3.  The  buccinator  is  a  sensory  nerve  for  the  mucous  membrane  of  the  cheek, 
and  the  angle  of  the  mouth  as  far  as  the  lips. 

According  to  Jolyet  and  Laffont,  it  contains,  in  addition,  vasomotor  fibres  for  the  mucous  mem- 
brane of  the  cheek,  lower  lip,  and  their  mucous  glands  ;  but  these  fibres  are  probably  derived  from 
the  symjiathetic. 

Trophic  Fibres. — As  this  region  of  the  mucous  membrane  of  the  mouth  ulcerates  after  section 
of  the  trigeminus,  some  have  supposed  that  the  buccinator  nerve  contains  trophic  fibres.  But,  as 
Rollett  pointed  out,  section  of  the  inferior  maxillary  nerve  paralyzes  the  muscles  of  mastication 
on  the  same  side,  and  hence  the  teeth  do  not  act  vertically  upon  each  other,  but  press  against  the 
cheek.  Owing  to  the  loss  of  the  sensibility  of  the  mouth,  food  passes  between  the  gum  and  the 
cheek,  where  it  may  remain  attached,  undergo  decomposition,  and  perhaps  chemically  irritate  the 
mucous  membrane.  At  a  later  stage,  owing  to  the  wearing  away  of  the  teeth  in  an  oblique  manner, 
ulcers  begin  to  form  on  the  sound  side.  Hence,  there  is  no  necessity  for  assuming  the  existence  of 
trophic  fibres  in  this  nerve.  After  section  of  the  trigeminus,  the  nasal  mucous  membrane  on  the 
same  side  becomes  red  and  congested.  This  is  due  to  the  fact  that  dust  or  mucus,  not  being  removed 
from  the  nose  by  the  usual  reflex  acts,  remains  there,  irritates,  and  ultimately  causes  inflammation. 

4.  The  lingual  (/')  receives  at  an  acute  angle  the  chorda  tympani  (/  /),  a  branch 
of  the  facial  coming  from  the  tympanic  cavity.  The  lingual  does  not  contain  any 
motor  fibres  ;  it  is  the  sensory  and  tactile  nerve  of  the  anterior  two-thirds  of 
the  tongue,  of  the  anterior  palatine  arch,  the  tonsil,  and  the  floor  of  the  mouth. 
These,  as  well  as  all  the  other  sensory  fibres  of  the  mouth,  when  stimulated,  cause 
a  reflex  secretion  of  saliva  (compare  §  145).  The  lingual  is  accompanied  by 
the  nerve  of  taste  (chorda)  for  the  tip  and  margins  of  the  tongue  (/.  e.,  the  parts 
not  supplied  by  the  glosso-pharyngeal).  After  section  of  the  lingual  nerve  in  man, 
Busch,  Inzani,  and  Lusanna  found  that  the  tactile  sensibility  was  lost  in  the  half  of 
the  tongue,  and  there  was  loss  of  taste  in  the  anterior  part  [two-thirds]  of  the 
tongue.  The  fibres  which  administer  to  the  sense  of  taste  do  not,  as  a  rule,  belong 
to  the  lingual  itself,  but  are  derived  from  the  chorda  tympani  (p.  650).  According 
to  Schiff,  the  lingual  nerve  is  the  gustatory  nerve,  and  some  cases  of  Erb  and  Sen- 
ator support  this  view.  Such  cases,  however,  seem  to  be  exceptions  to  the  general 
rule.  The  lingual  nerve  in  the  substance  of  the  tongue  is  provided  with  small 
ganglia  {Remak,  Stirling).  Schiff  observed  that  section  of  the  lingual  (and  also  of 
the  hypoglossal)  caused  redness  of  the  tongue,  so  that  vasomotor  fibres  are  present 
in  its  course.  It  is  unknown  whether  these  are  derived  from  the  anastomoses  of 
the  Gasserian  ganglion  with  the  sympathetic.  The  lingual  appears  to  receive  vaso- 
dilator fibres  from  the  chorda  for  the  tongue  and  gum  (§  349). 

After  section  of  the  trigeminus,  animals  frequently  bite  their  tongue,  as  they  cannot  feel  the 
position  and  movements  of  this  organ  in  the  mouth. 

5.  The  inferior  dental  is  the  sensory  branch  to  the  teeth  and  gum  ;  the  vaso- 
motor fibres  reach  it  from  the  superior  cervical  ganglion.  Before  it  passes  into  the 
canal  in  the  lower  jaw,  it  gives  off  the  mylo-hyoid  nerve,  which  supplies  motor 
fibres  to  the  mylo-hyoid  and  the  anterior  belly  of  the  digastric,  and  also  some  fibres 
to  the  triangularis  menti  and  the  platysma  ;  the  muscular  sensory  nerves  also 
lie  in  these  branches.  The  mental  nerve,  which  issues  from  the  mental  foramen,  is 
the  sensory  nerve  for  the  chin,  lower  lip,  and  the  skin  at  the  margin  of  the  jaw. 

6.  The  auriculo-temporal  gives  sensory  branches  to  the  anterior  wall  of  the 
external  auditory  meatus,  the  tympanic  membrane,  the  anterior  part  of  the  ear,  the 
adjoining  region  of  the  temple,  and  to  the  maxillary  articulation. 

Fig.  430  shows  the  distribution  of  the  branches  of  the  trigeminus  on  the  head,  and  the  cervical 
nerves,  so  that  the  distribution  of  anaesthetic  and  hyperaesthetic  areas  may  easily  be  made  out. 

The  otic  ganglion  (;«)  lies  beneath  the  foramen  ovale  on  the  inner  side  of  the 
third  division.  Its  roots  are — (i)  short  motor  fibres  from  the  third  division  ; 
(2)  vasomotor  from  the  plexus  around  the  middle  meningeal  artery  (ultimately 


THE    OTIC    GANGLION    AND    ITS    CONNECTIONS. 


647 


derived  from  the  cervical  ganglion  of  the  sympathetic) ;  (3)  fibres  {X)  run  from  the 
tympanic  branch  of  the  glosso-pharyngeal  to  the  tympanic  plexus,  and  from  thence 
through  the  canaliculus  petrosus  in  the  small  superficial  petrosal  in  the  cranium, 
then  through  a  small  canal  between  the  apex  of  the  petrous  bone  and  the  sphenoid, 
to  reach  the  otic  ganglion.  Through  the  chorda  tympani  the  facial  nerve  is  con- 
stantly connected  with  the  ganglion  (Fig.  430). 

The  branches  of  the  otic  ganglion  are — (i)  motor  twigs  for  the  tensor  tympani 
and  tensor  of  the  soft  palate  (these  fibres  are  mixed  with  muscular  sensory  fibres — 
Ludwig  and  Politzer)  ;  (2)  one  or  more  branches  connecting  the  ganglion  with  the 

Fig.  430. 


Hu^c.  temporalis. 


MuBC.  masseter 

N.  hypoglossns. 

Platysma  myoide ;. 
JIusc  sternohyoideus 

Muse,  sternothyreoideui. 

Muse,  oiuohyoideus. 
Nil.  tiiuraetci  auter^orea. 


Kusa  splenius. 

Muse.  stenioe1eidoma.sto'deus. 

Is,  accessoriu.s 

Muse,  levator  anguli  scapulae. 

Muse,  cucullaris  or  trapezius. 
N.  dorsa'-is  scapulae. 


K.  axillaris. 

^.  thoracicria  Ijign... 


N.  phrenicus.  Erb's 

Supraelavicular- 

■DOlPt. 

Distribution  of  the  sensory  nerves  on  the  head  as  well  as  the  position  of  the  motor  points  on  the  neck.  SO,  area  of 
distribution  of  the  supra-orbital  nerve;  57",  supra-trochlear ;  /7",  infra-trochlear;  X,  lachrymal ;  iV,  ethmoidal; 
JO,  infra-orbital;  .5,  buccinator  ;  SM,  subcutaneus  malse;  ^  7",  auriculo-temporal ;  ^Af,  great  auricular;  OMj, 
great  occipital  ;  OMi,  lesser  occipital ;  C3,  three  cervical  nerves  ;  CS,  cutaneous  branches  of  the  cervical  nerves  ; 
CIV,  region  of  the  central  convolutions  of  the  brain ;  SC,  region  of  the  speech  centre  (third  left  frontal  convolution). 

auriculo-temporal  are  carried  by  the  roots  2  and  3  from  the  sympathetic  and  glosso- 
pharyngeal, which  the  auriculo-temporal  nerve  (A),  as  it  passes  through  the  parotid 
gland  (P),  gives  off  to  the  gland.  These  are  the  secretory  fibres  for  the  parotid  ; 
their  functions  are  stated  in  §  145. 

Section  of  the  trigeminus  is  followed  by  inflammatory  changes  in  the  tympanic  cavity  (rabbit) ; 
the  degree  of  inflammation  varies  much  {Berthold  and  Gri'mhageti).  Section  of  the  sympathetic  or 
glosso-pharyngeal  has  no  effect. 

The  submaxillary  ganglion  (Fig.  429,  L)  lies  close  to  the  convex  arch  of  the 


648  THE    SUB-MAXILLARY    GANGLION    AND    ITS    CONNECTIONS. 

tympanico-lingual  nerve  and  the  excretory  duct  of  the  sub-maxillary  gland  (M). 
Its  roots  are — (i)  branches  of  the  chorda  tympani,  //.which  undergo  fatty 
degeneration  after  section  of  facial  nerve.  This  root  su])plies  secretory  fibres  to 
the  sub-maxillary  and  sub-lingual  glands,  but  it  also  sujjplies  vaso-dilator  fibres 
for  the  blood  vessels  of  the  same  glands  (§  145).  In  addition,  fibres  are  suj^plied 
to  the  smooth  muscular  fibres  in  Wharton's  duct.  All  the  fibres  of  the  chorda  do 
not  pass  into  the  gland  ;  some  jiass  along  with  the  lingual  nerve  into  the  tongue 
(see  Chortia,  under  Facial  Nerve).  (2)  The  sympathetic  root  of  the  ganglion 
arises  from  the  plexus  around  the  sub-mental  branch  of  the  external  maxillary  artery 
(^),  /.  ^.,  ultimately  from  the  superior  cervical  ganglion;  it  passes  to  the  gland, 
and  contains  secretory  fibres,  whose  stimulation  is  followed  by  the  secretion  of 
thick  concentrated  saliva  (trophic  nerve  of  the  gland).  It  also  carries  the  vaso- 
constrictor nerves  to  the  gland  (p.  256).  ■  (3)  The  sensory  root  springs  from  the 
lingual.  Some  of  the  fibres,  after  passing  through  the  ganglion,  supply  the  gland 
and  its  excretory  ducts,  while  a  few  issue  from  the  ganglion,  and  again  join  the 
tympanico-lingual  nerve  to  reach  the  tongue. 

Pathological. — Trismus,  or  spasm  of  the  muscles  of  mastication,  supplied  by  the  third  division, 
is  usually  bilateral;  it  may  be  clonic  in  its  nature  (chattering  of  the  teeth),  or  tonic,  when  it  con- 
stitutes the  condition  of  lockjaw  or  trismus.  The  spasms  are  usually  individual  symptoms  of  more 
extensive  convulsions;  more  rarely  when  they  occur  alone,  they  are  symptomatic  of  disease  of  the 
cerebrum,  medulla,  pons,  and  cortex  of  the  motor  convolutions  [Enienbitrg).  The  spasms  may  be 
caused  retlexly,  e.g'.,  by  stimul.ition  of  the  sensoiy  nerves  of  the  head. 

Paralysis. — Degeneration  of  the  motor  nuclei,  or  an  affection  of  the  intracranial  root  of  the 
nerve,  causes  paralysis  of  the  muscles  of  mastication,  which  is  very  rarely  bilateral.  Paralysis  of  the 
tensor  tympani  is  said  to  cause  difficulty  of  hearing  {J\omberg),  or  buzzing  in  the  ears  {^Benedict). 
We  require  further  observations  upon  this  point,  as  well  as  upon  paralysis  of  the  tensor  of  the  soft 
palate. 

Neuralgia  may  occur  in  all  the  branches  of  the  fifth.  It  consists  of  severe  attacks  of  pain  shooting 
into  the  expan.sions  of  the  nerves.  It  is  usually  unilateral,  and  in  fact  is  often  confined  to  one  branch, 
or  even  to  a  few  twigs  of  one  branch.  The  point  from  which  the  pain  proceeds  is  frequently  the  bony 
canal  through  which  the  branch  issues.  The  ear,  dura  mater,  and  tongue  are  rarely  attacked.  The 
attack  is  not  unfrequently  accompanied  by  contractions  or  twitchings  of  the  corresponding  group  of 
the  facial  muscles.  The  twitcliings  are  either  reflex,  or  are  due  to  direct  peripheral  irritation  of  the 
fibres  of  the  facial  nerve,  which  are  mixed  with  the  terminal  branches  of  the  trigeminus.  The  reflex 
twitchings  may  be  extensively  distributed,  involving  even  the  mu.scles  of  the  arm  and  trunk. 

Redness  or  congestion  of  the  affected  part  of  the  face  is  not  an  unfrequent  symptom  in  neuralgia, 
and  it  may  be  accompanied  by  increased  or  diminished  secretion  from  the  nasal  and  buccal  mucous 
membranes.  This  is  a  reflex  phenomenon,  the  sympathetic  being  affected.  Reflex  stimulation  of 
the  vasomotor  nerves  frequently  give  rise  to  disturbance  of  the  cerebral  activities,  owing  to  changes 
in  the  distribution  of  the  blood  in  the  head.  Ludwig  and  Dittmar  found  that  stimulation  of  sensory 
nerves  caused  a  reflex  contraction  of  the  arterial  blood  vessels,  and  increase  of  the  blood  pressure  in 
the  cerebral  vessels.  Sometimes  there  is  melancholy  or  hypochondriasis,  and  in  one  case  of  violent 
jiain  in  the  inferior  maxillary  nerve,  the  attack  was  accompanied  by  hallucinations  of  vision. 

The  trophic  disturbances  which  sometimes  accompany  affections  of  the  trigeminus  are  particu- 
larly interesting.  They  are  :  a  brittle  character  of  the  hair,  which  frequently  becomes  gray,  or  may 
fall  out;  circumsciibed  areas  of  inflammation  of  the  skin,  and  the  appearance  of  a  vesicular 
eruption  ujjon  the  face  [often  following  the  distribution  of  certain  nerves],  and  constituting  herpes, 
which  may  also  occur  on  the  cornea,  constituting  the  neuralgic  herpes  corneae  of  Schmidt- Rimpler. 
Lastly,  there  is  the  progressive  atrophy  of  the  face  which  is  usually  confined  to  one  side,  but  may 
occur  on  both  sides  {Eulenbttrg).  It  is  caused  very  probably  by  a  trophic  affection  of  the  trigeminus, 
although  the  vasomotor  nerves  may  also  be  aft'ected  reflexly.  Landois  found  that  in  the  famous  case 
of  Romberg,  a  man  named  Schwahn,  the  sphygmographic  tracing  of  the  carotid  pulse  of  the  atrophied 
side  was  distinctly  smaller  than  on  the  sound  side. 

Urbantschitsch  made  the  remarkable  observation  that  stimulation  of  the  branches  of  the  trigeminus, 
especially  those  going  to  the  ear,  caused  an  increase  of  the  sensation  of  light  in  the  person  so 
stimulated.  Blowing  upon  the  cheeks  or  nasal  mucous  membrane,  electrical  stimulation,  the  use  of 
snuff,  smelling  strong  perfumes — all  temporarily  increase  the  sensation  of  light.  The  senses  of  taste 
and  smell,  as  well  as  the  sensibility  of  certain  areas  of  the  skin,  can  all  be  exalted  reflexly  by  gentle 
stimulation  of  the  trigeminus.  In  intense  affections  of  the  ear,  whereby  the  fibres  of  the  trigeminus 
are  often  affected  sympathetically,  these  sensory  functions  may  be  diminished.  As  the  ear  malady 
begins  to  improve,  the  excitability  of  these  sense  organs  also  again  begins  to  improve. 

[Complete  section  of  the  trigeminus  results  in  loss  of  sensibility  in  all  the 


NERVUS    ABDUCENS.  649 

parts  supplied  by  it  (Fig.  430),  including  one  side  of  the  face,  temple,  part  of  the 
ear,  the  fore  part  of  the  head,  conjunctiva,  cornea,  mouth,  gums,  Schneiderian 
mucous  membrane,  anterior  two-thirds  of  the  tongue,  and  part  of  pharynx.  In 
drinking  from  a  vessel,  the  patient  feels  as  if  one  side  of  it  were  cut  away.  The 
muscles  of  mastication  are  paralyzed  on  that  side,  food  is  not  chewed  on  one  side, 
and  fur  accumulates  on  the  tongue  on  that  side.  The  mucous  membranes  tend  to 
ulcerate,  that  of  the  mouth  being  chafed  by  the  teeth,  the  gums  get  spongy,  the 
nasal  mucous  membrane  tends  to  ulcerate,  so  that  smelling  is  interfered  with,  and 
ammonia  excites  no  reflex  acts,  while  the  eye  undergoes  panophthalmia.] 

[Gowers  is  of  opinion  that  the  sensation  of  taste  on  the  posterior  part  of  the  tongue,  soft  palate, 
and  palatine  arch  depends  on  the  fifth  nerve  and  not  on  the  glosso-pharyngeal  nerve.] 

348.  VI.  NERVUS  ABDUCENS. — Anatomical. — It  arises  slightly  in  front  of  and  partly 
from  the  nucleus  of  the  facial  nerve  (which  corresponds  to  the  anterior  horn  of  the  spinal  cord), 
from  large  celled  ganglia  in  the  deeper  part  of  the  anterior  region  of  the  fourth  ventricle  (emenentia 
teres,  Fig.  427).  [Its  nucleus  is  connected  with  the  nucleus  of  the  third  nerve  of  the  opposite  side. 
It  appears  at  the  posterior  margin  of  the  pons  (Fig.  428,  VI).  This  nerve  has  a  very  long  course 
before  it  enters  the  orbit,  and  as  it  bends  over  the  posterior  margin  of  the  pons,  it  is  liable  to  be 
compressed  there  or  from  pressure  upon  the  tentorium  cerebelli,  so  that  both  nerves  are  very  liable 
to  paralysis.] 

Function. — It  is  the  voluntary  nerve  of  the  external  rectus  muscle.  In  coordi- 
nated movements  of  the  eyeballs,  however,  it  is  involuntary. 

Anastomoses. — Branches  reach  it  from  the  sympathetic  upon  the  cavernous  sinus  (Fig.  429). 
A  few  come  from  the  trigeminus,  and  their  function  is  analogous  to  similar  fibres  supplied  to  the 
trochlearis  and  oculomotorius. 

Pathological. —  Complete  paralysis  causes  squinting  inward  [or  convergent  squint']  and  conse- 
quent diplopia.  [The  eye  cannot  be  rotated  outward  beyond  the  middle  line,  the  double  images 
are  in  the  same  horizontal  plane  and  vertical,  the  false  one  is  to  the  left  of  the  patient's  eye  when 
the  left  eye  is  affected  (Fig.  426,  2).  The  feeling  of  giddiness  is  often  severe.  There  is  secondary 
deviation  to  the  inner  side,  and  the  head  is  turned  toward  the  affected  side.]  In  dogs,  section  of 
the  cervical  sympathetic  causes  a.  slight  deviation  of  the  eyeball  inward  [Petit).  This  is  explained 
by  the  fact  that  the  abducens  receives  a  few  motor  fibres  from  the  cervical  sympathetic.  Spasm 
of  the  abducens  causes  external  squint. 

Squint. — In  addition  to  paralysis  or  stimulation  of  certain  nerves  producing  squint,  it  is  to  be 
remembered  that  it  may  also  be  caused  by  a  primary  affection  of  the  muscles  themselves,  e.  g.,  con- 
genital shortness,  contracture,  or  injuries  of  these  muscles.  It  may  also  be  brought  about  owing  to 
opacities  of  the  transparent  media  of  the  eye  ;  a  person  with,  say  an  opacity  of  the  cornea,  rotates 
the  affected  eye  involuntarily,  so  that  the  rays  of  light  may  enter  the  eye  through  a  clear  part  of 
the  media. 

349.  VII.  NERVUS  FACIALIS.— Anatomical.— This  nerve  consists  entirely  of  efferent 
fibres,  and  arises  from  the  floor  of  the  fourth  ventricle  from  the  "  facial  nucleus  "  (Fig.  427,  7), 
which  lies  behind  the  origin  of  the  abducens,  and  also  by  some  fibres  from  the  nucleus  of  the 
abducens  [although  Gowers'  observations  do  not  confirm  this  (§  366)].  Other  fibres  arise  from  the 
cerebrum  of  the  opposite  side  (|  378,  I).  It  consists  of  two  roots,  the  smaller — portio  intermedia 
of  Wrisberg — forms  a  connection  with  the  auditory  nerve  (see  |  350).  The  original  fibres  of  the 
portio  intermedia  are  developed  from  the  glosso-pharnygeal  nucleus  [Safolini).  It  would  thus 
appear  that  the  sensory  and  gustatory  fibres  which  are  present  in  the  chorda  tympani  enter  it  through 
these  fibres  [Duval,  Schidtze,  Vulpian),  so  that  the  portia  intermedia  is  a  special  part  of  the  nerve 
of  taste,  which  becomes  conjoined  with  the  facial,  and  runs  to  the  tongue  in  the  chorda.  Along 
with  the  auditory  nerve,  it  traverses  the  porus  acusticus  internus,  where  it  passes  into  the  facial  or 
Fallopian  canal.  At  first  it  has  a  transverse  direction  as  far  as  the  hiatus  of  this  canal;  it  then 
bends  at  an  acute  angle  at  the  "  knee  "  [a)  above  the  tympanic  cavity,  to  descend  in  an  osseous 
canal  in  the  posterior  wall  of  this  space  (Fig.  429).  It  emerges  from  the  stylo-mastoid  foramen, 
pierces  the  parotid  gland,  and  is  distributed  in  a  fan-shaped  manner  (pes  anserinus  major).  [The 
superficial  origin  is  at  the  lower  margin  of  the  pons,  in  the  depression  between  the  olivary  body  and 
the  restiform  body,  as  indicated  in  Fig.  428,  VII  a.] 

Its  branches  are:  i.  The  motor  large  superficial  petrosal  (J).  It  arises 
from  the  "knee"  or  geniculate  ganglion  within  the  Fallopian  canal,  in  the  cavity 
of  the  skull,  runs  upon  the  anterior  surface  of  the  temporal  bone,  traverses  the 
foramen  lacerum  medium  on  the  under  surface  of  the  base  of  the  skull,  and  passes 
through  the  Vidian  canal  to  reach  the  spheno-palatine  ganglion  (p.  645).     It  is 


650  THE    CHORDA   TYMPANI    AND   TASTE. 

uncertain  whether  this  nerve  conveys  sensory  branches  from  the  second  division 
of  the  trigeminus  to  the  facial. 

2.  Connecting  branches  (,3)  pass  from  the  geniculate  ganglion  to  the  otic  gan- 
glion.     For  their  course  and  function,  see  Otic  ganglion  (j).  646). 

3.  The  motor  branch  to  the  stapedius  muscle  (^). 

4.  The  chorda  tympani  (/ /)  arises  from  the  facial  before  it  emerges  at  the 
stylo-mastoid  foramen  {s),  runs  through  the  tympanic  cavity  (above  the  tendon  of 
the  tensor  tympani,  between  the  handle  of  the  malleus  and  the  long  process  of  the 
incus),  passes  out  of  the  skull  through  the  petro-tympanic  fissure,  and  then  joins  the 
lingual  nerve  at  an  acute  angle  (p.  646,  4).  Before  it  unites  with  this  nerve,  it 
exchanges  fibres  with  the  otic  ganglion  (w).  Thus,  sensory  fibres  can  enter  the 
chorda  from  the  third  division  of  the  trigeminus,  which  may  run  centripetally  to 
the  facial  to  be  distributed  along  with  it.  In  the  same  way,  sensory  fibres  may 
pass  from  the  lingual  nerve  through  the  chorda  into  the  facial  {Longet).  Stimula- 
tion of  the  chorda — which  even  in  man  may  be  done  in  cases  where  the  tympanic 
membrane  is  destroyed — causes  a  prickling  feeling  in  the  anterior  margins  and  tip 
of  the  tongue  (^Trdltsch).  O.  Wolfe  found  that  the  section  of  the  chorda  in  man 
abolished  the  sensibility  for  tactile  and  thermal  stimuli  upon  the  tip  of  the 
tongue ;  and  the  same  was  true  of  the  sense  of  taste  in  this  region.  It  is  supposed 
byCalori,  that  these  fibres  enter  the  facial  nerve  at  its  periphery  (especially  through 
the  auriculo-temporal  into  the  branches  of  the  facial),  that  they  run  in  a  centripetal 
direction  in  the  facial,  and  afterward  pursue  a  centrifugal  course  in  the  chorda. 
[It  is  possible  that  sensory  fibres  pass  from  the  spheno-palatine  ganglion  of  the 
fifth  through  the  Vidian  nerve  and  large  superficial  petrosal  to  enter  the  facial. 
These  fibres  may  be  those  that  appear  in  the  seventh  as  the  chorda  fibres  which 
administer  to  taste.  Bigelow  asserts  that  the  chorda  tympani  is  not  a  branch  of 
the  facial,  but  the  continuation  of  the  ncrvus  intermedius  of  Wrisberg.]  The 
chorda  also  contains  secretory  and  vasodilator  fibres  for  the  sub-maxillary  and 
sub-lingual  glands  (§  145)- 

Gustatory  Fibres. — The  chorda  also  contains  fibres  administering  to  the  sense 
of  taste,  for  the  margin  and  tip  of  the  tongue  (anterior  two-thirds),  which  are 
conveyed  to  the  tongue  along  the  course  of  the  lingual.  Urbantschitsch  made 
observations  upon  a  man  whose  chorda  was  freely  exposed,  and  in  whom  its  stimu- 
lation in  the  tympanic  cavity  caused  a  sensation  of  taste  (and  also  of  touch)  in  the 
margins  and  tip  of  the  tongue. 

It  would  seem,  therefore,  that  the  gustatory  fibres  of  the  chorda  have  their 
origin  in  the  glosso-pharyngeal  nerve.  They  may  reach  the  chorda:  i.  Through 
the  portio  intermedia  of  Wrisberg,  as  already  mentioned. 

2.  There  is  a  channel  beyond  the  stylo-masioid  foramen,  \'iz.,  through  the  ramus  communicans 
cum  glosso-pharyngeo  (Fig.  429),  which  passes  from  the  last  menioned  nerve  in  that  branch  of  the 
facial  which  contains  the  motor  fibres  for  the  stylo-hyoid  and  posterior  belly  of  the  digastric  muscle 
(Ilenle's  X.  styloideus).  This  nerve  also  supplies  muscular  sensibility  to  the  stylo-hyoid  and  posterior 
belly  of  the  digastric  muscles.  It  is  also  assumed  that,  by  means  of  these  anastomoses,  motor  fibres 
are  supplied  by  the  facial  to  the  glosso-pharyngeal  nerve.  3.  A  union  of  the  glossopharyngeal  and 
facial  nerves  occurs  in  the  tympanic  cavity.  The  tympanic  branch  of  the  giosso-pharj'ngeal  (/.) 
passes  into  this  cavity,  where  it  unites  in  the  tympanic  plexus  with  the  small  superficial  petrosal 
nerve  (3),  which  springs  from  the  knee  on  the  facial.  The  gustatorj'  fibres  may  first  pass  into  the 
otic  ganglion,  which  is  always  connected  with  the  chorda  (Otic  ganglion,  p.  647,  3).  Lastly,  a 
connection  is  described  through  a  twig  (rr)  from  the  petrous  ganglion  of  the  glosso-pharyngeal, 
direct  to  the  facial  trunk  within  the  Fallopian  canal  {Garibaldi). 

According  to  some  observers,  the  chorda  contains  vaso- dilator  fibres  for  the 
anterior  two-thirds  of  the  tongue  {Vulpian). 

Pseudo-motor  Action. — From  one  to  three  weeks  after  the  section  of  the  hypoglossal  nerve, 
stimulation  of  the  chorda  causes  movements  in  the  tongue  iyPkilippeaux  and  Vulpiaii).  These 
movements  are  not  so  energetic  as,  and  occur  more  slowly  than,  those  caused  by  stimulation  of  the 
hypoglossal.  N'icotin  first  excites,  then  paralyzes,  the  motor  effect  of  the  chorda.  Even  after 
cessation  of  the  circulation,  stimulation  of  the  chorda   causes  movements.      Heidenhain  supposes 


PARALYSIS    OF   THE    FACIAL. 


651 


that,  owing  to  the  stimulation  of  the  chorda,  there  is  an  increased  secretion  of  lymph  within  the 
musculature,  which  acts  as  the  cause  of  the  muscular  contraction.  He  called  this  action  '■'■  pseudo- 
moior." 

[If,  after  the  union  of  the  central  end  of  the  lingualis  and  the  peripheral  end  of  the  hypoglossal 
nerve,  the  lingualis  be  stimulated,  there  is  a  genuine  contraction  of  the  musculature  of  the  toncrue 
on  that  side.  A  pseudo-motor  contraction  is  easily  distinguished  from  a  true  contraction,  for  when 
a  telephone  is  connected  with  the  tongue,  on  stimulating  the  hj'poglossal  the  tone  of  the  tetanus 
thereby  produced  is  heard,  but  on  stimulating  the  lingual,  although  the  pseudo-motor  contractions 
occur,  no  sound  is  heard  [Rogowicz).'] 

5.  Connection  with  Vagus. — Before  the  chorda  is  given  off,  the  trunk  of  the  facial  comes  into 
direct  relation  with  the  auricular  branch  of  the  vagus  (d),  which  crosses  it  in  the  mastoid  canal,  and 
supplies  it  with  sensory  nerves  (see  Vagtis). 

6.  Peripheral  Branches. — After  the  facial  issues  from  its  canal,  it  supplies 
motor  fibres  to  the  stylo-hyoid  and  posterior  belly  of  the  digastric,  occipitalis,  all 


Fig 


Upper  branches  of  the  Facial 
Trunk  of  the  Facial 

Mm.  retrahens  et  attolens  auncul. 

Muse,  occipitalib 

Middle  branches  of  the  Facial 

M.  stylohyoideus 

M.  digastncus 


Lower  branches  of  the  Facial 


M.  frontalis. 

M.  corrugator  supercilii. 
M.  orbicular,  palpebr. 


M.  compressor  nasi  etpyram. nasi. 
M.  levator  lab.  sup.  alaque  nasi. 
M.  levator  lab.  sup.  propr. 
M.  zygomatic  minor. 
M.  dilatat.  narium. 
M.  zygomatic  major. 


M.  orbicularis  oris. 


M.  levator  menti. 
M.  quadratus  menti. 
M.  triangularis  menti. 


Motor  points  of  the  facial  nerve  and  the  facial  muscles  supplied  by  it. 

the  muscles  of  the  external  'ear,  the  muscles  of  expression,  buccinator  and  platysma. 
The  facial  also  contains  secretory  fibres  for  the  face  (compare  §  288). 

Although  most  of  the  branches  of  the  facial  are  under  the  influence  of  the  will,  yet  most  men 
cannot  voluntarily  move  the  muscles  of  the  nose  and  ear. 

Anastomoses. — The  branches  of  the  seventh  nerve  on  the  face  anastomose 
with  those  of  the  trigeminus,  whereby  sensory  fibres  are  conveyed  to  the  muscles 
of  expression.  The  sensory  branches  of  the  auricular  branch  of  the  vagus,  and 
the  great  auricular,  enter  the  peripheral  ends  of  the  facial,  and  supply  sensibility  to 
the  muscles  of  the  ear ;  while  the  sensory  fibres  of  the  third  cervical  nerve  similarly 
supply  the  platysma  with  sensibility.      Section  of  the  facial  at  the  stylo-mastoid 


652  UNILATERAL   AND    DOUBLE    PARALYSIS   OF   THE    FACIAL. 

foramen  is  jiainful,  but  it  is  still  more  so  if  the  peripheral  branches  on  the  face  are 
divided  {^Recurrent  sensibility,  %  355). 

Pathological. — In  all  cases  of  paralysis  of  the  facial,  the  most  important  ]X)int  to  determine 
is  whether  tiie  seat  of  the  affection  is  in  the  jieriphery,  in  the  repjion  of  the  stylo-mastoid  foramen,  or 
in  the  course  of  the  lon;^  I'alloiiian  canal,  or  is  central  (cerebral)  in  its  origin.  This  point  must  be 
determined  by  an  analysis  of  the  symjitoms.  Paralysis  at  the  stylo-mastoid  foramen  is  very  frequently 
rheumatic,  and  jirobably  tlepends  upon  an  exudation  compressing  the  nerve;  the  exudation  prob- 
ably occupying  the  lymi)h  space  described  by  Riidinger  on  the  inner  side  of  the  Fallopian  canal, 
between  the  periosteum  and  the  nerve,  and  which  is  a  continuation  of  the  arachnoid  space.  Other 
causes  are — intlammation  of  the  parotid  gland,  direct  injury,  and  j^ressure  from  the  forceps  during 
delivery.  In  the  course  of  the  canal,  the  causes  are — fracture  of  the  temporal  bone,  effusion  of 
the  blood  into  the  canal,  syphilitic  etfusions,  and  caries  of  the  temporal  bone;  the  last  sometimes 
occurs  in  inflammation  of  the  ear.  Among  intra-cranial  cau.ses  are — affections  of  the  membranes 
of  the  brain,  and  of  the  base  of  the  skull  in  the  region  of  the  nerve,  disease  of  the  "  facial  nucleus  "  ; 
lastly,  affection  of  the  cortical  centre  of  the  nerve  and  its  connections  with  the  nucleus.  [No  nerve 
is  so  liable  as  the  seventh  to  be  paralyzed  independently.] 

Symptoms  of  Unilateral  Paralysis  of  the  Facial  [or  Bell's  Paralysis]. — i.  Paralysis  of 
the  muscles  of  expression:  The  forehead  is  smooth,  without  folds,  the  eyelids  remain  open 
(lagophthalmus  paralyticus),  the  outer  angle  being  slightly  lower.  The  anterior  surface  of  the 
eye  rapidly  becomes  dry,  the  cornea  is  dull,  as,  owing  to  the  paralysis  of  the  orbicularis,  the 
tears  are  not  properly  distributed  over  the  conjunctiva,  and,  in  fact,  in  consequence  of  the  dryness  of 
the  eyeball,  there  may  be  temporary  inflammation  (keratitis  xerotica).  In  order  to  protect  the 
eyeball  from  the  light,  the  patient  turns  it  upward  under  the  upper  eyelid  [Bell],  relaxes  the 
levator  palpebra.-,  which  allows  the  lid  to  fall  somewhat  {//iisse).  The  nose  is  immovable,  while  the 
naso-labial  fold  is  obliterated.  As  the  nostrils  cannot  be  ddated,  the  sense  of  smell  is  interfered 
with.  The  impairment  of  the  sense  of  smell  depends  more,  however,  upon  the  imperfect  con- 
duction of  the  tears,  owing  to  paralysis  of  the  orbicularis  palpebrarum  and  Horner's  muscle,  thus 
causing  dryness  of  the  corresponding  side  of  the  nasal  cavity.  Horses,  which  distend  the  nostrils 
widely  during  respiration,  after  section  of  both  facial  nerves,  are  said  by  CI.  Bernard  to  die  from 
interference  with  the  respiration,  or  at  least  they  suffer  from  s^xtrt  Ayspncea.  [Ellenberger).  The 
face  is  drawn  toward  the  sound  side,  so  that  the  nose,  mouth,  and  chin  are  ol)lique.  Paralysis 
of  the  buccinator  interferes  with  the  proper  formation  of  the  bolus  of  food ;  the  food  collects 
between  the  cheek  and  the  gum,  from  which  it  is  usually  removed  by  the  patient  with  his  fingers; 
saliva  and  fluids  escape  from  the  angle  of  the  mouth.  During  vigorous  expiration,  the  cheeks  are 
puffed  outward  like  a  sail.  The  speech  may  be  affected  owing  to  the  difificulty  of  sounding  the 
labial  consonants  (especially  in  double  paralysis),  and  the  vowels,  u,  ii  (ue)  6  (oe) ;  while  the 
speech,  in  paralysis  of  the  branches  to  both  sides  of  the  palate,  becomes  nasal  (§  628).  The  acts  of 
whistling,  sucking,  blowing,  and  spitting  are  interfered  with.  In  double  paralysis,  many  of 
these  symptoms  are  greatly  intensified,  while  others,  such  as  the  obli<]ue  position  of  the  features, 
disappear.  The  features  are  completely  relaxed;  there  is  no  mimetic  play  of  the  features;  the 
patients  weep  and  laugh,  "  as  it  were,  behind  a  mask  "  [Koinherg).  2.  In  paralysis  of  the  palate, 
when  the  uvula  is  directed  toward  the  sound  side,  and  the  paralyzed  half  of  the  palate  hangs  down 
and  cannot  be  raised  (large  superficial  petrosal  nerve),  it  is  not  determined  to  what  extent  this 
condition  influences  the  act  of  lieglutition  and  i}nt  formation  of  the  consonants.  3.  Taste  is  interfered 
with;  either  it  is  absent  on  the  anterior  two-thirds  of  the  tongue,  or  the  sensation  is  delayed  and 
altered.  This  is  due  to  an  affection  of  the  chorda.  4.  Diminution  of  saliva  on  the  affected 
side  was  first  described  by  Arnold;  still,  we  must  determine  to  what  extent  a  simultaneous  aft'ection 
of  the  sense  of  taste  may  cause  a  reflex  interference  with  the  secretion  of  saliva,  or  whether  rapid 
removal  of  the  saliva  through  the  opened  lips  and  angle  of  the  mouth  may  cause  the  drj'ness  on  the 
affected  side  of  the  mouth.  5.  Roux  pointed  out  that  hearing  is  affected,  the  sensibility  to  sounds 
lieing  increased  (oxyakoia,  hyperakusis  willisiana).  The  paralysis  of  the  stapedius  muscle 
makes  the  stapes  loose  in  the  fenestra  ovalis,  so  that  all  impulses  from  the  tympanum  act  vigor- 
ously upon  the  stapes,  which  consequently  excites  considerable  vibrat"ions  in  the  fluid  of  the  inner  ear. 
More  rarely,  in  paralysis  of  the  stapedius,  it  has  been  observed  that  low  notes  are  heard  at  a  greater 
distance  than  on  the  sound  side  (Lucae,  Moiv).  6.  As  the  facial  in  man  appears  to  contain  fibres  for 
the  secretion  of  sweat,  this  explains  the  loss  of  the  power  of  sweating  in  the  face  when  the  nerve 
begins  to  atrophy  {St>-aiiss,  Block). 

Section  of  the  facial  in  young  animals  causes  atrophy  of  the  corresjwnding  nmsclcs.  The 
facial  bones  are  also  imperfectly  develojied;  they  remain  smaller,  and  hence  the  bones  of  the  sound 
side  of  the  face  grow  toward,  and  ultimately  across,  the  middle  line  toward  the  affected  side  {^Broivn- 
Si'ijtiard).     The  salivary  glands  also  remain  smaller. 

Stimulation — or  irritation  in  the  area  of  the  facial — causes  partial  or  extensive,  either  direct  or 
reflex,  tonic  or  clonic  spasms.  The  extensive  forms  are  known  as  "  mimetic  facial  spasm." 
Among  the  partial  forms  are  tonic  contraction  of  the  eyelid  (blepharospasm),  which  is  most 
common;  and  is  caused  reflexly  by  stimulation  of  the   sensory  nerves  of  the  eye,  e.g.,  in  scrofulous 


NERVUS    ACUSTICUS.  653 

ophthalmia,  or  from  excessive  sensibility  of  the  retina  (photophobia).  More  rarely,  the  excitement 
proceeds  from  some  more  distant  part,  e.g.,  in  one  case  recorded  by  v.  Grafe,  from  inflammatory 
stimulation  of  the  anterior  palatine  arch.  The  centi-e  for  the  reflex  is  the  facial  nucleus.  The  clonic 
form  of  spasm — spas??iodtc  winking  (spasmus  nictitans) — is  usually. of  reflex  origin,  due  to  irrita- 
tion of  the  eye,  the  dental  nerves,  or  even  of  more  distant  nerves.  In  severe  cases,  the  affection  may 
be  bilateral,  and  the  spasms  may  extend  to  the  muscles  of  the  neck,  trunk,  and  upper  extremities. 
Contraction  of  the  muscles  of  the  lip  may  be  excited  by  emotions  (rage,  grief),  or  reflexly.  Fibrillar 
contractions  occur  after  section  of  the  facial  as  a  "  degeneration  phenomenon  "  (p- 525).  [If  the 
facial  be  torn  out  of  the  stylo-mastoid  foramen,  there  is  paralytic  oscillation  of  the  lip  muscles  {Sc/iiff). 
If,  in  such  an  animal,  the  posterior  root  of  the  annulus  of  Vieussens  be  stimulated  electrically,  as  it 
contains  vaso-dilator  fihres  [Dastre  and  Morat),  not  only  do  the  blood  vessels  of  the  cheek  and  lips 
dilate,  but  the  veins  pulsate  and  florid  blood  escapes  from  the  veins,  just  as  occurs  in  the  sub-maxillary 
gland  when  the  chorda  is  stimulated.  On  stimulating  the  ansa,  after  section  of  the  seventh,  there  is 
a  pseudo-motor  effect  on  the  muscles  of  the  cheek  and  lips,  so  that  there  is  an  analogy  between 
the  chorda  and  the  ansa  {^Rogo%!jicz).'\  /«/ra-irr««Z(?/ stimulation  of  the  most  varied  description  may 
cause  spasms.  Lastly,  facial  spasm  may  be  part  of  a  general  spasmodic  condition,  as  in  epilepsy, 
cholera,  hysteria,  tetanus.  Aretjeus  (81  a.d.)  made  the  interesting  observation  that  the  muscles 
of  the  ear  contracted  during  tetanus.  Very  rarely  have  spasmodic  elevation  of  the  palate  and 
increased  salivation  been  described  as  the  result  of  irritation  of  the  facial  i^Leube).  Moos  observed 
a  profuse  secretion  of  saliva  on  stimulating  the  chorda  during  an  operation  on  the  tympanic  cavity. 

350.  VIII.  NERVUS  ACUSTICUS.— Arises  by  iwo  roots  {Stieda)  ;  a  larger  anterior  and  a 
smaller  posterior  one.  From  the  former  proceeds  the  vestibular  nerve,  and  from  the  latter  the 
cochlear  nerve;  these  are  separated  in  the  sheep  and  horse  [Horbaczeivski).  Each  root  springs 
from  a  median  and  a  lateral  nucleus,  so  that  there  are  four  nuclei.  Some  fibres  come  from  the 
cerebellum,  and  these  may  be  connected  with  equilibration.  The  chief  mass  of  the  posterior  ganglion 
fibres  of  the  cochlear  nerve  cross  and  pass  to  the  corpora  quadrigemina,  the  internal  geniculate,  and 
Finally  to  the  temporo-sphenoidal  lobe  (^  378,  IV,  2).  After  extirpation  of  the  temporo-sphenoidal 
lobe,  these  fibres  atrophy  into  the  internal  capsule  and  internal  geniculate  body  {v.  Monakow).  The 
strise  acusticse  form  a  second  decussating  projection  system.  The  origins  of  both  acoustic  nerves  are 
connected  by  commissures  in  the  brain  i^Flechsig). 

In  the  course  of  the  internal  auditory  meatus,  the  auditory  and  portio  intermedia  of  the  facial 
exchange  fibres,  but  the  physiological  significance  of  this  is  unknown. 

Function. — The  acusticus  or  auditory  nerve  has  a  double  function  :  i.  It  is 
the  nerve  of  hearing;  when  stimulated,  either  at  its  origin,  in  its  course,  or  at  its 
peripheral  terminations,  it  gives  rise  to  sensations  of  sound.  Every  injury,  accord- 
ing to  its  intensity  and  extent,  causes  hardness  of  hearing  or  even  deafness. 

2.  Quite  distinct  from  the  foregoing  is  the  other  function,  which  depends  upon 
the  semicircular  canals,  viz.,  that  stimulation  of  the  peripheral  expansions  in 
the  ampullae  influences  the  movements  necessary  for  maintaining  the  equilibrium 
of  the  body. 

Brenner's  Formula.— The  relation  of  the  auditory  nerve  to  the  galvanic  current  is  very 
important.  In  healthy  persons,  when  there  is  closure  at  the  cathode,  there  is  the  sensation  of  a 
clang  (or  tone)  in  the  ear,  which  continues  with  variations  while  the  current  is  closed.  When 
the  anode  is  opened,  there  is  a  feebler  Xo^sx^  (^Brenner'' s  Normal  Acoitstic  Formula).  This  clang 
coincides  exactly  with  the  resonance  fundamental  tone  of  the  sound-conducting  apparatus  of  the 
ear  itself 

Pathological. — Increased  sensibility  oi  the  auditory  nerve  in  any  part  of  its  coiu"se,  its  centre, 
or  peripheral  expansions,  causes  the  condition  known  as  hyperakusis,  which  usually  is  a  sign  of 
greatly  increased  nervous  excitability,  as  in  hysteria.  When  excessive,  it  may  give  rise  to 
distinctly  painful  impressions,  which  condition  is  known  as  acoustic  hyperalgia  (^Etdenburg). 
Stimulation  of  the  parts  above  named  causes  sensations  of  sound,  the  most  common  being  the 
sensation  oi  singing  in  the  ears,  or  tinnitus.  This  condition  is  often  due  to  changes  in  the  amount 
of  blood  in  the  blood  vessels  of  the  ear — either  anaemic  or  hypersemic  stimulation.  There  is  well- 
marked  tinnitus  after  large  doses  of  quinine  or  salicin,  due  to  the  vasomotor  effect  of  these  drugs 
upon  the  vessels  of  the  labyrinth  (A'zVf/^w^/-).  Not  unfrequently,  in  cases  of  tinnitus,  the  reaction 
due  to  the  galvanic  current  is  increased.  More  rarely  there  is  the  so-called  '■'■paradoxical 
reaction" — z.^?.,  on  applying  the  galvanic  current  to  one  ear,  in  addition  to  the  reaction  in 
this  ear,  there  is  the  opposite  result  in  the  non- stimulated  ear.  In  other  cases  of  disease  of  the 
auditory  nerve,  noises  rather  than  musical  notes  are  produced  by  the  current;  stimulation, 
especially  of  the  cortical  centre  of  the  auditory  nerve,  chiefly  in  lunatics,  may  cause  auditory 
delusions  [\  378,  IV.).  According  as  the  excitability  of  the  auditory  nerve  is  diminished 
or  abolished,  there  is  the  condition  of  nervous  hardness  of  hearing  (hypakusis),  or  nervous 
deafness  (anakusis). 


054  THE   SEMICIRCULAR   CANALS. 

The  Semicircular  Canals  of  the  Labyrinth. — Section  or  injury  to  these 
canals  does  not  interfere  with  hearing,  l)ut  other  important  symptoms  follow  their 
injury,  such  as  disturbances  of  equilibrium  due  to  a  feeling  of  giddiness,  especially 
when  the  injury  is  bilateral  (yvVwr^/Zj-).  This  does  not  occur  in  ^<>\\Q<,{Kiese/bach). 
The  pendulum-like  movement  of  the  head,  in  the  direction  of  the  plane  of 
the  injured  canal,  is  very  characteristic.  If  the  horizontal  canal  be  divided,  the 
head  (of  the  pigeon)  is  turned  alternately  to  the  right  and  left.  The  rotation  takes 
place,  especially  when  the  animal  is  about  to  execute  a  movement :  when  it  is  at 
rest,  the  movement  is  less  pronounced.  The  phenomenon  may  last  for  months, 
and  injury  to  \\\q.  posterior  vertical  canals  causes  a  well-marked  up  and  down  move- 
ment or  nodding  of  the  head,  the  animal  itself  not  unfrequently  falling  forward  or 
backward.  Injury  to  the  superior  vertical  canals  also  causes  pendulum-like  vertical 
movements  of  the  head,  while  the  animal  often  falls  forward.  When  all  the  canals 
are  destroyed,  various  pendulum-like  movements  are  performed,  while  standing  is 
often  impossible.  Breuer  found  that  electrical  stimulation  of  the  canals  caused 
rotation  of  the  head,  while  Landois,  on  applying  a  solution  of  salt  to  the  canals, 
observed  pendulum-like  movements,  which,  however,  disappeared  after  a  time.  A 
25  per  cent,  solution  of  chloral  dropped  into  the  ear  of  a  rabbit  causes,  after  fifteen 
minutes,  a  similar  destruction  of  the  canals  (Vulpian).  Section  of  the  acoustic 
nerves  within  the  cranium  has  the  same  result  (^Bechterew). 

Explanation. — tioltz  regards  the  canals  as  organs  of  sense  for  ascertaining  the  equilibrium  or 
position  of  the  head  in  space ;  Mach,  as  an  organ  for  ascertaining  the  movements  of  the  head. 
According  to  Goltz's  statical  theory,  every  position  of  the  head  causes  the  endolymph  to  exert  the 
greatest  pressure  upon  a  certain  part  of  the  canals,  and  thus  e.xcites  in  a  varying  degree  the  nerve 
terminations  in  the  ampulla.  According  to  Breuer,  when  the  head  is  rotated,  currents  are  produced 
in  the  endolymph  of  the  canals,  which  must  have  a  fixed  relation  to  the  direction  and  extent  of  the 
movements  of  the  head,  and  these  currents,  therefore,  when  they  are  perceived,  afford  a  means  of 
determining  the  movement  of  the  head.  The  nervous  end  organs  of  the  ampullre  are  arranged  for 
ascertaining  this  perception.  If  the  semicircular  canals  are  an  apparatus — in  fact,  "  sense  organs  " — 
for  the  sensation  of  the  equilibrium,  and  if  their  function  is  to  determine  the  position  or  movements 
of  the  head,  necessarily  their  destruction  or  stimulation  must  alter  these  perceptions,  and  so  give  rise 
to  abnormal  movements  of  the  head.  Vulpian  regards  the  rotation  of  the  head  as  due  to  strong 
auditory  perceptions  (?)  in  consequence  of  affections  of  the  canals.  Bottcher,  Tomaszewicz,  and 
Baginsky  regard  the  injury  to  the  cerebellum  as  the  cause  of  the  phenomena.  The  pendulum-like 
movements,  however,  are  so  characteristic  that  they  cannot  be  confounded  with  disturbances  of  the 
equilibrium  which  result  from  injury  to  the  cerebellum. 

[Kinetic  Theory. — In  1S75  Crum  Brown  pointed  out  that,  if  a  person  be  rotated  passively,  his 
eyes  being  bandaged,  he  can,  up  to  a  certain  point,  indicate  pretty  accurately  the  amount  of  move- 
ment, but  after  a  time,  this  cannot  be  done,  and  if  the  rotation,  as  on  a  potter's  wheel,  be  stopped, 

the  sense  of  rotation  continues.     Crum    Brown  suggested  that  cur- 
FlG.  432.  rents  were   produced  in  the  endolymph,  while  the  terminal    hair 

ceils  lagged  behind,  and  were,  in  fact,  dragged  through  the  fluid. 
He  pointed  out  that  the  light  posterior  canal  is  in  line  with  the 
left  superior,  and  the  left  posterior  with  the  right  superior,  a  fact 
which  is  readily  observed  by  looking  from  behind  at  a  skull,  with 
the  semicircular  canals  exposed  (Fig.  432).  He  assumes  that  the 
canals  are  paired  organs,  and  that  each  pair  is  connected  with 
rotation  or  movement  of  the  head  in  a  particular  direction.] 

Giddiness. — This  feeling  of  false  impressions  as  to 

the  relations  of  the  surroundings  and  consequent  move- 

LP  ■/  N  Rp    ments  of  the  body,  occurs  especially  during  acquired 

Diagram  of  the  disposition  of  the    changes  in  the  normal  movements  of  the  eyes,  whether 

semicircular  canals.    Rs  and    (j^g  jq  invohmtary  to  and  fro  movemcnts  of  the  eye- 

L.S,  right   and  left  superior;   LP     ,      ,,      ,  ^  ,       .         ^  , 

and  RP,  right  and  left  posterior ;    balls  ( nystagmus),  or  to  paralysis  of  some  eye  muscle. 

^eLT'^  ^^'  ''^'''  ^"'^  ''^' ''''  Active  or  passive  movements  of  the  head  or  of  the 
body  are  normally  accompanied  by  simultaneous  move- 
ments of  both  eyeballs,  which  are  characteristic  for  every  position  of  the  body. 
The  general  character  of  these  "compensatory"  bilateral  movements  of  the 
eyes  consists  in  this,  that  during  the  various  changes  in   the  position  of  the  head 


GIDDINESS,  NYSTAGMUS,  MENIERE'S   DISEASE.  Q55 

and  body,  the  eyes  strive  to  maintain  their  primary  passive  position.  Section  of 
the  aqueduct  of  Sylvius  at  the  level  of  the  corpora  quadrigemina,  of  the  floor  of 
the  fourth  ventricle,  of  the  auditory  nucleus,  both  acustici,  as  well  as  destruction 
of  both  membranous  labyrinths,  causes  disappearance  of  these  movements;  while, 
conversely,  stimulation  of  these  parts  is  followed  by  bilateral  associated  move- 
ments of  the  eyeballs. 

Compensatory  movements  of  the  eyeballs,  under  normal  circumstances,  may  be 
caused  reflexly  from  the  membranous  labyrinth.  Nerve  channels,  capable  of  exciting 
reflex  movements  of  both  eyes,  proceed  from  both  labyrinths,  and,  indeed,  both 
eyes  are  affected  from  both  labyrinths.  These  channels  pass  through  the  auditory 
nerve  to  the  ce7itre  (nuclei  of  the  3d,  4th,  6th,  and  8th  cranial  nerves),  and  from 
the  latter  efferent  fibres  pass  to  the  muscles  of  the  eye  (^Hogyes). 

Cyon  found  that  stimulation  of  the  horizontal  semicircular  canal  was  followed  by  horizontal  nystag- 
mus ;  of  the  posterior,  by  vertical,  and  of  the  anterior  canal,  by  diagonal  nystagmus.  Stimulation  of 
one  auditory  nerve  is  followed  by  rotating  nystagmus,  and  rotation  of  the  body  of  the  animal  on  its 
axis  toward  the  stimulated  side. 

Poisons. — Chloroform  and  other  poisons  enfeeble  the  compensatory  movements  of  the  eyeballs, 
while  nicotin  and  asphyxia  suppress  them,  owing  to  their  action  on  their  nerve  centre. 

It  is  probable  that  the  disturbances  of  equilibrium  and  the  feeling  of  giddiness 
which  follow  the  passage  of  a  galvanic  current  through  the  head  between  the  mastoid 
processes,  are  also  due  to  an  action  upon  the  semicircular  canals  of  the  labyrinth 
(§  300).  Deviation  of  the  eyeballs  is  produced  by  such  agalvanic  current  {Hitzig). 
The  same  result  is  produced  when  the  two  electrodes  are  placed  in  the  external 
auditory  meatuses. 

Pathological. — Meniere's  Disease. — The  feeling  of  giddiness,  not  unfrequently  accompanied 
by  tinnitus,  which  occurs  in  Meniere's  disease,  mast  be  referred  to  an  affection  of  the  nerves  of  the 
ampullae  or  their  central  organs,  or  of  the  semicircular  canals  themselves.  By  injecting  fluid  violently 
into  the  ear  of  a  rabbit,  giddiness,  with  nystagmus  and  rotation  of  the  head  toward  the  side  operated 
on,  are  produced  i^Baginsky).  In  cases  in  man,  where  the  tympanic  membrane  was  defective, 
Lucas,  when  employing  the  so-called  ear  air  douche  at  o.i  atmosphere,  observed  abduction  of  the 
eyeball  with  diplopia,  giddiness,  darkness  in  front  of  the  eyes,  while  the  respiration  was  deeper  and 
accelerated.  These  phenomena  must  be  due  to  stimulation  or  exhaustion  of  the  vestibular  branch  of 
the  auditory  nerve  {^Hogyes).  In  chronic  gastric  catarrh,  a  tendency  to  giddiness  is  an  occasional 
symptom  (Trousseau's  gastric  giddiness).  This  may,  perhaps,  be  caused  by  stimulation  of  the  gastric 
nerves  exciting  the  vasomotor  nerves  of  the  labyrinth,  which  must  affect  the  pressure  of  the  endo- 
lymph.     Analogous  giddiness  is  excited  from  the  larynx  ( C^arcc'/'),  and  from  the  urethra  [Erlenmeyer) . 

[Vertigo  or  giddiness  is  a  very  common  symptom  in  disease,  and  may  be  produced  by  a  great 
many  different  conditions.  It  literally  means"  a  turning."  As  Cowers  points  out,  the  most  common 
symptom  is  that  the  patient  himself  has  a  sense  of  movement  in  one  or  other  direction ;  or  objects 
may  appear  to  move  before  him  ;  and  more  rarely  there  is  actual  movement"  commonly  in  the  same 
direction  as  the  subjective  sense  of  movement."  It  is  sometimes  due  to  a  want  of  harmony  between 
the  impressions  derived  from  different  sense  organs  or  "  contradictoriness  of  sensory  impressions 
lyGrainger  Steivart),  as  is  sometimes  felt  on  ascending  or  descending  a  stair,  or  by  some  persons 
while  standing  on  a  high  tower,  constituting  tower  or  cliff  giddiness.  One  of  the  most  remarkable 
conditions  is  that  called  "agoraphobia"  [Benedikt,  IVestphal).  The  person  can  walk  quite  well 
in  a  narrow  lane  or  street,  but  when  he  attempts  to  cross  a  wide  square,  he  experiences  a  feeling  closely 
allied  to  giddiness.  The  giddiness  of  sea-sickness  is  proverbial,  while  some  persons  get  giddy  with 
waltzing  or  swinging.  Besides  occurring  in  Meniere's  disease,  it  sometimes  occurs  in  locomotor 
ataxia,  and  some  cerebral  and  cerebellar  affections,  including  cerebral  anaemia.  Very  distressing 
giddiness  and  headache  are  often  produced  by  paralysis  of  some  of  the  ocular  muscles,  d'.^.,  the 
external  rectus.  Defective  or  perverted  ocular  impressions,  as  well  as  similar  auditory  impressions, 
may  give  rise  to  vertigo  ;  in  the  latter  or  labyrinthine  form  the  vertigo  may  be  very  severe.  Severe 
vertigo  is  often  accompanied  by  vomiting.  A  hard  plug  of  ear  wax  may  press  on  the  membrana  tym- 
pani  and  cause  severe  giddiness.  The  forms  of  dyspeptic  giddiness  and  the  toxic  forms  due  to  the 
abuse  of  alcohol,  tobacco,  and  some  other  drugs  are  familiar  examples  of  this  condition.] 

[Tinnitus  Aurium,  or  subjective  noises  in  the  ear,  is  a  very  common  symptom  in  disease  of  the 
ear ;  the  noise  may  be  continuous  or  discontinuous,  be  buzzing,  singing,  or  rumbling  in  character.] 

351.  IX.  NERVUS  GLOSSO-PHARYNGEUS.— Anatomical. — This  nerve  (Fig.  429, 
9)  arises  from  the  nucleus  of  the  same  name,  which  consists  partly  of  large  cells  (motor)  and  partly 
of  small  cells  (belonging  to  the  gustatory  fibres).     The   nucleus  lies  in  the  lower  half  of  the  fourth 


656  THE   GLOSSO-PHARYNGEAL   NERVE. 

ventricle,  deep  in  the  medulla  oblongata,  near  the  olive  (Fig.  427),  and  ]X)steriorly  it  abuts  on  that  ot 
the  vagus.  The  anterior  ])art  of  the  central  nucleus  is  regarded  as  the  root  of  the  portio  intermedia 
of  the  facial  (^  349)-  The  nerve  also  receives  tibres  from  the  vagal  centres.  The  tilires  collect  into  • 
two  trunks,  which  afterward  unite  and  leave  the  medulla  oblongata  in  front  of  the  vagus.  In  the 
fossula  petrosa  it  has  on  it  the  petrous  ganglion,  from  which,  occasionally,  a  special  part  on  the 
posterior  twig  is  separated  within  the  skull  as  the  ganglion  of  Ehrenritter.  Communicaling  branches 
are  sent  from  the  petrous  ganglion  to  the  trigeminus,  facial  (f  and  rr),  vagus  and  carotid  plexus. 
From  this  ganglion  also  the  tympanic  nerve  (/.)  ascends  vertically  in  the  tympanic  cavity,  where  it 
unites  with  the  tympanic  plexus.  This  branch  (|  349,  4)  gives  sensory  tibres  to  the  tympanic  cavity 
and  the  Eustachian  tube ;  while,  in  the  dog,  it  also  carries  secretory  fibres  for  the  parotid  into  the 
small  superficial  petrosal  nerve  {^Heidenhain — \  I45). 

Function. — i.  It  is  the  nerve  of  taste  for  the  posterior  third  of  the  tongue, 
the  lateral  part  of  the  soft  palate,  and  the  glosso-palatine  arch  (compare  §  422). 
[This  is  denied  by  Gowers  (p.  682,  Am.  Ed.,  1888).] 

The  nerve  of  taste  for  the  anterior  two-thirds  of  the  tongue  is  referred  to  under  the  lingual  {\  347, 
III,  4)  and  chorda  tympani  nerves  [\  349,  4).  The  glossal  branches  are  provided  with  ganglia, 
especially  where  the  nerve  divides  at  the  base  of  the  circumvallate  papilhx;  i^J\emak,  Kolliker,  Stir- 
lini;).  The  nerve  ends  in  the  circumvallate  papillce  (Fig.  429,  U),  and  the  end  organs  are  repre- 
sented l)y  the  taste  bull)S  (§  422). 

2.  It  is  the  sensory  nerve  for  the  posterior  third  of  the  tongue,  the  anterior 
surface  of  the  epiglottis,  the  tonsils,  the  anterior  palatine  arch,  the  soft  palate,  and 
a  part  of  the  pharynx.  From  this  nerve  there  may  be  discharged  reflexly,  move- 
ments of  deglutition,  of  the  palate  and  pharynx,  which  may  pass  into  those  of 
vomiting  (§  158).  These  fibres,  like  the  gustatory  fibres,  can  excite  a  reflex  secre- 
tion of  saliva  (§  145)- 

3.  It  is  motor  for  the  stylo-pharyngeus  and  middle  constrictor  of  the  pharynx 
^{VolkmanTi)  ;  and,  according  to  other  observers,  to  the  (?)  glasso-palatinus  (_Hein) 

and  the  (??)  levator  veli  palatini  and  azygos  uvulce  (coinpare  Spheno-palatine 
ganglion,  §  347,  II).  It  is  doubtful  whether  the  glosso-pharyngeal  nerve  is  really 
a  motor  nerve  at  its  origin — although  Meynert  and  others  have  described  a  motor 
nucleus — or  whether  the  motor  fibres  reach  the  nerv^e  at  the  petrous  ganglion, 
through  the  communicating  branch  from  the  facial. 

4.  A  twig  accompanies  the  lingual  artery;  this  nerve,  perhaps,  is  vaso-dilator  for  the  lingual 
blood  vessels. 

Pathological. — There  are  no  satisfactorj'  observations  on  man  of  uncomplicated  affections  of 
the  glosso-pharj^ngeal  nerves. 

352.  X.  NERVUS  VAGUS.^Anatomical. — The  nucleus  from  which  the  vagus  arises 
along  with  the  9th  and  iith  nerve  is  in  (i)  the  ala  cinerea  in  the  lower  half  of  the  calamus  scrip- 
torius  (Fig.  427,  10)  [and  it  is  very  probably  the  representative  of  the  cells  of  the  vesicular  column 
of  Clarke  (^  366)].  (2)  Other  fibres  come  from  the  "  longitudinal  bundle  "  or  "  respirator)-  bundle  " 
lying  outside  the  nucleus,  and  reaching  down  into  the  cervical  enlargement.  (3)  A  motor  nucleus 
— the  nucleus  ambiguus — a  prolongation  of  some  of  the  cells  of  the  anterior  horn  of  the  spinal 
cord,  gives  some  motor  fibres.  It  leaves  the  medulla  oblongata  by  10  to  15  threads  behind  the 
9th  nerve,  between  the  divisions  of  the  lateral  column,  and  has  a  ganglion  (jugular)  upon  it  in 
the  jugular  foramen  (Fig.  428,  VIII).     Its  branches  contain  fibres  which  subserve  different  functions. 

1.  The  sensory  meningeal  branch  from  the  jugular  ganglion  accompanies  the 
vasomotor  fibres  of  the  sympathetic  on  the  middle  meningeal  artery,  and  sends 
fibres  to  the  occipital  and  transverse  sinus. 

When  it  is  irritated,  as  in  congestion  of  the  head  and  inflammation  of  the  dura  mater,  it  gives  rise 
to  vomiting. 

2.  The  auricular  branch  (Fig.  433,  au.^  from  the  jugular  ganglion  receives  a 
communicating  branch  from  the  petrous  ganglion  of  the  9th  nerve,  traverses  the 
canaliculus  mastoideus,  crossing  the  course  of  the  facial,  with  which  it  exchanges 
fibres  whose  function  is  unknown.  On  its  course,  it  gives  sensory  branches  to 
the  posterior  part  of  the  auditory  meatus,  and  the  adjoining  part  of  the  outer  ear. 
A  branch  runs  along  with  the  posterior  auricular  branch  of  the  facial,  and  confers 
sensibility  on  the  muscles. 


THE  CONNECTING  AND  OTHER  BRANCHES  OF  THE  VAGUS.   657 

When  this  nerve  is  irritated,  either  through  inflammation  or  by  the  presence  of  foreign  bodies  in 
the  outer  ear  passage,  it  may  give  rise  to  vomiting.  Stimulation  of  the  deep  part  of  tlie  external 
auditory  meatus  in  the  region  supplied  by  the  auricular  branch  causes  coughing  reflexly  \_e.g.,  from 
the  presence  of  a  pea  in  the  ear] .  Similarly,  contraction  of  the  blood  vessels  of  the  ear  may  be  caused 
reflexly  {^Snellen,  Loven). 

The  nerve  is  the  remainder  of  a  considerable  branch  of  the  vagus  which  exists  in  fishes  and  the 
larvae  of  frogs,  and  runs  under  the  skin  along  the  side  of  the  body. 

3.  The  connecting  branches  of  the  vagus  are :  (i)  A  branch  which  directly 
connects  the  petrous  ganghon  of  the  9th  with  the  jugular  gangHon  of  the  loth;  its 
function  is  unknown.  (2)  Directly  above  the  plexus  gangliiformis  vagi,  the  vagus 
is  joined  by  the  whole  inner  half  of  the  spinal  accessory.  This  nerve  conveys  to 
the  vagus  the  motor  fibres  for  the  larynx,  and  the  cervical  part  of  the  oesophagus 
(which,  according  to  Steiner,  lie  in  the  inner  part  of  the  nerve  trunk),  as  well  as  the 
xrCtX'CoxXoxy  fibres  for  the  heart (^Cl.  Bernard).  (3)  The  plexus  ganghiformis  fibres, 
whose  function  is  unknown,  join  the  trunk  of  the  vagus  from  the  hypoglossal, 
superior  cervical  ganglion  of  the  sympathetic,  and  the  cervical  plexus. 

4.  Pharyngeal  Plexus. — The  vagus  sends  one  or  two  branches  (Fig.  433,  2) 
from  the  upper  part  of  the  plexus  gangliiformis  to  th.t  pharyngeal  plexus,  where  at 
the  level  of  the  middle  constrictor  of  the  pharynx,  it  is  joined  by  the  pharyngeal 
branches  of  the  9th  nerve  and  those  of  the  upper  cervical  sympathetic  ganglion,  near 
the  ascending  pharyngeal  artery,  to  form  the  pharyngeal  plexus.  The  vagal  fibres 
in  this  plexus  supply  the  three  constrictors  of  the  pharynx  with  motor  fibres,  while 
the  tensor  palati  (^Otic ganglion,  §  347,  III)  and  levator  of  the  soft  palate  (compare 
Spheno-palatine  ganglion,  %  347, 11)  also  receive  motor  (?  sensory)  fibres.  Sensory 
fibres  of  the  vagus  from  the  pharyngeal  plexus  supply  the  pharynx  from  the  part 
beneath  the  soft  palate  downward.  These  fibres  excite  the  pharyngeal  constrictors 
reflexly,  during  the  act  of  swallowing  (§  156).  If  stimulated  very  strongly,  they 
may  cause  vomiting.  (The  sympathetic  fibres  of  the  oesophageal  plexus  give  vaso- 
motor nerves  to  the  oesophageal  vessels ;  for  the  oesophageal  branches  of  the  9th 
nerve,  see  above.) 

5.  The  vagus  supplies  two  branches  to  the  larynx,  the  superior  and  inferior 
laryngeal. 

{a)  The  superior  laryngeal  (Fig.  433,  3)  receives  vasomotor  fibres  from 
the  superior  cervical  ganglion  of  the  sympathetic.  It  divides  into  two  branches, 
external  and  internal:  (i)  The  external  branch  receives  vasomotor  fibres  from 
the  same  source  (they  accompany  the  superior  thyroid  artery),  and  supply  the 
crico-thyroid  muscle  with  motor  fibres,  and  sensory  fibres  to  the  lower  lateral 
portion  of  the  laryngeal  mucous  membrane.  (2)  The  internal  branch  gives  off 
sensory  branches  only  to  the  glosso-epiglottidean  fold,  and  the  adjoining  lateral 
region  of  the  root  of  the  tongue,  the  ary-epiglottidean  fold,  and  to  the  whole  anterior 
part  of  the  larynx,  except  the  part  supplied  by  the  external  branch  {Longet). 
Stimulation  of  any  of  these  sensory  fibres  causes  coughing  reflexly.  Coughing 
is  produced  by  stimulation  of  the  boundaries  of  the  glottis  respiratoria,  but  not  of 
the  vocal  cords,  and  by  stimulation  of  the  sensory  branches  of  the  vagtis  to  the 
tracheal  mucous  membrane,  especially  at  the  bifurcation,  and  also  from  the  bronchial 
mucous  membrane  {Kohts).  Coughing  is  also  caused  by  stimulation  of  the  auricular 
branch  of  the  vagus,  especially  in  the  deep  part  of  the  external  auditory  meatus,  of 
the  pulmonary  tissue,  especially  when  altered  pathologically ;  in  pathological  con- 
ditions (inflammation)  of  the  pleura  (?  certain  changes  in  the  stomach  [stomach 
cough]),  of  the  liver  and  spleen  {Naunyn).  The  coughing  centre  is  said  to  lie 
on  each  side  of  the  raphe,  in  the  neighborhood  of  the  ala  cinerea  {Kohts).  _  Cases 
of  violent  coughing  may,  owing  to  stimulation  of  the  pharynx,  be  accompanied  by 
vomiting  as  an  associated  movement  (§  120). 

In  many  individuals,  coughing  can  be  excited  by  stimulation  of  distant  sensory  nerves  (|  120,  i), 
e.  g.,  from  the  outer  ear  (auricular  nerve),  nasal  mucous  membrane,  liver,  spleen,  stomach,  intestine, 
uterus,  mammse,  ovaries,  and  even  from  certain  cutaneous  areas  (£dstein).     It  is  uncertain  if  these 
42 


fi<;-  433- 


658 


SUPERIOR   AND    INFERIOR   LARYNGEAL  NERVES.  659 

conditions  act  directly  upon  the  coughing  centre,  or  first  of  all  affect  the  vascularization  and  secre- 
tion of  the  respiratory  organs,  which  in  their  turn  affect  the  coughing  centre. 

The  cough  (dog,  cat)  caused  by  stimulation  of  the  trachea  and  bronchi  occurs  at  once,  and  lasts 
as  long  as  the  stimulus  lasts ;  in  stimulation  of  the  larynx,  the  first  effect  is  inhibition  of  the  respira- 
tion accompanied  by  movements  of  deglutition,  while  the  cough  occurs  after  the  cessation  of  the 
stimulation  [Kandarazky). 

The  superior  laryngeal  contains  afferent  fibres  which,  when  stimulated,  cause  ai-rest  of  the  res- 
piration and  closure  of  the  rima  glotlidis  {^Rosenthal) — (see  Respiratory  centre,  \  368).  Lastly, 
fibres  which  are  efferent  and  serve  to  excite  the  vasomotor  centre,  and  are  in  fact  '■^  pressor  fibres  " 
— (see  Vaso?7iotor  centre,  \  371,  II). 

(U)  The  inferior  laryngeal  or  recurrent  bends  on  the  left  side  around  the 
arch  of  the  aorta,  and  on  the  right  around  the  subclavian,  and  ascends  in  the 
groove  between  the  trachea  and  oesophagus,  giving  motor  fibres  to  these  organs,  and 
the  lower  constrictors  of  the  pharnyx,  and  passes  to  the  larynx,  to  supply  motor 
fibres  to  all  its  muscles,  except  the  crico-thyroid.  It  also  has  an  inhibitory  action 
upon  the  respiratory  centre  (see  §  368). 

A  connecting  branch  runs  from  the  superior  laryngeal  to  the  inferior  (the  anastomosis  of  Galen), 
which  occasionally  gives  off  sensory  branches  to  the  upper  half  of  the  trachea  (sometimes  to  the 
larynx?);  perhaps  also  to  the  oesophagus  [Longet],  and  sensory  fibres  (?)  for  the  muscles  of  the 
larynx  supplied  by  the  recurrent  laryngeal.  According  to  Francois  Franck,  sensory  fibres  pass  by 
this  anastomosis  from  the  recurrent  into  the  superior  laryngeal.  According  to  Waller  and  Burck- 
hard,  the  motor  fibres  of  both  laryngeal  nerves  are  all  derived  from  the  accessorius  ;  while  Chauveau 
maintains  that  the  crico-thyroid  is  an  exception. 

Stimulation  of  the  superior  laryngeal  is  painful,  and  causes  contraction  of 
the  crico-thyroid  muscle  (while  the  other  laryngeal  muscles  contract  refikxly). 
Section  of  both  nerves,  owing  to  paralysis  of  the  crico-thyroids,  causes  slight 
slowing  of  the  respirations  (SklareK).  In  dogs,  the  voice  becomes  deeper  and 
hoarser,  owing  to  diminished  tension  of  the  vocal  cords  (JLonget).  The  larynx 
becomes  insensible,  so  that  saliva  and  particles  of  food  pass  into  the  trachea  and 
lungs,  without  causing  reflex  contraction  of  the  glottis  or  coughing.  This  excites 
''traumatic  pneumonia,"  which  results  in  death  (^Fried lander). 

Stimulation  of  the  recurrent  nerves  causes  spasfn  of  the  glottis.  Section 
of  these  nerves  paralyzes  the  laryngeal  muscles  supplied  by  them,  the  voice  becomes 
husky  and  hoarse  (in  the  pig — Galen,  Riolan,  i6i8)  in  man,  dog,  and  cat;  while 
rabbits  retain  their  shrill  cry.  The  glottis  is  small,  with  every  inspiration  the 
vocal  cords  approximate  considerably  at  their  anterior  parts,  while,  during  expira- 
tion they  are  relaxed  and  are  separated  from  each  other.  Hence,  the  inspiration, 
especially  in  young  individuals  whose  glottis  respiratoria  is  narrow,  is  difficult  and 
noisy  {Legallots)  ;  while  the  expiration  takes  place  easily.  After  a  few  days,  the 
animal  (carnivore)  becomes  more  quiet,  it  respires  with  less  effort,  and  the  passive 
vibratory  movements  of  the  vocal  cords  become  less.  Even  after  a  considerable 
interval,  if  the  animal  be  excited,  it  is  attacked  with  severe  dyspnoea,  which  dis- 
appears only  when  the  animal  has  become  quiet  again.  Owing  to  paralysis  of  the 
laryngeal  muscles,  foreign  bodies  are  apt  to  enter  the  trachea,  while  the  paralysis 
renders  difficult  the  first  part  of  the  process  of  swallowing  in  the  oesophageal 
region.     Broncho-pneumonia  may  be  produced  (^Arjisferger). 

FIGURE  433,  p.  658. 
I.  Scheme  0/  the  distribution  of  the  vagus  and  accessorius.— la,  Exit  of  left  vagus  from  the  skull;  loi,  right  vagus  • 
g,  glosso-pharyngeal ;  7,  facial;  i,  deep  post-auricular  from  the  facial;  2,  pharyngeal  branches  of  vagus ;  6, 
pharyngeal  branch  of  the  glosso-pharyngeal ;  3,  superior  lar>'ngeal,  with  its  anastomoses,/,  with  the  sympathetic 
and  its  division,  4,  into  its  internal,  v,  and  external  branches,  e\  5,  inferior  or  recurrent  laryngeal ;  au.,  auricular 
branch  of  vagus.  Cardiac  nerves  :  g,  cardiac  branches  from  the  vagus  and  superior  laryngeal;  /,  h,  the  three 
cardiac  branches  from  the  upper, j^,  middle,  x,  and  lower, >/,  cervical  ganglion  of  the  sympathetic;  k,  nng  of 
Vieusses;  /,  cardiac  branch  from  the  recurrent  laryngeal;  L,  lung  with  the  anterior  and  posterior  pulmonary 
plexuses  ;  r,  oesophageal  plexus  ;  00,  gastric  branches,  and  near  them  the  hepatic  branches,  n  ;  m,  cffihac  plexus  ; 
k,  splanchnic  entering  former;  11,  accessory  nerve  sending  its  inner  branch  into  the  gangliform  plexus  of  the 
vagus — its  outer  branch,  ac,  supplies  the  sterno-mastoid,  St  and  aci,  and  the  trapezius,  Cc  ;  O,  external  auditory 
meatus;  0/j,  hyoid  bone  ;  A',  thyroid  cartilage  ;  r,  trachea;  i7,  heart ;  P,  pulmonary  artery ;  ^  ^,  aorta;  c, 
right  carotid;  Ci,  left  carotid;  j  and  Si,  right  and  left  subclavian  artery;  Z  Z,  diaphragm;  iV,  kidney;  iV«, 
suprarenal  capsule;  j^f,  stomach ;  ;«,  spleen  ;  Z  Z,  lung  and  liver.  II.  Scheme  of  the  course  of  the  depressor 
and  accelerans  in  the  cat. 


660 


THE    DEPRESSOR    NERVE. 


Fi( 


434- 


VAfi 


6.  The  depressor  nerve,  whiih  in  the  rabbit  arises  by  one  l>ranch  from  the 
su])eri()r  laryngeal,  and  usually  also  by  a  second  root  from  the  trunk  of  the  vagus 
itself  [runs  down  the  neck  m  close  relation  with  the  vagus,  sympathetic,  and  carotid 
artery,  enters  the  thorax],  and  joins  the  cardiac  plexus  (Fig.  434,  sc).  It  is  an 
afferent  nerve,  and  when  its  cc/z/ra/  tnd  is  stimulated  [pro- 
vided both  vagi  be  divided],  it  diminishes  the  energy  of  the 
vasomotor  centre,  and  thus  causes  a  fall  of  the  blood  pres- 
sure (hence  the  name  given  to  it  by  Cyon  and  Ludvvig,  § 
371,  II).  At  the  same  time  [if  the  vagus  on  the  opposite 
side  be  intact],  its  stimulation  affects  the  cardio-inhibitory 
centre,  and  thus  reflexly  diminishes  the  number  of  heart 
beats.  [Its  stimulation  also  gives  rise  to  pain,  so  that  it  is 
the  sensory  nerve  of  the  heart.  If  in  a  rabbit  the  vagi  be 
divided  in  the  middle  of  the  neck,  and  the  central  end  of 
the  depressor  nerve,  which  is  the  smallest  of  the  three  nerves 
near  the  carotid,  be  stimulated,  after  a  short  time  there  is  no 
alteration  of  the  heart  beats,  but  there  is  a  steady  fall  of  the 
blood  pressure  (Fig.  106),  which  is  due  to  a  reflex  inhibi- 
tion of  the  vasomotor  centre,  resulting  in  a  dilatation  of 
the  blood  vessels  of  the  abdomen.  Of  course,  if  the  vagi  be 
intact,  there  is  a  reflex  inhibitory  effect  on  the  heart.  It  is 
doubtful  if  the  depressor  comes  into  action  when  the  heart  is 
over-distended.  If  it  did,  of  course  the  blood  prosure  would 
be  reduced  by  the  reflex  dilatation  of  the  abdominal  blood 
vessels.] 

The  depressor  nerve  is  present  in  the  cat  {\  370),  hedgehog  [Aitbert, 
/?07'er),  rat  and  mouse;  in  the  horse  and  in  man,  fibres  analogous  to  the 
depressor  reenter  the  trunk  of  the  vagus  {^Bernhardt,  Kreidinanti). 
Depressor  fibres  are  also  found  in  the  rabbit,  in  the  trunk  of  the  vagus 
{Dreschfeldt,  Stelling). 

7.  The  cardiac  branches  (Fig.  433,  g,  /),  as  well  as  the 
cardiac  plexus,  have  been  described  in  §  57.  These  nerves 
contain  the  inhibitory  fibres  for  the  heart  (Fig.  434,  ic — 
cardio-inhibitory  —  Edward  Weber,  November,  1845  j 
Biuli^e,  independently  m  May,  1846),  also  sensory  fibres 
for  the  heart  [in  the  frog  {Budge),  and  partly  in  mammals 
(Go/tz)'].  Lastly,  in  some  animals  the  heart  receives  some 
of  the  accelerating  fibres  through  the  trunk  of  the  vagtis. 
Feeble  stimulation  of  the  vagus  occasionally  causes  acceleration  of  the  beats  of 
the  heart  (^Schiff).  [This  occurs  when  the  vagus  contains  accelerator  fibres.]  In 
an  animal  poisoned  with  nicotin,  or  atropin,  which  paralyzes  the  inhibitory  fibres 
of  the  vagus,  stimulation  of  the  vagus  is  followed  by  acceleration  of  the  heart 
beats  {Schiff,  Schmiedeberg)  [owing  to  the  unopposed  action  of  any  accelerated 
fibres  that  may  be  present  in  the  nerve,  e.  g.,  of  the  frog]. 

8.  The  pulmonary  branches  of  the  vagus  join  the  anterior  and  posterior  pul- 
monary plexuses.  The  anterior  pulmonary  plexus  gives  sensory  and  motor 
fibres  to  the  trachea,  and  runs  on  the  anterior  surface  of  the  branches  of  the 
bronchi  into  the  lungs  (Z).  The  posterior  plexus  is  formed  by  three  to  five  large 
branches  from  the  vagus,  near  the  bifurcation  of  the  trachea,  together  with 
branches  from  the  lowest  cervical  ganglion  of  the  sympathetic  and  fibres  from  the 
cardiac  plexus.  The  plexuses  of  opposite  sides  exchange  fibres,  and  branches  are 
given  off  which  accompany  the  bronchi  in  the  lungs.  Ganglia  occur  in  the 
course  of  the  pulmonary  branches  in  the  frog  {Arnold,  W.  Stirling)  [newt — W. 
Stirling;  and  in  mammals  {Remak,  Egoroiv,  \V.  Stirling)'],  in  the  larynx  \_Cock, 
IV.  Stirling'],  in  the  trachea  and  bronchi  \^IV.  Stirling,  Kandarazki].      Branches 


Scheme  of  the  cardiac 
nerves  in  the  rabbit.  P, 
pons;  M,  meduUa  ob- 
longata ;  Vag,  v.igus  ; 
SL,  superior,  il,  inferior 
laryngeal  ;  sc,  superior 
cardiac  or  depressor  ; 
ic,  inferior  cardiac  or 
cardio-inhibitory  ;  H, 
heart. 


PULMONARY  BRANCHES  OF  THE  VAGUS.  661 

proceed  from  the  pulmonary  plexus  to  the  pericardium  and  the  superior  vena  cava 
{Luschka,  Zuckerkandl). 

The  functions  of  the  pulmonary  branches  of  the  vagus  are — (i)  they  supply 
motor  branches  to  the  smooth  muscles  of  the  whole  bronchial  system  (§  io6)  ; 
(2 )  they  supply  a  small  part  of  the  vasomotor  nerves  of  the  pulmonary  vessels 
(Sc/izjf),  but  by  far  the  largest  number  of  these  nerves  (?  all)  is  supplied  from  the 
connection  with  the  sympathetic  (in  animals  from  the  iirst  dorsal  ganglion) — 
(^BrowJi-Seqiiard,  A.  Fick,  Badoud,  Lichtheirn))  (3)  they  supply  sensory  (cough- 
exciting)  fibres  to  the  whole  bronchial  system,  and  to  the  lungs ;  (4)  they  give 
afferent  fibres,  which,  when  stimulated,  diminish  the  activity  of  the  vasomotor 
centre,  and  thus  cause  a  fall  of  the  blood  pressure  during  forced  expiration  •  (5) 
similar  fibres  which  act  upon  the  inhibitory  centre  of  the  heart,  and  so  influence 
it  as  to  accelerate  the  pulse  beats  (§  369,  II).  Simultaneous  stimulation  of  4  and 
5  alters  the  pulse  rhythm  {Sommerbrodt)  ;  (6)  they  also  contain  afferent  fibres  from 
the  pulmonary  parenchyma  to  the  medulla  oblongata,  which  stimulate  the  respira- 
tory centre.  [These  fibres  are  continually  in  action],  and  consequently  section  of 
both  vagi  is  followed  by  diminution  of  the  number  of  respirations ;  the  respirations 
become  at  the  same  time  deeper,  while  the  same  volume  of  air  is  changed  (  Valentin). 
Stimulation  of  the  central  ^.w^l  of  the  vagus  again  accelerates  the  respirations  (^Traube, 
/.  Rosenthal).  Thus,  labored  and  difficult  respiration  is  explained  by  the  fact 
that  the  influences  conveyed  by  these  fibres  which  excite  the  respiratory  centre 
reflexly  are  cut  off ;  so  it  is  evident,  that  centripetal  or  afferent  impulses  proceeding 
upward  in  the  vagus  are  intimately  concerned  in  maintaining  normal  reflex  respira- 
tion ;  after  these  nerves  are  divided,  conditions  exciting  the  respiratory  movements 
must  originate  directly,  especially  in  the  medulla  oblongata  itself  (§  368). 

Pneumonia  after  Section  of  both  Vagi. — The  inflammation  which  follows  section  of  both 
vagi  has  attracted  the  attention  of  many  observers  since  the  time  of  Valsalva,  Morgagni  (1740),  and 
Legallois  (1812).  In  attempting  to  explain  this  phenomenon,  we  must  bear  in  mind  the  following 
considerations :  (a)  Section  of  both  vagi  is  followed  by  loss  of  j?iotor  power  in  the  muscles  of 
the  larynx,  as  well  as  the  sensibility  ot  the  larynx,  trachea,  bronchi,  and  the  lungs,  provided  the 
section  be  made  above  the  origin  of  the  superior  laryngeal  nerves.  Hence,  the  glottis  is  not  closed 
during  swallowing,  nor  is  it  closed  reflexly  when  foreign  bodies  (saliva,  particles  of  food,  irrespirable 
gases)  enter  the  respiratory  passages.  Even  the  reflex  act  of  cotigkin^^,  which,  under  ordinary 
circumstances,  would  get  rid  of  the  offending  bodies,  is  abolished.  Thus,  foreign  bodies  may  readily 
enter  the  lungs,  and  this  is  favored  by  the  fact  that,  owing  to  the  simultaneous  paralysis  of  the  oeso- 
phagus, the  food  remains  in  the  latter  for  a  time,  and  may  therefore  easily  enter  the  larynx.  That 
this  constitutes  one  important  factor  was  proved  by  Traube,  who  found  that  the  pneumonia  was 
prevented  when  he  caused  the  animals  to  respire  by  means  of  a  tube  inserted  into  the  trachea  through 
an  aperture  in  the  neck.  If,  on  the  contrary,  only  the  motor  recuirent  nerves  were  divided  and  the 
oesophagus  ligatured,  so  that  in  the  process  of  attempting  to  swallow,  food  must  necessarily  enter  the 
respiratory  passages,  "  traumatic  pneumonia  "  was  the  invariable  result  (  Traube,  O.  Frey).  (b) 
A  second  factor  depends  on  the  circumstance  that,  owing  to  the  labored  and  difficult  respiration,  the 
lungs  become  surcha7-ged  with  blood,h&C2M%&AMx'Ya^\\\^\ong  time  that  the  thorax  is  distended,  the  pres- 
sure of  the  air  within  the  lungs  is  abnormally  low.  This  condition  of  congestion,  or  abnormal  filling 
of  the  pulmonary  vessels  with  blood,  is  followed  by  serous  exudation  (pulmonary  oedema),  and  even 
by  exudation  of  blood  and  the  formation  of  pus  in  the  air  vesicles  {Frey).  This  same  circumsance 
favors  the  entrance  of  fluids  through  the  glottis  (^  352,  b).  The  introduction  of  a  tracheal  cannula 
will  prevent  the  entrance  of  fluids  and  the  occurrence  of  inflammation.  It  is  probable  that  a  partial 
paralysis  oi  the  ptilmonary  vasomotor  nerves  maybe  concerned  in  the  inflammation,  as  this  conduces 
to  an  engorgement  of  the  pulmonary  capillaries,  (c)  Lastly,  it  is  of  consequence  to  determine 
whether  trophic  fibres  are  present  in  the  vagus,  which  may  influence  the  normal  condition  of  the 
pulmonary  tissues.  According  to  Michaelson,  the  pneumonia  which  takes  place  immediately  after 
section  of  the  vagi  occurs  especially  in  the  lower  and  middle  lobes ;  the  pneumonia  which  follows 
section  of  the  recurrents  occurs  more  slowly,  and  causes  catarrhal  inflammation,  especially  in  the 
upper  lobes.  Rabbits,  as  a  rule,  die  within  twenty- four  hours,  with  all  the  symptoms  of  pneumonia ; 
when  the  above-mentioned  precautions  are  taken,  they  may  live  for  several  days.  Dogs  may  live 
for  a  long  time.  If  the  9th,  lolh,  and  12th  nerves  be  torn  out  on  one  side  in  a  rabbit,  death  takes 
place  from  pneumonia  [Gri'inhagen).  In  birds,  bilateral  section  of  the  vagi  is  not  followed  by 
pneumonia  [^Blainville,  Billroth),  because  the  upper  larynx  remains  capable  of  closing  firmly — death 
takes  place  in  eight   to  ten  days  with   the   symptoms  of  ina7iitio7t  [Einbrodt,  Zander,  v.  Anrep), 


662  CESOPHAGEAL    AND    GASTRIC    PLEXUSES. 

while  the  heart  undergoes  fatty  degeneration  {Eich/icrst),  and  so  do  the  liver,  stomach  and 
muscles  {v.  Aiirep).  Accordiiii,'  to  WassilielV,  the  heart  shows  cloudy  swelling  and  slif,'ht  wax-hke 
de^eneraiion.  Frogs,  which  at  every  respiration  open  the  gloUis,  and  close  it  during  tlie  pause,  die 
of  "asphyxia.  Section  of  the  jnilnunary  i)ranches  has  no  injurious  efl'ect  {Bidder).  [Unilateral  sec- 
tion of  the  vagus  in  rabbits  is  fullowed  within  forty-eight  hours  hy  the  apiiearance  of  yellowish- while 
spots  on  the  myocardium,  especially  near  the  inter  ventricular  septum,  on  the  papillary  muscles,  and 
along  the  furrows  for  the  coronaiy  arteries.  The  muscular  fibres  exhibit  retrogressive  changes, 
whereby  their  strin;  disappear;  they  become  swollen  up  and  filled  with  albuminous  granules.  After 
eight  to  ten  days,  the  interstitial  tissue  of  these  foci  becomes  infiltrated  with  small  round  granular 
cells,  especially  near  the  blood  vessels.  At  a  later  stage,  the  interstitial  c  mncctive  tissue  increases 
in  amount,  and  the  muscle  atrophies.  No  efifect  is  produced  by  section  of  the  depressor  or  sympa- 
thetic, and  Kantino  concludes  that  some  of  the  fibres  of  the  vagus  exert  a  trophic  action  on  the 
myocardium.] 

9.  The  oesophageal  plexus  (Fig.  434,  ;-)  is  formed  principally  by  branches 
from  the  vagus  above  the  inferior  laryngeal,  from  the  pulmonary  ])lexiis,  and  below 
from  the  trunk  itself.  Thi.s  jjlexus  supplies  the  oesophagus  with  motor  power 
(§  156),  the  sensibility  which  is  present  only  in  the  upper  part,  and  it  also  sup- 
plies fibres  capable  of  exciting  reflex  actions. 

10.  The  gastric  plexus  {00)  consists  of  {a)  the  anterior  (left)  termination  of 
the  vagus,  which  supplies  fibres  to  the  oesophagus  and  courses  along  the  small 
curvature,  and  sends  a  few  fibres  through  the  portal  fissure  into  the  liver ;  (^)  the 
posterior  (right)  vagtis,  after  giving  off  a  few  fibres  to  the  oesophagus,  takes  part  in 
the  formation  of  the  gastric  plexus  to  which  (/)  sympathetic  fibres  are  added  at  the 
pylorus.  Section  of  the  vagi  is  followed  by  hyperaemia  of  the  gastric  mticous  mem- 
brane {Panuvi,  Fincus),  but  it  does  not  interfere  with  digestion  (Bidder  and 
Schmidt),  even  when  it  is  performed  at  the  cardia  {Kritzler,  Schiff). 

11.  About  two-thirds  of  the  right  vagus  on  the  stomach  joins  the  coeliac  plexus, 
and  from  it  branches  accompany  the  arteries  to  the  liver,  spleen,  pancreas,  duodenum, 
kidney,  and  suprarenal  capsules.  The  vagus  supplies  motor  fibres  to  the  stomach, 
which  belong  to  the  root  of  the  vagus  itself  and  not  to  the  acce.ssorius  {Stilling, 
Bischoff).  The  gastric  branches  also  contain  afferent  fibres,  which,  when  stimu- 
lated, catise  reflexly  a  secretion  of  saliva  (§  145).  It  is  undetermined  whether  they 
also  cause  vomiting.  For  the  effect  of  the  vagus  upon  the  movements  of  the 
intestine  (see  §  161).  According  to  some  observers,  stimulation  of  the  vagus  is 
followed  by  movement  of  the  large  as  well  as  of  the  small  intestine  {Stilling,  Kupffer, 
C.  Ludwig,  Remak).  Stimulation  of  the  peripheral  end  of  the  vagus  causes  con- 
traction of  the  smooth  muscular  fibres  in  the  capsule  and  trabeculae  of  the  spleen 
(m  the  rabbit  and  dog,  §  103).  Stimulation  of  the  vagus  at  the  cardia  causes  in- 
crease in  the  secretion  of  urine  with  dilatation  of  the  renal  vessels,  while  the  blood 
of  the  renal  vein  becomes  more  arterial  {CI.  Bernard^.  According  to  Ro.ssbach 
and  Quellhorst,  a  few  vasomotor  fibres  are  supplied  by  the  vagus  to  the  abdominal 
organs,  while  the  greatest  number  comes  from  the  splanchnic. 

12.  Reflex  Effects. — The  vagtis  and  its  branches  contain  fibres,  some  of  which 
have  been  referred  to  already,  which  act  reflexly  (afferent)  upon  certain  nervous 
mechanisms. 

(a)  On  the  vasomotor  centre  there  act  (o) /;wjo^  fibres  (especially  in  both  laryngeal  nerves), 
whose  stimulation  is  followed  by  a  reflex  contraction  of  the  arterial  blood  channels,  and  thus  cause 
a  rise  of  the  blood  pressure;  (/J)  depressor  fibres  (in  the  depressor  or  the  vagus  itself),  which 
have  exactly  an  opposite  effect.  (This  subject  is  specially  referred  to  under  the  head  of  the  Vaso- 
motor nerve  centre,  \  371.) 

{b)  On  the  respiratory  centre  there  act  (o)  fibres  (pulmonary  branches)  whose  stimulation  is 
followed  by  acceleration  of  the  respiration;  and  (,9)  inhibitory  fibres  (in  both  laryngeals),  whose 
stimulation  is  followed  by  slowing  or  arrest  of  the  re^piration.      (See  Respiratory  centre,  \  368.) 

(c)  On  the  cardio-inhibitory  system. — [When  the  central  end  of  one  vagus  is  stimulated, 
provided  the  other  vagus  is  intact,  the  heart  may  be  arrested  reflexly  in  the  diastolic  phase.]  Mayer 
and  Pribram  observed  that  sudden  distention  of  the  stomach  caused  slowing  and  even  arrest  of  the 
heart,  while,  at  the  same  time,  there  was  contraction  of  the  arteries  of  the  medulla  oblongata  and 
increase  of  the  blood  pressure. 

((/)  On  the    vomiting   centre. — This  centre   may    be  affected    by    stimulation    of   the    central 


PATHOLOGICAL    CONDITIONS   OF   THE    VAGUS.  663 

end  of  the  vagus,   and,  as   already  mentioned,  by  stimulation  of  many  afferent  fibres  in  the  vaarus 
(I  158). 

(e)  On  the  pancreatic  secretion. — Stimulation  of  the  cent}-al  end  of  the  vagus  is  followed  by 
arrest  of  this  secretion  (|  171). 

(/■)  According  to  CI.  Bernard,  there  are  fibres  present  in  the  pulmonary  nerves,  which,  when  they 
are  stimulated,  increase  reflexly  the  formation  of  sugar  in  the  liver,  perhaps  through  the  hepatic 
branches  of  the  vagus. 

Unequal  Excitability. — The  various  branches  of  the  vagus  are  not  all  endowed  with  the 
same  degree  of  excitability.  If  the  peripheral  end  of  the  vagus  be  stimulated,  first  of  all  with  a 
weak  stimulus,  the  laryngeal  muscles  are  first  affected,  and  afterward  the  heart  is  slowed  [Ruther- 
ford). If  the  central  end  be  stimulated  with  feeble  stimuli,  the  "  excito-respiratory "  fibres  are 
exhausted  before  the  "  inhibito-respiratory "  [Burkart).  According  to  Steiner,  the  various  fibres 
are  so  arranged  in  the  vagus  that  the  afferent  fibres  he  in  the  outer,  and  the  efferent  in  the  inner,  half 
of  the  trunk,  in  the  cervical  region. 

Pathological. — Stimulation  or  paralysis  in  the  area  of  the  vagus  must  necessarily  present  a  very 
different  picture  according  as  the  affection  is  referred  to  the  whole  trunk  or  only  to  some  of  its 
branches,  or  whether  the  affection  is  unilateral  or  bilateral.  Paralysis  of  the  pharynx  and 
oesophagus,  which  is  usually  of  central  or  intracranial  origin,  interferes  with  or  abolishes  degluti- 
tion, so  that  when  the  oesophagus  becomes  filled  with  food  there  is  difficulty  of  breathing,  and  the 
food  may  even  pass  into  the  nasal  cavities.  A  peculiar  sonorous  gurgling  is  occasionally  heard  in 
the  relaxed  canal  (deglutatio  sonora).  In  incomplete  paralysis,  the  act  of  deglutition  is  delayed 
and  rendered  more  difficult,  while  large  masses  are  swallowed  more  easily  than  small  ones.  In- 
creased contraction  and  spasmodic  stricture  of  the  oesophagus  are  referred  to  under  the  phenomena 
of  general  nervous  excitability  (§  186). 

Spasm  of  the  laryngeal  muscles  causes  spasmodic  closure  of  the  glottis  {^Spasnms  glottidis). 
This  condition  is  most  apt  to  occur  in  children,  and  takes  place  in  paroxysms,  with  symptoms 
of  dyspnoea  and  crowing  inspiration;  if  the  case  be  very  severe,  there  may  be  muscular  con- 
tractions (of  the  eye,  jaw,  digits,  etc.).  The  symptoms  are  very  probably  due  to  the  reflex  spasms 
which  may  be  discharged  from  the  sensory  nerves  of  several  areas  (teeth,  intestine,  skin).  The 
impulse  is  conducted  along  the  sensory  nerves  proceeding  from  these  areas  to  the  medulla 
oblongata,  where  it  causes  the  discharge  of  the  reflex  mechanism  which  produces  the  above- 
mentioned  results.  There  maybe  spasm  of  the  dilators  of  the  glottis  and  other  laryngeal  muscles 
[Frantzel). 

Stimulation  of  the  sensoj-y  nerves  of  the  larynx,  as  is  well  known,  produces  coughing.  If  the 
stimulation  be  very  intense,  as  in  whooping-cough,  the  fibres  lying  in  the  laryngeal  nerves,  which 
inhibit  the  respiratory  centre,  may  also  be  stimulated  ;  the  number  of  respirations  is  diminished,  and 
ultimately  the  respiration  ceases,  the  diaphragm  being  relaxed ;  while,  with  the  most  intense  stimu 
lation,  there  may  be  spasmodic  expiratory  arrest  of  the  respiration  with  closure  of  the  glottis,  which 
may  last  for  fifteen  seconds.  Paralysis  of  the  laryngeal  nerves,  which  causes  disturbances  of  speech, 
has  been  referred  to  in  \  313.  In  bilateral  paralysis  of  the  recurrent  nerves,  in  consequence  ot 
tension  upon  them  due  to  dilatation  of  the  aorta  and  the  subclavian  artery,  a  considerable  amount  of 
air  is  breathed  out,  owing  to  the  futile  efforts  which  the  patient  makes  in  trying  to  speak ;  expectora- 
tion is  more  difficult,  whUe  violent  coughing  is  impossible  [v.  Ziemssen).  Attacks  of  dyspnoea  occur 
just  as  in  animals,  if  the  person  make  violent  efforts.  Some  observers  [Salter,  Bergson)  have  referred 
the  paroxysms  of  nervous  asthma,  which  last  for  a  quarter  of  an  hour  or  more,  and  constitute 
asthma  bronchiale,  to  stimulation  of  the  pulmonary  plexus,  causing  spasmodic  contraction  of  the 
bronchial  muscle  (§  106).  Physical  investigation  during  the  paroxysms  reveals  nothing  but  the 
existence  of  some  rhonchi  (§  1 17).  If  this  condition  is  really  spasmodic  in  its  nature  (?  of  the  vessels), 
it  must  be  usually  of  a  reflex  character;  the  afferent  nerves  may  be  those  of  the  lung,  skin,  or  geni- 
tals (in  hysteria).  Perhaps,  however,  it  is  due  to  a  temporary  paralysis  of  the  pulmonary  nerves 
(afferent),  which  excite  the  respiratory  centre  (excito-respiratory). 

Stimulation  of  the  cardiac  branches  of  the  vagus  may  cause  attacks  of  temporary  suspension  of 
the  cardiac  contractions,  which  are  accompanied  by  a  feeling  of  great  depression  and  of  impending 
dissolution,  with  occasionally  pain  in  the  region  of  the  heirt.  Attacks  of  this  sort  may  be  produced 
reflexly,  e.g.,  by  stimulation  or  irritation  of  the  abdominal  organs  (as  in  the  experiment  of  Goltz  of 
tapping  the  intestines).  Hennoch  and  Silbermann  observed  slowing  of  the  action  of  the  heart  in 
children  suffering  from  gastric  irritation.  Similarly,  the  respiration  may  be  affected  reflexly  through 
the  vagus,  a  condition  described  by  Hennoch  as  asthma  dyspepticum.  In  cases  of  intermittenc 
paralysis  of  the  cardiac  branches  of  the  vagus,  we  rarely  find  acceleration  of  the  pulse  above  160 
[Riegel),  200  (  Tuczek,  L.  Langer) ;  even  240  pulse  beats  per  minute  have  been  recorded  [Kuppei't), 
and  in  such  cases,  the  beats  vary  much  in  rhythm  and  force,  and  they  are  very  irregular.  These  cases 
require  to  be  more  minutely  analyzed,  as  it  is  not  clear  how  much  is  due  to  paralysis  of  the  vagus 
and  how  much  to  the  action  of  the  accelerating  mechanism  of  the  heart.  Little  is  known  of  affec- 
tions of  the  intra-abdominal  fibres  of  the  vagus.  It  seems  that  the  sensory  branches  of  the  stomach 
do  not  come  from  the  vagus.  If  the  trunk  of  the  vagus  or  its  centre  be  paralyzed,  there  are  labored, 
deep,  slow  respirations,  such  as  follow  the  section  of  both  vagi  [Gutf>nann). 


(364  SPINAL   ACCESSORY    AND    HYPUCLOSSAL   NERVES. 

353.  XI.  NERVUS  ACCESSORIUS  WILLISII.— Anatomical— This  nerve  arises  by 
two  completely  separate  roots;  chc-  from  the  accessorius  nucleus  of  the  medulla  oblongata 
(F'ig.  427,  11),  which  is  connected  with  the  vagus  nucleus;  while  the  o/Aer  root  arises  between  the 
anterior  and  jx)sterior  nerve  roots  from  the  spinal  cord,  usually  between  the  5th  and  6th  cervical 
vertebra?.  In  the  sjiinal  cord,  its  fibres  can  be  traced  to  an  elonijated  nucleus  lying  on  the  outer  side 
of  the  anterior  cornu,  as  f.ir  downward  as  the  5th  cervical  vertebra.  Near  the  jugular  foramen  both 
portions  come  together,  but  do  not  exchange  fibres  (//o//);  both  roots  afterward  separate  from 
each  other  to  form  two  distinct  branches,  the  anterior  (inner),  which  arises  from  the  medulla 
oblongata,  passing  en  masse  into  the  plexus  gangliiformis  vagi.  This  branch  supplies  the  vagus 
with  most  of  its  motor  fibres  (compare  (J  352,  3),  and  also  its  ra/v//(5-/w///7'»/<»;j  fibres  (Fig.  433). 
[The  upper  cervical  metameres  or  segments  give  origin  not  only  to  the  anterior  and  posterior  roots 
of  the  corresponding  nerve  roots,  but  heticeen  these  roots  arise  the  roots  of  the  spinal  accessory  nerve. 
This  nerve  contains  large  meduUated  nerve  fibres,  and  fine  medullated  fibres  such  as  characterize  the 
visceral  branches  of  the  thoracic  and  sacral  regions  ( ^  356  )•  The  nerve  passes  by  the  jugular  ganglion 
of  the  vagus,  then  divides  into  the  external  and  internal  branch.  All  the  large  fibres  pass  into  the 
external  branch,  which,  along  with  branches  from  the  cervical  plexus,  supply  the  sterno-mastoid  and 
trapezius.  The  internal  branch,  composed  of  small  fibres,  passes  into  the  ganglion  of  the  trunk  of 
the  vagiis.  Gaskell  therefore  regards  the  internal  branch  "  as  formed  by  the  rami  viscerales  of  the 
upper  cervical  and  vagus  nerves."  These  fine  medullated  nerve  fibres  probably  arise  from  the  cells 
of  the  posterior  vesicular  column  of  Clarke.  The  motor  fibres  to  the  trapezius  and  sterno-mastoid 
arise  from  the  cells  of  the  lateral  horn  of  gray  matter.] 

If  the  accessorius  be  pulled  out  by  the  root  in  animals,  the  cardio-inhibitory  fibres 
midergo  degeneration.  If  the  trunk  of  the  vagus  be  stimulated  in  the  neck  four  to 
five  days  after  the  operation,  the  action  of  the  heart  is  no  longer  arrested  thereby 
[owing  to  the  degeneration  of  the  cardio-inhibitory  fibres]  (^JVal/er,  Schiff,  Dasz- 
kieivicz,  Heidenhain)  \  according  to  Heidenhain,  the  heart  beats  are  accelerated 
immediately  after  pulling  out  the  nerve. 

The  external  branch  arises  from  the  spinal  roots.  This  nerve  communicates 
with  the  sensory  branches  of  the  posterior  root  of  the  ist,  more  rarely  of  the  2d 
cervical  nerve,  and  these  fibres  supply  sensibility  to  the  muscles ;  it  then  turns 
backward  above  the  transverse  process  of  the  atlas,  and  terminates  as  a  motor 
nerve  in  the  sterno-mastoid  and  trajjezitis,  (Fig.  433).  The  latter  muscle  usually 
receives  motor  fibres  also  from  the  cervical  ple.vus  (Fig.  429). 

The  external  branch  communicates  with  several  cervical  nerves.  These  fibres  either  participate  in 
the  innervation  of  the  above-named  muscles,  or  the  accessorius  returns  pari  of  the  sensory  fibres  sup- 
plied by  the  posterior  roots  of  the  two  upper  cervical  nerves. 

Pathological. — Stimulation  of  the  outer  brancli  causes  tonic  or  clonic  spasm  of  the  above- 
named  muscles,  usually  on  one  side.  If  the  branch  to  the  sterno-mastoid  be  affected  alone,  the  head 
is  moved  with  each  clonic  spasm.  If  the  aftection  be  bilateral,  the  spasm  usually  takes  place  on 
opposite  sides  alternately,  while  it  is  rare  to  have  it  on  both  sides  simultaneously.  In  spasm  of  the 
trapezius  the  head  is  drawn  backward  and  to  the  side.  Tonic  contraction  of  the  tlexors  of  the 
head  causes  the  characteristic  jx)sition  of  the  head  known  as  caput  obstipum  (spasticum)  or  wryneck. 
\vi  paralysis  of  one  of  these  muscles,  the  head  is  drawn  toward  the  sound  side  (torticollis  paraly- 
ticus).    Paralysis  of  the  trapezius  is  usually  only  partial. 

Paralysis  of  the  whole  trunk  of  the  spinal  accessor)'  (usually  caused  by  central  conditions), 
besides  causing  paralysis  of  the  sterno-mastoid  and  trapezius,  also  paralyzes  the  motor  branches  of 
the  vagus  already  referred  to  {Erl>,  P'rlinkel). 

354.  XII.  NERVUS  HYPOGLOSSUS.— Anatomical.— It  arises  from  two  large-celled 
nuclei  within  the  lowest  part  of  the  calamus  scriptorius,  and  one  adjoining  small-celled  nucleus 
{Roller),  while  additional  fibres  come  from  the  brain  (^  378),  and  also  perhaps  from  the  olive  (Fig. 
427,  12  I.  It  springs  by  ID  to  15  twigs  in  a  line  with  the  anterior  roots  of  the  spinal  nerve  (Fig.  420, 
IX).     In  its  development  part  of  the  hypoglossal  behaves  as  a  spinal  nerve  (Froriep). 

Function. — It  is  motor  to  all  the  muscles  of  the  tongue,  including  the 
genio-hyoid  and  thyro-hyoid. 

Connections. — The  trunk  of  the  hypoglossal  is  connected  with  (i)  the  superior  cervical  gan- 
glion of  the  sy??ipathetic,  which  supplies  it  with  vasomotor  fibres  for  the  bl'^od  vessels  of  the 
tongue.  After  section  of  the  hypoglossal  and  lingual  nerves,  the  corresponding  half  of  the  tongue 
becomes  red  and  congested  [Schiff ).  (2)  There  is  also  a  branch  from  the  plexus  gangliiformis  vagi, 
its  small  lingual  branch,  to  the  commencement  of  the  hypoglossal  arch.  These  fibres  supply  the 
hypoglossal  with  sensory  fibres  for  the  muscles  of  the  tongtie,  for  even  after  section  of  the  lingual 
the  tongue  still  possesses  dull  sensibility.^    It  is  uncertain  whether  fibres  with   a  similar  function  are 


.  THE    SPINAL   NERVES.  665 

partly  derived  from  the  cervical  nerves  or  from  the  anastomosis  which  takes  place  with  the  lingual. 
(3)  It  is  united  with  the  upper  cervical  nerves  by  means  of  the  loops  known  as  the  ansa  hypoglossi. 
These  connecting  fibres  run  in  the  descendens  noni  to  the  sterno-hyoid,  omo-hyoid,  and  stemo-thyroid. 
Cervical  fibres  do  not,  as  a  rule,  enter  the  tongue ;  stimulation  of  the  root  of  the  hypoglossal  acts 
upon  the  above-named  muscles  only  very  rarely  and  to  a  very  slight  extent  (  Volk?7ianti) .  (Compare 
I  297,  3,  and  §  336,  III.) 

Bilateral  section  of  the  nerve  causes  complete  motor  paralysis  of  the  tongue. 
Dogs  can  no  longer  lap,  they  bite  the  flaccid  tongue.  Frogs,  which  seize  their  prey 
with  the  tongue,  must  starve  ;  when  the  tongue  hangs  from  the  mouth,  it  must 
prevent  the  closure  of  the  mouth,  so  that  these  animals  must  die  from  asphyxia,  as 
air  is  pumped  into  the  lungs  only  when  the  mouth  is  closed. 

Pathological. — Paralysis  of  the  hypoglossal  (glossoplegia),  which  is  usually  central  in  its 
origin,  causes  disturbance  of  speech  {\  319).  [In  unilateral  palsy,  the  tongue  lies  in  the  mouth  in 
its  normal  position,  but  the  base  is  more  prominent  on  the  paralyzed  side.  When  the  tongue  is  pro- 
truded, it  passes  to  the  sound  side  by  the  genio-hyoglossus  (|  155).]  Paralysis  of  the  tongue  also 
interferes  with  mastication,  the  formation  of  the  bolus  in  the  mouth,  and  deglutition  in  the  mouth. 
Owing  to  the  imperfect  movements  of  the  tongue,  taste  is  imperfect,  and  the  singing  of  high  notes 
and  the  falsetto  voice,  which  require  certain  positions  of  the  tongue,  appear  to  be  impossible  i^Bennati). 

Spasm  of  the  tongue,  which  causes  aphthongia  (|  318),  is  usually  reflex  in  its  origin,  and  is 
extremely  rare.  Idiopathic  cases  of  spasm  of  the  tongue  have  been  described ;  the  seat  of  the  irri- 
tation lay  either  in  the  cortex  cerebri  or  in  the  oblongata  {^Berger,  E.  Remak).  For  Pseudo-motor 
Action,  see  p.  650. 

355.  THE  SPINAL  NERVES. — Anatomical. — The  thirty-one  pairs  of  spinal  nerves  arise 
by  means  of  a  posterior  [superior,  gangliated]  root  (consisting  of  a  few  large  rounded  bundles), 
from  the  sulcus  between  the  posterior  and  lateral  columns  of  the  spinal  cord,  and  by  means  of  an 
anterior  [inferior,  non-gangliated]  root  (consisting  of  numerous  fine  flat  strands),  iirom  the  furrow 
between  the  anterior  and  lateral  columns.  Fig.  435.  The  posterior  roots,  with  the  exception  of  the 
1st  cervical  nerve,  are  the  larger.  Occasionally  the  roots  on  opposite  sides  are  not  symmetrical;  one 
or  other  root,  or  even  a  whole  nerve,  may  be  absent  from  the  dorsal  region  {Adamkiewicz).  On  the 
posterior  root  is  the  spindle-shaped  spinal  ganglion  (?  321,  II,  3),  which  is  occasionally  double 
on  the  lumbar  and  sacral  nerves.  Beyond  the  ganglion,  the  two  roots  unite  to  form  within  the  spinal 
canal  the  mixed  trunk  of  a  spinal  nerve.  The  branches  of  the  ners^e  trunk  invariably  contain 
fibres  coming  fi-om  both  roots.  The  number  of  fibres  in  the  nerve  trunk  is  exactly  the  same  as  in 
the  two  roots ;  hence,  we  must  conclude  that  the  nerve  cells  in  the  spinal  ganglion  ai-e  intercalated  in 
the  course  of  the  fibres  [Gaule  and  Birge). 

Varieties. — The  spinal  ganglion  is  sometimes  double,  and  according  to  Hyrtl,  isolated  ganglionic 
cells  frequently  occur  in  the  posterior  root,  between  the  ganglion  and  the  cord.  Occasionally  the 
roots  are  somewhat  unsym metrical  on  opposite  sides  ;  in  the  dorsal  part  one  or  other,  or  both  roots 
of  a  spinal  nerve  are  sometimes  absent  {Adamkiewicz). 

[Morphology  of  the  Spinal  Nerves  and  Limb  Plexuses. — A  typical  segmental  spinal  nerve 
(Fig.  435),  divides,  after  its  formation,  into  three  parts,  a  dorsal  branch,  or  superior  primary  division 
distributed  to  the  back,  a  somatic  branch,  or  inferior  primary  division,  supplying  the  body  wall  or 
limbs ;  and  a  splanchnic  or  visceral  branch,  or  ramus  communicans,  connected  with  the  sympa- 
thetic gangliated  cord,  and  distributed  to  the  large  vessels  and  viscera.  The  somatic  branch  is  the 
largest,  and  is  generally,  by  human  anatomists,  spoken  of  as  the  "  anterior  primary  division."  In 
the  thoracic  and  upper  lumbar  regions,  the  distribution  of  this  nerve  is  simple.  It  divides  into  an 
external  (or  lateral)  branch,  and  an  internal  (or  anterior)  branch,  which  supply  respectively  the 
lateral  and  anterior  portions  of  the  thoracic  and  abdominal  walls.] 

[In  the  region  of  the  neck,  and  in  relation  to  the  limbs,  the  arrangement  of  the  somatic  branches 
becomes  complicated  by  the  formation  of  the  plexuses.  In  the  embryo,  however,  the  distribution  of 
the  nerves  is  simpler,  and  a  comparison  can  be  made  both  with  the  adult  arrangement,  and  with  the 
typical  nerve  as  seen  in  the  thoracic  region.  In  the  embryo,  the  neck  as  such  does  not  exist,  and 
the  upper  limb  sprouts  out  directly  beyond  the  segmented  visceral  arches.  In  this  state,  the  somatic 
branch  is  distributed  as  in  the  thoracic  region ;  the  nerve  divides  into  an  external  and  an  internal 
branch,  distributed  to  the  side  and  front  of  the  corresponding  part  of  the  arches  in  the  neck,  in  the 
regions  where  the  limbs  are  appearing  as  two  flattened  buds  from  the  ventro-lateral  aspect  of  the 
body.  The  somatic  branch  sweeps  round  into  the  blastema  forming  the  limb,  and  divides  into  its 
two  branches,  external  and  internal,  or  dorsal  and  ventral,  which  are  distributed  to  the  outer  (dorsal) 
and  inner  (ventral)  surfaces,  respectively,  of  the  primitive  limb.  At  this  time,  the  cardlaginous  and 
muscular  elements  of  the  limb  have  not  become  differentiated.  Wbile  this  is  occurring,  the  dorsal 
and  ventral  parts  of  the  somatic  branches  of  the  nerves  entering  the  limb  unite  with  adjacent  dorsal 
and  ventral  branches,  in  various  combinations,  so  as  to  produce  the  limb  plexuses.  The  nerves  re- 
sulting from  these  combinations  are  distributed  to  the  primitive,  dorsal,  and  ventral  surfaces  of  the 
limbs.     Thus,  the  plexuses  are  formed,  and  the  peripheral  distribution  of  the  nerves  has  taken  place 


666 


STRUCTURE    OF    A    SPINAL   GANGLION. 


before  the  period  of  flexion  and  angulation  of  the  limbs.  These  processes  mark  the  conditions  in 
the  adult ;  but  even  then  it  is  easy  to  make  out  that  the  nerves  in  the  upper  limb  derived  from  the 
posteiior  (dorsal)  cords  of  the  l)rachiai  plexus  supply  the  scapular  region,  extensor  surface  of  the  arm 
and  forearm,  and  the  back  of  the  hand — parts  which  are  derived  from  the  dorsal  surface  of  the 
primitive  limb;  while  the  nerves  j^ro  luced  from  the  anterior  (ventral)  cords  supply  the  pectoral  region, 
front  of  the  arm,  forearm,  and  hand — parts  representing  the  jirimitive  ventral  surface.] 

[In  the  lower  limb,  the  nerves  deiived  from  a  union  of  the  posterior  branches  are  the  external 
cutaneous,  anterior  crural,  gluteal,  and  external  popliteal.  These  suj^iply  the  iliac  surfaces,  the  front 
of  the  thigh,  leg,  and  foot — belonging  to  the  primitive  dorsal  surface  of  the  limb.  The  nerves 
formed  by  the  union  of  anterior  branches — genito-crural,  obturator,  and  internal  |])opliteal,  in  like 
manner  supply  the  parts  of  the  limb  corresponding  to  the  ventral  surface — the  inner  side  and  back  of 
the  thiL;h.  the  back  of  tlie  leg,  and  the  sole  of  the  foot  (^.  M.  Pateison).'] 

[Structure  of  a  Spinal  Ganglion. — The  ganglion  is  invested  by  a  thin,  firmly  adherent,  sheath 
of  connective  tissue,  which  sends  processes  into  the  swelling,  and  is  continuous  with  the  sheaths  of 
the  nerve  entering  and  leaving  the  ganglion  (Fig.  436,  c).  In  mammals,  e.  ;■-.,  rabbit,  a  longitudi- 
nal stction  of  such   a   ganglion  exhibits  the  cells   arranged  in   grou]3s,  with   strands  of  nerve  fibres 


Fk;.  436. 

liiiiii 


Fig.  435. 


Diagram  of  a  spinal  nerve  ;  C,  spinal  cord  ;  />•,  ar,  posterior  and 
anterior  roots  ;  SPD,  IPD,  superiorand  inferior  prim,iry  divi- 
sions ;  d,  V,  dorsal  and  ventral  branches  ;  sr,  sympathetic  root 
(Ross). 


Longitudinal  section  of  a  spinal  ganglion,    a, 
nerve  fibre  ;  b,  nerve  cells  ;  c,  capsule. 

coursing  longitudinally  between  them  (Fig.  436,  a,  b).  The  nerve  cells  are  usually  globular  in  form, 
with  a  distinct  capsule  Imed  with  epithebum,  and  the  cell  substance  itself  contains  a  well-defined 
nucleus  with  a  nuclear  envelope  and  a  nucleolus.  The  capsule  of  the  cell  is  continuous  with  the 
sheath  of  Schwann  of  a  nerve  fibre.  The  exact  relation  between  the  nerve  fibres  and  the  nerve  cells 
is  difficult  to  establish,  but  it  is  probable  that  each  nerve  cell  is  connected  with  one  nerve  fibre,  i.  e., 
they  are  unipolar.  In  the  spinal  ganglia  of  the  vertebrates  above  fishes,  and  also  in  the  Gasserian 
ganglion,  cells  are  found  with  a  single  process  or  fibre  attached  to  them,  the  nerve  fibre  process  not 
unfrequently  coiling  a  few  times  within  the  capsule.  This  process,  after  emerging  from  the  capsule, 
becomes  coated  with  myelin,  and  usually  soon  divides  at  a  node  of  Ranvier  (Fig.  341,  /).  Ranvier, 
who  first  observed  this  arrangement,  describes  it  as  a  T-shaped  fibre.  These  nerve  cells  with  T- 
shaped  fibres  have  been  observed  in  the  spinal  ganglia  of  all  vertebrates  above  fishes,  in  the  Ciasse- 
rian  and  geniculate  ganglia,  as  well  as  in  the  jugular  and  cervical  ganglia  of  the  vagus.  In  fishes 
the  nerve  cells  of  the  spinal  ganglia  are  bipolar  (Fig.  368,  4).  There  is  a  rich  plexus  of  capillaries 
in  these  ganglia,  and  each  cell  is  surrounded  by  a  meshwork  of  capillaries,  which  never  penetrate 
the  cell  capsules.] 


bell's  law  and  deductions  therefrom.  667 

Bell's  Law. — Sir  Charles  Bell  discovered  (rSii)  that  the  anterior  roots  of 
the  spinal  nerves  are  motor,  the  posterior  are  sensory. 

Recurrent  Sensibility. — Magendie  discovered  (1822)  the  remarkable  fact  that 
sensory  fibres  are  also  present  in  the  anterior  roots,  so  that  their  stimulation  causes 
pain.  This  is  due  to  the  fact  that  sensory  fibres  pass  into  the  anterior  root  after  the 
two  roots  have  joined,  and  these  fibres  run  in  the  anterior  root  in  a  centripetal  direc- 
tion {Schiff,  CI.  Bernard^.  The  sensibility  of  the  anterior  root  is  abolished  at 
once  by  section  of  the  posterior  root.  This  condition  is  called  "recurrent  sensi- 
bility "  of  the  anterior  root.  When  the  sensibility  of  the  anterior  root  is  abolished, 
so  is  the  sensibility  of  the  surface  of  the  spinal  cord  in  the  neighborhood  of  the  root. 
A  long  time  after  section  of  the  anterior,  and  when  the  degeneration  phenomena 
have  had  time  to  develop  (§  325),  a  few  non-degenerated  sensory  fibres  are  always 
to  be  found  in  the  central  stump  {Schiff,  Vulpian').  Schiff  found  that,  in  cases 
where  the  motor  fibres  had  undergone  degeneration,  there  were  always  non-degene- 
rated fibres  to  be  found  in  the  anterior  root,  which  passed  into  the  membranes  of 
the  spinal  cord.  The  sensory  fibres  pass  into  the  motor  root,  either  at  the  angle 
of  union  of  the  roots,  or  in  the  plexus,  or  in  the  region  of  the  peripheral  termina- 
tions. Sensory  fibres  enter  many  of  the  branches  of  the  motor  cranial  nerves  at 
their  periphery,  and  afterward  run  in  a  centripetal  direction  (p.  650).  Even  into 
the  trunks  of  sensory  nerves,  sensory  branches  of  other  sensory  nerves  may  enter. 
This  explains  the  remarkable  observation,  that  after  section  of  a  nerve  trunk  {e.  g., 
the  median),  its  peripheral  terminations  still  retain  their  sensibility  {Arloing  and 
Tripier').  The  tissue  of  the  motor  and  sensory  nerves,  like  most  other  tissues  of 
the  body,  is  provided  with  sensory  nerves  (^IVervi  jzervorum,  p.  580). 

[It  does  not  follow  that  section  of  a  peripheral  cutaneous  nerve  will  cause  anaesthesia  in  the  part 
to  which  it  is  distributed;  in  fact,  one  of  the  principal  nerve  trunks  of  the  brachial  plexus  may  be 
divided  without  giving  rise  to  complete  anaesthesia  in  any  part  of  the  area  of  distribution  of  the  sensory 
branches  of  the  nerve,  and  even  if  there  be  partial  or  complete  cutaneous  anaesthesia,  it  is  much  less 
in  extent  than  corresponds  to  the  anatomical  area  of  distribution.  The  ansesthetic  area  tends  to 
become  smaller  in  extent  [Ross).  Thus,  there  is  not  complete  independence  in  the  distribution  of 
these  nerves.  These  results  are  explained  by  the  anastomosis  between  branches  of  nerves,  the 
exchange  of  fibres  in  the  terminal  networks,  while  some  sensory  fibres  enter  the  peripheral  parts  of  a 
nerve  and  run  centripetally,  perhaps  being  distributed  to  the  skin  and  conferring  recurrent  sensibility 
on  the  peripheral  part  of  the  nerve.] 

Relative  Position  of  Motor  and  Sensory  Fibres. — In  embryos  (rabbit)  the  motor  fibres 
stain  more  deeply  with  carmine  than  the  sensory  fibres,  so  that  their  position  in  the  peripheral  nerves 
of  distribution  may  thereby  be  made  out.  In  the  anterior  branch  of  a  spinal  nerve,  the  sensory 
fibres  lie  in  the  outer  part  of  the  branch,  the  motor  in  the  inner  part ;  while  this  relation  is  reversed 
in  the  posterior  root  (Z.  Lowe). 

Deduction  from  Bell's  Law. — Careful  observations  of  the  effects  of  section 
of  the  roots  of  the  spinal  nerves  {^Magendie,  1822),  as  well  as  the  discovery  of  the 
reflex  relation  of  the  stimulation  of  the  sensory  roots  to  the  anterior,  constituting 
reflex  movements  (^Marshall  Hall,  Johannes  Miiller,  1832),  enables  us  to  deduce 
the  following  conclusions  from  Bell's  law:  i.  At  the  moment  of  section  of  the 
anterior  root,  there  is  a  contraction  in  the  muscles  supplied  by  this  root.  2.  There 
is  at  the  same  time  a  sensation  of  pain  due  to  the  ''  recurrent  sensibility."  3.  After 
the  section,  the  corresponding  muscles  are  paralyzed.  4.  Stimulation  of  the  peri- 
pheral trunk  of  the  anterior  root  (immediately  after  the  operation)  causes  contraction 
of  the  muscles,  and  eventually  pain,  owing  to  the  recurrent  sensibility.  5.  Stimu- 
lation of  the  central  end  is  without  effect.  6.  The  sensibility  of  the  paralyzed  parts 
is  retained  completely.  7.  At  the  moment  of  section  of  the  posterior  root,  there 
is  stwQXQ.  pain.  8.  At  the  same  time  movements  are  discharged  reflexly.  9.  After 
the  section,  all  parts  supplied  by  the  divided  roots  are  devoid  of  sensibility.  10. 
Stimulation  of  the  peripheral  trunk  of  the  divided  nerve  is  without  effect.  1 1 . 
Stimulation  of  the  central  end  csiuses pain  and  reflex  movements.  12.  The  central 
end  ultimately  degenerates.  13.  Movement  is  retained  completely  in  the  paralyzed 
parts,  e.g.,  in  the  extremities. 


668 


INCUCJRDINATED    MOVEMENTS   OE    INSENSIBLE    LIMBS. 


The  ultimate  effect,  known  as  Wallerian  degeneration,  which  follows  section 
of  the  nerve  or  its  roots,  is  referred  to  in  §  325.  Recently,  Joseph  has  slightly 
modified  the  statements  of  Waller  on  the  degeneration  in  the  posterior  roots. 
According  to  him,  the  spinal  ganglion  is  the  nutritive  centre  for  by  far  the  largest 
number  of  the  fibres  of  this  root ;  but  individual  fibres  traverse  the  ganglion  with- 
out forming  connections  with  its  cells,  so  that  the  nutritive  or  trophic  centre  for 
this  small  number  of  nerve  fibres  is  in  the  spinal  cord. 

Incoordinated  Movements  of  Insensible  Limbs. — After  section  of  the  ix)sterior  roots,  e.g., 
of  the  nerves  for  the  ]io.sterior  exlremilies,  the  muscles  retain  their  movements;  nevertheless  there  are 
characteristic  disturbances  of  their  motor  power.     This  is 

expre-sed  in  the  awkward   manner  in  which   the  animal  V\c,.  438. 

executes  its  movement — it  has  lost  to  a  large  extent  iis 
harmony  and  elegance  of  motion.  This  is  due  to  the  fact 
that,  owing  to  the  absence  of  the  sensibility  of  the  muscles 
and  skin,  the  animal  is  no  longer  conscious  of  the  resistance 
which  IS  opposed  to  its  movements.  Hence,  the  degree  of 
muscular  energy  necessary  for  any  particular  effort  cannot 
be  accurately  graduated.  Animals  which  have  lost  the 
sensibility  of  their  extremities  often  allow  their  limbs  to  lie 
in  abnormal  positions,  such  as  a  healthy  animal  would  not 

Fir..  437. 


10  me 
Distribution  of  the  cutaneous  nerves  of  the  arm.  A,  Dorsal  surface 
— /  jf,  supra-clavicular;  5  a.r,  axillary  ;  _yf/j,  superior  posterior 
cutaneous  ;  4  cmd,  median  cutaneous ;  j  cpi,  inferior  posterior 
cutaneous  ;  6  cm,  median  cutaneous  ;  7  cl,  lateral  cutaneous  ; 
^»,  ulnar;  9  ra,  radial;  /o  w/^,  median.  B,  volar  surface — isc, 
supra-clavicular;  2  ax,  axillary;  j  cmtf,  internal  cutaneous; 
4  cl,  lateral  cutaneous  ;  j  cm,  cutaneous  medius  ;  6  me,  median  ; 
7  «,  ulnar. 


Distribution  of  the  cutaneous  nerves  of  the  leg 
{3.her  Henle).  A,  Anterior  surface — i,  crural 
nerve;  2,  external  lateral  cutaneous  ;  3,  ilio- 
inguinal ;  4,  lumbo-inguinal ;  5,  external 
spermatic;  6,  posterior  cutaneous;  7,  obtu- 
rator;  8,  great  saphenous  ;  9,  communicating 
peroneal;  10,  superficial  peroneal ;  11, deep 
peroneal;  12, communicating  tibial.  B,  Pos- 
terior surface — i,  posterior  cutaneous;  2, 
external  femoral  cutaneous;  3,  obturator; 
4,  median  posterior  femoral  cutaneous;  5, 
communicating  peroneal;  6,  great  saphe- 
nous; 7,  communicating  tibial;  8,  plantar 
cutaneous;  9,  median  plantar;  10,  lateral 
plantar. 


tolerate.     In  man  also,  when  the  peripheral  ends  of  the  cutaneous  nerves  are  degenerated,  there  are 
ataxic  phenomena  (?  364,  3). 


FUNCTIONS    OF   THE    SPINAL    ROOTS.  669 

Increased  Excitability. — Harless  (1858),  Ludwig,  and  Cyon  (controverted  by  v.  Bezold, 
Uspensky,.  Griinhagen,  and  G.  Heidenhain)  observed  that  the  anterior  root  is  more  excitable  as  long 
as  the  posterior  roots  remain  intact  and  are  sensitive,  and  that  their  excitability  is  diminished  as  soon 
as  the  posterior  roots  are  divided.  In  order  to  explain  this  phenomenon,  we  must  assume  that,  in  the 
intact  body,  a  series  of  gentle  impulses  (impressions  of  touch,  temperature,  position  of  limbs,  etc.)  are 
continuously  streaming  through  the  posterior  roots  to  the  spinal  cord,  where  they  are  transferred  to 
the  motor  roots,  so  that  a  less  stimulus  is  required  to  excite  the  anterior  roots  than  when  these  reflex 
impulses  of  the  posterior  root,  which  increase  the  excitability,  are  absent.  Clearly,  a  le<s  stimulus 
will  be  required  to  excite  a  nerve  already  in  a  gentle  state  of  excitement  than  in  the  case  cf  a  fibre 
which  is  not  so  excited.  In  the  former  case,  the  discharging  stimulus  becomes,  as  it  were,  superposed 
on  the  excitement  already  present.     (Compare  §  362.) 

The  anterior  roots  of  the  spinal  nerves  supply  efferent  fibres  to — 
T.  All  the  voluntary  muscles  of  the  trunk  and  extremities. 

Every  muscle  always  receives  its  motor  fibres  from  several  anterior  roots  (not  from  a  single  nerve 
root).  Hence,  eveiy  root  supplies  branches  to  a  particular  group  of  muscles  (^Preyer,  P.  Bert,  Gad). 
The  experiments  of  Ferrier  and  Yeo  show  that  stimulation  of  each  of  the  anterior  roots  in  apes 
(brachial  and  lumbo-sacral  plexuses)  caused  a  complex  coordinated  movement.  Section  of  one  root 
did  not  cause  complete  paralysis  of  the  muscles  concerned  in  these  coordinated  movements,  although 
the  force  of  the  movement  was  impaired.  These  experiments  confirm  the  results  of  clinical  observation 
on  man.  The  fibres  for  groups  of  muscles  of  different  functions  [e.g.,  for  flexors,  extensors)  arise 
from  special  limited  areas  of  the  spinal  cord.  The  cervical  and  lumbar  enlargements  of  the  spinal 
cord  are  great  centres  for  highly  coordinated  muscular  movements. 

2.  The  anterior  roots  also  supply  motor  fibres  for  a  number  of  organs  provided 
with  smooth  musctilar  fibres,  e.g.,  the  bladder  (§  280),  ureter,  uterus.  [These  are 
the  viscero-motor  nerves  of  Gaskell,  and  from  them  come  also  viscero-inhibitory 
nerves.] 

3.  Motor  fibres  for  the  smooth  muscular  fibres  of  the  blood  vessels,  the  vaso- 
motor, vaso-constrictor,  or  vaso-hypertonic  nerves  [also  accelerator  or  aug- 
mentor  nerves  of  the  heart].  They  run  in  the  sympathetic  for  a  part  of  their  course 
(§  371). 

4.  Inhibitory  fibres  for  the  blood  vessels.  These  are  but  imperfectly  known. 
They  are  also  called  vaso-dilator  or  vaso-hypotonic  nerves  (§  372).  [Also 
inhibitory  nerves  for  the  heart,  which  leave  the  spinal  axis  in  the  vagus.] 

5.  Secretory  fibres  for  the  sweat  glands  of  the  skin  (§  289).  For  a  part  of 
their  course  they  run  in  the  sympathetic. 

6.  Trophic  fibres  of  the  tissues  (§  342,  I,  c'). 

The  posterior  roots  contain  all  the  sensory  nerves  of  the  whole  of  the  skin 
and  the  internal  tissues,  except  the  front  part  of  the  head,  face,  and  the  internal 
part  of  the  head.  They  also  contain  the  tactile  nerves  for  the  areas  of  the  skin 
already  mentioned.  Stimuli  which  discharge  reflex  movements  are  conducted  to 
the  spinal  cord  through  the  posterior  roots.  The  sensory  fibres  of  a  mixed  nerve 
trunk  supply  the  cutaneous  area,  which  is  moved  by  those  muscles  (or  which  covers 
those  muscles)  to  which  the  same  branch  supplies  the  motor  fibres.  The  special 
distribution  of  the  motor  and  sensory  nerves  of  the  body  belongs  to  anatomy  (Figs. 

429,  43°.  437.  438)- 

[Physiology  of  the  Limb  Plexuses. — The  idea  that  the  nerve  strands  become  rearranged  m 
the  limb  plexuses  so  as  to  connect  nerves  derived  from  different  parts  of  the  spinal  cord  with  particular 
groups  of  muscles,  in  order  to  allow  of  "  coordination  of  muscular  action,"  does  not  seem  to  be  borne 
out  by  more  extended  observation.  Herringham  has  shown  by  dissection  (and  the  same  is  seen  in 
cases  of  paralysis  of  motion  and  sensation)  that  a  given  muscle  or  part  of  a  muscle,  and  a  given  spot 
of  skin,  are  supplied  by  particular  branches  of  individual  spinal  nerves  proceeding  directly  from  the 
spinal  cord.  The  reason  that  the  plexuses  exist  is,  apparently,  not  a  physiological  one.  Coordination 
cannot  be  effected  in  the  plexus,  where  the  axis  cylinders  of  the  nerves  do  not  divide;  but  only  in  the 
spinal  cord  and  central  nervous  system,  and  through  the  intervention  of  nerve  cells.  The  existence 
of  the  plexuses  is  due  to  the  fact  that  embryologically  the  limb  consists  of  a  flattened  lappet,  or  bud, 
derived  from  certain  somites,  but  at  first  presenting  no  signs  of  segmentation,  with  a  pre-axial  and  a 
post-axial  border,  and  outer  (dorsal)  and  inner  (ventral)  surfaces  of  skin,  covering  a  double  layer  of 
muscle  on  each  surface.  The  dorsal  and  ventral  branches  of  the  nerves  supply  these  respective 
surfaces;  and  after  the  nerves  have  grown  out,  the  simple  muscular  strata  become  split  up  mto 
individual  muscles,  which  contain  elements  derived  from  one  or  more  segments  represented  in  the 


670  THE    SYMPATHETIC    NERVE. 

primitive  limb.  Each  nerve  is  segmental,  and,  therefore,  supplies  a  muscle  derived,  for  example,  from 
the  elements  of  two  segments;  the  nerve  of  distribution  must  contani  corresponding  parts  of  two 
segmental  nerves.  The  plexuses  appear,  therefore,  from  an  enibryological  cause,  and  have  no  direct 
physiological  significance  (//.  M.  J'a/i-ison).'] 

356.  THE  SYMPATHETIC  NERVE. —  [Anatomical. — The  sympathetic  nervous  system 
contains  a  large  number  of  non-inedullated  or  Remak's  libres,  and  consists  of  a  series  of  ganglia 
lying  on  each  side  of  the  vertebral  column  and  connected  with  each  other  by  inter-ganglionic  fibres, 
'hie  ty])ical  distribution  obtains  in  the  thoracic  region,  where  the  lateral  or  vertebral  ganglia  lie  close 
on  the  vertebra'.  In  front  of  this  is  a  second  series  of  ganglia,  which  do  not  form  a  double  line,  but 
are  connected  with  the  former  and  with  each  other.  They  are  the  prevertebral  or  collateral  ganglia, 
^.  .,'•.,  semilunar,  inferior  mesenteric,  etc.,  the  nerves  connecting  them  with  the  former  being  called 
rami  eflerentes.  From  these,  fibres  proceed  to  connect  them  with  ganglia  lying  in  or  about  tissues  or 
organs — the  terminal  ganglia  (  Gnsl'ell).'] 

[Each  spinal  nerve  in  this  region  is  connected  with  its  corresponding  sympathetic  ganglion  by  the 
ramus  communicans,  which  is  formed  by  fibres  both  from  the  anterior  and  jiosierior  roots  of  a 
spinal  nerve.  It  corresjTOnds  to  the  visceral  nerve  of  the  lnorpilologi^t,  and  is  composed  of  two  parts 
— a  white  and  a  gray  ramus.  The  white  ramus  is  composed  entirely  of  medullated  fibres,  and 
coming  from  the  anterior  and  po.sterior  roots  of  a  spinal  nerve,  passes  into  the  lateral  and  collateral 
ganglia.  These  white  rami  occur  in  the  dog  only  from  the  2d  thoracic  to  the  2<1  lumbar  nerve  (Fig. 
439).  Above  and  below  this,  the  rami  are  all  gray  and  composed  of  non-medullated  nerve  fibres 
{Gaske//).'\ 

[In  man,  the  four  upper  rami  communicantes  from  the  four  upper  cervical  nerves  all  join  the 
superior  cervical  ganglion  (Fig.  428,  G g,  s),  the  5th  and  6th  join  the  middle  cervical,  the  7th  and 
8th  the  inferior  cervical  ganglion.  The  lowest  pair  of  ganglia  are  generally  united  by  a  loop  on  the 
front  of  the  first  coccygeal  vertebra,  and  they  lie  in  relation  with  the  coccygeal  ganglion.] 

[Cephalic  Portion. — As  the  sympathetic  ascends  to  the  head  it  forms  connections  with  many  of 
the  cranial  nerves,  and  there  is  a  free  exchange  of  fibres  between  these  nerves.  (The  function  and 
significance  of  these  exchanges  are  referred  to  under  the  physiology  of  the  cranial  nerves.)] 

[Dorsal  and  Abdominal  Portion. — Numerous  fibres  pass  into  these  parts  chiefly  to  the  thoracic 
and  abdominal  cavities,  where  they  form  large  gangliated  plexuses,  from  which  functionally  different 
fibres  proceed  to  the  different  organs.] 

[In  the  dog,  the  2d,  3d,  4th,  and  5th  thoracic  pass  upward  into  the  cervical  sympathetic,  those 
in  the  dorsal  region  being  directed  downward  from  the  lateral  ganglia  to  form  the  splanchnics 
(Fig.  439).  The  gray  non-medullated  nerve  fibres  of  each  gray  ramus  are  connected  with  the  cells 
of  its  ganglion  (lateral) ;  the  fibres  do  not  go  beyond  the  ganglion,  but  really  run  to  the  corresponding 
spinal  nerve  to  ramify  in  the  sheaths  of  the  nerves,  the  connective  tissue  on  the  vertebra-  and  the  dura 
mater,  and  perhaps  the  other  spinal  membranes;  .so  that,  according  to  Gaskell.no  non-medullated 
nerves  leave  the  central  nervous  system  by  the  spinal  nerve  roots.  Thus,  the  white  rami  communi- 
cantes alone  constitute  the  rami  viscerales  of  the  inoqjliologist,  and  all  the  visceral  nerves  passing  out 
from  the  central  nervous  system  into  the  sympathetic  system  pass  out  by  them  alone.  All  the  nerves 
in  the  white  ramus  aie  of  small  calibre  (1.8  /i  to  2.7  //)  and  medullated,  while  the  true  motor  fibres 
are  much  larger  (14.4/^10  19 /v).  The  small,  white  fibres  can  be  traced  upward  as  medullated 
fibres  into  the  .superior  cervical  ganglion,  and  in  the  thorax  over  the  lateral  ganglia  to  form  the 
splanchnics  into  the  collateral  ganglia,  beyond'which  they  cease  to  be  medullated.  15y  the  2d  and 
3d  sacral  nerves  .some  fibres  of  smallest  calibre  issue  to  form  the  nervi  erigentes,  which  pass  over 
and  do  not  communicate  with  the  lateral  ganglia,  but  enter  the  hyiwgastric  plexus,  whence  they  send 
branches  upward  to  the  inferior  mesenteric  plexus  and  downward  to  the  bladder,  rectum,  and  genera- 
tive organs.     Ga.skell  proposes  to  call  them  the  pelvic  splanchnic  nerves  (Fig.  439)-] 

[In  the  cervical  region,  there  is  no  white  ramus,  and  the  nerve  roots  contain  no  nerve  fibres  of 
small  calibre.  But  in  this  region  rises  the  spinal  accessory  nerve,  between  the  anterior  and 
posterior  roots.  It  contains  small  and  large  nerve  fibres;  the  former  pass  into  the  internal  division 
of  this  nerve  and  join  the  ganglion  of  the  trunk  of  the  vagus,  while  the  large  motor  fibres  form  its 
external  branch  and  supply  the  sterno-mastoid  and  trapezius  muscles.] 

[All  the  vasomotor  nerves  arise  in  the  central  nervous  system,  and  they  leave  the  spinal  cord 
as  the  finest  medullated  fibres  in  the  anterior  roots  of  all  the  spinal  nerves  between  the  2d  thoracc 
and  2d  lumbar  (dog)  "  along  the  corresponding  ramus  visceralis,  enter  the  lateral  or  main  sympathetic 
chain  of  ganglia,  where  they  become  non-medullated,  and  are  thence  distributed  either  directly  or 
after  communication  with  other  ganglia  "  (  Gaskell).'\ 

[The  vaso-dilator  nerves  leave  the  central  nervous  system  among  the  fine  medullated  fibres, 
which  help  to  form  the  cervico-cranial  and  sacral  rami  viscerales,  and  pass  without  altering  their 
character  into  the  dis'al  ganglia  (Gaskell).'] 

['•  The  visceromotor  nerves  upon  which  the  peristaltic  contraction  of  the  thoracic  portion  of  the 
cesophagus,  stomach,  and  intestines  depends,  leave  the  central  nervous  system  in  the  outflow  of  fine 
medullated  nerves  which  occurs  in  the  upper  part  of  the  cervical  region,  and  pass  by  way  of  the 
rami  viscerales  of  the  accessory  and  vagus  nerves  to  the  ganglion  Irunci  vagi,  where  they  become 
non-medullated  "  [Gaske/l).'\ 


THE    SYMPATHETIC    NERVE. 


671 


s     > 

5  S  a 

.Ht3  u 


H  S.2 


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w 


M 


f"  The  inhibitory  nerves  of  the  circular  muscles  of  the  alimentary  canal  and  its  appendages 
leave  the  central  nervous  system  in  the  anterior  roots,  and  pass  out  among  the  fine  medullated  fibres 
of  the  rami  viscerales  into  the  distal  ganglia  without   communication  with  the  proximal  ganglia" 

[Structure  of  a  Ganglion.— The  structure  _  ^  ■t^  5i  c 

of  the  sympathetic  nerve  fibres  and  nerve  cells 
has  already  been  de-cribed  in  ^321.  On  mak- 
ing a  section  of  a  sympathetic  ganglion, 
e.  g.,  the  human  superior  cervical,  we  observe 
groups   of  cells   with  bundles  of  nerve   fibres 

chiefly     non- medullated — running     between 

them,  and  the  whole  surrounded  by  a  laminated 
capsule  of  connective  tissue,  which  sends  septa 
into  the  ganglion.  The  nerve  cells  have 
many  processes,  and  are,  therefore,  multipolar, 
and  each  cell  is  surrounded  by  a  capsule  with 
nuclei  on  its  inner  surface  (Fig.  368,  II).  The 
processes  pierce  the  capsule,  and  one  of  them 
certainly — and  perhaps  all  the  processes — aie 
connected  with  a  nerve  fibre.  Ranvier  states 
that  each  cell  has  a  fibrillated  outer  portion  and 
a  more  granular  inner  part.  Each  of  the  pro- 
cesses becomes  continuous  with  a  fibre  of  Re- 
mak.  Not  unfrequently  yellowish-brown  pig- 
ment is  found  in  the  cell  substance.  Similar 
cells  have  been  found  in  the  ophthalmic,  sub- 
maxillary, otic,  and  spheno-palatine  ganglia. 
The  number  of  medullated  nerve  fibres  dimin- 
ishes as  the  sympathetic  nerves  are  traced 
toward  their  distribution.  Ranvier  states  that 
it  is  possible  in  the  rabbit  to  trace  the  conversion  ^ 
of  a  medullated  fibre  into  a  branched  fibre  of  "^J" 
Remak.  The  blood  vessels  of  the  sympa-  o 
thetic  ganglia  in  mammals  are  pecuhar.  The  fe 
arteries  are  small,  and  after  subdivision  form 
a  capillary  network,  each  mesh  of  which  en- 
closes several  ganglionic  cells.  The  veins,  on 
the  contrary,  are  very  large,  tortuous,  varicose, 
and  often  terminate  in  culsde-sac,  into  which 
several  capillaries  open.  The  arrangement  of 
the  veins  is  spoken  of  as  the  venous  sinuses 
of  these  ganglia,  being  compared  by  Ranvier 
to  the  sinuses   of  the  dura  mater  and  venous  ^ 

plexuses  of  the  spinal  canal.]  :| 

Functions.  —  The     following     is  t! 

merely  a  general  summary  : —  .| 

I.  Independent    Functions    of  | 

the   sympathetic  are   those  of  certain  t 

nerve  plexuses  which   remain  after  all  |  a 

the    nervous    connections    with     the  cb  ^ 

cerebro-spinal  branches  have  been  di-  |  (S 

vided.     The  activities  of  these  plexuses  |  | 

may  be  influenced — either  in  the  direc-  |  _ 

tion    of    inhibition    or    stimulation —  | 

through  fibres  reaching  them  from  the  '^ 

cerebro-spinal  nerves.  -■-.■•^^  m 

To  these  belong  : — 

1.  The  automatic  gangha  of  the  heart  _(§  58). 

2.  The  mesenteric  plexus  of  the  intestine  (§  161).  ^      .^     a       a 

3.  The  plexuses  of  the  uterus,  Fallopian  tubes,  ureters  (also  of  the  blood  ana 

lymph  vessels).  .        ,  •  ,     /n      +.1,^ 

II.  Dependent  Functions.— Fibres  run  in  the  sympathetic,  which  (like  the 


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cj  u  ca 


S  u  G  13 


672  THORACIC    AND    ABDOMINAL   SYMPATHETIC. 

j)eripheral  nerves)  are  active  only  when  their  connection  with  the  central  nervous 
system  is  maintained,  e.g.,  the  sensory  fibres  of  the  splanchnic.  Others  again  con- 
vey impulses  from  the  central  nervous  system  to  the  gang/ia,  while  the  ganglia  in 
turn  modify  the  impulses  which  inhibit  or  excite  the  movements  of  the  correspond- 
ing organs. 

The  following  statement  is  a  restinic  of  the  functions  of  the  sympathetic,  according  to  the  anatomi- 
cal arrangement : — 

A.  Cervical  Part  of  the  Sympathetic,  i.  Pupil-dilating  fibres  (com- 
l)arc  Ciliary  ganglion,  %  347,  I,  and  Iris,  %.  392).  According  to  Budge,  these  fibres 
arise  from  the  spinal  cord,  and  run  through  the  upper  two  dorsal  and  lowest  two 
cervical  nerves  into  the  cervical  sympathetic,  which  conveys  them  to  the  head. 
Section  of  the  cervical  synijjathetic  or  its  rami  commimicantes  causes  contraction 
of  the  pupil.  (The  central  origin  of  these  fibres  is  referred  to  in  §  362,  i,  and  § 
367,  S.) 

2.  Motor  fibres  tor  Miiller's  smooth  muscle  of  the  orbit,  and  partly  for  the 
external  rectus  muscle  (§  348). 

3.  Vasomotor  branches  for  the  outer  ear  and  the  side  of  the  face  {CI.  Bernard^, 
tympanum  (Frussak),  conjunctiva,  iris,  choroid,  retina  {only  in  part — see  Ciliary 
ganglion,  §  347,  I),  for  the  vessels  of  the  oesophagus,  larynx,  thyroid  gland — fibres 
for  the  vessels  of  the  brain  and  its  membranes  {Donders  and  Callen/els). 

4.  In  the  cervical  portion  are  afferent  fibres  which  excite  the  vasomotor  centre 
in  the  medulla  {Aubert'). 

5.  Secretory  ( troi>hic)  and  vasomotor  fibres  for  the  salivary  glands  (§  145). 

6.  Sweat-secretory  fibres  (see  §  288,  II). 

7.  According  to  Wolferz  and  Demtschenko  the  lachrymal  glands  receive  sympa- 
thetic secretory  fibres  (?). 

B.  Thoracic  and  Abdominal  Sympathetic. — First  of  all  there  is — 

1.  The  s\mi)athetic  portion  of  the  cardiac  plexus  (§  57,  2),  which  receives 
accelerating  or  augmentor  fibres  for  the  heart  from  the  lower  cervical  and  ist 
thoracic  ganglion  {CI.  Bernard,  v.  Bezold,  Cyon,  Schmiedeberg).  The  fibres  arise 
partly  from  the  sympathetic  and  partly  from  the  plexus  around  the  vertebral  artery 
{v.  Bezold,  Bever^.     (Compare  §  370.) 

2.  For  the  vasomotor  fibres  passing  through  the  sympathetic  to  the  extremities, 
skin  of  the  trunk,  and  lungs  (see  §  371).     For  vaso-dilators  (§  472). 

3.  The  cervical  sympathetic  and  the  splanchnic  contain  fibres  which,  when  their 
central  ends  are  stimulated,  excite  the  cardio-inhibitory  system  in  the  medulla 
oblongata  {Bernstein). 

4.  The  functions  of  the  splanchnic  are  referred  to  in  §§  164,  175,  276,  and  371. 

5.  The  functions  of  the  coeliac  and  mesenteric  plexuses  are  referred  to  in 
§§  183  and  192.  After  extirpation  of  the  coeliac  ganglion,  Lamansky  observed 
temporary  disturbance  of  digestion,  undigested  food  being  passed  per  anum. 

6.  For  the  secretory  fibres  for  sweating,  see  §  289,  II. 

7.  Lastly,  the  abdominal  portion  of  the  sympathetic  contains  motor  and  vaso- 
motor fibres  for  the  spleen,  the  large  intestine  (accompanying  its  arteries),  bladder 
(§  280),  jireters,  uterus  (running  in  the  hypogastric  plexus),  vas  deferens,  and  vesi- 
culse  seminales.  Stimulation  of  all  of  these  nerve  channels  causes  increased  move- 
ment of  the  organs,  but  it  must  be  remembered  that  the  diminished  supply  of  blood 
thereby  produced  also  acts  as  a  stimulus  (§  161).  Section  of  these  nerves  is  fol- 
lowed by  dilatation  of  the  blood  vessels,  with  subsequent  derangement  of  the 
circulation,  and  ultimately  of  the  nutrition.  The  relation  of  the  suprarenal 
bodies  to  the  sympathetic  is  referred  to  in  §  103,  IV.  The  renal  plexus  is 
referred  to  in  §  276,  while  the  cavernous  plexus  is  treated  of  in  §  436. 

Pathological. — Considering  the  numerous  connections  of  the  sympathetic,  we  would  naturally 
suppose  that  it  offers  an  extensive  area  for  pathological  changes.  Affections  involving  the  vaso- 
motor system  are  referred  to  in  \  371. 


SECTION    OF   THE    CERVICAL    SYMPATHETIC.  673 

The  cervical  sympathetic  is  most  frequently  paralyzed  or  stimulated  by  traumatic  conditions, 
wounds  by  bullets  or  knives,  tumors,  enlarged  lymph  glands,  aneurisms,  inflammations  of  the  apices 
of  the  lungs  and  the  adjacent  pleurae,  while  exostoses  of  the  vertebrcie  may  stimulate  it  in  part  or 
paralyze  it  in  part.  The  phenomena  so  produced  have  been  partly  analyzed  in  treating  of  the  ciliary 
ganglion  (§  347,  I).  Stimulation  of  the  cervical  sympathetic  in  man  causes  dilatation  of  the 
pupil  (mydriasis  spastica),  pallor  of  the  face,  and  occasionally  hyperidrosis  or  profuse  sweating 
(I  289,  2,  and  I  288) ;  disturbance  of  vision  for  near  objects,  as  the  pupil  cannot  be  contracted  (see 
AccofUfnodation),  and  hence  the  spherical  aberration  of  the  lens  (|  391)  must  also  interfere  with 
vision;  protrusion  of  the  eyeball  with  widening  of  the  palpebral  fissure.  Paralysis  or  section  of 
the  cervical  sympathetic  causes  increased  fullness  of  the  blood  vessels  of  the  side  of  the  head, 
with  occasional  anidrosis ;  contraction  of  the  pupil  (myosis  paralytica),  which  undergoes  changes 
in  its  diameter  during  accommodation,  but  not  as  the  effect  of  the  stimulation  of  light — atropin 
dilates  it  slightly.  The  slit  between  the  eyelids  is  narrowed,  the  eyeball  retracted  and  sunk  in  the 
orbit,  the  cornea  somewhat  flattened,  and  the  consistence  of  the  eyeball  diminished.  Stimulation  of 
the  sympathetic  is  followed  by  an  increased  secreiion  of  saliva  (|  145)-  The  above-described  symp- 
toms have  been  occasionally  accompanied  by  unilateral  atrophy  of  the  face. 

[Section  of  the  Cervical  Sympathetic. — This  experiment  is  easily  done  on 
a  rabbit,  preferably  an  albino  one.  Divide  tiie  nerve  in  the  neck,  and  immediately 
thereafter  (i)  the  ear  and  adjoining  parts  on  that  side  become  greatly  congested 
with  blood,  blood  vessels  appear  that  were  formerly  not  visible,  and  as  a  result  of 
the  increased  quantity  of  blood  in  the  ear  (hypersemia),  there  is  (2)  a  rise  of  the 
temperature  amounting  to  even  4°  to  6°  C.  (C/.  Bernard).  These  are  the  vaso- 
motor changes.  (3)  The  pupil  is  contracted,  the  cornea  flattened,  and  there  is 
retraction  of  the  eyeball  and  consequent  narrowing  of  the  palpebral  fissure.  These 
are  the  ocuh-pupillary  sym'ptoms.  Stimulation  (electrical)  of  the  peripheral  end 
produces  the  opposite  results, — pallor  of  the  ears,  owing  to  contraction  of  the  blood 
vessels,  with  consequent  fall  of  the  temperature ;  dilatation  of  the  pupil,  bulging 
of  the  cornea,  protrusion  of  the  eyeball  (exophthalmos),  and  widening  of  the 
palpebral  fissure.  At  the  same  time,  the  blood  vessels  to  the  salivary  glands  are 
contracted,  and  there  is  a  secretion  of  thick  saliva.  The  last  results  are  due  to 
the  vaso-constrictor  and  secretory  fibres.  The  vasomotor  and  oculo-pupillary 
fibres,  although  they  lie  in  the  same  trunk  in  the  neck,  do  not  issue  from  the  cord 
by  the  same  nerve  roots ;  the  latter  come  out  of  the  cord  with  the  anterior  roots 
of  the  ist  and  2d  dorsal  nerves  (dog),  while  section  of  the  cord  between  the  2d 
and  4th  dorsal  vertebrae  produces  the  vasomotor  changes  only.  The  nasal  mucous 
membrane  and  lachrymal  gland  are  influenced  by  the  sympathetic] 

[Division  of  the  cervical  sympathetic  in  young,  groiving  animals  results  in  hypertrophy  of  the 
ear  and  increased  growth  of  the  hair  on  that  side  [Bidde?-,  IV.  Siirling).'] 

[The  vago-sympathetic  nerve  (dog)  in  the  neck  contains  vaso-dilator  fibres  (really  in  the 
sympathetic)  for  the  skin  and  mucous  membranes  of  that  side  of  the  head.  Weak  stimulation  of  the 
central  end  of  the  sympathetic  causes  dilatation  of  the  blood  vessels  of  these  parts.  The  vaso-dilator 
fibres  of  the  superior  maxillary  nerve  probably  come  from  the  same  source.  The  centre  for  these 
nerves  is  in  the  dorsal  region  of  the  cord  between  the  ist  and  5th  dorsal  vertebrse,  where  the  fibres 
pass  out  with  the  rami  communicantes  to  enter  the  cervical  sympathetic  {Dastra  and  Morai).  The 
vaso-dilator  fibres  occiur  in  the  posterior  segment  of  the  ring  of  Vieussens,  and  when  they  are  stimu- 
lated after  section  of  the  7th  cranial  nerve,  there  is  a  "  pseudo-motor  "  effect  on  the  muscles  of  the 
cheek  and  lip  (|  349).] 

Irritation  in  the  area  of  the  splanchnic,  as  occurs  occasionally  in  lead  poisoning,  is  characterized 
by  violent  pain  (lead  colic),  inhibition  of  the  intestinal  movements  (hence  the  persistent  constipation), 
slowing  of  the  heart's  action,  brought  about  reflexly,  just  as  in  Goltz's  "tapping"  experiment 
(§  369).  Irritation  in  the  area  of  the  sensory  nerves  of  the  sympathetic  may  give  rise  to  that  con- 
dition which  is  called  by  Romberg  neuralgia  hypogastrica,  a  painful  affection  of  the  lower  abdominal 
and  sacral  regions,  hysteralgia,  neuralgia  testis,  which  are  locaUzed  in  the  plexuses  of  the  sympathetic. 
In  affections^of  the  abdojninal  sympathetic,  there  may  be  severe  constipation,  with  diminished  or 
increased  secretion  of  the  intestinal  glands  (|  186). 

357.  COMPARATIVE— HISTORICAL. — Comparative. — Some  of  the  cranial  nerves 

may  be  absent,  others,  again,  may  be  abortive,  or  exist  as  branches  of  other  nerves.  The  facial 
nerve,  which  supplies  the  muscles  of  expression  in  man,  and  is,  at  the  same  time,  the  nerve  for  facial 
respiratoi-y  movements,  diminishes  more  and  more  in  the  lower  classes  of  the  vertebrata,/ar?/aj-K< 
with  the  diminution  of  the  facial  muscle.     In  birds  and  reptiles,  it  supplies  the  muscles  of  the 

43 


674 


COMPARATIVE    AND    HISTORICAL. 


hyoid  bone,  or  the  superficial  cervical  muscles  of  the  nape  of  the  neck.  In  amphibians  (frog),  the 
facial  no  longer  exists  as  a  separate  nerve,  the  nerve  which  corresponds  to  it  sj'jringing  from  the 
trigeminus.  In  fishes,  the  5th  and  7lh  nerves  form  a  joint  complex  nerve.  The  part  corresponding 
to  the  facial  (also  called  ramus  opercularis  trigemini)  is  the  chief  motor  nerve  of  the  muscles  of  the 
gill  cover,  and  is,  therefore,  the  respiratory  nerve.  In  the  cyciostomata  (lamprey)  there  is  an  inde- 
pendent lacial.  The  2'<i:^'us  is  present  in  all  vertehrata ;  in  fishes  it  gives  ofi"  a  large  nerve,  the  lateral 
nene  of  the  body  (N.  lateralis),  which  runs  along  each  side  of  the  body  close  to  the  lateral  canal. 
It  is  also  present  in  the  tadpole.  Its  rudimentary  representative  in  man  is  the  auricular  branch.  In 
the  frog,  the  9th,  loth,  and  I  Ith  arise  together  from  one  trunk,  and  the  7th  and  Sth  from  another.  In 
tishes  and  amphibia,  the  hypoglossal  is  the  tirsl  cervical  nerve.  In  amphioxus,  the  cerebral  and 
spinal  nerves  are  not  distinct  from  each  other.  The  spinal  nerves  are  remarkably  similar  in  all 
classes  of  the  vertebrata.  The  sympathetic  is  absent  in  the  cyciostomata,  where  it  is  represented 
by  the  vagus.  Its  course  is  along  the  vertebral  column,  where  it  receives  the  rami  communicantes  of 
the  spinal  nerves.  In  the  region  of  the  head  its  connections  with  the  5th  and  loth  nerves  are 
speciallv  developed.  In  fiogs,  and  still  more  so  in  birds,  the  number  of  connections  with  the  cranial 
nerves  increases. 

Historical. — The  vagus  and  sympathetic  were  known  to  the  Hippocratic  School.  According 
to  Erasistratus,  all  the  nerves  proceed  from  the  brain  and  spinal  cord;  Herophilus  was  the  first  to 
distinguish  the  nerves  from  the  tendons,  which  Aristotle  confounded  with  each  other.  Marianus, 
(80  A.  D.)  recognized  seven  pairs  of  cranial  nerves.  Galen  was  in  possession  of  a  wide  range  of 
important  facts  in  the  physiology  of  the  nervous  system  (§  140) ;  he  observed  that  loss  of  voice 
followed  ligature  of  the  recurrent  nerves;  and  he  was  acquainted  with  the  accessorius,  and  the 
ganglia  on  the  abdominal  nerves.  The  Cauda  ecpina  is  referred  to  in  the  Talmud;  Coiter  (1573) 
described  exactly  the  anterior  and  posteiior  spinal  nerve  roots.  Van  Helmont  (f  1644)  states  that 
the  peripheral  motor  nerves  also  give  rise  to  impressions  of  pain,  and  Cesalpinus  (1 571)  remarks  that 
interrujition  of  the  blood  stream  makes  the  parts  insensible.  Thomas  Willis  described  the  chief 
ganglia  (1664).  In  Des  Cartes  there  is  the  first  indication  of  reflex  movements  ;  Steven  Hales  and 
Robert  Whytt  showed  that  the  spinal  cord  was  necessary  for  such  acts,  IVochaska  described  the 
reflex  channels  [while  Marshall  Hall  established  the  doctrine  of  reflex,  or,  as  he  called  them,  "  dias- 
taltic  "  actions].  Duvemey  (i  761)  discovered  the  ciliary  ganglion,  (iall  traced  more  carefully 
the  course  of  the  3d  and  6tli  nerves,  and  also  the  spinal  nerves  into  the  gray  matter.  Hitherto 
only  nine  nerves  of  the  biain  had  been  enumerated;  Sommerring  (1791)  separated  the  facial  from 
the  auditory  nerve,  Andersch  (1797)  the  9th,  loth,  and  I  Ith  nerves. 


Physiology  of  the  Nerve  Centres. 


358.  GENERAL. — [The  nerve  fibres  and  nerve  cells  constitute  the  elements 
out  of  which  nerve  centres  are  formed,  being  held  together  by  connective  tissue. 
In  the  process  of  evolution,  groups  of  nerve  cells  with  connecting  fibres  are 
arranged  to  constitute  nervous  masses,  whereby  there  is  a  corresponding  integration 
of  function.  Thus,  with  structural  integration  there  is  a  functional  integration. 
When  the  structure  suffers  so  also  does  the  function,  and  those  parts  which  are  most 
evolved,  as  well  as  those  actions  which  have  to  be  learned  by  practice,  are  the  first 
to  suffer  during  the  dissolution  of  the  nervous  system.] 

General  Functions. — The  central  organs  of  the  nervous  system  are  in  general 
characterized  by  the  following  properties  : — 

1.  They  contain  nerve  cells,  which  are  either  arranged  in  groups  in  the  interior 
of  the  central  organs  of  the  nervous  system,  or  embedded  in  the  peripheral  branches 
of  the  nerves.  [Nerve  cells  are  centres  of  activity,  originate  impulses  and  conduct 
impulses  as  well,  while  nerve  fibres  are  chiefly  conductors.] 

2.  The  nerve  centres  are  capable  of  discharging  reflexes,  e.g.,  reflex  motor, 
reflex  secretory,  and  reflex  inhibitory  acts. 

3.  The  centres  may  be  the  seat  of  automatic  excitement,  i.e.,  they  may 
manifest  phenomena,  without  the  application  of  any  apparent  external  stimulus. 
The  energy  so  liberated  may  be  transferred  to  act  upon  other  organs.  This  auto- 
matic state  of  excitement  or  stimulation  may  be  continuous,  i.e.,  may  be  continued 
without  interruption,  when  it  is  called  tonic  automatic  or  tonus  ;  or  it  may  be 
intermittent  and  occur  with  a  certain  rhythm  (rhythmical  automatic). 

4.  The  central  organs  are  trophic  centres  for  the  nerves  proceeding  from  them  ; 
they  may  also  perform  similar  functions  for  the  tissues  innervated  by  them. 

5.  The  psychical  activities  are  dependent  upon  an  intact  condition  of  the 
ganglionic  central  organs.  These  various  functions  are  distributed  over  different 
centres. 

[The  term  "  centre  "  is  merely  applied  to  an  aggregation  of  nerve  cells  so  related  to  each  other 
as  to  subserve  a  certain  function,  but,  inasmuch  as  these  cells  are  connected  to  each  other  and  with 
other  cells  in  many  ways,  various  combinations  of  them  may  result;  again,  we  have  also  to  take  into 
account  the  greater  or  less  resistance  in  some  paths  than  in  others,  so  that  the  variety  of  combinations 
which  these  cells  may  subserve  is  enormous.  These  cells  give  off  processes  which  branch,  and  anas- 
tomose with  processes  from  other  cells.  Thus,  innumerable  ways  are  opened  up  to  nervous  impulses 
by  these  combinations,  so  that  in  a  certain  way  we  may  regard  a  cell  as  a  junction  of  these  conduct- 
ing fibres,  or  a  "  shunt "  whereby  an  impulse  may  be  shunted  on  to  one  or  other  branch  in  the  direc- 
tion of  least  resistance,  or  in  the  best  beaten  path  as  it  were,  while  there  may  be  a  "  block  "  in  other 
directions.] 

[In  connection  with  the  histology  of  the  central  nervous  system  we  have  to 
study:  — 

A.  The  nervous  constituents.         B.  Non-nervous  constituents. 

(i)  Nerve  fibres.  (i)  Vessels  (blood  and  lymph). 

(2)  Nerve  cells.  (2)  Epithelium. 

(3)  Sustentacular  tissue. 


675 


{a)  Connective  tissue. 
{F)  Neuroglia.] 


THE   SPINAL   CORD. 


359.  STRUCTURE    OF    THE    SPINAL    CORD.— [The  key  to  the 

study  of  the  central  nervous  system  is  to  remember  that  it  begins  as  an  involution 
of  the  epiblast,  and  is  originally  tubular,  with  a  central  canal,  dilated  in  the  brain 
end  into  ventricles.  In  the  spinal  cord  there  are  three  concentric  parts:  first,  the 
columnar  ciliated  epithelium,  outside  this  the  central  gray  tube,  and  covering  in 
all,  the  outer  white  conducting  fibres  {Hi7l).~\ 

Structure. — The  spinal  cord  consists  of  white  matter  externally  and  gray  matter  internally. 
[It  is  invested  by  membranes — the  pia  mater,  composed  of  two  layers  and  consisting  of  con- 
nective tissue  with   blood  vessels,  being    firmly  adherent  to  the  white  matter  and  sending  septa  into 


P       P  P         P 

Transverse  section  of  the  spinal  cord  ;  in  the  centre  is  the  butterfly  form  of  the  gray  matter  surrounded  by  white 
matter.  /,  posterior,  and  a,  anterior,  horns  of  the  gray  matter;  PR,  posterior  roots  ;  AR,  anterior  roots  of  a 
spinal  nerve  ;  A,  A,  the  white  anterior  ;   L,  L,  the  lateral ;  P,  P,  the  posterior  columns. 


the  substance  of  the  cord.  Both  layers  dip  into  the  anterior  median  fissure,  and  only  the  inner  one 
into  the  posterior  median  groove.  The  arachnoid  is  a  more  delicate  membrane  and  non-vascular, 
while  the  dura  mater  is  a  tough  membrane  linin<j;  the  vertebral  canal,  and  forming  a  theca  or  pro- 
tective coat  for  the  cord  {§  3S1).]  The  gray  mater  has  the  form  of  two  crescents  )-(  placed  back 
to  back  [or  a  capital  H],  in  which  we  can  distinguish  an  anterior  {a)  and  a  posterior  horn  (/), 
a  middle  part,  and  a  gray  commissure  conneciing  the  two  crescents.  In  the  centre  of  this  gray 
commissure  is  a  canal — central  canal — which  runs  from  the  calamus  scriptorius  downward ;  it  is 
lined  throughout  by  a  single  layer  of  ciliated  cylindrical  epithelium  [in  the  foetus,  the  cilia  not  being 
visible  in  the  adult],  and  the  canal  itself  is  the  representative  of  the  embryonal  "medullary  tube" 
(Figs.  440,  446).  [The  part  of  the  graj' commissure  in  front  of  this  canal  is  called  the  anterior, 
and  the  part  behind,  the  posterior  gray  commissure.  In  front  of  the  gray  commissure,  and 
between  it  and  the  base  of  the  anterior  median  fissure,  are  bundles  of  white  nerve  fibres  passing 
in  a  horizontal  or  oblique  direction  from  the  anterior  column  of  one  side  to  the  gray  matter  of 

676 


STRUCTURE    OF   THE    WHITE    AND    GRAY    MATTER. 


677 


the  anterior  cornu  of  the  opposite  side  (Fig.  440).     These  decussating  fibres  constitute  the  white 
commissure.] 

The  white  matter  surrounds  the  gray,  and  is  arranged  in  several  columns  [anterior,  lateral 
and  posterior — by  the  passage  of  the  nerve  roots  to  the  cornua  (Figs.  440,  446)].  Along  the 
anterior  surface  of  the  cord  tliere  runs  a  well-marked  fissure,  which  dips  into  the  cord  itself,  but  does 
not  reach  the  gray  matter,  as  a  mass  of  white  matter — the  white  commissure — i-uns  from  one  side 
of  tlie  cord  to  ihe  other.  Between  this  fissure,  known  as  the  anterior  median  fissure,  and  the 
line  of  exit  of  the  anterior  roots  of  the  spinal  nerves,  lies  the  anterior  column  (A) ;  the  white  matter 
lying  laterally  between  the  origin  of  the  anterior  and  posterior  roots  of  the  spinal  nerves  is  the  lateral 
column  (L),  while  the  white  matter  lying  between  the  line  of  origin  of  the  posterior  roots  and  the 
so-called  posterior  median  fissure,  is  the  posterior  column  (P).  [The  posterior  median  fissure 
is  not  a  real  fissure,  but  is  filled  up  with  the  inner  layer  of  the  pia  mater,  which  dips  down  from  the 
under  surface  of  this  membrane  quite  to  the 


gray  matter  of  the  posterior  commissure.] 
Each  posterior  column,  in  certain  regions  of 
the  cord,  may  be  subdivided  into  an  inner 
part  lying  ne.xt  the  fissure,  the  postero- 
median or  Goll's  coliunn,  or  the  inner  root 
zone  {^Charcot,  Fig.  454,1:);  and  an  outer 
larger  part  next  the  posterior  root,  known  as 
the  postero-external  or  Biirdac/i's  cohwin, 
or  the  oilier  root  zone  [Charcot,  Fig.  454,  d). 

Fig.  441. 


Fig.  442. 


Fig.  441. — Transverse  section  of  the  white  matter  of  the  cord  ;  X  150.  ci,  peripheral  layer.  Besides  the  transverse 
sections  of  the  nerve  fibres,  large  and  fine,  there  are  three-branched  connective-tissue  corpuscles  (c). 

Fig.  442. — Multipolar  nerve  cells  from  the  gray  matter  of  the  anterior  horn  of  the  spinal  cord  (ox),  a,  nerve  cell; 
b,  axis  cylinder;  c,  gray  matter;  d,  white  matter  of  column;  e,  e,  branches  of  cells. 

The  white  matter  consists  chiefly  of  medullated  fibres  without  the  sheath  of  Schwann  and  Ran- 
vier's  nodes,  but  provided  with  the  neuro-keratin  sheaths  of  Kiihne  and  Ewald  (§  321),  the"fibres 
themselves  being  chiefly  arranged  longittidinally .     [The  incisures  of  Schmidt  exist  in  these  fibres, 

Fig.  443. 


1                          1 

j 

1 

^- --J 

■ 

•■^---'^X       ■  • AX 

/             A-^''~ 

'^-^..^ 

1                                           Ahs 

I  V  IV  m  u  L  ^  iv:  M  ji  I  xa  Ti  K  iXTmiYVTr  y  jv  m  n  I  vm  yayi  v  TV  m  n   1 
Sacral       Lumhar                          Bomal           ^,                   Cer\)ical 

Diagram  of  the  absolute  and  relative  extent  of  the  gray  matter,  and  of  the  white  columns  in  successive  sectional 
areas  of  the  spinal  cord,  as  well  as  the  sectional  areas  of  the  several  entering  nerve  roots.  NR,  nerve  roots; 
AC,  LC,  PC,  anterior,  lateral,  and  posterior  columns  ;  Gr,  gray  matter. 


andean  be  demonstrated  by  the  interstitial  injection  of  osmic  acid  (Ranvier).]  The  nerve  fibres  of 
the  nerve  roots,  as  well  as  those  that  pass  from  the  gray  matter  into  the  columns,  have  a  transverse 
or  oblique  course.     There  are  also  decussating  fibres  in  the  anterior  or  white  commissure.     [In  a 


678 


ARRANGEMENT   OF   NERVE    CELLS. 


l-'u:.  444. 


transverse  section  of  the  white  matter  of  the  spinal  cord,  the  nerve  fibres  are  of  different  sizes,  and 
appear  like  small  circles  with  a  rounded  dot  in  their  centre — the  axis  cylinder — the  latter  may  be 
stained  with  carmine  or  other  dye  (Fig.  441)-  They  are  smallest  in  the  postero-median  or  Goll's 
column,  and  largest  in  the  crossed  and  direct  pyramidal  tracts,  which  are  motor.  The  white  sub- 
stance of  Sclnvann,  especially  in  preparations  hardenetl  in  sails  of  chromium,  often  presents  the 
appearance  of  concentric  lines.  Fine  septa  of  connective  tissue  carrying  blood  vessels  lie  between 
groups  of  the  nerve  fibres,  while  here  and  there  between  the  nerve  fibres  may  be  seen  branched 
neuroglia  corpuscles,  hnmediately  underneath  the  ])ia  mater  there  is  a  pretty  thick  layer  of  neurog- 
lia, which  invests  the  prolongations  of  the  pia  into  the  cord.] 

[The  gray  matter  dilTers  in  shape  in  the  difierent  regions  of  the  cord,  and  so  does  the  gray  com- 
missure (Fig.  444).  The  latter  is  thicker  and  shorter  in  the  cervical  than  in  the  dorsal  region,  while 
it  is  very  narrow  in  the  lumbar  region.  The  amount  of  gray  matter  undergoes  a  great  increase 
opposite  the  origins  of  the  large  nerves,  the  increase  being  most  marked  opposite  the  cervical  and 
lumbar  enlargements.  Ludwig  and  Woroschiloff  constructed  a  series  of  curves  from  measurements  by 
Stilling  of  the  sectional  areas  of  the  gray  and  white  matter  of  the  cord,  as  well  as  of  the  several 
nerve  roots.  These  curves  have  been  arranged  in  the  annexed  convenient  form  by  Schiifer  after 
Woroschilort  (Fig.  443)]  : — 

[In  the  cervical  region,  the  lateral  white  columns  are  large,  the  anterior  cornu  of  the  gray  matter 
is  wide  and  large,  while  the  posterior  cornu  is  narrow ;  Goll's  column  is  marked  off  by  a  depression 
and  a  prolongation  of  the  pia  mater ;   the   cord   itself  is  broadest   from   side  to  side.     In  the  dorsal 

region,  the  gi"ay  matter  is  small  in  animals,  and  both 
cornua  are  narrow  and  of  nearly  e(iual  brendth,  while  the 
cord  itself  is  smaller  and  cylindrical.  In  it  the  intermedio- 
lateral  and  posterior  vesicular  groups  of  cells  arc  distinct. 
They  have  probably  relations  to  viscera.  The  commissure 
lies  well  forward  between  the  crescents.  In  the  lumbar 
region,  the  gray  matter  is  relatively  and  absolutely  great- 
est, while  the  white  lateral  columns  are  small,  the  central 
canal  in  the  commissure  being  nearly  in  the  middle  of  the 
cord.  In  the  conus  medullaris,  the  gray  matter  makes 
up  the  great  mass  of  it,  with  a  few  white  fibres  externally 
(Fig.  444).] 

The  anterior  cornu  of  the  gray  matter  is  shorter  and 
l.noader,  and  does  not  reach  so  near  to  the  surface  as  the 
posterior;  moreover,  each  anterior  nerve  root  arises  from 
it  by  several  bundles — it  contains  several  groups  of  large 
multipolar  ganglionic  cells  (Fig.  442)  ;  the  posterior 
cornu  is  more  pointed,  longer,  and  narrower,  and  reaches 
nearer  to  the  surface,  the  posterior  root  arising  l)y  a  single 
bundle  at  the  postero-lateral  fisHue  ;  while  the  cornu  itself 
contains  a  few  fusifoim  nerve  cells,  and  is  covered  by  the 
substantia  gelatinosa  of  Rolando,  which  is  in  part  an 
accumulation  of  neuroglia. 

[The  substantia  gelatinosa  on  the  posterior  cornu 
is  marked  by  striation  where  the  posterior  root  fibres  tra- 
verse it.  It  contains  some  connective-tissue  cells  and 
some  fusiform  nerve  cells,  especially  near  the  margins. 
The  substance  itself  stains  deeply  with  carmine.] 

[The  outer  margin  of  the  gray  matter  near  its  middle 
is  not  so  sharply  defined  from  the  white  matter  as  else- 
where ;  and,  in  fact,  a  kind  of  anastomosis  of  the  gray 
matter  projects  into  the  lateral  column,  especially  in  the 
cervical  region,  consUluUng  the  processus  re/t'cu/an's  (Fig. 
446).] 

[Arrangement  of  Nerve  Cells — The  nerve  cells 
are  arranged  in  four  groups,  forming  columns  more  or 
less  continuous.  There  are  those  of  the  anterior  and 
posterior  horns,  those  of  the  lateral  column  (intermedio- 
lateral),  and  the  posterior  vesicular  column  of  Clarke. 
The  anterior  and  posterior  groups  exist  as  continuous 
columns  along  the  entire  cord.  The  cells  in  the  anterior 
cornu  are  subdivided  into  smaller  groups,  w^hich  vary  in  the  difierent  regions  of  the  cord.  There  is 
an  inner  or //I re/tan  group  near  the  anterior  angle  of  the  cornu.  It  is  the  smallest  group,  and  is 
absent  in  the  lumbar  region.  Near  the  anterior  edge  is  the  anterior  group,  and  in  the  external  part 
of  the  cornu  is  the  antero-lateral group.  These  two  groups  are  often  united,  as  in  the  mid-cervical 
region.     There  is  usually  a  third  large  group — the  external  or  postero-lateral  in  the  posterior  outer 


Transverbc  sections  of  the  spinal  cord  in  dif- 
ferent regions.  A,  through  the  middle  of 
the  cervical :  B,  the  dorsal  ;  C,  the  lum- 
bar enlargement ;  D,  upper  part  of  the 
conus  medullaris ;  E,  at  the  5th  sacral 
vertebra  ;  K,  at  coccyx  ;  A,  B,  C,  en- 
larged twice ;  D,  E,  F,  thrice  :  a,  anterior, 
/,  posterior  root. 


ARRANGEMENT    OF    NERVE    CELLS. 


679 


angle  of  the  anterior  comu — the  cells  of  the  anterior  horn  being  very  large  (67  to  135  ju),  while  the 
fusiform  cells  of  the  posterior  horn  are  18  //  in  diameter.  Those  of  the  lateral  column  are  distinct, 
except  in  the  lumbar  and  cervical  enlargements,  where  they  blend  with  the  anterior  horn.  The  col- 
umn of  Clarke  (cells  40  to  90  //)  is  discontinued,  and  is  limited  to  (i)  the  thoracic  region,  (2)  cer- 
vico-cranial  region,  (3)  sacral  region,  being  most  conspicuous  in  (i),  where  it  corresponds  absolutely 
to  the  outflow  of  visceral  uex\QS  [Gaskell).  In  the  sacral  region  it  con-esponds  to  the  "sacral 
nucleus  of  Stilling,"  while  in  the  cervical  region  it  begins  in  the  dog  at  the  2d  cervical  nerve,  form- 
ing  the  cervical  nucleus,  being  continued  above  into  the  nuclei  of  the  vagus  and  glosso-pharyngeal 
nerves.  The  cells  of  this  column  give  rise  to  small  medullated  nerve  fibres  or  the  leucenteric  fibres 
of  Gaskell.] 

The  multipolar  ganglion  cells  are  largest,  and  arranged  in  groups  in  the  anterior  horns  of  the 
gray  matter  (Fig.  446 — ■"  motor  ganglionic  cells  ").  [They  also  occur  in  the  lateral  process  and  in 
the  processus  reticularis.  It  is  to  be  noted  that  the  cells  become  more  branched  as  we  proceed  up- 
ward among  the  vertebrata.    These  cells  usually  contain  pigment  granules,  and,  according  to  Pierret, 


Fig.  446. 
A.M.B' 


P.M.F 


Fig.  445.— Nerve  cell  from  Clarke's  column  (horse).     The  arrow  indicates  the  cerebral  end. 

Fig.  446.— Transverse  section  of  the  spinal  cord  (lower  dorsal).  A,  L,  P,  anterior,  lateral,  and  posterior  columns ; 
A.M.F.,  P.M.F.,  anterior  and  posterior  median  fissures  ;  a,  b,  c,  cells  of  the  anterior  horn  ;  d,  posterior  cornu 
and  substantia  gelatinosa ;  e,  central  canal ;  /,  veins  ;  g,  anterior  root  bundles ;  h,  posterior  root  bundles  ;  z, 
white  commissure ;  j,  gray  commissure  ;  /,  reticular  formation. 


their  size  has  a  direct  relation  to  the  length  of  the  nerve  fibre  proceeding  from  them  ;  so  that  they 
are  largest  in  the  lumbar  enlargement,  smaller  in  the  cervical  enlargement,  and  smallest  in  the  dorsal 
region.  Smaller  spindle-shaped  ("  sensory  ")  cells  occur  in  much  smaller  numbers  in  the  gray 
matter  of  the  posterior  horn.  The  cells  of  Clarke's  column  (Fig.  445)  are  smaller  (30-60  //),  and 
are  usually  arranged  with  their  long  axis  in  the  long  axis  of  the  cord.  The  processes  are  fewer,  but 
one  is  generally  directed  toward  the  head,  and  some  toward  the  caudal  end  of  the  body.  They 
usually  contain  much  pigment,  which  is  generally  disposed  toward  the  cerebral  pole  of  the  cell.] 

[In  a  longitudinal  section  of  the  cord  (Fig.  447),  these  cells  are  seen  to  be  arranged  in  columns, 
the  large  multipolar  cells  in  the  anterior  horn  (w) ;  in  the  same  section  are  shown,  the  longitudinal 
direction  of  the  nerve  fibres  in  the  anterior  {a)  and  posterior  white  columns  {c),  the  horizontal  direction 
of  the  fibres  of  the  anterior  and  posterior  nerve  roots  [b  and/). 

The  gray  matter  contains  an  exceedingly  delicate  fibrous  network  of  the  finest  nerve  fibrils 
{Gerlack),  which  is  produced  by  the  repeated  division  of  the  protoplasmic  processes  of  the  multipolar 


680 


GERLACH  S   NETWORK    AND    MULTIPOLAR    CELLS. 


gan<j;lionic  cells.     Medullated  nerve  fibres  traverse  and  divide  in  the  fjray  matter  and  become  non- 
meilullated;  seme  of  them  merely  pass  through  the  gray  matter  of  the  non-meduUated  fibres  and 


Kic.  447. 


Fu;.  448. 


Fig.  447.— Longitudinal  section  of  the  human  spinal  cord,     a,  anterior,  c,  posterior,  d,  lateral  white  columns;  6, 
ij  .  anterior,  c,  posterior  nerve  roots  ;  /",  horizontal  (pyramidal)  fibres  passing  to  tn,  cells  of  anterior  cornu  ;  n,  oblique 

fibres  of  posterior  root. 
Fig.  448. — Multipolar  nerve  cell,  from  the  anterior  horn  of  the  spinal  cord,     z,  axis-cylinder  process ;  y,  branched 

processes. 


Fig.  449. 


Scheme  of  the  course  of  the  fibres  in  the  spinal  cord.  The 
longitudinal  fibres  are  indicated  by  small  circles;  while 
the  nerve  cells  are  black. 


terminate  in  Gerlach's  network.  Fibres  pass 
from  the  gray  matter  of  one  side  to  that  of  the 
other  through  the  commissures  in  front  of  and 
behind  the  central  canal. 

[By  means  of  Wcigert's  method  of  staining 
medullated  nerve  fibres  (p.  579),  it  has  been 
proved  that  numerous,  fine,  medullated  nerve 
fibres  exist  in  the  gray  substance.] 

Gerlach's  Theory. — According  to  Gerlach, 
the  connection  of  the  fibres  and  cells  is  as 
follows  :  The  fibres  of  the  anterior  root  proceed 
directly  to  the  ganglionic  cells  of  the  anterior 
horn,  with  which  they  form  direct  communica- 
tions by  means  of  the  unbranched  axial  cylinder 
processes  (Fig.  448,  3).  The  gray  network  of 
protoplasmic  processes,  produced  by  the  re- 
peated branchings  of  the  fibres  of  these  cells, 
gives  origin  to  broad  fibres.  A  part  of  the  latter 
(the  median  bundle)  passes  through  the  anterior 
white  commissure  to  the  other  side,  and  then 
ascends  in  the  anterior  column  of  the  opposite 
side.  Other  fibres  (the  lateral  bundle)  pass 
into  the  lateral  column  of  the  same  side,  and 
ascend  in  it  as  far  as  the  decussation  of  the 
pyramids,  where  they  cross  in  the  medulla  to 
the  other  side.  The  fibres  of  the  posterior 
root  enter  the  posterior  horn,  and,  after  divid- 
ing, terminate  in  the  nervous  protoplasmic  net- 
work of  the  gray  matter.  By  means  of  this 
network  they  are  connected  indirectly  with  the 
ganglionic  cells  of  the  posterior  horn,  which 
are  said  not  to  have  an  axial  cylinder  process. 
The  gray  network,  which  connects  the  ganglia 


of  the'anterior  and  posterior  horns  with  each  other,  also  sends  fibres,  which  pass  to  the  other  side  of 
the  cord  in  front  of  and  behind  the  central  canal.  They  then  take  a  backward  course,  to  ascend 
partly  in  the  posterior  horns  and  partly  in  the  lateral  columns.  ' 


THE   NEUROGLIA   AND    BLOOD    VESSELS   OF   THE   CORD. 


681 


[The  anterior  root  enters  in  several  bundles  of  coarse  fibres  which  diverge  before  they  reach  the 
gray  matter.  Most,  or  perhaps  all,  the  fibres  end  in  the  large  motor  nerve  cells  in  the  anterior  cornu 
or  its  lateral  process  (Fig.  449,  a,  b,  c,  d,  e).  But  the  fibres  diverge  in  all  directions,  some  of  the 
fibres. of  the  bundle  nearest  the  middle  line  (3)  end  in  the  laterally  placed  cells  (c) ;  a  part  (4)  crosses 
the  anterior  commissure  to  end  in  cells  on  the  opposite  side  {d).  Some  of  them  (6)  run  upward  to 
become  connected  with  motor  cells  lying  further  up  the  cord.] 

[The  posterior  root  enters  as  a  single  bundle,  composed  of  finer  fibres  with  bundles  of  thicker 
ones.  The  finest  fibres,  which  are  usually  placed  most  laterally  (7),  or  outer  radicular  fibres 
curve  into  the  longitudinal  fibres,  so  that  they  are  cut  across  in  a  transverse  section,  but  they 
again  take  a  horizontal  course  and  enter  the  substantia  gelatinosa.  The  remainder  of  the  fibres 
split  into  an  outer  and  inner  part.  The  lateral  smaller  part  or  central  fibres  (8  to  10)  passes 
into  the  substantia  gelatinosa,  where  it  divides  into  several  strands,  some  of  which  pass  into  the 
central  part  of  the  gray  matter  (10),  while  others  (8)  pass  upward  and  downward  in  a  longitudinal 
direction.  Some  of  the  fibres  (9)  perhaps  end  in  the  nerve  cells  {/)  in  the  posterior  cornu.  The 
median,  inner  or  internal  radicular  fasciculus  (11  to  14),  sweeps  through  the  postero- external 
column,  and,  after  running  a  longitudinal  course  in  the  white  matter,  enters  the  gray  substance  of  the 
posterior  cornu.  Some  fibres  (li)  pass  to  the  small  fusiform  cells  [g);  and  others  (13)  pass  to  be 
connected  with  the  cells  of  Clarke's  column  [h),  when  it  is  present.  From  the  cells  of  Clarke's 
column,  fibres  seem  to  pass  to  the  direct  cerebellar  tract  (20).     Some  of  the  fibres  (12)  pass  into  the 


Fig.  450. 


Fig.  451. 


Isolated  connective-tissue  corpuscle  or  "  glia  cell  "  from  the  human  spinal  cord ; 


Longitudinal  section  of  the  spinal 
cord,  a,  white,  b,  gray  mat- 
ter; c,  crystals  of  mercuric 
chloride.  Prepared  by  Gol- 
gi's  mercuric  chloride  me- 
thod ;  X  80. 


posterior  gray  commissure,  to  reach  the  opposite  side.  This  so  far  only  accounts  for  a  part  of  the 
fibres.  Some  of  them  (8  to  10)  are  concerned  in  the  formation  of  the  fine  nerve  plexus  in  the  gray 
matter,  whereby,  perhaps,  they  become  connected  with  the  cells  in  the  anterior  cornu.  It  is  asserted 
that  some  of  the  fibres  (14)  ultimately  pass  into  Goll's  column.  Many  of  the  fibres  in  the  posterior 
root  have  been  proved  to  be  directly  connected  with  nerve  cells,  e.g.,  in  Petromyzon  by  Freund,  and 
in  the  Proteus  by  Klaussner,  so  that  it  is  very  doubtful  if,  in  the  higher  animals,  the  fibres  of  the 
posterior  root  are  directly  connected  with  the  plexus  of  gray  fibres  as  suggested  by  Gerlach  (p.  680).] 
Neuroglia. — The  connective  tissue  of  the  spinal  cord  arises  in  part  from  the  pia  mater  and 
passes  into  the  white  matter,  carrying  with  it  blood  vessels,  and  forming  septa,  which  separate  the 
nerve  fibres  into  bundles.  [The  connective  tissue  of  the  central  nervous  system  is  so  far  peculiar, 
that  the  inter-cellular  substance  is  reduced  to  a  minimum.  It  consists  of  a  reticulated  connective 
tissue  composed  of  fine  fibres,  which  form  a  network.  Fig.  450  shows  one  of  the  cells,  "glia  cells," 
isolated.  It  consists  of  a  small,  granular,  nucleated  body,  with  numerous  excessively  fine,  slightly- 
branched,  stiff  processes.  The  processes  form  a  sustentacular  tissue  for  the  nerve  fibres  and  blood 
vessels.  The  arrangement  and  distribution  of  these  cells  is  best  seen  in  sections  of  a  cord  hardened 
by  Golgi's  method  in  corrosive  sublimate  solution  (Fig.  451).  In  some  situations,  e.  g.,  the  white 
matter  of  the  cerebrum  and  cerebellum,  the  cells  are  smaller  and  more  angular,  and  the  processes 
are  often  connected  with  the  outer  coat  of  the  blood  vessels.  On  the  whole,  the  connective  tissue  is 
much  finer  in  the  brain  than  in  the  cord.     The   central  canal  is  surrounded  with  a  denser  layer  of 


682 


BLOOD    VESSELS    OF   THE    SPINAL    C\)KD. 


this  tissue,  known  as  the  "  central  ependyma,"  which  stains  deeply  with  carmine,  and  is  very  like 
the  substantia  gelatinosa  in  its  structure  (p.  678).  We  must  distinguish  from  this  form  of  connective 
tissue  that  special  form  in  the  gray  matter  to  which  Virchow  gave  the  name  of  neuroglia.  It  is 
specially  adapted  to  fill  up  the  spaces  left  hy  the  other  elements,  and  without  interfering  with  the 
exchange  of  lluids  serves  to  hold  the  elements  together.  It  is  an  excessively  hnely  granular  ground 
substance  in  the  gray  matter.  It  is  also  an  inter-cellular  substance,  but  in  the  adult  the  cells  to  which 
it  owes  its  origm  are  no  longer  to  be  found.  It  is  doubtful,  from  its  chemical  nature,  if  it  is  really  to 
be  reckoned  along  with  the  connective  tissues.  It  seems  to  be  rather  a  tissue  siii  generis,  belonging 
to  the  nervous  system,  and  it  is  present  in  very  small  amount.]  The  neuroglia  is  also  abundant  on 
the  sides  and  apex  of  the  posterior  horns,  where  it  is  called  the  gelatinous  substance  of 
Rolando. 

[Blood  Vessels. — The  spinal  cord  is  partly  supplied  with  blood  by  arteries 
from  the  vertebrals,  and  partly  by  branches  of  the  intercostal,  linnbar,  and  sacral 


l-'ic.  453- 


V.M.F. 


Semi-diagrammatic   arrangement  of  the  arteries   in   the  Injected  blood  vebsels  of  the  spinal  cord, 

spinal  cord.  S/a,  anterior  spinal ;  j,  sulcine  artery; 
sc,  sulco-commissural ;  an,  its  anastomosing  branch  ; 
cl,  to  Clarke's  column  ;  Fp,  posterior  fissure  ;  ra,  rp, 
branches  along  anterior  and  posterior  roots  ;  cf>,  for 
post,  cornu  ;  j/^,  inter-funicular;  la,  hit,  Ip,  anterior, 
median,  and  posterior  lateral. 

arteries,  which  reach  it  through  the  inter-vertebral  foramina,  and  pass  to  the  cord 
along  the  anterior  and  posterior  roots.] 

[Blood  Vessels. — The  anterior  median  (or  anterior  spinal)  (Fig.  452)  artery  gives  off  branches, 
which  dip  into  the  fissure  of  the  same  name,  pass  to  its  base,  and,  after  perforating  the  anterior 
commissure,  divide  into  two  branches,  one  for  each  mass  of  gray  matter,  and  each  branch  in  turn 
splits  into  three,  which  supply  part  of  the  anterior,  median,  and  posterior  gray  matter.  The  arteries 
lying  in  the  sulci  are  called  arteriae  sulci  {s)  by  Adamkiewicz.  In  the  gray  matter,  there  is  usually 
a  special  branch  to  Clarke's  column  [rl).  The  vaso-coronary  arteries  include  all  those  arterial 
branches  wliich  proceed  from  the  periphery  into  the  white  matter;  the  finer  branches  pass  only  into 
the  white  matter,  but  the  larger  into  the  gray  substance.  The  largest  branch  is  the  artery  of  the 
posterior  fissure  (./^), which  passes  along  the  posterior  septum  and  reaches  almost  to  the  commissure, 
giving  branches  in  its  course.  There  is  a  large  artery  between  the  column  of  (loll  and  the  postero- 
external column,  viz.,  the  inter-funicular  artery  [if).  Arteries  enter  along  the  anterior  and  posterior 
roots  (;'<7,  rp).     There  are  also  a  median  lateral  artery  (/w),  and   an  anterior  and  posterior  lateral 


flechsig's  systems  of  conducting  fibres.  683 

(Ip,  la),  which  enter  the  lateral  column.  The  generel  result  is  that  the  gray  matter  is  much  more 
vascular  than  the  white,  as  is  shown  in  Fig.  453.  Some  small  vessels  come  from  the  pia  and  send 
branches  to  the  white  matter,  and  unbranched  arteries  to  the  gray  matter,  where  they  form  a  capillary 
plexus.  The  blood  vessels  are  surrounded  by  perivascular  lymph  spaces  [His).'\  [With  regard 
to  the  blood  vessels  supplying  the  cord  as  a  whole,  Moxon  has  pointed  out  that,  owing  to  the  cord 
not  being  as  long  as  the  vertebral  canal,  the  lower  nerves  have  to  run  down  within  the  vertebral 
canal,  before  they  emerge  from  the  appropriate  inter- vertebral  foramina.  As  re-enforcing  arteries 
enter  the  cord  along  the  course  of  these  nerves,  necessarily  the  branches  entering  along  the  course  of 
the  lumbar  and  lower  dorsal  nerves  are  long,  and  this,  together  with  their  small  size,  offers  consider- 
able resistance  to  the  blood  stream.  Hence,  perhaps,  the  reason  why  the  lower  part  of  the  cord  is  so 
apt  to  be  affected  by  various  pathological  conditions.] 

[Functions  of  the  Spinal  Cord. — (i)  It  is  a  great  conducting  medium, 
conducting  impulses  upward  and  downward,  and  within  itself  from  side  to  side ; 
(2)  the  great  reflex  centre,  or  rather  series  of  so-called  centres;  (3)  impulses 
originate  within  it.] 

Conducting  Systems. — The  whole  of  the  longitudinal  fibres  of  the  spinal 
cord  may  be  arranged  systematically  in  special  bundles,  according  to  their  func- 
tion. 

[Methods. — The  course  of  the  fibres  and  their  division  into  so-called  systems  has  been  ascer- 
tained partly  by  anatomical  and  embryological,  partly  by  physiological  and  pathological 
means.  Apart  from  experimental  methods,  such  as  dividing  one  column  of  the  cord  and  observing 
the  results,  we  have  the  following  methods  of  investigation  :  (i)  Tiirck  found  that  injury  or  disease 
of  certain  parts  of  the  brain  was  followed  by  a  degeneration  downward,  or  secondary  descending 
degeneration  of  certain  of  the  nerve  fibres  connected  with  the  seat  of  injury,  /.  e.,  they  were  sepa- 
rated from  their  trophic  centres  and  underwent  degeneration.  (2)  P.  Schieferdecker  found  also, 
after  section  of  the  cord,  that  above  and  below  the  level  of  the  section,  certain  definite  tracts  of 
white  matter  underwent  degeneration  [thus  showing  that  certain  tracts  had  their  trophic  centre  below ; 
this  constitutes  secondary  ascending  degeneration].  [(3)  Gudden's  Method. — He  showed, 
as  regards  the  brain,  that  excision  of  a  sense  organ  in  a  young  growing  animal  was  followed  by 
atrophy  of  the  nerve  fibres  and  some  other  parts  connected  with  it.  Thus,  the  optic  nerve  and  anterior 
corpora  quadrigemina  atrophy  after  excision  of  the  eyeball  in  young  rabbits.]  (4)  Embryological. 
— Flechsig  showed  that  the  fibres  of  the  cord  [and  the  brain  also]  during  development  became 
covered  with  myelin  at  different  periods,  those  fibres  becoming  medullated  latest  which  had  the 
longest  course.     In  this  way  he  mapped  out  the  following  systems  : — 

Flechsig's  Systems  of  Fibres. — i.  In  the  anterior  column  lie  («)  the  un- 
crossed, anterior,  or  direct  pyramidal  tract  [also  called  the  Column  of  Tiirck']  ; 
and  external  to  it  is  (J?)  the  anterior  ground 
bundle,  or  anterior  radicular  zo7ie  (Fig.  454). 
[The  direct  pyramidal  tract  varies  in  size,  and  it 
generally   extends    downward    in    the    cord    to 
about  the  middle  of  the  dorsal  region,  diminish- 
ing steadily  in  its  course ;  so  that  it  would  seem     "^      ^^    \^^^^~X  f 
that  this  tract  contains  chiefly  fibres  for  the  arm.                   "                   '^ 
We  do  not  know,  exactly,  how  these  fibres  end, 
whether  they  cross  to  the  opposite  side,  or  re- 
main on  the  same  side,  but  most  probably  most  ^ 
of  them  pass  through  the  anterior  commissure  to 
the  gray  matter  of  the  opposite  side.]                                                  

2.  In  the  posterior  column  he  distinguishes  ^       """  "^liw 

((f)  GoU's  column,  or  the  postero-median  (pos-  ;  c 

tero-internal)   column;    and    (^)    the    funicu-  d; 

lus   cuneatus,  BurdacKs  column,  ox   the /^.-  Scheme^onhe^ conducing  p^^^^^^^^^ 

tenor    radicular    Z07ie,     or      the     pOSterO-external  part  is  the  gray  matter,     v,  anterior,  hm, 

J  posterior,  root ;    a,  direct,  and  g,  crossed, 

column.  pyramidal      tracts ;     b,    anterior     column 

■x.  In  the  lateral  column  are  (e~)  the  antero-       ground  bundle ,-  c  Goii's  column;  (/,pos- 

,'-',  i^/-\i  i\li  -J  tero-external    column ;     e    and  J,    mixed 

lateral      tract,     and    (/}     the      lateral    mixed  lateral  paths ;  a,  direct  cerebellar  tracts. 

paths,  or  lateral  limiting  tract,  (g)  the  lateral 

or  crossed  pyramidal  tract,  and  (/z)  the  direct  cerebellar  tract. 


(384  fleciisig's  systems  of  conducting  fibres. 

[All  the  impulses  from  the  central  convolutions  or  motor  areas  of  the  cerebrum, 
by  means  of  which  voluntary  movements  are  executed,  are  conducted  by  the  pyra- 
midal tracts  a  and,;,-  (>;  365).  The  fibres  in  these  tracts  descend  from  the  central 
convolutions,  /.  e.,  the  motor  areas  pass  througli  the  white  matter  of  the  cerebrum, 
converging  like  the  rays  of  a  fan  to  the  internal  capsule,  where  they  lie  in  the 
knee  and  anterior  two-thirds  of  its  ])Osterior  segment  (the  fibres  for  the  face  at  the 
knee,  and  behind  this  in  order  those  for  the  arm  and  leg),  they  then  enter  the  middle 
third  of  the  crusta  (Fig.  502,  Py),  pass  through  the  pons  into  the  anterior  pyramids 
of  the  medulla  oblongata,  where  the  great  mass  crosses  over  to  the  lateral  column 
of  the  opposite  side  of  the  cord  ( crossed  pyramidal  tract  i,  a  small  part  descend- 
ing in  the  cord  on  the  same  side  as  the  antero-median  tract  (direct  pyramidal 
tract,  a).  The  crossed  pyramidal  tract  lies  external  to  the  posterior  half  of  the 
gray  matter  in  the  lateral  column  (Fig.  454,  ^i,*-),  and  it  extends  throughout  the 
length  of  the  cord.  In  the  greater  part  of  its  course,  it  is  separated  from  the  surface 
by  the  direct  cerebellar  tract,  but  where  the  latter  lies  further  forward,  as  at  the 
third  cervical  segment  and  lower  dorsal  region,  its  posterior  surface  reaches  the 
surface,  while  from  the  last  dorsal  segment,  throughout  the  lumbar  region,  it  comes 
quite  to  the  surface,  as  the  direct  cerebellar  tract  ceases  at  the  first  lumbar  vertebra. 
The  i)yramidal  tract  diminishes  from  above  downward,  and  its  fibres  pass  into  the 
gray  matter  of  the  anterior  cornu,  and  in  all  probability  they  subdivide  to  form  fine 
fibrils,  which  become  connected  with  the  dense  plexus  of  fine  fibrils  produced  by 
the  subdivision  of  the  processes  of  the  multipolar  nerve  cells.  From  each  multi- 
polar nerve  cell,  a  nerve  fibre  proceeds  and  passes  into  the  anterior  root.  The 
direct  cerebellar  tract  {h)  begins  about  the  first  lumbar  nerve,  and  increases 
somewhat  in  thickness  from  below  upward,  but  most  of  its  fibres  enter  it  at  the  first 
lumbar  and  lowest  dorsal  nerves.  It  forms  a  thin  layer  on  the  surface  of  the  cord. 
Its  fibres  very  probably  arise  in  the  cells  of  Clarke's  column.  As  Clarke's  column 
is  connected  with  some  of  the  fibres  of  the  posterior  root  (for  the  trunk  of  the 
body),  it  follows  that  this  tract  connects  certain  parts  of  the  posterior  roots  with 
the  cerebellum.  The  fibres  pass  up  through  the  cord  and  restiform  body  to  the 
cerebellum.  When  it  is  divided,  it  degenerates  upward,  so  that  it  conducts  im- 
pulses in  a  centripetal  direction.]  The  anterior  (^)  and  lateral  paths  (/)  and  the 
anterior  ground  bundle  {b)  represent  the  channels  which  connect  the  gray  matter 
of  the  spinal  cord  and  that  of  the  medulla  oblongata  ;  they  represent  the  channels 
for  reflex  effects,  and  they  also  contain  those  fibres  which  are  the  direct  continua- 
tion of  the  anterior  spinal  nerve  roots,  which  enter  the  cord  at  different  levels  and 
penetrate  into  the  gray  matter.  In  e  and/ there  are  some  sensory  paths.  Lastly, 
c  unites  the  posterior  roots  with  the  gray  nuclei  of  the  funiculi  graciles  of  the  medulla 
oblongata  ;  d  connects  some  of  the  posterior  nerve  roots  through  the  restiform 
body  with  the  vermiform  process  of  the  cerebellum  {Flechsig).  The  direction  of 
conduction  in  the  posterior  columns,  which  are  continuations  of  some  of  the  fibres 
of  the  posterior  roots,  is  upward,  as  part  of  them  degenerates  upward  after  section 
of  the  posterior  root.  Of  the  fibres  of  each  posterior  root,  some  pass  directly  into 
the  posterior  horn,  another  part  ascends  in  the  posterior  column  of  the  same  side, 
and  gradually  as  it  ascends,  it  comes  nearer  the  posterior  median  fissure.  Some  of 
these  fibres  enter  the  gray  matter  of  the  posterior  horn  at  a  higher  level.  The  fibres 
of  the  posterior  columns  run  upward  as  far  as  the  inter-olivary  layer  and  the  decus- 
sation of  the  pyramids,  where  they  seem  to  end,  or  at  least  form  connections  with 
the  nerve  cells  of  the  funiculi  graciles  [clava]  and  cuneati  [triangular  nucleus].  A 
small  part  as  arcuate  fibres  join  the  restiform  body,  and  thus  the  cerebellum  is 
connected  with  the  posterior  columns. 

Further,  the  transverse  sectional  area  of  the  direct  and  crossed  pyramidal  tracts  (rr  and_§-),the 
lateral  cerebellar  tract  \h),  and  Goll's  column  (t)  gradually  diminish  from  alxjve  downward;  they 
serve  to  connect  intra-cranial  central  parts  with  the  ganglionic  centres  distributed  along  the  spinal  cord. 
The  anterior  root  bundle  (/'),  the  funiculus  cuneatus  (a'),  and  the  anterior  mixed  lateral  tracts  (^)  vary 


SECONDARY   DEGENERATION    OF   TROPHIC    CENTRES. 


685 


in  diameter  at  different  parts  of  the  cord,  corresponding  to  the  number  of  nerve  roots.  It  has  been 
concluded  from  this  that  these  tracts  serve  to  connect  the  gray  matter  at  different  levels  in  the  cord 
with  each  other,  and  ultimately  with  the  medulla  oblongata,  so  that  they  do  not  pass  directly  to  the 
higher  parts  of  the  brain  (Fig.  443). 

Nutritive  Centres  of  the  Conducting  Paths. — Tiirck  observed  that  the 
destruction  of  certain  parts  of  the  brain  caused  a  secondary  degeneration  of 
certain  parts  of  the  cord,  corresponding  to  the  parts  called  pyj-amidal  tracts  by 
Flechsig  (Fig.  455).  P.  Schieferdecker  found  the  same  effects  beloiv  where  he 
divided  the  spinal  cord  in  a  dog.  Hence,  it  is  concluded  that  the  nutritive  or  tro- 
phic centre  of  the  pyramidal  tracts  lies  in  the  cerebrum.  [Section  of  the  cord,  or 
an  injury  compressing  the  cord,  besides  giving  rise  to  loss  of  certain  functions 
(p.  698),  results  in  structural  changes  in  certain  limited  areas  of  the  cord  itself 
Below  the  section  after  a  time,  the  direct  and  crossed  pyramidal  tracts  (Fig.  455, 
I,  i',  2,  2')  degenerate  downward,  i.  e.,  they  undergo  descending  secondary 
degeneration,  because  they  are  cut  off  from  their  nutritive  or  trophic  centres, 
which  are  situated  above  in  the  pyramidal  cells  of  the  motor  areas  of  the  brain 
(§  378)'  The  trophic  centre  for  the  fibres  of  the  anterior  root  lies  in  the  multi- 
polar nerve  cells  of  the  anterior  cornu  of  the  gray  matter  of  the  cord.  After  section 
of  the  spinal  cord,  GoU's  column  and  the  direct  cerebellar  tracts  degenerate 
upward,  i.  e.,  they  undergo  ascending  secondary  degeneration.  If  the  pos- 
terior columns  even  be  divided,  Goll's  column  degenerates  upward  toward  the 
medulla   oblongata,    and    the 

degeneration  ends  in  the  pos-  ^^'^-  455- 

terior  pyramidal  nucleus  or 
clava.  The  same  result  occurs 
if  the  posterior  nerve  roots  of 
the  Cauda  equina  be  injured. 
Hence,  fibres  seem  to  pass  from 
the  posterior  root  into  these 
columns,  and  the  nerve  cells 
in  the  clava  must  also  have  an 
important  relation  to  these 
nerve  fibres  and  the  parts 
whence  they  are  derived.  The 
postero-external  column  re- 
mains undegenerated,  so  that 
there  is  a  very  sharp  'distinc- 
tion between  the  two  parts  of 
the  posterior  column.  As 
Goll's  column  degenerates  up- 
ward, it  points  to  its  fibres 
conducting  impulses  in  a  cen- 
tripetal direction,  and  to  the 
nutritive  centre  for  its  nerve 
fibres  being  below.  The  trophic  centre  is  probably  in  the  spinal  ganglion  of  the 
posterior  root.] 

[If  the  cord  be  divided  above  the  junction  of  the  dorsal  and  lumbar  regions,  the 
direct  cerebellar  tract  undergoes  ascending  degeneration,  which  extends 
through  the  restiform  body  to  the  cerebellum.  Its  trophic  centre  is  probably  in 
the  cells  of  Clarke's  column.]  Those  fibres  of  the  spinal  cord  which  do  not 
degenerate  after  section  of  the  cord,  especially  numerous  in  the  lateral  and 
anterior  columns  [anterior  ground  bundle,  the  anterior  and  lateral  mixed  zones  of 
the  lateral  column,  and  the  postero-external  part  of  the  posterior  column],  are 
commissural  in  function,  connecting  ganglionic  cells  with  each  other,  and  are, 
therefore,  provided  with  a  trophic  centre  at  both  ends. 


3'  3 


TR 


Transverse  section  of  the  spinal  cord,  showing  the  secondai-y  degenera- 
tion tracts.  AR,  anterior,  TR,  posterior  root;  i,  i' (CPT),  region 
of  the  crossed  pyramidal  tract;  2,  2'  (DPT),  direct  pyramidal  tract; 
PEC,  postero-external  column  ;  LC,  lateral  column. 


6S6 


SPINAL    REFLEX    ACTIONS    AND    SPASMS. 


Time  of  Development. — With  regard  to  the  time  of  development  of  the  individual  systems, 
Flechsig  tinds  thai  the  first  formed  paths  are  those  between  the  periphery  and  the  central  gray 
matter,  esjiecially  the  mn'^  roots,  t.  e.,  they  are  the  first  to  be  covered  with  the  myelin.  Then  fibres 
which  connect  the  gray  matter  at  different  levels  are  formed — the  fibres  which  connect  the  gray 
matter  of  the  cord  with  the  cerebellum,  and  also  the  former  with  the  tegmentum  of  the  cerebral 
peduncle.  At  la->t  the  fibres  which  coimect  the  ganglia  of  the  jiedunculus  cerebri,  and  jierhaps  also 
the  gray  matter  of  the  cortex  cerebri  with  the  gray  matter  of  the  cord  are  formed.  In  cases  of  anen- 
cephalous  fa-tuses,  /.  e.,  where  the  cerebrum  is  absent,  neither  the  pyramidal  tracts  nor  the  pyramids 
are  developed.  In  the  brain  before  birth,  medullated  nerve  fibres  are  formed  in  the  jiaracentral, 
central,  and  occipital  convolutions,  and  in  the  island  of  Reil,  and  last  of  all  in  the  frontal  convolu- 
tions (  Tticzek). 

360.  SPINAL  REFLEXES.— By  the  term  reflex  movement  is  meant  a 

movement  caused  by  the  stimulation  of  an  afferent  (sensory)  nerve.  The  stimuhis, 
on  being  apphed  to  an  afferent  nerve,  sets  up  a  state  of  excitement  (nervous 
impulse)  in  that  nerve,  which  state  of  excitement  is  transmitted  or  conducted  in  a 
lenfn'pefai  d'wQcUon  along  the  nerve  to  the  centre  (spinal  cord  in  this  case)  ;  where 
the  nerve  cells  represent  the  nerve  centre  in  the  cord,  the  impulse  is  transferred 
to  the  motor,  efferent  or  centrifugal  channel.  Three  factors,  therefore,  are 
essential  for  a  reflex  motor  act — a  centripetal  or  afferent  fibre,  a  transferring  centre, 
a  centrifugal  or  efferent  fibre ;  these  together  constitute  a  reflex  arc  (Fig.  456). 
In  a  purely  reflex  act,  all  voluntary  activity  is  excluded. 


Fig.  456. 


Fic.  457. 


Scheme  of  a  reflex  arc.  S,skin;M, 
muscle;  N,  nerve  cell,  with  a/, 
afferent,  and  e/,  efferent  fibres. 


Section  of  a  spinal  segment,  showing  a  unilateral  and  crossed 
reflex  act.  A,  anterior,  and  P,  posterior  surface ;  M, 
muscle;  S.skin;  G,  ganglion. 


Reflex  movements  may  be  divided  into  the  three  following  groups  :  — 
I.  The  simple  or  partial  reflexes,  which  are  characterized  by  the  fact  that 
stimulation  of  a  sensory  area  discharges  movement  in  one  muscle  only,  or  at  least 
in  one  limited  group  of  muscles.  Examples  :  A  blow  upon  the  knee  causes  a 
contraction  in  the  quadriceps  extensor  cruris;  contact  with  the  conjunctiva  causes 
closure  of  the  eyelids.  In  the  former  case,  the  aff"erent  channels  arise  in  the  tendon 
of  the  quadriceps,  and  the  eff"erent  channels  lie  in  the  nerve  which  supplies  the 
quadriceps;  in  the  latter  case,  the  afferent  nerve  is  the  5th  and  the  efferent  the  7th 
cranial  nerve.  In  the  former  case  the  centre  is  in  the  lumbar  region  of  the  cord  ; 
in  the  latter,  in  the  gray  matter  of  the  medulla  oblongata. 

IL  The  extensive  incoordinate  reflexes,  or  reflex  spasms. — These 
movements  occur  in  the  form  of  clonic  or  tetanic  contractions;  individual  groups 
of  muscles,  or  all  the  muscles  of  the  body  may  be  implicated.  Causes  :  A  reflex 
spasm  depends  upon  a  double  cause — (rt)  Either  the  gray  matter  or  the  spinal  cord 
is  in  a  condition  of  exalted  excitability,  so  that  the  nervous  impulse,  after  having 
reached  the  centre,  is  easily  transferred  to  the  neighboring  centres.  This  excessive 
excitability  is  produced  by  certain  poisons,  more  especially  by  strychnin,  brucia, 
caffein,  atropin,  nicotin,  carbolic  acid,  etc.  The  slightest  touch  applied  to  an 
animal   poisoned  with  strychnin  is  sufficient  to   throw  the  animal  at  once  into 


REFLEX   SPASMS   AND    SUMMATION    OF   STIMULI. 


687 


Fig.  4.';8. 


spasms.  Pathological  conditions  may  cause  a  similar  result ;  thus,  there  is  exces- 
sive excitability  in  hydrophobia  and  tetanus.  On  the  other  hand,  the  central 
organ  may  be  in  such  a  condition  that  extensive  reflexes  cannot  take  place ;  thus, 
in  the  condition  of  apnoea,  the  spasms  that  occur  in  poisoning  with  strychnin  do 
not  take  place  (y.  Rosenthal  and  Leube),  and  the  same  result  is  brought  about  by 
passive  artificial  respiratory  movements  (§  361,  3).  The  performance  of  other 
passive  periodic  movements  in  various  parts  of  the  body  also  produces  a  similar 
condition  {Bi/chheim).  If  the  spinal  cord  be  cooled  very  considerably,  reflex 
spasms  may  not  occur  (^Kunde).  {]?)  Extensive  reflex  movements  may  also  take 
place  when  the  discharging  stiinulus  is  very  strong.  Examples  of  this  condition 
occur  in  man,  thus — intense  neuralgia  may  be  accompanied  by  extensive  spasmodic 
movements. 

[Fig.  458  shows  the  mechanism  of  simple  and  complex  reflex  movements.  Suppose  the  skin  to  be 
stimulated  at  P,  an  impulse  is  sent  to  A  and  from  it  to  a  muscle  I  on  the  same  side,  resulting  in  a 
unilateral  simple  reflex  movement — the  resistance  being  less  in  this  direction  than  in  the  other 
channels.  If  the  impulse  be  stronger,  or  the  transverse  resistance  in  the  cord  diminished,  the 
impulse  may  pass  to  B,  thence  to  2,  resulting  in  a  symmetrical  reflex  movement  on  both  sides. 
But  if  a  very  strong  impulse  reach  the  cord,  or  if  the  excitability  of  the  gray  matter  be  increased,  e.g., 
by  strychnin,  the  resistance  to  the  diffusion  of  the  impulse  is  diminished,  and  it  passes  upvi^ard  to  C 
and  D,  resulting  in  more  complex  movements — thus  there  is  irradiation — or  it  may  even  affect  the 
centres  in  the  medulla  oblongata,  E,  giving  rise  to  general  convulsive  movements.] 

General  spasms  usually  manifest  themselves  as  "  extensor  tetanus,"  because  the  extensors 
overcome  the  flexor  muscles.  Nerves  which  arise  from  the  medulla  oblongata  may  be  excited 
through  the  stimulation  of  distant  afferent  nerves,  without  general  spasms  being  produced. 

Strychnin  is  the  most  powerful  reflex-producing  poison  we  possess,  and  it  acts  upon  the  gray 
matter  of  the  spinal  cord.  [An  animal  poisoned  with 
strychnin  exhibits  tetanic  spasms  on  the  application  of 
the  slightest  stimulus.  All  the  muscles  become  rigid, 
but  the  extensors  overcome  the  flexors.]  If  the  heart 
of  a  frog  be  ligatured,  and  the  poison  afterward  ap- 
plied directly  to  the  spinal  cord,  reflex  spasms  are 
produced,  proving  that  strychnin  acts  upon  the  spinal 
cord.  During  the  spasm  the  heart  is  arrested  in  dias- 
tole, owing  to  the  stimulation  of  the  vagus,  while  the 
arterial  blood  pressure  is  greatly  increased,  owing  to 
stimulation  of  the  central  vasomotor  centres  of  the 
medulla  oblongata  and  spinal  cord.  Mammals  may 
die  from  asphyxia  during  the  attack  ;  and,  after  large 
doses,  death  may  occur,  owing  to  paralysis  of  the 
spinal  cord,  due  to  the  frequently  recurring  spasms. 
Fowls  are  unaffected  by  comparatively  large  doses. 
[We  can  prove  that  strychnin  does  not  produce  spasms 
by  acting  on  the  brain,  muscle,  or  nerve.  Destroy  the 
brain  of  a  frog,  divide  one  sciatic  nerve  high  up,  and 
inject  a  small  dose  of  strychnin  into  the  dorsal  lymph 
sac ;  in  a  few  minutes  all  the  muscles  of  the  body, 
except  those  supplied  by  the  divided  nerve,  will  be  in 
spasm,  showing  that,  although  the  poisoned  blood  has 
circulated  in  the  nerves  and  muscles  of  the  leg,  it 
does  not  act  on  them.  Destroy  the  spinal  cord,  and 
the  spasms  cease  at  once.] 

Summation  of  Stimuli. — By  this  term 
is  meant,  that  a  single  weak  stimulus,  which 
in  itself  is  incapable  of  discharging  a  reflex 

act,  may,  if  repeated  sufficiently  often,  pro-  Scheme  ot  mode  ot  propagation  ot  reflex  move- 
j  ^v-  ,       Vpi  ■        1       •  1  ments.     P,  skm ;  A,   B,   C,  D,  motor  cells  m 

duce  this  act.     Ihe  single  impulses  are  con-        ^^-^^^y  ^^^^.^  j_  2;  3^ \^  {^  muscles. 
ducted  to  the  spinal  cord,  in  which  the  pro- 
cess of  "  summation  "    takes  place.     According  to  J.  Rosenthal,  3  feeble  stimuli 
per  second  are  capable  of  producing  this  effect,  although  16  stimuli  per  second  are 
most   effective.     On  increasing  the  number  of    stimuli  per    second,   no    further 
increase  of  the  reflex  act  is  possible.     Other  observers  {Stirling,  Ward')  have  found 


688  EFFECT   OF    DRUGS   ON    REFLEX    ACTION. 

that  stimuli,  such  as  induction  shocks,  are  active  within  much  wider  limits,  ^.  ^^., 
from  0.05  to  0.4  second  interval.  W.  Stirling  has  shown  it  to  be  extremely  prob- 
able that  all  reflex  acts  are  due  to  the  rei>etition  of  imi)ulses  in  the  nerve  centres. 

[Strychnin  interferes  with  tlie  summation  of  stimuli,  hut  the  reflex  excitability  is  so  greatly  exalted 
that  a  minimal  stimulus  is  at  the  same  lime  a  maximal  one.] 

Pfliiger's  Law  of  Reflex  Actions. — (l)  The  retlex  movement  occurs  on  the  same  side  on  which 
the  sensor}-  nerve  is  stimulated ;  while  only  those  muscles  contract  whose  nerves  arise  from  the  same 
segment  of  the  spinal  cord.  (2)  If  the  reflex  occur  on  the  other  side,  only  the  corresponding 
muscles  contract.  (3)  If  the  contractions  he  unequal  upon  the  two  sides,  then  the  most  vigorous 
contractions  always  occur  on  the  side  which  is  stimulated.  (4)  If  the  reflex  excitement  extend  to 
other  motor  nerves,  those  nerves  are  always  alTected  which  lie  in  the  direction  of  the  medulla  oblon- 
gata.     Lastly,  all  the  mu.scles  of  the  hotly  may  he  thrown  into  contraction. 

Crossed  Reflexes. —  There  are  exceptions  to  the.'^e  rules.  If  the  region  of  the  eye  he  irritated 
in  a  [xog  whose  cerebrum  is  removed,  there  is  frequently  a  rellex  contraction  in  the  hind  limb  of  the 
opposite  side  [Luchsini^er,  LangenJorff).  In  beheaded  tritons  and  tortoi.ses,  and  in  deeply  narcot- 
ized dogs  and  cats,  tickling  one  fore  limb  is  frequently  followed  by  a  movement  of  the  hind  limb  of 
the  opposite  side  (Z«<;7/««j,w).  This  phenomenon  is  called  a  "  crossed  reflex  "  (Fig.  457).  If 
the  spinal  cord  be  divided  along  the  middle  line  throughout  its  entire  extent,  then,  of  course,  the 
reflexes  are  conlined  to  one  side  only  [Schiff). 

III.  Extensive  co-ordinated  reflexes  are  due  to  stimulation  of  a  sensory 
nerve,  causing  the  discharge  of  complicated  reflex  movements  in  whole  groups  of 
different  muscles,  the  movements  being  "purposive  "  in  character,  /.  e.,  as  if 
they  were  intended  for  a  particular  purpose. 

Methods. — The  experiments  are  made  upon  cold-blooded  animals  (decapitated  or  pithed  frogs, 
tortoises,  or  eels)  or  upon  tnanunals.  In  the  latter,  artificial  respiration  is  kept  up,  and  the  four 
arteries  going  to  the  head  are  ligatured,  in  order  to  eliminate  the  action  of  the  brain  {Sig.  Mayer, 
Lucksinger).  The  reflexes  of  the  lower  part  of  the  spinal  cord  maybe  studied  on  animals  (or  men), 
in  cases  where  the  spinal  cord  is  divided  transversely  in  the  upper  dorsal  region.  In  such  ca.ses, 
some  time  must  elapse  in  order  that  the  primary  effect  of  the  lesion  (the  so-called  .shock),  which 
usually  causes  a  diminution  of  the  reflexes,  may  pass  oft".  Very  young  mammals  exhibit  reflexes  for 
a  considerable  time  after  they  are  beheaded. 

Examples  :  i.  The  protective  movements  of  pithed  or  decapitated  frogs.  [If 
a  drop  of  a  dilute  acid  be  applied  to  the  skin  of  such  a  frog,  immediately  it  strives 
to  get  rid  of  the  offending  body,  and  it  generally  succeeds  m  doing  so.]  Similarly, 
it  kicks  against  any  fixed  body  pushed  against  it.  These  movements  are  so  pur- 
posive in  their  character,  and  the  actions  of  groups  of  muscles  are  so  adjusted  to 
perform  a  particular  act,  that  Pfliiger  regarded  them  as  directed  by,  and  due  to 
"  consciousness  of  the  spinal  cord."  If  a  flame  be  applied  to  the  side  or  part  of 
the  body  of  an  eel,  the  body  is  moved  away  from  the  flame.  The  tail  of  a  decapi- 
tated triton,  tortoise,  newt,  eel,  or  snake  is  directed  toward  a  gentle  stimulus,  but 
if  a  violent  stunulus  is  used,  it  is  directed  away  from  it  {Ltichsi tiger). 

2.  Goltz's  Croaking  Experiment. — A  pithed  (male)  frog,  /.  e.,  one  with  its 
cerebral  lobes  alone  removed  (or  one  with  its  eyes  or  ears  destroyed — Latigeiidot'ff), 
croaks  every  time  the  skin  of  its  back  or  flanks  is  gently  stroked.  [Some  male 
frogs,  when  held  up  by  the  finger  and  thumb  immediately  behind  the  fore  legs, 
croak  every  tiine  gentle  pressure  is  made  on  their  flank.] 

3.  Goltz's  "  Embrace  Experiment." — During  the  breeding  season  in 
spring,  the  part  of  the  body  of  the  male  frog  between  the  skull  and  the  fourth 
vertebra,  embraces  every  rigid  object,  which  is  brought  into  contact  with,  and 
gently  stimulates,  the  skin  over  the  sternum. 

In  the  intact  animal,  the  exciting  stimulus  lies  in  the  degree  of  filling  of  the  male  seminal  organ 
{Tarchanoff).     The  reflex  ceases  at  once  on  gently  stimulating  the  optic  lobes  [Albertoni). 

4.  In  mammals  (dogs),  the  following  reflex  acts  are  performed  by  the  posterior 
part  of  the  spinal  cord,  even  after  it  is  separated  from  the  rest  of  the  cord  :  Scratch- 
ing with  the  hind  feet  a  part  of  the  skin  which  has  been  tickled  (just  as  in  intact 
animals)  ;  the  movements  necessary  for  emptying  the  bladder  and  for  defaecation, 


REFLEX   TIME   AND    INHIBITION    OF    REFLEXES.  689 

as  well  as  those  necessary  for  erection  ;  the  movements  necessary  for  parturition 
{Goltz,  Freusberg  and  Gergens).  Coordinated  movements  do  not,  as  a  rule,  occur 
simultaneously  in  portions  of  the  spinal  cord  lying  widely  apart  after  removal  of 
the  medulla  oblongata.  According  to  Ludwig  and  Owsjannikow,  the  medulla 
oblongata  perhaps  contains  a  reflex  organ  of  a  higher  order,  which  forms,  as  it 
were,  a  centre  for  combining,  through  the  medium  of  the  nerve  fibres,  the  various 
reflex  provinces  in  the  spinal  cord. 

5.  Coordinated  reflexes  may  occur  in  man  during  -sleep,  and  during  patho- 
logical comatose  conditions. 

Most  of  the  movements  which  we  perforin  while  we  are  awake,  and  which  we  execute  uncon- 
sciously— or  even  when  our  psychical  activities  are  concentrated  upon  some  other  object — really 
belong  to  the  category  of  coordinated  reflexes.  Many  complicated  motor  acts  must  first  be  learned 
— e.  g.,  dancing,  skating,  riding,  walking — before  unconscious  harmonious  coordinated  reflexes  can 
again  be  discharged.  The  coordinated  reflex  movements  of  coughing,  sneezing,  and  vomiting 
depend  upon  the  spinal  cord,  together  with  the  medulla  oblongata. 

The  following  facts  are  also  important : — 

1.  Reflexes  are  more  easily  and  more  completely  discharged,  when  the  specific 
end  organ  of  the  afferent  nerve  is  stimulated,  than  when  the  trunk  of  the  nerve 
is  stimulated  in  its  course  (^Marshall  Hall,  1837).  [Thus,  by  gently  tickling  the 
skin,  it  is  easy  to  discharge  a  reflex  act,  while  it  requires  a  strong  stimulus  to  be 
applied  to  an  exposed  sensory  nerve  in  order  to  do  so.] 

2.  A  j-/';^^;^^^r  j-^/wz^j/z^j  is  required  to  discharge  a  reflex  movement  than  for  the 
direct  stimulation  of  motor  nerves. 

3.  A  movement  produced  reflexly  is  of  shorter  duration  than  the  corresponding 
movement  executed  voluntarily.  Further,  the  occurrence  of  the  movement  after 
the  moment  of  stimulation  is  distinctly  delayed.  In  the  frog,  a  period  nearly  twelve 
times  as  long  elapses  before  the  occurrence  of  the  contraction,  than  is  occupied  in 
the  transmission  of  the  impulse  in  the  sensory  and  motor  nerves  (^Hebnholtz,  1854.) 
Thus,  the  spiiial  cord  offers  resistance  to  the  transmission  of  impulses  through  it. 

The  term  "reflex  time  "  is  applied  to  the  time  necessary  for  transferring  the  impulse  from  the 
afferent  fibre  to  the  nerve  cells  of  the  cord,  and  from  them  to  the  efferent  fibre.  In  the  frog  it  is 
equal  to  0.008  to  0.015  second.  The  time,  however,  is  increased  by  almost  one-third,  if  the  impulse 
pass  to  the  other  side  of  the  cord,  or  if  it  pass  along  the  cord,  e.  g.,  from  the  sensory  nerves  of  the 
anterior  extremity  to  the  motor  roots  of  the  posterior  limb.  Heat  diminishes  the  reflex  time  and 
increases  the  reflex  excitability.  Lowering  the  temperature  (winter  frogs),  as  well  as  the  reflex- 
exciting  poisons  already  mentioned,  lengthens  the  rejiex  time,  while  the  reflex  excitability  is  simulta- 
neously increased.  Conversely,  the  reflex  time  diminishes  as  the  strength  of  the  stimulus  increases, 
and  it  may  even  become  of  minimal  duration  (/.  Rosenthal).  The  reflex  time  is  determined  by  ascer- 
taining the  moment  at  which  the  sensory  nerve  is  stimulated,  and  the  subsequent  contraction  occurs. 
Deduct  from  this  the  time  of  latent  stimulation  (§  298,  I),  and  the  time  necessary  for  the  conduction 
of  the  impulse  (§  298)  in  the  afferent  and  efferent  nerves  (v.  Helmholtz,J.  Rosenthal,  Exner,  Wundt). 

[Influence  of  Poisons. — The  latent  period  and  reflex  time  are  influenced  by  a  large  number  of 
conditions.  In  a  research  as  yet  unpublished,  W.  Stirling  finds  that  the  latent  period  may  remain 
nearly  constant  in  a  pithed  frog  for  nearly  two  days,  when  tested  by  Tiirck's  method.  Sodic  chloride 
does  not  influence  the  time,  nor  does  sodic  bromide  or  iodide.  Potassic  chloride,  however,  lengthens 
it  enormously,  or  even  abolishes  reflex  action  after  a  very  short  time,  and  so  do  potassic  bromide, 
ammonium  chloride  and  bromide,  chloral  and  croton-chloral.  The  lithia  salts  also  lengthen  the 
reflex  time,  or  abolish  the  reflex  act  after  a  time.] 

361.  INHIBITION  OF  THE  REFLEXES.— Within  the  body  there 
are  mechanisms  which  can  suppress  or  inhibit  the  discharge  of  reflexes,  and  they 
may  therefore  be  termed  mechanisms  inhibiting  the  reflexes.     These  are  : — 

I.  Voluntary  Inhibition. — Reflexes  may  be  inhibited  voluntarily,  both  in  the 
region  of  the  spinal  cord  and  brain.  Examples  :  Keeping  the  eyelids  open 
when  the  eyeball  is  touched ;  arrest  of  movement  when  the  skin  is  tickled.  We 
must  observe,  however,  that  the  suppression  of  reflexes  is  possible  only  up  to  a 
certain  point.  If  the  stimulus  be  strong,  and  repeated  with  sufficient  frequency, 
the  reflex  impulse  ultimately  overcomes  the  voluntary  effort.  It  is  impossible  to 
44 


690  EXAMPLES    AND    NATURE    OF    INHIBITION. 

suppress  those  reflex  movements  which  cannot  at  any  time  be  performed  voluntarily. 
Thus,  erection,  ejaculation,  parturition,  and  the  movements  of  the  iris,  are  neither 
direct  voluntary  acts,  nor  can  they,  when  they  are  excited  reflexly,  be  suppressed 
by  the  will. 

2.  Setschenow's  inhibitory  centre  is  another  cerebral  apparatus,  which 
in  the  frog  is  placed  in  the  optic  lobes.  If  the  optic  lobes  be  separated  from  the 
rest  of  the  brain  and  spinal  cord,  by  a  section  made  below  it,  the  reflex  excitability 
is  increased.  If  the  lower  divided  surface  of  the  optic  lobes  be  stimulated  with  a 
crystal  of  common  salt  or  blood,  the  reflex  movements  are  suppressed.  The  same 
results  obtain  when  only  one  side  is  operated  on.  Similar  organs  are  supposed  to 
be  present  in  the  corpora  quadrigemina  and  medulla  oblongata  of  the  higher  verte- 
brates. From  I  and  2  we  may  exi)lain  why  reflex  movements  occur  more  regularly 
and  more  readily  after  separation  of  the  brain  from  the  spinal  cord. 

[Quinine  greatly  diminishes  the  reflex  excitability  in  the  frog,  but  if  the  medulla  oblongata  be 
divided,  the  reflex  excitability  of  the  cord  is  restored.  The  depression  is  ascribed  by  Chaperon  to 
the  action  of  the  quinine  on  Setschenow's  centres.] 

3.  Strong  stimulation  of  a  sensory  nerve  inhibits  reflex  movements.  The 
reflex  does  not  take  place  if  an  afterent  nerve  be  stimulated  very  powerfully  {Goifz, 
Lczuissofi).  Examples  :  Suppressing  a  sneeze  by  friction  of  the  nose  [compressing 
the  skin  of  the  nose  over  the  exit  of  the  nasal  nerve] ;  suppression  of  the  move- 
ments produced  by  tickling,  by  biting  the  tongue.  Very  violent  stimulation  may 
even  suppress  the  coordinated  reflex  movements  usually  controlled  by  voluntary 
impulses.  Violent  pain  of  the  abdominal  organs  (intestine,  uterus,  kidneys,  bladder, 
or  liver)  may  ])revent  a  person  from  walking  or  even  from  standing.  To  the  same 
category  belongs  the  fact  that  persons  fall  down  when  internal  organs  richly  sup- 
plied with  nerves  are  injured,  there  being  neither  injury  of  the  motor  nerves  nor  loss 
of  blood  to  account  for  the  phenomenon.  Excitement  of  the  central  organs  through 
other  centripetal  channels  (nerves  of  special  sense,  and  those  of  the  generative 
organs)  diminishes  the  reflexes  in  other  channels. 

4.  It  is  important  to  note  that  in  the  suppression  of  reflexes,  antagonistic  muscles  are  often 
thrown  into  action,  whetlier  voluntarily  or  by  the  stimulation  of  sensory  nerves,  i.  e.,  reflexly.  In 
some  cases,  in  order  to  cause  suppression  of  the  reflex,  it  appears  to  be  sufficient  to  direct  our  attention 
to  the  execution  of  such  a  complicated  reflex  act.  Thus,  some  persons  cannot  sneeze  when  they  think 
intently  upon  this  act  itself  (Diif~:ain).  The  voluntary  impulse  rapidly  reaches  tlie  reflex  centre,  and 
begins  to  influence  it  so  that  the  normal  course  of  the  reflex  stimulation,  due  to  an  impulse  from  the 
periphery,  is  interfered  with  (Sc/i/osser). 

5.  Poisons. — Chloroform  diminishes  the  reflex  excitability  by  acting  upon  the 
centre,  and  a  similar  effect  is  produced  by  picrotoxin,  morphia,  narcotin,  thebain, 
aconitin,  quinine,  hydrocyanic  acid.  [W.  Stirling  finds  that  chloral,  potassic 
bromide  and  chloride,  ammonium  chloride,  but  not  sodium  chloride,  greatly  dimin- 
ish the  reflex  excitability.      Nicotin  increases  it  in  frogs  {Freusl>erg).'\ 

A  constant  current  of  electricity  passed  longitudinally  through  the  cord 
diminishes  the  reflexes  {Ranke),  especially  if  the  direction  of  the  current  is  from 
above  downward  (^Legros  and  Oniinus,  Uspensky). 

[Some  drugs  affect  the  reflex  excitability  directly  by  acting  on  the  spinal  cord,  e.g.,  methylconine, 
but  other  drugs  may  produce  the  same  result  indirectly  by  afiecting  the  heart  and  the  l)lood  supply 
to  the  cord.  If  the  abdominal  aorta  of  a  rabbit  be  compressed  for  a  few  minutes  to  cut  off  the  supply 
of  blood  to  the  cord  and  lower  limbs,  temporary  paraplegia  is  produced.] 

If  frogs  be  asphyxiated  in  air  deprived  of  all  its  O,  the  brain  and  spinal  cord  become  completely 
unexcitable,  and  can  no  longer  discharge  reflex  acts.  The  motor  nerves  and  the  muscles,  however, 
suffer  very  little,  and  may  retain  their  excitability  for  many  days  {Aubert). 

[Nature  of  Inhibition. — The  foregoing  view  assumes  the  existence  of  inhibitory  centres,  but  it  is 
important  to  point  out  that  it  has  been  attempted  to  explain  this  phenomenon  without  postulating  the 
existence  of  inhibitory  centres.  During  inhibition  the  function  of  an  organ  is  restrained — during 
paralysis  it  is  abolished,  so  that  there  is  a  sharp  distinction  between  the  two  conditions.  The  analogy 
between  inhibitory  phenomena  and  the  effects  of  interference  of  waves  of  light  or  sound  has  been 
pointed  out  by  Bernard  and  Romanes,  while  Lauder  Brunton  has  tried  to  explain  the  question  on  a 


TURCK'S    method THEORY    OF    REFLEX   ACTION.  691 

physical  basis,  indicating  that  inhibition  is  not  dependent  on  the  existence  of  special  inhibitory  centres 
but  that  stimulation  and  inhibition  are  different  phases  of  excitement,  the  two  terms  being  relative 
conditions  depending  on  the  length  of  the  path  along  which  the  impulse  has  to  travel  and  the  rate  of 
its  transmission.  Brunton  points  out  that  the  known  facts  are  more  consistent  with  an  hypothesis  of 
the  interference  of  waves,  one  with  another,  than  with  the  supposition  that  they  are  inhibitory  centres 
for  every  so-called  inhibitory  act  in  the  body.  In  discussing  this  question  great  regard  must  be  had 
to  the  action  of  the  vagus  on  the  heart  (|  369).] 

Tiirck's  method  of  testing  the  reflex  excitability  of  a  frog  is  the  following:  A 
frog  is  pithed,  and  after  it  has  recovered  from  the  shock,  its  foot  is  dipped  into 
dilute  sulphuj'ic  acid  [2  per  1000].  The  time  which  elapses  between  the  leg  being 
dipped  in  and  the  moment  it  is  withdrawn  is  noted.  [The  time  may  be  estimated 
by  means  of  a  metronome,  or  the  movements  may  be  inscribed  upon  a  recording 
surface.     The  time  which  elapses  is  known  as  the  "  period  of  latent  stimulation."] 

This  time  is  greatly  prolonged  after  the  optic  lobes  have  been  stimulated  with  a  crystal  of  common 
salt  or  blood,  or  after  the  stimulation  of  a  sensory  nerve. 

Setschenow  distinguished  tactile  reflexes,  which  are  discharged  by  stimulation  of  the  nerves  oj 
touch;  and  pathic,  which  are  due  to  stimulation  of  sensory  (pain-conducting)  fibres.  He  and 
Paschutin  suppose  that  the  tactile  reflexes  are  suppressed  by  voluntary  impulses,  and  the  pathic  by 
the  centre  in  the  optic  lobes. 

Theory  of  Reflex  Movements. — The  following  theory  has  been  propounded  to  account  for  the 
phenomena  already  described:  It  is  assumed  that  the  affere7tt  fibre  within  the  gray  matter  of  the 
spinal  cord  joins  one  or  more  nerve  cells,  and  thus  is  placed  in  communication  in  all  directions  with 
the  network  of  fibres  in  the  gray  substance.  Any  impulse  reaching  the  gray  matter  of  the  cord  has 
to  overcome  considerable  resistance.  The  least  resistance  hes  in  the  direction  of  those  efferent 
fibres  which  emerge  in  the  same  plane  and  upon  the  same  side  as  the  entering  fibre.  Thus,  the 
feeblest  stimulus  gives  rise  to  a  simple  reflex,  which  generally  is  merely  a  simple  protective  movement 
for  the  part  of  the  skin  which  is  stimulated.  Still  greater  resistance  is  opposed  in  the  direction  of 
other  motor  ganglia.  If  the  reflex  impulse  is  to  pass  to  these  ganglia,  either  the  discharging  stimulus 
mu.st  be  considerably  increased,  or  the  resistance  within  the  connections  of  the  gangha  of  the  gray 
matter  must  be  diminished.  Ihe  latter  condition  is  produced  by  the  action  of  the  above-named 
poisons,  as  well  as  during  general  increased  nervous  excitability  (hysteria,  nervousness).  Thus, 
extensive  reflex  spasms  may  be  produced  either  by  increasing  the  stimulus,  or  by  diminishing  the 
resistance  to  conduction  in  the  spinal  cord.  Those  conditions  which  render  the  occurrence  of  reflexes 
more  difficult,  or  abolish  them  altogether,  must  be  regarded  as  increasing  the  resistance  in  the  reflex 
arc  in  the  cord.     The  action  of  the  reflex  inhibitory  mechanism  may  be  viewed  in  a  similar  manner. 

The  fibres  of  the  reflex  arc  must  have  a  connection  with  the  reflex  inhibitory  paths ;  we  must 
assume  that  equally  by  the  reflex  inhibitory  stimulation  resistance  is  introduced  into  the  reflex  arc. 
The  explanation  of  extensive  coordinated  movements  is  accompanied  with  difficulties.  It  is  assmned, 
that  by  use  and  also  by  heredity,  those  ganglionic  cells  which  are  the  first  to  receive  the  impulse  are 
placed  in  the  path  of  least  resistance  in  connection  with  those  cells  which  transfer  the  impulse  to  the 
groups  of  muscles,  whose  contraction,  resulting  in  a  coordinated  purposive  movement,  prevents  the 
body  or  the  limb  from  being  affected  by  any  injurious  influences. 

Pathological. — Anomalies  of  reflex  activity  afford  an  important  field  to  the  physician  in  the 
investigation  of  nervous  diseases.  Enfeeblement,  or  even  complete  abolition  of  the  reflexes  may 
occur:  (i)  Owing  to  diminished  sensibihty  or  complete  insensibility  of  the  afferent  fibres;  (2)  in 
analogous  affections  of  the  central  organ;  (3)  or,  lastly,  of  the  efferent  fibres.  Where  there  is  general 
depression  of  the  nervous  activity  (as  after  shocks,  compression  or  inflammation  of  the  central  nervous 
organs;  in  asphyxia,  in  deep  coma,  and  in  consequence  of  the  action  of  many  poisons),  the  reflexes 
may  be  greatly  diminished  or  even  abolished. 

[Reflexes. — The  physician,  by  studying  the  condition  of  the  reflexes,  can  form 
an  idea  as  to  the  condition  of  practically  every  inch  of  the  spinal  cord.  There  are 
three  groups  of  reflexes,  {a)  the  superficial,  {b)  the  deep  or  tendon,  (r)  the 
organic  reflexes.] 

[The  superficial  or  skin  reflexes  are  excited  by  stimulating  the  skin,  e.  g., 
by  tickling,  pricking,  scratching,  etc.  We  can  obtain  a  series  of  reflexes  from  below 
as  far  up  as  the  lower  part  of  the  cervical  region.  The  plantar  reflex  is  obtained 
by  tickling  the  soles  of  the  feet,  when  the  leg  on  that  side,  or,  it  may  be,  both  legs 
are  drawn  up.  It  is  always  present  in  health,  and  its  centre  is  in  the  lumbar 
enlargement  of  the  cord.  The  cremasteric  reflex  is  well  marked  in  boys,  and  is 
easily  produced  by  exciting  the  skin  on  the  inner  side  of  the  thigh,  when  the  testicle 
on  that  side  is  retracted.     The  gluteal  reflex  consists  in  a  contraction  of  the  gluteal 


692  THE    SUPERFICIAL    REFLEXES. 

muscles,  when  the  skin  over  the  buttock  is  stimulated.  The  abdominal  reflex 
consists  in  a  similar  contraction  of  the  abdominal  muscles,  when  the  skin  over  the 
abdomen  in  the  mammary  line  is  stimulated.  The  epigastric  reflex  is  obtained 
l)y  stimulating  the  skin  in  front  between  the  fourth  and  sixth  ribs.  The  inter- 
scapular reflex  results  in  a  contraction  of  the  muscles  attached  to  the  scapula, 
when  the  skin  between  the  scapul?e  is  stimulated.  Its  centre  corresponds  to  the 
lower  cervical  and  upper  dorsal  region.] 

[The  following  table,  after  Gowers,  shows  the  relation  of  each  reflex  to  the  spinal  segment  or 
segments  on  which  it  depends : — 

t:eryical, 6   l  \      Lumbar 1 1  Cremasteric. 

•••••••      7       Interscapular.      1  [[  '.'.'.'.'.'.'.    I)   \  Knee  Reflex. 

Dorsal,      \    '.'.'.'.'.'.       l  \  \  "  4 1  (j 


5  1  '  "  .      -5 


6  V  Epigastric. 

7  J 

8  ] 

9  I 

lo   j-  Abdominal. 

"    I 

12   J 


Sacral, i 

2  1-  "^  I    ]  Plantar. 

"  3J"^Cj|.  Vesical. 

"         4  (  Rectal. 

"  5  J  Sexual.] 


Another  important  diagnostic  reflex  is  the  "abdominal  reflex,"  which  consists 
in  this,  that  when  the  skin  of  the  abdomen  is  stroked,  ,?. ^j,--.,  with  the  handle  of  a 
percussion  hammer,  the  abdominal  muscles  contract.  When  this  reflex  is  absent 
on  both  sides  in  a  cerebral  affection,  it  indicates  a  diff'use  disease  of  the  brain ;  its 
absence  on  one  side  indicates  a  local  affection  of  the  opposite  half  of  the  brain. 
The  cremasteric,  conjunctival,  mammillary,  pupillary,  and  nasal  reflexes 
may  also  be  specially  investigated.  In  hemiplegia  complicated  with  cerebral  lesions, 
the  reflexes  on  the  paralyzed  side  are  diminished,  while  not  unfrequently  the  patellar 
reflex  may  be  increased.  In  extensive  cerebral  affections  accompanied  by  coma  the 
reflexes  are  absent  on  both  sides,  including,  of  course,  those  of  the  anus  and  bladder 
((?.  Rosenbach). 

[Horsley  finds  that  in  the  deepest  narcosis  produced  by  nitrous  oxide  gas  the  superficial  reflexes 
{e.g.,  plantar,  conjunctival)  are  abolished,  while  the  deep  (knee  jerk)  remain.  Anamia  of  the  lumbar 
enlargement  (compression  of  the  abdominal  aorta)  causes  disaj^pearances  of  both  reflexes  {Prevost). 
Chloroform  and  asphyxia  abolish  the  deep  as  well  as  the  superficial  reflexes.  Horsley  regards  the 
so-called  deep  reflex  or  knee  jerk  not  as  depending  on  a  centre  in  the  cord,  but  the  contraction  of 
the  rectus  femoris  is  due  to  local  irritation  of  the  muscle  from  sudden  elongation.] 

Deep  or  Tendon  Reflexes. — Under  pathological  conditions,  special  attention 
is  directed  to  the  so-called  tendon  reflexes,  which  depend  upon  the  fact  that  a  blow 
upon  a  tendon  {e.g.,  the  quadriceps  femoris,  tendo-Achilles,  etc.)  discharges  a 
contraction  of  the  corresponding  muscle  {IVestphal,  Erb,  1875).  The  patellar 
tendon  reflex  (also  called  ''  knee  phenomenon''^  or  simply  "  knee  reflex,"  or  "knee 
jerk,"  is  mvariably  absent  in  cases  of  ataxic  tabes  dorsalis,  while  in  spastic  spinal 
paralysis  it  is  abnormally  strong  and  extensive  {Erb).  [The  "knee  jerk"  is 
elicited  by  percussing  the  ligamentum  patellar,  and  is  due  to  a  single  spasm  of  the 
rectus.  The  latent  period  is  0.03  to  0.04  second,  and  it  is  argued  by  Waller  and 
others  that  it  is  doubtful  if  this  tendon  reflex  is  subserved  by  a  spinal  nervous  arc, 
while  admitting  the  effect  of  the  spinal  cord  in  modifying  the  response  of  the 
muscle.]  Section  of  the  motor  nerves  abolishes  the  patellar  phenomenon  in  rabbits 
{Schultz),  and  so  does  section  of  the  cord  opposite  the  5th  and  6th  lumbar  vertebrae 
{Tschirjew).  Landois  finds  that  in  his  own  person  the  contraction  occurs  0.048 
second  after  the  blow  upon  the  ligamentum  patellae.  According  to  Waller,  the 
patellar  reflex  and  the  tendo-Achilles  reflex  occur  0.03  to  0.04  second,  and  according 
to  Eulenburg,  0.032  second  after  the  blow.  According  to  Westphal,  these  phe- 
nomena are  not  simple  reflex  processes,  but  complex  conditions  intimately  dependent 


PATELLAR   REFLEX   AND    ANKLE    CLONUS.  693 

upon  the  muscle  tonus,  so  that  when  the  tonus  of  the  quadriceps  femoris  is  dimin- 
ished, the  phenomenon  is  abolished.  In  order  that  the  phenomenon  may  take 
place,  it  is  necessary  that  the  outer  part  of  the  posterior  column  of  the  spinal  cord 
remain  intact  (^Westphal).  [The  knee  jerk  can  be  increased  or  reinforced  by 
volitional  acts  directed  to  other  parts  of  the  body,  e.g.,  by  exercising  voluntary 
pressure  with  the  hand  (^JeiidrdssiK).'\  [A  "jaw  jerk  "  is  obtained  by  suddenly 
depressing  the  lower  jaw  {Gowe?-s,  Beezwr,  and  De  Waiteville),  and  the  last  observer 
finds  that  the  latent  period  is  0.02  second,  and  if  this  be  the  case,  it  is  an  argument 
against  these  so-called  "tendon  reflexes"  being  true  reflexes,  and  that  they  are 
direct  contractions  of  the  muscles  due  to  sudden  stimulation  by  extension.] 

[Method. — The  knee  jerk  is  easily  elicited  by  striking  the  patellar  tendon 
with  the  edge  of  the  hand  or  a  percussion  hammer  when  the  leg  is  semi-flexed,  as 
when  the  legs  are  hanging  over  the  edge  of  a  table  or  when  one  leg  is  crossed 
over  the  other.  It  is  almost  invariably  present  in  health,  but  it  becomes  greatly 
exaggerated  in  descending  degeneration  of  the  lateral  columns  and  lateral 
sclerosis.] 

[Ankle  clonus  is  another  tendon  reflex,  and  it  is  never  present  in  health.  If 
the  'leg  be  nearly  extended,  and  pressure  made  upon  the  sole  of  the  foot  so  as 
suddenly  to  flex  the  foot  at  the  ankle,  a  series  of  (5  to  7  per  second)  rhythmical 
contractions  of  the  muscles  of  the  calf  takes  place.  Gowers  describes  a  modi- 
fication elicited  by  tapping  the  muscles  of  the  front  of  the  leg,  the  '^ front-tap 
contraction.'^  Ankle  clonus  is  excessive  in  sclerosis  of  the  lateral  columns  and 
spastic  paralysis.] 

[In  "  ankle  clonus  "  excited  by  sudden  passive  flexion  of  the  foot,  there  is  a  multiple  spasm  of  the 
gastrocnemius.  Here  also  the  latent  period  is  about  0.03  to  0.04  second,  and  the  rhythm  8  to  10  per 
second.  This  short  latent  period  has  led  some  observers  to  doubt  the  essentially  reflex  nature  of 
this  act.] 

When  we  are  about  to  sleep  {\  374),  there  is  first  of  all  a  temporary  increase  of  the  reflexes  ;  in 
the  first  sleep  the  reflexes  are  diminished,  and  the  pupils  are  contracted.  In  deep  sleep  the  abdomi- 
nal, cremasteric,  and  patellar  reflexes  are  absent ;  while  tickling  the  soles  of  the  feet  and  the  nose 
only  acts  when  the  stimulus  is  of  a  certain  intensity.  In  narcosis,  e.g.,  chloroform  or  morphia,  the 
abdominal,  then  the  conjunctival  and  patellar  reflexes  disappear;  lastly,  the  pupils  contract  (C. 
RosenbacJi). 

Abnormal  increase  of  the  reflex  activity  usually  indicates  an  increase  of  the  excitability  of  the 
reflex  centre,  although  an  abnormal  sensibility  of  the  afferent  nerve  may  be  the  cause.  As  the  har- 
monious equilibrium  of  the  voluntary  movements  is  largely  dependent  upon  and  regulated  by  the 
reflexes,  it  is  evident  that  in  affections  of  the  spinal  cord  there  are  frequent  disturbances  of  the  vol- 
untary movements,  <?.  g.,  the  characteristic  disturbance  of  motion  in  attempting  to  walk,  and  in  grasp- 
ing movements  exhibited  by  persons  suffering  from  ataxic  tabes  dorsalis  [or,  as  it  is  more  generally 
called,  locomotor  ataxia]. 

[The  organic  reflexes  include  a  consideration  of  the  acts  of  micturition,  erec- 
tion, ejaculation,  defecation,  and  those  connected  with  the  motor  and  secretory 
digestive  processes,  respiration,  and  circulation.] 

362.  CENTRES  IN  THE  SPINAL  CORD.— Centres  capable  of  being 
excited  reflexly,  and  which  can  bring  about  the  discharge  of  certain  complicated, 
yet  well  coordinated,  motor  acts  exist  in  various  parts  of  the  spinal  cord.  They 
still  retain  their  activity  after  the  spinal  cord  is  separated  from  the  medulla 
oblongata ;  further,  those  centres  lying  in  the  lower  part  of  the  spinal  cord  still 
retain  their  activity  after  being  separated  from  the  higher  centres,  but  m  the  normal 
intact  body,  they  are  subjected  to  the  control  of  higher  reflex  centres  in  the  medulla 
oblongata.  Hence,  we  may  speak  of  them  as  subordinate  spinal  centres.  The 
cerebrum  also,  partly  by  the  production  of  perceptions,  and  partly  as  the  organ  of 
volition,  can  excite  or  suppress  the  action  of  certain  of  these  subordinate  spinal 
centres.     [For  the  significance  of  the  term  "  Centre,"  see  p.  675.] 

I.  The  cilio-spinal  centre  connected  with  the  dilatation  of  the  pupil  lies 
in  the  lower  cervical  part  of  the  cord,  and  extends  downward  to  the  region  of  the 


694  CENTRES    IN    THE    SPINAL   CORD. 

ist  to  the  3d  dorsal  vertebra.  It  is  excited  by  diminution  of  light ;  both  pupils 
always  react  simultaneously,  when  one  retina  is  shaded.  Unilateral  extirpation  of 
this  ])art  of  the  spinal  cord  causes  contraction  of  the  pui)il  on  the  same  side.  The 
motor  fibres  pass  out  by  the  anterior  roots  of  the  two  lower  cervical  and  two  upper 
dorsal  nerves,  into  the  cervical  sympathetic  (§  392).  I'2vcn  the  idea  of  darkness 
may  sometimes,  though  rarely,  cause  dilatation  of  the  pupil  {Budge). 

In  goats  and  cats,  this  centre,  even  after  being  separated  from  the  medulla  oblongata,  can  ht 
excited  directly  by  dyspnoeic  blood,  and  also  retlexly  by  the  stimulation  of  sensory  nerves,  e.  g.,  the 
median,  especially  when  the  reflex  excitability  of  the  cord  is  increased  by  the  action  of  strj'chnin  or 
atropin  (L/tc/isinger).     Tor  the  dilator  centre  in  the  medulla  oblongata,  see  g  367,  S. 

2.  The  ano-spinal  centre,  or  centre  controlling  the  act  of  defaecation.    The 

afferent  nerves  lie  in  the  hemorrhoidal  and  inferior  mesenteric  plexuses,  the  centre 
at  the  5th  (dog)  or  6th  to  ylh  (rabbit)  lumbar  vertebra  ;  the  efferent  fibres  arise 
from  the  pudendal  plexus  and  pass  to  the  sphincter  muscles.  For  the  relation  of 
this  centre  to  the  cerebrum,  see  §  160.  After  section  of  the  spinal  cord  [in  dogs], 
Goltz  observed  that  the  sphincter  contracted  rhythmically  upon  the  finger  intro- 
duced into  the  anus  ;  the  coordinated  activity  of  the  centre,  therefore,  would  seem 
to  be  possible  only  when  the  centre  remains  in  connection  with  the  brain. 

3.  The  vesico-spinal  centre  for  regulating  micturition,  or  Budge's  vesico- 
spinal centre.  The  centre  for  the  sphincter  muscle  lies  at  the  5th  (dog)  or  the  7th 
(rabbit)  lumbar  vertebra,  and  that  for  the  muscles  of  the  bladder  somewhat  higher. 
The  centre  acts  only  in  a  properly  coordinated  way  in  connection  with  the  brain 
(§  280). 

4.  The  erection  centre  also  lies  in  the  lumbar  region  (§  436).  The  afferent 
nerves  are  the  sensory  nerves  of  the  penis;  the  efferent  nerves  for  the  deep  artery 
of  the  penis  are  the  vaso-dilator  nerves,  arising  from  the  ist  to  3d  sacral  nerves, 
or  Fxkhard's  nervi  erigentes — while  the  motor  nerves  for  the  ischio-cavernosus 
and  deep  transverse  perineal  muscles  arise  from  the  3d  to  4th  sacral  nerves  (§  356). 
The  latter  may  also  be  excited  voluntarily,  the  former  also  partly  by  the  brain,  by 
directing  the  attention  to  the  sexual  activity.  Eckhard  observed  erection  to  take 
place  after  stimulation  of  the  higher  regions  of  the  spinal  cord,  as  well  as  of  the 
pons  and  crura  cerebri. 

5.  The  ejaculation  centre.  The  afferent  nerve  is  the  dorsal  of  the  penis,  the 
centre  (Budge's  cerebro-spinal  centre)  lies  at  the  4th  lumbar  vertebra  (rabbit);  the 
motor  fibres  of  the  vas  deferens  arise  from  the  4th  and  5th  lumbar  nerves,  which 
pass  into  the  sympathetic,  and  from  thence  to  the  vas  deferens.  The  motor  fibres 
for  the  bulbo-cavernosus  muscle,  which  ejects  the  semen  from  the  bulb  of  the 
urethra,  lie  in  the  3d  and  4th  sacral  nerves  (perineal). 

6.  The  parturition  centre  lies  at  the  ist  and  2d  lumbar  vertebrae  (§  453) ; 
the  afferent  fibres  come  from  the  uterine  plexus,  to  which  also  the  motor  fibres 
proceed  (Korner).  Goltz  and  Freusberg  observed  that  a  bitch  became  pregnant 
after  its  spinal  cord  was  divided  at  the  ist  lumbar  vertebra. 

7.  Vasomotor  Centres. — Both  vasomotor  and  vaso-dilator  centres  are  dis- 
tributed throughout  the  whole  spinal  axis.  To  them  belongs  the  centre  for  the 
sp/een,  which  in  the  dog  is  opposite  the  ist  to  4th  cervical  vertebrae  (Bu/gak). 
They  can  be  excited  reflexly,  but  they  are  also  controlled  by  the  dominating 
centre  in  the  medulla  oblongata  (§  371).  Psychical  disturbance  (cerebrum)  influ- 
ences them  (§  377). 

[8.   Perhaps  there  are  vaso-dilator  centres  (§  372).] 

9.  The  sweat  centre  is  perhaps  distributed  similarly  to  the  vasomotor  centre 
(§  288). 

The  reflex  movements  discharged  from  these  centres  are  orderly  coordinated  reflexes,  and  may 
thus  be  compared  to  the  orderly  reflexes  of  the  trunk  and  extremities. 

Muscle  Tonus. — Formerly  atitoinalic  functions  were  ascribed  to  the  spinal  cord,  one  of  these 
being  that  it  caused  a  moderate  active  tension  of  the  muscles — a  condition  that  was  termed  viuscle 


EXCITABILITY   OF   THE    SPINAL    CORD.  695 

ione,  or  tonus.  The  existence  of  tonus  in  a  striped  muscle  was  thought  to  be  proved  by  the  fact  that, 
when  such  a  muscle  was  divided,  its  ends  retracted.  This  is  due  merely  to  the  fact  that  all  the 
muscles  are  stretched  slightly  beyond  their  normal  length  (§  301).  Even  paralyzed  muscles,  which 
have  lost  their  muscular  tone,  show  the  same  phenomenon.  Formerly,  the  stronger  contraction  of 
certain  muscles,  after  paralysis  of  their  antagonists,  and  the  retraction  of  the  facial  muscles  to  the 
sound  side,  after  paralysis  of  the  facial  nerve,  were  also  regarded  as  due  to  tonus.  This  result  is  due 
to  the  fact  that,  during  the  activity  of  the  intact  muscles,  the  other  ones  have  not  sufficient  power  to 
restore  the  parts  to  their  normal  median  position.  The  following  experiment  of  Auerbach  and  Hei- 
denhain  is  against  the  assumption  of  a  chronic  contraction  :  If  the  muscles  of  the  leg  of  a  decapi- 
tated frog  be  stretched,  it  is  found  that  they  do  not  elongate  after  section  of  the  sciatic  nerve,  or  after 
it  is  paralyzed  by  touching  it  with  ammonia  or  carbolic  acid. 

Reflex  Tonus. — If,  however,  a  decapitated  frog  be  suspended  in  an  ahnor7?ial  position,  we 
observe,  after  section  of  the  sciatic  nerve,  or  the  posterior  nerve  roots  on  one  side,  that  the  leg  on 
that  side  hangs  limp,  while  the  leg  of  the  sound  side  is  shghtly  retracted.  The  sensory  nerves  of  the 
latter  are  slightly  and  continually  stimulated  by  the  weight  of  the  Umb,  so  that  a  slight  reflex  retrac- 
tion of  the  leg  takes  place,  which  disappears  as  soon  as  the  sensory  nerves  of  the  leg  are  divided.  It 
we  choose  to  call  this  slight  retraction  tonus,  then  it  is  a  reflex  tonus  [Brondgeest).  {See  the  experi- 
ments ol  Harless,  C.  Ludwig,  and  Cyan — \  355-) 

363.  EXCITABILITY    OF    THE    SPINAL    CORD.— Even   at   the 

present  time  observers  are  by  no  means  agreed  whether  the  spinal  cord,  like 
peripheral  nerves,  is  excitable,  or  whether  it  is  distinguished  by  the  remarkable 
peculiarity  that  most  of  its  conducting  paths  and  ganglia  do  not  react  to  direct 
■electrical  and  mechanical  stimuli. 

It  is  contended  by  some  observers  that  if  stimuli  be  cautiously  applied  either  to  white  or  gray 
m.atter,  there  is  neither  movement  nor  sensation  (  Van  Deen  (1841)  Brown-Seqzuird).  Care  must  be 
taken  not  to  stimulate  the  roots  of  the  spinal  nerves,  as  these  respond  at  once  to  stimuli,  and  thus 
may  give  rise  to  movements  or  sensations.  As  the  spinal  cord  conducts  to  the  brain  impulses  com- 
municated to  it  from  the  stimulated  posterior  roots,  but  does  not  itself  respond  to  stimuli  which  pro- 
duce sensations,  Schiff  has  applied  to  it  the  term  "  aesthesodic."  Further,  as  the  cord  can  conduct 
both  voluntary  and  reflex  motor  impulses,  without,  however,  itself  being  aff'ected  by  motor  impulses 
applied  to  it  directly,  he  calls  it  "  kinesodic." 

Schiff' s  views  are  as  follows  : — 

1.  In  the  posterior  columns  the  sensory  root  fibres  of  the  posterior  root 
which  traverse  these  columns  give  rise  to  painful  impressions,  but  the  proper  paths 
of  the  posterior  columns  themselves  do  not  do  so.  The  proof  that  stimulation  of 
the  posterior  column  produces  sensory  impressions,  he  finds  in  the  fact  that 
dilatation  of  the  pupil  occurred  with  every  stimulation  (§  292).  Removal  of 
the  posterior  column  produces  anaesthesia  (loss  of  tactile  sensation).  Algesia 
[or  the  sensation  of  pain]  remains  intact,  although  at  first  there  may  even  be 
hyperalgesia. 

2.  The  anterior  columns  are  non-excitable,  both  for  striped  and  non-striped 
muscle,  as  long  as  the  stimuli  are  applied  only  to  the  proper  paths  of  this  column. 
But  movements  may  follow,  either  when  the  anterior  nerve  roots  are  stimulated, 
or  when,  by  the  escape  of  the  current,  the  posterior  columns  are  affected,  whereby 
reflex  movements  are  produced. 

According  to  Schiff,  therefore,  all  the  phenomena  of  irritation,  which  occur  when  an  uninjured 
cord  is  stimulated  (spasms,  contracture),  are  caused  either  by  simultaneous  stimulation  of  the  anterior 
roots,  or  are  reflexes  from  the  posterior  columns  alone,  or  simultaneously  from  the  posterior  columns 
and  the  posterior  roots.  Diseases  affecting  only  the  anterior  and  lateral  colunms  alone  never  produce 
symptoms  of  irritation,  but  always  of  paralysis.  In  complete  anaesthesia  and  apnoea,  every  form  of 
stimulus  is  quite  inactive.  According  to  Schift's  view,  all  centres,  both  spinal  and  cerebral,  are 
inexcitable  by  artificial  means. 

Direct  Excitability. — Many  observers,  however,  oppose  these  views,  and  contend  that  the  spinal 
cord  is  excitable  to  direct  stimulation.  Fick  observed  movements  to  take  place  when  he  stimu- 
lated the  white  columns  of  the  cord  of  a  frog,  isolated  for  a  long  distance  so  as  to  avoid  the  escape 
of  the  stimulating  currents.  Sirotinin,  also,  who  stimulated  the  transverse  section  of  the  frog's  cord 
from  point  to  point,  obtained  contraction  of  the  muscles  both  by  mechanical  and  electrical  stimuU. 
Biedermann  comes  to  the  following  conclusions :  The  transverse  section  of  a  motor  nerve  is  most 
excitable.  Weak  stimuli  (descending  opening  shocks)  excite  the  cut  surface  of  the  transversely 
divided  spinal  cord,  but  do  not  act  when  applied  further  down.     Luchsinger  asserts  that,  after  dipping 


696  HYPER/liSTHESlA. 

the  anterior  part  of  a  l>eheadecl  snake  into  warm  water,  the  reflex  movements  of  the  upper  part  of 
the  cord  are  abolished,  while  the  direct  excitability  remains. 

3.  Excitability  of  the  Vasomotors. — The  vaso-constrictor  nerves, 
which  proceed  from  the  vasomotor  centre  and  run  downward  in  the  lateral 
columns  of  the  cord,  are  excitable  by  all  stimuli  along  their  whole  course  ;  direct 
stimulation  of  any  transverse  section  of  the  cord  constricts  all  the  blood  vessels 
below  the  point  of  section  (C.  Luihcig  and  Thiry).  In  the  same  way,  the  fibres 
which  ascend  in  the  cord,  and  increase  the  action  of  the  vasomotor  centre — 
pressor  fibres,  are  also  excitable  (C  Luihing  and  Dittmar — §  364,  10).  Stimula- 
tion of  these  fibres,  although  it  affects  the  vasomotor  centre  reflexly,  does  not 
cause  sensation. 

4.  Chemical  stimuli  such  as  the  application  of  common  salt,  or  wetting  the 
cut  surface  with  blood,  appear  to  excite  the  spinal  cord. 

5.  The  motor  centres  are  directly  excited  by  blood  heated  above  40°  C, 
or  by  asphyxiated  blood,  or  by  sudden  and  complete  anaemia  of  the  cord  produced 
by  ligature  of  the  aorta  {Sigm.  Mayer)  \  and  also  by  certain  poisons — picrotoxin, 
nicotin,  and  compounds  of  barium  {Luchsinger). 

Action  of  Blood  and  Poisons. — In  experiments  of  this  kind,  the  spinal  cord  ought  to  be  divided 
at  the  1st  lumbar  vertebra,  at  least  twenty  hours  before  the  experiment  is  begun.  It  is  well  to 
divide  the  posterior  roots  beforehand  to  avoid  reflex  movements.  If,  in  a  cat  thus  operated  on, 
dyspnoea  be  produced,  or  its  diood  overheated,  then  spasms,  contraction  of  the  vessels,  and  secretion 
of  siveat  occur  in  the  hind  limbs,  together  with  evacuation  of  the  contents  of  the  bladder  and  rectum, 
while  there  are  movements  of  the  uterus  and  vas  deferens.  Some  poisons  act  in  a  similar  manner. 
In  animals  with  the  medulla  oblongata  divided,  rhythmical  re.spiratory  movements  may  be  produced 
if  the  spinal  cord  has  been  previously  rendered  very  sensitive  by  strychnin  or  overheated  blood  [P.  v. 
Rokitansky,  v.  Schroff — |  368). 

The  ganglion  cells  of  the  anterior  cornu  can  be  excited  mechanically 
{Birge),  and  according  to  Biedermann  the  gray  matter  also  responds  to  electrical 
stimuli. 

Hyperaesthesia. — After  unilateral  section  of  the  cord,  or  even  only  of  the 
posterior  or  lateral  columns,  there  is  hyperesthesia  on  the  same  side  below  the 
point  of  section  {Fodcra,  1823,  and  others),  so  that  rabbits  shriek  on  the  slightest 
touch.  The  phenomenon  may  last  for  three  weeks,  and  then  give  place  to  normal 
or  sub-normal  excitability.  On  the  sound  side  the  sensibility  remains  permanently 
diminished.  A  similar  result  has  been  observed  in  cases  of  injury  in  man.  An 
analogous  phenomenon,  or  a  tendency  to  contraction  in  the  muscles  below  the 
section  (hyperkinesia),  has  been  observed  by  Brown-Sequard  after  section  of  the 
anterior  columns. 

The  excitability  of  the  cord  is  intimately  dependent  on  the  continuance  of  the 
circulation,  for  ligature  of  the  abdominal  aorta  rapidly  paralyzes  the  lower  extremi- 
ties {Stenson,  1667),  due  to  anaemia  of  the  cord  {Schiffer).  Later,  the  anterior 
roots  of  the  spinal  nerves,  and  the  anaemic  part  of  the  gray  matter  of  the  cord, 
undergo  degeneration. 

364.  THE  CONDUCTING    PATHS    IN    THE    SPINAL  CORD. 

— [Posterior  Root. — {a)  The  inner  part,  or  internal  radicular  fasciculus 
is  supposed  to  convey  the  impressions  from  tendons  and  those  for  touch  and 
locality.  When  the  postero-external  column  is  diseased,  as  in  locomotor  ataxia, 
the  deep  reflexes,  especially  the  patellar  tendon  reflex,  are  enfeebled,  or  it  may 
be  abolished,  while  the  implication  of  the  fibres  of  the  internal  fasciculus  gives 
rise  to  severe  pain,  {b)  The  outer  radicular  fibres  enter  the  gray  matter 
of  the  posterior  horn,  and  are  supposed  to  convey  the  impressions  for  cutaneous 
reflexes  and  temperature,  {c)  The  central  fibres  pass  directly  into  the  gray 
matter,  and  are  supposed  to  conduct  painful  impressions  into  the  gray  matter 
(Fig.  449)-]. 

I.   Localized  tactile  sensations  (temperature,  pressure,  and  the  muscular 


CONDUCTING   PATHS    IN    SPINAL   CORD.  697 

sense  impressions)  are  conducted  upward  through  the  posterior  roots  to  the 
ganglia  of  the  posterior  cornu,  and  lastly  into  the  posterior  column  of  the  same 
side. 

In  man,  the  conducting  path  from  the  legs  runs  in  GoU's  column,  while  those  for  the  arms  run 
in  the  ground  bundle  (Fig.  454)  [Flecksig).  In  rabbits,  the  path  of  locahzed  tactile  impressions 
lies  in  the  lower  dorsal  region  in  the  lateral  cdhimns  [^Ludwig  and  Woroschiloff,  Oit  and  Meade- 
Smith^. 

Anaesthesia. — Section  of  individual  parts  of  the  lateral  columns  abolishes  the  sensibility  for 
the  parts  of  the  skin  connected  with  the  part  destroyed,  while  total  section  produces  the  same 
result  for  the  whole  of  the  opposite  side  of  the  body  below  the  section.  The  condition  where  tactile 
and  muscular  sensibiliiy  is  lost  is  known  as  anmsthesia. 

Localized  voluntary  movements  in  man  are  conducted  on  the  same  side 
through  the  anterior  and  lateral  columns  (§§  358  and  365),  in  the  parts  known  as 
the  pyramidal  tracts.  The  impulses  then  pass  into  the  cells  of  the  anterior 
cornu,  and  thence  to  the  corresponding  anterior  nerve  roots  to  the  muscles.  The 
exact  section  experiments  of  Ludwig  and  Woroschiloff  showed  that,  in  the  lower 
dorsal  region  of  the  rabbit,  these  paths  were  confined  to  the  lateral  columns. 
Every  motor  nerve  libre  is  connected  with  a  nerve  cell  in  the  anterior  horn  of  the 
frog's  spinal  cord  (6^az^/^  a;^^^/;'_o-,f).  Section  of  one  lateral  column  abolishes 
voluntary  movement  in  the  corresponding  individual  muscles  below  the  point  of 
section.  It  is  obvious,  from  the  conduction  in  i  and  2,  that  the  lateral  columns 
must  increase  in  thickness  and  number  of  fibres  from  below  upward  {Stilling, 
Woroschiloff)  [see  Fig.  443]. 

3.  Tactile  reflexes  (extensive  and  coordinated). — The  fibres  enter  by  the 
posterior  root,  and  proceed  to  the  posterior  cornu.  The  groups  of  ganglionic 
cells,  which  control  the  coordinated  reflexes,  are  connected  together  by  fibres 
which  run  in  the  anterior  tracts,  the  anterior  ground  bundle  and  (?)  the  direct 
cerebellar  tracts  (p.  684).  The  fibres  for  the  muscles  which  are  contracted  pass 
from  the  motor  ganglia  outward  through  the  anterior  roots. 

In  ataxic  tabes  dorsalis,  or  locomotor  ataxia,  there  is  a  degeneration  of  the  posterior  columns, 
characterized  by  a  peculiar  motor  disturbance.  The  voluntary  movements  can  be  executed  with  full 
and  normal  vigor,  but  the  finer  harmonious  adjustments  are  wanting  or  impaired,  both  in  intensity 
and  extent  These  depend  in  part  upon  the  normal  existence  of  tactile  and  muscular  impressions, 
whose  channels  lie  in  tne  posterior  columns.  After  degeneration  of  the  latter,  there  is  not  only 
ansesthesia,  but  also  a  disturbance  in  the  discharge  of  tactile  reflexes,  for  which  the  centripetal  arc  is 
interrupted.  But  a  simultaneous  lesion  of  the  sensory  nerves  alone  may  in  a  similar  manner 
materially  influence  the  harmony  of  the  movements,  owing  to  the  analgesia  and  the  disappearance 
of  the  pathic  reflexes  (§  355)-  As  the  fibres  of  the  posterior  root  traverse  the  white  posterior 
columns,  we  can  account  for  tlie  disturbances  of  sensation  which  characterize  the  degenerations  of 
these  parts  [Chai-cot  and  Pier7-ei).  But  even  the  posterior  roots  themselves  may  undergo  degenera- 
tion, and  this  may  also  give  rise  to  disturbances  of  sensation  (p.  667).  The  sensory  disturbances 
usually  consist  in  an  abnormal  increase  of  the  tactile  or  pamful  sensations,  with  lightning  pains 
shooting  down  the  limbs,  and  this  condition  may  lead  to  one  where  the  tactile  and  painful  sensations 
are  abolished.  At  the  same  time,  owing  to  stimulation  of  the  posterior  columns,  the  tactile  sensi- 
bility is  altered,  giving  rise  to  the  sensation  of  formication,  or  a  feehng  of  constriction  ["  girdle 
sensation  "].  The  conduction  of  sensory  impressions  is  often  slowed  (g  337).  The  sensibility  of 
the  muscles,  joints,  and  internal  parts  is  altered. 

The  maintenance  of  the  equilibrium  is  largely  guided  by  the  impulses  which  travel  inward  to 
the  coordinating  centres  through  the  sensory  nerves,  special  and  general,  deep  and  superficial.  In 
many  cases  of  locomotor  ataxia,  if  the  patient  place  his  feet  close  together  and  close  his  eyes,  he 
sways  from  side  to  side  and  may  fall  over,  becaiise  by  cutting  off  the  guiding  sensations  obtained 
through  the  optic  nerve,  the  other  enfeebled  impulses  obtained  from  the  skin  and  the  deeper  struc- 
tures are  too  feeble  to  excite  propor  coordination. 

4.  The  inhibition  of  tactile  reflexes  occurs  through  the  anterior  columns  : 
the  impulses  pass  from  the  anterior  column  at  the  corresponding  level  into  the  gray 
matter,  where  they  form  connections  with  the  reflex  conducting  apparatus. 

5.  The  conduction  of  painful  impressions  occurs  through  the  posterior  roots, 
and  thence  through  the  whole  of  the  gray  matter.     There  is  a  partial  decussation 


698  CONDUCTION    IN    THE    SPINAL   CORD. 

of  these  impulses  in  the  cord,  the  conducting  fibres  j)assing  from  one  side  to  tlie 
other.     The  further  course  of  these  fibres  to  the  brain  is  given  in  §  365. 

If  all  the  gray  matter  be  divided,  except  a  small  connecting  portion,  this  is  sufficient  to  conduct 
painful  impressions.  In  this  case,  however,  ihe  conduction  is  slower  [Schiff).  Only  when  the  gray 
matter  is  comjiletely  divided,  is  the  conduction  of  jiainful  im])re.ssions  from  below  completely  inter- 
rupted. This  gives  rise  to  the  condition  of  analgesia,  in  which,  when  (he  posterior  columns  are 
still  intact,  tactile  impressions  are  still  conducted.  This  condition  is  sometimes  obser\'ed  in  man 
during  incomplete  narcosis  from  chloroform  and  morphia  (  Thiersrh).  Those  poisons  act  sooner 
on  the  nerves  which  administer  to  painful  sensations  than  on  those  for  tactile  impressions,  so  that 
the  person  operated  on  is  conscious  of  the  contact  of  a  knife,  but  not  of  the  painful  sensations  caused 
by  the  knife  dividing  the  parts.  As  painful  impressions  are  conducted  by  tiie  whole  of  the  gray 
matter,  and  as  the  impressions  are  more  powerful  the  stronger  the  painful  impression,  we  may  thus 
explain  the  so-called  irradiation  of  painful  impressions.  During  violent  pain,  the  pain  seems  to 
extend  to  wide  areas;  thus,  in  violent  toothache,  ])roceeding  from  a  particular  tooth,  the  pain  may  be 
felt  in  the  whole  jaw,  or  it  may  be  over  one  side  of  the  head. 

According  to  Bechterew,  the  paths  for  the  conduction  of  painful  impressions  lie  in  the  anterior 
part  of  the  lateral  column  (dog,  rabbit). 

The  experiments  of  Weiss  on  dogs,  by  dividing  the  lateral  column  at  the  limit  of  the  dorsal  and 
lumbar  regions,  showed  that  each  lateral  column  contains  sensory  fibres  for  both  sides.  The  chief 
mass  of  the  motor  fibres  remains  on  the  same  side.  Section  of  both  lateral  columns  abolishes  com- 
pletely sensibility  and  motility  on  both  sides.  The  anterior  columns  and  the  gray  matter  are  not 
sufficient  to  maintain  these. 

The  conduction  of  spasmodic,  involuntary,  inco-ordinated  movements 
takes  place  through  the  gray  matter,  and  from  the  latter  through  the  anterior 
roots. 

It  occurs  in  epilepsy,  poisoning  with  .strjxhnin,  uraemic  poisoning,  and  tetanus  {'i  360,  II).  The 
ansemic  and  dyspnoeic  spasms  are  excited  in  and  conducted  from  the  medulla  oblongata,  and  commu- 
nicated through  the  whole  of  the  gray  matter. 

7.  The  conduction  of  extensive  reflex  spasms  takes  place  from  the  posterior 
roots,  perhaps  to  the  cells  of  the  posterior  cornu  and  then  to  the  cells  of  the 
anterior  cornu,  above  and  below  the  plane  of  the  entering  impulse  (Fig.  458), 
and,  lastly,  into  the  anterior  roots,  under  the  conditions  alreadv  referred  to  in 
§  360,  II. 

8.  The  inhibition  of  pathic  reflexes  occurs  through  the  anterior  columns 
downward,  and  then  into  tiie  gray  matter  to  the  connecting  channels  of  the  reflex 
organ,  into  which  it  introduces  resistance. 

9.  The  vasomotor  fibres  run  in  the  lateral  columns  (Dittmar),  and,  after  they 
have  passed  into  the  ganglia  of  the  gray  matter  at  the  corresponding  level,  they 
leave  the  spinal  cord  by  the  anterior  roots.  They  reach  the  muscles  of  the  blood 
vessels  either  through  the  paths  of  the  spinal  nerves,  or  they  pass  through  the 
rami  communicantes  into  the  sympathetic,  and  thence  into  the  visceral  plexuses 
(§356). 

Section  of  the  spinal  cord  paralyzes  all  the  vasomotor  nerves  below  the  point  of  section ;  while 
stimulation  of  the  peripheral  end  of.  the  spinal  cord  causes  contraction  of  all  these  vessels.  [Ott's 
experiments  on  cats  show  that  the  vasomotor  fibres  run  in  the  lateral  columns,  and  that  they  as  well 
as  the  sudorific  nerves  decussate  in  the  cord.] 

10.  Pressor  fibres  enter  in  the  posterior  roots,  run  upward  in  the  lateral 
columns,  and  undergo  an  incomplete  decussation  {Ludwig  and  Miescher). 

They  ultimately  terminate  in  the  dominating  vasomotor  centre  in  the  medulla  oblongata,  which 
they  excite  reflexly.  Similarly,  depressor  fibres  must  pass  upward  in  the  spinal  cord,  but  we  know 
nothing  as  to  their  course. 

11.  From  the  respiratory  centre  in  the  medulla  oblongata,  respiratory 
nerves  run  downward  in  the  lateral  columns  on  the  satne  side,  and  after  forming 
connections  with  the  ganglia  of  the  gray  matter  pass  through  the  anterior  roots 
into  the  motor  nerves  of  the  respiratory  muscles  (Schiff). 

Unilateral,  or  total  destruction  of  the  spinal  cord,  the  higher  up  it  is  done,  accordingly  paralyzes 
more  and  more  of  the  respiratory  nervts,  on  the  same  or  on  both  sides.     Section  of  the  cord  above 


EFFECTS    OF    SECTION    OF    THE    CORD. 


699 


Fig.  459. 


the  origin  of  the  phrenic  nerves  causes  death,  owing  to  the  paralysis  of  these  nerves  of  the  diaphragm 

(?ii3).  .     , 

In  pathological  cases,  in  degeneration  of,  or  direct  injury  to,  the  spinal  cord  or  its  individual 
parts,  we  must  be  careful  to  observe  whether  there  may  not  be  present  simultaneously  paralytic  and 
irritative  phenomena,  whereby  the  symptoms  are  obscured. 

[Complete  transverse  section  of  the  cord  results  immediately  in  com- 
plete paralysis  of  motion  and  sensation  in  all  the  parts  supplied  by  nerves  below 
the  seat  of  the  injury,  although  the  muscles  below  the  injury  retain  their  normal 
trophic  and  electrical  conditions.  There  is  a  narrow  hypersesthetic  area  at  the 
upper  limit  of  the  paralyzed  area,  and  when  this  occurs  in  the  dorsal  region,  it 
gives  rise  to  the  feeling  of  a  belt  tightly  drawn  round  the  waist,  or  the  "  girdle 
sensation."  There  is  also  vasomotor  paralysis  below  the  lesion,  but  the  blood 
vessels  soon  regain  their  tone,  owing  to  the  subsidiary  vasomotor  centres  in  the 
cord.  The  remote  effects  come  on  much  later,  and  are  secondary  descending 
degeneration  in  the  crossed  and  direct  pyramidal  tracts  and  ascending  degenera- 
tion in  the  postero-internal  columns  (Fig.  455).  According  to  the  seat  of  the 
lesion,  the  functions  of  the  bladder  and  rectum  may  be  interfered  with.  Injury 
to  the  upper  cervical  region  sometimes  causes  hyperpyrexia.] 

[Unilateral  section  results  in  paralysis  of  voluntary  motion  in  the  muscles 
supplied  by  nerves  given  off  below  the  seat  of  the  injury,  although  the  muscles  do 
not  atrophy,  but  when  secondary  descending  degeneration 
occurs  they  become  rigid,  and  exhibit  the  ordinary  signs  of 
contracture.  There  is  vasomotor  paralysis  on  the  same  side, 
although  this  passes  off  below  the  injury,  while  the  ordinary  and 
muscular  sensibility  are  diminished  on  both  sides  (Fig.  459). 
There  is  bilateral  anaesthesia.  On  the  opposide  side  there  is 
total  anaesthesia  and  analgesia  below  the  lesion,  but  on  the  same 
side  in  the  dorsal  region  there  is  a  narrow  circular  anaesthetic 
zone  (Fig.  459,  d),  corresponding  to  the  sensory  nerve  fibres 
destroyed  at  the  level  of  the  section.  The  sensory  nerves 
decussate  shortly  after  they  enter  the  cord,  hence  the  anaes- 
thesia on  the  opposite  side,  but  they  do  not  cross  at  once,  but 
run  obliquely  upward  before  they  enter  the  gray  matter  of  the 
opposite  side,  so  that  a  unilateral  section  will  involve  some 
fibres  coming  from  the  same  side,  and  hence  the  slightly  dimin- 
ished sensibility  in  a  circular  area  on  the  same  side.  There  is 
a  narrow  hyperaesthetic  area  on  the  same  side  as  the  lesion,  at 
the  upper  limit  of  the  paralyzed  cutaneous  area  (Fig.  459,  c), 
due  perhaps  to  stimulation  of  the  cut  ends  of  the  sensory  fibres 
on  that  side.  In  man  there  is  hyperaesthesia  (to  touch,  tickling, 
pain,  heat,  and  cold)  on  the  parts  below  the  lesion  on  the  same 
side,  but  the  cause  of  this  is  not  known.  The  remote  effects 
are  due  to  the  usual  descending  and  ascending  degeneration 
which  set  in.] 

[In  monkeys,  after  hemi-section  of  the  cord  in  the  dorsal  region,  there  is 
paralysis  of  voluntary  motion  and  retention  of  sensibility  with  vasomotor 
paralysis  of  the  same  side,  and  retention  of  voluntary  motion  with  anaes- 
thesia and  analgesia  on  the  opposite  side.  The  existence  of  hyperaesthesia 
on  the  side  of  the  lesion  is  not  certain  in  these  animals,  but  there  is  no  doubt 
of  it  in  man.  Ferrier  also  finds  (in  opposition  to  Brown-Sequard)  that  the  muscular  sense  is  para- 
lyzed as  well  as  all  other  forms  of  sensibility,  on  the  side  opposite  to  the  lesion,  but  unimpaired  on 
the  side  of  the  lesion.  The  muscular  sense,  in  fact,  is  entirely  separable  from  the  motor  innervation 
of  muscle  {Ferrier).     The  power  of  emptying  the  bladder  and  rectum  was  not  affected.] 


Diagrammatic  represen- 
tation of  a  lesion  of 
the  left  half  of  the 
spinal  cord  in  the 
dorsal  region,  (a) 
oblique  lines,  motor 
and  vasomotor  para- 
lysis ;  {b,  d),  com- 
plete anaesthesia ;  {a, 
c),  hyperaesthesia  of 
the  skin. 


THE  BRAIN. 


365.  GENERAL  SCHEMA  OF  THE  BRAIN.— In  an  organ  so  complicated  in  its  structure 
as  the  brain,  it  is  necessary  to  have  a  general  view  of  the  chief  arrangements  of  its  individual  parts. 
Me\nertgave  a  plan  of  the  general  arrangement  of  this  organ,  and  although  this  plan  may  not  be 

quite  correct,  still  it    is    useful    in  the 
Fin.  460.  study  of  brain  function.     The  weight 

of  the  brain  is  in  man  aljout  1358 
grammes,  and  in  woman  1 220  grammes 
[^Bischoff'). 

[A  special  layer  of  gray  matter  of 
the  cerebrum  is  placed  externally  and 
spread  as  a  thin  coating  over  the  white 
matter  or  centrum  ovale — which  lies 
internally,  and  consists  of  nerve  fibres 
or  the  white  matter.  That  part  lying 
in  each  hemisphere  is  the  centrum  semi- 
ovalc.  The  gray  matter  is  folded  into 
gyri  or  convolutions  separated  from 
ach  other  liy  fissures  or  sulci.  Some 
uf  the  latter  are  veiy  marked,  and 
serve  to  separate  adjacent  lobes,  while 
the  lobes  themselves  are  further  sub- 
divided by  sulci  into  convolutions. 
For  a  description  c  f  the  lobes  see 
\  375-  Some  masses  of  gray  matter 
are  disposed  at  the  base  of  the  brain, 
forming  the  corpus  striatum  (pro- 
jecting into  the  lateral  ventricles), 
which  in  reality  is  composed  of  two 
parts,  the  nucleus  caudatus  and  lenticu- 
lar nucleus  (Fig.  460,  b),  the  optic 
thalamus  which  lies  behind  the 
former,  and  bounds  the  3d  ventricle 
(Fig.  460,^/),  the  corpora  quadri- 
gemina  lying  on  the  upper  surface  of 
the  crura  cerebri  (Fig.  480,  hi); 
within  the  tegmentum  of  the  crura 
cerebri  are  the  red  nucleus  and  locus 
niger  (Fig.  502).  Lastly,  there  is  the 
continuation  of  the  gray  matter  of  the 
cord  up  through  the  medulla,  pons, 
and  around  the  iter,  forming  the  cen- 
tral gray  tube  and  terminating  an- 
teriorly at  the  tuber  cinereum.  These 
various  parts  are  connected  in  a  variety 
of  ways  wuth  each  other,  some  by  transverse  fibres  stretching  between  the  two  sides  of  the  brain, 
while  other  longitudinal  fibres  bring  the  hinder  and  lower  parts  into  relation  with  the  fore  parts.] 

[Under  cover  of  the  occipital  lobes,  but  connected  with  the  cerebrum  in  front,  and  the  spinal  cord 
below,  is  the  cerebellum,  which  has  its  gray  matter  externally  and  its  white  core  internally.  Thus 
we  have  to  consider  cerebro-spinal  and  cerebello-spinal  connections.] 

Meynert's  Projection  Systems. — The  cortex  of  the  cerebrum  consists  of  convolutions  and 
sulci,  the  "peripheral  gray  matter"  (Fig.  461,  C),  which  is  recognized  as  a  nervous  structure, 
from  the  presence  in  it  of  numerous  ganglionic  cells  \\  358,  l).  From  it  proceed  all  the  motor  fibres 
which  are  excited  by  the  will,  and  to  it  proceed  all  the  fibres  coming  from  the  organs  of  special 
sense   and  sensory  organs,  which  give  rise  to  the  psychical  perception  of  external  impressions.     [In 

700 


Dissection  of  the  brain  from  above,  showing  the  lateral,  3d,  and  4th 
ventricles,  with  the  basal  ganglia,  and  surrounding  parts,  a,  knee  of 
the  corpus  callosum  ;  ^.anterior  part  of  the  right  corpus  striatum; 
b' ,  gray  matter  dissected  off  to  show  white  fibres  ;  c,  points  to 
taenia  semicircularis  ;  dy  optic  thalamus  ;  e,  anterior  pillars  of 
fornix,  with  5th  ventricle  in  front  of  them,  between  the  two 
laminae  of  the  septum  lucidum  ;  f,  middle  or  soft  commissure  ;  g, 
3d  ventricle;  A, /,  corpora  quadrigemina  ;  ^,  superior  cerebellar 
peduncle;  /,  hippocampus  major;  nt,  posterior  cornu  of  lateral 
ventricle  ;  «,  eminentia  collateralis  ;  o,  4th  ventricle  ;  /,  medulla 
oblongata  ;  s,  cerebellum,  with  r,  arbor  vita:. 


SCHEME    OF   THE    CENTRAL    NERVOUS    SYSTEM. 


701 


Fig.  461  the  decussation  of  the  sensory  fibres  is  represented  as  occurring  near  the  medulla  oblongata. 
It  is  more  probable  that  a  large  number  of  the  sensory  fibres  decussate  shortly  after  they  enter  the 
cord,  as  is  represented  in  Fig.  463.  Some  observers  assert  that  some  of  the  sensory  fibres  decussate 
in  the  medulla  oblongata.] 

First  Projection  System. — The  channels  lead  to  and  from  the  cortex  cerebri,  some  of  them 
traversing  the  basal  ganglia,  or  ganglia  of  the  cerebrum — the  corpus  striatum  {C.s)    (composed 


I,  Scheme  of  the  brain. — C,  C,  cortex  cerebri ;  C.J,  corpus  striatum  ;  N./,  nucleus  lenticularis  ;  T.o,  optic  thalamus ; 
V,  corpora  quadrigemina ;  P,  pedunculus  cerebri;  H,  tegmentum ;  and/,  crusta  ;  i,  i,  corona  radiata  of  the 
corpus  striatum ;  2,  2,  of  the  lenticular  nucleus  ;  3,  3,  of  the  optic  thalamus  ;  4,  4,  of  the  corpora  quadrigemina  ; 
S,  pyramidal  fibres  from  the  cortex  cerehri  {/^/ec/tsig-) ;  6,  6,  fibres  from  the  corpora  quadrigemina  to  the  teg- 
mentum ;  }>i,  further  course  of  these  fibres  ;  8,  8,  fibres  from  the  corpus  striatum  and  lenticular  nucleus  to  the 
crusta  of  the  pedunculus  cerebri;  M,  further  course  of  these;  S,  S,  course  of  the  sensory  fibres;  R,  trans- 
verse section  of  the  spinal  cord;  z/.W,  anterior,  and  /i.W,  posterior  roots,  (Z,  a,  association  system  of  fibres, 
c,  c,  commissural  fibres.  II,  Transverse  section  through  the  posterior  pair  of  the  corpora  quadrigemina  and  the 
pedunculi  cerebri  of  man, — /,  crusta  of  the  peduncle;  j,  substantia  nigra;  z/,  corpora  quadrigemina,  with  a 
section  of  the  aqueduct.     Ill,  The  same  of  the  dog  ;  IV,  of  an  ape  ;  V,  of  the  guinea  pig.     [See  p.  700.] 


of  the  caudate  nucleus  and  lenticular  nucleus  (N./),)  optic  thalamus  (T.o),  and  corpora  quadrigemina 
— some  fibres  form  connections  with  cells  within  this  central  gray  matter.  The  fibres  which  proceed 
from  the  cortex  through  the  corona  radiata  in  a  radiate  direction  constitute  Meynerf  s  first  projection 
system.  Besides  these,  the  white  substance  also  contains  two  other  systems  of  fibres:  {a)  Com- 
missural fibres,  such  as  the  corpus  callosum  and  the  anterior  commissure  {c,  c),  which  are  supposed 


702 


CEREBRO-SPINAL    CONNECTIONS. 


to  connect  the  two  hemispheres  with  each  other ;  and  (i>)  a  connecting:;  or  association  system, 
whereby  two  ditVerent  areas  of  tlie  same  side  are  connected  together  (</,  a').  The  ganghonic  gray 
matter  of  tlie  l)asal  ganglia  forms  the  first  stage  in  tlie  course  of  a  large  number  of  the  lilires.  W'lien 
they  enter  the  central  gray  matter,  they  are  interrupted  \\\  their  course.  According  to  Meynert,  the 
corona  radiata  contains  bundles  of  fibres  from  the  corpus  striatum  (l,  i),  lenticular  nucleus  (2,  2) 
optic  thalamus  (3,  3),  and  coq^ora  quadrigemina  (4,  4). 

The  second  projection  system  consists  of  longitudinal  bundles  of  fibres,  which  proceed  down- 
ward and  reach  the  so-called  "  central  gray  tube,"  which  is  the  ganglionic  gray  matter  reaching 
from  the  3d  ventricle  through  the  aqueduct  of  Sylvius,  and  the  medulla  oblongata,  to  the  lowest 
part  of  the  gray  matter  of  the  spinal  cord.  It  lines  the  inner  surface  of  the  medullary  tube.  It  is 
the  second  stage  in  the  course  of  the  fibres  extending  from  the  basal  ganglia  to  the  central  tubular 
gray  matter.  The  fibres  of  this  system  must  obviously  vary  gi-eatly  in  length  ;  some  fibres  end  in  the 
central  gray  matter  above  the  medulla  oblongata,  e.  g.,  in  the  oculomotor  nucleus,  while  others  reach 
to  the  level  of  the  last  .spinal  nerves.  In  the  central  gray  matter,  not  only  is  the  course  of  the  tibres 
interrupted,  but  there  is  in  it  an  increase  in  the  number  of  fibres,  for  far  more  fibres  proceed  periph- 
erally from  the  gray  matter  of  the  medulla  and  spinal  cord,  than  are  sent  to  it  from  the  central  gray 
matter  of  the  brain. 

As  to  the  arrangement  of  the  fibres  in  this  second  system,  the  fibres  descending  from  the  caudate 

and    lenticular   nucleus    (8,  8)  are   giouped 
Fic.  462.  into   a    special    channel,     which    descends 

through  the  crusta  of  the  cerebral  peduncle, 
and  enters  the  medulla  oblongata,  or  (accord- 
ing to  Flechsig)  the  pons.  In  the  same  way 
there  proceeds  from  the  thalamus  (S)  and 
corpora  fiuadrigemina  (6,  6)  a  bundle  which 
descends  through  the  tegmentum  (II)  of  the 
cerebral  peduncle.  Both  sets  of  fibres — 
those  in  the  crusta  and  in  the  tegmentum — 
come  together  in  the  cord. 

According  to  Wernicke,  the  lenticular 
nucleus  and  caudate  nucleus  are  not  the 
parts  of  the  brain  into  which,  from  the  cere- 
bral cortex  and  through  the  corona,  radiate 
fibres  enter  ;  but  they  are  independent  parts, 
analogous  to  the  cortex,  and  from  them 
fibres  proceed.  These  fibres  pass  into  the 
crusta  and  run  along  with  those  fibres  pro- 
ceeding from  the  thalamus  and  corpora 
quadrigemina. 

According  to    Meynert,   the   fibres    which 

pass  from  the  thalamus  and   coipora  quadri- 

Floor  of  the  4th  ventricle  and  the  connections  of  the  cerebclh.m.  gemina,  through  the  tegmentum  of  the  cere- 
On  the  left  side  the  three  cerebellar  peduncles  are  cut  .short:  bral  peduncle,  are  rcHex  channels;  so  that 
on  the  right  the  connections  of  the  superior  and  inferior  these  portions  of  the  brain  are  centres  for 
peduncles  have  been  preserved,  while  the  middle  one  has  j     extensive  Coordinated  reflexes.      This 

been   cut  short:     i,   median  groove   of  the   4th   ventricle,     .  1        1       r  1-1  .  \. 

with  the  fasciculi  teretes  ;  2,  the  strise  of  the  auditory  nerve  IS  shown  by  the  fact  that,  after  destruction  of 
on  each  side  emerging  from  it:  3.  inferior  peduncle;  4,  the  voluntary  motor  paths  in  animals,  the 
posterior  pyramid  and  clava,  with  the  calamus  scriptorius  technical  comnleteness  of  mnvements  sn  far 
above  it;  5,  superior  peduncle;  6,  fillet  to  the  side  of  the  ^^ecnnicai  Completeness  oi  movements,  so  tar 
crura  cerebri  ;  8,  corpora  quadrigemina.  as  these  are  discharged  reflexly,  IS  Still  intaCt. 

These   channels  run  in  the  spinal  cord,  at 
first  on  the  .side  (w),  and  proliably  ultimately  cross  in  the  spinal  cord  itself. 

The  Third  Projection  System. —  Lastly,  from  the  central  tubular  gray  matter  there  proceeds 
the  third  system,  or  the  peripheral  nerves,  motor  and  sensory.  These  are  more  numerous  than 
the  fibres  of  the  second  system. 

[While  there  are  three  concentric  tubes  in  the  spinal  cord  (§  359),  in  the  part  which  forms  the 
l)rain  an  extra  layer  of  gray  matter  is  added — the  peripheral  gray  tube — constituting  the  cortex  of 
the  cerebral  hemispheres  and  cerebellum,  and  the  corpora  ciuadrigemina.  Thus,  the  white  matter 
lies  between  two  concentric  masses  of  gray  matter  (Hill).'] 

Connections  of  the  Cerebellum. — The  cerebellum  consists  of  two  somewhat  flattened  hemi- 
spheres connected  across  the  middle  line  by  the  middle  lobe  or  vermiform  process  which  is  the 
fundamental  portion  of  the  organ,  as  it  is  best  developed  in  lower  animals,  while  as  yet  the  lateral 
lobes  are  but  small  or  al)sent,  e.  g.,  in  birds.  The  surface  is  furrowed  by  sulci  so  as  to  cause  it  to 
resemble  a  series  of  folia,  leaflets  or  laminae;  larger  fissures  divide  it  into  lobes.  Peduncles. — 
The  two  superior  peduncles  connect  it  with  the  corpora  f|uadrigemina  and  the  crura  cerebri.  The 
fibres  come  from  the  lower  part  of  the  cerebellum  and  from  its  dentate  nucleus,  and  a  number  of 
these  fibres  decussate  in  the  upper  part  of  the  pons  and  the  tegmentum,  some  of  them  becoming 


CEREBRO-SPINAL    CONNECTIONS.  703 

connected  with  the  red  nucleus  in  the  tegmentum  of  the  opposite  side.  Some  of  the  fibres  seem  to 
connect  the  cerebellum  witli  the  frontal  lobes,  constituting  a  fronto-cerebellar  tract,  and  they  are  also 
crossed  (Go7oers).  When  the  cerebellum  is  congenitally  absent,  these  fibres  are  absent  (/^/c'c/zj-zV). 
By  the  two  inferior  peduncles  or  restiform  bodies,  it  is  connected  with  all  the  columns  of  the  spinal 
cord,  and  it  is  to  be  noted  that  some  of  the  fibres  forming  these  peduncles  are  connected  with  the 
oUvary  body  of  the  opposite  side,  so  that  they  decussate.  The  middle  peduncle  is  formed  by  the 
transverse  fibres  of  the  pons  (Figs.  462,  503).  It  is  evident  that  there  is  a  cerebello-spinal,  as  well 
as  a  cerebro- spinal  connection  to  be  considered. 

[The  gray  matter  is  external  and  the  white  internal,  and  on  section  the  foliated  branched 
appearance  of  the  cerebellum  constitutes  the  (irdor  vitct:.  Within  each  lateral  lobe  is  a  folded  mass 
of  gray  matter  like  that  in  the  olivary  body,  called  the  corpus  dentatum,  and  fiom  its  interior  white 
fibres  proceed.  Stilling  describes  in  the  front  part  of  the  middle  lobe  roof  nuclei — so  called  because 
they  lie  in  the  roof  of  the  4th  ventricle.  As  is  shown  in  Fig.  462,  the  white  fibres  of  the  superior 
peduncle  pass  to  the  gi-ay  matter  on  the  inferior  surface  of  the  cerebellum,  while  the  inferior  pedun- 
cular fibres  pass  to  the  superior  surface,  chiefly  of  the  median  part;  but  both  are  said  to  form  con- 
nections with  the  corpus  dentatum ;  the  middle  peduncle  is  connected  with  the  gray  matter  of  the 
lateral  lobes.     The  minute  structure  is  described  in  §  380.] 

The  distribution  of  the  blood  vessels  of  the  brain  is  of  much  practical  importance.  The  middle 
cerebral  artery  of  the  Sylvian  fissure  supplies  the  motor  areas  of  the  brain  in  animals;  in  man,  the 
paracentral  lobule  is  supplied  by  the  anterior  cerebral  artery  [Buret).  The  region  of  the  third  left 
frontal  convolution,  which  is  the  speech  centre,  is  supplied  by  a  special  branch  of  the  middle  cerebral. 
According  to  Ferrier,  that  part  of  the  brain,  any  injury  to  which  causes  disturbance  of  intelligence, 
is  supplied  by  the  anterior  cerebral ;  w^hile  those  regions,  where  injury  is  followed  by  hemi-ansesthesia, 
are  supplied  by  the  posterior  cerebral.  It  is  stated  that  anaemia  of  isolated  parts  of  this  area  of  the 
brain  is  associated  with  melancholia  in  man. 

Conduction  to  and  from  cerebrum — Voluntary  motor  fibres. — The 

course  of  the  fibres  which  convey  impulses  for  voluntary  motion — the  pyramidal 
tracts — proceeds  from  the  motor  regions  of  the  cerebrum  (§§  375,  378,  I),  passing 
into  and  through  the  white  matter  of  the  cerebrum  through  the  corona  radiata,  and 
converges  to  the  internal  capsule,  which  lies  between  the  nucleus  caudatus  and 
opticus  thalamus  internally  and  the  lenticular  nucleus  externally  (Fig.  500).  [The 
motor  fibres  for  the  face  and  tongue  occupy  the  knee  of  the  capsule  (F),  those  for 
the  arm  the  anterior  third  of  the  posterior  segment  or  limb  (A),  and  those  for  the 
leg  the  middle  third  (L).  They  pass  beneath  the  optic  thalamus,  enter  the  crusta 
of  the  cerebral  peduncle,  and  occupy  its  middle  third,  or  two-fifths,  extending 
almost  to  the  substantia  nigra,  the  fibres  for  the  face  being  next  the  middle  line, 
and  those  for  the  leg  most  external,  the  fibres  for  the  arm  lying  between  the  two. 
They  pass  into  the  pons  on  the  same  side,  where  the  fibres  for  the  face  (and  tongue) 
cross  to  the  opposite  side,  to  become  connected  with  the  nuclei  from  which  the 
facial  and  hypoglossal  nerves  arise.  The  fibres  for  the  arm,  and  leg  (and  trunk) 
continue  their  course  to  the  medulla  oblongata,  where  they  form  the  anterior  pyra- 
mids. In  the  pons,  the  pyramidal  tracts  are  broken  up  into  bundles  lying  between 
its  superficial  and  deep  transverse  fibres,  and  surrounded  by  gray  matter  (Fig.  503)  ; 
but  they  have  no  connection  with  the  gray  matter  of  the  pons.  By  far  the  greater 
proportion  of  the  fibres  cross  at  the  decussation  of  the  pyramids  to  form  the  crossed 
pyramidal  tracts,  or  lateral  pyramidal  tracts,  of  the  lateral  column  of  the  oppo- 
site side.  The  small  uncrossed  portion  is  continued  as  the  direct  pyramidal 
tract  on  the  same  side.  The  latter  fibres,  perhaps,  supply  those  muscles  of  the  trunk 
{e.g.,  respiratory,  abdominal,  and  perineal),  which  always  act  together  on  both 
sides.  According  to  other  observers,  however,  they  cross  to  the  other  side  of  the 
cord  through  the  anterior  white  commissure,  and  descend  in  the  crossed  pyramidal 
tract  or  pyramidal  tract  of  the  lateral  column.  The  fibres  of  the  pyramidal  tracts 
split  up  into  fine  fibrils,  which  form  connections  with  the  fibrils  produced  by  the 
subdivision  of  the  processes  of  the  multipolar  nerve  cells.  Thus,  fibres  form  con- 
nections with  the  multipolar  ganglionic  cells  of  the  anterior  cornu  of  the  gray 
matter  of  the  spinal  cord  at  successively  lower  levels,  and  from  each  multipolar 
cell  is  directed  peripherally  a  single  unbranched  process,  which  ultimately  becomes 
a  nerve  fibre.  The  pyramidal  tracts  thus  end  in  the  multipolar  nerve  cells  of  the 
gray  matter  of  the  spinal  cord,  from  which  the  anterior  roots  of  the  spinal  nerves  arise. 


704  COURSE    OF   THE    SENSORY    NERVES. 

[The  course  of  the  pyramidal  tracts  and  the  decussation  of  these  fibres  in  the 
medulla  oblongata,  exi)lain  why  a  hemorrhage  involving  the  cerebral  motor  centres, 
or  affecting  these  fibres  in  any  part  of  their  course  above  the  decussation,  results 
in  paralysis  of  the  muscles  supplied  by  the  fibres  so  involved  on  the  opposite  side  of 
the  body.  In  their  passage  through  the  brain,  the  paths  for  direct  motor  impulses 
are  not  interrupted  anywhere  in  their  course  by  ganglion  cells,  not  even  in  the 
corpus  striatum  or  pons.  They  pass  in  a  direct  uninterrupted  line,  until  each  fibre 
becomes  connected  with  a  multipolar  nerve  cell  in  the  anterior  horn  of  the  gray 
matter  of  the  spinal  cord,  so  that  they  have  the  longest  course  of  any  fibres  in  the 
central  nervous  system.] 

Variation  in  Decussation. — There  are  variations  as  to  the  number  of  fibres  which  cross  at  the 
jnTamiiis  [FUchsi;^).  In  some  cases  the  usual  arrangement  is  reversed,  and  in  some  rare  instances 
there  is  no  decussation,  so  that  the  p)Tamidal  tracts  from  the  brain  remain  on  the  same  side.  In  this 
way  we  may  explain  the  very  rare  cases  where  paralysis  of  the  voluntary  movements  takes  place 
on  the  same  side  as  the  lesion  of  the  cerebrum  [^Morgagni,  Pierrel).  This  is  direct  paralysis. 
[Usually  about  90  per  cent,  of  the  fibres  decussate.] 

The  motor  cranial  nerves  have  the  centres  through  which  they  are  excited 
voluntarily  in  the  cortex  cerebri  (§  378).  The  paths  for  such  voluntary  impulses 
also  pass  through  the  internal  capsule  and  the  crusta  of  the  cerebral  peduncle.  [In 
the  internal  capsule,  the  fibres  for  the  face  (and  tongue)  lie  in  the  knee,  while  they 
occupy  the  part  of  the  middle  of  the  crusta  next  the  middle  line.  Their  course  is 
then  directed  across  the  middle  line  to  their  respective  nuclei,  from  which  fibres 
proceed  to  the  muscles  supplied  by  these  nuclei.]  The  exact  course  of  many  of 
the  fibres  is  still  unknown.  The  hypoglossal  nerve  runs  with  the  pyramidal  tracts, 
and  behaves  like  the  anterior  root  of  a  spinal  nerve  (§§  354,  357). 

[Sensory  Paths. — Our  knowledge  is  by  no  means  precise.  Sensory  impulses, 
jiassing  into  the  cord,  enter  it  by  the  posterior  nerve  roots,  and  may  pass  to  the 
cerebrum  or  cerebellum.  If  to  the  cerebellum,  the  course,  probablv,  is  partly  to 
the  direct  cerebellar  tract  and  posterior  column  to  the  restiform  body,  thence  to  the 
cerebellum.  If  to  the  cerebrum,  they  cross  the  middle  line  in  the  cord  not  far 
above  where  they  enter  and  pass  to  the  lateral  column,  in  front  of  the  pyramidal 
tract.  Some  enter  the  posterior  column,  and  others  ascend  in  the  gray  matter  to 
pass  upward.  As  the  two  subdivisions  of  the  posterior  column  terminate  above  in 
the  nuclei  of  the  funiculus  gracilis  and  funiculus  cuneatus,  and  this  column  contains 
fibres  from  the  posterior  root,  it  is  suggested  that  above  the  clava  and  cuneate 
nucleus  the  fibres  cross  in  the  superior  pyramidal  decuss:ation  to  reach  the  pons  and 
tegmentum.  In  the  medulla,  it  is  probable  that  those  fibres  which  do  not  decussate 
there  do  so  in  the  pons,  the  impulses  perhaps  traveling  upward  in  the  formalio  reti- 
cularis, thence  into  the  posterior  half  of  the  pons,  into  the  tegmentum  of  the  crus 
under  the  corpora  quadrigemina,  to  enter  the  posterior  third  of  the  posterior  limb 
of  the  internal  capsule  (Fig.  500,  S).  But,  of  course,  the  sensory  fibres  from  the 
face  have  to  be  connected  with  the  sensory  centres  in  the  cerebrum,  so  that  the 
sensory  paths  from  the  cord,  /.  e.,  from  the  trunk  and  limbs,  are  joined  by  those 
from  the  face  in  the  pons,  and  they  also  occupy  part  of  the  posterior  third  of  the 
posterior  segment  of  the  internal  capsule,  so  that  this  important  part  of  the  internal 
capsule  conducts  sensory  impulses  from  the  opposite  half  of  the  body.  Some  of 
the  fibres  pass  into  the  optic  thalamus,  and  others  enter  the  white  matter  of  the 
cerebrum,  but  their  exact  course  is  very  uncertain.  The  sensory  fibres  derived 
from  the  organs  of  special  sense,  e.  g.,  the  ear,  go  to  the  superior  temporo-sphenoidal 
convolution,  but  whether  directly  or  indirectly  we  do  not  know;  perhaps  some  of 
those  for  vision  traverse  the  optic  thalamus.  Some  of  the  afferent  fibres  perhaps 
go  to  the  occipital  region,  and  Gowers  a.sserts  that  some  of  them  go  to  the  parietal 
and  central  regions,  /'.  e.,  to  the  "  motor"  regions,  for  he  holds  "that  disease  of 
the  niotor  cortex  often  causes  impairment  of  the  tactile  sensibility."] 

[Charcot  has  called  the  posterior  third  of  the  posterior  segment  of  the  internal 


SENSORY    IMPULSES   AND    THE    MEDULLA   OBLONGATA.  705 

capsule,  lying  between  the  posterior  part  of  the  lenticular  nucleus  and  the  optic 
thalamus,  the  "  carefour  sensitiv  "  or  "sensory  crossway  "  (Fig.  500,  Sj.  If 
it  be  divided  there  is  hemi-angesthesia  of  the  opposite  side.] 

Sensory  Decussation  in  Cord. — As  the  greater  part  of  the  sensory  fibres 
from  the  skin  decussate  in  the  spinal  cord,  and  thus  pass  to  the  opposite  side  of  the 
cord  (Fig.  463),  unilateral  section  of  the  spinal  cord  in  man  (and  monkey) 
Ferrier)  abolishes  sensibility  on  the  opposite  side  below  the  lesion.  There  is 
hyperaesthesia  of  the  parts  below  the  seat  of  the  section  on  the  side  of  the  injury 
(§  363).  From  experiments  on  mammals,  Brown-Sequard  concludes  that  the 
decussating  sensory  nerve  fibres  pass  to  the  opposite  side  within  the  cord  at  different 
levels,  the  lowest  being  the  fibres  for  touch,  then  those  for  tickling  and  pain,  and, 
highest  of  all,  those  which  administer  to  sensations  of  temperature. 

All  the  fibres,  therefore,  which  connect  the  spinal  cord  with  the  gray  matter 
of  the  brain,  undergo  a  complete  decussation  in  their  course.  Hence,  in  man  a 
destructive  affection  of  one  hemisphere  usually  causes  complete  motor  paralysis 
and  loss  of  sensibility  on  the  opposite  side  of  the  body.  The  fibres  proceeding 
from  the  nuclei  of  orign  of  the  cranial  nerves  also  cross  within  the  cranium. 

Not  unfrequently  the  motor  paralysis  and  anaesthesia  occur  on  the  same  side  of  the  head,  in  which 
case  the  lesion  (due  to  pressure  or  inflammation)  involves  the  cranial  nerves  lying  at  the  base  of  the 
brain. 

The  positions  of  decussation  are  (i)  in  the  spinal  cord,  (2)  in  the  medulla  oblongata,  and 
lastly  (3)  in  the  pons.     The  decussation  is  complete  in  the  peduncle. 

Alternate  Paralysis. — Gubler  obser\-ed  that  unilateral  injury  to  the  pons  caused  paralysis  of  the 
facial  nerve  on  the  same  side,  but  paralysis  of  the  opposite  half  of  the  body.  He  concluded  that  the 
nerves  of  the  trunk  decussate  before  they  reach  the  pons,  while  the  facial  fibres  decussate  within  the 
pons.  To  these  rare  cases  the  name  ''alternate  hemiplegia"  is  given.  [WTien  hemorrhage  takes 
place  into  the  lozuer  part  of  the  lateral  half  of  the  pons,  there  may  be  alternate  paralysis,  but  when 
the  tipper  part  of  the  lateral  half  is  injured,  the  facial  is  paralyzed  on  the  same  side  as  the  body, 
I  379-1 

The  olfactory  nerve  is  said  not  to  decussate  (?),  while  the  optic  nerve  undergoes  a  partial  decussa- 
tion at  the  chiasma  (§  344).  Some  observers  assert  that  the  fibres  of  the  trochlearis  decussate  at 
their  origin. 

366.  THE  MEDULLA  OBLONGATA.— [Structure.— In  the  medulla  oblongata,  the 
fibres  from  the  cord  are  rearranged,  the  gray  matter  is  also  much  changed,  while  new  gray  matter  is 
added.  Each  half  of  the  medulla  oblongata  consists  of  the  following  parts,  from  before  backward  : — 
The  anterior  pyramid,  olivary  body,  restiform  body,  and  posterior  pyramid,  or  funiculus 
gracilis  (Figs.  464,  465,  466).  By  the  divergence  of  the  posterior  pyramids  and  the  restiform  bodies, 
the  floor  of  the  4th  ventricle  is  exposed.  As  the  central  canal  of  the  cord  gradually  comes  nearer  to 
the  posterior  surface  of  the  medulla,  it  opens  into  the  4th  ventricle.  At  the  lower  end  of  the 
medulla  oblongata,  on  separating  the  anterior  pyramids,  we  may  see  the  decussation  of  the  pyra- 
mids, where  the  fibres  cross  over  to  the  lateral  columns  of  the  cord.  The  anterior  pyramid 
receives  the  direct  pyramidal  tract  of  the  anterior  column  of  the  cord  from  its  own  side,  and  the 
crossed  pyramidal  tract  fi-om  the  lateral  column  of  the  cord  of  the  opposite  side  (Fig.  464).  The 
decussating  fibres  (crossed  pyramidal  tract)  of  the  lateral  column  pass  across  in  bundles  to  form  the 
decussation  of  the  pyramids.  Most  of  the  pyramidal  fibres  pass  through  the  pons  directly  to  the  cere- 
brum, a  few  fibres  pass  to  the  cerebelliun,  while  some  join  fibres  proceeding  from  the  olivary  body  to 
form  the  olivary  fasciculus  or  fillet.] 

[Thus,  only  a  part  of  the  anterior  column  of  the  cord — direct  pyramidal  tract — is  continued  into 
the  anterior  pyramid,  where  it  lies  external  to  the  fibres  which  pass  to  the  lateral  column  of  the 
opposite  side.  The  remainder  of  the  anterior  column — the  antero-extemal  fibres — are  continued 
upward,  but  lie  deeper  under  cover  of  the  anterior- pyramid,  where  they  serve  to  form  part  of  the 
formatio  reticularis  (p.  709).] 

[Of  the  fibres  of  the  lateral  column  of  the  cord,  some,  the  direct  cerebellar  tract,  pass  backward 
to  join  the  restiform  body  and  go  to  the  cerebellum.  These  fibres  lie  as  a  thin  layer  on  the  surface  of 
the  restiform  body.  The  crossed  pyramidal  &orts  cross  obhquely,  at  the  lower  end  of  the  medulla, 
to  the  anterior  pyramid  of  the  opposite  side,  and  in  their  course  they  traverse  the  gray  matter  of  the 
anterior  comu  (Fig.  464,  py).  These  fibres  form  the  larger  and  mesial  portion  of  the  anterior 
pyramid.  The  remaining  fibres  of  the  lateral  columns  are  continued  upward,  and  pass  beneath 
the  oHvary  body,  where  they  are  concealed  by  this  structure  and  also  by  the  arcuate  fibres,  but 
they  appear  in  the  floor  of  the  medulla  oblongata  and  are  here  known  as  \hs.  fascicuhis  teres,  which 
goes  to  the  cerebrum.  As  they  pass  upward,  they  help  to  form  the  lateral  part  of  the  formatio 
reticularis.] 

45 


Fig.  463. 


Diagram  of  a  spinal  segmenl  as  a  spinal  centre  and  conducting  meduim.  B  right  B'  left  cerebral  hemisphere  ;  MO, 
bt^rend^f  medulla  oblongata ;  i.  motor  tract  from  the  right  hemisphere  the  larger  part  decussating  at  MO 
and  passing  down  the  lateral  column  of  the  cord  on  the  opposite  side  to  the  muscles  M  and  M  ;  2,  motor  tract 
from  the  left  hemisphere  ;  S,  S',  sensitive  areas  on  the  left  side  of  the  body  ;  3',  3,  the  main  sensory  tract  from 
the  left  side  of  the  body-it  decussates  shortly  after  entering  the  cord;  S^,  S3  sensitive  areas  and  4  ,  4.  tracts 
from  the  right  side  of  the  body.  The  arrows  indicate  the  direction  of  the  impulses  {Bramwell).  [Here  all  the 
sensory  fibres  are  shown  as  crossing  in  the  cord.] 

706 


THE    SUBDIVISIONS   OF   THE    MEDULLA   OBLONGATA. 


707 


[The  posterior  pyramid  of  the  oblongata  is  merely  the  upward  continuation  of  the  postero- 
median column,  or  funiculus  gracilis  of  the  cord.  As  it  passes  upward  at  the  medulla  it  broadens 
out,  forming  the  clava,  which  tapers  away  above.  The  clava  contains  a  mass  of  gray  matter — the 
clavate  nucleus.] 

[The  restiform  body  consists  chiefly  of  the  upward  continuation  of  the  postero-external  column 
or  funiculus  cuneatus  of  the  cord.  It  contains  a  mass  of  gray  matter,  called  the  cuneate  or  trian- 
gular nucleus.  Above  the  level  of  the  clava,  the  funiculus  cuneatus  forms  part  of  the  lateral 
boundary  of  the  4th  ventricle.  Immediately  outside  this,  i.e.,  between  it  and  the  continuation  of  the 
posterior  nerve  roots,  is  a  longitudinal  prominence,  which  Schwalbe  has  called  the  funiculus  of 
Rolando.  It  is  formed  by  the  head  of  the  posterior  comu  of  gray  matter  coming  nearer  the 
surface.  It  also  forms  part  of  the  restiform  body.  Some  arcuate  fibres  issue  from  the  anterior 
median  fissure,  turn  transversely  outward  over  the  anterior  pyi-amids  and  olivary  body,  and  pass 
along  with  the  funiculus  cuneatus,  the  funiculus  of  Rolando,  and  the  direct  cerebellar  fibres,  to  enter 
the  corresponding  lateral  lobe  of  the  cerebellum,  all  these  structures  forming  its  inferior  peduncle. 
Some  observers  suggest  that  the  funiculus  cuneatus  and  funiculus  of  Rolando  do  not  pass  into  the 
cerebellum.] 


Section  of  the  decussation  of  the  pyramids,  fla,  anterior  median  fissure,  displaced  laterally  by  the  fibres  decussating 
at  d;  V,  anterior  column;  Ca,  anterior  comu,  with  its  nerve  cells,  a,  b;  cc,  central  canal;  S,  lateral 
column;  fr,  formatio  reticularis  ;  ce,  neck,  and^,  head  of  the  posterior  comu  ;  rpCI,  posterior  root  of  the  ist 
cervical  nerve;  nc,  first  indication  of  the  nucleus  of  the  funiculus  cuneatus;  ng,  nucleus  (clava)  of  the  funiculus 
gracilis;  //l,  funiculus  gracilis  ;  //^^  fLmiculus  cuneatus;  j/?>,  posterior  median  fissure;  jr,  groups  of  ganglionic 
cells  in  the  base  of  the  posterior  cornu.  X  6. 


[The  olivary  body  forms  a  well  marked  oval  or  olive-shaped  body,  which  does  not  extend  the 
whole  length  of  the  medulla  (Fig.  466,  o).  Above  it  is  separated  from  the  pons  by  a  groove  from 
which  the  6th  nerve  emerges.  In  the  groove  between  it  and  the  anterior  pyramid  arise  the  strands 
of  the  hypoglossal  nerve,  while  in  a  corresponding  groove  along  its  outer  surface  is  the  line  of  exit  of 
the  vagus,  glosso-pharyngeal,  and  spinal  accessory  nerves.  It  is  covered  on  its  surface  by  longitudinal 
and  arcuate  fibres,  while  in  its  interior  it  contains  the  dentate  nucleus.] 

[The  functions  of  the  olivary  bodies  are  quite  unknown,  but  it  is  important  to  remember  that 
they  are  connected  by  fibres  with  the  dentate  nuclei  of  the  cerebellum.  Fibres  pass  into  the  olivary 
body  from  the  posterior  column  of  the  cord  of  the  opposite  side,  and  it  is  also  connected  with  the 
dentate  body  of  the  opposite  side,  while,  as  we  know,  the  dentate  body  is  connected  with  the  teg- 
mentum, so  that  through  the  left  dentate  body  of  the  opposite  side,  the  tegmentum  of,  say,  the  right 
crus,  is  connected  with  the  right  olivary  body  [^Go'wers).'\ 

[Decussation  of  the  pyramids  is  the  term  given  to  those  fibres  which  cross  obliquely  in  several 
bundles,  at  the  lower  part  of  the  medulla,  fi-om  the  anterior  pyramid  of  the  medulla  into  the  lateral 


708 


STRUCTURE    OF   TIIK    MEDULLA    OBLONGATA. 


column  of  the  cord  of  tlie  opposite  side  (Fig.  4^4.  ''')  to  form  its  lateral  pyramid  tracts,  or  crossed 
p>Tamidal  tracts.  The  number  of  fibres  wliich  decussate  varies,  and  in  some  cases  all  the  fibres  may 
Cross.]  . 

[  Ihe  gray  matter  of  ihe  medulla  is  largely  a  continuation  of  that  of  the  cord,  although  it  is 
arranged  ditVerently.  As  the  fibres  from  the  lateral  column  of  the  cord  pass  over  to  form  part  of  the 
anterior  pyramid  of  the  medulla  on  the  opj^site  side,  they  traverse  the  gray  matter,  and  thus  cut  off 
the  tip  of  the  anterior  cornu,  which  is  also  pu--hed  backward  i)y  the  olivary  body,  and  exists  as  a  dis- 
tinct mass,  the  nucleus  lateralis  (Fig.  465,  til).  Part  of  the  anterior  gray  matter  also  appears  in 
the  floor  of  the  4th  ventricK-  as  the  eminence  of  the  fasciculus  teres,  and  from  part  of  it  springs  the 
hypoglossal  nerve  (Fig.  466,  X/I).  The  neck  joining  the  modified  anterior  and  posterior  cornua  is 
much  broken  up  bv  the  passage  of  longitudinal  and  transverse  fibres  tlirough  it,  so  that  it  forms  a 
formatio  reticularis,  separating  the  two  cornua  (Fig.  465,/;).     The  caput  cornu  posterioris  comes 


Fin.  465. 


Section  of  the  medulla  oblongata  at  the  so-called 
upper  decussation  of  the  pyramids.  _/?«,  ante- 
rior, slfi,  posterior  median  fissure  ;  nX/,  nu- 
cleus of  the  accessorius  vagi ;  nX!I,  nucleus 
of  the  hypoglossal :  cia,  the  so-called  superior 
or  anterior  decussation  of  the  pyramids;  py, 
anterior  pyramid;  n.ar,  nucleus  arciformis; 
f,  median  parolivary  body:  O,  beginning  of 
the  nucleus  of  the  olivary  body  :  nl,  nucleus  of 
the  lateral  column;  Fr,  formalio  reticularis; 
g,  substantia  gelatinosa,  with  {a  K)  the  ascend- 
ing root  of  the  trigeminus;  nc,  nucleus  of  the 
funiculus  cuneatus;  «f',  external  nucleus  of 
the  funiculus  cuneatus ;  ng,  nucleus  of  the  fu- 
niculus gracilis  (or  clava)  ;  //',  funiculus  gra- 
cilis ;  //'.funiculus  cuneatus  ;  cc,  central  canal ; 
/a,/a^ ,/a'^ ,  external  arciform  fibres.  X  4- 


Fig.  466. 


nc. 


n.ar 


Section  of  the  medulla  oblongata  through  the  olivary  body. 
nXlI,  nucleus  of  the  hypoglossal;  nX,  nX^,  more  or 
less  celhilar  parts  of  the  nucleus  of  the  vagus  ;  XII,  hypo- 
glossal nerve;  A',  vagus ;  ti.atn,  nucleus  ambiguus ;  nl, 
nucleus  lateralis;  tj,  olivary  nucleus;  fla/,external,  and 
oa»t,  internal  parolivary  body  ;  /s,  the  round  bundle,  or 
funiculus  solitarius ;  CV,  restiform  body  ;  /,  anterior 
pyramid,  surrounded  by  arciform  fibres  ;  fae,pol,  fibres 
proceeding  from  the  olive  to  the  raphe  (pedunculus 
olivae) ;  r,  raphe.  X  4- 


to  be  covered  higher  up  by  the  a.scending  root  of  the  5th  nerve  (Fig.  465,  a  V),  and  arcuate  fibres 
passing  to  the  resiiform  body.  The  jwsterior  cornu  is  also  i)roken  up  and  is  thrown  outward,  its 
caput  giving  rise  to  ])art  of  the  elevation  seen  on  the  surface  and  described  as  the  funiculus  of 
Rolando,  while  jiart  of  the  base  now  greatly  enlarged  forms  the  gray  matter  in  the  funiculus  gracilis 
[clavate  nucleus]  (Fig.  464,  ng)  and  funiculus  cuneatus  [cuneate  or  triangular  nucleus]  (Fig.  464, 
nc).  Nearer  the  middle  line,  tlie  gray  matter  of  the  posterior  gray  cornu  appears  in  the  floor  of  the 
4th  ventricle,  above  the  jwint  where  the  central  canal  opens  into  it,  as  the  nuclei  of  the  spinal  acces- 
sory, vagus,  and  glosso-pharj'ngeal  nerves.] 

[In  the  floor  of  the  4th  ventricle  near  the  raphe,  and  quite  superficial,  is  a  longitudinal  mass  of 
large  multipolar  nerve  cells,  derived  from  the  base  of  the  anterior  cornu  from  which  spring  the  several 
bundles  forming  the  hypoglossal  nerve;  it  is  the  hypoglossal  nucleus  (Fig.  466,  nX//),ihe 
nerve  fibres  passing  obliquely  outward  to  appear  between  the  anterior  pyramid  and  the  olivary  body. 


THE  GRAY  MATTER  OF  THE  MEDULLA  OBLONGATA.      709 

Internal  to  it,  and  next  the  median  groove,  is  a  small  mass  of  cells  continuous  with  those  in  the 
raphe,  and  called  the  nucleus  of  the  funiculus  teres  (Fig.  466,  nt).  Around  the  central  canal  at  the 
lower  part  of  the  medulla  is  a  group  of  cells  (Fig.  466,  tiXI),  which  becomes  displaced  laterally  as 
it  comes  nearer  the  surface  in  the  floor  of  the  medulla  oblongata,  where  it  lies  outside  the  hypo- 
glossal nucleus,  and  corresponds  to  the  prominence  of  the  ala  cinerea  (Fig.  466,  nX') ;  and  from  it 
and  its  continuation  upward  arise  from  below  upward  part  of  the  spinal  accessory  (nth),  and  the 
vagus  (loih),  corresponding  to  the  position  of  the  eminentia  cinerea  (Fig.  466,  X),  so  that  this 
colunnn  of  cells  forms  the  vago-accessorius  nucleus.  External  to  and  in  front  of  this  is  the 
nucleus  for  the  glosso-phar}'ngeal  nerve.  Further  up  in  the  medulla,  on  a  level  with  the  auditory 
striae  and  outside  the  previous  column,  is  a  tract  of  cells  from  which  the  auditory  nerve  (Sth)  in 
great  part  arises ;  it  is  the  principal  auditory  nucleus,  and  lies  just  under  the  commencement  of 
the  inferior  cerebellar  peduncle  (Fig.  427,  8^,  8^^,  8^^^).  It  consists  of  an  outer  and  inner  nucleus, 
which  extend  to  the  middle  line.  It  forms  connections  with  the  cerebellum,  and  some  fibres  are 
said  to  enter  the  inferior  cerebellar  peduncle.  This  is  an  important  relationship,  as  we  know  that 
the  vestibular  branch  of  the  auditory  nerve  comes  partly  from- the  semicircular  canals,  so  that  in  this 
way  these  organs  may  be  connected  with  the  cerebellum.] 

[Superadded  Gray  Matter. — There  is  a  superadded  mass  of  gray  matter  not  represented  in  the 
cord,  that  of  the  olivary  body,  enclosing  a  nucleus,  the  corpus  dentatum,  with  its  wavy  strip  of 
gray  matter  containing  many  small  multipolar  nerve  cells  embedded  in  neuroglia.  The  gray  matter 
is  covered  on  the  surface  by  longitudinal  and  transverse  fibres.  It  is  open  toward  the  middle  line 
(hilum),  and  into  it  run  white  fibres  forming  its  peduncle  (Fig.  466,/,  o,  /).  These  fibres  diverge 
like  a  fan,  some  of  them  ending  in  connection  with  the  small  multipolar  cells  of  the  dentate  body, 
while  others  traverse  the  lamina  of  gray  matter  and  pass  backward  to  appear  as  arcuate  fibres  which 
join  the  restiform  body;  others,  again,  pass  directly  through  to  the  surface  of  the  olivary  body,  which 
they  help  to  cover  as  the  superficial  arcuate  fibres.  The  accessory  olivary  nuclei  (Fig.  465,  0^, 
o^')  are  two  small  masses  of  gray  matter  similar  to  the  last,  and  looking  as  if  they  were  detached 
from  it,  one  lying  above  and  external,  sometimes  called  the  parolivary  body,  and  the  other  slightly 
below  and  internal  to  the  olivary  nucleus,  the  latter  being  separated  from  the  dentate  body  by  the 
roots  of  the  hypoglossal  nerve.  The  latter  is  sometimes  called  the  internal  parolivary  body,  or 
nucleus  of  the  pyramid.] 

[The  formatio  reticularis  occupies  the  greater  part  of  the  central  and  lateral  parts  of  the  medulla, 
and  is  produced  by  the  inter-crossing  of  bundles  of  fibres  running  longitudinally  and  more  or  less 
transversely  in  the  medulla  (Fig.  465, y^).  In  the  more  lateral  portions  are  large  multipolar  nerve 
cells,  perhaps  continued  upward  from  part  of  the  anterior  cornu,  while  the  part  next  the  raphe  has 
no  such  cells.  The  longitudinal  fibres  consist  of  the  upward  prolongation  of  the  antero-external 
columns  of  the  cord,  while  some  seem  to  arise  from  the  clavate  nuclei  and  olives  as  arcuate  fibres 
passing  upward.  In  the  lateral  portions,  the  longitudinal  fibres  are  the  direct  continuation  upward 
of  Flechsig's  antero-lateral  mixed  tracts  of  the  lateral  columns  (p.  683).  The  horizontal  fibres 
are  formed  by  arcuate  fibres,  some  of  which  run  more  or  less  transversely  outward  from  the 
raphe.  The  superficial  arctiate  fibres  (Fig.  466,  y,  a,  e)  appear  in  the  anterior  median  fissure,  and 
perhaps  come  through  the  raphe  from  the  opposite  side  of  the  medulla,  curve  round  the  anterior 
pyramids,  form  a  kind  of  capsule  for  the  olives,  and  join  the  restiform  body  (p.  707),  but  they  are 
reinforced  by  some  of  the  deep  arcuate  fibres  which  traverse  the  olivary  body  (p.  707)-  The  deep 
arcuate  fibres  run  from  the  clavate  and  triangular  nuclei  horizontally  inward  to  the  raphe,  and  cross 
to  the  other  side;  others  pass  from  the  raphe  to  the  olivary  body,  and  through  it  to  the  restiform 
body.  In  the  raphe,  which  contains  nerve  cells,  some  fibres  run  transversely,  others  longitudinally, 
and  others  from  before  backward.] 

[Other  Nerve  Nuclei — Sixth  Nerve. — Under  the  elevation  called  eminentia  teres  (Fig.  427) 
in  front  of  the  auditory  striae,  close  to  the  middle  line,  is  a  tract  of  large  multipolar  nerve  cells.  It 
was  once  thought  to  be  the  common  nucleus  of  the  6th  and  7th  facial  nerves,  but  Gowers  has  shown 
that  "the  facial  ascends  to  this  nucleus,  forms  a  loop  round  it  (some  fibres  indeed  go  through  it),  and 
then  passes  downward  foi"ward  and  outward,  to  a  column  of  cells  more  deeply  placed  in  the  medulla 
than  any  other  nucleus  in  the  lower  part."  But  the  seventh  has  no  real  origin  from  this  nucleus. 
Facial  Nerve. — The  nucleus  Ues  deep  in  the  formatio  reticularis  of  the  pons  under  the  floor  of  the 
4th  ventricle,  but  outside  the  position  of  the  nucleus  of  the  6th  (Fig.  427,  7).  It  extends  downward 
about  as  far  as  the  auditory  strife,  or  a  httle  lower.  The  fifth  nerve  arises  from  its  motor  nucleus 
(with  large  multipolar  cells),  which  lies  more  superficially  above  and  external  to  the  6th  (Fig.  427, 
5).  The  fibres  run  backward,  where  they  are  joined  by  fibres  from  the  upper  sensory  nucleus, 
but  another  sensory  nucleus  extends  down  nearly  to  the  lower  end  of  the  medulla  (5^^).  Doubtless 
this  extensive  origin  brings  this  nerve  into  intimate  relation  with  the  other  cranial  nerves,  and 
accounts  for  the  numerous  reflex  acts  which  can  be  discharged  through  the  fifth  nerve.  Some  sen 
sory  fibres  are  said  to  pass  up  beneath  the  corpora  quadrigemina  [Goivers').  The  fourth  nerve 
arises  from  the  valve  of  Vieussens,  i.  e.,  the  lamina  of  white  and  gray  matter  which  stretches  between 
the  superior  cerebellar  peduncles.  It  arises,  therefore,  behind  the  fourth  ventricle,  but  some  of  the 
fibres  spring  from  nerve  cells  at  the  lower  part  of  the  nucleus  of  the  3d  nerve.     Some  fibres  also 


710  FUNCTIONS   OF   THE    MFIDULLA    OBLONGATA. 

descend  in  the  pons  to  form  n  connection  with  the  nucleus  of  the  6th  nerve.  The  fil)res  decussate 
behind  the  aque<luct,  so  that  in  it  alone,  of  all  the  cranial  nerves,  decussation  occurs  between  its 
nucleus  anil  its  superticial  orijjin  (Gowt-rs).  The  third  nerve  arises  from  a  tract  of  cells  beneath 
the  aiiueduct  and  near  the  midiile  line,  and  the  iibrcs  descend  through  the  tegmentum  to  appear  at 
the  inner  side  of  the  cms  cerebri.  Ciowcrs  points  out  that,  in  reality,  there  are  three  distinct  func- 
tional centres  (l)  for  accommod.ition  (ciliary  muscle),  (2)  for  the  light  rellex  of  the  iris,  and  (3) 
most  of  the  external  muscles  of  the  eyeball.  It  is  imporiant  to  notice  the  connection  between  the 
nuclei  of  the  3d,  4th,  and  6th  nerves,  in  relation  to  the  innervation  of  the  ocular  muscles.] 

Functions. — The  medulla  oblongata,  which  connects  the  si)inal  cord  with  the 
brain,  has  many  points  of  resemblance  with  the  Ibrmer.  [Like  the  cord  it  is  con- 
cerned (I)  in  the  conduction  of  impulses.]  (2)  In  it,  numerous  reflex  centres 
are  present,  ^•.  ^i,^,  for  s///i/'/<-  n-Jhwcs  similar  to  the  nerve  centres  in  the  s])inal  cord, 
e.g.,  closure  of  the  eyelids  [so  tJiat  they  subserve  the  transference  of  afferent  into 
efferent  impulses].  There  are  other  centres  present  which  seem  to  dominate  or 
control  similar  centres  placed  in  the  cord,  e.g.,  the  great  vasomotor  centre,  the 
sweat-secreting,  pupil-dilating  centres,  and  the  centre  for  combining  the  reflex 
movements  of  the  body.  Some  of  the  centres  are  ca])able  of  being  excited  reflexly 
(§  358,  2).  (3)  It  is  also  said  to  contain  automatic  centres  (§  358,  3).  The 
normal  functions  of  the  centres  depend  u|)on  the  exchanges  of  blood  gases, 
eflected  by  the  circulation  of  the  blood  through  the  medulla.  If  this  gaseous 
exchange  be  interrui)ted  or  interfered  with,  as  by  asphyxia,  sudden  anaemia,  or 
venous  congestion,  these  centres  are  first  excited,  and  exhibit  a  condition  of  increased 
excitability,  and  at  last,  if  they  are  over-stimulated,  they  are  paralyzed.  An 
excessive  temperature  also  acts  as  a  stimulus.  All  the  centres,  however,  are  not 
active  at  the  same  time,  and  they  do  not  all  exhibit  the  same  degree  of  excitability. 
Normally,  the  respiratory  centre  and  the  vasomotor  centre  are  contmually  in  a  state 
of  rhythmical  activity.  In  some  animals,  the  inhibitory  centre  of  the  heart  remains 
continuallv  non-excited  ;  in  others,  it  is  stimulated  very  slightly  under  normal  con- 
ditions, simultaneously  with  the  stimulation  of  the  respiratory  centre,  and  only 
during  inspiration.  The  sjjasm  centre  is  not  stimulated  under  normal  conditions; 
and  during  intra-uterine  life,  the  respiratory  centre  remains  quiescent.  The  medulla 
oblongata,  therefore,  contains  a  collocation  of  nerve  centres  which  are  essential  for 
the  maintenance  of  life,  as  well  as  various  conducting  paths  of  the  utmost  importance. 
We  shall  treat  of  the  reflex,  and  afterward  of  the  automatic  centres. 

367.  REFLEX  CENTRES  OF  THE  MEDULLA  OBLONGATA. 

— The  medulla  ol)lungata  contains  a  number  of  reflex  centres,  which  minister  to  the 
discharge  of  a  large  number  of  coordinated  movements. 

1.  Centre  for  closure  of  the  eyelids. — The  sensory  branches  of  the  5th 
cranial  nerve  to  the  cornea,  conjunctiva,  and  the  skin  in  the  region  of  the  eye,  are 
the  afferent  nerves.  They  conduct  impulses  to  the  medulla  oblongata,  where  they 
are  transferred  to,  and  excite  part  of,  the  centre  of  the  facial  nerve,  whence,  through 
branches  of  the  facial,  the  eff"erent  impulses  are  conveyed  to  the  orbicularis  palpe- 
brarum. The  centre  extends  from  about  the  middle  of  the  ala  cinerea  upward  to 
the  posterior  margin  of  the  pons  {Nickell'). 

The  reflex  closure  of  the  eyelids  always  occurs  on  both  sides,  but  closure  may  be  produced  volun- 
tarily on  one  side  (winking).  When  the  stimulation  is  stronr^,  the  corrugator  and  other  groups  of 
muscle?  which  raise  the  cheek  and  nose  toward  the  eye  may  also  contract,  and  so  form  a  more  perfect 
protection  and  closure  of  the  eye.  Intense  stimulation  of  the  retina  causes  closure  of  the  eyelids 
[and  in  this  case  the  shortest  reflex  known,  the  latent  period,  is  0.05  second  ( IValler)']. 

2.  Sneezing  centre. — The  afferent  channels  are  the  internal  nasal  branches 
of  the  trigeminus  and  the  olfactory,  the  latter  in  the  case  of  intense  odors.  The 
efferent  or  motor  paths  lie  in  the  nerves  for  the  muscles  of  expiration  (§§  120,  3, 
and  347,  II).  Sneezing  cannot  be  performed  voluntarily  [but  it  may  be  inhibited 
by  compressing  the  nasal  nerve  at  its  exit  on  the  nose]. 


REFLEX    CENTRES    OF   THE    MEDULLA    OBLONGATA.  711 

3.  Coughing  centre. — According  to  Kohts,  it  is  placed  a  little  above  the 
inspiratory  centre ;  the  afferent  paths  are  the  sensory  branches  of  the  vagus 
(§  352,  5,  ^)-  The  efferent  paths  lie  in  the  nerves  of  expiration  and  those  that 
close  the  glottis  (§  120,  i). 

4.  Centre  for  sucking  and  mastication. — The  afferent  paths  lie  in  the 
sensory  branches  of  the  nerves  of  the  mouth  and  lips  (2d  and  3d  branches  of  the 
trigeminus  and  glosso-pharyngeal).  The  efferent  nerves  for  sucking  axe.  (§  152)  : 
Facial  for  the  lips,  hypoglossal  for  the  tongue,  the  inferior  maxillary  division  of 
the  trigeminus  for  the  muscles  which  elevate  and  depress  the  jaw.  For  the  move- 
ments oi  masticaiion,  the  same  nerves  are  m  action  (§  153)  ;  but  when  food  passes 
within  the  dental  arch,  the  hypoglossal  is  concerned  in  the  movements  of  the 
tongue,  and  the  facial  for  the  buccinator. 

5.  Centre  for  the  secretion  of  saliva  (p.  259)  lies  in  the  floor  of  the  4th 
ventricle.  Stimulation  of  the  medulla  oblongata  causes  a  profuse  secretion  of 
saliva  when  the  chorda  tympani  and  glosso-pharyngeal  nerves  are  intact,  a  much 
feebler  secretion  when  the  nerves  are  divided,  and  no  secretion  at  all  when  the 
cervical  sympathetic  is  extirpated  at  the  same  time  (^Grittznef'). 

6.  Swallowing  centre  lies  in  the  floor  of  the  4th  ventricle  (§  156). — The 
afferent  paths  lie  in  the  sensory  branches  of  the  nerves  of  the  mouth,  palate,  and 
pharynx  (2d  and  3d  branches  of  the  trigeminus,  glosso-pharyngeal,  and  vagus)  ; 
the  efferent  channels,  in  the  motor  branches  of  the  pharyngeal  plexus  (§  352,  4). 
Stimulation  of  the  glosso-pharyngeal  nerve  does  not  cause  deglutition  ;  on  the 
contrary,  this  act  is  inhibited  (p.  273). 

According  to  Steiner,  every  time  we  swallow  there  is  a  slight  stimulation  of  the  respiratory  centre, 
resulting  in  a  contraction  of  the  diaphragm.  [Kronecker  has  shown  that  if  a  glass  of  water  be  sipped 
slowly,  the  action  of  the  cardio-inhibitory  centre  is  interfered  with  reflexly,  so  that  the  heart  beats 
much  more  rapidly,  whereby  the  circulation  is  accelerated,  hence  probably  the  reason  why  sipping 
an  alcoholic  drink  intoxicates  more  rapidly  than  when  it  is  quickly  swallowed  (p.  719)-] 

7.  Vomiting  centre  (§  158). — The  relation  of  certain  branches  of  the  vagus 
to  this  act  are  given  at  §  352,  2,  and  12,  d. 

8.  The  upper  centre  for  the  dilator  pupillae  muscle,  the  smooth  muscles 
of  the  orbit,  and  the  eyelids  lies  in  the  medulla  oblongata.  The  fibres  pass  out 
partly  in  the  trigeminus  (§  347,  I,  3),  partly  in  the  lateral  columns  of  the  spinal 
cord  as  far  down  as  the  cilio-spinal  region,  and  proceed  by  the  two  lowest  cervical 
and  the  two  upper  dorsal  nerves  into  the  cervical  sympathetic  (§  356,  A,  i).  The 
centre  is  normally  excited  reflexly  by  shading  the  retina,  i.  e.,  by  diminishing 
the  amount  of  light  admitted  into  the  eye.  It  is  directly  excited  by  the  circulation 
of  dyspnoeic  blood  in  the  medulla.  (The  centre  for  contracting  the  pupil  is  referred 
to  at  §§  345  and  392.) 

The  centre  may  be  excited  reflexly  by  stimulation  of  sensory  nerve,  e.  g.,  the  sciatic.  These 
afferent  fibres  pass  upward  through  both  lateral  columns  to  their  centre  {Kowalewskyi). 

9.  There  is  a  subordinate  centre  in  the  medulla  oblongata,  which  seems  to  be 
concerned  in  bringing  the  various  reflex  centres  of  the  cord  into  relation  with  each 
other.  Owsjannikow  found  that,  on  dividing  the  medulla  6  mm.  above  the  calamus 
scriptorius  (rabbit),  the  general  reflex  movements  of  the  body  still  occurred,  and 
the  anterior  and  posterior  extremities  participated  in  such  general  movements.  If, 
however,  the  section  was  made  i  mm.  nearer  the  calamus,  only  local  partial  reflex 
actions  occurred  (§  360,  III,  4);  [thus,  on  stimulating  the  hind  leg,  the  fore  legs 
did  not  react — the  transference  of  the  reflex  was  interfered  with].  The  centre 
reaches  upward  to  slightly  above  the  lowest  third  of  the  oblongata. 

The  medulla  in  the  frog  also  contains  the  general  centre  for  movements  from  place  to  place.  Sec- 
tion of  this  region  abolishes  the  power  to  move  from  place  to  place ;  when  external  stimuli  are 
applied,  there  remains  only  simple  reflex  movements  [Steiner). 


712  POSITION    OF   THE    RESPIRATORY    CENTRE. 

PatholoRical. — The  medulla  oblongata  is  sometimes  the  scat  of  a  typical  disease,  known  as  bul- 
bar paralysis,  or  t;losso-pharynpo-lal>ial  paralysis  (Dii<:h,nnf,  iS6o),  in  which  there  is  a  progressive 
invasion  of  the  dilTcrent  nene  nuclei  (centres)  of  the  cranial  nerves  which  arise  within  the  medulla, 
these  centres  being  the  motor  portions  of  an  important  reflex  apparatus.  Usually,  the  disease  begins 
with  paralysis  of  the  /outfit,-,  accomjianied  by  tibrillar  contractions,  whereby  speech,  formation  of  the 
food  into  a  bolus,  and  swallowing  are  inlirfcred  with  (jS  354).  The  secretion  of  thick,  viscid  saliva 
points  to  the  imjKissibility  of  secreting  a  thin,  wnlery, /<iiiii/  su/irt7  (''}_  145,  A),  owing  to  paralysis  of 
this  nerve  nucleus.  .Swallowing  may  be  impossible,  owing  to  paralysis  of  the  pharynx  and  palate. 
This  interferes  with  the  formation  of  lonsotujnts  [especially  the  Unguals,  /,  /,  s,  r,  and,  by  and  by, 
the  labial  explosives,  b,  p]  (g  318,  C) ;  the  speech  becomes  nasal,  while  fluids  and  solid  food  often 
pass  into  the  nose.  Then  follows  paralysis  of  the  branches  of  the  facial  to  the  lips,  and  there  is  a 
chaiacteri.'.tic  expression  of  the  mouth  "  as  if  it  were  frozen."  All  the  muscles  of  the  face  m.iy  be 
paralyzeil  ;  sometimes  the  laryw^eal  muscles  are  paralyzed,  leading  to  loss  of  voice  and  the  entrance 
of  focKi  into  the  windpijie.  The  heart  heats  are  often  retarded,  pointing  to  stimulation  of  the  cardio- 
inhibitory  fibres  (arising  from  the  accessorius).  Attacks  of  dyspiicca,  like  those  following  paralysis  of 
the  recurrent  nerves  (>i  313,  II,  i,  and  \  352,  5,/'),  and  death  may  occur.  Paralysis  of  the  muscles 
of  mastication,  contraction  of  the  pupil,  and  paralysis  of  the  abducens  are  rare.  [This  disease  is 
always  bilateral,  and  it  is  important  to  note  that  it  afiects  the  nuclei  of  those  muscles  that  guard  the 
orifices  of  the  mouth,  including  the  tongue,  the  posterior  nares  including  the  soft  palate,  and  the  rima 
glottidis  with  the  vocal  cords.] 

368.  RESPIRATORY  CENTRE.  INNERVATION  OF  THE 
RESPIRATORY  ORGANS.— Ihc  respiratory  centre  lies  in  the  medulla 
oblongata  {Lfi^a/Zois,  iSii).  behind  the  su[)erficial  origin  of  the  vagi,  on  both  sides 
of  the  posterior  aspect  of  the  ajjex  of  the  ( alamiis  scriptorius,  between  the  nuclei 
of  the  vagus  and  accessorius,  and  was  named  by  Flourens  the  vital  point,  or  nceud 
vital.  The  centre  is  double,  one  for  each  side,  and  it  may  be  separated  by  means 
of  a  longitudinal  incision  {Longef,  1847),  whereby  the  respiratory  movements  con- 
tinue symmetrically  on  both  sides.  Section  of  Vagi. — If  one  vagus  be 
divided,  rcsi)iration  on  that  side  is  shmu'd.  If  both  vagi  l)e  divided,  the  respirations 
become  much  slower  and  deeper^  but  the  respiratory  movements  are  symmetrical  on 
both  sides.  Stimulation  of  the  central  end  of  one  vagus,  both  being  divided, 
causes  an  arrest  of  the  respiration  only  on  the  same  side,  the  other  side  continues 
to  breathe.  The  same  result  is  obtained  by  stimulation  of  the  trigeminus  on  one 
side  {Lartgendorff).  When  the  centre  is  divided  transversely  on  one  side,  the 
respiratory  movements  on  the  same  side  cease  {Scliiff).  Most  probably  the  domi- 
nating respiratory  centre  lies  in  the  medulla  oblongata,  and  upon  it  depend  the 
rhythm  and  symmetry  of  the  respiratory  movements ;  but,  in  addition,  other  and 
subordinate  centres  are  placed  in  the  spinal  cord,  and  these  are  governed  by 
the  oblongata  centre.  If  the  spinal  cord  be  divided  in  newly-born  animals  (dog, 
cat)  below  the  medulla  oblongata,  respiratory  movements  of  the  thorax  are  some- 
times observed  {Bracket,  1835). 

[If  the  cord  be  divided  below  the  medulla,  or  the  cranial  arteries  ligatured  (rabbit),  there  may 
still  be  respiratory  movements,  which  become  more  distinct  if  strychnin  be  previously  administered, 
so  that  I^ngendorff  assumes  the  existence  of  a  spinal  respiratory  centre,  which  he  finds  is  also 
influenced  by  reflex  stimulation  of  sensory  nerves.] 

Nitschmann,  by  means  of  a  vertical  incision  into  the  cervical  cord,  divided  the  spinal  centre  into 
two  equal  halves,  each  of  which  acted  on  both  sides  of  the  diaphragm  after  the  medulla  was  divided 
just  below  the  calamus  scriptorius.  'Die  spinal  centres  mu.st,  therefore,  be  connected  with  each  other 
in  the  cord.     The  spinal  respiratory  centre  can  be  excited  or  inhibited  reflexly  (  Wertheimer). 

Anatomical. — Schift'  locates  the  respiratory  centre  near  the  lateral  margins  of  the  gray  matter  in 
the  floor  of  the  4th  ventricle,  but  not  reaching  so  far  backward  as  the  ala  cinerea.  According  to 
Gierke,  Heidenhain,  and  I^ngendorfl^,  those  parts  of  the  medulla  oblongata  whose  destruction  causes 
cessation  of  the  respiratory  movements  are  single  or  double  strands  of  nervous  matter,  containing 
gray  nervous  substance  with  small  ganglion  cells,  and  running  downward  in  the  substance  of  the 
medulla  oblongata.  These  strands  are  said  to  arise  partly  from  the  roots  of  the  vagus,  trigeminus, 
spinal  accessory,  and  glossopharyngeal  {Meynert),  forming  connections  by  means  of" fibres  with  the 
other  side,  and  descending  as  far  downward  as  the  cervical  enlargement  of  the  spinal  cord  [Golf). 
According  to  this  view,  this  strand  represents  an  inter-central  band  connecting  the  spinal  cord  (the 
place  of  origin  of  the  motor  respiratory  nerves)  with  the  nuclei  of  the  above-named  cranial  nerves. 


CEREBRAL   RESPIRATORY    CENTRE. 


713 


Fig.  467. 


Cerebral  Inspiratory  Centre. — According  to  Christiani,  there  is  a  cerebral 
inspiratory  centre  in  tlie  optic  thalamus  in  the  floor  of  the  3d  ventricle,  which  is 
stimulated  through  the  optic  and  auditory 
nerves,  even  after  extirpation  of  the  cerebrum 
and  corpora  striata ;  Avhen  it  is  stimulated 
directly,  it  deepens  and  accelerates  the  inspira- 
tory movements,  and  may  even  cause  a  stand- 
still of  the  respiration  in  the  inspiratory  phase. 
This  inspiratory  centre  may  be  extirpated. 
After  this  operation,  an  expiratory  centre  is 
active  in  the  substance  of  the  anterior  pair  of 
the  corpora  quadrigemina,  not  far  from  the 
aqueduct  of  Sylvius.  Martin  and  Booker  de- 
scribe a  second  cerebral  inspiratory  centre  in 
the  posterior  pair  of  the  corpora  quadrige- 
mina. These  three  centres  are  connected  with 
the  centres  in  the  medulla  oblongata. 

The  respiratory  centre  consists  of  two 
centres,  which  are  in  a  state  of  activity  alter- 
nately— an  inspiratory  and  an  expiratory 
centre  (Fig.  467),  each  one  forming  the 
motor  central  point  for  the  acts  of  inspiration 
and  expiration  (§  112).  The  centre  is  auto- 
matic,  for,  after   section   of  all  the   sensory  ^  ^        ^  ^     ^.  ^^'^' 

,  ._,      _    „       _t    „„£]„    1  „„„   i-U„ i   ^     bcheme  01  the  chiei  respiratory  nerves 

""""         "  spiratory,  and  ^^/,  expiratorj' centre — motor 

nerves  are  in  smooth  lines  Expiratory 
motor  nerves  to  abdominal  muscles,  ah  ;  to 
muscles  of  back,  do.  Inspiratory  motor 
nerves.  /A,  phrenic  to  diaphragm,  d\  int, 
intercostal  nerves;  r/,  recurrent  laryngeal; 
e.r,  pulmonary  fibres  of  vagus  that  excite  in- 
spiratory centre  ;  ex' ,  pulmonary  fibres  that 
excite  expiratory'  centre  ;  ejc" ,  fibres  of  sup. 
larj'ngeal  that  excite  expiratory  centre  ;  ink, 
fibres  of  sup.  laryngeal  that  inhibit  the  in- 
spiratory centre. 


nerves  which  can  act  reflexly  upon  the  centre, 
it  still  retains  its  activity.  The  degree  of 
excitability  and  the  stimulation  of  the  centre 
depend  upon  the  state  of  the  blood,  and 
chiefly  upon  the  amount  of  the  blood  gases, 
the  O  and  CO2  (/■  -Rosenthal).  Accord- 
ing to  the  condition  of  the  centre,  there 
are  several  well-recognized  respiratory  con- 
ditions :  — 

I.  Apnoea. — Complete  cessation  of  the  respiration  constitutes  apncea,  i.  e., 
cessation  of  the  respiratory  movements,  owing  to  the  absence  of  the  proper  stimu-' 
lus,  due  to  the  blood  being  saturated  with  O  and  poor  in  CO2.  Such  blood  satu- 
rated with  O  fails  to  stimulate  the  centre,  and  hence  the  respiratory  muscles  are 
quiescent.  This  seems  to  be  the  condition  in  the  foetus  during  intra-uterine  life. 
If  air  be  vigorously  and  rapidly  forced  into  the  lungs  of  an  animal  by  artificial 
respiration,  the  animal  will  cease  to  breathe  for  a  time,  after  cessation  of  the  arti- 
ficial respiration  {Hook,  1667),  the  blood  being  so  arterialized  that  it  no  longer 
stimulates  the  respiratory  centre.  If  a  person  takes  a  series  of  rapid,  deep  respi- 
rations his  blood  becomes  surcharged  with  oxygen,  and  long  "  apnceic  pauses  " 
occur. 

Apnceic  Blood. — -A.  Ewald  found  that  the  arterial  blood  of  apnoeic  animals  was  completely- 
saturated  with  O,  while  the  CO2  was  diminished ;  the  venous  blood  contained  less  O  than  normal — 
this  latter  condition  being  due  to  the  apnceic  blood  causing  a  considerable  fall  of  the  blood  pressure 
and  consequent  slowing  of  the  blood  stream,  so  that  the  O  can  be  more  completely  taken  from  the 
blood  in  the  capillaries  [PJliiger).  The  amount  of  O  used  in  apnoea  on  the  whole  is  not  increased 
(^  127).  Gad  remarks  that  during  forced  ai-tificial  respiration,  the  pulmonary  alveoli  contain  a 
very  large  amount  of  atmospheric  air;  hence,  they  are  able  to  arterialize  the  blood  for  a  longer  time, 
thus  diminishing  the  necessity  for  respiration.  According  to  Gad  and  Knoll,  the  excitability  of  the 
respiratory  centre  is  reduced  during  apnoea,  and  this  is  caused  reflexly  during  artificial  respiration  by 
the  distention  of  the  lungs  stimulating  the  branches  of  the  vagus.  In  quite  young  mammals  apnoea 
cannot  be  produced  {^Rtmge). 

[Drugs. — If  the  excitability  of  the  respiratory  centre  be  diminished  by  chloral,  apnoea  is  readily 
induced,  while,  if  the  centre  be  excited,  as  by  apomorphine,  it  is  difficult  to  produce  it.] 


711  EUPNCEA,    DVSPNfEA    AND    ASPHYXIA. 

2.  Eupnoea.— The  normal  stimulation  of  the  resiMratory  centre,  eupmva,  is 
caused  by  the  blood,  in  which  the  amount  of  O  and  CO,  does  not  exceed  the 
normal  limits  (vj§  35  and  36).  . 

3.  Dyspnoea. — All  conditions  which  diminisli  the  O  and  increase  the  CO,,  in 
the  blood  t  ir<  ulating  through  the  medulla  and  respiratory  centre  cause  acceleration 
and  deepening  of  the  respirations,  which  may  ultimately  i)ass  into  vigorous  and 
labored  activity  of  all  the  respiratory  muscles,  constituting  dyspnea,  \\\\t\\  the 
difficulty  of  breathing  is  very  great  (§  134).     [Changes  in  the  rhythm,  §  iii.] 

During  normal  respiration,  and  witli  the  commencement  of  the  need  for  more  air,  according  to 
Gad,  the  gases  of  the  blood  excite  only  the  inspiratory  centre;  while  the  expiration  follows  owing  to 
reflex  stimulation  of  the  pulmonary  vagus  by  the  distention  of  the  lungs  (p.  716).  He  is  also  of 
opinion  that  the  normal  respiratory  movements  are  excited  by  the  CO.^. 

[Muscular  work,  as  is  well  known,  increases  tlie  respirations  and  may  even  cause  dyspnoea. 
Tins  is  not  due  to  the  nervous  connections  of  the  muscles  or  other  organs  with  the  respiratory  centre, 
but  to  changes  in  the  blood,  t'icppert  and  Zunlz  have  shown,  however,  that  the  result  cannot  be 
explained  by  changes  in  the  blood  caused  cither  by  diminution  of  O  or  increase  of  QO.,.  It  seems 
to  lie  due  to  the  blood  taking  up  some  as  yet  unknown  products  from  the  contracting  muscle,  and 
carrying  them  to  the  resjiiratory  centre,  which  is  directly  excited  by  them.  The  nature  of  these 
sultttances  is  unknown.  It  has  been  shown  that  the  alkalinity  of  the  blood  is  reduced  by  the  forma- 
tion of  an  acid.  The  substances,  whatever  they  may  be,  are  not  excreted  l)y  the  urine,  and  are 
therefore,  perhaps  readily  oxidized  {^Lonoy).  C.  Lehmann  has  proved  that,  in  rabbits,  the  acidifica- 
tion of  the  blood  produced  by  muscular  exertion  plays  an  imjiortant  part  in  the  stimulation  of  the 
respiratory  centre.] 

4.  Asphyxia. — If  blood,  abnormal  as  regards  the  amount  and  quality  of  its 
gases,  continue  to  circulate  in  the  medulla,  or  if  the  condition  of  the  blood  become 
still  more  abnormal,  the  respiratory  centre  is  over-stimulated,  and  ultimately 
exhausted.  The  respirations  are  diminished  both  in  number  and  depth,  and  they 
become  feeble  and  gasping  in  character;  ultimately  the  movements  of  the  respira- 
tory muscles  cease,  and  the  heart  itself  soon  ceases  to  beat.  This  constitutes  the 
condition  oi  asphyxia,  zwd.  if  it  be  continued,  death  from  suffocation  takes  place. 
(LangendorfT  asserts  that  in  asphyxiated  frogs  the  muscles  and  gray  nervous  sub- 
stance have  an  acid  reaction.)  If  the  conditions  causing  the  abnormal  condition 
of  the  blood  be  removed,  the  asphyxia  may  be  i)revented  under  favorable  circum- 
stances, esjjecially  by  using  artificial  respiration  (§  134);  the  respiratory 
muscles  begin  to  act  and  the  heart  begins  to  beat,  so  that  the  normal  eupnoeic 
stage  is  reached  through  the  condition  of  dyspnoea.  If  the  venous  condition  of 
the  blood  be  produced  slowly  and  very  gradually,  asphyxia  may  occur  without 
there  being  any  symptoms  of  dyspnoea,  as  happens  when  death  takes  place  quietly 
and  very  gradually  (!;  324,  5). 

Causes  of  Dyspnoea. — (i)  Direct  limitation  of  the  activity  of  the  respiratory  organs; 
diminution  of  the  respiratory  surface  by  inflammation,  acute  oudema  [\  47),  or  collapse  of  the  alveoli, 
occlusion  of  the  capillaries  of  the  alveoli,  compression  of  the  lungs,  entrance  of  air  into  the  pleura, 
obstruction  or  compression  of  the  windpipe.  (2)  Obstruction  to  the  entrance  of  the  normal 
amount  of  air  by  strangulation,  or  enclosure  in  an  insufficient  space.  (3)  Enfeeblement  of  the 
circulation,  so  that  the  medulla  oblongata  does  not  receive  a  sufficient  amount  of  blood;  in  degenera- 
tion of  the  heart,  valvular  cardiac  disease,  and  artificially  by  ligature  of  the  carotid  and  vertebral 
arteries  {Kmsmaul  and  Tenner),  or  by  preventing  the  free  eillux  of  venous  blood  from  the  skull,  or 
by  the  injecti  n  of  a  large  quantity  of  air  or  indifferent  particles  into  the  right  heart.  (4)  Direct 
loss  of  blood,  which  acts  by  arresting  the  exchange  of  gases  in  the  medulla  (/.  Rosenthal).  This 
is  the  cause  of  the  "biting  or  .snapping  at  the  air"  manifested  by  the  decapitated  heads  of  young 
animals,  e.  ^.,  kittens.  [The  phenomenon  is  well  marked  in  the  head  of  a  tortoise  separated  from 
the  body  (  W.  Stirling)!] 

If  we  study  the  rapidly  fatal  effects  of  these  factors  on  the  respiratory  activity,  we  observe  that  at 
first  the  respirations  become  quicker  and  deeper,  then  after  an  attack  of  general  convulsions,  ending 
in  expiratory  spasm,  there  follows  a  stage  of  complete  cessation  of  respiration.  Before  death  takes 
place,  there  are  usually  a  few  "  snapping"  or  gasping  efforts  at  inspiration  {Bogyes,  Sigm.  Mayer — 
^  "0- 

Condition  of  the  Blood  Gases. — As  a  general  rule,  in  the  production  of  dyspnoea,  the  want  of 
O  and  the  excess  of  CO_,  act  simultaneously  {Ffliiger  and  Dohtnen),  but  each  of  these  alone  may 
act  as  an  efficient  cause.     According  to  Bernstein,  blood  containing  a  small  amount  of  O  acts  chiefly 


CONDITIONS   ACTING   ON    THE    RESPIRATORY    CENTRE.  715 

upon  the  inspiratory  centre,  and  blood  rich  in  COj  on  the  expiratory  centre,  (i)  DyspncEa,  from 
want  of  O,  occurs  during  respiration  in  a  space  of  77ioderate  size  (|  133),  in  spaces  where  the  tension 
of  the  air  is  diminished,  and  by  breathing  indifferent  gases  or  those  containing  no  free  O.  When  the 
blood  is  freely  ventilated  with  N  or  H,  the  amoimt  of  COj  in  the  blood  may  even  be  diminished, 
and  death  occurs  with  all  the  signs  of  asphyxia  {Pfli'iger).  (2)  Dyspncea,  from  the  blood  being 
overcharged  with  COj,  occurs  by  breathing  air  containing  much  COj  (§  133)-  Air  containing 
much  CO2  may  cause  dyspncea,  even  when  the  amount  of  O  in  the  blood  is  greater  than  that  in  the 
atmosphere  (^T/iiry).     The  blood  may  even  contain  more  O  than  normal  [P/iuger). 

Heat  Dyspncea. — An  increased  temperature  increases  the  activity  of  the  respiratory  centre 
(§  214,  II,  3).  This  occurs  when  blood  warmer  than  natural  flows  through  the  brain,  as  Fick  and 
Goldstein  observed  when  they  placed  the  exposed  carotids  in  warm  tubes,  so  as  to  heat  the  blood 
passing  through  them.  In  this  case  the  heated  blood  acts  directly  upon  the  brain,  the  medulla,  and 
the  cerebral  respiratory  centres  [Gad).  Direct  cooling  diminishes  the  excitability  [Fredericq). 
When  the  temperature  is  increased,  vigorous  artificial  respiration  does  not  produce  apnoea,  although 
the  blood  is  highly  arterialized  [Ackermantt).  Emetics  act  in  a  similar  .manner  [Hermann  and 
Gn>?im). 

Electrical  stimulation  of  the  medulla  oblongata,  after  it  is  separated  from  the  brain,  discharges 
respiratory  movements  or  increases  those  already  present  [Kronecker  and  Mai-ckwald).  Langen- 
dorff  found  that  electrical,  mechanical,  or  chemical  (salts)  stimulation  usually  caused  an  expiratory 
effect,  while  stimulation  of  the  cervical  spinal  cord  (subordinate  centre)  gave  an  inspiratory  effect. 
According  to  Laborde,  a  superficial  lesion  in  the  region  of  the  calamus  scriptorius  causes  standstill 
of  the  respiration  for  a  few  minutes.  If  the  peripheral  end  of  the  vagus  be  stimulated,  so  as  to  arrest 
the  action  of  the  heart,  the  respirations  also  cease  after  a  few  seconds.  Arrest  of  the  heart's  action 
causes  a  temporary  anaemia  of  the  medulla,  in  consequence  of  which  its  excitability  is  lowered,  so 
that  the  respirations  cease  for  a  time  [Langendorff). 

Action  on  the   Centre. — The  respiratory  centre,  besides  being  capable  of 
being  stimulated  directly,  may  be  influenced  by  the  will,  and  also  reflexly  by  ' 
stimulation  of  a  number  of  afferent  nerves. 

1.  By  a  voluntary  impulse  we  may  arrest  the  respiration  for  a  short  time,  but 
only  until  the  blood  becomes  so  venous  as  to  excite  the  centre  to  increased  action. 
The  number  and  depth  of  the  respirations  may  be  voluntarily  increased  for  a  long 
tinie,  and  we  may  also  voluntarily  change  the  rhythm  of  respiration. 

2.  The  respiratory  centre  maybe  influenced  reflexly  both  by  fibres  which  excite 
it  to  increased  action  and  by  others  which  inhibit  its  action,  (a)  The  exciting 
fibres  lie  in  the  pulmonary  branches  of  the  vagus,  in  the  optic,  auditory,  and  cuta- 
neous nerves;  normally  their  action  overcomes  the  action  of  the  inhibitory  fibres. 
Thus,  a  cold  bath  deepens  the  respirations,  and  causes  a  moderate  acceleration  of 
the  pulmonary  ventilation  (Speck). 

Section  of  both  vagi  causes  slo\ver  and  deeper  respiratory  movements, 
owing  to  the  cutting  off  of  those  impulses  which  under  normal  conditions  pass 
from  the  lungs  to  excite  the  respiratory  centre  (p.  712).  The  amount  of  air 
taken  in  the  CO.,  given  off,  however,  is  unchanged,  but  the  inspiratory  efforts  are 
more  vigorous  and  not  so  purposive  {Gad).  Weak  tetanizing  currents  applied  to 
the  central  &wA  of  the  vagus,  cause  acceleration  of  the  respirations,  while,  at  the 
same  time,  the  efforts  of  the  respiratory  muscles  may  be  increased,  or  diminished, 
or  remain  unchanged  (Gad).  Strong  tetanizing  currents  cause  standstill  of  the 
respiration  in  the  inspiratory  phase  (Traube),  or  especially  in  fatigue  of  the  nerves, 
in  the  expiratory  phase  {Budge,  Burkart).  Single  induction  shocks  have  no  effect 
{Marckwald  and  Kronecker). 

[Marckwald,  while  admitting  that  the  respiratory  centre  is  automatically  active,  as  well  as  capable 
of  being  affected  reflexly,  comes  to  the  conclusion,  that,  when  the  centre  is  separated  from  all  nerve 
channels  by  which  afferent  impulses  can  be  conveyed  to  it,  it  is  incapable  of  discharging  rhythmical 
respiratory  movements.  He  also  asserts  that  the  normal  rhythmical  respiration  is  a  reflex  act 
discharged  chiefly  through  the  vagi,  and  that  the  normal  excitant  of  the  respirator)^  centre  is  not 
dependent  on  the  condition  of  the  blood,  either  on  the  diminution  of  O,  or  the  increase  of  CO2. 
These  results  are  opposed  to  the  usually  accepted  view,  and  they  are  controverted  by  Loewy. 
Division  of  the  medulla  oblongata  above  the  respiratory  centre,  so  as  to  cut  off"  all  cerebral  channeb 
of  communication,  has  very  little  effect  on  the  respirations.  If,  after  this,  one,  or  both  vagi  be 
divided,  there  is  (i)  an  exfraordinary  slowing  oi  the  respiration;  the  number  of  respirations  may 
fall  in  the  rabbit,  from  20  to  2  or  4  per  minute;   (2)  the  rhythm  is   changed,  in  some   cases   the 


716 


CONDITIONS    ACTING    ON    THE    RESPIRATORY    CENTRE. 


inspiration  mav  l)e  twice  or  thrice  as  long  as  the  expiration,  l)ut,  whatever  the  ratio  of  inspiration  to 
expiration,  the  respiration  is  rhythmical;  (3)  the  vp!u>,u-  of  air  respired  is  diminished  (p.  715),  but 
the  volume  for  each  respiration  is  deeper;  1^4)  the  intra  thoracic  pressure  is  increased,  during  inspira- 
tion, and  during  expiration  it  is  the  same  as  before  the  vagotomy.] 


Before 

Vagotomy. 

1 

After  Vagotomy. 

J 

a 

K 

Intra-thoracic 
Pressure. 

B 
u 

3 

v 

d 

•IS. 

> 

Intra-thoracic 
Pressure. 

c 

•Sd 

2.  d 

1)   X 

KM 

d 

It 

> 

3  V 

c  a 

1? 

■IS. 

> 

Is- 

,5<2 

mm. 

com. 

com. 

c.cm. 

!< 

?< 

I 

-30  to  -40 

20 

3»o-35o 

16 

-60  to  -70 

4 

•y2 

130-140 

59 

33 

100 

2 

-22  to  -24 

32 

530-540 

16 

-50  to  -60 

^y^ 

'A 

105-120 

79-5 

40 

150 

[The  above  table  (from  Loewy)  shows  the  result.  Loewy  finds  that,  if  a  centre  be  separated 
from  all  centripetal  channels,  it  still  discharges  respiratory  movements,  which  are  rhythmical,  and  he 
has  shown  that  these  ihylhmical  discharges  are  due  to  the  condition  of  the  blood.] 

[If  one  lung  be  made  atelectic,  /.  e.,  devoid  of  air,  e.g.,  by  plugging  its  bronchus  with  a  sponge 
tent,  then  the  pulmonary  fibres  of  the  vagus  from  this  lung  are  no  longer  excited  during  respiration, 
and  their  section  has  no  effect  on  the  respiration.  Section  of  the  vagus  on  the  sound  side,  however, 
has  the  same  consecjuence  as  double  vagotomy  (Zc^«'j').] 

Wedenski  and  Heidenhain  find  that  a  temporary,  7veak,  electrical  stimulus  applied  to  the  central 
end  of  the  vagus,-at  the  beginning  of  inspiration  (rabbit),  affects  the  depth  of  the  succeeding  inspira- 
tions, while  a  similar  strong  stinmlus  affects  also  the  depth  of  the  following  expiration.  If  the 
stimulus  be  applied  just  at  the  commencement  of  expiration,  stronger  stimuli  being  required  in  this 
case,  there  is  a  diminution  of  the  expiration  and  of  the  following  inspiration.  Continued  tetanic 
stimulation  of  the  vagus  may  cause  decrease  in  the  depth  of  the  expirations,  or  at  the  same  time 
alteration  in  the  depth  of  the  inspirations,  without  affecting  the  respiratory  rhythm;  when  the 
stimulation  is  stronger,  inspiration  and  expiration  are  dimini-hed  with  or  without  alteration  of  the 
frequency,  and  with  the  strongest  stimuli,  respirations  cease  either  in  the  inspiratory  or  expiratory 
phase. 

{b)  The  inhibitory  nerves  which  affect  the  respiratory  centre  run  in  the  supe- 
rior laryngeal  nerve  {Rosenthal),  and  also  in  the  inferior  {Pfliiger  and  Burkart, 
Hering,  Breuer),  to  the  respiratory  centre  (Fig.  467,  ink). 

According  to  I^ngendorff,  direct  electrical,  mechanical,  or  chemical  stimulation  of  the  centre 
may  arrest  respiration,  perhaps  in  consequence  of  the  stimulus  affecting  the  central  ends  of  these 
inhibitory  nerves  where  they  enter  the  ganglia  of  the  res[)iratory  centre.  During  the  reflex  inhibition 
of  the  respiration  in  the  expiratory  phase,  there  is  a  suppression  of  the  motor  impulse  in  the  inspiratory 
centre  ( iVegete). 

Stimulation  of  the  superior  or  inferior  laryngeal  nerves  (<5)  or  their  central  ends 
causes  slowing,  and  even  arrest  of  the  respiration  (in  expiration — Rosenthal). 
Arrest  of  the  respiration  in  expiration  is  also  caused  by  stimulation  of  the  nasal 
{Hering  and  Kratschmer)  and  ophthalmic  branches  of  the  trigeminus  (Christiani), 
of  the  olfactory,  and  glosso-pharyngeal  {Marckwalii).  [Kratschmer  found  that 
tobacco  smoke  blown  into  a  rabbit's  nostrils,  or  puffed  through  a  hole  in  the 
trachea  into  the  nose,  by  stimulating  the  nasal  branch  of  the  fifth  nerve,  arrested 
the  respiration  in  the  expiratory  phase  ;  while  it  had  no  effect  when  blown  into  the 
lungs.  Ammonia  vapor  applied  to  the  nostrils  arrests  it  in  the  same  way.  If 
ammonia  vapor  be  blown  into  the  lungs  (the  nasal  cavity  being  protected  from  its 
action),  the  respiration  may  be  accelerated,  or  deepened,  or  arrested  occasionally 
in  expiration,  /.  e.,  according  to  the  fibres  of  the  vagus  acted  on  by  the  vapor  in  the 
lungs  (A'/w//).]  Stimulation  of  the  pulmonary  branches  of  the  vagus  by  breathing 
irritating  gases  (Knoll)  causes  standstill  in  expiration,  although  some  other  gases 
cause  standstill  in  inspiration.  Chemical  stimulation  of  the  trunk  of  the  vagus — 
by  dilute  solutions  of  sodic  carbonate — causes  expiratory  inhibition  of  the  respira- 
tion ;  and  mechanical  stimulation — rubbing  with  a  glass  rod — inspiratory  inhibition 


STIMULATION  AND  REGULATION  OF  THE  RESPIRATORY  CENTRE.    717 

{Knon).  The  stimulation  of  sensory  cutaneous  nerves,  especially  of  the  chest  and 
abdomen  (as  occurs  on  taking  a  cold  douche),  and  stimulation  of  the  splanchnics, 
cause  standstill  in  expiration,  the  first  cause  often  giving  rise  to  temporary  clonic 
contractions  of  the  respiratory  muscles.  The  respirations  are  often  slowed  to  a 
very  great  extent  by  pressure  upon  the  brain  [whether  the  pressure  be  due  to  a 
depressed  fracture  or  effusion  into  the  ventricles  and  subarachnoid  space].  The 
respiration  may  be  greatly  oppressed  and  stertorous. 

The  amount  of  work  done  by  the  respiratory  muscles  is  altered  during  the  reflex  slowing  of  the 
respiratory  muscles,  the  work  being  increased  during  slow  respiration,  owing  to  the  ineffectual  inspi- 
ratory efforts  [Gad).  The  volume  of  the  gases  which  passes  through  the  lungs  during  a  given 
time  remains  unchanged  (  Valentiti),  and  the  gaseous  exchanges  are  not  altered  at  first  (  Voit  and 
Rauber) . 

Automatic  Regulation. — Under  normal  circumstances,  it  would  seem  that 
the  pulmonary  branches  of  the  vagus  act  upon  the  two  respiratory  centres,  so  as  to 
set  in  action  what  has  been  termed  the  self-adjusting  xi\Qc\\2js\\'i'ca. ;  thus,  the  inspira- 
tory dilatation  of  the  lungs  stimulates  mechanically  the  fibres  which  reflexly  excite 
the  expiratory  centres,  while  the  diminution  of  the  lungs  during  expiration  excites 
the  nerves  which  proceed  to  the  inspiratory  ctvAxt  i^Hering  a^id  Breuer,  ffead). 
[Thus,  blowing  into  the  lungs  excites  the  act  of  expiration,  and  sucking  air  out 
of  them  excites  inspiration.] 

In  this  way  we  may  explain  the  alternate  play  of  inspiration  and  expiration.  In  deep  narcosis, 
however,  dilatation  of  the  thorax  in  animals  is  followed  first  by  cessation  of  the  respiratory  movements, 
and  then  by  inspiration  [P.  Giittmann). 

Discharge  of  the  First  Respiration. — The  foetus  is  in  an  apnoeic  condition 
until  birth,  when  the  umbilical  cord  is  cut.  During  intra-uterine  life,  O  is  freely 
supplied  to  it  by  the  activity  of  the  placenta.  All  conditions  which  interfere  with 
this  due  supply  of  O,  as  compression  of  the  umbilical  vessels  and  prolonged  labor 
pains,  cause  a  decrease  of  the  O  and  an  increase  of  the  CO2  in  the  blood,  so  that 
the  condition  of  the  fcetal  blood  is  so  altered  as  to  stimulate  the  respiratory  centre, 
and  thus  the  impulse  is  given  for  the  discharge  of  the  first  respiratory  movement 
{Schwartz).  A  foetus,  still  within  the  unopened  foetal  membranes,  may  make 
respiratory  movements  {Vesalius,  1542).  If  the  exchange  of  gases  be  interrupted 
to  a  sufficient  extent,  dyspnoea  and  ultimately  death  of  the  foetus  may  occur.  If, 
however,  the  venous  condition  of  the  mother's  blood  develops  very  slowly,  as  in 
cases  of  quiet,  slow  death  of  the  mother,  the  medulla  oblongata  of  the  fcetus  may 
gradually  die  without  any  respiratory  movement  being  discharged  (§  324,  5). 

According  to  this  view,  the  respiratory  movements  are  due  to  the  direct  action  of  the  dyspnceic 
blood  upon  the  medulla  oblongata.  [The  excitability  of  the  respiratory  centre  is  less  in  the  foetus 
than  in  the  newly  born,  and  it  increases  from  day  to  day  after  birth.  Among  the  causes  of  the  dimin- 
ished excitability  are  the  small  amount  of  O  in  fcetal  blood,  and  the  slow  velocity  of  the  circulation. 
If  an  inspiration  is  discharged  in  the  foetus,  it  is  at  once  inhibited  by  fluid  passing  into  the  nostrils  and 
inhibiting  the  act  reflexly.  The  chief  cause  of  the  first  respiration  after  birth,  is  undoubtedly  the 
increasing  venosity  of  the  blood,  and  also  the  disappearance  of  the  above  named  reflex  inhibitory 
process.]  Death  of  the  mother  acts  like  compression  of  the  umbiHcal  cord.  In  the  former  case,  the 
maternal  venous  blood  robs  the  foetal  blood  of  its  O,  so  that  death  of  the  foetus  occurs  more  rapidly 
{Ztmtz).  If  the  mother  be  rapidly  poisoned  with  CO  (§  17),  the  foetus  may  live  longer,  as  the 
CO-h^moglobin  of  the  maternal  blood  cannot  take  any  O  from  the  fcetal  blood  (g  16 — Hogyes).  In 
slow  poisoning  the  CO  passes  into  the  foetal  blood  {Grekant  and  Quinquand). 

In  many  cases,  especially  in  cases  of  very  prolonged  labor,  the  excitability  of  the  respiratory  centre 
may  be  so  diminished,  that  after  birth,  the  dyspnceic -condition  of  the  blood  alone  is  not  sufficient  to 
excite  respiration  in  a  normal  rhythmical  manner.  In  such  cases  stimulation  of  the  skin  also  acts, 
e.  g.,  partly  by  the  cooling  produced  by  the  evaporation  of  the  amniotic  fluid  from  the  skin.  _  When 
air  has  entered  the  lungs  by  the  first  respiratory  movements,  the  air  within  the  lungs  also  excites  the 
pulmonary  branches  of  the  vagus  [Pflilger],  and  thus  the  respiratory  centre  is  stimulated  reflexly  to 
increased  activity.  According  to  v.Preuschen's  observations,  stimulation  of  the  cutaneous  nerves  is 
more  effective  than  that  of  the  pulmonary  branches  of  the  vagus.  In  animals  which  have  been 
rendered  apnoeic  by  free  ventilation  of  their  lungs,  respiratory  movements  may  be  discharged  by 
strong  cutaneous  stimuli,  e.  g.,  dashing  on  of  cold  water.     The  mechanical  stimulation  of  the  skin  by 


718        DIRECT  STIMULATION  OF  THE  CARDIO-INHIBITORY  CENTRE. 

friction  or  sharp  blows,  or  the  application  of  a  cold  douche,  excites  the  respiratory  centre.  When 
the  placental  circulation  is  intact,  cutaneous  stimuli  do  not  discharge  respiratory  movements  (Z«m/« 
and  Ci'/instrin\,  (Artificial  respiration.  ^  i.u)- 

[Action  of  Drugs  on  the  Respiratory  Centre. — .\mmonia,  salts  of  zinc  and  copper,  strychnin, 
atropin.  dulioisin,  aponiorphin,  emctin,  the  di(;il.ilis  group,  and  heat  increase  the  rapidity  and  depth 
of  the  respirations,  while  they  become  frequent  and  shallower  after  the  u<e  of  alcohol,  ojiium,  chloral, 
chloroform,  phy.sostigmin.  The  excitability  of  the  centre  is  first  increased  .ind  then  diminished  by 
caffein.  r.icotin,  i|uinine,  and  saponin  \^Brniilon).']\ 

369.  CENTRE  FOR  THE  INHIBITORY  NERVES  OF  THE 
HEART-  CARDIO  INHIBITORY).— Ihe  fibres  of  the  vagus,  when 
moderately  stiimilated,  diminish  the  action  of  the  heart  ;  when  strongly  stimulated, 
however,  they  arrest  its  action  and  cause  it  to  stand  still  in  diastole  (§  352,  7)  ; 
they  are  supplied  to  the  vagus  through  the  spinal  accessory  nerve,  and  have  their 
centre  in  the  medulla  oblongata  (§  353). 

[Gaskell  has  shown  that  stimulation  of  the  vagus  not  only  influences  the  rhythm 
of  the  heart's  action,  but  modifies  the  other  functions  of  the  cardiac  muscle. 
Stimulation  of  the  vagus  influences  {a)  the  automatic  rhythm,  i.  e.,  the  rate  at 
which  the  heart  contracts  automatically;  {7^)  i\\&  force  oi  the  contractions,  more 
esj)ecially  the  auricles,  although  in  some  animals,  e.  g.,  the  tortoise,  the  ventricles 
are  not  affected  ;  {c)  ihc  power  of  conduction,  i.  e.,  the  capacity  for  conducting  the 
muscular  contractions.  According  to  Gaskell,  the  vagus  acts  upon  the  rhythmical 
power  of  the  muscular  fibres  of  the  heart.] 

This  centre  may  be  excited  directly  in  the  medulla,  and  also  reflexly,  by 
stimulating  certain  afferent  nerves. 

Many  observers  assume  that  this  centre  is  in  a  state  of  tonic  excitement,  /.  <•.,  that  there  is  a 
continuous,  uninterruptcxl,  regulating,  and  inhibitory  action  of  this  centre  upon  the  heart  through  the 
fibres  of  the  vagus.  According  to  Bernstein,  this  tonic  excitement  is  caused  reflexly  through  the 
alxlominal  and  cervical  syni])atlulic. 

I.  Direct  Stimulation  of  the  Centre. —  This  centre  may  be  stimulated 
directly,  by  the  .same  stimuli  that  act  upon  the  respiratory  centre,  (i)  Sudden 
anctmia  of  the  oblongata,  ligature  of  both  carotids  or  both  subclavians,  or  decapi- 
tating a  rabbit,  the  vagi  alone  being  left  undivided,  cause  slowing  and  even  tempo- 
rary arrest  of  the  action  of  the  heart.  (2)  Sudden  venous  hypercBtnia  acts  in  a 
similar  manner,  e.g.,  by  ligaturing  all  the  veins  returning  frorn  the  head.  (3)  In- 
creased venosity  of  the  blood,  produced  either  by  direct  cessation  of  the  respira- 
tions (rabbit),  or  by  forcing  into  the  lungs  a  quantity  of  air  containing  much  CO.^ 
{Traube).  As  the  circulation  in  the  placenta  (the  respiratory  organ  of  the  foetus) 
is  interfered  with  during  severe  labor,  this  sufficiently  explains  the  enfeeblement  of 
the  action  of  the  heart  which  occurs  during  protracted  labor  ;  it  is  due  to  stimula- 
tion of  the  central  end  of  the  vagus  by  the  dyspnceic  blood  {B.  S.  Schultze).  (4) 
At  the  moment  the  respiratory  centre  is  excited,  and  an  inspiration  occurs,  there  is 
a  variation  in  the  inhibitory  activity  of  the  cardiac  centre  {Bonders,  Pfluger, 
Frcdericij—%  74,  a,  4).  (5)  The  centre  is  excited  by  mcreased  blood  pressure 
within  the  cerebral  arteries. 

II.  The  centre  may  be  excited  reflexly  by— (i)  Stimulation  of  sensory  nerves 
{Loven).  (2)  Stimulation  of  the  central  end  of  one  vagus,  provided  the  other 
vagus  is  intact.  (3)  Stimulation  of  the  sensory  nerves  of  the  intestines,  by  tapping 
upon  the  belly  (Goltz's  tapping  experiment),  whereby  the  action  of  the  heart  is 
arrested.  Stimulation  of  the  splanchnic  directly  {Asp  and  Zudioig),  or  of  the 
abdominal  or  cervical  sympathetic,  produces  the  same  result.  Very  strong  stimula- 
tion of  sensory  nerves,  however,  arrests  the  above-named  reflex  eff"ects  upon  the 
vagus  (§  361,  3). 

Tapping  Experiment.— Goltz's  experiment  succeeds  at  once,  by  tapping  the  intestines  of  a  frog 
directly,  say,  with  the  handle  of  a  scalpel,  especially  if  the  intestine  has  been  exposed  to  the  air  for  a 
short  tmie,  so  as  to  become  inflamed  ( Tarclianoff).  Stimulation  of  the  stomach  of  the  do^  causes 
slowmg  of  the  heart  beat  (5/-.  Mayer  and  Pribram).     [M'William   finds   that  the   action  of  the 


STIMULATION    OF   THE   TRUNK   OF   THE   VAGUS. 


719 


^fmmnw 


Heart  Beat. 


Time  in  Sees. 


Stimulation. 


Beating  of  a  frog's  heart  taken  by  means  of  a  lever  resting  on  the 
heart.  The  lowest  curve  shows  when  the  vagus  was  stimulated 
and  the  consequent  arrest  of  the  heart  beat  (Stirling). 


heart  of  the  eel  may  be  arrested  reflexly  with  very  great  facihty.  The  reflex  inhibition  is  obtained 
by  slight  stimulation  of  the  gills  (through  the  branchial  nerves),  the  skin  of  the  head  and  tail,  and 
parietal  peritoneum,  by  severe  injury  of  almost  any  part  of  the  animal,  except  the  abdominal  organs.] 

[Effect  of  Swallowing  Fluids. — Kronecker  has  shown  that  the  act  of  swallowing  interferes 
with  or  abolishes  temporarily  the  cardio-inhibitory  action  of  the  vagus,  so  that  the  pulse  rate  is  greatly 
accelerated.  Merely  sipping  a  wineglassful  of  water  may  raise  the  rate  30  per  cent.  Hence,  sip- 
ping cold  water  acts  as  a  powerful  cardiac  stimulant.] 

According  to  Hering,  the  excitability  of  the  cardio-inhibitory  centre  is  diminished  by  vigorous 
artificial  ventilation  of  the  lungs  with  atmospheric  air.  At  the  same  time,  there  is  a  considerable  fall 
of  the  blood  pressure  (^  352,  8,  4).  In  man,  a  vigorous  expiration,  owing  to  the  increased  intra- 
pulmonary  pressure,  causes  an  acceleration  of  the  heart  beat,  which  Sommerbrodt  ascribes  to  a 
diminution  of  the  activity  of  the  vagi.  At  the  same  time  the  activity  of  the  vasomotor  centre  is 
diminished  (§  60,  2). 

Stimulation  of  the  trunk  of  the  vagus  from  the  centre  downward,  along  its 
whole  course,  and  also  of  certain  of  its  cardiac  branches  [inferior  cardiac],  causes 
the   heart  either   to   beat   more 

slowly,  or   arrests  its   action    in  Fig.  468. 

diastole.  The  result  depends 
upon  the  strength  of  the  stimulus 
employed ;  feeble  stimuli  slow 
the  action  of  the  heart,  while 
strong  stimuli  arrest  it  in  dias- 
tole. The  frog's  heart  may  be 
arrested  by  stimulating  the  fibres 
of  the  vagus  upon  the  sinus  ve- 
nosus  [or  by  stimulating  the 
vagus  in  its  course  as  in  Fig. 
468].  If  strong  stimuli  be  applied,  either  to  the  centre  or  to  the  course  of  the 
nerve,  for  a  long  thne,  the  part  stimulated  becomes  fatigued  and  the  heart  beats 
more  rapidly  in  spite  of  the  continued  stimulation.  If  a  part  of  the  nerve  lying 
nearer  the  heart  be  stimulated,  inhibition  of  the  heart's  action  is  brought  about, 
as  the  stimulus  acts  upon  a  fresh  portion  of  nerve. 

The  following  points  have  also  been  ascertained  regarding  the  stimulation  of  the  inhibitory 
fibres : — 

1.  The  experiments  of  Lowit  on  the  frog's  heart,  confirmed  by  Heidenhain,  showed  that  electrical 
and  chemical  stimulation  of  the  vagus  produce  different  results,  as  regards  the  extent  of  the  ventricu- 
lar systole,  as  well  as  the  number  of  heart  beats  ;  the  contractions  either  become  smaller,  or  less 
frequent,  or  they  become  smaller  and  less  frequent  simultaneously.  Strong  stimuli  cause,  in  addition, 
well-marked  relaxation  of  the  heart  muscle  during  diastole. 

2.  In  order  to  cause  inhibition  of  the  heart,  a  continuous  stimulus  is  not  necessary.  A  rhythmi- 
cally inierrtipted  moderate  stimulus  suffices  [v.  Bezold) ;  18  to  20  stimuli  per  second  are  required 
for  mammals,  and  2  to  3  per  second  for  cold-blooded  animals. 

3.  Bonders,  with  Prahl  and  Niiel,  observed  that  arrest  of  the  heart's  action  did  not  take  place 
immediately  the  stimulus  was  applied  to  the  vagus;  but  about  y^  oi  z  second — period  of  latent 
stimulation — elapsed  before  the  effect  was  produced  on  the  heart. 

4.  If  the  heart  be  arrested  by  stimulation  of  the  vagus,  it  can  still  contract,  if  it  be  excited  directly, 
e.g.,  by  pricking  it  with  a  needle,  when  it  executes  a  single  contraction.  [This  holds  good  only  for 
some  animals,  e.g.,  frog,  tortoise,  birds  and  mammals.  In  fishes,  only  the  ventricle  responds  to 
stimulation  during  marked  inhibition;  in  the  newt,  only  the  bulbus  arteriosus.  In  the  newt's  heart, 
the  sinus,  auricles,  and  ventricle  are  all  inexcitable  to  direct  stimulation  during  strong  inhibition.] 

5.  According  to  A.  B.  Meyer,  inhibitory  fibres  are  present  only  in  the  right  vagus  in  the  turtle. 
It  is  usually  stated  that  the  right  vagus  is  more  effective  than  the  left  in  other  animals,  e,g.,  rabbit 
(Masoin) ;  but  this  is  subject  to  many  exceptions  {^Landois  and  Langendorff).  [In  the  newt,  the 
right  vagus  acts  more  readily  on  the  ventricle  than  on  the  other  parts  of  the  heart;  slight  stimulation 
of  the  right  vagus  can  arrest  the  ventricle,  while  the  sinus  and  auricles  go  on  beating.] 

6.  The  vagus  has  been  compressed  by  the  finger  in  the  neck  of  man  {Czermak,  Concato) ;  but  this 
experiment  is  accompanied  by  danger,  and  ought  not  to  be  undertaken.  The  electrotonic  condition 
of  the  vagus  is  stated  in  \  335,  HI. 

7.  Schiff"  found  that  stimulation  of  the  vagus  of  the  frog  caused  acceleration  of  the  heart  beat,  when 
he  displaced  the  blood  of  the  heart  with  sahne  solution.  If  blood  serum  be  supplied  to  the  heart, 
the  vagus  retains  its  inhibitory  action. 


720  CENTRE    FOR   THE    ACCELERATING    CARDIAC    NERVES. 

8.  Many  soda  salts  in  a  projier  concentration  arrest  the  inhibitory  action  of  the  vagus,  while 
potash  salts  restore  llie  inhibitory  function  of  tlic  vagi  susjiendeii  i)y  the  soda  salts.  If,  however, 
the  soda  or  ]iotash  salts  act  too  lon^  i\\-<ou  the  heart,  they  protluce  a  condition  in  which,  after  the 
inhibitory  function  of  the  vagi  is  alxjlished,  it  is  not  again  restored.  The  heart's  action  in  this 
condition  is  usually  arhythniical  (Lowit\. 

9.  If  the  intracardial  pressure  be  greatly  increased,  so  as  to  accelerate  greatly  the  cardiac  pul- 
sations, the  activity  of  the  xaijus  is  correspondingly  diminished  (J.  J/.  I.udwii^  ami  Luchshti^er). 

[Differences  in  Animals. —  Perhaps  the  most  remarkable  fact  in  connection  with  the  influence 
of  the  vagus  on  the  eel's  heart  and  that  of  all  other  fishes  cxannned,  is,  that  vagus  stimulation  causes 
the  sinus  and  auricle  to  be  entirely  inexcitable  to  direct  stimulation  during  strong  inhibition.  Nerve 
stimulation  has  in  this  case  the  very  peculiar  effect  of  rendering  the  muscular  tissue  temporarily 
incapable  of  resixjndiiig  to  even  the  strongest  direct  stimuli,  <■. ,^,^,  jiowcrful  induction  shocks.  This 
would  a|>ix.'ar  to  be  decisive  evidence  that  the  vagus  acts  on  muscle  directly,  and  not  simply  on 
automatic  motor  ganglia,  as  was  liehl  according  to  the  old  view  (.1/'  W'llliiim).^ 

Poisons. — Muscariti  stimulates  the  tenninations  of  the  vagus  in  the  heart,  and  causes  the  heart 
to  stand  still  in  diastole  (Schiniedeber)^ and  A'op/'e).  [See  p.  127  for  Gaskell's  views.]  \i a/ropin  be 
applied  in  solution  to  the  heart,  this  action  is  set  aside,  and  the  heart  begins  to  beat  again.  [Atropin 
alx>lishes  completely  the  inhibitory  action  of  the  vagus  on  the  heart.  If  it  be  injected  into  the  jugular 
vein-of  a  rabbit,  the  pulse  beats  are  increased  27  per  cent  ,  in  the  dog,  they  may  be  trebled,  and  in  a 
man  under  its  full  influence  the  pulse  beats  may  rise  from  70  to  150  or  more.  After  atropin,  it  is 
impossible  to  arrest  the  action  of  the  heart  by  stimulation  of  the  vagus,  and  in  the  frog  this  cannot  be 
done  even  by  siimulalion  of  the  inhibitory  centre  in  the  heart  itself,  so  that  atropin  must  be  regarded 
as  paralyzing  the  iiitra-cardiac  termiuatious  of  the  vagus.  J  Dii^italiit  dimini.shes  the  number  of 
heart  beats  by  stimul.iting  the  cardio-inhibitory  centre  (vagus)  in  the  medulla.  Large  doses  diminish 
the  excitability  of  the  vagus  centre,  and  increase  at  the  same  time  the  accelerating  cardiac  ganglia, 
so  that  the  heart  l>eats  are  thereby  increa'^ed.  In  small  doses,  digitalin  raises  the  blood  j^ressure  by 
stimulating  the  vasomotor  centre  and  the  elements  of  the  vascular  wall  (A'/z/j,').  Nicotin  first  excites 
the  vagus,  then  rapidly  paralyzes  it.  Hydrocyanic  acid  has  the  same  eft'ect  (Preyer).  Atropin  {v. 
Bezold)  and  ciirara  (large  dose — CI.  Bernard  and  A'dlliker)  paralyze  the  vagi,  and  so  does  a  very 
low  temperature  or  high  fever. 

370.  CENTRE  FOR  THE  ACCELERATING  CARDIAC 
NERVES. — Nervus  Accelerans. — It  is  more  than  prcjbable  that  a  centre 
exists  in  the  medulla  oblongata,  which  sends  accelerating  fibres  to  the  heart. 
These  fibres  pass  from  the  medulla  oblongata — but  from  which  ]jart  thereof  has 
not  been  exactly  ascertained — through  the  spinal  cord,  and  leave  the  cord  through 
the  rami  communicantes  of  the  lower  cervical  and  upper  six  dorsal  nerves 
{Strieker^,  to  ])ass  into  the  sympathetic  nerve.  Some  of  these  fibres,  issuing  from 
the  spinal  cord,  pass  through  the  first  thoracic  sympathetic  ganglion  and  the  ring 
of  Vieussens,  to  join  the  cardiac  plexus  ( Figs.  469,  470).  [These  fibres,  i)rocceding 
from  the  spinal  cord,  frequently  accompany  the  nerve  running  along  the  vertebral 
artery],  and  they  constitute  the  Nenms  accelerans  con/is.  [Fig.  470  shows  the 
accelerator  fibres  passing  through  the  ganglion  stellatum  of  the  cat  to  join  the 
cardiac  plexus.]  If  the  vagi  of  an  animal  be  divided,  stimulation  of  the  medulla 
oblongata,  of  the  lower  end  of  the  divided  cervical  spinal  cord,  even  of  the  lower 
cervical  ganglion,  or  of  the  upi)er  dorsal  ganglion  of  the  sympathetic  {Gang, 
stellatum),  causes  acceleration  of  the  heart  beats  in  the  dog  and  rabbit,  withotit 
the  blood  jiressure  undergoing  any  change  {CI.  Bernard,  v.  Bezold,  Cyan'). 

On  stimulating  the  medulla  oblongata,  or  the  cervical  portion  of  the  spinal  cord,  the  vasomotor 
net-fes  are,  of  course,  simultaneously  excited.  The  consequence  is  that  the  blood  vessels,  supplied 
by  vasomotor  nerves  from  the  spot  which  is  stimulated,  contract,  and  the  blood  pressure  is  greatly 
increased.  Again,  a  simple  increase  of  the  blood  pressure  accelerates  the  action  of  the  heart;  this 
experiment  does  not  prove  directly  the  existence  of  accelerating  fibres  lying  in  the  upper  part  of  the 
spinal  cord.  If,  however,  the  splanchnic  nerves  be  divided  beforehand  (when,  as  they  supply  the 
largest  vasomotor  area  in  the  body,  the  result  of  their  division  is  to  cause  a  great  fall  of  the  blood 
pressure),  then  on  stimulating  the  above-named  parts,  after  this  operation,  the  heart  beats  are  still 
increased  in  number,  so  that  this  increase  cannot  be  due  to  the  increased  blood  pressure.  Indirectly 
it  may  be  shown,  by  dividing  or  extiq^aling  all  the  ner\-es  of  the  cardiac  plexus,  or  at  least  all  the 
nerves  going  to  the  heart,  that  stimulation  of  the  medulla  oblongata,  or  cervical  part  of  the  spinal 
cord,  no  longer  causes  an  increased  frequency  of  the  heart's  action  to  the  same  extent  as  before 
division  of  these  nerves.  The  slightly  increased  frequency  in  this  case  is  due  to  the  increased  blood 
pressure. 


THE    NERVUS   ACCELERANS   AND    CARDIAC    PLEXUS. 


721 


The  accelerating  centre  is  certainly  not  continually  in  a  state  of  tonic  excite- 
ment, as  section  of  the  accelerans  nerve  does  not  cause  slowing  of  the  action  of 
the  heart ;  the  same  is  true  of  destruction  of  the  medulla  oblongata  or  of  the 
cervical  spinal  cord.  In  the  latter  case,  the  splanchnic  nerves  must  be  divided 
beforehand,  to  avoid  the  slowing  effect  on  the  action  of  the  heart  produced  bv 
the  great  fall  of  the  blood  pressure  consequent  upon  destruction  of  the  cord, 
otherwise  we  might  be  apt  to  ascribe  the  result  to  the  action  of  the  accelerating 
centre,  when  it  is  in  reality  due  to  the  diminished  blood  pressure  (^Cyoii). 

According  to  the  results  of  the  older  observers  {v.  Bezold  and  others),  some 
accelerating  fibres  run  in  the  cervical  sympathetic.     A  few  fibres  pass  through  the 


Fig.  469. 


Fig.  470. 


Fig.  469. — Scheme  of  the  course  of  the  accelerans  fibres.  P,  pons;  MO,  medulla  oblongata;  C,  spinal  cord;  V, 
inhibitory  centre  for  heart ;  A,  accelerans  centre  ;  Vag., vagus;  SL,  superior;  I L,  inferior  laryngeal ;  SC,  supe- 
rior, IC,  inferior  cardiac ;  H,  heart;    C,  cerebral  impulse ;  S,  cervical  sympathetic  ;  a,  «,  accelerans  fibres. 

Fig.  470. — Cardiac  ple.xus,  and  ganglion  stellatum  of  the  cat.  R,  right,  L,  left  X  i/4;  i,  vagus;  2',  cervical  sym- 
pathetic, and  in  the  annulus  of  Vieussens;  2,  communicating  branches  from  the  middle  cervical  ganglion  and 
the  ganglion  stellatum  ;  2',  thoracic  sympathetic  ;  3,  recurrent  laryngeal;  4,  depressor  nerve  ;  5,  middle  cervical 
ganglion  ;  5',  communication  between  5  and  the  vagus  ;  6,  ganglion  stellatum  (ist  thoracic  ganglion) ;  7,  commu- 
nicating branches  with  the  vagus  ;  8,  nervus  accelerans  ,  8,  8',  8",  roots  of  accelerans  ;  9,  branch  of  the  ganglion 
stellatum. 


vagus  to  reach  the  heart  (§  352,  7),  and  when  they  are  stimulated,  either  the  heart 
beat  is  accelerated  or  the  cardiac  contractions  strengthened  {Heidenhain  and 
Lowit),  or  the  latter  alone  occurs  (^Pawlow).  The  inhibitory  fibres  of  the  vagus 
lose  their  excitability  more  readily  than  the  accelerating  fibres,  but  the  vagus  fibres 
are  more  excitable  than  those  of  the  accelerans. 

Tarchanoff  has  described  some  very  rare  cases  of  individuals  who,  by  a  merely  voluntary  effort, 
and  while  at  rest,  the  respirations  remaining  unaffected,  could  nearly  double  the  number  of  their 
pulse  beats. 

Modifying  Conditions. — When  the  peripheral  end  of  the  nervus  accelerans  is  stimulated,  a 
considerable  time  elapses  before  the  effect  upon  the  frequency  of  the  heart  takes  place,  i.e.,  it  has  a 
46 


722  niE  VASOMOTOR  CENTRE. 

long  latent  period.  Further,  the  acceleration  thus  produced  disappears  gradually.  If  the  vagus 
ami  accelerans  fibres  be  stimulated  simultaneously,  only  the  inhibitory  action  of  the  vagus  is 
manifested.  If.  \ohile  ihc  acccleraus  is  beini;  stimulated,  the  v.agus  be  suddenly  excited,  llicre  is  a 
prompt  diminution  in  the  number  of  the  heart  beats;  and  if  the  stimulation  of  the  vagus  is  stopped, 
the  accelerating  effect  of  the  accelerans  is  again  rajiidly  manifested  {C.  Liiihvij^  with  SchmieJeberf^^ 
Bo-wdilch,  Haxt).  According  to  the  experiments  of  Strieker  and  SVa^ner  on  dogs,  with  both  vagi 
divided,  a  diminution  of  the  number  of  the  heart  beats  occurred  when  both  accelerantes  were  divided. 
This  would  indicate  a  tonic  innervation  of  the  latter  nerves. 

[Accelerans  in  the  Frog. — (iaskell  showed  that  stimulation  of  the  vagus 
might  produce  two  opposing  efferts  ;  the  one  of  the  nature  of  inhibition,  the  other 
of  augmentation.  In  the  crocodile,  the  accelerans  fibres  leave  the  symi)athetic 
chain  at  the  large  ganglion  corresponding  to  the  ganglion  stellatum  of  the  dog, 
and  run  along  the  vertebral  artery  up  to  the  superior  vena  cava,  and,  after  anasto- 
mosing with  branches  of  the  vagus,  pass  to  the  heart.  "Stimulation  of  these 
fibres  increases  the  rate  of  the  cardiac  rhythm,  and  augments  \.\\t  force  of  auricular 
contractions;  while  stimulation  of  the  vagus  slows  the  rhythm,  and  diminishes 
the  strength  of  the  auricular  contractions."  The  strength  of  the  ventricular  con- 
traction,  both  in  the  tortoise  and  crocodile,  does  not  seem  to  be  influenced  by 
stimulation  of  the  vagus,  and  probably  also  it  is  unaffected  by  the  symi)athetic. 
The  so-called  vagus  of  the  frog,  in  reality,  consists  of  ])ure  vagus  fibres  and  sym- 
pathetic fibres,  and  is  in  fact  a  vago-symjxithetic.  Ciaskell  finds  that  stimulation 
of  the  sympathetic,  before  it  joins  the  combined  ganglion  of  the  sympathetic  and 
vagus,  produces  purely  augmentor  or  accelerating  effects  ;  while  stimulation  of  the 
vagus,  before  it  enters  the  ganglion,  produces  purely  inhibitory  effects.  The  two 
sets  of  fibres  are  quite  distinct,  so  that  in  the  frog,  the  sympathetic  is  a  purely 
augmentor  (accelerator),  and  the  vagus  a  purely  inhibitory  nerve.  Acceleration 
is  merely  one  of  the  effects  produced  by  stimulation  of  these  nerves;  hence, 
Gaskell  suggests  that  they  ought  to  be  called  "  augmentor,"  or  simply  cardiac 
sympathetic  nerves.] 

[In  his  more  recent  researches  Gaskell  asserts  that  vagus  stimulation  produces  /fr^/  an  inhibitory  or 
depressing  effect,  but  that  it  ultimately  improves  the  condition  of  the  heart  as  regards  force,  rate,  or 
regularity — one  or  all  of  these.     He  regar  Is  it  as  a  true  anabolic  nerve  [\  342,  d).] 

371.  VASOMOTOR  CENTRE  AND  VASOMOTOR  NERVES. 
— Vasomotor  Centre. —  The  chief  dominating  or  general  centre,  which 
supplies  all  the  non-striped  muscles  of  the  arterial  system  with  motor  nerves 
(vasomotor,  vaso-constrictor,  vaso-hypertonic  nerves),  lies  in  the  medulla 
oblongata,  at  a  point  which  contains  many  ganglionic  cells  (Ludwig  and  Thiry). 
Those  nerves  which  pass  to  the  blood  vessels  are  known  as  vasomotor  nerves. 
The  centre  (which  is  3  millimetres  long  and  1J2  millimetre  broad  in  the  rabbit) 
reaches  from  the  region  of  the  upper  part  of  the  floor  of  the  medulla  oblongata  to 
within  4  to  5  mm.  of  the  calamus  scriptorius.  P2ach  half  of  the  body  has  its  own 
centre,  placed  2)^2  millimetres  from  the  middle  line  on  its  own  side,  in  that  part 
of  the  medulla  oblongata  which  represents  the  upward  continuation  of  the  lateral 
columns  of  the  spinal  cord  ;  according  to  Ludwig,  Owsjannikow,  and  Dittmar,  in 
the  lower  part  of  the  superior  olives.  Stimulation  of  this  central  area  causes 
contraction  of  all  the  arteries,  and,  in  consequence,  there  is  great  increase  of  the 
arterial  blood  pressure,  resulting  in  swelling  of  the  veins  and  heart.  Paralysis 
of  this  centre  causes  relaxation  and  dilatation  of  all  the  arteries,  and  consequently 
there  is  an  enormous  fall  of  the  blood  pressere.  Under  ordinary  circumstances, 
the  vasomotor  centre  is  in  a  condition  of  moderate  ionic  excitement  (§  366). 
Just  as  in  the  case  of  the  cardiac  and  respiratory  centres,  the  vasomotor  centre 
mav  be  excited  directly  and  reflexly. 

[Position — How  ascertained. — As  stimulation  of  the  central  end  of  a 
sensory  nerve,  e.g.,  the  sciatic,  in  an  animal  under  the  influence  of  curara,  causes 
a  rise  in  the  blood  pressure,  even  after  removal  of  the  cerebrum,  it  is  evident  that 


DIRECT   STIMULATION    OF   THE   VASOMOTOR    CENTRE.  723 

the  centre  is  not  in  the  cerebrum  itself.  For  the  effect  of  chloral,  under  the 
same  conditions,  see  p.  724.  By  making  a  series  of  sections  from  above  down- 
ward, it  is  found  that  this  reflex  effect  is  not  affected  until  a  short  distance  above 
the  medulla  oblongata  is  reached.  If  more  and  more  of  the  medulla  oblongata 
be  removed  from  above  downward,  then  the  reflex  rise  of  the  blood  pressure 
becomes  less  and  less  until,  when  the  section  is  made  4  to  5  mm.  above  the 
calamus  scriptorius,  the  effect  ceases  altogether.  This  is  taken  to  be  the 
lower  limit  of  the  general  vasomotor  centre.  The  bilateral  centre  corresponds 
to  some  large  multipolar  nerve  cells,  described  by  Clarke  as  the  antero-lateral 
nucleus.] 

I.  Direct  Stimulation  of  the  Centre. — The  atnount  and  quality  of  the 
gases  contained  in  the  blood  flowing  through  the  medulla  are  of  primary  import- 
ance. In  the  condition  of  apnoea  (§  368,  i),  the  centre  seems  to  be  very 
slightly  excited,  as  the  blood  pressure  undergoes  a  considerable  decrease.  When 
the  mixture  of  blood  gases  is  such  as  exists  under  normal  circumstances,  the  centre 
is  in  a  state  of  moderate  excitement,  and  running  parallel  with  the  respiratory 
movements  are  variations  in  the  excitement  of  the  centre  (Traube-Hering  curves — 
§  85),  these  variations  being  indicated  by  the  rise  of  the  blood  pressure.  When 
the  blood  is  highly  venous,  produced  either  by  asphyxia  or  by  the  inspiration  of 
air  containing  a  large  amount  of  C0„  the  centre  is  strongly  excited,  so  that  all 
the  arteries  of  the  body  contract,  while  the  venous  system  and  the  heart  become 
distended  with  blood  {Thiry).  At  the  same  time,  the  velocity  of  the  blood 
stream  is  increased  {Heidenhain).  The  same  result  is  produced  by  ligature  of 
both  the  carotid  and  subclavian  arteries,  thus  causing  sudden  ansemia  of  the 
medulla  oblongata ;  and,  no  doubt,  also  by  the  sudden  stagnation  of  the  blood  in 
venous  hyperaemia. 

Emptiness  of  the  Arteries  after  Death. — The  venosity  of  the  blood  which  occurs  after  death 
always  produces  an  energetic  stimulation  of  the  vasomotor  centre,  in  consequence  of  which  the 
arteries  are  firmly  contracted.  The  blood  is  thereby  forced  toward  the  capillaries  and  veins,  and 
thus  is  explained  the  "  emptiness  of  the  arteries  after  death." 

Effect  on  Hemorrhage. — Blood  flows  much  more  freely  from  large  wounds,  when  the  vaso- 
motor centre  is  intact,  than  if  it  be  destroyed  (frog).  As  psychical  excitement  undoubtedly 
influences  the  vasomotor  centre,  we  may  thus  explain  the  influence  of  psychical  excitement 
(speaking,  etc.)  upon  the  cessation  of  hemorrhage.  If  the  hemorrhage  be  severe,  stimulation  ot 
the  medulla  oblongata,  due  to  the  ansemia,  may  ultimately  cause  constriction  of  the  small  arteries, 
and  thus  arrest  the  bleeding.  Thus,  surgeons  are  acquainted  with  the  fact  that  dangerons 
hemorrhage  is  often  arrested  as  soon  as  unconsciousness,  due  to  cerebral  anaemia,  occurs.  If  the 
heart  be  ligatured  in  a  froj,  all  the  blood  is  ultimately  forced  into  the  veins,  and  this  result  is 
also  due  to  the  anaemic  stimulation  of  the  oblongata  [Goltz).  In  mammals,  when  the  heart  is 
ligatured,  the  equilibration  of  the  blood  pressure  between  the  arterial  and  venous  systems  takes 
place  more  slowly  when  the  medulla  oblongata  is  destroyed  than  when  it  is  intact  {v.  Bezold, 
Gscheidleii). 

[Effect  of  Destruction  of  the  Vasomotor  Centre. — If  two  frogs  be  pithed  and  their  hearts 
exposed,  and  both  be  suspended,  then  the  hearts  of  both  will  be  found  to  beat  rhythmically  and  fill 
with  blood.  Destroy  the  medulla  oblongata  and  spinal  cord  of  one  of  them,  then  immediately  in 
this  case,  the  heart,  although  continuing  to  beat  with  an  altered  rhythm,  ceases  to  be  filled  with  blood; 
it  appears  collapsed,  pale,  and  bloodless.  There  is  a  great  accumulation  of  the  blood  in  the  abdominal 
organs  and  veins,  and  it  is  not  returned  to  the  heart,  so  that  the  arteries  are  empty.  This  experiment 
of  Goltz  is  held  to  show  the  existence  of  venous  tonus  depending  on  a  cerebro-spinal  centre.  If  a 
limb  of  this  frog  be  amputated,  there  is  little  or  no  hemorrhage,  while  in  the  other  frog  the  hemor- 
ihage  is  severe.     The  bearing  of  this  experiment  on  conditions  of  "  shock"  is  evident.] 

Action  of  VQ\sor^s.— Strychnin  stimulates  the  centre  directly,  even  in  curarized  dogs,  and  so  do 
nicotin  and  Calabar  bean. 

Direct  Electrical  Stimulation. — On  stimulating  the  centre  directly  in  animals,  it  is  found  that 
single  induction  shocks  only  become  effective  when  they  succeed  each  other  at  the  rate  of  2  to  3 
shocks  per  second.  Thus  there  is  a  "  summation  "  of  the  single  shocks.  The  maximum  contrac- 
tion of  the  arteries,  as  expressed  by  the  maximum  blood  pressure,  is  reached  when  10  to  12  strong., 
or  20  to  25  moderately  strong  shocks  per  second  are  applied  {Kronecker  and  AUcolaides'). 

Course  of  the  Vasomotor  Nerves. — From  the  vasomotor  centre  fibres  proceed  directly 
through  some  of  the  cranial  nerves  to  their  area  of  distribution ;  through  the  trigeminus  partly  to 


724  COURSE    OF   THE    VASOMOTOR    FIBRES. 

the  interior  of  the  eye  (§  347,  I,  2),  through  the  hngual  and  hypoglossal  to  the  tongue  (§  347, 
III,  4),  through  the  vagus  to  a  limited  extent  to  the   lungs  (^  352,  8,  2),  and  to  the  intestines 

(?  352.  >i). 

All  the  other  vasomotor  nerves  descend  into  the  lateral  columns  of  the  spinal  cord  (^  364,  9); 
hence,  stimulation  of  the  lower  cut  end  of  the  spinal  cord  causes  contraction  of  the  hlootl  vessels 
supplied  by  the  nerves  below  the  point  of  section  [P/liij^ei).  In  their  course  through  the  cord,  these 
fibres  form  connections  with  the  subordinate  vasomotor  centres  in  the  gray  matter  of  the  cord  (^  362, 
7),  and  then  leave  the  cord  either  directly  through  the  anterior  roots  of  the  spinal  nerves  to  their 
areas  of  distribution,  or  pass  through  the  rami  communicantes  into  the  sympathetic,  and  from  them 
reach  the  blood  vessels  to  which  they  are  distributed  (?  356)  [see  Fig.  439]. 

The  following  is  the  arrangement  of  these  nerves  in  the  region  of  the  head:  Thtcerficaf  portion 
0/ the  sympathetic  supplies  the  great  majority  of  the  blood  vessels  of  the  htz(\  [set  Sympathetic, 
§  356,  A,  3).  In  some  animals,  i\\Q  great  auricular  nerve  supplies  a  few  vasomotor  fibres  to  its  own 
area  of  distribution  [Sc/iiff,  Lovin,  Moreau).  The  vasomotor  ners'es  to  tlie  upper  extremities  pass 
through  the  anterior  roots  of  the  middle  dorsal  nerves  into  the  thoracic  sympathetic,  and  upward  to 
the  I't  th  )racic  ganglion,  and  from  thence  through  the  rami  communicantes  to  the  brachial  plexus 
{Schiff,Cyon).  The  skin  of  the  trunk  receives  its  vasomotor  nerves  through  the  dorsal  and  lumbar  nerves. 
The  vasomotor  nerves  to  the  lower  extremities  pass  through  the  nerves  of  the  lumbar  and  sacral  plex- 
uses into  the  sympathetic,  and  from  thence  to  the  lower  limbs  (P/iiiger,  Schiff,  CI.  Bernard).  The 
lungs,  in  addition  to  a  few  fibres  through  tiie  vagus,  are  supplied  from  the  cervical  spinal 
cord  through  the  1st  thoracic  ganglion  (Bro-wn-Scijuard,  Pick  and  Badoitd,  Lichtheim).  The 
splanchnic  is  the  greatest  vasomotor  nerve  in  the  body,  and  supplies  the  abdominal  viscera  (|  356, 
B — V.  Bezold,  Lud-wig  and  Cyon).  The  vasomotor  nerves  of  the  liver  (^  173,  6),  kidney  (|  276), 
and  spleen  (^  103)  have  been  referred  to  already.  According  to  Strieker,  most  of  the  vasomotor 
nerves  leave  the  spinal  cord  between  the  5th  cervical  and  the  ist  dorsal  vertebrae.  [Gaskell  finds 
that  in  the  dog  (Fig.  439)  they  begin  to  leave  the  cord  at  the  2d  dorsal  nerve  y\  366).] 

As  a  general  rule,  the  blood  vessels  for  the  skin  of  the  trunk  and  extremities  are  innervated  from 
those  nerves  which  give  other  fibres  [e.  g.,  sensory)  to  those  regions.  The  different  vascular  areas 
behave  differently  with  regard  to  the  intensity  of  the  action  of  the  vasomotor  nerves.  The  most 
powerful  vasomotor  nerves  are  those  that  act  upon  the  blood  vessels  of  peripheral  parts,  ;>.  ^'•.,the  toes, 
the  fingers,  and  ears ;  while  those  that  act  upon  central  parts  seem  to  be  less  active  [Lewaschew), 
e.g.,  on  the  pulmonic  circulation  (§  88). 

II.  Reflex  Stimulation  of  the  Centre. — There  are  fibres  contained  in  the 
different  afferent  nerves,  whose  stimulation  affects  the  vasomotor  centre.  There  are 
nerve  fibres  whose  stimulation  excites  the  vasomotor  centre,  thus  causing  a  stronger 
contraction  of  the  arteries,  and  consequently  an  increase  of  the  arterial  blood 
pressure.  These  are  called  *'  pressor  "  fibres.  Conversely,  there  are  other  fibres 
whose  stimulation  reflexly  diminishes  the  excitability  of  the  vasomotor  centre.  These 
act  as  reflex  inhibitory  nerves  on  the  centre,  and  are  known  as  "depressor ' '  fibres. 

Pressor,  or  e.Kcito-vasomotor  nerves,  have  already  been  referred  to  in  connec- 
tion with  the  superior  and  inferior  laryngeal  nerves  (§  352,  12,  a,),  in  the  trigem- 
inus, which,  when  stimulated  directly  (§347),  causes  a  pressor  action,  as  well  as 
when  stimulating  vapors  are  blown  into  the  nostrils  {Hering  and Kratschmer). 
[The  rise  of  the  blood  pressure  in  this  case,  however,  is  accompanied  by  a  change 
in  the  character  of  the  heart's  beat  and  in  the  respirations.  Rutherford  has  shown 
that  in  the  rabbit  the  vapor  of  chloroform,  ether,  amyl  nitrite,  acetic  acid,  or 
ammonia  held  before  the  nose  of  a  rabbit,  greatly  retards  or  even  arrests  the  heart's 
action,  and  the  same  is  true  if  the  nostrils  be  closed  by  the  hand.  This  arrest  does 
not  occur  if  the  trachea  be  opened,  and  Rutherford  regards  the  result  as  due  not  to 
the  stimulation  of  the  sensory  fibres  of  the  trigeminus,  but  to  the  state  of  the  blood 
acting  on  the  cardio-inhibitory  nerve  apparatus.]  Hubert  and  Roever  found 
pressor  fibres  in  the  cervical  sympathetic ;  S.  Mayer  and  Pribram  found  that 
mechanical  stimulation  of  the  stomach,  especially  of  its  serosa,  caused  pressor  effects 
(§  352,  12,  c).  According  to  Loven,  the  first  effect  of  stimulating  every  sensory 
ner\-e  is  a  pressor  action. 

[If  a  dog  be  poisoned  with  curara,  and  the  central  end  of  one  sciatic  nerve  be 
stimulated,  there  is  a  great  and  steady  rise  of  the  blood  pressure,  chiefly  owing  to 
the  contraction  of  the  abdominal  blood  vessels,  and  at  the  same  time  there  is  no 
change  in  the  heart  beat.  If,  however,  the  animal  be  poisoned  with  chloral,  there 
is  a  fall  of  the  blood  pressure  resembling  a  depressor  effect.] 


REFLEX   STIMULATION    OF   THE    VASOMOTOR    CENTRE.  725 

O.  Naumann  found  that  weak,  electrical  stimulation  of  the  skin  caused  at  first  contraction  of  the 
blood  vessels,  especially  of  the  mesentery,  lungs,  and  the  web,  with  simultaneous  excitement  of  the 
cardiac  activity  and  acceleration  of  the  circulation  (frog).  Strong  stimuli,  however,  had  an  opposite 
effect,  i.  e.,  a  depressor  effect,  with  simultaneous  decrease  of  the  cardiac  activity.  Griitzner  and 
Heidenhain  found  that  contact  with  the  skin  caused  a  pressor  effect,  while  painful  impressions 
produced  no  effect.  The  application  of  heat  and  cold  to  the  skin  produces  reflexly  a  change  in  the 
lumen  of  the  blood  vessels  and  in  the  cardiac  activity  [Rohrig,  Winterniiz).  Pinching  the  skin 
causes  contraction  of  the  vessels  of  the  pia  mater  of  the  rabbit  [Sckiiner),  and  the  same  result  was 
produced  by  a  warm  bath,  while  cold  dilated  the  vessels.  These  results  are  due  partly  to  pressor  and 
partly  to  depressor  effects,  but  the  chief  cause  of  the  dilatation  of  the  blood  vessels  is  the  increased 
blood  pressure  due  to  the  coldconstrictingthe  cutaneous  vessels.  Heat,  of  course,  has  the  opposite  effect. 
Inman,most  stimuli  appliedtosensorynerves  produce  an  effect :  feeble  cutaneous  stimuli,  tickling  (even 
unpleasant  odors,  bitter  or  acid  tastes,  optical  and  acoustic  stimuli)  at  the  parts  where  they  are  applied, 
cause  a  fall  of  the  cutaneous  temperature,  and  diminution  of  the  volume  of  the  corresponding  limb, 
sometimes  increase  of  the  general  blood  pressure  and  charge  of  the  heart  beat.  The  opposite  effects 
are  produced  by  painful  stimulation,  the  action  of  heat  (and  even  by  pleasant  odors  and  sweet  tastes). 
The  former  cause  simultaneously  dilatation  of  the  cerebral  vessels  and  increase  the  vascular  contents 
of  the  skull — the  latter  cause  the  opposite  results  i^Isiominow  and  Tarchanoff). 

Depressor  fibres,  /,  e.,  fibres  whose  stimulation  diminishes  the  activity  of  the 
vasomotor  centre,  are  present  in  many  nerves.  They  are  specially  numerous  in  the 
superior  cardiac  branch  of  the  vagus,  which  is  known  as  the  depressor  nerve  (§  352, 
6).  The  trunk  of  the  vagus  below  the  latter  also  contains  depressor  fibres  (v.Bezold), 
as  well  as  the  pulmonary  fibres  (dog).  The  latter  also  act  as  depressors,  during 
expiratory  efforts  (§  74);  while  Hering  found  that  inflating  the  lungs  (to  50  ram. 
Hg  pressure)  caused  a  fall  of  the  blood  pressure  (and  also  accelerated  the  heart 
beats — §  369,  TI).  Stimulation  of  the  central  end  of  sensory  nerves,  especially 
when  it  is  intense  and  long  continued,  causes  dilatation  of  the  blood  vessels  in  the 
area  supplied  by  them  {Loven).  According  to  Latschenberger  and  Deahna,  all 
sensory  nerves  contain  both  pressor  and  depressor  fibres. 

[If  a  rabbit  be  poisoned  with  curara,  and  the  cefitrai&ud  of  the  great  auricular 
nerve  be  stimulated,  there  is  a  double  effect — one  local  and  the  other  general; 
the  blood  vessels  throughout  the  body,  but  especially  in  the  splanchnic  area,  con- 
tract, so  that  there  is  a  general  rise  of  the  blood  pressure,  while  the  blood  vessels 
of  the  ear  are  dilated.  If  the  central  end  of  the  tibial  nerve  be  stimulated,  there 
is  a  rise  of  the  general  blood  pressure,  but  a  local  dilatation  of  the  saphena  artery 
in  the  limb  of  that  side  (^Lovai).  Again,  the  temperature  of  one  hand  and  the 
condition  of  its  blood  vessels  influence  that  of  the  other.  If  one  hand  be  dipped 
in  cold  water,  the  temperature  of  the  other  hand  falls.  Thus,  pressor  and  depressor 
effects  may  be  obtained  from  the  same  nerve.  The  vasomotor  centre,  therefore, 
primarily  regulates  the  condition  of  the  blood  vessels,  but  through  them  it  obtains 
its  importance  by  regulating  and  controlling  the  blood  supply  2iZCOxA\x\g\.o  the  needs 
of  an  organ.] 

The  central  artery  of  a  rabbit's  ear  contracts  regularly  and  rhythmically  3  to  5  times  per  minute. 
Schiff  observed  that  stimulation  of  sensoiy  nerves  caused  a  dilatation  of  the  artery,  which  was  pre- 
ceded by  a  slight  temporary  constriction. 

Depressor  effects  are  produced  in  the  area  of  an  artery  on  which  direct  pressure  is  made,  as  occurs, 
for  example,  when  the  sphygmograph  is  applied  for  a  long  time — the  pulse  curves  become  larger, 
and  there  are  signs  of  diminished  arterial  tension  (^  75). 

Rhythmical  Contraction  of  Arteries.— In  the  intact  body  slow  alternating  contraction  and 
dilatation,  without  a  uniform  rhythm,  have  been  observed  in  the  arteries  of  the  ear  of  the  rabbit,  the 
membrane  of  a  bat's  wing,  and  the  web  of  a  frog's  foot.  This  arrangement,  observed  by  Schiff, 
supplies  more  or  less  blood  to  the  parts  according  to  the  action  of  external  conditions.  It  has  been 
called  a  "  periodic  regulatory  vascular  movement."  This  movement  maybe  useful  when  a 
vessel  is  occluded,  as  after  ligatiu-e,  and  may  help  to  establish  more  rapidly  the  collateral  circulation. 
Stefani  has  shown  that  this  occurs  with  more  difficulty  after  section  of  the  nerves. 

Direct  local  applications  may  influence  the  lumen  of  the  blood  vessels;  cold  and  moderate 
electrical  stimuli  cause  contraction;  while,  conversely, heat  and  strong  mechanical  or  electri- 
cal stimuli  cause  dilatation,  although  with  the  last  two  there  is  usually  a  preliminar}^  constriction. 

Poisons. — Almost  all  the  digitalis  group  of  substances  cause  constriction;  quinine  and  salicin 
constrict  the  splenic  vessels.     The  other  febrifuges  dilate  the  vessels  [Thomson).     See  p.  138. 


726        LOCAL   AND    SECONDARY    RESULTS   OF    VASOMOTOR    ACTION. 

Effect  on  Temperature. — The  vasomotor  nerves  influence  the  temperature, 

not  only  of  individual  parts,  but  of  the  whole  body. 

1.  Local  Effects. — Section  of  a  peripheral  vasomotor  nerve,  e.  g.,  the  cer- 
vical sympathetic,  is  followed  by  dilatation  of  the  blood  vessels  of  the  parts 
supplied  by  it  (siich  as  the  ear  of  the  rabbit),  the  intra-arterial  pressure  dilating 
the  j)aralyzed  walls  of  the  vessels.  IMuch  arterial  blood,  therefore,  passes  into 
and  causes  congestion  and  redness  of  the  parts,  or  hyperaemia,  while,  at  the  same 
time,  the  temperature  is  increased.  There  is  also  increased  transudation  through 
the  dilated  capillaries  within  the  dilated  areas ;  the  velocity  of  the  blood  stream  is 
of  course  diminished,  and  the  blood  pressure  increased.  The  pulse  is  also  felt 
more  easily,  because  the  blood  vessels  are  dilated.  Owing  to  the  increase  of  the 
blood  stream,  the  blood  may  flow  from  the  veins  almost  arterial  (bright  red)  in  its 
characters,  and  the  pulse  may  even  be  propagated  into  the  veins,  so  that  the  blood 
spouts  from  them  (C/.  Bernard).  Stimulation  of  the  peripheral  end  of  a  vaso- 
motor nerve  causes  the  opposite  results — pallor,  owing  to  contraction  of  the  vessels, 
diminished  transudation,  and  fall  of  the  temperature  on  the  surface.  The  smaller 
arteries  may  contract  so  much  that  their  lumen  is  almost  obliterated.  Continued 
stimulation  ultimately  exhausts  the  nerve,  and  causes  at  the  same  time  the  phe- 
nomena of  i)aralysis  of  the  vascular  wall. 

Secondary  Results. — The  immediate  results  of  paralysis  of  the  vasomotor  nerves  lead  to  other 
effects;  the  paralysis  of  the  muscles  of  the  blood  vessels  must  lead  to  congestion  of  the  blood  in  the 
part ;  the  blood  moves  more  slowly,  so  that  the  parts  in  contact  with  the  air  cool  more  easily,  and 
hence  the  first  stage  of  increase  of  the  temperature  may  be  followed  by  a  fall  of  the  temperature. 
The  ear  of  a  rabbit  with  the  sympathetic  divided,  after  several  weeks  becomes  cooler  than  the  ear 
on  the  sound  one.  If  in  man  the  motor  muscular  nerves,  as  well  as  the  vasomotor  fibres,  are  para- 
lyzed, then  the  paralyzed  limb  becomes  cooler,  because  the  par.ily/ed  muscles  no  longer  contract  to 
aid  in  the  production  of  heat  (jJ  338),  and  also  because  the  dilatation  of  the  muscular  arteries,  which 
accompanies  a  muscular  contraction,  is  absent.  Should  atrophy  of  the  paralyzed  muscles  set  in,  the 
blood  vessels  also  become  smaller.  Hence,  paralyzed  limbs  in  man  generally  become  cooler  as  time 
goes  on.  The  primary  effect,  however,  in  a  limb,  e.  g.,  after  section  of  the  sciatic  or  lesion  of  the 
brachial  plexus,  is  an  increase  of  the  temperature. 

If,  at  the  same  time,  the  vasomotor  nerves  of  a  large  area  of  the  skin  be  para- 
lyzed, e.  g.,  the  lower  half  of  the  body  after  section  of  the  spinal  cord,  then  so 
much  heat  is  given  off  from  the  dilated  blood  vessels  that,  either  the  warming  of 
the  skin  lasts  for  a  very  short  time  and  to  a  slight  degree,  or  there  may  be  cooling 
at  once.  Some  observers  (Tse/ietse/iu/iin,  Naitnyn,  Quincke)  observed  a  rise  of  the 
temperature  after  section  of  the  cervical  spinal  cord,  but  Riegel  did  not  observe 
this  increase. 

2.  Effect  on  the  Temperature  of  the  Body. — Stimulation  or  paralysis 
of  the  vasomotor  nerves  of  a  small  area  has  practically  no  effect  on  the  general 
temperature  of  the  body.  If,  however,  the  vasomotor  nerves  of  a  considerable  area 
of  the  skin  be  suddenly  paralyzed,  then  the  temperature  of  the  entire  body  falls, 
because  more  heat  is  given  off  from  the  dilated  vessels  than  under  normal  circum- 
stances. This  occurs  wiien  the  spinal  cord  is  divided  high  up  in  the  neck.  The 
inhalation  of  a  few  drops  of  amyl  nitrite,  which  dilates  the  blood  vessels  of  the 
skin,  causes  a  fall  of  the  temperature  {Sassetki  and  Manassein).  Conversely, 
stimulation  of  the  vasomotor  nerves  of  a  large  area  increases  the  temperature, 
because  the  constricted  vessels  give  off  less  heat.  The  temperature  in  fever  may 
be  partly  explained  in  this  way  (§  220,  4). 

The  activity  of  the  heart,  /.  e.,  the  number  and  energy  of  the  cardiac  con- 
tractions, is  intiuenced  by  the  condition  of  the  vasomotor  nerves.  When  a  large 
vasomotor  area  is  paralyzed,  the  blood  channels  are  dilated,  so  that  the  blood  does 
not  flow  to  the  heart  at  the  usual  rate  and  in  the  usual  amount,  as  the  pressure  is 
considerably  diminished.  Hence,  the  heart  executes  extremely  small  and  feeble 
contractions.  Strieker  observed  that  the  heart  of  a  dog  ceased  to  beat  on  extir- 
pating the  spinal  cord  from  the  ist  cervical  to  the  8th  dorsal  vertebra.    Conversely, 


CONDITIONS   AFFECTING   THE   VASOMOTOR   CENTRE.  727 

we  know  that  stimulation  of  a  large  vasomotor  area,  by  constricting  the  blood 
vessels,  raises  the  arterial  blood  pressure  considerably.  As  the  arterial  pressure 
affects  the  pressure  within  the  left  ventricle,  it  may  act  as  a  mechanical  stimulus 
to  the  cardiac  wall,  and  increase  the  cardiac  contractions  both  in  number  and 
strength.     Hence,  the  circulation  is  accelerated  (^Heidenhain,  Slavja?isky). 

Splanchnic. — By  far  the  largest  vasomotor  area  in  the  body  is  that  controlled  by  the  splanchnic 
nerves,  as  they  supply  the  blood  vessels  of  the  abdomen  (§  i6i) ;  hence,  stimulation  of  their  peri- 
pheral ends  is  followed  by  a  great  rise  of  the  blood  pressure.  When  they  are  divided,  there  is  such 
a  fall  of  the  blood  pressure  that  other  parts  of  the  body  become  more  or  less  ansemic,  and  the  animal 
may  even  die  from  '■  being  bled  into  its  own  belly,"  i.  e.,  from  what  has  been  called  "  intra- vascular 
hemorrhage."  Animals  whose  portal  vein  is  ligatured  die  for  the  same  reason  (C  Ludwig  and 
Thiry)  [see  \  87].  The  capacity  of  the  vascular  system,  depending  as  it  does  in  part  upon  the 
condition  of  the  vasomotor  nerves,  influences  the  body  weight.  Stimulation  of  certain  vascular 
areas  may  cause  the  rapid  excretion  of  water,  and  we  may  thus  account  in  part  for  the  diminution 
of  the  body  weight,  which  has  been  sometimes  observed  after  an  epileptic  attack  terminating  with 
polyuria. 

Trophic  disturbances  sometimes  occur  after  affections  of  the  vasomotor  nerves  (|  342,  I,  c). 
Paralysis  of  the  vasomotor  nerves  not  only  causes  dilatation  of  the  blood  vessels  and  local  increase 
of  the  blood  pressure,  but  it  may  also  cause  increased  transudation  through  the  capillaries  [|  203]. 
When  the  active  contraction  of  the  muscles  is  abolished,  the  blood  stream  at  the  same  time  becomes 
slower,  and  in  some  cases,  the  skin  becomes  livid,  owing  to  the  venous  congestion.  There  is  a 
diminution  of  the  normal  transpiration,  and  the  epidermis  may  be  dry  and  peel  off  in  scales.  The 
growth  of  the  hair  and  nails  may  be  affected  by  the  congestion  of  blood,  and  other  tissues  may 
also  suffer. 

Vasomotor  Centres  in  the  Spinal  Cord. — Besides  the  dominating  centre 
in  the  medulla  oblongata,  the  blood  vessels  are  acted  upon  by  local  or  subordinate 
vasomotor  centres  in  the  gray  matter  of  the  spinal  cord,  as  is  proved  by  the  follow- 
ing observations :  If  the  spinal  cord  of  an  animal  be  divided,  then  all  the  blood 
vessels  supplied  by  vasomotor  nerves  below  the  point  of  section  are  paralyzed,  as 
the  vasomotor  fibres  proceed  from  the  medulla  oblongata.  If  the  animal  lives, 
the  blood  vessels  regain  their  tone  and  their  former  calibre,  while  the  rhythmical 
movements  of  their  muscular  walls  are  ascribed  to  the  subordinate  centres  in  the 
lower  part  of  the  spinal  cord  (^Lister,  Goltz — §  362,  7). 

The  subordinate  spinal  centres  may,  further,  be  stimulated  directly  by  dyspnoeic  blood,  and 
also  reflexly,  in  the  rabbit  and  fiog  {Ustimowilsch).  After  destruction  of  the  medulla  oblongata, 
the  arteries  of  the  frog's  web  still  contract  reflexly  when  the  sensory  nerves  of  the  hind  leg  are 
stimulated  (^Putnam,  Niissbaum,  Vidpian).  In  the  dog,  opposite  the  3d  to  6th  dorsal  nerve  is  a 
spinal  vasomotor  centre  (origin  of  the  splanchnic),  which  can  be  excited  reflexly  [Smirnow),  and 
there  is  a  similar  one  in  the  lower  part  of  the  spinal  cord  (  Viilpiaii). 

If  the  lower  divided  part  of  the  cord  be  crushed,  the  blood  vessels  again  dilate, 
owing  to  the  destruction  of  the  subordinate  centres.  In  animals  which  survive 
this  operation,  the  vessels  of  the  paralyzed  parts  gradually  recover  their  normal 
diameter  and  rhythmical  movements.  This  effect  is  ascribed  to  ganglia  which 
are  supposed  to  exist  along  the  course  of  the  vessels.  [It  is  to  be  recollected  that 
the  existence  of  these  peripheral  nervous  mechanisms  has  not  been  proved.] 
These  ganglia  [or  peripheral  nervous  mechanisms]  might  be  compared  to  the  gan- 
glia of  the  heart,  and  seem  by  themselves  capable  of  sustaining  the  movements  of 
the  vascular  wall.  Even  the  blood  vessels  of  an  excised  kidney  exhibit  periodic 
variations  of  their  calibre  {C.  Ludwig  and Mosso).  It  is  important  to  observe 
that  the  walls  of  the  blood  vessels  contract  as  soon  as  the  blood  becomes  highly 
venous.  Hence,  the  blood  vessels  offer  a  greater  resistance  to  the  passage  of 
venous  than  of  arterial  blood  (C.  Ludwig).  Nevertheless,  the  blood  vessels, 
although  they  recover  part  of  their  tone  and  mobility,  never  do  so  completely. 

The  effects  of  direct  mechanical,  chemical,  and  electrical  stimuU  on  blood  vessels  may  be  due  to 
their  action  on  these  peripheral  nervous  mechanisms.  The  arteries  may  contract  so  much  as  almost 
to  disappear,  but  sometimes  dilatation  follows  the  primary  stimulus. 


728  PATHOLOGICAL   VASOMOTOR    PHENOMENA. 

Lewaschew  found  that  limbs  in  which  the  vasomotor  fibres  had  undergone  degeneration  reacted 
like  intact  limbs  to  variations  of  temperature;  heat  relaxed  the  vessels,  and  cold  contracted  them. 
It  is,  however,  doubtful  if  the  variations  of  the  vascular  lumen  depend  upon  the  stimulation  of  the 
peripheral  nervous  mechanisms.  Ani}  1  nitiiie  and  digitalis  are  supposed  to  act  on  those  hypothetical 
mechanisms. 

T\\t  pulsating  veins  in  the  bat's  wing  still  continue  to  beat  after  section  of  all  their  nerves,  which 
is  in  favor  of  the  existence  of  local  nervous  mechanisms  [Lttchsinger,  Schiff). 

Influence  of  the  Cerebrum. — The  cerebrum  influences  the  vasomotor  centre, 
as  is  proved  by  the  sutldcn  i)alIor  that  accompanies  some  psychical  conditions, 
such  as  fright  or  terror.  There  is  a  centre  in  the  gray  matter  of  the  cerebrum 
where  stimulation  causes  cooling  of  the  opposite  side  of  the  body. 

Although  there  is  one  general  vasomotor  centre  in  the  medulla  oblongata,  which 
influences  all  the  blood  vessels  of  the  body,  it  is  really  a  complex  composite  centre, 
consisting  of  a  number  of  closely  aggregated  centres,  each  of  which  presides  over 
a  particular  vascular  area.  We  know  something,  e.  g.,  of  the  hepatic  (§  175)  and 
/-(?;/«/ centres  (§  276). 

Many  poisons  excite  the  vasomotor  nerves,  such  as  ergotin,  tannic  acid,  copaii>a,  and  cubebs; 
others  first  excite,  and  then  paralyze,  e.g.,  chloral  hydrate,  morphia,  laudanosin,  veratrin,  nicotin. 
Calabar  bean,  alcohol ;  others  rapidly  pa ?-alyze  them,^._f'.,  amyl  nitrite,  CO  (|  17),  atropin,  muscarin. 
The  paralytic  action  of  the  poison  is  proved  by  the  fact  that,  after  section  of  the  vagi  and  accele- 
rantes,  neither  the  pressor  nor  the  depressor  nerves,  when  stimulated,  produce  any  effect.  Many 
pathological  infective  agents  affect  the  vasomotor  nerves. 

The  veins  are  also  influenced  by  vasomotor  nerves,  and  so  are  the  lymphatics, 
but  we  know  very  little  about  this  condition. 

Pathological. — The  angio-neuroses,  or  nervous  affections  of  blood  vessels,  form  a  most 
important  group  of  diseases.  The  parts  primarily  affected  may  be  either  the  peripheral  nervous 
mechanisms,  tlie  subordinate  centres  in  the  cord,  the  doniinatini;  centre  in  the  medulla,  or  the  gray 
matter  of  the  cerebrum.  The  effect  may  be  direct  or  reflex.  The  dilatation  of  the  vessels  may  al?o 
be  due  to  stimulation  of  vaso-dilator  nerves,  and  the  physician  must  be  careful  to  distinguish  whether 
the  result  is  due  to  paralysis  of  the  vaso-constrictor  nerves  or  stimulation  of  the  vaso-dilator 
fibres. 

Angio-neuroses  of  the  skin  occur  in  affections  of  the  vasomotor  nerves,  either  as  a  diffuse 
redness  or  pallor;  or  there  maybe  circumscribed  affections.  Sometimes,  owing  to  the  stimulation 
of  indiviilual  vasomotor  nerves,  there  are  local  cutaneous  arterio-spasms  i^Xothnagelj.  In  certain 
acute  febrile  attacks — after  previous  initial  violent  stimulation  of  the  vasomotor  nerves,  especially 
(luring  the  cold  stage  of  fever — there  maybe  different  forms  of  paralytic  phenomena  of  the  cutaneous 
vessels.  In  some  cases  of  epilepsy  in  man.  Trousseau  observed  irregular,  red,  angio-paralytic 
patches  (ataches  cer^brales).  Continued  strong  stimulation  may  lead  to  interruption  of  the  cir- 
culation, which  may  result  in  gangrene  of  the  skin  and  deeper-seated  parts  {^IVeiss). 

Hemicrania,  due  to  unilateral  spasm  of  the  branches  of  the  carotid  on  the  head,  is  accompanied 
by  severe  headache  {Du  BoisReymomf).  The  cervical  sympathetic  nerve  is  intensely  stimulated — 
a  pale,  collapsed,  and  cool  side  of  the  face,  contraction  of  the  temporal  artery  like  a  finn  whipcord, 
dilatation  of  the  pupil,  secretion  of  thick  saliva,  are  sure  signs  of  this  afifedion.  This  form  may  be 
followed  by  the  opposite  condition  of  paralysis  of  the  cervical  sympathetic,  where  the  effects  are 
reversed.     Sometimes  the  two  conditions  may  alternate. 

Basedow's  disease  is  a  remarkable  condition,  in  which  the  vasomotor  nerves  are  concerned; 
the  heart  beats  very  rapidly  (90  to  129-200  beats  per  minute),  causing  palpitation;  there  is  swelling 
of  the  thyroid  gland  (struma),  and  projection  of  the  eyeballs  (exophthalmos"),  with  unperfectly 
coordinated  mo*'ements  of  the  upper  eyelid,  whereby  the  plane  of  vision  is  raised  or  lowered.  Perhaps 
in  this  disease  we  have  to  deal  with  a  simultaneous  stimulation  of  the  accelerans  cordis  (<!  370),  the 
motor  fibres  of  Miiller's  muscles  of  the  orbit  and  eyelids  (^  347,  I),  as  well  as  of  the  vaso-dilators 
of  the  thyroid  gland.  The  disease  may  be  due  to  direct  stimulation  of  the  sympathetic  channels  or 
their  spinal  origins,  or  it  may  be  referred  to  some  reflex  cause.  It  has  also  been  explained,  however, 
thus,  tiiat  the  exophthalmos  and  struma  are  the  consequence  of  vasomotor  paralysis,  which  results  in 
enlargement  of  the  blood  vessels,  while  the  increased  cardiac  action  is  a  sign  of  the  fiiminished  or 
arrested  inhibitory  action  of  the  vagus.  All  these  phenomena  may  be  caused,  according  to  Filehne, 
by  injury  to  the  upper  part  of  both  re?tiform  bodies  in  rabbits. 

Visceral  Angio-neuroses. — The  occurrence  of  sudden  hypersemia,  with  transudations  and 
ecchymoses  in  some  thoracic  or  abdominal  organs  may  have  a  neurotic  basis.  As  already  men- 
tioned, injury  to  the  pons,  corpus  striatum,  and  optic  thalamus  may  give  rise  to  hyperemia,  and 


COURSE    OF   THE    VASO-DILATOR   NERVES.  729 

ecchymoses  in  the  lungs,  pleura,  intestines  and  kidneys.  According  to  Brown-Sequard,  compres- 
sion or  section  of  one-half  of  the  pons  causes  ecchymoses,  especially  in  the  lung  of  the  opposite  side; 
he  also  observed  ecchymoses  in  the  renal  capsule  after  injury  of  the  lumbar  portion  of  the  spinal 
cord  (§  379). 

The  dependence  of  diabetes  mellitus  upon  injury  to  the  vasomotor  nerves  is  referred  to  in  ^  175 ; 
the  action  of  the  vasomotor  nerves  on  the  secretion  of  urine  in  |  276;  and  fever  in  §  220. 

372.  VASO-DILATOR  CENTRE  AND  NERVES.— Although  a 
vaso-dilator  centre  has  not  been  definitely  proved  to  exist  in  the  medulla,  still 
its  existence  there  has  been  surmised.  Its  action  is  opposite  to  that  of  the  vaso- 
motor centre.  The  centre  is  certainly  not  in  a  continuous  or  tonic  state  of  excite- 
ment. The  vaso-dilator  nerves  behave  in  their  functions  similarly  to  the  cardiac 
branches  of  the  vagus ;  both,  when  stimulated,  cause  relaxation  and  rest  {Schiff, 
CI.  Bernard^.  Hence,  these  nerves  have  been  called  vaso-mhibito?y,  vaso-hypo- 
tonic,  or  vaso-dilator  nerves.  Dyspnoeic  blood  stimulates  this  centre  as  well 
as  the  vasomotor  centre,  so  that  the  cutaneous  vessels  are  dilated,  while  simulta- 
neously the  vessels  of  the  internal  organs  are  contracted  and  the  organs  ansemic, 
owing  to  the  stimulation  of  their  vasomotor  centre  {Dastre  and  Morat).  Nicotin 
is  a  powerful  excitant  of  the  vaso-dilator  nerves  {^Ostroumoff^  :  it  raises  the  tem- 
perature of  the  foot  Cdog),  and  increases  the  formation  of  lymph  {Rogowicz). 

[The  existence  of  vaso-dilator  nerves  is  assumed  in  accordance  with  such 
facts  as  the  following :  If  the  chorda  tympani  be  divided,  there  is  no  change 
in  the  blood  vessels  of  the  submaxillary  gland  ;  but  if  its  peripheral  end  be 
stimulated,  in  addition  to  other  results,  (§  145),  there  is  dilatation  of  the  blood 
vessels  of  the  submaxillary  gland,  so  that  its  veins  discharge  bright  florid  blood, 
while  they  spout  like  an  artery.  Similarly,  if  the  nervi  erigentes  be  divided, 
there  is  no  effect  on  the  blood  vessels  of  the  penis  (§  362,  4) ;  but  if  Xhtix  periphe- 
ral qu^s  be  stimulated  with  Faradic  electricity,  the  sinuses  of  the  corpora  cavernosa 
dilate,  become  filled  with  blood,  and  erection  takes  place  (§  436).  Other  exam- 
ples in  muscle  and  elsewhere  are  referred  to  below.] 

Course  of  the  Vaso-dilator  Nerves. — To  some  organs  they  pass  as  special  nerves — to  other 
parts  of  the  body,  however,  they  proceed  along  with  the  vasomotor  and  other  nerves.  According 
to  Daslre  and  Morat,  the  vaso-dilator  nerves  for  the  bucco-labial  region  (dog)  pass  out  from  the 
cord  by  the  1st  to  the  3d  dorsal  nerves,  and  go  through  the  rami  communicantes  into  the  sympathetic, 
then  to  the  superior  cervical  ganglion,  and  lastly  through  the  carotid  and  inter-carotid  plexus  into 
the  trigeminus.  [The  fibres  occur  in  the  posterior  segment  of  the  ring  of  Vieussens,  and  if  they  be 
stimulated  there  is  dilatation  of  the  vessels  in  the  lip  and  cheek  on  that  side  (p.  673).]  The  maxil- 
lary branch  of  the  trigeminus,  however,  also  contains  vaso-dilator  fibres  proper  to  itself  [Laffont). 
In  the  gray  matter  of  the  cord,  there  is  a  special  subordinate  centre  for  the  vaso-dilator  fibres  of  the 
bucco-labial  region.  This  centre  may  be  acted  on  reflexly  by  stimulation  of  the  vagus,  especially  its 
pulmonary  branches,  and  even  by  stimulating  the  sciatic  nerve.  The  ear  receives  its  nerves  from 
the  1st  dorsal  and  lowest  cervical  ganglion,  the  upper  limb  from  the  thoracic  portion,  and  the  lower 
limb  from  the  abdominal  portion  of  the  sympathetic.  The  vaso-dilator  fibres  run  to  the  submaxil- 
lary and  sublingual  glands  in  the  chorda  tympani  (|  349,  4),  while  those  for  the  posterior 
part  of  the  tongue  run'  in  the  glosso -pharyngeal  nerve  (^  351,  4 — Vulpian).  Perhaps  the  vagus 
contains  those  for  the  kidneys  (|  276).  Slimulation  of  the  nervi  erigentes  proceeding  from  the 
sacral  plexus  causes  dilatation  of  the  arteries  of  the  penis,  together  with  congestion  of  the  corpora 
cavernosa  (|  436)  {Eckkard,  Loven).  Eckhard  found  that  erection  of  the  penis  can  be  produced  by 
stimulation  of  the  spinal  cord  and  of  the  pons  as  far  as  the  peduncles,  which  may  explain  the  phe- 
nomenon of  priapism  in  connection  with  pathological  irritations  in  these  regions.  The  muscles 
receive  the  vaso-dilator  fibres  for  their  vessels  through  the  trunks  of  the  motor  nerves.  Sdmidatiott 
of  a  motor  nerve  or  the  spinal  cord  causes  not  only  contraction  of  the  corresponding  muscles,  but 
also  dilatation  of  their  blood  vessels  (|  294,  II — C.  Ludwig  and  Sczelkozv^  Hafiz,  Gaskell) — 
the  dilatation  of  the  vessels  taking  place  even  when  the  muscle  is  prevented  from  shortening. 
[Gaskell  observed  under  the  microscope  the  dilatation  produced  by  stimulation  of  the  nerve 
to  the  mylo-hyoid  muscle  of  the  frog.]  The  vaso-dilators  remain  medullated  up  to  their  terminal 
ganglion  {^Gaskell). 

The  vaso-dilators  (like  the  vasomotors,  p.  727)  also  have  subordinate 
centres  in  the  spinal  cord;   e.  g.,  the  fibres  of  the  labio-buccal  region  at  the 


730  SPASM    AND    SWEAT   CENTRE. 


# 


ist  to  3d  dorsal  vertebrae.  This  centre  may  be  influenced  reflexly  through  ihe 
pulmonary  fibres  of  the  vagus,  and  also  through  the  sciatic  {Laffont,  S/zi/rnoic). 
According  to  Holtz,  a  similar  centre  lies  in  the  lowest  part  of  the  cord. 

Goltz  showed  that,  in  the  nerves  to  the  limbs  {c'.j,\,  in  the  sciatic  nerve),  the  vasomotor  and 
vasodilator  fibres  lie  side  by  side  in  the  same  nerve.  If  the  peripheral  end  of  this  nerve  be  stimu- 
lated immediately  after  it  is  divided,  the  action  of  the  vasoconstrictor  fibres  overcomes  that  of  the 
dilators.  If  the  peripheral  end  be  stimulated  4  to  6  days  after  the  section,  when  the  vaso  constric- 
tors have  lost  their  excitability,  the  bloodvessels  dilate  under  the  action  of  the  vasodilator  fibres. 
Stimuli  7uhiih  are  applied  at  long  intenmh  to  the  nerve  net  especially  on  the  7'aso-dilator  fibres  ; 
-while  tetanizing  stimuli  act  on  the  vasomotors.  The  latent  period  of  the  vaso-dilators  is  longer,  and 
they  are  more  easily  exhaitsted  than  the  vasomotors  [Bo-wditch  and  Warren).  The  sciatic  nerve 
receives  both  kinds  of  fibres  from  the  sympathetic.  It  is  assumed  that  the  peripheral  nervous  mech- 
anisms in  connection  with  the  blood  vessels  are  influenced  by  both  kinds  of  vascular  nerves ;  the 
vasomotors  (constrictors)  increase,  while  the  vaso-dilators  diminish  the  activity  of  these  mechanisms 
or  ganglia.  [It  is,  however,  possible  to  explain  their  effects  by  supposing  that  they  act  directly  upon 
the  muscular  fibres  of  the  blood  vessels  without  the  intervention  of  any  nervous  ganglionic  struc- 
tures.] 

[Section  of  the  spinal  cord  high  up  in  the  neck  causes,  of  course,  a  great  fall  of  the  blood  pressure, 
owing  to  the  division  of  the  vasomotor  nerves.  In  the  dog  the  pressure  may  fall  to  30-40  mm.  Hg. 
After  i.solation  of  the  cord,  in  rabbits  alone,  stimulation  of  the  central  end  of  a  sensory  nerve  causes 
a  rise  of  the  blood  pressure;  in  dogs,  however,  under  the  same  conditions,  the  blood  pressure /a/A. 
Dyspnceic  blood  also  causes  a  rise  of  the  blood  pressure,  which  is  preceded  by  a  fall  {Ustimowitch). 
This  reflex  fall  of  the  blood  pressure  takes  place  after  section  of  the  splanchnics,  and  the  nerves  to 
the  extremities,  but  it  does  not  take  place  if  the  spinal  cord  be  divided  at  the  lumbar  or  lower  dorsal 
ret^ion.  If  the  cord  be  divided  in  the  lower  dorsal  region,  stimulation  of  the  brachial  plexus  has  no 
effect,  while  the  fall  occurs  after  stimulation  of  the  central  end  of  the  sciatic.  These  experiments 
indicate  that  the  vaso-dilator  nerves  which  cause  the  fall  of  the  blood  pressure  arise  in  the  lower  part 
of  the  spinal  cord  (lumbar),  and  that  they  are  probably  contained  in  the  visceral  nerves  and  not  in 
those  for  the  extremities  (Thayer  and  Pal).'] 

In  the  muscles  of  the  face,  paralyzed  by  extirpation  of  the  facial  nerve,  stimu- 
lation of  the  ring  of  Vieussens  causes  pseudo-motor  contractions  of  these 
muscles,  just  as  stimulation  of  the  chorda  tymi)ani  causes  such  contractions  in  the 
paralyzed  tongue  (§  349,  4),  after  section  of  the  hypoglossal  nerve  {Rogowicz). 

In  analyzing  the  vascular  phenomena  resulting  from  experiments  on  these  nerves,  we  must  be  very 
careful  to  determine  whether  the  dilatation  is  the  result  of  stimulation  of  the  vaso-dilators,  or  a 
consequence  of  paralysis  of  the  vaso-conslrictors.  Psychical  conditions  act  upon  the  vaso-dilator 
nerves — the  blush  of  shame,  which  is  not  confined  to  the  face,  but  may  even  extend  over  the  whole 
skin,  is  probably  due  to  stimulation  of  the  vaso-dilator  centre. 

Influence  on  Temperature. — The  vaso  dilator  nerves  obviously  have  a  considerable  influence  on 
the  temperature  of  the  body  and  on  the  heat  of  the  individual  parts  of  the  body.  Both  vascular 
centres  must  act  as  importmt  regulatory  mechanisms  for  the  radiation  of  heat  through  the  cutaneous 
vessels  {\  214,  II).  Probably  they  are  kept  in  activity  reflexly  by  sensory  nerves.  Disturbances  in 
their  function  may  lead  to  an  abnormal  accumulation  of  heat,  as  in  fever  {\  220),  or  to  abnormal 
cooHng  {\  213,  7).  Some  observers,  however,  assume  the  existence  of  an  intra-cranial  "  heat-regu- 
lating centre  ■'  (  Tschetschichin,  Naunyn,Quincke).  According  to  Wood,  separation  of  the  midulla 
oblongata  from  the  pons  causes  an  increased  radiation  and  a  diminished  production  of  heat,  due  to 
the  cu'tting  oft"  of  the  influences  from  the  heat-regulating  centre  (ii  377). 

373.   SPASM    CENTRE— SWEAT    CENTRE.— Spasm    Centre.— 

In  the  medulla  oblongata,  just  where  it  joins  the  pons,  there  is  a  centre,  whose 
stimulation  cdiWies  general  spasms.  The  centre  maybe  excited  by  suddenly  pr'^- 
ducing  a  highly  venous  condition  of  the  blood  ("asphyxia  spasms"),  in  cases  of 
drowning  in  mammals  (but  not  in  frogs),  sudden  anaemia  of  the  medulla  oblon- 
gata, either  in  consequence  of  hemorrhage  or  ligature  of  both  carotids  and  sub- 
clavians  {Kiissmaiil  and  Tenner),  and  lastly,  by  sudden  venous  stagnation  caused 
by  compressing  the  veins  coming  from  the  head.  In  all  these  cases,  the  stimula- 
tion of  the  centre  is  due  to  the  sudden  interruption  of  the  normal  exchange  of  ihe 
gases.  When  these  factors  act  quite  gradually,  death  may  take  place  without  con- 
vulsions.   Direct  stimulation  by  means  of  chemical  substances  (ammonia  carbonate, 


PSYCHICAL    FUNCTIONS   OF   THE   BRAIN.  731 

potash,  and  soda  salts,  etc.),  applied  to  the  medulla,  quickly  causes  general  con- 
vulsions (-Papel/ier).  Intense  direct  mei:/iam'i:a/ stimu.\a.tion  of  the  medulla,  as  by 
its  sudden  destruction,  causes  general  convulsions. 

Position. — Nothnagel  attempted  by  direct  stimulation  to  map  out  the  position  of  the  spasm  centre 
in  rabbits;  it  extends  from  the  area  above  the  ala  cinerea  upward  to  the  corpora  quadrigemina.  It  is 
limited  externally  by  the  locus  coeruleus  and  the  tuberculum  acusticum.  In  the  frog,  it  lies  in  the 
lower  half  of  the  4tli  ventricle  {Heuber).  The  centre  is  affected  in  extensive  reflex  spasms  (|  364, 
6),  e.  g.,  in  poisoning  with  strychnin  and  in  hydrophobia. 

Poisons. — Many  inorganic  and  organic  poisons,  most  cardiac  poisons,  nicotin,  picrotoxin,  ammo- 
nia (^  277),  and  the  compounds  of  barium  cause  death  after  producing  convulsions,  by  acting  on  the 
spasm  centre  i^Rober,  Heubel,  Bohni). 

If  the  arteries  going  to  the  brain  be  ligatured  so  as  to  paralyze  the  medulla  oblongata,  then,  on 
ligaturing  the  abdominal  aorta,  spasms  of  the  lower  limbs  occur,  owing  to  the  anaemic  stimulation  of 
the  motor  ganglia  of  the  spinal  cord  [Sigm.  Mayer). 

Pathological — Epilepsy. — Schroeder  van  der  Kolk  found  the  blood  vessels  of  the  oblongata 
dilated  and  increased  in  cases  of  epilepsy.  Brown-Sequard  observed  that  injury  to  the  central  or 
peripheral  nervous  system  (spinal  cord,  oblongata,  peduncle,  corpora  quadrigemina,  sciatic  nerve)  of 
guinea  pigs  produced  epilepsy,  and  this  condition  even  became  hereditaiy.  Stimulation  of  the  cheek 
or  of  the  face  "  epileptic  zone,"  on  the  same  side  as  the  injury  (spinal  cord),  caused  at  once  an 
attack  of  epilepsy;  but  when  the  peduncle  was  injured,  the  opposite  side  must  be  stimulated.  West- 
phal  made  guinea  pigs  epileptic  by  repeated  light  blows  on  the  skull,  and  this  condition  also  became 
hereditary.  In  these  cases,  there  was  effusion  of  blood  in  the  medulla  oblongata  and  upper  part  of 
the  spinal  cord  (^§  375  and  378,  I).  Direct  stimulation  of  the  cerebrum  also  produces  epileptic 
convulsions.  Strong  electrical  stimulation  of  the  motor  areas  of  the  cortex  cerebri  is  often  followed 
by  an  epileptic  attack  (|  375).  [It  is  no  unfrequent  occurrence,  while  one  is  stimulating  the  motor 
areas  of  the  cortex  cerebri  of  a  dog,  to  find  the  animal  exhibiting  symptoms  of  local  or  general 
epilepsy.] 

Sweat  Centre. — A  dominating  centre  for  the  secretion  of  the  sweat  of  the 
entire  surface  of  the  body  (§  289,  II) — with  subordinate  spinal  centres  (§  362,  8) 
— occurs  in  the  medulla  oblongata  {^Adamkiewicz,  Manne,  Nawrocki\  It  is 
double,  and  in  rare  cases  the  excitability  is  unequal  on  the  two  sides,  as  is  mani- 
fested by  unilateral  perspiration  (§  289,  2). 

Poisons. — Calabar  bean,  nicotin,  picrotoxin,  camphor,  and  ammonium  acetate,  cause  a  secretion 
of  sweat  by  acting  directly  on  the  sweat-centre.  Muscarin  causes  local  stimulation  ot  the  peripheral 
sweat  fibres — it  causes  sweating  of  the  hind  limbs  after  section  of  the  sciatic  nerves.  Atropin 
arrests  the  action  of  muscarin  i^Oti,  Wood,  Field,  Nawrocki). 

[Regeneration  of  the  Spinal  Cord. — In  some  animals,  true  nervous  matter  is  reproduced  after 
part  of  the  spinal  cord  has  been  destroyed,  at  least  this  is  so  in  tritons  and  lizards  lyH.  Mii/ler).  In  these 
animals,  when  the  tail  is  removed,  it  is  reproduced,  and  Miiller  found  that  a  part  of  the  spinal  cord 
corresponding  to  the  new  part  of  the  tail  is  reproduced.  Morphologically,  the  elements  were  the 
same,  but  the  spinal  nerves  were  not  reproduced,  while  physiologically,  the  new  nerve  substance  was 
not  functionally  active ;  it  corresponds,  as  it  were,  to  a  lower  stage  of  development.  According  to 
Masius  and  Vanlair,  an  excised  portion  of  the  spinal  cord  of  a  frog  is  reproduced  after  six  months; 
while  Brown-Sequard  maintains  that  reunion  of  the  divided  surfaces  of  the  cord  takes  place  in 
pigeons  after  six  to  fifteen  months.  A  partial  reunion  is  asserted  to  occur  in  dogs  by  Dentan,  Naunyn 
and  Eichhorst,  although  Schieferdecker  obtained  only  negative  results,  the  divided  ends  being  united 
only  by  connective  tissue  {_Schwalbe').'\ 

374.  PSYCHICAL  FUNCTIONS  OF  THE  BRAIN.— The  hemi- 
spheres of  the  cerebrum  are  usually  said  to  be  the  seat  of  all  the  psychical  activities. 
Only  when  they  are  intact  are  the  processes  of  thinking,  feeling  and  willing  possi- 
ble. After  they  are  destroyed,  the  organism  comes  to  be  like  a  complicated 
machine,  and  its  whole  activity  is  only  the  expression  of  the  external  and  internal 
stimuli  which  act  upon  it.  The  psychical  activities  appear  to  be  located  in  both 
hemispheres,  so  that  after  destruction  of  a  considerable  part  of  one  of  them,  the 
other  seems  to  act  in  place  of  the  part  destroyed.  [Objection  has  been  taken  to 
the  term  the  "  seat  of"  the  will  and  intelligence,  and  undoubtedly  it  is  more  con- 
sistent with  what  we  know,  or  rather  do  not  know,  to  say,  that  the  existence  of 
volition  and  intelligence  is  dependent  on  the  connection  of  the  cerebral  cortex 
with  the  rest  of  the  brain.] 


732  REMOVAL    OF    THE    CEREBRUM. 

[That  a  certain  condition  of  the  cerebral  hemispheres  is  necessar)'  for  the  manifestation  of  the 
intellectual  faculties,  is  admitted  on  all  hands ;  for,  compression  of  the  brain,  <•.  4'-.,  by  a  depressed 
fracture  of  the  skull,  and  sudden  cessation  of  the  supply  of  blood  to  the  brain,  abolish  consciousness. 
The  intellectual  faculties  aic  atVccted  by  inllammation  of  the  meninges  involviiif;  the  surface  of  the 
brain,  the  action  of  drugs  alTects  the  intellectual  and  other  faculties;  but  while  all  this  is  admitted  we 
cannot  say  precisely  upon  what  parts  of  tiie  brain  ideation  depends.  The  pre-frontal  area,  or  the 
convolutions  in  front  of  the  ascending  frontal  supplied  by  the  anterior  cerebral  artery,  are  sometimes 
regarded  as  the  anatomical  substratum  of  certain  mental  acts.  At  any  rate,  electrical  stimulation  of 
these  parts  is  not  followed  by  muscular  motion,  and,  according  to  Fenier,  if  this  region  be  extiq>ated 
in  the  monkey,  there  is  no  motor  or  sensory  disturbance  in  this  animal  ;  it  still  exhibits  emotional 
feeling,  all  its  special  senses  remain,  and  the  power  of  voluntary  motion  is  retained  ;  but,  nevertheless, 
there  is  a  decided  alteration  in  the  animal's  character  and  behavior,  so  that  it  exhibits  considerable 
psychological  alterations,  and,  according  to  Fcrrier,  "  it  has  lost  to  all  appearance  the  faculty  of 
attention  and  intelligent  observation."] 

Observations  on  Man. — Cases  in  which  considerable  unilateral  lesions  or  destruction  of  one 
hemisphere  have  taken  place,  without  the  psychical  activities  appearing  to  suffer,  sometimes  occur. 
The  following  is  a  case  communicated  by  Longet :  A  boy,  i6  years  of  age,  had  his  parietal  bone 
fractured  by  a  stone  falling  on  it,  so  that  part  of  the  protruding  brain  matter  had  to  be  removed.  On 
reapplying  the  bandages,  more  brain  matter  had  to  be  removed.  After  18  days  he  fell  out  of  bed,  and 
more  brain  matter  protnided,  which  was  removed.  On  the  35th  day  he  got  intoxicatetl,  tore  off  the 
bandages,  and  with  them  a  part  of  tiie  brain  matter.  After  his  recovery,  the  boy  still  retained  his 
intelligence,  but  he  was  hemiplegic.  Even  when  both  hemispheres  are  wo^/^'r^/^'A' destroyed,  the 
intelligence  appears  to  be  intact ;  thus,  Trousseau  describes  the  case  of  an  officer  whose  fore-brain 
was  pierced  transversely  by  a  bullet.  There  was  scarcely  any  appearance  of  his  mental  or  bodily 
faculties  being  affected.  In  other  cases,  destruction  of  parts  of  the  brain  peculiarly  alters  the  charac- 
ter. We  must  be  extremely  careful,  however,  in  forming  conclusions  in  all  such  cases  [In  the 
celebrated  "  American  crow-bar  case"  recorded  by  Bigelow ,  a  young  man  was  hit  by  a  bar  of  iron 
I '4  inch  in  diameter,  which  traversed  the  anterior  part  of  the  left  hemisphere,  going  clean  out  at 
the  top  of  his  head.  This  man  lived  for  thirteen  years  without  any  permanent  alterations  of  motor 
or  sensory  functions;  but  "the  man's  disposition  and  character  weie  observed  to  have  undergone  a 
serious  change.  There  were,  however,  some  changes  which  might  I  e  referable  to  injury  to  the  frontal 
region."  In  all  cases  it  is  most  important  to  know  both  the  exact  site  and  the  extent  of  the  lesion. 
Ross  points  out  that  the  characteristic  features  of  lesions  in  the  pre  frontal  cortical  region  are  affected 
by  "  psychical  disturb.inces,  consisting  of  dementia,  apathy  and  somnolency."] 

Imperfect  development  of  the  cerebrum. — Microcephalia  and  hydrocephalus  yield  every 
result  between  diminution  of  the  psychical  activities  and  idiocy.  Extensive  inllammation,  degene- 
ration, pressure,  anremia  of  the  blood  vessels  and  the  actions  of  many  poisons  produce  the  same 
effect. 

Flourens'  Doctrine. — Flourens  assumed  that  the  whole  of  the  cerebrum  is  concerned  in  every 
l>sychical  process.  From  his  experiments  on  pigeons,  he  concluded  that,  if  a  small  part  of  the  hemi- 
spheres remained  intact,  it  was  sufficient  for  the  manifestation  of  the  mental  functions;  just  in  pro- 
portion as  the  gray  matter  of  the  hemispheres  is  removed,  all  the  functions  of  the  cerebrum  are 
enfeebled,  and  when  all  the  gray  matter  is  removed,  all  the  functions  are  abolished.  According  to 
this  view,  neither  the  different  faculties  nor  the  different  perceptions  are  localized  in  special  areas, 
(loltz  holds  a  somewhat  similar  view  to  that  of  Flourens.  lie  assumes  that  if  an  uninjured  part  of 
the  cerebrum  remain  it  can  to  a  certain  extent  perform  the  functions  of  the  parts  that  have  been 
removed.     This  Vulpian  has  called  the  law  of  "  functional  substitution"  (loi  de  suppleance). 

The  Phrenological  doctrine  of  Gall  (f  1828)  and  Spurzheim  assumes  that  the  different  mental 
faculties  are  located  in  difierent  parts  of  the  brain,  and  it  is  as>umed  that  a  large  development  of  a 
particular  organ  maybe  detected  by  examining  the  external  configuration  of  the  head  (Cranioscopy). 

Removal  of  the  Cerebrum. — After  the  removal  of  both  cerebral  hemi- 
spheres, in  most  animals,  every  vohintary  movement  and  all  conscious  impression 
and  sensory  perception  entirely  ceases.  On  the  other  hand,  the  whole  mechanical 
movements  and  the  maintenance  of  the  equilibrium  of  the  movements  are  retained. 
The  maintenance  of  the  equilibrium  depends  upon  the  mid-brain,  and  is 
regulated  by  important  reflex  channels  (§  379). 

Sudden  cessation  of  the  circulation  in  the  brain,  e.g.,  by  decapitation,  is  followed  at  once  by  cessa- 
tion of  the  mental  faculties.  When  Hayem  and  Barrier  perfused  the  blood  of  a  horse  through  the 
carotids  of  a  decapitated  dog's  head,  the  head  showed  signs  of  consciousness  and  will  for  10  seconds, 
but  not  longer. 

The  mid-brain  (corpora  quadrigeniina)  is  connected  not  only  with  the  gray 
matter  of  the  spinal  cord  and  medulla  oblongata,   the  seat  of  extensive  reflex 


REMOVAL   OF   THE    CEREBRUM    FROM    A    FROG. 


733 


Fig.  472. 


mechanisms  (§  367).  but  it  also  receives  fibres  coming  from  the  higher  organs  of 
sense,  which  also  excite  movements  reflexly.  The  corpora  quadrigemina  are  also 
supposed  to  contain  a  reflex  inhibitory  apparatus  (§  361,  2).  The  joint  action  of 
all  these  parts  makes  the  corpora  quadrigemina  one  of  the  most  important  organs 
for  the  harmonious  execution  of  movements,  and  this  even  in  a  higher  degree  than 
the  medulla  oblongata  itself  (6^(?//s).  Animals  with  their  corpora  quadrigemina 
intact  retain  the  equilibrium  of  their  bodies  under  the  most  varied  conditions,  but 
they  lose  this  power  as  soon  as  the  mid-brain  is  destroyed  {Goltz).  Christiani 
locates  the  coordinating  centre  for  the  change  of  place  and  the  maintenance  of 
the  equilibrium,  in  mammals,  in  front  of  the  inspiratory  centre  in  the  3d 
ventricle  (§  368). 

That  impressions  from  the  skin  and  sense  organs  are  concerned  in  the  maintenance  of  the 
equilibrium,  is  proved  by  the  following  facts  :  A  frog  without  its  cerebrum  at  once  loses  its  power 
of  balancing  itself  as  soon  as  the  skin  is  removed  from  its  hind  limbs.  The  action  of  impressions 
communicated  through  the  eyes  is  proved  by  the  difficulty  or  impossibility  of  maintaining  the  equilib- 
rium in  nystagmus  (§  350),  and  by  the  vertigo  which  often  accompanies  paralysis  of  the  external 
ocular  muscles.  In  persons  whose  cutaneous  sensibility  is  diminished,  the  eyes  are  the  chief  organs 
for  the  maintenance  of  the  equilibrium ;  they  fall  over  when  the  eyes  are  closed.  [This  is  well  illus- 
trated in  cases  of  locomotor  ataxia  (p.  697).] 

Frog. — A  frog  with  its  cerebrum  removed  retains  its  power  of  maintaining  its 
equilibrium.     It  can  sit,  spring,  or  execute  complicated  coordinated  movements 
when  appropriate  stimuli  are  applied  ;  when  placed  on  its  back,  it  immediately 
turns  into  its  normal  position 
on  its  belly  ;  if  stimulated  it  Fig.  471. 

gives  one  or  two  springs,  and 
then  comes  to  restj  when 
thrown  into  water,  it  swims 
to  the  margin  of  the  vessel, 
and  it  may  crawl  up  the  side, 
and  sit  passive  upon  the  edge 
of  the  vessel.  When  incited 
to  move,  it  exhibits  the  most 
complete  harmony  and  unity 
in  all  its  movements.  Unless 
it  is  stimulated,  it  never  makes 
independent,  voluntary,  purposive  movements.  It  sits  in  the  same  place  con- 
tinually as  if  in  sleep,  it  takes  no  food,  it  has  no  feelings  of  hunger  and  thirst,  it 
shows  no  symptoms  of  fear,  and  ultimately,  if  left  alone,  it  becomes  desiccated 
like  a  mummy  on  the  spot  where  it  sits.  [If  the  flanks  of  such  a  frog  be  stroked, 
it  croaks  with  the  utmost  regularity  according  to  the  number  of  times  it  is  stroked. 
Langendorff  has  shown  that  a  frog  croaks  under  the  same  circumstances,  when  both 
optic  nerves  are  divided.  It  seems  to  be  influenced  by  light ;  for,  if  an  object  be 
placed  in  front  of  it  so  as  to  throw  a  strong  shadow,  then  on  stimulating  the  frog 
it  will  spring  not  against  the  object,  a,  but  in  the  direction,  b  (Fig.  471).  Steiner 
finds  that  if  a  glass  plate  be  substituted  for  an  opaque  object  like  a  book,  the  frog 
always  jumps  against  this  obstacle.  Its  balancing  movements  on  a  board  are 
quite  remarkable  and  acrobatic  in  character.  If  it  be  placed  on  a  board,  and  the 
board  gently  inclined  (Fig.  472),  it  does  not  fall  off,  as  a  frog  with  only  its  spinal 
cord  will  do,  but  as  the  board  is  inclined,  so  as  to  alter  the  animal's  centre  of 
gravity,  it  slowly  crawls  up  the  board  until  its  equilibrium  is  restored.  If  the 
board  be  sloped  as  in  Fig.  472,  it  will  crawl  up  until  it  sits  on  the  edge,  and  if  the 
board  be  still  further  tilted,  the  frog  will  move  as  indicated  in  the  figure.  It  only 
does  so,  however,  when  the  board  is  inclined,  and  it  rests  as  soon  as  its  centre  of 
gravity  is  restored.  It  responds  to  every  stimulus,  just  like  a  complex  machine, 
answering  each  stimulus  with  an  appropriate  action.] 


'    i 

I  / 


Frog  without  its  cere- 
brum avoiding  an 
object  placed  in  its 
path. 


Frog  without    its  cerebrum   moving  on 
inclined  board  {Goltz). 


734  REMOVAL   OF   THE    CEREBRUM. 

A  pigeon  without  its  cerebral  hemispheres  behaves  in  a  similar  manner  (Fig. 
473).     When  undisturbed  it  sits  continuously,  as  if  in  sleep,  but  when  stimulated, 

it    shows    complete   harmony  of    all    its 
'     ^'^^'  movements;  it  can  walk,  fly,  perch,  and 

balance  its  body.  The  sensory  nerves 
and  those  of  special  sensation  conduct 
impulses  to  the  brain ;  they  only  dis- 
charge reflex  movements,  but  they  do 
not  excite  conscious  impressions.  Hence, 
the  bird  starts  when  a  pistol  is  fired  close 
to  its-  ear  ;  it  closes  its  eyes  when  it  is 
brought  near  a  flame,  and  the  pupils  con- 
tract ;  it  turns  away  its  head  when  the 
vapor  of  ammonia  is  applied  to  its  nos- 

_ trils.     All  these  impressions  are  not  per- 

- '  f'-\'  ''-■':^"r^'^^       7'         ceived    as   conscious   percei)tions.     The 

ilIjimI  hcnusplicres  removed.  •  ' 

perceptive  faculties — the  will  and  memory 
— are  abolished  ;  the  animal  never  takes  food  or  drinks  spontaneously.  But  if 
food  be  placed  at  the  back  part  of  its  throat  it  is  swallowed  [reflex  act],  and  in 
this  way  the  animal  may  be  maintained  alive  for  months  {Flourens). 

Fish  appear  to  behave  differently.  A  carp  with  its  cerebrum  removed  (Fig. 
483,  VI,  i)  can  see  and  may  even  select  its  food,  and  seems  to  execute  its  move- 
ments voluntarily  {Sfeiiier,  Vulpiati). 

Mammals  (rabbit),  owing  to  the  great  loss  of  blood  consequent  on  removal  of 
the  cerebrum,  are  not  well  suited  for  experiments  of  this  kind.  Immediately  after 
the  operation  they  show  great  signs  of  muscular  weakness.  When  they  recover, 
they  present  the  same  general  phenomena  ;  only  when  they  are  stimulated  they  run, 
as  it  were,  blindfolded  against  an  obstacle.  Vulpian  observed  a  peculiar  shriek  or 
cry  which  such  a  rabbit  makes  under  the  circumstances.  Sometimes  even  in  man 
a  peculiar  cry  is  emitted  in  some  cases  of  pressure  or  inflammation  rendering  the 
cerebral  hemispheres  inactive. 

Observations  on  somnambulists  show  that  in  man,  also,  complete  harmony 
of  all  movements  may  be  retained,  without  the  assistance  of  the  will  or  conscious 
impressions  and  perceptions.  As  a  matter  of  fact,  many  of  our  ordinary  move- 
ments are  accomplished  without  our  being  conscious  of  them.  They  take  place 
under  the  guidance  of  the  basal  ganglia. 

The  degree  of  intelligence  in  the  animal  kingdom  is  in  relation  to  the  size  of  the  cerebral 
hemispheres,  in  proportion  to  the  mass  of  the  other  parts  of  the  central  nervous  system.  Taking 
the  brain  alone  into  consideration,  we  observe  th.at  those  animals  have  the  highest  intelligence 
in  which  the  cerebral  hemispheres  greatly  exceed  the  mid-brain  in  weight.  The  mid-brain  is  repre- 
sented by  the  optic  lobes  in  the  lower  vertebrates,  and  by  the  corpora  quadrigemina  in  the  higher 
vertebrates.  In  Fig.  483,  VI,  represents  the  brain  of  a  carp ;  V,  of  a  frog ;  and  IV,  of  a  pigeon.  In 
all  these  cases  I  indicates  the  cerebral  hemispheres;  2,  the  optic  lobes;  3,  the  cerebellum  ;  and  4  the 
medulla  oblongata.  In  the  carp,  the  cerebral  hemispheres  are  smaller  than  the  optic  lobes;  in  the 
frog,  they  exceed  the  latter  in  size.  In  the  pigeon  the  cerebrum  begins  to  project  backward  over 
the  cerebellum.  The  degree  of  intelligence  increases  in  these  animals  in  this  proportion.  In  the 
dog's  brain  (Fig.  483,  II)  the  hemispheVes  completely  cover  the  corpora  quadrigemina, but  the  cere- 
bellum stdl  lies  behind  the  cerebrum.  In  man  the  occipital  lobes  of  the  cerebrum  completely  over- 
lap the  cerebellum  (Fig.  479).  [The  projection  of  the  occipital  lobes  over  the  cerebellum  is  due  to 
the  development  of  the  frontal  lobes  pushing  backward  the  convolutions  that  lie  behind  them,  and 
not  entirely  to  increased  development  of  the  occipital  lobes.] 

Meynert's  Theory. — According  to  Meynert,  we  may  represent  this  relation  in  another  way.  As 
is  known,  fibres  proceed  downward  from  the  cerebral  hemispheres,  through  the  crusta  or  basis  of  the 
cerebral  peduncle.  These  fibres  are  separated  from  the  upper  fibres  or  tegmentum  of  the  peduncle 
by  the  locus  niger,  the  tegmentum  being  connected  with  the  corpora  quadrigemina  and  the  optic 
thalamus.  The  larger,  therefore,  the  cerebral  hemispheres,  the  more  numerous  will  be  the  fibres 
proceeding  from  it.  In  Fig.  461,  II,  is  a  transverse  section  of  the  posterior  corpora  quadrigemina, 
with  the  aqeduct  of  Sylvius  and  both  cerebral  peduncles  of  an  adult  man  ;  /,  /,  is  the  crusta  of  each 


REACTION   TIME. 


735 


peduncle,  and  above  it  lies  the  locus  niger,  s.     Fig.  461,  IV,  shows  the  same  parts  in  a  monkey  ; 

III,  in  a  dog;  and  V,  in  a  guinea-pig.  The  crusta  diminishes  in  the  above  series.  There  is  a  corre- 
sponding diminution  of  the  cerebral  hemispheres,  and,  at  the  same  time,  in  the  intelligence  of  the 
corresponding  animals. 

Sulci  and  Gyri. — The  degree  of  intelligence  also  depends  upon  the  number  and  depth  of  the 
convolutions.     In  the  lowest  vertebrates  (fish,  frog,  bird)  the  furrows  or  sulci  are   absent  (Fig.  461, 

IV,  V,  VI) ;  in  the  rabbit  there  are  two  shallow  furrows  on  each  side  (III).  The  dog  has  a  com- 
pletely furrowed  cerebrum  (I,  II).  Most  remarkable  is  the  complexity  of  the  sulci  and  convolutions 
of  the  cerebrum  of  the  elephant,  one  of  the  most  intelligent  of  animals.  Nevertheless,  some  very 
stupid  animals,  as  the  ox,  have  very  complex  convolutions. 

The  absolute  weight  of  the  brain  cannot  be  taken  as  a  guide  to  intelligence.  The  elephant  has 
absolutely  the  heaviest  brain,  but  man  has  relatively  the  heaviest  brain.  [We  ought  also  to  take  into 
account  the  complexity  of  the  convolutions  and  the  depth  of  the  gray  matter,  its  vascularity,  and 
the  extent  of  anastomoses  between  its  nerve  cells.] 

Time  an  Element  in  all  Psychical  Processes. — Every  psychical  process 
requires  a  certain  time  for  its  occurrence — a  certain  time  always  elapses  between 
the  application  of  the  stimulus  and  the  conscious  reaction. 


Nature  of  Stimulus. 


Shock  on  left  hand, 

Shock  on  forehead, 

Shock  on  toe  of  left  foot, 

Sudden  noise, 

Visual  impressions  of  electric  spark. 
Hearing  a  sound, 

Currrent  to  tongue  causing  taste, 

Saline  taste, 

Taste  of  sugar, 

"  acids, 

"  quinine, 


Reaction  Time. 


.12 
•13 
•17 
•13 
•15 
.16 

.16 

•15 
.16 
.16 
•23 


Name  of  Observer. 


Exner. 
do. 
do. 
do. 
do. 
Bonders. 

v.  Vintschgau  and 
Honigschmied. 
do. 
do. 
do. 
do. 


Reaction  Time. — This  time  is  known  as  "  reaction  tit?te"  and  is  distinctly  longer  than  the 
simple  reflex  time  required  for  a  reflex  act.  It  can  be  measured  by  causing  the  person  experimented 
on  to  indicate  by  means  of  an  electrical  signal  the  moment  when  the  stimulus  is  applied.  The 
reaction  time  consis's  of  the  following  events:  (l)  The  duration  of  perception,  i.  e.,  when  we 
become  conscious  of  the  impression ;  (2)  the  duration  of  the  time  required  to  direct  the  attention  to 
the  impression,  i.  e.,  the  duration  of  apperception  ;  and  (3)  the  duration  of  the  voluntary  impulse, 
together  with  (4)  the  time  required  for  conducting  the  impulse  in  the  afferent  nerves  to  the  centre, 
and  (5)  the  time  for  the  impulse  to  travel  outward  in  the  motor  nerves.  If  the  signal  be  made 
with  the  hand,  then  the  reaction  time  for  the  impression  oi  sound  is  0.136  to  0.167  second;  for 
taste,  0.15  to  0.23;  touch,  0.133  to  0.201  second  [Horsck,v.  Vintschgau  and  Honigschniect);  iox 
olfactory  impressions,  which,  of  course,  depend  upon  many  conditions  (the  phase  of  respiration, 
current  of  air),  0.2  to  0.5  second.  Intense  stimulation,  increased  attention,  practice,  expectation, 
and  knowledge  of  the  kind  of  stimulants  to  be  applied,  all  diminish  the  time.  Tactile  impressions 
are  most  rapidly  perceived  when  they  are  applied  to  the  most  sensitive  parts  (v.  Vintschgati).  The 
time  is  increased  with  very  strong  stimuli,  and  when  objects  difficult  to  be  distinguished  are  applied 
(y.  Helmholtz  and  Baxt).  The  time  required  to  direct  the  attention  to  a  number  consisting  of  I 
to  3  figures,  Tigerstedt  and  Bergquist  found  to  be  0.015  to  0.035  second.  Alcohol  and  the  anaes- 
thetics alter  the  time;  according  to  their  degree  of  action  they  shorten  or  lengthen  it  {Kraplin).  In 
order  that  two  shocks  applied  after  each  other  be  distinguished  as  two  distinct  impressions,  a  certain 
interval  must  elapse  between  the  two  shocks — for  the  ear,  0-002  to  0-0075  second;  for  the  eye, 
0.044  to  0.47  second;  for  the  finger,  0.277  second. 

[The  Dilemma. — When  a  person  is  experimented  on,  and  he  is  not  told  whether  the  right  or 
left  side  is  to  be  stimulated,  or  what  colored  disc  may  be  presented  to  the  eye,  then  the  time  to 
respond  correctly  is  longer.] 

[Drugs  and  other  conditions  affect  the  reaction  time.  Ether  and  chloroform  lengthen  it,  while 
alcohol  does  the  same,  but  the  person  imagines  he  really  reacts  quicker.     Noises  also  lengthen  it.] 

In  sleep  and  waking,  we  observe  the  periodicity  of  the  active  and  passive  conditions  of  the  brain. 
During  sleep,  there  is  diminished  excitability  of  the  whole  nervous  system,  which  is  only  partly  due 
to  the  fatigue  of  afferent  nerves,  but  is  largely  due  to  the  condition  of  the  central  nervous  system. 
During  sleep,  we  require  to  apply  strong  stimuli  to  produce  reflex  acts.     In  the  deepest  sleep  the 


736  HYPNOTISM. 

psychical  or  mental  processes  seem  to  be  completely  in  abeyance,  so  that  a  person  asleep  might  be 
compared  to  an  animal  with  its  cerebral  hemispheres  removed.  Toward  the  approach  of  the  period 
when  a  person  is  about  to  waken,  psychical  activity  may  manifest  itself  in  the  form  of  dreams, 
which  differ,  however,  from  normal  mental  processes.  They  con'^ist  either  of  impressions,  where 
there  is  no  objective  cause  (^hallucinations),  or  of  voluntary  impulses  which  are  not  executed,  or 
trains  of  thought  where  the  reasoning  and  judging  powers  are  disturbed.  Often,  especially  near 
the  time  of  waking,  the  actual  stimuli  may  so  act  as  to  give  rise  to  impressions  which  become  mixed 
with  the  thoughts  of  a  dream.  The  diminished  activity  of  the  heart  (iii  70,  3,  f),  the  respiration 
(g  127,  4),  the  gastric  and  intestinal  movements  (§  213,  4),  the  formation  of  heat  (^  216,  4),  and  the 
secretions  point  to  a  diminished  excitability  of  the  corresponding  nerve  centres,  and  the  diminished 
reflex  excitability  to  a  corresponding  condition  of  the  spinal  cord.  The  pupils  are  contracted  dur- 
ing sleep,  the  deeper  the  latter  is;  so  that  in  the  deepest  sleep  they  do  not  become  contracted  on 
the  apj)lication  of  light.  The  pupils  dilate  when  sensory  or  auditory  stimuli  are  applied,  and  the 
lighter  the  sleep,  the  more  is  this  the  case;  they  are  widest  at  the  moments  of  awaking  (^Plotke). 
[Huglilings  Jackson  fmds  that  the  retina  is  more  ancemic  than  in  the  waking  state.]  During  sleep, 
there  seems  to  be  a  condition  of  increased  action  of  certain  sphincter  muscles — those  for  contracting 
the  pupil  and  closing  the  eyelids  (Rosenbac/i).  The  soundness  of  the  sleep  may  be  determined  by 
the  intensity  of  the  sound  required  to  waken  a  person.  Kohlschiiiter  found  that  at  first  sleep 
deepens  verv  quickly,  then  more  slowly,  and  the  maximum  is  reached  after  cne  hour  (according  to 
Monninghoff  and  Preisbergen  after  i^^  hour);  it  then  rapidly  lightens,  until  several  hours  before 
waking  it  is  very  light.  External  or  internal  stimuli  may  suddenly  diminish  the  depth  of  the  sleep, 
but  this  may  be  followed  again  by  deep  sleep.  The  deeper  the  sleep,  the  longer  it  lasts.  [Durham 
asserts  that  the  brain  is  anremic,  that  the  arteries  and  veins  of  the  pia  mater  are  contracted  during 
sleep  and  the  brain  smaller ;  but  is  this  cause  or  effect  ?] 

The  cause  of  sleep  is  the  using  up  of  the  potential  energy,  especially  in  the  central  nervous 
system,  which  renders  a  restitution  of  energy  necessary.  Perhaps  the  accumulation  of  the  decompo- 
sition products  of  the  nervous  activity  may  also  act  as  producers  of  sleep  (  ?  lactates — Preyer.) 
Sleep  cannot  be  kept  up  for  above  a  certain  time,  nor  can  it  be  interrupted  voluntarily.  Many  nar- 
cotic-, rapidly  produce  sleep.  [The  "  diastolic  phase  of  cerebral  activity,"  as  sleep  has  been  called, 
is  largely  dependent  on  the  absence  of  stimuli.  We  must  suppose  that  there  are  two  factors,  one 
central,  represented  by  the  excitability  of  the  cerebrum,  which  will  vary  under  different  conditions, 
and  the  other  external,  represented  by  the  impulses  reaching  the  cerebrum  through  the  different 
sense  organs.  We  know  that  a  tendency  to  sleep  is  favored  by  removal  of  external  stimuli,  by  shut- 
ting the  eyes,  retiring  to  a  quiet  place,  etc.  The  external  sensory-  impressions,  indeed,  influence  the 
whole  metabolism.  Strumpell  describes  the  case  of  a  boy  whose  sensory  inlets  were  all  paralyzed 
except  one  eye  and  one  ear,  and  when  these  inlets  were  closed  the  boy  fell  asleep,  showing  how 
intimately  the  waking  condition  is  bound  up  with  sensory  afferent  impulses  reaching  the  cerebral 
centres.] 

[Hypnotics,  such  as  opium,  morphia,  KBr,  chloral,  are  drugs  which  induce  sleep.] 

Hypnotism,  or  Animal  Magnetism. — [Most  important  observations  on  this  subject  were  made 
by  Braid  of  Manchester,  whose  results  are  confirmed  by  many  of  the  recent  re-discoveries  of  Wein- 
hold,  Heidenhain,  and  others.]  Heidenhain  assumes  that  the  cause  of  this  condition  is  due  to  an 
inhibition  of  the  ganglionic  cells  of  the  cerebrum,  produced  by  continuous  feeble  stimulation  of  the 
face  (slightly  stroking  the  skin  or  electrical  applications),  or  of  the  optic  nerv'e  (as  by  gazing  steadily 
at  a  small  brilliant  object),  or  of  the  auditory  nerve  (by  uniform  sounds) ;  while  sudden  and  strong 
stimulation  of  the  same  nerves,  especially  blowing  upon  the  face,  abolishes  the  condition.  Berger 
attributes  great  importance  [as  did  Carpenter  and  Braid  long  ago]  to  the  psychological  factor,  whereby 
the  attention  was  directed  to  a  particular  part  of  the  body.  The  facility  with  which  different  per- 
sons becotne  hypnotic  varies  very  greatly.  When  the  hypnotic  condition  has  been  produced  a 
number  of  times,  its  subsequent  occurrence  is  facilitated,  <?.  g.,  by  merely  pressing  upon  the  brow,  by 
placing  the  body  passively  in  a  certain  position,  or  by  stroking  the  skin.  In  some  people  the  mere 
idea  of  the  condition  suffices.  A  hypnotized  person  is  no  longer  able  to  open  his  eyelids  when  they 
are  pressed  together.  This  is  followed  by  spasm  of  the  apparatus  for  accommodation  in  the  eye, 
the  range  of  accommodation  is  diminished,  and  there  may  be  deviation  of  the  position  of  the  eye- 
balls ;  then  follow  phenomena  of  stimulation  of  the  sympathetic  in  the  oblongata  ;  dilatation  of  the 
fissure  of  the  eyelids  and  the  pupil,  exophthalmos,  and  increase  of  the  respiration  and  pulse.  At  a 
certain  stage,  there  may  be  a  great  increase  in  the  sensitiveness  of  the  functions  of  the  sense-organs, 
and  also  of  the  muscular  sensibility.  Afterward  there  may  be  analgesia  of  the  part  stroked,  and 
loss  of  taste ;  the  sense  of  temperature  is  lost  less  rapidly,  and  still  later  that  of  sight,  of  smell,  and 
of  hearing.  Owing  to  the  abolition  or  suspension  of  consciousness,  stimuli  applied  to  the  sense 
organs  do  not  produce  conscious  impressions  or  perceptions.  But  stimuli  applied  to  the  sense  organs 
of  a  hypnotized  person  cause  movements,  which,  however,  are  unconscious,  although  they  stimulate 
voluntary  acts.  In  persons  with  greatly  increased  reflex  excitability,  voluntary  movements  may 
excite  reflex  spasms;  the  person  may  be  unable  to  coordinate  his  organs  for  speech. 

Types. — According  to  Griitzner,  there  are  several  forms  of  hypnotism:  (l)  Passive  sleep,  where 
words  are  still  understood,  which  occurs  especially  in  girls;  (2)  owing  to  the  increased  reflex  excita- 


STRUCTURE  OF  THE  CEREBRUM.  737 

bility  of  the  striped  muscles,  certain  groups  of  muscles  may  be  contracted — a  condition  which  may 
last  for  days,  especially  in  strong  people;  at  the  same  time  ataxia  may  occur,  and  the  muscles  may 
fail  to  perform  their  functions  (artificial  katalepsy).  During  the  stage  of  lethargy  in  hysterical 
persons,  the  tendon  reflexes  are  absent  often  (^Charcot  and  Richer) ;  (3)  autonomy  at  call,  i.  e.,  the 
hypnotized  person — in  most  cases  the  consciousness  is  still  retained — obeys  a  command,  in  his  con- 
dition of  light  sleep.  When  the  hand  is  grasped  or  the  head  stroked,  he  executes  involuntary  move- 
ments— runs  about,  dances,  rides  on  a  stool,  and  the  like;  (i,)  hallucinations  occur  only  in  some 
individuals  when  they  waken  from  a  deep  sleep,  the  hallucinations  (usually  consisting  of  the  sensa- 
tion of  sparks  of  fire  or  odors)  being  very  strong  and  well  pronounced;  (5)  imitation  is  rare,  ordi- 
nary movements,  such  as  walking,  are  easily  imitated,  the  finer  movements  o'ccur  rarely.  The 
"  echo  speech  "  is  produced  by  pressure  upon  the  neck,  speaking  into  the  throat,  or  against  the 
abdomen.  Pressure  over  the  right  eyebrow  often  ushers  in  the  speech.  Color  sensation  is  sus- 
pended by  placing  the  warm  hand  on  the  eye,  or  by  stroking  the  opposite  side  of  the  head  (Cohti). 
Stroking  the  limbs  in  the  reverse  direction  gradually  removes  the  rigidity  of  the  limbs  and  causes 
the  person  to  waken.  Blowing  on  a  part  does  so  at  once.  Insane  persons  can  be  hypnotized.  Dis- 
agreeable results  follow  only  when  the  condition  is  induced  too  often  and  too  continuously. 

Hypnotism  in  Animals. — A  hen  remains  in  a  fixed  position  when  an  object  is  suddenly  placed 
before  its  eyes,  or  when  a  straw  is  placed  over  its  beak,  or  when  the  head  of  the  animal  is  pressed 
on  the  ground  and  a  chalk  line  made  before  its  beak  (Kircher's  experimentum  mirabile,  1644). 
[Langley  has  hypnotized  a  crocodile.]  Birds,  rabbits  and  frogs  remain  passive  for  a  time  after  they 
have  been  gently  stroked  on  the  back.     Crayfish  stand  on  their  head  and  claws  [Czermak). 

375.  STRUCTURE  OF  THE  CEREBRUM— MOTOR  CORTICAL  CENTRES.— 
[Cerebral  Convolution. — A  vertical  section  of  a  cerebral  convolution  consists  of  a  thin  layer  of 
gray  matter  externally  enclosing  a  white  core  (Fig.  478).  The  cortex  consists  of  cells  and  fibres 
embedded  in  a  matrix,  and  to  the  nerve  cells  nerve  fibres  proceed  from  the  white  matter.  The 
nerve  cells  of  the  cortex  vary  in  size,  form  and  distribution  in  the  different  layers  and  also  in  different 
convolutions.  Taking  such  a  convolution  as  the  ascending  frontal  or  motor  area  type,  we  get  the 
appearances  shown  in  Fig.  474.  It  is  covered  on  its  surface  by  the  pia  mater,  (i)  The  most 
superficial  layer  is  narrow,  and  consists  of  much  neuroglia,  a  network  of  branched  nerve  fibrils,  a 
few  scattered  small  multipolar  nerve  cells,  and  a  layer  of  very  small  medullated  nerve  fibres;  (2)  a 
layer  of  close-set,  small,  angtclar,  or  short,  pyramidal  nerve  cells  ;  (3)  the  thickest  layer  or  forma- 
tion of  the  cornu  ammonis,  consisting  of  many  layers  of  la7-ger  pyramidal  cells,  which  are  larger  in 
the  deeper  than  in  the  more  superficial  layers.  They  are  not  so  closely  packed  together,  as  many 
granules  lie  between  them.  At  the  lowest  part  of  this  layer  the  cells  are  larger  than  elsewhere, 
presenting  some  resemblance  to  the  cells  of  the  anterior  cornu  of  the  gray  matter  of  the  spinal  cord. 
By  some  it  is  described  as  a  special  layer,  and  termed  the  ganglio7t-cell  layer.  This  layer  is 
specially  well  marked  in  those  convolutions  which  are  described  as  containing  motor  centres. 
Among  the  large  cells  are  a  few  small  angular-looking  cells,  which  become  more  numerous  lower 
down,  and  from  (4)  a  narrow  layer  of  numerous  small,  branched,  irregular,  ganglionic  cells — the 
'■^granular  formation  "  of  Meynert.  In  the  motor  areas  mixed  with  these  are  large  pyramidal 
cells,  disposed  in  groups  called  "cell  clusters."  (5)  A  layer  of  s^pindle-shzTptA  fusiform  branched 
cells — the  claustral  formation  of  Meynert — lying  for  the  most  part  parallel  to  the  surface  of  the 
convolution.  No  layer  is  composed  exclusively  of  one  form  of  cell.  The  above  represents  the 
motor  type.  Then  follows  the  white  matter  (w),  consisting  of  medullated  nerve  fibres,  which  run 
in  groups  into  the  gray  matter,  where  they  lose  their  myelin.  The  fibres  are  somewhat  smaller 
than  in  the  other  parts  of  the  nervous  system  (diameter  xoVo  i^ch),  and  between  them  lie  a  few 
nuclear  elements.] 

[In  the  sensory  type,  as  in  the  occipital  lobe  (Fig.  475),  the  first  and  second  layers  are  not  unlike 
the  corresponding  layers  in  the  motor  type,  and  the  fusiform  cells  in  the  seventh  layer  also  resemble 
the  latter.  The  layer  of  pyramidal  cells  (3)  is  not  so  large,  while  its  deeper  part,  sometimes  called 
the  "  ganglion-cell-iayer,"  contains  no  large  cells.  (5)  Between  the  two  is  (4)  a  layer  with  numerous 
angular  granule-like  bodies  or  cells,  called  the  "  granule  layer."] 

[The  hippocampus  major  contains,  besides  a  layer  of  neurolgia  and  some  white  matter  on  the 
surface,  a  regular  series  of  pyramidal  cells,  which  give  it  a  characteristic  appearance.  This  is  the 
part  which  varies  most.  It  is  to  be  remembered  that  the  transition  from  one  type  to  the  other  takes 
place  gradually.] 

[Pyramidal  Cells  of  the  Cortex. — Each  cell  is  more  or  less  pyramidal  in  shape,  giving  off 
several  processes — (a)  an  apical  process,  which  is  often  very  long,  and  runs  toward  the  surface  of 
the  cerebrum,  where  it  is  said  to  terminate  in  an  ovoid  corpuscle,  closely  resembling  those  in  which 
the  ultimate  branches  of  Purkinje's  cells  of  the  cerebellum  end  ;  [b)  the  unbranched  median  basilar 
process,  which  is  an  axial  cylinder  process,  and  becomes  continuous  with  the  axial  cylinder  of 
a  nerve  fibre  of  the  white  matter.  It  ultimately  becomes  invested  by  myelin,  [c)  The  lateral 
processes  are  given  off  chiefly  near  the  base  of  the  cell,  and  they  soon  branch  to  form  part  of  the 
ground  plexus  of  fibrils  which  everywhere  pervades  the  gray  matter.] 

Each  cell  is  surrounded  by  a  lymph  space,  and  so  are  the  blood  vessels,  in  the  latter  case 
forming  a  perivascular  space,  which  communicates  with  the  pericellular  lymph  space,  as  in  Fig.  476' 

47 


Fic.  474. 


mm 

m 


Cortex  of  motor  area  of  brain  ot 
monkey  (X  150)-  ',  super- 
ficial layer  ;  2,  small  angular 
cells  ;  3,  pyramidal  cells  ;  4, 
ganglionic  cells  and  cell  clus- 
ters ;  5,  fusiform  cells  (Fer- 
rier,  after  Bevan  Leivis). 


Fig.   475. 


Fig.  476. 


kMi 


)i 


^ 


>2 


3 


/4 


^wi/*f* 


A* 


Cortex  of  occipital  lobe,  i,  super- 
ficial layer;  2,  small  angular 
cells  ;  3,  5,  pyramidal  cells ;  4, 
granule  layer ;  6,  granules  and 
ganglionic  layer ;  7,  spindle 
cells.  {Ferrier,  after  Bevan 
Leiois.) 

738 


Perivascular    and    1  :  >  in  jj  h 

spaces,  a,  capill.iry  wjili  .i  lymph 
space  communicating  with  the  peri- 
cellular lymph  space  b,  round  the 
cell  a  lymph  space  c,  containing  two 
lymph  corpuscles.  X  150. 


Fig.  477. 


Vertical  section  of  a  frontal  con- 
volution (Weigert's  method) 
X  50.  P.  pia  mater;  1-5,  five 
layers  of  ^leynert;  a,  super- 
ficial layer  of  connective  tissue; 
b,  i,  successive  layers  of  medul- 
lated  nerve  fibres;  /t,  white 
matter. 


BLOOD    VESSELS    OF   THE    CEREBRUM. 


739 


[Nerve  Fibres  in  the  Cortex. — The  ordinary  methods  of  hardening  the  brain  do  not  enable 
us  to  detect  the  enormous  number  of  medullated  nerve  fibres  in  the  gray  matter.  By  using 
Exner's  osmic  acid  method,  or  Weigert's  or  Pal's  method,  we  obtain  such  a  result  as  is  shown  in 
Fig.  477.  Under  the  pia  (P)  is  a  layer  of  connective  tissue  («)  devoid  of  nerve  fibres.  Beneath 
it  is  a  layer  ((^)  occupying  about  the  half  of  the  outer  layer,  which  is  almost  entirely  taken  up  by 
medullated  nerve  fibres;  most  of  these  are  fine,  but  a  few  of  them  are  coarse,  and  run  parallel  to  the 
surface  and  tangential  to  the  arc  of  the  outer  contour  of  the  convolution.  Internal  to  this  is  a  layer 
of  medullated  fibres  (<:),  which  cross  each  other  in  various  directions;  while  a  similar  network  [d) 
occurs  in  the  small-celled  layer.  (2)  In  the  layer  of  large  pyramidal  cells  (3)  there  are  bundles 
of  medullated  fibres,  running  radially  (^e) ;  but  at  the  lower  part  of  this  layer  there  is  a  very  dense 
network  (/),  ft^rming  (in  a  Weigert's  preparation")  a  dense,  dark  band,  corresponding  to  the  outer 
layer  of  Baillanger.  In  the  layers  marked  {^g  and  h),  which  are  partly  in  the  third  and  partly  in  the 
fourth  cortical  layer,  the  radial  arrangement  is  more  marked  and  more  compact,  and  the  thick  fibres 
are  more  numerous.  In  the  middle  is  {h)  a  narrow,  dense  network  corresponding  to  Baillanger's 
inner  layer.  The  lower  part  of  the  fourth  layer,  and  the  whole  of  the  fifth,  are  occupied  by  i.  It 
is  to  be  remembered  that  all  the  convolutions  do  not  present  exactly  the  same  structure  and 
arrangement  [Obersteinei-).'] 

[Variations. — The  gray  matter  diifers  in  different  parts  of  the  brain.  In  the  gray  matter  of  the 
cornu  ammonis,  the  large  pyramidal  cells  of  (3)  make  up  the  chief  mass ;  in  the  claustrum  (4)  is 
most  abundant.  In  the  central  convolutions  (ascending  frontal  and  parietal),  according  to  Betz, 
Mierzejewski,  and  Bevan  Lewis,  very  large  pyramidal  cells  are  found  in  the  lower  part  of  the  third 
layer.  Similar  cells  have  been  found  in  the  posterior  extremities  of  the  frontal  convolutions  in  some 
animals — the  posterior  parietal  lobule,  and  para-central  lobule,  all  of  which  have  motor  functions. 
In  those  convolutions  which  are  regarded  as  subserving  sensory  functions,  a  somewhat  different 
type  prevails,  e.g.,  the  occipital  gyri  or  annectant  convolution  [B.  Lezvis).  The  very  large  pyra- 
midal cells  are  absent,  while  the  granule  layer  exists  as  a  well-marked  layer  between  the  layer  of 
large  pvramidal  cells  and  the  ganglion  cell  layer  (Fig.  475).] 

[Fuchs  finds  that  there  are  no  medullated  fibres  either  in  the  cortex  or  medulla  until  the  end  of 
the  first  month  of  life.  The  medullated  fibres  appear  in  the  uppermost  layer  at  the  fifth  month, 
and  in  the   second   at  the  end  of  the 

first  year,  the   radial  bundles   in   the  y\g  478 

deeper  layers  at  the  second  month. 
The  medullated  fibres  increase  until 
the  seventh  or  eighth  year,  when  they 
have  the  same  arrangement  as  in  the 
adult.] 

[Blood  Vessels. — The  adventitia 
of  the  small  cerebral  vessels  contains 
pigment  and  granular  cells,  filled  with 
oil  granules.  In  the  newborn  child 
the  bloodvessels  of  the  brain  are  beset 
with  cells,  filled  with  fatty  granules. 
Perhaps  the  gi-anules  supply  part  of 
the  material  for  the  formation  of  the 
myelin  sheath  on  the  nerve  fibres. 
About  the  fifth  year  the  fat  is  repla'^ed 
by  a  yellow  pigment.  In  adults,  yellow 
or  brown  glancing  pigment  granules 
are  found  i'l  the  adventitia  of  the 
arteries.  In  the  adventitia  of  the  veins 
there  is  no  pigment,  but  generally  some 
fat.  The  gray  matter  is  much  more 
vascular  than  the  white,  and  when 
injected,  a  section  of  a  convolution  pre- 
sents the  appearance  shown  in  Fig.  478. 
The  nutritive  arteries  consist  of  \a) 
the  long  medullary  arteries  (i)  which 
pass  from  the  pia  mater  through  the 
gray  matter  into  the  central  white  matter 
or  centrum  ovale.  They  are  terminal 
arteries,  and  do  not  communicate  with 
each  other  in  their  course;  thus,  they 
supply  independent  vascular  areas  ;  nor 
do  they  anastomose  with  any  of  the 
arteries  derived  from  the  ganglionic  system  of  blood  vessels;  12  to  15  of  them  are  seen  in  a  section 
of  a  convolution,  (b')  The  short  cortical  nutritive  articles  (2)  are  smaller  and  shorter  than  the 
foregoing.     Although  some  of  them  enter  the  white  matter,  they  chiefly  supply  the  cortex,  where 


medullary  arter  es  ;  and  i',  i",  in  groups  between  the  convolu- 
tions, 2,  2,  arteries  of  the  cortex  cerebri;  a,  large-meshed  plexus 
in  first  layer;  b,  closer  plexus  in  middle  layer;  c,  opener  plexus 
in  the  gray  matter  next  the  white  substance,  with  its  vessels  {d). 


740 


CONVOLUTIONS  OF  THE  CEREBRUM. 


they  form   an  open-meshed  plexus  in  the  first  layer  (a),  while  in   the   next  layer  (/;)  the  plexus 
of  capillaries  is  dense,  the  plexus  again  being  wider  in  the  inner  layers  (c).] 

[Central  or  Ganglionic  Arteries. — From  the  trunks  constituting  the  circle  of  Willis  (Fig.  in 
<S  381),  branches  are  given  otT,  which  pass  upward  an<l  cuter  the  brain  to  supply  the  basal  ganglia 
with  blood,  ihey  are  arranged  in  several  groups, but  they  are  all  terminal,  each  one  supplying  its 
own  area,  nor  do  tliey  anastomose  with  the  arteries  of  the  cortex.] 

Cerebral  Arteries. — From  a  practical  jioint  of  view,  the  distribution  of  the  blood  vessels  of  the 
brain  is  important.  The  artery  of  the  Sylvian  fissure  supplies  the  motor  areas  of  the  brain  in  animals; 
in  man,  the  precentral  lobule  is  supplied  by  a  branch  of  the  anterior  cerebral  artery  {Ditret). 
The  region  of  the  third  left  frontal  convolution,  which  is  connected  with  the  function  of  speech,  is 
supplied  by  a  special  branch  of  the  Sylvian  artery.  Those  areas  of  the  frontal  lobes  whose  injury 
results  in  disturbance  of  the  intelligence,  are  supplied  by  the  anterior  cerebral  artery.  Those  regions 
of  the  cortex  cerebri,  whose  injur)",  according  to  Ferrier,  causes  hemianesthesia,  are  supplied  by  the 
posterior  cerebral   artery. 

Fig.  479. 


Left  side  of  the  human  brain  (diagrammatic).  F,  frontal ;  P,  parietal;  (J,  occipital :  T,  temporo-sphenoidal  lobe  ; 
S,  fissure  of  Sylvius  ;  S',  horizontal,  S",  ascending  ramus  of  S  ;  c,  sulcus  centralis,  or  fissure  of  Rolando  ;  A, 
ascending  frontal,  and  15,  ascending  parietal  convolution  ;  F],  superior,  Fo,  middle,  and  F3,  inferior  frontal  convo- 
lutions ;  yi,  superior,  and  /n.  inferior  frontal  fissures  ;  /^,  sulcus  praecentralis  ;  P,  superior  parietal  lobule  ;  Pj, 
inferior  parietal  lobule,  consisting  of  Po,  supra-marginal  gyrus,  and  Pj',  angular  gyrus  ;  ip,  sulcus  interparietalis  ; 
cm,  termination  of  calloso-marginal  fissure;  Oi,  first,  Oo,  second,  Os,  third  occipital  convolutions;  /lo,  parietal- 
occipital  fissure;  o,  transverse  occipital  fissure;  oo,  inferior  longitudinal  occipital  fissure;  Tj,  first,  To,  second, 
T3,  third  temporo-sphenoidal  convolutions  ;  t^,  first,  t«,  second  temporo-sphenoidal  fissures. 

[In  connection  with  the  localization  of  the  centres  in  the  cortex,  it  is  important  to  be  thoroughly 
acquainted  with  the  arrangement  of  the  cerebral  convolutions.  Each  half  of  the  outer  cerebral 
surface  is  divided  by  certain  fissures  into  five  lobes — frontal,  parietal,  occipital,  temporo- 
sphenoidal,  and  central,  or  island  of  Reil  (Fig.  4811.  The  frontal  lobe  (Fig.  479)  consists  of 
three  convolutions,  with  numerous  secondary  folds  running  nearly  horizontal,  named  superior  (F,), 
middle  (Fj),  and  inferior  (F.j)  frontal  convolutions.  Behind  these  is  a  large  convolution,  the 
ascending  frontal  (A),  which  ascends  almost  vertically,  immediately  behind  these — separated  from 
them,  however,  by  the  precentral  fissure  (/■,),  and  mapped  off  behind  by  the  fissure  of  Rolando,  or 
the  central  sulcus  {c).'] 

[The  parietal  lobe  (Fig.  479,  P)  is  limited  in  front  by  the  fissure  of  Rolando,  below  in  part  by 
the  Sylvian  fissure,  and  behind  by  the  parieto-occipital  fissure.  It  consists  of  the  ascending  parietal 
(posterior  central)  convolution  (Fig.  479,  B),  which  ascends  just  behind  the  fissure  of  Rolando,  and 
parallel  to  the  ascending  frontal,  with  which  it  is  continuous  below ;  above,  it  becomes  continuous 


CONVOLUTIONS    OF    THE    CEREBRUM. 


741 


with  the  superior  parietal  lobule  (Pi),  while  the  latter  is  separated  from  the  inferior  parietal  lobule 
("//?  courbe")  by  the  inter-parietal  sulcus.  The  inferior  parietal  lobule  consists  of  [a)  a  part  arching 
over  the  upper  end  of  the  Sylvian  fissure,  the  supra-marginal  convolution  (Pj),  which  is  continuous 
with  the  superior  temporo-sphenoidal  convolution.  Behind  is  [b)  the  angular  gyrus  (P,^),  which 
arches  round  the  posterior  end  of  the  parallel  fissure,  and  becomes  connected  with  the  middle 
temporo-sphenoidal  convolution.] 

[The  temporo-sphenoidal  or  temporal  lobe  (Fig.  479,  T)  consists  of  three  horizontal  convo- 
lutions— superior,  middle,  and  inferior — the  two  former  being  separated  by  the  parallel  sulcus,  while 
the  whole  lobe  is  mapped  off  from  the  frontal  by  the  Sylvian  fissure  (S).] 

[The  occipital  lobe  (Fig.  479,  O)  is  small,  forms  the  rounded  posterior  end  of  the  cerebrum,  and 
is  separated  fi^om  the  parietal  lobe  by  the  parieto-occipital  fissure,  which  fissure  is  bridged  over  at 
the  lower  part  by  the  four  annectant  gyri  {pits  de passage  of  Gratiolet).  It  has  three  convolutions — 
superior  (Oj),  middle  (Oj),  and  inferior  (O3) — on  its  outer  surface.] 

[The  central  lobe  or  island  of  Rail,  consists  of  five  or  six  short,  straight  convolutions  (gyri 
operti — Fig.  481),  radiating  outward  and  backward  from  near  the  anterior  perforated  spot,  and  can 
only  be  seen  when  the  margins  of  the  Sylvian  fissure  are  pulled  asunder.  The  operculum,  con- 
sisting of  the  extremities  of  the  inferior  frontal,  ascending  parietal,  and  firontal  convolutions,  lie  outside 
it,  cover  it,  and  conceal  it  from  view.] 

Fig.  480. 


Median  aspect  of  the  right  hemisphere.  CC,  corpus  callosum  divided  longitudinally;  Gf,  gyrus  fornicatus  ;  H, 
gyrus  hippocampi;  k,  sulcus  hippocampi;  U,  uncinate  gyrus;  cm,  calloso-marginal  fissure;  F,  first  frontal 
convolution  ;  c,  terminal  portion  of  fissure  of  Rolando  ;  A,  ascending  frontal;  B,  ascending  parietal  convolution 
and  paracentral  lobule  ;  P^',  precuneus  or  quadrate  lobule  ;  Oz,  cuneus;  Po,  parieto-occipital  fissure  ;  oi,  trans- 
verse occipital  fissure;  oc,  calcarine  fissure  ;  oc' ,  superior,  oc" ,  inferior  ramus  of  the  same  ;  D,  gyrus  descendens  ; 
T4,  gyrus  occipito-temporalis  lateralis  (lobulus  fusiformis) ;  T5,  gyrus  occipito-temporalis  medialis  (lobulus 
lingualis). 

[On  the  inner  or  mesial  surface  of  the  cerebrum  are — the  gyrus  fornicatus  (Fig.  480,  Gf),  or 
convolution  of  the  corpus  callosum,  which  runs  parallel  to  and  bends  round  the  anterior  and  posterior 
extremities  of  the  corpus  callosum,  terminating  posteriorly  in  the  gyrus  uncinatus  or  gyrus  hippocampi 
(Fig.  480,  H),  and  ending  anteriorly  in  a  crooked  extremity,  the  subiculum  cornu  ammonis  (Fig. 
480,  U).  Above  it  is  the  calloso-marginal  fissure  (Fig.  480,  cm),  and  running  parallel  to  it  is  the 
marginal  convolution  (Fig.  480),  which  lies  between  the  latter  fissure  and  the  margin  of  the 
longitudinal  fissure;  it  is,  however,  merely  the  mesial  aspect  of  the  frontal  and  parietal  convolutions. 
The  quadrate  lobule  or  praecuneus  lies  (Fig.  480,  Pi),  between  the  posterior  extremity  of  the 
calloso-marginal  fissure  and  the  parieto-occipital  fissure ;  it  is  merely  the  mesial  aspect  of  the  ascending 
parietal  convolution.  The  parieto-occipital  fissure  terminates  below  in  the  calcarine  fissure  (Fig. 
480,  oc),  and  the  latter  runs  backward  in  the  occipital  lobe  dividing  it  into  two  branches,  oc^ ,  oc'^. 
Between  the  parieto-occipital  and  calcarine  fissures  lies  the  wedge-shaped  lobule  termed  the  cuneus 
(Fig.  480,  Oz).  The  calcarine  fissure  indicates  on  the  surface  the  position  of  the  calcar  avis  or 
hippocampus  minor,  in  the  posterior  cornu  of  the  lateral  ventricle.  The  dentate  fissure  or 
sulczis  kippocafHpi  (Fig.  480,  h)  marks  the  position  of  the  elevation  of  the  hippocampus  major,  or 
cornu  ammonis,  in  the  lateral  ventricle.  The  temporo-sphenoidal  lobe  terminates  anteriorly  in 
the  uncinate  gyrus,  while,  running  along  the  former  and  the  occipital  lobes,  is  the  collateral 
fissure  (occipito-temporal  sulcus),  which  marks  the  position  of  the  eminentia  collateralis  in  the 


742 


CONDITIONS   AFFECTING   THE    MOTOR   CENTRES. 


Fig.  481. 


descending  cornu  of  the  lateral   ventricle,  while   it   also  separates  the  superior  from  the  inferior 
lemporo- occipital  convolutions  (T,  and  T^).] 

Motor  Centres. — In  1870  Fritsch  and  Hitzig  discovered  a  series  of  circum- 
scribed regions  on  tlie  surface  of  the  cerebral  convolutions,  whose  stimulation  by- 
means  of  electricity  causes  coordinated  tnovemetits  in  quite  distinct  groups  of 
muscles  of  the  opposite  side  of  the  body  (Fig.  483,  I,  II). 

Methods — Stimulation. — The  surface  of  the  cerebrum  is  exposed  in  an  animal  (dog,  monkey) 
by  removing  a  part  of  ihe  skull  covering  the  so-called  motor  convolutions  and  dividing  the  dura 
mater.  When  the  convolutions  are  fully  exposed,  a  pair  of  blunt  nonpolarizable  (^  328)  needle 
electrodes  are  applied,  near  each  other,  to  various  parts  of  the  cerebral  surface.  We  may  employ  the 
closing  or  opening  shock  of  a  constant  current,  or  the  constant  current  may  be  rapidly  interrupted, 
the  current  being  of  such  a  strength  as  to  be  distinctly  perceived  when  it  is  applied  to  the  tip  of  the 
tongue  [Fritsch  and  Ni(zii^).  Or,  the  induced  current  may  be  used,  also  of  such  a  strength  that 
it  is  readily  felt  when  applied  to  the  tip  of  the  tongue  [Ferrier,  1873).  ^  he  cerebrum  is  completely 
insensible  to  severe  operations  made  upon  it. 

The  areas  of  the  cerebral  cortex  whose  stimulation  discharges  the  characteristic 
movements,  are  regarded  by  some  as  actual  centres,  because  the  reaction  time  after 
stimulation  of  the  centres  and  the  duration  of  the  muscular  contraction  are  longer 
than  when  the  sub-cortical  fibres  which  lead  toward  the  deeper  parts  of  the  brain 
are  stimulated.  Another  circumstance  favoring  this  view  is,  that  the  excitability 
of  these  areas  is  influenced  by  the  stimulation  of  afferent  nerves  {Bubnoff  and 
Heidenhain).  It  may  be  that  these  centres  are  acted  upon  by  voluntary  impulses 
in  the  execution  of  voluntary  movements.  Hence,  they  have  been  called  ^^psy- 
chomotor centres,''  [At  any  rate,  the.se  areas  have  a  definite  relation  to  certain 
motor  acts,  and  perhaps  it  is  well  to  speak  of  them  as  "areas  of  representation" 

of  the  function  to  which  they  are  related.] 
The  motor  areas  of  the  cerebrum  (dog,  cat, 
sheep)  are  characterized  by  the  presence  of 
specially  large  pyramidal  cells  {Betz,  Merze- 
jewsky,  Bevan  Leiois)  ;  while  similar  cells 
were  found  by  Obersteiner  in  the  areas  marked 
4  and  8  (Fig.  483),  and  Betz  found  them  in 
the  ascending  frontal  convolution  of  man,  in 
the  third  frontal  convolution,  and  in  the  island 
of  Reil.  O.  Soltmann  found  that  stimulation 
of  the  motor  areas  in  newly-born  animals 
is  without  result,  while  only  the  deeper  fibres 
of  the  corona  radiata  are  excitable. 

Modifying  Conditions. — In  the  condition  of  deep 
narcosis  produced  by  chloroform,  ether,  chloral,  morphia, 
or  in  apncea,  the  excitability  of  the  centres  is  abolished 
{Schiff),  while  the  sub-cortical  conducting  paths  still 
retain  their  excitability  (Bubnoff  and  Heidenhain). 
Small  doses  of  these  poisons  and  also  of  atropin  at  first 
increase  the  excitability  of  the  centres.  Moderate  loss 
of  blood  excites  them,  while  a  great  loss  of  blood  dimin- 
ishes and  then  abolishes  the  excitability  ( Munk  and 
Orschansky).  Slight  inflammation  increases,  while 
cooling  diminishes,  the  excitability.  If  the  cortex 
cerebri  be  removed  in  animals,  the  excitability  of  the 
fibres  of  the  corona  radiata  is  completely  abolished 
about  the  fourth  day,  just  as  in  the  case  of  a  peripheral 
nerve  separated  from  its  centre  {Atbertoni,  Dupuy, 
Franc  k  and  Pit  res). 

Stimulation  of  Sub-cortical  Parts. — As  the  fibres 
of  the  corona  radiata  converge  toward  the  centre  of  the 
hemisphere,  it  is  evident  that,  after  removal  of  the  cor- 
tex, stimulation  of  these  fibres  in  the  deeper  parts  of  the 
hemisphere  is  followed  by  the  same  mo'or  results  [Gliky 
and  Eckhard).     The  stimulus  is  applied  merely  to  a 


Orbital  surface  of  the  left  frontal  lobe  and  the 
island  of  Reil,  the  tip  of  the  temporo-sphe- 
noidal  lobe  removed  to  show  the  latter.  17, 
convolution  of  the  margin  of  the  longitudinal 
fissure  ;  O,  olfactory  fissure,  with  the  olfactory 
lobe  removed  ;  TR,  tri-radiate  fissure  ;  1"  and 
1'",  convolutions  on  the  orbital  surface;  i,  i, 
I,  I,  under  surface  of  the  infero-frontal  convo- 
lution ;  4,  under  surface  of  the  ascending 
frontal,  and,  5,  of  the  ascending  parietal  convo- 
lutions;   C,  central  lobe  or  island. 


CONDITIONS    AFFECTING    THE    MOTOR    CENTRES. 


743 


deeper  part  of  the  motor  path.  If  the  stimulus  be  applied  to  parts  situated  still  more  deeply,  as  for 
example  to  the  hiternal  capsule,  general  contraction  of  the  muscles  on  the  opposite  side  is  the  result. 
Time  Relations  of  the  Stimulation. — According  to  Franck  and  Pitres,  the  time  which 
elapses  between  the  moment  of  stimulation  of  the  cortex  and  the  resulting  movement,  after  deducting 
the  period  of  latent  stimulation  for  the  muscles,  and  the  time  necessary  for  the  conduction  of  the 
impulse  through  the  cord  and  nerves  of  the  extremities,  is  0.045  second.  Heidenhain  and  Bubnoff 
found  that,  during  moderate  morphia  narcosis,  when  the  stimulating  current  was  increased  in 
strength,  the  muscular  contraction  and  the  reaction  time  became  shorter.  After  removal  of  the 
cortex,  the  occurrence  of  the  muscular  contraction  from  the  moment  of  stimulation  of  the  white 
matter  is  diminished  3^  to  j^.  The  form  of  the  muscular  contraction  is  longer  and  more  extended 
when  the  cortex,  than  when  the  sub-cortical  paths,  are  stimulated.  If  the  animal  (dog)  be  in  a  state 
of  high  reflex  excitability,  these  differences  disappear;  in  both  cases  the  contraction  follows  very 
rapidly  (^Bubnoff  and  Heidenhain).     If  the  stimulus  be  very  strong  the  muscles  of  the  same  side 


Fig.  482. 


View  of  the  brain  from  above  (semi-diagrammatic).     Si,  end  of  ramus  of  the  Sylvian  fissure. 

refer  to  the  same  parts  as  in  Fig.  479. 


The  other  letters 


may  contract,  but  somewhat  later  than  those  of  the  opposite  side.     If  the  motor  areas  for  the  fore 
and  hind  limbs  be  stimulated  simultaneously,  the  latter  contract  somewhat  after  the  former. 

Number  of  Stimuli. — If  40  stimuli  per  second  be  applied  to  a  motor  area,  then  the  corre- 
sponding muscles  yield  40  single  contractions  ;  while  with  46  single  stimuli  per  second  there  results 
a  continued  complete  contraction  [Franck  and  Pitres).  In  one  and  the  same  animal,  the  same  nuvi- 
ber  of  stimtili  is  required  to  produce  a  continuous  contraction,  whether  the  cortical  centre,  the  motor 
nerve,  or  even  the  muscle  itself  be  stimulated.  With  very  feeble  stimuli,  summation  of  stimuli 
takes  place,  for  the  muscular  contraction  only  begins  after  several  ineffective  stimuli  have  been 
applied.  [It  is  generally  held  that  the  rhythm  of  a  contracting  muscle  is  the  same  as  the  rhythm  of 
the  stimuli  applied  to  its  motor  nerve,  but  Schafer  and  Horsley  contend  that  this  holds  good  for  rates 
of  stimuU  to  about  10  or  12  per  second.  They  find  that  the  same  is  true  for  the  cortex  cerebri, 
corona  radiata,  and  medulla  spinalis,  viz.,  that  the  muscular  response  does  not  vary  with  the  rhythm 


744  POSITION    OF   THE    MOTOR    CENTRES    IN    THE    DOG. 

(/.^.,  number  of  stimuli  per  sec),  but  that  the  rhythm  is  constant — about  lo  per  sec. — and  inde- 
pendent of  the  number  of  stimuli  per  sec,  provided  they  are  above  lO  per  sec.  ap])lie(l  to  these 
parts.  Indeed,  all  voluntary  contractions  show  a  similar  rate  of  undulation  in  the  muscle  curve. 
Perhaps  the  rhythm  of  the  eflerent  impulses  is  modified  in  the  motor  nerve  cells  of  the  spinal  cord. 

[The  matter,  as  regards  electrical  stimulation  of  the  cortex  cerebri,  resolves  itself 
into  this,  that  stimulation  of  certain  cortical  areas  always  causes  contraction  in 
definite  muscles  or  groups  of  muscles,  resulting  in  definite  coordinated  movements 
on  the  opposite  side  of  the  body;  the  areas  have  been  called  "  motor  areas." 
They  have  been  mapped  out  and  ascertained  in  a  large  number  of  animals,  and 
the  question  comes  to  be,  Are  there  similar  areas  in  man  ?] 

Primary  Fissures  and  Convolutions  of  the  Dog's  Brain. — The /('.t/V/om  of  the  motor  centres 
in  the  dog's  brain  is  indicated  in  Fig.  4S3,  I  and  II.  The  dog's  brain  is  marked  by  two  "  primary 
fissures,"  viz.,  the  sulcus  cruciatus  (S),  which  intersects  the  longitudinal  fissure  at  a  right  angle  at 
the  junction  of  its  anterior  with  its  middle  third.  This  fissure  has  been  called  the  sulcus  frontalis,  or 
the  fissura  coronalis.  The  second  primary  fissure  is  the  fossa  Sylvii  (F).  Four  "  primary  con- 
volutions," in  addition,  are  arranged  with  reference  to  these  primary  fissures.  The  first  primary 
convolution  (I),  in  the  form  of  a  sharply  curved  knee,  embraces  the  fossa  Sylvii  (F).  The  second 
convolution  (II)  runs  nearly  parallel  to  the  first.  The  fourth  primary  convolution  (IV)  bounds  the 
longitudinal  fissure,  and  is  separated  from  its  fellow  of  tiie  opposite  side  by  the  falx  cerebri  ;  anteriorly 
it  embraces  the  sulcus  cruciatus  (.S),  so  that  it  is  divided  into  two  parts,  by  this  sulcus,  a  part,  the  gyrus 
preecruciatus  or  proefrontalis,  lying  in  front  of  the  sulcus,  and  the  gynrs  postcruciatus  (postfrontalis) 
lying  behind  it.  The  third  primary  convolution  (III)  runs  parallel  to  the  fourth.  Some  authors 
count  the  convolutions  from  the  longitudinal  fissure  outward.  In  Fig.  483,1  and  II,  the  motor 
areas  or  centres  are  indicated  by  dots  on  the  individual  primary  convolutions.  We  must  remember, 
however,  that  the  centres  are  not  mere  points,  but  that  they  vary  in  size  from  that  of  a  pea  upward, 
according  to  the  size  of  the  animal.  Motor  areas  have  been  mapped  out  in  the  brain  of  the  monkey, 
rabbit,  rat,  bird,  and  frog. 

Position  of  the  Motor  Centres  (Dog). — Fritsch  and  Hitzig,  in  1870,  mapped  out  the  follow- 
ing  motor  areas,  whose  position  may  be  readily  found  on  referring  to  F'ig.  483  :  I,  is  the  centre  for 
the  muscles  of  the  neck;  2,  for  the  extensors  and  adductors  of  the  fore  limb;  3,  for  the  flexion  and 
rotation  of  the  fore  leg ;  4,  for  the  movements  of  the  hind  limb,  which  Luciani  and  Tamburini 
resolved  into  two  antagonistic  centres;  5,  for  the  muscles  of  the  face,  or  the  facial  centre.  In  1873 
Ferrier  discovered  the  following  additional  centres :  6,  for  the  lateral  switching  movements  of  the 
tail,  7,  for  the  retraction  and  abduction  of  the  fore  limb  ;  8,  for  the  elevation  of  the  shoulder  and 
extension  of  the  fore  limb,  as  in  walking;  the  area  marked  9,  9,  9,  controls  the  movements  of  the 
orbicularis  palpebrarum,  and  of  the  zygomaticus  (closure  of  the  eyelids),  together  with  the  upward 
movement  of  the  eyeball  and  narrowing  of  the  pupil.  Stimulation  of  the  areas  a,  a  (Fig.  II)  is  fol- 
lowed by  retraction  and  elevation  of  the  angle  of  the  mouth,  with  partial  opening  of  the  mouth  ;  at  b, 
Ferrier  observed  opening  of  the  mouth  with  protrusion  and  retraction  of  the  tongue,  while  the  dog 
not  unfrequently  howled.  He  called  this  centre  the  "  oral  centre.''^  Stimulation  of  c  c  causes  retrac- 
tion of  the  angle  of  the  mouth,  owing  to  the  action  of  the  platysma,  while  c'  causes  elevation  of  the 
angle  of  the  mouth  and  of  one-half  of  the  face,  until  the  eye  may  be  closed,  just  as  in  9.  Stimulation 
of  d  is  followed  by  opening  of  the  eye  and  dilatation  of  the  pupil,  while  the  eyes  and  head  are  turned 
toward  the  other  side.  According  to  H.  Munk,  the  prefrontal  region  has  an  influence  upon  the  atti- 
tude of  the  body  (?).  The  perineal  muscles  contract  when  the  gyrus  postcruciatus  is  stimulated. 
Stimulation  of  the  gyrus  prrecruciatus  on  its  anterior  and  sloping  aspect  causes  movements  in  the 
pharynx  and  larynx. 

The  position  of  the  individual  motor  areas  may  vary  somewhat,  and  they  may 
be  slightly  different  on  the  two  sides  (^Luciani  and  Tamburini). 

Strong  Stimuli. — If  the  stimulation  be  very  strong,  not  only  the  muscles  on 
the  opposite  side,  but  lho.se  on  the  same  side,  may  contract.  These  latter  move- 
ments belong  to  the  class  of  associated  movements,  and  are  due  to  conduction 
through  commissural  fibres.  Those  muscles,  which  usually  (muscles  of  mastication) 
or  always  (muscles  of  eye,  larynx,  and  face)  act  together,  appear  to  have  a  centre 
not  only  in  the  opposite  but  also  in  the  hemisphere  of  the  same  side  (Exner). 
[All  observers  have  found  that  stimulation  of  the  facial  centre  causes  identical 
(associated)  movements  on  both  sides  of  the  face,  so  that  both  sides  of  the  face 
seem  to  be  represented  in  each  hemisphere.  Schafer  and  Horsley's  experiments 
make  it  very  probable  that  some  other  muscles,  e.g.,  some  of  the  trunk  muscles, 
pectorals,  and  recti  abdominis,  are  represented  bilaterally  in   the  hemispheres. 


POSITION    OF   THE    MOTOR    CENTRES    IN    THE    DOG. 


745 


This  is  an  important  point  in  relation  to  recovery  after  the  supposed  destruction 
of  a  centre,  and  has  an  intimate  bearing  on  the  question  of  "  Substitution,"  in 
reference  to  the  restoration  of  nerve  function  (p.  732).] 

Fig.  483. 


1,  Cerebrum  of  the  dog  from  above;  II,  from  the  side;  I,  II,  III,  IV,  the  four  primary  convolutious,— S,  sulcus 
cruciatus;  F,  Sylvian  fossa;  o,  olfactory  lobe;  /,  optic  nerve;  i,  motor  area  for  the  muscles  of  the  neck;  2, 
extensors  and  abductors  of  the  fore  limb;  3,  flexors  and  rotators  of  the  fore  limb;  4,  the  muscles  of  the  hind 
limb;  5,  the  facial  muscles;  6,  lateral  switching  movements  of  the  tail;  7,  retraction  and  abduction  of  the  fore 
limb ;  8,  elevation  of  the  shoulder  and  extension  of  fore  limb  (movements  as  in  walking) ;  9,  9,  orbicularis 
palpebrarum,  zygomaticus,  closure  of  the  eyelids.  II,  a,  a,  retraction  and  elevation  of  the  angle  cf  the  mouth  ; 
b,  opening  of  the  mouth  and  movements  of  the  oral  centre  ;  c,  c,  platysma  ;  d,  opening  of  the  eye  ;  I,  t,  thermic 
centre,  according  to  Eulenburg  and  Landois.  Ill,  cerebrum  of  the  rabbit  from  above;  IV,  cerebrum  of  the 
pigeon  from  above ;  V,  cerebrum  of  the  frog  from  above ;  VI,  cerebrum  of  the  carp  from  above  (in  all  these  o  is 
the  olfactory  lobe  ;  i,  cerebrum  ;  2,  optic  lobe  ;  3,  cerebellum ;  4,  medulla  oblongata). 

Mechanical  stimulation,  e.g.,  scraping  the  motor  areas  for  the  limbs,  pro- 
duces movements  in  these  parts  (Luciani). 

Cerebral  Epilepsy. — It  is  of  great  practical  diagnostic  importance  to  ascertain 
if  stimulation  of  the  motor  areas  in  man,  due  to  local  diseases  (inflammation, 


746  EFFECT   OF    STIMULI    ON    THE    MOTOR   CENTRES. 

tumors,  softening,  degenerative  irritation),  causes  movements.  [Hughlings- 
Jackson  has  shown  that  local  diseases  of  the  cortex  may  cause  spasmodic  contrac- 
tions in  certain  groups  of  muscles,  a  condition  known  as  "Jacksonian  Epilepsy," 
and  he  explains  in  this  way  the  occurrence  of  unilateral  local  epileptiform  spasms, 
which  were  observed  by  Ferrier  and  Landois  to  occur  after  inflammatory  irritation.] 
Luciani  observed  these  spasms  in  dogs,  and  sometimes  they  were  so  violent  and 
general  as  to  constitute  an  attack  of  epilepsy.  This  condition  became  hereditary, 
and  the  animals  ultimately  died  from  epilepsy  (§  373).  According  to  Eckhard, 
epileptic  attacks  are  never  produced  by  stimulation  of  the  surface  of  the  posterior 
convolutions. 

Strong  stimulation  of  the  motor  regions  may  give  rise  in  dogs  to  a  complete  general  convulsive 
epileptic  attack,  whicli  usually  begins  with  contractions  of  the  groups  of  muscles  specially  related 
to  the  stimulated  centre  [Ferrier,  Euleiiburg  and  Landois,  Albertoni,  Luciani  and  Ta/nlmrini); 
then  often  passes  to  tlie  corresponding  limb  of^  the  opposite  side  (associated  movements) ;  and  lastly, 
all  the  muscles  of  the  body  are  thrown  into  tonic  and  then  into  clonic  spasms.  The  opposite  side 
of  the  body  has  been  observed  to  pass  into  spasm  from  below  upward,  after  the  contractions  were 
developed  in  the  other  side.  The  spasmodic  excitement  passes  from  centre  to  centre,  an  intermediate 
motor  region  never  being  passed  over.  After  this  condition  has  once  been  produced,  the  slightest 
stimulation  may  suffice  to  bring  on  a  new  epileptic  attack  (<!  373).  During  the  attack,  the  cerebral 
circulation  is  accelerated.  According  to  Eckhard  and  Danillo,  epileptic  attacks  cannot  be  discharged 
from  the  posterior  part  of  the  cerebrum  by  means  of  weak  currents.  Stimulation  of  the  sub-cortical 
white  matter  causes  epilepsy,  which,  however,  begins  in  the  muscles  of  the  same  side  [Bubnoff  and 
Neiden/iain).  These  contractions  are  due  to  an  escape  of  the  electrical  currant,  which  thus  reaches 
the  medulla  oblongata  (^  373)- 

If  certain  motor  areas  are  extirpated,  the  epileptic  attack  is  absent  from  the  muscles  controlled 
by  these  areas  (Luciani).  Separation  of  the  motor  conical  area  by  means  of  a  horizontal  section 
during  an  attack  cuts  short  the  latter  (A/uni-).  During  an  epileptic  attack  it  is  possible  to  excise 
the  motor  area  of  one  extremity,  and  thus  exclude  this  limb  from  the  attack  while  the  rest  of  the 
body  is  convulsed. 

Drugs. — The  continued  use  of  potassium  bromide  prevents  the  production  of  epilepsy  on  stimu- 
lating the  cortical  areas. 

Chemical  Stimulation. — Substances  such  as  occur  in  urine,  e.g.,  kreatinin, 
kreatin,  acid  potassic  phosphate,  and  sediment  of  urates,  when  sprinkled  on  the 
motor  areas  of  the  dog,  cause  pronounced  eclampsic,  clonic  convulsions,  which 
recur  spontaneously,  and  are  followed  by  deep  coma.  These  symptoms  are  like 
those  of  uraemic  poisoning.  The  sensory  centres,  especially  that  for  vision,  seem 
also  to  be  affected  by  chemical  stimulation  [Landois). 

[Motor  Centres  in  the  Monkey. — Ferrier  has  mapped  out  a  large  number 
of  centres  on  the  outer  surface  of  the  brain  in  the  monkey,  and  to  each  centre  he 
has  given  a  number.  These  numbers  have  been  transferred  to  corresponding  con- 
volutions on  the  human  brain,  numbered  accordingly.  These  areas  are  specially 
distributed  on  the  convolutions  around  the  fissure  of  Rolando,  including  in  the 
monkey,  the  posterior  extremities  of  the  posterior  and  middle  frontal  convolutions, 
the  ascending  frontal,  ascending  parietal,  and  part  of  the  parietal  lobule.] 

[Fig.  484  represents  these  areas  transferred  to  the  corresponding  areas  in  man.  (l)  On  the 
superior  parietal  lobule  (advance  of  the  opposite  hind  limb,  as  in  walking).  (2),  (3),  (4)  Around 
the  upper  extremity  of  the  fissure  of  Rolando  (complex  movements  of  the  opposite  leg  and  arm,  and 
of  the  trunk,  as  in  swimming),  [a),  [b),  (c),  [d)  On  the  ascending  parietal  or  posterior  central 
convolution  (individual  and  combined  movements  of  the  fingers  and  wrist  of  the  opposite  hand 
or  prehensile  movements).  (5)  Posterior  end  of  the  superior  frontal  convolution  (extension  forward 
of  the  opposite  arm  and  hand).  (6)  Upper  part  of  the  ascending  frontal  or  anterior  central  con- 
volution (supination  and  flexion  of  the  opposite  forearm).  (7)  Middle  of  the  same  convolution 
(retraction  and  elevation  of  the  opposite  angle  of  the  mouth).  (8)  At  the  lower  end  of  the  same 
convolution  (elevation  of  the  ali  nasi  and  upper  lip,  and  depression  of  the  lower  lip  on  the  opposite 
side).  (9),  (10)  Broca's  convolution  (opening  of  the  mouth  with  protrusion  and  retraction  of  the 
tongue — aphasic  region).  (11)  Between  10  and  the  lower  end  of  the  ascending  parietal  convolution 
(retraction  of  the  opposite  angle  of  the  mouth,  the  head  turns  toward  one  side).  (12)  Posterior  part 
of  the  superior  and  middle  frontal  convolutions  (the  eyes  open  widely,  the  pupils  dilate,  and  the  head 
and  eyes  turn  toward  the  opposite  side).  (13),  (13^)  Supra-marginal  and  angular  gyrus  (the  eyes 
move  toward  the  opposite  side,  and  upward  or  downward — centre  of  vision).     (14)  Superior  tem- 


MOTOR   CENTRES    IN    THE    MARGINAL   CONVOLUTION. 


747 


poro-spbenoidal  convolution  (pricking  of  the  opposite  ear,  pupils  dilate,  and  the  head  and  eyes  turn 
to  the  opposite  side — ^hearing  centre).] 

[Experiments  on  Monkeys. — Electrical  stimulation  of  the  anterior  part  of 
the  frontal  lobes  yields  negative  results ;  but  behind  the  anterior  end  of  the  sagittal 
limb  of  the  precentral  sulcus,  there  are  lateral  movements  of  the  head  and  eyes. 
If  the  anterior  third  or  fourth  be  removed,  Schafer  and  Horsley  observed  no  motor 
paralysis  nor  any  deficiency  of  general  or  special  sensibility.  Excitation  of  the 
external  surface  {motor  area)  led  Ferrier  to  map  out  the  areas  named  on  p.  744. 
Schafer  and  Horsley's  experiments  agree  with  Ferrier's,  and  they  map  out  the 

Fig.  484. 


The  brain  with  the  chief  convolutions  (after  Ecker).  See  also  Figs.  498,  499  in  their  relation  to  the  skull.  The  num- 
bers I  to  14,  and  the  letters  a  to  d,  indicate  cortical  areas  (p.  746).  S,  Sylvian  fissure  ;  C,  central  sulcus,  or 
fissure  of  Rolando ;  A,  anterior,  and  B,  posterior  central  convolutions;  F,,  upper,  F„,  middle,  and  F3,  lowest 
frontal  convolutions  ;  f-^,  superior,  andy"2,  inferior  frontal  fissure;  /"a,  sulcus  prsecentralis  ;  Pj,  superior,  P^,  infe- 
rior parietal  lobe,  with  P^,  gyrus  supra-marginalis  ;  Pji,  gyrus  angularis  ;  7^,  sulcus  interparietalis  ;  c?«,  end  of 
calloso-marginal  fissure  ;  Oi,  Oj,  O3,  occipital  convolutions  ;  po,  parieto-occipital  fissure  ;  Tj,  Tj,  T3,  temporo- 
sphenoidal  convolutions  ;  K^,  K2,  K3,  points  in  the  coronal  suture;  41,  42,  in  the  lambdoidal  suture. 

motor  area  into  a  number  of  main  areas,  each  of  which  is  particularly  concerned 
with  the  movement  of  a  particular  part  or  limb,  and  in  some  of  which,  centres 
concerned  with  more  specialized  movements  may  be  marked  out.  The  arm  area 
is  roughly  triangular  (Fig.  485),  and  "  occupies  most  of  the  upper  half  of  the 
ascending  parietal  and  ascending  frontal  gyri,  from  a  little  beneath  the  level  of  the 
sagittal  part  of  the  precentral  fissure  below,  nearly  to  the  margin  of  the  hemisphere 
above,  together  with  the  adjacent  part  of  the  frontal  lobe  below  the  small  antero- 
posterior sulcus."  It  bends  round  and  is  continuous  with  a  part  of  the  marginal 
gyrus.     The  special  movements  of  the  arm  are  indicated  in  Fig.  485.] 


748 


MOTOR    CENTRES    IN    THE    MARGINAL   CONVOLUTION. 


[The  face  area  gives  rise  not  only  to  movements  of  the  facial  muscles,  but  also 
of  the  whole  of  the  upper  end  of  the  alimentary  tube.  It  comprises  the  whole  of 
the  surrounding  parietal  and  frontal  convolutions  below  the  arm  area,  down  to 
the  fissure  of  Sylvius,  and  including  the  external  surface  of  the  operculum.] 

[The  head  area,  or  area  for  visual  direction,  comprises  part  of  the  frontal  lobe 
from  the  margin  of  the  hemisphere  to  the  face  area.  In  front  it  is  bounded  by 
the  non-excitable  part  of  the  frontal  lobe.  Its  stimulation  gives  the  results 
obtained  by  Ferrier  on  stimulating  his  No.  12  centre.  The  leg  area  is  partly 
situate  on  the  mesial  surface,  but  it  extends  over  to  the  external  surface  from  the 
parieto-occipital  fissure  nearly  to  the  level  of  the  anterior  end  of  the  small  sulcus 
marked  .v.  The  trunk  area  scarcely  extends  over  the  margin  to  reach  the 
external  surface.] 

[Schafer  and  Horsley  have  extended  Ferrier's  researches,  and  shown  that  motor 
centres  exist  in  the  marginal  convolution  (Fig.  486),  which  is  excitable  only 
in  that  portion  corresi)onding  in  extent  (antero  posteriorly)  to  the  excitable 
portion  of  the  outer  surface  of  the  hemisphere.  Anteriorly  it  reaches  forward  to 
a  line  which  is  opposite  the  junction  of  the  posterior  and  middle  thirds  of  the 


Fig.  485. 


Fig.  486. 


Diagram  of  the  motor  areas  on  the  outer  surface  of  a 
monkey's  brain  (^Horsley  and  Schafer). 


Diagram  of  the  motor  areas  on  the  marginal  convolution 
of  a  monkey's  brain  {Horsley  and  Schafer), 


superior  frontal  convolution  (centre  12),  while  posteriorly  it  extends  backward 
opposite  to  the  parietal  lobule,  including  the  paracentral  lobule,  which  contains 
large  multipolar  pyramidal  motor  cells.  The  rest  of  the  mesial  surface  is  excitable. 
They  find  that  the  centres  are  arranged  from  before  backward  in  the  following 
order  :  (i)  Movements  of  the  head — this  area  is  very  small,  and  belongs  to  the 
large  head  area  on  the  external  surface ;  (2)  of  the  forearm  and  hand  ;  (3)  of  the 
arm  at  the  shoulder ;  (4)  of  the  upper  dorsal  part  of  the  trunk ;  (6)  of  the  leg  at 
the  hip;  (7)  of  the  lower  leg  at  the  knee  ;  (8)  of  the  foot  and  toes.] 

Excitation  of  the  Area  AS  produces  movements  of  the  arm  (Fig.  489).  These  vaiy  according 
to  the  spot  stimulated,  but  toward  the  anterior  part  of  the  area,  movements  of  the  wrist  and  forearm, 
toward  the  posterior  part  movements  of  the  arm  and  shoulder,  are  more  frequently  the  result  of  the 
excitation.  Excitation  of  Tr  produces  movements  of  the  trunk,  generally  arching  and  rotation. 
Those  movements  which  are  called  forth  by  stimulating  the  anterior  part  of  the  area  are  usually  con- 
fined to  the  upper  part  of  the  trunk  (thoracic  region),  and  are  often  associated  with  movements  of  the 
shoulder  and  arm  ;  those  called  forth  by  stimulating  the  posterior  parts  are  movements  of  the  abdomi- 
nal and  pelvic  regions  and  of  the  tail,  and  are  often  associated  with  movements  of  the  hip  and  leg. 
Excitation  of  the  area  L  produces  movements  in  the  lower  limb.  These  vary  according  to  the  part 
stimulated,  extension  of  the  hip  being  especially  associated  with  excitation  of  the  anterior  part  of  the 
area,  and  contraction  of  the  hamstrings  with  excitation  of  the  middle  part.] 


MOTOR   CENTRES    IN    MAN.  749 

[Do  similar  Centres  exist  in  Man  ? — The  results  of  clinical  and  patho- 
logical investigations  show,  that  similar  although  not  absolutely  identical  areas 
exist  in  man.  The  motor  areas,  or  those  which  have  a  special  relation  to  volun- 
tary motion  in  man,  exist  in  part  on  the  convolutions  bounding  the  fissure  of 
Rolando,  and  occupy  the  "central"  convolutions,  i.  e.,  the  ascending  frontal 
and  ascending  parietal  convolutions  along  with  the  superior  parietal  lobule,  and 
along  the  mesial  surface  of  the  hemisphere,  the  paracentral  lobule  and  precuneus 
(Fig.  488).  In  this  region,  the  upper  third  of  the  ascending  frontal  and  parietal 
convolutions  along  with  the  superior  parietal  are  the  leg  area  (Fig.  488,  leg),  the 
middle  third  of  the  ascending  parietal  and  ascending  frontal  for  the  arm,  and 
the  upper  part  of  the  lowest  third  of  these  convolutions  for  the  face,  while  the 
very  lowest  part  of  the  ascending  frontal  convolution  is  the  area  for  the  move- 
ments of  the  lips  (L)  and  tongue  (T).  (Compare  Figs.  485,  490.)  The  last  area, 
with  the  posterior  extremity  of  the  third  left  frontal  convolution,  is  the  centre  for 
voluntary  speech.  We  cannot  say  whether  these  "  centres  "  are  sharply  mapped 
off  from  each  other.  In  any  case  a  very  strong  stimulation  of  one  centre  may 
involve  an  adjacent  area.  So  far  as  is  yet  known,  centres  Nos.  5  and  12,  as  rep- 
resented on  the  monkey's  brain — those  on  the  posterior  extremity  of  the  superior 
and  middle  frontal  convolutions, — (5)  for  extension  forward  of  the  arm  and  hand, 
and  (12)  for  opening  the  eyes  and  turning  the  head  toward  the  opposite  side  (as 
in  surprise),  are  not  represented  in  the  human  brain.  So  accurately  have  certain 
of  these  areas  been  located,  that  surgeons,  in  suitable  cases,  have  been  able  to 
excise  a  tumor  causing  certain  symptoms,  with  relief  of  those  symptoms.] 

[We  may,  therefore,  assert  as  a  general  proposition  that  the  muscles  of  one 
lateral  half  of  the  body  are  regulated  by  certain  areas  in  the  opposite  cerebral 
hemispheres.] 

[Gowers  maintains  that  the  motor  region  is  not  exclusively  motor,  but  that  destruction  of  this 
area  also  leads  to  some  loss  of  sensation.  Starr  also  asserts  that  perceptions  occur  in  the  gray 
matter  of  the  cortex  of  the  "  central  "  region  and  parietal  convolutions,  and  that  the  various  sensory 
areas  for  the  various  parts  of  the  body  lie  about,  and  coincide  to  some  extent  with,  the  motor  various 
areas  for  similar  parts,  but  the  sensory  area  is  more  extensive  than  the  motor  area,  extending 
into  the  parietal  behind  the  motor  area,  which  is  confined  to  the  ascending  frontal  and  parietal 
convolutions.] 

II.  Method  of  Destruction  or  Ablation  of  Parts  of  the  Cortex. — Much  confusion  in  this 
matter  has  arisen  from  comparing  the  results  obtained  on  animals  of  different  species.  [It  seems 
quite  certain  that  the  results  obtained  in  the  dog  are  quite  different  from  those  in  the  monkey.  The 
motor  areas  may  be  simply  excised  with  a  knife,  or  the  sm'face  of  the  brain  may  be  washed  away 
with  a  stream  of  water,  as  was  done  by  Goltz  in  dogs,] 

[In  thedog,  the  areas  which  are  described  as  motor  may  be  removed  either  by  the  knife  (Zi'frwaww) 
or  by  means  of  a  stream  of  water  so  directed  as  to  wash  away  the  gray  matter  i^Goltz).  In  both 
cases,  although  there  was  some  paralysis  on  the  opposite  side  of  the  body,  this  was  but  temporary, 
for  the  paralysis  disappeared  within  a  few  days,  the  animals  having  very  decided  control  over  their 
muscles,  although  Goltz  admits  that  certain  acts,  especially  those  which  the  dogs  had  been  trained 
to  execute,  e.g.,  giving  a  paw,  were  executed  "  clumsily,"  indicating  some  failure  of  complete 
control,  which  Goltz  ascribed  to  loss  of  tactile  sensibility.  Goltz  thinks  that  the  extent  of  the 
injury  has  more  to  do  with  the  result  than  the  locality.  The  restoration  of  motion  was  not  due  to 
the  action  of  the  corresponding  centre  of  the  opposite  side,  as  destruction  of  this  centre,  although  it 
produced  the  usual  symptoms  on  the  side  which  it  governed,  had  no  effect  on  the  previous  result 
[Carville  and  Durei).^ 

[In  the  monkey,  there  can  be  no  doubt,  from  the  experiments  of  Ferrier,  that 
destruction  of  a  motor  centre,  e.g.,  that  for  the  arm,  results  in /^r;//a/z^«/ paraly- 
sis of  the  arm  of  the  opposite  side,  and  if  the  centres  for  the  arm  and  leg  are 
destroyed,  there  is  permanent  hemiplegia  of  the  opposite  side.  "  In  order  that 
the  hemiplegia  or  paraplegia  produced  by  cortical  ablation  shall  be  complete, 
it  is  necessary  to  include  the  part  of  the  marginal  gyrus  corresponding  in  longi- 
tudinal extent  to  the  excitable  areas  of  the  external  surface."  The  amount 
of  paralysis  produced  by  ablation  of  the  marginal  gyri  alone  is  as  great  as 
that  caused  by  removal  of  the  much  more  extensive  external  areas  ;    but  the 


750  EXTIRPATION    OF   THE    MOTOR    CENTRES. 

complexity  of  the  muscular  movements  which  are  governed  from  these  areas 
is  much  greater  than  in  those  governed  from  the  marginal  gyrus  {Schii/er  and 
Horsley).'\ 

[In  man,  records  of  destructive  lesions  of  the  motor  areas  in  whole  or  part 
have  now  accumulated  to  such  an  extent  as  to  leave  no  doubt,  that  if  there  be,  say, 
a  destructive  lesion  of  the  middle  third  of  the  cortex  of  the  ascending  frontal  and 
ascending  parietal  convolutions,  there  will  be  paralysis  of  the  arm  of  the  opposite 
side  ;  and  the  same  is  true  for  the  other  centres.] 

[In  extirpation  or  ablation  of  the  motor  centres,  again,  much  confusion 
has  arisen  from  comparing  the  results  obtained  on  different  animals.  In  the  dog, 
there  is  no  permanent  motor  paralysis,  in  the  monkey  and  man  there  is.  The 
difference  is  this,  that  in  the  dog  the  lower  centres,  perhaps  the  basal  ganglia,  are 
able  to  subserve  the  execution  of  those  coordinated  movements  required  for  stand- 
ing, progression,  etc.  As  we  proceed  higher  in  the  animal  scale,  the  motor  cor- 
tical centres  assume  more  and  more  of  the  functions  subserved  by  the  basal 
ganglia  in  lower  animals.  There  is,  as  it  were,  a  gradual  disi)lacement  of  motor 
centres  to  the  cortical  region,  as  we  ascend  in  the  zoological  scale.] 

Differences  in  Animals. — The  higher  the  development  of  the  intelligence  of  animals,  the  more 
have  their  movements  been  learned,  and  the  more  have  they  gradually  come  to  be  controlled  by 
the  will;  in  them  the  disturbance  of  the  motor  phenomena  becomes  more  pronounced  and  per- 
sistent after  destruction  of  the  cortical  psychomotor  centres.  While  in  the  lower  vertebrates, 
including  the  birds,  extirpation  of  the  whole  hemispheres  does  not  materially  interfere  with  move- 
ments, the  coordinated  reflex  movements  being  sufficient — in  dogs  occasionally,  but  exceptionally, 
extirpation  of  several  motor  areas  produces  visible  permanent  disturbance  of  motor  acts — and  in 
monkeys  and  man  {\  378),  the  paralytic  phenomena  may  be  intense  and  persistent. 

Acquired  Movements. — Among  the  movements  performed  by  men  are  many  which  have  been 
acquired  after  much  practice,  and  have  been  subjected  to  voluntary  control,  e.g.,  the  movements  of 
the  hands  for  many  manual  occupations.  After  a  lesion  of  certain  motor  areas,  such  movements  are 
reacquired  only  very  slowly  and  incompletely,  or  it  may  be  not  at  all.  [The  interference  with  these 
finer  acquired  movements  sometimes  becomes  very  marked  in  lesions  of  the  motor  areas  produced 
by  hemorrhage,  and  in  some  cases  of  hemiplegia.]  Those  movements,  however,  which  are,  as  it 
were,  innate  [or  as  they  are  sometimes  termed  fundamental  in  opposition  to  acquired],  and  are 
under  control  of  the  will  without  much  practice — such  as  the  associated  movements  of  the  eyes,  face, 
.some  of  those  of  the  limbs — are  either  rapidly  restored  after  ihe  lesion,  or  they  appear  to  suffer  but 
slightly  after  a  lesion  of  the  cerebral  cortex ;  the  facial  muscles  are  never  so  completely  paralyzed 
as  from  a  lesion  of  the  trunk  of  the  facial  nerve ;  usually  the  eye  can  be  closed  in  the  former  case. 
The  movements  necessaiy  for  sucking  have  been  performed  by  hemicephalic  infants. 

Theoretical. — Hitzig  ascribes  the  disturbance  of  movement,  after  the  removal  of  the  motor 
centres,  to  the  loss  of  the  "  tnuscular  sensibility^  Schiff  refers  it  to  the  loss  of  tactile  sensibility. 
According  to  Ferrier,  the  tactile  and  sensory  impressions  are  not  appreciably  diminished  or  altered. 
The  descending  degeneration  of  the  pyramidal  tracts  in  the  lateral  columns,  according  to  Schiflf, 
occurs  after  section  of  the  posterior  half  of  the  cervical  spinal  cord,  or  even  after  section  of  the 
posterior  part  of  the  lateral  columns.  After  dividing  the  latter,  and  allowing  secondary  degenera- 
tion to  take  place,  it  is  not  possible  to  discharge  movements  by  stimulating  the  cortex  cerebri. 
[Schiff  divided  the  posterior  column  of  the  cord,  and  found  that  stimulation  of  the  opposite  motor 
cortex  failed  to  excite  movements  in  the  opposite  fore  limbs.  He  supposed  that  this  result  was  due 
to  ascending  degeneration.  Horsiey  finds,  however,  that  SchifT's  results  are  due  to  transverse  aseptic 
myelitis  at  the  seat  of  operation,  thus  causing  a  "  block"  there  in  the  motor  tract.]  The  posterior 
columns,  and  their  continuation  upward  to  the  brain,  are  supposed  to  carry  the  impulses  upward  to 
the  cerebrum  (ascending  the  limb  of  the  reflex  arc),  where,  after  being  modified  in  the  centres,  they 
are  carried  outward  by  the  pyramidal  tracts  (descending  limb  of  the  reflex  arc).  [Some  hold  that 
the  posterior  columns  are  directly  connected  with  the  cortical  motor  area,  while  others  think  that  a 
sensory  perceptive  centre  is  interposed  between  the  aflerent  and  efterent  impulses.]  Between,  but 
deeper  in  the  brain,  lie  the  centres  for  tactile  sensibility.  Landois  and  Eulenljurg  observed  in  a  dog, 
from  which  the  motor  centres  for  the  extremities  had  been  removed  on  both  sides,  that  the  move- 
ments became  completely  ataxic,  i.e.,  the  animal  could  not  execute  such  coordinated  movements 
as  walking,  standing,  etc.  Goltz  regards  the  disturbances  of  movement  after  injury  of  the  cortex 
as  due  to  inhibition.  Schiff  maintains  that  when  the  cortex  cerebi  is  stimulated  we  do  not  stimulate 
a  cortical  centre,  but  only  the  sensory  channels  of  a  reflex  arc,  the  continuation  of  the  posterior 
columns,  so  that  on  this  supposition  the  movements  resulting  from  stimulation  of  the  motor 
points  would  be  reflex  movements.  The  centres  lie  deeper  in  the  brain.  This  view  is  not  generally 
entertained. 


CONDITIONS    AFFECTING   THE    MOTOR   CENTRES.  751 

Modifying  Conditions. — The  excitability  of  the  motor  centres  is  capable  of 
being  considerably  modified.  Stimulation  of  sensory  nerves  diminishes  it  ; 
thus,  the  curve  of  contraction  of  the  muscles  becomes  lower  and  longer,  while  the 
reaction- time  is  lengthened  simultaneously.  Only  when,  owing  to  strong  stimu- 
lation, the  reflex  muscular  contractions  are  vigorous,  the  excitability  of  the  cortical 
centres  appears  to  be  increased.  Specially  noteworthy  is  the  fact  that,  in  a 
certain  stage  of  morphia  narcosis,  a  stimulus  which  is  too  feeble  to  discharge 
a  contraction  becomes  effective  at  once,  if  immediately  before  the  stimulus  is 
applied  to  the  cortical  centre,  the  skin  of  certain  cutaneous  areas  be  subjected 
to  gentle  tactile  stimulation.  When  strong  pressure  is  applied  to  the  foot,  the 
contractions  become  tonic  in  their  nature,  so  that  all  stimuli,  which  under 
normal  conditions  produce  only  temporary  stimulation,  now  stimulate  these 
centres  continuously.  If,  during  the  tonic  contraction,  one  gently  strokes  the 
back  of  the  foot,  blows  on  the  face,  gently  taps  the  nose,  or  stimulates  the  sciatic 
nerve,  suddenly  relaxation  of  the  muscles  again  occurs.  The  phenomena  call 
to  mind  the  analogous  observations  in  hypnotized  animals  (§  374).  Another 
very  remarkable  observation  is,  that  when  either  owing  to  a  reflex  effect,  or  to 
strong  electrical  stimulation  of  a  cortical  centre,  contraction  of  the  corresponding 
muscles  is  produced,  x}citxi  feeble  stimulation  of  the  same  centre,  but  also  of  other 
centres,  suppresses  the  movement.  Thus,  we  have  the  remarkable  fact  that, 
according  to  the  strength  of  the  stimulus  applied  to  the  motor  apparatus,  we  can 
either  produce  movement  or  suppress  a  movement  already  in  progress  {^Bubnoff 
and  Heidenhairi) . 

[Excision  of  the  Thyroid  affects  the  nerve  centres.  After  thyroidectomy  (twenty-four  hours) 
the  tetanus  obtained  by  stimulating  the  cortex  is  greatly  changed.  It  ceases  when  the  stimulating 
current  is  shut  off,  as  suddenly  as  that  observed  on  stimulating  the  corona  radiata.  In  more  advanced 
cases,  the  tetanus  is  soon  exhausted,  and  is  often  followed  by  clonic  epileptoid  spasms.  In  the  latter 
stages,  after  thyroidectomy,  there  may  be  only  a  feeble  tetanus,  or  none  at  all,  on  stimulating  the 
motor  areas,  so  great  is  the  state  of  depression  of  function  of  these  centres  {^Horsle}').'\ 

[Warner  has  directed  attention  to  visible  muscular  movements  apart  from  those  studied  in 
epilepsy,  chorea,  athetosis — and  including  attitude,  gait,  movements  of  the  eyeballs,  position  of  the 
hand,  and  posture  in  general,  etc. — as  expressive  of  states  of  the  brain  and  nerve  centres.] 

376.  SENSORY  CORTICAL  CENTRES.— [There  must  be  some  con- 
nection between  the  surface  of  the  brain  and  the  afferent  channels  through  which 
sensory  impulses  pass  inward,  and  although  the  channels  for  sensory  impulses 
are,  perhaps,  not  so  definitely  localized  as  those  for  voluntary  motion,  still  we 
know  that  sensory  impulses  for  the  opposite  half  of  the  body  travel  upward  through 
the  posterior  third  of  the  posterior  limb  of  the  internal  capsule  (Fig.  500,  S),  to 
radiate  in  all  probability  into  the  occipital  and  temporo-sphenoidal  lobes.  Parts 
of  these  convolutions  are  sometimes  spoken  of  as  "sensory  centres"  or 
"  psycho-sensorial  "  areas.] 

[The  same  methods  have  been  applied  to  the  investigation  of  these  centres,  viz.,  stimulation  and 
extirpation.  Stimulation. — Ferrier  found  that  electrical  stimulation  of  the  angular  gyrus  (monkey) 
caused  movements  of  the  eyeballs  toward  the  side,  with  sometimes  associated  movements  of  the 
head,  but  he  regarded  these  as  reflex  movements,  so  that  for  this  and  other  reasons  he,  in  his  earliest 
contributions,  considered  the  angular  gyrus  and  adjacent  parts  as  the  "  centre  for  vision."  On  stimu- 
lating the  first  temporo  sphenoidal  convolution,  the  monkey  pricked  the  opposite  ear,  the  pupils  dilated, 
while  the  head  and  ears  turned  to  the  opposite  side,  it  exhibited  movements  similar  to  those  caused 
by  a  loud  sound  ;  these  movements  are  also  reflex  phenomena,  so  that  he  located  the  "  auditory 
centre"  in  this  region,  and  on  somewhat  similar  grounds.  As  the  result  of  inferences  from  the 
stimulation  and  extirpation  of  other  parts,  he  referred  the  centres  for  smell  and  taste  to  the  tip  of 
the  temporo-sphenoidal  lobe,  and  for  touch  to  the  hippocampus  major,  but  all  these  statements  have 
not  been  confirmed.] 

[Goltz  experimented  on  dogs  by  washing  away  the  cortex  cerebri,  and  found  that  when  a 
sufficient  amount  of  the  gray  matter  is  removed,  and  after  recovery  from  the  immediate  effects  of  the 
operation,  there  is  apeculiar  defect  of  vision  and  other  sensory  defects,  but  so  far  Goltz  has  not  found 
that  there  is  any  difference  in  this  respect  between  removal  of  the  anterior  and  posterior  lobes  of  the 
dog's  brain.     The  dog  is  not  blind,  as  it  can  see  and  use  its  eyes  to  avoid  obstacles,  but  it  seemed  as 


762 


SENSORY  CORTICAL  CENTRES. 


Fig.  487. 


if  the  animal  failed  to  recognize  food  or  flesh  as  such,  when  placed  before  it ;  while  exhibitions 
which  before  the  operation  greatly  excited  the  dog,  ceased  to  do  so.  Goltz  caused  his  servant  to  dress 
himself  in  a  mummer's  red  colored  garb,  which  previously  had  greatly  excited  the  dog,  but  after  the 
operation  the  dog,  although  it  was  not  blind,  was  no  longer  excited  thereby.  Nor  was  it  afterward 
cowed  by  the  appearance  of  a  whip.  After  a  time  there  was  recovery  to  a  certain  extent  if  the 
animal  was  trained,  whether  by  the  deposition  of  new  impressions,  or  by  opening  up  new  channels, 
or  by  the  partial  recovery  of  some  parts  of  the  gray  mitter  not  removed,  it  is  impossible  to  say.] 

[Munk  has  mapped  out  the  surface  of  the  Ijrain  into  a  series  of  "sensory"  or  psycho-sensorial 
centres,  but  he  distinguishes  between  complete  and  total  extirpation  of  these  centres  and  the  phe- 
nomena which  follow  these  operations.] 

When  these  centres  are  partially  disorganized,  the  mechanism  of  the  sensory 
activity  may  remain  intact,  but  "  the  conscious  link  is  wanting."  A  dog  with  its 
centres  thus  destroyed,  sees,  hears, or  smells,  but  it  no  longer  knows  what  it  sees, 
hears,  or  smells.  These  centres  are  in  a  certain  sense  the  seat  of  experience  that 
has  been  acquired  through  the  organs  of  sense.  Stimulation  of  these  centres 
may  give  rise  to  movements,  such  as  occur  when  sudden  intense  sensory  impres- 
sions are  produced.  These  movements,  therefore,  are  to  be  regarded  as  reflex, 
partly  as  extensive  coordinated  reflex  movements,  and  are  in  no  way  to  be  con- 
founded with  the  movements  which  result  from  direct  stimulation  of  the  motor 
cortical  centres.  To  this  belongs  dilatation  of  the  pupil  and  the  fissure  of  the 
eyelids,  as  well  as  lateral  movements  of  the  eyeball. 

I.  The  "  visual  area,"  according  to  Munk,  embraces  the  outer  convex  part 
of  tlie  occipital  lobe  of  the  dog's  brain.  [This  area  and  its  connections  are  repre- 
sented in  Fig.  487.  It  is,  therefore,  in  the  area  sup- 
plied by  the  posterior  cerebral  artery.]  If  the  occipi- 
tal lobes  be  completely  destroyed,  the  dog  remains 
permanently  blind  ("  cortical  or  absolute  blind- 
ness ").  If,  however,  only  the  central  circular  area 
be  destroyed,  there  is  loss  of  the  conscious  visual  sensa- 
tion, which  may  be  called  "  psychical  blindness  " 
{Mioik)  [a  condition  of  visual  defect  like  that  observed 
by  Goltz  in  the  dog,  in  which  the  dog  saw  an  object, 
e.  g.,  its  food,  but  failed  to  recognize  it  as  such.  There 
is  a  certain  amount  of  recovery  if  the  whole  visual 
area  be  not  removed.  According  to  Schafer,  the  visual 
area  of  the  cerebral  cortex  in  the  monkey  comprises  the 
whole  of  the  occipital  lobe,  and  perhaps  a  part  of  the 
angular  gyrus.  He  finds,  with  Munk,  that  removal  of 
one  occipital  lobe  is  followed  by  hemianopia,  t.  e., 
blindness  in  the  lateral  half  of  each  retina  corresponding 
to  the  side  operated  on.  The  blindness  passes  off. 
Removal  of  both  occipital  lobes  is  said  to  produce  total 
and  permanent  blindness,  whereas  destruction  of  the 
cortex  of  both  angular  gyri  is  not  followed  by  any 
appreciable  permanent  defect  of  vision.  Ferrier,  how- 
ever, does  not  accept  these  statements.] 

[Ferrier  and  Yeo  find  that  after  operations  conducted 
antiseptically,  removal  of  both  occipital  lobes  (monkeys)  does  not  cause  any 
recognizable  disturbance  of  vision,  or  other  bodily  or  mental  derangement,  pro- 
vided the  lesion  does  not  extend  beyond  the  parieto-occipital  fissure.  Nor  does 
destruction  of  both  angular  gyri  cause  permanent  loss  of  vision  ;  such  loss  of  vision 
lasts  only  three  days,  so  that  in  Ferrier's  original  experiments,  the  animals  lived  for 
too  short  a  time  after  the  operation,  to  enable  a  just  conclusion  to  be  arrived  at. 
Destruction  of  both  angular  gyri  and  occipital  lobes  causes  total  and  permanent 
blindness  in  both  eyes  in  monkeys,  without  any  impairment  of  the  other  senses  or 
motor  power.     This  region  Ferrier  calls  the  "  occipito-angular  region." 


Course  of  the  psycho-optic  fibres 
(after  Munk). 


THE   VISUAL    CENTRE,  753 

[Stimulation  of  the  angular  gyrus  causes  movements  of  the  eyes  to  the  opposite 
side,  with  closure  of  the  eyelids  and  contraction  of  the  pupil.  The  eyeballs  were 
directed  upward  or  downward  according  as  the  electrodes  were  applied  to  the 
anterior  or  posterior  limb  of  the  angular  gyrus  {Ferrier).  Stimulation  of  the 
whole  of  the  cortex  of  the  occipital  lobe,  including  its  mesial  and  under  surfaces, 
causes  conjugate  deviation  of  the  eyes  to  the  opposite  side,  the  direction  of  move- 
ment varying  with  the  position  of  the  electrodes.] 

Mauthner  denies  the  existence  of  cortical  blindness,  and  believes  that,  after  destruction  of  the 
middle  of  the  visual  centre,  the  reason  why  the  dog  does  not  recognize  the  object  with  the  opposite 
eye  is  because,  owing  to  there  being  only  indirect  vision,  there  is  no  distinct  impression  on  the  retina. 
The  position  of  the  visual  centre  has  been  Variously  stated  by  different  observers.  According  to 
Ferrier,  in  the  dog  it  lies  in  the  occipital  part  of  the  III  primary  convolution,  near  the  spot  marked 
e,  e,  e,  in  Fig.  483 ;  according  to  his  newer  researches,  in  the  occipital  lobe  and  gyrus  angularis. 

Connection  with  the  Retina. — Munk  asserts  that  in  dogs  both  retinae  are  connected  with  each 
visual  cortical  centre,  and  in  such  a  manner  that  the  greatest  part  of  each  retina  is  connected  with 
the  opposite  cortical  centre,  and  only  by  its  most  external  lateral  marginal  part  with  the  centre  of  the 
same  side  (Fig.  487).  If  we  imagine  the  surface  of  one  retina  to  be  projected  upon  the  centres,  then 
the  most  external  margin  of  the  first  is  connected  with  the  centre  of  the  same  side,  the  inner  margin 
of  the  retina  with  the  inner  area  of  the  opposite  centre,  the  upper  margin  with  the  anterior  area,  and 
the  lower  marginal  part  of  the  retina  with  the  posterior  area  of  the  opposite  side.  The  (shaded) 
middle  of  the  centre  corresponds  to  the  position  of  direct  vision  of  the  retina  of  the  opposite  side 
(compare  ^  344). 

Stimulation  of  the  visual  centre  in  dogs  causes  movements  of  the  eyes  toward 
the  other  side,  sometimes  with  similar  movements  of  the  head  and  contraction  of 
the  pupils.  If  one  eye  be  excised  from  newborn  dogs  the  opposite  visual  centre 
after  several  months  is  less  developed  {Munk).  After  extirpation  of  the  visual 
centre  in  young  dogs,  the  channels  which  connect  it  with  the  optic  nerve  undergo 
degeneration  (^Monakoiv)  (§  344). 

In  monkeys,  the  centre  occupies  the  occipital  lobe.  Unilateral  destruction  causes  temporary  blind- 
ness of  the  halves  of  both  retinae,  i.  e.,  hemianopia  on  the  side  of  the  injury.  The  visual  centre  in 
pigeons  (Fig.  483,  IV,  where  i  is  placed)  lies  somewhat  behind  and  internal  to  the  highest  curvature 
of  the  hemispheres  ^M'' Kendrick,  Ferrier,  Mitsehold).  The  visual  centre  in  the  frog  lies  in  the 
optic  lobe  [Blaschko). 

[The  visual  path  is  along  the  optic  nerve  to  the  chiasma,  where  the  fibres  from  the  nasal  half  of 
each  retina  cross  to  the  optic  tract,  some  of  the  fibres  perhaps  becoming  connected  with  the  external 
corpora  geniculata,  and  some  with  the  pulvinar  of  the  optic  thalamus  and  corpora  quadrigemina, 
while  the  great  mass  sweeps  backward  to  the  occipital  lobes  as  the  optic  expansion  of  Gratiolet. 
Destruction  of  this  path  behind  the  chiasma  causes  hemiopia  or  hemianopia,  and  certain  diseases 
of  the  occipital  cortex  cause  a  similar  result.  Perhaps,  however,  there  is  another  centre  in  the  angu- 
lar gyrus  (and  supra-marginal  lobe),  for  in  cases  of  word  blindness  disease  has  been  found  in  these 
regions.  Sometimes  flashes  of  light  or  the  appearance  of  a  ball  of  fire  form  the  aura  in  epilepsy, 
and  Hughlings- Jackson  thinks  that  discharging  lesions  of  the  right  occipital  lobe  cause  colored  vision 
more  frequently  than  on  the  left.] 

2.  The  centre  for  hearing,  or  "  auditory  area,"  lies  in  the  dog,  according 
to  Ferrier,  in  the  region  of  the  second  primary  convolution  at/",/, /(Fig.  483,  II), 
while  in  the  monkey  and  man  it  is  in  the  first  temporal  or  temporo-sphenoidal 
gyrus  (Ferrier's  centre,  No.  14).  Munk  locates  it  in  the  same  region.  Accord- 
ing to  Munk,  destruction  of  the  entire  region  causes  deafness  of  the  opposite  ear, 
while  destruction  of  the  middle  shaded  part  alone  causes  "psychical  deafness  " 
(^'  Seelentaiibheii'').  Electrical  irritation  of  the  upper  two-thirds  of  the  superior 
temporal  convolution  is  followed  by  a  reaction  which  closely  resembles  that  pro- 
duced by  a  sudden  fright,  or  that  produced  by  a  sudden  unexpected  noise.  [There 
is  a  quick  retraction  of  the  opposite  ear,  i.  <?.,  "  pricking  "  of  the  ear  as  if  toward 
the  supposed  origin  of  the  sound,  combined  generally  with  turning  of  the  head 
and  eyes  to  that  side,  and  dilatation  of  the  pupil.]  Ferrier  locates  the  centre  for 
hearing  in  the  monkey  in  the  superior  teftiporo-sphefioidal  convolution,  and  he  finds 
that  when  the  centres  on  both  sides  are  extirpated,  the  animal  is  absolutely  deaf; 
it  takes  no  cognizance  of  a  pistol  fired  in  its  neighborhood.     [From  his  experi- 


754  OLFACTORY   AND   TACTILE   CENTRES. 

merits  on  monkeys,  Schafer  denies  absolutely  the  conclusions  of  the  above-named 
experiments.  Schafer  points  out  that  it  is  not  difficult  to  substantiate  hearing  in 
monkeys  ;  it  is  difficult  to  substantiate  deafness,  for  cjuite  normal  monkeys  will 
often  fail  to  pay  the  least  attention  to  loud  sounds.  In  six  monkeys,  Schafer 
asserts  that  after  more  or  less  complete  destruction  of  the  superior  temporal  gyrus 
on  both  sides,  hearing  was  not  perceptibly  affected.  In  one  case,  both  temporal 
lobes  were  completely  removed  without  any  permanent  diminution  in  the  acute- 
ness  of  hearing.  These  results  are  opposed  to  the  ordinary  clinical  teaching  on 
this  subject.]  In  man,  injuries  to  the  first  and  second  temporo-sphenoidal  convo- 
lutions on  one  side  do  not  appear  to  cause  comi)lete  deafness  of  one  ear,  as  it 
seems  that  the  sense  of  hearing  for  each  ear  "is  perhaps  represented  on  both  sides. 
Bilateral  lesions  of  these  convolutions  in  man  cause  complete  deafness.  Disease 
of  these  two  convolutions  is  associated  with  word  deafness  (p.  763).  Wernicke 
cites  the  case  of  a  person  first  affected  with  word  deafness,  who  afterward  became 
completely  deaf;  and  after  death,  a  bilateral  lesion  was  found  in  the  first  temporo- 
sphenoidal  convolution.  These  convolutions'  are  supplied  with  blood  by  the 
middle  cerebral  or  Sylvian  artery. 

[The  auditory  paths  are  from  the  auditory  nuclei  in  the  medulla  oblongata 
through  the  pons,  where  they  perhaps  cross  into  the  tegmentum,  thence  into  the 
"  sensory  crossway,"  and  onward  to  the  auditory  centre.] 

[Auditory  Aurae. — Equally  important  with  these  effects  of  disease  are  the  sensory  impressions, 

or  "  aurae,"  which   sometimes  usher  in  an  attack  of  epilepsy;  sometimes  these  aurjE  consist  of 

sounds  or  noises,  and  in  these  cases  the  seat  of  the  disease  is  often  in  the  first  temporo-sphenoidal 
convolution.] 

[3.  The  olfactory  centre  has  not  been  so  definitely  settled  as  some  of  the 
others.  There  is  strong  presumptive  evidence  that  it  is  situated  in  the  hippocam- 
pal  region  of  the  temporal  lobe,  at  its  lower  extremity.  This  view  is  strengthened 
by  the  anatomical  relations  of  this  region  to  the  olfactory  tract  and  anterior  com- 
missure {Ferrier).  M'Lane  Hamilton  has  recorded  a  case  of  epilepsy  ushered  in 
by  an  aura  of  a  disagreeable  odor,  in  which  there  was  atrophy  of  the  gray  matter 
of  the  right  uncinate  gyrus.] 

[Olfactory  Path. — Although  the  outer  root  of  the  olfactory  tract  runs  direct  to  the  uncinate  gyrus, 
in  liemianListhesia  resulting  from  injury  to  the  "  sensory  crossway,"  smell  is  lost  on  the  opposite 
side,  while  it  is  lost  on  the  same  side  when  the  uncinate  g>Tus  is  involved.  It  may  be  that  the 
impulses  go  first  to  their  own  side,  and  cross  afterward.] 

[4.  We  do  not  know  the  centre  for  taste,  and  even  the  course  of  the  nerve  of 
taste  is  disputed.     Ferrier  places  it  close  to  that  of  smell.] 

On  stimulating  the  subiculum  in  monkeys,  dogs,  cats,  and  rabbits,  he  observed  peculiar  move- 
ments of  the  lips  and  partial  closure  of  the  nostrils  on  the  same  side  [\  365).  In  man,  subjective 
olfactory  and  gustatory  perceptions  are  regarded  as  irritative  phenomena,  while  loss  of  these  sen- 
sory activities,  often  complicated  with  other  cerebral  phenomena,  is  regarded  as  a  symptom  of  their 
paralysis. 

[The  gustatory  path  crosses  in  the  posterior  part  of  the  posterior  segment  of  the  internal  cap- 
sule. While  Gowers  admits  that  the  chorda  tymjjani  is  the  nerve  of  taste  for  the  anterior  two-thirds 
of  the  tongue,  he  thinks  that  it  reaches  the  facial  nerve  from  the  spheno-palatine  ganglion  through 
the  Vidian  nerve.  He  denies  that  the  glosso-pharyngeal  is  concerned  in  ta.ste,  and  "he  believes  that 
taste  impressions  reach  the  brain  solely  by  the  roots  of  the  5th  nerve."  lie  admits  that  the  nerves 
of  taste  to  the  back  part  of  the  tongue  may  be  distrihuled  with  the  glosso-pharj'ngeal,  reaching 
them  through  the  otic  ganglion  by  the  small  superficial  petrosal  and  tympanic  plexus.] 

[5.  Ferrier  places  the  centre  for  tactile  sensation  in  the  hippocampal  region 
close  to  the  distribution  of  part  of  the  posterior  cerebral  artery ;  so  far  this  has 
not  been  confirmed.  The  centre  for  the  sensation  of  pain  has  not  been  defined  ; 
probably  it  is  very  diffuse.  The  limbic  lobe,  according  to  Broca,  includes  the 
hippocampal  convolution  and  the  gyrus  fornicatus.  Ferrier  found  that 
removal  of  the  hippocampal  region  resulted  in  a  diminution  of  the  sensibility  of 
the  opposite  side  of  the  body.     Horsley  and  Schafer  observed  only  a  temporary 


THERMAL   CORTICAL   CENTRES.  755 

hemiangesthesia,  but  they  found  that  an  extensive  lesion  of  the  gyrus  fornicatus 
was  followed  by  hemianaesthesia,  more  or  less  marked  and  persistent.  From  their 
experiments,  these  observers  conclude  that  the  limbic  lobe  "is  largely,  if  not 
exclusively,  concerned  in  the  appreciation  of  sensations,  painful  and  tactile."] 

6,  Munk  is  of  opinion  that  the  surface  of  the  cerebrum  in  the  region  of  the  motor  centres  acts  at  the 
same  time  as  "  sensory  areas  "  {'^Fiihlsphdre"),  i.  e.,  they  serve  as  centres  for  the  tactile  and 
muscular  sensations  and  those  of  the  innervation  of  the  opposite  side.  He  asserts  that  after  injury 
to  these  regions  the  corresponding  functions  are  affected. 

According  to  Bechterew,  the  centres  for  the  perception  of  tactile  impressions,  those  of  innervation, 
of  the  muscular  sense,  and  painful  impressions  are  placed  in  the  neighborhood  of  the  motor  areas 
(dog) ;  the  first  immediately  behind  and  external  to  the  motor  areas,  the  others  in  the  region  close  to 
the  origin  of  the  Sylvian  fissure.      [So  far  this  agrees  with  the  views  of  Starr  (p.  749).] 

Goltz,  who  first  accurately  described  the  disturbances  of  vision  following  upon  injuries  to  the 
cortex  in  dogs,  is  opposed  to  the  view  of  sensory  localization.  He  believes  that  each  eye  is  connected 
with  both  hemispheres.  He  asserts  that  the  disturbance  of  vision,  after  injm-y  to  the  brain,  consists 
merely  in  a  diminished  color  and  space  sense.  The  recovery  of  the  visual  perception  of  one  eye 
after  injury  of  one  side  of  the  cortex  cerebri,  he  explains  by  supposing  that  this  injury  merely  causes 
a  temporary  inhibition  of  the  visual  activity  in  the  opposite  eye,  which  disappears  at  a  later  period. 
Instead  of  psychical  blindness  and  deafness  he  speaks  of  a  "  cerebro- optical  and  "  cerebro-acoustical 
weakness." 

377.  THERMAL  CORTICAL  CENTRES.— Eulenberg  and  Landois  discovered  an  area 
on  the  cortex  cerebri,  whose  stimulation  produced  an  undoubted  effect  upon  the  temperature  and 
condition  of  the  blood  vessels  of  the  opposite  extremities.  This  region  (Fig.  483,  I,  /)  generally 
embraces  the  area  in  which,  at  the  same  time,  the  motor  centres  for  the  flexors  and  rotators  of  the 
fore  limb  (3),  and  for  the  muscles  of  the  hind  limb  (4)  are  placed.  The  areas  for  the  anterior  and 
posterior  limbs  are  placed  apart ;  that  for  the  anterior  limb  lies  somewhat  more  anteriorly,  close  to 
the  lateral  end  of  the  crucial  sulcus.  Destruction  of  this  region  causes  increase  of  the  temperature 
of  the  opposite  extremities;  the  temperature  may  vary  considerably  (1.5°  to  2°,  and  even  rising  to 
13°  C).  This  result  has  been  confirmed  by  Hitzig,  Bechterew,  Wood,  and  others.  This  rise  of 
the  temperature  is  usually  present  for  a  considerable  time  after  the  injury,  although  it  may  undergo 
variations.  Sometimes  it  may  last  three  months,  in  other  cases  it  gradually  reaches  the  normal  in 
two  or  three  days.  In  well-marked  cases,  there  is  a  diminution  of  the  resistance  of  the  wall  of  the 
femoral  artery  to  pressure,  and  the  pulse  curve  is  not  so  high  [Reinke).  Local  electrical  stimula- 
tion of  the  area  causes  a  slight  temporary  cooling  of  the  opposite  extremities,  which  may  be  detected 
by  the  thermo-electric  method.  Stimulation  by  means  of  common  salt  acts  in  the  same  way,  but  in 
this  case  the  phenomena  of  destruction  of  the  centre  soon  appear.  As  yet,  it  has  not  been  proved 
that  there  is  a  similar  area  for  each  half  of  the  head.  The  cerebro-epileptic  attacks  (|  375)  increase 
the  bodily  temperature,  partly  owing  to  the  increased  production  of  heat  by  the  muscles  (§  302), 
partly  owing  to  diminished  radiation  of  heat  through  the  cutaneous  vessels,  in  consequence  of 
stimulation  of  the  thermal  cortical  nerves.  The  experiments  led  to  no  definite  results  when  per- 
formed on  rabbits.  According  to  Wood,  destruction  of  these  centres  occasions  an  increased  produc- 
tion of  heat  that  can  be  measured  by  calorimetric  methods,  while  stimulation  causes  the  opposite 
result. 

These  experiments  explain  how  psychical  stimulation  of  the  cerebrum  may  have  an  effect  upon 
the  diameter  of  the  blood  vessels  and  on  the  temperature,  as  evidenced  by  sudden  paleness  and 
congestion  (§378,111). 

[Heat  Production. — Injury  to  the  fore-brain  has  no  effect  on  the  temperature.  If  the  brain  of 
a  rabbit  be  punctured  through  the  large  fontanelle,  and  the  stylet  be  forced  through  the  gray 
matter  on  the  surface,  white  matter  and  the  median  portion  of  the  corpus  striatum  right  to  the  base 
of  the  brain,  there  is  a  rapid  rise  of  the  temperature  which  may  last  several  days.  Injury  to  the  gray 
cortex  does  not  affect  the  temperature.  After  puncture  of  the  corpus  striatum,  the  highest  tempera- 
ture is  reached  only  after  twenty-four  to  seventy  hours,  but  when  the  puncture  reaches  the  base  of 
the  brain  this  result  occurs  in  two  to  four  hours.  Electrical  stimulation  of  these  areas  causes  the 
same  effect  on  the  temperature.  Direct  injury  to  certain  parts  of  the  brain  is  followed  by  a  rise  of 
the  temperature — or  fever.  See  also,  p.  376,  for  further  evidence  of  the  existence  of  thermal  centres. 
There  is  at  the  same  time  an  increase  of  the  O  taken  in,  the  COj  given  off  and  a  decided  increase  of 
the  N  given  off,  indicating  an  increase  in  the  proteid  metabolism,  which  points  to  an  increased  pro- 
duction of  heat  [Aronsokn  and  Sacks,  Richet,  Wood^.'\ 

General  and  Theoretical. — Goltz's  View. — Goltz  uses  a  different  method  to  remove  the  cortex 
cerebri — he  makes  an  opening  in  the  skull  of  a  dog,  and  by  means  of  a  stream  of  water  washes 
away  the  desired  amount  of  bram  matter.  He  describes,  first  of  all,  inhibitory  phenomena,  which 
are  temporary  and  due  to  a  temporary  suppression  of  the  activity  of  the  nervous  apparatus,  which, 
however,  is  not  injured  anatomically;  this  may  be  explained  in  the  same  way  as  the  suppression  of 
reflexes  by  strong  stimulation  of  sensory  nerves  (|  361,  3).     In  addition,  there  are  the  permanent 


756 


TOPOGRAPHY  OF  THE  MOTOR  CENTRES. 


phenomena,  due  to  the  disappearance  of  the  activity  of  the  nervous  apparatus,  which  is  removed 
by  the  operation.  A  dog,  with  a  large  mass  of  its  cerebral  cortex  removed,  may  be  compared  to  an 
eating,  complex,  retlcx  machine.  It  behaves  like  an  intensely  stupid  dog,  walks  slowly,  with  its 
head  hanging  down  ;  its  cutaneous  sensibility  is  diminished  in  all  its  ([ualities — it  is  less  sensitive  to 
pressure  on  the  skin;  it  takes  less  cognizance  of  variations  of  temperature,  and  does  not  comprehend 
how  to  feel;  it  can  with  difficulty  accommodate  itself  to  the  outer  world,  especially  with  regard  to 
seeking  out  and  taking  its  food.  On  the  other  hand,  there  is  no  paralysis  of  its  muscles.  The  dog 
still  sees,  but  it  does  not  understand  what  it  does  see ;  it  looks  like  a  somnambulist,  who  avoids 
obstacles  without  obtaining  a  clear  perception  of  their  nature.  It  hears,  as  it  can  be  wakened  from 
sleep  by  a  call,  but  it  hears  like  a  person  just  wakened  from  a  deep  sleep  by  a  voice — such  a  person 
does  not  at  once  obtain  a  distinct  perception  of  the  sound.  The  same  is  the  case  with  the  other 
senses.  It  howls  from  hunger,  and  eats  until  its  stomach  is  tilled  ;  it  manifests  no  symptoms  of 
sexual  excitement. 

Goltz  supposes  that  every  part  of  the  brain  is  concerned  in  the  functions  of  willing,  feeling,  percep- 
tion, and  thinking.  Every  section  is,  independently  of  the  others,  connected  by  conducting  paths 
with  all  the  voluntary  muscles,  and,  on  the  other  hand,  with  all  the  sensory  nerves  of  the  body.  He 
regards  it  as  possible  that  the  individual  lobes  have  different  functions. 

After  removal  of  the  anterior  or  frontal  convolutions  and  the  motor  areas,  there  is  at  first  uni- 
lateral motor  and  sensory  paralysis  and  affection  of  vision.  After  some  months,  there  remains  only 
the  loss  of  the  muscular  sense.  If  the.  operation  be  bilateral,  the  phenomena  are  more  marked; 
there  are  innumerable  purposeless  associated  movements,  and  the  dogs  become  vicious.  Marked 
and  permanent  disturbance  in  the  capacity  to  utilize  the  impressions  from  the  sen.se  organs  is  not  a 
necessary  consequence  of  removal  of  the  frontal  convolutions. 

Removal  of  the  occipital  lobes  interferes  most  with  vision.  Bilateral  removal  makes  the  animal 
almost  blind.  The  dog  remains  obedient  and  lively.  There  is  no  disturbance  of  motion  or  of  the 
muscular  sense. 

Inhibitory  Phenomena. — Injury  to  the  brain  also  causes  inhibitory  phenomena,  such  as  the 
disturbances  of  motion,  the  complete  hemiplegia  which  is  frequently  ol)served  after  large  unilateral 
injuries  of  the  cortex  cerebri ;  these  are  regarded  by  Goltz  as  inhibitoiy  phenomena,  due  to  the  injury 
acting  on  lower  infra-cortical  centres,  whose  action  inhibits  movement,  but  these  movements  are 
recovered  as  soon  as  the  inhibitory  action  ceases. 

378.    TOPOGRAPHY    OF    THE    CORTEX    CEREBRI.— A   short 

resinne  of  the  arrangement  of  convolutions,  according  to  Kcker,  is  given  in  §  375. 

I.  The  cortical  motor  areas  for  the  face  and  the  limbs  are  grouped  around 


Fig.  488. 


Fn;.  4S9. 


Motor  areas  in  man  shaded— outer  surface  of  the  left  side  Inner  surface  of  right  hemisphere.  AS,  area  governing 
of   human   brain.       Dotted    area,   the  aphasic   region  the  movements  of  the  arm  and  shoulder;    Tr,  ot 

(modified  from  Gowers).  the  trunk  ;  leg,  those  of  the  leg  :   Gf,  gyrus  forni- 

catus  ;   CC, corpus  callosum  ;  i/,  uncinate  gyrus  ;  O, 

occipital  lobe. 


the  fissure  of  Rolando,  including  the  ascending  frontal,  ascending  parietal,  and 
part  of  the  parietal  lobule  (Fig.  4883.  The  centre  for  the  face  occupies  the 
lowest  third  of  the  ascending  frontal  convolution,  and  reaches  also  to  the  lowest 
fifth  of  the  ascending  parietal.  The  arm  centre  occupies  the  middle  third  of  the 
ascending  frontal  and  middle  three-fifths  of  the  ascending  parietal  convolutions, 
while  the  leg  centre  lies  at  the  upper  end  of  the  sulcus  and  extends  backward  into 
the  parietal  lobule  (and  perhaps  on  to  the  superior  frontal  convolution)  (Fig.  488). 


TOPOGRAPHY  OF  THE  MOTOR  CENTRES. 


757 


The  leg  centre  is  continued  over  on  to  the  paracentral  lobule,  opposite  the  upper 
end  of  the  fissure  of  Rolando,  in  the  marginal  convolution  on  the  mesial  aspect 
of  the  hemisphere  (Fig.  490),  where  the  centres  for  the  muscles  of  the  trunk  also 
exist  (p.  748).  The  centre  for  speech  is  in  the  posterior  part  of  the  third  left 
frontal  convolution  (Fig.  488). 

Blood  Supply. — These  convolutions  are  supplied  with  blood  from  four  to  five  branches  of  the 
Sylvian  artery,  which  may  sometimes  be  plugged  with  an  embolon.  When  a  clot  lodges  in  this 
artery,  the  branches  to  the  basal  ganglia  may  remain  pervious,  while  the  cortical  branches  may  be 
plugged  {Duvet,  Heubner^  (|  381). 

[Hemiplegia  consists  of  motor  paralysis  of  one-half  of  the  body,  although,  as 
a  rule,  all  the  muscles  are  not  paralyzed  to  the  same  extent ;  in  some  there  may  be 
complete  paralysis,  /.  e.,  they  are  entirely  removed  from  voluntary  control,  while  in 
others,  there  is  merely  impaired  voluntary  control.  It  may  be  caused  by  affections 
of  the  cortical  areas  or  by  lesion  of  the  motor  tracts  above  the  medulla,  and  the 

paralysis  is  always  on  the  side  op- 


FiG.  490. 


posite  to  the  lesion,  owing  to  the 
decussation  of  the  motor  paths  in  the 
medulla.  If  the  case  be  a  severe  one, 
we  have  what  Charcot  terms  hemiplegie 
centralevulgai7-e,  or  "complete  hemi- 
plegia," due  to  lesion  of  the  corti- 
cal centres  for  the  face,  arm,  and  leg. 
While  the  arm  and  leg  are  com- 
pletely paralyzed,  the  lower  part  of 
the  face  is  more  affected  than  the 
upper  half,  which  is  usually  not 
much  affected.  All  those  move- 
ments under  voluntary  control,  and 


Transverse  section  of  a  cerebral  hemisphere.  CCa,  corpus  cal- 
losum;  NC,  caudate  nucleus;  NL,  lenticular  nucleus;  IC, 
internal  capsule;  CA,  internal  carotid  artery;  aSL, lenticulo- 
striate  artery;  ("Artery  of  hemorrhage");  F,  A,  L,  T, 
position  of  motor  areas  governing  the  movements  of  the  face, 
arm,  leg,  and  trunk  muscles  of  the  opposite  side  {Uorsley). 


Scheme   of   the   innervation  of   bilaterally 
associated  muscles  {Ross). 


especially  those  that  have  been  learned,  are  abolished,  while  the  associated 
and  bilateral  movements,  which  even  animals  can  execute  immediately  after 
birth,  remain  more  or  less  unaffected.  Hence,  the  hand  is  more  paralyzed 
than  the  arm;  this,  again,  than  the  leg;  the  lower  facial  branches  more  than  the 
upper ;  the  nerves  of  the  trunk  scarcely  at  all  (^Ferrier).  When  an  extraordi- 
nary effort  is  made,  it  will  be  found  that  there  is  some  impairment  of  the  power 
of  the  muscles  of  mastication  and  respiration,  although  the  muscles  on  opposite 
sides  act  together  {Gowers).  The  trunk  muscles,  as  a  rule,  are  but  slightly  affected, 
or  not  all,  as  their  centre  is  elsewhere.  There  may  be  alterations  of  sensibility 
and  of  the  reflexes.] 


758  HEMIPLEGIA. 

[Conduction  through  the  whole  of  the  pyramidal  fibres  coming  from  one  hemisphere  may  be 
interrupted,  and  yet  all  the  muscles  on  the  opposite  side  of  the  body  are  not  paralyzed.  The  muscles 
which  are  comparatively  unafl'ected  are  those  associated  in  their  action  with  the  muscles  of  the 
opposite  side,  <'.,i,':,  the  respiratory  muscles.  Broadbent  assumes  that  such  muscles  have  a  bilateral 
representation  in  the  motor  areas.  Suppose  in  Fig.  491,  15,  B'',  to  represent  the  cerel)ral  cortex;  M, 
M,  motor  centres  in  it ;  N,  N'',  nerve  nuclei  in  the  spinal  cord  or  medulla  oblongata;  P,  P'',  the 
pyramidal  tracts  passing  to  spinal  nuclei  N,  N**;  w,  m' ,  nerves  proceeding  from  the  last.  1,  2,  3,  4, 
5,  represent  difl'erent  lesions.  In  the  case  of  muscles  on  opposite  sides  of  the  body,  which  act 
independently,  c•._^^,  those  of  the  hand,  this  is  all  the  mechanism,  but  in  bilaterally  associated  muscles 
there  is  another  mechanism,  viz.,  commissural  fibres  between  the  nerve  nuclei,  the  one  c  conducting 
from  right  to  left,  and  c'  from  left  to  right.  When  there  is  an  injury  at  I  or  3,  impulses  can  still  pass 
from  the  uninjured  side  M  to  N'  and  through  c'  to  the  muscles  in,  m' .  In  this  way,  both  muscles 
receive  motor  impulses  from  one  hemisphere  (;?cw).] 

Conjugate  deviation  of  the  eyes,  with  rotation  of  the  head,  is  frequently  present  in  the  early 
period  of  hemiplegia,  aitliough  it  usually  disappears.  When  a  person  turns  his  head  to  one  side,  there 
is  an  associated  movement  of  certain  of  the  ocular  muscles  with  those  of  the  neck.  The  head  and  eyes 
are  usually  turned  to  the  side  of  the  lesion  ;  this  is  termed  "  conjugate  deviation,"  so  that  the  power 
of  voluntarily  moving  the  eyes  and  head  to  the  paralyzed  side  is  temporarily  lost.  The  unopposed 
muscles  rotate  the  head  and  eyes  to  the  sound  side.  If  the  lesion  be  in  the  posterior  part  of  the 
pons,  the  deviation  is  to  the  paralyzed  side  {Frevost). 

[Subsequent  Effects. — If  there  be  a  hemorrhage,  say  into  these  motor  regions,  or  from  the 
lenticulo-striate  artery,  so  as  to  compress  the  pyramidal  fibres  in  the  knee  and  anterior  two-thirds  of 
the  posterior  segment  of  the  internal  capsule,  then  there  is  usually  tonic  or  persistent  contraction  of 
the  muscles  affected.  These  tonic  spasms  may  accompany  the  hemorrhage,  or  come  on  a  few  days 
after  it,  and  set  up  the  condition  of  early  rigidity.  The  contraction  or  spasm — if  any — accompany- 
ing the  hemon'hage,  is  due  to  direct  irritation  of  the  pyramidal  fibres,  while  that  which  comes  on  a 
few  days  later,  and  usually  lasts  a  few  weeks,  is  also  due  to  irritation  of  these  fibres,  probably 
produced  by  inflammatory  action  in  and  around  the  seat  of  the  lesion.  The  affected  limb  is  stiff  and 
resists  passive  movement.  After  a  few  weeks,  late  rigidity  sets  in  and  is  persistent,  and  it  is  character- 
ized by  structural  changes  in  the  pyramidal  paths  which  lead  to  other  results.  There  is  secondary 
descending  degeneration  in  the  pyramidal  tracts,  which  causes  "  contracture  "  in  the  paralyzed 
limbs,  while  at  the  same  time,  the  deep  or  tendinous  and  periosteal  reflexes  (ankle  clonus,  rectus 
clonus,  and  the  deep  reflexes  of  the  arm  tendons,  are  exaggerated).  The  spastic  rigidity  is  usually 
more  marked  in  the  arm  than  in  the  leg,  and  it  generally  aflects  the  flexors  more  than  the  extensors, 
so  that  the  upper  arm  is  drawn  close  to  the  trunk,  the  elbow,  arm,  and  fingers  flexed ;  in  the  leg,  the 
extensors  of  the  leg  overcome  the  peronei.  Hitzig  has  pointed  out  that  the  contracture  is  less  during 
sleep,  and  after  rest.  The  muscles  at  first  can  be  stretched  by  sustained  pressure,  l)ut  after  months  or 
years,  structural  changes  occur  in  the  muscles,  ligaments,  and  tendons,  and  the  limbs  assume  a  per- 
manent and  characteristic  attitude.] 

In  hemiplegic  persons,  the  power  of  the  unparalyzed  side  is  sometimes  diminished,  which  is  not 
sufficiently  explained  by  the  fact  that  some  bundles  of  the  pyramidal  tracts  remain  on  the  same  side 
i^Brown- Sequard ,  Charcot). 

Acquired  Movements. — Some  movements  performed  by  man  are  learned  only  after  much 
practice,  and  are  only  completely  brought  under  the  influence  of  the  will  after  a  time,  such  as  the 
movements  of  the  hand  in  learning  a  trade.  Such  movements  are  re-acquired  only  very  slowly,  or  not 
at  all,  after  injury  to  the  motor  areas  in  which  they  are  represented.  Those  movements,  however, 
which  the  body  performs  without  previous  training,  such  as  the  associated  movements  of  the  eyeballs, 
the  face,  and  some  of  those  of  the  legs,  are  rapidly  recovered  after  such  an  injury,  or  they  suffer 
but  little,  if  at  all.  Thus,  the  facial  muscles  seem  never  to  be  so  completely  paralyzed  after  a  lesion 
of  the  facial  cortical  centre,  as  in  affections  of  the  trunk  of  the  facial  nerve ;  the  eye  especially  can 
be  closed.     Sucking  movements  have  been  observed  in  hemicephalous  foetuses. 

Degeneration  of  the  Pyramidal  Tracts. — After  destruction  of  the  cortical 
motor  areas,  descending  degeneration  of  the  cortico-motor  paths,  or  "pyramidal 
tracts,''  takes  place  (§  365).  Degenerative  changes  have  been  found  to  occur 
within  the  white  matter  under  the  cortex  in  the  anterior  two-thirds  of  the 
posterior  segment  of  the  internal  capsule,  [in  the  middle  third  of  the  crusta  (Figs. 
492,  *,  493,  L],  pons,  in  the  anterior  pyramids  of  the  medulla  oblongata  (Fig. 
492),  and  thence  they  have  been  traced  into  the  pyramidal  paths  (direct  and 
crossed)  of  the  spinal  cord  (Charcot,  Si>iger).  It  is  evident  that  lesions  of  these 
tracts  at  any  part  of  their  course  must  have  the  same  result,  viz.,  to  produce  hemi- 
plegia. (For  the  subsecjuent  effects,  see  p.  699.)  In  a  case  of  congenital  absence 
of  the  left  forearm,  Edinger  found  that  the  right  central  convolutions  were  less 
developed. 


DEGENERATION    OF   THE    PYRAMIDAL   TRACTS. 


759 


It  is  doubtful  if  the  muscular  sense  is  represented  in  the  motor  areas ;  Nothnagel  supposes  it  to 
be  located  in  the  temporal  parietal  lobes.  It  is  to  be  noted,  however,  that  in  man  there  may  be 
general  loss  of  the  muscular  sense  or  of  motor  representations,  and,  on  the  other  hand,  a  pure  motor 
paralysis  without  loss  of  the  former. 

Ataxic  motor  conditions,  similar  to  those  that  occur  in  animals  (p.  750),  take  place  in  man,  and 
are  known  as  cerebral  ataxia. 

The  position  of  the  centres  is  given  at  p,  746. 

[But  we  may  have  localized  lesions  affecting  one  or  more  of  the  cortical 
motor  areas ;  these  are  called  monoplegise.  Cases  in  man  are  now  sufficiently 
numerous  to  permit  of  accurate  diagnosis.]  Crural  monoplegia  [rare  lesions 
recorded  in  the  convolutions  at  the  upper  end  of  the  fissure  of  Rolando,  and 
the  continuation  of  this  area  on  to  the  paracentral  lobule  of  the  marginal  convolu- 
tion],— brachio-crural,  more  common,  in  the  upper  and  middle  thirds  of  the 


Fig.  492. 


Secondary  descending  degeneration  in  middle  third  of  right  crus 
and  medulla,  after  destruction  of  the  cortical  motor  centres 
on  the  right  side. 


Horizontal  section  of  the  cerebral  peduncle  in  second- 
ary degeneration  of  the  pyramidal  tracts,  where 
the  lesion  was  limited  to  the  middle  third  of  the  pos- 
terior segment  of  the  internal  capsule.  F,  healthy 
crusta;  L,  locus  niger  ;  P,  internal  third  of  the 
crustaon  the  diseased  side;  D,  secondary  degenera- 
tion in  the  middle  third  of  the  crusta  ;  CQ,  corpora 
quadrigemina  with  the  iter  below  them. 


ascending  frontal  and  ascending  parietal  convolutions — brachial,  brachio-facial 
— facial,  the  last  in  the  lowest  part  of  the  central  convolutions. 

Paralysis  of  the  muscles  of  the  neck  and  throat  indicates  a  lesion  of  the  central  convolutions,  and 
so  does  paralysis  of  the  muscles  of  the  eye.  Lesions  of  the  cortex  always  cause  simultaneous  move- 
ments of  the  head  and  eyeballs. 

Irritation  of  the  Motor  Centres. — If  the  motor  centres  are  irritated  by 
pathological  processes,  such  as  hypersemia,  or  inflammation  in  a  syphilitic  diathesis 
— more  rarely  by  tumors,  tubercle,  cysts,  cicatrices,  fragments  of  bone — there 
arise  spasmodic  movements  in  the  corresponding  muscle  groups.  This  condition 
of  a  sudden  discharge  of  the  gray  matter  resulting  in  local  spasms  is  called  "  Jack- 
sonian  cerebral  epilepsy." 

[Convulsions  and  spasms  may  be  discharged  from  motor  cortical  lesions,  and 


760  POSITION    OF   THE    MOTOR    CENTRES. 

these,  whether  they  affect  the  general  or  localized  areas,  give  rise  to  unilateral  con- 
volutions and  monospasm  respectively.] 

Monospasm. — According  to  the  seat  of  the  spasm,  it  is  called /^rw/,  brachial,  crural  mono- 
spasm, etc.  Of  course  these  spasms  may  affect  several  groups  of  muscles.  Bartholow  and  Sciamanna 
have  stimulated  the  exposed  human  brain  successfully  with  electricity. 

Cerebral  Epilepsy. — Very  powerful  stimulation  of  one  side  may  give  rise  to 
bilateral  spasms,  with  loss  of  consciousness.  In  this  case,  impulses  are  conducted 
to  the  other  hemisphere  by  commissural  fibres  (§  379). 

Movements  of  the  Eye. — Nothing  definite  is  known  regarding  the  centre  in  the  corte.x  for  volun- 
tary combined  movemenls  of  the  eyeballs  in  man.  In  paralytic  alTectious  of  the  cortex  and  of  the 
paths  proceeding  from  it,  we  occasionally  find  both  eyes  with  a  lateral  deviation.  If  the  paralytic 
affection  lies  in  one  cerebral  hemisphere,  the  conjugate  deviation  of  the  eyeballs  is  toward  the 
sound  side  (p.  638).  If  it  is  situated  in  the  conducting  paths,  after  these  have  decussated,  viz.,  in 
the  pons,  the  eyes  are  turned  toward  the  paralyzed  side  {Pri-vost). 

If  the  part  be  irritated  so  as  to  produce  spasms  in  the  opposite  side  of  the  body,  of  course  the  eyes 
are  turned  in  the  direction  opposite  to  that  in  pure  paralysis.  Instead  of  the  lateral  deviation  of  the 
eyeballs  already  described,  there  is  occasionally  in  cerebral  paralysis  merely  a  weakening  of  the 
lateral  recti  muscles,  so  that  during  rest  the  eyes  are  not  yet  turned  toward  tlie  sound  side,  but  they 
cannot  be  turned  strongly  toward  the  affected  side  {Leichtenstem,  Niinnius).  The  centre  for  the 
levator  palpebne  superioris  appears  to  be  placed  in  the  angular  gyrus  {Grassel,  Landouzy). 

II.  The  Centre  for  Speech. — The  investigations  of  Bouilland  [1825],  Dax 
[1S36],  Kroca  [1861],  Kussmaul,  Broadbent  and  others  have  shown  that  the 
third  left  frontal  convolution  of  the  cerebrum  (Figs.  484,  F3,  and  488)  is  of 
essential  importance  for  speech,  while  probably  the  island  of  Reil  is  also  concerned. 
The  island  is  deeply  placed,  and  is  seen  on  lifting  up  the  overhanging  part  of  the 
brain  called  the  operculum,  lying  between  the  two  branches  of  the  Sylvian  fissure 
(S).  The  motor  centres  for  the  organs  of  speech  (lips,  tongue)  lie  in  this  region, 
and  here,  also,  the  psychical  processes  in  the  act  of  speech  are  completed.  In  the 
great  majority  of  mankind,  the  centre  for  speech  is  located  in  the  left  hemisphere. 
The  fact  that  most  men  are  right-ha?ided  a-ho  points  to  a  finer  construction  of  the 
motor  apparatus  for  the  upper  extremity,  which  must  also  be  located  in  the  left 
hemisphere.  Men,  therefore,  with  pronounced  right-handedness  ("droiters")  are 
evidently  left- brai ned  {"  ga.nchQrs  du  cerveau" — Broca).  By  far  the  greater  num- 
ber of  mankind  are  ''  left-brained  speakers^  ^  (^Kussmaul)  ;  still  there  are  exceptions. 
As  a  matter  of  fact,  cases  have  been  observed  of  left-handed  persons  who  lost  their 
power  of  speech  after  a  lesion  of  the  right  hemisphere  {Ogle').  Investigations  on 
the  brains  of  remarkable  men  have  shown  that  in  them  the  third  frontal  convolu- 
tion is  more  extensive  and  more  complex  than  in  men  of  lower  mental  calibre. 
In  deaf  mutes  it  is  very  simple ;  microcephales  and  monkeys  possess  only  a  rudi- 
mentary third  frontal  {Riidinger). 

The  motor  tract  for  speech  passes  along  the  upper  edge  of  the  island  of  Reil,  then  into  the 
substance  of  the  hemispheres  internal  to  the  posterior  edge  of  the  knee  of  the  internal  capsule  ;  from 
thence,  through  the  crusla  of  theleft  cerebral  peduncle  into  the  left  half  of  the  pons,  where  it  crosses 
then  into  the  medulla  oblongata,  which  is  the  place  where  all  the  motor  nerves  (trigeminus,  facial, 
hypoglossal,  vagus  and  the  respiratory  nerves)  concerned  in  speech  arise.  Total  destruction  ot  these 
paths,  therefore,  cause  total  aphasia  ;  while  partial  destruction  causes  a  greater  or  less  disturbance  of 
the  mechanism  of  articulation, which  has  been  called"  anarthria"  by  Leyden  and  Wernicke. 

Conditions. — Three  activities  are  required  for  speech — (i)  the  normal  move- 
ment of  the  vocal  apparatus  (tongue,  lips,  mouth  and  respiratory  apparatus)  ;  (2) 
a  knowledge  of  the  signs  for  objects  and  ideas  (oral,  written  and  imitative  or 
mimetic  signs)  ;  (3)  the  correct  union  of  both. 

Aphasia  («  priv.  and  ^aiTj?  speech) — Injury  of  the  speech  centre  causes  either 
a  loss  or  more  or  less  considerable  disturbance  of  the  power  of  speech.  The  loss 
of  the  power  of  speech  is  called   "aphasia.'^     [Aphasia,   as  usually  understood. 


APHASIA. 


761 


means  the  partial  or  complete  loss  of  the  power  of  articulate  speech  from  cerebral 
causes.] 

The  following  forms  of  aphasia  may  be  distinguished : — 

1.  Ataxic  aphasia  (or  the  oro-lingual  hemiparesis  of  Ferrier),  i.  e.,  the  loss  of  speech  owing  to 
inability  to  execute  the  various  movements  of  the  mouth  necessary  for  speech.  Whenever  such  a 
person  attempts  to  speak,  he  merely  executes  incoordinated  grimaces  and  utters  inarticulate  sounds. 
[The  muscles  concerned  in  articulation,  however,  are  not  paralyzed,  but  there  is  an  absence  of 
coordination  of  these  muscles  due  to  disease  of  the  cortical  centre.]  Hence,  the  patient  cannot 
repeat  what  is  said  to  him.  Nevertheless,  \h&  psychical  processes  necessary  for  speech  are  completely 
retained,  and  all  words  are  remembered ;  and  hence,  these  persons  can  still  give  expression  to  their 
thoughts  graphically  or  by  writing.  If,  however,  the  finely  adjusted  movements  necessary  for 
writing  are  lost,  owing  to  an  affection  of  the  centre  for  the  hand,  then  there  arises  at  the  same  time 
the  condition  of  agraphia,  or  inability  to  execute  those  movements  necessary  for  writing.  Such  a 
person,  when  he  desires  to  express  his  ideas  in  writing,  only  succeeds  in  making  a  few  unintelligible 
scrawls  on  the  paper.  Occasionally  such  patients  sufler  from  loss  of  the  power  of  imitation  or  the 
execution  of  particular  movements  of  the  limbs  and  body  constituting /flw/cwz'wf  speech  or  amimia 
i^Ktisstnaul'). 

2.  Amnesic  Aphasia,  or  Loss  of  the  Memory  of  Words. — Should  the  patient,  however,  hear  the 
word,  its  significance  recurs  to  him.  The  movements  necessary  for  speech  remain  intact ;  hence, 
such  a  patient  can  at  once  repeat  or  write  down  what  is  said  to  him.  Sometimes  only  certain  kinds 
of  words  are  forgotten,  or  it  may  be  even  only  parts  of  certain  words,  so  that  only  part  of  these 
words  is  spoken.  [Nouns  and  proper  names  usually  go  first.]  Cases  of  amnesic  aphasia,  or  the 
mixed  ataxic-amnesic  form  of  disturbance  of  speech,  point  to  a  lesion  of  the  third  frontal  convolu- 
tion and  of  the  island  of  Reil  on  the  left  side.  Another  form  of  amnesic  aphasia  consists  in  this 
that  the  words  remain  in  one's  memory  but  do  not  come  when  they  are  wanted,  i.  e.,  the  association 
between  the  idea  and  the  proper  word  to  give  expression  to  it  is  inhibited  i^Kussmaul).  It  is  common 
for  old  persons  to  forget  the  names  of  persons  or  proper  names;  indeed,  such  a  phenomenon  is 
common  within  physiological  limits,  and  it  may  ultimately  pass  into  the  pathological  condition  of 
amnesia  senilis.  Among  the  disturbances  of  speech  of  cerebral  origin,  Kussmaul  reckons  the 
following : — 

3.  Paraphasia,  or  the  inability  to  connect  rightly  the  ideas  with  the  proper  words  to  express  these 
ideas,  so  that,  instead  of  giving  expression  to  the  proper  ideas,  the  sense  may  be  inverted,  or  the 
form  of  word^  may  be  unintelligible.  It  is  as  if  the  person  were  continually  making  a  "  slip  of  the 
tongue." 

4.  Agrammatism  and  ataxaphasia,  or  the  inability  to  form  the  words  grammatically  and  to 
arrange  them  synthetically  into  sentences.     Besides  these,  there  is — 

5.  A  pathological  slow  way  of  speaking  (bradyphasia),  or  a  pathological  and  stuttering  way  of 
reading  (tumultus  sermonis),  both  conditions  being  due  to  derangement  of  the  cortex  {^Ktissmaul). 
The  disturbances  of  speech  depending  essentially  upon  affections  of  the  peripheral  nerves,  or  or 
the  muscles  of  the  organs  of  the  voice  and  speech,  are  already  referred  to  in  \\  319,  349,  and  354. 

[In  word  blindness,  the  person  cannot  name  a  letter  or  a  word,  so  that  he 
cannot  understand  symbols,  such  as  printed  or  written  words,  or  it  may  be  any 
familiar    o  b  j  e  c  t,    al- 
though    he     can      see  ^ig.  494-  Fig.  495- 
quite    well,    while    he 
can  speak  fluently  and 
write  correctly.] 

[In  wo  r  d  d  e  a  f- 
ness,  the  person  hears 
other  sounds  and  is  not 
deaf,  but  he  does  not 
hear  words.] 

[The  study  of  aphasia  in 
its  various  forms  is  simplified 
by  a  study  of  the  mode  of 
acquisition  of  language 
by  a  child.  The  child  hears 
spoken  words  and  obtains 
auditory  memories  or  impres- 
sions of  these  sounds  (called  by  Lichtheim  "  auditory  word  representations  "),  and  this  must 
form  the  starting-point  of  language,  and  by  and  by  it  begins  to  coordinate  its  muscles  to  produce 


Schemes  of  aphasia.  A,  centre  for  auditory  images;  M,  for  motor  images; 
B,  perception  centre;  Oc,  eye;  E,  reading  centre;  i  to  7,  lesions  {Lich- 
theim'). 


762 


APHASIA. 


sounds  imitative  of  these.  Thus  we  have  two  centres,  one  for  ••  auditory  images  "  (Fig.  494,  A), 
and  the  other  for  "  motor  images  "  (Fig.  494,  M),  and  these  two  must  be  connected,  thus  estab- 
hshini^  a  retlex  arc.  There  is  a  receptive  and  an  emissive  department  as  represented  in  the  scheme. 
We  must  .issume  the  existence  of  a  higher  centre  (B),  "in  which  concepts  are  elaborated,"  where 
these  sounds  become  intelligible.  Volitional  language  reijuires  a  conneciion  between  H  and  M,  as 
well  as  between  A  and  M.  But  we  have  also  reading  and  writing.  Suppose  O  to  re|)resent  a 
centre  for  visual  impressions  (printed  words  or  writing) :  these  we  can  understand  through  the  con- 
nection between  such  visual  impressions  and  auditory  inijiressions,  whereby  a  jiath  is  estal)lished 
through  ().\  (Fig.  495).  In  reading  aloud,  however,  the  oro-lingual  muscles  must  be  coordinated, 
so  we  have  the  path  OAM  opened  up.  In  writing,  or  copying  written  characters,  the  movements  of 
the  hand  are  special,  and  perhaps  require  a  special  centre,  or  at  least  a  special  arrangement  of  the 
channels  for  impulses  in  the  centre;  the  movements  are  learned  under  the  guidance  of  ocular  impres- 
sions, so  we  connect  O  and  E,  E  being  the  centre  guiding  the  movements  in  writing.  As  to 
volitional  writing,  the  impulse  passes  through  M — but  does  it  pass  directly  to  E,  or  indirectly  through 
A  ?  Lichtheim  assumes  that  it  goes  direct  from  M  to  E.  It  is  evident  that  there  are  seven  channels 
which  may  be  interrupted,  each  one  giving  rise  to  a  different  form  of  aphasia  (l  to  7).] 

[Looked  at  from  another  point  of  view,  either  the  ingoing  (,-7)  or  outgoing  ( w)  channels  or  centres, 
or  the  commissural  fibres  between  both,  may  be  affected.  If  the  motor  centre  is  affected,  we  have 
Wernicke's  "motor  aphasia;"  if  the  sensory,  his  "  sensory  aphasia."] 

[In  the  most  common  form,  or  ataxic  aphasia  [A'uss///<!///),  which  was  that  described  by  Broca, 
or  the  "motor  aphasia"  of  Wernicke,  the  lesion  is  in  Fig.  494,  in  M.,  /.  e.,  in  the  motor,  or  what 
Ross  calls  the  emissive  department.  In  such  a  case,  it  is  obvious  that  there  will  be  loss  of  (l)  voli- 
tional speech,  (2)  repetition  of  words,  (3)  reading  aloud,  (4)  volitional  writing,  and  (5)  writing  to 

dictation ;  while  there  will  exist  (a)  understanding 
of  spoken  words,  {/>)  also  of  written  words,  (c)  and 
the  faculty  of  copying.  If  the  lesion  be  in  A,  we  have 
the  "  sensorial  aphasia "  of  Wernicke,  ?'.  e.,  in  the 
acoustic  word  centre;  we  find  loss  of  (i)  understand- 
ing of  spoken  language,  (2)  also  of  written  language, 
(3)  faculty  of  repeating  words,  (4)  and  of  writing  to 
dictation,  (5)  and  of  reading  aloud;  there  will  exist 
(tr)  the  faculty  of  writinn;,  (6)  of  copying  words,  and  (c) 
of  volitional  speech,  but  the  volitional  speech  is  imper- 
fect, the  wrong  word  being  often  used,  so  that  there  is 
the  condition  of  "paraphasia."  If  the  connection 
between  A  and  M  be  destroyed,  other  results  will  follow, 
and  such  cases  of  "commissural"  apha'^ia  have  been 
described  by  Wernicke.  If  the  interruption  be  between 
B  and  M,  we  have  a  not  uncommon  variety  of  motor 
aphasia  (4).  when  there  is  loss  of  (i)  volitional  speech, 
and  (2)  volitional  writing,  and  there  exist  (a)  under- 
standing of  spoken  language,  [/>)  of  written  language, 
(c)  and  the  faculty  of  copying;  but  it  differs  from 
Broca's  aphasia  in  that  there  also  exists  the  faculty  [d) 
of  repeating,  words,  (e)  of  writing  to  dictation,  {/)  and 
of  reading  aloud.  If  the  lesion  is  in  Mm  (5),  the 
symptoms  will  be  those  of  Broca's  aphasia,  but  there 
will  exist  (i)  the  faculty  of  volitional  writing,  and  (2) 
of  writing  to  dictation.  Many  examples  of  this  occur 
where  patients  have  lost  the  faculty  of  speaking,  but 
can  express  their  thoughts  in  writing.  In  lesions  of  the 
path  A  B  (6),  there  will  be  loss  of  (l)  understanding 
of  spoken  language,  and  (2)  of  written  language,  and 
there  will  exist  (<?)  volitional  speech  (but  it  will  be 
paraphasic),  (/>)  volitional  writing  (but  it  will  have  the 
characters  of  paragraphia),  (c)  the  faculty  of  repeating 
words,  (d)  reading  aloud,  {e)  writing  to  dictation,  and 
(/)  power  of  copying  words.  The  person  will  be 
quite  unable  to  understand  what  he  repeats,  reads  aloud,  or  copies.] 

[Fig.  496  shows  diagrammatically  the  conditions  in  motor  and  sensory  aphasia.  From  the  eye 
and  ear  centripetal  fibres  (v  and  a)  ascend  to  terminate  in  the  visual  (V)  and  auditory  centres  (A), 
in  the  cortex,  while  afferent  fibres  (s,  s'',  s^'),  indicated  by  dotted  lines,  also  pass  from  the  articula- 
tions, muscles  of  the  hand,  and  orbit  to  the  cerebnnn.  The  dotted  lines  on  the  surface  of  the  cortex 
represent  the  association  system  of  fibres  which  connects  the  centres  with  each  other.  The  centres 
for  vocal  (V)  and  written  expression  (W)  are  connected  by  centrifugal  fibres,  m  and  m'',  with  the 
hand  and  larynx  respectively  (A'(?yj-).] 


THE  AUDITORY,  GUSTATORY,  AND  OLFACTORY  CENTRES.     763 

III.  The  thermal  centre  for  the  extremities  is  associated  with  the  motor  areas  (^  377).  Injury 
or  degeneration  of  these  areas  causes  inequality  of  the  temperature  on  both  sides  {^Bechierew). 

IV.  The  sensory  regions  are  those  areas  in  which  conscious  perceptions 
of  the  sensory  impressions  are  accomplished.  Perhaps  they  are  the  substratum  of 
sensory  perceptions,  and  of  the  memory  of  sensory  impressions. 

1.  The  visual  centre,  according  to  Munk,  includes  the  occipital  lobes  (Fig. 
484,  o^,  o^  o^),  while,  according  to  Ferrier,  it  also  includes  the  angular  gyrus. 
Huguenin  observed,  in  a  case  of  long-standing  blindness,  consecutive  disappear- 
ance of  the  occipital  convolutions  on  both  sides  of  the  parieto-occipital  fissure, 
while  Giovanardi,  in  a  case  of  congenital  absence  of  the  eyes,  observed  atrophy  of 
the  occipital  lobes,  which  were  separated  by  a  deep  furrow  from  the  rest  of  the 
brain.  Stimulation  of  the  centre  gives  rise  to  the  phenomena  of  light  and  color. 
Injury  causes  disturbance  of  vision,  especially  hemiopia  of  the  same  side  (§  344 — 
Westphal).  When  o/ie  centre  is  the  seat  of  irritation,  there  is  photopsia  of  the  same 
halves  of  both  eyes  (  Charcot).  Stimulation  of  both  centres  causes  the  occurrence  of 
the  phenomena  of  light  or  color,  or  visual  hallucinations  in  the  entire  field  of  vision. 
Cases  of  injury  to  the  brain,  where  the  sensations  of  light  and  space  are  quite  intact, 
and  where  the  color  sense  alone  is  abolished,  seem  to  indicate  that  the  color  sense 
centre  must  be  specially  localized  in  the  visual  centre  {SamelsoJui).  After  injury  of 
certain  parts,  especially  of  the  lower  parietal  lobe,  ^^  psychical  blindness''''  may  occur, 
A  special  form  of  this  condition  is  known  as  "  word  blindness  "  or  alexia 
(Coecitas  verbalis),  which  consists  in  this,  that  the  patient  is  no  longer  able  to 
recognize  ordinary  written  or  printed  characters  (p.  761). 

Charcot  records  an  interesting  case  of  psychical  blindness.  After  a  violent  paroxysm  of  rage,  an 
intelligent  man  suddenly  lost  the  memory  of  visual  impressions;  all  objects  (persons,  streets,  houses) 
which  were  well  known  to  him  appeared  to  be  quite  strange,  so  that  he  did  not  even  recognize 
himself  in  a  mirror.     Visual  perceptions  were  entirely  absent  from  his  dreams. 

Clinical  observations  on  hemianopia  (§  344)  show  that  the  field  of  vision  of  each  eye  is  divided 
into  a  larger  outer  and  a  smaller  inner  portion,  separated  from  each  other  by  a  vertical  line  passing 
through  the  macula  lutea.  Each  right  or  left  half  of  both  visual  fields  is  related  to  (?«^  hemisphere ; 
both  left  halves  are  projected  upon  the  left  occipital  lobes,  and  both  right  upon  the  right  occipital 
lobes  (Fig.  487).  Thus,  in  binocular  vision,  every  picture  (when  not  too  small)  must  be  seen  in 
two  halves ;  the  left  half  by  the  left,  the  right  half  by  the  right  hemisphere  (  Wei-tticke). 

As  a  result  of  pathological  stimulation  of  the  visual  centre,  especially  in  the  insane,  visual  spectres 
may  be  produced.  Pick  observed  a  case  where  the  hallucinations  were  confined  to  the  right  eye. 
Celebrated  examples  of  ocular  spectra  occurred  in  Cardanus,  Swedenborg,  Nicolai,  J.  Kerner,  and 
Holderlin. 

After  degeneration  of  the  cortical  centre,  the  fibres  which  connect  the  occipital  lobes  with  the 
external  geniculate  body,  the  anterior  corpora  quadrigemina,  pulvinar,  these  structures  themselves, 
and  the  origin  of  the  optic  tract  undergo  degeneration  {y.  Monakow) . 

2.  The  auditory  centre  lies  on  both  sides  (crossed)  in  the  temporo-sphenoidal 
lobes  [according  to  Ferrier  in  the  superior  temporal  convolution]  ;  when  it  is 
completely  removed,  deafness  results,  while  partial  (left  side)  injury  causes  psychical 
deafness.  [See  p.  754  for  contradictory  results.]  Among  the  phenomena  caused  by 
partial  injury  is  sicrditas  ve7'balis  (\A^ord  deafness),  which  may  occur  alone  or  in 
conjunction  with  coecitas  verbalis.  Wernicke  found  in  all  cases  of  word  deafness 
softening  of  the  first  left  temporo-sphenoidal  convolution  (p.  754).  In  left-handed 
persons,  the  centre  lies  perhaps  in  the  right  temporo-sphenoidal  lobes  {JVestphal'). 

Clinical. — We  may  refer  word  blindness  and  word  deafness  to  the  aphataxic  group  of  diseases, 
in  so  far  as  they  resemble  the  amnesic  form.  A  person  word  blind  or  word  deaf  resembles  one  who 
in  early  youth  has  learned  a  foreign  tongue,  which  he  has  completely  forgotten  at  a  later  period. 
He  hears  or  reads  the  words  and  written  characters;  he  can  even  repeat  or  write  the  words,  but  he 
has  completely  lost  the  significance  of  the  signs.  While  an  amnesic- aphasic  pei'son  has  only  lost 
the  key  to  open  his  vocal  treasure,  in  a  person  who  is  word  blind  or  word  deaf  even  this  is  gone. 
From  a  case  of  recovery  it  is  known  that  to  the  patient  the  words  sound  like  a  confused  noise. 
Huguenin  found  atrophy  of  the  temporo-sphenoidal  lobes  after  long-continued  deafness. 

3.  Gustatory  and  Olfactory  Centre. — In  the  uncinate  gyrus  on  the  inner 
side  of  the  temporo-sphenoidal  lobe  (especially  on  the  inner  side  of  that  marked 


764 


THE    PSYCHO-SENSORIAL    PATHS. 


U  in  Fig.  480),  Ferrier  locates  the  joint  centres  for  smell  and  taste.     These  two 
centres  do  not  seem  to  be  distinct,  locally,  from  each  other. 

4.  Tactile  Areas. — According  to  Tripier  and  others,  all  the  tactile  cerebral 
fields  from  different  parts  of  the  body  coincide  with  the  motor  cortical  centres  for 
these  parts  [compare  p.  755]. 

Occasionally,  in  epileptics,  strong  stimulation  of  the  sensory  centres,  as  expressed  in  the  excessive 
subjective  sensations,  accompanies  the  spasmodic  attacks  (compare  i!  393,  12).  Such  epileptiform 
hallucinations,  however,  occur  without  spasms,  and  are  accompanied  only  by  disturbances  of  con- 
sciousness of  very  short  duration  i^Berger). 

Course  of  the  Sensory  Paths. — The  nerve  fibres  which  condnct  impulses 
from  the  sensory  organs  to  the  sensory  cortical  centres  pass  through  the  posterior 
third  of  the  posterior  limb  of  the  internal  capsule  between  the  optic  thalamus  and 
the  lenticular  nucleus  (Fig.  500,  S).  Hence,  section  of  this  part  of  the  internal 
capsule  causes  hemianaesthesia  of  the  opposite  half  of  the  body  {Charcot).  In 
such  a  case,  sensory  functions  are  abolished — only  the  viscera  retaining  their  sensi- 
bility. There  may  also  be  loss  of  hearing,  smell,  and  taste, — and  hemiopia  {Bech- 
tereiu). 

Pathological  — In  cases  where  there  is  more  or  less  injury  or  degeneration  of  these  paths,  there 
is  a  corresponding  greater  or  less  pronounced  loss  of  the  pressure  and  temperature  sense,  of  the 
cutaneous  and  muscular  sensibility,  of  taste,  smell,  and  hearing.  The  eye  is  rarely  quite  blind,  but 
the  shai-pness  of  vision  is  interfered  with,  the  field  of  vision  is  narrowed,  while  the  color  sense  may 
be  partially  or  completely  lost.     The  eye  on  the  same  side  may  suffer  to  a  slight  extent. 

V.  Numerous  cases  of  injury  of  the  anterior  frontal  region,  without  inter- 
ference with  motor  or  sensory  functions  have  been  collected  by  Charcot,  Ferrier, 

and  others.    On  the  other  hand, 


Fig.  497. 


enfeeblement  of  the  intelligence 
and  idiocy  are  often  observed 
in  acquired  or  congenital  de- 
fects of  the  prefrontal  region. 
In  highly  intellectual  men,  Rii- 
dinger  found  in  addition  a  con- 
siderable development  of  the 
temporo-sphenoidal  lobe.  Ac- 
cording to  Flechsig,  there  is  no 
doubt  that  the  frontal  lobes  and 
the  temporo-occipital  zone  are 
related  to  intellectual  processes, 
more  especially  the  "higher" 
of  these. 

Topography  of  the  Brain. — The 
relations  of  the  chief  fissures  and 
convolutions  of  the  brain  to  the  sur- 
face of  the  skull  are  given  in  Fig. 
484,  the  brain  being  represented  after 
Ecker.  [Turner  and  others  have 
given  minute  directions  for  finding 
the  position  of  the  different  convolu- 
tions by  reference  to  the  sutures  and 
other  prominent  parts  of  the  skull. 
The  annexed  diagram  by  R.  W. 
Reid  shows  the  relations  of  the  con- 
volutions to  certain  fixed  lines  (Fig. 

497)0 

[The  position  of  the  fissure  of  Ro- 
lando, where  its  upper  end  joins  the 
great  longitudinal  fissure,  is  ob- 
tained by  measuring  on  the  scalp,  K,  in  the  middle  line,  the  distance  between  the  glabella  and  the 
external  occipital  protuberance,  or  the  inion,  which,  in  ordinary  heads,  varies  from  11  to  13  inches 


Relation  of  the  fissures  and  convolutions  to  the  surface  of  the  scalp. 
-f- ,  most  prominent  part  of  the  parietal  eminence;  a,  convex 
line  bounding  parietal  lobe  below ;  b,  convex  line  bounding  the 
temporo-sphenoidal  lobe  behind  (/?.  \V.  Reid). 


THE    BASAL    GANGLIA. 


765 


(Fig.  499).  Measured  from  before  backward,  along  this  line,  the  distance  from  the  glabella  to  the 
top  of  the  fissure  is  55.7  per  cent,  of  the  length  of  the  whole  line.  The  direction  of  the  fissure  is 
downward  and  forward,  and  the  long  axis  of  the  fissure  forms,  with  the  average  mesi.1l  line,  an  angle 


of    67°,  the  angle  opening  forward. 

[The  fissure  of  Sylvius  is  found 
by  drawing  a  line  from  the  external 
angular  process  of  the  frontal  bone 
backward  to  the  occipital  protuber- 
ance, taking  the  nearest  route  between 
these  two  points.  A  point  l^^  i°ch 
backward  from  the  angular  process 
along  this  line,  marks  the  origin  of 
the  fissure ;  while  a  straight  line 
drawn  to  the  centre  of  the  parietal 
eminence  marks  the  course  of  its 
posterior  limb.  The  parieto-occipital 
fissure  will  be  two  inches  behind  the 
upper  end  of  the  Rolandic  fissure 
{A.  W.  Hare).'] 

[Corpus  Callosum. — It  is  usually 
stated  that  the  corpus  callosum  con- 
nects the  convolutions  of  one  side  of 
the  brain  with  those  on  the  other,  i.  e., 
that  it  is  an  inter-hemispherical  com- 
missure. D.  T-  Hamilton,  however, 
is  of  opinion  that  it  is  not  an  inter- 
hemispheric  commissure,  but  is  due  to 
cortical  fibres  coming  from  the  cortex 
cerebri  to  be  connected  with  the  basal 
ganglia  of  the  opposite  side.  On  this 
view,  the  "corona  radiata,"  as  usually 
understood,  consists  only  of  the  fibres 
which  pass  from  the  cerebral  peduncle 
directly  up  to  the  cortex  on  the  same 
side,  and  are  contained  in  the  poste- 
rior division  and  knee  of  the  internal 
capsule.  They  correspond  to  the 
motor  pyramidal  tracts.  Hamilton 
maintains  that  all  the  other  fibres  of 
the  internal  capsule  pass  into  the 
crossed  callosal  tract,  and  instead 
of  running  directly  up  to  the  cortex 
on  the  same  side,  cross  in  the  corpus 
callosum  to  the  cortex  of  the  opposite 
side.  Beevor,  relying  on  the  exam- 
ination of  the  brain  of  monkeys,  by 
•Weigert's  method,  denies  that  any 
fibres  of  the  corpus  callosum  pass 
into  the  external  or  internal  capsules, 
and  he  supports  the  old  view  that  the 
corpus  callosum  is  a  commissure  be- 
tween the  two  hemispheres.] 

Erb  observed  a  case  of  its  almost 
complete  destruction  without  any  con- 
siderable effect  on  motility,  coordi- 
nation, sensibility,  reflexes,  senses, 
speech,  or  any  marked  impairment  of 
intelligence. 

379.  BASAL  GANGLIA 
—  MID  -  BRAIN.  —  [The 
corpus  striatum  consists  of 
two  parts,  an  intra-ventricular 
portion  projecting  into  the 
lateral  ventricle,  the  caudate 


Its  average  length  is  3^  inches.] 


The  fissures  of  Rolando  and  Sylvius  are  marked  as  broad  dark  lines. 
The  shaded  circles  mark  approximately  the  motor  areas.  i»  lower 
extremity  ;  2,  3,  4,  5,  6,  and  a,  b,  c,  d,  upper  extremity  ;  7,  8, 9,  10 
II,  oro-Iingual  muscles  (^.  Jf.  Zfcr^). 

Fig.  499. 


PDF 


O.P 


Head,  skull,  and  cerebral  fissures.  OPr,  occipital  protuberance  : 
KAP,  external  angular  process  ;  SF,  Sylvian  fissure;  A,  its 
ascending  limb ;  "FR,  fissure  of  Rolando;  PE,  parietal_ 
eminence;  INIMA,  middle  meningeal  artery;  _TS,  tipot 
temporo-sphenoidal  lobe;  B,  Broca's  convolution:  IF,  in- 
ferior frontal  sulcus;  POF,  parieto-occipital  fissure;  IFF, 
iutra-parietal  sulcus  {A.  IV.  Hare). 


766  THE    BASAL    GANGLIA. 

nucleus,  and  an  extra-ventricular  portion,  the  lenticular  nucleus.  Between 
the  head  of  the  caudate  nucleus  internally,  and  the  lenticular  nucleus  externally, 
lies  the  anterior  division  of  the  internal  capsule.  The  fibres  which  pass  between 
these  ganglia  do  not  seem  to  form  connections  with  them.  The  expanded  head 
of  the  caudate  nucleus  is  in  front,  and  lies  inside  and  around  the  front,  of  the 
lenticular  nucleus,  with  which  and  the  anterior  ]:)erforated  space  it  is  continuous ; 
it  sweeps  backward  into  a  tailed  extremity,  which  nearly  surrounds  the  lenticular 
nucleus  like  a  loop.  The  lenticular  nucleus  is  biconvex  in  a  horizontal  section, 
but  triangular  and  subdivided  into  three  divisions  when  seen  in  a  vertical  section 
(Fig.  501).  The  older  observations  on  the  corpora  striata  in  man  may  be  dis- 
missed, as  a  distinction  was  not  drawn  between  injury  to  its  two  parts  on  the  one 
hand  and  the  internal  cai)sule  on  the  other. 

[The  caudate  nucleus  and  lenticular  nucleus  in  their  development  are 
codrdinate  with  the  develoi)ment  of  the  cortex  cerebri.  Electrical  stimulation 
of  these  ganglia  causes  general  muscular  contractions  in  the  opposite  half  of  the 
body,  which  are  due  to  simultaneous  stimulation  of  the  neighboring  cortico-mus- 
cular  paths.  The  same  result  is  obtained  as  if  all  the  motor  cortical  centres  were 
stimulated  simultaneously.] 

Gilky  did  not  obsa-ve  movements  on  stimulating  the  corpus  striatum  in  rabbits ;  it  would  seem 
that,  in  these  animals  the  motor  paths  do  not  traverse  these  ganglia,  but  merely  pass  alongside  of 
them. 

[Lesions  of  the  lenticular  nucleus  or  of  the  caudate  nucleus  do  not  seem  to 
give  rise  to  any  permanent  symptoms,  provided  the  internal  capsule  be  not  injured.] 
Destruction  of  the  internal  capsule,  however,  causes  paralysis  of  motion  or  sen- 
sibility, or  both,  on  the  opposite  side  of  the  body,  according  to  the  part  of  it 
which  is  injured.  The  corpus  striatum  is  quite  insensible  to  painful  stimulation 
{Longet). 

PathologicaL — In  man,  a  lesion,  not  too  small,  destrojing  the  anterior  part  of  the  corpus  striatum 
is  followed  by  permanent  paralysis  of  the  opposite  side,  provided  the  internal  capsule  is  injured,  but 
the  paralysis  gradually  disappears,  if  the  lenticular  and  caudate  nucleus  only  are  affected  (compare 
i  365).  Sometimes  there  is  dilatation  of  the  blood  vessels  in  consequence  of  vasomotor  paralysis 
(I  377)  'f  'h^  posterior  part  is  injured  [Xothnagel)  ;  redness  and  a  slightly  increased  temperature  of 
the  paralyzed  extremities,  at  least  for  a  certain  time;  swelling  or  fedema  of  the  extremities ;  sweating ; 
anomalies  of  the  pulse  detectable  by  the  sphygmograph  ;  decubitus  aculus  on  the  paralyzed  side; 
abnormalities  of  the  nails,  hair,  skin  ;  acute  inflammation  of  joints,  especially  of  the  shoulder.  Later, 
contracture  or  permanent  contraction  of  the  paralyzed  muscles  takes  place  (Hiiguenin,  Charcot). 
In  some  cases  there  is  cutaneous  anajsthesia,  and  occasionally  enfeeblement  of  the  sense  organs  of 
the  paralyzed  side,  and  both  when  the  posierior  third  or  sensory  crossway  of  the  posterior  section  of 
the  internal  capsule  is  affected.     Usually,  however,  hemiplegia  and  hemianasthesia  occur  together. 

Optic  Thalamus. — Ferrier  did  not  observe  any  movements  on  stimulating  the. 
optic  thalami  with  electricity.  As  the  pulvinar,  or  posterior  extremity  of  the  optic 
thalamus,  is  in  part  the  origin  of  the  optic  nerve,  and  is  also  connected  by  fibres 
with  the  cortex  cerebri,  it  is  probably  related  to  the  sense  of  sight.  Injury  to 
its  posterior  third  in  man,  results  in  disturbance  of  vision  (^■olh?jagel).  Ferrier 
surmises  that  the  sensory  fibres  pass  through  the  optic  thalami  on  their  way  to  the 
cortex,  so  that  when  they  are  destroyed,  insensibility  of  the  opposite  half  of  the 
body  is  produced.  Removal  of  the  optic  thalamus,  or  destruction  of  the  part  in 
the  neighborhood  of  the  inspiratory  centre  in  the  wall  of  the  third  ventricle,  influ- 
ences the  coordinated  movements  in  the  rabbit  {Christiani). 

We  know  very  little  definitely  as  to  the  functions  of  these  organs.  After  injur}-  to  one  thalamus, 
there  has  been  observed  enfeeblement  or  paralysis  of  the  muscles  of  the  opposite  side,  together  with 
mouvements  de  manege ;  ar.d  sometimes  hemianaesthesia  of  the  opposite  side,  with  or  without  affec- 
tions of  the  motor  areas,  have  been  recorded.  Extirpation  of  certain  cortical  areas  (rabbit)  is  followed 
by  atrophy  of  certain  parts  of  the  thalamus  (z'.  Monakow). 

[Internal  Capsule. — In  connection  with  the  functions  of  the  basal  ganglia  it 
is  most  important  to  remember  their  relation  to  the  internal  capsule.     The  corpus 


THE    INTERNAL   CAPSULE. 


767 


striatum  consists  of  an  intra-ventricular  part,  the  caudate  nucleus ;  and  an  extra- 
ventricular  part,  the  lenticular  nucleus.  The  lenticular  nucleus  consists  of  three 
parts,  best  seen  in  a  vertical  section  (501,  i,  2,  3),  with  white  matter  between 
them,  the  striae  medullares.     The  anterior  limb  of  the  internal  capsule  sweeps 


Fig.  500. 


Sepituu  lucidum 
Columnae  fomicis 

Corpus  striatum. 
Stria  terminalis. 
Thalamus  opticus. 


Cornu  anticum. 


Caput  uuclel  caudati 


Capsnla  interna 
(anterior  limb). 

Capsula  externa. 

Island  of  BeiL 

leus  lentiformis. 
Claustnim. 


Brachium  conjunc- 
tiynm  anticum. 
Peduuculus  ceiebr 

f  ad  corpora 

iquadrige- 
miua. 
Crus       J  ad  medullam 
jerebelli  |       ot>longa*nm 


Capsula  interna 
(posterior  limb). 
Thalamus  opticas. 


Corpus  genicula- 
tum  niedlale. 


Caudate  nucleus 


Hippocampus. 


'\~il^  Funiculus  gracilis. 


Human  brain  with  the  hemispheres  removed  by  a  horizontal  incision  on  the  right  side.  4,  trochlear ;  8,  acoustic 
nerve;  6.  origin  of  the  abducens  ;  F,  A,  L,  position  of  the  pyramidal  (motor)  fibres  for  the  face,  arm,  and  leg; 
S,  sensory  fibres. 

between  the  caudate  and  lenticular  nucleus,  while  the  posterior  segment  lies  between 
the  optic  thalamus  and  the  lenticular  nucleus  (Fig.  500).  External  to  the  first 
division  of  the  lenticular  nucleus  is  the  external  capsule  (Figs.  500,  501),  whose 
function  is  unknown.     External  to  this  is  the  claustrum,  whose  function  is  also 


768 


PEDUNCLE    AND    PONS. 


unknown.  It  is  evident  that  hemorrhage  into  or  about  the  basal  ganglia  is  apt  to 
involve  the  fibres  of  the  internal  capsule.]  When  the  lenticulo-striate  artery,  or 
as  it  is  called  the  "artery  of  hemorrhage,"  ruptures  (Fig.  490,  aSL),  it  may  not 
only  destroy  the  lenticular  nucleus,  but  the  internal  capsule  will  be  compressed  ; 
and  the  same  is  the  case  with  the  lenticulo-optic  artery — the  external  capsule  will 
tend  to  force  the  blood  inward.  We  know  that,  in  the  posterior  segment  of 
the  capsule,  the  volitional  or  pyramidal  fibres  lie  in  the  following  order  from  before 
backward — those  for  the  face  (and  tongiie)  in  the  knee,  in  the  anterior  third  those 
for  the  arm  and  hand,  and  in  the  middle  third  for  the  leg,  and  perhaps  behind  these 
those  for  the  trunk  (Fig.  500,  F,  A,  L),  so  that  a  very  small  lesion  in  this  region 
will  affect  a  large  number  of  these  fibres,  converging  as  they  do  like  the  rays  of  a 
fan  from  the  motor  cortical  areas,  where  the  arrangement  of  these  centres  is  a 
supero-inferior  one  (Fig.  488),  to  become  an  antero-posterior  one  in  the  knee 

and  posterior  limb  of  the  in- 
I''     501  ternal  capsule  (Fig.  500).  The 

posterior  third  of  this  limb  is 
sensory  and  is  the  "  sensory 
cross  way. ' ' 

[Horsley  points  out  that  hemor- 
rhage from  the  lenticulo-striate 
artery  affects  in  order  the  muscles 
of  the  face,  arm,  leg  and  trunk, 
while  recovery  is  in  the  inverse 
order.] 

[Tlie  crura  cerebri  Fig. 
461,  P),  or  cerebral  pedun- 
cles, are  two  thick  strands  as 
they  emerge  above  the  pons, 
and  as  they  are  much  larger 
than  the  pyramidal  tracts, 
they  must  receive  many  fibres 
within  the  pons.  A  trans- 
verse section  (Fig.  502)  shows 
that,  on  them  posteriorly  and 
connecting  them,  are  the  cor- 
pora quadrigemina.  (CQ). 
The  crus  proper  is  divided 
by  the  substantia  nigra  (SN) 
into  a  lower  part,  the  crusta 
or  basis,  and  an  upper  part,  or 
tegmentum.  The  crusta  is  composed  of  ascending  and  descending  nerve  fibres; 
but  the  tegmentum,  in  addition  to  many  nerve  fibres,  contains  much  gray  matter 
with  nerve  cells.  Near  the  middle  is  the  "  red  nucleus  "  or  "  tegmental  nucleus  " 
(RN).  Outside  this  is  the  fillet  (F),  a  well-defined  bundle  of  nerve  fibres  running 
upward  from  the  pons.  Above  the  nucleus,  near  the  middle  line,  is  the  "posterior 
longitudinal  bundle"  (p.  1.  b),  which  is  triangular  in  section.  Above  the  tegmen- 
tum lie  many  nerve  cells,  the  origin  of  the  third  nerve  (III),  and  arranged  around 
the  iter  is  much  gray  matter.] 

Injury  to  one  cerebral  peduncle  causes,  in  the  first  place,  violent  pain  and 
spasm  of  the  opposite  side,  while  the  blood  vessels  on  that  side  contract,  and  the 
salivary  glands  secrete.  These  phenomena  of  irritation  are  followed  by  paralytic 
symptoms  of  the  opposite  side,  viz.,  anaesthesia  (§  365)  and  paresis,  or  incomplete 
voluntary  control  over  the  muscles,  as  well  as  paralysis  of  the  vasomotor  nerves. 
In  affections  of  the  cerebral  peduncle  in  man,  we  must  remember  the  relation  of 
the  oculomotorius  to  it,  as  the  latter  is  often  paralyzed  on  the  same  side  [while  the 


Nucleus 
caudatus. 


Corpus 
caliosum. 

Pillars  of 
the  fornix. 


Internal 
capsule. 

Optic 
thalamus. 

Soft  com- 


Extemal 
capsule. 


Claustrum.   — — == 


Frontal  section  through  the  right  cerebral  hemisphere  in  front  of  the  soft 
commissure  (posterior  surface  of  the  section). 


PONS    VAROLII. 


769 


extremities,  tongue,  and  half  the  face  are  paralyzed  on  the  opposite  side  from  the 
lesion]. 

The  middle  third  of  the  crusta  of  the  cerebral  peduncle  (Fig.  502)  includes  the  direct  pyramidal 
tracts  (1^  365,  378).  The  fibres  of  the  inner  third  connect  the  frontal  lobes  with  the  cerebellum 
through  the  superior  cerebellar  peduncles.  In  the 
outer  third  are  fibres  which  connect  the  pons  with 
the  temporal  and  occipital  cerebral  lobes  {Flech- 
sig).  The  fibres  which  pass  from  the  tegmentum 
into  the  corona  radiata  conduct  sensory  impulses 
[Flechsig) . 

[The  pons  varolii  contain  ascending 
and  descending  fibres,  as  well  as  transverse 
ones,  and,  in  addition,  the  continuation 
upward  of  gray  matter  from  the  medulla, 
special  masses  of  gray  matter,  and  the 
nuclei  of  certain  cranial  nerves.  Its 
appearance  in  section  necessarily  varies 
with  the  region  where  the  section  is  made. 
Fig.  503  is  a  transverse  section  through 
part  of  the  seventh  nerve.  The  lower 
part  shows  the  superficial  (s.t.f.)  and  deep 
(d.t.f.)  transverse  fibres,  with  the  pyra- 
midal fibres  (Py)  between  them.] 

Stimulation  or  section  of  the  pons 
causes  pain  and  spasms;  after  the  section, 
there  may  be  sensory,  motor,  and  vasomotor  paralysis,  together  with  forced 
movements.  For  diagnostic  purposes  in  man,  it  is  important  to  observe  if  alter- 
nate hemiplegia  be  present. 

[In  lesions  situated  in  the  lower  half  of  one  side  of  the  pons,  there  is  facial  paralysis  on  the  same 
side  as  the  lesion  and  paralysis  (motor  and  sensory,  and  more  or  less  complete)  on  the  opposite  side 


Scheme  of  transverse  section  of  the  cerebral  peduncles. 
CQ,  corpora  quadrigemina  ;  Aq,  aqueduct;  p.l.b., 
posterior  longitudinal  bundle  ;  F,  fillet  or  lemniscus  ; 
RN,  red  nucleus  ;  SN,  substantia  nigra;  III,  third 
nerve;  Py,  pyramidal  tracts  ;  FC,fronto-cerebellar; 
and  TOC,  temporo-occioital  fibres  of  the  crusta; 
CC,  caudate-cerebellar  fibres  in  upper  part  of  crusta 
(after  Wernicke  and  Gowers). 


Fig.  503. 


Transverse  section  of  the  pons  through  part  of  the  seventh  nerve.  X  2-  F.R., 
formatio  reticularis;  VII,  seventh  nerve  ;  Va,  ascending  root,  and  Vm,  motor 
root  of  the  fifth  nerve;  F,  fillet ;  s.o.,  superior  olive;  s.l.b.,  superior  longi- 
tudinal bundle ;  Py,  pyramidal  fibres ;  R,  restiform  body;  M.P.,  middle 
peduncles  ot  cerebellum  ;  d.t.f.  and  s.t.f.,  deep  and  transverse  superficial  fibres 
of  the  pons  (after  Wernicke). 


Scheme  of  the  fibres  in  the  pons. 
PT,  pyramidal  tracts ;  F, 
facial  fibres  ;  ti,  upper ;  /, 
lower  lesjon  ;  MO,  medulla 
oblongata  ;  DP,  decussation 
of  pyramids. 


of  the  body — this  is  called  alternate  paralysis  ;  while,  if  the  lesion  be  in  the  upper  half  of  one 
side  of  the  pons,  the  facial  paralysis  is  on  the  same  side  as  the  paralysis  of  the  body.  But  the  parts 
supplied  by  the  5th  and  6th  nerves  may  also  be  involved.  This  is  explained  by  Fig.  504,  where  the 
upper  facial  fibres  cross  in  the  pons.     Sudden  and  extensive  lesions  of  the  pons  are  frequently  asso- 

49 


770  CORPORA   QUADRIGEMINA. 

ciated  with  hyperpyrexia,  the  temperature  often  rising  rapidly  within  an  hour,  perhaps  from  the  gray 
matter  in  the  floor  of  the  4th  ventricle  being  affected  ;  but  whether  it  is  due  to  some  effect  on  a  heat- 
regulating  or  heat-producing  centre  is  uncertain.  Tumors  of  considerable  size  may  press  on  the 
pons  without  producing  very  marked  symptoms,  as  tumors  tend  to  push  aside  tissues,  unless  they  be 
infiltrating  in  their  character.  Lesions  of  the  transverse  superficial  fibres  (middle  cerebellar 
peduncles)  often  give  rise  to  involuntary  forced  movements,  there  being  a  tendency  to  move  to  one 
side  or  the  other.] 

The  Corpora  Quadrigemina. — Destruction  of  these  bodies  on  one  side  in 
mammals  (or  their  homologues,  the  optic  lobes  in  birds,  amphibians,  and  fishes) 
causes  actual  blindness,  which  may  be  on  the  same  or  the  opposite  side,  according 
to  the  relation  of  the  fibres  crossing  at  the  optic  chiasma  (§  344).  Total  destruc- 
tion causes  blindness  of  both  eyes.  At  the  same  time,  the  reflex  contraction  of  the 
pupil,  due  to  stimulation  of  the  retina  with  light,  no  longer  takes  place  {Flourens'), 
where  the  optic  is  the  afferent  and  the  oculomotorius  the  efferent  nerve  (§  345). 
If  the  cerebral  hemispheres  alone  be  removed,  the  pupil  still  contracts  to  light,  as 
well  as  after  mechanical  stimulation  of  the  optic  nerve  {H.  Aaayo).  Destruction 
of  the  corporo  quadrigemina  interferes  with  the  comj)lete  harmony  of  the  motor 
acts  ;  disturbance  of  equilibrium  and  incoordination  of  movements  occur  (Serres). 
In  frogs,  Goltz  observed  not  only  awkward,  clumsy  movements,  but  at  the  same 
time  the  animals  have  to  a  large  extent  lost  the  power  of  completely  balancing  the 
body  (p.  733).  A  similar  result  was  observed  in  pigeons  i^M' Kendrick)  and  rab- 
bits {Ferrier).  Extirpation  of  the  eyeball  is  followed  by  atrophy  of  the  opposite 
anterior  corpus  quadrigeminum  {Gudden'). 

According  to  Bechterew,  the  fibres  of  one  optic  tract  pass  through  the  anterior  brachium  (Fig.  500) 
into  the  anterior  pair  (nates)  of  the  corpora  quadrigemina ;  while  those  fibres  which  cross  in  the 
chiasma  (Fig.  425)  pass  into  the  posterior  pair  (testes).  According  to  this  arrangement  we  have 
partial  blindness,  according  as  one  or  other  pair  of  these  bodies  is  destroyed. 

[In  man,  very  little  is  known  regarding  the  effects  of  disease  of  tiie  corpora  quadrigemina,  inter- 
ference with  the  ocular  muscles  being  the  most  marked  symptom;  t)ut  the  incoordination  of  move- 
ment which  has  been  observed  may  be  due  to  pressure  upon  the  superior  cerebellar  peduncle,  while 
it  is  by  no  means  certain  that  the  defects  of  vision  are  directly  due  to  lesions  of  these  bodies.] 

Stimulation  of  the  Corpora  Quadrigemina. — The  corpora  quadrigemina  react  to  electrical, 
chemical,  and  mechanical  stimuli.  The  results  of  stimulation  are  very  variously  stated.  According 
10  some  observers,  there  is  dilatation  of  the  pupil  on  the  same  side ;  according  to  Ferrier,  it  may  be 
the  pupil  on  the  opposite  or  on  the  same  side.  The  stimulation  may  be  conducted  from  the  corpora 
(|uadrigemina  to  the  medulla  oblongata,  and  to  the  origin  of  the  sympathetic,  for,  after  section  of  the 
sympathetic  nerve  in  the  neck,  dilatation  of  the  pupil  no  longer  takes  place.  According  to  Knoll, 
the  contraction  of  the  pupil  observed  by  the  older  experimenters  occurs  only  when  the  adjoining 
optic  tract  is  stimulated.  Stimulation  of  the  right  anterior  corpus  quadrigeminum  causes  deviation 
of  botk  eyes  to  the  left  (and  conversely);  on  continuing  the  stimulation,  the  head  is  turned  to  this 
side.  On  dividing  the  corpora  quadrigemina  by  a  vertical  median  incision,  stimulation  of  one  side 
causes  the  result  to  take  place  only  on  one  side  {Adamiik).  Ferrier  observed  signs  of  pain  on 
stimulating  these  organs  in  mammals.  Carville  and  Duret  conclude  from  their  experiments,  that 
these  organs  are  centres  for  the  extensor  movements  of  the  trunk.  Ferrier  found,  on  stimulating  one 
optic  lobe  in  a  pigeon,  dilatation  of  the  opposite  pupil,  turning  of  the  head  toward  the  other  side  and 
backward,  movement  of  the  opposite  wing  and  leg;  strong  stimulation  caused  flapping  movements 
of  both  wings.  Danilewsky,  Ferrier,  and  Lauder  Brunton  observed  a  rise  of  the  blood  pressure  and 
slowing  of  the  heart  beat,  together  with  deeper  inspiration  and  expiration. 

Bechterew  ascribes  all  the  phenomena,  except  those  of  vision  itself,  which  accompany  injur>'  or 
stimulation  of  these  bodies,  to  affections  of  deeper-seated  parts.  He  asserts  that  the  corpora  quadri- 
gemina contain  neither  the  centre  for  the  movements  of  the  pupils  nor  that  for  the  combined  move- 
ments of  the  eyeballs;  not  even  the  centre  for  maintaining  the  equilibrium  of  the  body.  Stimulation 
of  these  bodies  causes  the  animals  to  perform  marked  movements.  Reflex  phenomena,  nystagmus, 
forced  movements,  and  unsteadiness  of  the  gait  only  occur,  however,  when  the  deeper  parts  are 
injured. 

Pathological. — Lesions  of  the  anterior  pair  in  man,  according  to  the  extent  of  the  lesion,  cause 
disturbance  of  vision,  failure  of  the  pupil  to  contract  to  light,  and  even  blindness ;  there  may  be 
paralysis  of  the  oculomotorii  on  both  sides.  Disease  of  the  posterior  pair  may  be  associated  with 
•disturbances  of  coordination  [A^othnagel). 

Forced  Movements. — It  is  evident  from  what  has  been  said  regarding  the 
importance  of  the  corpora  quadrigemina  for  the  harmonious  execution  of  move- 


FORCED    MOVEMENTS NYSTAGMUS.  771 

merits,  that  unilateral  injury  of  such  parts  as  are  connected  with  them  by  conducting 
channels,  must  give  rise  to  peculiar  unilateral  disturbance  of  the  equilibrium, 
causing  variations  from  the  symmetrical  movements  of  both  sides  of  the  body. 
These  movements  are  cdX^^td.  forced  movements.  To  this  class  belong  the  "  mouve- 
ments  de  manege,"  where  the  animal,  instead  of  moving  in  a  straight  line,  runs 
round  in  a  circle;  index  movements,  where  the  anterior  part  of  the  body  is 
moved  round  the  posterior  part,  which  remains  in  its  place,  just  like  the  movements 
of  an  index  round  its  axis  ;  and  rolling  movements,  when  the  animal  rolls  on 
its  long  axis.  All  these  forms  of  movement  may  pass  into  each  other,  and  they 
are,  in  fact,  merely  different  varieties  of  the  same  kind  of  movement.  The  parts 
of  the  nervous  system  whose  injury  produces  these  movements  are  the  corpus 
striatum,  optic  thalamus,  cerebral  peduncle,  pons,  middle  cerebellar  peduncles, 
and  certain  parts  of  the  medulla  oblongata.  Eulenburg  observed  index  movements 
in  the  rabbit,  after  injury  to  the  surface  of  the  brain,  and  Bechterew  observed  the 
same  in  dogs.  Forced  movements,  together  with  nystagmus  and  rotation  of  the 
eyeballs,  are  caused  by  injury  to  the  olives  (^Bechterew).  The  statements  of 
observers  vary  as  to  the  direction  and  kind  of  movement  produced  by  injuring 
individual  parts.  The  following  observations  have  been  made :  Section  of  the 
anterior  part  of  the  pons,  and  of  the  crura  cerebelli  causes  index,  or,  it  may 
be,  rolling  movements  toward  the  other  side ;  section  of  the  posterior  part  of 
the  same  regions  causes  rolling  movements  toward  the  same  side,  while  the  same 
result  is  caused  by  a  deeper  puncture  into  the  tuberculum  acusticum,  or  into  the 
restiform  body.  Section  of  one  cerebral  peduncle  causes  mouvements  de  manege, 
while  the  body  is  curved  with  the  convexity  toward  the  same  side.  The  nearer  to 
the  pons  the  section  is  made,  the  smaller  is  the  circle  described ;  ultimately  index 
movements  occur.  Injury  to  one  optic  thalamus  produces  results  similar  to  punc- 
ture of  the  anterior  part  of  the  cerebral  peduncle,  because  the  latter  is  injured 
along  with  it  at  the  same  time.  Injury  to  the  anterior  part  of  one  optic  thalamus 
causes  the  opposite  kind  of  forced  movement,  viz.,  with  the  concavity  of  the  body 
toward  the  injured  side.  Injury  to  the  spinal  portion  of  th'='  medulla  oblongata  is 
followed  by  bending  of  the  head  and  vertebral  column,  with  the  convexity  toward 
the  injured  side,  along  with  movements  in  a  circle.  When  the  anterior  end  of 
the  calamus  and  the  part  above  it  are  injured,  the  movements  are  toward  the  sound 
side. 

Strabismus  and  Nystagmus. — Among  the  forced  movements  may  be  reck- 
oned deviation  of  the  eyeballs,  strabismus  or  squinting,  and  involuntary  oscillation 
of  the  eyeballs,  constituting  nystagmus.  The  latter  condition  occurs  after  super- 
ficial lesions  of  the  restiform  body,  as  well  as  of  the  floor  of  the  4th  ventricle.  A 
unilateral,  deep,  transverse  injury,  from  the  apex  of  the  calamus  upward  as  far  as 
the  tuberculum  acusticum,  causes  the  eye  of  the  same  side  to  squint  downward  and 
forward,  that  of  the  other  side  backward  and  upward.  Section  of  both  sides  causes 
this  condition  to  disappear  {Schwahn).  Hence,  Eckhard  assumes  that  the  medulla 
oblongata  is  the  seat  of  an  apparatus  controlling  the  movements  of  the  eyes 
(^Eckhard'),  which  can  be  excited  by  sudden  anaemia,  e.  g.,  ligature  of  the  cephalic 
arteries  in  a  rabbit. 

In  pathological  degeneration  of  the  olivary  body  of  the  medulla  oblongata  in  man,  Meschede 
observed  intense  rotatory  movements  toward  the  same  side. 

Theory. — In  order  to  explain  the  occurrence  of  forced  movements,  it  is  suggested  that  there  is 
unilateral  incomplete  paralysis  i^L  afar  que),  so  that  the  animal  in  its  efforts  to  move  onward  leaves 
the  paralytic  side  slightly  behind  the  other,  and  hence  there  is  a  variation  from  the  symmetry  of  the 
movements.  Brown-Sequard  regards  the  matter  in  exactly  an  opposite  light,  viz.,  as  due  to  stimulation 
from  injury,  causing  an  excessive  activity  of  one-half  of  the  body.  Henle  ascribes  the  movements  to 
vertigo,  or  a  feeling  of  giddiness  caused  by  the  injury.  In  all  operations  on  the  central  nervous 
system,  where  the  equilibrium  is  deeply  affected,  there  is  a  considerable  increase  in  the  number  and 
depth  of  the  respirations  {^Landois). 

Other  Effects. — Some  observers  noticed  variations  of  the  blood  pressure  and  a  change  in  the 


772 


PINEAL   AND    PITUITARY    BODIES. 


^     SG  Teh  z 


number  of  heart  beats  after  stimulation  of  the  cortex  cerebri,  e.g.,  after  electrical  stimulation  of  the 
motor  areas  for  the  extremities  [Boc/iefotttaine).  Balogh  observed  acceleration  of  the  pulse,  on 
siiniulaling  several  points  on  the  cortex  cerebri  of  a  Ao^,  and  from  one  point  slowing  of  the  pulse. 
Eckhard  stimulated  the  surface  of  the  brain  in  rabbits,  and,  as  a  rule,  he  observed  that,  as  long  as 
single  crossed  movements  occurred  in  the  anterior  exiremiiies,  there  was  no  effect  upon  the  heart, 
but  that  the  heart  became  affected  as  soon  as  other  movements  occurred.  This  consists  in  slow 
strong  pulse  beats,  with  occasional  weaker  beats,  while  at  the  same  time  the  blood  pressure  is  slightly 
increased  ^Bochefontaine).  If  the  vagi  be  divided  beforehand,  the  effect  upon  the  pulse  disappears, 
while  the  increase  of  the  blood  pressure  remains.  That  jjsychical  processes  affect  the  action  of  the 
heart  was  known  to  Homer  and  Chrysipp.  Bochefontaine  and  Lupine,  on  stimulating  several  points, 
especially  in  the  neighborhood  of  the  sulcus  cruciatus  in  the  dog,  observed  increased  secretion  of 
saliva,  slowing  of  the  movements  of  the  stomach,  peristalsis  of  the  intestine,  contraction  of  the  spleen, 
of  the  uterus,  of  the  bladder,  and  increased  respirations.  Bufalini,  on  stimulating  those  parts  of  the 
cortex  which  cause  movements  of  the  jaw,  observed  secretion  of  gastric  juice  with  increase  of  the 
temperature  of  the  stomach.  Schiff,  Brown-Sequard,  El>tein,  Klosterhalfen,  and  others  have  observed 
that  injury  to  the  pons,  corpus  striatum,  thalamus,  cerebral  peduncle,  and  medulla  oblongata  often 
causes  hyperemia  and  hemorrhage  into  the  lung  (according  to  Brown-S^quard,  especially  after 
injury  to  one  side  of  the  pons,  which  affects  the  opposite  lung),  under  the  pleura,  in  the  stomach, 
intestine,  and  kidneys.  Gastric  hemorrhage  is  common  after  injury  to  the  pons  just  where  the 
cerebral  peduncles  join  it.  Similar  phenomena  have  been  observed  in  man  after  apoplexy  or  cerebral 
hemorrhage. 

Specially  interesting  is  the   cerebral  unilateral  decubitus   acutus   or  bedsore,  described   by 
Charcot,  which  always  occurs  on  the  paralyzed  side  of  the  body,  i.  e.,  on  the  side  opposite  to  the 

cerebral  injury.     It  begins  on  the  second 
YiQ   CQ-  or   third   day,   rapidly    causes   enormous 

destruction  and  sloughing  of  the  tissues 
on  the  back  and  lower  extremities,  and 
death  soon  takes  place.  Tiie  decubitus 
which  occurs  after  spinal  injuries,  usually 
begins  in  the  middle  line  of  the  buttocks, 
and  extends  symmetrically  on  both  sides. 
In  cases  of  unilateral  injury  to  the  spinal 
cord,  the  decubitus  occurs  on  the  corres- 
ponding side  of  the  sacral  regijn  Cp.  632). 
[The  Pineal  Gland  or  epiphysis 
cerebri  lies  on  the  back  of,  and  is  con- 
nected with,  the  third  ventricle  (Fig.  505, 
Z).  It  projects  backward  between  the 
corpora  quadrigemina.  It  is  originally 
developed  as  a  hollow  outgrowth  from 
that  part  of  the  embryonic  brain  which 
becomes  the  third  ventricle.  The  hollow 
centre  usually  disappears,  while  the  distal 
portion  becomes  enlarged  and  is  often 
lobulated.  Its  distal  portion  may  ter- 
minate outside  the  skull ;  and  in  some 
animals  there  is  developed  in  the  median 
line  of  the  skull  an  eve — pineal  eye — 
arranged  on  the  invertebrate  plan,  as  in 
Anguis,  Hatteria,etc.  {^De  Graaf,  Spencer) 

{I  405).] 

[The  pituitary  body  or  hypophysis 

cerebri  consists  of  two  lobes,  different  in 
origin  and  structure  (Fig.  505,  H).  T\it  posterior  lobe  is  developed  as  a  hollow  outgrowth  from  the 
part  of  the  embryonic  brain  connected  with  the  third  ventricle.  It  loses  its  cavity  and  its  nervous 
tissue;  is  permeated  by  connective  tissue  and  blood  vessels;  and  is  connected  with  the  floor  of  the 
third  ventricle  by  the  infundibulum.  The  anterior  lobe  is  developed  as  a  tubular  invagination  of  the 
stomodreum,  i.  e,  from  the  ectoderm  of  the  buccal  cavity;  but  it  soon  loses  its  connection  with  this 
cavity  as  the  upper  end  enlarges,  and  the  stalk  atrophies.  In  mammalia,  the  upper  expanded  end 
unites  with  the  anterior  lobe   to   form  the  pituitary  body.     For  the   effects  of  its  removal,  see  § 

103,  v.] 

380.  STRUCTURE  AND   FUNCTIONS   OF  THE  CEREBELLUM.— [Structure. 

— On  examining  a  vertical  section  of  a  cerebral  leaflet,  we  observe  the  following  microscopic  appear- 
ances:  Externally  is  the  pia  mater  with  its  lilood  vessels  (Fig.  506,  «),  which  penetrate  into  the 
gray  matter;  within  is  the  medulla,  composed  of  white  fibres.  The  gray  matter  consists  of  b,  a 
broad  outer  or  molecular  layer,  largely  composed  of  branched  fibrils;   and  internal  lo  it  is  d,  the 


JM' 


HIT 


Longitudinal  section  of  an  adult  human  brain.  Ag,  aqueduct  of 
Sylvius;  ^,  corpus  callosum  ;  Gi,  anterior  commissure  ;  Cm, 
middle  commissure;  Col,  lamina  terminalis  ;  C/>,  posterior 
commissure;  ^iV/,  foramen  of  Munro  ;  (J,  fornix;  //.pituitary 
body  :  ////,  cerebellum  ;  MH,  corpora  quadrigemina  ;  />///, 
medulla  oblongata;  P,  pons  Varolii:  i^,  spinal  cord;  Sp, 
septum  lucidum  ;  /.infundibulum;  7VA,  tela  choroidea ;  'Jo, 
optic  thalamus  ;  VH,  cerebrum  ;  Z,  pineal  gland  ;  /,  olfactory 
lobe  and  nerve  ;  //,  optic  nerve. 


STRUCTURE    AND    FUNCTIONS    OF   THE    CEREBELLUM. 


773 


"  granular,"  nuclear,  or  rust-colored  layer.     On  the  boundary  line  between  these  two,  is  the  layer 
of  Purkinje's  cells,  c.     The  cells  of  Purkinje  form  a  single  layer  of  large  multipolar  flask-shaped 

nerve  cells,  which  have  been  compared  to  the 
Fig.  506.  branched  antlers  of  a  stag  (Fig.  507).     From 

their  outer  surface  is  given  off  a  process  which 
rapidly  divides,  and  gives  rise  to  a  large  num- 
ber of  smaller  processes  running  outward  in 
the  outer  gray  layer.  Some  of  these  processes 
form  part  of  the  ground  plexus  of  fibrils  in  this 
layer.  An  unbranched  axial  cylinder  process 
is  sent  inward  to  the  granular  layers,  where  it 
becomes  continuous  with  a  nerve  fibre — every 
cell  of  Purkinje  being  continuous  with  a 
straight  unbranched  medullated  nerve  fibre. 
The  unbranched  fibres  run  straight  firom  the 
medulla  through  the  granular  layer,  forming 
no  connection  with  its  granules.  A  second 
set  of  bi-anched  or  anastomosing,  often  vari- 
cose, nerve  fibres,  finer  than  the  foregoing, 
pass  from  the  medulla  into  the  granular  layer, 
where  they  form  a  network  which  is  continued 

Fig.  507. 


Vertical  section  of  the  cerebellum,  a,  pia  mater;  h,  external 
layer;  c,  layer  of  Purkinje's  cells;  d,  inner  layer;  e, 
medullary  white  matter. 


Purkinje's  cell,  sublimate  preparation. 

X    120. 


into  the  molecular  layer.  The  granular  layer  is  composed  of  closely  packed  granules  of  two 
kinds;  one  is  stained  by  hgematoxylin,  and  the  other  with  eosin  {Denissenko).  The  hsematoxylin 
stained  cells  are  most  numerous ;  they  consist  of  a  nucleus  surrounded  by  protoplasm,  and  are  what 
were  formerly  called  granules.  The  eosin-stained  cells,  which  are  also  stained  by  nigrosin  {Beevoi-), 
are  interposed  in  the  course  of  medullated  nerve  fibres.  The  hsematoxylin  cells,  called  glia  cells 
by  Beevor,  have  processes,  and  form  a  network  throughout  the  granular  layer,  which  also  extends 
into  the  molecular  layer.  This  network  is  regarded  as  the  continuation  of  the  modified  myelin  of 
the  nerve  fibres,  and  it  forms  a  capsule  for  the  cells  of  Purkinje.  The  molecular  layer  consists  of  a 
ground  substance,  composed  of  a  spongy  network  of  fine  fibrils,  which  seem  to  be  of  the  nature  of 
neuro-keratin,  strengthened  here  and  there  by  stronger  fibres.  In  the  meshes  lies  a  homogeneous 
substance.  Some  of  this  substance  is  more  condensed  to  form  a  limiians  externa  on  the  surface  of 
the  cerebellum,  while  on  the  boundary  line  next  the  granular  layer  the  branches  of  the  gha  cells 
form  a  liinitans  interna,  and  between  the  two  stretches  the  neuro-keratin  network.  Some  small 
variocose  nerve  fibres  exist  in  this  layer  continuous  with  those  in  the  granular  layer.  The  branched 
process  of  the  cells  of  Purkinje  is  fibrillated,  and  the  finer  processes  are  composed  also  of  fibrils, 
which  are  gradually  distributed  until  they  become  isolated.  It  is  suggested  by  Beevor  that  these 
fibrils  bend  at  a  right  angle  in  a  plane  parallel  to  the  smrface,  and  rearrange  themselves  as  fibres 


774 


FUNCTIONS    OF   THE    CEREBELLUM. 


surrounded  by  a  medullated  sheath,  and  that  these  fibres  run  inward  through  the  molecular  and 
granular  layers — as  the  branched  fibres — to  the  medulla.] 

Function. — Injuries  of  the  cerebellum  cause  disturbances  in  the  harmony  of 
the  movements  of  the  body.  Most  probably,  the  cerebellum  is  a  great  and 
important  central  organ  for  the  finer  coordination  and  integration  of  movements. 
The  fact  that  it  is  connected  with  all  the  columns  of  the  spinal  cord  and  with  all 
the  central  ganglionic  masses,  renders  this  very  probable.  The  direct  cerebellar 
tracts  from  the  lateral  column  of  the  cord  conduct  sensory  impressions  to  the 
cerebellum,  and  thus  indicate  the  posture  of  the  trunk.  The  cerebellum  may 
affect  the  motor  nerves  of  the  cord  through  fibres  whicli  pass  downward  in  the 
lateral  columns  of  the  cord  from  the  restiform  bodies  {F/echsig).  Injury  of  the 
cerebellum  neither  produces  disturbance  of  the  psychical  activities,  nor  does  it 
interfere  with  the  will  or  consciousness.  Injuries  to  the  cerebellum  itself  do  not 
give  rise  to  pain. 

According  to  SchifT,  the  cerebellum  does  not  actually  regulate  the  coordination  of  movements. 
According  to  him,  there  is  a  mechanism  on  both  sides  of  the  middle  line,  which  increases  all  the 
complicated  muscular  movements — not  only  those  for  powerful  contractions,  but  also  the  peculiar 
fine  movements  which  fix  the  limbs  and  joints.  Luciani  asserts  that  destruction  of  the  cerebellum 
produces  a  condition  of  incomplete  tonus,  there  being  a  want  of  energy  to  control  the  voluntary 
muscles.     Each  half  of  the  organ  acts  on  both  halves  of  the  body. 

Injury  or  Removal  of  Cerebellum. — The  immediate  results  produced  by 
injury  to  or  removal  of  the  cerebellum  have  been  admirably  described  by  Flourens 

(Fig.    508).       On    removing    the    most 
Fig.  508.  superficial  layers  in  a  pigeon,  the  ani- 

mal merely  showed  signs  of  weakness 
and  interference  with  the  uniformity  of 
its  movements.  On  removing  more  of 
the  cerebellum,  the  animal  became 
greatly  excited,  and  made  violent  ir- 
regular movements,  which  did  not  par- 
take of  the  character  of  convulsions. 
The  sensorium  was  unaffected,  while 
vision  and  hearing  were  intact.  Co- 
ordinated movements,  such  as  walking, 
flying,  springing,  and  turning,  could  be 
executed  but  imperfectly.  After  re- 
moval of  the  deepest  layers,  the  power 
of  executing  the  above-named  move- 
ments was  completely  abolished.  On 
placing  the  pigeon  on  its  back,  it  could  not  get  on  its  legs ;  at  the  same  time  it 
made  continually  the  greatest  exertions  in  its  movements,  but  these  were  always 
incoordinated,  and  therefore  without  any  satisfactory  result.  The  will,  intelli- 
gence, and  perception  remained  intact;  the  animal  could  see  and  hear,  and 
sought  to  avoid  obstacles  placed  in  its  way.  It  gradually  exhausted  itself  in 
fruitless  efforts  to  get  on  its  legs,  and  ultimately  remained  in  its  abnormal  position, 
quite  exhausted.  Flourens  concluded  from  these  experiments  that  the  cerebellum 
is  the  centre  for  coordinating  voluntary  movements.  Lussana  and  Morganti 
regard  the  cerebellum  as  the  seat  of  the  muscular  sense. 

[Extirpation  in  Mammals. — The  dangers  attending  this  operation  are  so  great,  that  but  few 
animals  survive.  Luciani,  however,  by  using  antiseptic  and  other  precautions,  has  been  able  to 
operate  so  that  complete  cicatrization  was  obtained,  the  animal  (young  bitch)  being  restored  to  health 
for  a  few  months.  The  cerebellum  alone  was  removed,  but  not  its  peduncles.  As  in  all  other 
similar  operations,  we  must  distinguish  sharply  the  phenomenon  manifested  during  recovery  from 
those  after  complete  recovery.  During  \.\\e  first  period  oi  sw  weeks,  from  the  time  of  the  operation 
until  complete  recovery,  the  symptoms  are  those  of  injury  and  irritation  of  the  divided  peduncles, 
along  with  those  resulting  from  the  removal  of  the   organ.     They  are  clonic  contractions  of  the 


Pigcuii  Willi  lib  cerebellum  removed. 


EXTIRPATION    OF   THE    CEREBELLUM.  775 

muscles  of  the  fore  limb,  neck,  and  back,  passing  into  tonic  contractions  when  the  animal  attempts 
to  move,  and  also  weakness  of  the  hind  legs,  so  that  all  the  normal  voluntary  movements  are  inter- 
fered with,  i.  e.,  incoordinated,  although  these  symptoms  may  be  explained  by  the  injury  to  adjoining 
parts.  There  was  no  sensory  disturbance  or  loss  of  the  muscular  sense,  although  closing  the  eyes 
rendered  standing  impossible.  As  recovery  takes  place,  these  symptoms  disappear,  and  the  animal 
enters  on  the  second  period,  where  the  symptoms  depending  on  the  actual  loss  of  the  organ  are  pro- 
nounced. The  contracture  and  pseudo-paralytic  weakness  disappear,  while  there  are  alterations 
in  the  tone  of  the  individual  muscles,  producing  a  sort  of  "  cerebellar  ataxy."  The  dog  could 
swim  in  quite  a  normal  manner,  its  power  of  equilibration  was  not  interfered  with,  but  acts  requiring 
a  greater  development  of  muscular  energy  could  not  be  properly  executed.  This  period  lasted  four 
to  five  months.  After  this  time  its  health  gave  way,  there  was  otitis,  conjunctivitis,  articular  and 
cutaneous  inflammations,  while  a  peculiar  form  of  marasmus  set  in,  the  animal  dying  after  eight 
months.  In  fishes,  also,  the  removal  of  the  cerebellum  does  not  affect  their  power  of  locomotion 
{Bandeloi)^^ 

Duration  of  the  Phenomena. — After  superficial  lesions,  or  after  a  deep 
incision,  the  disturbances  of  coordination  soon  pass  away  {^Floiirens).  If  the 
injury  affects  the  lowest  third  of  the  cerebellum,  the  motor  disturbances  remain 
permanently.  Symmetrical  lesions  do  not  disturb  coordination  {Schiff).  After 
removing  the  greater  portion  of  the  cerebellum  in  birds,  Weir  Mitchell  has 
observed  that  the  original  disturbances  gradually  disappear;  and  after  inonths  only 
slight  weakness  and  a  condition  of  rapid  fatigue  remain. 

After  ablation  of  the  cerebellum,  secondary  degeneration  occurs  in  the  part  of  the  pons  around 
the  pyramids,  the  lower  olives,  all  the  cerebellar  peduncles  and  the  direct  cerebellar  tract,  usually  on 
the  same  side  [Flecksig).  It  is  found  also  in  individual  fibres  in  all  the  cranial  nerves  and  the 
anterior  roots  of  the  spinal  nerves  [Marchi). 

In  the  dog,  superficial  injuries  of  the  vermiform  process,  or  of  one-half  of  the  organ,  produce 
merely  temporary  disturbances;  while  deep  injuries  to  the  vermiform  process,  or  removal  of  one 
hemisphere  and  a  part  of  the  vermiform  process,  cause  permanent  rigidity  of  the  legs  and  shaking 
of  the  head ;  if  the  worm  and  both  halves  are  destroyed,  there  follows  permanent  pronounced  dis- 
turbance of  coordination  {v.  Mering).  According  to  Baginsky,  destruction  of  a  large  part  of  the 
vermiform  process  alone  causes  in  mammals  permanent  disturbance  of  coordination.  Ferrier  found 
that  a  vertical  section  of  the  cerebellum  in  monkeys  produced  only  inconsiderable  disturbances  of 
the  equilibrium;  after  injury  of  the  anterior  part  of  the  middle  lobe,  the  animal  often  tumbles  for- 
ward; while,  when  the  posterior  part  is  injured,  it  falls  backward.  After  injury  of  the  lateral  lobe, 
the  animal  is  drawn  toward  the  affected  side  [Sckiff,  Vidpian,  Ferrier,  Hiizig).  If  the  middle 
commissure  be  injured,  the  animal  rolls  violently  on  its  long  axis  toward  the  injured  side  [Afagendie) . 
Paralysis  never  occurs  after  injuries  of  the  cerebellum,  nor  is  there  ever  disturbance  of  sensation  or 
of  the  sense  of  touch.  Luciani  found  that,  in  animals  with  the  cerebellum  extirpated,  marasmus 
ultimately  set  in.  In  frogs,  an  important  organ  concerned  with  motion  lies  at  the  junction  of  the 
oblongata  with  the  cerebellum  {£c^/iard).  After  it  is  removed  the  animal  can  no  longer  execute 
coordinated  jumping  movements,  nor  can  it  crawl  i^Goltz). 

[In  man,  the  cerebellum  is  connected  with  the  maintenance  of  the  equilibrium.  There  may  be 
a  lesion  of  the  hemispheres  without  any  marked  symptoms;  but  if  the  middle  lobe  be  injured  or 
pressed  on  by  a  tumor,  there  is  usually  a  reeling  or  staggering  gait,  like  that  of  a  drunken  man. 
Ross  points  out  that,  if  the  tumor  affect  the  upper  part  of  this  lobe,  the  tendency  is  to  fall  backward, 
and  if  in  the  lower  part,  to  fall  forward  or  to  revolve  round  a  horizontal  axis.  Vomiting  is  fre- 
quently persistent  and  well  marked,  while  there  may  be  nystagmus  and  tonic  retraction  of  the  head.] 

After  injuries  of  the  cerebellum,  involuntary  oscillations  of  the  eyeballs  or  nystagmus,  as  well  as 
squinting  \Magendie,  Heriwig),  have  been  observed;  while  Ferrier  observed  movements  of  the  eye- 
balls after  electrical  stimulation.  According  to  Curschmann,  Eckhard  and  Schwann,  this  occurs  only 
when  the  medulla  oblongata  is  involved  (\  379). 

Effects  of  Electricity  and  Vertigo  — If  an  electrical  current  be  passed  through  the  head,  by 
placing  the  electrodes  in  the  mastoid  fossae  behind  both  ears,  with  the  -j-  pole  behind  the  right  and 
the  —  pole  behind  the  left  ear,  then  on  closing  the  current,  there  is  severe  vertigo,  and  the  head  and 
body  lean  to  the  -{-  pole,  while  the  objects  around  seem  to  be  displaced  to  the  left.  If  the  eyes  be 
closed,  while  the  current  is  passing,  the  movements  appear  to  be  transferred  to  the  person  himself,  so 
that  he  has  a  feeling  of  rotation  to  the  left  [Purkinje).  At  the  moment  the  head  leans  toward  the 
anode,  the  eyes  turn  in  that  direction,  and  often  exhibit  nystagmus.  The  electrical  current  probably 
stimulates  the  nerves  of  the  ampullae,  as  we  know  that  affections  of  these  bodies  cause  vertigo 
(§  31^0).  The  cerebellum  has  no  relation  to  the  sexual  activities,  as  was  maintained  by  Gall.  The 
contractions  of  the  uterus  observed  by  Valentin,  Budge,  and  Spiegelberg,  after  stimulation  of  the 
cerebellum,  are  as  yet  unexplained. 


776         PROTECTIVE    AND    NUTRmVE    APPARATUS   UF   THE    BRAIN. 


Vertical  section  of  the  cortex  cerebri  and  its  membranes  ;  X  sj-j.  co, 
cortex  cerebri ;  /,  intima  pise  dipping  into  the  sulci ;  a,  arach- 
noid, connected  with  />  by  means  of  the  loose  subarachnoid  tra- 
beculae  in  the  subarachnoid  space,  sa;  v,  v,  blood  vessels  ;  d, 
dura  ;  sd,  subdural  space. 


Pathological. — Lesions  of  one  hemisphere  may  give  rise  to  no  symptoms;  but  if  the  middle 
lobe  is  involved,  there  is  incoordination  of  movement,  especially  a  tendency  to  fall,  unsteady  gait 
and  pronounced  vertigo.  Irritative  lesions  of  the  middle  peduncle  cause  complete  gyrating  move- 
ments of  the  body  around  its  axis,  together  with  rotation  of  the  eyes  and  head  {A'othna<rel\. 

381.  PROTECTIVE  APPARATUS  OF  THE  BRAIN.— The  Membranes.— The 
dura  mater  cerebralis  is  intimately  united  to  the  periosteum  of  the  cavity  of  the  skull,  while  the 
spinal  dura  mater  finnis  around  the  spinal  cord  a  freely  suspended  long  sac,  fixed  only  on  its  anterior 
surface.     It  is  a  fibrous  membrane,  consisting  of  firm  bundles  of  connective  tissue  intermixed  with 

numerous    elastic   fibres,  and    provided 
tiG.  509.  with  flattened  connective-tissue  corpus- 

'^  a  a,  cles  and  Waldeyer's  plasma  cells.    The 

smooth,  inner  surface  is  covered  with  a 
layer  of  endothelium.  It  is  but  slightly 
supplied  with  blood  vessels,  although 
they  are  more  numerous  in  the  outer 
layers;  the  lymphatics  are  numerous, 
while  nerves  whose  terminations  are 
unknown  give  to  the  dura  its  exquisite 
sensibility  to  painful  operations  on  it. 
Pacinian  corpuscles  have  been  found  in 
the  dura  over  the  temporal  bone.  The 
lymphatic  subdural  space  {Key  and 
jRetzius)  lies  between  the  dura  and 
the  arachnoid,  and  between  the  pia 
and  arachnoid  is  the  subarachnoid 
space  (Fig.  509).  These  two  spaces 
do  not  communicate  directly.  The 
delicate  arachnoid,  thin  and  partially 
perforated,  poor  in  blood  vessels  and 
without  nerves,  is  covered  on  both  sur- 
faces with  squamous  endothelium.  Only 
on  the  spinal  cord  is  it  separated  from 
the  pia,  so  that  between  the  two  lies  the  lymphatic  subarachnoid  space;  over  the  brain,  the  two 
membranes  are  for  the  most  part  united  together,  except  the  parts  bridging  over  the  sulci  between 
adjacent  consolutions.  The  arachnoid  passes  from  convolution  to  convolution  without  dipping  into 
the  sulci,  while  the  pia  dips  into  each  sulcus  (Fig.  509,  a).  The  ventricles  of  the  brain  communi- 
cate freely  with  the  lymphatic  subarachnoid  space,  but  not  with  the  subdural  space.  The  pia  con- 
sists of  delicate  bundles  of  connective  tissue  without  any  admixture  of  elastic  fibres;  it  is  richly 
supplied  with  blood  vessels  and  lymphatics,  and  carries  nerves  which  accompany  the  blood  vessels 
into  the  substance  of  the  brain.     The  lymphatics  open  into  the  subarachnoid  space  (§  I96). 

[Subarachnoid  Fluid,  or  cerebro-spinal  fluid,  lies  in  the  subarachnoid  space,  which  is 
traversed  by  trabecular  of  connective  tissue.  Within  the  brain  are  a  series  of  cavities  called  ven- 
tricles, which  communicate  one  with  another  in  a  definite  way.  The  fourth  ventricle  is  lined  by  a 
layer  of  columnai-  epithelium,  and  covered  in  dorsally  by  a  membrane  and  continuation  of  the  pia 
mater,  from  the  middle  of  which  there  hangs  into  the  roof  of  the  fourth  ventricle  two  vascular  pro- 
cesses composed  of  capillaries — the  choroid  plexuses  of  the  fourth  ventricle,  which  are  comparable 
to  the  larger  plexuses  of  the  lateral  ventricles.  In  this  membrane  is  the  foramen  of  Magendie 
and  two  other  smaller  foramina,  whereby  the  fluid  in  the  subarachnoid  space  communicates  with 
that  in  the  fourth  ventricle ;  but  the  lymphatics  of  the  nerve  sheaths  can  ije  injected  from  the  sub- 
arachnoid space,  so  that  there  is  direct  continuity  of  the  fluid  in  the  ventricles  of  the  brain  with  that 
in  the  subarachnoid  space,  perivascular  spaces  of  the  cerebral  substance,  and  the  perineural  lymph- 
atics of  ner\'es.  The  average  quantity  is  about  2  ounces,  and  if  it  be  suddenly  withdrawn,  epile|)sy 
or  convulsions  may  be  produced  ;  or,  if  it  be  rapidly  increased  in  amount,  coma  may  be  produced. 
The  middle  and  posterior  parts  of  the  brain  and  the  medulla  oblongata  do  not  rest  directly  on  bone, 
but  are  separated  by  a  distinct  interval  from  their  osseous  case,  an  interval  occupied  by  the  cerebro- 
spinal fluid  and  traversed  by  trabecukie,  so  that,  as  Hilton  expresses  it,  this  fluid  forms  a  perfect 
water  bed  for  those  parts,  being  sustained  by  the  venous  circulation  and  the  elasticity  of  the  dura. 
It  has  important  mechanical  functions,  protecting  delicate  parts  of  the  brain  from  injury;  by  dis- 
tributing vibratory  impulses  it  insulates  the  nerve  roots,  and  has  important  relations  to  the  quantity 
of  blood  in  the  brain  and  the  cerebral  circulation  (Chemical  Composition,  ^  198).] 

[Spina  bifida. — Sometimes  the  lamina-  of  the  vertebra'  in  the  lumbar  or  other  region  of  the  spinal 
column  are  imperfectly  developed,  in  which  case  the  membranes  project  through  as  a  tumor  distended 
by  cerebro-spinal  fluid  and  covered  by  skin.  The  effects  of  rapid  tapping  or  compressing  the  sac  are 
readily  studied  in  such  cases.] 


PACCHIONIAN    BODIES    AND    MOVEMENTS    OF   THE    BRAIN.  777 

The  Pacchionian  bodies,  or  granulations,  are  connective-tissue  villi,  which  serve  for  the  outflow 
of  lymph  from  the  subdural  and  subarachnoid  spaces  into  the  sinuses  of  the  dura  mater,  especially 
the  longitudinal  sinus.  The  subarachnoid  space  also  communicates  with  the  spaces  in  the  spongy 
bone  of  the  skull,  and  with  the  veins  of  the  skull  and  surface  of  the  face  {Kollmann).  The  sub- 
dural space  also  communicates  with  the  lymphatic  spaces  in  the  dura,  while  the  latter  communicate 
directly  with  the  veins  of  the  dura.  Both  the  subdural  and  subarachnoid  lymphatic  spaces  communi- 
cate with  the  lymphatics  of  the  nasal  mucous  membrane.  The  space  outside  the  dura  of  the  spinal 
cord  is  called  the  epidural  space,  and  may  be  regarded  as  lymphatic  in  its  nature ;  the  pleural  and 
peritoneal  cavities  may  be  filled  from  it ;  but  it  does  not  communicate  with  the  cavity  of  the  skull. 
The  plexuses  of  blood  vessels  are  surrounded  by  undeveloped  connective  tissue.  The  telse  cho- 
roidese  in  the  newborn  are  still  covered  with  ciliated  epithelium. 

Movements  of  the  Brain. — The  pulsations  of  the  large  basal  cerebral  vessels 
communicate  their  pulsatile  movements  (§  79,  6)  to  the  brain — the  respiratory 
movements  also  affect  it,  so  that  the  brain  rises  during  expiration  and  sinks  during 
inspiration.  Lastly,  there  are  slight  alternating  vascular  elevations  and  depres- 
sions, occurring  2  to  6  times  per  minute,  due  to  the  periodic  dilatation  and  con- 
traction of  the  blood  vessels  (§  371).  Psychical  excitement  influences  these,  and 
they  are  most  regular  during  sleep.  The  movements  are  best  seen  especially  where 
the  membranes  of  the  brain  offer  little  resistance,  e.g.,  over  the  fontanelles  in 
children,  and  where  the  membranes  have  been  exposed  by  trephining.  The 
presence  of  the  cerebro-spinal  fluid  is  most  important  for  the  occurrence  of  these 
movements,  as  it  propagates  the  pressure  uniformly,  so  that  every  systolic  and 
expiratory  dilatation  of  the  blood  vessels  is  concentrated  upon  those  parts  of  the 
cerebral  membrane  which  do  not  offer  any  resistance  (^Dondei's).  When  the  fluid 
escapes,  the  movements  may  almost  disappear. 

Mental  excitement  increases  the  pulsations  of  the  brain.  At  the  moment  of  awaking,  the  amount 
of  blood  in  the  brain  diminishes ;  sensory  stimuli  applied  during  sleep,  so  that  the  sleeper  does  not 
awake,  increase  the  amount  of  blood.  As  the  arteries  within  the  rigid  skull  case  change  their  vol- 
ume with  each  pulse  beat,  the  veins  (sinuses)  exhibit  at  every  beat  a  pulsatile  variation  in  volume, 
the  opposite  of  that  occurring  in  the  arteries  [Afosso). 

The  Cerebral  Blood  Vessels. — The  blood  vessels  of  the  pia,  of  course,  are  regulated  by  the 
vasomotor  nerves  (^  356,  A  3),  and  their  calibre  may  also  be  influenced  by  the  stimulation  of  more 
distant  parts  of  the  body  (|  347).  Donders  trephined  the  skull  so  as  to  make  around  hole,  and  filled 
it  w^ith  a  piece  of  glass,  so  that  with  a  microscope  he  could  observe  changes  in  the  calibre  of  the 
blood  vessels.  Paralysis  of  the  vasomotor  nerves  and  narcotics  dilate  the  blood  vessels ;  they  become 
greatly  contracted  at  death  (^  373,  I).  The  blood  vessels  are  dilated  during  cerebral  activity  (§  100, 
A),  as  well  as  during  sleep.  Increased  pressure  within  the  skull  causes  gi-eat  derangement  of  the 
cerebral  activity — labored  respiration  (^  368,  B),  unconsciousness  even  to  coma,  and  paralytic  pheno- 
mena— all  of  which  may  in  part  be  referable  to  disturbances  of  the  circulation.  If  all  the  cranial 
arteries  be  ligatured  suddenly,  there  is  immediate  loss  of  consciousness,  together  with  strong  stimula- 
tion of  the  medulla  oblongata  and  its  centres,  and  death  takes  place  rapidly  with  convulsions  (com- 
pare ^  373). 

By  the  free  anastomosis  which  takes  place  at  the  base  of  the  brain,  forming  the  circle  of  Willis 
(Fig.  510),  the  individual  parts  of  the  brain  are  preserved  from  want  of  blood,  when  one  or  other 
blood  vessels  is  compressed  or  ligatured.  Within  the  brain,  the  arteries  are  distributed  as  "  termi- 
nal" arteries,  i.e.,  the  terminal  blanches  of  any  one  artery  end  in  their  own  area,  and  do  not 
anastomose  with  those  of  adjoining  areas  {Coknheim).  On  the  other  hand,  the  peripheral  arteries 
(arteries  of  the  corpus  callosum,  Sylvian  fissure,  and  deep  cerebral)  which  run  externally  on  the 
brain,  form  free  anastomoses  {Tichot?iirow). 

[The  nutrient  or  ganglionic  arteries  for  the  central  ganglia  arise  in  groups  from  the  circle  of 
Willis,  or  from  the  first  two  centimetres  of  its  trunks.  The  antero-median  group  (i)  supplies  the 
anterior  part  of  the  head  of  the  caudate  nucleus.  The  postero-median  (2)  enter  the  posterior  per- 
forated space  and  supply  the  internal  surface  of  the  optic  thalami  and  the  walls  of  the  third  ventricle. 
The  antero-lateral  groups  (3,  3)  from  the  middle  cerebral  enter  the  anterior  perforated  space, 
supply  the  corpora  striata,  the  anterior  part  of  the  optic  thalamus,  and  the  internal  capsule.  These 
branches  are  apt  to  rupture.  The  postero-lateral  (4,  4)  supply  a  large  part  of  the  optic  thalami 
[Charcot).  A  line  drawn  at  a  distance  of  two  centimetres  outside  the  circle  of  Willis,  encloses  the 
ganglionic  area.  The  cerebral  convolutions  are  supplied  by  the  large  branches  of  the  circle  of 
WiUis.  The  anterior  cerebral  curves  round  the  corpus  callosum,  and  supplies  the  gyrus  rectus  and 
the  supra-orbital,  the  first  and  second  frontal  convolutions,  the  upper  part  of  the  ascending  frontal, 
and  the  inner  surface  of  the  hemisphere  as  far  as  the  quadrate  lobule  (Fig.  510,  I).     The  posterior 


778 


THE    GANGLIONIC    CEREBRAL   ARTERIES. 


cerebral  ijoes  to  tlie  retjion  of  the  occipital   lohe  nnd  the  inferior  aspect  of  the  temporal  lobe;  the 
middle  cerebral  or  Sylvian  artery  divides  into  four  branches,  which  go  to  the  posterior  parlof  the 

frontal   lobe,  ascending  frontal,  and 
510. 


Fir,. 


to  all  the  parietal  lobes,  i.e.,  chiefly 
to  the  motor  areas  (III),  the  angular 
gyrus,  and  to  the  first  lemijoro- 
sphenoidal  lobule.  The  terminal 
branches  of  these  ganglionic  arteries 
do  not  anastomose  with  the  cortical 
system.  Fig.  5 1 1  shows  the  gangli- 
onic arteries  piercing  the  liasal  gan- 
glia. Obviously,  when  hemorrhage 
of  the  lenticulo-striate  artery  or 
"  artery  of  hemorrhage"  (4,  4) 
occurs,  it  will  compress  the  leniicu- 
lar  nucleus,  or  tear  it  up,  and  may 
even  injure  the  parts  outside,  such 
as  the  e.xternal  capsule,  claustrum 
(T).  and  island  of  Reil  (R),or  those 
inside,  e.g.,  the  internal  capsule.] 

[Thus,  the  anterior  cerebral 
supplies  the  prefrontal  area  and  a 
small  part  of  the  motor  area,  that 
for  the  leg  centre  in  the  para  central 
lobule  and  upper  end  of  the  ascend- 
ing frontal  (and  perhaps  that  for  the 
trunk).  The  posterior  cerebral 
supplies  the  centre  for  vision,  and 
that  connected  with  the  course  of 
the  posterior  part  of  the  optic  ex- 
pansion, and  also  the  sensory  part 
of  the  internal  capsule.  The  mid- 
dle cerebral  supplies  the  motor 
areas  of  the  cortex,  except  part  ot 
the  leg  centreand  the  basal  ganglia, 
the  auditor)-  centre,  and  that  for 
speech.] 

[The  cerebral  circulation  has 
many  peculiarities.  The  curves  on 
the  arteries  serve  to  modify  the 
effect  of  the  cardiac  shock,  the  circle  of  Willis  permits  within  limits  a  free  circulation  ;  but,  in 
as  far  as  the  skull  is  largely  a  rigid  box,  it  was  at  one  time  taught  that,  as  the  brain  substance  and  its  fluids 
were  practically  incompressible,  it  was  impossible  to  alter  the  amount  of  blood  in  the  brain.  This  is 
a  mistake.  The  amount  of  blood  undergoes  an  alteration  in  tnis  way,  that  when  more  blood  passes 
in,  some  cerebro- spinal  fluid  moves  out,  and  vice  versa,  so  that  there  is  an  intimate  relation  between 
these  fluids.  In  the  developing  skull,  the  cerebro-spinal  fluid  may  accumulate  in  large  amount 
within  the  ventricles,  and  greatly  distend  both  them  and  the  yielding  skull  case  from  internal  pressiu-e, 
as  in  acute  hydrocephalus.  The  peculiarities  and  independence  of  the  cortical  and  ganglionic 
arteries  have  already  been  referred  to.  Plugging  by  means  of  a  clot,  vegetation  or  wart,  carried 
from  the  heart,  is  common  in  the  left  middle  cerebral  artery.  Why  ?  When  the  plug  is  washed 
away  by  the  blood  stream,  owing  to  the  left  carotid  springing  from  the  aorta  nearly  in  line  with  the 
blood  current,  the  plug  readily  passes  into  the  carotid  and  so  into  the  left  middle  cerebral  which  is 
in  line  with  the  internal  carotid.  In  such  a  case,  the  convolutions  and  parts  supplied  by  it  are  sud- 
denly deprived  of  blood  with  immediate  and  serious  results.] 

[The  venous  circulation  is  peculiar.  The  sinuses  are  really  spaces  between  the  layers  of  the 
tough  dura  mater,  and  partly  bounded  by  bone.  The  blood  moves  in  the  longitudinal  sinus  from 
before  backward,  but  most  of  the  cortical  veins  open  into  it  in  a  forward  direction,  so  that  their  stream 
is  opposed  to  that  in  the  sinus.  Thus,  the  blood  which  enters  the  brain  by  ascending  arteries  reaches 
the  sinuses  by  ascending  veins,  the  reverse  of  what  obtains  elsewhere,  in  parts  where  ascending  veins 
convey  blood  from  descending  arteries,  whereby  the  hydrostatic  pressure  and  gravity  aid  the  circula- 
tion, but  here  gravitation  is  opposed  to  the  flow  of  blood  in  the  cerebral  veins.  This  will  help  to 
explain  the  occuirence  of  thrombosis  in  these  vessels.  Some  of  the  veins  on  the  surface  communi- 
cate with  intra-cranial  veins,  e.g.,  those  of  the  nose,  the  facial  through  the  ophthalmic,  ma.stoid  veins, 
and  veins  of  the  diploe.  Hence,  morbid  processes  affecting  the  scalp  (erj'sipelas),  ear  (caries),  or 
face  (carbuncle)  may  readily  affect  intra  cranial  structures  {Gowers).'\ 


Arteries  of  the  base  of  the  brain,  or  circle  of  Willis.  C,  C,  internal  caro- 
tids;  CA,  anterior  cerebral ;  S.  S,  Sylvian  arteries  ;  V,  V,  vertebrals; 
B,  basilar  ;  CP,  posterior  cerebrals  ;  1,  2,  3,  3,  4,  4,  groups  of  nutrient 
arteries.     The  dotted  line  shows  the  limit  of  the  ganglionic  area. 


EFFECTS    OF    PRESSURE    ON    THE    BRAIN. 


779 


If  a  person  who  has  been  in  bed  for  a  long  time,  and  whose  blood  is  small  in  amount,  be  suddenly- 
raised  into  the  erect  position,  cerebral  anaemia  is  not  unfrequently  produced,  owing  to  hydrostatic 
causes.  At  the  same  time,  there  may  be  loss  of  consciousness  and  impairment  of  the  senses.  Lie- 
bermeister  regards  the  thyroid  gland  as  a  collateral  blood  reservoir  which  empties  its  blood  toward 
the  head  during  such  changes  of  the  position  of  the  body.  Perhaps  this  may  explain  the  swelling 
of  the  thyroid  as  a  compensatory  act,  when  the  heart  beats  violently,  and  the  brain  is  surcharged 
with  blood  (II  103,  III,  and  371).  Very  violent  muscular  exertion,  as  well  as  marked  activity  of 
other  organs,  causes  a  very  considerable  fall  of  the  blood  pressure  in  the  carotid. 

Pressure  on  the  Brain. — The  brain  and  the  fluid  surrounding  it  are  constantly  subjected  to  a 
certain  mean  pi'essiire,  which  must  ultimately  depend  upon  the  blood  pressure  within  the  vascular 
system.  The  investigations  of  Naunyn  and  Schreiber  on  the  cerebral  presstire  (or  cerebro-spinal 
pressure)  showed  that  the  pressure  must  be  slightly  less  than  the  pressure  within  the  carotid,  before 
the  symptoms  proper  to  pressure  on  the  brain  occur.  These  are,  sudden  attacks  of  headache,  with 
vertigo,  or  it  may  be  loss  of  consciousness,  vomiting,  slowing  of  the  pulse,  slow  and  shallow  respira- 
tion, convulsions — while  the  pressure  of  the  cerebro-spinal  fluid  is  increased.  The  cause  of  these 
phenomena  lies  in  the  anaemia  of  the  brain.  If  the  pressure  is  moderate,  the  above  named  symp- 
toms may  remain  latent ;  nevertheless,  disturbances  of  the  nutrition  of  the  brain  occur,  with  consec- 
utive phenomena,  such  as  persistent  slight  headache,  feeling  of  vertigo,  muscular  weakness  and 
disturbances  of  vision  (owing  to  neuro-retinitis  with  choked  disk).     Increase  of  the  blood  pressure 

Fig.  511. 


Transverse  section  of  the  cerebrum  behind  the  optic  chiasma.  Arteries  of  the  corpus  striatum.  C  h,  optic  chiasma ; 
B,  section  of  optic  tract;  L,  lenticular  nucleus;  1,  internal  capsule,  C,  caudate  nucleus;  E,  external  capsule; 
T,  claustrum  ;  R,  convolutions  of  the  island  of  Reil ;  V,  V,  section  of  the  lateral  ventricles  ;  P,  P,  pillars  of 
the  fornix ;  O,  gray  substance  of  the  third  ventricle.  Vascular  areas — I,  anterior  cerebral  artery ;  II,  Sylvian 
artery  ;  III,  posterior  cerebral  artery;  i,  internal  carotid;  2,  Sylvian  ;  3,  anterior  cerebral  artery  ;  4,  4,  lenticulo- 
striate  arteries  ;  5,  5,  lenticular  arteries. 

diminishes  the  symptoms,  while  diminution  of  the  blood  pressure  causes  more  pronounced  phe- 
nomena of  cerebro-spinal  pressure.  In  the  dog,  pain  begins  with  a  pressure  of  70  to  80  mm.  Hg. 
Consciousness  is  abolished  when  the  pressure  is  higher,  and  at  80  to  100  mm.  spasms  take  place.  A 
pressure  of  100  to  120  mm.  causes  slowing  of  the  pttlse,  owing  to  stimulation  of  the  vagus  at  its 
origin;  the  respirations  are  temporarily  accelerated  and  then  diminish.  Long-continued  severe 
compression  always,  sooner  or  later,  ends  fatally.  •  The  blood  pressure  at  first  is  increased,  owing  to 
reflex  stimulation  of  the  vasomotor  centre  from  the  pressure  stimulating  the  sensory  nerves ;  ulti- 
mately, the  blood  pressure  falls,  and  the  pulse  becomes  very  slow.  Irregular  variations  in  the  blood 
pressure  point  to  a  direct  central  stimulation  of  the  vasomotor  centre  by  pressure.  The  application 
of  continued  slowly  increasing  pressure  compresses  the  brain  (Adamkiewicz). 

382.  COMPARATIVE — HISTORICAL. — Comparative. — Nerves  are  absent  in  the 
protozoa.  Neuro-muscular  cells  occur  in  the  ccelenterata,  in  the  hydroida  and  medusae,  and 
they  are  the  first  indications  of  a  nervous  apparatus  (|  296).  The  umbrella  of  the  medusa  is  cov- 
ered with  a  plexus  of  nerve  fibrils,  which  at  various  parts  along  its  margin  is  provided  with  small 
cellular  thickenings  corresponding  to  ganglia,  and  from  these,  nerve  fibres  proceed  to  the  sense 
organs.  Many  of  the  worms  possess  a  nervous  ring  in  the  cephalic  portion,  and  in  those  provided 
with  an  intestine  a  single  or  double  nervous  cord,  in  the  form  of  a  ring,  smTOunds  the  pharynx. 
Branches  (often  two)  pass  from  this  into  the  elongated  body,  and  usually  these  carry  ganglia  corre- 
sponding to  each  ring  of  the  body  of  the  animal.     In  the  leech,  only  one  ganghated  cord  is  present. 


780 


COMPARATIVE    AND    HISTORICAL. 


In  the  echinodermata,  a  large  nerve  ring  surrounds  the  mouth ;  and  from  it  large  nerves  proceed, 
corresponding  to  the  chief  trunks  of  the  water  vascular  system.  At  the  ])oints  where  the  nerves  are 
given  olT,  tlie  nervous  ring  is  provided  with  the  so-called  "  amhulacral  brains."  Tlie  arthropoda 
are  provided  with  a  large  cephalic  ganglion  jjjaced  above  the  pharynx,  from  which  nerves  pass  to 
the  sense  organs.  Another  ganglion  lies  on  the  under  surface  of  the  pharynx,  and  is  connected 
with  the  fonner  by  commissures.  The  pharynx  is  thus  embraced  by  a  gangliated  ring,  and  from  it 
proceeds  the  alxlo'minal  gangliated  double  chain  along  the  ventral  surface  of  the  body,  through  the 
thorax  and  abdomen.  Sometimes  several  ganglia  unite  to  form  a  large  compound  ganglion,  while, 
in  other  cases,  each  segment  of  the  body  contains  its  own  ganglia.  In  the  mollusca  the  fcsopha- 
geal  nervous  ring  is  present,  although  the  ganglionic  masses  vary  much  in  position  within  it.  A 
number  of  compound  ganglia  lie  scattered  in  different  parts  of  the  body,  and  are  united  by  nerves 
to  the  former.  They  represent  the  sympathetic  system.  In  cephalopoda,  the  oesophageal  ring 
has  almost  no  commissure,  and  a  part  of  the  ganglionic  matter  is  enclosed  in  a  cartilaginous  capsule, 
and  is  often  spoken  of  as  a  "  brain."  Additional  ganglia  are  found  in  the  mantle,  heart  and 
stomach.  In  vertebrates,  the  nervous  system  invariably  lies  on  the  dorsal  aspect  of  the  body.  In 
the  amjihioxus,  there  is  no  separation  into  brain  and  spinal  cord.     (See  gg  374  and  375.) 

Historical. — Alkmaon  (580  n.  c.)  placed  the  seat  of  consciousness  in  the  brain;  Galen 
(131-203  A.  D.)  regarded  it  as  the  seat  of  the  impulses  for  voluntary  movements.  Aristotle 
(384  H.  C.)  ascribed  the  relatively  largest  brain  to  man  ;  he  stated  that  it  was  inexcitable  to  stimuli 
(insensible).  One  of  the  fimctions  he  ascribed  to  the  brain  was  to  cool  the  heat  ascending  from  the 
heart.  Herophilus  (300  i!.  c.)  gave  the  name  calamus  scriptorius ;  and  he  regarded  the  4th  ventricle 
as  the  most  important  organ  for  the  maintenance  of  life.  Even  in  Homer  there  are  repeated  refer- 
ences to  the  dangers  of  injuries  of  the  neck.  Aretx-us  and  Cassius  Felix  (97  A.  D.)  were  aware  of 
the  fact  that  lesion  of  one  cerebral  hemisphere  caused  paralysis  on  the  opposite  side  of  the  body. 
Galen  was  acquainted  with  the  path  in  the  .spinal  cord  connected  with  movement  and  sensation. 
Vesalius  (1540)  described  the  five  ventricles  of  the  brain.  R.  Colombo  (1559)  observed  the  move- 
ments of  the  brain  isochronous  with  the  action  of  the  heart.  A  more  careful  description  of  these 
movements  was  given  by  Riolan  (1618).  Goiter  (1573)  discovered  that  an  animal  can  live  after 
removal  of  its  cerebrum.  About  the  middle  of  the  17th  century,  Wepfer  discovered  the  hemorrhagic 
nature  of  apoplexy.  Schneider  (1660)  estimated  the  weight  of  the  brain  in  different  animals. 
Mistichelli  (1709)  and  Petit  (17 10)  described  the  decussation  of  the  fibres  of  the  spinal  cord 
below  the  pons.  Gall  discovered  the  partial  origin  of  the  optic  nerve  from  the  anterior  pair  of  the 
corpora  quadrigemina,  and  by  dissecting  the  brain  from  below,  he  attempted  to  trace  the  course  of 
the  nerve  fibres  to  the  convolutions  (iSio).  Rolando  described  more  accurately  the  form  of  the 
gray  matter  of  the  spinal  cord.  Carus  (1814)  discovered  the  central  canal.  The  most  compendious 
work  on  the  brain  was  written  by  Burdach  (1819-1826).  The  most  recent  observations  are  referred 
to  in  the  text. 


Physiology  of  the  Sense  Organs. 


383.  INTRODUCTORY  OBSERVATIONS.  —  Requisite  Condi- 
tions. — The  sense  organs  have  the  function  of  transferring  to  the  sensorium 
impressions  of  the  various  phenomena  of  the  external  world ;  they  are,  in  fact,  the 
intermediate  instruments  of  s ens oiy  perceptions.  In  order  that  this  may  occur,  the 
following  conditions  must  be  fulfilled:  (1)  The  sense  organ,  provided  with  its 
specific  end  organ,  must  be  anatomically  perfect,  and  capable  of  acting  physio- 
logically. (2)  A  "  specific  stimulus  "  must  be  present,  which  under  normal 
conditions  acts  upon  the  end  organ.  (3)  The  sense  organ  must  be  connected  with 
the  cerebrum  by  means  of  a  nerve,  and  the  conduction  through  this  path  must  be 
uninterrupted.  (4)  During  the  act  of  stimulation,  the  psychical  activity  (atten- 
tion) must  be  directed  to  the  process,  and  then  the  sensation  results,  e.  g.,  of 
light  or  sound,  through  the  sense  organ.  (5)  Lastly,  when,  by  a  psychical  act,  the 
sensation  is  referred  to  the  external  cause,  then  there  is  a  conscious  sensory  percep- 
tion. Often,  however,  this  relation  is  completed  as  an  unconscious  conclusion,  as 
it  is  essentially  a  deduction  from  previous  experience. 

Stimuli. — With  regard  to  the  stimuli  which  are  applied  to  the  sensory  apparatus,  we  distinguish : 
(l)  Adequate  or  homologous  stimuli,  i.  e.,  stimuU  for  whose  action  the  sense  organs  are  specially 
adapted,  such  as  the  rods  and  cones  of  the  retina  for  the  vibrations  of  the  ether.  Tlius,  each  sense 
organ  has  a  specific  form  of  stimulus  best  adapted  to  act  upon  it.  This  is  what  Johannes  Miiller 
called  the  "  law  of  specific  energy."  (2)  There  are  many  other  forms  of  stimuli  (mechanical, 
thermal,  chemical,  electrical,  internal  somatic)  which  act  upon  the  sense  organs,  producing  the  flash 
of  light  beheld  when  the  eye  is  struck  ;  singing  in  the  ears  when  there  is  congestion  of  the  head. 
These  heterologous  stimuli  act  upon  the  nervous  elements  of  the  sensory  apparatus  along  their 
entire  course,  from  the  end  organ  to  the  cortex  cerebri.  The  homologous  stimuli,  on  the  other  hand, 
act  only  on  the  end  organ,  i.  e.,  light  has  no  effect  whatever  upon  the  trunk  of  the  exposed  optic 
nerve. 

Strength  and  Liminal  Intensity. — Homologous  stimuli  act  upon  the  sensory 
organs  only  within  certain  limits  as  to  stre?igth.  Very  feeble  stimuli  at  first  pro- 
duce no  effect.  That  strength  of  stimulus  which  is  just  sufficient  to  cause  the  first 
trace  of  a  sensation  is  called  by  Fechner  the  "  liminal  intensity  "  of  the  sensa- 
tion. As  the  strength  of  the  stimulus  increases,  so  also  do  the  sensations,  but  the 
sensations  increase  equally  when  the  strength  of  the  stimulus  increases  in  relative 
proportions.  Thus,  we  have  the  same  sensation  of  equal  increase  of  light  when, 
instead  of  10  candles,  11,  or  instead  of  100  candles,  no  are  lighted — the  propor- 
tion of  increase  in  both  cases  is  equal  to  one-tenth.  As  the  logarithm  of  the  num- 
bers increases  in  an  equal  degree,  when  the  numbers  increase  in  the  same  relative 
proportion,  the  law  may  be  expressed  thus:  ''  The  sensations  do  not  increase  with 
the  absolute  strength  of  the  stimuli,  but  nearly  as  the  logarithm  of  the  strength  of 
the  stimulus."  This  is  FecJuier' s  "psycho-physical  law,"  but  its  accuracy 
has  recently  been  challenged  by  E.  Bering.  [It  holds  good  only  with  regard  to 
stimuli  of  medium  strength.]  If  the  specific  stimulus  be  too  intense,  it  gives  rise 
to  peculiar  painful  sensations,  e.  g.,  a  feeling  of  blindness  or  deafness,  as  the  case 
maybe.  The  sense  organs  respond  to  adequate  stimuli,  but  only  within  certain 
limits  of  the  stimulus,  <?.  g.,  the  ear  responds  only  to  vibrating  bodies  emitting  a 
certain  range  of  vibrations  per  second  ;  the  retina  responds  only  to  the  vibrations 

781 


782  fechner's  law. 

of  the  ether  between  red  and  violet,  but  not   to  the  so-called  heat  vibrations  or  to 
the  chemically  active  vibrations. 

[It  was  Weber  who  worked  out  the  relation  between  the  intensity  of  stimuli  and  the  changes  in 
the  quantity  of  the  resulting  sensations.  He  used  the  method  of  "  le.ist  observable  dilTerences,"  as 
applied  to  sensations  of  pressure  and  the  measurements  of  lines  by  the  eye.  Hence,  it  is  called 
Weber's  Law ;  but  Fechner  expanded  it  and  assumed  that  all  just  observable  dift'erences  are  equally 
great,  and  so  the  law  is  sometimes  called  by  his  name.] 

[Fechner's  Law. — Expressed  in  another  way,  the  result  depends  on  (i)  the  strength  of  the 
stimulus,  and  {2)  the  degree  of  excitability.  Supposing  the  latter  to  be  constant,  while  the  former  is 
varied,  it  is  found  that  if  the  stimulus  be  doubled,  tripled,  or  quadrupled,  the  sensation  increases  only 
as  the  loi^arithin  of  the  stinitilus.  Suppose  the  stimulus  to  be  increased  10,  100,  or  1000  times,  then 
the  sensation  increases  only  as  i,  2,  or  3.  Just  as  there  is  a  lower  limit  of  excitation  liiitinal  inten- 
sity (or  threshold'),  so  there  is  an  upper  limit  or  muximum  of  excitation  or  height  of  sensibility, 
when  any  further  increase  produces  no  appreciable  increase  in  the  sensation.  Thus,  we  do  not  notice 
any  difference  between  the  central  and  peripheral  portion  of  the  sun's  disk,  though  the  difference  of 
light  intensity  is  enormous  [Sitllv).  Between  these  two  is  the  range  of  sensibility  (  Wundt^.  There 
is  always  a  constant  ratio  between  the  strength  of  the  stimulus  and  the  intensity  of  the  sensation. 
The  stronger  the  stimulus  already  applied,  the  stronger  must  be  the  increase  of  the  stimulus  in  order 
to  cause  a  perceptible  increase  of  tlie  sensation  (Weber's  Law).  The  necessary  increment  is  pro- 
portional to  the  intensity  of  the  stimulus,  and  it  varies  for  each  sense  organ.  If  a  weight  of  10 
grammes  be  placed  in  the  hand,  it  is  found  that  3.3  grammes  must  be  added  or  removed  before  a 
difference  in  the  sensation  is  perceptible  ;  if  lOO  gi'ammes  are  held,  33.3  grammes  mu.st  be  added  or 
removed  to  obtain  a  perceptible  difference  in  the  sensation.  The  magnitude  of  the'fraciion  indica- 
ting the  increment  of  stimulus  necessary  to  obtain  a  perceptible  difference  of  the  sensation,  is  spoken 
of  as  the  constant  proportion  or  the  discriminative  sensibility.  In  the  above  case  it  is  I  :  3.  The 
following  table  gives  approximately  the  constant  proportion  for  each  sense : — 


Muscular  Sensation,  .    .    .  6  :  loo.^Jjjj 
Visual  "  .    .    .  I  :  loo.j^^.] 


Tactile  Sensation, 1:3.^ 

Thermal       "  \  :  t,.   % 

Auditory       "  1:3.;^ 

[The  a])i)lication  of  the  law  to  temperature  sensations  is  beset  with  great  difficulties,  while  for 
taste  and  smell  we  do  not  know  that  it  is  really  applicable.  From  an  experimental  point  of  view, 
it  cannot  be  said  to  be  proved,  and  its  application  is  obviously  somewhat  restricted  to  certain  sensa- 
tions, and  to  these  only  within  a  certain  range.  It  certainly  does  not  hold  good  for  sensations  of 
pressure,  and  muscular  sense,  near  the  lower  limits  for  these  senses.  At  best  it  is  only  an  approxi- 
mately correct  statement  of  what  holds  true  of  the  relative  intensity  of  certain  sensations  of  light  and 
hearing,  and  less  exactly  of  pressure  and  the  muscular  sense,  when  these  sensations  are  of  moderate 
strength"  i^Ladd)?^ 

The  term  after-sensation  is  applied  to  the  following  phenomenon,  viz.,  that, 
as  a  rule,  the  sensation  lasts  longer  than  the  stimulus  producing  it  ;  thus,  there  is 
an  after-sensation,  after  pressure  is  applied  to  the  skin.  Subjective  sensations 
occur  when  stimuli  due  to  internal  somatic  causes  excite  the  nervous  apparatus  of 
the  sense  organ.  The  highest  degrees  of  these,  depending  mostly  upon  pathologi- 
cal stimulation  of  the  sensory  cortical  centres,  are  characterized  as  hallucinations, 
e.  g.,  when  a  delirious  person  imagines  he  sees  figures  or  hears  sounds  which  have 
no  objective  reality.  In  opposition  to  this  condition,  the  term  illusion  is  applied 
to  modifications  by  the  sensorium  of  sensations  actually  caused  by  external  objects, 
e.  g.,  when  the  rolling  of  a  wagon  is  mistaken  for  thunder. 

In  a  newborn  child,  the  sense  of  touch  is  strongly  developed,  that  of  pain  slightly,  muscular 
sensations  are  undoubtedly  present,  while  smell  and  taste  are  frequently  confounded.  Auditory 
stimuli  are  heard  from  the  second  day  onward,  the  stimulus  of  light  im.mediately  after  birih,  but  a 
peripheral  field  of  vision  does  not  yet  exist  [Cuignet).  Toward  the  fourth  to  fifth  week,  the  move- 
ments of  convergence  and  accommodation  are  noticeable,  while  after  four  months,  colors  are  distin- 
guished. The  various  stimuli  are  not  perceived  simultaneously — a  reflex  inhibitory  centre  is  not  yet 
developed  [Genzmer). 


THE  VISUAL  APPARATUS-THE  EYE. 


384.  HISTOLOGICAL  OBSERVATIONS.— In  the  following  remarks 
it  is  assumed  that  the  student  is  familiar  with  the  anatomical  structure  of  the 
eye : — 

The  Cornea,  for  the  sake  of  simplicity,  is  regarded  as  uniformly  spherical,  although,  properly 
speaking,  it  differs  slightly  from  this  form.  It  is  more  like  a  vertical  section  of  a  somewhat  obUque 
ellipsoid,  which  we  must  suppose  to  be  formed  by  rotating  an  ellipse  around  its  long  axis  [Brilcke). 
It  is  nearly  of  uniform  thickness  throughout,  only  in  the  infant  it  is  slightly  thicker  in  the  centre,  and 
in  the  adult  slightly  thinner.     The  cornea  consists  of  the  following  layers  : — 


[l.  Anterior  stratified  epithelium. 

2.  Anterior  elastic  lamina. 

3.  Substantia  propria. 


4.  Posterior  elastic  lamina. 

5.  Single  layer  of  epithelium.] 


I.  The  anterior  epithelium,  stratified  and  nucleated,  consists  of  many  layers  of  cells  (Fig.  514, 
a).  The  deeper  cells  are  more  or  less  columnar,  are  arranged  side  by  side,  and  are  called  supporting 
cells.  The  cells  of  the  middle  layers  are  more  arched,  and  dip  with  finger-shaped  processes  into 
corresponding  spaces  between  their  neighbors.  The  most  superficial  cells  are  flat,  perfectly  smooth, 
hard,  keratin,  containing,  squamous  epithelium.     2.  The  epithelial  layer  rests  upon  the  anterior 


Fig.  512. 


Fig.  513. 


isk^h^-^.. 


Cornea  of  the  frog  treated  with  chloride  of  gold,  show-        Cornea  of  the  frog  treated  with  silver  nitrate  ;  the  ground 
ing  the  corneal  corpuscles  stained,  and  a  few  nerve  substance  is  stained,  while  the  spaces  for  the  corneal 

fibrils.  corpuscles  are  left  unstained. 


elastic  membrane  (Bowman's  elastic  lamina),  a  structureless,  clear,  basement-like  membrane  {b), 
whose  existence  is  denied  by  Briicke.  3.  The  substantia  propria  of  the  cornea  consists  of 
(chondrin-yielding)  fibres  composed  of  delicate  fibrils  of  connective  tissue.  The  fibres  are  arranged 
in  mat-like  thin  lamellae  (/),  more  or  less  united  together,  and  are  placed  in  layers  over  each  other. 
Toward  the  anterior  elastic  lamina,  the  fibres  bend  round  and  perforate  the  superficial  lamellae,  thus 
serving  as  supporting  fibres.     [These  perforating  fibres  are  comparable  to  Sharpey's  fibres  in  bone.] 

783 


784 


THE  NERVES  OF  THE  CORNEA. 


Between  the  lamellx  are  a  series  of  inter-communicating  spaces  lined  by  endothelium.  These 
s])aces  are  really  lymph  spaces,  and  ihey  communicate  wiih  the  lymi)hatics  of  the  conjunctiva. 
Tiie  I'lxed  corneal  corpuscles  lie  in  lhe.se  spaces  (r),  and  are  provided  with  numerous  ]irocesses, 
which  anastomose  with  the  })rocesses  of  corpuscles  lyinj^  between  the  laniell.e  above  and  below,  and 
on  either  side  of  them.  Kiihne  observed  that  stimulation  of  the  corneal  nerves  was  followed  by 
contraction  of  these  cells  (^  201,  7),  while  Kiihne  and  Waldeyer  maintain  that  they  are  connected 
with  the  corneal  nerve  tibrils. 

[The  corneal  corpuscles  are  looked  upon  as  branched  connective- tissue  corpuscles  lying  in  and 
not  quite  hlhng  the  branched  spaces  between  the  lamella-.  The  processes  anastomose  freely  with 
similar  cells  in  the  same  plane,  and  to  a  less  extent  with  the  processes  of  cells  in  planes  immediately 


Antero-posterior  section  at  the  junction  of  the  cornea  with  the  sclerotic,  a,  anterior  corneal  epithelium  ;  b.  Bowman's 
lamina ;  c,  corneal  corpuscles ;  /,  corneal  lamellae  (the  whole  thickness  lying  between  b  and  d  is  the  substantia 
propria  cornese) :  d,  Descemet's  membrane  :  e,  its  epithelium  ;  /,  junction  of  cornea  with  the  sclerotic  ;  g,  limbus 
conjunctiva; ;  /(,  conjunctiva  ;  i,  canal  of  Schlemm  ;  k,  Leber's  venous  plexus  (is  regarded  by  Leber  as  belonging 
to  /') ;  111.  lit,  meshes  in  the  tissues  of  the  lig.  iridis  pectinatum  ;  «,  attachment  of  the  iris;  o,  longitudinal,  /, 
circular  (divided  transversely)  bundles  of  fibres  of  the  sclerotic;  g,  perichoroidal  space;  s,  meridional  [radiating], 
i,  equatorial  (circular)  bimdles  of  the  ciliary  muscle  ;  u,  transverse  section  of  a  ciliary  artery;  v,  epithelium  of 
the  iris  (a  continuation  of  that  oi\  the  posterior  surface  of  the  cornea) ;  w,  substance  of  the  iris ;  x,  pigment  of 
the  iris ;  2,  a  ciliary  process. 


above  and  below  them.  In  a  section  stained  with  gold  chloride,  they  present  the  appearance  seen 
in  Fig.  512.  In  a  vertical  section  of  the  cornea,  they  appear  fusiform  and  parallel  to  the  free  surface 
of  the  cornea  (Fig.  514).  If  the  cornea  of  a  frog  be  penciled  with  silver  nitrate,  the  cement  sub- 
stance between  the  lamellae  is  blackened,  and  the  branched  cell  spaces  remain  clear,  as  in  Fig.  513. 
The  one  figure  represents,  as  it  were,  the  positive,  and  the  other  the  negative  image.] 

Leucocytes  also  pass  into  these  lym]ih  spaces  or  juice  canals.  The  importance  of  these  leucocytes 
in  inflammation  is  referred  to  in  ?  200.  4.  The  transparent,  structureless,  posterior  elastic  mem- 
brane («/),  the  membrane  of  Descemet  or  Demours,  is  in  many  animals  fibrillated,  and  shows 
evidence  of  stratification,  while  toward  the  margin  of  the  cornea  there  are  occasionally  slight  conical 


THE  NERVES  OF  THE  CORNEA. 


785 


elevations.  This  membrane  is  very  tough  and  very  resistant  (of  great  importance  in  inflammation). 
If  it  be  removed,  it  rolls  up  toward  the  convex  side.  At  its  periphery  it  becomes  continuous  with 
the  fibro-elastic  reticulated  ligamentum  pectinatum  iridis,  whose  trabeculse  are  covered  by  epithelium. 
5.  The  posterior  single  layer  of  epithelium  consists  of  flat,  delicate,  nucleated  cells  (c),  which 
are  continued  from  the  margin  of  the  cornea  on  to  the  anterior  surface  of  the  iris  (z/).  Fme  juice 
canals  exist  in  the  spaces  between  the  individual  cells  {v.  Recklmghattsen').  These  spaces  commu- 
nicate with  a  system  of  fine  tubes  under  the  epithelium,  perforate  Descemet's  membrane,  and  thus 
communicate  with  the  corneal  spaces. 

[Bowman's  tubes  are  artificial  productions,  formed  by  forcing  air  or  a  colored  fluid  between 
the  lamellae,  when  it  passes  between  the  bundles  of  fibrils,  forming  a  series  of  tubes  with  dilata- 
tions on  them  and  running  at  right  angles  to  one  another  between  the  lamellse.] 

The  nerves  of  the  cornea,  which  are  derived  from  the  long  and  short  ciliary  nerves  (§  347),  are 
partly  sensory  in  function.  They  enter  the  cornea  at  its  margin  as  meduUated  fibres,  but  the  myelin 
soon  disappears,  while  the  axial  cylinders  split  up  into  fibrils.  [The  axial  cylinders  branch  and  form 
a  plexus  between  the  lamellse,  especially  near  the  anterior  surface,  the  fundamental  or  ground 
plexus  (Fig.  515,  n).  There  are  triangular  nuclei  at  the  nodal  points,  but  they  probably  belong  to 
the  sheath  of  flattened  cells  which  cover  the  larger  branches.  There  is  a  finer  and  denser  plexus  of 
fibrils  immediately  under  the  anterior  epithelium,  sub-epithelial  plexus,  which  is  derived  from  the 
former,  the  fibrils  arising  in  pencils  or  groups  (Fig.  516).  Some  fibrils  perforate  the  anterior  elastic 
lamina,  rami  perforantes,  and  pass  between  the  anterior  epithelial  cells  to  form  the  intra-epithelial 
network  (Fig.  515,1^, /).  Some  observers  suppose  that  they  terminate  in  free,  pointed,  or  bulbous  ends. 
There   is  also  a  fine  plexus  of 

fibrils    in    the    posterior    layers  Y\G.  515. 

of  the  cornea,  near  Descemet's  j 

membrane.  It  gives  off  numerous  ''' 

fine  fibrils  which  come  into  inti- 
mate, if  not  direct,  anatomical 
relation  with  the  corneal  corpus- 
cles. The  trophic  fibres  of  the 
cornea  (§  347)  are,  perhaps,  those 
deeper  branches  which  are  con- 
nected with  the  corneal  corpus- 
cles.] 

[Method. — These  fibrils  are 
best  revealed  by  staining  a  cornea 
with  chloride  of  gold,  which 
tinges  them  of  a  purplish  line 
after  exposure  to  light  (^Cohn- 
heii>i).'\ 

Blood  vessels  occur  only  in 

the    outer  margm   of  the   cornea   Vertical  section  of  the  cornea  stained  with  gold  chloride.     71,  nerve  fibrils  ;  a, 

\r\g.  5IS,  v),  and  extend  2   mm.  perforated  branch  ;  r,  nucleus  ;  p,  b,  inter-epithelial  termination  of  fibrils  ; 

over   the    cornea   above,  1.5  mm.  j,  anterior  elasticlamina. 

below,  and  I   mm.  laterally — the 

most  external  capillaries  form  arched  loops,  and  thus  turn  on  themselves.     The  cornea  is  nourished 

from  the  blood  vessels  in  its  margin.     Opacities  of  the  cornea  give  rise  to  many  forms  of  visual 

detects. 

The  sclerotic  is  a  thick  fibrous  membrane,  composed  of,  p,  circular  (equatorial)  and,  u,  longi- 
tudinal (meridional)  bundles  of  connective  tissue  woven  together  (Fig.  514).  The  spaces  between 
the  bundles  contain  colorless  and  pigmented  connective-tissue  corpuscles  and  also  leucocytes.  It  is 
thickest  posteriorly,  thinner  at  the  equator,  while  in  front  of  this  it  again  becomes  thicker,  owing  to 
the  insertion  of  the  tendons  of  the  straight  muscles  of  the  eyeball.  It  contains  few  blood  vessels, 
which  form  a  wide-meshed  capillary  plexus,  immediately  under  its  deep  sui-face.  Other  vessels  form 
an  arterial  ring  around  the  entrance  of  the  optic  nerve.  It  rarely  is  quite  spherical ;  it  rather  resem- 
bles an  ellipsoid,  which  we  might  imagine  to  be  formed  by  the  rotation  of  an  elhpse  around  its  short 
axis  (short  eyes)  or  around  its  long  axis  (long  eyes).  Above  and  below,  the  sclerotic  overlaps  like  a 
fold  the  clear  margin  of  the  cornea;  hence,  when  the  cornea  is  viewed  from  before,  it  appears  trans- 
versely elliptical,  when  seen  from  behind,  it  appears  circular.  Following  the  margin  of  the  cornea, 
but  lymg  still  within  the  substance  of  the  sclerotic,  is  the  circular  canal  of  Schlemm  (z),  which 
communicates  with  other  anastomosing  veins,  the  venous  plexus  of  Leber  [k).  Schwalbe  and  Wal- 
deyer  regard  Schlemm's  canal  as  a  lymphatic.  Posteriorly,  the  sclerotic  becomes  continuous  with  the 
fibrous  covering  of  the  optic  nerve  derived  from  the  dura  mater.  The  sclerotic  is  provided  with 
nerves,  which  are  said  to  terminate  in  the  cells  of  the  scleral  substance  {Helfreicli). 

The  tunica  uvea,  or  the  uveal  tract,  is  composed  of  the  choroid,  the  ciliary  part  of  the  choroid, 
and  the  iris. 

The  choroid  is  composed  of  the  following  layers  (Fig.  517) :  (i)  Most  internally  is  the  trans- 

50 


786 


THE    IRIS. 


parent  limiting  membrane,  0.7 // in  thickness,  but  it  is  slightly  tliickor  anteriorly.  (2)  The  very 
vascular  capillary  network  of  the  chorio-capillaris,  or  membrane  of  Kuysch,  embedded  in  a 
homogeneous  layer.  Then  follows  (3)  a  Iner  of  a  thick  elastic  network, covered  on  both  surfaces 
by  endothelium  {Saft/er).  (4)  The  choroid  proper  consists  of  a  layer  with  pigmented  connective- 
tissue  corpuscles,  together  with  a  thick  elastic  network,containing  the  numerous  venous  vessels  as  well 
as  the  arteries.  The  pigmented  layers  are  known  as  the  supra-choroidea,  or  lamina  fusca,  which 
surrounds  the  large  lymphatic  space  lined  with  endothelium  and  called  the  perichoroidal  space,  q. 
In  newborn  infants,  which  according  to  Aristotle  have  the  iris  dark  blue,  the  uveal  tissue  is  devoid 
of  pigment ;   in  brunettes  it  is  developed  later,  and  in  blondes  not  at  all. 

In  the  ciliary  part  of  the  choroid,  the  pigmented  connective-tissue  corpuscles  are  not  so  numerous. 
The  ciliary  muscle  (tensor  choroidea\  or  muscle  of  accommodation)  is  placed  in  this  region.  It 
arises  (.?),  by  means  of  a  l)ranched,  reticulated,  connective-tissue  origin,  from  the  inner  side  of  the 
junction  of  the  cornea  and  the  sclerotic,  near  the  canal  of  Schlemm,  and  passes  backward  to  be 
inserted  into  the  choroid.  This  con.stitutes  the  radiating  fibres.  Other  fibres  lying  internal  to  these 
are  arranged  circularly,  /,  in  bundles  in  the  ciliary  margin.  These  circular  fibres  are  sometimes  called 
Heinrich  Midler's  muscle.  The  muscle  consists  of  smooth  muscular  fibres,  and  is  supplied  by  the 
oculomotorius  (^^  345,  3). 

Fig.  517. 


Fig.  516, 


Nerve  plexus  in  the  cornea  after  gold   chloride.     «,  nerve ; 
a,  fibrils. 


Vertical  section  of  the  choroid  and  a  part  of  the  scle- 
rotic, (i)  sclerotic;  (2)  lamina  supra-choroidea; 
(3)  layer  of  large  vessels;  (4)  limiting  layer;  (5) 
chorio-capillaris;  (6)  hyaline  membrane;  (7)  pig- 
ment epithelium  ;  (g)  large  blood  vessels  ;  {/>) 
pigment  cells ;  (c)  sections  of  capillaries. 


The  iris  consists  of  the  following  parts  from  before  backward  :  a  layer  of  epithelial  cells  {v)  con- 
tinuous with  those  covering  the  posterior  surface  of  the  cornea,  a  layer  of  reticulated  connective  tissue, 
the  layer  of  blood  vessels,  and  lastly  a  posterior  limiting  membrane,  which  contains  the  pigmentary 
epithelium  {x)  {Mic/iel).  In  brunettes,  the  texture  of  the  iris  contains  pigmented  connective  tissue 
corpuscles.  The  iris  in  some  animals  is  described  as  containing  two  muscles  composed  of  smooth 
muscular  fibres — one  set  constituting  the  sphincter  pupillae  (circular — Fig.  533),  which  surrounds 
the  pupil,  and  lies  nearer  the  posterior  than  the  anterior  surface  of  the  iris  (J.  392).  Its  nerve  of 
supply  is  derived  from  the  oculomotorius  (§  345,  2).  The  other  fibres  constitute  the  dilator 
pupillse  (radiating),  which  consists  of  a  thinner  layer  of  fibres  ananged  in  a  radiate  manner.  Some 
of  the  fibres  reach  to  the  margin  of  the  pupil,  while  others  bend  into  the  sphincter.  [The  existence 
of  a  dilator  pupillne  in  man  is  denied  (|  392).]  Ax.  the  outer  margin  of  the  iris,  the  radial  bundles 
are  arranged  in  anastomosing  arches,  and  form  a  circular  muscular  \diy ex  (Merkel).  The  chief  nerve 
of  supply  for  the  dilator  fibres  is  the  sympathetic  (?  347,  3").  Ganglia  occur  in  the  ciliary  nerves  in 
the  choroid  [and  they  are  found  also  in  the  iris].  Gerlach  has  recently  applied  the  temi  ligarnentum 
anfiulare  bulbi  to  that  complex  fibrous  arrangement  which  sunounds  the  iris,  and  at  the  same  time 


BLOOD    VESSELS    OF    THE    EYEBALL. 


787 


Fig.  518. 


forms  the  point  of  union  of  the  ciliary  body,  iris,  ciliary  muscle,  sinus  venosus  iridis,  and  the  line  of 
junction  of  the  cornea  and  sclerotic. 

The  choroidal  vessels  are  of  great  importance  in  connection  with  the  nutrition  of  the  eye. 
According  to  Leber,  they  are  arranged  as  follows  : 
The  arteries  are — i.  The  short  posterior  cili- 
ary, which  are  about  twenty  in  number  and  per- 
forate the  sclerotic  near  the  optic  nerve  (Fig.  518, 
a,  a).  They  terminate  in  the  vascular  network 
of  the  chorio-capillaris  (/«),  which  reaches  as  far 
as  the  era  serrata.  2.  The  long  posterior  ciliary ; 
one  of  these  lies  on  the  nasal  and  the  other  on  the 
temporal  side,  and  they  run  (b)  to  the  ciliary  part 
of  the  choroid,  where  they  divide  dichotoniously, 
and  penetrate  into  the  iris,  where  they  help  to  form 
the  circulus  arteriosus  iridis  major  (/).  3.  The 
anterior  ciliary  (<r),  which  arise  from  the  muscu- 
lar branches,  perforate  the  sclerotic  anteriorly,  and 
give  branches  to  the  ciliary  part  of  the  choroid  and 
to  the  iris.  About  twelve  branches  run  backward 
(0)  from  them  to  the  chorio-capillaris. 

Veins. — i.  The  anterior  ciliary  veins  (c) 
receive  the  blood  from  the  anterior  part  of  the  uvea 
and  carry  it  outward.  These  branches  are  con- 
nected with  Schlemm's  canal  and  Leber's  venous 
plexus.  They  do  not  receive  any  blood  from  ihe 
iris.  2.  The  venous  plexus  of  the  ciliary  pro- 
cesses (;■)  receives  the  blood  from  the  iris  {q),  and 
passes  backward  to  the  choroidal  veins.  3.  The 
large  vasa  vorticosa  Stenosis  (/^)  perforate  the 
sclerotic  behind  the  equator  of  the  bulb. 

The  inner  margin  of  the  iris  rests  upon  the 
anterior  surface  of  the  lens  ;  the  posterior  chamber 
is  small  in  adults,  and  in  the  newborn  child  it 
may  be  said  scarcely  to  exist — it  is  so  small. 
When  Berlin  blue  is  injected  into  the  anterior 
chamber  of  the  eye,  it  generally  passes  into  the 
anterior  ciliary  veins  [^ScJnuaibe).  Even  in  living 
animals,  carmin  also  behaves  in  a  similar  manner 
[Heisj'ath) ;  hence,  these  observers  conclude  that 
there  is  a  direct  communication  between  the  veins 
and  the  aqueous  chamber,  as  these  substances  do  Diagram  of  the  blood  vessels  of  the  eye  (horizontal  view. 


not  diffuse  through  membranes. 

Internal  to  the  choroid  lies  the  single  layer  of 
hexagonal  cells  (0.0135  to  0.02  mm.  in  breadth) 
filled  with  crystalline  pigment.  This  layer  really 
belongs  to  the  retina.  It  consists  of  a  single  layer 
of  cells  as  far  as  the  ora  serrata — it  is  continued  on 
to  the  ciliary  processes  and  the  posterior  surface 
of  the  iris,  where  it  forms  several  layers  (Fig.  514, 
x).  In  albinos  it  is  devoid  of  pigment;  on  the 
other  hand,  the  uppermost  cells,  which  lie  on  the 
ridges  of  the  ciliary  processes,  are  always  devoid 
of  pigment.      [The  processes  of  the?e  cells  vary  in 


veins  black,  arteries  light,  with  a  double  contour). 
a,  a,  short  posterior  ciliary ;  i,  long  posterior  ciliary ; 
c,  c',  anterior  ciliary  artery  and  vein;  d,  d' ,  artery 
and  vein  of  the  conjunctiva  ;  e,  e' ,  central  artery  and 
vein  of  retina  ;  f,  blood  vessels  of  the  inner,  and  g; 
of  the  outer  optic  sheath;  A,  vorticose  vein;  z',  pos- 
terior short  ciliary  vein  confined  to  the  sclerotic  ;  k, 
branch  of  the  posterior  short  ciliary  artery  to  the 
optic  nerve  ;  /,  anastomosis  of  the  choroidal  vessels 
with  those  of  the  optic;  /?/,  chorio-capillaris;  n, 
episcleral  branches  ;  o.  recurrent  choroidal  artery  ;  p, 
great  circular  artery  of  iris  (transverse  section)  ;  y, 
blood  vessels  of  the  iris  ;  r,  ciliary  process  ;  s,  branch 
of  a  vorticose  vein  from  the  ciliary  muscle  ;  t,  branch 
of  the  anterior  ciliary  vein  to  the  ciliary  muscle  ;  a, 
circular  vein  ;  v.  marginal  loops  of  vessels  on  the 
cornea  ;  w,  anteriorartery  and  vein  of  the  conjunctiva. 


length  whh  the  nature  and  kind  of  light  acting  on 
the  retina  (|  398).] 

The  retina  externally  is  in  contact  with  the  layer  of  hexagonal  pigment  cells  (.Pi),  which  in  its 
development  and  functions  really  belongs  to  the  retina.  The  cells  are  not  flat,  but  they  send  pig- 
mented processes  into  the  space  between  the  ends  of  the  rods.  In  some  animals  (rabbit)  the  cells 
contain  fatty  granules  and  other  substances.  The  cells  are  larger  and  darker  at  the  ora  serrata 
i^Kuhne).     The  retina  is  composed  of  the  following  layers,  proceeding  from  without  inward  : — 


[l.  Layer  ot  pigment  cells. 

2.  Rods  and  cones. 

3 .  Extern  a  I  li?H  it  big  membrane. 

4.  Outer  nuclear  layer. 

5.  Outer  molecular  (granular  or  inter- 

nuclear)  layer. 


6.  Inner  nuclear  layer. 

7.  Inner  molecular  (granular)  layer. 

8.  Layer  of  nerve  cells  (ganglionic  layer) 

9.  Layer  of  nerve  fibres. 

10.   Internal  limiting  membrane^ 


788 


THE    RETINA. 


I.  The  hexagonal  pigment  cells  already  described.  2.  The  layer  of  rods  and  cones  (.9/)  or 
neiiro-epitheliiim  of  Schwalhe  \^bacillary  layer,  ox  \\\&  visual  cclh,  ox  visual  epilltcliutn  oi  Kiihne] 
( Fiij.  520).  These  lie  externally  next  the  choroid,  Init  they  are  absent  at  tiie  entrance  of  the  optic 
nerve.  Then  follows  the  external  limiting  membrane  {Le),  which  is  perforated  by  the  bases  of 
the  rods  and  cones.  3.  The  external  nuclear  layer  yau.K) ;  this  and  all  the  succeeding  layers  are 
called  "  brain  layers  "  by  Schwalbe.  4.  The  external  granular  {iiu.gr),  or  internuclear  layer,  which 
is  perforated  by  the  fibres  which  proceed  inward  from  llie  nuclei  of  3  to  reach  5,  the  nuclei  of  the 
internal  nuclear  layer  (/wA').     The  nuclei  of  this  layer,  which  are  connected  by  fibres  with  the 


Fk;.  520. 


Fig.  519. 


■  ■■-<;?  ■;(- 


nyr 


A.. 


r 


Vertical  section  of  human  retina,  a,  rods  and 
cones;  b,  ext.,  and  j,  int.  limit,  memb.;  c, 
ext  ,  and  /,  int.  nucl.  layers  ;  e,  ext.,  and^, 
int.  gran,  layers  ;  h,  blood  vessel  and  nerve 
cells  ;  i,  nerve  fibres. 


XJi  Li 

Layers  of  the  retina.  Fi,  hex- 
agonal pigment  cells ;  St, 
rods  and  cones  ;  Le,  ext. 
limiting  membrane;  du.K, 
ext.  nuclear  layer;  du.gr, 
ext.  granular  layer ;  inK, 
int.  nuclear  ;  in.gr,  int. 
granular ;  Ggl,  ganglionic 
nerve  cells  ;  o,  fibres  of  optic 
nerve;  /,/,  int.  limit,  mem- 
brane ;  Rk,  fibres  of  Miiller  ; 
K,  nuclei  :  Sy,  spaces  for  the 
nervous  elements. 


rods  and  cones,  are  marked  by  transver.-e  lines  in  the  macula  lutea  [A'rause,  Denissenko).  6.  The  finely 
granular  internal  granular  layer  [iti.gr),  through  which  the  fibres  proceeding  from  the  inner  nuclear 
layer  cannot  be  traced.  It  would  seem  as  if  these  fibres  break  up  into  the  finest  fibrils,  into  which 
also  the  branched  processes  of  the  ganglionic  cells  of  7,  the  ganglionic  layer,  extend.  According 
to  V.  Vintschgau,  the  processes  of  the  gans^lionic  cells  are  connected  with  the  fibres.  8.  The  next,  or 
fibrous  layer,  consists  of  the  fibres  of  the  optic  nerve  [o),  and  most  internally  is  the  internal 
limiting  membrane  {Li).  According  to  W.  Krause,  there  are  400,000  broad,  and  as  many  narrow, 
optic  fibres,  so  that  for  every  fibre  there  are  7  cones,  about  lOO  rods,  and  7  pigment  cells.     The  optic 


THE    RETINA. 


789 


fibres  are  absent  from  the  macula  lutea,  where,  however,  there  are  numerous  ganglionic  cells.  Be- 
tween the  two  homogeneous  limiting  membranes  {^Le  and  Z?)  lies  the  connective-tissue  substance 
of  the  retina.  It  contains  the  perforating  fibres,  or  Miiller's  fibres,  which  run  in  a  radiate  manner 
between  the  two  membranes,  and  hold  the  various  layers  of  the  retina  together.  They  begin  by  a 
wing-shaped  expansion  at  the  internal  limiting  membrane  {Rk'),  and  in  their  course  outward  contain 
nuclei  [k).  They  are  absent  at  the  yellow  spot.  The  supporting  tissue  forms  a  network  in  all  the 
layers,  holes  being  left  for  the  nervous  portions  {Sg).  The  inner  segments  of  the  rods  and  cones 
are  also  surrounded  by  a  sustentacular  substance.  As  the  retina  passes  forward  to  the  ora  serrata,  it 
becomes  thinner  and  thinner,  gradually  becoming  richer  in  connective-tissue  elements  and  poorer  in 
nerve  elements,  until,  in  the  ciliary  part,  only  the  cylindrical  cells  remain  (Fig.  519). 

[Macula  Lutea  and  Fovea  Centralis. — There  are  no  rods  in  the  fovea,  while  the  cones  are 
longer  and  narrower  than  in  the  other  parts  of  the  retina  (Fig.  521).  The  other  layers  also  are 
thinner,  especially  at  the  macula  lutea,  but  they  become  thicker  toward  the  margins  of  the  fovea, 
where  the  ganglionic  layer  consists  of  several  rows  of  bipolar  cells.  The  yellow  tint  is  due  to  pig- 
ment lying  between  the  layers  composing  the  yellow  spot.] 

The  blood  vessels  of  the  retina  lie  in  the  inner  layers  near  the  inner  granular  layer.  Only 
near  the  entrance  of  the  optic  nerve  are  they  connected  by  fine  branches  with  the  choroidal  vessels  ; 
they  are  surrounded  by  perivascular  lymph  spaces.  The  greatest  number  of  capillaries  runs  in  the 
layers  external  to  the  inner  granular  layer  {Hesse).  The  fovea  centralis  is  devoid  of  blood  vessels 
{Nettleship,  Becker).  Except  in  mammals,  the  eel  [Denissenko),  and  some  tortoises  {H.  Ali'dler), 
the  retina  receives  no  blood  vessels.     Destruction  of  the  retina  is  followed  by  blindness. 


Fig.  521. 


\h 


li%!l^liillr/^n'U''-\\\{n\ 


Section  of  the  fovea  centralis,     a,  cones ;  i  and  £■,  int.  and  ext.  limit,  memb. ;  c,  ext.,  and  e,  nuclear  layer  ; 

d,  fibres  ;  _/,  nerve  cells. 


[Retinal  Epithelium. — -The  single  layer  of  pigmentary  cells  containing  granules  of  melanin 
sends  processes  downward,  like  the  hairs  of  a  brush,  between  the  rods  and  cones  (|  398V  Kiihne 
has  shown  that  the  nature  and  amount  of  light  influence  the  condition  of  these  processes  (Fig.  563). 
The  protoplasm  of  these  cells  in  a  frog  kept  for  several  hours  in  the  dark,  is  retracted,  and  the  pig- 
ment granules  lie  chiefly  in  the  body  of  the  cell  and  in  the  processes  near  the  cell.  In  a  frog  kept 
in  bright  daylight,  the  processes  loaded  with  pigment  penetrate  downward  between  the  rods  and 
cones  as  far  as  the  external  limiting  membrane.] 

Each  rod  and  cone  consists  of  an  outer  and  an  inner  segment.  During  life,  the  outer  segment 
contains  a  reddish  pigment  or  the  visual  purple  {Boll). 

Visual  purple  [or  rhodopsin]  may  be  preserved  by  keeping  the  eye  in  darkness ;  but  it  is  soon 
bleached  by  daylight,  while  it  is  again  restored  when  the  eye  is  placed  in  darkness.  It  can  be 
extracted  from  the  retina  by  means  of  a  2.5  percent,  solution  of  the  bile  acids,  especially  from  eyes 
that  have  been  kept  in  10  per  cent,  solution  of  common  salt  {Ayres).  The  rods  are  0.04  to  0.06  mm. 
high  and  0.0016  to  0.0018  mm.  broad,  and  exhibit  longitudinal  striation,  produced  by  the  presence 
of  fine  grooves;  a  fine  fibril  runs  in  their  interior  {Bitter).  The  external  segment  occasionally 
cleaves  transversely  into  a  number  of  fine  transparent  disks.  [It  is  a  very  resistant  structure,  and  in 
this  respect  resembles  neuro-keratin.]  Krause  found  an  ellipsoidal  body,  the  "  rod  ellipsoid,"  at  the 
junction  of  the  inner  and  outer  segments  of  the  rods.  The  cones  are  devoid  of  visual  purple,  but 
their  outer  segment  is  striated  longitudinally,  and  it  also  readily  breaks  across  into  thin  disks.  Only 
cones  are  present  in  the  macula  lutea.  In  the  neighborhood  of  the  yellow  spot,  each  cone  is  sur- 
rounded by  a  ring  of  rods.  The  cones  become  less  numerous  toward  the  periphery  of  the  retina. 
In   nocturnal  animals,  such  as  the  owl  and  bat,  there  are  either  no  cones  or  imperfect  ones.     The 


790 


STRUCTURE   OF   THE    LENS. 


retinx^  of  binls  contain  many  cones,  that  of  the  tortoise  only  cones.  The  rods  and  cones  rest  on  the 
sieve-like  perforated  external  limiting  membrane  (Le).  Both  send  processes  through  the  membrane, 
the  cones  to  the  larger  and  liigher-placed  nuclei,  the  rods  to  the  nuclei,  with  transverse  markings  in 
the  external  nuclear  layer.  [The  cones  are  particularly  large  in  some  fishes,  <f.,^^,  tlie  cod,  while  the 
skate  has  no  cones  but  only  rods.  The  same  is  the  case  in  the  shark  and  sturgeon,  hedgehog,  bat, 
and  mole.] 

I  Distribution  and  Regeneration  of  Rhodopsin. — Keep  a  rabbit  in  the  dark  for  some  time, 
kill  it,  remove  its  eyeball,  and  examine  its  retina  by  the  aid  of  monochromatic  (sodium)  light.  The 
retina'will  be  purple  red  in  color,  all  except  the  macula  lutea  and  a  small  jjart  at  the  ora  serrata. 
The  i)igment  is  confmed  to  the  oitfrr  sei^meft/s  of  the  rods.  It  is  absent  in  pigeons,  hens,  and 
one  bat,  although  the  last  has  only  rods.  It  is  found  both  in  nocturnal  and  diurnal  animals.  Its 
color  is'  quickly  bleached  bv  light,  and  it  fades  rapidly  at  a  temperature  of  50°  to  76°  C,  while 
trypsin,  alum,  and  ammonia'do  not  affect  it  It  is  restored  in  the  retina  by  the  action  of  the  retinal 
epithelium.  If  the  retinal  epithelium  or  choroid  be  Hfted  off  from  an  excised  eye  exposed  to  light, 
the  purple  is  destroyed  ;  but  if  the  eye  be  placed  in  darkness  and  the  retinal  epithelium  replaced, 
the  color  is  restored.] 

Chemistry  of  the  Retina. — The  reaction  of  the  retina,  when  quite  fresh,  is  acid,  and  becomes 
alkaline  in  darkness.  The  rods  and  cones  contain  albumin,  neuro-ker.atin,  nuclein,  and  in  the  cones 
are  the  pigmented  oil  globules,  the  so-called  "  chromophanes."  The  other  layers  contain  the 
constituents  of  the  gi-ay  matter  of  the  brain. 

[Cones. — There  is  no  coloring  matter  in  the  outer  segment  of  the  cones,  but  in  fishes,  reptiles, 
and  birds  the  inner  segment  contains  a  globular-colored  body,  often  red  and  yellow,  the  pigment 
being  held  in  solution  by  a  fatty  body.  Kuhne  has  separated  a  green  (chlorophane),  a  yellow 
(xanthophane),  and  a  red  (rhodophane)  pigment.  They  all  give  a  blue  with  iodine,  and  are 
bleached  by  light  {Schwalbe).'\ 

The  crystalline  lens  is  enclosed  in  a  transparent  capsule,  thicker  anteriorly  than  posteriorly,  and 
it  is  covered  on  the  inner  surface  of  the  anterior  wall  by  a  layer  of  low  epithelium.  Toward  the 
margin  of  the  lens,  these  cells  elongate  into  nucleated  fibres,  which  all  bend  round  the  margin  of 
the  'lens,  and  on  both  sides  of  the  lens  abut  with  their  ends  against  each  of  the  iriradiate  figures. 
The  lens  fibres  contain  globulin  enclosed  in  a  kind  of  membrane.  Owing  to  mutual  pressure,  they 
are  hexagonal  when  seen  in  transverse  section  (Fig.  522,  2),  while  in  many  animals,  especially  fishes, 
their  margins  are  serrated  [the  teeth  dovetail  into  each  other].  For  the  sake  of  simplicity,  we  may 
regard  the  lens  as  a  biconvex  body  with  spherical  surfaces,  the  posterior  surface  being  more  curved. 
As  a  matter  of  fact,  the  anterior  part  is  part  of  an  ellipsoid  formed  by  rotation  on  a  short  axis.  The 
posterior  surface  resembles  the  section  of  a  paraboloid,  /.  e.,  we  might  regard  it  as  formed  by  the 
rotation  of  a  parabola  on  its  axis  {Briicke).  The  outer  layers  of  the  lens  have  less  refractive  power 
than  the  more  internal  layers.     The  central  part  of  the  lens  or  nucleus  is,  at  the  same  time,  firmer, 

and  more  convex  than  the  entire  lens.     The  margin  of  the  lens 
is  always  separated  from  the  ciliary  processes  by  an  interme- 
....,,-  „w  diate  space. 

\\    1 1 1  f  fi  y.  [Chemistry. — The  lens  contains  about  two-thirds  of  its  weight 

Will  //  y^y^     of  water,  while  its  chief  solid  is  a  globulin,  called  by  Berzelius 

^  I  '  I  I  ill        /y  ry^       crystallin  (24.6  per  cent),  with  a  little  serum  albumin,  salts, 

choleslerin,  and  fats.] 

[Cataract. — Sometimes  the  lens  becomes  more  or  less 
opaque,  the  opacity  beginning  either  in  the  middle  or  outer 
parts  of  the  lens.  This  is  generally  due  to  fatty  degeneration 
of  the  fibres,  cholesterin  being  deposited.  An  opaque,  cataract- 
ous  condition  of  the  lens  may  be  produced  in  frogs,  by  injecting 
a  solution  of  some  salts  or  sugar  in  the  lymph  sacs ;  the  result 
is  that  these  salts  absorb  the  water  from  the  lens,  and  thus  make 
it  opaque.  The  cataract  of  diabetes  is  probably  jjroduced  from 
the  presence  of  grape  sugar  in  the  blood.] 

The  zonule  of  Zinn,  at  the  ora  serrata,  is  applied  as  a 
folded  membrane  to  the  ciliary  part  of  the  uvea,  so  that  the 
ciliar}'  processes  are  pressed  into  its  folds,  and  are  united  to  it. 
It  passes  to  the  margins  of  the  lens,  where  it  is  inserted  by  a 
series  of  folds  into  the  anterior  part  of  the  capsule  of  the  lens. 
Behind  the  zonule  of  Zinn,  and  reaching  as  far  as  the  vitreous 
humor,  is  the  canal  of  Petit.  The  zonule  is  a  fibrous  per- 
forated membrane.  According  to  Merkel,  the  canal  of  Petit  is 
enclosed  by  very  fine  fibres,  so  that  it  is  really  not  a  canal,  but 
a  complex  communicating  system  of  spaces  [Gerlach).  Never- 
theless, the  zonule  represents  a  stretched  membrane,  holding  the  lens  in  position,  and  may  therefore 
be  regarded  as  the  suspensory  ligament  of  the  lens. 

Opacity  or  cloudiness  of  the  lens  (gray  cataract)  hinders  the  passage  of  light  into  the    eye. 


Fig 


I,  Fibres  of  the  lens ;  2,  transverse  sec- 
tion of  the  lens  fibres. 


THE    VITREOUS    HUMOR. 


791 


Aphakia,  or  the  absence  of  the  lens  (as  after  operation  for  cataract)  may  be  remedied  by  a  pair  of 
strong  convex  spectacles.     Of  course,  such  an  eye  does  not  possess  the  power  of  accommodation. 

The  vitreous  humor,  as  far  as  the  ora  serrata,  is  bounded  by  the  internal  limiting  membrane  ot 
the  retina  (^Henle,  Iwanoff').  From  here  forward,  lying  between  both,  are  the  meridional  fibres  of  the 
zonule,  which  are  united  with  the  surface  of  the  vitreous  and  the  ciliary  processes.  A  part  of  the 
fibrous  layer  bends  into  the  saucer-shaped  depression,  and  bounds  it.  A  canal,  2  mm.  in  diameter, 
runs  from  the  optic  papilla  to  the  posterior  surface  of  the  capsule  of  the  lens ;  it  is  called  the  hyaloid 
canal,  and  was  formerly  traversed  by  blood  vessels.  The  peripheral  part  of  the  vitreous  humor  is 
laminated  like  an  onion,  the  middle  is  homogeneous;  in  the  former,  especially  in  the  fcetus,  are 
round  fusiform  or  branched  cells  of  mucous  tissue  of  the  vitreous,  while  in  the  centre  there  are 
disintegrated  remains  of  these  cells  [Iwanoff).  The  vitreous  humor  contains  a  very  small  percentage 
of  solids,  1.5  per  cent,  of  mucin  [and,  according  to  Picard,  there  is  0.5  per  cent,  of  urea,  and  about 
.75  of  sodic  chloride]. 

[Structure. — The  vitreous  humor  consists  essentially  of  mucous  tissue,  in  whose  meshes  lie  a 
very  watery  fluid,  containing  tlie  organic  and  inorganic  bodies  in  solution.  According  to  Younan,  the 
vitreous  contains  two  types  of  cells — (i)   amcEboid  cells  of  various  shapes  and  sizes.     They  lie  on 

Fig.  523. 


Horizontal  section  of  the  entrance  of  the  optic  nerve  and  the  coats  of  the  eye.  a,  inner,  b,  outer  layers  of  the  retina ; 
c,  choroid  ;  d,  sclerotic  ;  e,  physiological  cup  ;/,  central  artery  of  retina  in  axial  canal  ;  g-,  its  point  of  bifurcation  ; 
h,  lamina  cribrosa;  /,  outer  (dural)  sheath  ;  w,  outer  (subdural)  space  ;  n,  inner  (subarachnoid)  space  ;  r,  middle 
(arachnoid)  sheath ;  /,  inner  (pial)  sheath  ;  z,  bundles  of  nerve  fibres  ;  k,  longitudinal  septa  of  connective  tissue. 


the  inner  surface  of  the  lining  hyaloid  membrane  and  the  other  membranes  in  the  cortex  of  the 
vitreous;  (2)  large  branching  multipolar  cells.  The  vitreous  is  permeated  by  a  large  number  of 
transparent,  clear,  homogeneous  hyaloid  membranes,  which  are  so  disposed  as  to  give  rise  to  a 
concentric  lamination.  The  canal  of  Stilling  represents  in  the  adult  the  situation  of  the  hyaloid 
artery  of  the  foetus.     It  can  readily  be  injected  by  a  colored  fluid.] 

The  lymphatics  of  the  eye  consist  of  an  anterior  and  a  posterior  set.  The  anterior  consist  of 
the  anterior  and  posterior  chambers  of  the  eye  (aqueous)  which  communicate  with  the  lymphatics 
of  the  iris,  ciliary  processes,  cornea,  and  conjunctiva.  The  posterior  consist  of  the  perichoroidal 
space  between  the  sclerotic  and  the  choroid  \Schwalbe).  This  space  is  connected  by  means  of  the 
perivascular  lymphatics  around  the  trunks  of  the  vasa  vorticosa,  with  the  large  lymph  space  of  Tenon, 
which  lies  between  the  sclerotic  and  Tenon's  capsule.  Posteriorly,  this  is  continued  into  a  lymph 
channel,  which  invests  the  surface  of  the  optic  nerve;  while  anteriorly  it  communicates  directly  with 
the  sub-conjunctival  lymph  spaces  of  the  eyeball.  The  optic  nerve  has  three  sheaths — (i)  the 
dural;  (2)  the  arachnoid;  and  (3)  the  pial  sheath,  derived  from  the  corresponding  membranes  of 
the  brain.  Two  lymph  spaces  lie  between  these  three  sheaths — the  subdural  space  between  i 
and  2,  and  the  subarachnoid  space  between  2  and  3  (Fig.  509).     Both  spaces  are  lined  by  endo- 


792  INTRAOCULAR    PRESSURE. 

thelium ;  and  the  fine  trabecuUe  passing  from  one  wall  to  the  other  are  similarly  covered.  According 
to  Axel  Key  and  Ret/ius,  these  lymph  spaces  communicate  anteriorly  with  the  perichoroidal  space. 
The  aqueous  humor  closely  resembles  the  cerebro-spinal  fluid,  and  contains  albumin  and  sugar  ; 
the  former  is  increased,  and  the  latter  disappears  after  death.  The  same  occurs  in  the  vitreous.  The 
albumin  increases  when  the  difterence  between  the  blood  pressure  and  the  intraocular  pressure  rises. 
Such  variations  of  pressure,  and  also  intense  stimuli  applied  to  the  eye,  cause  the  production  of 
fibrin  in  the  anterior  cliamber  {Jesner  and  Griinhageti). 

Intraocular  Pressure. — The  cavity  of  the  bulb  is  practically  filled  with  watery  fluids,  which, 
during  life,  are  constantly  subjected  to  a  certain  pressure,  the  "  intraocular  pressure."  Ultimately, 
this  depends  upon  the  blood  pressure  within  the  arleries  of  the  retina  and  uvea,  and  must  rise  and 
fall  with  it.  The  pressure  is  determined  by  pressing  upon  the  eyeball,  and  ascertaining  whether  it 
is  tense,  or  soft  and  compressible.  Just  as  in  the  case  of  the  arterial  pressure,  the  intraocular  pressure 
is  influenced  by  many  circumstances";  it  is  increased  at  eveiy  pulse  beat  and  at  every  expiration,  while 
it  is  decreased  during  inspiration.  The  elastic  tension  of  the  sclerotic  and  cornea  regulates  the 
increase  of  the  arterial  pressure  by  acting  like  the  air  chamber  in  a  fire  engine  ;  thus,  when  more 
arterial  blood  is  pumped  into  the  eyeball,  more  venous  blood  is  also  expelled.  The  constancy  of  the 
intraocular  pressure  is  also  influenced  by  the  fact  that,  just  as  the  aqueous  humor  is  removed,  it  is 
secreted,  or  rather  formed,  as  rapidly  as  it  is  absorbed  (^  392).  [Pick  has  invented  an  in.strument 
for  the  direct  measurement  of  the  intraocular  pressure,  a  small  plate  of  known  size  is  pressed  against 
the  eyeball,  and  the  pressure  exerted  is  registered  by  means  of  a  spring  and  index.] 

The  secretion  of  the  aqueous  humor  occurs  pretty  rapidly,  as  may  be  surmised  from  the  fact, 
that  hcemoglobin  is  found  in  the  aqueous  humor  half  an  hour  after  dissolved  blood  (lamb's)  is  injected 
into  the  blood  vessels  of  a  dog.  It  is  rapidly  reformed,  after  evacuation,  through  a  wound  in  the 
cornea.  According  to  Knies,  the  watery  fluid  within  the  eyeball  is  secreted,  especially  from  the 
chorio-capillaris,  and  reaches  the  supra-choroidal  space,  in  the  lymph  sheaths  of  the  oplic  nerve,  and 
partly  through  the  network  of  the  sclerotic.  It  saturates  the  retina,  vitreous,  lens,  and  for  the  most 
part  passes  through  the  zonula  ciliaris  into  the  posterior  chamber,  and  through  the  pupil  into  the 
anterior  chamber.  The  movements  of  the  fluid  within  the  eyeball  have  been  recently  studied  by 
Ehrlich,  who  used  fluorescin,  an  indiflerent  substance,  which,  on  being  introduced  into  the  body, 
passes  into  the  fluids  of  the  eyeball,  and  in  a  ver)-  dilute  solution  may  be  recognized  by  its  green 
fluorescence  in  reflected  light.  From  observations  on  the  entrance  of  this  substance  into  the  eye, 
Scholer  and  Uhthoff  regard  the  posterior  surface  of  the  iris  and  the  ciliarj'  body  as  the  secretory 
organs  for  the  aqueous  humor.  It  passes  through  the  pupil  into  the  anterior  chamber;  some  passes 
into  the  lens,  and  along  the  canal  of  Petit  into  the  vitreous  humor  {PjUiger').  Section  of  the  cervical 
sympathetic,  and  still  more  of  the  trigeminus,  accelerates  the  secretion  of  the  aqueous,  but  its  amount 
is  diminished.  If  the  substance  is  dropped  into  the  conjunctival  sac,  it  percolates  toward  the  centre 
of  the  cornea,  and  through  the  latter  into  the  anterior  chamber  {Pfliiger). 

A  current  passes  forward  fi-om  the  vitreous  humor  around  the  lens,  and  there  is  an  outflow  along 
the  central  artery  of  the  retina  backward  through  the  optic  nerve  to  the  cavity  of  the  skull  {Gifford). 
The  current  in  the  spaces  between  the  sheaths  flows  from  the  brain  to  the  eye  i^Quincke). 

The  outflow  of  the  aqueous  humor,  according  to  Leber  and  Heisrath,  takes  place  chiefly  between 
the  meshes  of  the  ligamentum  pectinatum  iridis  (Fig.  514,  m,  m),  and  the  canal  of  Schlemm  {i,  k), 
into  the  anterior  circular  veins  (p.  787).  A  small  part  of  the  aqueous  humor  diffuses  into  the 
posterior  layers  of  the  cornea  to  nourish  it  (Leber).  None  of  the  water  is  conducted  from  the  eye- 
ball by  any  special  efferent  lymphatics  [Leber).  Under  nomial  circumstances,  the  pressure  is 
nearly  the  same  in  the  vitreous  and  aqueous  chambers,  but  atropin  seems  to  diminish  the  pressure  in 
the  former  and  to  increase  it  in  the  latter,  while  Calabar  bean  has  an  opposite  action  [Ad. ^  IVeber). 
Arrest  of  the  outflow  of  the  venous  blood  often  increases  the  pressure  in  the  vitreous,  and  diminishes 
that  in  the  aqueous  chamber.  Compression  of  the  bulb  from  without  causes  more  fluid  to  pass  out 
of  the  eye  temporarily  than  enters  it.  The  diminution  of  the  intraocular  pressure  is  well  marked 
after  section  of  the  trigeminus,  while  it  rises  when  this  nerve  is  stimulated.  The  statements  of 
observers  regarding  the  effect  of  the  sympathetic  nerve  upon  the  pressure  vary.  Interruption  to  the 
venous  outflow  increases  the  pressure,  while  an  imperfect  supply  of  blood,  the  outflow  being  normal, 
diminishes  the  pressure.     The  innervation  of  the  blood  vessels  of  the  eye  is  referred  to  at  I  347. 

385.  DIOPTRIC  OBSERVATIONS. — The  eye  as  an  optical  instrument  is  corhparable 
to  a  camera  obscura ;  in  both,  an  inverted  diminished  image  of  the  objects  of  the  external 
world  is  formed  upon  a  background,  the  field  of  projection.  Instead  of  the  single  lens  of  the  camera, 
however,  the  eye  has  several  refractive  media  placed  behind  each  other — cornea,  aqueous 
humor,  lens  (whose  individual  parts — capsule,  cortical  layers,  and  nucleus,  all  possess  different 
refractive  indices),  and  vitreous  humor.  Every  two  of  these  adjacent  media  are  bounded  by  a 
"  refractive  surface,"  which  may  be  regarded  as  spherical.  The  field  of  projection  of  the  eye  is 
the  retina,  which  is  colored  with  the  visual  purple  [Boll,  Kiihne).  As  this  substance  is  bleached 
chemically  by  the  direct  action  of  light,  so  that  the  pictures  maybe  temporarily  fixed  upon  the  retina, 
the  comparison  of  the  eye  with  the  camera  of  the  photographer  becomes  more  striking.  In  order 
that  the  passage  of  the  rays  of  light  through  the  media  of  the  eye  may  be  rightly  understood,  we 
must  know  the  following  factors:   (l)  the  refractive   indices  of  all  the  media;    (2)  the  form  of  the 


ACTION    OF    LENSES    ON    LIGHT. 


793 


refractive  surfaces;  (3)  tne  distance  of  the  various  media  from  each  other  and  from  the  field  of  pro- 
jection or  retina. 

Action  of  a  Converging  Lens. — We  must  know  how  a  convex  lens  acts  upon  light.  In  a  convex 
lens  we  distinguish  the  centre  of  curvature,  /.  e.,  the  centre  of  both  spherical  surfaces  (Fig.  524,  I, 
711,  Wj).  The  line  connecting  both  is  called  the  chief  axis ;  the  centre  of  this  line  is  the  optical 
centre  of  the  lens  {0).  All  rays  which  pass  through  the  optical  centre  of  the  lens  pass  through 
tmbent,  or  without  being  refracted;  they  are  called  the  chief  or  principal  rays  (n,  n-^.  The  following 
are  the  laws  regulating  the  action  of  a  convex  lens  upon  rays  of  light : — 

1.  Rays  which  fall  upon  the  lens,  parallel  with  the  principal  axis  (11,/",  a),  are  so  refracted  that 
they  are  collected  on  the  other  side  of  the  lens,  at  a  point  called  the  focus  or  principal  focus  (/). 
The  distance  of  this  point  from  the  central  point  {0)  of  the  lens,  is  called  the  focal  distance  of  the 
lens  (y,  o).  The  converse  of  this  condition  is  evident,  viz.,  rays  which  diverge  from  a  focus  and 
reach  the  lens,  pass  through  it  to  the  other  side,  parallel  with  the  principal  axis,  without  again  coining 
together. 

2.  Rays  of  light  proceeding  from  a  soiurce  of  light  (IV,  /)  in  the  prolonged  principal  axis,  but 
beyond  the  focal  point  (/),  again  converge  to  a  point  on  the  other  side  of  the  lens.  The  following 
cases  may  occur  :   (a)  When  the  distance  of  the  light  from  the  lens  is  equal  to  twice  the  focal  distance. 

Fig.  524. 


Figures  illustrating  the  action  of  lenses  upon  rays  of  light  passing  through  them. 


the  focus  or  point  of  convergence  lies  at  the  same  distance  on  the  other  side  of  the  lens,  i.  e.,  twice 
the  focal  distance,  {^b)  If  the  luminous  point  be  moved  nearer  to  the  focus,  then  the  focal  point  is 
moved  further  away,  (f)  If  the  light  is  still  further  from  the  lens  than  twice  the  focal  distance,  then 
the  focal  point  comes  correspondingly  near  to  the  lens. 

3.  Rays  proceeding  from  a  point  of  the  chief  axis  (III,  b)  within  the  focal  distance,  pass  out  at  the 
other  side  less  divergent,  but  do  not  come  to  a  focus  again.  Conversely,  rays  which  are  convergent, 
and  pass  through  a  collecting  lens,  have  their  focal  point  within  the  focal  distance. 

4.  If  the  luminous  point  (V,  a)  is  placed  in  the  secondary  ray  {a,  b),  the  same  laws  obtain, 
provided  the  angle  formed  by  the  secondary  ray  with  the  principal  axis  is  small. 

Formation  of  images  by  convex  lenses. — After  what  has  been  stated,  regarding  the  position 
of  the  point  of  convergence  of  rays  proceeding  from  a  luminous  point,  the  construction  of  the  image 
of  any  object  by  a  convex  lens  is  easily  accomplished.  This  is  done  simply  by  projecting  images  of 
the  various  parts  of  the  object.  Thus,  evidently  (in  V),  b  is  the  focal  point  of  the  object,  a,  while  v 
is  the  focal  point  of  the  object,  /.  The  picture  is  inverted.  Collecting  lenses  form  an  invei-ted  and 
real  image  [i.  e.,  upon  a  screen)  only  of  stick  objects  as  are  placed  beyond  the  focal  point  of  the  lens. 

With  regard  to  the  size  and  distance  of  the  image  from  the  lens,  there  are  the  following  cases : 
[a]  If  the  object  be  placed  at  twice  the  focal  distance  from  the  lens,  the  image  of  the  same  is  just  the 


794 


FORMATION    OF    IMAGES    BY    CONVEX    LENSES. 


same  size  and  at  the  same  distance  from  tlie  lens  as  the  object  is.  [6)  If  the  object  be  nearer  than 
the  focus,  the  image  recedes  and  at  the  same  time  becomes  larger,  (c)  If  the  ol)ject  be  further 
removed  from  the  lens  than  twice  the  focal  distance,  then  the  image  is  nearer  to  the  lens  and  at  the 
same  time  becomes  smaller. 

Position  of  the  Focal  Point. — The  distance  of  the  focal  point  from  the  lens  is  readily  calculated 
according  to  the  following  formula:  Where  /=^  the  distance  of  the  luminous  point,  6  =^  the  distance 

I       ^  I         I         I 

6  cm.    Then   ,  =- =,7;  so  that /^^  8  cm., /.f., 

i^        6       24       8 
the  image  is  formed  8  cm.  behind  the  lens.     Further,  let  /=r  10  cm.,y=  5  cm.  {i.e.,  /=  2/). 

Thea    ,  = =       ;  so  that  i  =:  10,  /.  e.,  the  image  is  placed  at  twice  the  focal  distance  of  the 

(J        5        10       10 


of  the  image,  andy" 

Example. — Let  /  =  24  centimetres, y 


the  focal  distance  of  the  lens :       -f- 


lens.     Lastly,  let  /  : 


Then  — 
o 


-/,  i.  e.,  the  image  of  parallel  rays  coming 


II  1       , 

;  so  that  0 

/,     =* 

from  inhnity  lies  in  the  focal  point  of  the  lens. 

Refractive  Indices. — A  ray  of  light,  which  passes  in  a  peq^endicular  direction  from  one  medium 

into  another  medium  of  different  density,  passes  through  the  latter  without  changing  its  course  or 

being  refracted.     In  Fig.  525,  if  G  I)  is  _l  -'^  B>  'hen  so  is  D  D,  j^  A  B;  for  a  plane  surface  A  B  is 

the  horizontal,  and  G  D  the  vertical  line.     If  the  surface  be  spherical,  then  the  vertical  line  is  the 


Fir..  526. 


■-""f" 


irj'trnirn 


fi  llliUUiiii!!|it'i;li:;;::j;;iJ, ;;;:;  i,;:.;:.!l 


prolonged  radius  of  this  sphere.  If,  however,  the  ray  of  light  fall  obliquely  upon  the  surface,  it  is 
"refracted,"  /.  e.,  it  is  bent  out  of  its  original  course.  The  incident  and  the  refracted  ray  never- 
theless lie  in  one  plane.  When  the  oblique  incident  ray  passes  from  a  less  dense  medium  {e.  _s^.,  air) 
into  one  wcri?  a'(?«.f^' (^.^^.,  water),  the  refracted  or  excident  ray  is  htni  foivard  ih^  perpendicular. 
If,  conversely,  it  pass  from  a  more  dense  to  a  less  dense  medium,  it  is  bent  azuay  from  the  perpen- 
dicular. The  angle  (/,  G  D  S)  which  the  incident  ray  (S  IJ)  forms  with  the  perpendicular  (G  D) 
is  called  the  angle  of  incidence,  the  angle  fjrmed  by  the  refracted  ray  (D  S,)  with  the  prolonged 
perpendicular  (D  D)  is  called  the  angle  of  refraction,  D  D  S,  [r].  The  refractive  power  is 
expressed  as  the  refractive  index.  The  term  refractive  index  («)  means,  that  number  which 
shows  for  a  certain  substance,  how  many  times  the  sine  of  the  angle  of  incidence  is  greater  than  the 
s:ne  of  the  angle  of  refraction,  w-hen  a  ray  of  light  passes  from  the  air  into  that  substance.  Thus,  n 
=  sin.  i  :  sin.  r  =  ad,  :  id.  On  comparing  the  refractive  indices  of  two  media,  we  always  assume 
that  the  ray  passes  from  air  into  the  medium.  On  passing  from  the  air  into  water,  the  ray  of  light 
is  so  refracted  that  the  sine  of  the  angle  of  incidence  is  to  the  sine  of  the  angle  of  refraction,  as  4  :  3  ; 

the  refractive  index  =  —  (or  more  exactly  =  1.336).     With  glass  the  proportion   is  ^  3  :  2  (^ 

1.535 — Snellitis,  1620 ;  Descartes).  The  sine  of  the  incident  and  refractive  angles  are  related  as 
the  velocity  of  light  with  both  media. 

The  construction  of  the  refracted  ray,  the  refractive  index  being  given,  is  simple :  Example. 
— Suppose  in  Fig.  526,  L  =r  the  air,  G  ^  a  dense  medium  (glass)  with  a  spherical  surface,  xy,  and 
with  its  centre  at  ;«;  p  0  ^  the  oblique  incident  ray  the  tn  Z  is  the  peqDcndicular  <^ )  ^  e  the  angle 


ACTION    OF   A    CONVEX    LENS. 


795 


■5 

of  incidence.     The  refractive  index  given  is  — ;  the  object  is  to  find  the  direction  of  the  refracted 

way.  From  o  as  centre  describe  a  circle  with  a  radius  of  any  length ;  from  a  draw  a  perpendicular, 
a  b  to  m  Z-  then  a  b  \s  the  sine  of  the  angle  of  incidence,  i.  Divide  the  line  a  b  into  three  equal 
parts,  and  prolong  it  to  the  extent  of  two  of  these  parts,  viz.,  \o  p.  Draw  the  line  p  parallel  to  m  Z. 
The  hne  joining  o  to  n  is  the  direction  of  the  refracted  ray.  On  making  a  line,  n  s,  perpendicular  to 
m  Z,n  s  ^  b  p.     Further,  n  s  ■=  sine  <)  =  r.     So  that  a  b  :  s  n  ox  :  b  p')=^  ^  :  i  or  sin.  i  :  sin.  r 

_3 

2* 
Optical  cardinal  point  of  a  simple  collecting  system. — Two  refractive  media  (Fig.  527,  L 
and  G),  which  are  separated  firom  each  other  by  a  spherical  surface  («,  b),  form  a  simple  collecting 
sy.'item.  It  is  easy  to  estimate  the  construction  of  an  incident  ray  coming  from  the  iirst  medium  (L) 
and  falhng  obliquely  upon  the  surface  {a,  b)  separating  the  two  media,  as  well  as  to  ascertain  its 
direction  in  the  second  medium,  G,  and  also  from  the  position  of  a  luminous  point  in  the  first  medium, 
to  estimate  the  position  of  the  corresponding  focal  point  in  the  second  medium.  The  factors  required 
to  be  known  are  the  following:  L  (Fig.  527)  is  the  first,  and  G  the  second  medium,  a,  b  =  the 
spherical  surface  whose  centre  is  m.  Of  course,  all  the  radii  drawn  from  f/i  to  a  b  {m  x,  vi  n)  are 
perpendiculars,  so  that  all  rays  falhng  in  the  direction  of  the  radii  must  pass  unrefracted  through  m. 
All  rays  of  this  sort  are  called  rays  or  lines  of  direction  ;  m,  as  the  point  of  intersection  of  all  these, 
is  called  the  nodal  point.  The  hne  which  connects  m  with  the  vertex  of  the  spherical  surface,  x, 
and  which  is  prolonged  in  both  directions,  is  called  the  optic  axis,  O  Q.  A  plane  (E,  F)  in  x, 
perpendicular  to  O  Q,  is  called  the  principal  plane,  and  in  it  x  is  the  principal  point.     The  fol- 

FiG.  527. 


lowing  facts  have  been  ascertained  :  (i)  All  rays  {a  to  a-^,  which  in  the  first  medium  are  parallel 
with  each  other  and  with  the  optic  axis,  and  fall  upon  a  b,  are  so  refracted  in  the  second  medium  that 
they  are  all  again  united  in  one  point  [p^  of  the  second  medium.  This  is  called  the  second  principal 
focus.  A  plane  in  this  point  perpendicular  to  O  Q  is  called  the  second  focal  plane  (C  D).  (2)  All 
rays  {c  to  c^,  which  in  the  first  medium  are  parallel  to  each  other,  but  not  parallel  to  O  Q,  reunite 
in  a  point  of  the  second  focal  plane  {f),  where  the  non-refracted  directive  ray  [c-^,  m  r)  meets  this. 
(In  this  case,  the  angle  formed  by  the  rays  c  to  c^  with  C  Q  must  be  very  small.)  The  propositions 
I  and  2  of  course  may  be  reversed ;  the  divergent  rays  proceeding  from  p  toward  a  b  pass  into  the 
first  medium  parallel  to  each  other,  and  also  with  the  axis  C  Q  («:  to  a.^  ;  and  the  rays  proceeding 
from  r  pass  into  the  first  medium  parallel  to  each  other,  but  not  parallel  to  the  axis  O  Q  (as  ^  to  c^. 
(3)  All  rays,  which  in  the  second  medium  are  parallel  to  each  other  [b  to  b-^  and  with  the  axis  O  Q, 
reunite  in  a  point  in  the  first  medium  (/),  called  the  first  focal  point ;  of  course,  the  converse  of  this  is 
true.  A  plane  in  this  point  perpendicular  to  O  Q  is  called  the  first  focal  plane  (A,  B).  The  radius  of  the 
refractive  surface  {m,  x)  is  equal  to  the  difference  of  the  distance  of  both  focal  points  (/  and  p^ 
from  the  principal  focus  {x) ;  thus  m  x  ^  p^  x  — p  x.  From  these  comparatively  simple  proposi- 
tions it  is  easy  to  determine  the  following  points  : — 

I.  The  construction  of  the  refracted  ray. — Let  A  be  the  first  (Fig.  528) ;  B,  the  second 
medium ;  c  d,  the  spherical  surface  separating  the  two ;  a  b,  the  optical  axis ;  k,  the  nodal  point ;  /, 
the  first  and  /j  the  second  principal  focus  ;  C,  D,  the  second  focal  plane.  Suppose  x  y  to  represent 
the  direction  of  the  incident  ray,  what  is  the  construction  of  the  refracted  ray  in  the  second  medium? 
Prolong  the  refracted  ray,  P,  i,-Q  parallel  to  x,y,  then  y,  Q  is  the  direction  of  the  refracted  ray 
(according  to  2). 


796 


ACTION    OF    A   CONVEX    LENS. 


2.  Construction  of  the  image  for  a  given  object.- 
FiG.  528. 


In   Fig.  529,  H,  c,  d,  a,  b,  k,  p,  and  /,, 
C,   1)  are  as  before.     Suppose  a 
luminous    ]X)int    {o]    in    the    first 
medium,  vhat   is  the  position  of 
the  image  in  the  second  medium  ? 
Prolong  the   unrefracled    ray   (t?, 
I      /•,   P),  and   draw  the   ray  (<?,  jr) 
parallel  to  the  axis  (a,  b).     The 
parallel  rays  [a,  e  and  o,  x)   re- 
— A  unite   in  /  (according  to  projx)si- 
I      tioii    i)      Prolong   x,  />,    until    it 
!      intersects  the  ray  {o,  P),  then  the 
j      image   of  0  is  at    P,  the  rays  of 
I      light  (o  X  and  o    k)    proceeding 
ii.i      from   the  luminous  point  {o)   re- 
'"  unite  in  P. 

Construction  of  the  refracted  ray  and  the  image  in  several  refractive  media. — If  several 
refractive  media  be  placed  behind  each  other,  we  must  proceed  from  medium  to  medium  with  the 
same  metliods  as  above  described.  This  would  be  very  tedious,  especially  when  dealing  with  small 
objects.  Gauss  (1840)  calculated  that  in  such  cases  the  method  of  construction  is  very  simple.  If 
the  several  media  are  ♦'  centred,"  /.  e.,  if  all  have  the  same  optic  axis,  then  the  refractive  indices  of 

Fig.  529. 


such  a  centred  system  may  be  represented  by  two  equal,  strong,  refractive  surfaces  at  a  certain  dis- 
tance. The  rays  falling  upon  the  first  surface  are  not  refracted  by  it,  but  are  essentially  projected 
forward  parallel  with  themselves  to  the  second  surface.  Refraction  takes  place  first  at  the  second 
surface,  just  as  if  only  one  refractive  surface  was  present.  In  order  to  make  the  calculation,  we  must 
know  the  refractive  indices  of  the  media,  the  radii  of  the  refractive  surfaces,  and  the  distance  of  the 
refractive  surfaces  from  each  other. 

Construction  of  the  refracted  ray  is  accomplished  as  follows  :  Let  a  b  represent  the  optical 
axis  (Fig.  530,  I)  ;  H,  the  first  focal  point  determined  by  calculation;  h  h,  the  principal  plane;  H, 
the  second  focal  point;  //j,  /^,,  the  second  princijial  plane;  X',  the  first,  and  k^  the  second  nodal 
point;  F,  the  second  focal  point;  and  I*",,  F,,  the  second  focal  plane.  Make  the  ray  of  direction  / /^j 
parallel  to  in.,  w,.  According  to  proposition  2,/,  /(•,  and  /«,.  «,  mu-t  meet  in  a  point  of  the  plane 
F,  Fj.  As/>  k^  passes  through  unrefracted,  the  ray  from  «,  must  fall  at  r;  «j  r  is,  therefore,  the 
direction  of  the  refracted  ray. 

Construction  of  the  focal  point. — Let  <?  be  a  luminous  point  (Fig.  530,  II),  what  is  the  posi- 
tion of  its  image  in  the  last  medium  ?  Prolong  from  0  the  ray  of  direction  o  k,  and  make  0,  x  par- 
allel to  a  b.  Both  rays  are  prolonged  in  a  parallel  direction  to  the  second  focal  plane.  The  ray 
parallel  to  a  b  goes  through  V ;  tii,  k^  as  the  ray  of  direction  passes  through  unrefracted.  O,  where 
«,  F,  and  w  k^  intersect  each  other,  is  the  po-ition  of  the  image  of  o. 

386.  DIOPTRICS— RETINAL  IMAGE— OPHTHALMOMETER. 
— Position  of  the  cardinal  points. — The  eye  stirrounded  with  air  on  the 
anterior  surface  of  the  cornea,  represents  a  concentric  system  of  refractive  media 
with  spherical  separating  surfaces  In  order  to  ascertain  the  course  of  the  rays 
through  the  various  media  of  the  eye,  we  mtist  know  the  position  of  both  principal 
foci  of  both  nodal  points  as  well  as  the  two  principal  focal  points.  Gauss,  Listing, 
and  V.  Helmholtz  have  calculated  the  position  of  these  points.  In  order  to  make 
this  calculation,  we  require  to  know  the  refractive  indices  of  the  media  of  the  eye, 
the  radii  of  the  refractive  surfaces,  and  the  distance  of  the  latter  from  each  other. 
These  will  be  referred  to  afterward,     (i)  The  first  principal  poinl  is  2.1746  mm. ; 


CARDINAL   OPTIC    POINTS. 


797 


and  (2)  the  second  principal  point  is  2.5724  mm.  behind  the  anterior  surface  of  the 
cornea.  (3)  T\\&  first  nodal  point,  0.7580  mm.  ;  and  (4)  the  second  nodal  point, 
0.3602  mm.  in  front  of  the  posterior  surface  of  the  lens.  (5)  i:\i&  second  prin- 
cipal focus,  14.6470  mm.  behind  the  posterior  surface  of  the  lens;  and  (6)  the 
first  principal  focus,  12.8326  in  front  of  the  anterior  surface  of  the  cornea. 

Fig.  530. 


h  h. 


Listing's  reduced  eye. — The  distance  between  the  two  principal  points,  or 
the  two  nodal  points,  is  so  small  (only  0.4  mm.),  that,  practically,  without  introduc- 
ing any  great  error  in  the  construction,  we  may  assume  ^/z<?mean  nodal  or  principal 
point  lying  between  the  two  nodal  or  principal  points.     By  this  simple  procedure 

Fig.  531. 


we  gain  one  refractive  surface  for  all  the  media  of  the  eye,  and  only  one  nodal 
point,  through  which  all  the  rays  of  direction  from  without  must  pass  without  being 
refracted.  This  schematic  simplified  6ye  is  called  "the  reduced  eye"  of 
Listing. 


798  THE    OPHTHALMOMETER. 

Formation  of  the  retinal  image. — Tims,  the  construction  of  the  image  on 
the  retina  becomes  very  simple.  In  distinct  vision,  the  inverted  image  is  formed 
on  the  retina.  Let  A  B  represent  an  object  ])laced  vertuall)  in  front  of  the  eye 
(Fig.  531).  A  pencil  of  rays  passes  from  A  into  the  eye  ;  the  ray  of  direction,  A  d, 
passes  without  refraction  through  the  nodal  point,  k.  Further,  as  the  focal  point 
for  the  luminous  point,  A,  is  upon  the  retina,  all  the  rays  proceeding  from  A  must 
reunite  in  d.  The  same  is  true  of  the  rays  proceeding  from  B,  and,  of  course,  for 
rays  sent  out  from  an  intermediate  point  of  the  body,  A  B.  The  retinal  image  is, 
as  it  were,  a  mosaic,  composed  of  innumerable  foci  of  the  object.  As  all  the  rays 
of  direction  must  pass  through  the  common  nodal  point,  k,  this  is  also  called  the 
'^'^  point  of  inicrsection  of  the  visual  rays.'" 

The  inverted  image  on  the  retina  is  easily  seen  in  the  excised  eye  of  an  albino  rabliit,  by  holding 
up  any  object  in  front  of  the  cornea  and  observing  the  inverted  image  through  the  transparent  coats 
of  the  eyeball. 

The  size  of  the  retinal  image  may  also  be  calculated,  provided  we  know  the  size  of  the  object, 
and  its  distance  from  the  cornea  As  the  two  triangles,  A  B  i'  and  c  d  k  are  similar,  A  15  :  c  it  ^^  fk 
:  /!:  g,  so  that  c  d  ^^  (A  V>,  k  i^^  :  f  k.  All  these  values  are  known,  viz.,  k  g  ^  15- 1 6  mm.;  further, 
f  k  ^  a  k  yC^  a,f,  where  a  f  is  measured  directly,  and  a  k  =  7.44  mm.  The  size  of  A  B  is  meas- 
ured directly. 

The  angle,  \k  B,  is  called  the  visual  angle,  and  of  course  it  is  equal  to  the 
angle  c  k  d.  It  is  evident  that  the  nearer  objects,  x  y,  and  r  s,  must  have  the  same 
visual  angle.  Hence,  all  the  three  objects,  A  B,  x  y,  and  r  s,  give  a  retinal  image 
of  the  same  size.  Such  objects,  whose  ends  when  united  with  the  nodal  point  form 
a  visual  angle  of  the  same  size,  and  consecpiently  form  retinal  images  of  the  same 
size,  have  the  same  "  apparent  size." 

In  order  to  determine  the  ojitical  cardinal  points  by  calculation,  after  the  method 
of  Gauss,  we  must  know  the  following  factors:  — 

1.  The  refractive  indices:  for  the  cornea,  1.377  ;  aqueous  humor,  1.377: 
lens,  1.454  (as  the  mean  value  of  all  the  layers)  ;  vitreous  humor,  1.336  ;  air  being 
taken  as  i,  and  water  1.335. 

2.  The  radii  of  the  spherical  refractive  surfaces  :  of  the  cornea,  7.7 
mm.  ;   of  the  anterior  surface  of  the  lens,  10.3  ;   of  the  posterior,  6.1  mm. 

3.  The  distance  of  the  refractive  surfaces  :  from  the  vertex  of  the  cornea 
to  the  anterior  surface  of  the  lens,  3.4  mm.  ;  from  the  latter  to  the  posterior  surface 
of  the  lens  (axis  of  the  lens),  4  mm.;  diameter  of  the  vitreous  humor,  14.6  mm. 
The  total  length  of  the  optic  axis  is  22.0  mm. 

[Kiihne's  Artificial  Eye. — The  formation  of  an  inverted  image,  and  the  other  points  in  the 
dioptrics  of  the  eye  can  be  studied  most  effectively  on  Kiihne's  artilicial  eye,  the  course  of  the  rays 
of  light  being  visible  in  water  tinged  with  eosine.] 

Ophthalmometer. — This  is  an  instrument  to  enable  us  to  measure  the  radii  of  the  refractive 
media  of  the  eye.  As  the  normal  curvature  cannot  be  accurately  measured  on  the  dead  eye,  owing 
t3  the  rapid  collapse  of  the  ocular  tunics,  we  have  recourse  to  the  process  of  Kohhausch,  for  calcu- 


Scheme  of  the  ophthalmometer  of  Helmhohz. 


lating  the  radii  of  the  refractive  surfaces  from  the  size  of  the  reflected  images  in  the  living  eye.  TAe 
size  of  a  luminous  body  is  to  the  size  of  its  reflected  image,  as  the  distance  of  both  to  half  the  7-adius 
of  the  convex  mirror.     Hence,  it  is  necessary  to  measure  the  size  of  the  reflected  image.     This  is 


ACCOMMODATION    OF   THE    EYE.  799 

done  by  means  of  the  ophthalmometer  of  Helmholtz  (Fig.  532).  The  apparatus  is  constructed  on 
the  following  principle :  If  we  observe  an  object  through  a  glass  plate  placed  obliquely,  the  object 
appears  to  be  displaced  laterally ;  the  displacement  becomes  greater,  the  more  obliquely  the  plate  is 
moved.  Suppose  the  observer,  A,  to  look  through  the  telescope,  F,  which  has  the  plate,  G,  placed 
obhquely  in  front  of  the  upper  half  of  its  objective,  he  sees  the  corneal  reflected  image,  a  b,  of  the 
eye,  B,  and  the  image  appears  to  be  displaced  laterally,  viz.,  Xoa'  b' .  If  a  second  plate,  G,  be  placed 
in  front  of  the  lower  half  of  the  telescope,  but  placed  in  the  opposite  direction,  so  that  both  plates,  cor- 
responding to  the  middle  line  of  the  objective,  intersect  at  an  angle,  then  the  observer  sees  the  re- 
flected image,  a  b,  displaced  laterally  to  a^'  b" .  As  both  glass  plates  rotate  round  their  point  of 
intersection,  the  position  of  both  is  so  selected,  that  both  reflected  images  just  touch  each  other  with 
their  inner  margins  (so  that  b'  abuts  closely  upon  a'').  The  size  of  the  reflected  image  can  be 
determined  from  the  size  of  the  angle  formed  by  both  plates,  but  we  must  take  into  calculation  the 
thickness  of  the  glass  plates  and  their  refractive  indices.  The  size  of  the  corneal  image,  and  also 
that  in  the  lens,  may  be  ascertained  in  the  passive  eye,  and  also  in  the  eye  accommodated  for  a  near 
object,  and  the  length  of  the  radius  of  the  curved  surface  may  be  calculated  therefrom  {^Helmholtz 
and  others^. 

Fluorescence. — All  the  media  of  the  eye,  even  the  retina,  are  slightly  fluorescent ;  the  lens 
most,  the  vitreous  humor  least  {v.  Helmholtz). 

Erect  Vision. — As  the  retinal  image  is  inverted,  we  must  explain  how  we 
see  objects  iipright.  By  a  'psychical  d.zl,  the  impulses  from  any  point  of  the  retina 
are  again  referred  to  the  exterior,  in  the  direction  through  the  nodal  point ;  thus 
the  stimulation  of  the  point  ^  is  referred  to  A,  that  of  <r  to  B  (Fig.  531).  The 
reference  of  the  image  to  the  external  world  happens  thus,  that  all  points  appear  to 
lie  in  a  surface  floating  in  front  of  the  eye,  which  is  called  the  field  of  vision. 
The  field  of  vision  is  the  inverted  surface  of  the  retina  projected  externally  ;  hence, 
the  field  of  vision  appears  erect  again,  as  the  inverted  retinal  image  is  again  pro- 
jected internally  but  inverted  (Fig.  531). 

That  the  stimulation  of  any  point  is  again  projected  in  an  inverse  direction  through  the  nodal 
point,  is  proved  by  the  simple  experiment,  that  pressure  upon  the  outer  aspect  of  the  eyeball  is  pro- 
jected or  referred  to  the  imier  aspect  of  the  field  of  vision.  The  entoptical  phenomena  of  the  retina  are 
similarly  projected  externally  and  inverted  ;  so  that,  e.g.,  the  entrance  of  the  optic  nerve  is  referred 
externally  to  the  yellow  spot  (see  \  393).     All  sensations  from  the  retina  are  projected  externally. 

387.  ACCOMMODATION  OF  THE  EYE.— According  to  No.  2  (p.  793),  the  rays  of 
light  proceeding  from  a  luminous  point,  e.g.,^  flame,  and  acted  upon  by  a  collecting  (convex)  lens, 
are  brought  to  a  focus  or  focal  point,  which  has  always  a  definite  relation  to  the  luminous  object.  If  a 
projection  surface  or  screen  be  placed  at  this  distance  fi'om  the  lens,  a  real  and  inverted  image  of 
the  object  is  obtained  upon  the  screen.  If  the  screen  be  placed  nearer  to  the  lens  (Fig.  524,  IV,  a,  b), 
or  further  away  from  it  [c,  d),  no  distinct  image  of  the  object  is  formed,  but  diffusion  circles  are 
obtained;  because,  in  the  former  case, the  rays  have  not  united,  and  in  the  latter,  because  the  ra)s, 
after  uniting,  have  crossed  each  other  and  become  divergent.  If  the  luminous  point  be  brought 
nearer  to,  or  removed  further  from  the  lens,  in  order  to  obtain  a  distinct  image,  in  every  case,  the 
screen  must  be  brought  nearer,  or  removed  from  the  lens,  to  keep  the  same  distance  between  the 
lens  and  the  screen.  If,  however,  the  screen  be  fixed  permanently,  while  the  distance  between  the 
luminous  point  and  the  lens  varies,  a  distinct  image  can  only  be  obtained  upon  the  screen,  provided 
the  lens,  as  the  luminous  point  approaches  it,  becomes  more  convex,  i.  e.,  refracts  the  rays  of  light 
more  strongly — conversely,  when  the  distance  between  the  luminous  point  and  the  lens  becomes 
greater,  the  lens  must  become  less  curved,  i.  e.,  refract  less  strongly. 

In  the  eye,  the  projection  surface  or  screen  is  represented  by  the  retina,  which  is  permanently  fixed 
at  a  certain  distance;  but  the  eye  has  the  power  of  forming  distinct  images  of  near  and  distant 
objects  upon  the  retina,  so  that  the  refi-active  power,  i.  e.,  the  form  of  the  crys-talline  lens  in  the  eye, 
must  undergo  a  change  in  curvature  corresponding  in  every  case  to  the  distance  of  the  object.  [It  is 
important  to  remember,  that  we  cannot  see  a  near  object  and  a  distant  one  with  equal  distinctness  at 
the  sa?netime,  and  hence  arises  the  necessity  for  accommodation.] 

Accommodation. — By  the  term  "accommodation  of  the  eye,"  is  understood 
that  property  of  the  eye,  whereby  it  forms  distinct  images  of  distant  as  well  as  near 
objects  upon  the  retina.  This  power  depends  upon  the  fact,  that  the  crystalline 
lens  alters  its  curvature,  becoming  more  convex  (thicker),  or  less  curved 
(flatter),  according  to  the  distance  of  the  object.  When  the  lens  is  absent  from 
the  eyeball,  accommodation  is  impossible  {Th.  Young,  in  Danders,  "Accommoda- 
tion and  Refraction  of  the  Eye)." 

During  rest  [or  negative  accommodation],  or  when  the  eye  is  passive,  it  is 


800 


ACCOMMODATION. 


accommodated  for  the  ^i^rccj/cs/  tiistanie,  i.  e.,  images  of  objects  placed  at  an  infi- 
nite distance  {e.  g.,  the  moon)  are  found  upon  the  retina.  In  this  case,  rays  coming 
from  such  a  distance  are  practically /^^/v/Z/d"/,  and  when  they  enter  the  eye,  are  in 
\.\\e  passive  normal  est  (emmetropic)  brought  to  a  focus  on  the  retina.  When 
looking  at  a  distant  object,  a  distinct  image  is  formed  on  the  retina  without  the  aid 
of  any  muscular  action. 

That  distant  objects  are  seen  without  the  aid  of  any  muscular  action  issliown  by  the  fuUowing  con- 
siderations :  ( I )  With  the  normal,  or  emmetropic  eye,  we  can  see  distant  objects  clearly  and  distinctly, 
without  experiencing  any  feeling  of  effort.  On  opening  the  eyelids  after  along  period  of  rest,  the  objects 
at  a  distance  are  at  once  distinctly  visible  in  the  field  of  vision.  (2)  If,  in  conse(iuence  of  paralysis  of 
the  mechanism  of  accommodation  [e.g.,  through  paralysis  of  the  oculomotor  nerve — \  345,  7),  the 
eye  is  unable  to  focus  images  of  objects  placed  at  different  distances,  still  distinct  images  are  obtained 

F'fi-  533- 


Anterior  quadrant  of  a  horizontal  section  of  the  eyeball,  cornea,  and  lens.  «,  substantia  propria  of  the  cornea;  b. 
Bowman's  elastic  membrane  ;  c,  anterior  corneal  epithehiim  ;  d,  Desccmet's  membrane  ;  e,  its  epithelium  ;  /, 
conjunctiva  ;  g,  sclerotic  ;  h,  iris  :  i,  sphincter  iridis  ;  j,  ligam.entum  pectinatum  iridis,  with  the  adjoining  vacuo- 
lated tissue ;  k,  canal  of  Schlemm  ;  /,  longitudinal ;  ;«,  circular  muscular  fibres  of  the  ciliary  muscle  ;  n,  ciliary 
process  ;  o,  ciliary  part  of  the  retina  ;  q,  canal  of  Petit,  with  Z,  zonule  of  Zinn  in  front  of  it  ;  and  /,  the  posterior 
layer  of  the  hyaloid  membrane  ;  r,  anterior,  s,  posterior  part  of  the  capsule  of  the  lens  ;  t,  choroid  ;  u,  pericho- 
roidal space;   T,  pigment  epithelium  of  the  iris  ;  x,  margin  of  the  lens. 

of  distant  objects.  Thus,  paralysis  of  the  mechanism  of  accommodation  is  always  accompanied  by 
inability  to  focus  a  near  object,  never  a  distant  object.  A  temj)orary  paralysis  occurs  with  the  same 
results  when  a  solution  of  atropin  or  duboisin  is  dropped  into  the  eye,  and  also  in  poisoning  with 
these  drugs  (^  392). 

When  the  eye  is  accommodated  for  a  near  object  [positive  accommoda- 
tion], the  lens  is  thicker,  its  anterior  surface  is  more  curved  (convex),  and  pro- 
jects further  into  the  anterior  chamber  of  the  eye  (^Cramer,  185 1,  v.  Helmholiz, 
1853).  The  mechanism  producing  this  result  is  the  following  :  During  rest,  the  lens 
is  kept  somewhat  flattened  against  the  vitreous  humor  lying  behind  it,  by  the  tension 
of  the  stretched  zonule  of  Zinn,  which  is  attached  round  the  margin  of  the  lens 
(Fig.  533,  Z).  When  the  muscle  of  accommodation,  the  ciliary  muscle  (/,  vi), 
contracts,  it  pulls  forward  the  margin  of  the  choroid,  so  that  the  zonule  of  Zinn  in 


NERVES. 


801 


intimate  relation  with  it  is  relaxed.  [When  we  accommodate  for  a  near  object, 
the  ciliary  muscle  contracts,  pulls  forward  the  choroid,  relaxes  the  zonule  of 
Zinn,  and  this  in  turn  diminishes  the  tension  of  the  anterior  part  of  the  capsule  of 
the  lens.]  The  lens  assumes  a  more  curved  form,  in  virtue  of  its  elasticity,  so  that 
it  becomes  more  convex  as  soon  as  the  tension  of  the  zonule  of  Zinn,  which  keeps 
it  flattened,  is  diminished  (Fig.  534).  As  the  posterior  surface  of  the  lens  lies  in 
the  saucer-shaped  unyielding  depression  of  the  vitreous  humor,  the  anterior  sur- 
face of  the  lens  in  becoming  more  convex  must  necessarily  protrude  more  forward. 
Nerves. — According  to  Hensen  and  Volckers,  the  origin  of  the  nerves  of  accom- 
modation lies  in  the  most  anterior  root  bundles  of  the  oculomotorius.  Stimulation 
of  the  posterior  part  of  the  floor  of  the  third  ventricle  causes  accommodation;  if  a 
part  lying  slightly  posterior  to  this  be  stimulated,  contraction  of  the  pupil  occurs. 
On  stimulating  the  limit  between  the  third  ventricle  and  the  aqueduct,  there  results 

Fig.  534. 


Scheme  of  accommodation  for  near  and  distant  objects.  The  right  side  of  the  figure  represents  the  condition  of  the 
lens  during  accommodation  for  a  near  object,  and  the  leftside  when  the  eye  is  at  rest.  The  letters  indicate  the 
same  parts  on  both  sides;  those  on  the  right  side  are  marked  thus';  ^,left,  .S,  right  half  of  the  lens;  C, 
cornea  ;  S,  sclerotic  ;  C.S.,  canal  of  Schlemm  ;  V.K.,  anterior  chamber  ;  J,  iris  ;  P,  margin  of  the  pupil ;  V,  an- 
terior surface  ;  H,  posterior  surface  of  the  lens  ;  R,  margin  of  the  lens  ;  F,  margin  of  the  ciliary  processes  ;  a  and 
b,  space  between  the  two  former  ;  the  line  Z,  X,  indicates  the  thickness  of  the  lens  during  accommodation  for  a 
near  object ;  Z,  V,  the  thickness  of  the  lens  when  the  eye  is  passive. 

contraction  of  the  internal  rectus  muscle,  while  stimulation  of  the  other  parts  around 
the  tier  causes  contraction  of  the  superior  rectus,  levator  palpebrse,  rectus  inferior, 
and  inferior  oblique  muscles. 

Proofs. — That  the  lens  undergoes  an  alteration  in  its  curvature,  during  accommodation,  is  proved 
by  the  following  facts  : — 

I.  Purkinje-Sanson's  Images. — If  a  lighted  candle  be  held  at  one  side  of  the  eye,  or  if  light 
be  allowed  to  fall  on  the  eye  through  two  triangular  holes,  placed  above  each  other  and  cut  in  a 
piece  of  cardboard,  in  the  latter  case  the  observer  will  see  three  pairs  of  reflected  images  [in  the 
former,  three  images].  The  brightest  and  most  dis- 
tinct image  (or  pair  of  images)  is  erect  and  is  pro-  Pjq_  ctc. 
duced  by  the  anterior  surface  of  the  cornea  (Fig. 
535,  a).  The  second  image  (or  pair  of  images)  is 
also  erect.  It  is  the  largest,  but  it  is  not  so  bright 
[h),  and  it  is  reflected  by  the  anterior  surface  of  the 
lens.  (The  size  of  a  reflected  image  from  a  convex 
mirror  is  greater,  the  longer  the  radius  of  curvature  of 
the  reflecting  surface.)  The  latter  image  hes  8  mm. 
^^/zz;?^;' the  plane  of  the  pupil.  The  third  image  (or 
pair  of  images)  is  of  medium  size  and  medium  bright- 
ness—it  is  inverted  and  lies  nearly  in  the  plane  of 
the  pupil  (c).  The  posterior  capsule  of  the  lens, 
which  reflects  the  last  image,  acts  like  a  concave 
mirror.  If  a  luminous  object  be  placed  at  a  distance  from  a  concave  mirror,  its  inverted,  diminished, 
rea/ima.ge  lies  close  to  the  focus  toward  the  side  of  the  object.  If  the  images  be  studied  when  the 
observed  eye  is  passive,  i.  e.,  in  the  phase  of  negative  accommodation,  on  asking  the  person  experi. 
51 


Sanson-Purkinje's  images,  a,  h,  c,  during  negative, 
and  a,,  bj,  c,,  positive  accommodation. 


802 


THE    PHAKOSCOPE. 


I-'IC.    v^i- 


mented  upon  to  accommodate  his  eye  for  a  near  object,  at  once  a  change  in  the  relative  position  and 
size  of  some  of  the  imatjes  is  apparent.  The  middle  pair  of  imaj^es  reflected  by  the  anterior  sur- 
face of  the  lens  diminish  in  size  and  approach  each  other  {/?),  which  depends  uixjn  the  fact  that 
the  anterior  surface  of  the  lens  has  become  more  convex.  At  the  same  time,  the  imaj;c  (or  pair  of 
images)  comes  nearer  to  the  image  formed  by  the  cornea  {a^  and  c^)  as  the  anterior  surface  of  the 
lens  lies  nearer  to  the  cornea.  The  other  images  (or  pair  of  images)  neither  change  their  size  nor 
position.  Helmhoitz,  with  the  aid  of  the  ophthalmometer,  has  measured  the  dimiinition  of  the 
radius  of  curvature  of  the  anterior  surface  of  the  lens  during  accommodation  for  a  near  oliject. 

[Phakoscope. — These  images  may  be  readily  shown 
by  means  of  ilie  phakoscope  of  v.  Helmhoitz  (I'ig.  53^)' 
It  consists  of  a  triangular  box  with  its  angles  cut  off  and 
l)lackened  inside.  The  observer's  eye  is  placed  at  tj,  while 
on  the  opposite  side  of  the  box  aie  two  prisms,  l>,  /^  ;  the 
observed  eye  is  placed  at  the  side  of  the  box  opjx)site  to  C. 
When  a  candle  is  held  in  front  of  the  prisms,  b  and  ^', 
three  pairs  of  images  are  seen  in  the  observed  eye.  Ask 
the  person  to  accommodate  for  a  distant  object,  and  note 
the  position  of  the  images.  On  pushing  up  the  slide  C 
witli  a  pin  attached  to  it,  and  asking  him  to  accommodate 
for  the  pin,  ;.  f.,  for  a  near  object,  the  position  and  size  of 
the  middle  images  chiefly  will  be  seen  to  alter  as  described 
above.] 

2.  In  consequence  of  the  increased  curvature  of  the  lens 
during  accommodation  for  a  near  object,  the  refractive 
indices  within  the  eye  must  undergo  a  change.  According 
to  v.  Helmhoitz,  the  annexed  measurements  obtain  in  nega- 
tive and  jjositive  accommodation  respectively. 

3.  Lateral  View  of  the  Pupil. — If  the  passive  eye  be 
looked  at  from  the  side,  we  observe  only  a  small  black 
strip  of  the  pupil,  which  becomes  broader  as  soon  as  the 
person  experimented  on  accommodates  for  a  near  object, 
as  the  whole  pupil  is  pushed  more  forward. 

4.  Focal  Line. — If  light  be  admitted  through  the  cor- 
nea into  the  anterior  chamber,  the  "  focal  line  "  formed  by 

Phakoscope  of  Helmhoitz.  '^^  concave  surface  of  the  cornea  falls  upon  the  iris.     If 

the  experiment  be  made  upon  a  person  whose  eye  is  accom- 
modated foradistant  object,  so  that  the  line  lies  near  the  margin  of  the  pupil,  it  gradually  recedes 


Accommodation. 


iNegative — Mm.      Positive — Mm 


Radius  of  the  cornea, 

Radius  of  anterior  surface  of  lens, 

Radius  of  posterior  surface  of  lens 

Position  of  the  vertex  of  the  outer  surface  of  the  lens  behind  the  1 

vertex  of  the  cornea J 

Position  of  the  posterior  vertex  of  the  lens, 

Position  of  the  anterior  focal  point, 

Position  of  the  first  principal  point, 

Position  of  the  second  principal  point, 

Position  of  the  posterior  focal  point  behind  the  anterior  vertex  of) 

the  cornea J 


8 

8 

10 

6 

6 

5-5 

3-6 

3-2 

7.2 

7.2 

12.9 

11.24 

1.94 

2.03 

6.96 

6.51 

22.23 


20.25 


toward  the  scleral  margin  of  the  iris,  as  soon  as  the  person  accommodates  for  a  near  object,  because 
the  iris  becomes  more  oblique  as  its  inner  margin  is  pushed  forward. 

5.  Change  in  Size  of  Pupil. — On  accommodating  for  a  near  object,  the  pupil  contracts, 
while  in  accommodation  for  a  distant  object,  it  dilates  (Descartes,  1637).  The  contraction  takes 
place  slightly  after  the  accommodation  [Do/u/ers).  This  phenomenon  may  be  regarded  as  an  asso- 
ciated movement,  as  both  the  ciliary  muscle  and  the  sphincter  pupiilce  are  supplied  by  the  oculomo- 
torius  (^.  345.  2,  3).  A  reference  to  Fig.  533  shows  that  the  latter  also  directly  supports  the  ciliary 
muscle;  as  the  inner  margin  of  the  iris  passes  inward  (toward  r),  its  tension  tends  to  be  propagated 
to  the  ciliary  margin  of  the  choroid,  which  also  must  pass  inward.  The  ciliary  processes  are  made 
tense,  chiefly  by  the  ciliaiy  muscle  (tensor  choroidse).  Accommodation  can  still  be  performed,  even 
though  the  iris  be  absent  or  cleft. 

6.  Internal  Rotation  of  the  Eye. — On  rotating  the  eyeball  inward,  accommodation  for  a  near 
object  is  performed  involuntarily.     As  rotation  of  both  eyeballs  inward  takes  place  when  the  axes  of 


SCHEINER  S   EXPERIMENT. 


803 


Fig.  537. 


vision  are  directed  to  a  near  object,  it  is  evident  that  this  must  be  accompanied  involuntarily  by  an 
accommodation  of  the  eye  for  a  near  object. 

7.  Time  for  Accommodation. — A  person  can  accommodate  from  a  near  to  a  distant  object 
(which  depends  upon  relaxation  of  the  cihary  muscle)  much  more  rapidly  than  conversely,  from  a 
distant  to  a  near  object  (  Vierordi,  Aeby).  The  process  of  accommodation  requires  a  longer  time, 
the  nearer  the  object  is  brought  to  the  eye  (  Vierordi,  Volckers  and  Hensen).  The  time  necessary 
for  the  image  reflected  from  the  anterior  surface  of  the  lens  to  change  its  place  during  accommodation 
is  less  than  that  required  for  subjective  accommodation  {^Aiibei-t  and  Angelucci). 

8.  Line  of  Accommodation. — When  the  eye  is  placed  in  a  certain  position  during  accommoda- 
tion, we  may  see  not  one  point  alone  distinctly,  but  a  whole  series  of  points  behind  each  other. 
Czerm^ak  called  the  line  in  which  these  points  lie  the  line  of  accotnmodation.  The  more  the  eye  is 
accommodated  for  a  distant  object,  the  longer  does  this  line  become.  All  objects  placed  at  a  greater 
distance  from  the  eye  than  60  to  70  metres  appear  equally  distinct  to  the  eye.  The  line  becomes 
shorter  the  more  we  accommodate  for  a  near  object — i.  e.,  when  we  accommodate  as  much  as  possi- 
ble for  a  near  object,  a  second  point  can  only  be  seen  indistinctly  at  a  skori  distance  behind  the  object 
looked  at. 

9.  The  nerves  concerned  in  the  mechanism  of  accommodation  are  referred  to  under  Oculomotoritis 
{I  345,  and  again  in  I  704). 

Scheiner's  Experiment. — The  experiment  which  bears  the  name  of  Scheiner 
(1619)  serves  to  illustrate  the  refractive  action  of  the  lens  during  accommodation 
for  a  near  object,  as  well  as  for  a  distant  object.  Make  two  small  pin  holes  (S,  d^ 
in  a  piece  of  cardboard  (Fig.  537,  K,  Kj),  the  holes  being  nearer  to  each  other 
than  the  diameter  of  the  pupil.  On  look- 
ing through  these  holes,  S,  d,  at  two  needles 
(/  and  r)  placed  behind  each  other,  then 
on  accommodating  for  the  near  needle  (/) 
the  far  needle  (r)  becomes  double  and  in- 
verted. On  accommodating  for  the  near 
needle  (/),  of  course  the  rays  proceeding 
from  it  fall  upon  the  retina  at  the  focus 
(a)  'i  while  the  rays  coming  from  the  far 
needle  (r)  have  already  united  and  crossed 
in  the  vitreous  humor,  whence  they  diverge 
more  and  more  and  form  two  pictures 
(^/'O  ^'^  ^^  retina.  If  the  right\\o\^  in 
the  cardboard  (^)  be  closed,  the  left  picture 
on  the  retina  (r^^)  of  the  double  images  of 
the  far  needle  disappears.  An  analogous 
result  is  obtained  on  accommodating  for 
the  far  needle  (R).  The  near  needle  (P)  | 
gives  a  double  image  (P^,  P^^),  because  the 
rays  from  it  have  not  yet  come  to  a  focus. 
On  closing  the  right  hole  {d^,  the  right 
double  image  (P^)  disappears  (Forterjieid). 
When  the  eye  of  the  observer  is  accommo- 
dated for  the  near  needle,  on  closing  one 
aperture  the  double  image  of  the  distant 
point  disappears  on  that  side ;  but  if  the 
eye  is  accommodated  for  the  distant  needle,  on  closing  one  hole  the  crossed  image 
of  the  near  needle  disappears. 

388.  REFRACTIVE  POWER  OF  THE  EYE— ANOMALIES  OF 
REFRACTION. — The  limits  of  distinct  vision  vary  very  greatly  in  different 
eyes.  We  distinguish  the  far  point  [p.  r.,  punctum  remotum]  and  the  near 
point  [p.  p.,  punctum  proximum]  ;  the  former  indicates  the  distance  to  which 
an  object  may  be  removed  from  the  eye,  and  may  still  be  seen  distinctly ;  the 
latter,  the  distance  to  which  any  object  may  be  brought  to  the  eye,  and  may  still 
be  seen  distinctly.  The  distance  between  these  two  points  is  called  the  range  of 
accommodation.     The  types  of  eyeball  are  characterized  as  follows:  — 


K 


P.   ••  '■"   R, 

Scheiner's  Experiment. 


804 


EMMETROPIC    AND    MYOPIC    EYES. 


I.  The  normal  or  emmetropic  eye  is  so  arranged  when  at  rest  that  parallel 
rays  (Fig.  538,  r,  r)  coming  from  tlie  most  distant  objects  can  be  focused  on  the 
retina  (r,).  The /?r  point,  therefore,  is  =  00  (infinity).  When  accommodating 
as  much  as  possible  for  a  near  object,  whereby  the  convexity  of  the  lens  is  increased 
(Fig.  538,  a)  rays  from  a  luminous  point  placed  at  a  distance  of  5  inches  are  still 

focused  on  the  retina,  ;".  e.,  the  near 
^'^'*  53°-  /o/fi/  is  =r  5   inches  (i   inch  =  27 

mm.).  The  range  of  accommoda- 
tion, or  \_"//ie  range  of  distinct 
vision^^\  therefore,  is  from  5  inches 
(10-12  cm.)  to  00. 

2.  The  short-sighted,  myopic 
eye  (or  long  eye)  cannot,  when  at 
rest,  bring  parallel  rays  from  infinity 
to  a  focus  on  the  retina  (Fig.  539). 
These  rays  decussate  within  the  vit- 
reous humor  (at  O),  and  after  cross- 
ing form  diffusion  circles  upon  the 
retina.  The  object  must  be  removed 
from  \k\e  passive  eye  to  a  distance  of 
60  to  1 20  inches  (to/),  in  order  that 

Condition  of  refraction   in   the   nox\n^\  passive  eye  and  during  ^J^g     raVS     maV      be     foCUSCd     On     the 

retina.      The   passive   myopic   eye, 
therefore,  can  only  focus  divergent  rays  upon  the  retina.     The  far  point,  therefore, 
lies  abnormally  near.     With  an  intense  effort  at  accommodation,  objects  at  a  dis- 
tance of  4  to  2  inches,  or  even 
Fig.  539.  less,  from  the  eye  may  be  seen 

distinctly.  The  fwar  point, 
therefore,  lies  abnormally  near; 
the  range  of  accommodation  is 
diminished. 

Short-sightedness,  or  myopia, 
usually  depeiuls  u])on  congenital, 
and  frequently  hereditary,  elongation 
of  the  eyeball.  This  anomaly  of  the 
refractive  media  is  easily  corrected 
by  using  a  diverging  lens  (con- 
Myopic  Eye.  cave),    which    makes  parallel   rays 

divergent,  so  that  they  can  be  brought 
to  a  focus  on  the  retina.  It  is  remarkable  that  most  children  are  myopic  when  they  are  born.  This 
myopia,  however,  depends  upon  a  too-curved  condition  of  the  cornea  and  lens,  and  on  the  lens  being 
too  near  the  cornea.     As  the  eye  grows,  this  short-sightedness  disappears.     The  cause  of  myopia  in 

children  is  ascribed  to  the  continued  activity  of 

Fig. 


.^^^ 


540. 


the  ciliary  muscle  in  reading,  writing,  etc.,  or  Ihe 
continued  convergence  of  the  eyeballs,  whereby 
the  external  pressure  upon  the  eyeball  is  in- 
creased. 

3.  The  long-sighted,  hyperme- 
tropic eye,  hyperoptic  (flat  eye)  when 
at  rest,  can  only  cause  convergent  rays 
to  come  to  a  focus  on  the  retina  (Fig. 
540).  Distinct  images  can  only  be  formed 
when  the  rays  proceeding  from  objects 
are  rendered  convergent  by  means  of  a 
convex  lens,  as  parallel  rays  would  come 
to  a  focus  behind  the  retina  (at/).  All 
rays   proceeding    from    natural  objects  are  either  divergent,  or   at  most    nearly 


-:~^^^f 


Hypermetropic  Eye. 


THE    POWER    OR    FORCE    OF   ACCOMMODATION. 


805 


parallel,  never  convergent.  Hence,  a  long-sighted  person,  when  the  eye  \% passive, 
i.  e.,  is  negatively  accommodated,  cannot  see  distinctly  without  a  convex  lens. 
When  the  ciliary  muscle  contracts,  slightly  convergent,  parallel,  and  even  slightly 
divergent  rays  may  be  focused,  according  to  the  increasing  degree  of  the  accom- 
modation. The  far  point  of  the  eye  is  negative,  the  near  point  abnormally  distant 
(over  8  to  80  inches),  while  the  range  of  accommodatio7i  is  infinitely  great. 

The  cause  of  hypermetropia  is  abnormal  shortness  of  the  eye,  which  is  generally  due  to  imperfect 
development  in  all  directions.     It  is  corrected  by  using  a  convex  lens. 

[Defective  Accommodation. — In  the  presbyopic  eye,  or  long-sighted  eye 
of  old  people,  the  near  point  is  further  away  than  normal,  but  the  far  point  is  still 
unaffected.  In  such  cases,  the  person  cannot  see  a  near  object  distinctly,  unless 
it  be  held  at  a  considerable  distance  from  the  eye.  It  is  due  to  a  defect  in  the 
mechanism  of  accommodation,  the  lens  becoming  somewhat  flatter,  less  elastic, 
and  denser  with  old  age,  while  the  ciliary  muscle  becomes  weaker.  In  hyperme- 
tropia, on  the  contrary,  the  mechanism  of  accommodation  may  be  perfect,  yet 
from  the  shape  of  the  eye  the  person  cannot  focus  on  his  retina  the  rays  of  light 
from  a  near  object.  In  presbyopia  the  range  of  distinct  vision  is  diminished. 
The  defect  is  remedied  by  weak  convex  glasses.  The  defect  usually  begins  about 
forty-five  years  of  age.] 

Estimation  of  the  Far  Point — Snellen's  Types. — In  order  to  determine  the yh:r/(?zW  of  an 
eye,  gradually  bring  nearer  to  the  eye  objects  which  form  a  visual  angle  of  5  minutes  [e.g.,  Snellen's 
small-type  letters,  or  the  7nedium  type,  4  to  8,  of  Jaeger),  until  they  can  be  seen  distinctly.  The 
distance  from  the  eye  indicates  the  far  point.  In  order  to  determine  the  far  point  of  a  tnyopic  person, 
place  at  20  inches  distant  from  the  eye  the  same  objects  which  give  a  visual  angle  of  5  minutes,  and 
ascertain  the  concave  lens  which  will  enable  the  person  to  see  the  objects  distinctly.  To  estimate  the 
near  point,  bring  small  objects  {e.g.,  the  finest  print)  nearer  and  nearer  to  the  eye,  until  it  finally 
becomes  indistinct.     The  distance  at  which  one  can  still  see  distinctly  indicates  the  far  point. 

Optometer. — The  optometer  may  also  be  used  to  determine  the  near  a.ndi  far  points.  A  small 
object,  e.g.,  a  needle,  is  so  arranged  as  to  be  movable  along  a  scale,  along  which  the  eye  to  be 
investigated  can  look  as  a  person  looks  along  the  sight  of  a  rifle.  The  needle  is  moved  as  near  as 
possible,  and  then  removed  as  far  as  possible,  in  each  case  as  long  as  it  is  seen  distinctly.  The 
distance  of  the  near  and  far  point  and  the  range  of  accommodation  can  be  read  off  directly  upon  the 
scale  [Graefe). 

389.  FORCE  OF  ACCOMMODATION. — Force.— The  range  of  accommodation,  which  is 
easily  determined  experimentally,  does  not  by  itself  determine  the  proper  power  or  force  of  accom- 
modation. The  measure  of  the  latter  depends  upon  the  mechanical  work  done  by  the  muscle  of 
accommodation,  or  the  ciliary  muscle.  Of  course  this  cannot  be  directly  determined  in  the  eye  itself. 
Hence,  this  force  is  measured  by  the  optical  effect,  which  results  in  consequence  of  the  change  in  the 
shape  of  the  lens,  brought  about  by  the  energy  of  the  contracting  muscle. 

In  the  normal  eye,  during  the  passive  condition,  the  rays  coming  from  infinity,  and  therefore 
parallel  (which  are  dotted  in  Fig.  541),  are  focused  upon  the  retina  at  _/".  If  rays  coming  from  a 
distance  of  5  inches  (p.  806)  are  to  be 
focused,  the  whole  available  energy  of 
the  ciliary  muscle  must  be  brought  into 
play  to  allow  the  lens  to  become  more 
convex,  so  that  the  rays  may  be  brought 
to  a  focus  2X  f  The  energy  of  accom- 
modation, therefore,  produces  an  optical 
effect  in  as  far  as  it  increases  the  con- 
vexity of  the  anterior  surface  of  the 
passive  lens  (A),  by  the  amount  indi- 
cated by  B.  Practically,  we  may  regard 
the  matter  as  if  a  new  convex  lens  (B) 
were  added  to  the  existing  convex  lens 

(A).  What,  therefore,  must  be  the  focal  distance  of  the  lens  (B),  in  order  that  rays  coming  from  the 
near  point  (5  inches)  may  be  focused  upon  the  retina  at/?  Evidently,  the  lens  B  must  make  the 
diverging  rays  coming  from/,  parallel,  and  then  A  can  focus  them  at/.  Convex  lenses  cause  those 
rays  proceeding  from  their:  focal  points  to  pass  out  at  the  other  side  as  parallel  rays  (|  385,  I). 
Hence,  in  our  case,  the  lens  must  have  a  focal  distance  of  5  inches.     The  normal  eye,  therefore,  with 


Fig.  541. 


806  SPECTACLES. 

ihe  far  point  =  oc  ,  and  the  near  point  =  5  inches,  has  a  ]io\ver  of  accommodation  equal  to  a  lens  of 
5  inches  focal  distance.  When  the  lens  by  the  energy  of  accommodation  is  rendered  more  powerfully 
refractive,  the  increase  (B)  can  readily  be  eliminated  l)y  placin}^  before  the  eye  a  concave  lens  which 
possesses  exactly  the  opjiosite  optical  effect  of  the  increxse  of  accommodation  (H).  Hence,  it  is 
possii)le  to  indicate  the  jwwer  (force)  of  accommodation  of  the  eye  by  a  lens  of  a  definite  focal 
distance,  /.  e.,  by  tlie  optical  effect  produced  by  the  latter.  Therefore,  according  to  Doiulers,  the 
measure  of  the  force  of  accommodation  of  the  eye  is  the  reciprocal  value  of  the  focal  distance  of  a 
concave  lens,  which,  when  placed  before  the  accommodated  eye,  so  refracts  the  rays  of  light  coming 
from  the  near  jioint  (/>)  as  if  they  came  from  the  far  ]ioint. 

Example. — We  may  calculate  the  force  of  the  accommodation  according  to  the  following  formula: 

^  ^ ,  ;.  €.,  the  force  of  accommodation,  expressed  as  the  dioptric  value  of  a  lens  (of  j«r  inch 

X        p         r 

focal  distance),  is  equal  to  the  difference  of  the  reciprocal  values  of  the  distances  of  the  near  point  (/>) 

and  of  the  far  point  (r)  of  the  eye.     In  the  emmetropic  eye,  as  already  mentioned,  />  ^  5,  r  =  00  . 

Its  force  of  accommodation  is  therefore       = ,  so  that  jc  =  5,  i.  e,,  it  is  equal  to  a  lens  of  5 

X       p        a  III. 

inches  focal  distance.     In  a  myopic  eye,/  =  4,  r  =  12,  so  that  -= ,  t.  e.,  x  ^  6.     In 

X         4         I  ^ 
another  myopic  eye,  with /^ 4  and  r=  20,  then  jr  =  5,  which  is  a  normal  force  of  accommodation. 
Hence,  it  is  evident  that  two  different  eyes,  possessing  a  very  different  ran^e  of  accommodation,  may 
nevertheless  have  the  svivat  force  of  accommodation.     Example. — The  one  eye  has/  ^4,  r  z^ao  , 

the  other,  /  =  2,  r  =  4.     In  both  cases,  -  =      ,  so  that  the  force  of  accommodation  of  both  eyes 

X        4 
is  equal  to  the  dioptric  value  of  a  lens  of  4  inches  focal  distance.     Conversely,  two  eyes  may  have  the 
same  range  of  accommodation,  and  yet  their  force  of  accommodation  be  very  unequal.      Example. 
— The  one  eye  has  /  =  3,  r  ^  6  ;   the  other  /  =  6,  r  =  9.     Both,  therefore,  have  a  range  of 

accommodation  of  3   inches.     P'or  these,  the   force  of  accommodation,    -  z= -,x=^6;   and 

i  =  J  —Ijc—lS  Jr        3         6 

X       6        9 ' 

Relation  of  range  to  force  of  accommodation. — The  general  law  is,  that,  the  ranges  of 
accommodation  of  two  eyes  being  eciually  great,  then  \\\€\x  forces  of  accommodation  are  eriual,  ])ro- 
vided  that  their  near  points  are  the  same.  If  the  rrtw^'^  of  accommodation  for  both  eyes  are  equally 
great,  but  their  near  jioints  unequal,  then  the  forces  of  accommodation  are  also  unequal — the  latter 
being  greater  in  the  eyes  with  the  smallest  near  point.  This  is  due  to  the  fact  that  every  difference 
of  distance  near  a  lens  has  a  much  greater  effect  upon  the  image  as  compared  with  differences  in  the 
distance y(zr  from  a  lens.  The  emmetropic  eye  can  see  distinctly  objects  at  60  to  70  metres,  and  even 
to  infinity,  without  accommodation. 

While/  and  r  may  he  directly  estimated  in  the  emmetropic  and  myopic  eyes,  this  is  impossible 
with  the  hj-permetropic  (long-sighted)  eye.  The  far  point  in  the  latter  is  negative;  indeed,  in  very 
pronounced  hypermetropia  even  the  near  point  may  l)e  negative.  The  far  point  may  be  estimated  by 
making  the  hypermetropic  eye  practically  a  normal  eye  by  using  suitable  convex  lenses.  The  relative 
near  jx)int  may  then  be  determined  by  means  of  the  lens. 

Even  from  the  15th  year  onward,  the  power  of  accommodation  is  generally  diminished  for  near 
objects— perhaps  this  is  due  to  a  diminution  of  the  elasticity  of  the  lens  [Donders). 

390.  SPECTACLES. — The  focal  distance  of  concave  (diverging),  as  well  as  convex  (converg- 
ing), spectacles,  depends  upon  the  fefractive  index  of  the  glass  (usually  3:2),  and  on  the  length  of 
the  radius  of  curvature.  If  the  curvature  of  both  sides  of  the  lens  is  the  same  (biconcave  or  bicon- 
vex), then,  with  the  ordinary'  refractive  index  of  glass,  the  focal  distance  is  the  same  as  the  radius  of 
curvature.  If  one  surface  of  the  lens  is  plane,  then  the  focal  distance  is  twice  as  great  as  the  radius 
of  the  spherical  surface.  Spectacles  are  arranged  according  to  \ht\r  focal  distance  in  inches,  but  a 
lens  of  shorter  focal  distance  than  I  inch  is  generally  not  used.  They  may  also  be  arranged  according 
to  their  refractive  power.  In  this  case,  the  refractive  power  of  a  lens  of  i  inch  focus  is  taken  as  the 
unit.  A  lens  of  2  inches  focus  refracts  light  only  half  as  much  as  the  unit  measure  of  i  inch  focus; 
a  lens  of  3  inches  focus  refracts  ^^  as  strongly,  etc.  This  is  the  case  l^oth  with  convex  and  concave 
lenses,  the  latter,  of  course,  having  a  negative  focal  distance;  thus,  "  concave — ^,"  indicates  that  a 
concave  lens  diverges  the  rays  of  light  one  eighth  as  strongly  as  the  concave  lens  of  I  inch  (negative) 
focal  distance. 

Choice  of  Spectacles. — Having  determined  the  near  point  in  a  myopic  eye,  of  course  we 
require  to  render  parallel  the  divergent  rays  coming  from  the  far  point,  just  as  if  they  came  from 
infinity.  This  is  done  by  selecting  a  concave  lens  of  the  focal  distance  of  the  far  i)oint.  The  greatest 
distance  is  the  far  point  of  the  emmetropic  eye.  Suppose  a  myopic  eye  with  a  far  point  of  6  inches, 
then  such  a  person  requires  a  concave  lens  of  6  inches  focus  to  enalile  him  to  see  distinctly  at  the 
greatest  distance.  Thus,  in  a  myopic  eye,  the  distance  of  the  far  point  from  the  eye  is  directly  equal 
to  the  focus  of  the  (weakest)  concave  lens,  which  enables  one  to  see  distinctly  objects  at  the  greatest 
distance.     These  lenses  generally  have  the  same  number  as  the  spectacles  required  to  correct  the 


DIOPTRIC CHROMATIC    ABERRATION,  807 

defect.  Example. — A  myopic  eye  with  a  far  point  of  8  inches  requires  a  concave  lens  of  8  inches 
focus,  i.  e.,  the  concave  spectacles  No.  8.  For  the  hypermetropic  (long-sighted)  eye,  the  focal 
distance  of  the  strongest  convex  lens,  which  enables  the  hypermetropic  eye  to  see  the  most  distant 
objects  distinctly,  is  at  the  same  time  the  distance  of  the  far  point  from  the  eye.  Example. — A 
hypermetropic  eye  which  can  see  the  most  distant  objects  with  the  aid  of  a  convex  lens  of  I2  inches 
focus  has  a  far  point  of  I2 ;  the  proper  spectacles  are  convex  No.  I2. 

[Diopter  or  Dioptric. — The  focal  length  of  a  lens  used  to  be  expressed  in  inches;  and  as  the 
unit  was  taken  as  i  inch,  necessarily  all  weaker  lenses  were  expressed  in  fractions  of  an  inch.  In 
the  method  advocated  by  Bonders,  the  standard  is  a  lens  of  a  focal  distance  of  i  metre  (39.370 
English  inches,  about  40  inches),  and  this  unit  is  called  a  dioptric.  Thus,  the  standard  is  a  weak 
lens,  so  that  the  stronger  lenses  are  multiples  of  this.  Hence,  a  lens  of  2  dioptrics  =  one  of  about 
20  inches  focus;  10  dioptrics  =  4  inches  focus;  and  so  on.  The  lenses  are  numbered  Irom  No.  I, 
i.  e.,  I  dioptric  onward.  It  is  convenient  to  use  signs  instead  of  the  words  convex  and  concave. 
For  convex  the  sign  pbcs  -\-  is  used,  and  for  concave  the  sign  mimts  — .  Thus  a  -\-  4.0  means  a 
convex  lens  of  4  dioptrics,  and  a  — 4.0  =  a  concave  lens  of  4  dioptrics.] 

In  all  cases  of  myopia  or  hypermetropia,  the  person  ought  to  wear  the  proper  spectacles.  In  a 
myopic  eye,  when  the  far  point  is  still  more  than  5  inches,  the  patient  ought  always  to  wear  spec- 
tacles; but  generally  the  working  distance,  e.  g.,  for  reading,  writing  and  for  handicrafts,  is  about 
12  inches  from  the  eye.  If  the  person  desires  to  do  finer  work  (etching,  drawing),  requiring  the 
object  to  be  brought  nearer  to  the  eye,  so  as  to  obtain  a  larger  image  upon  the  retina,  then  he  should 
either  remove  the  spectacles  altogether  or  use  a  weaker  pair. 

The  hypermetropic  person  ought  to  wear  his  convex  spectacles  when  looking  at  a  near  object, 
and  especially  when  the  illumination  is  feeble,  because  then,  owing  to  the  dilatation  of  the  pupil,  the 
diffusion  circles  of  the  eye  tend  to  become  very  pronounced.  It  is  advisable  to  wear  at  first  convex 
spectacles,  which  are  slightly  too  strong.  Cylindrical  lenses  are  referred  to  under  Astigmatism. 
Spectacles  provided  with  dull  colored  or  blue  glasses  are  used  to  protect  the  retina  when  the  light 
is  too  intense.  Stenopaic  spectacles  are  narrow  diaphragms  placed  in  front  of  the  eye,  which 
cause  it  to  move  in  a  definite  direction  in  order  to  see  through  the  opening  of  the  diaphragm. 

391.  CHROMATIC  AND  SPHERICAL  ABERRATION,  ASTIG- 
MATISM.— Chromatic  Aberration. — All  the  rays  of  white  light  which 
undergo  refraction  are  at  the  same  titne  broken  up  by  dispersion  into  a  bundle  of 
rays  which,  Avhen  they  are  received  on  a  screen,  form  a  spectrum.  This  is  due  to 
the  fact  that  the  different  colors  of  the  spectrum  possess  different  degrees  of  refran- 
gibility.     The  violet  rays  are  refracted  most  strongly ;  the  red  rays  least. 

A  white  point  on  a  black  ground  does  not  form  a  sharp  simple  image  on  the  retina,  but  many 
colored  points  appear  after  each  other.  If  the  eye  is  accommodated  so  strongly  as  to  focus  the 
violet  rays  to  a  sharp  image,  then  all  the  other  colors  must  form  concentric  diffusion  circles,  which 
become  larger  toward  the  red.  In  the  centre  of  all  the  circles,  where  all  the  colors  of  the  spectrum 
are  superposed,  a  white  point  is  produced  by  their  mixture,  while  around  it  are  placed  the  colored 
circles.  The  distance  of  the  focus  of  the  red  rays  from  that  of  the  violet  in  the  eye  =  0.58  to  0.62 
mm.  The  focal  distance  for  red  is,  according  to  v.  Helmholtz,  for  the  reduced  eye,  20.524  mm.; 
for  violet,  20.140  mm.  Thus,  the  near  and  far  points  for  violet  light  are  nearer  each  other  than  in 
the  case  of  red  light ;  white  objects,  therefore,  appear  reddish  when  beyond  the  far  point,  but  when 
nearer  than  the  near  point  they  are  violet.  Hence  the  eye  must  accommodate  more  strongly  for 
red  rays  than  for  violet,  so  that  we  judge  red  objects  to  be  nearer  us  than  violet  objects  placed  at  an 
equal  distance  (^Brilcke). 

Monochromatic,  or  Spherical  Aberration. — Apart  from  the  decomposition  or  dispersion  of 
white  light  into  its  components — the  rays  of  white  light,  proceeding  from  a  point  if  transmitted 
through  refractive  spherical  surfaces — we  find  that,  before  the  rays  are  again  brought  to  a  focus  the 
marginal  ra.ys  are  more  strongly  refracted  than  those  passing  through  the  central  parts  of  the  lens. 
Hence,  there  is  not  otte  focus,  but  many.  In  the  eye  this  defect  is  naturally  corrected  by  the  iris, 
which,  acting  as  a  diaphragm,  cuts  off  the  marginal  rays  (Fig.  531),  especially  when  the  lens  is  most 
convex,  when  the  pupil  also  is  most  contracted.  In  addition,  the  margin  of  the  lens  has  less 
refractive  power  than  the  central  substance;  lastly,  the  margins  of  the  refractive  spherical  surfaces 
of  the  eye  are  less  curved  toward  their  margins  than  the  parts  lying  nearer  to  the  optical  axis. 
Compare  the  form  of  the  cornea  (p.  783)  and  the  lens  (p.  790). 

Imperfect  Centring  of  the  Refractive  Surfaces. — The  sharp  projection  of  an  image  is  some- 
what interfered  with  by  the  fact  that  the  refractive  surfaces  are  not  exactly  centred  (^Brilcke). 
Thus,  the  vertex  of  the  cornea  is  not  exactly  in  the  termination  of  the  optic  axis ;  the  vertices  of 
both  surfaces  of  the  lens,  and  even  the  different  layers  of  the  lens  itself,  are  not  exactly  in  the  optic 
axis.     The  variations,  however,  and  the  disturbances  produced  thereby  are  very  small  indeed. 

Regular  Astigmatism. — When  the  curvature  of  the  refractive  surfaces  of  the  eye  is  unequally 
great  in  its  different  meridians,  of  course  the  rays  of  light  cannot  be  united  or  focused  in  one  point. 
Generally,  in  such  cases,  the  cornea  is  more  curved  in  its  vertical  meridian  and  least  in  the  horizontal 


808 


ASTIGMATISM. 


(as  is  shown  by  ophthalmometric  measurements,  p.  798).  The  rays  passing  through  the  vertical 
meridian  come  to  a  focus,  y//'.f/,  in  a  horizontal  focal  line;  while  the  rays  entering  horizontally  unite 
afterward  in  a  vertical  line.  There  is  thus  no  common  focus  for  the  light  rays  in  the  eye;  hence 
the  name  "  astigmatism."  The  lens  also  is  unequally  curved  in  its  meridians,  hut  it  is  the  reverse 
of  the  cornea;  consequently,  a  part  of  the  inequality  of  the  curvature  of  the  cornea  is  thereby  com- 
pensated, and  only  a  part  of  it  affects  the  rays  of  light.  The  emmetropic  eye  has  a  very  slight 
degree  of  this  inequality  (normal  astigmatism).  If  two  very  fine  lines  of  equal  thickness  be  drawn 
on  white  paper,  so  as  to  intersect  each  other  at  right  angles,  it  will  be  found  that,  in  order  to  see  the 
horizontal  line  quite  sharply,  the  paper  must  be  brought  slightly  nearer  to  the  eye  than  when  we 
focus  the  vertical  line.  When  the  inequality  of  curvature  of  the  meridian  is  considerable,  of  course 
exact  vision  is  no  longer  possible. 

[Kig.  542  shows  the  efiect  of  an  astigmatic  surface  on  the  rays  of  light.     Let  a  d  c  dhs  such  a 
surface,  and  suppose  diverging  rays  to  proceed  from  /.     The  rays  passing  through  c  d  come  to  a 

Fig.  542. 


Action  of  an  astigmatic  surface  on  a  cone  of  light  {Frost). 


focus  at  /j,  while  those  passing  through  the  vertical  meridian  are  focused  atyT,.  The  outline  of  the 
cone  of  rays  between  abed  and  f^_  varies,  as  shown  in  the  figure.  At  a  certain  part  it  is  oval, 
with  its  axis  vertical,  at  another  the  long  axis  of  the  oval  is  horizontal,  while  at  other  places  it  is 
circular,  or  the  rays  are  focused  in  a  horizontal  or  vertical  line.] 

Correction. — This  condition  is  corrected  by  a  cylindrical  lens,  /.  e.,  a  lens  so  cut  as  to  be 
without  curvature  in  one  direction,  while  in  the  other  direction  (vertical  to  the  former)  it  is  curved. 
The  lens  is  placed  in  front  of  the  eye,  so  that  the  direction  of  its  curvature  coin- 
cides with  the  direction  of  least  curvature  of  the  eye  [v.  Hehnholtz,  Knapp, 
Donders).  The  section  Q.  a  b  c  </of  the  cylindrical  lens  (Fig.  543)  represents  a 
plano-convex,  the  section  C  a  3  y  (5,  a  concavo-convex  lens. 

[Test. — Draw  two  lines  of  equal  thickness  at  right  angles  to  each  other.  An 
astigmatic  person  cannot  see  both  lines  with  equal  distinctness  at  the  same  time, 
one  line  will  appear  thicker  than  the  other.  Or,  a  series  of  lines  radiating  from 
a  centre  may  be  used  (astigmatic  clock)  when  that  line  which  is  parallel  to 
the  astigmatic  meridian  will  be  seen  most  distinctly;  while,  with  the  vertical 
meridian  most  curved,  it  would  be  the  vertical  line.] 

Irregular  Astigmatism. — Owing  to  the  radiate  arrangement  of  the  fibres  in 
the  interior  of  the  crystalline  lens,  and  in  consequence  of  the  unequal  course 
of  the  fibres  within  the  different  parts  of  one  and  O'le  satne  ?neridian  of  the  lens, 
the  rays  of  light  passing  through  one  meridian  of  the  lens  cannot  all  be  brought 
to  one  focus.  Hence,  we  do  not  obtain  a  distinct  sharp  image  of  distant 
luminous  points,  such  as  stars  or  street  lamps,  but  we  see  a  radiate  jagged  figure 
provided  with  rays.  The  same  obtains  on  holding  a  piece  of  cardboard  with 
a  small  hole  in  it  toward  the  light,  at  a  distance  from  the  eye  slightly  greater 
than  the  far  point.  Slight  degrees  of  this  irregular  astigmatism  are  normal,  but 
when  it  is  highly  developed  it  greatly  interferes  with  vision,  by  forming  several 
foci  of  an  object  instead  of  one  (Polyopia  monocularis).  Of  course  this  con- 
dition cannot  obtain  in  an  eye  devoid  of  a  lens. 

392.  IRIS. — Functions. —  i.  The  iris  acts  like  a  diaphragm  in  an  optical 
apparatus  by  cutting  off  the  marginal  rays,  which,  if  they  entered  the  eye,  would 
cause  spherical  aberration,  and  thus  produce  indistinct  vision  TFig.  531). 

2.  As  the  pupil  contracts  strongly  in  a  bright  light,  and  dilates  when  the  light 
is  feeble,  it  regulates  the  amount  of  light  entering  the  eye  ;  thus,  fewer  rays 
enter  the  eye  when  the  light  is  strong  than  when  it  is  feeble. 

3.  To  a  certain  extent  it  supports  the  action  of  the  ciliary  muscle. 


Cylindric.1l  glasses 
for  astigmatism. 


MOVEMENTS    OF   THE    IRIS.  809 

Muscles  and  Nerves. — The  iris  is  usually  described  as  being  provided  with 
two  sets  of  viuscular  fibres — the  sphincter,  which  immediately  surrounds  the  pupil 
and  is  supplied  by  the  oculomotorius  (§  345,  2),  and  the  dilator  pupillae  (p.  786), 
supplied  chiefly  by  the  cervical  sympathetic  (§  356,  A,  i),  and  the  trigeminus 
(§  347j  3)-  Both  muscles  stand  in  an  atitagonisiic  relation  to  each  other  (§  345), 
the  pupil  dilates  moderately  after  section  or  paralysis  of  the  oculomotorius,  owing 
to  the  contraction  of  the  dilator  fibres  which  are  supplied  by  the  cervical  sym- 
pathetic ;  conversely,  the  pupil  contracts  when  the  sympathetic  is  divided  or 
extirpated  {Petit,  1727).  When  both  nerves  are  stimulated  simultaneously, 
the  pupil  contracts,  so  that  the  excitability  of  the  oculomotorius  overcomes  the 
sympathetic. 

[The  existence  of  a  dilator  pupillae  muscle  is  not  universally  recognized,  and  in  fact  some 
observers  doubt  its  existence.  The  muscular  nature  of  the  radial  fibres  in  the  posterior  limiting  mem- 
brane of  the  iris  is  denied  by  Griinhagen,  while  Koganei  regards  these  as  in  no  case  muscular,  and 
the  dilating  fibres  as  represented  by  fibres  radiating  from  the  iris.  These  fibres  are  well  developed 
in  birds  and  the  otter,  exist  in  traces  in  the  rabbit,  and  are  absent  in  man.  Gaskell  points  out  that  in 
this  case  the  size  of  the  pupil  must  in  part  depend  on  the  elasticity  of  the  radial  fibres  of  the  iris,  while 
the  dilator  nerve  fibres  must  act  on  the  sphincter  fibres,  causing  them  to  relax.  Gaskell  groups  the 
sphincter  of  the  iris  with  those  muscles  "supplied  by  two  nerves  of  opposite  character,  the  one  motor, 
the  other  inhibitory."  The  dilatation  of  the  pupil  caused  by  stimulation  of  the  cervical  sympathetic 
is  usually  explained  by  the  hypothesis  that  this  nerve  contains  motor  fibres,  which  act  on  the  dilator 
fibres.  Griinhagen  thought  that  it  might  be  due  chiefly  to  the  constriction  of  the  blood  vessels  of  the 
iris ;  Gaskell  suggests  that  the  nerve  acts  on  the  sphincter  muscle,  and  is  the  inhibitory  nerve  of  that 
muscle,  dilatation  taking  place  because  the  sphincter  is  normally  in  a  condition  of  tonic  contraction, 
and  also  because  the  posterior  limiting  membrane  is  elastic] 

Nerves. — -Amstein  and  A.  Meyer  have  studied  the  mode  of  termination  of  the  nerve  fibres  in  the 
iris.  All  the  medullated  nerve  fibres  lose  their  white  sheaths  after  a  time ;  most  of  the  fibres  [niotor) 
in  the  region  of  the  sphincter  consist  of  naked  bundles  of  fibrils.  A  network  of  ver^  ^eX\C2XQ  sensory 
nerves  lies  under  the  anterior  epithelium.  Numerous  fibrils  pass  to  the  capillaries  and  arteries  2&vaso- 
viotor  nerves.     [Many  ganglionic  cells  are  intercalated  in  the  course  of  the  fibres.] 

Movements  of  the  iris  occur  under  the  following  conditions  : — 

1.  Action  of  light  on  the  retina  cause?  (according  to  its  intensity  and  amount)  a  corresponding 
contraction  of  the  pupil ;  the  same  effect  is  produced  \>y  stimidation  of  the  optic  nerve  itself  (^Herbe7-t 
MayOjf  1852).  This  movement  is  a  reflex  act  [the  (T^^rt'w^  nerve  being  the  optic  and  the  e_ferentlhe 
oculomotorius  ;  the  impulse  is  transferred  from  the  former  to  the  latter  in  a  centre  situated  somewhere 
below  the  corpora  quadrigemina  (Fig.  544,  C)].  The  older  observers  locate  the  centre  in  the  corpora 
quadrigemina,  the  recent  observers  in  the  medulla  oblongata  (p.  711).  .5(?/^  pupils  always  react, 
although  only  one  retina  be  stimulated ;  generally  under  normal  circumstances  both  contract  to  the 
same  extent  (Donders),  owing  to  intercentral  communication  [coupling]  of  the  two  pupillo-constrict- 
ing  centres.  [This  is  called  consensual  contraction  of  the  pupil.]  After  section  of  the  optic  nerve 
the  pupil  dilates,  and  subsequent  section  of  the  oculomotorius  no  longer  produces  any  further  dilata- 
tion [Knoll). 

2.  The  centre  for  the  dilator  fibres  of  the  pupil  (pupillo-dilating  centre)  is  excited  by  dysp- 
nxic  blood  (§  367,  8).  If  the  dyspncea  ultimately  passes  into  asphyxia,  the  dilatation  of  the  pupil 
diminishes.  Of  course,  if  the  peripheral  dilating  fibres  (|  247,3)  ['^-^'-jthe  sympathetic  nerve  in  the 
neck]  be  previously  divided,  this  effect  cannot  take  place,  as  the  dyspnceic  blood  acts  on  the  centre 
and  not  on  the  nerve  fibres. 

3.  The  centre,  as  well  as  the  subordinate  "  cilio-spinal  region  "  of  the  spinal  cord  (§  362,  i), 
is  also  capable  of  being  excited  refiexly ;  painful  stimulation  of  sensory  nerves,  in  addition  to  causing 
protrusion  of  the  eyeballs  (|  347),  a  fact  proved  in  the  case  of  persons  subjected  to  torture,  produces 
dilatation  of  the  pupils  {Arndt,  Bernard,  Westphal,  Luchsingei-) ;  while  a  similar  effect  is  caused  by 
labor  pains,  a  loud  call  in  the  ear,  stimulation  of  the  nerve5  of  the  sexual  organs,  and  even  by  sligtit 
tactile  impressions  (Fod  and  Schiff).  According  to  Bechterew,  the  foregoing  results  are  due  to  inhi- 
bition of  the  light  reflex  in  the  sense  expressed  in  \  361,  3. 

4.  The  condition  of  the  blood  vessels  of  the  iris  influences  the  size  of  the  pupil ;  all  conditions 
causing  injection  or  congestion  of  these  vessels  contract  the  pupil,  all  conditions  diminishing  them  dilate 
it.  The  pupil,  therefore,  is  contracted  by  forced  expiration,  which  prevents  the  return  of  venous 
blood  from  the  head,  momentarily  by  evtry pulse-beat,  owing  to  the  diastolic  filling  of  the  arteries; 
diminution  of  the  ititraoctdar pressure,  e.g.,  after  puncture  of  the  anterior  chamber,  because,  owing 
to  the  diminished  intraocular  pressure,  there  is  less  resistance  to  the  passage  of  blood  into  the  blood 
vessels  of  the  iris  [Hensen  and  Volckers);  paralysis  of  the  vasomotor  fibres  of  the  iris  (|  347,  2). 
Conversely,  the  pupil  is  dilated  by  conditions  the  reverse  of  those  already  mentioned,  and  also  by 
strong  muscular  exertion,  whereby  blood  flows  freely  into  the  dilated  muscular  blood  vessels ;  also,when 


810 


ACTION    OF    DRUGS    ON    THE    I'UPIL. 


¥u:.  544. 


death  lakes  place.  The  condition  of  the  filHng  of  the  hlood  vessels  also  explains  tho  fact  that  the 
pupil  dilated  with  atropin  becomes  smaller  when  a  part  of  the  sympathetic  in  tlie  upper  cervical 
ganglion,  carrying  the  vasomotor  fibres  of  the  iris,  is  excised  ;  also,  that  after  extirpation  of  this  gan- 
gli'in,  atro[)in  always  causes  a  loss  diminution  of  the  jiujiil  on  this  side.  The  fact  that  when  the  pupil 
is  already  tlilated  by  stimulation  of  the  sympathetic,  it  is  further  dilated  byatro])in,  is  due  to  a  dimin- 
ishe<l  injection  of  the  blood  vessels  of  the  iris.  If  an  animal  with  its  pupils  dilated  with  atropin  be 
rapiilly  bled,  the  jiupils  conlract,  owing  to  ihc  anamic  stimulation  of  the  origin  of  the  oculomotorius 
{A/orii^X'o)-  The  dilatation  of  the  pupils  observed  in  cases  of  neuralgia  of  the  trigeminus,  is  partly 
due  to  the  stimulation  of  the  dilating  iil)res,  partly  to  the  stimulation  of  the  vasomotor  fibres  of  the 
iris  (§  347,  2). 

5.  Contraction  of  the  pupil  occurs  as  an  associated  movement,  during  accomniodalion  for  a 
near  object  (p.  S02,  5),  and  when  the  eyeballs  are  rotated  itt'oard,  which  is  the  case  during  sleep 
(p.  7^5).  Conversely,  intense  movements  of  the  iris,  causetl  l)y  variations  in  the  brightness  of  daz- 
zling' illumination,  e.  g.,  of  the  electric  light,  are  followed  by  disturliing  associated  movements 
of  the  ciliary  muscle  ^Ljubinsky).  In  certain  movements  discharged  from  the  medulla  oblongata 
(forced  respiration,  chewing,  swallowing,  vomiting),  dilatation  of  the  pupil  occurs,  as  a  kind  of 
associated  movement. 

[Argyll  Robertson  Pupil. — In  this  condition  the  pupil  does  not  contract  to  light,  although  it 
contracts  when  the  eye  is  accommodated  for  a  near  object,  vision  usually  being  normal.     The  lesion 

is  situated  in  those  .structures  connecting  the  afferent 
and  efferent  fibres  at  tiieir  central  ends  (at  A  in  Fig.  544), 
i.  e.,  the  connection  between  the  corpora  f|uadrigemina 
and  the  oculomotorius.  It  is  most  fref]uently  found  in 
locomotor  ataxia,  although  it  also  occurs  in  progressive 
paralysis  of  the  insane.] 

Direct  stimulation  at  the  margin  of  the  cornea  causes 
dilatation  of  the  pupil  {E.  H.  IVeber)  ;  in  fact,  direct 
.stimulation  of' circumscribed  areas  of  the  margin  of  the 
iris  causes  partial  contraction  of  the  dilator  fibres 
{Ber>istein  and Dogiel).  Stimulation  near  the  centre 
of  the  cornea  contracts  the  i)upi!  {E.  II.  IVeber).  In 
addition,  we  must  assume  that  the  iris  itself  contains 
elements  that  iniluencc  the  diameter  of  the  pupil  {Sig. 
Alayer  and  Pribram). 

Our  knowledge  of  the  action  of  poisons  on  the 
iris  is  still  very  obscure.  Those  sutwtances  which  dilate 
the  pupil  are  called  mydriatics,  e.g.,  atropin,  homa- 
tropin,  duboisin,dalurin,  and  hyoscyamin.  They  act 
chiefly  by  paralyzing  the  oculomotorius.  But,  in  addi- 
tion, there  must  be  also  an  effect  upon  the  dilating 
fibres  for  after  complete  paralysis  (section)  of  the  ocu- 
lomotorius, the  wo(j'i?rrt'/^  dilatation  of  the  pupil  thereby 
produced  [\  345,  5)  is  still  further  increased  by  atropin. 
Minimal  doses  of  atropin  contract  the  pupil,  owing  to 
stimulation  of  the  pupillo-constrictor  filires;  enormous 
doses  cause  moderate  dilatation  of  the  pupil  in  con- 
sequence of  paralysis  of  the  dilating  as  well  as  of  the 
constricting  nerve  fibres.  Atropin  acts  after  destruc- 
tion of  the  ciliary  [ophthalmic]  ganglion  [Hensen  and 
Volekers)  [and  division  of  all  the  nerves  except  the 
optic],  and  in  the  excised  eye  [De  Riiyter),  (so  that 
atropin  is  a  local  mydriatic.  In  moderate  do.ses  it 
paralyzes  the  nervous  terminations  of  the  3d  nerve  (but  not  in  birds  whose  iris  contains  striped 
mu.scle),andin  larger  doses  it  also  paralyzes  the  muscular  fibres].  [Cocaine,  or  cocaine,  is  obtained 
from  the  leaves  of  Erythroxylon  coca.  When  applied  locally  it  acts  as  a  powerful  local  anaesthetic, 
and  hence  it  is  very  useful  for  operations  about  the  mucocutaneous  orifices.  A  4  per  cent,  solution 
dropped  into  the  eye  produces  complete  insensibility  of  the  cornea  in  a  few  minutes.  It  causes  dila- 
tation of  the  pupils,  though  they  react  to  light  and  to  the  movements  of  accommodation.  It  also 
causes  temporary  paralysis  of  accommodation,  a  sensation  of  heaviness  and  coldness  of  the  eyeball, 
enlargement  of  the  palpebral  fissure,  constriction  of  the  small  peripheral  vessels,  and  slight  lachry- 
mation. 

Myotics  are  those  substances  which  contract  the  pupil  :  Physostigmin  (=  Eserin,  the  alkaloid 
of  Calabar  bean),  nicotin,  pilocarpin,  muscarin,  morphia,  according  to  some  observers  {Griinhagen) 
cau>e  stimulation  of  the  oculomotorius,  while  others  say  they  paralyze  the  sympathetic.  As  these 
substances  cause  spasm  of  the  ciliary  muscle,  it  is  suppo.sed  that  the  first  of  these  has  an  analogous 
action  on  the  sphincter.     It  \s  probable  that  they  paralyze  the  dilator  fibres  and  stimulate  the  oculo- 


Schemeof  the  nerves  of  the  iris.  B,  centrum  optici  ; 
C,  oculomotor  centre  ;  D,  dilator  centre  (spinal); 
E,  iris  ;  G,  optic  nerve  ;  H,  oculomoior  (sphinc- 
ter) roots  ;  1,  sympathetic  (dihttor) ;  K,  L,  an- 
terior roots:  M,  N,  O,  posterior  roots;  A,  seat 
of  lesion,  causing  pupillary  immobility  ;  *  prob- 
able seat  of  lesion,  causing  myosis. 


GORHAM  S    PUPIL   PHOTOMETER. 


811 


motor  fibres.  [Among  local  myotics,  i.  e.,  those  which  act  on  the  eye,  some  act  on  the  muscular 
fibres  of  the  iris,  e.  g.,  physostigmin  or  eserin,  while  others  act  on  the  peripheral  terminations  of  the 
3d  nerve,  e.g.,  pilocarpin,  muscarin.  Muscarin  causes  very  great  contraction  of  the  pupil  from  spasm 
of  the  circular  fibres,  due  to  its  action  on  the  3d  nerve;  eserin,  on  the  other  hand,  although  contract- 
ing the  pupil,  also  affects  the  dilator  fibres.  The  contraction  of  the  pupil  due  to  opium  is  central  in 
its  cause.] 

If  the  one  pupil  be  contracted  or  dilated  by  these  substances,  the  other  pupil,  conversely,  is  dilated 
or  contracted,  owing  to  the  change  in  the  amount  of  light  admitted  into  the  eye  into  which  the  poison 
has  been  introduced.  The  anaesthetics  (ether,  chloroform,  alcohol,  etc.),  when  they  begin  to  cause 
stupor,  contract  the  pupil,  and  when  their  action  is  intense  they  dilate  it  [Dogiel).  Chloroform  dur- 
ing the  stage  when  it  causes  excitement  (preceding  the  narcosis),  stimulates  the  centre  for  the  dilata- 
tion of  the  pupil ;  after  a  time  this  centre  is  paralyzed,  so  that  the  pupil  no  longer  dilates  on  the 
application  of  external  stimuli.  Thereafter  the  pupilloconstrictor  centre  is  stimulated,  whereby  the 
pupil  may  be  contracted  to  the  size  of  a  pin's  head  ;  ultimately  this  centre  is  paralyzed,  and  the  pupil 
becomes  dilated. 

Time  for  Movements  of  Iris. — The  reflex  dilatation  of  the  pupil  occurs  slightly  later  than  the 
reflex  contraction,  the  time  in  the  two  cases  being  0.5  and  0.3  second  respectively,  after  stimulation 
by  light  {v.  Vintschgaii).  A  certain  time  always  elapses,  until  the  iris,  corresponding  to  the  strength 
of  the  stimulus  of  light  exciting  the  retina,  "  adapts"  itself  to  produce  a  suitable  size  of  the  pupil 
[Aubert).  Contraction  of  the  pupil  occurs  very  rapidly  after  stimulation  of  the  oculomolorius  in 
birds;  in  rabbits  0.89  second  elapses  after  stimulation  of  the  sympathetic,  until  the  dilatation  begins 
{Arli). 

Excised  Eye. — Light  causes  contraction  of  the  pupil  in  the  excised  eye  of  amphibians  and  fishes 
[Arnola).     Even  the  iris  of  the  eel,  when  cut  out  and  placed  in  normal  saline  solution,  contracts  to 


Fig.  545. 


Fig.  546. 


Gorham's  pupil  photometer.     Fig.  545  shows  the  disk  with  a  slot  and  two  holes.    Fig.  546  gives  a  side  view  with  the 
diameter  of  the  pupil  marlied  on  it.     The  upper  end  is  closed  by  the  disk,  while  the  lower  end  is  open. 

light  [Arnold),  the  green  and  blue  rays  being  most  active.  Increase  of  the  temperature  causes 
mydriasis  in  the  excised  eye  of  the  frog  or  eel,  while  cooling  causes  myosis  (//.  Mi'dler). 

[Size  of  the  Pupil. — Jonathan  Hutchinson  recommends  a  pupilometer,  consisting  of  a  metal 
plate  perforated  with  a  series  of  holes  of  different  sizes.  The  smallest  hole  measures  about  ^^Jof 
aline,  and  the  largest  is  41^  lines.  The  plate  is  placed  just  below  the  patient's  eye,  and  the  hole  is 
selected  which  corresponds  with  the  size  of  the  pupil.] 

[Gorham's  Pupil  Photometer. — This  ingenious  instrument  may  be  used  as  a  pupilometer,  and 
also  as  a  photometer.  It  consists  of  apiece  of  bronzed  tubing  1.9  in.  long  and  1.5  in.  diameter 
(Figs.  545  and  546).  One  end  is  closed  by  a  disk  or  cap,  which  is  pierced  in  its  radii  by  a  series  of 
holes  at  distances  varying  from  .05  m.  to  .28  ?n.  There  is  a  slot  in  the  cap  which  allows  one  pair 
of  holes  to  be  visible  at  a  time,  while  on  the  cyhnder  is  engraved  the  linear  distance  of  each  pair  of 
holes.  In  using  the  instrument  as  a  pupilometer,  look  through  the  open  end  of  the  tube  (the  bot- 
tom in  Fig.  546),  with  both  eyes  open,  toward  a  sheet  of  white  paper  or  the  sky,  when  two  disks  of 
light  will  be  seen.  Then  revolve  the  lid  or  cap  slowly  until  the  two  white  A\sks  just  touch  one 
another  at  their  edges.  The  decimal  fraction  opposite  the  two  apertures  seen  on  the  scale  outside 
indicates  the  diameter  of  the  pupil  in  looths  of  an  inch.  When  using  it  as  a  photometer,  it  is 
assumed  that  the  size  of  the  pupil  gives  an  index  of  the  intensity  of  the  amount  of  light  which  influ- 
ences the  diameter  of  the  pupil.] 

Intraocular  Pressure. — The  movements  of  the  iris  are  always  accompanied  by  variations  of  the 
intraocular  pressure.  The  muscles  of  the  iris  affect  the  intraocular  pressure,  in  that  the  dilatation  of 
the  pupil  increases  it,  while  contraction  of  the  pupil  diminishes  it.  The  increased  or  diminished 
tension  can  be  felt  when  two  fingers  are  pressed  on  the  eyeball.  Stimulation  of  the  sympathetic 
increases,  while  its  section  diminishes  the  pressure.     Action  of  Drugs. — Atropin  dropped  into  the 


812  ENTOPTICAL    PHENOMENA. 

eye,  after  producing  a  short  temporary  diminution  of  the  tension,  increases  it;  eserin,  after  a  primary 
increase,  causes  a  Jiniinution  of  the  pressure  [Griist-r  uiui  J/o/zkt-). 

393.  ENTOPTICAL  PHENOMENA.— Entoptical  phenomena  de- 
pend upon  the  perception  of  objects  present  within  the  eyeball  itself. 

I.  Shadows  are  formed  upon  the  retina  by  different  opaque  bodies.  In  orderto  see  them  in  one's  own 
eye,  proceed  thus :  I>y  means  of  a  strong  convex  lens  project  a  small  image  of  a  flame  upon  a  paper 
screen,  prick  a  small  opening  through  the  image  of  the  Hame,  and  place  one  eye  at  the  other  side  of 
the  screen,  so  that  the  illuminated  puncture  lies  in  the  anterior  focus  of  the  eye,  ;.  e.,  al)Out  13  mm. 
in  front  of  the  cornea.  As  the  rays  proceeding  from  this  point  pass  parallel  through  the  media  of 
the  eye,  a  diffuse  bright  field  of  vision,  surrounded  by  the  black  margins  of  the  iris,  is  obtained.  All 
dark  bodies  which  lie  in  the  course  of  the  rays  of  light  throw  a  shadow  upon  the  retina,  and  appear 
as  specks.     There  are  various  forms  of  these  shadows  (Fig.  547) : — 

(a)  The  spectrum  mucro-lacrimale,  especially  upon  the  margin  of  the  eyelids,  depending 
upon  particles  of  mucus,  fat  globules  from  the  Meibomian  glands,  dust  mixed  with  tears,  causing 
cloudy  or  drop-like  retinal  shadows,  which  are  removed  by  winking. 

(b)  Folds  in  the  cornea. — If  the  cornea  be  pressed  laterally  with  the  finger,  wrinkled  shadows, 
due  to  temporary  w  rinkles  in  the  cornea,  are  produced. 

(c)  Lens  shadows. — IJead-like  or  dark  specks,  bright  and  star-like  figures,  the  former  due  to 
deposits  on  and  in  tlie  lens,  the  latter  to  the  radiate  structure  of  the  lens. 

(d)  Muscae  volitantes  (T)echales,  1690),  like  strings  of  beads,  circles,  groups  of  balls  or  pale 
stripes,  depend  upon  opaque  particles  (cells,  disintegrating  cells,  granular  fibres)  in  the  vitreous 
humor.  They  move  about  when  the  eye  is  moved  rapidly.  I.istmg  (1845)  showed  that  one  may 
determine  pretty  accurately  the  position  of  these  objects.  While  making  the  observation  upon  one's 
own  eyes,  raise  or  depress  the  source  of  light ;  those  shadows  which  are  caused  by  bodies  on  a  level 


Entoptical  shadows 


with  the  pupil  retain  their  relative  positions  in  the  bright  fields  of  vision.  Shadows  which  appear  to 
move  in  the  same  direction  as  the  source  of  light  are  caused  by  bodies  which  lie  in  front  ol\\i& 
plane  of  the  pupil  — those,  however,  which  appear  to  move  in  the  opposite  direction  depend  upon 
objects  behind  the  plane  of  the  pupil. 

2.  Purkinje's  figure  (1819)  depends  upon  the  blood  vessels  within  the  retina,  which  cast 
a  shadow  upon  the  most  external  layer  of  the  retina,  viz.,  upon  the  rods  and  cones,  these  being  the 
parts  acted  upon  by  light.  In  ordinary'  virion  we  do  not  observe  these  shadows.  According  to  v. 
Helmholtz,  this  is  due  to  the  fact  that  the  sensibility  of  the  shaded  parts  of  the  retina  is  greater,  and 
their  excitability  is  less  exhausted,  than  ail  the  other  parts  of  the  retina.  .\s  soon,  however,  as  we 
change  the  position  of  the  shadow  of  the  blood  vessels,  instead  of  being  directly  behind,  so  that  the 
blood  vessels  come  to  lie  more  laterally  and  behind  them,  i.  ^.,upon  places  which  do  not  receive 
shadows  from  the  blood  vessels  when  the  rays  of  light  pass  through  the  eye  in  the  ordinary  way, 
then  the  figure  of  the  blood  vessels  becomes  apparent  at  once.  All  that  is  necessary  is  to  cause  the 
light  to  enter  the  eyeball  obliquely.  Method. — (l)  This  may  be  done  bypassing  an  intense  light 
through  the  sclerotic,  e.g.,  by  throwing  upon  the  sclerotic  a  small,  bright,  luminous  image  from  a 
source  of  light.  On  moving  the  source  of  light,  the  figure  of  the  blood  vessels  moves  in  the  same 
direction.  (2)  Look  directly  upward  to  the  sky,  wink  with  the  upper  eyelid  drooping,  so  that  for  a 
moment,  corre>ponding  to  the  act  of  winking,  rays  of  light  enter  obliquely  the  lowest  part  of  the 
pupils.  (3)  Look  through  a  small  aperture  toward  a  bright  sky,  and  move  the  aperture  rapidly  to 
and  fro,  so  that  from  both  sides  of  the  blood  vessels  shadows  fall  rapidly  upon  the  nearest  series  of 
rods  and  cones.  (4)  In  a  darkened  room  look  straight  ahead,  and  move  a  light  to  and  fro  close 
under  the  eyes.  Occasionally,  while  performing  this  experiment,  one  may  see  the  macula  lutea  as  a 
non-vascular  shaded  depression,  and,  owing  to  the  inversion  of  the  objects,  it  lies  on  the  inner  side 
of  the  entrance  of  the  optic  nerve. 


ENTOPTICAL    PHENOMENA.  813 

3.  Movements  of  the  blood  corpuscles  in  the  retinal  capillaries. — On  looking,  without 
accommodating  the  eye,  toward  a  large  bright  surface,  or  through  a  dark  blue  glass  toward  the  sun, 
we  see  bright  spots,  like  points,  formmg  longer  or  shorter  chains,  moving  in  tortuous  paths.  The 
phenomenon  is,  perhaps,  caused  by  the  red  blood  corpuscles  (in  the  capillaries  posterior  to  the  exter- 
nal granular  layer)  acting  as  small  light  collecting  concave  disks,  concentrating  the  light  falling  upon 
them  fiom  bright  surfaces,  and  throwmg  it  upon  the  rods  of  the  retina.  Each  corpuscle  must  be  in 
a  special  position  ;  should  it  rotate,  the  phenomenon  disappears.  Vierordt,  who  projected  the  move- 
ment upon  a  screen,  calculated,  from  the  velocity  of  their  motion,  the  velocity  of  the  blood  stream  in 
the  retinal  capillaries  as  equal  to  0.5  to  0.75  mm.  in  a  second,  which  corresponds  very  closely  with 
the  results  obtained  directly  in  other  capillaries  by  E.  H.  Weber  and  Volkmann  (^  90,  4).  When 
the  carotids  are  compressed,  the  movement  is  slower  on  freeing  them  from  the  compression  ;  during 
short  forced  expirations  the  movement  is  accelerated  (^La7tdois). 

4.  The  entoptical  pulse  (^  79,  2)  depends  upon  the  pulsating  arteries  irritating  mechanically  the 
rods  lying  outside  them. 

5.  Pressure  Phosphenes. — Pressure  applied  to  the  eye  causes  a  series  of  phenomena :  (a)  Par- 
tial pressure  upon  the  eyeball  causes  the  so-called  illuminated  "  pressure  picture  "  ox  phosphene,  which 
was  known  to  Aristotle.  As  the  impression  upon  the  retina  is  referred  to  something  outside  the  eye, 
the  phosphene  is  always  perceived  on  the  side  of  the  field  of  vision  opposite  to  where  the  pressure 
affects  the  retina,  f.  ^.,  pressure  upon  the  outer  surface  of  the  eyeball  causes  the  flash  of  light  to 
appear  on  the  inner  side.  If  the  retina  is  not  well  lighted,  the  phosphene  appears  luminous  ;  if  the 
retina  is  well  lighted,  it  appears  as  a  dark  speck,  within  which  the  visyal  perception  is  momentarily 
abolished,  (li)  If  a  uniform  pressure  be  applied  to  the  eyeball  continuously  from  before  backward, 
as  Purkinje  pointed  out,  after  some  time  there  appear  in  the  field  of  vision  very  sparkling  variable 
figures,  which  perform  a  wonderful  fantastic  play,  and  often  resemble  the  sparkling  effects  obtained 
in  a  kaleidoscope  [y.  Hehnholtz),  and  are  probably  comparable  to  the  feeling  of  formication  produced 
by  pressure  upon  sensory  nerves  ("  sleeping  of  the  limbs  ").  [c)  By  applying  equable  and  continued 
pressure,  Steinbach  and  Purkinje  observed  a  network  with  moving  contents  of  a  bluish-silvery  color, 
which  seemed  to  correspond  to  the  retinal  veins.  Vierordt  and  Laiblin  observed  the  branching  of 
the  blood  vessels  of  the  choroid &%  a  red  network  upon  a  black  ground,  [d)  According  to  Houdin, 
we  may  detect  the  position  of  the  yellow  spot  by  pressure  upon  the  eyeball. 

6.  The  entrance  of  the  optic  nerve  may  be  detected  on  moving  the  eye  rapidly  backward,  and 
especially  inward,  as  a  fiery  ring  or  semicircle  about  the  size  of  a  pea.  Probably,  owing  to  the 
movement  of  the  retina,  the  entrance  of  the  optic  nerve  is  stimulated  mechanically  by  the  rapid 
bending.  Purkinje  and  others  observed  that  the  ring  remained  persistent  on  turning  the  eye  strongly 
inward.  If  the  retina  be  brightly  illuminated,  the  ring  appears  dark,  and  when  the  field  of  vision  is 
colored,  the  ring  has  a  different  tint.  If  Purkinje's  figure  be  produced  at  the  same  time,  one  may 
observe  that  the  vascular  trunk  proceeds  from  this  ring — a  proof  that  the  ring  corresponds  to  the 
entrance  of  the  optic  nerve  i^Landois). 

7.  Accommodation  Spot. — On  accommodating  the  eye  strongly  toward  a  white  surface,  there 
appears  in  the  middle  a  small,  bright,  trembling  shimmer,  and  in  its  centre  a  coarse  brown  speck, 
about  the  size  of  a  pea,  is  seen  [Ptirkinje).  If  pressure  be  applied  externally  to  the  eyeball,  this 
speck  becomes  more  distinct.  After  having  once  observed  the  phenomenon,  occasionally  on  pressing 
laterally  upon  the  opened  eye  we  may  see  it  as  a  bright  speck  in  the  field  of  vision — another  proof 
that  the  intraocular  pressure  is  increased  during  accommodation. 

8.  Mechanical  Optical  Stimulation. — On  dividing  the  optic  nerve  in  man,  as  in  extirpation  of 
the  eyeball,  a  flash  of  light  is  observed  at  the  moment  of  section  by  the  person  operated  on.  The 
section  of  the  nerve  fibres  themselves  is  painless,  but  section  of  the  sheaths  is  painful. 

9.  The  accommodation  phosphene  is  the  occurrence  of  a  fiery  ring  at  the  periphery  of  the 
field  of  vision,  seen  on  suddenly  bringing  the  eyes  to  rest  after  accommodating  for  a  long  time  in  the 
dark  (^Purkinje').  The  sudden  tension  of  the  zonule  of  Zinn  resulting  from  the  relaxation  causes  a 
mechanical  stretching  of  the  outermost  part  of  the  margin  of  the  retina,  or  it  may  be  of  a  part  of  the 
retina  behind  this.  Purkinje  observed  the  phenomenon  after  suddenly  relaxing  the  pressure  on  the 
eye. 

10.  Electrical  Phenomena. — Electrical  currents,  when  applied  to  the  eye,  cause  a  strong  flash 
of  light  over  the  whole  field  of  vision.  One  pole  of  the  battery  may  be  placed  on  the  under  eyelid 
and  the  other  on  the  neck.  The  flash  at  closing  [making]  the  current  is  strongest  with  an  ascend- 
ing current,  that  with  opening  [breaking]  the  current  with  a  descending  current.  If  a  uniform  con- 
tinuous ascending  current  be  transmitted  through  the  closed  eyes,  the  dark  disk  of  the  elevation  at 
the  entrance  of  the  optic  nerve  appears  in  a  vi\\\iv^h.-violet  field  of  vision ;  with  a  descending  current, 
the  field  of  vision  is  reddish  and  dark,  in  which  the  position  of  the  optic  nerve  appears  light  blue 
[y.  Hehnholtz).  If  external  colors  are  looked  at  simultaneously,  these  colors  blend  to  form  a  violet 
or  yellow  with  the  colors  looked  at  [Schelske).  During  the  passage  of  the  ascending  current  we  see 
external  objects  indistinctly  and  smaller  when  the  eyes  are  open;  while  with  the  descending  current 
they  are  larger  and  more  dis.inct  (Riiter).  Sometimes  the  position  of  the  macula  lutea  appears  dark 
on  a  bright  ground,  or  the  reverse,  according  to  the  direction  of  the  current.  If  the  current  be 
opened  [broken]  the  phenomena  are  reversed  (|  335),  and  the  eye  soon  returns  to  rest. 


814  ILLUMINATION    OF    THE    EYE. 

11.  The  yellow  spot  appears  sometimes  as  a  dark  circle  when  there  is  a  uniform  blue  illumina- 
tion. In  a  strong  light  the  position  of  the  yellow  spot  is  surrounded  by  a  bright  area,  twice  or  thrice 
as  large,  called  "  Lowe's  ring."  [Clerk  Maxwell's  Experiment. — On  looking  through  a  solu- 
tion of  chrome  alum  in  a  bottle  or  vessel  with  parallel  gl.iss  sides,  we  observe  an  oval  ])urplish  spot 
in  the  greenish  color  of  the  alum.     This  is  due  to  the  pigment  of  the  yellow  spot.] 

Haidinger's  Brushes. — On  directing  the  eye  toward  a  source  of  polarized  light,  "  Haidinger's 
polarized  brushes  "  appear  at  the  point  of  fixation.  They  are  seen  on  looking  through  a  Nicol's 
prism  at  a  bright  cloud  (-'.  Helinhollz).  They  are  bright  and  bluish  on  a  surface,  bounded  by  two 
neighboring  hyperbola  on  a  white  field  ;  the  dark  bundle  separating  them  is  smallest  in  the  centre 
and  yellow.  Of  the  various  colors  of  homogeneous  light,  blue  alone  shows  the  brushes  [Stokes). 
According  to  v.  Ilelmholtz,  the  seat  of  the  phenomenon  is  the  yellow  spot,  and  is  due  to  the  yellow- 
colored  elements  of  the  yellow  .spot  being  slightly  doubly  refractive,  while  at  one  part  they  absorb 
more,  at  another  less,  of  the  rays  entering  the  eye. 

12.  Lastly,  there  are  the  visual  sensations  depending  on  internal  causes,  e.  ;'.,  increased  bound- 
ing of  the  blood  through  the  retina,  as  during  violent  coughing,  increased  intraocular  pressure. 
Stimulation  of  the  visual  areas  {\  378,  IV)  may  produce  spectra,  which  Cardanus  (1550),  Goethe, 
Kicolai,  and  Johannes  Miiller  could  produce  voluntarily. 

394.  ILLUMINATION  OF  THE  EYE.— OPHTHALMOSCOPE. - 

The  light  which  enters  the  eye  is  partly  absorbed  by  the  black  uveal  pigment,  and 
partly  again  reflected  from  the  eye,  and  always  in  the  same  direction  in  which  the 
rays  entered  the  eye.  By  placing  one's  self  in  front  of  the  eye  of  another  person, 
of  course,  the  head,  being  an  opaque  body,  cuts  off  a  large  number  of  rays. 
Owing  to  the  position  of  the  head,  no  rays  of  light  can  enter  the  eye  ;  and  of 
course  none  can  be  reflected  back  to  the  eye  of  the  observer.  Hence,  the  eye  of 
the  person  being  examined  always  appears  black,  because  those  rays  which  alone 

Fig.  548. 


Arrangement  for  examining  the  eye  of  B.     A,  eye  of  observer  ;  .r,  source  of  light ;  S,  S,   plate  of  glass  directed 

obliquely,  reflecting  light  into  B. 

could  be  reflected  in  the  direction  of  the  eye  of  the  observer  are  cut  off.  As  soon, 
however,  as  we  succeed  in  causing  rays  of  light  to  enter  the  eye  at  the  same  time 
and  in  the  same  direction  in  which  we  observe  the  eye  of  another  person,  the 
fundus  of  the  eye  appears  brightly  illuminated. 

The  following  simple  arrangement  is  sufficient  for  the  purposes  (Fig.  548) :  Let  B  be  the  eye  of  the 
patient,  A  that  of  the  obser\-er,  and  let  a  flame  be  placed  at  x.  The  rays  of  light  proceeding  from 
X  impinge  upon  the  obliquely  placed  plate  of  glass  (S,  S),  and  are  reflected  in  the  direction  of  the 
dotted  lines  into  the  eye  (B).  The  fundus  of  the  eye  appears  in  this  position  to  be  brightly  illu- 
minated in  diffusion  circles  around  b.  \%  the  observer  (A)  can  .see  through  the  obliquely  placed 
glass  plate  (S,  S),  and  in  the  same  direction  as  the  reflected  rays  (-v,  j'),  he  sees  the  retina  around 
b  brightly  illuminated. 


THE    OPHTHALMOSCOPE. 


815 


In  order  that  this  method  be  made  available  for  practical  purposes,  we  must,  of  course,  be  able  to 
distinguish  the  details,  such  as  the  blood  vessels  of  the  fundus  of  the  eye,  the  macula  lutea,  the 
entrance  of  the  optic  nerve,  abnormalities  of  the  retina,  and  the  choroidal  pigment,  etc.  The  follow- 
ing considerations  show  us  how  to  proceed  in  order  to  accomplish  this.     As  already  mentioned,  and 

Fig.  549. 


as  Fig.  531  shows,  a  small  inverted  image  is  formed  on  the  retina  (c,  d)  when  we  look  at  an  object 
(A,  B)  ;  conversely,  according  to  the  same  dioptric  law,  an  enlarged  inverted  real  image  of  a  small 
distinct  area  of  the  retina  (c,  d — depending  on  the  distance  for  which  the  eye  was  accommodated) 
must  be  formed  outside  the  eye  (A,  B). 

Fig.  550. 

5. 


If  the  fundus  of  this  eye  be  sufficiently  illuminated,  this  aerial  image  will  be  correspondingly 
bright. 

In  order  to  see  the  individual  parts  of  the  retinal  picture  more  distinctly,  the  observer  must  accom- 
modate his  own  eye  for  the  position  of  this  image.  In  such  circumstances  the  eye  of  the  observer 
would  be  too  near  the  observed  eye.     His  eye  when  so  accommodated  is  removed  from  the  eye  of 

Fig.   551. 


the  patient  by  his  own  visual  distance,  and  by  the  visual  distance  of  the  patient.  As  this  distance 
is  considerable,  the  individual  small  details  of  the  fundus  cannot  be  seen  distinctly.  Further,  owing 
to  the  contraction  of  the  pupil  of  the  patient,  only  a  small  area  of  the  fundus  can  be  seen,  and  this 
only  under  a  small  visual  angle,  quite  apart  from  the  fact  that  it  is  often  impossible  to  accommodate 
for  the  real  image  of  the  fundus  of  the  patient. 


816 


THE    OPHTHALMOSCOPE. 


Hence,  the  eye  of  the  observer  must  be  brought  nearer  to  the  eye  of  the  patient.  This  may  be 
done  in  two  ways:  (l)  Either  by  placing  in  front  of  the  eye  of  the  patient  a  slronfj  conzrx  lens 
(of  I  to  3  inches  focus — Kig.  549,  C).  This  causes  the  retinal  image  to  be  nearer  to  the  eye  (at  H), 
owin.^  to  the  strong  lens  refracting  the  rays  of  light.  'Ihe  observer  (M)  can  come  nearer  to  the 
eye,  and  can  still  accommodate  for  the  image  of  the  fundus  of  the  eye.  (2)  Or  a  concave  lens  is 
l)laced  immediately  in  front  of  the  eye  of  the  patient  (Fig.  550,  0).  The  rays  of  light  emerging 
from  the  eye  of  the  patient  (P)  are  ei'her  made  parallel  by  the  concave  lens  (o),  and  are  brought  to 
a  focus  on  the  retina  of  the  emmetropic  observer  (A) ;  or,  if  the  lens  causes  the  rays  to  diverge 
(Fig.  551),  an  erect,  virtual  image  is  formed  at  a  distance  behind  the  eye  of  the  patient  (at  R).  In 
these  cases,  also,  the  observer  can  go  much  nearer  to  the  eye  of  the  patient. 

The  ophthalmoscope  invented  by  v.  Heliiiholtz  enables  us  to  examine  the 
whole  of  the  fundus  of  the  eye. 

[Direct  Method. — Use  a  concave  mirror  of  20  centimetres  focal  distance,  with  a  central  opening. 
Reflect  a  beam  of  light  into  the  patient's  eye,  where  the  rays  cro-;s  in  the  vitreous  and  illuminate  the 
fundus  of  the  eye.  These  rays  again  pass  out  of  the  eye  and  reach  the  observer's  eye  through  the 
central  hole  in  the  mirror.  If  the  observer  be  emmetropic  they  come  to  a  focus  on  his  retina.  In 
this  way  all  the  parts  of  the  retina  are  seen  in  their  normal  position,  but  enlarged.     Hence,  it  is  some- 


F:g.  553. 


The  entrance  of  the  optic  nerve  with  the  adjacent  parts  of 
the  fundus  of  the  normal  eye.  a,  ring  of  connective 
tissue  ;  b,  choroidal  ring  ;  c,  arteries  ;  d,  veins  ;  g,  divi- 
sion of  the  central  artery ;  h,  division  of  the  central 
vein;  L,  lamina  cribrosa ;  /,  temporal  (outer)  side;  n, 
nasal  (inner;  side. 


Morton's  Ophthalmoscope. 


times  called  the  examination  of  the  upright  image.  The  eye  of  the  patient  and  observer  must  be 
at  rest,  i.  e.,  be  negatively  accommodated,  while  the  mirror  must  be  brought  as  near  as  possible  to 
the  eye  of  the  patient.] 

[Indirect  Method,  by  which  a  more  general  view  of  the  fundus  is  obtained.  Throw  the  light 
into  the  patient's  eye  by  an  ophthalmoscopic  mirror  as  above,  but  held  at  a  distance  of  about  50  cm. 
(10  inches)  from  the  patient's  eye.  Hold  a  biconvex  lens  of  14  dioptrics  focal  length  vertically 
between  the  mirror  and  the  patient's  eye  (Fig.  549),  the  observer  looking  through  the  hole  of  the 
minor.  What  he  does  see  is  an  inverted  aerial  image  at  B.  Only  a  small  part  of  the  fundus 
oculi  can  be  seen  at  one  lime.] 

[The  ophthalmoscope,  besides  being  used  for  examining  the  interior  of  the  eyeball,  is  of  the  utmost 
use  in  determining  the  existence  and  amount  of  anomalies  of  refraction  in  the  refractive  media. 
I-'or  this  purpose  an  ophthalmoscope  requires  to  be  provided  with  f>!its  and  i/itntts  lense^,  which  can 
be  readily  brought  before  the  eye  of  the  observer.  This  is  readily  done  by  an  incienious  mechanism 
devised  by  Couper,  and  made  use  of  in  the  handy  students'  ophthalmoscope  of  Morton  (Fig.  553). 
The  lenses  are  moved  by  a  driving  wheel  on  the  left  figure,  while  at  the  same  time  is  indicated  at  a 
certain  aperture  the  lens  presented  at  the  sight  hole.     The  instrument  is  also  provided  with  a  mov- 


RETINOSCOPY. 


817 


able  arrangement  carrying  a  concave  mirror  at  either  end.  One  of  these  mirrors  is  lo  inches  in 
focus,  and  is  used  for  indirect  examination  and  retinoscopy,  while  the  other  is  of  3  inches  focus  for 
direct  examination,  and  is  fixed  at  an  angle  of  25°.] 

[Retinoscopy. — The  ophthalmoscope  is  used  also  for  this  purpose.  A  beam  of  light  is  reflected 
into  the  eye  by  the  ophthalmoscopic  mirror,  and  the  play  of  light  and  shade  on  the  fundus  oculi 
observed.  A  study  of  this  is  important  in  determining  anomalies  of  refraction.  P'or  the  method  the 
student  is  referred  to  a  text-book  on  "  Diseases  of  the  Eye."] 

[Artificial  Eye. — The  student  may  practice  the  use  of  the  ophthalmoscope  on  an  artificial  eye, 
such  as  that  of  Frost  (Fig.  554")  or  Perrin.] 

Illumination. — In  oi'der  to  illuminate  the  interior  of  the  eye,  v.  Helmholtz  used  several  plates  of 
glass,  placed  behind  each  other,  in  the  position  of  S,  S,  in  Fig.  548.  Afterward  he  used  a  plane  or 
concave  mirror  of  7  inches  focus  (Fig.  549),  with  a  hole  in  the  centre.  Fig.  552  shows  the  appear- 
ance of  the  fundus  of  the  eye,  as  seen  with  the  ophthalmoscope.  In  albinos  the  fundus  of  the  eye 
appears  red,  because  light  passes  into  the  eye  through  the  sclerotic  and  uvea,  which  are  devoid  of 


Fig.  554. 


Frost's  Artificial  Ej'e. 


Action  of  the  Orthoscope. 


pigment.  If  a  diaphragm  be  placed  over  the  eye,  so  that  the  pupil  alone  is  free,  the  eye  appears 
black  {Danders). 

Tapetum. — In  many  animals  the  eyes  have  a  bright  green  lustre.  These  eyes  have  a  special 
layer,  the  tapetum,  or  the  membrane  versicolor  of  Fielding ;  in  carnivora  it  consists  of  cells,  in  her- 
bivora  of  fibres,  placed  between  the  capillaries  of  the  choroid  and  the  stroma  of  the  uvea.  These 
structures  exhibit  interference  colors  and  reflect  much  light,  so  that  the  colored  lustre  appears  in  the 
eye. 

Oblique  illumination  is  used  with  advantage  for  investigating  the  anterior  chamber.  A  bright 
beam  of  light,  condensed  by  a  convex  lens,  is  thrown  laterally  upon  the  cornea  into  the  eye,  and  so 
directed  upon  the  point  to  be  investigated  as  to  illuminate  it.  A  point  so  illuminated,  e.g.,  a  part  of 
the  iris,  may  be  examined  from  a  distance  by  means  of  a  lens,  or  even  by  a  microscope  {Liebreich). 

The  Orthoscope. — Czermak  constructed  this  instrument,  in  which  the  eye  is  placed  under  water 
(Fig.  555).  It  consists  of  a  small  glass  trough  with  one  of  its  walls  removed.  The  margins  of  the 
open  side  are  pressed  firmly  against  the  region  of  the  eye.  The  eye  and  its  surroundings  form,  as  it 
were,  the  sixth  side  of  the  trough,  which  is  filled  with  water,  so  that  the  cornea  is  bathed  therewith. 
As  the  refractive  index  of  water  is  almost  the  same  as  the  refractive  index  of  the  media  of  the  eye,  the 

52 


818  EXPERIMENTS   ON    THE    RETINA. 

rays  of  light  pass  into  the  eye  in  a  straight  direction  without  being  refracted.  Hence,  ol)jects  in  the 
anterior  chamber  can  be  seen  directly,  as  if  they  were  not  within  the  eye  at  all.  Another  advantage 
is  that  ihe  objects  can  be  brought  nearer  to  the  eye  of  tlie  ol)server.  The  rays  of  light  emerging  from 
the  point  (<?)  of  the  fundus,  if  ihe  e)e  were  surrounded  by  air,  would  leave  the  eye  as  the  parallel 
lines,  b,  c,  b,  c.  Under  water,  these  rays,  a,  l\  coniinue  in  the  direction  a,  b,  as  far  as  /',  </,  where 
they  emeige  fiom  the  water,  and  are  bent  from  the  perpendicular  to  d,  e,  </,  e.  The  eye  of  the  oi)server, 
looking  in  the  direction  e,  d,  sees  the  point,  <?,  nearer,  viz.,  in  the  direction  e,  d,  a',  lying  at  a. 

395.  ACTIVITY  OF  THE  RETINA  IN  VISION.— I.  Blind  Spot. 
—  llic  rods  and  cones  alone  arc  the  i)arts  of  the  retina  sensitive  to  light,  they 
alone  are  excited  by  the  vibrations  of  the  ether.  This  is  confirnied  by  jSIariotte's 
experiment  (1688),  which  proves  that  the  entrance  of  the  optic  nerve,  where  rods 
and  cones  are  absent,  is  devoid  of  visual  sensibility.  Hence  it  is  spoken  of  as  the 
'' blind  spot y 

[Mariotte's  Experiment. — Make  two  marks,  abotit  three  inches  apart,  upon 
])aper  (Fig.  556).  Look  at  the  cross  with  the  right  eye,  keeping  the  left  eye  closed, 
and  hold  the  paper  about  a  foot  from  the  eye,  when  both  the  cross  and  the  circle 
will  be  seen.  Gradually  approximate  the  paper  to  the  eye,  keeping  the  open  eye 
steadily  fixed  on  the  cross;  at  a  certain  moment  the  circle  will  disapi)ear,  and  on 
bringing  the  paper  nearer  to  the  eye  it  will  reappear.  The  moment  wh^n  the  circle 
disappears  is  when  its  image  falls  upon  the  entrance  of  the  optic  nerve.] 

Position  and  Size. — The  entrance  of  the  optic  nerve  lies  about  3.5  mm.  internal  to  the  visual 
axis  of  the  eyeball  in  the  retina.  Its  diameter  is  1.8  mm.  The  apparent  diameter  of  the  blind  spot 
in  the  field  of  vision  is  in  a  horizontal  direction  6°  56' — this  lies  12°  35'  to  18°  55'  horizontally  from 

Fig.  556. 


+ 


the  fixed  point.  Eleven  full  moons  placed  side  by  side  would  disappear  on  the  surface,  and  so  would 
a  human  face  at  a  distance  of  over  2  metres. 

Proofs. — The  following  facts  prove  that  the  entrance  of  the  optic  nerve  is  insensible  to  light : 

(1)  Bonders  projected,  by  means  of  a  mirror,  the  small  image  of  a  flame  ujxjn  the  entrance  of  the 
optic  nerve  of  another  person,  and  the  person  had  no  sensation  of  light.  But  a  sensation  of  light  was 
experienced,  when  the  image  of  the  flame  was  projected  upon  the  neighboring  parts  of  the  rttina. 

(2)  On  combining  with  Mariotte's  experiment  the  experiment  which  causes  entoptical  phenomena  at 
the  entrance  of  the  optic  nerve,  this  coincides  with  the  blind  spot  (^  393,  6  and  7). 

Form  of  Blind  Spot. — In  order  to  determine  the  form  and  apparent  size  of  the  blind  spot  in 
one's  own  eye,  tix  the  head  at  about  25  centimetres  from  a  surface  of  white  paper;  select  a  small 
point  on  the  latter  and  keep  the  eye  directed  toward  it;  then,  starting  from  the  position  of  the  blind 
spot,  move  a  white  feather  in  all  directions  over  the  paper;  whenever  the  tip  of  the  feather  becomes 
visible,  make  a  mark  at  this  spot.  The  blind  spot  may  be  mapped  out  in  this  way.  It  has  an 
irregular,  elliptical  form  from  which  processes  proceed,  due  to  the  equally  non-sensitive  origins  of  the 
large  blood  vessels  of  the  retina  [^Hueck).  (Mariotte  concluded  from  his  experiment  that  the  choroid, 
which  is  perforated  by  the  optic  nerve,  is  the  membrane  sensitive  to  light,  as  the  nerves  are  nowhere 
absent  from  the  retina.) 

The  blind  spot  causes  no  appreciable  gap  in  the  field  of  vision. — As  this  area  is  not  ex- 
cited by  light,  a  black  spot  cannot  appear  in  the  field  of  vision,  for  the  sensation  of  black  implies  the 
presence  of  retinal  elements,  which,  however,  are  absent  from  the  blind  spot.  The  circumstance, 
however,  that  in  spite  of  the  existence  of  an  inexcitable  spot  during  vision,  no  part  of  the  field  of  vision 
appears  to  be  unoccupied,  is  due  to  a  psychical  action.  The  unoccupied  area  of  the  field  of  vision, 
corresponding  to  the  blind  spot,  is  filled  in,  according  to  probability,  l)y  a  psychical  process  [E.  H. 
Weber).  Hence,  when  a  white  point  disappears  from  a  black  surface,  the  whole  surface  appears  to 
us  black  ;  a  while  surface,  from  which  a  black  point  falls  on  the  blind  spot,  appears  quite  white ;  a 
page  of  print,  gray  throughout,  etc.  According  to  the  probabilities,  certain  parts  are  supplied — parts 
of  a  circle,  the  middle  parts  of  a  long  line,  the  central  part  of  a  cross.     Such  images,  however,  as 


IMAGES    FALLING    ON    THE    RODS    AND    CONES.  819 

cannot  be  constructed  according  to  the  probabilities,  are  not  perfected,  e.  g.,  the   end  of  a  line  or  a 

human  face.     In  other  cases  the  condition  known  as  "  contraction  "  of  the  field  of  vision  tends  to  fill 

up  the  gap.     This  will  be  evident  on  looking  at  the  nine  adjoining  letters,  so 

that  e  disappears;  we  no  longer  see  the  three  letters  on   each  side  of  it  in  . 

straight  lines,  but  b,  f,  h,  d  are  turned  in  toward  e.     The  adjoining  parts  of    3,  Q  C 

the  field  of  vision  seem  to  extend  over  and  around  the  blind  spot,  and  thus 

help  to  compensate  for  the  blind  spot.  ^  , 

II.  Optic  Fibres  Inexcitable  to  Light.— The  layer  of  ^         ^^^  ■'• 
\}(\^fib7'es  of  the  optic  nerve  in  the  retina  is  7iot  sensitive  to  light. 

This  is  proved  by  the  fact  that,  in  the  fovea  centralis,  which   ff  D  1 

is  the  area  of  most  acute  vision,  there   are  no  nerve  fibres. 
Further,  Purkinje's  figure  proves  that  as  the  arteries  of  the  retina  lie  behind  the 
optic  fibres,  the  latter  cannot  be  concerned  in  the  perception  of  the  former. 

III.  Rods  and  Cones. — The  outer  segments  of  the  rods  and  cones  have 
rounded  outlines,  and  are  packed  close  together;  but  natural  spaces  must  exist 
between  them,  corresponding  to  the  spaces  that  must  exist  between  groups  of 
bodies  with  a  circular  outline.  These  parts  are  insensible  to  light,  so  that  a  retinal 
image  is  composed  like  a  mosaic  of  round  stones.  The  diameter  of  a  cone  in  the 
yellow  spot  is  2  to  2.5  //.  {M.  Schuitze).  If  two  images  of  two  small  points,  placed 
very  near  each  other,  fall  upon  the  retina,  they  will  still  be  distinguished  as  distinct 
images,  provided  that  both  images  fall  upon  two  different  cones.  The  two  images 
on  the  retina  need  only  be  3-4-5.4  ij.  apart,  in  order  that  each  may  be  seen  sepa- 
rately, for  then  the  images  still  fall  upon  two  adjoining  cones.  If  the  distance  be 
diminished  so  very  much  that  both  images  fall  upon  one  cone,  or  one  upon  one 
cone  and  the  other  upon  the  intermediate  or  cement  substance,  then  only  one  image 
is  perceived.  The  images  must  be  further  apart  in  the  peripheral  portion  of  the 
retina  in  order  that  they  may  be  separately  distinguished. 

As  the  rounded  end  surfaces  of  the  cones  do  not  lie  exactly  under  each  other,  but  are  so  arranged 
that  one  series  of  circles  is  adapted  to  the  interstices  of  the  following  series,  this  explains  why  fine 
dark  lines  lying  near  each  other  appear  to  have  alternating  twists  upon  them,  as  the  images  of  these 
must  fall  upon  the  cones,  at  one  time  to  the  right,  at  another  to  the  left. 

IV.  The  fovea  centralis  is  the  region  of  most  acute  vision,  where  only 
cones  are  present,  and  where  they  are  very  numerous  and  closely  packed  (Fig.  521). 
The  cones  are  less  numerous  in  the  peripheral  areas  of  the  retina,  and  consequently 
vision  is  much  less  acute  in  these  regions.  We  may  therefore  conclude  that  the 
cones  are  more  important  for  vision  than  the  rods.  When  we  wish  to  see  an  object 
distinctly,  we  involuntarily  turn  our  eyes  so  that  the  retinal  image  falls  upon  the 
fovea  centralis.  In  doing  this  we  are  said  to  '^  fix'''  our  eyes  upon  an  object.  The 
Ime  drawn  from  the  fovea  to  the  object  is  called  the  axis  of  vision  (Fig.  557,  S  r). 
It  forms  an  angle  of  only  3.5-7°  with  the  "  optical  axis"  {O  A),  which  unites  the 
centres  of  the  spherical  surfaces  of  the  refractive  media  of  the  eye.  The  point 
of  intersection,  of  course,  lies  in  the  nodal  point  {Kn)  of  the  lens  (p.  820). 
The  term  "  direct  vision"  is  applied  to  vision  when  the  direction  of  the  axis  of 
vision  is  inline  with  the  object  [i.e.,  when  the  image  of  the  object  falls  directly 
on  the  fovea  centralis]. 

"  Indirect  vision"  occurs  when  the  rays  of  light  from  an  object  fall  upon  the 
peripheral  parts  of  the  retina.     Indirect  vision  is  much  less  acute  than  the  direct. 

To  test  the  acuity  of  direct  vision,  draw  two  fine  parallel  lines  close  to  each  other,  and  gradu- 
ally remove  them  more  and  more  from  the  eye,  until  both  appear  almost  to  unite  and  form  one  line. 
The  size  of  the  retinal  image  may  be  ascertained  by  determining  the  distance  of  the  two  lines  fi-om 
each  other,  and  the  distance  of  tlie  lines  from  the  eye,  or,  from  the  corresponding  visual  angle,  which 
is  generally  firom  60  to  90  seconds. 

Perimetry. — In  order  to  test  indirect  vision,  we  may  use  the  perit?ieter  of  Aubert  and  Forster. 
The  eye  is  placed  opposite  a  fixed  point,  from  which  a  semicircle  proceeds,  so  that  the  eye  lies  in  the 
centre  of  it.  As  the  semicircle  rotates  round  the  fixed  point,  on  rotating  the  former  we  can  circum- 
scribe the  surface  of  a  hemisphere,  in  the  centre  of  which  the  eye  is  placed.  Proceeding  from  the 
fixed  point,  objects  are  placed  upon  semicircles,  and  are  gradually  pushed  more  and  more  toward  the 


820 


M  HARDY  S    PERIMETER. 


periphery  of  the  field  of  vision,  until  the  ol>ject  becomes  indistinct,  and  finally  disajijx;ars.  The  process 
of  testini;  is  continued  by  placing  the  arc  successively  in  the  different  meridians  of  the  field  of  vision. 
[M'Hardy's  perimeter  is  a  very  convenient  form  (Fig.  55S).  It  consists  of  two  ujirights  (C  and 
D),  which  are  fixed  to  the  opposite  ends  of  a  tlat  basal  plate  (A).'  C  carries  an  arrangement  for  sup- 
porting the  patient's  head,  while  D  carries  the  automatic  arrangement  lor  the  perimetric  record.  Both 
of  these  can  be  raised  or  dei^ressed  by  the  screws  (Cj  and  /').  The  patient's  chin  rests  on  tlie  chin- 
rest  (E),  while  in  the  mouth  is  placed  Landoll's  l)iting  fixation  (L),  which  is  detachable.  The  posi- 
tion of  the  head  can  be  altered  by  sliding  F  on  L,  which  can  be  fixed  in  any  position  by  the  screw 


'initu 


Horizontal  section  of  the  right  eye.  «,  cornea;  ^.conjunctiva;  c,  sclerotic;  d,  anterior  chamber  containing  the 
aqueous  humor  ;  e,  iris  ;  _/"/',  pupil  ;  g,  posterior  chamber;  /,  Petit's  canal ;  j,  ciliary  muscle  ;  k,  corneo-scleral 
limit ;  :,  canal  of  Schlemm  ;  >«,  choroid  ;  «,  retina  ;  o,  vitreous  humor  ;  A'o,  optic  nerve  ;  y,  nerve  sheaths  ;  /, 
nerve-fibres  ;  /c,  lamina  cribrosa.  The  line  O  A  indicates  the  optic  axis  ;  S  r,  the  a.\is  of  vision  ;  r,  the  posi- 
tion of  the  fovea  centralis. 


(O).  The  porcelain  button  (I)  just  below  the  patient's  eye  (/)  is  connected  with  the  adjustment  of 
the  "  fixation  point."  The  automatic  recording  apparatus  consists  of  a  revolving  quadrant  (>4,  ^,), 
which  describes  a  hemisphere  round  a  horizontal  axis  passing  through  the  centre  of  the  hollow  male 
axle,  turning  in  the  female  end  of  a,  which  is  supported  by  D.  The  quadrant  can  be  fixed  at  any 
point  by  <>-.  On  the  front  concave  surface  of  the  quadrant  is  fixed  a  circular  white  piece  of  ivory, 
representing  the  "  fixation  point,"  from  which  a  needle  projects,  and  which  is  the  zero  of  the  instru- 
ment. A  carriage  (?'),  in  which  the  test  objects  are  placed,  can  be  moved  in  the  concave  face  of  the 
quadrant  by  means  of  the  milled  head  (y),  which  moves  the  carriage  by  means  of  a  tooth  and  pinion 
wheel.] 


PRIESTLEY   SMITH  S    PERIMETER. 

Fig.  558. 


821 


M'Hardy's  perimeter,  I,  porcelain  button;  M,  bit;  E,  for  fixing  the  head;  ^,  A,  quadrant ;  o,  fixation  point;/, 
pointer  for  piercing  the  record  chart  held  in  the  frame  {e)  which  moves  on  c ;  D,  upright  supporting  the  quadrant 
and  the  automatic  arrangement  of  slides  (A  and  I),  which  are  moved  hyj. 


[When  the  milled  head  (j)  is  turned,  it  moves  the 
carriage  and  two  slides  (/&  and  /),  the  two  slides 
moving  in  the  ratio  of  2  to  i.  The  rate  of  the  carriage 
is  so  adjusted  that  it  travels  ten  times  faster  than  /, 
and  five  times  faster  than  /e.  The  pointer  (/)  is  con- 
nected with  these  slides,  so  that  it  moves  when  they 
move,  and  records  its  movements  by  piercing  the 
record  chart,  which  is  fixed  in  the  double-faced 
frame  (f).  The  frame  for  the  record  chart  is  hinged 
near  c  to  the  upright  (D).  The  frame,  when  upright, 
comes  so  near  the  pointer  that  the  latter  can  pierce  a 
chart  placed  in  the  frame.  The  patient  is  directed  to 
look  at  the  "  fixation  point,"  which  is  merely  a  small 
ivory  button  placed  in  the  imaginary  axis  of  the  hemi- 
sphere on  the  front  of  the  centre  of  the  concave  surface 
of  the  quadrant ;  the  projecting  needle  point  (o)  indi- 
cates its  position.  This  is  the  zero  of  the  quadrant, 
and  on  each  side  of  it  the  quadrant  is  divided  into 
90°.] 

[In  testing  the  field  of  vision,  place  the  carriage 
so  as  to  cover  zero,  adjust  the  eye  for  the  fixation 
point,  and  look  steadily  at  it,  when,  if  all  is  right, 
the  pointer  ( p)  ought  to  pierce  the  centre  of  the 
chart.  Move  the  carriage  along  the  quadrant  by 
y  until  it  disappears  from  the  field  of  vision,  and 
when  it  does  so  the  pointer  is  made  to  pierce  the 
chart.  Make  another  observation  in  another  direc- 
tion by  altering  the  position  of  the  quadrant,  an'l 
go  on  doing  so  until  a  complete  record  is  obtained 


Fig.  559. 


Priestley  Smith's  Perimeter. 


822 


PERIMETRIC    CHARTS. 


of  the  field  of  vision.  Test  the  other  eye  in  the  same  way.  The  color  field  may  he  tested  hy  using 
colored  papers  in  the  carriasjc] 

[Priestley  Smith's  Perimeter  (Fig.  559V — The  wooden  knob  on  the  left  of  the  figure  is  placed 
under  the  eye  of  the  p.iticnt,  who  stares  at  the  fixed  jxjint  in  the  axis  of  the  (juadrant,  which  can  be 
moved  in  any  meridian.  The  test  object  is  a  square  piece  of  white  paper,  which  is  moved  along  the 
quadrant  The  chart  is  placed  on  the  posterior  surface  of  the  hand  wheel  and  moves  with  it,  so  that 
the  meridians  of  the  chart  move  with  the  quadrant.  There  is  a  scale  behind  the  hand  wheel  corre- 
sjiondinij  with  the  circles  on  the  chart,  so  that  the  observer  can  prick  off  his  observations  directly.] 

[Scotoma  is  tlic  term  applied  to  dimness  or  blindness  in  certain  parts  of  the  field  of  vision, 
which  may  be  central,  marginal,  or  in  patches.] 

The  capacity  for  distinguishing  colors  diminishes  more  rapidly  at  the  periphery  of  the  retina, 
than  that  for  distinguishing  differences  in  the  brightness  or  intensity  of  light.  In  fact,  the  periphery 
of  the  retina  is  slightly  red  blind.  The  diminution  is  greater  in  the  vertical  meridian  of  the  eye 
than  in  the  horizontal,  and  it   diminishes  with   the   distance  from  the   fixation   point  [Aubert  and 

Fig.  560. 


Perimetric  chart  of  a  healthy  and  a  diseased  eye. 


Forster).  These  observers  also  state  that,  during  accommodation  for  a  distant  object,  the  diminution 
of  the  capacity  to  distinguish  brightness  and  color  toward  the  periphery  of  the  lens,  occurs  more 
rapidly  than  with  near  vision.  The  excitability  of  the  retina  for  colors  and  brightness  is  greater 
at  a  point  equally  distant  from  the  fovea  centralis  on  the  temporal  than  on  the  nasal  side  of  the 
eye  (Sf/ion). 

Perimetric  Chart. — If  the  arc  of  the  perimeter  (Fig.  559)  be  divided  into  90  degrees,  beginning 
at  the  fixation  point  (central  point),  and  proceeding  to  L  and  M  (Fig.  560);  and  if  a  .series  of 
concentric  circles  be  inscribed  on  this,  with  the  point  of  fixation  as  their  centre,  we  can  construct  a 
topographical  chart  of  the  visual  capacity  of  the  normal  or  healthy  eye  from  the  data  obtained  by 
the  examination  of  the  retina. 

Fig.  560  is  an  example ;  the  i/izci  lines  indicate  a  diseased  eye,  the  corresponding  fkhi  lines  a 
healthy  eye.  The  continuous  line  indicates  the  limits  for  the  perception  of  white;  the  interrupted 
line  that  for  blue;  the  punctuated  and  interrupted  line  that  for  red ;  ;«  is  the  blind  spot.  In  the 
normal  eye  the  limits  for  the  perception  of  colors  are  as  follows : — 


RETINAL   STIMULATION OPTOGRAM.  823 


Externally, 
Internally, 
Upward,  . 
Downward, 


7o°-88° 
50°-6o° 

45°-55° 
650-70° 


Blue. 


65° 
60° 

45° 
60° 


Red. 


60° 
50° 
40° 
50° 


Green. 


40° 

40° 

30°-35° 

35° 


V.  Specific  Energy. — The  rods  and  cones  alone  are  endowed  with  what 
Johannes  Miiller  called  '■'specific  energy,''''  i.  e.,  they  alone  are  set  into  activity  by 
the  ethereal  vibrations,  to  produce  those  impulses  which  result  in  vision.  Mechan- 
ical 2s\^  electrical  stimuli,  however,  when  applied  to  any  part  of  the  course  of  the 
nervous  apparatus,  produce  visual  phenomena.  Mechanical  stimuli  are  more  intense 
stimuli  than  light  rays,  as  is  shown  by  performing  the  dark-pressure  figure  with  the 
eyes  open  (§  393,  5,  a),  whereby  the  circulation  in  the  retina  is  interfered  with; 
in  the  region  of  pressure,  we  cannot  see  external  objects  which  affect  the  retina 
uniformly  and  continuously. 

VI.  The  duration  of  the  retinal  stimulation  must  be  exceedingly  short,  as 
the  electrical  spark  lasts  only  0.000000868  second ;  still,  as  a  general  rule,  a  shorter 
time  is  required,  the  larger  and  brighter  the  object  looked  at.  Alternate  stimu- 
lation with  light  17  to  18  times  per  minute,  is  perceived  most  intensely  {Brilcke). 
Further,  an  increase  or  diminution  of  o.oi  part  of  the  intensity  of  the  light  is 
perceptible  (§  383).  A  shorter  time  is  required  to  perceive  yellow  than  is  required 
for  violet  and  red  {yierorcW).  The  retina  becomes  more  sensitive  to  light,  after  a 
person  has  been  kept  in  the  dark  for  a  long  time,  and  also  after  repose  during  the 
night.  If  light  be  allowed  to  act  on  the  eyes  for  a  long  time,  and  especially  if  it 
be  intense,  it  causes  fatigue  of  the  retina,  which  begins  sooner  in  the  centre  than 
in  the  periphery  of  the  organ  (^AuberC).  At  first  the  fatigue  comes  on  rapidly  and 
afterward  develops  more  slowly — it  is  most  marked  in  the  morning  {A.  Pick). 
The  periphery  of  the  retina  is  specially  characterized  by  its  capacity  for  distin- 
guishing movements  (^Exner). 

VII.  Visual  Purple. — The  mode  of  the  action  of  light  upon  the  end  organs 
of  the  retina  has  already  been  referred  to  (p.  789)  in  connection  with  the  "  visual 
pu7'ple''''  or  rhodopsin  {Boll,  Kiihne).  Kiihne  showed  that,  by  illuminating  the 
retina,  actual  pictures  {e.  g.  the  image  of  a  window)  could  be  produced  on  the 
retina,  but  they  gradually  disappeared.  From  this  point  of  view  we  might  regard 
the  retina  as  comparable,  to  a  certain  extent,  to  the  sensitive  plate  of  a  photographic 
apparatus. 

Optogram. — The  visual  purple  is  formed  by  the  pigment  epithelium  of  the  retina.  Perhaps  we 
might  compare  the  process  to  a  kind  of  secretion.  The  visual  purple  may  be  restored  in  a  retina  by 
laying  the  latter  upon  living  choroidal  epithelium.  The  pigment  disappears  from  the  mammalian 
retina  by  the  action  of  light  60  times  more  rapidly  than  from  the  retina  of  the  frog.  In  a  rabbit's 
eye,  whose  pupil  was  dilated  with  atropin,  Ewald  and  Kiihne  obtained  a  sharp  picture  or  optogram 
of  a  bright  object  placed  at  a  distance  of  24  cm.  from  the  eye — the  image  was  "  fixed  "  by  a  4  per 
cent,  solution  of  alum.  Vibual  purple  withstands  all  the  oxidizing  reagents ;  zinc  chloride,  acetic 
acid,  and  corrosive  sublimate  change  it  into  a  yellow  substance — it  becomes  white  only  through  the 
action  of  light ;  the  dark  heat  rays  are  without  effect,  while  it  is  decomposed  above  a  temperature  of 
52°  C.  [As  visual  purple  is  absent  from  the  cones,  and  cones  only  are  present  in  the  fovea  centralis, 
we  cannot  explain  vision  by  optograms  formed  by  the  visual  purple.] 

VIII.  Destruction  of  the  rods  and  cones  of  the  retina  causes  corresponding 
dark  spots  in  the  field  of  vision. 

396.  PERCEPTION  OF  COLORS. — Physical. — The  vibrations  of  the  light  ether  are  per- 
ceived by  the  retina  only  within  distinct  limits.  If  a  beam  of  white  light,  e.g.,  from  the  sun,  be 
transmitted  through  a  prism,  the  light  rays  are  refracted  and  dispersed,  and  a  "  prismatic  spectrum  " 
is  obtained  (Fig.  17).  Whiite  light  contains  rays  of  very  different  wave  lengths  or  periods  of  vibration. 
The  dark  heat  rays,  whose  wave  length  is  0.00194  mm.,  are  refracted  least  {^Fizeau).     They  do  not 


824  PERCEPTION    OF   COLORS. 

act  upon  the  retina,  and  are  therefore  invisible.  They  act,  however,  upon  sensory  nerves.  Aoou. 
90  per  cent,  of  these  rays  is  absorbed  by  the  media  of  the  eye  [Briicl-e  and  Ktioblaticli).  From 
Frauenhofer's  line,  A,  onward,  the  oscillations  of  the  light  ether  excite  the  retina  in  the  following 
order:  /iV(/ with  4S1  billions  of  vibrations  per  second,  oram^e  with  ^t,2,  ye/hmi  with  563,  ^v^fw  with 
607,  l>liie  with  653,  indigo  with  676,  and  violet  with  764  billion  vibrations  per  second.  The  sen- 
sation of  color  therefore  depends  on  the  number  of  vibrations  of  the  light  ether,  just  as  the 
pitch  of  a  note  depends  on  the  number  of  vibrations  of  the  sounding  body  [A'ewton,  1704;  Hartley, 
1 772V  Beyond  the  violet  lie  the  chemically-active  [actinic]  rays  of  the  spectrum.  After  cutting 
out  all  the  spectrum,  including  the  violet  rays,  v.  Helmholtz  succeeded  in  seeing  the  ultra'^violet  rays, 
which  had  a  feeble  grayish-blue  color.  The  heat  rays  in  the  colored  part  of  the  spectrum  are  trans- 
mitted by  the  media  of  the  eye  in  the  same  way  as  through  water.  The  existence  of  the  ultra-violet 
rays  is  best  ascertained  by  the  phenomenon  of  fluorescence.  \'on  Helmholtz,  on  illuminating  a 
solution  of  sulphate  of  quinine  with  the  ultra-violet  rays,  saw  a  bluish-white  light  proceeding  from 
all  parts  of  the  solution  which  were  acted  on  by  the  ultra-violet  rays.  As  the  media  of  the  eye 
themselves  exhibit  fluorescence  {v.  Helmholtz),  they  must  increase  the  power  of  the  retina  to  distin- 
guish these  rays.     The  ultra-violet  rays  are  not  largely  absorbed  by  the  media  of  the  eye  [Briicke). 

In  order  that  a  color  be  perceived,  it  is  essential  that  a  certain  amount  of  light  fall  upon  the  retina. 
Blue,  when  at  the  lowest  degree  of  brightness,  gives  a  color  sensation  with  an  amount  of  light  which 
is  sixteen  times  less  than  that  required  for  red  {Dobro~wloskyY 

Intensity  of  the  Impression  of  Light. — ^Vhile  light  of  different  periods  of  vibration  applied 
to  the  eye  excites  the  different  sensations  of  color,  the  amplitude  of  the  vibrations  (height  of  the 
waves)  determines  the  intensity  of  the  impression  of  light;  just  as  the  loudness  of  a  note  depends 
on  the  ampHtude  of  the  vibrations  of  the  sounding  body.  The  sun's  light  contains  all  the  rays  which 
excite  the  sensation  of  color  in  us,  and  when  all  these  rays  fall  simultaneously  upon  the  retina  we  ex- 
perience the  sensation  of  white.  If  the  colors  of  the  spectrum  ol)tained  by  means  of  a  prism  be 
reunited,  white  light  is  again  obtained.  If  no  vibrations  of  the  light-ether  reach  the  retina,  every 
sensation  of  light  and  color  is  absent,  but  we  can  scarcely  apply  the  term  black  to  this  condition. 
It  is  rather  the  absence  of  sensation,  such  as,  for  example,  is  the  case  when  a  beam  of  light  falls 
on  the  skin  of  the  back.  This  does  not  give  the  sensation  of  black,  but  rather  that  of  no  sensation 
of  light. 

Simple  and  Mixed  Colors. — We  distinguish  simple  colors,  e.  g.,  those  of 
the  spectrum.  In  order  to  perceive  these,  the  retina  must  be  excited  (set  into 
vibration)  by  a  distinct  number  of  oscillations  (see  above).  Further,  we  distinguish 
"mixed  colors,"  whose  sensations  are  produced  when  the  retina  is  excited  by 
two  or  more  simple  colors,  simultaneously  or  rapidly  alternating.  The  most  com- 
plex mixed  color  is  white,  which  is  composed  of  a  mixture  of  all  the  simple 
colors  of  the  sjjectrum. 

The  "  complementary  colors"  are  important.  Any  two  colors  which 
together  give  the  sensation  of  white  are  complementary  to  each  other.  The  "  con- 
trast colors"  are  mentioned  here  merely  to  complete  the  list.  They  are  closely 
related  to  the  complementary  colors.  Any  two  colors  which,  when  mixed,  supple- 
ment the  generally  prevailing  tone  of  the  light,  are  contrast  colors.  When  the  sky 
is  blue,  the  two  contrast  colors  must  be  bhiish-white  :  with  bright  gaslight  they  must 
be  yellowish-white,  and  in  pure  white  light  of  course  all  the  complementary  are  the 
same  as  the  contrast  colors  {^Briicke). 

Methods  of  Mixing  Colors. — i.  Two  solar  spectra  are  projected  upon  a  screen,  and  the  spectra 
are  so  arranged  as  to  cause  any  one  part  of  one  spectrum  to  cover  any  part  of  the  other. 

2.  Look  obliquely  through  a  vertically  arranged  glass  plate  at  a  color  placed  behind  it.  Another 
color  is  placed  m  front  of  the  glass  plate,  so  that  its  image  is  also  reflected  into  the  eye  of  the  observer; 
thus,  the  light  of  one  color  transmitted  through  the  glass  plate  and  the  reflected  light  from  the  other 
color  reach  the  eye  simultaneously.  [Lambert's  Method. — This  is  easily  done  by  Lambert's 
method.  Use  colored  wafers  and  a  slip  of  glass ;  place  a  red  wafer  on  a  sheet  of  black  paper,  and 
about  3  inches  behind  it  another  blue  one.  Hold  the  plate  of  glass  midway  and  vertically  between 
them,  and  so  incline  the  glass  that,  while  looking  through  it  at  the  red  wafer,  a  reflected  image  of  the 
blue  one  will  be  projected  into  the  eye  in  the  same  direction  as  that  of  the  red  image,  when  we  have 
the  sensation  of  purple], 

3.  A  rotatory  disk,  with  sectors  of  various  colors,  is  rapidly  rotated  in  front  of  the  eyes.  On  rapidly 
rotating  the  colored  disk,  the  impressions  produced  by  the  individual  colors  are  united  to  produce  a 
mixed  color.  If  the  rotating  disk,  which  yields,  let  us  suppose,  white,  on  mixing  the  colors  of  the 
spectrum,  be  reflected  in  a  rapidly  rotating  mirror,  then  the  individual  components  of  the  while 
reappear. 

4.  Place  in  front  of  each  of  the  small  holes  in  the  cardboard  used  for  Scheiner's  experiment 


GEOMETRICAL   COLOR   TABLE. 


825 


(Fig.  537)  two  differently  colored  pieces  of  glass  ;  the  colored  rays  of  light  passing  through  the  holes 

unite  on  the  retina,  and  produce  a  mixed  color  [CzermaJi). 

Complementary  Colors. — Investigation  shows  that  the  following  colors  of  the  spectrum  are 

complementary,  {.  e.,  every  pair  gives  rise  to  white : — 

Red  and  greenish-blue,  Orange  and  Cyan  blue. 

Yellow  and  indigo  blue,  '  Greenish-yellow  and  violet, 

while  green  has  the  compound  complementary  color,  purple  {v.  Hehnholtz). 

The  mixed  colors  may  be  determined  from  the  following  table.     At  the  top  of  the  vertical  and 

horizontal  columns  are  placed  the  simple  colors ;  the  mixed  colors  occur  where  they  intersect  the 

corresponding  vertical  and  horizontal  columns  (Dk.  =  dark;  wh.  =  whitish) : — 


Violet. 

Indigo. 

Cyan  blue. 

Bluish-green. 

Green. 

Greenish- 
yellow. 

Yellow. 

Red 
Orange 
Yellow 
Gr. -yellow 
Green 

Bluish -green 
Cyan  blue 

Purple 
Dk.  rose 
Wh.  rose 
White 
White-blue 
Water  blue 
Indigo 

Dk.  rose 
Wh.  rose 
White 
Wh.-green 
Water  blue 
Water  blue 

Wh.  rose 

White 

Wh.-green 

Wh.-green 

Bl.-green. 

White 
Wh.-yellow 
Wh.-yellow 
Green 

Wh.-yellow 

Yellow 

Gr.-yellow 

Gold-yellow 
Yellow 

Orange 

The  following  results  have  been  obtained  from  observations  on  the  mixture  of 
colors : — 

1.  If  two  simple,  but  non-complementary,  spectral  colors  be  mixed  with  each 
other,  they  give  rise  to  a  color  sensation,  which  may  be  represented  by  a  color 
lying  in  the  spectrum  between  both,  and  mixed  with  a  certain  quantity  of  white. 
Hence  we  may  produce  every  impression  of  mixed  colors  by  a  color  of  the  spec- 
trum -L  white  (^Grassmati). 

2.  The  less  white  the  colors  contain,  the  more  "  saturated  "  they  are  said  to 
be ;  the  more  white  they  contain,  the  more  unsaturated  do  they  appear.  The 
saturation  of  a  color  diminishes  with  the  intensity  of  the  illumination. 

Geometrical  Color  Table. — Since  the  time  of  Newton,  attempts  have  been  made  to  construct 
a  so-called  "  geometrical  color  table,"  which  will  enable  any  mixed  color  to  be  readily  found.  Fig. 
561  shows  such  a  color  table  ;  white  is  placed 
in  the  middle,  and  from  it  to  every  point  in 
the  curve — which  is  marked  with  the  names 
of  the  colors — suppose  each  color  to  be  so 
placed  that,  proceeding  from  white,  the  colors 
are  arranged,  beginning  with  the  brightest 
tone,  always  followed  by  the  most  saturated 
tone,  until  the  pure  saturated  spectral  color 
lies  in  the  point  of  the  curve  marked  with 
the  name  of  the  color.  The  mixed  color, 
purple,  is  placed  between  violet  and  red.  In 
order  to  determine  from  this  table  the  mixed 
color  of  any  two  spectral  colors,  unite  the 
points  of  these  colors  by  a  straight  line. 
Suppose  weights  corresponding  to  the  units 
of  intensity  of  these  colors,  to  be  placed  on 
both  points  of  the  curve  indicating  colors, 
then  the  position  of  the  centre  of  gravity  of 
both  in  the  line  connecting  the  colors  indi- 
cates the  position  of  the  mixed  color  in  the 
table.  The  mixed  color  of  two  .spectral 
colors  always  lies  in  the  color  table  in  the 
straight  line   connecting  the  two  color  points. 


Vioiet 


YeUow 


Orange 


Red 


Geometrical  color  cone  or  table. 


Further,  the  impression  of  the  mixed  color  cor- 
responds to  an  intermediate  spectral  color  mixed  with  white.  The  complementary  color  of  any 
spectral  color  is  found  at  once  by  making  a  line  from  the  point  of  tliis  color  through  white,  until  it 
intersects  the  opposite  margin  of  the  color  table;  the  point  of  intersection  indicates  the  complementary 
color.  If  pure  white  be  produced  by  mixing  two  complementary  co'ors,  the  color  lying  nearest 
white  on  the  connecting  line  must  be  specially  strons;,  as  then  only  would  the  centre  of  gravity  of 
the  lines  uniting  both  colors  lie  in  the  point  marked  white. 


826 


YOUNG-HELMHOLTZ   THEORY    OF   COLOR    SENSATION. 


By  means  of  the  color  table  we  may  ascertain  the  mixed  color  of  three  or  more  colors.  For 
example,  it  is  required  to  find  the  mixed  color  resuhin;T  from  the  union  of  the  point,  a  (pale  yellow), 
/'  (fairly  saturated  l)luisli-gieen),  and  c  (fairly  saturated  blue).  On  the  three  jxiints  place  weights 
corresixjnding  to  their  intensities,  and  ascertain  the  centre  of  gravity  of  the  weight,  a,  />,  c  ;  it  will 
lie  at  /.  It  is  obvious,  however,  that  the  impression  of  this  mixed  color,  whitish  green-blue,  can  be 
produced  by  green-blue  -J-  white,  su  that  /  may  be  also  the  centre  of  gravity  of  two  weights,  which 
lie  in  the  line  connecting  white  and  green-blue. 

We  may  describe  a  triangle,  V,  Gr,  R,  about  the  color  table  so  as  to  enclose  it  completely.  The 
three  fundamental  or  primary  colors  lie  in  the  angles  of  this  triangle,  red,  green,  violet.  It  is 
evident  that  each  of  the  colored  impressions,  /.  e.,  any  point  of  the  color  table,  may  be  determined 
by  placing  weights  corresponding  to  the  intensity  of  the  primary  colors  at  the  angles  of  the  triangle, 
so  that  the  point  of  the  color  table,  or  what  is  the  same  thing,  the  desired  mixed  color,  is  the  centre 
of  gravity  of  the  triangle  with  its  angles  weighted  as  above.  The  intensity  of  the  three  primary 
colors,  in  order  to  proiluce  the  mixed  color,  must  be  represented  in  the  same  proportion  as  the 
weights. 

Theories. — Various  theories  have  been  proposed  to  account  for  color  sensation. 

1.  According  to  one  theory,  color  sensation  is  produced  by  one  kind  of  element  present  in  the 
retina,  being  excited  in  different  ways  by  light  of  different  colors  (oscillations  of  the  light  ether  of 
different  wave  lengths,  number  of  vibrations,  and  refractive  indices). 

2.  Young-Helmholtz  Theory. — The  theory  of  Thomas  Young  (1807)  and 
V.  Helmholtz  (1852)  assumes  that  three  different  kinds  of  nerve  elements, 
corresponding  to  the  three  primary  colors,  are  present  in  the  retina.  Stimulation 
of  the  first  kind  causes  the  sensation  of  red,  of  the  second  green,  and  of  the 
third  violet. 

The  elements  sensitive  to  red  are  most  strongly  excited  by  light  with  the  longest  wave  length,  the 
red  rays ;  those  for  green  by  medium  wave  lengths,  green  rays ;  those  for  violet  by  the  rays  of  shortest 
wave  length,  violet  rays.  Further,  it  is  assumed,  in  order  to  explain  a  number  of  phenomena,  that 
every  color  of  the  spectrum  excites  all  the  kinds  of  fibres,  some  of  them  feebly,   others   strongly. 


Fig.  562. 


Suppose  in  Fig.  562  the  colors  of  the  spectrum  are  arranged  in  their  natural  order  from  red  to  violet 
horizontally,  then  the  three  curves  raised  upon  the  abscissa  might  indicate  the  strength  of  the  stimu- 
lation  of  the  three  kinds  of  retinal  elements.  The  continuous  curve  corresponds  to  the  rays  pro- 
ducing the  sensation  of  red,  the  dotted  line  that  of  green,  and  the  broken  line  that  of  violet.  Pure 
rc</ light,  as  indicated  by  the  height  of  the  ordinates  in  R,  strongly  excites  the  elements  sensitive  to 
red,  and  feebly  the  other  two  kinds  of  terminations,  resulting  in  the  sensation  of  red.  Simple 
yellow  excites  moderately  the  elements  for  red  and  green,  and  feebly  those  for  violet  =  sensation  of 
yellozii.  Simple  green  excites  strongly  the  elements  for  green,  but  much  more  feebly  the  two  other 
kinds  ==  sensation  of  j^reen.  Simple  blue  excites  to  a  moderate  extent  the  elements  for  green  and 
violet ;  more  feebly  those  for  red  ==  sensation  of  bine.  Simple  violet  excites  strongly  the  corre- 
sponding elements,  feebly  the  others  =  sensation  of  violet.  Stimuhtion  of  any  two  elements 
excites  the  impression  of  a  mixed  color ;  while,  if  all  of  them  be  excited  in  a  nearly  equal  degree, 
the  sensation  of  white  is  produced.  As  a  matter  of  fact,  the  Young-Helmholtz  theory  gives  a  simple 
explanation  of  the  phenomena  of  the  physiological  doctrine  of  color.  It  has  been  attempted  to 
make  the  results  obtained  by  examination  of  the  structure  of  the  retina  accord  with  this  view. 
According  to  Max  Schultze,  the  cones  alone  are  end  organs  connected  with  the  perception  of  color. 
The  presence  of  longitudinal  striation  in  their  outer  segments  is  regarded  as  constituting  them  multiple 
terminal  end  organs.  Our  power  of  color  sensation,  so  far  as  it  depends  on  the  retina,  would,  on 
this  view  of  the  matter,  bear  a  relation  to  the  number  of  cones.  The  degree  of  color  sensation  is 
most  developed  in  the  macula  lutea,  which  contains  only  cones,  and  diminishes  as  the  distance 
from  the  point  increases,  while  it  is  absent  in  the  peripheral  parts  of  the  retina.  The  rods  of  the 
retina  are  said  lo  be  concerned  only  with  the  capacity  to  distinguish  between  quantitative  sensations 
of  light. 


hering's  theory.  827 

3.  Hering's  Theory. — Ew.  Hering,  in  order  to  explain  the  sensation  of  Hght,  proceeds  firom  the 
axiom  stated  under  I,  p.  825.  What  we  are  conscious  of,  and  call  a  visual  sensation,  is  the  physical 
expression  for  the  metabolism  in  the  visual  substance  ["■  Sehstibsianz^^),  i.  e.,  in  those  nerve 
masses  which  are  excited  in  the  process  of  vision.  Like  every  other  corporeal  matter  this  substance 
during  the  activity  of  the  metabolic  process  undergoes  decomposition  or  "  disassimilation  "  ;  while 
during  rest  it  must  be  again  renewed,  or  "  assimilate  "  new  material.  Hering  assumes  that  for  the 
perception  of  white  and  black,  two  different  qualities  of  the  chemical  processes  take  place  in  the 
visual  substance,  so  that  the  sensation  of  white  corresponds  to  the  disassimilation  (decomposition), 
and  that  of  black  to  the  assimilation  (restitution)  of  the  visual  substance.  According  to  this 
view,  the  different  degrees  of  distinctness  or  intensity  with  which  these  two  sensations  appear,  occur 
in  the  several  transitions  between  pure  white  and  deep  black ;  or  the  proportions  in  which  they 
appear  to  be  mixed  (gray),  correspond  to  the  intensity  of  these  two  psycho-physical  processes. 
Thus,  the  consumption  and  restitution  of  matter  in  the  visual  substance  are  the  primary  processes  in 
the  sensation  of  white  and  black.  In  the  production  of  the  sensation  of  white,  the  consumption  of 
the  visual  substance  is  caused  by  the  vibrating  ethereal  waves  acting  as  the  discharging  force  or 
stimulus,  while  the  degree  of  the  sensation  of  whiteness  is  proportional  to  the  quantity  of  the  matter 
consumed.  The  process  of  restitution  discharges  the  sensation  of  black ;  the  more  rapidly  it 
occurs  the  stronger  is  the  sensation  of  black.  The  consiDuplion  of  the  visual  substance  at  one 
place  cattses  a  greater  restitutio7t  in  the  adjoining  parts.  Both  processes  influence  each  other 
simultaneously  and  conjointly.  [In  the  production  of  a  visual  sensation,  it  is  important  to  remember 
that  the  condition  of  one  part  of  the  retina  influences  contemporaneously  the  condition  of  adjoining 
parts  of  the  retina,  i.  e.,  "  the  sensation  which  arises  through  the  stimulation  of  any  given  point  of 
the  retina,  is  also  a  function  of  the  state  of  6ther  immediately  contiguous  points."]  This  explains 
physiologically  the  phenomenon  of  contrast  of  which  the  old  view  could  give  only  a  psychical  in- 
terpretation (p.  832). 

Similarly,  color  sensation  is  regarded  as  a  sensation  of  decomposition  (disassimilation)  and  of 
restitution  (assimilation) ;  in  addition  to  white,  red  and  yellow  are  the  expression  of  decomposi- 
tion ;  while  green  and  blue  represent  the  sensation  of  restitution.  Thus,  the  visual  substance  is 
subject  to  three  different  ways  of  chemical  change  or  metabolism.  We  may  explain  in  this  way  the 
c^/or^i/ phenomena  of  contrast  and  the  complimentary  after  images.  The  sensation  of  black  white 
may  occur  simultaneously  with  all  colors;  hence,  every  color  sensation  is  accompanied  by  that  of 
dark  or  bright,  so  that  we  cannot  have  an  absolutely  pure  color.  There  are  three  different  constitu- 
ents of  the  visual  substance;  that  connected  with  the  sensation  of  black-white  (colorless),  that  with 
blue-yellow,  and  that  with  red-green.  All  the  rays  of  the  visible  spectrum  act  in  disassimilating  the 
black-white  substance,  but  the  different  rays  act  in  different  degrees.  The  blue-yellow  or  the  red- 
green  substances,  on  the  other  hand,  are  disassimilated  only  by  certain  rays,  some  rays  causing  assimi- 
lation, while  others  are  inactive.  Mixed  light  appears  colorless  when  it  causes  an  equally  strong  dis- 
assimilation and  assimilation  in  the  blue-yellow  and  in  the  red-green  substance,  so  that  the  two 
processes  mutually  antagonize  each  other,  and  the  action  on  the  black-white  substance  appears  pure. 
Two  objective  kinds  of  light,  which  together  yield  white,  are  not  to  be  regarded  as  complementary, 
but  as  antagonistic,  kinds  of  hght,  as  they  do  not  supplement  each  other  to  produce  white,  but  only 
allow  this  to  appear  pure,  because,  being  antagonistic,  they  mutually  prevent  each  other's  action. 

The  imperfection  of  the  Young-Helmholtz  theory  of  color  sensation  is  that  it  recognizes  only  one 
kind  of  excitability,  excitement  and  fatigue  (corresponding  to  Hering's  disassimilation),  and  that  it 
ignores  the  antagonistic  relation  of  certain  light  rays  to  the  eye.  It  does  not  regard  white  as  consist- 
ing of  complementary  light  rays,  which  neutralize  each  other  by  their  action  on  the  colored  visual 
substance,  but  as  uniting  to  form  white  i^Hering). 

[While  it  suffices  to  explain  a  great  many  of  the  phenomena  of  light  and  color,  e.g.,  the  mixing  of 
colors  and  complementary  colors,  it  does  not  satisfactorily  explain  contrast  or  color  blindness.  Fick 
admits  that  it  does  not  explain  the  following  important  fact :  Every  ray  of  light,  while  exciting  a  color 
sensation  if  it  falls  on  a  sufficient  area  of  the  posterior  polar  part  of  the  eyeball,  provided  it  acts  on 
an  extremely  limited  part  of  the  retina,  even  if  it  be  colored  light,  produces  a  whitish  impression. 
This  is  exactly  the  opposite  of  what  we  should  expect,  viz.,  the  smaller  the  area  of  retina  acted 
on,  the  more  readily  should  the  particular  nerve  ending  be  excited  and  a  pure  color  sensation 
result.] 

In  applying  this  theory  to  color  blindness  (§  397),  we  must  assume  that 
those  who  are  red-blind  want  the  red-green  visual  substance ;  there  are  but  two 
partial  spectra  in  their  solar  spectrum,  the  black-white  and  the  yellow-blue.  The 
position  of  green  appears  to  such  an  one  to  be  colorless ;  the  rays  of  the  red  part 
of  the  spectrum  are  visible,  so  far  as  the  sensation  of  yellow  and  white  produced 
by  these  rays  is  strong  enough  to  excite  the  retina.  Hering  divides  his  spectrum 
into  a  yellow  and  a  blue  half.  A  violet-blind  person  wants  the  yellow-blue  visual 
substance  j  in  his  spectrum  there  are  only  two  partial  spectra,  the  black-white  and 
the   red-green.     In  cases  of  complete   color  blindness,   the  yellow-blue  and 


828  COLOR    BLINDNESS. 

red-green  substances  are  absent.  Hence,  such  a  person  has  only  the  sensation  of 
bright  and  dark.  The  sensibility  to  light  and  the  length  of  the  spectrum  are  re- 
tained ;  the  brightest  part  in  this  case,  as  in  the  normal  eye,  is  in  the  yellow 
{Heri/ig). 

397.  COLOR  BLINDNESS  AND  ITS  PRACTICAL  IMPORT- 
ANCE.— Causes. — \->\  the  term  color  blindness  ( dyschromatopsy)  is 
meant  a  pathological  condition  in  which  .some  individuals  are  unable  to  distinguish 
certain  colors.  Huddart  (1777)  was  acquainted  with  tlie  condition,  but  it  was  first 
accurately  described  by  Dalton  (1794),  who  himself  was  red  blind.  The  term 
color  blindness  was  given  to  it  by  Brewster. 

The  supporters  of  the  Young-Helmhohz  theory  assume  that,  corresponding  to  the  paralysis  of  the 
three  color  perceiving  elements  of  the  retina,  there  are  the  following  kinds  of  color  blindness : — 

I.  Red  blindness.       2.  Green  blindness.       3.  Violet  blindness. 
The  highest  degree  being  termed  complete  color  blindness. 

The  supporters  of  E.  Bering's  theorj-  of  color  sensation  distinguish  the  following  kinds: — 

1.  Complete  Color  Blindness  (Achromatopsy). —  The  spectrum  appears  achromatic;  the 
position  of  the  greenish-yellow  is  the  brightest,  while  it  is  darker  on  both  sides  of  it.  A  colored  pic- 
ture appears  like  a  photograph  or  an  engraving.  Occasionally  the  difierent  degrees  of  light  intensity 
are  perceived  in  one  shade  of  color,  e.  g.,  yellow,  which  cannot  be  compared  with  any  other  color. 
O.  Becker  and  v.  Hippel  observed  cases  of  unilateral  congenital  complete  color  blindness,  while  the 
other  eye  was  normal  for  color  perception. 

2.  Blue-yellow  blindness. — The  spectrum  is  dichromatic,  and  consists  only  of  red  and  green. 
The  blue-violet  end  of  the  spectrum  is  usually  greatlv  shortened.  In  pure  cases  only  the  red  and 
green  are  coirectly  distinguished  (Mauthner's  erythrochloropy),  but  not  the  other  colors.  Unilateral 
cases  have  been  observed. 

3.  Red-green  Blindness. — The  spectrum  is  also  dichromatic.  Yellow  and  blue  are  correctly 
distinguished  ;  violet  and  blue  are  both  taken  for  blue.  The  sensations  for  red  and  green  are  absent 
altogether.  There  are  several  forms  of  this — {a)  Green  blindness,  or  the  red-green  blindness, 
with  undiminished  spectrum  (Mauthner's  xanthokyanopy),  in  which  bright  green  and  dark  red  are 
confounded.  In  the  spectrum  yellow  abuts  directly  on  blue,  or  between  the  two,  at  most  there  is  a 
strip  of  gray.  The  maximum  of  brightne^s  is  in  the  yellow.  It  is  often  unilateral  and  often  heredi- 
tary. (/')  Red  blindness  (or  the  red-green  blindness  with  undiminished  spectrum,  also  called 
Daltonism ),  in  which  bright  red  and  dark  green  are  confounded.  The  spectrum  consists  of  yellow 
and  blue,  but  the  yellow  lies  in  the  orange.  The  red  end  of  the  spectrum  is  uncolored,  or  even  dark. 
The  greatest  brightness,  as  well  as  the  limit  between  yellow  and  blue,  lies  more  toward  the  right. 

4.  Incomplete  color  blindness,  or  a  diminished  color  sense,  indicates  the  condition  in  which  the 
acuteness  of  color  perception  is  fiiminished,  so  that  the  colors  can  be  detected  only  in  large  objects, 
or  only  when  they  are  near,  and  when  they  are  mixed  with  white  they  no  longer  appear  as  such.  A 
certain  degree  of  this  form  is  frequent,  in  as  far  as  many  persons  are  unable  to  distinguish  greenish- 
blue  from  bluish-green. 

Acquired  color  blindness  occurs  in  diseases  of  the  retina  and  atrophy  of  the  optic  nerve  in 
commencing  tabes,  in  some  forms  of  cerebral  disease  (p.  763),  and  intoxications.  At  first  green- 
blindness  occurs,  which  is  soon  followed  by  red  blindness.  The  peripheral  zone  of  the  retina 
suffers  sooner  than  the  central  area.  In  hysterical  per.sons  there  may  be  intermittent  attacks  of  color- 
blindness [Charcot) ;  and  the  same  occurs  in  hypnotized  persons  (p.  736). 

H.  Cohn  found  that,  on  heating  the  eyeball  of  some  color-blind  persons,  the  color  blindness 
disappeared  temporarily.  Occasionally  in  persons  without  a  lens  red  vision  is  present,  and  is  due  to 
unknown  causes.  Percentage. — Holmgren  found  that  2.7  per  cent,  of  persons  were  color  blind, 
most  being  red  &nA  green  blind,  and  very  few  violet  blind. 

Limits  of  Normal  Color  Blindness. — The  investigations  on  the  power  of  color  perception  in 
the  normal  retina  are  best  carried  out  by  means  of  Aubert-Forster's  perimeter,  or  that  of  MTIardy 
(?  395)'  It  's  found  that  oitr  color  perception  is  complete  only  in  the  middle  of  the  field  of  vision. 
Around  this  is  a  middle  zone,  in  which  only  blue  and  yellow  are  perceived,  in  which,  therefore, 
there  is  red  blindness.  Outside  this  zone,  there  is  a  peripheral  girdle,  where  there  is  complete  color 
blindness  (^  395).  Hence  a  red-blind  person  is  distinguished  from  a  person  with  normal  vision,  in 
that  the  central  area  of  the  normal  field  of  vision  is  absent  in  the  former,  this  being  rather  included 
in  the  middle  zone.  The  field  of  vision  of  a  green-blind  person  diflers  from  that  of  a  person  with 
normal  vision,  in  that  his  peripheral  zone  corresponds  to  the  intermediate  and  peripheral  zones  of  the 
normal  eye.  The  violet-blind  person  is  distinguished  by  the  complete  absence  of  the  normal  peri- 
pheral zone.  The  incomplete  color  blindness  of  these  two  kinds  is  characterized  by  a  uniformly 
diminished  central  field.  [When  very  intense  colors  are  used,  such  as  those  of  the  solar  spectrum, 
the  retina  can  distinguish  them  quite  up  to  its  margin  [Lattdolt).'] 


STIMULATION    OF    THE    RETINA. 


829 


In  poisoning  with  santonin,  violet  blindness  (yellow  vision)  occurs  in  consequence  of  the  pa- 
ralysis of  the  violet  perceptive  retinal  elements,  which  not  unfrequently  is  preceded  by  stimula- 
tion of  these  elements,  resulting  in  violet  vision,  i.  e.,  objects  seem  to  be  colored  violet  (^Hilfitei-). 
Such  is  the  explanation  of  this  phenomenon  given  by  Holmgren.  Max  Schultze,  however, 
refen-ed  the  yellow  vision,  i.  e.,  seeing  objects  yellow,  to  an  increase  of  the  yellow  pigment  in  the 
macula  lutea. 

^^^len  colored  objects  are  very  small,  and  illuminated  only  for  a  short  time,  the  normal  eye  first 
fails  to  perceive  red  i^Aubert) ;  hence,  it  appears  that  a  stronger  stimulus  is  required  to  excite  the 
sensation  of  red.  Briicke  found  that  very  rapidly  intermittent  white  light  is  perceived  as  green, 
because  the  short  duration  of  the  stimulation  fails  to  excite  the  elements  of  the  retina  connected  with 
the  sensation  of  red. 

[The  practical  importance  of  colorblindness  was  pointed  out  by  George  Wilson,  and  again 
more  recently  by  Holmgren.]  No  person  should  be  employed  in  the  marine  or  railway  service  until 
he  has  been  properly  certified  as  able  to  distinguish  red  i^rom  green. 

Methods  of  Testing  Color  Blindness. — Following  Seebeck,  Holmgren  used  small  skeins  of 
colored  wools  as  the  simplest  material,  in  red,  orange,  yellow,  greenish-yellow,  green,  greenish- 
blue,  blue,  violet,  purple,  rose,  brown,  gray.  There  are  five  finely  graduated  shades  of  each  of  the 
above  colors.  ^Vhen  testing  a  person,  select  only  one  skein — e-  g-,  a  bright  red  or  rose — from  the 
mass  of  colored  wools  placed  in  front  of  him,  and  place  it  aside,  asking  him  to  seek  out  those  skeins 
which  he  supposes  are  nearest  to  it  in  color. 

Mace  and  Nacati  have  measured  the  acuteness  of  vision  by  illuminating  a  small  object  with  differ- 
ent parts  of  the  spectrum.  They  compared  the  observations  on  red-  and  green-blind  persons  with 
their  own  results,  and  found  that  a  red-blind  person  perceives  green  light  as  much  brighter  than  it 
appears  to  a  normal  person.  The  green-blind  had  an  excessive  sensibility  for  red  and  violet.  It 
appears  that  what  the  color  blind  lose  in  perceptive  power  for  one  color  they  gain  for  another. 
They  have  also  a  keen  sense  for  variations  in  brightness. 

398.  STIMULATION  OF  THE  RETINA.— As  with  every  other  ner- 
vous apparatus,  a  certain  but  determinable  time  elapses  after  the  rays  of  light  fall 
upon  the  eye  before  the  action  of  the  light  takes  place,  whether  the  light  acts  so  as 
to  produce  a  conscious  impression,  or  produces  merely  a  reflex  effect  upon  the 
pupil.  The  strength  of  the  impression  produced  depends  partly  and  chiefly  upon 
the  excitability  of  the  retina  and  the  other  nervous  structures.  If  the  light  acts  for 
a  long  time  with  equal  intensity,  the  excitation,  after  having  reached  its  culminat- 
ing point,  rapidly  diminishes  again,  at  first 
more  rapidly,  and  afterward  more  and  more 
slowly. 

[When  the  retina  is  stimulated  by- 
light,  there  is  (i)  an  effect  on  the  rhodopsin 
(p.  790).  (2)  The  electro-motive  force  is 
diminished  (§  332).  (3)  The  processes  of 
the  hexagonal  pigment  cells  of  the  retina 
dipping  between  the  rods  and  cones  are 
affected  ;  thus  they  are  retracted  in  darkness, 
and  protruded  in  the  light  (Fig.  563).  (4) 
Engelmann  has  shown  that  the  length  and 
shape  of  the  cones  vary  with  the  action  of 
light.  The  cones  are  retracted  in  darkness 
and  protruded  under  the  influence  of  light 
(Fig.  563).  This  alteration  in  the  shape  of 
the  cones  takes  place  even  if  the  light  acts 
on  the  skin,  and  not  on  the  eyeball  at  all.] 

After-images. — If  the  light  acts  on  the 
eye  for  some  time  so  as  to  excite  the  retina, 

and  if  it  be  suddenly  withheld,  the  retina  still  remains  for  some  time  in  an  excited 
condition,  which  is  more  intense  and  lasts  longer,  the  stronger  and  the  longer  the 
light  may  have  been  applied,  and  the  more  excitable  the  condition  of  the  retina. 
Thus,  after  every  visual  perception,  especially  if  it  is  very  distinct  and  bright,  there 
remains  a  so-called  "  after-image.''  We  distinguish  a  "  positive  after-image," 
which  is  an  image  of  similar  brightness,  and  a  similar  color. 


Fig.  563 


The  cones  of  the  retina  and  pigment  cells  (of  the 
frog)  as  affected  by  light  and  darkness ;  i 
after  two  days  in  darkness ;  2.  after  ten 
minutes  in  daylight. 


830  AFTER-IMAGES. 

"  That  the  impression  of  any  picture  remains  for  ?ome  time  ujion  the  eye  is  a  jiliysiological  phe- 
nomenon ;  when  such  an  im])ression  can  be  seen  for  a  long  time,  it  becomes  ])athological.  The 
weaker  the  eye  is,  the  lunger  tlie  image  remains  upon  it.  The  retina  does  not  recover  itself  so  ([uickly, 
and  we  may  regard  the  action  as  a  kind  of  paralysis.  This  is  not  to  be  wondered  at  in  the  case  of 
dazzling  pictures.  After  looking  at  the  sun,  the  image  may  remain  on  the  retina  for  several  days.  A 
similar  result  sometime-;  occurs  w  ith  pictures  which  are  not  dazzling.  Husch  reconls  that  the  impres- 
sion of  an  engraving,  with  all  its  detads,  remained  on  his  eye  for  17  minutes"  {Goetfie). 

Experiments  and  Apparatus  for  Positive  After-images. —  1.  When  a  burning  stick  is  rapidly 
rotated,  it  appears  as  a  liery  circle. 

2.  The  phanakistoscope  {Plateau)  or  the  stroboscopic  6\%\i%  [Slaiiipfer).  Upon  a  di.sk  or 
cylinder,  a  series  of  objects  is  so  depicted  that  successive  drawings  rejiresent  individual  factors  of 
one  continuous  movement.  On  looking  through  an  opening  at  such  a  disk  rotated  rapidly,  we  see 
pictures  of  the  ditTerent  phases  moving  so  quickly  that  each  rapidly  follows  the  one  in  front  of  it. 
As  the  imjiression  of  the  one  picture  remains  until  the  following  one  takes  its  ]>lace,  it  has  the  ajipear- 
ance  as  if  the  successive  phases  of  the  movement  were  continuous,  and  one  and  the  same  figure. 
The  apparatus  under  the  name  of  zoetrope,  which  is  extensively  used  as  a  toy,  is  generally  stated  to 
have  been  invented  in  1832.  It  was  described  by  Cardanus  in  1 550.  It  may  be  u.sed  to  represent 
certain  movements,  t".  ^^•■.,  of  the  spermatozoa  and  ciliary  motion,  the  movements  of  the  heart  and 
those  of  locomotion. 

3.  The  color  top  contains  on  the  sectors  of  its  disk  the  colors  which  are  to  he  mixed.  As  the 
color  of  each  sector  leaves  a  condition  of  excitation  for  the  whole  duration  of  a  revolution,  all  the 
colors  must  be  perceived  simultaneously,  /.  e.,  as  a  mixed  color. 

[Illusions  of  Motion. — Silvanus  V.  Thompson  points  out  that  if  a  series  of  concentric  circles 
in  black  and  white  be  made  on  paper,  and  the  sheet  on  which  the  circles  are  drawn  be  moved  with 
a  motion,  as  if  one  were  rinsing  out  a  pail,  but  with  a  very  minute  radius,  then  all  the  circles  appear 
to  rotate  with  the  same  angular  velocity  as  that  imparted.  Professor  Thompson  has  contrived  other 
forms  of  this  illusion,  in  the  form  of  strobic  disks.] 

Negative  After-images. — Occasionally,  when  the  sthnulation  of  the  retina 
is  strong  and  very  intense,  a  "  negative,"  instead  of  a  positive  after-image,  appears. 
In  a  negative  after-image,  the  bright  parts  of  the  object  appear  dark,  and  the  colored 
parts  in  corresponding  contrast  colors  (p.  824). 

Examples  of  Negative  After-images. — After  looking  for  a  long  time  at  a  dazzlingly  illumi- 
nated white  window,  on  closing  the  eyes  we  have  the  impression  of  a  bright  cross,  or  crosses,  as  the 
case  may  be,  with  dark  panes. 

Negative  colored  after-images  are  beautifully  shown  by  Norrenberg's  apparatus.  Look  steadily  at 
a  colored  surface,  e.  g.,  a  yellow  board  with  a  small  blue  square  attached  to  the  centre  of  its  surface. 
A  white  screen  is  allowed  to  fall  suddenly  in  front  of  the  board — the  white  surface  now  has  a  bluish 
appearance,  with  a  yellow  square  in  its  centre. 

The  usual  explanation  of  dark  negative  after-images  is  that  the  retinal  elements  are  fatigued  by 
the  light,  so  that  for  some  time  they  become  less  excitable,  and  consequently  light  is  but  feebly  per- 
ceived in  the  corresponding  areas  of  the  retina  ;  hence,  darkness  prevails. 

Ilering  explains  the  dark  after-images  as  due  to  a  process  of  assimilation  in  the  black-white  visual 
substance.  In  explaining  colored  after  images,  the  Young-Helmholtz  theory  assumes  that,  under  the 
action  of  the  light  waves,  e.  g.,  red,  the  retinal  elements  connected  with  the  perception  of  this  color 
are  paralyzed.  On  now  looking  suddenly  on  a  white  surface,  the  mixture  of  all  the  colors  appears 
as  white  minus  red,  i.e.,  the  white  afipears  green.  In  bright  daylight  the  contrast  color  lies  very 
near  the  complementary  color.  According  to  Ilering,  the  contrast  after-image  is  explained  by  the 
assimilation  of  the  corresponding  colored  visual  substance,  in  this  case,  of  the  "  red-green  "  (§  397)- 
From  the  commencement  of  a  momentary  illumination  until  the  appearance  of  an  after-image,  0.344 
sec.  elapses  (y.  V'intschgau  and  Lusdg). 

Not  unfrequently,  after  intense  stiinulation  of  the  retina,  positive  and  negative 
after-images  alternate  with  each  other  until  they  gradually  fuse.  After  looking  at 
the  dark-red  setting  sun  we  see  alternate  disks  of  red  and  green. 

The  phenomena  of  contrast  undergo  some  modification  in  the  peripheral  areas  of 
the  retina,  owing  to  the  partial  color  blindness  which  occurs  in  these  areas  (^Ada- 
jni'ick  and  IVoinow). 

Irradiation  is  the  tenn  applied  to  certain  phenomena  where  we  forin  a  false 
estimate  of  visual  impressions,  owing  to  inexact  accommodation.  If,  from  inexact 
accommodation,  the  margins  of  the  object  are  projected  upon  the  retina  in  diffusion 
circles,  the  mind  tends  to  add  the  undefined  margin  to  those  parts  of  the  visual 
image  which  are  most  prominent  in  the  image  itself.     What  is  bright  appears  larger 


SIMULTANEOUS    CONTRAST. 


831 


and  overcomes  what  is  dark,  while  an  object,  without  reference  to  brightness  or 
color,  has  the  same  relation  to  its  background  (Fig.  564).  When  the  accommoda- 
tion is  quite  accurate,  the  phenomenon  of  irradiation  is  not  present.  [On  looking 
at  Fig.  565  from  a  distance,  the  white  squares  appear  larger  and  as  if  they  were 
united  by  a  white  band.] 

"  A  dark  object  appears  smaller  than  a  bright  one  of  the  same  size.  On  looking  at  the  same  time 
from  a  certain  distance  at  two  circles  of  the  same  size,  a  white  one  on  a  black  background,  and  a 
black  on  a  white  background,  we  estimate  the  latter  to  be  about  one-fifth  less  than  the  former  (Fig. 
564).  On  making  the  black  circle  one-fifth  larger  they  will  appear  equal.  Tycho  de  Brahe  remarks 
that  the  moon,  when  in  conjunction  (dark),  appears  to  be  one-fifth  smaller  than  in  opposition  (full, 
bright).  The  first  lunar  crescent  appears  to  belong  to  a  larger  disk  than  the  dark  one  adjoining  it, 
which  can  occasionally  be  distinguished  at  the  time  of  the  new  light.  Black  clothes  make  persons 
appear  to  be  much  smaller  than  light  clothes.  A  light  seen  behind  a  margin  gives  the  appearance 
of  a  cut  in  the  margin.  A  ruler,  behind  which  is  placed  a  lighted  candle,  appears  to  the  observer 
to  have  a  notch  in  it.  The  sun,  when  rising  and  setting,  appears  to  make  a  depression  in  the 
horizon"  {^Goethe). 

[Contrast. — The  fundamental  phenomena  are  such  as  these,  that  a  bright  object 
looks  brighter  surrounded  by  objects  darker  than  itself;  and  darker  with  surround- 
ings brighter  than  itself.  There  may  be  contrasts  either  with  bright  or  dark  objects 
or  with  colored  ones.] 


Fig.  564. 


Fig.  565. 


For  Irradiation. 


For  Irradiation. 


Simultaneous  Contrast. — By  this  term  is  meant  a  phenomenon  like  the  fol- 
lowing :  When  bright  and  dark  parts  are  present  in  a  picture  at  the  same  time, 
the  bright  (white)  parts  always  appear  to  be  more  intensely  bright  the  less  white 
there  is  near  them,  or,  what  is  the  same  thing,  the  darker  the  surroundings,  and, 
conversely,  they  appear  less  bright  the  more  white  tints  that  are  present  near  them. 
A  similar  phenomenon  occurs  with  colored  pictures.  A  color  in  a  picture  appears 
to  us  to  be  more  intense  the  less  of  this  color  there  is  in  the  adjoining  parts,  that 
is,  the  more  the  surroundings  resemble  the  tints  of  the  contrast  color.  Simul- 
taneous contrast  arises  from  simultaneous  impressions  occurring  in  two  adjoining 
and  different  parts  of  the  retina. 

Examples  of  Contrast  for  Bright  and  Dark. — i.  Look  at  a  white  network  on  a  black  ground ; 
the  parts  where  the  white  lines  intersect  appear  darker,  because  there  is  least  black  near  them. 

2.  Look  at  a  point  of  a  small  strip  of  dark  gray  paper  in  front  of  a  dark  black  background.  Push 
a  large  piece  of  wliite  paper  between  the  strip  and  the  background;  the  strip  on  the  white  ground 
now  appears  to  be  much  darker  than  before.  On  again  removing  the  white  paper,  the  strip  at  once 
again  appears  bright  [Hering). 

3.  Look  with  both  eyes  toward  a  grayish-white  surface,  e.  g.,  the  ceiling  of  a  room.  After  gazing 
for  some  time,  place  in  firont  of  the  eye  a  papei  tube  eight  inches  long,  and  an  inch  to  an  inch  and  a 
quarter  in  diameter,  blackened  in  the  inside.  The  part  of  the  ceiling  seen  through  the  tube  appears 
as  a  round  white  spot  i^Landois). 


832  EXAMPLES  OF  CONTRAST. 

Examples  for  Colors. — i.  Place  a  piece  of  gray  paper  on  a  red,  yellow,  or  blue  ground;  the 
contrast  colors  appear  at  once,  viz.,  green,  blue,  or  yellow.  The  phenomenon  is  made  still  more 
distinct  by  covering  the  whole  with  transparent  tracing  paper  [I/erni.  Meyer).  Under  similar  cir- 
cumstances, printed  matter  on  a  colored  ground  appears  in  its  complementary  color  ( /F.  v.  BtzoU). 

2.  An  air  bubble  in  the  stron<;ly  tinged  field  of  vision  of  a  thick  microscopical  preparation  appears 
with  an  intense  contrast  color  {^Lattdois). 

3.  Paste  four  green  sectors  upon  a  rotatory  white  disk,  leave  a  ring  round  the  centre  of  the  disk 
imcovered  by  green,  and  cover  it  with  a  black  strip.  On  rotating  such  a  disk  the  black  part  appears 
red  and  not  gray  [Biiicke). 

4.  Ix)ok  with  both  eyes  toward  a  grayish-white  surface,  and  place  in  front  of  one  eye  a  tube  about 
the  length  and  breadth  of  a  finger,  composed  of  transparent  oiled  paper,  gummed  together  to  such 
thickness  as  will  permit  light  to  pass  through  its  walls.  The  part  of  the  surface  seen  through  the 
tube  appears  in  its  contrast  color.  The  experiment  also  shows  the  contrast  in  the  intensity  of  the 
illumination  (LanJois).  A  white  piece  of  j^aper,  with  a  round  black  spot  in  its  centre,  when  looked 
at  through  a  blue  glass  appears  blue  with  a  black  spot.  If  a  white  spot  of  the  same  size  on  a  black 
ground  be  placed  in  front,  so  that  it  is  reflected  in  the  glass  plate  and  just  covers  the  black  spot,  it 
shows  the  contrast  color  yellow  {Rai^ona  Sana). 

5.  The  colored  shadows  also  belong  to  the  group  of  simultaneous  contrasts.  "  Two  conditions 
are  necessary  for  the  production  of  colored  shadows — fii^stly,  that  the  light  gives  some  kind  of  a  color 
to  the  white  surface;  second,  that  the  shadow  is  illuminated,  to  a  certain  extent,  by  another  light. 
During  the  twilight,  place  a  short  lighted  candle  on  a  white  surface,  between  it  and  the  fading  day- 
light hold  a  pencil  vertically,  so  that  the  shadow  thrown  by  the  candle  is  illuminated,  but  not  abol- 
ished by  the  feeble  daylight;  the  shadow  appears  of  a  beautiful  />///e.  The  blue  shadow  is  easily 
seen,  but  it  requires  a  little  attention  to  observe  that  the  white  paper  acts  like  a  reddish-yellow  sur- 
face, whereby  the  blue  color  apparent  to  the  eye  is  improved.  One  of  the  most  beautiful  cases  of 
colored  shadows  is  seen  in  connection  with  the  full  moon.  The  light  of  the  candle  and  that  of  the 
moon  can  be  completely  equalized.  Both  shadows  can  be  obtained  of  efpal  strength  and  distinct- 
ness, so  that  both  colors  are  completely  balanced.  Place  the  plate  opjjosite  the  light  of  the  moon, 
the  lighted  candle  a  little  to  one  side  at  a  suitable  distance.  In  front  of  the  plate  hold  an  opaque 
body,  when  a  double  shadow  appears,  the  one  thrown  by  the  moon  and  lighted  by  the  candle  being 
bright  reddish-yellow ;  and,  conversely,  the  one  thrown  by  the  candle  and  lighted  by  the  moon 
appears  of  a  beautiful  blue.     Where  the  two  shadows  come  together  and  unite  is  black  "  [Goethe). 

6.  "  Take  a  plate  of  green  glass  of  considerable  thickness  and  hold  it  so  as  to  get  the  bars  of  a 
window  rellected  in  it,  the  bars  will  be  seen  double,  the  image  formed  by  the  under  surface  of  the 
glass  being  green,  while  the  image  coming  from  the  under  surface  of  the  glass,  and  which  ought 
really  to  be  colorless,  appears  to  l>e  purple.  The  experiment  may  be  performed  with  a  vessel  filled 
with  water,  with  a  mirror  at  its  base.  With  pure  water  colorless  images  are  obtained,  while  by 
coloring  the  water  colored  images  are  produced"  [Goethe). 

Explanation  of  Contrast. — Some  of  these  phenomena  may  be  explained  as  due  to  an  error  of 
judgment.  During  the  simultaneous  action  of  several  impressions,  the  judgment  errs,  so  that  when 
an  effect  occurs  at  one  place,  this  acts  to  the  slightest  extent  in  the  neighbormg  parts.  When,  there- 
fore, brightness  acts  upon  a  part  of  the  retina,  the  judgment  ascribes  the  smallest  possible  action  of 
the  brightness  to  the  adjoining  parts  of  the  retina.  It  is  the  same  with  colors.  It  is  far  more 
probable  that  the  phenomena  are  to  be  referred  to  actual  physiological  processes  [I/ering).  Partial 
stimulation  toith  light  affects  not  only  the  part  so  acted  on,  but  also  the  surrounding  area  of  the 
retina  (p.  827) ;  the  part  directly  excited  undergoing  increased  disassimilalion,  the  (indirectly  stimu- 
lated) adjoining  area  undergoing  increased  assimilation  ;  the  increase  of  the  latter  is  gi-eatest  in  the 
immediate  neighborhood  of  the  illuminated  portion,  and  rapidly  diminishes  as  the  distance  from  it 
increases.  By  the  increase  of  the  assimilation  in  those  parts  not  acted  on  by  the  image  of  the  object, 
this  is  prevented,  so  that  the  diffused  light  is  perceived.  The  increase  of  the  assimilation  in  the 
immediate  neighborhood  of  the  illuminated  spot  is  greatest  so  that  the  perception  of  this  relatively 
stronger  different  light  is  largely  rendered  impossible  [Hering). 

[Helmholtz  thus  ascribed  the  phenomena  of  contrast  to  psychical  conditions,  i.  e.,  errors  of  judg- 
ment, but  this  explanation  is  certainly  not  complete.  A  far  more  satisfactory  solution  of  the  problem 
is  that  of  Hering,  that  stmiulation  of  one  part  of  the  retina  affects  the  condition  of  adjoining  parts. 
If  a  white  disk  on  a  black  background  be  looked  at  for  a  tim-;,  and  then  the  eyes  be  closed,  a  nega- 
tive after-image  of  the  disk  appears,  but  it  is  darker  and  blacker  than  the  visual  area,  and  it  has  a 
light  area  around,  brightest  close  to  the  di-.k,  /.  e.,  the  adjacent  part  of  the  retina  is  affected.  This 
Hering  has  called  successive  light  induction.] 

Successive  Contrast. — Look  for  a  long  time  at  a  dark  or  bright  object,  or  at  a  colored  [e.  g., 
red)  one,  and  then  allow  the  effect  of  the  contrast  to  occur  on  th=  retina,  /.  <?.,  with  reference  to  the 
above,  bright  and  dark,  or  the  contra.st  color  green,  then  these  become  very  intense.  This  phe- 
nomenon has  also  been  called  '■'■successive  contrast.'^  In  this  case  the  negative  afterimage  obviously 
plays  a  part. 

[Some  drugs  cause  subjective  visual  sensations,  but  these  do  so  by  acting  on  the  brain,  e.  g.,  alco- 
hol, as  in  delirium  tremens,  cannabis  indica,  sodic  salicylate,  and  large  doses  of  digitalis  [Brunton).'\ 


MOVEMENTS    OF   THE    EYEBALLS.  833 

399.  MOVEMENTS  OF  THE  EYEBALLS— EYE  MUSCLES.— 

The  globular  eyeball  is  capable  of  extensive  and  free  movement  on  the  corres- 
pondingly excavated  fatty  pad  of  the  orbit,  just  like  the  head  of  a  long  bone  in 
the  corresponding  socket  of  a  freely  movable  arthrodial  joint.  The  movements 
of  the  eyeball,  however,  are  limited  by  certain  conditions,  by  the  mode  in  which 
the  eye  muscles  are  attached  to  it.  Thus,  when  one  muscle  contracts,  its  antago- 
nistic muscle  acts  like  a  bridle,  and  so  limits  the  movement ;  the  movements  are 
also  limited  by  the  insertion  of  the  optic  nerve.  The  soft  elastic  pad  of  the  orbit 
on  which  the  eyeball  rests  is  itself  subject  to  be  moved  forward  or  backward,  so 
that  the  eyeball  also  must  participate  in  these  movements. 

Protrusion  of  the  eyeball  takes  place — i.  By  congestion  of  the  blood  vessels,  especially  of  the 
veins  in  the  orbit,  such  as  occurs  when  the  overflow  of  the  venous  blood  from  the  head  i>  interfered 
with,  as  in  cases  of  hanging.  2.  By  contraction  of  the  smooth  muscular  fibres  in  Tenon's  capsule, 
in  the  spheno-maxillary  fissure,  and  in  the  eyelids  (|  404),  which  are  innervated  by  the  cervical 
sympathetic  nerve.  3.  By  voluntary  forced  opening  of  the  palpebral  fissure,  whereby  the  pressure 
of  the  eyelids  acting  on  the  eyeball  is  diminished.  4.  By  the  action  of  the  oblique  muscles,  which 
act  by  pulling  the  eyeball  inward  and  forward  If  the  superior  oblique  be  contracted  when  the  eye- 
lids are  forcibly  opened,  the  eyeball  may  be  protruded  about  I  mm.  When  protrusion  of  the  eyeball 
occurs  pathologically  (as  in  i  and  2),  the  condition  is  called  exophthalmos. 

Retraction  of  the  eyeball  is  the  opposite  condition,  and  is  caused^  i.  By  closing  the  eyelids 
forcibly.  2.  By  an  empty  condition  of  the  retro-bulbar  blood  vessels,  diminished  succulence,  or  dis- 
appearance of  the  tissue  of  the  orbit.  3.  Section  of  the  cervical  sympathetic  in  dogs  causes  the  eye- 
ball to  sink  somewhat  in  the  orbit.  The  smooth  muscular  fibres  of  Tenon's  capsule  are  perhaps 
antagonistic  in  their  action  to  the  four  recti  when  acting  together,  and  thus  prevent  the  eyeball  from 
being  drawn  too  far  backward.  Many  animals  have  a  special  retractor  bulbi  muscle,  e.g..,  amphibi- 
ans, reptiles,  and  many  mammals ;  the  ruminants  have  four. 

The  movements  of  the  eyes  are  almost  always  accompanied  by  similar  move- 
ments of  the  head,  chiefly  on  looking  upward,  less  so  on  looking  laterally,  and 
least  of  all  when  looking  downward. 

The  difficult  investigations  on  the  movements  of  the  eyeballs  have,  been  carried  out,  especially  by 
Listing,  Meissner,  Helmholtz,  Bonders,  A.  Fick,  and  E.  Hering. 

Axes. — All  the  movements  of  the  eyeball  take  place  round  its  point  of  rotation  (Fig.  566,  O), 
which  lies  1. 77  mm.  behind  the  centre  of  the  visual  axis,  or  10.957  mm.  from  the  vertex  of  the 
cornea  i^Donders).  In  order  to  determine  more  carefully  the  movements  of  the  eyeball,  it  is  neces- 
sary to  have  certain  definite  data:  i.  The  visual  axis  (S,  Sj),  or  the  antero-posterior  axis  of  the 
eyeball,  unites  the  point  of  rotation  with  the  fovea  centralis,  and  is  continued  straight  forward  to  the 
vertex  of  the  cornea.  2.  The  transverse,  or  horizontal  axis  (Q,  Qj),  is  the  straight  linj  connect- 
ing the  points  of  rotation  of  both  eyes  and  its  extension  outward.  Of  course,  it  is  at  right  angles  to  i. 
3.  The  vertical  axis  passes  vertically  through  the  point  of  rotation  at  right  angles  to  i  and  2. 
These  three  axes  form  a  coordinate  system.  We  must  imagine  that  in  the  orbit  there  is  a  fixed 
determinate  axial  system,  whose  point  of  intersection  corresponds  with  the  point  of  rotation  of  the 
eyeball.  When  the  eye  is  at  rest  (primary  position),  the  three  axes  of  the  eyeball  completely  coincide 
with  the  three  axes  of  the  coordinate  system  in  the  orbit.  When  the  eyeball,  however,  is  moved, 
two  or  more  axes  are  displaced  from  this,  so  that  they  must  form  angles  with  the  fixed  orbital  system. 

Planes  of  Separation. — In  order  to  be  more  exact,  and  also  partly  for  further  estimations,  let  us 
suppose  three  planes  passing  through  the  eyeball,  and  that  their  position  is  secured  by  any  two  axes. 
I.  The  horizontal  plane  of  separation  divides  the  eyeball  into  an  upper  and  lower  half;  it  is  deter- 
mined by  the  visual  transverse  axis.  In  its  course  through  the  retina  it  forms  the  horizontal  line 
of  separation  of  the  latter;  the  coats  of  the  eyeball  itself  cut  it  in  their  horizontal  meridian.  2. 
The  vertical  plane  divides  the  eyeball  into  an  inner  and  outer  half;  it  is  determined  by  the  visual 
and  vertical  axes.  It  cuts  the  retina  in  the  vertical  line  of  separation  of  the  latter  and  the  pe- 
riphery of  the  bulb  in  the  vertical  meridian  of  the  eyeball.  3.  The  equatorial  plane  divides  the 
eyeball  into  an  anterior  and  posterior  half;  its  position  is  determined  by  the  vertical  and  transverse 
axes,  and  it  cuts  the  sclerotic  in  the  equator  of  the  eyeball.  The  horizontal  and  vertical  lines  of 
separation  of  the  retina,  which  intersect  in  the  fovea  centralis,  divide  the  retina  into  four  quadrants. 

In  order  to  define  more  precisely  the  movements  of  the  eyeball,  v.  Helmholtz  has  introduced  the 
following  terms  :  He  calls  the  straight  line  which  connects  the  point  of  rotation  of  the  eye  with  the 
fixed  pomt  in  the  outer  world,  the  visual  line  ("  Blicklinie"),  while  a  plane  passing  through  these 
lines  in  both  eyes  he  called  the  visual  plane  ;  the  ground  line  of  this  plane  is  the  line  uniting  the 
two  points  of  rotation,  viz.,  the  transverse  axis  of  the  eyeball.  Suppose  a  sagittal  section  (antero- 
posterior) to  be  made  through  the  head,  so  as  to  divide  the  latter  into  a  right  and  left  half,  then  this 

53 


834  POSITIONS    OF   THE    EYEBALL. 

plane  would  halve  the  ground  line  of  the  visual  plane,  and  when  prolonged  forward  would  intersect 
the  visual  plane  in  the  median  line.  The  visual  point  of  the  eye  can  lie  (i)  raised  or  lowered — the 
field  which  it  traverses  being  called  the  visual  tield  ("  Hlickfeld  ")  ;  it  is  part  of  a  spherical  surface 
with  the  point  of  rotation  of  the  eye  in  its  centre.  Proceedinjj  from  the  primary  position  of  both 
eves,  which  is  characterized  by  botli  visual  lines  being  parallel  with  each  other  and  horizontal,  then 
the  elevation  of  the  visual  plane  can  be  determineti  by  the  angle  which  this  forms  with  the  plane  of 
the  primary  jx)sition.  This  angle  is  called  the  ani^le  of  e/nuition — it  is  positive  when  the  visual 
plane  is  raised  (to  the  forehead),  and  negative  when  it  is  lowered  (chinward).  (2)  From  the  pri- 
mary  position,  the  visual  line  can  be  turned  laterally  in  the  visual  plane.  The  extent  of  this  lateral 
deviation  is  measured  by  the  angle  of  lateral  rotation,  /.  ,•.,  by  the  angle  which  the  visual  line 
forms  with  the  median  line  of  the  visual  plane;  it  is  said  to  be  positive  when  the  posterior  part  of 
the  visual  line  is  turned  to  the  right,  negative  when  to  the  left.  The  following  are  the  positions  of  the 
eyeball : — 

1.  Primary  position  [or  "position  of  rest"],  in  which  both  the  lines  of 
vision  are  parallel  with  each  other,  and  the  visual  planes  are  horizontal.  The  three 
axes  of  the  eyeball  coincide  with  the  three  fixed  axes  of  the  coordinate  system  in 
the  orbit. 

2.  Secondary  positions  are  due  to  movements  of  the  eye  from  the  primary 
position.  There  are  two  different  varieties — i^a)  where  the  visual  lines  are  parallel, 
but  are  directed  upward  or  dinomvard.  The  transverse  axis  of  both  eyes  remains 
the  same  as  in  the  primary  position  ;  the  deviations  of  the  other  two  axes  expressed 
by  the  amount  of  the  angle  of  elevation  of  the  line  of  vision.  (/')  The  second 
variety  of  the  secondary  position  is  produced  by  the  convergence  or  divergence  of 
the  lines  of  vision.  In  this  variety  the  vertical  axis,  round  which  the  lateral  rota- 
tion takes  place,  remains  as  in  the  primary  position;  the  other  axes  form  angles; 
the  amount  of  the  deviation  is  expressed  by  the  "  angle  of  lateral  rotation."  The 
eye,  when  in  the  primary  position,  can  be  rotated  from  this  position  42°  outward, 
45°  inward,  34°  upward,  and  57°  downward  {Schuurmann'). 

3.  Tertiary  position  is  the  position  brought  about  by  the  movements  of  the 
eye,  in  which  the  lines  of  vision  are  convergent,  and  are  at  the  same  time  inclined 
upward  or  downward. 

[Listing's  Law  is  that  which  expresses  the  movements  of  the  eyeball.  When  the  eyeball  moves 
from  the  primary  position,  or  position  of  rest,  the  angle  of  rotation  of  the  eye  in  the  second  position 
is  the  same  as  if  the  eye  were  turned  about  a  fixed  axis  perpendicular  to  botli  the  first  and  the  second 
positions  of  the  visual  line  {^Hel»iholtz).'\ 

All  the  three  axes  of  the  eye  are  no  longer  coincident  with  the  axes  in  the  pri- 
mary position.  The  exact  direction  of  the  visual  lines  is  determined  by  the 
amount  of  the  angle  of  lateral  rotation  and  the  angle  of  elevation.  There  is  still 
another  important  point.  The  eyeball  is  always  rotated  at  the  same  time  round 
the  line  of  vision  and  round  its  axis  {Volkmann,  Hering^.  As  the  iris  rotates 
round  the  visual  line  like  a  wheel  round  its  axis,  this  rotation  is  called  "  circular 
rotation  "  ("  Raddrehung'')  of  the  eye,  which  is  always  connected  with  the  ter- 
tiary positions.  Even  oblique  movements  may  be  regarded  as  composed  of — (i) 
a  rotation  round  the  vertical  axis,  and  (2)  round  the  transverse  axis;  or  it  may 
be  referred  to  rotation  round  a  single  constant  axis  placed  between  the  above- 
named  axes,  passing  through  the  point  of  rotation  of  the  eyeball,  and  at  right 
angles  to  the  secondary  and  primary  direction  of  the  visual  axis  (line  of  vision) — 
{Listing).  The  amount  of  circular  rotation  is  measured  by  the  angle  which  the 
horizontal  separation  line  of  the  retina  forms  with  the  horizontal  separation  of  the 
retina  of  the  eye  in  the  primary  position.  This  angle  is  said  to  be  positive,  when 
the  eye  itself  rotates  in  the  same  direction  as  the  hand  of  a  watch  observed  by  the 
same  eye,  /.  e.,  when  the  upper  end  of  the  vertical  line  of  separation  of  the  retina 
is  turned  to  the  right. 

According  to  Bonders,  the  angle  of  rotation  increases  with  the  angle  of  elevation  and  the  angle  of 
lateral  rotation — it  may  exceed  10°.  With  equally  great  elevation  or  depression  of  the  visual  plane, 
the  rotation  is  greater,  the  greater  the  elevation  or  depression  of  the  line  of  vision. 


THE    OCULAR    MUSCLES. 


835 


On  looking  upward  in  the  tertiary  position,  the  upper  ends  of  the  vertical  lines  of  separation  of 
the  retina  diverge ;  on  looking  downward  they  converge.  If  the  visual  plane  be  raised,  the  eye, 
when  it  deviates  laterally  to  the  right,  makes  a  circular  rotation  to  the  left.  When  the  visual  plane  is 
depressed,  on  deviating  the  eye  to  the  right  or  left,  there  is  a  corresponding  circular  rotation  to  the 
right  or  left.  Or  we  may  express  the  result  thus  :  When  the  angle  of  elevation  and  the  angle  of  devia- 
tion have  the  same  sign  (-|-  or  — ),  then  the  rotation  of  the  eyeball  is  negative;  when,  however,  the 
signs  are  unequal,  the  rotation  is  positive.  In  order  to  make  the  circular  rotation  visible  in  one's  own 
eye  accommodate  one  eye  for  a  sirrface  divided  by  vertical  and  horizontal  lines  until  a  positive  after- 
image is  produced,  and  then  rapidly  rotate  the  eye  into  the  third  position.  The  lines  of  the  after- 
image then  form  angles  with  the  lines  of  the  background.  As  the  position  of  the  vertical  meridian 
of  the  eye  is  important  from  a  practical  point  of  view,  it  is  necessary  to  note  that,  in  the  primary  and 
secondary  positions  of  the  eyes,  the  vertical  meridian  retains  its  vertical  position.     On  looking  to 


^A^^ 


'S>^^ 


E  i  I 

Scheme  of  the  action  of  the  ocular  muscles. 


the  left  and  upward,  or  to  the  right  and  downward,  the  vertical  meridians  of  both  eyes  are  turned  to 
the  left ;  conversely,  they  are  turned  to  the  right  on  looking  to  the  left  and  downward,  or  to  the  right 
and  upward. 

In  the  secondary  positions  of  the  eye,  rotation  of  the  axis  of  the  eye  never  occurs  [Listing). 
Very  shght  rolling  of  the  eyes  occurs,  however,  when  the  head  is  inclined  toward  the  shoulder,  and 
in  the  direction  opposite  to  that  of  the  head,  it  is  about  i°  for  every  io°  of  inclination  of  the  head 
{Skrebitzk). 

Ocular  Muscles. — The  movements  of  the  eyeball  are  accomplished  by  means 
of  the  four  straight  and  two  oblique  ocular  muscles.  In  order  to  understand 
the  action  of  each  of  these  muscles,  we  must  know  the  plane  of  traction  of  the 
muscles  and  the  axis  of  rotation  of  the  eyeball.  The  plane  of  traction  is  found 
by  the  plane  lying  in  the  middle  of  the  origin  and  insertion  of  the  muscle  and 


836 


ACTION    OF   THE    OCULAR    MUSCLES. 


the  point  of  rotation  of  the  eyeball.  Tlie  axis  of  rotation  is  always  at  right 
angles  to  the  jtlane  of  traction  in  the  point  of  rotation  of  the  eyeball. 

I.  The  rectus  internus  (I)  and  externus  (E)  rotate  the  eye  almost  exactly 
inward  and  outward  (Fig.  566).  The  plane  of  traction  lies  in  the  plane  of  the 
paper;  Q,  E,  is  the  direction  of  the  traction  of  the  external  rectus,  Q,,  I,  that  of 
the  internal.  The  axis  of  rotation  is  in  the  point  of  rotation,  O,  at  right  angles 
to  the  plane  of  the  paper,  so  that  it  coincides  with  the  vertical  axis  of  the  eyeball. 

2.  The  axis  of  rotation  of  the  R.  superior  and  inferior  (the  dotted  line,  R. 
sup.,  R.  inf.),  lies  in  the  horizontal  plane  of  separation  of  the  eye,  but  it  forms 
an  angle  of  about  20°  with  the  transverse  axis  (Q,  Q,)  ;  the  direction  of  the  trac- 
tion for  both  muscles  is  indicated  by  the  line  s,  i.  By  the  action  of  these  muscles, 
the  cornea  is  turned  upward  and  slightly  inward,  or  downward  and  slightly  inward. 

3.  The  axis  of  rotation  of  both  oblique  muscles  (the  dotted  lines,  Obi.  sup.  and 
Obi.  inf.)  also  lies  in  the  horizontal  i)lane  of  separation  of  the  eyeball,  and  it 
forms  an  angle  of  60°  with  the  tran.sverse  axis.  The  direction  of  the  traction  of 
the  inferio?-  oblique  gives  the  line,  a,  b  ;  that  of  the  superior,  the  line,  c,  d.  The 
action  of  these  muscles,  therefore,  is  in  the  one  case  to  rotate  the  cornea  out- 
ward and  upward,  and  in  the  other  outward  and  downward.  These  actions,  of 
course,  only  obtain  when  the  eyes  are  in  the  primary  position  ;  in  every  other 
position  the  axis  of  rotation  of  each  muscle  changes. 

When  the  eyes  are  at  rest,  the  muscles  are  in  equilibrium.  Owing  to  the  power 
of  the  internal  recti,  the  visual  axes  converge  and  would  meet,  if  prolonged  40 
centimetres  in  front  of  the  eye.  In  the  movements  of  the  eyeball,  one,  two,  or 
three  muscles  may  be  concerned.  One  muscle  acts  only  when  the  eye  is  moved 
directly  outward  or  inward,  especially  the  internal  and  external  rectus.  Two 
muscles  act  when  the  eyeball  is  moved  directly  upward  (superior  rectus  and  infe- 
rior oblique)  or  downward  (inferior  rectus  and  superior  oblique).  Three  muscles 
are  in  action  when  the  eyeballs  take  a  diagonal  direction,  especially  for  imvard 
and  upioard,  by  the  internal  and  the  superior  rectus  and  inferior  oblique  ;  for  inward 
and  doivnward,  the  internal  and  inferior  rectus  and  superior  oblique  ;  for  outward 
and  downward,  the  external  and  inferior  rectus  and  superior  oblique ;  for  outward 
and  up'ivard,  the  external  and  superior  rectus  and  inferior  oblique. 

[The  following  table  shows  the  action  of  the  muscles  of  the  eyeball : — 


In- card. 
Outward, 

Upward, 
Dowmvard, 

Inward  and 

upivard. 


Rectus  inturnus. 

Rectus  externus. 
f  Rectus  superior. 
\  Obliquus  inferior, 
f  Rectus  inferior. 
\  Obliquus  superior. 

{Rectus  internus. 
Rectus  superior. 
Obliquus  inferior. 


Inward  and 
doxonward , 

Outward  and 
upward. 

Outward  and 
downward, 


Rectus  internus. 
Rectus  inferior. 
Obliquus  superior. 
Rectus  externus. 
Rectus  superior. 
Obliquus  inferior. 
Rectus  externus. 
Rectus  inferior. 
Obliquus  superior.] 


Ruete  imitated  the  movements  of  the  eyeballs  by  means  of  a  model,  which  he  called  the 
ophthalmotrope. 

The  size  of  the  eyeball  and  its  length  diminish  with  age.  The  mobility  is  less  in  the  vertical  than 
in  the  lateral  direction,  and  less  upward  than  downward.  The  normal  and  myopic  eye  can  be  moved 
more  outward,  and  the  long-sighted  eye  more  inward;  the  external  and  internal  recti  act  most  when 
the  eye  is  moved  outward,  the  obliqui  when  it  is  rotated  inward.  An  eye  can  be  turned  inward  to  a 
greater  extent  when  the  other  eye  at  the  same  time  is  turned  outward  than  when  the  other  is  turned 
inward.  During  near  vision,  the  right  eye  can  be  turned  less  to  the  right,  and  the  left  to  the  left, 
than  during  distant  vision  [Hering). 

Simultaneous  Ocular  Movements. — Both  eyes  are  always  moved  simul- 
taneously. Even  when  one  eye  is  quite  blind,  the  ocular  muscles  move  when  the 
whole  eyeball  is  excited.  When  the  head  is  straight,  the  movements  always  take 
place  so  that  both  visual  planes  (visual  axes)  lie  in  the  same  plane.  In  front  both 
visual  axes  can  diverge  only  to  a  trifling  extent,  while  they  can  converge  consider- 


BINOCULAR   VISION.  837 

ably.  If  individual  ocular  muscles  are  paralyzed,  the  position  of  the  visual  axis  in 
the  same  place  is  disturbed,  and  squinting  results,  so  that  the  patient  no  longer  can 
direct  both  visual  axes  simultaneously  to  the  same  point,  but  he  directs  the  one 
eye  after  the  other.  Even  nystagmus  (p.  771)  occurs  in  both  eyes  simultaneously, 
and  in  the  same  direction.  The  innate  simultaneous  movement  of  both  eyes  is 
spoken  of  as  an  associated  movement  (/<?/?.  Milller).  E.  Hering  showed  that 
in  all  ocular  movements  there  is  a  uniformity  of  the  innervation  as  well.  Even  during 
such  movements,  in  which  one  eye  apparently  is  at  rest,  there  is  a  movement,  due 
to  the  action  of  two  antagonistic  forces,  the  movements  resulting  in  a  slight  to  and 
fro  motion  of  the  eyeball. 

The  motor  nerves  of  the  ocular  muscles  are  the  oculomotorius  (|  345),  the  trochlearls  (^  346), 
and  iheabducens  (^  348).  The  centre  lies  in  the  corpora  quadrigemina,  and  below  it  (§  379),  and 
partly  in  the  medulla  oblongata  (|  379]. 

400.  BINOCULAR  VISION.— Advantages.— Vision  with  both  eyes 
affords  the  following  advantages  :  (i)  ThQ  field  of  vision  of  both  eyes  is  considerably 
larger  than  that  of  one  eye.  (2)  The  perception  of  depth  is  rendered  easier,  as 
the  retinal  images  are  obtained  from  two  different  points.  (3)  A  more  exact  esti- 
mate of  the  distance  and  size  of  an  object  can  be  formed,  in  consequence  of  the 
perception  of  the  degree  of  convergence  of  both  eyes.  (4)  The  correction  of 
certain  errors  in  the  one  eye  is  rendered  possible  by  the  other. 

When  the  position  of  the  head  isfxed,  we  can  easily  form  a  conception  as  to  the  form  of  the  entire 
field  of  vision  if  we  close  one  eye  and  direct  the  open  eye  inward.  We  observe  that  it  is  pear-shaped, 
broad  above  and  smaller  below;  the  silhouette,  or  profile  of  the  nose  causes  the  depression  between 
the  upper  and  lower  part  of  the  field. 

401.  IDENTICAL  POINTS— HOROPTER.— Identical  Points.— 

If  we  imagine  the  retinse  of  both  eyes  to  be  a  pair  of  hollow  saucers  placed  one 
within  the  other,  so  that  the  yellow  spots  of  both  eyes  coincide,  and  also  the 
similar  quadrants  of  the  retinae,  then  all  those  points  of  both  retinse  which  coincide 
or  cover  each  other  are  called  "identical"  or  "  corresponding  points  "  of  the 
retina.  The  two  meridians  which  separate  the  quadrants  coinciding  with  each 
other  are  called  the  "lines  of  separation."  Physiologically,  the  identical 
points  are  characterized  by  the  fact  that,  when  they  are  both  simultaneously  ex- 
cited by  light,  the  excitement  proceeding  from  them  is,  by  a  psychical  act,  referred 
to  one  and  the  same  point  of  the  field  of  vision,  lying,  of  course,  in  a  direction 
through  the  nodal  point  of  each  eye.  Stimulation  of  both  identical  points  causes 
only  07ie  image  in  the  field  of  vision.  Hence  all  those  objects  of  the  external 
world,  whose  rays  of  light  pass  through  the  nodal  points  to  fall  upon  identical 
points  of  the  retina,  are  seen  singly,  because  their  images  from  both  eyes  are  re- 
ferred to  the  same  point  of  the  field  of  vision,  so  that  they  cover  each  other.  All 
other  objects  whose  images  do  not  fall  upon  identical  points  of  the  retina  cause 
double  vision,  or  diplopia. 

Proofs. — If  we  look  at  a  linear  object  with  the  points  I,  2,  3,  then  the  corresponding  retinal 
images  are  i,  2,  3  and  I,  2,  3,  which  are  obviously  identical  points  of  the  retinae  (Fig.  567).  If, 
while  looking  at  this  line,  there  be  a  point,  A,  nearer  the  eyes,  or  B,  further  from  them,  then,  on  focus- 
ing for  I,  2,  3,  neither  the  rays  (A,  a.  A,  a)  coming  from  A,  nor  those  (B,  b,  B,  b)  from  B,  fall  upon 
identical  points ;  hence  A  and  B  appear  double. 

Make  a  point  {e.g.,  2)  with  ink  on  paper ;  of  course  the  image  will  fall  upon  both  foveae  centrales 
of  the  retinse  (2,  2),  which  of  course  are  identical  points.  Now  press  laterally  upon  one  eye,  so  as 
to  displace  it  slightly,  then  two  points  at  once  appear,  because  the  image  of  the  point  no  longer  falls 
upon  the  fovea  centralis  of  the  displaced  eye,  but^  on  an  adjoining  non-identical  part  of  the  retina. 
When  we  squint  voluntarily  all  objects  appear  double. 

The  vertical  surfaces  of  separation  of  the  i-etina  do  not  exactly  coincide  with  the  vertical  meridians. 
There  is  a  certain  amount  of  divergence  (0.5°— 3°),  less  above,  which  varies  in  different  individuals,  and 
it  may  be  in  the  same  individual  at  different  times  {Hering),  The  horizontal  lines  of  separation, 
however,  coincide.     Images  which  fall  upon  the  vertical  lines  of  separation  appear  to  be  vertical  to 


838 


THE    HOROPTER. 


those  on  the  horizontal  Hnes,  although  they  are  not  actually  so.  Hence,  the  vertical  lines  of  separa- 
tion are  the  apparent  vertical  meridians.  Some  observers  regard  the  identical  points  of  the  retina  as 
an  acquircii  arrangement ;  others  regard  it  as  normally  innate.  Persons  who  have  had  a  sijuint  from 
their  birth  see  singly;  in  these  cases,  the  identical  points  must  be  differently  disix)sed. 

The  horopter  represents  all  those  points  of  the  outer  world  from  which  rays  of 
light  passing  into  both  eyes  fall  upon  identical  points  of  the  retina,  the  eyes  being 
in  a  certain  position.     It  varies  with  the  different  positions  of  the  eyes. 

1.  In  the  primary  position  of  both  eyes  with  the  visual  axes  parallel,  the  rays  of  direction  pro- 
ceeding from  two  identical  points  of  the  two  retinx  are  parallel  and  intersect  only  at  infinity.  Hence 
for  the  primary  jiosition  the  horopter  is  a  plane  in  infinity. 

2.  In  the  secondary  position  of  the  eyes  with  converging  visual  axes,  the  horopter  for  the 
transverse  lines  of  separation  is  a  circle  which  passes  through  tlie  nodal  points  of  i)Oth  eyes  (Fig.  568, 
K,  K),  and  through  the  fixed  points  I,  II,  III.  Tlie  horopter  of  the  vertical  lines  of  separation  is 
in  this  position  vertical  to  the  plane  of  vision. 

3.  In  the  symmetrical  tertiary  position,  in  which  the  horizontal  and  vertical  lines  of  separation 
form  an  angle,  the  horopter  of  the  vertical   lines  of  separation  is  a  straight  line  inclined  toward  the 


Fig.  568. 


Scheme  of  identical  and  non-identical  points  of  the 
retina. 


Horopter  for  the  secondary  position,   with 
convergence  of  the  visual  axes. 


horizon.     There  is  no  horopter  for  the  identical  points  of  the  horizontal  lines  of  separation,  as  the 
lines  of  direction  prolonged  from  the  identical  points  of  these  points  do  not  intersect. 

4.  In  the  unsymmetrical  tertiary  position  (with  rolling)  of  the  eyes,  in  which  the  fixed  point  lies 
at  imequal  distances  from  both  nodal  points,  the  horopter  is  a  curve  of  a  complex  form. 

All  objects,  the  rays  proceeding  from  which  fall  upon  non-identical  points  of 
the  retinae,  appear  double.  We  can  distinguish  director  crossed  double  images, 
according  as  the  rays  prolonged  from  the  non-identical  points  of  the  retina  inter- 
sect in  front  o^  or  behind  iX^^  fixed  point. 

Experiment. — Hold  two  fingers — the  one  behind  the  other — before  both  eyes.  Accommodate 
for  the  far  one  and  then  the  near  one  appears  double,  and  when  we  accommodate  for  the  near  one  the 
far  one  appears  double.  If,  when  accommodating  for  the  near  one,  the  right  eye  be  closed,  the  left 
(cro.ssed)  image  of  the  far  finger  disappears.  On  accommodating  for  the  far  finger  and  closing  the 
right  eye,  the  right  (direct)  double  image  of  the  near  finger  disappears. 

Double  images  are  referred  to  the  proper  distance  from  the  eyes,  just  as  single 
images  are. 


/ 

B 

.       » 

STEREOSCOPIC   VISION.  839 

Neglect  of  Double  Images. — Notwithstanding  the  very  large  number  of 
double  images  which  must  be  formed  during  vision,  they  do  not  disturb  vision.  As 
a  general  rule  they  are  "  neglected,"  so  that  the  attention  must,  as  a  rule,  be  directed 
to  them  before  they  are  perceived.     This  condition  is  favored  thus  : — 

1.  The  attention  is  always  directed  to  the  point  of  the  field  of  vision  which  is  accommodated  for 
at  the  time.  The  image  of  this  part  is  projected  on  to  both  yellow  spots,*which  are  identical  points 
of  the  retina. 

2.  The  form  and  color  of  objects  on  the  lateral  parts  of  the  retina  are  not  perceived  so  sharply. 

3.  The  eyes  axe  always  accommodated  for  those  points  which  are  looked  at.  Hence,  indistinct 
images  with  diffusion  circles  are  always  formed  by  those  objects  which  yield  double  images,  so  that 
they  can  be  more  readily  neglected. 

4.  Many  double  images  lie  so  close  together  that  the  greater  part  of  them,  when  the  images  are 
large,  covers  the  other. 

5.  By  practice  images  which  do  not  exactly  coincide  may  be  united. 

402.   STEREOSCOPIC  VISION.— On  looking  at  an  object,  both  eyes  do 
not  yield  exactly  similar  images  of  that  object — the  images  are  slightly  different, 
because  the  two  eyes  look  at  the  object  from  two  differ- 
ent points  of  view.     With  the  right  eye  we  can  see  ^*^"  ^  ^' 

more  of  the  side  of  the  body  directed  toward  it,  and  A C     a_ 

the  same  is  the  case  with  the  left  eye.  Notwithstanding 
this  inequality,  the  two  images  are  united.  How  two 
different  images  are  combined  is  best  understood  by 
analyzing  the  stereoscopic  images. 

Let,  in  Fig.  569,  L  and  R  represent  two  such  images  as  are 
obtained  with  the  left  and  right  eyes.     These  images,  when  seen  L 

with  a  stereoscope,  look  like  a  truncated  pyramid,  which  projects         Two  Stereoscopic  Drawings, 
toward  the  eye  of  the  observer,  as  the  points  indicated  by  the  same 

signs  cover  each  other.  On  measuring  the  distance  of  the  points,  which  coincide  or  cover  each  other 
in  both  figures,  we  find  that  the  distances  A,  a,  B,  d,  C,  c,  D,  d  are  equally  great,  and  at  the  same 
time  are  the  widest  of  all  the  points  of  both  figures;  the  distances  E,  e,  '?,/,  G,  ^,  H,  h  are  also 
equal,  but  are  smaller  than  the  former.  On  looking  at  the  coinciding  lines  (A,  E,  a,  e,  and  B,  F,  b, 
f),  we  observe  that  all  the  points  of  this  line  which  he  nearer  to  A  «  and  B  b  are  further  apart  than 
those  lying  nearer  E  e  and  ¥  f. 

Comparing  these  results  with  the  stereoscopic  image,  we  have  the  following  laws 
for  stereoscopic  vision  :  i.  All  those  points  of  two  stereoscopic  images,  and 
of  course  of  two  retinal  images  of  an  object,  which  in  both  images  are  equally 
distant  from  each  other,  appear  on  the  same  plane.  2.  All  points  which  are  nearer 
to  each  other,  compared  with  the  distance  of  other  points,  appear  to  be  nearer  to  the 
observer.  3.  Conversely,  all  points  which  lie  further  apart  from  each  other  appear 
perspectively  in  the  background. 

The  cause  of  this  phenomenon  lies  in  the  fact  that,  ''in  vision  with  both  eyes 
we  constantly  refer  the  position  of  the  individual  images  in  the  direction  of  the 
visual  axis  to  where  they  both  intersect." 

Proofs. — The  following  stereoscopic  experiment  proves  this  (Fig.  570)  :  Take  both  images  of 
two  pairs  of  points  (a,  b,  and  a,  ,'?),  which  are  at  unequal  distances  from  each  other  on  the  surface 
of  the  paper.  By  means  of  small  stereoscopic  prisms  cause  them  to  coincide,  then  the  combined 
point,  A  of  a,  and  a  appears  at  a  distance  on  the  plane  of  the  paper,  while  the  other  point,  B,  pro- 
duced by  the  superposition  of  b  and  /?,  floats  in  the  air  before  the  observer.  Fig.  570  shows  how 
this  occurs.  The  following  experiment  shows  the  same  result :  Draw  two  figures,  which  are  to  be 
superposed  similar  to  the  lines  B,  A,  A,  E,  b,  a,  and  a,  e,  in  Fig.  569.  In  the  lines  B,  A,  and  b,  a, 
all  the  points  which  are  to  be  superposed  lie  equally  distant  from  each  other,  while,  on  the  contrary, 
all  the  points  in  A,  E,  and  a,  e,  which  lie  nearer  E  and  e,  are  constantly  nearer  to  each  other.  When 
looked  at  with  a  stereoscope,  the  superposed  verticals.  A,  e,  and  B,  b,  he  in  the  plane  of  the  paper, 
while  the  superposed  lines,  A,  a,  and  E,  e,  project  obliquely  toward  the  observer  from  the  plane 
of  the  paper.  From  these  two  fundamental  experiments  we  may  analyze  all  pairs  of  stereoscopic 
pictures.  Thus,  in  Fig.  569,  if  we  exchange  the  two  pictures,  so  that  R  hes  in  the  place  of  L, 
then  we  must  obtain  the  impression  of  a  truncated  hollow  pyramid. 


840 


THEORY    OF   STEREOSCOPIC    VISION. 


Two  stereoscopic  pictures,  whicii  are  so  constructed  that  the  one  contains  the  body  from  the 
front  and  above,  and  the  other  contains  it  from  the  front  and  below  (suppose  in  I'ig.  569  the  lines 
A  B,  and  a  b,  were  the  ground  lines),  can  never  be  superposed  by  means  of  the  stereoscope. 

This  process  has  been  explained  in  another  way.  Of  the  two  figures,  R  and  L 
(Fig.  569),  only  A  B  C  D,  and  a  b  c  d,  fall  upon  identical  points  of  the  retina,  hence 
these  alone  can  be  superposed  ;  or,  when  there  is  a  different  convergence  of  the 
visual  axis,  only  E  F  G  H,  and  efgh,  can  be  superposed,  for  the  same  reason. 
Suppose  the  square  ground  surfaces  of  the  figures  are  first  superposed,  in  order  to 
explain  the  stereoscopic  impression,  it  is  further  assumed  that  both  eyes,  after  super- 
position of  the  ground  squares,  are  rapidly  moved  toward  tlie  apex  of  the  pyramid. 
As  the  axis  of  the  eyes  must  thereby  converge  more  and  more,  the  apex  of  the 
pyramid  appears  to  project;  as  all  points  which  require  the  convergence  of  the 
eyes  for  their  vision  appear  to  us  to  be  nearer  (see  below).  Thus,  all  corresponding 
parts  of  both  figures  would  be  brought,  oiie  after  the  other,  upon  identical  points 
of  the  retina   by  the  movements  of  the  eyes  {Brilcke). 


Fig.  570. 


Fig.  571. 


Wheatstone's  Stereoscope. 


Scheme  of  Brewster's  Stereoscope. 


It  has  been  urged  against  this  view  that  the  duration  of  an  electrical  spark  suffices 
for  stereoscopic  vision  {Dove) — a  time  which  is  quite  insufficient  for  the  move- 
ments of  the  eyes.  Although  this  may  be  true  for  many  figures,  yet  in  the  cor- 
rect combination  of  complex  or  extraordinary  figures,  these  movements  of  the 
visual  axes  are  not  excluded,  and  in  many  individuals  they  are  distinctly  advanta- 
geous. Not  only  the  actual  movements  necessary  for  this  act,  but  the  sensations 
derived  from  the  muscles  are  also  concerned. 

When  two  figures  are  momen/anVy  combined  to  form  a  stereoscopic  picture,  there 
being  no  movement  of  the  eyes,  clearly  many  points  in  the  stereoscopic  pictures  are 
superposed  which,  strictly  speaking,  do  not  fall  upon  identical  points  of  the  retina. 
Hence  we  cannot  characterize  the  identical  points  of  the  retina  as  coinciding 
mathematically;  but  from  a  physiological  point  of  view  we  must  regard  such  points 
as  identical,  which,  as  a  rule,  by  simultaneous  stimulation,  give  rise  to  a  single 
image.  The  mind  obviously  plays  a  part  in  this  combination  of  images.  There  is 
a  certain  psychical  tendency  to  fuse  the  double  images  on  the  retinae  into  one 


THE    STEREOSCOPE. 


841 


image,  in  accordance  with  the  fact  that  we,  from  experience,  recognize  the  existence 
of  a  single  object.  If  the  diiferences  between  two  stereoscopic  pictures  be  too 
great,  so  that  parts  of  the  retina  too  wide  apart  are  excited  thereby,  or  when  new 
lines  are  present  in  a  picture,  and  do  not  admit  of  a  stereoscopic  effect,  or  disturb 
the  combination,  then  the  stereoscopic  effect  ceases. 

The  stereoscope  is  an  instrument  by  means  of  which  two  somewhat  similar  pictures  drawn  in 
perspective  may  be  superposed  so  that  they  appear  single.  Wheatstone  (1838)  obtained  this  result 
by  means  of  two  mirrors  placed  at  an  angle  (Fig.  570);  Brewster  (1843)  ^Y  two  prisms  (Fig.  571). 
The  construction  and  mode  of  action  are  obvious  from  the  illustrations. 

Some  pairs  of  two  such  pictures  may  be  combined,  without  a  stereoscope,  by  directing  the  visual 
axis  of  each  eye  to  the  picture  held  opposite  to  it. 

Two  completely  identical  pictures,  i.  e.,  in  which  all  corresponding  points  have  exactly  the  same 
relation  to  each  other  as  the  same  sides  of  two  copies  of  a  book,  appear  quite  flat  under  the  stereo- 
scope ;  as  soon,  however,  as  in  one  of  them  one  or  more  points  alters  its  relation  to  the  correspond- 
ing points,  this  point  either  projects  or  recedes  from  the  plane. 

Telestereoscope. — When  objects,  placed  at  a  great  distance,  are  looked  at,  e.  g.,  the  most  distant 
part  of  a  landscape,  they  appear  to  us  to  be  flat,  as  in  a  picture,  and  do  not  stand  out,  because  the 
slight  differences  of  position  of  our  eyes  in  the  head  are  not  to  be  compared  with  the  great  distance. 
In  order  to  obtain  a  stereoscopic  view  of  such  objects,  v.  Helmholtz  constructed  the  telestereoscope 
(Fig.  572),  an  apparatus  which  by  means  of  two  parallel  mirrors,  places,  as  it  were,  the  point  of  view 
of  both  eyes  wider  apart.  Of  the  mirrors,  L  and  R  each  projects  its 
image  of  the  landscape  upon  /  and  r,  to  which  both  eyes,  O,  0,  are  FiG.  573. 

directed.  According  to  the  distance  between  L  and  R  the  eyes  O,  0,  as 
it  were,  are  displaced  to  O^,  Oy.  The  distant  landscape  appears  like  a 
stereoscopic  view.  In  order  to  see  distant  parts  more  clearly  and  nearer, 
a  double  telescope  or  opera  glass  may  be  placed  in  front  of  the  eyes. 

Take  two  corresponding  stereoscopic  pictm^es,  with  the  surfaces  black 
in  one  case  and  light  in  the  other.     Draw  two  truncated  pyramids  like 


0        0 

Telestereoscope  of  v.  Helmholtz. 


Wheatstone's  Pseudoscope. 


Fig.  569,  make  one  figure  exactly  like  L,  i.  e.,  with  a  white  surface  and  black  lines,  and  the  other  with 
white  lines  and  a  black  surface,  then  under  the  stereoscope  such  objects  glance.  The  cause  of  the 
glancing  condition  is  that  the  glancing  body  at  a  certain  distance  reflects  bright  light  into  one  eye  and 
not  into  the  other,  because  a  ray  reflected  at  an  angle  cannot  enter  both  eyes  simultaneously  [Dove). 

Wheatstone's  Pseudoscope  consists  of  two  right-angled  prisms  (Fig.  573,  A  and  B)  enclosed 
in  a  tube,  through  which  we  can  look  in  a  direction  parallel  with  the  surfaces  of  the  hypothenuses. 
If  a  spherical  surface  be  looked  at  with  this  instrument,  the  image  formed  in  each  eye  is  inverted 
laterally.  The  right  eye  sees  the  view  usually  obtained  by  the  left  eye,  and  conversely;  the  shadow 
which  the  body  in  the  light  throws  upon  a  light  grc  und  is  reversed.      Hence  the  ball  appears  hollow. 

Struggle  of  the  Fields  of  Vision. — The  stereoscope  is  also  useful  for  the  following  purpose : 
In  vision  with  both  eyes,  both  eyes  are  almost  never  active  simultaneously  and  to  the  same  extent; 
both  undergo  variations,  so  that  first  the  impression  on  the  one  retina  and  then  that  on  the  other 
is  stronger.  If  two  different  surfaces  be  placed  in  a  stereoscope,  then,  especially  when  they  are 
luminous,  these  two  alternate  in  the  general  field  of  vision,  according  as  one  or  other  eye  is  active 
[Panu??i).  Take  two  surfaces  with  lines  ruled  on  them,  so  that  when  the  surfaces  are  superposed  the 
lines  will  cross  each  other,  then  either  the  one  or  the  other  system  of  lines  is  more  prominent 
iyPami7?t).  The  same  is  true  with  colored  stereoscopic  figures,  so  that  there  is  a  contest  or  struggle  of 
the  colored  fields  of  vision. 

403.    ESTIMATION    OF    SIZE    AND    DISTANCE.— Size.— We 

estimate  the  size  of  an  object — apart  from  all  other  factors — from  the  size  of  the 


842 


ESTIMATION    OF   SIZE    AND    DISTANCE. 


retinal  image  ;  thus  the  moon  is  estimated  to  be  larger  than  the  stars.  If,  while 
looking  at  a  distant  landscape,  a  fly  should  suddenly  pass  across  our  field  of  vision, 
near  to  our  eye,  then  the  image  of  the  fly,  owing  to  the  relatively  great  size  of  the 
retinal  image,  may  give  one  the  impression  of  an  object  as  large  as  a  bird.  If, 
owing  to  defective  accommodation,  the  image  gives  rise  to  diffusion  circles,  the 
size  may  appear  to  be  even  greater.  But  objects  of  very  unequal  size  give  equally 
large  retinal  images,  esi)ecially  if  they  are  placed  at  such  a  distance  that  they  form 
the  same  visual  angle  (Fig.  531)  ;  so  that  in  estimating  the  actual  size  of  an 
object,  as  opposed  to  the  apparent  size  determined  by  the  visual  angle,  the  esti- 
mate of  distance  is  of  the  greatest  importance. 

As  to  the  distance  of  an  object,  we  obtain  some  information  from  the  feeling 
of  accommodation,  as  a  greater  effort  of  the  muscle  of  accommodation  is  required 
for  exact  vision  of  a  near  object  than  for  seeing  a  distant  one.  But,  as  with  two 
objects  at  unequal  distances  giving  retinal  images  of  the  same  size,  we  know  from 
experience  that  that  object  is  smaller  which  is  near,  then  that  object  is  estimated 
to  be  the  smaller  for  which,  during  vision,  we  must  accommodate  more  strongly. 

In  this  way  we  explain  the  following :  A  person  beginning  to  use  a  microscope  always  observes 
with  his  eyes  accommodated  for  a  near  object,  while  one  used  to  the  microscope  looks  through  it 
without  accommodating.  Hence  beginners  always  estimate  microscopic  objects  as  too  small,  and  on 
making  a  drawing  of  them  it  is  too  small.  If  we  produce  an  after-image  in  one  eye,  it  at  once 
appears  smaller  on  accommodating  for  a  near  object,  and  again  becomes  larger  daring  negative 
accommodation.  If  we  look  with  one  eye  at  a  small  body  placed  as  near  as  possible  to  the  eye,  then 
a  body  lying  behind  it,  but  seen  only  indirectly,  appears  smaller. 

Angle    of  Convergence    of  Visual  Axes. — In  estimating  the  size  of  an 

object,  and  taking  into  account  our  estimate  of  its  distance,  we  also  obtain  much 
more  important  information  from  the  degree  of  convergence  of  the  visual 
axes.  We  refer  the  position  of  an  object,  view^ed  with  both  eyes,  to  the  point 
where  both  visual  axes  intersect.  The  angle  formed  by  the  two  visnal  axes  at  this 
])oint  is  called  the  "  angle  of  convergence  of  the  visual  axes"  {^^  GesichtswinkeV'). 
The  larger,  therefore,  the  visual  angle,  the  size  of  the  retinal  image  remaining  the 
same — we  judge  the  object  to  be  nearer.     The  nearer  the  object  is,  it  may  be  the 

smaller,  in  order  to  form  a  "  visual  angle"  of 
Fig.  574.  the  same  size,  such  as  a  distant  large  object  would 

give.  Hence,  w^e  conclude  that  with  the  same 
apparent  size  (equally  large  visual  angle,  or  reti- 
nal images  of  the  same  size)  we  judge  that  object 
to  be  smallest  which  gives  the  greatest  converg- 
ence of  the  visual  axes  during  binocular  vision. 
As  to  the  muscular  exertion  necessary  for  this 
purpose,  we  obtain  information  from  the  mus- 
cular sense  of  the  ocular  muscles. 

Experiments  and  Proofs. — The  chess-board  phe- 
nomenon of  II.  Meyer.  i.  If  we  look  at  a  uniform 
chess-board  like  pattern  (tapestry  or  carpet),  then,  when  the 
visual  axes  are  directed  directly  forward,  tlie  spaces  on  the 
pattern  appear  of  a  certain  size.  If,  now,  we  look  at  a 
nearer  object,  we  may  cause  the  visual  axes  to  cross,  when 
the  pattern  apparently  moves  toward  the  plane  of  the  fixed 
point,  so  that  the  crossed  double  images  are  superposed, 
and  the  pattern  at  once  appears  smaller. 

2.  Rollett  looks  at  an  object  through  two  thick  prisms  of 
glass  placed  at  an  angle.  The  plates  are  at  one  time  so 
placed  that  the  apex  of  the  angle  is  directed  toward  the 
observer  (Fig.  574,  II),  at  another  in  the  reverse  posi- 
tion (I).  If  both  eyes,y"  and  /,  are  to  see  the  object  a,  in  I,  then  as  the  glass  plates  so  displace  the 
rays,  a,  ^,  and  a,g,  as  to  make  them  parallel  with  the  direction  of  these  rays,  viz.,  e,f,  and  //,/,  then 
the  eyes  must  converge  more  than  when  they  are  turned  directly  toward  a.  Hence  the  object  appears 
nearer  and  smaller,  as  at  a.     In   II,  the  rays,  b^  k,  and  b^  0,  from  the  nearer  object  b^,  fall  upor 


Rollett's  glass  plate  apparatus. 


THE    EYELIDS. 


843 


the  glass  plates.     In  order  to  see  b^,  the  eyes  [n  and  q)  must  diverge  more,  so  that  b  appears  more 
distant  and  larger. 

3.  In  looking  through  Wheatstoiie' s  reflecting  stereoscope  (Fig.  571),  it  is  obvious  that  the  more  the 
two  images  approach  the  observer,  the  more  must  the  observer  converge  his  visual  axes,  because  the 
angles  of  incidence  and  reflexion  are  greater.  Hence  the  compound  picture  now  appears  to  him  to 
be  smaller.  If  the  centre  of  the  image,  R,  recedes  to  R^,  then  of  course  the  angle,  S^p  ;-  p,  is  equal 
to  Sj,  r  Rj,  and  the  same  on  the  left  side. 

4.  In  using  the  telesiereoscope,  the  two  eyes  are,  as  it  were,  separated  from  each  other,  then  of 
course  in  looking  at  objects  at  a  certain  distance  the  convergence  of  the  visual  axes  must  be  greater 
than  in  normal  vision.  Hence,  objects  in  a  landscape  appear  as  in  a  small  model.  But  as  we  are 
accustomed  to  infer  that  such  small  objects  are  at  a  great  distance,  hence  the  objects  themselves 
appear  to  recede  in  the  distance. 

Estimation  of  Distance. — When  the  retinal  images  are  of  the  same  size,  we 
estimate  the  distance  to  be  greater  the  less  the  effort  of  accommodation,  and 
conversely.  In  binocular  vision,  when  the  retinal  images  are  of  the  same  size,  we 
infer  that  that  object  is  most  distant  for  which  the  optic  axes  are  least  converged, 
and  conversely.  Thus,  the  estimation  of  size  and  distance  go  hand  in  hand,  in 
great  part  at  least,  and  the  correct  estimation  of  the  distance  also  gives  us  a  correct 
estimate  of  the  size  of  objects  {Descartes).  A  further  aid  to  the  estimation  of 
distance  is  the  observation  of  the  apparent  displacement  of  objects,  on  moving  our 
head  or  body.  In  the  latter,  especially,  lateral  objects  appear  to  change  their 
position  toward  the  background,  the  nearer  they  are  to  us.  Hence,  when  travel- 
ing in  a  train,  in  which  case  the  change  of  position  of  the  objects  occurs  very 
rapidly,  the  objects  themselves  are  regarded  as  nearer,  and  also  smaller  {Dove). 
Lastly,  those  objects  appear  to  us  to  be  nearest  which  are  most  distinct  in  the  field 
of  vision. 

Example. — A  light  in  a  dark  landscape,  and  a  dazzling  crown  of  snow  on  a  hill,  appear  to  be 
near  to  us;  looked  at  from  the  top  of  a  high  mountain,  the  silver  glancing  curved  course  of  a  river 
not  unfrequently  appears  as  if  it  were  raised  from  the  plane. 

False  Estimates  of  Size  and  Direction. — i.  Aline  divided  by  intermediate  points  appears 
longer  than  one  not  so  divided.  Hence  the  heavens  do  not  appear  to  us  as  a  hollow  sphere,  but  as 
curved  like  an  ellipse ;  and  for  the  last  reason  the  disk  of  the  set- 
ting sun  is  estimated  to  be  larger  than  the  sun  when  it  is  in  the 
zenith.  2.  If  we  move  a  circle  slowly  to  and  fro  behind  a  slit,  it 
appears  as  a  horizontal  ellipse ;  if  we  move  it  rapidly,  it  appears  as 
a  vertical  ellipse.  3.  If  a  very  fine  line  be  drawn  obliquely  across  a 
vertical  thick  black  line,  then  the  direction  of  the  fine  line  beyond 
the  thick  one  appears  to  be  different  from  its  original  direction.  4. 
ZoUner's  Lines. — Draw  three  parallel  horizontal  lines  i  centimetre 
apart,  and  through  the  upper  and  lower  ones  draw  short  oblique 
parallel  lines  in  the  direction  from  above  and  the  left  to  below  and 
the  right ;  through  the  middle  line  draw  similar  oblique  lines,  but 
in  the  opposite  direction,  then  the  three  horizontal  lines  no  longer 
appear  to  be  parallel.  [Fig.  575  shows  a  modification  of  this.  The 
lines  are  actually  parallel,  although  some  of  them  appear  to  con- 
verge and  others  diverge.]  If  we  look  in  a  dark  room  at  a  bright 
vertical  line  and  then  bend  the  head  toward  the  shoulder,  the  line 
appears  to  be  bent  in  the  opposite  direction  I^Aubert). 

404.  PROTECTIVE  ORGANS  OF  THE  EYE.— I.  The  eyelids  are  represented  in 
sections  in  Fig.  576.  The  tarsus  is  in  reality  not  cartilage,  but  merely  a  rigid  plate  of  connective 
tissue,  in  which  the  Meibomian  glands  are  imbedded;  acinous  sebaceous  glands  moisten  the 
edges  of  the  eyelids  with  fatty  matter.  At  the  basal  margin  of  the  tarsus,  especially  of  the  upper 
one,  close  to  the  reflection  of  the  conjunctiva,  open  the  acino-tubular  glands  of  Krause.  The  con- 
junctiva covers  the  anterior  surface  of  the  bulb  as  far  as  the  margin  of  the  cornea,  over  which  the 
epithelium  alone  is  continued.  On  the  posterior  surface  of  the  eyelid,  the  conjunctiva  is  partly 
provided  with  papillae.  It  is  covered  by  stratified  prismatic  epithelium.  Coiled  glands  occur  in 
ruminants  just  outside  the  margin  of  the  cornea,  while  outside  this,  toward  the  outer  angle  of  the 
eye  in  the  pig,  there  are  simple  glandular  sacs.  Waldeyer  describes  modified  sweat  glands  in  the 
tarsal  margins  in  man.  Small  lymphatic  sacs  in  the  conjunctiva  are  called  trachoma  glands.  Krause 
found  end  bulbs  in  the  conjunctiva  (|  424).     The  blood  vessels  in  the  conjunctiva  communicate 


Fig 


ZoUner's  Lines. 


844 


THE    LACHRYMAL    APPARATUS. 


with  the  juice  canals  in  the  cornea  and  sclerotic  (p.  787).     The  secretion  of  the  conjunctiva,  besides 
some  mucus,  consists  of  tears,  which  may  be  as  abundant  as  that  formed  in  the  lachrymal  glands. 

Closure  of  the  eyelids  is  effected  by  the  orbicularis  palpebrarum  (^facial  neme, 

^  349),  whereby  the  upper  lid  falls 
in  virtue  of  its  own  weight.  This 
muscle  contracts — (i)  voluntarily; 
J^  (2)  involuntarily  (single  contrac- 
tions) ;  (3)  reflexly  by  stimulation 
of  all  the  sensory  fibres  of  the  tri- 
geminus distributed  to  the  bulb  and 
its  immediate  neighborhood  (§  347), 
also  by  intense  stimulation  of  the 
retina  by  light ;  (4)  continued  in- 
voluntary closure  occurs  during 
sleejj. 

Opening  of  the  eyehds  is  brought 
about  by  the  passive  descent  of  the 
lower  one,  and  the  active  elevation 
of  the  upper  eyelid  by  the  levator 
palpebrae  superioris  (§  345).  The 
smooth  muscular  fibres  of  the  eye- 
lids also  aid  (p.  643).  In  looking 
downward,  the  lower  eyelid  is 
pulled  downward  by  bands  of  con- 
nective tissue  which  run  from  the 
inferior  rectus  to  the  inferior  tarsal 
cartilage  iSchwalbe). 

IL  The  lachrymal  apparatus  consists 
of  the  lachrymal  glands,  which  in  struc- 
ture closely  resemble  the  parotid,  their  acini 
being  lined  by  low  cylindrical  granular 
epithehum.  Four  to  five  larger,  and  eight 
to  ten  smaller  excretory  ducts  conduct 
the  tears  above  the  outer  angle  of  the  lid 
into  the  fornix  conjunctivae.  The  tear 
ducts,  beginning  at  the  puncta  lachrymalis, 
are  composed  of  connective  and  elastic 
tissue,  and  are  lined  by  stratified  squamous 
epithelium.  Striped  muscle  accompanies 
the  duct,  and  by  its  contraction  keeps  the 
duct  open.  Toldt  found  no  sphincter  sur- 
rounding the  puncta  lachrymalia,  while 
Gerlach  found  an  incomplete  circular  mus- 
culature. The  connective-tissue  covering 
of  the  tear  sac  and  canal  is  united  with  the 
The  thin  mucous 
G,  conjunctiva ;  y,  inner  /r,  outer  edge  of  the  lid ;  4,pig-  membrane, 'which  contains  much  adenoid 
ment  cells;    5,    sweat    glands;  6,  hair  lollicles;  0   and  23,     .  '  ,,      •      i-       j  1  •      1 

sections  of  nerves ;  o,  arteries;  10,  veins;  11,  cilia;  12,  tissue  and  lymph  cells,  IS  Imed  by  a  Single 
modified  sweat  glands;  13,  circular  muscle  of  Riolan  ;  14,  layer  of  ciliated  Cylindrical  epithelium,  which 
Meibomian  gland;    15.  section  of  an  acinus  of  the  same;  16,   j^gj^^^,  ^^  j^^q   ,hg  Stratified   form.      The 

posterior  tarsal  glands  ;   18  and  19,  tissue  of  the  tarsus ;  20,  ■  r    i_       j  •       1-  -j    j        -lU 

pre-tarsal  or  sub-muscular  connective  tissue  ;  21  and  22,  con-   opening  Ot   the    duct    IS  often  provided   With 
junctivae,   with    its  epithelium ;    24,  fat;  25,  loosely   woven  a  valve-like  fold  (Hasner's  valve). 
posterior  end  of  the  tarsus  ;  26,  section  of  a  palpebral  artery. 

The  conduction  of  the  tears 
occurs  between  the  lids  and  the  bulb  by  means  of  capillarity,  the  closure  of  the 
eyelids  aiding  the  process.  The  Meibomian  secretion  prevents  the  overflow  of  the 
tears  [just  as  greasing  the  edge  of  a  glass  vessel  prevents  the  water  in  it  from  over- 
flowing].    The  tears  are  conducted  from  the  puncta  through  the  duct,  chiefly  by  a 


epider- 


Vertical  section  through  the  upper  eyelid.     /),  cutis 

mis  ;  2,  chorium  ;  B,  and  3,  subcutaneous  connective  tissue 
Cand  7,  orbicularis  muscle  ;  D,  loose  sub-muscular  connec 
live  tissue;  £,  insertion  of  H.  Mijller's  muscle;  j"^,  tarsus;    adjoining     periosteum 


THE  SECRETION  OF  TEARS.  845 

siphon  action.  Horner's  muscle  (also  known  to  Duvernoy,  1678)  likewise  aids,  as 
every  time  the  eyelids  are  closed  it  pulls  upon  the  posterior  wall  of  the  sac,  and 
thus  dilates  the  latter,  so  that  it  aspirates  tears  into  it  (^Henke). 

E.  H.  Weber  and  Hasner  ascribe  the  aspiration  of  the  tears  to  the  diminution  of  the  amount  of  air 
in  the  nasal  cavities  during  inspiration.  Arlt  asserts  that  the  tear  sac  is  compressed  by  the  contraction 
of  the  orbicularis  muscle,  so  that  the  tears  must  be  forced  toward  the  nose.  Lastly,  Stellwag  supposes 
that  when  the  eyelids  are  closed  the  tears  are  simply  pressed  into  the  puncta,  while  Gad  denies  that 
there  is  any  kind  of  pumping  mechanism  in  the  nasal  canal.  Landois  points  out  that  the  tear  ducts 
are  surrounded  by  a  plexus  of  veins,  which  according  to  thek  state  of  distention  may  influence  the 
size  of  these  tubes. 

The  secretion  of  tears  takes  place  only  by  direct  stimulation  of  the  lachrymal 
nerve  (§  347,  I,  2),  subcutaneous  malar  (§  347,  II,  2),  and  cervical  sympathetic 
(§  356,  A,  6),  which  have  been  called  secretory  nerves.  Secretion  may  also 
be  excited  reflexiy  (j^.  641)  by  stimulation  of  the  nasal  mucous  membrane  only  on 
the  same  side  {Herzenstein).  The  ordinary  secretion  in  the  waking  condition  is 
really  a  reflex  secretion  produced  by  the  stimulation  of  the  anterior  surface  of  the 
bulb  by  the  air,  or  by  the  evaporation  of  tears.  A  very  bright  light  also  causes 
a  reflex  secretion  of  tears,  the  optic  being  the  afferent  nerve.  The  centre  in  the 
rabbit  does  not  extend  forward  beyond  the  origin  of  the  fifth  nerve,  but  it  extends 
downward  to  the  fifth  vertebra  {Eckhard).  During  sleep  all  these  factors  are  absent, 
and  there  is  no  secretion.  Histological  changes. — Reichel  found  that  in  the 
active  gland  (after  injection  of  pilocarpin)  the  secretory  cells  became  granular, 
turbid,  and  smaller,  while  the  outlines  of  the  cells  became  less  distinct,  and  the 
nuclei  spheroidal.  In  the  resting  gland,  the  cells  are  bright  and  slightly  granular, 
with  irregular  nuclei.  Intense  stimulation  by //^/// acting  on  the  optic  nerve  causes 
a  reflex  secretion  of  tears.  The  flow  of  tears  accompanying  certain  violent  emo- 
tions, and  even  hearty  laughing,  is  still  unexplained.  During  coughing  and 
vomiting  the  secretion  of  tears  is  increased  partly  reflexly,  and  partly  by  the  out- 
flow being  prevented  by  the  expiratory  pressure. 

Function. — The  tears  moisten  the  bulb,  protect  it  from  drying,  and  float  away 
small  particles,  being  aided  in  this  by  the  closure  of  the  eyelids.  Atropin  dimin- 
ishes the  tears  (^Mogaard). 

Composition. — The  tearsarealkaline,  saline  to  taste,  and  representa  "^serous" 
secretion.  Water  98.1  to  99  ;  1.46  organic  substances  (o.i  albumin  and  mucin, 
0.1  epithelium)  ;  0.4  to  0.8  salts  (especially  NaCl). 

[Action  of  Drugs. — Essential  volatile  oils  and  eserin  increase  the  secretion  of  tears,  atropin 
arrests  it,  while  eserin  antagonizes  the  effect  of  atropin  and  causes  an  increased  secretion.] 

405.  COMPARATIVE— HISTORICAL.^Comparative. — The  simplest  form  of  visual 
apparatus  is  represented  by  aggregations  of  pigment  cells  in  the  outer  coverings  of  the  body,  which 
are  in  connection  with  the  termination  of  afferent  nerves.  The  pigment  absorbs  the  rays  of  light, 
and  in  virtue  of  the  light  ether  discharges  kinetic  energy,  which  excites  the  terminations  of  the 
nervous  apparatus.  Collections  of  pigment  cells,  with  nerve  fibres  attached,  and  provided  wiih  a 
clear  refractive  body,  occur  on  the  margin  of  the  bell  of  the  higher  medusae,  while  the  lower  forms 
have  only  aggregations  of  pigment  on  the  bases  of  their  tentacles.  Also,  in  many  lower  worms 
there  are  pigment  spots  near  the  brain.  In  others,  the  pigment  lies  as  a  covering  round  the  termina- 
tions of  the  nerves,  which  occur  as  "  crystalline  rods"  or  "  crystalline  spheres."  In  parasitic  worms, 
the  visual  apparatus  is  absent.  In  star-fishes,  the  eyes  are  at  the  tips  of  the  arms,  and  consist  of  a 
spherical  crystal  organ  surrounded  with  pigment,  with  a  nerve  going  to  it.  In  all  other  echinoder- 
mata  there  are  only  accumulations  of  pigment.  Among  the  annulosa  there  are  several  grades  of 
visual  apparatus.  (l)  Without  a  cornea,  there  may  be  only  one  crystal  sphere  (nervous  end 
organ)  near  the  brain,  as  in  the  young  of  the  crab ;  or  there  may  be  several  crystal  spheres  forming 
a  compound  eye,  as  in  the  lower  crabs.  (2)  With  a  cornea,  consisting  of  a  lenticular  l:ody  formed 
from  the  chitin  of  the  outer  integument,  the  eye  itself  may  be  simpb,  merely  consisting  of  one 
crystal  rod,  or  it  may  be  compound.  Ttie  compound  eye  consists  of  only  one  large  lenticular  cornea, 
common  to  all  the  crystal  rods,  as  in  the  spiders ;  or  each  crystal  rod  has  a  special  lenticular  cornea 
for  itself  The  numerous  rods  surrounded  by  pigment  are  closely  packed  together,  and  are  arranged 
upon  a  curved  surface,  so  that  their  free  ends  also  form  a  part  of  a  sphere.  The  chitinous  invest- 
ment of  the  head  is  faceted,  and  forms  a  small  corneal  lens  on  the  free  end  of  each  rod.     According 


846  COMrARATIVE HISTORICAL. 

to  one  view,  each  facette,  with  the  lens  and  crystal  sphere,  is  a  special  eye,  and  just  as  man  has 
two  eyes  so  insects  have  several  hundred.  Each  eye  sees  the  picture  of  the  outer  world  in  toto.  This 
view  is  supported  by  the  following  experiment  of  van  Leeuwenhoek  :  If  tlie  cornea  he  sliced  oflf, 
each  facette  thereof  gives  a  special  image  of  an  object.  If  a  cross  be  made  on  the  mirror  of  a  micro- 
scope, while  a  piece  of  the  facetted  cornea  is  placed  as  an  oliject  ujjon  the  stage,  then  we  see  an 
image  of  the  cro.ss  in  each  facette  of  the  cornea.  Thus  for  each  rod  (crystal  sphere)  there  would  be 
a  special  image.  Each  corneal  facette,  however,  forms  only  a  part  of  the  image  of  the  outer  world, 
so  that  we  must  regard  the  image  as  composed  like  a  mosaic.  Among  mollusca,  the  fixed  brachi- 
opoda  have  two  pigment  spots  near  tiie  brain,  but  only  in  their  larval  condition  ;  while  the  mussel 
has,  under  similar  conditions,  pigment  spots  with  a  refractive  l)ody.  The  atiult  mussel,  however,  has 
pigment  spots  (ocelli)  only  in  the  margin  of  the  mantel,  but  some  moUusks  have  stalked  and  highly 
developed  eyes.  Some  of  the  lower  snails  have  no  eyes,  some  have  pigment  spots  on  the  iiead, 
while  the  garden  snail  has  stalked  eyes  provided  with  a  cornea,  an  optic  nerve  with  retina  and  pig- 
ment, and  even  a  lens  and  vitreous  body.  Among  cephalopoda,  the  nautilus  has  no  cornea  or  lens, 
so  that  the  sea  water  flows  freely  into  the  orbits.  Others  have  a  lens  and  no  cornea,  while  some  have 
an  opening  in  the  cornea  (I.oligo,  Sepia,  Octopus).  All  the  other  partsof  the  eye  are  well  developed. 
Among  vertebrata,  Amphioxus  has  no  eyes.  They  exist  in  a  degenerated  condition  in  Proteus 
and  the  mammal  Spalax.  In  many  tishes,  amphibians,  and  reptiles,  the  eye  is  covered  by  a  piece  of 
transpapent  skin.  [Pineal  or  Epiphysial  Eye. — Some  li/ards,  e.g.,  Hatteria,  have  a  rudimentary 
median  eye  in  the  median  line  of  the  head,  and  lodged  in  the  parietal  foramen.  It  is  developed 
from  the  pineal  body,  and  its  lens  is  formed  from  the  optic  cup,  so  that  light  falls  upon  the  retina  with- 
out penetrating  the  fibres  of  the  optic  nerve.  Thus,  it  is  an  invertebrate  type  of  eye,  where  the  retina 
and  lens  are  developed  from  epidermal  structures,  while  in  the  vertebrate  eye,  the  retina  is  developed 
from  the  cerebrum.]  Some  hag-fishes,  the  crocodile,  and  birds  have  eyelids,  and  a  nictitating 
membrane  at  the  inner  angle  of  the  eye.  Connected  with  it  is  the  Harderian  gland.  In  mam- 
mals the  nictitating  membrane  is  represented  only  by  the  plica  semilunaris.  There  is  no  lachrymal 
apparatus  in  fishes.  The  tears  of  snakes  remain  under  the  watch-glass- like  cutis  with  which  the  eyes 
are  covered.  The  sclerotic  often  contains  cartilage  which  may  ossify.  A  vascular  organ,  the  pro- 
cessus falciformis,  passes  from  the  middle  of  the  choroid  into  the  interior  of  the  vitreous  body  in 
osseous  fishes,  its  anterior  extremity  being  termed  the  campanula  lialleri.  Similarly,  there  is  the 
pecten  in  birds,  but  it  is  provided  with  muscular  fibres.  In  birds  the  cornea  is  surrounded  by  a 
bony  ring.  The  whale  has  an  enormously  thick  sclerotic.  In  aquatic  animals,  the  lens  is  nearly 
spherical.  The  muscles  of  the  iris  and  choroid  are  transversely  striped  in  birds  and  reptiles.  The 
retinal  rods  in  all  vertebrates  are  directed  from  before  backward,  while  the  analogous  elements  (crystal 
rods  and  spheres)  in  invertebrata  are  directed  from  behind  forward. 

Historical. — The  Ilippocratic  School  were  acquainted  with  the  optic  nerve  and  lens.  Aristotle 
(3S4  B.C.)  mentions  that  section  of  the  optic  nerve  causes  blindness — he  was  acquainted  with  after- 
images, short  and  long  sight.  Herophilus  (307  B.C.)  discovered  the  retina,  and  the  ciliarj'  processes 
received  their  name  in  his  school.  Galen  (131-203  a.d.)  described  the  six  muscles  of  the  eyeball, 
the  puncta  lachrymalia,  and  tear  duct.  Aerengar  (1521)  was  aware  of  the  fatty  matter  at  the  edge 
of  the  eyelids.  Stephanus  (1545)  and  Casseri  (1609)  described  the  Meibomian  glands,  which  were 
afterward  redescribed  l)y  Meibom  ( 1666).  Fallopius  described  the  vitreous  membrane  and  the  ciliary 
ligament.  Plater  (1583)  mentions  that  the  posterior  surface  of  the  lens  is  more  curved.  Altlrovandi 
observed  the  remainder  of  the  pupillary  membrane  (1599).  Observations  were  made  at  the  time  of 
Vesalius  (1540)  on  the  refractive  action  of  the  lens.  Leonardo  da  Vinci  compared  the  eye  to  a 
camera  obscura.  Maurolykos  compared  the  action  of  the  lens  to  that  of  a  lens  of  glass,  but  it  was 
Kepler  ( 161 1)  who  first  showed  the  true  refractive  index  of  the  lens  and  the  formation  of  the  retinal 
image,  but  he  thought  that  during  accommodation  the  retina  moved  forward  and  backward.  The 
Jesuit,  Scheiner  (f  1650),  mentions,  however,  that  the  lens  becomes  more  convex  by  the  ciliary  pro- 
cesses, and  he  assumed  the  existence  of  muscular  fibres  in  the  uvea.  He  referred  long  and  short 
sight  to  the  curvature  of  the  lens,  and  he  first  showed  the  retinal  image  in  an  excised  eye.  With 
regard  to  the  use  of  spectacles  there  is  a  reference  in  Pliny.  It  is  said  that  at  the  beginning  of  the 
14th  century  the  Florentine,  Salvino  d'Armato  degli  Armati  di  Fir  (11317),  and  themonk,  Alessandro 
de  Spina  (11313),  invented  spectacles.  Kepler  (1611)  and  Descartes  (1637)  described  their  action. 
Mayo  (tl852)  described  the  3d  nerve  as  the  constrictor  nerve  of  the  pupil.  Zinn  contributed  con- 
siderably to  our  knowledge  of  the  structure  of  the  eye.  Ruysch  described  muscular  fibres  in  the 
iris,  and  Monro  described  the  sphincter  of  the  pupil  (1794)  Jacob  described  the  bacillary  layer  of 
the  retina — Scemmering  (1791)  the  yellow  spot.  Brewster  and  Chossat  (1819)  tested  the  refractive 
indices  of  the  optical  media.     Purkinje  (1819)  studied  subjective  vision. 


Hearing. 


406.  THE  ORGAN  OF  HEARING.— Stimulation  of  the  Auditory 
Nerve. — The  normal  manner  in  which  the  auditory  nerve  is  excited,  is  by  means 
of  sonorous  vibrations,  which  set  in  motion  the  end  organs  of  the  acoustic 
nerve,  which  lie  in  the  endolymph  of  the  labyrinth  of  the  inner  ear,  on  membra- 
nous    expansions    of    the 

cochlea  and    semicircular  F"^"  577- 

canals.       Hence,    the   so-  -f''-'^^^^^^^^- 

norous  vibrations  are  first  ,-^ T^S ?^'^^%. 

transmitted  to  the  fluid  m 
the  labyrinth,  and  this,   m 
turn,  is  thrown  into  waves, 
which  set   the  end  organs 
into  vibration.      Thus,  the 
excitement  of  the  auditory 
nerves  is  brought  about  by    ;^'^^1 
the  mechanical  stimulation  ^';^^^ 
of  the  wave   motion  of  the  \'^^^ 
lymph  of  the  labyrinth. 

The   fluid    or  lymph  of 
the  labyrinth  is  surrounded 
by   the   exceedingly    hard 
osseous   mass  of  the   tern 
poral    bone     (Fig.     577) 
Only  at  one  small  roundish 


and  slightly  triangular  area,  c  I,        e  ,u  ru     ■       a<-      .      1     j-^ 

o         -'  o  '  Scheme  of  the  organ  of  neanng.  AG,  external  auditory 


meatus  ;  T,  tympanic 
membrane;  K,  malleus  with  its  head  (k),  short  process  (/i/^,  and  handle 
(/«) ;  a,  incus,  its  short  process  (jr),  and  its  long  process  united  to  the 
stapes  (j)  by  means  of  the  Sylvian  ossicle  (3) :  P,  middle  ear;  0,  fenestra 
ovalis  ;  r,  fenestra  rotunda ;  jr,  beginning  of  the  lamina  spiralis  of  the 
cochlea;  //,  scala  tympani,  and  vi,  scala  vestibuli  ;  V,  vestibuli ;  S,  sac- 
cule ;  U,  utricle ;  H,  semicircular  canals  ;  TE,  Eustachian  tube.  The 
long  arrow  indicates  the  line  of  traction  of  the  tensor  tympani ;  the  short 
curved  one,  that  of  the  stapedius. 


the  fenestra  rotunda  (r), 
the  fluid  is  bounded  by  a 
delicate  yielding  mem- 
brane, which  is  in  contact 
with  the  air  in  the  middle 
ear  or  tympanum  (P).  Not 
far  from  the  fenestra  rotunda  is  the  fenestra  ovalis  (o),  in  which  the  base  of  the 
stapes  (i-)  is  fixed  by  means  of  a  yielding  membranous  ring.  The  outer  surface  of 
this  also  is  in  contact  with  the  air  in  the  middle  ear.  As  the  perilymph  of  the 
inner  ear  is  in  contact  at  these  two  places  with  a  yielding  boundary,  it  is  clear  that 
the  lymph  itself  may  exhibit  oscillatory  movements,  as  it  must  follow  the  move- 
ments of  the  yielding  boundaries. 

The  sonorous  vibrations  may  set  the  perilymph  in  vibration  in  three  diff'erent 
ways  : — 

I.  Conduction  through  the  Bones  of  the  Head. — This  occurs  especially 
when  the  vibrating  solid  body  is  applied  directly  to  some  part  of  the  head,  e.  g.,  a 
tuning  fork  placed  on  the  head,  the  sound  being  propagated  most  intensely  in  the 
direction  of  the  prolongation  of  the  handle  of  the  instrument — also  when  the 
sound  is  conducted  to  the  head  by  means  of  fluid,  as  when  the  head  is  ducked 

847 


848  CONDUCTION    OF   SOUND   TO    THE    LABYRINTH. 

under  water.  Vibrations  of  the  air,  however,  are  practically  not  transferred 
directly  to  the  bones  of  the  head,  as  is  shown  by  the  fact  that  wc  are  deaf  when 
the  ears  are  stopped. 

The  soft  parts  of  the  head,  which  lie  immediately  upon  bone,  conduct  sound  best,  and  of  the  project- 
ing part,  the  best  conductor  is  the  cartilaginous  portion  of  the  external  ear.  But  even  under  the  most 
favorable  circumstance,  conduction  through  the  bones  of  the  head  is  far  less  effective  tlian  the  con- 
duction of  the  sound  waves  through  the  external  auditory  meatus.  If  a  tuning  fork  be  made  to 
vibrate  between  the  teeth  until  we  no  longer  hear  it,  its  lone  may  still  be  heard  on  bringing  it  near 
the  ear  (AV;///^).  The  conduction  through  the  bones  is  favored  wiien  tlie  oscillaiions  are  not  trans- 
ferred from  the  bones  to  the  tympanic  membrane,  and  are  thus  transferred  to  the  air,  in  the  outer  ear. 
Hence,  we  hear  the  sound  of  a  tuning  fork  applied  to  the  head  better  when  the  ears  are  stopped,  as 
this  prevents  the  propagation  of  the  sound  waves  through  the  air  in  the  outer  ear.  If,  in  a  </«•<;/" per- 
son, the  conduction  is  still  normal  through  the  cranial  bones,  then  the  cause  of  the  deafness  is  not  in 
the  nervous  part  of  the  ear,  but  in  the  external  sound-conducting  part  of  the  apparatus. 

2.  Normal  hearing  takes  place  through  the  external  auditory  meatus. 
The  enormous  vibrations  of  the  air  first  set  the  tympanic  membrane  in  vibration 
(Fig.  577,  T)  ;  this  moves  the  malleus  {h),  whose  long  process  is  inserted  into  it ; 
the  malleus  moves  the  incus  (a),  and  this  the  stapes  (^s),  which  transfers  the  move- 
ments of  its  plate  to  the  perilymph  of  the  labyrinth. 

3.  Direct  Conduction  to  the  Fenestra. — In  man,  in  consequence  of  occasional  disease  of  the 
middle  ear,  whereby  the  tympanic  membrane  and  auditory  ossicles  may  be  destroyed,  the  auditory 
apparatus  may  be  excited,  although  only  in  a  very  feeble  manner,  by  the  vibrations  of  the  air  being 
directly  transferred  to  the  membrane  of  the  fenestra  rotunda  (r),  and  the  parts  clo^^ing  the  fenestra 
ovalis  ((?).  The  membrane  of  the  fenestra  rotunda  may  vibrate  alone,  even  when  the  oval  window 
is  closed  with  a  rigid  body  ( IVeber-Liel). 

407.  PHYSICAL  INTRODUCTION. — Sound  is  produced  by  the  vibration  of  elastic  bodies 
capable  of  vibration.  Alternate  condensation  and  rarefaction  of  the  surrounding  air  are  thus 
produced;  or,  in  other  words,  soundwaves  in  which  the  particles  vibrate  longitudinally  or  in  the 
direction  of  the  propagation  of  the  sound  are  excited.  Around  the  point  of  origin  of  the  sound, 
these  condensations  and  rarefactions  occur  in  equal  concentric  circles,  which  conduct  the  sound  vibra- 
tions to  our  outer  ear.  The  vibrations  of  the  sounding  body  are  .so  called  "stationary  vibrations," 
i.  e.,  all  the  particles  of  the  vibrating  body  are  always  in  the  same  phase  of  movement,  in  that  they 
pass  into  movement  simultaneously,  they  reach  the  maximum  of  movement  simultaneously,  e.  g.,  in 
the  particles  of  a  sounding  vibrating  metal  rod.  Sound  is  produced  by  the  stationary  vibrations  of 
elastic  bodies ;  it  is  propagated  by  progressive  wave  motion  of  elastic  media,  generally  the  air.  The 
wave  length  of  a  tone,  i.  e.,  the  distance  of  one  maximum  of  condensation  to  the  next  one  in  the  air, 
is  proportional  to  the  duration  of  the  vibration  of  the  body,  whose  vibrations  produce  the  sound 
waves. 

If  7.  is  the  wave  length  of  a  tone,  /  in  second  the  durations  of  a  vibration  of  the  body  pro'lucing 
the  wave,  then  Z  =  «  /,  where  «  :=  340.88  metres,  which  is  the  rate  per  second  of  propagation  of 
sound  waves  in  the  air.  The  rapidity  of  the  transmission  of  sound  waves  in  water  =1435  metres 
per  second,  ?'.  <?.,  nearly  four  times  as  rapid  as  in  air;  wliile,  in  solids  capal)le  of  vibration,  it  is  pro- 
pagated from  seven  to  eighteen  times  faster  than  in  the  air.  Sound  waves  are  conducted  best  through 
the  same  medium  ;  when  they  have  to  pass  through  several  media  they  are  always  weakened. 

Reflection  of  the  sound  waves  occurs  when  thev  impinge  upon  a  solid  obstacle,  in  which  case 
the  angle  of  reflection  is  always  equal  to  the  angle  of  incidence. 

Wave  Movements. — We  distinguish — I.  Progressive  wave  movements  which  occur  in  two 
forms — (i)  \s  longitudinal  loaves,  \n  which  the  individual  particles  of  the  vibrating  body  vibrate 
around  their  centre  of  gravity  in  the  direction  of  the  propagation  of  the  wave  ;  examjiles  are  the 
waves  in  water  and  air.  This  movement  causes  an  accumulation  of  the  particles  at  certain  places, 
^.,^.,  on  the  crests  of  the  waves  in  w.Uer  waves,  while  at  other  places  they  are  diminished.  This 
kind  of  wave  is  called  a  wave  of  condensation  and  rarefaction.  (2)  If,  however,  each  particle 
in  the  progressive  wave  moves  vertically  up  and  down,  i.  e.,  transversely  to  the  direction  of  the  pro- 
pagation of  the  wave,  then  we  have  the  simple  transverse  waves,  or  progressive  waves,  in  which 
there  is  no  condensation  or  rarefaction  in  the  direction  of  propagation,  as  each  particle  is  merely 
displaced  laterally.     An  example  of  this  is  (he progressive  waves  in  a  rope. 

II.  Stationary  Flexion  Waves. — When  all  the  particles  of  an  elastic  vibrating  body  so  oscil- 
late that  all  of  them  are  alu  ays  in  the  same  phase  of  movement  as  the  limbs  of  a  vibrating  tuning 
fork  or  a  plucked  string,  then  this  kind  of  movement  is  described  as  stationary  flexion  waves.  As 
bodies,  whose  expansion  in  the  direction  of  oscillation  is  very  slight,  vibrate  to  and  fro  in  the  sta- 
tionary flexion  wave,  so  we  see  that  the  small  parts  of  the  auditory  apparatus  (tympanic  membrane, 
ossicles,  lymph  of  the  labyrinth)  oscillate  in  stationary  flexion  waves. 


THE    EAR    MUSCLES   AND    EXTERNAL   AUDITORY   MEATUS. 


849 


408.  EAR  MUSCLES— EXTERNAL  AUDITORY  MEATUS.— When  the  external 

ear  is  absent,  Httle  or  no  impairment  of  the  hearing  is  observed;  hence,  the  physiological  functions 
of  these  organs  are  but  slight.  Boerhaave  thought  that  the  elevations  and  depressions  of  the  outer 
ear  might  be  connected  with  the  reflection  of  the  sound  waves.  Numerous  sound  waves,  however, 
must  be  again  reflected  outward;  and  those  waves  which  reach  the  deep  part  of  the  concha  are 
said  to  be  reflected  toward  the  tragus,  to  be  reflected  by  it  into  the  external  auditory  meatus. 
According  to  Schneider,  when  the  depressions  in  the  ear  are  filled  up  with  wax,  hearing  is  impaired  ; 
other  observers,  however,  have  found  the  hearing  to  be  unaffected.  Mach  points  out  that  the  dimen- 
sions of  the  external  ear  are  proportionally  too  small  to  act  as  reflecting  organs  for  the  wave  lengths 
of  noises. 

Muscles  of  the  External  Ear. — (i)  The  whole  ear  is  moved  by  the  retrahentes,  attrahens, 
and  attollens.  (2)  The  form  of  the  ear  may  be  altered  by  the  tragicus,  antitragicus,  helicis  major 
and  minor  internally  ;  and  by  the  transversus  and  obliquus  auriculse  externally.  Persons  who  can 
move  their  ears  do  not  find  that  the  hearing  is  influenced  during  the  movement.  The  Mm.  helicis 
major  and  minor  are  regarded  as  elevators  of  the  helix;  the  transversus  and  obliquus  auricalse  as 
dilators  of  the  concha ;  the  tragicus  and  antitragicus  as  constrictors  of  the  meatus.  In  animals,  the 
external  ear  and  the  action  of  its  muscles  have  a  marked 
effect  upon  hearing.  The  muscles  point  the  ear  in  the 
direction  of  the  sound,  while  other  muscles  contract  or 
dilate  the  space  within  the  external  ear.  In  many  diving 
animals,  the  meatus  can  be  closed  by  a  kind  of  valve. 

The  external  meatus  is  3  to  3.25  cm. 
long  [i^  to  i;54^  inch],  8  to  9  mm.  high,  and 
6  to  8  mm.  broad  at  its  outer  opening  (Fig. 
578).  It  is  the  conductor  of  the  sound  waves 
to  the  tympanic  membrane,  so  that  almost  all 
the  sound  waves  first  impinge  upon  its  wall,  and 
are  then  reflected  toward  the  tympanic  mem- 
brane. To  see  well  down  into  the  meatus,  we 
must  pull  the  auricle  upward  and  backward. 
Occlusion  of  the  meatus,  especially  by  a  plug 
of  inspissated  wax  (§  287),  of  course  interferes 
with  the  hearing  [and  when  it  presses  on  the 
membrana  tympani  may  give  rise  to  severe 
vertigo]. 

409.  TYMPANIC  MEMBRANE.— 
The  tympanic  membrane,  which  is  tolera- 
bly laxly  fixed  in  a  special  osseous  cleft,  with  a 
thickened  margin,  is  an  elastic,  unyielding,  and  almost  non -extensible  membrane 
of  about  0.1  ram.  in  thickness,  and  with  a  superficial  area  of  50  square  millimetres 
(Fig.  581).  It  is  elliptical  in  form,  its  greater  diameter  being  9.5  to  10  mm.,  and 
its  lesser  8  mm.,  and  it  is  fixed  in  the  floor  of  the  external  meatus  obliquely,  at  an 
angle  of  40°,  being  directed  from  above  and  outward,  downward  and  inward. 
Both  tympanic  membranes  converge  anteriorly,  so  that  if  both  were  prolonged 
they  would  meet  to  form  an  angle  of  130°  to  135°.  The  oblique  position  enables 
a  larger  surface  to  be  presented  than  would  be  obtained  if  it  were  stretched  verti- 
cally, so  that  more  sound  waves  can  fall  vertically  upon  it.  The  membrane  is  not 
stretched  flat,  but  a  little  under  its  centre  (umbilicus)  it  is  drawn  slightly  inward 
by  the  handle  of  the  malleus,  which  is  attached  to  it ;  while  the  short  process  of 
the  malleus  slightly  bulges  out  the  membrane  near  its  upper  margin  (Figs.  577,  584). 

Structure. — The  tympanic  membrane  consists  of  three  layers  :  (i)  The  membrana  propria 
is  a  fibrous  membrane  with  radial  fibres  on  its  outer  surface,  and  circularly  arranged  fibres  on  its 
inner  aspect.  (2)  The  surface  directed  toward  the  meatus  is  covered  with  a  thin  and  semi-trans- 
parent part  of  the  cutis.  (3)  The  side  toward  the  tympanum  is  covered  with  a  delicate  mucous 
membrane,  with  simple  squamous  epithelium.  Numerous  nerves  and  lymph  vessels,  as  well  as 
inner  and  outer  blood  vessels,  occur  in  the  membrane. 

[The  middle  layer,  or  substantia  propria,  is  fixed  to  a  ring  of  bone,  which  is 
deficient  above.     It  is  filled  up  by  a  layer  composed  of  the  mucous  and  cutaneous 
layers,  called  the  membrana  flaccida,  or  Shrapnell's  membrane.] 
54 


The  external  auditory  meatus  and  the  tj'mpanic 
cavity.  M,  osseous  spaces  in  the  temporal 
bone  ;  Pe,  cartilaginous  part  of  the  meatus  ; 
L,  membranous  union  between  both ;  F, 
auricular  surface  for  the  condyle  of  the  lower 
jaw. 


850 


THE    MEMBRANA    TYMPANI, 


[Examination. — When  examining  iheouler  ear  and  membrana  lympani,  pull  the  auricle  upward 
and  backward.  The  membrana  tymp.ini  is  examined  by  means  of  an  ear  sp'jculum  (Fig.  582). 
The  speculum  is  placed  in  the  ear,  and  lii;ht  is  reflected  into  it  by  means  of  a  concave  minor,  per- 
forated in  the  centre,  and  having  a  focal  dislance  of  four  or  five  inches.  It  is  convenient  to  have  the 
mirror  fi.xed  to  a  band  placed  round  the  head,  as  in  the  case  of  the  larj'ngoscopic  reflector  (Fig. 
359).  It  is  important  to  remember  that  the  membrane  is  placed  obliquely,  so  that  the  posterior  and 
upper  parts  are  nearer  the  surface.  The  membrane  in  health  is  grayish  in  color  and  transparent,  so 
that  the  handle  of  the  malleus  is  seen  running  from  above  downward  and  backward,  while  at  the 
anterior  and  inferior  part  there  is  a  cone  of  light  with  its  ape.x  directed  inward.] 

Fig.  579. 


Fig.  580. 


Fig.  582. 


Tympanic  membrane 
with  the  auditory  os- 
sicles (left)  seen  from 
within.  Ci,  incus ; 
Ctn,  malleus  ;  Ch, 
chorda  tympani ;  T, 
pouch-like  depression 
(after  Urbantschitsch). 


Tympanic  membrane  and  the  auditory  ossicles  (left)  seen 
from  within, /.i".,  from  the  tympanic  cavity.  M,  ma- 
nubrium or  handle  of  the  malleus  ;  T,  insertion  of  the 
tensor  tympani ;  A,  head  ;  /F,  long  process  of  the 
malleus;  a,  incus,  with  the  short  (K)  and  the  long  (/) 
process  ;  S,  plate  of  the  stapes  ;  hx,  Ax,  is  the  com- 
mon axis  of  rotation  of  the  auditory  ossicles  ;  S,  the 
pinion-wheel  arrangement  between  the  malleus  and 
incus. 


Ear  specula,  of  various 
sizes. 


Tympanic  membrane  of 
a  newborn  child,  seen 
from  without,  with  the 
handle  of  the  malleus 
visible  on  it.  A/,  tym- 
panic ring,  with  its  an- 
terior (t/)  and  posterior 
(A)  ends. 

Function. — The  tympanic  membrane  catches  up  the  sound  waves  which  pene- 
trate into  the  external  meatus,  and  is  set  into  vibration  by  them,  the  vibrations  cor- 
responding in  number  and  amplitude  to  the  vibrating  movements  of  the  air. 
Politzer  connected  the  auditory  ossicles  fixed  to  the  tympanic  membrane  of  a  duck 
with  a  recording  apparatus,  and  could  thus  register  the  vibrations  produced  by 
sounding  any  particular  tone.  Owing  to  its  small  dimensions,  the  tympanic  mem- 
brane can  vibrate  in  toto,  to  and  fro  in  the  direction  of  the  sound  waves  corre- 
sponding to  the  condensations  and  rarefactions  of  the  vibrating  air,  and  therefore 
executes  transverse  vibrations,  for  which  it  is  specially  adapted,  owing  to  the  rela- 
tively slight  resistance. 

Fundamental  Note. — Stretched  strings  and  membranes  are  generally  only 
thrown  into  actual  and  considerable  sympathetic  vibration  when  they  are  affected 
by  tones  which  correspond  with  their  own  fundamental  tone,  or  whose  number 
of  vibrations  is  some  multiple  of  the  number  of  vibrations  of  the  same,  as  the 
octave.  When  other  tones  act  on  them,  they  exhibit  only  inconsiderable  sympa- 
thetic vibration.  If  a  membrane  be  stretched  over  a  funnel  or  cylinder,  and  if  a 
nodule  of  sealing  wax  attached  to  a  silk  thread  be  made  just  to  touch  the  centre  of 
the  membrane,  then  the  sealing  wax  remains  nearly  at  rest  when  tones  or  soands 


FUNCTIONS   OF   THE    OUTER   EAR. 


851 


are  made  in  the  neighborhood;  as  soon,  however,  as  the  fundamental  or  proper 
tone  of  this  arrangement  is  sounded,  the  nodule  is  propelled  by  the  strong  vibra- 
tions of  the  membrane. 

If  we  apply  this  to  the  tympanic  membrane,  then  it  also  should  exhibit  very  great 
vibrations  Avhen  its  own  fundamental  note  is  sounded,  but  only  slight  vibrations 
when  other  tones  are  produced.  This,  however,  would  produce  great  inequality 
in  the  audible  sounds.  There  is  an  arrangement  of  the  membrane  whereby  this  is 
prevented,  (i)  Great  resistance  is  offered  to  the  vibrations  of  the  tympanic 
membrane,  owing  to  its  union  with  the  auditory  ossicles.  These  act  as  a  damping 
apparatus,  which  provides,  as  in  damped  membranes  generally,  that  the  tympanic 
membrane  shall  not  exhibit  excessive  sympathetic  vibrations  for  its  own  funda- 
.  mental  note.  But  the  damping  also  makes  the  sympathetic  vibrations  less  for  all 
the  other  tones.  In  this  way,  a// vibrations  of  the  tympanic  membrane  are  modi- 
fied ;  especially,  however,  is  the  excessive  vibration  diminished  during  the  sound- 
ing of  its  fundamental  tone.  The  membrane  is  at  the  same  time  rendered  more 
capable  of  responding  to  the  vibrations  of  different  wave  lengths.  The  damping 
dX%o prevents  of te7' vibrations.  (2)  Corresponding  to  the  small  waij-j- of  the  tym- 
panic membrane,  its  sympathetic  vibrations  must  also  be  small.  Nevertheless,  these 
slight  elongations  are  quite  sufficient  to  convey  the  sonorous  movements  to  the 
most  delicate  end  organs  of  the  auditory  nerve  ;  in  fact,  there  are  arrangements  in 
the  tympanum  which  still  further  diminish  the  vibrations  of  the  tympanic  membrane. 

As  V.  Helmholtz  lias  shown,  the  strong  sympathetic  vibrations  of  the  tympanic  membrane  are  not 
completely  set  aside  by  this  damping  aixangement.  The  painful  sensations  produced  by  some  tones 
are,  perhaps,  due  to  the  sympathetic  vibration  of  the  membrana  tympani.  According  to  Kessel, 
certain  parts  of  the  membrane  vibrate  to  certain  tones ;  the  shortest  radial  fibres  at  the  upper  part  of 
the  anterior  and  upper  segment  vibrate  with  the  highest  tones,  the  longest  fibres  at  the  posterior  segment 
with  the  deepest  tones.     At  the  upper  part  of  the  posterior  segment  noises  are  transmitted. 

According  to  Fick,  the  tympanic  membrane,  besides  possessing  the  property  of  taking  up  all 
vibrations  with  nearly  equal  intensity,  has  also  the  properties  of  a  resonance  apparatus;  i.  e.,\X. 
causes  a  summation  of  the  energy  of  successive  vibrations.  This  is  due  to  the  funnel  shape  of  the 
membrane,  and  to  the  radial,  rigid  insertion  of  the  handle  of  the  malleus. 

Pathological. — Thickenings  or  inequalities  of  the  tympanic  membrane  interfere  with  the  acute- 
ness  of  hearing,  owing  to  the  diminished  capacity  for  vibration  thereby  produced.  Holes  in  and  loss 
of  its  substance  act  similarly.  In  extensive  destruction,  an  artificial  tympanum  is  placed  in  the 
external  meatus,  and  its  vibrations,  to  a  certain  extent,  replace  those  of  the  lost  membrane  [Toynbee). 
[Fig.  583  shows  an  artificial  tympanic  membrane.] 

410.    AUDITORY    OSSICLES    AND    THEIR    MUSCLES.— The 

auditory  ossicles  have  a  double  function. — (i)  By  means  of  the  "chain  "  which 
they  form,  they  transfer  the 
vibrations  of  the  tympanic 
membrane  to  the  perilymph  Fig.  583. 

of  the  labyrinth.  (2)  They 
also  afford  points  of  attach- 
ment for  the  muscles  of  the 
middle  ear,  which  can  alter 
the  tension  of  the  mem- 
brana tympani,  and  the 
pressure  on  the  lymph  of 
the  labyrinth. 

Mechanis  m. — The 
form  and  position  of  the 
ossicles  are  given  in  Fig- 
ures 584  and  585.     They 


form  a  jointed  chain  which    Toynbee's    artificial 

,  ,  ,  •  membrana     tym- 

connects    the     tympanic        pani. 


The  auditory  ossicles  (right).  C.?«,  head  ;  C,  neck  ; 
Pbr,  short  process  ;  Prl,  long  process  ;  M,  handle 
of  the  malleus  ;  Ci,  body  ;  G,  articular  surface  ; 
A,  short,  and  z/,  long  process  of  the  incus;  O.S, 
so-called  lenticular  ossicle  ;  C.s,  head  ;  a,  anterior, 
and  /,  posterior  limb  ;  P,  plate  of  the  stapes. 


membrane,    M,  by  means 

of  the  malleus,  h,  incus,  a,  and  stapes,  S,  with  the  perilymph  of   the  labyrinth. 


852 


MECHANISM    OF   THE    AUDITORY   OSSICLES. 


Ax 


585- 


^ii 


The  mode  of  movement  of  the  ossicles  is  of  special  importance.  The  handle 
of  the  malleus  is  firmly  united  to  the  fibres  of  the  tympanic  membrane  (Fig.  585,  //). 
Besides  this,  the  malleus  is  fixed  by  /h^amcn/s  which  prescribe  the  direction  of  its 
movements.  Two  ligaments — the  lig.  mallei  anticum  (passing  from  the  processus 
Folianus)  and  the  posticuin  (from  a  small  crest  on  the  neck) — together  form  a  com- 
mon axial  band  {v.  HelmJioltz),  which  acts  in  the  direction  from  behind  forward, 
/,  e.,  parallel  to  the  surftice  of  the  tympanic  membrane.  The  neck  of  the  malleus 
lies  between  the  insertions  of  both  ligaments.     The  united   ligament  determines 

the  "  axis  of  rotation  "  of  the 
movement  of  the  malleus. 

When  the  handle  of  the  mal- 
leus is  drawn  itnvard,  of  course 
its  head  moves  in  the  opposite 
direction,  or  outward.  The 
incus,  a,  is  only  ])artially  fixed 
by  a  ligament,  which  attaches 
its  short  process  to  the  wall  of 
the  tympanic  cavity,  in  front 
of  the  entrance  to  the  mastoid 
cells,  k.  The  not  very  tense 
articulation  joining  it  to  the 
head  of  the  malleus,  h,  which 
lies  with  its  saddle-shai)cd  artic- 
ular surface  in  the  hollow  of  the 
incus,  is  important.  The  lower 
margin  of  the  incus  (Fig.  584, 
S)  acts  like  a  tooth  of  a  cog 
wheel.  Thus,  when  the  handle 
of  the  malleus  moves  inward 
to  the  tympanic  cavity,  the  incus, 
and  its  long  process,  b,  which 
is  parallel  to  the  handle. of  the 
malleus,  also  pass  inward.  The 
incus  forms  almost  a  right  angle 
with  the  stapes,  S,  through  the 
intervention  of  the  Sylvian  ossi- 
cle, s.  If,  however,  as  by  con- 
densation of  the  air  in  the 
tymi)anum,  the  membrana  tympani  and  the  handle  of  the  malleus  move  outward, 
the  long  process  of  the  incus  does  not  make  a  similar  movement,  as  the  malleus 
moves  away  from  this  margin  of  the  incus.  Hence,  the  stapes  is  not  liable  to  be 
torn  from  its  socket.  The  malleus  and  incus  form  an  angular  lever,  which  moves 
round  a  common  axis  (Fig.  581  and  Fig.  585,  Ajc,  Aa-).  In  the ///rftzr^/ movement, 
the  malleus  follows  the  incus,  as  if  both  formed  one  piece.  The  common  axis 
(Fig.  5S0)  is  not,  however,  the  axial  ligament  of  the  malleus,  but  it  is  formed 
anteriorly  by  the  processus  Folianus,  IF,  directed  forward,  and  posteriorly  by  the 
short  process  of  the  incus  directed  backward.  The  rotation  of  both  ossicles  around 
this  axis  occurs  in  a  plane  vertical  to  the  plane  of  the  membrana  tympani.  During 
the  rotation,  of  course  the  parts  above  this  axis  (head  of  the  malleus  and  upper 
part  of  the  body  of  the  incus)  take  a  direction  opposite  to  the  parts  lying  below  it 
(the  handle  of  the  malleus  and  the  long  process  of  the  incus),  as  is  indicated  in 
Fig.  585  by  the  direction  of  the  arrows.  The  movement  of  the  handle  of  the 
malleus  must  follow  that  of  the  membrana  tympani,  and  vice  versa,  while  the  move- 
ment of  the  stapes  is  connected  with  the  movement  of  the  long  process  of  the 
incus.     As  the  long  process  of  the  incus   is  only  two-thirds  of  the  length  of  the 


and  auditory  ossicles  (left)  magnified.  A.G.,  external 
M,  membrana  tympani,  which  is  attached  to  the  handle 
of  the  malleus,  «,  and  near  it  the  short  process,/;  /;,  head  of 
the  malleus  ;  a,  incus  ;  k,  its  short  process  with  its  ligament ;  /, 
long  process  ;  s.  Sylvian  ossicle  ;  S,  stapes  ;  A.v,  \x,  is  the  axis 
01  rotation  of  the  ossicles,  it  is  shown  in  perspective,  and  must 
be  imagined  to  penetrate  tne  plane  of  thepaper;  t,  line  of  traction 
of  the  tensor  tympani.  The  other  arrows  indicate  the  movement 
of  the  ossicles  when  the  ttiisor  contracts. 


MOVEMENTS   OF   THE   AUDITORY   OSSICLES.  853 

handle  of  the  malleus  (Figs.  577,  581,  585),  of  course  the  excursio?i  of  the  tip 
of  the  former,  and  Avith  it  of  the  stapes,  must  be  correspondingly  less  than  the 
movement  of  the  tip  of  the  handle  of  the  malleus ;  while,  on  the  other  hand,  the 
force  of  the  movement  of  the  tip  of  the  handle  of  the  malleus,  corresponding  to  the 
diminution  of  the  excursion,  will  be  increased. 

Mode  of  Vibration. — Thus,  the  movement  of  the  membrana  tympani  inward 
causes  a  less  extensive  but  a  more  powerful  movement  of  the  foot  of  the  stapes 
against  the  perilymph  of  the  labyrinth,  v.  Helaiholtz  and  Politzer  calculated  the 
extent  of  the  movement  to  be  0.07  mm.  The  mode  in  which  the  vibrations  of  the 
membrana  tympani  are  conveyed  to  the  lymph  of  the  labyrinth,  through  the  chain 
of  ossicles,  is  quite  analogous  to  the  mechanism  of  these  parts  already  described. 
Long  delicate  glass  threads  have  been  fixed  to  these  ossicles,  and  their  movements 
were  thus  graphically  recorded  on  a  smoked  surface  {Politzer,  Henseii).  Or,  strongly 
refractive  particles  are  fixed  to  the  ossicles,  while  the  beam  of  light  reflected  from 
them  can  be  examined  by  means  of  a  microscope  {Buck,  v.  Helmholtz).  All  the 
experiments  showed  that  the  transference  of  the  sound  waves  is  accomplished  by 
means  of  the  mechanism  of  the  angular  lever,  composed  of  the  auditory  ossicles 
already  described.  As  the  vibrations  of  the  membrana  tympani  are  conveyed  to 
the  handle  of  the  malleus,  they  are  weakened  to  about  one-fourth  of  their  original 
strength  {Politzer^.  [The  membrana  tympani  is  many  times  (30)  larger  than  the 
fenestra  ovalis,  and  the  relation  in  size  might  be  represented  by  a  funnel.  The 
arm  of  the  malleal  end  of  the  lever  where  the  power  acts  is  9^  mm.  long,  while  the 
short  or  stapedial  arm  is  6^^'  mm.,  so  that  the  latter  moves  less  than  the  former, 
but  what  is  lost  in  extent  is  gained  in  force.] 

[Methods. — Politzer  attached  small,  very  light  levers  to  each  of  the  ossicles,  and  inscribed  their 
movements  on  a  revolving  cylinder.  An  organ  pipe  was  sounded,  and  when  the  levers  were  of  the 
same  length,  the  malleus  made  the  greatest  excursion  and  the  stapes  the  least.  Buck  attached  starch 
grains  to  the  ossicle-;,  illuminated  them,  and  observed  the  movements  of  the  refractive  starch  granules 
by  means  of  a  microscope  provided  with  a  micrometer.] 

[The  ossicles,  move  en  masse,  and  not  in  the  way  of  propagating  molecular 
vibrations.]     As  the  excursions  of  the  ossicles  during  sonorous  vibrations  are,  how- 
ever, only  nominal,  there  is  practically  no  change  ^        „, 
in  the  position  of  the  joints  with  each  vibration. 
The  latter  will  only  occur  when  extensive  move- 
ments take  place  by  means  of  the  muscles. 

The  muscles  of  the  auditory  ossicles  alter  the 
position  and  tension  of  the  membrana  tympani,  as 
well  as  the  pressure  of  the  lymph  of  the  labyrinth. 
The  tensor  tympani,  which  lies  in  an  osseous 
groove  above  the  Eustachian  tube,  has  its  tendon 
deflected  round  an  osseous  projection  [processus 
cochleariformisl,  which  lies  external  to  it,  almost  at 
right  angles  to  the  groove  above  it,  and  is  inserted 
immediately  above  the  axes  of  rotation  of  the' 
malleus  (Fig.  580,  M).    When  the  muscle  contracts 

in  the  direction  of   the  arrow,   /,   then  the  handle  of   Tensor    tympani-the   Eustachian     tube 

the  malleus  {n)  pulls   the   membrana  tympani  (M) 

inward  and  tightens  it  (Fig.  585).  This  also  causes  a  movement  of  the  incus  and 
stapes  (S)  which  must  be  pressed  more  deeply  into  the  fenestra  ovalis  as  already 
described.  When  the  muscle  relaxes,  then,  owing  to  the  elasticity  of  the  rotated 
axial  ligament  and  the  tense  membrana  tympani  itself,  the  position  of  equilibrium 
is  again  restored.  The  motor  nerve  of  this  muscle  arises  from  the  trigeminus, 
and  passes  through  the  otic  ganglion  (p.  647).  C.  Ludwig  and  Politzer  observed 
that  stimulation  of  the  fifth  nerve  within  the  cranium  [dog]  caused  the  above  men- 
tioned inovement. 


854  ACTION    OF   THE   STAPEDIUS. 

Use  of  the  Tension. — The  tension  of  the  membrana  tympani  caused  by  the 
tensor  tympani  has  a  double  function  {Joh.  MiUIer)—!.  The  tense  membrane  offers 
very  great  resistance  to  sympathetic  vibrations  when  the  sound  waves  are  very  in- 
tense, as  it  is  a  physical  fact  that  stretched  membranes  are  more  difficult  to  throw 
into  sympathetic  vibrations  the  tenser  they  are.  Thus,  the  tension  so  far  protects 
the  auditory  organ,  as  it  prevents  too  intense  vibrations  applied  to  the  membrana 
tympani  from  reaching  the  terminations  of  the  nerves.  2.  The  tension  of  the 
membrana  tympani  must  vary  according  to  the  degreeof  contraction  of  the  tensor. 
Thus,  the  membrana  for  the  time  being  has  a  different  fundamental  tone,  and  is 
thereby  capable  of  vibrating  to  the  correspondingly  higher  tone,  it,  as  it  were,  being 
in  a  certain  sense  accommodated  for. 

Comparison  with  Iris. —  The  membrana  tympani  has  been  compared  with  the  iris.  Both  mem- 
branes prevent  by  contraction — narrowing  of  tlie  pupil  and  tension  of  the  membrana  Ijinpani — the 
too  intense  action  of  tiie  specific  stimulus  from  causing  too  great  stimulation,  and  both  a(iii/>(  the 
sensory  apparatus  for  the  action  of  moderate  or  weak  stimuli.  This  movement  in  both  membranes  is 
brought  about  rejlexly,  in  the  ear  through  the  N.  acusticus,  which  causes  a  reflex  stimulation  of  the 
motor  fibres  for  the  tensor  tympani. 

Effect  of  Tension. — That  increased  tension  of  the  membrana  tympani  renders  it  less  sensitive 
to  sound  waves  is  easily  proved,  thus:  Close  the  mouth  and  nose,  and  make  either  a  forced  expi- 
ration, so  that  the  air  is  forced  into  the  Eustachian  tube,  which  bulges  out  the  membrana  tympani,  or 
inspire  forcibly,  whereby  the  air  in  the  tympanum  is  diminished,  so  that  the  membrana  bulges  inward. 
In  both  cases  hearing  is  interfered  with  as  long  as  the  increased  tension  lasts.  If  a  funnel' with  a 
small  lateral  opening,  and  whose  wide  end  is  covered  by  a  membrane,  be  placed  in  the  external 
meatus,  hearing  becomes  less  distinct  when  the  membrane  is  stretched  {Joh.  Mi'dler).  If  air  be 
blown  into  the  external  auditory  meatus,  both  tensores  tympani  contract,  and  in  consequence  of  this 
the  hearing  of  the  other  ear  is  temporarily  affected  [Gellc). 

Normally,  the  tensor  tympani  is  excited  reflexly.  The  muscle  is  not  directly  and  by  itself  subject 
to  the  control  of  the  will.  According  to  L.  Fick,  the  following  phenomenon  is  due  to  an  "  associated 
movement  "  of  the  tensor  :  When  he  jjressed  his  jaws  firmly  against  each  other,  he  heard  in  his 
ear  a  piping,  singing  tone,  while  a  capiilaiy  tube,  which  was  fixed  air-tight  into  the  meatus,  had  a 
drop  of  water  which  was  in  it  rapidly  drawn  inward.  During  this  experiment,  a  person  with 
normal  hearing  hears  all  musical  tones  as  if  they  were  louder,  while  all  the  highest  non-musical  tones 
are  enfeebled  ( Lucae).  When ya-vnifig,  v.  Helmholtz  and  Tolitzer  found  that  hearing  was  enfeebled 
for  certain  tones. 

Contraction  of  the  Tensor. — Hensen  showed  that  the  contraction  of  the  tensor 

tympani  during  hearing  is  not  a  continued  contraction,  but  what  might  be  termed 

a  "twitch."     A  twitch  takes  place  at  the  beginning  of  the  act  of  hearing,  which 

favors  the  perception  of  the  sound,  as  the  membrana  tympani  thus  set  in  motion 

g         vibrates  more  readily  to  higher  tones  than  when  it  is  at  rest.     On 

^^  ■        exposing  the  tympanum  in  cats  and  dogs,  it  was  found  that  this 

contraction  or  twitch  occurs  only  at   the  beginning  of  the  sound, 

and  that  it  soon  ceases,  although  the  sound  may  continue. 

Action  of  the  Stapedius. — The  muscle  arises  within  the  emi- 
nentia  pyramidalis,  and  is  inserted  into  the  head  of  the  stapes  and 
Sylvian  ossicle  (Fig.  583);  when  it  draws  upon  the  head  of  the 
stapes,  as  indicated  in  Fig.  577,  by  the  small  curved  arrow,  it  must 
place  the  bone  obliquely,  whereby  the  posterior  end  of  the  plate  of 
Right  stapedius  the  stapes  is  pressed  somewhat  deeper  inward  into  the  fenestra 
muscle.  ovalis,  whilc  the  anterior  is,  as  it  were,  displaced  somewhat  out- 

ward. The  stapes  is  thereby  more  fixed,  as  the  fibrous  mass  [annular  ligament] 
which  surrounds  the  fenestra  ovalis  and  keeps  the  stapes  in  its  place  becomes  more 
tense.  The  activity  of  this  muscle,  therefore,  prevents  too  intense  shocks,  which 
may  be  communicated  from  the  incus  to  the  stapes,  from  being  conveyed  to  the 
perilymph.     It  is  supplied  by  the  facial  nerve  (§  349,  3). 

The  stapedius  in  many  persons  executes  an  associated  movement,  when  the  eyelids  are  forcibly 
closed  (I  349).  Some  persons  can  cause  it  to  contract  reflexly  by  scratching  the  skin  in  front  of  the 
meatus,  or  by  gently  stroking  the  outer  margin  of  the  orbit  (Henle).  It  seems  to  be  excited  reflexly 
in  many  diseases  of  the  ear  when  the  tympanum  is  being  syringed. 

Other  Views. — According  to  Lucae,  when  the  stapes  is  displaced  obliquely,  its  head  forces  the 


THE    EUSTACHIAN    TUBE.  855 

long  process  of  the  incus,  and  also  the  membrana  tjTnpani,  outward,  so  that  it  is  regarded  as  an 
a7itagonist  of  the  tensor  tympani.  Politzer  observed  that  the  pressure  within  the  labyrinth  fell  when 
he  stimulated  the  muscle.  According  to  Toynbee,  the  stapedius  acts  as  a  lever  and  moves  the  stapes 
slightly  out  of  the  fenestra  ovalis,  thus  making  it  more  free  to  move,  so  that  it  is  more  capable  of 
vibrating.  Henle  supposes  that  the  stapedius  is  more  concerned  in  fixing  than  in  moving  the 
stapes,  and  that  it  comes  into  action  when  there  is  danger  of  too  great  movement  being  communi- 
cated to  the  stapes  from  the  incus.  Landois  agrees  with  this  opinion,  and  compares  the  stapedius 
with  the  orbicularis  palpebrarum,  both  being  protective  muscles. 

Pathological. — Immobility  of  the  auditory  ossicles,  either  by  adhesions  or  anchyloses,  causing 
diminished  vibrations,  interferes  with  hearing;  while  the  same  result  occurs  when  the  stapes  is  firmly 
anchylosed  into  the  fenestra  ovalis.  The  tendon  of  the  tensor  tympani  has  been  divided  in  cases  of 
contracture  of  the  muscles.     For  paralysis  of  the  tensor,  see  p.  648,  and  for  the  stapedius,  p.  652. 

411.  EUSTACHIAN  TUBE— TYMPANUM.— The  Eustachian 
tube  [4  centimetres  in  length,  if^  in.]  is  the  ventilating  tube  of  the  tympanic 
cavity.  It  keeps  the  tension  of  the  air  within  the  tympanum  the  same  as  that 
within  the  pharynx  and  outer  air  (Figs.  577,  586).  Only  when  the  tension  of  the 
air  is  the  same  outside  and  inside  the  tympanum,  is  the  normal  vibration  of  the 
membrana  tympani  possible.  The  tube  is  generally  closed,  as  the  surfaces  of  the 
mucous  membrane  lining  it  come  into  apposition.  During  swallowing,  how- 
ever, the  tube  is  opened,  owing  to  the  traction  of  the  fibres  of  the  tensor  veli  pala- 
tini [spheno-salpingo-staphylinus  sive  abductor  tubae  (v.  TrdlfscJi),  sive  dilator 
tubae  {Rudinger)']  inserted  into  the  membrano-cartilaginous  part  of  the  tube 
{Toynbee,  Politzer).  (Compare  §  139,  2.)  When  the  tube  is  closed,  the  vibra- 
tions of  the  mem.brana  tympani  are  transferred  in  a  more  undiminished  condition 
to  the  auditory  ossicles  than  when  it  is  open,  whereby  part  of  the  vibrating  air  is 
forced  through  the  tube  {Mach  and  Kessel).  If,  however,  the  tympanic  cavity  is 
closed  permanently,  the  air  within  it  becomes  so  rarefied  (§  139)  that  the  mem- 
brana tympani,  owing  to  the  abnormally  low  tension,  becoixies  drawn  inward,  thus 
causing  difficulty  of  hearing.  As  the  tube  is  lined  by  ciliated  epithelium  it  carries 
outward  to  the  pharynx  the  secretions  of  the  tympanum  (p.  501). 

Noise  in  the  Tube. — K  sharp  hissing  noise  is  heard  in  the  tube  during  swallowing,  when  we 
swallow  slowly  and  at  the  same  time  contract  the  tensor  tympani,  due  to  the  separation  of  the  adhe- 
sive surfaces  of  its  lining  membrane.  Another  person  may  hear  this  noise  by  using  a  stethoscope  or 
his  ear. 

In  Valsalva's  experiment  (^  60),  as  soon  as  the  pressure  of  the  air  reaches  10  to  40  mm.  Hg, 
air  enters  the  tube.  The  sound  is  heard  first,  and  then  we  feel  the  increased  tension  of  the  tjTnpanic 
membrane,  owing  to  the  entrance  of  air  into  the  tympanum.  During  forced  inspiration,  when  the 
nose  and  mouth  are  closed,  air  is  sucked  out,  while  the  tympanum  is  ultimately  drawn  inward. 

The  M.  levator  veli  palatini,  as  it  passes  under  the  base  of  the  opening  of  the  tube  into  the  pharynx, 
forms  the  levator  eminence  or  cushion  (Fig.  354,  W).  Hence,  when  this  muscle  contracts  and  its 
belly  thickens,  as  at  the  commencement  of  the  act  of  deglutition  and  during  phonalion,  the  lower 
wall  of  the  pharyngeal  opening  is  raised,  and  the  opening  thereby  narrowed  [Lucae).  The  contrac- 
tion of  the  tensor,  occurring  during  the  latter  part  of  the  act  of  deglutition,  dilates  the  tube. 

Other  Views. — According  to  Riidinger,  the  tube  is  always  open,  although  only  by  a  very  narrow 
passage  in  the  upper  part  of  the  canal,  while  the  canal  is  dilated  during  swallowing.  According 
to  Cleland,  the  tube  is  generally  open,  and  is  closed  during  swallowing. 

[Practical  Importance.- — The  tympanic  cavity  forms  an  osseous  box,  and 
therefore  a  protective  organ  for  the  auditory  ossicles  and  their  muscles,  while  the 
increased  air  space  obtained  by  its  communication  with  the  mastoid  cells  permits 
free  vibration  of  the  membrana  tympani.  The  six  sides  of  the  tympanum  have 
important  practical  relations.  It  is  about  half  an  inch  in  height,  and  one  or  two 
lines  in  breadth,  i.  e.,  from  without  inward.  Its  roof  is  separated  from  the  cavity 
of  the  brain  by  a  very  thin  piece  of  bone,  which  is  sometimes  defective,  so  that 
encephalitis  may  follow  an  abscess  of  the  middle  ear.  The  outer  vfdXl  is  formed  by 
the  membrana  tympani,  while  on  the  ^t^ner^\3l\  are  the  fenestra  ovalis  and  rotunda, 
the  ridge  of  the  aqueductus  Fallopii,  the  promontory,  and  the  pyramid.  The  floor 
consists  of  a  thin  plate  of  bone,  which  roofs  in  the  jugular  fossa  and  separates  it 
from  the  jugular  vein.  Fractures  of  the  base  of  the  skull  may  rupture  the  carotid 
artery  or  internal  jugular  vein  ;  hence,  hemorrhage  from  the  ears  is  a  bad  symptom 


856 


CONDUCTION    OF   SOUND    IN    THE    LABYRINTH. 


in  these  cases.  Caries  of  the  ear  may  extend  to  other  organs.  The  anterior  wall 
is  in  close  relation  with  the  carotid  artery,  while  the  posterior  communicates  with 
the  mastoid  cells,  so  that  fluids  from  the  middle  ear  sometimes  escape  through  the 
mastoid  cells.] 

That  the  air  in  the  tympanum  can  communicate  its  vibrations  to  the  membrane  of  the  fenestra 
rotunda  is  true  (p.  S4S,  3),  but  normally  this  is  so  slight,  when  compared  with  the  conduction 
through  the  auditor)'  ossicles,  that  it  scarcely  need  be  taken  into  account. 

Structure. — The   tube   and   tympanum    are   lined    l>y   common   mucous   membrane,  covered  by 
ciliated  epithelium,  while  the  membrana  is  lined  by  a  layer  of  squamous  epithelium.     Mucous  glands 
were  found  by  Tn'^ltsch  and  \Vcndt  in  the  mucous  membrane.      [The  epi- 
FlG.  588.  thelium  covering  the  ossicles  and  tensor  tympani  is  not  ciliated.] 

^^  Pathological. — The  tube  is  often  occluded,  owing  to  chronic  catarrh 

^^^  and  narrowing  from  cicatrices,  hypertrophy  of  the   mucous   membrane,  or 

the  presence  of  tumors.  The  deafness  thereby  produced  may  often  be 
cured  by  calheterizini;  the  tube  from  the  nose  (Fig.  5SS).  Eflusions  into 
or  suppuration  within  the  tympanum  of  course  paralyze  the  sound-conduct- 
ing mechanism,  while  indammation  often  causes  subsequent  affections  of  the 
plexus  tympanicus.    If  the  temporal  bone  be  destroyed  by  progressive  caries 

Fi<;.  5S9. 


Eustachian  Catheter. 


Politzer's  Ear  Bag. 


within  the  tympanum,  inflammation  of  the  neighboring  cerebral  structures  may  occur  and  cause  death. 
[Methods. — Not  unfrequent'y  the  aurist  is  called  upon  to  dilate  the  Eustachian  tube,  which  in 
certain  cases  requires  the  use  of  a  Eustachian  catheter  introduced  into  the  tube  along  the  floor 
of  the  nose  (Fig.  588K  At  other  times  he  requires  to  till  the  tympanic  cavity  with  air,  which  is  easily 
done  by  means  of  a  Politzer's  bag  (Fig.  589).  The  nozzle  is  introduced  into  one  nostril,  while  the 
other  nostril  is  closed,  and  the  patient  is  directed  to  swallow,  while  at  the  same  moment  the  surgeon 
compresses  the  bag,  and  the  patient's  mouth  being  closed,  air  is  forced  through  the  open  Eustachian 
tube  into  the  middle  ear.  Sometimes  a  small  curved  narrow  manometer,  containing  a  drop  of 
colored  water,  is  placed  in  the  outer  ear  [Politzer).  Normally,  when  the  patient  swallows,  the  fluid 
ought  to  move  in  the  tube.] 

412.  CONDUCTION  OF  SOUND  IN  THE  LABYRINTH.— The 

vibrations  of  the  foot  of  the  stapes  in  the  fenestra  ovalis  give  rise  to  waves  in  the 
perilymph  within  the  inner  ear  or  labyrinth.  These  waves  are  so-called  ''flexion 
waves,''  i.  e.,  the  perilymph  moves  in  mass  before  the  impulse  of  the  base  of  the 
stapes.  This  is  only  possible  from  the  existence  of  a  yielding 
membrane — that  filling  the  fenestra  rotunda,  and  sometimes 
called  the  meinbrana  secundaria,  which  dtiring  rest  bulges  in- 
ward to  the  scala  tympani,  and  can  be  bulged  outward  toward 
the  tympanic  cavity  by  the  impulse  communicated  to  it  by  the 
movement  of  the  perilymph  (Fig.  577,  ;-).  The  flexion  waves 
must  correspond  in  number  and  intensity  to  the  vibrations  of 
the  auditory  ossicles,  and  must  also  excite  the  free  terminations 
External    appea.ance  of  of  the  auditorv  nerve,  which  float  free  in  the  endolymph. 

the  labyrinth,  fenestra  .         ,  /  ,  ,         /-      ,  1  1  •    1       1     •  ■        ^i 

ovalis,  cochlea  to  the  As  the  endolymph  of  the  saccule  and  utricle  lying  in  the 
(l^'hor1z^lai',\nd^")  vestibule  receives  the  first  impulse,  and  as  these  communicate 
posterior  sem'icircuiar  anteriorly  with  the  cochlea,  and  posteriorly  with  the  semicir- 
'^^"^  ^^'^'  cular  canals,  consequently  the  motion  of  the  perilymph  must 

be  propagated  through  these  canals.    To  reach  the  cochlea,  the  movement  passes 


Fig 


METHOD    OF   TESTING    SOUND    CONDUCTION.  857 

from  the  saccule  (lying  in  the  fovea  hemispherica)  along  the  scala  vestibuli  to  the 
helicotrema,  where  it  passes  into  the  scala  tympani,  where  it  reaches  the  membrane 
of  the  fenestra  rotunda,  and  causes  it  to  bulge  outward.  From  the  utricle  (lying  in 
the  fovea  hemielliptica),  in  a  similar  manner  the  movem.ent  is  propagated  through 
the  semicircular  cafials.  Politzer  observed  that  the  endolyraph  in  the  superior 
semicircular  canal  rose  when  he  caused  contraction  of  the  tensor  tympani  by  stimu- 
lating the  trigeminus,  just  as  the  base  of  the  stapes  must  be  forced  against  the 
perilymph  with  every  vibration  of  the  membrana  tympani. 

[Practical. — It  is  well  to  view  the  organ  of  hearing  as  consisting  of  two 
mechanisms :  — 

1.  The  sound-conducting  apparatus. 

2.  The  sound-perceiving  apparatus. 

The  former  includes  the  outer  ear,  with  its  auricle  and  external  meatus  :  the 
middle  ear  and  the  parts  which  bound  it,  or  open  into  it.  The  latter  consists  of 
the  inner  ear  with  the  expansion  of  the  auditory  nerve  in  the  labyrinth,  the  nerve 
itself,  and  the  sound-perceiving  and  interpreting  centre  or  centres   in  the  brain 

(P-  753)-] 

[Testing  the  Sound  conduction. — In  any  case  of  deafness,  it  is  essential  to 
estimate  the  degree  of  deafness  by  the  methods  stated  at  p.  848,  and  it  is  well  to 
do  so  both  for  such  sounds  as  those  of  a  watch  and  conversation.  We  have  next 
to  determine  whether  the  sound-conducting  or  the  sound-perceivi^ig  apparatus  is 
aifected.  If  a  person  is  deaf  to  sounds  transmitted  through  the  air,  on  applying  a 
sounding  tuning  fork  to  the  middle  line  of  the  head  or  teeth,  if  it  be  heard  dis- 
tinctly, then  the  sound-perceiving  apparatus  is  intact,  and  we  have  to  look  for  the 
cause  of  deafness  in  the  outer  or  middle  ear.  In  a  healthy  person,  the  sound  of 
the  tuning  fork  is  heard  of  equal  intensity  in  both  ears.  In  this  case  the  sound  is 
conducted  directly  to  the  labyrinth  by  the  cranial  bones.  In  cases  of  disease  of  the 
sound-conducting  mechanism,  the  sound  of  the  tuning  fork  is  heard  loudest  in  the 
deafer  ear.  Ed.  Weber  pointed  out  that,  if  one  ear  be  stopped  and  a  vibrating 
tuning  fork  placed  on  the  head,  the  sound  is  referred  to  the  plugged  ear,  where  it 
is  heard  loudest.  It  is  assumed  that  when  the  ear  is  plugged,  the  sound-waves 
transmitted  by  the  cranial  bones  are  prevented  from  escaping  (^Macli).  If,  on  the 
contrary,  the  sound  be  heard  loudest  in  the  good  ear,  then  in  all  probability  there 
is  some  affection  of  the  sound-perceiving  apparatus  or  labyrinth,  although  there  are 
exceptions  to  this  statement,  especially  in  elderly  people.  Another  plan  is  to  con- 
nect two  telephones  with  an  induction  machine,  provided  with  a  vibrating  Neef's 
hammer.  The  sounds  of  the  vibrations  of  the  latter  are  reproduced  in  the  tele- 
phones, and  if  they  be  placed  to  the  ears,  then  the  healthy  ears  hear  only  one 
sound,  which  is  referred  to  the  middle  line,  and  usually  to  the  back  of  the  head. 
In  diseased  conditions  this  is  altered — it  is  referred  to  one  side  or  the  other.] 

413.  LABYRINTH  AND  AUDITORY  NERVE.— Scheme.— The  vestibule  (Fig.  591, 
III)  contains  two  separate  sacs:  one  of  them,  the  saccule,  j  (round  sac  or  S.  hemisphasricus),  com- 
municates with  the  ductus  cochlearis,  Cc,  of  the  cochlea  :  the  other,  the  utricle,  U  (elliptical  sac, 
or  sacculus  hemiellipticus),  communicates  with  the  semicircular  canals,  Cs,  Cs. 

The  cochlea  consists  of  2}^  turns  of  a  tube  disposed  round  a  central  column  or  modiolus.  The 
tube  is  divided  into  two  compartments  by  a  horizontal  septum,  partly  osseous  and  partly  membranous, 
the  lamina  spiralis  ossea  and  membranacea  (Fig.  595  ;  Fig.  591,1).  The  lower  compartment 
is  the  scala  tympani,  and  is  separated  from  the  cavity  of  the  tympanum  by  the  membrane  of  the 
fenestra  rotunda. 

The  upper  compartment  is  the  scala  vestibuli,  which  communicates  with  the  vestibule  of  the 
labyrinth  (Fig.  591,  I).  These  two  compartments  communicate  directly  by  a  small  opening  at  the 
apex  of  the  cochlea,  a  sickle-shaped  edge  ["hamulus"]  of  the  lamina  spiralis  bounding  the  helico- 
trema (Fig.  577).  The  scala  vestibuli  is  divided  by  Reissner's  membrane  (Fig.  591,  I),  which 
arises  near  the  outer  part  of  the  lamina  spiralis  ossea,  and  runs  obliquely  outward  to  the  wall  of  the 
cochlea  so  as  to  cut  off  a  small  triangular  canal,  the  ductus  or  canalis  cochlearis,  or  scala  media, 
Cc,  whose  floor  is  formed  for  the  most  part  by  the  lamina  spiralis  membranacea,  and  on  which  the 
end  organ  of  the  auditory  nerve — Corti's  organ — is  placed.    The  lower  end  of  the  canaUs  cochlearis 


858 


STRUCTURE    OF   THE    COCHLEA. 


is  blind.  Ill,  and  divided  toward  the  saccule,  wiih  which  it  communicates  by  means  of  the  small 
canalis  reuniens,  Cr  {//ensen).  The  utricle  (Fig.  591,  III,  U)  communicates  with  the  three 
semicircular  canals,  Cs,  Cs — each  by  means  of  an  ampulla,  within  which  lie  the  terminations  of  the 
ampullary  nerves,  but  as  the  posterior  and  the  superior  canals  unite,  there  is  only  one  common 
ampulla  for  them.     The  membranous  semicircular  canals   lie  within  the  osseous  canals,  perilymph 

Fig.  591. 


I,  transverse  section  of  a  turn  of  the  cochlea  ;  II,  A,  ampulla  of  a  semicircular  canal  with  the  crista  acustica  ;  a,p, 
auditory  cells;  /,  provided  with  a  fine  hair ;  T,  otoliths;  HI,  scheme  of  the  human  labyrinth;  IV,  scheme  of^a 
bird's  labyrinth  ;  V,  scheme  of  a  fish's  labyrinth. 

lying  between  the  two.  Perilymph  also  fills  the  scala  vestibuli  and  tympani,  so  that  all  the  spaces 
within  the  labyrinth  are  filled  by  tluid,  while  the  spaces  themselves  are  lined  by  short  cylindrical 
epithelium. 

The  system  of  spaces,  filled  by  endolymph,  is  the  only  part  containing  the  nervous  end  organs 
for  hearing.     All  these  spaces  communicate  with  each  other ;  the  semicircular   canals  directly  with 

Fig.  593. 


The  interior  of  the  right  labyrinth  with  its  membranous  canals  and  nerves. 

In  Fig.  592,  the  outer  wall  of  the  bony  labyrinth  is  removed  to  show  the  membranous  parts  within — i,  commencement 
of  the  spiral  tube  of  the  cochlea;  2,  posterior  semicircular  canal,  partly  opened  ;  3,  horizontal ;  4,  superior  canal; 
5,  utricle;  6,  saccule;  7,  lamina  spiralis  ;  7',  scala  tympani ;  8,  ampulla  of  the  superior  membranous  canal;  9,  of 
the  horizontal ;  10,  of  the  posterior  canal. 

Fig.  593  shows  the  membranous  labyrinth  and  nerves  detached— i,  facial  nerve  in  the  internal  auditory  meatus ;  2,  an- 
terior division  of  the  auditory  nerve  giving  branches  to  5, 8,  and  9,  the  utricle  and  the  ampullae  of  the  superior  and 
horizontal  canals;  3,  posterior  division  of  the  auditory  nerve,  giving  branches  to  the  saccule. 6,  and  posterior  ampulla, 
10,  and  cochlea,  4  ;  7,  united  part  of  the  posterior  and  superior  canals  ;  ir,  posterior  extremity  of  the  horizontal  canal. 

the  utricle,  the  ductus  cochlearis  with  the  saccule  through  the  canalis  reuniens ;  and  lastly,  the  saccule 
and  utricle  through  the  "  saccus  endolymphaticus,"  which  springs  by  an  isolated  limb  from  each 
sac ;  the  limbs  then  unite,  as  in  the  letter  Y,  and  pass  through  the  osseous  aqueductus  vestibuli  to 
end  blindly  in  the  dura  mater  of  the  brain  (Fig.  Ill,  R — Boucher,  Retzhis).  The  aqueductus  coch- 
lea; is  another  narrow  passage,  which  begins  in  the  scala  tympani,  immediately  in  front  of  the  fenestra 


CRISTA   ACUSTICA   AND    COCHLEA.  859 

rotunda,  and  opens  close  to  tlie  fossa  jugularis.     It  forms  a  direct  means  of  communication  between 
the  perilymph  of  the  cochlea  and  the  subarachnoid  space. 

Semicircular  Canals  and  Vestibular  Sacs. — The  membranous  semicircular  canals  do  not 
fill  the  corresponding  osseous  canals  completely,  but  are  separated  from  them  by  a  pretty  wide  space, 
which  is  filled  with  perilymph  (Fig.  592).  At  the  concave  margin  they  are  fixed  by  connective 
tissue  to  the  osseous  walls.  The  ampuUse,  however,  completely  fill  ihe  corresponding  osseous  dilata- 
tions. The  canals  and  ampullae  consist  externally  of  an  outer,  vascular,  connective-tissue  layer,  on 
which  there  rests  a  well-marked  hyaline  layer,  bearing  a  single  layer  of  flattened  epithelium. 

Crista  Acustica. — The  vestibular  branch  of  the  auditory  nerve  sends  a  branch  to  each  ampulla  and 
to  the  saccule  and  utricle  (Fig.  593).  In  the  ampullae  (Fig.  591,  II,  A),  the  nerve  {c)  terminates  in 
connection  with  the  crista  acustica,  which  is  a  yellow  elevation  projecting  into  the  equator  of  the 
ampulla.  The  medullated  nerve  fibres,  n,  form  a  plexus  in  the  connective-tissue  layer,  lose  their 
myelin  as  they  pass  to  the  hyaline  basement  membrane,  and  each 

ends  in  a  cell  provided  with  a  rigid  hair  {0,  p)  90  //  in  length,  so  that  YiG.  594. 

the  crista    is  largely  covered  with  these    hair  cells,   but  between  t\      a        /it 

them  are  supporting  cells   hke  cylindrical  epithelium  (a),  and  not  /I       1       I 


unfrequently  containing  granules  of  yellow  pigment.     The  hairs  or  [      il       //        If" 

"  auditory  hairs  "  [M.  Schultze)  are  composed  of  many  fine  fibres       ^  __ZL.  /\^A — _Zi 
[Relzius).     An  excessively  fine   membrane  (membrana  tectoria)  -         "  ^ — " 

covers  the  hairs  [Friickard,  Lang).  ] 

Maculae  Acusticae. — The  nerve  terminations  in  the  maculae  acus- 
ticse  of  the  saccule  and  utricle  are  exactly  the  same  as  in  the  am- 
pullae, only  the  free  surface  of  their  membrana  tectoria  is  sprinkled 
with  small  white  chalk-like  crystals  or  otoliths  (II,  T),  composed  ?_ 

of  calcic  carbonate,  which  are  sometimes  amorphous  and  partly  in  ^^ 

the  form  of  arragonite,  lying  fi.xed  in   the  viscid  endolymph.     The 

non-medullated  axis  cylinders  of  the  saccular  nerves  enter  directly         '' ~~~     7^ — c — ^ 

into  the  substance  of  the  hair  cells.     The  terminations  of  the  nerves              ",  /,"!?/,  1      "  /  I  ) 
have  been  investigated,  chiefly  in  fi.shes,  in  the  rays.  1    |  /*^'  '         I  C „ 

[Fig.  594  is  a  vertical  section  of  a  macula  acustica  of  the  rabbit.  "j  /  )  '       -CS 

The  medullated  nerves  («)  lose  their  myelin  at  the  external  limiting  -     /  P^'-  '\ -i  "^ 

membrane,  become  non-medullated,  pierce  this  membrane,  and  form  ^~    '  ^  — -^ 

a  basal  plexus  [pi>)  between  (z)  the   epithelial  cells,  and  finally  ter- 
minate in  the  sensory  ciliated  cells  (;■).     The  epithelium  itself  con-  .  <  -^ 
sists  of  basal  cells  (cd),  fusiform  or  supporting  cells  {/),  and  the              /f  ,     \  '         'n  -^ 
ciliated  neuro-epithelium  (r),*each  cell  being  provided  with  a  cilium,              "-=/-,  ^  ,     *.*_'.  \  1 
which  perforates  the  external  limiting  membrane  [a).     There  is  thus 
a  remarkable  likeness  to  the  olfactory  epithelium.]                                        ^^"  aclisdcaTf  iVibbU^*^"'^ 

Cochlea. — The  terminations  of  the  cochlear  branch  of  the  auditory 
nerve  lie  in  connection  with  Corti's  organ,  which  is  placed  in  the  canalis  or  ductus  cochlearis  (Fig. 
591,  I,  Q.C,  and  III,  Cr,  and  Fig.  595),  the  small  triangular  chamber  [or  scala  media,]  cut  off"  from 
the  scala  vestibuU  by  the  membrane  of  Reissner.  Corti's  organ  is  placed  on  the  lamina  spiralis  mem- 
branacea,  and  consists  of  a  supporting  apparatus  composed  of  the  so-called  Corti's  arches,  each 
of  which  consists  of  two  Corti's  rods  {z,y),  which  lie  upon  each  other  like  the  beams  of  a  house. 
But  every  two  rods  do  not  form  an  arch,  as  there  are  always  three  inner  to  two  outer  rods  [Clatidius). 
There  are  about  4500  outer  rods  (  Waldeyer). 

The  ductus  cochlearis  becomes  larger  toward  the  apex  of  the  cochlea,  and  the  rods  also  become 
longer;  the  inner  ones  are  30  //  long  in  the  first  turn,  and  34  /i  in  the  upper,  the  outer  rods  47  fi 
and  69  fjL  respectively.  The  span  of  the  arches  also  increases  [Hensen).  [The  arches  leave  a  tri- 
angular tunnel  beneath  them.]  The  proper  end  organs  of  the  cochlear  nerve  are  the  cylindrical 
"  hair  cells  "  {^KoUiker')  previously  observed  by  Corti,  which  are  from  16,400  to  20,000  in  number 
[Heitsett,  Waldeyer).  There  is  one  row  of  inner  cells  (z)  which  rests  on  a  layer  of  small  granular 
cells  (K)  {Bottcher,  Waldeyer) ;  the  outer  cells  {a,  a)  number  12,000  in  man  {Retzius),  and  rest 
upon  the  basement  membrane,  being  disposed  in  three  or  even  four  rows.  Between  the  outer  hair 
cells  there  are  other  cellular  structures,  which  are  either  regarded  as  special  cells  (Deiter's  cells), 
or  are  regarded  merely  as  processes  of  the  hair  cells  (Lavdowsky).  [The  cochlear  branch  of  the 
auditory  nerve  enters  the  modiolus,  and  runs  upward  in  the  osseous  channels  there  provided  for  it, 
and  as  it  does  .so  gives  branches  to  the  lamina  spiralis,  where  they  nin  between  the  osseous  plates 
which  form  the  lamina.]  The  fibres  (N)  come  out  of  the  lamina  spiralis  after  traversing  the  gan- 
glionic cells  in  their  course  (Figs.  591,  595,  I,  G),  and  end  by  fine  varicose  fibrils  in  the  hair  cells 
(Fig.  595)  {Waldeyer,  Gottstein,  Lavdowsky,  Retzhis). 

Membrana  Reticularis. — Corti's  rods  and  the  hair  cells  are  covered  by  a  special  membrane  (o), 
the  membrana  reticularis  of  Kolliker.  The  upper  ends  of  the  hair  cells,  however,  project  through 
holes  in  this  membrane,  which  consists  of  a  kind  of  cement  substance  holding  these  parts  together 
[Lavdowsky).  [Springing  from  the  outer  end  of  the  lamina  spiralis,  or  crista  spiralis,  is  the  mem- 
brana  tectoria,  sometimes  called   the  membrane  of  Corti.     It   is  a  well-defined  structure,  often 


860 


MUSICAL   TUNES    AND    NOISES. 


librillated  in  appearance,  and  extends  outward  over  the  organ  of  Corli.]  Waldeyer  regards  it  as  a 
dani])ing  apparatus  for  this  organ  (Fig.  595,  Mb.  Corli). 

[Basilar  Membrane. — Its  hreaclth  incre.ises  from  the  base  to  the  ape.x  of  the  cochlea.  This 
fact  is  imj  ortaiit  in  connection  with  the  theory  of  the  ]ierception  of  lone.  It  is  supposed  that  high 
notes  are  appreciated  by  structures  in  connection  wilii  the  former,  and  low  notes  liy  the  ujjper  parts 
of  the  basilar  memiirane.  In  one  case,  recorded  by  Moos  and  Steinbrugge,  a  patient  heard  low  notes 
only  in  the  right  ear,  and  after  death  it  was  found  that  the  auditory  nerve  in  the  first  turn  of  the 
cochlea  was  atro]ihied.] 

Intra-Labyrinthine  Pressure. — The  lymph  within  the  labyrinth  is  under  a  certain  pressure. 
Every  diminuiion  of  the  pressure  of  the  air  in  the  tympanum  is  accompanied  by  a  corresponding 
diminution  of  the  intra-labyrinthine  pressure,  while  conversely  every  increase  of  pressure  is  accom- 
panied by  an  increase  of  the  lymph  pressure  [F.  Bezol<i). 

The  perilymph  of  the  inner  ear  flows  away  chiefly  through  the  aqueductus 
cochleee,  in  the  circumference  of  the  foramen  jugulare,  into  the  peripheral  lymph- 
atic system,  which  also  takes  up  the  cerebro-spinal  fluid  of  the  sul)arachnoid  space, 


Fig.  595. 


Scheme  of  the  diicuis  cochlearis  and  the  organ  of  Corti.  N,  cochlear  nerve  :  K,  inner,  and  P,  outer  hair  cells  ;  n. 
nerve  fibrils  terminating  in  P ;  ti,  a,  supporting  cells  ;  d,  cells  in  the  sulcus  spiralis  ;  z,  inner  rod  of  Corti ;  Mb, 
Corti,  membrane  of  Corti,  or  the  membrana  tectoria ;  <?,  the  membrana  reticularis;  H,  G,  cells  filling  up  the 
space  near  the  outer  wall. 

while  a  small  part  drains  away  to  the  sub-dural  space  through  the  internal  auditory 
meatus.  The  endolymph  flows  through  the  arachnoid  sheath  of  the  N.  acusticus 
into  the  subarachnoid  space  (C  Hasse). 

414.  AUDITORY  PERCEPTIONS.— Every  normal  ear  is  able  to  distin- 
guish musical  tones  and  noises.  Physical  experiments  prove  that  tones  are 
produced  when  a  vibrating  elastic  body  executes  periodic  movements,  /.  e.,  when 
the  sounding  body  executes  the  same  movement  in  etpial  intervals  of  time,  as  the 
vibrations  of  a  string  which  has  been  plucked.  A  noise  is  produced  by  non- 
periodic  movements,  /.  e.,  when  the  sounding  body  executes  unequal  movements 
in  equal  intervals  of  time.  [The  non-periodic  movements  clash  together  on  the 
ear,  and  produce  dissonance,  as  when  we  strike  the  keyboard  of  a  piano  at  random.] 
This  is  readily  proved  by  means  of  the  siren.  Suppose  that  there  are  forty  holes 
in  the  rotatory  disk  of  this  instrument,  placed  at  exactly  the  same  distance  from  each 
other,  on  rotating  the  disk  and  directing  a  current  of  air  against  it,  obviously  with 


PERCEPTION    OF    PITCH.  861 

every  rotation  the  air  will  be  rarefied  and  condensed  exactly  forty  times.  Every 
two  condensations  and  rarefactions  are  separated  from  each  other  by  an  eqical 
interval  of  time.  This  arrangement  yields  a  characteristic  musical  tone  or  note. 
If  a  similar  disk  with  holes  perforated  in  it  at  ?/;^(f^//a/ distances  be  used,  on  air 
being  forced  against  it,  a  whirring  non-musical  noise  is  produced,  because  the 
movements  of  the  sounding  body  (the  condensations  and  rarefactions  of  the  air)  are 
non-periodic.  [The  double  siren  of  v.  Helmholtz  is  an  improved  instrument  for 
showing  Ihe  same  facts.] 

The  normal  ear  alsj  distinguishes  in  every  tone  three  distinct  factors  ; — 
[(i)  Intensity  or  force;   (2)  Pitch;  (3)   Quality,  timbre  or  '■'■  klangy^ 

1.  The  intensity  of  a  tone  depends  upon  the  greater  or  lesser  amplitude  of 
the  vibrations  of  the  sounding  body.  It  is  well  known  that  a  vibrating  string 
emits  a  feebler  sound  when  its  excursions  are  smaller.  (The  intensity  of  a  sound 
corresponds  to  the  degree  of  illumination  or  brightness  in  the  case  of  the  eye.) 

2.  The  pitch  depends  upon  the  number  of  vibrations  which  occur  in  a  given 
time  [or  the  length  of  time  occupied  by  a  single  vibration].  This  is  proved  by 
means  of  the  siren.  If  the  rotating  disk  have  a  series  of  forty  holes  at  equal  inter- 
vals, and  another  series  of  eighty  equidistant  from  each  other,  on  blowing  a  stream 
of  air  against  the  rotating  disk  we  hear  two  sounds  of  unequal  pitch,  one  being  the 
octave  of  the  other.  (The  perception  of  pitch  corresponds  to  the  sensation  of  color 
in  the  case  of  the  eye.) 

3.  The  quality  or  timbre  {^' Klangfarbe'')  is  peculiar  to  different  sonorous 
bodies.  [It  is  the  peculiarity  of  a  musical  tone  by  which  we  are  enabled  to  dis- 
tinguish it  as  coming  from  a  particular  instrument,  or  from  the  human  voice. 
Thus,  the  same  note  struck  on  a  piano  and  sounded  on  a  violin  differ  in  quality  or 
iimbre.'\  It  depends  upon  the  peculiar  fortn  of  the  vibration,  or  the  form  of  the 
wave  of  the  sonorous  body.    (There  is  no  analogous  sensation  in  the  case  of  light.) 

I.  Perception  of  Pitch. — By  means  of  the  organ  of  hearing,  we  can  determine  that  different 
tones  have  a  different  pitch.  In  the  SD-called  musical  scale,  or  gamut,  this  difference  is  very  marked 
to  a  normal  ear.  But  in  the  scale  there  are  again  four  tones,  which,  when  they  are  sounded  tOTether, 
cause  in  a  normal  ear  the  sensation  of  an  agreeable  sound,  which  once  heard  can  readily  be  repro- 
duced. This  is  the  tone  of  the  so-called  accord.  Triad,  or  Common  Chord,  consisting  of  the  1st, 
3d,  and  5th  tones  of  the  scale,  to  which  the  8th  tone  or  octave  is  added.  We  have  next  to  determine 
the  pitch  of  the  tones  of  the  chord,  and  then  that  of  the  other  tones  of  the  scale.  The  siren  is  used 
for  the  fundamental  experiment,  from  which  the  others  can  easily  be  calculated.  Four  concentric 
circles  are  drawn  upon  the  rotatory  disk  of  the  siren;  the  inner  circle  contains  40  holes,  the  second 
50,  the  third  60,  and  the  outer  80 — all  the  holes  being  at  equal  distances  from  each  other.  If  the 
disk  be  rotated,  and  air  forced  against  each  series  of  holes  in  turn,  we  distinguish  successively  the 
four  tones  of  the  accord  (major  chord  with  its  octave) ;  when  all  the  four  series  are  blown  upon 
simultaneotisly,  we  hear  in  complete  purity  the  major  chord  itse'f  The  relative  miinber  of  the  holes 
in  the  four  series  indicates  in  the  simplest  manner  the  relative  pitch  of  the  tones  of  the  major  chord. 
While  one  revolution  of  the  disk  is  necessary  to  produce  xht  fujidaniental  gro2ind  tone  (key  note  or 
tonic)  with  40  condensations  and  rarefactions  of  the  air — in  order  to  produce  the  octave,  we  must 
have  double  the  number  of  condensations  and  rarefactions  during  one  revolution  in  the  same  time. 
Thus,  the  relation  of  the  number  of  vibrations  of  the  Ground  tone  or  Tonic  to  the  Octave  next  above 
it,  is  I  :  2.  In  the  second  series  we  have  50  holes,  which  causes  the  pitch  of  the  third;  hence,  the 
relation  of  the  Ground  tone  to  the  Third  in  this  case  is  40  :  50,  or  \  :  \\^\,i.  e.,  for  every 
vibration  of  the  Ground  tone  there  are  f  vibrations  in  the  Third.  In  the  third  series  are  60 
holes,  which,  when  blown  upon,  yield  the  fifth;  hence,  the  ratio  of  the  Ground  tone  to  the  Fifth  in 
our  disk  is  40  :  60,  or  i  :  i^  =  | .  In  the  same  way  we  can  estimate  the  pitch  of  the  Fourth  tone,  and 
we  find  that  the  number  of  vibrations  of  the  First,  Third,  Fifth,  and  Octave  are  to  each  other  as 
1.5.3.2 

The  minor  chord  is  quite  as  charactenstic  to  a  normal  ear  as  the  major.  It  is  distinguished 
essentially  from  the  latter  by  its  Third  being  half  a  tone  lower.  We  can  easily  imitate  it  by  the  siren, 
as  the  Minor  Third  consists  of  a  number  of  vibrations  which  stand  to  the  Ground  tone  as  6:5,  i.  e., 
if  5  vibrations  occur  in  a  given  time  in  the  Ground  tone,  then  6  occur  in  the  Minor  Third ;  its  vibra- 
tion number,  therefore,  is  |. 

From  these  relations  of  the  Major  and  Minor  common  chords,  we  may  calculate  the  relative  tones 
in  the  scale,  and  we  must  remember  that  the  Octave  of  a  tone  always  yields  the  fullest  and  most  com- 
plete harmony.     It  is  evident  that  as  the  Major  Third,  and  Minor  Third,  and  the  Fifth  harmonize 


862  LIMITS   OF    AUDITORY    PERCEPTION. 

with  the  fundamental  Ground  tone  or  key  note,  they  must  also  harmonize  with  the  Octave  of  the  key 
note.  We  obtain  from  the  Major  Third  with  the  number  of  vibrations  |,  the  Minor  Sixth  J,  from 
the  Minor  Third  with  0,  the  Major  Sixth  =  ( ,'; j  =  )  ?. ;  from  the  Fifth  with  J,  the  Fourth  =  |. 
These  relations  are  known  as  the  "  Inversions  of  the  intervals."  These  relations  of  the  tones  are, 
collectively,  the  consonant  intervals  of  the  scale.  The  dissonant  stages,  or  discords,  of  the  scale 
can  be  obtained  as  follows :  Suppose  that  we  have  the  Ground  tone  or  key  note  C,  with  the  number 
of  vibrations  =  i,  the  Third  E  =  ^,  the  Fifth  G  =  |.  and  the  Octave  =  2,  we  then  derive  from  the 
Fifth  or  Dominant  G  a  Major  chord;  this  is  G,  B,  D'  The  relative  number  of  vibrations  of  these  3 
tones  is  the  same  as  in  the  Major  chord  of  C  ,  C,  E,  G.  Hence,  the  number  of  vibrations  of  G  :  B  is  as 
C  :  E.  When  we  substitute  the  values  we  obtain  | :  B  ^  I  :  J,  /.  e.,  B  ^  '/.  But  D  :  B  ^  G  :  E ; 
so  that  D  :  1/  =  5  :  J,  i.e.,  D  =  Y-  or  an  octave  lower,  we  have  D  =  f .  Deduce  from  F  (sub- 
dominant)  a  Major" chord,  F,  A,  €'.  The  relation  of  A  :  C'  =  E  :  G,  or  A  :  2  =  J  :  §,  t.  e.,  A  =  \. 
Lastly,  F :  A  =  C  :  E,  or  F  :  §  =  I  :  J,  ?'.  e.,  F  =  \.  So  that  all  the  tones  of  the  scale  have  the 
following  number  of  vibrations  :  I,  C  =  I ;  II,  D  =  |;  III,  E=J;  IV,  F=f;  V,  G=|;VI, 
A  =  ^  ;  VII,  B  =  Y  ;  VIII,  C  =  2. 

Conventional  Estimate  of  Pitch. — Conventionally,  the  pitch  or  concert  pitch  of  the  note,  a, 
is  taken  at  440  vibrations  in  the  second  {Scheibler,  1834),  although  in  France  it  is  taken  at  435 
vibrations  per  second.  From  this  we  can  estimate  the  absolute  number  of  vibrations  for  the  tones  of 
the  scale:  C  =  33,  D  =  37.125,  E  =  41.25,  F  =44,  G  =  49.5,  A=  55,  B  =  61.875  vibrations. 
The  numl)er  of  vibrations  of  the  next  highest  octave  is  found  at  once  by  multiplying  these  numbers 
by  2. 

Musical  Notes. — The  lowest  notes  used  in  music  are  the  double  bass,  E,  with  41.2^  vibra- 
tions, pianoforte  C  with  33,  grand  piano  A,  with  27.5  and  organ  C  with  16. 5.     The  highest   notes 
in  mu.sic  are  the  pianoforte  c"  with  4224,  and  d^'  on  the  piccolo  flute,  with  4752  vibra- 
Fio.  596.      tions  per  second. 

Limits  of  Auditory  Perception. — ^According  to  Preyer,  the  limit 
of  the  perception  of  the  lowest  audible  tone  lies  between  t6  and  23 
vibrations  per  second,  and  e''"  with  40,960  vibrations  as  the  highest 
audible  tone;  so  that  this  embraces  about  11^  octaves. 

[Audibility  of  Shrill  Notes. — This  varies  very  greatly  in  different  persons  (  Wol- 
laston).  Thereisaremirkablc  fallingoffof  the  power  as  age  advances  (Cfz/Zow).  Fortest- 
ing  this  Galton  uses  a  small  whistle  made  of  a  brass  tube,  with  a  diameter  of  less  than 
Jj  of  an  inch  (Fig.  596).  A  plug  is  fitted  at  the  lower  end  to  lengthen  or  shorten  the 
tube,  whereby  the  pitch  of  the  note  is  altered.  Among  animals  Galton  finds  none  supe- 
rior to  cats  in  the  power  of  hearing  shrill  sounds,  and  he  attributes  this  "  to  differentiation 
by  natural  selection  among  these  animals  until  they  have  the  power  of  hearing  all 
Gallon's  the  high  notes  made  by  mice  and  other  little  creatures  they  have  to  catch.''] 
Whistle.  Variations  in  Auditory  Perception. — It  is  rare  to  find  that  tones  produced  by  more 

than  35,000  vibrations  per  second  are  heard.  When  the  tensor  tympani  is  contracted, 
the  perception  may  be  increased  for  tones  3000  to  5000  vibrations  higher,  but  rarely  more.  Patho- 
logically, the  perception  for  high  notes  maybe  abnormally  acute — (i)  When  the  tension  of  the 
sound  conducting  apparatus  generally  is  increased.  (2)  By  elimination  of  the  sound-conducting 
apparatus  of  the  middle  ear,  which  offers  greater  or  less  resistance  to  the  propagation  of  very  high 
notes,  as  perforation  of  the  membrana  tympani,  or  loss  of  the  incus  and  malleus.  In  these  ca<es,  the 
stapes  is  directly  set  in  vibration  by  the  sound  waves,  when  tones  up  to  80,000  vibrations  have  been 
perceived.  Diminished  tension  of  the  sound-conducting  apparatus  causes  diminution  of  the  percep- 
tion for  high  tones  [B/nke). 

A  smaller  number  of  vibrations  than  16  per  second  (as  in  the  organ)  are  no  longer  heard  as  a  tone, 
but  as  single  dull  impulses.  The  tones  that  are  produced  beyond  the  highest  audible  note,  as  by 
stroking  small  tuning-forks  with  a  violin  bow,  are  also  no  longer  heard  as  tones,  but  they  cause  a 
painful  cutting  kind  of  impression  in  the  ear.  In  the  musical  scale  the  range  is,  approximately,  from 
C  of  the  first  octave  wiih  16.5  vibrations  to  e,  the  eighth  octave. 

Comparison  of  Ear  and  Eye. — In  comparing  the  perception  of  the  eye  with  that  of  the  ear, 
we  see  at  once  that  the  range  of  accommodation  of  the  ear  is  much  greater.  Red  has  456  billions 
of  vibrations  per  second,  while  the  visible  violet  has  but  667,  so  that  the  eye  only  takes  cognizance  of 
vibrations  which  do  not  form  even  one  octave. 

Lowest  Audible  Tone. — As  to  the  smallest  uumh&r  of  successive  vibrations 
which  the  ear  can  perceive  as  a  sensation  of  tone,  Savart  and  Pfaundler  considered 
that  two  would  suffice.  If,  however,  we  exclude  in  our  experiments  the  possibility 
of  the  occurrence  of  overtones,  4  to  8  {Mach)  or  even  16  to  20  vibrations  {F. 
Auerbach,  KohlrauscK)  are  necessary  to  produce  a  characteristic  tone. 

When  tones  succeed  each  other  rapidly,  they  are  still  perceived  as  distinct,  when 


PERCEPTION    OF    QUALITY.  863 

at  least  o.i  second  intervenes  between  two  successive  tones  (v.  Helmholtz)  ;  if  they 
follow  each  other  more  rapidly,  they  fuse  with  each  other,  although  a  short-time 
interval  is  sufficient  for  many  musical  tones. 

By  the  term,  "Jine?iess  of  the  ear,'"  or,  as  we  say,  a  "good  ear,"  is  meant  the 
capacity  of  distinguishing  from  each  other,  as  different,  two  tones  of  nearly  the 
same  number  of  vibrations.  This  power  can  be  greatly  increased  by  practice,  so 
that  musicians  can  distinguish  tones  that  differ  in  pitch  by  only  -g-L.^  or  even  -prVo' 
of  their  vibrations. 

With  regard  to  the  time  sense,  it  is  found  that  beats  are  more  precisely  per- 
ceived by  the  ear  than  by  the  other  sense  organs  {Horing,  Mack). 

Pathological. — According  to  Lucae,  there  are  some  ears  that  are  better  adapted  for  hearing  low 
notes  and  others  for  high  notes.  Both  conditions  are  disadvantageous  for  hearing  speech.  Those 
who  hear  low  notes  best  hear  the  highest  consonants  imperfectly.  The  low  notes  are  heard  abnorm 
ally  loud  in  rheumatic  facial  paralysis,  while  the  high  tones  are  heard  abnormally  loud  in  cases  of 
loss  of  the  membrana  tympani,  incus,  and  malleus.  The  stapedius  is  in  full  action,  whereby  the 
highest  tones  are  heard  louder  at  the  expense  of  the  lower  notes.  Many  persons  with  normal  hearing 
hear  a  tone  higher  with  one  ear  than  with  the  other.  This  condition  is  called  diplacusis  binauralis. 
In  rare  cases,  sudden  loss  of  the  perception  of  certain  tones  has  been  observed,  c.  g.,  the  bass  deaf- 
ness of  Moos.     In  a  case  described  by  Magnus,  the  tones  d,  b,  were  not  heard  (§  316). 

II.  Perception  of  the  Intensity  of  Tone. — The  intensity  of  a  tone  depends  upon  the  ampli- 
tude of  the  vibratio7is  of  the  sounding  body.  The  intensity  of  the  tone  is  proportional  to  the  square 
of  the  amplitude  of  vibration  of  the  sounding  body,  i.  e.,  with  2,  3,  or  4  times  the  amplitude  the  in- 
tensity of  the  tone  is  4,9,  16  times  as  strong.  As  sonorous  vibrations  are  communicated  to  our  ears 
by  the  wave  movements  of  the  air,  it  is  evident  that  the  tones  must  become  less  and  less  intense  the 
further  we  are  from  the  source  of  the  sound.  The  intensity  of  the  sound  is  inversely  proportional  to 
the  square  of  the  distance  of  the  source  of  the  sound  from  the  ear. 

Tests. — I.  Place  a  watch  horizontally  near  the  ear,  and  test  how  close  it  may  be  brought  to  the 
ear,  and  also  how  far  it  may  be  removed,  and  still  its  sounds  be  heard.  Measure  the  distance.  2. 
Itard  uses  a  small  hammer  suspended  like  a  pendulum,  and  allowed  to  fall  upon  a  hard  surface.  3. 
Balls  of  different  weights  are  allowed  to  fall  from  varying  heights  upon  a  plate.  In  this  case  the 
intensity  of  the  sound  is  proportional  to  the  product  of  the  weight  of  the  ball  into  the  height  it  falls. 

As  to  the  limits  of  the  perception  of  the  intensity  of  tone,  it  is  found  that  a  spherule  weighing  i 
milligram,  and  falling  from  a  height  of  I  mm.  upon  a  glass  plate,  is  heard  at  a  distance  of  5  centi- 
metres [Sckafhault). 

415.  PERCEPTION  OF  QUALITY— VOWELS.— By  the  term  quality  ("  Klangfarbe"), 
musical  color  or  timbre,  is  understood  a  peculiar  character  of  the  tone,  by  which  it  can  be  dis- 
tinguished apart  from  its  pitch  and  intensity.  Thus,  a  flute,  horn,  violin,  and  the  human  voice  may 
all  sound  the  same  note  with  equal  intensity,  and  yet  all  the  four  are  distinguished  at  once  by  their  spe- 
cific quality.  Wherein  lies  the  essence  ("  Wesen")  of  tone-color?  The  investigations  of  v.  Helm- 
holtz have  proved  that,  among  mechanisms  which  produce  tones,  only  those  that  produce  pendulum- 
like vibrations,  /.  e.,  the  to-and-fro  vibrations  of  a  metallic  rod  with  one  end  fixed,  and  tuning  forks, 
execute  simple  pendulum-like  vibrations.  This  can  be  shown  by  making  a  tuning  fork  write  off  its 
vibrations  on  a  i-ecording  surface,  when  a  completely  uniform  wave  line,  with  equal  elevations  and 
depressions,  is  noted.  The  term  "  tone  "  is  restricted  to  those  sounds,  hardly  ever  occurring  in 
nature,  which  are  due  to  simple  pendulum-like  vibrations. 

Other  investigations  have  shown  that  the  tones  of  musical  instruments  and  of  the  human  voice,  all 
of  which  have  a  characteristic  quality  of  their  own,  are  composed  of  many  single  simple  tones. 
Among  these  one  is  characterized  by  its  intensity,  and  at  the  same  time  it  determines  the  pitch  of  the 
whole  compound  musical  "tone  picture."  This  is  called  the  fundamental  tone  or  keynote.  The 
other  weaker  tones  which,  as  it  were,  spring  from  and  are  mingled  with  this,  vary  in  different  instru- 
ments both  in  intensity  and  number.  They  are  "upper  tones,"  and  their  vibrations  are  always 
some  multiple — 2,  3,  4,  5  ....  times — of  the  fundamental  tone  or  keynote.  In  general,  we  say  that 
all  those  outbursts  of  sound  which  embrace  numerous  strong  upper  tones,  especially  of  high 
pitch,  in  addition  to  the  fundamental  tone,  are  characterized  by  a  sharp,  piercing,  and  rough 
quality,  such  as  emanates  fi-om  a  trumpet  or  clarionet,  and  that  conversely  the  quality  is  char- 
acterized by  mildness  and  softness  when  the  overtones  are  few,  feeble,  and  low,  e.g.^  such  as 
are  produced  by  the  flute.  It  requires  a  well-trained  musical  ear  to  distinguish,  in  an  instni- 
mental  burst,  the  overtones  apart  from  the  fundamental  tone.  But  this  is  very  easily  done 
with  the  aid  of  resonators  (Fig.  600).  These  consist  of  spherical  or  funnel-shaped  hollow 
bodies,  made  of  brass  or  some  other  substance,  which,  by  means  of  a  short  tube,  can  be  placed 
in  the  outer  ear.  If  a  resonator  be  placed  in  the  ear,  we  can  hear  the  feeblest  overtone  of  the 
same  number  of  vibrations  as  the  fundamental  tone.  Thus,  musical  instruments  are  distinguished 
by  the  number,  intensity,  and  pitch  of  the   overtones  which    they  produce.     A  vibrating  metaUic 


864 


ANALYSIS    OF    VOWELS. 


d\ 


Curves  of  a  musical  tone  obtained  by  compounding  the 
curve  of  a  fundamental  tone  with  that  of  its  overtones. 


rod  and  a  tuning  fork  have  no  overtones ;  they  only  give  the  fundamental  tone.  As  already  men- 
tioned, the  term  simple  tone  is  applied  to  sounds  due  to  simple  pendulum-like  vibrations,  while  a 
sound  composed  of  a  fundamental  tone  and  overtones  is  called  a  "  klang  "  or  coinpoiiud  musical  tone. 

Vibration    Curve    of   a    Musical    Tone. — 
Fk;.   597.  When  we  remem'ier  that  a  musical  tone  or  clang 

consists  of  a  fundamental  tone,  and  a  number  of 
overtones  of  a  certain  intensity,  which  determine  its 
(jualily,  tiien  we  ought  to  be  able  to  construct  geo- 
metrically the  vibraiion  curve  of  the  musical  tone. 
Let  A  represent  the  vibration  curve  of  the  fundamen- 
tal tone,  and  H  that  of  the  first  moderately  weak 
overtone  (Fig.  597).  The  combination  of  these 
two  curves  is  obtained  simjily  by  computing  the 
height  of  the  ordinates,  whereby  the  ordinates  of  the 
overtone  curve,  lying  above  the  abscissa  or  horizon- 
tal line,  are  added  to  the  fundamental  tone  curve, 
while  those  of  the  ordinates  below  the  line  are 
subtracted  from  it.  Thus  we  obtain  the  curve  C, 
which  is  not  a  .simple  pendulum-like  curve,  but  one 
which  corresponds  to  an  unsteady  movement.  A 
new  curve  of  the  second  overtone  may  be  added  to 
C,  and  so  on.  The  result  of  all  these  combinations 
is  that  the  vibration  curves  corresponding  to  the 
compound  musical  tones  are  unsteady  periodic 
curves.  All  these  curves  must,  of  course,  vary 
with  the  number  and  pitch  of  the  compound  over- 
tone curves. 
Displacement  of  the  Phases. — The  form  of  the  vibration  of  one  and  the  same  musical  tone 
may  vary  very  greatly  if,  in  compounding  the  curves  A  and  B,  the  curve  B  is  only  slightly  displaced 
laterally.  If  B  is  displaced  so  that  the  hollow  of  the  wave  r  falls  under  A,  the  addition  of  both  curves 
yields  the  curve  r,  r,  r,  with  small  elevations  and  broad  valleys.  If  B  be  displaced  still  further,  until 
the  elevation  of  the  wave,  //,  coincides  with  A,  w-e  obtain  still  another  form,  so  that  by  displacement 
of  the  phases  of  the  wave  motions  of  the  compounded  simple  pendulum  like  vibrations,  we  obtain 
numerous  different  forms  of  the  same  musical  tone.  The  displacement  of  the  phases,  howe%'er,  has 
no  effect  on  the  ear. 

The  general  result  of  these  observations,  and  those  of  Fourier,  is  that  the  quality  of  a  musical  tone 
depends  up  jn  the  characteristic  form  of  the  vibratory  movement. 

Analysis  of  Vowels. — The  human  voice  represents  a  reed  instrument  with  vibrating  elastic 
membranes,  the  vocal  cords  (^  312).  In  uttering  the  various  vowels  the  mouth  assumes  a  character- 
istic form,  SD  that  its  cavity  has  a  certain  fundamental  tone  peculiar  to  itself.  Thus,  to  the  funda- 
mental tone  of  a  certain  pitch  produced  within  the  larynx,  there  are  added  certain  overtones,  which 
communicate  to  the  laryngeal  tone  the  vocal  or  vowel  quality.  Hence,  a  vowel  is  the  timbre  or 
quality  of  a  musical  tone  which  is  produced  in  the  larynx.  The  quality  depends  upon  the  number, 
intensity,  and  pitch  of  the  overtones,  and  the  latter,  again,  depend  on  the  configuration  of  the 
"  vocal  cavity"  in  uttering  the  different  vowels  (^  317). 

Suppose  a  person  to  sing  the  vowels  one  after  the  other  on  a  special  note,  e.  g.,  b  b,  we  can,  with 
the  aid  of  resonators,  determine  the  overtone-,  and  in  what  intensity  they  are  mixed  with  the  funda- 
mental tone,  b  >,  to  give  the  characteristic.quality.  Accordmg  to  v.  Ilelmholtz,  when  we  sound 
the  vowels  on  b  b,  for  each  of  the  three  vowels,  one  overtone  is  specially  characteristic  for  A-b^  1> ; 
for  O-b'  b ;  for  U-f.  The  other  vowels  and  the  diphthongs  have  each  two  specially  characteristic 
overtones,  because  in  these  cases  the  mouth  is  so  shaped  that  the  posterior  larger  cavity,  and  also 
the  anterior  narrower  part,  each  yields  a  special  tone  (^  316,  I  and  E).  These  two  overtones  are 
for  E-B"i  b  and  f  ;  for  I-div  and  f;  for  A-g'"  and  d" ;  6-c"i  #  and  f  I ;  for  U-glH  and  f.  These, 
however,  are  only  the  special  upper  tones.  There  are  many  more  upper  tones,  but  they  are  not  so 
prominent. 

Artificial  Vowels. — Just  as  it  is  possible  to  analyze  a  vowel  into  its  fundamental  tone  and  its 
upper  tones,  it  is  possible  to  compound  tones  to  produce  the  vowels  by  simultaneously  sounding  the 
fundamental  tone  and  the  corresponding  upper  tones.  (l)  A  vowel  is  produced  simply  by  singing 
loudly  a  vowel,  e.  g..  A,  upon  a  certain  note  against  the  free  strings  of  an  open  piano,  while  by  the 
pedal  the  damper  is  kept  raised.  As  soon  as  we  stop  singing,  the  characteristic  vowel  is  sounded  by 
the  strings  of  the  piano.  The  voice  sets  into  sympathetic  vibration  all  those  strings  whose  overtones 
(in  addition  to  the  fundamental  tone)  occur  in  the  vocal  compound  tone,  so  that  they  vibrate  for  a 
time  after  the  voice  ceases  {v.  Ilelmholtz).  (2)  The  vowel  apparatus  devised  by  v.  Helmholtz  con- 
sists of  numerous  tuning  forks,  which  are  kept  vibrating  by  means  of  electro-magnets.  The  lowest 
tuning  fork  gives  the  fundamental  tone,  B  b,  and  the  others  the  overtones.  A  resonator  is  placed  in 
front  of  each  tuning  fork,  and    the  distance  between  the  two    can   be  varied   at  pleasure.     The 


koenig's  apparatus. 


865 


resonators  can  be  opened  and  closed  by  a  lid  passing  in  front  of  their  openings.  When  the  resonator 
IS  closed,  we  cannot  hear  the  tone  emitted  by  the  tuning-fork  placed  in  front  of  it;  but  when  one  or 
more  resonators  are  opened  the  tone  is  heard  distinctly,  and  it   is  louder  the  more  the  resonator  is 


Fig.  598. 


Koenig's  raanometric  capsjile  (A)  and  mirror  {lli)~(Koenig). 


Fig.  599. 


55 


Flame  pictures  of  the  vowels  ou,  o,  and  A  (Koenig). 


866 


KOENIG  S   APPARATUS. 


opened.  By  means  of  a  series  of  keys,  like  the  keys  of  a  pianoforte,  we  can  rapidly  open  and  close 
the  resonators  at  will,  and  thus  combine  various  overtones  with  the  fundamental  tone  so  as  to  pro- 
duce vowels  with  different  tiuali  ies.  v.  lldniliollz  makes  the  following  compositions  :  U  =  B  b  with 
b  ?  weak  and  f  i  ;  C)  ;=  clamped  B  ?  with  hi  ;'  strong  and  weaker  b  ?,  f '  ,  d" ;  A  =  b  b  (fundamental 
tone)  with  moderately  strong  bl  i>  and  f",  and  strong  b"  t>  and  dm  ;  A  =  b  l>  (fundamental  tone) 
with  b' ?  and  f"  somewhat  stronger  than  for  A,  tl  strong,  b'l  1?  weaker,  d'H  and  fm  as  strong  as 
possible;  E  =  b  b  (as  fundament.al  tone)  moderately  strong,  with  b'  b  and  f  moderate  also,  and  f  "' , 
ab'"  ,  and  bm  b  as  strong  as  possible ;  I  could  not  be  jiroduced. 

In  Appunn's  apparatus,  the  fundamental  tone  and  the  overtones  are  produced  by  means  of 
organ  jiipes,  whose  tones  can  be  combined  to  produce  the  vowels,  but  it  is  not  so  good  as  the  tuning 
forks,  since  tiie  organ  pipes  do  not  yield  simple  tones,  but  nevertheless  some  of  the  vowels  can  be 
admirably  reproduced  with  this  apparatus. 

Edison's  Phonograph. — If  we  utter  the  vowels  against  a  delicate  membrane. stretched  over  the 

Fitt.  600. 


Koenig's  apparatus  for  analyzing  a  conipound  tone  with  the  funJamenlal  tone  UTo. 

end  of  a  hollow  cylinder,  and  if  a  writing  style  be  fixed  to  the  centre  of  the  membrane,  and  the 
style  be  so  arranged  that  it  can  write  or  record  its  movements  on  a  piece  of  soft  tinfoil  arranged  on  a 
revolving  apparatus,  then  the  vowel  curve  is  stamped  as  it  were  upon  the  tinfoil.  If  the  style  now  be 
made  to  touch  the  tinfoil  while  the  latter  is  moved,  then  the  style  is  moved — it  moves  the  membrane, 
and  we  hear  distinctly  by  resonance  the  vowel  sound  reproduced. 

[Koenig's  Manometric  Flames. — By  means  of  this  apparatus  the  quality  of  the  vowel  sounds 
is  easily  shown.  It  consists  of  a  small  wooden  capsule,  A,  divided  into  two  compartments  by  a  piece 
of  thin  sheet  india-rubber.  Ordinary  gas  passes  into  the  chamber  on  one  side  of  the  membrane, 
through  the  stop-cock,  and  it  is  lighted  at  a  small  burner.  To  the  other  compartment  is  attached  a 
wider  tube  with  a  mouthpiece.  The  whole  is  fixed  on  a  stand,  and  near  it  is  placed  a  four-sided 
rotating  mirror,  M,  as  suggested  by  Wheatstone  (Fig.  598).  On  speaking  or  singing  a  vowel  into 
the  mouthpiece,  and  rotating  the  mirror,  a  toothed  or  zigzag  flame  picture  is  obtained  in  the  mirror. 
The  form  of  the  flame  pic'ure  is  characteristic  for  each  vowel,  and  varies,  of  course,  with  the  pitch]. 


ACTION    OF    THE    LABYRINTH    DURING    HEARING.  867 

[Fig.  599  shows  the  form  of  the  flame  picture  obtained  in  the  rotating  mirror  when  the  vowels,  ou, 
O,  A,  are  sung  at  a  pitch  of  ut^,  sol^,  and  iit^.     This  series  shows  how  they  differ  in  quality.] 

[Koenig  has  also  invented  the  apparatus  for  analyzing  any  compound  tone  whose  fundamental 
tone  is  UXj  (Fig.  600).  It  consists  of  a  series  of  resonators,  from  UT,  to  uXj,  fixed  in  an  iron  frame. 
Each  resonator  is  connected  with  its  special  flame,  which  is  pictured  in  a  long,  narrow,  square,  rotating 
muTor.  If  a  tuning  fork  UT^  be  sounded,  only  the  flame  UTj  is  affected,  and  so  on  with  each  tuning 
fork  of  the  harmonic  series.  Suppose  a  compound  note  containing  the  flmdamental  tone  UT2,  and 
its  harmonics  be  sounded,  then  the  flame  of  VY^,  and  those  of  the  other  harmonics  in  the  note  are 
also  affected,  so  that  the  tone  can  be  analyzed  optically.     The  same  may  be  done  with  the  vowels.] 

416.  LABYRINTH  DURING  HEARING.— If  we  ask  what  role  the  ear 
plays  in  the  perception  of  the  quality  of  sounds,  then  we  must  assume  that,  just 
as  with  the  help  of  resonators  a  musical  note  can  be  resolved  into  its  fundamental 
tone  and  overtones,  so  the  ear  is  capable  of  performing  such  an  analysis.  The 
ear  resolves  the  complicated  wave  forms  of  musical  tones  into  their  components. 
These  components  it  perceives  as  tones  harmonious  with  each  other  ;  with  marked 
attention  each  is  perceived  singly,  so  that  the  ear  distinguishes  as  different  tone 
colors  only  different  combinations  of  these  simple  tone  sensations.  The  resolution 
of  complex  vibrations,  due  to  quality,  into  simple  pendulum-like  vibrations  is  a 
characteristic  function  of  the  ear.  What  apparatus  in  the  ear  is  capable  of  doing 
this?  If  we  sing  vigorously,  e.  g.,  the  musical  vowel  A  on  a  definite  note,  say 
b  b — against  the  strings  of  an  open  pianoforte  while  the  damper  is  raised,  then 
we  cause  all  those  strings,  and  o/i/y  those,  to  vibrate  sympathetically,  which  are 
contained  in  the  vowel  so  sung.  We  must,  therefore,  assume  that  an  analogous 
sympathetic  apparatus  occurs  in  the  ear,  which  is  tuned,  as  it  were,  for  different 
pitches,  and  which  will  vibrate  sympathetically  like  the  strings  of  a  pianoforte. 
"If  we  could  so  connect  every  string  of  a  piano  with  a  nerve  fibre  that  the  nerve 
fibre  would  be  excited  and  perceived  as  often  as  the  string  vibrated,  then,  as  is  actually 
the  case  in  the  ear,  every  rnusical  note  which  affected  the  instrument  would  excite 
a  series  of  sensations  exactly  corresponding  to  the  pendulum-like  vibrations  into 
which  the  original  movements  of  the  air  can  be  resolved ;  and  thus  the  existence 
of  each  individtial  overtone  would  be  exactly  perceived,  as  is  actually  the  case  with 
the  ear.  The  perception  of  tones  of  different  pitch  would,  under  these  circum- 
stances, depend  upon  different  nerve  fibres,  and  hence  would  occur  quite  independ- 
ently of  each  other.  Microscopic  investigation  shows  that  there  are  somewhat 
similar  structures  in  the  ear.  The  free  ends  of  all  the  nerve  fibres  are  connected 
with  small  elastic  particles  which  we  must  assume  are  set  into  sympathetic  vibra- 
tion by  the  sound  waves"  (v.  HelmJioltz). 

Resolution  by  the  Cochlea. — Formerly  v.  Helmholtz  considered  the  rods 
of  Corti  to  be  the  apparatus  that  vibrated  and  stimulated  the  terminations  of  the 
nerves.  But,  as  birds  and  amphibians,  which  certainly  can  distinguish  musical 
notes,  have  no  rods  {Hasse),  the  stretched  radial  fibres  of  the  membrana  basilaris, 
on  which  the  organ  of  Corti  is  placed,  and  which  are  shortest  in  the  first  turn  of 
the  cochlea,  becoming  longer  tOAvard  the  apex  of  the  cochlea,  are  now  regarded 
as  the  vibrating  threads  {Henseii).  Thus,  a  string-like  fibre  of  the  membrana  basi- 
laris, which  is  capable  of  vibrating,  corresponds  to  every  possible  simple  tone. 
According  to  Hensen,  the  hairs  of  the  labyrinth,  which  are  of  unequal  length, 
may  serve  this  purpose.  Destruction  of  the  apex  of  the  cochlea  causes  deafness  to 
deeper  tones  (^Baginsky). 

[Hensen' s  Experiments. — That  the  hairs  in  connection  with  the  hair  cells 
vibrate  to  a  particular  note  is  also  rendered  probable  by  the  experiments  of  Hensen 
on  the  crustacean  Mysis.  He  found  that  certain  of  the  minute  hairs  (auditory 
hairs)  in  the  auditory  organ  of  this  animal,  situate  at  the  base  of  the  antennae, 
vibrated  when  certain  tones  were  sounded  on  a  keyed  horn.  The  movements  of 
the  hairs  were  observed  by  a  low-power  microscope.  In  mammals,  however,  there 
is  a  difficulty,  as  the  hairs  attached  to  the  cells  appear  to  be  all  about  the  same 
length.     We  must  not  forget  that  the  perception  of  sound  is  a  mental  act.] 


868  SIMULTANEOUS    ACTION    OF    TWO    TONES. 

This  assumption  also  explains  the  perception  of  noises. 

Of  noises  in  the  strictly  physical  sense,  it  is  a-^sumed  that  they,  like  single 
im])iilses,  arc  perceived  by  the  aid  of  the  saccules  and  the  ampulla. 

it  is  assumed  that  tlie  saccules  and  the  ampullae  are  concerned  in  the  general 
perception  of  hearing,  /.  f.^  of  shocks  ( omnnmicated  to  the  auditory  nerve  (by 
impulses  and  noises);  while  by  the  cochlea  we  estimate  the  pitch  and  depth  of 
the  vibrations,  and  musical  character  of  the  vibrations  produced  by  tones. 

The  relation  of  the  semicircular  canals  to  the  cciuilibrium  of  the  body  is 
referred  to  in  §  350. 

417.  SIMULTANEOUS  ACTION  OF  TWO  TONES— HAR- 
MONY-BEATS—DISCORDS— DIFFERENTIAL  TONES.— When 

huo  tones  of  different  pitch  fall   upon    the   ear  simultaneously,  they  cause  different 
sensUions  according  to  the  difference  in  pitch. 

1.  Consonance. — If  the  number  of  vibrations  of  the  two  tones  is  in  the  ratio 
of  simple  multii)les,  as  i  :  2  :  3  :  4,  so  that  when  the  low  notes  make  one  vibration 
the  higher  one  makes  2  :  3  or  4  .  .  .  .  then  we  experience  a  sensation  of  complete 
harmony  or  concord. 

2.  Interference. — If,  however,  the  two  tones  do  not  stand  to  each  other  in 
the  relation  of  simple  multiples,  then  when  both  tones  are  sounded  simultaneously 
interference  takes  place.  The  hollows  of  the  one  sound  wave  can  no  longer  coin- 
cide with  the  hollows  of  the  other,  and  the  crests  with  the  crests,  but,  correspond- 
ing to  the  difference  of  number  of  vibrations  of  both  curves,  sometimes  a  wave 
crest  must  coincide  with  a  wave  hollow.  Hence,  when  wave  crest  meets  wave  crest, 
there  must  be  an  increase  in  the  strength  of  the  tone,  and  when  a  hollow  coincides 
with  a  crest,  the  sound  must  be  weakened.  Thus  we  obtain  the  impression  of  those 
variations  in  tone  intensity  which  have  been  called  "  beats." 

The  number  of  vibrations  is  of  course  always  equal  to  the  difference  of  the  number  of  vibrations 
of  both  tones.  Tlie  beats  are  perceived  most  distinctly  when  two  organ  tones  of  low  pitch  are 
sounded  together  in  unison,  but  slightly  out  of  tune.  Suppose  we  take  two  organ  pipes  with  2,Z 
vibrations  per  second,  and  so  alter  one  pipe  that  it  gives  34  vibrations  per  second,  then  one  distinct 
beat  will  be  heard  every  second.  The  beats  are  heard  more  frequently  the  greater  the  difference 
between  the  number  of  vibrations  of  the  two  tones. 

Successive  Beats. — The  beats,  however,  produce  very  different  impressions 
upon  the  ear  according  to  the  rapidity  with  which  they  succeed  each  other. 

1.  Isolated  Beats. — When  they  occur  at  long  intervals,  we  may  perceive  them 
as  completely  isolated,  but  single  intensifications  of  the  sound  with  subsequent 
enfeeblement,  so  that  they  give  rise  to  the  impression  of  isolated  beats. 

2.  Dissonance. — When  the  beats  occur  more  rapidly  they  cause  a  continuous 
disagreeable  wliirring  impression,  which  is  spoken  of  as  dissonance,  or  an  unhar- 
monious  sensation.  The  greatest  degree  of  unpleasant  painful  dissonance  occurs 
when  there  are  33  beats  per  second. 

3.  Harmony. — If  the  beats  take  place  more  rapidly  than  33  times  per  second, 
the  sensation  of  dissonance  gradually  diminishes,  and  it  does  so  the  more  rapidly 
the  beats  occur.  The  sensation  passes  gradually  from  moderately  inharmonious 
relations  (which  in  music  have  to  be  resolved  by  certain  laws)  toward  consonance 
or  harmony.  The  tone  relations  are  successively  the  Second,  Seventh,  Minor 
Third,  Minor  Sixth,  Major  Third,  Major  Sixth,  Fourth  and  Fifth. 

4.  Action  of  the  Musical  Tones  {"  K/dnge"). — Two  musical  "klangs," 
or  compound  tones,  falling  on  the  ear  simultaneously,  produce  a  result  similar  to 
that  of  two  simple  tones ;  but  in  this  case  we  have  to  deal  not  only  with  the  two 
fundamental  tones;  but  also  with  the  overtones.  Hence  the  degree  of  dissonance 
of  two  musical  tones  is  the  more  pronounced  the  more  the  fundamental  tones  and 
the  overtones  (and  the  "  differential  "  tones)  produce  beats  which  number  about 
33  per  second. 

5.  Differential  Tones. — Lastly,  two  "klangs,"  or  two  simple  musical  tones 


PERCEPTION    OF   THE    DIRECTION    OF    SOUNDS.  869 

sounding  simultaneously,  may  give  rise  to  new  tones  when  they  are  uniformly  and 
simultaneously  sounding  in  corresponding  intensity.  We  can  hear,  if  we  listen 
attentively,  a  third  new  tone,  whose  number  of  vibrations  corresponds  to  the 
difference  between  the  two  primary  tones,  and  hence  it  is  called  a  '■'■  differe?itial 
tone. ' ' 

Summational  Tones. —  It  was  formerly  supposed  that  new  tones  could  arise  from  the  summa- 
tion or  addition  of  their  number  of  vibrations,  but  it  has  been  shown  that  these  tones  are  in  reality 
differential  tones  of  a  high  order  (^Appunn,  Preyer). 

418.  PERCEPTION  OF  SOUND— OBJECTIVE  AND  SUB- 
JECTIVE AUDITION— AFTER-SENSATION.— Objective  and 
Auditory  Perceptions. — When  the  stimulation  of  the  terminations  of  the 
nerves  of  the  labyrinth  is  referred  to  the  outer  world,  then  we  have  objective 
auditory  perceptions.  Such  stimulations  are  only  referred  to  the  outer  world  as  are 
conveyed  to  the  membrana  tympani  by  vibrations  of  the  air,  as  is  shown  by  the 
fact  that  if  the  head  be  immersed  in  water,  and  the  auditory  meatuses  be  filled 
thereby,  we  hear  all  the  vibrations  as  if  they  occurred  within  our  head  itself  {^Ed. 
Weber),  and  the  same  is  the  case  with  our  own  voices,  as  well  as  with  the 
sound  waves  conducted  through  the  bones  of  the  head,  when  both  ears  are  firmly 
plugged. 

Perception  of  Direction. — As  to  the  perception  of  the  direction  whence 
sound  comes,  we  obtain  some  information  from  the  relation  of  both  meatuses  to 
the  source  of  the  sound,  especially  if  we  turn  the  head  in  the  supposed  direction  of 
the  sound.  We  distinguish  more  easily  the  direction  from  which  noise  mixed  with 
musical  tones  come  than  that  of  tones  (^Rayleigli).  When  both  ears  are  stimulated 
equally,  we  refer  the  source  of  the  sound  to  the  middle  line  anteriorly,  but  when 
one  ear  is  stimulated  more  strongly  than  the  other,  we  refer  the  source  of  the 
sound  more  to  one  side  {Kessel).  The  position  of  the  ear  muscles,  which  perhaps 
act  like  an  ear  funnel,  is  important.  According  to  Ed.  Weber,  it  is  more  difiicult 
to  determine  the  direction  of  sound  when  the  ears  are  firmly  fixed  to  the  side  of 
the  head.  Further,  if  we  place  the  hollow  of  both  hands  in  front  of  the  ear,  so  as 
to  form  an  open  cavity  behind  them,  we  are  apt  to  suppose  that  a  sounding  body 
placed  in  front  is  behind  us.  The  semicircular  canals  are  said  also  to  be  concerned, 
as  sound  coming  from  a  certain  direction  must  always  excite  one  canal  more  than 
the  others.  Thus,  the  left  horizontal  canal  is  most  stimulated  by  horizontal 
sound  waves  coming  from  the  left  (^Preyer').  Other  observers  assert  that  the 
membrana  tympani  localizes  the  sound,  as  only  certain  parts  of  it  are  affected  by 
the  sound  waves. 

The  distance  of  a  sound  is  judged  of  partly  by  the  intensity  or  loudness  of  the 
sound,  such  as  we  have  learned  to  estimate  from  sound  at  a  known  distance.  But 
still  we  are  subject  to  many  misconceptions  in  this  respect. 

Among  subjective  auditory  sensations  are  the  after  vibratiotis ,  especially  of  intense  and 
continued  musical  tones ;  the  tinnitus  aurium  (p.  655),  which  often  accompanies  abnormal  move- 
ments of  the  blood  in  the  ear,  may  be  due  to  a  mechanical  stimulation  of  the  auditory  fibres,  perhaps 
by  the  blood  stream  {^Brenner). 

[Drugs. — Cannabis  indica  seems  to  act  on  the  hearing  centre,  givingrise  to  subjective  sounds;  the 
hearing  is  rendered  more  acute  by  strychnin ;  while  quinine  and  sodic  salicylate  in  large  doses  cause 
ringing  in  the  ears  {B}-imto7t).'\ 

Entotical  perceptions,  which  are  due  to  causes  within  the  ear  itself,  are  such  as  hearing  the 
pulse  beats  in  the  surrounding  arteries,  and  the  rushing  sound  of  the  blood,  which  is  especially  strong 
when  there  is  increased  resonance  of  the  ear  (as  when  the  meatus  or  tympanum  is  closed,  or  when 
fluid  accumulates  in  the  latter),  during  increased  cardiac  action,  or  in  hypereesthesia  of  the  auditory 
nerve  [Bremtef).  Sometimes  there  is  a  cracking  noise  in  the  maxillary  articulation,  the  noise  pro- 
duced by  traction  of  the  muscles  on  the  Eustachian  tube  (^  411),  and  when  air  is  forced  into  the 
latter,  or  when  the  membrana  tympani  is  forced  outward  or  inward  (|  350)- 

Fatigue. — The  ear  after  a  time  becomes  fatigued,  either  for  one  tone  or  for  a  series  of  tones  which 
have  acted  on  it,  while  the  perceptive  activity  is  not  affected  for  other  tones.  Complete  recovery, 
however,  takes  place  in  a  few  seconds  i^Urbantschitsch). 


870         AUDITORY    AFTER-SENSATIONS    AND    COLOR    ASSOCIATIONS. 

Auditory  After-Sensations. — (l)  Those  that  correspond  to /^j/V/fi?  after-sensations,  where  the 
after-sensation  is  so  closely  connected  with  the  original  tone  that  both  appear  to  be  continuous.  (2) 
There  are  some  after-sensations,  where  a  pause  intervenes  between  the  end  of  the  objective  and  the 
beginning  of  the  subjective  tone  ( Urbanlschilsch).  (3)  There  seems  also  to  be  a  form  corresjxjnding 
to  negative  after-images. 

In  some  persons,  the  perception  of  a  tone  is  accompanied  by  the  occurrence  of  subjective  colors, 
or  the  sensation  of  light,  e.g.,  the  sound  of  a  trumpet,  accompanied  by  the  sensation  of  yellow. 
More  seldom  visual  sensations  of  this  kind  are  observed  when  the  nerves  of  taste,  smell,  or 
touch  are  excited  [iViisslximiier,  Lehinann  and  Blculer).  It  is  more  common  to  find  that  an 
intense  sharp  sound  is  accompanied  by  an  associated  sensation  of  the  sensory  nerves.  Thus 
many  people  experience  a  cold  shudder  when  a  slate  pencil  is  drawn  in  a  peculiar  manner  across  a 
slate. 

[Color  Associations. — Color  is  in  some  persons  instantaneously  associated  with  .sound,  and 
Galton  remarks  that  it  is  rather  common  in  children,  although  in  an  ill-developed  degree,  and  the 
tendency  seems  to  be  very  hereditary.  Sometimes  a  particular  color  is  associated  with  a  particular 
letter,  vowel  sounds  particularly  evoking  colors.  Galton  has  given  colored  rcj  re=entations  of  these 
color  associations,  and  he  points  out  their  relation  to  what  he  calls  number  forms,  or  the  associa- 
tion of  certain  fornis  with  certain  numbers.] 

An  auditory  impulse  communicated  to  one  ear  at  the  same  time  often  causes  an  increase  in  the 
auditory  function  of  the  other  ear,  in  consequence  of  the  stimulation  of  the  auditoi-y  centres  of  both 
sides  {Vrbaiiischitsch,  Eitelherg^. 

Other  Stimuli. — The  auditor)-  apparatus,  besides  being  excited  by  sound  waves,  is  also  affected 
by  heterologous  stimuli.  It  is  stimulated  mechanically  by  a  sudden  blow  on  the  ear.  The  effects 
of  electricity  and  pathological  conditions  are  referred  to  in  \  350. 

419.  COMPARATIVE— HISTORICAL.— The  lowest  fishes,  the  cyclostomata  (Petromy- 
zon),  have  a  saccule  provided  witli  auditory  hairs  containing  otoliths,  and  communicating  with  twa 
semicircular  canals,  while  the  myxinoids  have  only  one  semicircular  canal.  Most  of  the  other  fishes, 
however,  have  a  utricle  communicating  with  three  semicircular  canals.  In  the  carp,  prolongations  of 
the  labjTinth  communicate  with  the  swimming  bladder.  In  amphibia,  the  structure  of  the  labyrinth 
is  somewhat  like  that  in  fishes,  but  the  cochlea  is  not  tyjjically  developed.  Most  amphibia,  except 
the  frog,  are  devoid  of  a  membrana  tympani.  Only  the  fenestra  ovalis  (not  the  rotunda)  exists,  and 
it  is  connected  in  the  frog  by  three  ossicles  with  the  freely-exposed  membrana  tympani.  Among 
reptiles  the  appendix  to  the  saccule,  corresponding  to  the  cochlea,  begins  to  be  prominent.  In 
the  tortoise  it  is  saccular,  but  in  the  crocodile  it  is  longer,  and  somewhat  curved  and  dilated  at  the 
end.  In  all  reptiles  the  fenestra  rotunda  is  developed,  whereby  the  cochlea  is  connected  with  the 
labyrinth.  In  crocodiles  and  birds,  the  cochlea  is  divided  into  a  scala  vestibuli  and  S.  tympani. 
Snakes  are  devoid  of  a  tympanic  cavity.  In  birds  both  saccules  (Ing.  591,  IV,  U  S'')  are  united 
i^Hasse),  the  canal  of  the  cochlea  (U  C),  which  is  connected  by  means  of  a  fine  tube  (C)  with  the 
saccule,  is  larger,  and  shows  indications  of  a  spiral  arrangement,  and  has  a  flask- like  blind  end,  the 
lagena  (L).  The  auditory  ossicles  in  reptiles  and  birds  are  reduced  to  otie  column-like  rod,  cor- 
responding to  the  stapes,  and  called  the  columella.  The  lowest  mammals  (Echidna)  have 
structures  very  like  those  of  birds,  while  the  higher  mammals  have  the  same  type  as  in  man  (Fig. 
591,  IIIl.     The  Eustachian  tube  is  always  open  in  the  whale. 

Among  invertebrata,  the  auditoiy  organ  is  very  simple  in  medusa;  and  mollusca.  It  is  merely 
a  bladder  filled  with  fluid,  with  the  auditory  nerves  provided  with  the  ganglia  in  its  walls.  Hair 
cells  occur  in  the  interior,  provided  with  one  or  more  otoliths.  Hensen  observed  that  in  some  of 
theannulosa,  when  sound  was  conducted  into  the  water,  some  of  the  auditory  bristles  vibrated,  being 
adapted  for  special  tones.  In  cephalopoda,  we  distinguish  the  first  differentiation  into  a  membranous 
and  cartilaginous  labyrinth. 

Historical. — Empcdocles  (473  n.  c.)  referred  auditory  impressions  to  the  cochlea.  The  Hippo- 
cratic  School  was  acquainted  with  the  tympanum,  and  Aristotle  (384  K.  c. )  with  the  Eu.stachian  tube. 
Vesalius  (1561)  described  the  tensor  tympani;  Cardanus  (1560)  the  conduction  through  the  bones 
of  the  head;  while  Fallopius  (1561)  described  the  vestibule,  the  semicircular  canals,  chorda  tympani, 
the  two  fene.strse,  the  cochlea,  and  the  aqueduct.  Eustachius  (t  1570)  described  the  modiolus,  the 
lamina  spiralis  of  the  cochlea,  the  Eustachian  tube,  as  well  as  the  muscles  of  the  ear ;  Plater  the 
ampullae  (1583);  Casseri  (1600)  the  lamina  spiralis  membranacea.  Sylvius  (1667)  discovered  the 
ossicle  called  by  his  name;  Vesling  (i64i)the  .stapedius.  Mersenne  (1618)  was  acquainted  with 
overtones;  Gassendus  (1658)  experimented  on  the  conduction  of  sound.  Acoustics  were  greatly 
advanced  by  the  work  of  Chladni  (1802).  The  most  recent  and  largest  work  on  the  ear  in  vertebrates 
is  by  G.  Retzius  (1881-84). 


THE  SENSE  OF  SMELL. 


420.  STRUCTURE  OF  THE  ORGAN  OF  SMELL.— Regio  Olfactoria.— The  area 
of  the  distribution  of  the  olfactory  nerve  is  the  regio  olfactoria,  which  embraces  the  upper  part  of 
the  septum,  the  upper,  and  part  of  the  middle  [Cm)  turbinated  bone  (Fig.  601,  Cs).  AH  the 
remainder  of  the  nasal  cavity  is  called  the  regio  respiratoria.  These  two  regions  are  distinguished 
as  follows  :  (i)  The  regio  olfactoria  has  a  thicker  mucous  membrane.  (2)  It  is  covered  by  a  single 
layer  of  cylindrical  epithelium,  the  cells  being  often  branched  at  their  lower  ends,  and  contain  a  yel- 
low or  brownish-red  pigment  (Figs.  602,  603,  E).  (3)  It  is  colored  by  this  pigment,  and  is  thereby 
distinguished  from  the  uncolored  regio  respiratoria,  which  is  covered  by  ciliated  epithelium.     (4)   It 


Nasal  and  pharyngo-nasal  cavities.  L,  levator  eleva- 
tion ;  P.s.p.,  plica  salpingo-palatina ;  Cs,  Cm, 
Ci,  the  three  turbinated  bones  {UrbantschitscJi). 


ar/-^ 


Vertical  section  of  the  olfactory  region  (rabbit),  . 
X  560.     s,  disk  :  zo,  zone  of  oval,  and  zr  of 
spherical  nuclei;   ^,  basal  cells;  (/r,  part  of  a 
Bowman's  gland  ;  n,  branch  of  the  olfactory 
nerve. 


contains  peculiar  tubular  glands  (Bowman's  glands),  described  as  "  mixed  glands"  by  Paulsen 
(§  142),  while  the  rest  of  the  mucous  membrane  contains  numerous  acinous  serous  glands  [Heiden- 
hain) ;  but  in  man  the  latter  are  said  to  be  mixed  glands  [Stohr)  (Fig.  602).  Lymph  follicles  lie  in 
the  mucous  membrane,  and  from  them  numerous  leucocytes  pass  out  on  to  free  surface  [Stohr).  (5) 
Lastly,  the  regio  olfactoria  embraces  the  end  organs  of  the  olfactory  nerve.  The  long,  narrow  olfactory- 
cells  (Fig.  603,  N)  are  distributed  between  the  ordinary  cylindrical  epithelium  (E)  covering  the 
regio  olfactoria.  The  body  of  the  cell  is  spindle-shaped,  with  a  large  nucleus  containing  nucleoli, 
and  it  sends  upward  between  the  cylindrical  cells  a  narrow  (0.9  to  1.8  ji)  smooth  rod,  quite  up  to  the 
free  surface  of  the  mucous  membrane.  In  the  frog  [n)  the  free  end  carries  delicate  projecting  hairs 
or  bristles.  In  the  deeper  part  of  the  mucous  membrane,  the  olfactory  cells  pass  into,  and  become 
continuous  with,  varicose  fine  nerve  fibres,  which  pass  into  the  olfactory  nerve  (|  321, 1,  i).  Accord- 
ing to  C.  K.  Hoffmann  and  Exner,  after  section  of  the  olfactory  nerve,  the  specific  olfactory  end 
organs  become  changed  into  cylindrical  epithelium  (frog),  and  in  warm-blooded  animals  they  undergo 

871 


872 


OLKACTOKY    SENSATIONS. 


fatty  degeneration,  even  on  the  15th  day.     v.  Hrunn  fi)unil  a  homogeneous  limiting  membrane,  which 
had  holes  in  it  for  transmitting  the  processes  of  the  olfactory  cells  only. 

[The  respiratory  part  of  ihe  nasal  mucous  membrane  is  lined  by  ciliated  epithelium  stratified 
like  that  in  the  trachea  ard  resinig  on  a  basement  membrane.  Below  tliis  there  are  many  lymph 
corpuscles  and  ai^gregalions  of  adenoid  tissue.] 

[The  organ  of  Jacobson  is  present  in  all  mammals,  and  consists  of  two  narrow  tubes  protected 
by  cartilage,  and  placed  in  the  lower  and  anterior  part  of  the  nasal  septum. 
Each  tube  terminates  blindly  behind,  but  anteriorly  it  opens  into  the  nasal  fur- 
FlG.  603.  row  or  into  the  naso-palatine  canal  (dog).     The  wall   next  the  middle   line  is 

covered  by  olfactory  tpiliielium,  and  receives  olfactory  nerves  (rabliit,  guinea- 
pig),  and  it  contains  glands  similar  to  iho^e  of  the  olfactory  region;  the  outer 
wall  is  covered  by  columnar  epithelium  ciliated  in  some  animals  (A7«*«).] 

421.  OLFACTORY  SENSATIONS.— Olfactory  sensa- 
tions are  produced  by  the  action  of  gaseous,  odorous  substances, 
being  brought  into  direct  contact  with  the  olfactory  cells, 
during  Ciie  act  of  hreathin:^.  The  current  of  air  is  divided  by  the 
anterior  projection  of  the  lowest  turbinated  bone,  so  that  a  part 
above  the  latter  is  conducted  to  the  regio  olfactoria.  Odorous 
bodies  taken  into  the  mouth  and  then  expired  through  the  pos- 
terior nares  are  said  not  to  be  smelt  {Bidder).  [This  is  certainly 
not  true,  as  has  been  i)roved  by  Aronsohn.] 

[It  is  usually  stated  that  only  odorous  particles  suspended  in  air  excite  the 
sensation  of  smell.  This  is  certainly  not  the  whole  truth — otherwise,  how  do 
aquatic  animals,  like  fish,  smell  ?  Moreover,  the  mucous  membrane  is  always 
moist,  and  in  some  cases  where  tliere  is  a  profuse  secretion  from  the  olfactory 
mucous  membrane,  tiiere  is  no  impairment  of  the  sense  of  smell.] 

During  inspiration,  the  air  streams  along  close  to  the  septum,  while  little  of  it 
passes  through  the  nasal  passages,  especially  the  superior  [Paulsen  afid Exner). 
[The  expired  air  takes  almost  the  same  course  as  the  inspired  air.] 

The yfz-j/ moment  of  contact  between  the  odorous  body  and 
the  olfactory  mucous  membrane  appears  to  be  the  time  when  the 
sensation  takes  place,  as,  when  we  wish  to  obtain  a  more  exact  per- 
ception, we  sniff  stwtxdA  times,  /.  e. ,  a  series  of  rapid  inspirations  are  taken,  the  mouth 
being  kept  closed.  During  sniffing,  the  air  within  the  nasal  cavities  is  rarefied,  and 
as  air  rushes  in  to  equilibrate  the  pressure,  the  air,  laden  with  odorous  particles, 
streams  over  the  olfactory  region.  Odorous  fluids  are  said  not  to  give  rise  to 
the  sensation  of  smell  when  they  are  brought  into  direct  contact  with  the  olfactory 
mucous  membrane,  as  by  pouring  eau  de  Cologne  into  the  nostrils  (7'<?/^/-/'W, 
1827;  E.  H.  Weber,  1847).  [Aronsohn  has,  however,  shown  that  these  experi- 
ments are  not  accurate,  for  one  can  smell  eau  de  Cologne,  clove  oil,  etc.,  when  d 
mixture  of  these  bodies  with  .73  per  cent.  NaCl  is  applied  to  the  olfactory  mucous 
membrane;  the  most  .suitable  medium  is  .73  per  cent.  NaCl  and  its  temperature 
40-43°  C]  Even  water  alone  temporarily  affects  the  cells.  We  know  practically 
nothing  about  the  nature  of  the  action  of  odorous  bodies,  but  many  odorous  vapors 
have  a  considerable  power  of  absorbing  heat  {Tyndall).  [Odorous  bodies  dimin- 
ish the  number  of  respirations  (^Gourewiisch).'\ 

The  intensity  of  the  sensation  depends  on— i.  The  size  of  the  olfactory 
surface,  as  animals  with  a  very  keen  sense  of  smell  are  found  to  have  complex  turbi- 
nated bones  covered  by  the  olfactory  mucous  membrane.  2.  The  concentration 
of  the  odorous  mixture  of  the  air.  Still,  some  substances  may  be  attenuated 
enormously  (e.  g.,  musk  to  the  two-millionth  of  a  milligramme),  and  still  be 
smelt.  3.  The  fretiuency  of  the  conduction  of  the  vapor  to  the  olfactory  cells 
(sniffing). 

[The  acuteness  of  the  sense  of  smell  is  greatly  improved  by  practice.  A  boy 
named  James  Mitchell,  who  was  deaf,  dumb,  and  blind,  used  his  sense  of  smell, 
like  a  dog,  to  distinguish  persons  and  things.] 


N,  olfactory  cells  (hu- 
man); «,  from  the 
frog;  E,  epithe- 
lium of  the  regio 
olfactorin. 


OLFACTORY    SENSATIONS.  .        873 

[As  in  the  case  of  sight  and  hearing,  it  has  been  sought  to  connect  the  quality  of  taste  and  smell 
with  the  kind  of  vibrating  stimulus.  Ramsay  showed  that  many  facts  pointed  to  the  dependence  of 
smell  upon  the  vibratory  motion  of  odorous  particles  ;  thus,  many  gases  and  vapors  of  low  specific 
gravity — i.  e.,  with  a  very  rapid  vibration  of  their  molecules — are  perfectly  odorless,  while  such  sub- 
stances as  the  alcohols  and  fatty  acids,  alike  in  chemical  and  physical  properties,  can  excite  generic 
smells,  the  higher  members  of  the  group  being  more  powerful  in  this  respect  than  the  lower  ones. 
Taking  the  elements  as  arranged  in  a  "  Natural  Classification  "  by  Mendelejeff,  Haycraft  has  shown 
that  elements  in  the  same  gi'oup  are  capable  of  producing  similar  or  related  tastes,  and  the  same 
seems  to  be  true  for  smell  {^Haycrafi).~\ 

We  can  smell  the  following  substances  in  the  following  proportions:  Bromine  7,-oioo'  sulphm-etted 
hydrogen  3^0^00  milhgramme  in  i  c.cm.  of  air  (  Valentin  ;  also  ^^^^^^^  of  a  milligramme  of  chlor- 
phenol,  and  ^gooooooo'  ^^^  ^  milligramme  of  mercaptan  {E.  Fischer  and  Penzoldt). 

Electrical  stimuli  give  rise  to  olfactory  sensations.  [Althaus  found  that  electrical  stimulation 
of  the  olfactory  mucous  membrane  gave  rise  to  the  sensation  of  the  smell  of  phosphorus,  and  Aron- 
sohn  found  that  he  smelt  on  making  the  current  when  the  cathode — and  on  breaking  the  current 
when  the  anode — was  in  the  nose. 

The  variations  are  referred  to  in  \  343.  If  the  two  nostrils  are  filled  with  different  odorous  sub- 
stances  there  is  no  mixture  of  the  odors,  but  we  smell  sometimes  the  one  and  sometimes  the  other 
(  Valentin').  [Some  substances  appear  to  affect  some  regions  of  the  olfactory  membrane,  while  others 
affect  other  parts.]  The  sense  of  smell,  however,  is  very  soon  blunted,  or  even  paralyzed.  [It  can 
be  blunted  or  fatigued  in  a  few  minutes ;  but  after  it  is  completely  fatigued  it  can  recover  in  a 
minute.]  Morphia,  when  mixed  with  a  httle  sugar  and  taken  as  snuff,  paralyzes  the  olfactory  appa- 
ratus, while  strychnin  makes  it  more  sensitive  [Lichtejtfels  and  Frohlicli). 

The  sensory  nerves  of  the  nasal  mucous  membrane  {\  347,  II)  [z.  e.,  those  supplied  from  the 
fifth  cranial  nerve]  are  stimulated  by  irritating  vapors,  and  may  even  cause  pain,  e.  g.,  ammonia  and 
acetic  acid.  In  a  very  diluted  condition  they  may  even  act  on  the  olfactory  nerves.  The  nose  is 
useful  as  a  sentinel  for  guarding  against  the  introduction  of  disagreeable  odors  and  foods.  The  sense 
of  .smell  is  aided  by  the  sense  of  taste,  and  conversely. 

[Flavor  depends  on  the  sense  of  smell,  and,  to  test  it,  use  substances,  solid  or  fluid,  wiih  an 
aroma  or  bouquet,  such  as  wine  or  roast  beef.] 

[Method  of  Testing. — In  doing  so,  avoid  the  use  of  pungent  substances  like  ammonia,  which 
excite  the  fifth  nerve.  Use  some  of  the  essential  volatile  oils,  such  as  cloves,  bergamot,  and  the 
fetid  gum  resins,  or  musk  and  camphor.  Electrical  stimuli  are  not  available.  Action  of  Drugs, 
I  343] 

Comparative. — In  the  lowest  vertebrata,  pits,  or  depressions  provided  with  an  olfactory  nerve, 
represent  the  simplest  olfactory  organ.  Amphioxus  and  the  cyclostomata  have  only  one  olfactory  pit ; 
all  other  vertebrates  have  two.  In  some  animals  (fi-og)  the  nose  communicates  with  the  mouth  by 
ducts.     The  olfactory  nerve  is  absent  in  the  whale. 

Historical. — Rufus  Ephesius  (97  a.d.)  described  the  passage  of  the  olfactory  nerve  through  the 
ethmoid  bone.  Rudius  (1600)  dissected  the  body  of  a  man  with  congenital  anosmia,  in  whom  the 
olfactory  nerves  were  absent.  Magendie  originally  supposed  that  the  nasal  branch  of  the  fifth  was 
the  nerve  of  smell,  a  view  successfully  combated  by  Eschricht. 


THE  SENSE  OF  TASTE. 


422.  STRUCTURE  OF  THE  GUSTATORY  ORGANS— Gusta- 
tory Region. —  There  is  considerable  difference  of  opinion  as  to  what  regions  of 
the  mouth  are  endowed  with  taste:  (i)  The  root  of  the  tongue  in  the  neighbor- 
hood of  the  circumvallate  papillae,  the  area  of  distribution  ot  the  glosso-pharyn- 
geal  nerve,  is  undoubtedly  endowed  with  taste  (§  351).  (2)  The  tip  and  margins 
of  the  tongue  are  gustatory,  but  there  are  very  considerable  variations.  (3)  The 
lateral  part  of  the  soft  palate  and  the  glosso-palatine  arch  are  endowed  with  taste 
from  the  glosso-pharyngeal  nerve.  (4)  It  is  uncertain  whether  the  hard  palate 
and  the  entrance  to  the  larynx  are  endowed  with  taste  (^Drielsma).  The  middle 
of  the  tongue  is  not  gustatory. 

[Tongue — Mucous  Membrane.— The  structure  of  the  tongue,  as  a  muscular  organ  covered 
witli  mucous  membrane,  has  already  been  described  (\  I5S).  The  dorsal  surface  of  the  tongue,  in 
front  of  the  blind  foramen,  is  beset  with  elevations  of  the  mucous  membrane,  which  extend  to  its  tip 
and  borders.  These  elevations,  or  papillae,  are  of  three  kinds;  filiform,  fungiform,  and  circum- 
vallate. They  consist  of  elevations  of  the  mucous  membrane,  visible  to  the  naked  eye,  and  cov- 
ered by  stratified  squamous  epithelium,  while  the  central  core  of  connective  tissue  contains  blood 
and  lymph  vessels  and  nerves.  The  filiform  papillae  occur  over  the  whole  tongue,  and  are  small- 
est and  most  numerous.     They  are   conical   eminences   covered   by  str.itiheJ   squamous   epithelium, 


P"ic..  604. 


Fig.  605. 


Epithelium 


Epithelium. 


Fig.  604. — Longitudinal  section  of  the  dorsum  of  the  human  tongue  i,  section  of  two  filiform  papillse,  with  secon- 
dary papillae  (2)  :  3,  double,  4,  single  process  of  epithelium  with  loose  epithelial  scales.    X  3°- 

Fig.  605. — Longitudinal  section  of  the  human  tongue,  i,  secondary  papillae  on  2,  the  fungiform  papillae;  3,  base  of  2; 
4,  small  filiform  papilla.     X  30. 


and  often  beset  with  secondary  papillae  (Fig.  604).  The  fungiform  papillae  occur  chiefly  over  the 
middle  and  front  part  of  the  tongue,  and  are  not  so  numerous  as  the  last.  They  are  club-shaped, 
with  a  narrow  base,  and  broad,  expanded,  rounded  head.  They  also  have  secondary  papillre.  They 
are  generally  brighter  red  than  the  others  (Fig.  605).  The  circumvallate  papillae,  8  to  12  in 
number,  diverge  from  the  foramen  ctecum  at  the  back  part  of  the  tongue  in  two  rows  in  the  form  of 
a  wide  V,  the  open  angle  of  the  V  being  directed  forward.  They  are  large,  with  a  broad,  expanded 
top,  and  are  lodged  in  a  depression  of  the  mucous  membrane,  being  surrounded  by  a  wall  of  mucous 

874 


STRUCTURE    OF   THE   ORGANS    OF    TASTE. 


875 


membrane,  and  separated  from  it  by  a  circular  trench,  into  the  base  of  which  gland  ducts  often  open. 
They  have  numerous  secondary  papillse,  and  in  them  are  taste  bulbs,  Fig.  606,  L] 

Taste  bulbs. — The  end  organs  of  the  gustatory  nerves  are  the  taste  bulbs  or  taste  buds  dis- 


I,  Transverse  section  of  a  circumvallate  papilla  ;  W,  the  papilla  ;  vi,  vi,  the  wall  in  section  ;  R,  R,  the  circular  slit 
or  fossa;  K,  K,  the  taste  bulbs  in  position;  N,  N,  the  nerves.  II,  Isolated  taste  bulb;  D,  supporting  or  pro- 
tective cells  ;  K,  under  end;  E,  free  end,  open,  with  the  projecting  apices  of  the  taste  cells.  Ill,  Isolated  pro- 
tective cell  {d)  with  a  taste  cell(^). 


Epithelium. 


covered  by  Schwalbe  and  Loven  (1867).  They  occur  on  the  lateral  surfaces  of  the  circumvallate 
papillae  (Fig.  606, 1),  and  upon  the  opposite  side  K,  of  the  fossa  or  capillary  slit,  R,  R,  which  sur- 
rounds the  central  eminence  or  papilla; 

they  occur   more  rarely  on  the  surface.  Fig.  607. 

They  also  occur  on  the  fungiform  papillae, 
in  the  papillae  of  the  soft  palate  and 
uvula  {A.  Hoffmanti),  on  the  under  sur- 
face of  the  epiglottis,  the  upper  part  of  the 
posterior  surface  of  the  epiglottis,  and  the 
inner  side  of  the  arytenoid  cartilages 
[Ve7'son,  Davis),  and  on  the  vocal  cords 
{Simanowsky).  Many  buds  or  bulbs  dis- 
appear in  old  age. 

[In  the  rabbit  and  some  other  animals, 
there  is  a  folded  laminated  organ  on  each 
side  of  the  posterior  part  of  the  tongue, 
called  the  papilla  foliata ;  the  folds  have 
on  each  side  of  them  numerous  taste  buds 
(Fig.  607).] 

Structure  of  the  taste  bulbs. — They 
are  81  «  high  and  t,t,  ji  thick,  barrel- 
shaped,  and  embedded  in  the  thick  strati- 
fied squamous  epithelium  of  the  tongue. 
Each  bulb  consists  of  a  series  of  lancet- 
shaped,  bent,  nucleated,  outer  support- 
ing or  protective  cells,  arranged  like 
the  staves  of  a  ban-el  (Fig.  606,  II,  D,  inso- 
lated  in  III,  «).  They  are  so  arranged  as  Vertical  section  of  two  septa  of  the  papilla  foliata  (rabbit).  X  80. 
to  leave  a  small  opening,  or  the  "  gUSta-  Each  septum,   /,  has  secondary  septa    ^':  /■,  taste   buds;    n. 

,,  ,^     ^    °'        1      r    1      1     11  medullated  nerve ;   rf,  seroiis  gland,  and  part  or  its  duct,  a;  itr, 

tory  pore,"  at  the  free  end  of  the  bulb.  muscular  fibres  of  the  tongue. 

Surrounded  by  these  cells,  and  lying  in 

the  axis  of  the  bud,  are  i  to  10  gustatory  cells  (IT,  E),  some  of  which  are  provided  with  a  delicate 
process  (III,  e)  at  their  free  ends,  while  their  lower  fixed  ends  send  out  basal  processes,  which  be- 
come continuous  with  the  terminations  of  the  nerves  of  taste,  which  have  become  non- medullated. 
After  section  of  the  glosso-pharyngeal,  the  taste  buds  degenerate,  while  the  protective  eel's  become 
changed  into  ordinary  epithelial  cells  within  four  months  {y.  Vintschgau  attd  IIdnigsckt?iied).     Very 


876  GUSTATORY    SENSATIONS. 

similar  structures  were  found  hy  l.eydis^  in  tlie  stein  of  fresh-water  fishes.     '\'\\c  f^lniKh  of  the  tongue 
and  their  secretory  fibres  from  llie  q\\\  (  r.uiial  nerve  are  referred  to  in  i/  I4I  [Drasc/i). 

423.  GUSTATORY  SENSATIONS.— Varieties.— There  are  >///- dif- 
ferent gustatory  qualities,  the  sensations  of  i.  Sweet;  2.  Bitter;  3.  Acid;  4. 
Saline.  Acid  and  saline  substances  at  the  same  time  also  stimulate  the  sensory 
nerves  of  the  tongue,  but  when  greatly  diluted,  they  only  excite  the  end  organs  of 
the  specific  nerves  of  taste.  Perhaps  there  are  special  nerve  fibres  for  each  different 
gustatory  quality  (v.  Vinischgaii). 

Conditions. — Sapid  substances,  in  order  that  they  may  be  tasted,  require  the 
following  conditions:  They  must  be  dissolved  in  the  fluid  of  the  mouth,  espe- 
cially substances  that  are  solid  or  gaseous.  The  intensity  of  the  gustatory  sensa- 
tion depends  on  :  I.  The  size  of  the  surfyce  acted  on.  Sensation  is  favored  by 
rubbing  in  the  substance  between  the  papill?c,  in  fact,  this  is  illustrated  in  the  rub- 
bing movements  of  the  tongue  during  mastication  (§  354).  2.  The  concentration 
of  the  sapid  substance  is  of  great  importance.  Valentin  found  that  the  following 
series  of  substances  ceased  to  be  tasted  in  the  order  here  stated,  as  they  were  gradu- 
ally diluted — syrup,  sugar,  common  salt,  aloes,  quinine,  sidphuric  acid.  Quinine 
can  be  diluted  20  times  more  than  common  salt  and  still  be  tasted  (^Camerer).  3. 
The  //;«^  which  elapses  between  the  application  of  the  sapid  substance  and  the  pro- 
duction of  the  sensation  varies  with  different  substances.  Saline  substances  are 
tasted  most  rapidly  (after  0.17  second,  according  to  v.  Vintschgaii),  then  sweet, 
acid  and  bitter  (quinine  after  0.258  second,  v.  Vintschgau).  This  even  occurs  with 
a  mixture  of  these  substances  {Schirmer).  The  last-named  substances  produce  the 
most  persistent  "  after-taste."  4.  The  delicacy  of  the  sense  of  taste  is  partly 
congenital,  but  it  can  be  greatly  improved  by  practice.  If  a  person  continues  to 
taste  the  same  sapid  substance,  or  a  nearly  related  one,  or  even  any  very  intensely 
sapid  substance,  tlie  gustatory  sense  is  soon  affected,  and  it  becomes  impossible  to 
give  a  correct  judgment  as  to  the  taste  of  the  sapid  body.  5.  Taste  is  greatly  aided 
by  the  sense  of  smell,  and  in  foct  we  often  confound  taste  with  smell ;  thus,  ether, 
chloroform,  musk,  and  assafoetida  only  affect  the  organ  of  smell.  [The  combined 
action  of  taste  and  smell  in  some  cases  gives  rise  to  flavor  (p.  873).]  The  eye 
even  may  aid  the  determination,  as  in  the  experiment  where  in  rapidly  tasting  red 
and  white  wine  one  after  the  other,  when  the  eyes  are  covered,  we  soon  become 
unable  to  distinguish  between  the  one  and  the  other.  6.  The  most  advantageous 
temperature  for  taste  is  between  10°  to  35°  C. ;  hot  and  cold  water  temporarily 
paralyze  taste. 

Ice  placed  on  the  tongue  suppresses,  sometimes  entirely,  the  whole  gustatory  apparatus;  cocain 
alone,  bitter  tastes,  and  water  containing  2  per  cent,  of  H._,S04,  excite  afterward  a  sweet  taste 
[Aducco  and  Jllosso). 

Electrical  Current. — The  constant  current,  when  applied  to  the  tongue,  excites,  both  during 
its  passage  and  when  it  is  opened  or  closed,  a  sensation  of  acidity  at  the  -j-  pole,  and  at  the  —  pole 
an  alkaline  taste,  or,  more  correctly,  a  harsh,  burning  sensation  [Sulzer,  1752).  This  is  not  due  to 
the  action  of  the  electrolytes  of  the  fluid  in  the  mouth,  for  even  when  the  tongue  is  moistened  with 
an  acid  fluid  the  alkaline  sensation  is  experienced  at  the  —  pole  (  Volla).  We  cannot,  however,  set 
aside  the  supposition  that  perhaps  electrolytes,  or  decomposition  products,  may  be  formed  in  the 
deeper  parts  and  excite  the  gustatory  tilnes.  Rapidly  interrupted  currents  do  not  excite  taste 
{Gn'inkagen).  v.  Vintschgau,  who  has  only  incomplete  taste  on  the  tip  of  tiie  tongue,  fmds  that 
when  the  tip  of  the  tongue  is  traversed  by  an  electrical  current,  there  is  never  a  gustatory  sensation, 
but  always  a  distinct  tactile  one.  In  experiments  on  Ilonigschmied,  who  is  possessed  of  normal 
taste  in  the  tip  of  thetongue,  there  was  often  a  metallic  or  acid  taste  at  the  +  pole  on  the  tip  of  the 
tongue,  while  at  the  —  pole  taste  was  often  absent,  and  when  it  was  present  it  was  almost  always 
alkaline,  and  acid  only  exceptionally.  After  interrupting  the  current  there  was  a  metallic  after- 
taste with  both  directions  of  the  current. 

[Testing  Taste. — Direct  the  pers-:on  to  put  out  his  tongue  and  close  his  eyes, 
and  after  drying  the  tongue  apply  the  sapid  substance  by  means  of  a  glass  rod  or 
a  small  brush.  Try  to  confine  the  stimulus  as  much  as  possible  to  one  place,  and 
after  each  experirnent  rinse  the  mouth  with  water.     A  wine-taster  chews  an  olive 


PATHOLOGICAL COMPARATIVE HISTORICAL.  877 

to  "clean  the  palate,"  as  he  says.  For  testing  bitter  {zsie.  use  a  solution  of  qui- 
nine or  quassia;  for  sweet,  sugar  [or  the  intensely  sweet  substance  '-'saccharine" 
obtained  from  coal  tar];  saline,  common  salt;  and  acid,  dilute  citric  or  acetic  acid. 
The  galvanic  current  may  also  be  used.] 

Pathological. — Diseases  of  the  tongue,  as  well  as  dryness  of  the  mouth  caused  by  interference  with 
the  salivary  secretion,  interfere  with  the  sense  of  taste.  Subjective  gustatory  impressions  are 
common  among  the  insane,  and  are  due  to  some  central  cause,  perhaps  to  irritation  of  the  centre  for 
taste  (^  378,  IV,  3).  After  poisoning  with  santonin,  a  bitter  taste  is  experienced,  while  after  the 
subcutaneous  injection  of  morphia,  there  is  a  bitter  and  acid  taste.  The  terms  hypergeusia,  hypo- 
geusia,  and  ageusia  are  applied  to  the  increase,  dimmution,  and  abolition  of  the  sense  of  taste. 
Many  tactile  impressions  on  the  tongue  are  frequently  confounded  with  gustatory  sensations,  e.g.,  the 
so-called  biting,  cooling,  prickling,  sandy,  mealy,  astringent,  and  harsh  tastes. 

Comparative. — About  1760  taste  bulbs  occur  on  the  circumvallate  papillae  of  the  ox.  The  term 
papilla  foliata  is  applied  to  a  large  folded  gustatory  organ  placed  laterally  on  the  side  of  the  tongue 
(Fig.  607),  especially  of  the  rabbit  [Rapf,  1832),  which  in  man  is  represented  by  analogous  organs, 
composed  of  longitudinal  folds,  lying  in  the  fimbriae  lingase  on  each  side  of  the  posterior  part  of  the 
tongue  {^Kraiise,  v.  Wyss).  Taste  bulbs  are  absent  in  reptiles  and  birds.  They  are  numerous  in  the 
gill  slits  of  the  tadpole  [F.  E.  Schultze),  while  the  tongue  of  the  frog  is  covered  with  epithelium 
resembling  gustatory  cells  {^Billroth,  Axel  Key^.  The  goblet-shaped  organs  in  the  skin  of  fishes 
and  tadpoles  have  a  structure  similar  to  the  taste  bulbs,  and  may  perhaps  have  the  same  function. 
There  are  taste  bulbs  in  the  mouth  of  the  carp  and  ray. 

Historical. — Bellini  regarded  the  papillee  as  the  organs  of  taste  (171 1).  Richerand,  Mayo,  and 
Fodera  thought  that  the  lingual  was  the  only  nerve  of  taste,  but  Magendie  proved  that,  after  it  was 
divided,  the  posterior  part  of  the  tongue  was  still  endowed  with  taste.  Panizza  (1834)  described  the 
glosso-pharyngeal  as  the  nerve  of  taste,  the  gustatory  as  the  nerve  of  touch,  and  the  hypoglossal  as  the 
motor  nerve  of  the  tongue. 


THE  SENSE  OF  TOUCH. 


424.  TERMINATIONS  OF  SENSORY  NERVES.— i.  The  touch  corpuscles  of 
\Vagner  and  Meissner  lie  in  the  papillae  of  the  cutis  vera  (^  283),  and  are  most  numerous 
in  the  palm  of  the  hand  and  the  sole  of  the  foot,  especially  in  the  fingers  and  toes,  there  being  alwut 
21  to  every  square  millimetre  of  skin,  or  loS  to  400  of  the  papilke  containing  bloodvessels.  They 
are  less  abundant  on  the  back  of  the  hand  and  foot,  mamma,  lips,  and  tii^  of  the  tongue,  rare  on  the 
glans  clitoridis,  and  occur  singly  and  .scattered  on  the  volar  side  of  the  forearm,  even  in  the  anthro- 
poid apes.  They  are  oval  or  elliptical  liodies,  40-200  //  long  [^i^  in.],  and  60-70  //  broad  [-^^j^  to 
j-^jf  in.],  and  are  covered  externally  by  layers  of  connective  tissue  arranged  transversely  in  layers,  and 
within  is  a  granular  mass  with  elongated  striped  nuclei  (Figs.  60S,  609,  e).  One  to  three  medullated 
nerve  fibres  pass  to  tlie  lower  end  of  each  corpuscle,  and  surround  it  in  a  spiral  manner  two  or  three 

Fig.  608. 


Fig.  609. 


Wagner's     touch    corpuscle     from    the 
palm,   treated  with   gold   chloride: 
n,   nerve   fibres ;    a,   a,   groups    ot 
d  C  glomeruli. 

Vertical  section  of  the  skin  of  the  palm  of  the  hand,  a,  blood  vessels  ;  l>, 
papilla  of  the  cutis  vera;  c,  capillary;  d,  nerve  fibre  passing  to  a 
touch  corpuscle  ;  /",  nerve  fibre  divided  transversely ;  e,  Wagner's 
touch  corpuscle ;  g;  cells  of  the  Malpighian  layer  of  the  skin. 

times;  the  fibres  then  lose  their  myelin,  and,  after  dividing  into  4  to  6  fibrils,  branch  within  the  cor- 
puscle. The  exact  mode  of  termination  of  the  fibrils  is  not  known.  Some  observers  suppose  that 
the  transverse  fibrillation  is  due  to  the  coils  or  windings  of  the  nerve  fibrils  ;  while  according  to  others, 
the  inner  part  consists  of  numerous  flattened  cells  lying  one  over  the  other,  between  which  the  pale 
terminal  fibres  end  either  in  swellings  or  with  disk-like  expansions,  such  as  occur  in  Merkel's 
corpuscles. 

[These  do  not  contain  a  soft  core  such  as  exists  in  Pacini's  corpuscles.  The  corpuscles  appear  to 
consist  of  connective  tissue  with  imperfect  septa  passing  into  the  interior  from  the  fibrous  capsule. 
After  the  nerve  fibre  enters  it  loses  its  myelin,  and  then  branches,  while  the  branches  anastomose 

878 


PACINI  S    CORPUSCLES. 


879 


and  follow  a  spiral  course  within  the  corpuscle,  finally  to  terminate  in  slight  enlargements.  According 
to  Thin,  there  are  simple  and  compound  corpuscles,  depending  on  the  number  of  nerve  fibres  enter- 
ing them.] 

Kollmann  describes  three  special  tactile  areas  in  the  hand  :  (i)  The  tips  of  the  fingers  with  24 
touch  corpuscles  in  a  length  of  10  mm. ;  (2)  the  three  eminences  lying  on  the  palm  behind  the  slits 
between  the  fingers,  with  5.4-2.7  touch  corpuscles  in  the  same  length;  and  (3)  the  ball  of  the  thumb 
and  little  finger  with  3.1-3.5  touch  corpuscles.  The  first  two  areas  also  contain  many  of  the  cor- 
puscles of  Vater  or  Pacini,  while  in  the  latter  these  corpuscles  are  fewer  and  scattered.  In  the  other 
parts  of  the  hand  the  nervous  end  organs  are  much  less  developed. 

2.  Vater's  (1741)  or  Pacini's  corpuscles  are  oval  bodies  (Fig.  610),  1-2  mm.  long,  lying  in 
the  subcutaneous  tissue  on  the  nerves  of  the  fingers  and  toes  (600-1400),  in  the  neighborhood  of 


Fig.  610. 


Fig.  611. 


End  bulb  from  human  conjunctiva,  a,  nucleated 
capsule ;  b,  core ;  c,  fibre  entering  and 
branching,  terminating  in  core  at  d. 

Fig.  612. 


Vater's  or  Pacini's  corpuscle,  a,  stalk  ; 
b,  nerve  fibre  entering  it ;  c,  d,  con- 
nective-tissue envelope;  e,  axis  cylin- 
der, with  its  end  divided  aty. 


Tactile  corpuscles,  clitoris  of  rabbit. 


joints  and  muscles,  the  sympathetic  abdominal  plexuses,  near  the  aorta  and  coccygeal  gland  on  the 
dorsum  of  the  penis  and  clitoris,  and  in  the  mesocolon  [and  mesentery]  of  the  cat.  [They  also 
occur  in  the  course  of  the  intercostal  and  periosteal  nerves,  and  Stirling  has  seen  them  in  the  capsule 
of  lymphatic  glands.  They  are  attached  to  the  nerves  of  the  hand  and  feet,  and  are  so  large  as  to 
be  visible  to  the  naked  eye,  both  in  these  regions  and  between  the  layers  of  the  mesentery  of  the  cat. 
They  are  whitish  or  somewhat  transparent,  with  a  white  line  in  the  centre  (cat) ;  in  man  they  are  -^^ 
to  Y^Q  inch  long,  and  J^  to  Jg-  inch  broad,  and  are  attached  by  a  stalk  or  pedicle  (Fig.  610,  a)  to  the 
nerve.]  They  consist  of  numerous  nucleated  connective- tissue  capsules  or  lamellae  lined  by  endo- 
thelium, separated  firom  each  other  by  fluid,  and  lying  one  within  the  other  like  the  coats  of  an  onion, 
while  in  the  axis 'is  a  central  core.     A  meduUated  nerve  fibre  passes  to  eachj  where  its  sheath  of 


880 


TERMINATIONS   OF    SENSORY    NERVES. 


Schwann  unites  with  the  capsule.  It  loses  its  myelin,  and  passes  into  the  interior  as  an  axial  cylinder 
(Fig.  6io  f),  where  it  either  ends  in  a  small  knob  or  may  divide  dichotomously  (Fig.  6io,/),  each 
branch  terminating  in  a  small  pear-shaped  enlargement.  [Each  large  corpuscle  is  covered  by  40-50 
lamellae,  or  tunics,  which  are  thinner  and  closer  to  each  other  (?"ig.  610,  d)  internally  than  in  the 
outer  part,  where  they  are  thicker  and  wider  apart.  The  lamelUv;  are  like  the  laminx  in  the  1am- 
ellated  sheath  of  a  nerve,  and  are  composed  of  an  elastic  basis  mixed  with  white  libres  of  connective 
tissue,  while  the  inner  surface  of  each  lamella  is  lined  by  a  single  continuous  layer  of  endothelium 
continuous  with  that  of  the  perineurium.  It  is  easily  stained  with  silver  nitrate.  The  efferent  nerve 
fibre  is  covered  with  a  thick  sheath  of  lamellated  connective  tissue  (sheath  of  Henle),  which  becomes 
blended  with  the  outer  lamella.'  of  the  corpuscle.  The  medullatcd  nerve  is  sometimes  accompanied 
by  a  blood  vessel,  and  pierces  the  various  tunics,  retaining  its  myelin  until  it  reaches  the  core,  where 
it  terminates  as  already  described.] 

3.  Krause's  end  bulbs  very  probably  occur  as  a  regular  mode  of  nerve  termination  in  the  cutis 
and  mucous  membranes  of  all' mammals  (Fig.  61 1).  They  are  elongated,  oval  or  round  bodies, 
0.075  'o  °'4  "^"^-  'o"g>  ^"'1  \\7^\^  been  found  in  the  deeper  layers  of  the  conjunctiva  bulbi,  floor  of 
the  mouth,  margins  of  the  lips,  nasal  mucous  membrane,  epiglottis,  fungiform  and  circumvallate 
papilhi;,  glans  penis  and  clitoris,  volar  surface  of  the  toes  of  the  guinea  pig,  ear  and  body  of  the 
mouse,  and  in  the  wing  of  the  bat.  [In  the  calf,  the  "  cylindrical  end  bulbs  "  are  oval,  with  a 
nerve  fibre  terminating  within  them.  The  .sheath  of  Henle  becomes  continuous  with  the  nucleated 
capsule,  while  the  axial  cylinder,  devoid  of  its  myelin,  is  continued  into  the  soft  core.  In  man  the 
end  bulbs  are  "  spheroidal,"  and  consist  of  a  nucleated  connective-tissue  capsule  continuous  with 
Henles  sheath  of  the  nerve,  and  enclosing  many  cells,  among  which  the  axis  cylinder  which  enters 


Fic.  614. 


Fir,.  613. 


0^^^';m^^.^ 


Tactile  corpuscles  from  the  duck's  tongue.  A, 
composed  of  three  cells  with  two  interposed 
disks.with  axis  cylinder,  «,  passing  into  them. 
B,  two  tactile  cells  and  one  disk. 


Bouchon  epidermique  from  the  groin  of  a  guinea-pig,  after  the 
action  of  gold  chloride,  k,  nerve  fibre;  a.  tactile  cells; 
»•/,  tactile  disks  ;  c,  epithelial  cells. 


the  bulb  branches  and  terminates.]  The  spheroidal  end  bulbs  occur  in  man,  in  the  nasal  mucous 
membrane,  conjunctiva,  mouth,  epiglottis,  and  the  mucous  folds  of  the  rectum.  According  to 
Waldeyer  and  Longworth,  the  nerve  fibrils  terminate  in  the  cells  within  the  capsule.  These  cells 
are  said  to  be  comparable  to  Merkcl's  tactile  cells  ( IVaUeyer). 

The  genital  corpuscles  of  Krause,  which  occur  in  the  skin  and  mucous  membrane  of  the  glans 
penis,  clitoris,  and  vagina,  appe.ir  to  be  end  bulbs  more  or  less  fused  together  (Fig.  612). 

The  articulation  nerve  corpuscles  occur  in  the  synovial  mucous  membrane  of  the  joints  of  the 
fingers.  They  are  larger  than  the  end  bulbs,  and  have  numerous  oval  nuclei  externally,  while  one  to 
four  nerve  fibres  enter  them. 

4.  Tactile  or  touchcorpuscles  of  Merkel,  sometimes  also  called  the  corpuscles  of  Grandry, 
occur  in  the  beak  and  tongue  of  the  duck  and  goose,  in  the  epidermis  of  man  and  mammals,  and  in 
the  outer  root  sheath  of  tactile  hairs  or  feelers  (Fig.  613).  They  are  small  bodies  composed  of  a 
capsule  enclosing  two,  three,  or  more  large,  granular,  somewhat  flattened  nucleated  and  nucleolated 
cells,  piled  one  on  the  other  in  a  vertical  row  like  a  row  of  cheeses.  Each  corpuscle  receives  at  one 
side  a  medullated  nerve  fibre  which  loses  its  myelin,  and  branches,  to  terminate,  according  to  some 
observers  (Merkel),  in  the  cells  themselves,  and  according  to  others  [Ranvier,  Izqtiieriio,  Hesse)  in 
the  protoplasmic  transparent  substance  or  disk  lying  between  the  cells.  [This  intercellular  disk  is 
the  "  disk  tactil  "  of  Ranvier,  or  the  "  Tastplatte  "  of  Hesse.]  When  there  is  a  great  aggregation 
of  these  cells,  large  structures  are  formed  which  appear  to  form  a  kind  of  transition  between  these 
and  touch  corpuscles.  [According  to  Klein,  the  terminal  fibrils  end  neither  in  the  touch  cells  nor 
tactile  disk,  but  in  minute  swellings  in  the  interstitial  substance  between  the  touch  cells,  in  a  manner 
very  similar  to  that  occurring  in  the  end  bulbs.] 


SENSORY   AND    TACTILE    SENSATIONS.  881 

[According  to  Merkel,  tactile  cells,  either  isolated  or  in  groups,  but  in  the  latter  case  never  forming 
an  independent  end  organ,  occur  in  the  deeper  layers  of  the  epidermis  of  man  and  mammals  and 
also  in  the  papillse.  They  consist  of  round  or  ilask-shaped  cells,  with  the  lower  pointed  neck  of  the 
flask  continuous  with  the  axis-cylinder  of  a  nerve  fibre.  They  are  regarded  by  Merkel  as  the  simplest 
form  of  a  tactile  end  organ,  but  their  existence  is  doubted  by  some  observers.] 

Among  animals  there  are  many  other  forms  of  sensory  end  organs.  [Herbst's  corpuscles 
occur  in  the  mucous  membrane  of  the  tongue  of  the  duck,  and  resemble  small  Vater's  corpuscles,  but 
their  lamellae  are  thinner  and  nearer  each  other,  while  the  axis  cylinder  within  the  central  core  is 
bordered  on  each  side  by  a  row  of  nuclei.]  In  the  nose  of  the  mole  there  is  a  peculiar  end  organ 
[Einier),  while  there  are  "  end  capsules  "  in  the  penis  of  the  hedgehog  and  the  tongue  of  the  elephant, 
and  "  nerve  rings"  in  the  ears  of  the  mouse. 

5.  [Other  Modes  of  Ending  of  Sensory  Nerves. — Some  sensory  nerves  terminate  not  by 
means  of  special  end  organs,  but  their  axis  cylinder  splits  up  into  fibrils  to  form  a  nervous  network, 
from  which  fine  fibrils  are  given  off  to  terminate  in  the  tissue  in  which  the  nerve  ends.  These  fibrils, 
as  in  the  cornea  (|  384),  terminate  by  means  of  free  ends  between  the  epithelium  on  the  anterior 
surface  of  the  cornea,  and  some  observers  state  that  the  free  ends  are  provided  with  small  enlarge- 
ments ["  boidons  terminals''')  (Fig.  614,12).  These  enlargements  or  "tactile  cells"  occur  in  the 
groin  of  the  guinea-pig  and  mole.  A  similar  mode  of  termination  occurs  between  the  cells  of  the 
epidermis  in  man  and  mammals  (Fig.  293).] 

6.  Tendons,  especially  at  their  junction  with  muscles,  have  special  end  organs  [Sachs,  Rollett, 
Golgi),  which  assume  various  forms;  it  may  be  a  network  of  primitive  nerve  fibrils,  or  flattened  end 
flakes  or  plates  in  the  sterno-radial  muscle  of  the  frog,  or  elongated  oval  end  bulbs,  not  unlike  the 
end  bulbs  of  the  conjunctiva,  or  small  simple  Pacinian  corpuscles. 

Prus  found  ganglion  cells  more  frequently  in  the  subcutaneous  tissue  than  in  the  corium,  and  they 
appeared  to  have  some  relation  to  the  blood  vessels  and  sweat  glands. 

425.  SENSORY  AND  TACTILE  SENSATIONS.— In  the  sensory 
nerve  trunks  there  are  two  functionally  different  kinds  of  nerve  fibres  :  (i)  Those 
which  administer  to  /azVz/z^/ impressions,  which  are  sensory  nerves  in  the  narrower 
sense  of  the  word  ;  and  (2)  those  which  administer  to  tactile  impressions  and  may 
therefore  be  called  tactile  nerves.  The  sensations  of  temperature  and  pressure 
are  also  reckoned  as  belonging  to  the  tactile  group.  It  is  extremely  probable  that 
the  sensory  and  tactile  nerves  have  different  end  organs  and  fibres,  and  that  they 
have  also  special  perceptive  nerve  centres  in  the  brain,  although  this  is  not  definitely 
proved.     This  view,  however,  is  supported  by  the  following  facts  : — 

I.  That  sensory  and  tactile  impressions  cannot  be  discharged  at  the  same  time 
from  all  the  parts  which  are  endowed  with  sensibility.  Tactile  sensations,  mclud- 
ing  pressure  and  temperature,  are  only  discharged  from  the  coverings  of  the  skin, 
the  mouth,  the  entrance  to  and  floor  of  the  nose,  the  pharynx,  the  lower  end  of  the 
rectum  and  genito-urinary  orifices;  feeble  indistinct  sensations  of  temperature  are 
felt  in  the  oesophagus.  Tactile  sensations  are  absent  from  all  internal  viscera,  as 
has  been  proved  in  man  in  cases  of  gastric,  intestinal,  and  urinary  fistulae.  Pain 
alone  can  be  discharged  from  these  organs.  2.  The  conduction  channels  of  the 
tactile  and  sensory  nerves  lie  in  different  parts  of  the  spinal  cord  (§  364,  i  and  5). 
This  renders  probable  the  assumption  that  their  central  and  peripheral  ends  also 
are  different.  3.  Very  probably  the  reflex  acts  discharged  by  both  kinds  of  nerve 
fibres — the  tactile  and  pathic — are  controlled,  or  even  inhibited,  by  special  central 
nerve  organs  (§  361 — ?).  4.  Under  pathological  conditions,  and  under  the  action 
of  narcotics,  the  one  sensation   may  be  suppressed  while  the  other  is  retained 

(§  364,  5)-  .         . 

Sensory  Stimuli. — In  order  to  discharge  a  painful  impression  from  sensory 
nerves,  relatively  strong  stimuli  are  required.  The  stimuli  may  be  mechanical, 
chemical,  electrical,  thermal,  and  somatic,  the  last  being  due  to  inflammation  or 
anomalies  of  nutrition  and  the  like. 

Peripheral  Reference  of  the  Sensations. — These  nerves  are  excitable 
along  their  entire  course,  and  so  is  their  central  termination,  so  that  pain  may  be 
produced  by  stimulating  them  in  any  part  of  their  course,  but  this  pain,  according 
to  the  "  law  of  peripheral  perception,"  is  always  referred  to  the  periphery. 

The  tactile  nerves  can  only  discharge  a  tactile  impression  or  sensation  of  contact 
when  moderately  strong  mechanical  pressure  is  exerted,  while  thermal  stimuli  are 
56 


882  THE    SENSE    OF    LOCALITY. 

reciiiired  to  produce  a  temperature  sensation,  and  in  both  cases,  the  results  are 
obtained  only  when  the  appropriate  stimuli  are  ajiplied  to  the  end  organs.  If 
pressure  or  cold  be  applied  to  the  course  of  a  nerve  trunk,  e.g.,  to  the  ulna  at  the 
inner  surface  of  tlie  elbow  joint,  we  are  conscious  of  painful  sensations,  but  never 
of  those  of  temperature,  referable  to  the  peripheral  terminations  of  the  nerves  in 
the  inner  fingers.  All  strong  stimuli  disturb  normal  tactile  sensations  by  over- 
stimulation, and  hence  cause  pain. 

The  law  of  the  specific  energy  of  nerves  leads  us  to  assume  that  the  cutaneous 
nerves  contain  different  kinds  of  nerve  fibres  with  different  kinds  of  end  organs, 
which  subserve  different  kinds  of  impressions,  e.g.,  pressure,  temperature,  and  pain. 
Blix  and  Goldscheider  have  found  such  differences.  Electrical  stimulation  causes 
different  sensations  according  to  the  part  of  the  skin  where  it  is  applied  ;  at  one 
spot,  pain  only  is  produced,  at  another  a  sensation  of  cold,  at  a  third  a  sensation 
of  heat,  and  at  a  fourth,  a  sensation  of  pressure.  At  every  temperature^  point  or 
spot,  there  is  insensibility  for  pain  or  pressure.  The  "pressure  points"  or 
pressure  spots  lie  much  closer  together,  and  are  more  numerous  than  the  tempera- 
ture points.  There  are  special  "  pain  spots  "  and  even  "  tickling  spots."  These 
spots  are  arranged  in  a  linear  chain,  which  usually  radiates  from  the  hair  follicles. 
The  "  tickling  spots  "  coincide  with  the  pressure  and  pain  spots.  The  feeling  of 
tickling  corresponds  to  the  feeblest  stimulation  of  a  nerve  fibre,  and  pain  to  the 
strongest.  The  pain  spots  can  be  isolated  by  means  of  a  needle,  or  electrically, 
especially  in  the  cutaneous  furrows,  in  which  the  pressure  sense  is  absent. 

Goldscheider  removed  from  his  own  body  small  pieces  of  skin,  in  which  he  had  previously  ascer- 
tained the  presence  of  these  "  spots,"  and  then  investigated  the  excised  skin  microscopically.  At 
each  such  spot  he  found  a  rich  supj^Iy  of  nerves  ;  at  the  pressure  sjiots,  there  were  no  touch  corpuscles. 
[By  means  of  the  skin,  impressions  are  supplied  also  to  the  brain,  whereby  we  become  conscious 
of  the  amount  and  direction  of  a  body  moved  in  contact  with  the  skin.  Indeed,  the  discriminative 
sensibility  is  more  acute  for  motion  than  for  touch  ;  but  the  liability  to  error  in  judging  of  the  distance 
and  direction  is  great  [HuH).'] 

[Very  complex  sensations  are  obtained  by  means  of  the  combined  action  of  the  skin  and  muscles, 
£.  o-.,  those   kn^wn  as  "  feelings  of  double   contact."     These  sensations  are  of  the  greatest  ad- 
vantage in  acquiring  the  use  of  instrumenls  and  tools.      If  we  touch  an  object  with  a  rod,  we  seem  to 
feel  the  object  at  the  point  of  the  tod,  and  not  in    the  hand  where  the  cuta- 
FlG.  615.  neous  nerves  are  actually  stimulated.     With  a  walking  stick,  we  feel  the  ground 

at  the  end  of  the  stick.  Touch  the  tips  of  the  hair,  or  a  tooth,  and  the  sensa- 
tion is  referred  to  the  tips  of  the  hair  in  the  one  case,  and  the  crown  of  the 
tooth  in  the  otherJ(Zaa'(?).] 

426.  SENSE  OF  LOCALITY.— We  are  not  only  able 
to  distinguish  differences  of  pressure  or  temperature  by  our  sensory 
nerves,  but  we  are  able  to  distinguish  the  part  which  has  been 
touched.  This  capacity  is  spoken  of  as  the  sense  of  space  or 
locality. 


Methods  of  Testing. —  i.  Place  the  two  blunted  points  of  a  pair  of  com- 
passes (Fig.  615)  upon  the  part  of  the  skin  to  be  investigated,  and  determine 
the  smallest  distance  at  which  the  two  points  are  felt  only  as  one  impression. 
Sieveking's  aesthesiometer  may  be  used  instead  (Fig.  616) ;  one  of  the  points 
is  movable  along  a  gi-aduated  rod,  while  the  other  is  fixed.  2.  The  distance  be- 
tween the  points  of  the  instrument  being  kept  the  same,  touch  several  part*  of 
the  skin,  and  ask  if  the  person  feels  the  impression  of  the  points  coming  nearer  to 
^sthesiometer.  or  going  wider  apart.  3.  Touch  apartol  the  skin  with  a  blunt  instrument,  and 
observe  if  the  point  touched  is  correctly  indicated  by  the  patient.  4.  Separate 
the  points  of  two  pairs  of  compasses  unequally,  and  place  their  points  upon  difterent  parts  of  the  skin, 
and  ask  the  person  to  state  when  the  points  of  both  appear  to  be  equally  far  apart.  A  distance  of  4 
lines  on  the  forehead  appears  to  be  equal  to  a  distance  of  2.4  lines  on  the  upper  lip.  This  is  Fech- 
ner's  "methods  of  equivalents." 

The  following  results  have  been  obtained.     The  sense  of  locality  of  a  part  of  the 
skin  is  more  actite  under  the  following  conditions  : — 

I.  The  greater  the  number  of  tactile  nerves'm  the  corresponding  part  of  the  skin. 


MODIFYING   CONDITIONS. 


883 


2.  The  greater  the  mobility  of  the  fart,  ^o  that  it  increases  in  the  extremities 
toward  the  fingers  and  toes.  The  sense  of  locality  is  always  very  acute  in  parts  of 
the  body  that  are  very  rapidly  moved  {Vierordt). 

3.  The  sensibility  of  the  limbs  is  finer  in  the  transverse  axis  than  in  the  long 
axis  of  the  limb,  to  the  extent  of  yi  on  the  flexor  surface  of  the  upper  limb,  and 
i^  on  the  extensor  surface. 

4.  The  mode  of  application  of  the  points  of  the  sesthesiometer  :  (d)  According 
as  they  are  applied  one  after  the  other,  instead  of  simultaneously,  or  as  they  are 
considerably  warmer  or  colder  than  the  skin  {^Klug),  a  person  may  distinguish  a 
less  distance  between  the  points.  (^F)  If  we  begin  with  the  points  wide  apart  and 
approximate  them,  then  we  can  distinguish  a  less  distance  than  when  we  proceed 
from  imperceptible  distances  to  larger  ones,  {c)  If  the  one  point  is  warm  and  the 
other  cold,  on  exceeding  the  next  distance  we  feel  two  impressions,  but  we  cannot 
rightly  judge  of  their  relative  positions  {CzertJiak). 

5.  Exercise  greatly  improves  the  sense  of  locality;  hence  the  extraordinary 
acuteness  of  this  sense  in  the  blind,  and  the  improvement  always  occurs  on  both 
sides  of  the  body  {Volkmann). 

[Fr.  Galton  finds  that  the  reputed  increased  acuteness  of  the  other  senses  in  the  case  of  the  blind 
is  not  so  gi-eat  as  is  generally  alleged.     He  tested  a  large  number  of  boys  at  an  educational  blind 

Fig.  616. 


^sthesiometer  of  Sieveking. 


asylum,  with  the  result  that  the  performances  of  the  blind  boys  were  by  no  means  superior  to  those 
of  other  boys.  He  points  out,  however,  that  "  the  guidance  of  the  blind  depends  mainly  on  the 
multitude  of  collateral  indications,  to  which  they  give  much  heed,  and  not  in  their  superiority  in  any 
of  them."] 

6.  Moistening  the  skin  with  indifferent  fluids  increases  the  acuteness.  If,  how- 
ever, the  skin  between  two  points,  which  are  still  felt  as  two  distinct  objects,  be 
slightly  tickled,  or  be  traversed  by  an  imperceptible  electrical  current,  the  im- 
pressions become  fused  {Suslowd).  The  sense  of  locality  is  rendered  more  acute 
at  the  cathode  when  a  constant  current  is  used  {Suslowd),  and  when  the  skin  is 
congested  by  stimulation  {Klinkenberg),  and  also  by  slight  stretching  of  the  skin 
iSchney)  ;  further,  by  baths  of  carbonic  acid  {v.  Basch  and  v.  Dietl),  or  warm 
common  salt,  and  temporarily  by  the  use  of  caffein  i^Rumpf). 

7.  Ancemia,  produced  by  elevating  the  limbs,  or  venous  hypercemia  (by  compress- 
ing the  veins),  blunts  the  sense,  and  so  does  too  frequent  testing  of  the  sense  of 
locality,  by  producing  fatigue.  The  sense  is  also  blunted  by  cold  applied  to  the 
skin,  the  influence  of  the  anode,  strong  stretching  of  the  skin,  as  over  the  abdomen 
during  pregnancy,  previous  exertions  of  the  muscles  under  the  part  of  the  skin 
tested,  and  some  poisons,  e.  g.,  atropin,  daturin,  morphin,  strychnin,  alcohol, 
potassium  bromide,  cannabin,  and  chloral  hydrate. 


884 


.ESTHESIOMETRY. 


Smallest  Appreciable  Distartce. —  J'hc  following  statement  gives  the  smallest 

distance,  in  millnneires,  at  which  two  points  of  a  pair  of  compasses  can  still  be 
distinguished  as  double  by  an  adult.  The  corresponding  numbers  for  a  boy  twelve 
years  of  age  are  given  within  brackets. 


Millimetres. 
I.I  [I.I] 


.3[..7j 


Tip  of  tongue 

Third  phalanx  of  finger,  volar  sur 

face, 

Red  part  of  the  lip, 4.5  [3.9 

Second    phalanx   of    finger,  volar 

surface, 4.  -4.5  [3.9] 

First  phalanx  of  finger,  volar  sur- 
face,      5.  -5.5 

Third    phalanx   of    finger,  dorsal 

surface, 6.8  [4.5] 

Tip  of  nose, 6.8  [4.5] 

Head  of  metacarpal  bone,  volar,  5.  -6.8  [4.5] 

liall  of  thumb, 6.5-7. 

Ball  of  little  finger, 5-5-6. 

Centre  of  palm, 8.  -9. 

Dorsum  and  side  of  tongue,  white 

of  the   lips,   metacarpal    part  of 

the  thumb, 

Tiiird   phalanx   of  the    great  toe, 

plantar  surface, 

Second    phalanx   of    the   fingers, 

dorsal  surface. 

Back,  ...  .... 


[6.8] 
[6.8] 


[9-  ] 
[9-  ] 


Millimetres. 

Eyelid, 11.3  [  9.  ] 

Centre  of  hard  palate, 13-5  ["-3] 

Lower  third   of  the  forearm,  volar 

surface, 15. 

In  front  of  the  zygoma, 15.8  [11.3' 

Plantar  surface  of  the  great  toe,  .    .  1 5.8   "  9. 

Inner  surface  of  the  lip, 20.3     13.5 

I5ehind  the  zygoma, 22.6  f  15. 8' 

Porehead, 22.6  [18. 

Occiput,      27.1  [22.6 

Back  of  the  hand 31.6    22.6 


•  33-8  [22.6] 
'      "31.6- 


22.6' 


Under  the  chin, 33.8 

Vertex 

Knee 36.1 

Sacrum,  gluteal  region, 44.6  |  33.8' 

Forearm  and  leg, 45.1  [33.8" 

Neck, 54.1  [36.1" 

Back,  at    the    fifth  dorsal   vertebra, 

lower  dorsal  and  lumbar  region,  54. 1 

Middle  of  the  neck, 67.7 

Upper  arm,  thigh,  and  centre  of  the 

back, 67.7  [31.6-40.6] 


Illusions  of  the  sense  of  locality  occur  very  frequently;  the  most  marked  are  :  (i)  A  uniform 
movement  over  a  cutaneous  surface  apj^iears  to  be  quicker  in  those  places  which  have  the  finest  sense 
of  locality.  (2)  If  we  merely  touch  the  skin  with  the  two  points  of  an  a^sthesiometer,  then  they  feel 
as  if  they  were  wider  apart  than  when  the  two  points  are  moved  along  the  skin  [Fcchner).  (3)  A 
sphere,  when  touched  with  short  rods,  feels  larger  than  when  long  rods  are  used  (  Tourlual).  (4) 
When  the  fingers  of  one  hand  are  crossed,  a  small  pebble  or  sphere  placed  between  them  feels  double 
(Aristotle's  experiment).  [When  a  pebble  is  rolled  between  the  crossed  index  and  middle 
finger  (Fig.  617,  B),  it  feels  as  if  two  balls  were  present,  but  with  the  fingers  uncrossed  single  ] 

(5)  When  i)ieces  of  skin  are  transplanted,  e.  g., 
Fig.  617.  from  the  forehead,  lo  form  a  nose,  the  person 

operated  on  feels,  often  for  a  long   time,  the 
new  nasal  jiart  as  if  it  were  his  forehead. 

Theoretical. — Numerous  experiments  were 
made  by  E.  II.  Weber,  Lotze,  Meissner,  Czer- 
mak,  and  others,  to  explain  the  phenomena  of 
the  sense  of  space.  Weber's  theory  goes 
upon  the  assumption,  that  one  and  the  same 
nerve  fibre  proceeding  from  the  brain  to  the 
skin  can  only  take  up  one  kind  of  impression, 
and  administer  thereto,  lie  called  the  part  of 
the  skin  to  which  each  single  nerve  fibre  is 
distributed  a  "circle  of  sensation."  When 
two  stimuli  act  simultaneously  upon  the  tactile 
end  organ,  then  a  double  sensation  is  felt,  when 
one  or  more  circles  of  sensation  lie  between 
g  the  tsvo  points  stmiulated.     This  explanation, 

Aristotle's  Experiment.  *  based  upon  anatomical  considerations,  does  not 

explain  how  it  is  that,  with  practice,  the  circles 
of  sensation  become  smaller,  and  also  how  it  is  that  only  one  sensation  occurs,  when  both  points  of 
the  instruments  are  so  applied  that  both  points,  although  further  apart  than  the  diameter  of  a  circle 
of  sensation,  at  one  time  lie  upon  two  adjoining  circles,  at  another  between  two  others  with  another 
circle  intercalated  between  them. 

Wundt's  Theory. —  In  accordance  wnth  the  conclusions  of  Lotze,  Wundt  proceeds  from  a 
psycho-physiological  basis,  that  every  part  of  the  skin  with  tactile  sensibility  always  conveys  to  the 
brain  the  (ocaiiiy  of  the  sensation.     Every  cutaneous  area,  therefore,  gives  to  the  tactile  sensation  a 


THE    PRESSURE    SENSE.  885 

"local  color  ^^  or  quality,  which  is  spoken  of  as  the  local  sign.  He  assumes  that  this,  local  color 
diminishes  from  point  to  point  of  the  skin.  This  gradation  is  very  sudden  in  those  parts  of  the  skin 
where  the  sense  of  space  is  very  acute,  but  occurs  very  gradually  where  the  sense  of  space  is  more 
obtuse.  Separate  impressions  unite  into  a  common  one,  as  soon  as  the  gradation  of  the  local  color 
becomes  imperceptible.  By  practice  and  attention  differences  of  sensation  are  experienced,  which 
ordinarily  are  not  observed,  so  that  he  explains  the  diminution  of  the  circles  of  sensation  by  practice. 
The  circle  of  sensation  is  an  area  of  the  skin,  within  which  the  local  color  of  the  sensation  changes 
so  little  that  two  separate  impressions  fuse  into  ojie. 

427.  PRESSURE  SENSE. — By  the  sense  of  pressure  we  obtain  a  knowl- 
edge of  the  amount  of  weight  or  pressure  which  is  being  exercised  at  the  time  on 
the  different  parts  of  the  skin. 

A  specific  end  apparatus  arranged  in  a  punc-  y\g.  618. 

tated  manner  is  connected  with  the  pressure  sense 

(Fig.   618).     These   points  or  spots  are   called      .•...*.;••;•         :'••*.•;*••'■.*.'        ;".v :•••;.. 
"pressure  spots"  or  "  pressure  points"       '...  y'.'-.^:       ':•'•.;.••:•.*•       '-v^i:-^ 
i^Blix),  and  are  endowed  with  varying  degrees  of     "•-■.■.••  .::••.".        .■•■•"*•:•'•/.*        *""■•'■ 
sensibility ;  at  some  places  (back,  thigh)  they  are  "'  *    ' :    " 

distinguished  by  a  markedly  pronounced  after-  "'  . ,  f     ,  ,         '  .  , 

.  rr>i  ,         r    ^^  Pressure  spots,     a,  middle  of  the  sole  of  the 

sensation.  Ihe  arrangement  of  the  pressure  foot;  ^,  skin  of  zygoma ;  t,  skin  of  the  back. 
spots  follows  the  type   of  the   arrangement   of 

the  temperature  spots.  The  pressure  spots  have  usually  another  direction  than  that 
of  hot  and  cold  spots ;  as  a  rule,  they  are  denser.  The  minimal  distance  at  which 
two  pressure  spots,  when  simultaneously  stimulated,  are  felt  as  double,  is— on  the 
back,  4  to  6  mm.;  breast,  0.8;  abdomen,  1.5  to  2;  cheek,  0.4  to  0.6;  upper 
arm,  0.6  to  0.8  ;  forearm,  0.5  ;  back  of  the  hand,  0.3  to  0.6;  palm,  o.i  to  0.5  ; 
leg,  0.8  to  2  ;  back  of  foot,  0.8  to  i ;  sole  of  foot,  0.8  to  i  mm. 

Methods. — i.  Place,  on  the  part  of  the  skin  to  be  inve.stigated,  different  weights,  one  after  the 
other,  and  ascertain  what  perceptions  they  give  rise  to,  and  the  sense  of  the  difference  of  pressure  to 
which  they  give  rise.  We  must  be  careful  to  exclude  differences  of  temperature  and  prevent  the  dis- 
placement of  the  weights — the  weights  must  always  be  placed  on  the  same  spot,  and  the  skin  should 
be  covered  beforehand  with  a  disk,  while  the  muscular  sense  must  be  eliminated  (^  430).  [This  is 
done  by  supporting  the  hand  or  part  of  the  skin  which  is  being  tested,  so  that  the  action  of  all  the 
muscles  is  excluded.]  2.  A  process  is  attached  to  a  balance  and  made  to  touch  the  skin,  while  by 
placing  weights  in  the  scale  pan  or  removing  them,  we  test  what  differences  in  weight  the  person 
experimented  on  is  able  to  distinguish  [Dohrn).  3.  In  order  to  avoid  the  necessity  of  changing  the 
weights,  A.  Eulenburg  invented  his  baraesthesiometer,  which  is  constructed  on  the  same  principle 
as  a  spiral  spring  paper  clip  or  balance.  There  is  a  small  button  which  rests  on  the  skin  and  is 
depressed  by  the  spring.  An  index  shows  at  once  the  pressure  in  grammes,  and  the  instrument  is  so 
arranged  that  the  pressure  can  be  very  easily  varied.  4.  Goltz  uses  a  pulsating  elastic  tube,  in 
which  he  can  produce  waves  of  different  height.  He  tested  how  high  the  latter  must  be  before  they 
are  experienced  as  pulse  waves,  when  the  tube  is  placed  upon  the  skin.  5.  Landois  uses  a  mercu- 
rial balance  (Fig.  619).  The  beam  of  a  balance  (W)  moves  upon  two  knife  edges  (O,  O),  and  is 
carried  on  the  horizontal  arm  [b)  of  a  heavy  support  (T).  One  arm  of  the  beam  is  provided  with  a 
screw  (w)  on  which  an  equilibrating  weight  (S)  can  be  moved.  The  other  arm  [d)  passes  into  a 
vertical  calibrated  tube  (R).  Below  this  is  the  pressure  pad  (P)  which  can  be  loaded  as  desired  by 
a  weight  (G),  and  which  can  be  placed  upon  the  part  of  the  skin  to  be  tested  (H).  From  an  adjoin- 
ing burette  (B)  held  in  a  clamp  (A),  mercury  can  pass  through  a  tube  in  the  direction  of  the  arrows, 
to  one  part  of  the  balance  and  into  the  tube  (R).  On  the  stop-cock  [h)  being  closed,  whenever 
pressure  is  exerted  on  the  tube  (D,  D),  the  mercury  rises  through  d  into  R,  and  increases  the  pressure 
on  P.  We  measure  the  weight  of  the  mercury  corresponding  to  each  division  of  the  tube  (R).  This 
instrument  enables  rapid  variations  of  the  weight  to  be  made  without  giving  rise  to  any  shock.  In 
estimating  both  the  pressure  sense  and  temperature  sense,  it  is  best  to  proceed  on  the  .principle  of 
"the  least  perceptible  difference,"  i.  e.,  the  different  pressures  or  temperatures  are  graduated, 
either  beginning  with  great  differences,  or  proceeding  from  the  smallest  difference,  and  determining 
the  limit  at  which  the  person  can  distinguish  a  difference  in  the  sensation. 

Results. — I.  The  smallest  perceptible  pressure,  when  applied  to  different  parts  of 
the  skin,  varies  very  greatly  according  to  the  locality.  The  greatest  acuteness  of 
sensibility  is  on  the  forehead,  temples  and  the  back  of  the  head  and  forearm, 
which  perceive  a  pressure  of  0.002  grm.  ;   the  fingers  first  feel  with  a  weight  of 


886 


RESULTS   OF   THE    PRESSURE    SENSE. 


0.005   ^o  0-015  grin-  '.   the  chin,  abdomen   and   nose  with  0.04  to  0.05  grm.  ;  the 
finger  nail  1  grm.  {Kam/nler  and  Auberi). 

The  greater  the  sensibility  of  the  skin,  the  more  r.ipidly  can  stimuli  succeed  each  other,  and  still 
be  perceived  as  single  impressions ;  52  stimuli  per  second  may  be  applied  to  the  volar  side  of  the 
upper  arm,  61  on  the  back  of  the  hand,  70  to  the  tips  of  the  lingers,  and  still  be  felt  singly  {Block). 

2.  Intermittent  variations  of  pressure,  as  in  Goltz's  tube,  are  felt  more  acutely 
by  the  tips  of  the  fingers  than  with  the  forehead. 

'  3.  Differences  between  two  weights  are  perceived  by  the  tips  of  the  fingers  when 
the  ratio  is  29  :  30  (in  the  forearm  as  1S.2  :  20),  provided  the  weights  are  not  too 
light  or  too  heavy.  In  jiassing  from  the  use  of  very  light  to  heavy  weights,  the 
acuteness  or  fineness  of  the  perception  of  difference  increases  at  once,  but  with 

Fig.  619. 


Landois'  Mercurial  Balance  for  Testing  the  Pressure  Sense. 


heavier  weights,  the  power  of  distinguishing  differences  rapidly  diminishes  again 
{E.  Hering,  Biedermanti).  This  observation  is  at  variance  with  the  psycho-physical 
law  of  Fechner  (§  383). 

4.  A.  Eulenburg  found  the  following  gradations  in  the  fineness  of  the  pressure 
sense  :  The  forehead,  lips,  dorsum  of  the  cheeks  and  temples  appreciate  differences 
of  J^  to  Jq  (200  :  205  to  300  :  310  grm.).  The  dorsal  surface  of  the  last  phalanx 
of  the  fingers,  the  forearm,  hand,  ist  and  2d  phalanx,  the  volar  surface  of  the 
hand,  forearm  and  upper  arm,  distinguish  differences  of  ^  to  -^  (200:  220  to 
220 :  210  grm.).  The  anterior  surface  of  the  leg  and  thigh  are  similar  to  the  fore- 
arm. Then  follow  the  dorsum  of  the  foot  and  toes,  the  sole  of  the  foot,  and  the 
posterior  surface  of  the  leg  and  thigh.     Dohrn  determined  the  smallest  additional 


THE   TEMPERATURE    SENSE.  887 

weight,  which,  when  added  to  i  grm.  already  resting  on  the  skin,  was  appreciated 
as  a  difference,  and  he  found  that  for  the  3d  phalanx  of  the  finger  it  was  0.499 
grm.  ;  back  of  the  foot,  0.5  grm.  ;  2d  phalanx,  0.771  grm.  ;  ist  phalanx,  0.02 
grm.  j  leg,  i  grm.  ;  back  of  the  hand,  1.156  grm.  ;  palm,  1.018  grm.  ;  patella,  1.5 
grm.  ;  forearm,  1.99  grm.  ;  mubilicus,  3.5  grms.  ;  and  the  back,  3.8  grms. 

5.  Too  long  time  must  not  elapse  between  the  application  of  two  successive 
weights,  but  100  seconds  may  elapse  when  the  difference  between  the  weights  is 
4 :  5  (^.  H.   Weber). 

6.  The  sensation  of  an  after  pressure  is  very  marked,  especially  if  the  weight 
is  considerable  and  has  been  applied  for  a  length  of  time.  But  even  light  weights, 
when  applied,  must  be  separated  by  an  interval  of  at  least  ^I-q  to  -gJ-g-  second,  in 
order  to  be  perceived.  When  they  are  applied  at  shorter  intervals  the  sensations 
become  fused.  When  Valentin  pressed  the  tips  of  his  fingers  against  a  wheel 
provided  with  blunt  teeth  he  felt  the  impression  of  a  smooth  margin,  when  the 
teeth  were  applied  to  the  skin  at  the  intervals  above  mentioned ;  when  the  wheel 
was  rotated  more  slowly,  each  tooth  gave  rise  to  a  distinct  impression.  Vibrations 
of  strings  are  distinguished  as  such  when  the  number  of  vibrations  is  1506  to  1552 
l)er  second  (v.  Witiich  atid  Grilnhageri). 

7.  It  is  remarkable  that  pressure  produced  by  the  uniform  compression  of  a  part 
of  the  body,  e.  g.,  by  dipping  a  finger  or  arm  in  mercury,  is  not  felt  as  such ;  the 
sensation  is  felt  only  at  t/ie  limit  of  the  fluid,  on  the  volar  surface  of  the  finger,  at 
the  limit  of  the  surface  of  the  mercury. 

428.  TEMPERATURE  SENSE.— The  temperature  sense  makes  us 
acquainted  with  the  variations  of  the  heat  of  the  skin. 

A  specific  end  apparatus  arranged  in  a  punctated  manner  is  connected  with  the 
temperature  sense. 

These  "temperature  spots  "  are  arranged  in  a  linear  manner  or  in  chains, 
which  are  usually  slightly  curved  (Figs.  620,  621).  They  generally  radiate  from 
certain  points  of  the  skin,  usually  the  hair  roots.  The  chain  of  the  "  cold  spots  " 
usually  does  not  coincide  with  those  of  the  "  hot  spots,"   although  the  point 

Fig.  620. 

(^■F.  W.F. 


-<-«■ 


C  D 

C,  cold  spots,  and  D,   warm  spots  of  the  radial 

A,  cold  spots,  B,  hot  spots,  from  the  volar  surface  of  half  of  the  dorsal  surface  of  the  wrist.     The 

the  terminal  phalanx  of  the  index   finger  to   the  arrow  indicates  the  direction  in  which  the  hair 

margins  of  the  nail.  points. 

from  which  they  radiate  may  be  the  same.  Frequently,  these  punctated  lines  are 
not  complete,  but  they  may  be  indicated  by  scattered  points,  between  which,  not 
unfrequently  points  or  spots  for  other  qualities  of  sensation  may  be  intercalated. 
Near  the  hairs  there  are  almost  always  temperature  spots.  In  parts  of  the  skin, 
where  the  temperature  sensibility  is  slight,  the  temperature  points  are  present  only 
near  the  hairs. 

The  sensation  of  cold  occurs  at  once,  while  the  sensation   of  heat  develops 
gradually.     Mechanical  and  electrical  stimulation   also   excite   the  sensation   of 


888  THE    TEMPERATURE    SENSE. 

temperature.  A  gentle  touch  of  the  temperature  spots  is  not  perceived ;  these 
points  seem  to  be  aniv:sthetic  toward  pressure  and  i)ain.  As  a  general  rule,  the 
cold  spots  are  more  abundant  over  the  whole  body — there  are  more  of  them  in  a 
given  area — while  the  hot  spots  may  be  cjuite  absent.  The  hot  spots  are,  as  a  rule, 
perceived  as  double  at  a  greater  distance  apart  than  the  cold  spots.  Tiie  minimal 
distance  on  the  forehead  is  o.S  mm.  for  the  cold  spots,  and  4  to  5  mm.  for  the 
warm  spots  ;  on  the  breast  the  corresponding  numbers  are  2  and  4  to  5  ;  back,  1.5 
to  2  and  4  to  6  ;  back  of  hand  2  to  3  and  3  to  4  ;  palm,  0.8  to  2  .;  thigh  and  leg, 
2  to  3  and  3  to  4  mm. 

Method. — To  test  the  hot  and  cold  spots,  use  a  hot  or  cold  metallic  rod;  at  the  cold  spots,  when 
they  are  lightly  touched,  only  the  sensation  of  cold  will  be  felt,  and  a  corresponding  effect  with  a 
hot  rod  at  tlie  hot  spots.     Both  spots  are  insensible  to  objects  of  the  same  temperature  as  the  skin. 

According  to  E.  Hering,  what  determines  the  sensation  of  temperature  is  the 
temperature  of  the  thermic  end  apparatus  itself,  /.  e.,  its  zero  temperature.  As 
often  as  the  temperature  of  a  cutaneous  area  is  above  its  zero  temperature,  we 
feel  it  as  viarm ;  in  the  opposite  case,  cold.  The  one  or  the  other  sensation  is 
more  marked,  the  more  the  one  or  other  temperature  varies  from  the  zero  tem- 
perature. The  zero  temperature  can  undergo  changes  within  considerable  limits, 
owing  to  external  conditions. 

Methods. — To  the  surface  of  the  skin  objects  of  the  same  size  and  with  the  same  thermal  con- 
ductivity are  applied  successively  at  different  temperatures :  i.  Nothnagel  uses  small  wooden  cups 
with  a  metallic  base,  and  filled  with  warm  and  cold  water,  the  temperature  being  registered  by  a 
thermometer  placed  in  the  cups.  [2.  Clinically,  two  test-tubes  filled  with  cold  and  warm  water,  or 
two  spoons,  the  one  hot  and  the  other  cold,  may  be  used.] 

Results.— ^i.  Asa  general  rule,  the  feeling  of  cold  is  produced  when  a  body 
applied  to  the  skin  robs  it  of  heat  ;  and,  conversely,  we  have  a  sensation  of  warmth 
when  heat  is  communicated  to  the  skin. 

2.  The  greater  the  thermal  conductivity  of  the  substance  touching  the  skin,  the 
more  intense  is  the  feeling  of  heat  or  cold  (§  218). 

3.  At  a  temperature  of  i5.5°-35°  C,  we  distinguish  distinctly  differences  of 
temperature  of  o.2°-o.i6°  R.  with  the  tips  of  the  fingers  {^E.  H.  Weber).  Tem- 
peratures just  below  that  of  the  blood  (33°-27°  C. — Nothnagel)  are  distinguished 
most  distinctly  by  the  most  sensitive  parts,  even  to  differences  of  0.05°  C.  {Linder- 
mann).  Differences  of  temperature  are  less  easily  made  out  when  dealing  with 
temperatures  of  33°-39°  C,  as  well  as  between  i4°-2  7°  C.  A  temperature  of 
55°  C,  and  also  one  a  few  degrees  above  zero  (2.8°  C),  cause  distinct  pain  in 
addition  to  the  sensation  of  temperature. 

4.  The  sensibility  for  cold  is  generally  greater  than  for  warmth, — that  of  the  left 
hand  is  greater  than  the  right  {Goldscheider).  The  different  parts  of  the  skin  also 
vary  in  the  acuteness  of  their  thermal  sense,  and  in  the  following  order :  Tip 
of  the  tongue,  eyelids,  cheeks,  lips,  neck  and  body.  The  perceptible  minimum 
Nothnagel  found  to  be  0.4°  on  the  breast;  0.9°  on  the  back;  0.3°,  back  of  the 
hand;  0.4°,  palm;  0.2,  arm;  0.4°,  back  of  the  foot;  0.5°,  thigh;  0.6°, leg; 
o.4°-o.2°,cheek  ;  o.4°-o.3°  C,  temple.  The  thermal  sense  is  less  acute  in  the 
middle  line,  e.g.,  the  nose,  than  on  each  side  of  it  {E.If.  Weber).  Fig.  622 
shows  that  in  one  and  the  same  portion  of  skin,  the  cold  and  hot  spots  are 
differently  located,  i.e.,  their  different  topography. 

If  the  mucous  membrane  of  the  mouth  be  penciled  with  a  10  per  cent,  solution  of  cocain,  the 
sensibility  for  heat  is  abolished;  the  cooling  sensation  of  menthol  depends  upon  its  stimulation  of  the 
cold  nerves;   CO2  applied  to  the  skin  excites  the  heat  nerves  (^Goldscheider). 

5.  Differences  of  temperature  are  most  easily  perceived  when  the  same  part  of  the 
skin  is  affected  successively  by  objects  of  different  temperature.  If,  however,  two 
different  temperatures  act  simultaneously  and  side  by  side,  the  impressions  are  apt 
to  become  fused,  especially  when  the  two  areas  are  very  near  each  other. 


THE    TEMPERATURE    SENSE. 


889 


6.  Practice  improves  the  temperature  sense  ;  congestion  of  venous  blood  in  the 
skin  diminishes  it ;  diminution  of  the  amount  of  blood  in  the  skin  improves  it  {M. 
Alsberg).  When  la7'ge  areas  of  the  skin  are  touched,  the  perception  of  differ- 
ences is  more  acute  than  with  small  areas.  Rapid  variations  of  the  temperature 
produce  more  intense  sensations  than  gradual  changes  of  temperature.  Fatigue 
occurs  soon. 

Illusions  are  very  common  :  i.  The  sensations  of  heat  and  cold  sometimes  alternate  in  a 
paradoxical  manner.  When  the  skin  is  dipped  first  into  water  at  io°  C.  we  feel  cold,  and  if  it  be 
then  dipped  at  once  into  water  at  i6°  C,  we  have  at  first  a  feeling  of  warmth,  but  soon  again  of 
cold.  2.  The  same  temperature  applied  to  a  large  surface  of  the  skin  is  estimated  to  be  greater 
than  when  it  is  applied  to  a  small  area,  eg.,  the  whole  hand  when  placed  in  water  at  29  5°  C.  feels 
warmer  than  when  a  finger  is  dipped  into  water  at  32°  C.  3.  Cold  weights  are  judged  to  be  heavier 
than  warm  ones. 

Pathological. — Tactile  sensibility  is  only  seldom  increased  (hyperpselaphesia),  but  great 
sensibility  to  differences  of  temperature  is  manifested  by  areas  of  the  skin  whose  epidermis  is  partly 
removed  or  altered  by  vesicants  or  herpes  zoster,  and  the  same  occurs  in  some  cases  of  locomotor 
ataxia ;   while  the  sense  of  locality  is  rendered  more  acute  in  the  two  former  cases  and  in   erysipelas. 

Fig.  622. 


••::::::K::illill!j'---lillll 


Cold  and  hot  spots  from  the  same  part  of  the  anterior  surface  of  the  forearm,  a,  cold  spots  ;  ^,  hot  spots.  The 
dark  parts  are  the  most  sensitive,  the  hatched  the  medium,  the  dotted  the  feebly,  and  the  vacant  spaces  the  non- 
sensitive. 


An  abnormal  condition  of  the  sense  of  locality  was  described  by  Brown-Sequard,  where  three  points 
were  felt  when  only  two  were  applied,  and  two  when  one  was  applied  to  the  skin.  Landois  finds 
that  in  himself  pricking  the  .skin  of  the  sternum  over  the  angle  of  Ludovicus  is  always  accompanied 
by  a  sensation  in  the  knee.  [Some  persons,  when  cold  water  is  applied  to  the  scalp,  have  a  sensa- 
tion referable  to  the  skin  of  the  \6vai,  {Stir ling). '\  A  remarkable  variation  of  the  sense  of  locahiy 
occurs  in  moderate  poisoning  with  morphia,  where  the  person  feels  himself  abnormally  large  or 
greatly  diminished.  In  degeneration  of  the  posterior  columns  of  the  cord,  Obersteiner  observed 
that  the  patient  was  unable  to  say  whether  his  right  or  left  side  was  touched  ( '•  allochiria  "  ). 
Ferrier  observed  a  case  where  a  stimulus  applied  to  the  right  side  was  referred  to  the  left,  and 
vice  versa. 

Diminution  and  paralysis  of  the  tactile  sense  (Hypopselaphesia  and  Apselaphesia) 
occur  either  in  conjunction  with  simultaneous  injury  to  the  sensory  nerves,  or  alone.  It  is  rare  to 
find  that  one  of  the  qualities  of  the  tactile  sense  is  lost,  e.g.,  either  the  tactile  sense  or  the  sense  of 
temperature — a  condition  which  has  been  csXltdi  " partial  tactile  paralysis."  Limbs  which  are 
"  sleeping''^  feel  heat  and  not  cold  i^Herzen). 

429.  COMMON  SENSATION— PAIN.— By  the  term  common  sensa- 
tion we  understand  pleasant  or  unpleasant  sensations  in  those  parts  of  our  bodies 


800  COMMON    SENSATION I'MX. 

which  :ire  encluwcd  with  sensibility,  and  which  arc  not  referable  to  external  objects, 
and  whose  cliaracters  are  difficult  to  describe,  and  cannot  be  compared  with  other 
sensations.  Each  sensation  is,  as  it  were,  a  peculiar  one.  To  this  belong  pain, 
hunger,  thirst,  malaise,  fatigue,  horror,  vertigo,  tickling,  well-being,  illness,  the 
respiratory  feeling  of  free  or  impeded  breathing. 

Pain  may  occur  wherever  sensory  nerves  are  distributed,  and  it  is  invariably 
causctl  by  a  stronger  stimulus  than  normal  being  applied  to  sensory  nerves.  Every 
kind  of  stimulation,  mechanical,  thermal,  chemical,  electrical,  as  well  as  somatic 
(inflammation  or  disturbances  of  nutrition),  may  excite  pain.  The  last  appears  to 
l)e  especially  active,  as  many  tissues  become  extremely  painful  during  inflamma- 
tion {e.^.,  muscles  and  bones),  while  they  are  comparatively  insensible  to  cutting. 
Pain  may  be  produced  by  stimulating  a  sensory  nerve  in  any  part  of  its  course, 
from  its  centre  to  the  periphery,  but  the  sensation  is  invariably  referred  to  the 
perijiheral  end  of  the  nerve.  This  is  the  law  of  the  peripheral  reference  of 
sensations.  Hence,  stimulation  of  a  nerve,  as  in  the  scar  of  an  amputated  limb, 
may  give  rise  to  a  sensation  of  pain  which  is  referred  to  the  parts  already  removed. 
Too  violent  stimulation  of  a  sensory  nerve  in  its  course  may  render  it  incapable  of 
conducting  impressions,  so  that  peripheral  impressions  are  no  longer  perceived.  If 
a  sufficient  stimulus  to  produce  pain  be  then  applied  to  the  central  part  of  the 
nerve,  such  an  impression  is  still  referred  to  the  peri])heral  end  of  the  nerve.  Thus 
we  explain  the  paradoxical  anaesthesia  dolorosa.  In  connection  with  painful 
impressions,  the  patient  is  often  unable  to  localize  them  exactly.  This  is  most 
easily  done  when  a  small  injury  (prick  of  a  needle)  is  made  on  a  peripheral  part. 
When,  however,  the  stimulation  occurs  in  the  course  of  the  nerve,  or  in  the  centre, 
or  in  nerves  whose  peripheral  ends  are  not  accessible,  as  in  the  intestines,  pain  (as 
belly-ache),  which  cannot  easily  be  localized,  is  the  result. 

Irradiation. — During  violent  pain  there  is  not  unfrequently  irradiation  of  the 
pain  (§  364,  5),  whereby  localization  is  impossible.  It  is  rare  for  pain  to  remain 
continuous  and  uniform  ;  more  generally  there  are  exacerbations  and  diminutions 
of  the  intensity,  and  sometimes /(^/w^^Z/V  intensification,  as  in  some  neuralgias. 

The  intensity  of  the  jjain  depends  especially  upon  the  excitability  of  the  sensory 
nerves.  There  are  considerable  individual  variations  in  this  resi)ect,  some  nerves, 
e.g.,  the  trigeminus  and  splanchnic,  being  very  sensitive.  The  larger  the  number 
of  fibres  affected  the  more  severe  the  pain.  The  duration  is  also  of  importance,  in 
as  far  as  the  same  stimulation,  when  long  continued,  may  become  unbearable.  We 
speak  of  piercing,  cutting,  boring,  burning,  throbbing,  pressing,  gnawing,  dull,  and 
other  kinds  of  pain,  but  we  are  quite  unacquainted  with  the  conditions  on  which 
such  different  sensations  depend.  Painful  impressions  are  abolished  by  anaesthe- 
tics and  narcotics,  such  as  ether,  chloroform,  morphia,  etc.  (§  364,  5). 

Methods  of  Testing. — To  test  the  cutaneous  sensibility,  we  usually  employ  the  constant  or 
induced  electrical  current.  Determine  first  the  niiniiiiuni  sensibility,  i.  e.,  the  strength  of  the  current 
which  excites  the  first  trace  of  sensation,  and  also  the  minimum  of  pain,  i.  e.,  the  feeblest  strength 
of  the  current  which  first  causes  distinct  impressions  of  pain.  The  electrodes  consist  of  thin  metallic 
needles,  and  are  placed  i  to  2  cm.  apart. 

Pathological. — When  the  excitability  of  the  nerves  which  administer  to  painful  sensations  is 
increased,  a  slight  touch  of  the  skin,  nay,  even  a  breath  of  cold  air,  may  excite  the  most  violent  pain, 
constituting  cutaneous  hyperalgia,  especially  in  inflammatory  or  exanthematic  conditions  of  the 
skin.  The  term  cutaneous  paralgia  is  applied  to  certain  anomalous,  disagreeable,  or  painful 
sensations  which  are  frequently  referred  to  the  skin — itching,  creeping,  formication,  cold,  and  burning. 
In  cerebro-spinal  meningitis,  sometimes  a  prick  in  the  sole  of  the  foot  produces  a  double  sensation  of 
pain  and  a  double  reflex  contraction.  Perhaps  this  condition  may  be  explained  liy  supposing  that  in 
a  part  of  the  nerve  the  condition  is  delayed  (^  337,  2).  In  neuralgia  there  is  severe  pain,  occurring 
in  paroxysms,  with  violent  exacerbations  and  pain  shooting  into  other  parts  (p.  648).  Very  frequently 
excessive  pain  is  produced  by  pressure  on  the  nerve  where  it  makes  its  exit  from  a  foramen  or 
traverses  a  fascia. 

Valleix's  Points  Douloureux  (1841). — The  skin  itself  to  which  the  sensory  nerve  runs,  espe- 
cially at  first,  may  be  very  sensitive ;  and  when  the  neuralgia  is  of  lon^  duration  the  sensibility  may 


MUSCULAR   SENSE.  891 

be  diminished  even  to  the  condition  of  analgesia  (  Tilrck)  ;  in  the  latter  case  there  may  be  pronounced 
anaesthesia  dolorosa  (p.  890). 

Diminution  or  paralysis  of  the  sense  of  pain  (hypalgia  and  analgia)  may  be  due  to  affections 
of  the  ends  of  the  nerves,  or  of  their  course,  or  central  terminations. 

Metalloscopy. — In  hysterical  patients  suffering  from  hemianeesthesia,  it  is  found  that  the  feeling 
of  the  paralyzed  side  is  restored,  when  small  metallic  plates  or  larger  pieces  of  different  metals  are 
applied  to  the  affected  parts  {Burcq,  Charcot).  At  the  same  time  that  the  affected  part  recovers  its 
sensibility  the  opposite  limb  or  side  becomes  anaesthetic.  This  condition  has  been  spoken  of  as 
transference  of  sensibility.  The  phenomenon  is  not  due  to  galvanic  currents  developed  by  the  metals  ; 
but  it  may  be,  perhaps,  explained  by  the  fact  that,  under  physiological  conditions,  and  in  a  healthy 
person,  every  increase  of  the  sensibility  on  one  side  of  the  body,  produced  by  the  application  of  warm 
metallic  plates  or  bandages,  is  followed  by  a  diminution  of  the  sensibility  of  the  opposite  side. 
Conversely,  it  is  found  that  when  one  side  of  the  body  is  rendered  less  sensitive  by  the  application 
of  cold  plates,  the  homologous  part  of  the  other  side  becomes  more  sensitive  [Rti?npf). 

430.  MUSCULAR  SENSE.— Muscular  Sensibility.— The  sensory 
nerves  of  the  muscles  (§  292)  always  convey  to  us  impressions  as  to  the  activity 
or  non-activity  of  these  organs,  and  in  the  former  case,  these  impressions  enable 
us  to  judge  of  the  degree  of  contraction.  It  also  informs  us  of  the  amount  of  the 
contraction  to  be  employed  to  overcome  resistance.  Obviously,  the  muscular  sense 
must  be  largely  supported  and  aided  by  the  sense  of  pressure,  and  conversely.  E. 
H.  Weber  showed,  however,  that  the  muscle  sense  is  finer  than  the  pressure  sense, 
as  by  it  we  can  distinguish  weights  in  the  ratio  of  39  :  40,  while  the  pressure  sense 
only  enables  us  to  distinguish  those  in  the  ratio  of  29  :  30.  In  some  cases  there 
has  been  observed  total  cutaneous  insensibility,  while  the  muscular  sense  was  retained 
completely.  A  frog  deprived  of  its  skin  can  spring  without  any  apparent  disturb- 
ance. The  muscular  sense  is  also  greatly  aided  by  the  sensibility  of  the  joints, 
bones,  and  fasciae.  Many  muscles,  e.g.,  those  of  respiration,  have  only  slight 
muscular  sensibility,  while  it  seems  to  be  absent  normally  in  the  heart  and  non- 
striped  muscle. 

[The  muscular  sense  stands  midway  between  special  and  common  sensations,  and 
by  it  we  obtain  a  knowledge  of  the  condition  of  our  muscles,  and  to  what  extent 
they  are  contracted  ;  also  the  position  of  the  various  parts  of  our  bodies  and  the 
resistance  offered  by  external  objects.  Thus,  sensations  accompanying  muscular 
movement  are  twofold — (a)  the  movements  in  the  unopposed  muscles,  as  the  move- 
ments of  the  limbs  in  space;  and  (/^)  those  of  resistance  where  there  is  opposition 
to  the  movetxient,  as  in  lifting  a  weight.  In  the  latter  case  the  sensations  due  to 
innervation  are  important,  and  of  course  in  such  cases  we  have  also  to  take  into 
account  the  sensations  obtained  from  mere  pressure  upon  the  skin.  Our  sensations 
derived  from  muscular  movements  depend  on  the  direction  and  duration  of  the 
movements.  On  the  sensations  thus  conveyed  to  the  sensorium,  we  form  judg- 
ments as  to  the  direction  of  a  point  in  space,  as  well  as  of  the  distance  between  two 
points  in  space.  This  is  very  marked  in  the  case  of  the  ocular  muscles.  It  is  also 
evident  that  the  muscular  sense  is  intimately  related  to,  and  often  combined  with, 
the  exercise  of  the  sensation  of  touch  and  sight  (^Sully').'\ 

Methods  of  Testing. — Weights  are  wrapped  in  a  towel  and  suspended  to  the  part  to  be  tested. 
The  patient  estimates  the  weight  by  raising  and  lowering  it.  The  electro-muscular  sensibility  also 
may  be  proved  thus :  cause  the  muscles  to  contract  by  means  of  induction  shocks,  and  observe  the 
sensation  thereby  produced.  [Direct  the  patient  to  place  his  feet  together  while  standing,  and  then 
close  his  eyes.  A  healthy  person  can  stand  quite  steady,  but  in  one  with  the  muscular  sense  impaired, 
as  in  locomotor  ataxia,  the  patient  may  move  to  and  fro,  or  even  fall  (p.  697),  Again,  a  person  with 
his  muscular  sense  impaired  may  not  be  able  to  touch  accurately  and  at  once  some  part  of  his  body, 
when  his  eyes  are  closed.] 

A  healthy  person  perceives  a  weight  of  I  gramme  applied  to  his  upper  arm;  when  a  weight  of  15 
grms.  is  applied,  he  perceives  an  addition  of  i  grm.  If  the  original  weight  be  50  grms. ,  he  will  detect 
the  addition  of  2  grms. ;  if  the  original  weight  be  loo  grms.,  he  will  detect  3  grms.  The  weight 
detectable  by  the  individual  finger  varies.  With  the  leg,  when  the  weight  is  applied  at  the  knee,  the 
individual  may  detect  30  to  40  grms. ;  but  sometimes  only  a  greater  weight.  Often  one  can  detect  a 
difference  of  10  to  20,  or  30  to  70  grms. 


892  MUSCULAR    SENSE. 

Section  of  a  sensory  nerve  causes  disturbance  of  the  fine  graduation  of  movement 
(p.  668).  Meynert  supposes  that  the  cerebral  centre  for  muscular  sensibility  lies 
in  ihe  motor  cortical  centres,  the  muscles  being  connected  by  motor  and  sensory 
paths  with  the  ganglionic  cells  in  these  centres. 

Too  severe  muscular  exercise  causes  the  sensation  of  fatigue,  oppression,  and 
weight  in  the  limbs  (§  304). 

Pathological. — Abnormal  increase  of  the  muscular  sense  is  rare  [muscular  hyperali^ia  ami  hvper- 
trsthesiii),zs,  in  an.xietas  libianiin,A  painful  condition  of  unrest  which  leads  to  a  continual  chani^e  in 
the  i^osition  of  ihe  limbs.  In  cramp  there  is  intense  pam,  due  to  stimulation  of  the  sensory  nerves  of 
the  muscle,  and  the  same  is  tliecase  in  inflammaiion.  Diminution  of  the  muscular  sensibility  occurs 
in  some  choreic  and  ataxic  persons  (^  364,  5).  In  locomotor  ataxia  the  muscular  sense  of  the  upper 
extremities  may  lie  normal  or  weakened,  while  it  is  usually  considerably  diminished  in  the  legs. 
[The  muscular  sense  is  said  to  be  increased  in  the  hypnotic  condition,  and  in  somnambulists.] 


Reproduction  and  Development 


431.  FORMS  OF  REPRODUCTION.— I.  Abiogenesis  (Generatio  aequivoca,  sive 
spontanea,  spontaneous  generation). — It  was  formely  assumed  that,  under  certain  circumstances, 
non-living  matter  derived  from  the  decomposition  of  organic  materials  became  changed  sponta- 
neously into  living  beings.  While  Aristotle  ascribed  this  mode  of  origin  to  insects,  the  recent 
observers  who  advocate  this  form  of  generation  restrict  its  action  solely  to  the  lowest  organisms. 
Experimental  evidence  is  distinctly  against  spontaneous  generation.  If  organized  matter  be  heated 
to  a  very  high  temperature  in  sealed  tubes,  and  be  thus  deprived  of  all  living  organisms  or  their 
spores,  there  is  no  generation  of  any  organism.  Hence,  the  dictum,  "  Omne  vivum  ex  ovo " 
{Harvey,  or,  ex  vivo).  Some  highly  organized  invertebrate  animals  (Gordius,  Anguillula,  Tardi- 
grada,  and  Rotatoria)  may  be  dried,  and  even  heated  to  140°  C.,  and  yet  regain  their  vital  activities 
on  being  moistened  (Anabiosis). 

II.  Division  or  fission  occurs  in  many  protozoa  (amoeba,  infusoria).  The  organism,  just  as  is 
the  case  with  cells,  divides,  the  nucleus  when  present  taking  an  active  part  in  the  process,  so  that 
two  nuclei  and  two  masses  of  protoplasm  forming 

two  organisms   are   produced.     The   Ophidiasters  Fig.  624. 

among  the  echinoderms  divide  spontaneously,  and 
they  are  said  to  throw  off  an  arm  which  may 
develop  into  a  complete  animal.  According  to 
Trembley  (1744),  the  hydra  maybe  divided  into 
pieces,  and  each  piece  gives  rise  to  a  new  individ- 
ual [although  under  normal  circumstances  the 
hydra  gives  off  buds,  and  is  provided  with  genera- 
tive organs]. 

[Division  of  Cells. — Although  a  cell  is  de- 
fined as  a  "nucleated  mass  of  living  protoplasm," 
recent  researches  have  shown  that,  from  a   histo- 

FiG.  623. 


Fig.  623. — Changes  in  a  cell  nucleus  during  karyokinesis. 

Fig.  624  — Typical  nucleated  cell  of  the  intestinal  epithelium  of  a  flesh  maggot,  mc,  membrane  of  cell ;  vin,  mem- 
brane of  nucleus ;  pc,  cellular  protoplasm,  with  the  radiating  retictdutii,  and  the  enchylema  enclosed  in  its 
meshes  ;  j>n,  plasma  of  nucleus  ;  bn,  nuclear  filament  showing  numerous  twists. 

logical  as  well  as  from  a  chemical  point  of  view,  a  cell  is  really  a  very  complex  structure.  The 
apparently  homogeneous  cell  substance  is  traversed  by  a  fine  plexus  of  fibrils,  with  a  homogene- 
ous substance  in  its  meshes,  while  a  similar  network  of  fibrils  exists  within  the  nucleus  itself  (Fig. 
623).] 

[The  nucleus  of  a  typical  cell  is  a  spherical  vesicle,  consisting  of  a  membrane  containing  what 
is  called  "  achromatin,"  because  it  is  not  readily  stained  by  staining  reagents.  Flemming  has  also 
called  it  nuclear  fluid,  or  intermediate  substance.  The  achromatin  substance  is  permeated  by  a  deli- 
cate reticular  network,  or  plexus  of  fibrils,  which  has  been  called  "  chromatin,"  "  nucleoplasm," 
"karyoplasma,"  and  "  karyomiton."  The  network  stains  readily  with  pigments,  hence  the 
name  "  chromatin"  given  to  it  by  Flemming.  The  nodal  points  of  the  network  give  a  dotted  or 
granular  appearance  to  the  nucleus,  especially  when  it  is  examined  with  a  low  power.     The  nuclear 

893 


894 


DIVISION    OF    CELLS. 


membrane  also  consists  of  chromatin  (Vig.  624).  In  tlie  meshes  of  the  network  lie  nucleoli,  which 
seem  to  differ  in  constitution,  ami  perhaps  in  function.  According  to  Flemming,  there  are  principal 
and  accessory  nucleoli  in  some  nuclei.  In  Carnoy's  nomenclature  the  several  parts  are  spoken  of  as 
a  line  reticulum  of  lihrils,  enclosing  in  its  meshes  a  fluid — the  enchyUma — which  contains  various 
particles  in  suspension.] 

[Direct  Cell  Division. — A  cell  may  divide  directly,  as  it  were,  by  simple  cleavage,  and  in  the 
process  the  nucleus  usually  divides  before  the  cell  protoplasm.  The  nucleus  becomes  constricted 
in  the  centre,  has  an  hour-glass  shape,  and  soon  divides  into  two.] 

[Indirect  Cell  Division. — Recent  observations,  confirmed  by  a  great  number  of  investigators, 
conclusively  prove  that  the  process  of  division  in  cells  is  a  very  complicated  one,  the  changes  in  the 
nucleus  being  very  remarkable.  The  terms  karyokinesis,  mitosis,  or  indirect  division  have 
been  applied  to  this  process.  Figs.  623,  625  show  the  changes  that  take  ])lace  in  the  nucleus.  The 
chromatin  or  intranuclear  network  (^,  B)  passes  into  a  convolution  of  tibrils,  while  the  nuclear 
envelope  becomes  less  distinct,  the  fibiils  at  the  .same  time  becoming  thicker  and  forming  loops, 
which  gradually  .arrange  themselves  around  a  centre  {c  and  d)  in  the  form  of  a  wreath,  rosetie,  or 
spirem  (C).  The  fibres  curve  round  both  at  the  periphery  and  the  centre  and  form  loops;  but 
when  their  peripheral  connections  are  severed  or  dissolved,  we  obtain  a  star-shaped  former  aster 
(D),  composed  of  single  loops  radiating  from  the  centre  (f).  The  loops  divide  in  the  direction  of 
their  length;  their  number  is  doubled,  but  they  are  thinner.  By  this  further  subdivision,  the  whole 
is  compo.sed  of  tine  radiating  fibrils  (/),  which  gradually  arrange  themselves  around  two  poles,  or 
new  centres,  to  form  the  barrel-form  or  pithode  (E)  ;  the  two  groups  of  loops  then  .separate  still 
further,  and  arrange  themselves  so  as  form  a  diaster,  or  double  star  {g),  the  two  groups  being  sepa- 


Mitosis.    A,  nuclear  reticulum,  resting  state ;  B,  preparing   for  division;  C,  wreath  stage;   D,  monaster  stage; 
barrel  stage  ;  F,  diaster  stage  ;  G,  daughter  wreath  stage  ;   H,  daughter  cells,  passing  to  resting  stage. 


E, 


•  rated  by  a  .substance  called  the  equatorial  plate.  Each  of  the  groups  of  fibrils  becomes  more 
elongated,  and  forms  a  nuclear  spindle,  which  indicates  the  position  of  a  new  nucleus.  The  proto- 
plasm separates  into  two  parts.  In  each  of  these  parts  the  chromatin  rearranges  itself  into  an  irreg- 
ular coil,  and  the  whole  is  called  dispirem  (G),  and  when  division  is  complete,  the  chromatin  fila- 
ments assume  the  form  seen  in  a  resting  nucleus.  This  whole  complex  process  may  be  accomplished 
in  I  to  4  hours.  The  separate  groups  of  fibrils  again  become  convoluted,  each  group  gets  a  nuclear 
membrane,  while  the  cell  protoplasm  divides,  and  two  daughter  nuclei  are  obtained  from  the  origi- 
nal cell.] 

The  following  scheme  represents  some  of  the  more  important  changes : — 

Mother  nuc/eus.  I  Daughter  nuclei, 

1.  Network.  |  8.  Network. 

2.  Convolution.  I  7.  Convolution. 

3.  Wreath  or  Spirem.  6.   Dispirem. 

4.  A.ster.  I  5.   Disaster. 

Equatorial  grouping  of  chromatin. 
III.  Budding  or  gemmation  occurs  in  a  well-marked  form  among  the  polyps  and  in  some  infu- 
soriaHS  (\'orticella).  A  bud  is  given  off  by  the  parent,  and  gradually  comes  more  and  more  to 
resemble  the  latter.  The  bud  either  remains  permanently  attached  to  the  parent,  so  that  a  complex 
organism  is  produced,  in  which  the  digestive  organs  communicate  with  each  other  directly,  or  in  some 
cases  there  may  be  a  ''  colony  "  with  a  common  nervous  system,  such  as  thepolyzoa.  In  .some  com- 
posite animals  (siphonophora)  the  different  polyps  perform  different  functions.  Some  have  a  diges- 
tive, others  a  motor,  and  a  third  a  generative  function,  so  that  there  is  a  physiological  division  of 
labor.     Buds  which  are  given  off  from  the  parent  are   formed  internally  in  the  rhizopoda.     In  some 


FORMS   OF    REPRODUCTION. 


895 


animals  (polyps,  infusoria),  which  can  reproduce  themselves  by  buds  or  division,  there  is  also  the 
formation  of  male  and  female  elements  of  generation,  so  that  they  have  a  sexual  and  a  non-sexual 
mode  of  reproduction. 

IV.  Conjugation  is  a  form  of  reproduction  which  leads  up  to  the  sexual  form.  It  occurs  in  the 
unicellular  Gregarinje.  The  anterior  end  of  one  such  organism  unites  with  the  posterior  end  of 
another;  both  become  encysted,  and  form  one  passive  spherical  body.  The  conjoined  structures  form 
an  amorphous  mass,  from  which  numerous  globular  bodies  are  formed,  and  in  each  of  which  numer- 
ous oblong  structures — the  pseudo  navicelli — are  developed.  Those  bodies  become,  or  give  rise  to 
an  amoeboid  structure,  which  forms  a  nucleus  and  an  envelope,  and  becomes  transformed  into  a 
gregarina. 

Sexual  reproduction  requires  the  formation  of  the  embryo  from  the  conjunction  of  the  male  and 
female  reproductive  elements,  the  sperm  cell  and  the  germ  cell.  These  products  may  be  formed 
either  in  one  individual  (hermaphroditism,  as  in  the  flat  worms  and  gasteropods),  or  in  two  separate 
organisms  (male  or  female).     Sexual  reproduction  embraces  the  following  varieties  : — 

V.  Metamorphosis  is  that  form  of  sexual  reproduction  in  which  the  embryo  fiom  an  early  period 
undergoes  a  series  of  marked  changes  of  external  form,  e.g ,  the  chrysalis  stage,  and  the  pupa  stage, 
and  in  none  of  these  stages  is  reproduction  possible.  Lastly,  the  final  sexually  developed  form  (the 
imago  stage  in   butterflies)  is  produced,  which    forms  the 

sexual  products  whose  union  gives  rise  to  organisms  which  Y\G.  627. 

repeat  the  same  cycle  of  changes.     Metamorphosis  occurs 

extensively  among  the  insrcts;  some  of  them  have  several  ap/////  /'///'//'// 

stages  (holo-metabolic),  and  others  have  few  stages  (hemi-  mmt  sllllM'mt'  '  '' 

metabolic).     It  also  occurs  in  some  arthropoda,  and  worms, 

^.^.,  trichina;  the  sexual  form  of  the  animal  occurs  in  the 

intestine,  the   numerous    larva  wander  into   the   muscles, 

where  they  become  encysted,  and  form  undeveloped  sexual 

Fig.  626. 


A  ripe  egg  taken  from  the  uterus 
of  Taenia  solium,  a.  Albumi- 
nous envelope ;  b,  remains 
of  the  yelk;  c,  covering  of 
the  embryo ;  d,  embryo  with 
embryonal  booklets. 


Encapsuled  cysticercus  from  Taenia  solium  em- 
bedded in  a  human  sartorius.     Natural  size. 


organs,  constituting  the  pupa  stage  of  the  muscular  trichina.  When  the  encysted  form  is  eaten  by 
another  animal,  the  sexual  organs  come  into  activity,  a  new  brood  is  formed,  and  the  cycle  is  repeated. 
Metamorphosis  also  occurs  in  the  frog  and  in  petromyzon.  [This  is  really  a  condition  in  which  the 
embryo  undergoes  marked  changes  of  form  before  it  becomes  sexually  mature.] 

VI.  Alternation  of  Generations  (5V^^«i-/ri//).— In  this  variety  some  of  the  members  of  the  cycle 
can  produce  new  beings  non-sexually,  while  in  the  final  stage  reproduction  is  always  sexual.  From 
a  medical  point  of  view,  the  life  history  of  the  tapeworm  or  Taenia  is  most  important.  The  seg- 
ments of  the  tapeworm  are  called  proglottides  (Fig.  631 ),  and  each  segment  is  hermaphrodite,  with 
testes,  vas  deferens,  penis,  ovary,  etc..  and  numerous  ova.  The  segments  are  evacuated  with  the 
faeces.  The  eggs  are  fertilized  after  they  are  shed  (Fig.  626),  and  from  them  is  developed  an  elliptical 
embryo,  provided  with  six  booklets,  which  is  swallowed  by  another  animal,  the  host.  These  embryos 
bore  their  way  into  the  tissues  of  the  host,  where  they  undergo  development,  forming  the  encysted 
stage  (Cysticercus  (Fig.  627),  Coenurus,  or  Echinococcus  (Fig.  630).  The  encysted  capsule  may 
contain  one  (cysticercus)  or  many  (coenurus)  sessile  heads  of  the  taenia.  In  order  to  undergo  further 
development,  the  cysticercus  must  be  eaten  alive  by  another  animal,  when  the  head  or  scolex  fixes 
itself  by  the  booklets  and  suckers  to  the  intestine  of  its  new  host  (Fig.  629),  where  it  begins  to  bud 
and  produce  a  series  of  new  segments  between  the  head  and  the  last  formed  segment,  and  thus  the 
cycle  is  repeated. 

The  most  important  flat  worms  are :  Taenia  solium,  in  man;  the  Cysticercus  cellulosas  (Fig.  628), 
in  the  pig,  when  it  con-titutes  the  7neasle  in  pork;  Taenia  mediocanellata  (Fig.  631),  the  encysted 


896 


TESTIS. 


stage,  in  the  ox  ;  Taenia  coenurus,  in  the  dog's  intestine;  the  encysted  stage,  or  Coenurus  cere- 
bralis,  in  llie  brain  of  the  sheep,  where  it  j^ives  rise  to  the  condition  of  "staggers"  ;  Taenia  echi- 
nococcus,  in  the  dog's  intestine :  the  embryos  or  scolices  occur  in  the  hverof  man  as  "  hydatids." 

The  medusLV  also  exhibit  alternation  of  generations,  and  so  ilo  some  insects,  especially  the  plant 
lice  or  aphides. 

VII.  Parthenogenesis  {Owen,  v.  Sie/whi). — In  this  variety,  in  addition  to  sexual  reproduction, 
new  individuals  may  be  produced  without  sexual  union.     The  nonsexually  produced  brood  is  always 


Fig.  628. 


Fig.  630. 


Cysticerci  from  Taenia  solium  removed  from 
their  capsule,  i,  natural  size  ;  2,  magni- 
fied a,  embryo  sac  :  <^,  cavity  produced 
by  budding  of  the  embryo  sac;  c,  suc- 
torial disks  and  booklets. 


Cysticercus  of  Taenia  soli- 
um, with  its  head  and 
segments  protruded. 
a,  caudal  sac  ;  b,  head 
of  the  tapeworm,  with 
disksand  booklets  (sco- 
lex) ;   c,  neck. 


Part  of  an  Kchinococcus  capsule, 
with  developing  buds.  «,  sheath; 
^,  parenchymatous  layer ;  «^,  ger- 
muiating  capsule  tilled  with 
scolices. 


of  one  sex,  as  in  the  bees.  A  bee  hive  contains  a  queen,  the  workers,  and  the  drones  or  males. 
During  the  nuptial  (light,  the  queen  is  impregnated  by  the  males,  and  the  seminal  fluid  is  stored  up 
in  the  receptaculum  seminis  of  the  queen,  and  it  appears  that  the  queen  may  voluntarily  permit  the 
contact  of  this  fluid  with  the  ova  or  withhold  it.  All  fertilized  eggs  give  rise  to  female,  and  all 
unfertilized  ones  to  male  bees. 

VIII.  Sexual  reproduction  without  any  intermediate  stages  occurs  in,  besides  man,  mammals, 
birds,  reptiles,  and  most  fishes. 

432.  TESTIS — SEMINAL  FLUID. —  [Testis. — In  the  testis  or  male  reproductive  organ, 
the  seminal  fluid  which  contains  the  male  element  or  spermatozoa  is  formed.  The  framework  of 
the  gland  consists  of  a  thick,  strong,  while,  fibrous  covering,  the  tunica  albuginea,  composed 
chiefly  of  white,  interlacing,  fibrous  tissue.     Externally,  this  layer  is  covered  by  the  visceral  layer 

Fig.  6-, I. 


Taenia  Mediocanellata.     Natural  size. 

of  the  serous  membrane,  or  the  tunica  vaginalis,  which  invests  the  testis  and  epididymis.  The 
tunica  albuginea  is  prolonged  f)r  some  di.stance  as  a  vertical  septum  into  the  posterior  part  of  the 
testis,  to  furm  the  mediastinum  testis  or  corpus  Highmori.  Septa  or  trabeculae— more  or  less 
complete— stretch  from  the  under  surface  of  the  T.  albuginea  toward  the   mediastinum,  so  that  the 


STRUCTURE  OF  A  SEMINAL  TUBULE. 


897 


organ  is  subdivided  thereby  into  a  number  of  compartments  or  lobules,  with  their  bases  directed 
outward  and  their  apices  toward  the  mediastinum.  From  these,  finer  sustentacular  fibres  pass  into 
the  compartments  to  support  the  structures  lying  in  these  compartments.] 

[Arrangement  of  Tubules. — Each  compartment  contains  several  seminal  tubules,  long  con- 
voluted tubules  (ji^  in.  in  diam.)  which  rarely  branch  except  at  their  outer  end  ;  they  are  about  2  feet 
in  length  and  exceed  800  in  number.  These  tubules  run  toward  the  mediastinum,  those  in  one 
compartment  uniting  at  an  acute  angle  with  each  other,  to  form  a  smaller  number  of  narrower 
straight  tubules — tubuli  recti  (Fig.  632).  These  straight  tubules  open  into  a  network  of  tubules 
in  the  mediastinum  to  form  the  rete  testis,  a  dense  network  of  tubules  of  irregular  diameter  (Fig. 
632).  From  this  network  there  proceed  12  to  15  wider  ducts,— the  vasa  efferentia — which  after 
emerging  from  the  testis  are  at  first  straight,  but  soon  become  convoluted — and  form  a  series  of 
conical  eminences — the  coni  vascu- 

losi — which  together  form  the  head  -"^i*^-  "32. 

of    the    epididymis.     These    tubes  T.  albuginea. 

gradually  unite  with  each  other  and 
form  the  body  and  globus  minor  of  the 
epididymis,  which,  when  unraveled, 
is  a  tube  about  20  feet  long,  terminat- 
ing in  the  vas  deferens  (2  feet  long), 
which  is  the  excretory  duct  of  the 
testis.] 

[Structure  of  a  Tubule. — The 
seminal  tubules  consist  of  a  thick, 
well-marked  basement  membrane, 
composed  of  flattened  nucleated  cells 
arranged  like  membranes  (Fig.  637). 
These  tubes  are  lined  by  several 
layers  of  more  or  less  cubical  cells ; 
there  is  an  outer  row  of  such  cells 
next  the  basement  membrane,  and 
often  showing  a  dividing  large 
nucleus.  Internal  to  these  are  several 
layers  of  inner  large  clear  cells,  with 
nuclei  often  dividing,  so  that  they  form 
many  daughter  cells  which  lie  internal 
to  them  and  next  the  lumen.  From 
these  daughter  cells  are'  formed  the 
sperm a'.ozoa,  and  they  constitute  the 
spermatoblasts.  These  several 
layers  of  cells  leave  a  distinct  lumen. 
The  tubuli  recti  are  narrow  in  diame- 
ter, and  lined  by  a  single  layer  of 
squamous  or  flattened  epithelium 
(Fig.  633).  The  rete  testis  consists 
merely  of  channels  in  the  fibrous 
stroma  without  a  distinct  memhrana 
propria,  but  lined  by  flattened  epithe- 
lium. The  vasa  efferentia  and  coni 
vasculosi  have  circular  smooth  mus- 
cular fibres  in  their  walls,  and  are 
lined  by  a  layer  of  columnar  ciliated 
epithelium  with  striated  protoplasm. 
At  the  bases  of  these  cells  in  some 
parts  is  a  layer  of  smaller  granular 
cells.  These  tubules  form  the  epi- 
didymis, whose  tubules  have  the 
same  structure  (Fig.  634).  In  sheep, 
pigment  cells  are  often  found  in  the 
basement  membrane.  The  vas  deferens  is  lined  by  several  layers  of  columnar  epithelium  resting 
on  a  dense  layer  of  fibrous  tissue — the  mucosa.  Outside  this  is  the  muscular  coat,  a  thick  layer 
of  non-striped  muscle  composed  of  a  thick  inner  circular,  and  thick  outer  longitudinal  layer,  a  thin 
submucous  coat  connecting  the  muscular  and  mucous  coats  together;  outside  all  is  the  fibrous 
adventitia.] 

[The  interstitial  tissue  (Fig.  632),  supportiijg  the  seminal  tubules,  is  laminated  and  covered 
by  endothelial  plates,  with  slits  or  spaces  between  the  lamellae,  which  form  the  origin  of  the  lym- 
phatics.    These  lymph  spaces  are  easily  injected  by  the  puncture  method.     In  fact,  if  Berlin  blue 

57 


Septum. 


Transverse  section  of  the  testis  (low-power  view 


898 


CHEMICAL   COMPOSITION    OF    THE    SEMINAL   FLUID. 


be  forced  into  the  testis,  the  lymphatics  of  the  testis  and  spermatic  cord  are  readily  filled  with  the 
injection.  In  some  animals  (boar^l,  and  to  a  less  extent  in  man,  dog,  there  are  also  fairly  large  poly- 
hedral interstitial  cells,  often  with  a  large  nucleus  and  sometimes  pigmented.  They  represent 
the  residue  of  the  epithelial  cells  of  the  Wollhan  bodies  (A'/f/M),  or,  according  to  Waldeyer,  they  are 
plasma  cells.  Tlie  blood  vessels  are  numerous,  and  form  a  dense  plexus  outside  the  basement 
ineml)rane  of  the  seminal  tubules.] 

Chemical  Composition. — The  seminal  fluid,  as  discharged  from  the 
urethra,  is  mixed  with  the  secretion  of  the  glands  of  the  vas  deferens,  Cowper's 
glands,  and  those  of  the  prostate,  and  with  the  fluid  of  the  vesiculic  seminales. 
Its  reaction  is  neutral  or  alkaline,  and  it  contains  82  per  cent,  of  water,  serum 
albumin,  alkali  albuminate,  nuclein.  lecithin,  cholesterin,  fats  (protamin  ?),  phos- 
phorized  fat,  salts  (2  per  cent.),  especially  phosphates  of  the  alkalies  and  earths, 
together  with  sulphates,  carbonates,  and  chlorides.  The  odorous  body,  whose 
nature  is  unknown,  was  called  ^'  spermatin  "  by  Vauquelin. 

Seminal  Fluid. — The  sticky,  whitish-yellow  seminal  fluid,  largely  composed  of  a  mixture  of  the 
secretions  of  the  above-named  glands,  when  exposed  to  the  air,  becomes  more  fluid,  and  on  adding 

Fir..  6??. 


Tubulus 
rectus. 


End  of 
convolu- 
ted tube. 


Narrow 
part. 


Fig.  63t. 


Bloodvessel. 


Rete 

testis. 


Convoluted  seminal 
opening  into  a 
straight  tube. 


tubule 
narrow 


Blood  vessel 

Interstitial  — 
connective 
tissue. 


Transverse  section  of  the  tubules  of  the  epi- 
didymis. 


water  it  becomes  gelatinous,  and  from  it  separate  whitish  transparent  flakes.  When  long  exposed, 
it  forms  rhomboidal  crystals,  which,  according  to  Schreiner,  consist  of  phosphatic  salts  with  an  organic 
base  (C.II-N).  These  crystals  (Fig.  635)  are  said  to  be  derived  from  the  prosta'ic  fluid,  and  are 
identical  with  the  so-called  Charcot's  cr)-stals  (Fig.  149,  c,  and  iJ  138).  The  prostatic  fluid  is  thin, 
milky,  amphoteric,  or  of  slightly  acid  reaction,  and  is  possessed  of  the  seminal  odor.  The  phos- 
phoric acid  necessary  for  the  formation  of  the  cry.stals  is  obtained  from  the  seminal  fluid.  A  some- 
what similar  odor  occurs  in  the  albumin  of  eggs  not  quite  fresh.  The  non-poisonous  ptomain, 
cadaverin  (pentamethyldiamin  of  LanJenhurg),  isolated  by  Brieger  from  dead  bodies,  has  a  similar 
odor.     The  secretion  of  the  vesiculae  seminales  of  the  guinea-pig  contains  much  fibrinogen  (p.  424). 

The  spermatozoa  are  50/7.  long,  and  consist  of  a  flattened  pear-shaped  head 
(Fig.  636,  I  and  2,  k),  which  is  followed  by  a  rod-shaped  middle  piece,  w 
(Schweigger-Seidel'),  and  a  long  tail-like  prolongation  or  cilium,/.  The  sperma- 
tozoon is  propelled  forward  by  the  to-and-fro  movements  of  the  tail,  at  the  rate  of 
0.05  to  0.5  mm.  per  second  ;  the  moverrient  is  most  rapid  immediately  after  the 
fluid  is  shed,  but  it  gradually  becomes  feebler. 


SPERMATOZOA. 


899 


Fig.  635. 


Finer  Structure. — The  observations  of  Jensen  have  shown  that  the  middle  piece  and  head  are 
still  more  complex,  although  this  is  not  the  case  in  human  spermatozoa  and  those  of  the  bull  [G. 
Jietzius).  These  consist  of  a  flattened,  long,  narrow,  transparent,  protoplasmic  mass,  with  a  fibre 
composed  of  many  delicate  threads  in  both  margins.  At  the  tip  of  the  tail  both  fibres  unite  into  one. 
The  fibre  of  the  one  margin  is  generally  straight,  the  other  is  thrown  into  wave-like  folds,  or  winds 
in  a  spiral  manner  round  the  other  (  W.  Kranse,  Gibbes).  G.  Retzius  describes  a  special  terminal 
filament  (Fig.  636,  e).  An  axial  thread  surrounded  by  an  envelope  of  protoplasm,  traverses  the 
middle  piece  and  the  tail  [Einier,  v.  Braun).  [Leydig  showed  that  in  the  salamander  there  is  a 
delicate  membrane  attached  to  the  tail,  and  Gibbes  has  described  a  spiral  thread  attached  to  the  head 
(newt)  and  connected  with  the  middle  piece  by  a  hyaline  membrane.] 

Motion  of  the  Spermatozoa. — [After  the  discharge  of  the  seminal  fluid,  the  spermatozoa 
exhibit  spontaneous  movements  for  many  hours  or  days.]  The  movements  are  due  to  the  lash- 
ing movements  of  the  tail,  which  moves  in  a  circle  or  rotates  on  its  long  axis,  the  impulse  to  move- 
ment proceeding  from  the  protoplasm  of  the  middle  piece  and  the  tail,  which  seem  to  be  capable  of 
moving  when  they  are  detached  [^Evner).  These  movements  are  comparable  to  those  that  occur  in 
cilia  (g  292),  and  there  are  transition  forms  between  ciliary  and  amoeboid  movements,  as  in  the 
Monera.  Reagents. — Within  the  testis  they  do  not  exhibit  movement,  as  the  fluid  is  not  sufficiently 
dilute  to  permit  them  to  move.  Their  movements  are  specially  lively  in  the  normal  secretion  of 
the  female  sexual  organs  [Bischoff),  and  they  move  pretty  freely,  and  for  a  long  time,  in  all  normal 
animal  secretions  except  saliva.  Their  movements  are  paralyzed  by  water,  alcohol,  ether,  chloro- 
form, creosote,  gum,  dextrin,  vegetable  mucin,  syrup  of  grape  sugar,  or  very  alkaline  or  acid  uterine 
or  vaginal  mucus  i^Donne),  acids  and  metallic  salts,  and  a  too  high  or  too  low  temperature.  The 
narcotics,  as  long  as  they  are  chemically  indifferent,  behave  as  indifferent  fluids,  and  so  do  medium 
solutions  of  urea,  sugar,  albumin,  common  salt,  glycerin,  amygdalin,  etc.;  but  if  these  be  too  dilute 
or  too  concentrated,  they  alter  the  amount  of  water 
in  the  spermatozoa  and  paralyze  them.  The  qui- 
escence produced  by  water  may  be  set  aside  by 
dilute  alkalies  (  Virchow),  as  with  cilia  (p.  501). 
Engelmann  finds  that  minute  traces  of  acids,  alco- 
hol, and  ether  excite  movements.  The  spermato- 
zoa of  the  frog  may  be  frozen  four  times  in  succes- 
sion without  killing  them.  They  bear  a  heat  of 
43.75°  C,  and  they  will  live  for  70  days  when 
placed  in  the  abdominal  cavity  of  another  frog 
(^Mantegazzd). 

Resistance. — Owing  to  the  large  amounts  of 
earthy  salts  which  they  contain,  when  dried  upon 
a  microscopical  slide,  they  still  retain  their  form 
(  Valentin).  Their  form  is  not  destroyed  by  nitric, 
sulphuric,  hydrochloric,  or  boiling  acetic  acid,  or 
by  caustic  alkalies  ;  solutions  of  NaCl  and  salt- 
petre (10 to  15  per  cent.)  change  them  into  amor- 
phous masses.  Their  organic  basis  resembles  the 
semi-solid  albumin  of  epithelium. 

Seminal  fluid,  besides  spermatozoa,  also  con- 
tains seminal  cells,  a  few  epithelial  cells  from 
the  seminal  passages,  numerous  lecithin  granules, 
stratifled  amyloid  bodies  (inconstant),  granular 
yellow  pigment,  especially  in  old  age,  leucocytes, 
and  sperma  crystals  {^Fiir binge j-). 

Development  of  Spermatozoa. — The  walls  of  the  seminal  tubules,  n,  which 
are  made  up  of  spindle-shaped  cells,  are  lined  by  a  nucleated,  protoplasmic  layer 
(Fig.  637,  I,  b,  and  IV,  }i),  from  which  there  project  into  the  lumen  of  the  tube 
long  (0.053  mm.),  column-like  prolongations  (I,  c,  and  II,  III,  IV),  which  break 
up  at  their  free  end  into  several  round  or  oval  lobules  (II) — the  spermatoblasts 
{v.  Ebner)\  these  consist  of  soft,  finely  granular  protoplasm,  and  usually  have  an 
oval  nucleus  in  their  lower  part.  During  development,  each  lobule  of  the  sper- 
matoblast elongates  into  a  tail  (IV,  r),  while  the  deeper  part  forms  the  head  and 
middle  pieces  of  the  future  spermatozoon  (IV,  ^).  At  this  stage  the  spermatoblast 
is  like  a  greatly  enlarged,  irregular,  cylindrical,  epithelial  cell.  When  develop- 
ment is  complete,  the  head  and  middle  piece  are  detached  (III,  t),  and  ultimately 
the  remaining  part  of  the  spermatoblast  undergoes  fatty  degeneration.  Not  un- 
frequently  in  spermatozoa  we  may  observe  a  small  mass  of  protoplasm  adhering  to 


Crj'stals  from  spermatic  fluid. 


900 


DEVELOPMENT   OF    SPERMATOZOA. 


the  tail  and  the  middle  piece  (III,  /).     Between  the  spermatoblasts  are  numerous 
round  ama>boid  cells  devoid  of  an  envelope,  and  connected  to  each  other  by  pro- 


Fir,.  6^,6. 


Sper.Tiatozoa.  i,  human  (X  600),  ihc  head  seen  Iruui  the  side  ;  2,  on  edge  ;  k,  head  ;  ;//,  middle  piece  ;  /,  tail.;  e, 
terminal  filament;  3,  from  the  mouse  :  4,  bothriocephalus  latus  ;  5,  deer:  6,  mole;  7,  green  woodpecker;  8,  black 
swan  ;  9,  from  a  cross  between  a  goldfinch  (M)  and  a  canary  (F) ;  10,  from  cobitis. 

ces  65.  They  seem  to  secrete  the  y?///V/part  of  the  semen,  and  they  may  therefore 
be  called  seminal  cells  (I,  s,  II,  III,  IV,  />).  A  sjiermatozoon,  therefore,  is  a 
detached,  independently  mobile  cilium  of  an  enlarged  eijithelial  cell.     Some  ob- 

Fin.  637. 


•""M-O^^ 


Semi-diagrammatic  spermatogenesis  :  I,  Transverse  section  of  a  seminal  tubule — a,  membrane  ;  b,  protoplasmic  inner 
lining ;  c,  spermatoblast ;  s,  seminal  cells.  II,  Unripe  spermatoblast— y.  rounded  clavate  lobules  ;  p,  seminal  cells. 
IV,  Spermatoblast,  with  ripe  spermatozoa  (k)  not  yet  detached  ;  tail,  r  ;  «,  wall  of  the  seminal  tubule  ;  h,  its  pro- 
toplasmic layer.     Ill,  Spermatoblast  with  a  spermatozoon  free,/. 

servers  adhere  to  the  view  that  the  spermatozoa  are,  in  part  at  least,  formed  within 
round  cells,  by  a  process  of  endogenous  development. 


STRUCTURE    OF   THE    OVARY. 


901 


Section  of  a  cat's  ovary.     The   place   of  attachment  or  hilum  is 
below.     On  the  left  is  a  corpus  luteum. 


According  to  Benda  and  v.  Ebner,  the  spermatoblasts  are  formed  by  the  coalescence  (copula- 
tion) of  a  group  of  seminal  cells  with  the  lower  part  of  the  foot  plate  and  stalk  of  the  spermato- 
blasts.    Each    seminal    cell    forms    firom 

its  nucleus  the    head,   and  from  its  pro-  yig    6''8 

toplasm  the  tail  of  a  spermatozoon. 
For  the  complete  formation  of  these 
])arts,  there  must  be  a  coalescence  of 
the  seminal  cells  with  the  spermato- 
blasts. 

Shape. — The  spermatozoa  of  most 
animals  are  like  cilia  with  larger  or 
smaller  heads.  The  head  is  elliptical 
(mammals),  or  pear-shaped  (mammals), 
or  cylindrical  (birds,  amphibians,  fish), 
or  corkscrew  (singing  birds,  paludina), 
or  merely  like  hairs  (insects — Fig.  636). 
Immobile  seminal  cells,  quite  different 
from  the  ordinary  forms,  occur  in  myria- 
poda  and  the  oyster. 

433.  THE  OVARY  —  OVUM  — 
UTERUS. — [Structure  of  the  Ovary. 

— The    ovary    consists    of  a    connective- 
tissue   framework,    with    blood   vessels, 
nerves,  lymphatics    and   numerous    non- 
striped   muscular  fibres.     The  ova  are  embedded  in  this   matrix  (Fig.  638).     The  surface  of  the 
ovary  is    covered  with  a   layer  of  columnar  epithelium   (Fig.   639,  e),  the  remains   of  the   germ 
epithelium.     The    most   super- 
ficial  layer   is   called   the    albu-  Fig    639. 
ginea ;  it  does  not    contain  any 
ova.     Below   it   is   the    cortical 
layer  of  Schron,  which  contains 
the    smallest     Graafian     follicles 
(1^0     inch— Fig.     638),     while 
deeper  down  are  the  larger  folli- 
cles (Jq  to  jig  inch).     There  are 
40,000  to  70,000   follicles  in  the 
ovary  of  a   female  infant.     Each 
ovum    lies    within    its  follicle   or 
Graafian  vesicle.] 

Structure  of  an  Ovum.  — 
The  human  ovum  (C  £.  v.  Bear, 
1827)  is  0.18  to  0.2  mm.  [xio  ^"0 
in  diameter,  and  is  a  spherical 
cellular  body  with  a  thick,  solid, 
elastic  envelope,  the  zona  pel- 
lucida,  with  radiating  strise  (Fig. 
640).  The  zona  pellucida  en- 
closes the  cell  contents  repre- 
sented by  the  protoplasmic,  gran- 
ular, contractile  vitellus  or  yelk, 
which  in  turn  contains  the  eccen- 
trirallv  nlared  =;nhprirnl  niiHeiiq  Section  ot  an  ovary.  ^,  germ  epithelmm ;  i,  large  sized  follicles ;  22, 
mcaiiy  piacea    spnerical    nucleus  middle  sized,  and  3,  3,  smaller  sized  follicles  ;  o,  ovum  within  a  Graafian 

or    germinal   vesicle   (40-50   /z  follicle;  v,  z/,  blood  vessels   of  the  stroma;^,  cells   of  the  membrana 

— Purkinje,  1825  ;     Coste,  1834).  granulosa. 

The    germinal    vesicle    contains 

the  nucleolus  or  germinal  spot  (5-7  {i — R.  Wagner,  1835).     The  chemical  composition  is  given 
in  \  232. 

[Ovum.  Cell 

Zona  pellucida  corresponds  to  the  Cell  wall. 

Vitellus  "  "       Cell  contents. 

Germinal  vesicle     "  "       Nucleus. 

Germinal  spot  "  "       Nucleolus.] 

[This  arrangement  shows  the  corresponding  parts  in  a  cell  and  the  ovum,  and  in  fact  the  ovum 
represents  a  typical  cell.] 

The  zona  pellucida  ^(Figs.  640,  641,  V,  Z),  to  which  cells  the  Graafian  folUcles  are  often 
adherent,  is  a  cuticular  membrane  formed  secondarily  by  the  follicle  i^PflUger).     According  to  Van 


902 


DEVELOPMENT    OF   Till-:    OVA. 


Beneden,  it 
original  cell 


is  lined  hy  a  thin  membrane  next  the  vitellus,  and  he  regards  the  thin  membrane  as  the 
membrane  of  the  ovum.     The  fine  radiating  stria'  in  the  zona  arc  said  to  be  due  to  the 

existence     of     numerous    canals 


Fig.  640. 

Cells  of  discus  proligerus. 


Ger- 
minal 
spots. 


Acces- 
sory nu- 
cleoli, 
alsoyC 


[A'olliker,  v.  Sc/ikn).  It  is  still 
undecided  whether  there  is  a 
special  tnicropyle  or  hole  for  the 
entrance  of  the  spermatozoa. 

A  micropyle  has  been  ob- 
served in  some  ova  (holothurians, 
many  fishes,  mussels).  The  ova 
of  some  animals  (many  insects, 
e.  g.,  the  tlea)  have  porous  canals 
in  some  part  of  their  zona,  and 
these  serve  both  for  the  entrance 
of  the  spermatozoa  and  for  the 
respiratory  exchanges  in  the  ovum. 


The  development  of 
the  ova  takes  place  in  the 
following  manner :  Tlie 
surface  of  the  ovary  is  cov- 
ered with  a  layer  of  cylin- 
drical epithelium — the  so- 
called  "  germ  epithe- 
lium " — and  between  these 
cells  lie  somewhat  spherical 
Ripe  ovum  of  rabbit.  "  primordial  ova  "  (Fig. 

641,  I,  a,  a).  The  epithe- 
lium covering  the  surface  dips  into  the  ovary  at  various  places  to  form  "  ovarian 
tubes"  (Fig.  683).  These  tubes,  from  and  in  which  the  ova  are  developed 
(  Waldeyer),  become  deeper  and  deeper,  and  they  contain,  in  their  interior,  large, 
single  spherical  cells  with  a  nucleus  and  a  nucleolus,  and  other  smaller  and  more 
numerous  cells  lining  the  tube.  The  large  cells  are  the  cells  (primordial  ova) 
that  are  to  develop  into  ova,  while  the  smaller  cells  are  the  epithelium  of  the  tube, 
and  are  direct  continuations  of  the  cylindrical  epithelium  on  the  surface  of  the 
ovary.  The  upper  extremities  of  the  tubes  become  closed,  while  the  tube  itself 
is  divided  into  a  number  of  rounded  compartments — snared  off,  as  it  were,  by  the 
ingrowth  of  the  ovarian  stroma  (I,  c).  Each  compartment  so  snared  off  usually 
contains  one,  or  at  most  two,  ova  (IV,  o,  0),  and  becomes  developed  into  a 
(iraafian  follicle.  The  embryonic  follicle  enlarges,  and  fluid  appears  within  it ; 
while  its  lateral  small  cells  become  changed  into  the  epitheliimi  lining  the  Graafian 
follicle  itself,  or  those  of  the  raembrana  granulosa.  The  cells  of  the  membrana 
granulosa  form  an  elevation  at  one  part — the  discus  proligerus — by  which  the 
ovum  is  attached  to  the  membrana  granulosa.  The  follicles  are  at  first  only  0.03 
mm.  in  diameter,  but  they  become  larger,  especially  at  puberty.  [The  smaller 
ova  are  near  the  surface  of  the  ovary,  the  larger  ones  deeper  in  its  substance 
(Fig.  639).]  When  a  Graafian  follicle  with  its  ovum  is  about  to  ripen  (IV), 
it  sinks  or  passes  downward  into  the  substance  of  the  ovary,  and  enlarges  at  the 
same  time  by  the  accumulation  of  fluid — the  liquor  folliculi — between  the  tunica 
and  membrana  granulosa.  It  is  covered  by  a  vascular  outer  membrane — the 
theca  folliculi — which  is  lined  by  the  e])itlielium  constituting  the  membrana 
granulosa  (IV,  ^).  When  a  Graafian  follicle  is  about  to  burst,  it  again  rises 
to  the  surface  of  the  ovary,  and  attains  a  diameter  of  i.o  to  1.5  mm.,  and  is  now 
ready  to  burst  and  discharge  its  ovum.  [The  tissue  between  the  enlarged  Graafian 
follicle  and  the  surface  of  the  ovary  gradually  becomes  thinner  and  thinner  and 
less  vascular,  and  at  last  gives  way,  when  the  ovum  is  discharged  and  caught  by 
the  fimbriated  extremity  of  the  Fallopian  tube  embracing  the  ovary,  so  that  the 
ovum  is  shed  into  the  Fallopian  tube  itself.]     Only  a  small  number  of  the  Graafian 


DEVELOPMENT   OF   THE    OVA. 


903 


follicles  undergo  development  normally,  by  far  the  greatest  number  atrophy  and 
never  ripen.  (The  study  of  the  development  of  the  ova  and  the  ovary  was  ad- 
vanced particularly  by  Martin  Barry,  Pfliiger,  Billroth,  Schron,  His,  Waldeyer, 
Kolliker,  Koster,  Lindgren,  Schulin,  Foulis,  Balfour  and  others.) 

According  to  Waldeyer,  the  mammalian  ovum  is  not  a  simple  cell,  but  a  compound  structure.  The 
original  primitive  ovum  is,  according  to  him,  formed  only  of  the  germinal  vesicle  and  germinal  spot, 
vi^ith  the  surrounding  membranous  clear  part  of  the  vitellus  (Fig.  641,  III).  The  remainder  of  the 
vitellus  is  developed  by  the  transformaiion  of  granulosa  cells,  which  also  form  the  zona  pellucida. 

Holobiastic  and  Meroblastic  Ova. — The  ova  of  frogs  and  cyclostomata  have  the  same  type  as 
mammalian  ova;  they  are  called  holobiastic  ova,  because  all  their  contents  go  to  form  cells  vv^hich 
take  part  in  the  formation  of  the  embryo.  In  contrast  with  these,  the  birds,  the  mono:remes  alone 
among  the  mammals  {Caldwell),  the  reptiles  and  the  other  fishes  have  meroblastic  ova  {Reicheri). 

Fig.  641. 


I,  An  ovarian  tube  in  process  of  development  (newborn  girl),  a,  a,  young  ova  between  the  epithelial  cells  on  the 
surface  of  the  ovary  ;  b,  the  ovarian  tube  with  ova  and  epithelial  cells  ;  c,  a  small  follicle  cut  off  and  enclosing  an 
ovum.  II,  Open  ovarian  tube  from  a  bitch.  Ill,  Isolated  primordial  ovum  (human).  IV,  Older  follicle  with 
two  ova  {o,  d)  and  the  tunica  granulosa  {g)  of  a  bitch.  V,  Part  of  the  surface  of  a  ripe  ovum  of  a  rabbit— s, 
zona  pellucida  ;  d,  vitellus  ;  e,  adherent  cells  of  the  membrana  granulosa.  VI,  First  polar  globule  formed.  VII, 
Formation  of  the  second  polar  globule  [Fol). 

The  latter,  in  addition  to  the  white  or  formative  yelk,  which  corresponds  to  the  yelk  of  the  holo- 
biastic eggs,  and  gives  rise  to  the  embryonic  cells,  contains  the  food-yelk  (yellow  in  birds),  which 
during  development  is  a  reserve  store  of  food  for  the  developing  embryo. 

Hen's  Egg. — The  small,  white,  round,  finely  granular  speck,  the  cicatricula,  blastoderm,  or 
tread,  which  is  2.5-3.5  i""^-  broad  and  0.28-0.37  thick,  lying  upon  the  surface  of  the  yellow  yelk, 
corresponds  to  the  contents  of  the  mammalian  ovum,  and  is,  therefore,  the  formative  yelk.  In  the 
cicatricula  lie  the  germinal  vesicle  and  spot  (Fig.  642).  From  the  tread  in  which  lie  the  charac- 
teristic white  yelk  elements,  processes  pass  into  the  yellow  yelk.  A  part  passes  as  an  exceedingly 
thin  layer  round  the  yelk,  or  cortical  protoplasm.  [The  cicatricula  in  an  unincubated  egg  is  always 
uppermost  whatever  the  position  of  the  egg,  provided  the  contents  can  rotate  freely,  and  this  is  due 
to  the  lighter  specific  gravity  of  that  part  of  the  yelk  in  connection  with  the  cicatricula.  In  a  fecun- 
dated egg  the  cicatricula  has  a  white  margin  (the  area  opaca),  smrrounding  a  clear  transparent 
area,  the  beginning  of  the  area  pellucida,  containing  an  opaque  spot  in  its  centre.  If  an  egg  be 
boiled  very  hard  and  a  section  made  of  the  yelk,  it  will  be  found  to  consist  of  alternating  layers  of 


904 


STRUCTURK    OF    A    HEN  S    EGG. 


white  and  yellow  yelk.  The  outermost  layer  is  a  thin  layer  of  white  yelk,  which  is  slightly  thicket 
at  the  margin  of  the  cicatricula.  Within  the  centre  of  the  yelk  is  a  flask-shaped  mass  of  white 
yelk,  the  neck  of  the  llask  being  connected  with  the  while  yelk  outside.  This  flask  shaped  mass 
does  not  become  so  hard  on  being  boiled,  and  its  upper  expandeil  end  is  known  as  the  "  nucleus  of 
Pander."  The  great  mass  of  the  yelk  is  made  up,  however,  of  yellow  yelk.]  Microscopically, 
the  yellow  yelk  consists  of  soft  yellow  spheres,  of  from  23-100  /i  in  diameter,  and  tlity  are  often 
polvhedral  from  mutual  pressure' (Fig.  643, /').  [They  are  very  delicate  and  non-nucleated,  but 
filled  with  fine  granules,  which  are,  perhaps,  proteid  in  their  nature,  as  they  are  in.soluble  in  ether 
and  alcohol.  They  are  developed  by  the  proliferation  of  the  granulosa  cells  of  the  Graalian  follicle, 
which  also  seem  ultimately  to  form  the  granulo-tibrous  double  envelope  or  the  vitelline  membrane 
{Eimt-r).  The  whole  yelk  of  the  hen's  egg  is  regarded  by  some  observers  as  c<|uivalent  to  the 
mammalian  ovum////.f  (he  corpus  luteum.  Microscopically,  the  white  yelk  consists  of  small  vesicles 
(5-75  ,")  containing  a  refractive  substance  and  larger  spheres  containing  several  smaller  spherules 
(Fig.  643,  a).  The  whole  yelk  is  enveloped  by  the  vitelline  membrane,  which  is  transparent, 
but  possesses  a  fine  fibrous  structure,  and  it  .seems  to  be  allied  to  elastic  tissue.] 

When  the  yelk  is  fully  developed  within  the  Clraafian  follicles  of  the  hen's  ovarium,  the  follicle 
bursts  and  discbarges  the  yelk,  which  passes  into  the  oviduct,  where  in  its  passage  it  rotates,  owing 
to  the  direction  of  the  folds  of  the  mucous  membrane  of  the  oviduct.  The  numerous  glands  of  the 
oviduct  secrete  the  albumin,  or  white  of  the  egg,  which  is  deposited  in  layers  around  the  yelk  in 
its  passage  along  the  duct,  and  forms  at  the  anterior  and  posterior  chalazae.  [The  chalazae  are 
two  twisted  cords  composed  of  twisted  layers  of  the  outer  denser  part  of  the  albumin.     They  extend 


Fig.  642. 


Fig.  643. 


Blastoderm. 


Its  processes. 


Scheme  of  a  meroblastic  egg. 


a,  White  ;  6,  yellow  yelk  granules. 


from  the  poles  of  the  yelk  not  quite  to  the  outer  part  of  the  albumin.]  [The  albumin  is  invested 
by  the  membrana  testacea,  or  shell  membrane,  which  is  composed  of  two  layers — an  outer 
thicker  and  an  inner  thinner  one  (Fig.  644).  Over  the  greater  part  of  the  albumin  these  two  layers 
are  united,  but  at  the  broad  end  of  the  hen's  egg  they  tend  to  separate,  and  air  passing  through  the 
porous  shell  separates  thein  more  and  more  as  the  fluid  of  the  egg  evaporates.  This  air  space  is  not 
found  in  fresh-laid  eggs.]  The  layers  consist  of  spontaneously  coagulated  keratin-like  fibres 
arranged  in  a  spiral  manner  around  the  albumin  ^Lindvall  and  Ilamarsien).  [F^xternal  to  this  is 
the  test,  or  shell,  which  consists  of  an  organic  matrix  impregnated  with  lime  salts.]  The  shell 
consists  of  albumin  impregnated  with  lime  salts,  which  form  a  very  porous  mortar.  [The  shell  is 
porous,  and  its  inner  layer  is  perforated  by  vertical  canals,  through  which  the  respiratory  exchange 
of  the  gases  can  take  place.]  In  the  eggs  of  .some  birds  there  is  an  outer,  structureless,  porous, 
slimy,  or  fatty  cuticula.  The  shell  is  secreted  in  the  lower  part  of  the  oviduct.  The  shell  is  partly 
used  up  for  the  development  of  the  bones  of  the  chick  [Pt-oiit,  Gritwe,  although  this  is  denied  by 
Poll  and  Preyei-).  The  pigment  which  often  occurs  in  many  layers  of  the  surface  of  the  eggs  of 
some  birds  appears  to  be  a  derivative  of  haemoglobin  and  biliverdin. 

Chemical  Composition, — The  yellow  yelk  is  alkaline,  and  colored  yellow  owing  to  the  pres- 
ence of  lutein,  which  contains  iron.  It  contains  several  proteids  [including  a  globulin  body  called 
vitellin  (p.  424)],  a  body  resembling  nuclein,  lecithin,  vitellin,  glycerin-phosphoric  acid,  choles- 
terin,  olein,  palmitin,  dextrose,  potassic  chloride,  iron,  earthy  phosphates,  fluoric  and  .silicic  acids. 
The  presence  of  cerebrin,  glycogen,  and  starch  is  uncertain.      [Dareste  states  that  starch  is  present.] 


STRUCTURE    OF   THE    UTERUS. 


905 


[The  albumin  of  egg  contains — water,  86  per  cent.;   proteids,  12;   fat  and  extractives,  1.5; 
saline  matter,  including  sodic  and  potassic  chlorides,  phosphates,  and  sulphates,  .5  per  cent.] 

[The  uterus,  a  thick,  hollow  muscular  organ,  is  covered  externally  by  a  serous  coat,  and  lined 

Fig.  645. 


Fowl's  egg'after  thirty  hours'  incubation,  a,  shell ;  /', 
shell  membrane ;  i',  air  chamber;  c,  boundary 
between  outer  and  middle  portion  of  albumin  ;  d, 
more  fluid  albumin;  e,  chalazae;  v,  yelk;  av, 
area'opaca;  ao,  area  vasculosa,  and  in  its  centre 
is  the  embrj'O.  ; 


Vertical  section  of  the  mucous  membrane  of  the  human 
uterus,  e,  columnar  epithelium,  the  cilia  absent  ;  £■£■, 
utricular  glands  ;  ci.  intra-glandular  connective  tissue  ; 
21V,  blood  vessels  ;  mm,  muscularis  mucosae. 

Fig.  646. 


Left  broad  ligament.  Fallopian  tube,  ovary,  and  parovarium,     a,  uterus  ;  5,  isthmus  of  Fallopian  tube;  c,  ampulla; 
^,  fimbriated  end  of  the  tube,  with  the  parovarium  to  its  right ;  e,  ovary  ;  y,  ovarian  ligament. 

internally  by  a  mucous  membrane,  while  between  the  two  is  the  thick  muscular  coat  com- 
posed of  j^smooth  muscular  fibres  arranged  in  a  great  number  of  layers  and  in  different  directions. 


906 


FALLOPIAN    TUBES. 


The  mucous  membrane  of  the  body  of  the  uterus  in  the  unimpregnated  condition  has  no  folds, 
while  the  muscularis  mucosae  is  very  well  developed,  and  forms  a  great  part  of  the  uterine  muscular 
wall.  The  mucous  membrane  is  lined  by  a  single  layer  of  columnar  ciliated  ejiithelium.  A  vertical 
section  shows  the  mucous  memlrane  to  contain  numerous  tubular  glands  (Kig.  645)— the  uterine 
glands — which  branch  toward  tlieir  lower  ends.  They  have  a  membrana  propria,  and  are  lined 
by  a  single  layer  of  ciliated  epithelium,  a  small  lumen  being  left  in  the  centre.  The  utricular 
glands  are  not  formed  during  intrauterine  life  {T/t/nfr),  nor  are  there  any  glands  in  the  human 
uterus  at  birth  {(J./.  Engelmann).     There  are  numerous  slit-like  lymphatic  spaces  in  the  mucous 

Fic.  647. 


Transverse  section  of  the  Fallopian  tube. 

membrane  {Leopold^,  which  communicate  with  well-marked  lymphatic  vessels  existing  in  this  and 
the  other  layers  of  the  organ.  In  the  cervix,  the  mucous  membrane  is  folded,  presenting  in  the 
virgin  the  appearance  known  as  the  arbor  vitx.  The  external  surface  of  the  vaginal  part  of  the 
neck  is  covered  by  stratified  squamous  epithelium,  like  the  vagina.] 

[The  Fallopian  tubes  are  really  the  ducts  of  the  ovaries  (Fig.  646).  They  consist  of  a  serous, 
muscular  (an  external  longitudinal,  and  an  internal  circular)  layer  of  non-striped  muscle,  and  a 
mucous  layer  thrown  into  many  folds  and  lined  by  a  single  layer  of  ciliated  columnar  epithelium, 
but  no  glands  (Fig.  647).] 

434.  PUBERTY. — The  term  puberty  is  applied  to  tlie  period  at  which  a 
human  being  becomes  capable  of  procreating,  which  occurs  from  the  13th  to  15th 
years  in  the  female,  and  the  14th  to  i6th  in  the  male.  In  warm  climates,  puberty 
may  occur  in  girls  even  at  8  years  of  age.  Toward  the  40th  to  50th  year,  the  pro- 
creative  faculty  ceases  in  the  female  with  the  cessation  of  the  menses;  this  con- 
stitutes the  menopause  or  grand  climacteric,  while  in  man  the  formation  of 
seminal  fluid  has  been  observed  up  to  old  age.  From  the  period  of  puberty  onward, 
the  sexual  appetite  occurs,  and  the  ripe  ova  are  discharged  from  the  ovary.  [But 
ova  are  discharged  even  before  puberty  or  menstruation  has  occurred.]  At  puberty, 
the  internal  and  external  generative  organs  and  their  annexes  become  more  vas- 
cular and  undergo  development ;  the  pelvis  of  the  female  assumes  the  character- 
istic female  shape.  For  the  changes  in  the  mammse  see  §  230.  At  the  same  time 
hair  is  developed  on  the  pubes  and  axilla,  and  in  the  male  on  the  face,  while  the 
sebaceous  glands  become  larger  and  more  active. 

Other  changes  occur,  especially  in  the  larynx.  In  the  boy  the  larynx  elongates  in  its  antero- 
posterior diameter,  the  thyroid,  or  Adam's  apple,  becomes  more  prominent,  while  the  vocal  cords 
lengthen,  so  that  the  voice  is  hoarse,  or  husky,  or  "  breaks,"  the  voice  being  lowered  at  least  an 
octave.  In  the  female  the  lar\nx  becomes  longer,  while  the  compass  of  the  voice  is  increased. 
The  vital  capacity  (|  io8\  corresponding  to  the  increase  in  the  size  of  the  chest,  undergoes  a  con- 
siderable increase;  the  whole  form  and  expression  assume  the  characteristic  sexual  appearance, 
while  the  psychical  energies  also  receive  an  impulse. 


SIGNS    OF    MENSTRUATION. 


907 


435.  MENSTRUATION.— External  Signs.— At  regular  intervals  of 
time,  of  27^-28  days  in  a  mature  female,  there  is  a  rupture  of  one  or  more  ripe 
Graafian  follicles,  while  at  the  same  time  there  is  a  discharge  of  blood  from  the 
external  genitals.  This  is  known  as  the  process  of  menstruation  (or  menses,  cata- 
menia,  or  periods).  Most  women  menstruate  during  the  first  quarter  of  the  moon, 
and  only  a  few  at  new  and  full  moon  {Strohl').  In  mammals,  the  analogous  con- 
dition is  spoken  of  as  the  period  of  heat  [or  the  "  rut "  in  deer].  There  is  a  slightly 
bloody  discharge  from  the  external  genitals  in  carnivora,  the  mare  and  cow  {Aris- 
totle), while  apes  in  their  wild  condition  have  a  well-marked  menstrual  discharge 
{Neiibert^.  [Observations  on  cases  where  abdominal  section  has  been  performed 
have  shown  that  the  Graafian  follicles  mature  and  burst  at  any  time  {Lawson  Tait, 
Leopold').'] 

The  onset  of  menstruation  is  usually  heralded  by  constitutional  and  local  phenomena — there  is 
an  increased  feeling  of  congestion  in  the  internal  generative  organs,  pain  in  the  back  and  loins,  ten- 
sion in  the  region  of  the  uterus  and  ovaries,  which  are  sensitive  to  pressure,  fatigue  in  the  limbs, 
alternate  feeling  of  heat  and  cold,  and  even  a  slight  increase  of  the  temperature  of  the  skin  [Kersch). 
There  may  be  retardation  of  the  process  of  digestion  and  variations  in  the  evacuation  of  the  faeces 
and  urine,  and  in  the  secretion  of  sweat.  The  discharge  is  sli?ny  at  first,  and  then  becomes  bloody, 
lasting  three  to  four  days ;  the  blood  is  venous,  and  shows  little  tendency  to  coagulate,  provided  it  is 
mixed  with  much  alkaline  mucus  from  the  genital 

passages  ;  but,  if  the  hemorrhage  be  free,  the  blood  Yio.  648.  Fig.  640. 

may  be  clotted.     The  quantity  of  blood  is  100  to 
200  grms.      [The  blood  contains  many  white  blood 

corpuscles  and  epithelial  cells.]     After  cessation  of          -  . 

the  discharge  of  blood  there  is  a  moderate  amount          /  \ 

of  mucus  given  off.  /  

The  characteristic  internal  phenomena 
which  accompany  menstruation  are :  (i) 
The  changes  in  the  uterine  mucous  mem- 
brane ;  and  (2)  the  rupture  of  the  Graafian 
follicle. 

1.  Changes  in  the  uterine  mucous 
membrane. — The  uterine  mucous  mem- 
brane is  the  chief  source  of  the  blood.  The 
ciliated  epithelium  of  the  congested,  swol- 
len, and  folded,  soft,  thick  (3  to  6  mm.) 
mucous  membrane  is  shed.  The  orifices  of 
the  numerous  mucous  glands  of  the  mucous 
membrane  are  distinct,  the  glands  enlarge, 
and  the  cells  undergo  fatty  degeneration, 
and  so  do  the  tissue  and  the  blood  vessels 
lying  between  the  glands.  The  tissue  con- 
tains more  leucocytes  than  normal.  This 
fatty  degeneration  and  the  excretion  of  the 
degenerated  tissue  occur,  however,  only  in 
the  superficial  layers  of  the  mucosa,  whose 
blood  vessels,  when  torn  across,  yield  the 
blood.  The  deeper  layers  remain  intact,  and  from  them,  after  menstruation  is 
over,  the  new  mucous  membrane  is  developed  {Kundrai  and  G.  J.  Engelmanft). 
[Leopold  denies  the  existence  of  this  fatty  degeneration.  According  to  Williams, 
the  entire  mucous  membrane  is  removed  at  each  menstrual  period,  and  it  is  regen- 
erated from  the  muscular  coat  (Fig.  649).  The  mucous  membrane  of  the  cervix 
remains  free  from  these  changes.] 

2.  Ovulation. — The  second  important  internal  phenomenon  is  ovulation,  in 
which  process  the  ovary  becomes  more  vascular — the  ripe  follicle  is  turgid  with 
fluid,  and  in  part  projects  above  the  surface  of  the  ovary.     The  follicle  ultimately 


Diagram  of  the  uterus  j  ust 
before  menstruation. 
The  shaded  portion 
represents  the  mu- 
cous membrane. 


Uterus  when  menstrua- 
tion has  just  ceased, 
showing  the  cavity  of 
the  body  deprived  of 
mucous  membrane 
(J.  WiUiams). 


908 


THEORIES   OF   OVULATION. 


bursts,  its  membranes  and  the  epithelium  covering  of  the  ovary  are  torn  or  give 
way  under  the  pressure,  the  bursting  being  accompanied  by  the  discharge  of  a 
small  amount  of  blood.  At  the  same  time,  the  congested,  turgid,  and  erected 
fimbriated  extremity  of  the  Fallopian  tube  is  applied  to  the  ovary,  so  that  the  dis- 
charged ovum,  with  its  adherent  granulosa  cells,  and  the  liquor  foUiculi,  are  caught 
by  the  funnel-shaped  extremity  of  the  tube  (Fig.  646).  The  ovum,  when  dis- 
charged, is  carried  toward  the  uterus  by  the  ciliated  epithelium  (§  433)  of  the  tube, 
and  perhaps  also  partly  by  the  contraction  of  its  muscular  coat.  Ducalliez  and 
Kiiss  found  that,  by  fully  injecting  the  blood  vessels,  they  could  imitate  the  erection 
of  the  Fallopian  tube.  Rouget  points  out  that  the  non-striped  muscle  of  the  broad 
ligaments  may  cause  constriction  of  the  vessels,  and  thus  secure  the  necessary 
injection  of  the  blood  vessels  of  the  Fallopian  tube. 

Pfliiger's  Theory. — There  are  two  theories  as  to  the  connection  between  ovulation  or  the  dis- 
charge of  an  ovum  and  the  escape  of  blood  from  the  uleiine  mucous  membrane.  Pfliiger  regards  the 
bloody  discharge  from  the  superficial  layers  of  the  uterine  mucous  membrane  as  a  phy.'-ioiogical  prepa- 
ration or  "  freshening"'  of  the  tissue  (in  the  surgical  sense),  by  which  it  will  be  prepared  to  receive 
the  ovum  when  the  latter  reaches  the  uterus,  so  that  union  can  lake  place  between  the  ovum  and  the 
freshly-exposed  surface  of  the  mucous  membrane,  and  thus  the  ovum  will  receive  nourishment  from 
a  new  surface. 

Reichert's  Theory. — This  view  is  opposed  to  that  of  Reichert,  Engelmann,  Williams,  and  others. 
According  to  Reichert's  theory,  before  an  ovum  is  discharged  at  all  there  is  a  sympathetic  change 

in  the  uterine  mucous  membrane,  wherel)y 


Fig.  650. 


Fresh  corpus  luteum. 


it  becomes  more  vascular,  more  spongy,  and 
swollen  up.  The  mucous  membiane  so  al- 
tered is  spoken  of  as  the  tneinbrana  decidua 
tiienstrudlis,  and  from  its  nature  it  is  in  a 
proper  condition  to  receive,  retain,  and  nour- 
ish a  ferlilized  ovum  which  may  come  into 
contact  with  it.  If  the  ovum,  however,  be 
layer  and  tunica  propria,  not  fertilized,  and  escape  from  the  genital 
passages,  then  the  uterine  mucous  membrane 
degenerates,  and  blood  is  shed  as  above 
described.  According  to  this  view,  the  hem- 
orrhage  from  the  uterine  mucous  membrane 
is  a  sign  of  the  non-occurrence  of  pregnancy  ; 
the  mucous  membrane  degenerates  because 
it  is  not  required  for  this  occasion ;  the  men- 
FlG.  651. 


Stroma  of  ovary. 

Outer  layer  of  follicle. 
Vessels  between  outer 


Folded  and  thickened 
tunica  propria. 


(  Corpus 

1  luteum 

-<  with  a 

/  fibrous 


Stroma 
of  ovary 
with 
blood- 
vessels. 


Fig.  652. 


Lutein  cells  from  the  corpus  luteum  of 
cow. 


Corpus  luteum  of  cow  (;< 


stnial  blood  is  an  external  sign  that  the  ovum  has  not  been  impregnated.  So  that  pregnancy,  i.e., 
the  development  of  the  embryo  in  utero,  is  to  be  calculated,  not  from  the  last  menstruation,  but  from 
some  time  between  the  last  menstruation  and  the  period  which  does  not  occur. 


ERECTION    OF   THE    PENIS. 


909 


In  some  cases  the  ovulation  and  the  formation  of  the  decidua  menstrualis  occur  separately,  so  that 
there  may  be  menstruation  without  ovulation,  and  ovulation  without  menstruation. 

Corpus  Luteum. — When  a  Graafian  follicle  bursts,  it  discharges  its  contents  and  collapses ;  in 
the  interior  are  the  remains  of  the  membrana  granulosa  and  a  small  efiusion  of  blood,  which  soon 
coagulates.  The  small  rupture  soon  heals,  after  the  serum  is  absorbed.  The  vascular  wall  of  the 
follicle  swells  up.  Villous  prolongations  or  granulations  of  young  connective  tissue,  rich  in 
capillaries  and  cells,  grow  into  the  interior  of  the  follicle  (Fig.  651).  Colorless  blood  corpuscles 
also  wander  into  the  interior.  At  the  same  time  the  cells  of  the  granulosa  proliferate,  and  form 
several  layers  of  cells,  which  ultimately,  after  the  disappearance  of  a  number  of  blood-vessels 
undergo  fatty  degeneration,  lutein,  and  fatty  matter  being  formed,  and  it  is  this  mass  which 
gives  the  corpus  luteum  its  yellow  color  (Fig.  652).  The  capsule  becomes  more  and  more  fused 
with  the  ovarian  stroma.  If  pregnancy  does  not  take  place  after  the  menstruation,  then  the  fatty 
matter  is  rapidly  absorbed,  and  the  effused  blood  is  changed  into  haematoidin  (§  20)  and  other  deriva- 
tives of  hemoglobin,  while  there  is  a  gradual  shriveling  of  the  whole  mass,  which  is  complete  in  about 
four  weeks,  only  a  very  small  remainder  being  left.  Such  a  corpus  luteum  i.e.,  one  not  accompanied 
by  pregnancy,  is  called  a  false  corpus  luteum.  If,  however,  pregnancy  occurs,  then  the  corpus 
luteum,  instead  of  shriveling,  grows  and  becomes  a  large  body,  especially  at  the  third  and  fourth 
month,  the  walls  are  thicker,  the  color  deeper,  so  that  the  corpus  luteum  at  the  period  of  delivery 
may  be  6  to  10  mm.  in  diameter,  and  its  remains  may  be  found  in  the  ovary  for  a  very  long  time 
thereafter  (Fig.  651).  This  form  is  sometimes  spoken  of  as  a  true  corpus  luteum.  [We  cannot 
draw  a  sharp  distinction  between  these  two  forms.]  Only  a  very  small  number  of  the  ova  in 
the  ovary  undergo  development  and  are  discharged;  by  far  the  greater  number  degenerate 
iySlavjaiisky'). 

436.  PENIS — ERECTION. — Penis. — [The  penis  is  composed  of  the  two  long  cylindrical  cor- 
pora cavernosa,  the  corpus  spongiosum,  which  lies  between  and  below  them,  and  surrounds 
the  urethra;  these  are  held  together  by  fibrous  and  muscular  sheaths,  and  are  composed  of  erectile 
tissue.]  Our  knowledge  of  the  distribution  of  the  blood  within  the  penis  is  chiefly  due  to  C.  Langer's 
researches.  The  albuginea  of  the  corpus  spongiosum  consists  of  tendinous  connective  tissue,  con- 
taining thickly- woven  elastic  tissue  and  smooth  muscular  fibres,  which  together  form  a  solid  fibrous 
envelope,  from  which  numerous  interlacing  trabeculse  pass  into  the  interior,  so  that  the  corpus  spongi- 
osum comes  to  resemble  a  sponge.  The  anastomosing  spaces  bounded  by  these  trabeculse  form  a 
series  of  inter-communicating  venous 

spaces  or   sinuses  filled  with   blood  FiG.  653. 

and  lined  by  a  layer  of  endothelium 
constituting  erectile  tissue  (Fig.  653). 
The  largest  sinuses  lie  in  the  lower 
and  external  part  of  the  corpus  caver- 
nosum,  while  they  are  less  numerous 
and  smaller  in  the  upper  part.  The 
small  arteries  arise  from  the  A. 
profunda  penis,  which  runs  along 
the  septum,  and  pass  to  the  trabecule 
after  following  a  very  sinuous  course. 
At  the  outer  part  of  the  corpus 
spongiosum,  some  of  the  small  arte- 
ries become  directly  continuous  with 
the  larger  venous  sinuses ;  some  of 
them,  however,  terminate  in  capilla- 
ries, both  in  the  outer  part  and  within 
the  corpus  spongiosum,  the  capillaries 
ultimately  terminating  in  the  venous 
sinuses.  The  helicine  arteries  of  the 
penis  described  by  Joh.  Miiller  are 
merely  much  twisted  arteries.  The 
deep  veins  of  the  penis  arise  by  fine 
veinlets  within  the  body  of  the  organ, 
while  the  veins  proceeding  fi^om 
the  cavernous  spaces  pass  to  the 
dorsum  of  the  penis  to  form  the  vena 
dorsalis  penis.  As  these  vessels  have  to  traverse  the  meshes  of  the  vascular  network  in  the  cortex 
of  the  corpora  cavernosa  penis,  it  is  evident  that,  when  the  network  is  congested  by  being  filled  with 
blood,  it  must  compress  the  outgoing  venous  trunks.  The  corpus  cavernosum  urethrse  consists  for 
the  most  part  of  an  external  layer  of  closely  packed  anastomosing  veins,  which  surround  the  longitu- 
dinally directed  blood  vessels  of  the  urethra. 

In  the  dog,  all  the  arteries  of  the  penis  run  at  first  toward  the  surface,  where  they  divide  into 
penicilli.     The  veins  arise  from  the  capillary  loops  in  the  papillre,  and  they  empty  their  blood  into 


Erectile  tissue. 


a,  trabeculse  of  connective  tissue  with  elastic  fibres  and 
smooth  muscle  (c) ;  b,  venous  spaces. 


910 


MECHANISM    OF    ERECTION. 


the  cavernous  spaces.     Only  a  small  part  of  the  blood  passes  to  the  cavernous  spaces  through  the 
internal  capillaries  and  veins,  but  arterial  blood  never  Hows  directly  into  these  spaces  [M.  v.  Frey). 

Mechanism  of  Erection. — Erection  is  due  to  the  overfilling  of  the  blood 
vessels  of  the  penis  with  blood,  whereby  the  volume  of  the  organ  is  increased  four 
or  five  times,  while,  at  the  same  time,  there  are  also  a  higher  temperature,  increased 
blood  pressure  (to  \  of  that  in  the  carotid — Eckhard),  with  at  first  a  pulsatile 
movement,  increased  consistence,  and  erection  of  the  organ. 

Regner  de  Graaf  obtained  complete  erection  of  the  penis  by  forcibly  injecting  its  blood  vessels 
(1668). 

The  preliminary  phenomena  consist  in  a  considerable  increase  of  the  arterial 
blood  supply,  the  arteries  being  dilated  and  pulsating  strongly.  The  arteries  are 
controlled  by  the  nervi  erigentes.  The  nervi  erigentes  [called  by  Gaskell  the 
pelvic  splanchnics  (Fig.  439)]  arise  chiefly  from  the  second  (more  rarely  the  third) 
sacral  nerves  (dog),  and  have  ganglionic  cells  in  their  course  {Lovc/i,  Nikolsky). 
These  nerves  contain  vaso-dilator  fibres,  which  can  be  excited  in  part  reflexly 
from  the  sensory  nerves  of  the  penis,  the  transference  centre  being  in  the  centre 
for  erection  in  the  spinal  cord  (§  372,  4).  Sensory  impressions  produced  by 
voluntary  movements  of  the  genital  apparatus  (by  the  ischio-  and  bulbo-cavernosi 

and  cremaster  muscles)  can   also  dis- 


Fic.  654. 


charge  this  reflex;  while  the  thought 
of  sexual  impulses,  referable  to  the 
penis,  tends  to  induce  erection.  The 
nervi  erigentes  also  supply  the  longi- 
tudinal fibres  of  the  rectum  {Fellner). 
The  centre  for  erection  in  the 
spinal  cord  (§  362,  2)  is,  however, 
controlled  by  the  dominating  vaso- 
dilator centre  in  the  medulla  oblon- 
gata (§  372),  and  the  two  centres  are 
connected  by  fibres  within  the  cord ; 
hence  stimulation  of  the  upper  part 
of  the  cord,  as  by  asphyxiated  blood 
(§  362,  5)  or  muscarin,  may  also  be 
followed  by  erection  {Niko/sky).  [The 
seminal  fluid  is  frequently  found  dis- 
charged in  persons  who  have  been 
hanged.] 

The  psychical  activity  of  the  cerebrum 
has  a  decided  influence  on  the  genital 
vaso-dilator  nerves.  Just  as  the  psychi- 
cal disturbance  which  accompanies 
anger  or  shame  is  followed  by  dilata- 
tion of  the  blood  vessels  of  the  head, 
owing  to  stimulation  of  the  vaso-dilator 
fibres,  so  when  the  attention  is  directed 
to  the  sexual  centres  there  is  an  action 
upon  the  nervi  erigentes.  This  action 
of  the  brain  is  more  comprehensible, 
since  we  know  that  the  diameter  of  the 
blood  vessels  is  affected  by  the  cortex  cerebri  (§  377).  The  fibres  probably  pass 
from  the  cerebrum  through  the  peduncles  of  the  cerebrum  and  the  pons ;  as  a 
matter  of  fact,  if  these  parts  be  stimulated  erection  may  take  place  (§  362,  4) 
i^Eckharcf). 

When  the  impulse  to  erection  is  obtained  by  the   increased  supply  of  arterial 
blood,  the  full  completion  of  the  act  is  brought  about  by  the  activity  of  the  following 


Anterior  wall  of  the  pelvis  with  the  uro-genital  septum  seen 
from  the  front.  The  corpus  cavernosum  (4)  with  the 
urethra  (3)  is  cut  across  below  its  exit  from  the  pelvis. 
'  I,  symphysis  pubis;  2,  dorsal  vein  of  the  penis;  5, 
part  of  the  bulbo-cavernosus  ;  /,  deep  transversus  peri- 
nei  with  its  fascia  (/);  6,  vena  profunda  penis;  7, 
artery  and  vein  of  the  bulbo-cavernosus. 


EJACULATION    AND    RECEPTION    OF   THE    SEMEN.  911 

transversely  striped  muscles  :  (i)  The  ischio-cavernosus  arises  from  the  coccyx, 
and  by  its  tendinous  union  surrounds  the  root  of  the  penis  (Fig.  172).  When  it 
contracts,  it  compresses  the  root  of  the  penis  from  above  and  laterally,  so  that  the 
outflow  of  blood  from  the  penis  is  hindered.  It  has  no  action  on  the  dorsal  vein 
of  the  penis,  as  this  vessel  lies  in  a  groove  on  the  dorsum  of  the  penis,  and  is 
therefore  protected  from  compression  by  the  tendon.  (2)  The  deep  transversus 
perinei  is  perforated  by  the  venae  profundae  penis,  which  come  from  the  corpora 
cavernosa,  so  that  when  it  contracts  it  must  compress  these  veins  between  the 
tense  horizontal  fibres  (Fig.  654,  6).  The  deep  veins  of  the  penis  join  the  common 
pudendal  vein  and  the  plexus  Santorini.  (3)  Lastly,  the  bulbo-cavernosiis  is  con- 
cerned in  the  hardening  of  the  urethral  corpus  spongiosum,  as  it  compresses  the 
bulb  of  the  urethra  (Figs.  654,  5,  172).  All  these  muscles  are  partly  under  the 
control  of  the  will,  whereby  the  erection  may  be  increased.  Normally,  however, 
their  contraction  is  excited  reflexly  by  stimulation  of  the  sensory  nerves  of  the 
penis  (§  362,  4). 

The  congestion  of  blood  is  not  complete,  else,  in  pathological  cases,  continuous  erection,  as  in 
satyriasis,  would  give  rise  to  gangrene.  The  accumulation  of  the  blood  in  the  penis  is  favored  by 
the  fact  that  the  origins  of  the  veins  of  the  penis  lie  in  the  corpus  cavernosum,  which,  when  it 
enlarges,  must  compress  them.  There  are  also  trabecular,  smooth,  muscular  fibres, which  compress  the 
large  venous  plexus  of  Santorini. 

That  erection  is  a  complex  motor  act  depending  on  the  nervous  system,  is  proved  by  an  experiment 
of  Hausmann,  who  found  that  section  of  the  nerves  of  the  penis  prevented  erection  in  a  stallion. 
The  imperfect  erection  which  occurs  in  the  female  is  confined  to  the  corpora  cavernosa  clitoridis  and 
the  bulbi  vestibuli.  During  erection,  the  passage  from  the  urethra  to  the  bladder  is  closed,  partly  by  the 
swelling  of  the  caput  gallinaginis,  and  partly  by  the  action  of  the  sphincter  urethrse,  which  is  con- 
nected with  the  deep  transversus  perinei. 

437.  EJACULATION— RECEPTION  OF  THE  SEMEN.— In  con- 
nection with  the  ejaculation  of  the  seminal  fluid,  we  must  distinguish  two  differ- 
ent factors — (i)  its  passage  from  the  testicles  to  the  vesiculse  seminales;  (2)  the 
act  of  ejaculation  itself.  The  former  is  caused  by  the  newly-secreted  fluid  forcing 
on  that  in  front  of  it,  by  the  action  of  the  ciliated  epithelium  (which  lines  the 
epididymis  to  the  beginning  of  the  vas  deferens),  and  also  by  the  peristaltic  move- 
ments of  the  smooth  muscular  fibres  of  the  vas  deferens.  Ejaculation,  however, 
requires  strong  peristaltic  contractions  of  the  vasa  deferentia  and  the  vesiculae  semi- 
nales, which  are  brought  about  by  the  reflex  stimulation  of  the  ejaculation  centre 
in  the  spinal  cord  (§  362,  5).  As  soon  as  the  seminal  fluid  reaches  the  urethra, 
there  is  a  rhythmical  contraction  of  the  bulbo-cavernosus  muscle  (produced  by  the 
mechanical  dilatation  of  the  urethra),  whereby  the  fluid  is  forcibly  ejected  from 
the  urethra.  Both  vasa  deferentia  and  vesiculse  do  not  always  eject  their  contents 
into  the  urethra  simultaneously.  With  moderate  excitement  the  contents  of  only 
one  may  be  discharged.  The  ischio-cavernosus  and  deep  transversus  perinei  con- 
tract at  the  same  time  as  the  bulbo-cavernosus,  although  the  former  have  no  effect 
on  the  act  of  ejaculation.  In  the  female  also,  under  normal  circumstances,  at  the 
height  of  the  sexual  excitement  there  is  a  reflex  movement  corresponding  to  ejacu- 
lation. It  consists  of  a  movement  analogous  to  that  in  man.  At  first  there  is  a 
reflex  peristaltic  movement  of  the  Fallopian  tube  and  uterus,  proceeding  from  the 
end  of  the  tube  toward  the  vagina,  and  produced  reflexly  by  the  stimulation  of  the 
genital  nerves.  Dembo  observed  that  stimulation  of  the  anterior  upper  wall  of  the 
vagina  in  animals  caused  a  gradual  contraction  of  the  uterus.  By  this  movement, 
corresponding  to  that  of  the  vasa  deferentia  in  man,  a  certain  amount  of  the  mucus 
normally  lining  the  uterus  is  forced  into  the  vagina. 

This  is  followed  by  the  rhythmical  contraction  of  the  sphincter  cunni  (analogous 
to  the  bulbo-cavernosus),  also  of  the  ischio-cavernosus,  and  deep  transversus 
perinei.  The  uterus  is  erected  by  the  powerful  contraction  of  its  muscular  fibres 
and  round  ligaments,  while  at  the  same  time  it  descends  toward  the  vagina,  its 
cavity  is  more  and  more  diminished,  and  its  mucous  contents  are  forced  out.  When 


912  FERTILIZATION    OF   THE   OVUM. 

the  uterus  relaxes  after  the  stage  of  excitement,  it  aspirates  into   its  cavity  the 
seminal  fluid  injected  into  the  vestibule  (^Aristotle,  Bischojff"). 

But  the  suction  of  the  greatly  excited  uterus  is  not  necessary  for  the  reception  of  the  semen  {Aris' 
totlf).  The  spermatozoa  may  wrigt;le  by  their  own  movements  from  the  vagina  into  the  orilice  of  the 
uterus  {A'riste/ler).  The  cases  of  pregnancy  where,  from  some  pathological- causes  (partial  closure 
of  the  vagina  or  vulva),  the  penis  has  not  passed  into  the  vagina  during  coition,  prove  that  the  sperma- 
tozon  can  traverse  the  whole  length  of  the  vagina,  and  pass  into  the  uterus. 

438.  FERTILIZATION  OF  THE  OVUM.— The  ovum  is  fertilized  by 
one  spermatozoon  i)assing  into  it. 

Swanimerdani  (f  l6^)5)  proved  that  contact  of  the  semen  with  the  ovum  was  necessary  for  fertiliza- 
tion. Spallanzani  (1768)  jiroved  that  the  fertilizing  agent  was  the  spermatozoa,  and  not  the  clear 
filtered  fluid  part  of  the  semen,  and  that  the  spermatozoa,  even  after  being  enormously  diluted,  were 
still  capable  of  action.  Martin  Barry  (1S50)  was  the  first  to  observe  the  entrance  of  a  spermatozoon 
into  the  ovum  of  the  r.ibbit.  This  occurs  pretty  rapidly,  by  a  boring  movement  through  the  vitelline 
membrane  {Leuck/tart).  The  entrance  is  effected  either  through  the  porous  canals  or  the  micropyle 
{^Keber,  p.  902). 

Theories. — As  to  the  manner  in  which  the  spermatozoon  affects  the  ovum,  there  are  great  differ- 
ences of  opinion.  Aristotle  compaied  it  to  an  action  like  that  of  rennet  on  milk;  Bischoff,  to 
that  of  yeast  on  a  fermentable  mass,  i.  c,  to  a  catalytic  action.  These  theories,  however,  are  quite 
unsatisfactory,  as  we  know  that  the  unfertilized  ova  of  the  hen,  rabbit  [I/enxen),  pig  (Bischoff^, 
saljia  {/\ii/>/>/e)-)  (but  not  the  frog — Pfluger')  can  undergo  the  initial  .stages  of  development  as  far 
as  the  stage  of  cleavage,  and  the  star  fishes  even  as  far  as  the  larval  form  (^Greef.) 

Place  of  Fertilization. — The  place  where  fertilization  occurs  is  either  the 
ovary,  as  indicated  by  the  occurrence  of  abdominal  pregnancy,  or  the  Fallopian 
tube,  and  the  numerous  recesses  in  the  latter  afford  a  good  temporary  nidus  for  the 
spermatozoa.  This  view  is  supported  by  the  occurrence  of  tubal  pregnancy.  Thus, 
the  spermatozoa  must  be  able  to  pass  through  the  Fallopian  tube  to  the  ovary,  which 
is  probably  brought  about  chiefly  by  the  movements  proper  to  the  spermatozoa 
themselves.  It  is  uncertain  whether  the  peristaltic  movements  of  the  uterus  and 
Fallopian  tube  are  concerned  in  this  process ;  certainly  ciliary  movement  is  not 
concerned,  as  the  cilia  of  the  Fallopian  tube  act  from  above  downward.  When 
once  the  ovum  has  passed  unfertilized  into  the  uterus,  it  is  not  fertilized  in  the 
uterus.  It  is  assumed  that  the  ovum  reaches  the  uterus  within  2  to  3  weeks  (in  the 
bitch,  8  to  14  days). 

T\vins  occur  in  i  in  87  pregnancies,  but  oftener  in  warm  climates;  triplets, 
I  :  7600  ;  four  at  a  birth,  i  :  330,000.  More  than  six  at  a  time  have  not  been 
observed.     The  average  number  of  pregnancies  in  a  woman  is  4^. 

Superfecundation. — By  this  term  is  understood  the  fertilization  of  two  ova  at  the  same  men- 
slniatioi:,  by  two  ditTerent  ads  of  coition.  Thus,  a  mare  may  throw  a  foal  and  a  mule,  after  being 
covered  first  by  a  stallion  and  then  by  an  ass.  A  white  and  a  black  child  have  been  born  as  twins  by 
a  woman. 

Superfoetation  is  when  a  second  impregnation  takes  place  at  a  later  period  of  pregnancy,  as 
in  the  second  or  third  month.  This,  however,  is  only  possible  in  a  double  uterus,  or  when  men- 
struation persists  until  the  time  of  the  second  impregnation.     It  is  said  to  occur  frequently  in  the  hare. 

Hybrids  are  produced  when  there  is  a  cross  between  different  species  (horse,  ass,  zebra — dog, 
jackal,  wolf — goat,  ibex — goat,  sheep — species  of  llama — camel,  dromedary — tiger,  lion— species  of 
pheasant — goose,  swan — carp,  crucian — species  of  butterflies).  Most  hylirids  are  sterile,  especially 
as  regards  the  formation  of  properly  formed  spermatozoa  ;  while  the  hybrid  females  are  for  the  most 
part  fertile  with  the  male  of  both  parents,  e.g.,  the  mule;  but  the  characters  of  the  offspring  tend  to 
return  to  those  of  the  species  of  the  parents.  Very  few  hybrids  are  fertile  when  crossed  l>y  hybrids. 
In  many  species  of  frogs  the  absence  of  hybrids  is  accounted  for  by  the  mechanical  obstacles  to  fer- 
tilizalion  of  the  ova. 

Tubal  Migration  of  the  Ovum. — Under  exceptional  circumstances,  the 
ovum  discharged  from  a  ruptured  Graafian  follicle  passes  into  the  Fallopian  tube  of 
the  o/her  side,  as  is  proved  by  the  occurrence  of  tubal  pregnancy  and  pregnancy 
of  an  abnormal  rudimentary  horn  of  the  uterus,  in  which  case  the  true  corpus 
luteum  is  found  on  the  other  side  of  the  ovary.  This  is  spoken  of  as  "  external 
migration  "  (Kussinaul,  Leopold^.  This  observation  coincides  with  experiment, 
as  granular  fluids,  e.g.,  China-ink,  when  injected  into  the  peritoneal  cavity,  pass 


IMPREGNATION CLEAVAGE  OF  THE  YELK. 


913 


into  both  Fallopian  tubes,  and  are  carried  by  the  ciliated  epithelium  to  the  uterus 
(JPinner).  In  animals  with  a  double  uterus  with  two  orifices,  the  ova  may  migrate 
through  the  os  of  the  one  into  the  other  uterus,  a  condition  which  is  spoken  of  as 
"  internal  migration." 

439.  IMPREGNATION— CLEAVAGE— LAYERS  OF  THE  EM- 
BRYO.— Maturation  of  the  Ovum. — In  birds  and  mammals,  important 
changes  occur  in  the  ovum  before  impregnation.  The  germinal  vesicle  comes 
to  the  surface  and  disappears  from  view,  while  the  germinal  spot  also  disappears. 
In  place  of  the  germinal  vesicle,  a  spindle-shaped  body  appears.  The  granular 
elements  of  the  protoplasmic  vitellus  arrange  themselves  around  each  of  the  two 
poles  of  the  spindle,  in  the  form  of  a  star,  the  double  star,  or  diaster  of  Fol — 
nuclear  spindle  (Figs.  655,  656).  When  this  takes  place,  the  peripheral  pole 
of  the  nucleus  or  altered  germinal  vesicle,  along  with  some  of  the  cellular  substance 
of  the  ovum,  protrudes  upon  the  surface  of  the  vitellus,  where  they  are  nipped  off 
from  the  ovum  in  the  form  of  small  corpuscles  just  like  an  excretory  product  (Fig. 
657).  These  bodies,  which  are  not  made  use  of  in  the  further  development  and 
growth  of  the  ovum,  are  called  polar  or  directing  globules  i^Fol,  Butschli,  O. 
Hertwig'),  although  the  elimination  of  small  bodies  from  the  yelk  was  known  to 


Fig.  655. 


•Fig.  656. 


Formation  of  polar  globules  in  a  star-fish  (Asterias  glacialis).     A,  ripe  ovum        Egg  of  Scorpaena  scrofa.   The  ger- 
with  eccentric  germinal  vesicle  and  spot ;   B-E,  gradual  |metamorphosis  of  minal    vesicle   is    extruding  a 

germinal  vesicle  and  spot,  as  seen  in  the  living  egg,\x\to  two  asters  ;   F,  polar  globule,  and  vi'ithdrawing 

formation  of  first  polar  globule,  and  withdrawal  of  the  remaining  part  of  toward  the  centre  of  the  ovum, 

the  nuclear  spindle  within  the  ovum  ;  G,  surface  view  of  living  ovum  with  Near  it  is  the  male  pronucleus, 

view  of  first  polar  globule  ;  H,  formation  of  second  polar  globule  ;  I,  a  later 
stage,  showing  the  remaining  internal  part  of  the  spindle  in  the  form  of  two 
clear  vesicles;  K,  ovum  with  two  polar  globules  and  radial  striae  around 
the  female  pronucleus ;  L,  extrusion  of  polar  globule.  (Geddes  :  A-K,  after 
Fol:  L,  after  O.  Hej-iwig.) 

Dumortier  [1837],  Bischoff,  P.  J.  van  Beneden,  Fritz  Miiller  [1848],  Rathke,  and 
others.  The  remaining  part  of  the  germinal  vesicle  stays  within  the  vitellus  and 
travels  back  toward  the  centre  of  the  ovum,  to  form  the  female  pronucleus  {O. 
Hertwig,  Fol,  Selenka,  E.  van  Beneden).  [Before,  however,  the  altered  germinal 
vesicle  travels  downward  again  into  the  substance  of  the  ovum,  it  divides  again 
as  before,  and  from  it  is  given  off  the  second  polar  globule,  and  then  the  remain- 
der of  the  germinal  vesicle  forms  the  female  pronucleus  (Fig.  655).  At  the  same 
time  the  vitellus  shrinks  somewhat  within  the  vitelline  membrane.] 

Impregnation. — As  a  rule,  only  one  spermatozoon  penetrates  the  ovum,  and 
as  it  does  so,  it  moves  toward  the  female  pronucleus,  while  its  head  becomes 
surrounded  with  a  star;  it  then  loses  its  head  and  cilium,  or  tail,  the  latter  only 
serving  as  a  motor  organ,  while  the  remaining  middle  piece  swells  up  to  form  a 
second  new  nucleus,  the  male  pronucleus  {Fol,  Selenka).  According  to  Flem- 
ming,  it  is  the  anterior  part  of  the  head,  and  according  to  Rein  and  Eberth,  it  is  , 
the  head  which  is  so  changed.  Thereafter,  the  male  and  female  pronucleus  unite, 
undergoing  amcBboid  movements  at  the  same  time,  to  form  the  new  nucleus  of 
the  fertilized  ovum.  The  female  pronucleus  receives  the  male  pronucleus  in  a 
little  depression  on  its  surface.  Thereafter  the  yelk  assumes  a  radiate  appearance 
58 


914 


CLEAVAGE    OF   THE    YELK. 


{Reifi).     [The  union  of  the  representatives  of  tlie  male  and  female  elements  forms 
\\\t  first  entbryotiic  segmentation  sphere  ox  blastosphere,  which  divides  into  two 

cells,  and  these  again   into  four,  and  so  on 
Fig.  657.  (Fig.  658).] 

In  Echinoderms,  O.  Ilertwig  and  Fol  observed 
that  several  emliryos  were  formed  when,  under  ab- 
normal conditions,  several  spermatozoa  penetrated  an 
ovum.  The  male  pronuclei,  formed  from  the  several 
spermatozoa,  then  fused  each  with  a  fragment  of  the 
female  pronucleus.  Under  similar  circumstances, 
liorn  observed  in  amphibians  abnormal  cleavage,  but 
t.-.  .■•.  ■   .         .  V     -    .'-     .••■■•     :\    1         no  further  development. 

k!? /;•;;;'.'">  Cleavage  of  the  Yelk. — In  an  ovum  so 

^i^i'- ;■  ■      ■';  -■  ■■  fertilized  the  yelk  contracts  somewhat  around 

the  newly-formed  nucleus,  so  that  it  becomes 
slightly  separated  from  the  vitelline  mem- 
brane, and  for  the  first  time  the  nucleus 
and  the  yelk  divides  into  two  nucleated 
spheres.  This  process  is  spoken  of  as  a  complete  cleavage  or  fission  (Fig.  658). 
Each  of  these  two  cells  again  divides  into  two,  and  the  process  is  repeated,  so  that 


Egg  of  .1  Star-Ti-h  '^Astcr. 
triided  pol.ir  globules, 
nuclei  near  each  other. 


inlhion)  with   two  ex- 
Male  and  female  pro- 


Segmentation  of  a  rabbit's  ovum,  a,  two-celled  stagcl;  /',  four-celled  stage  ;  c,  eight-celled  stage  ;  d,  e,  many  blasto- 
meres  showing  the  more  rapid  division  of  the  outer-layer  cells,  and  the  gradual  enclosure  of  the  inner-layer  cells  ; 
ect,  outer-layer  cells;  ent,  inner-layer  cells;  /£■/,  polar  globules;  ;:/,  zona  pellucida. 

4,  8,  16,  32,  and  so  on,  spheres  are  formed  (Fig.  659).    This  constitutes  the  cleav- 
age of  the  yelk,  and  the  process  goes  on  until  the  whole  yelk  is  subdivided  into 
P       ,  numerous  small,   nucleated  spheres,  the 

'"^'  "mulberry  mass"  or  "segmenta- 

tion spheres"  or  "morula,"  or  the 
protoplasmic  primordial  spheres  (20  to 
25  ,'j.)  which  are  devoid  of  an  envelope. 
[Each  cell  divides  by  a  process  of  karyo- 
kinesis.  According  to  Van  Beneden, 
the  segmentation  begins  in  1-2  hours 
after  the  union  of  the  pronuclei,  and  the 
process  is  complete  in  about  75  hours. 
These  primitive  cells,  from  which  all  the  tissues  of  the  future  embryo  are  formed, 
are  called  blastomeres.] 


Cleavage  of  the  yelk  of  the  egg  of  Anchylostomum  duo- 
denale. 


STRUCTURE    OF   THE    BLASTODERM. 


915 


Variation  of  Lines  of  Cleavage. — According  to  the  observations  of  Pfluger,  the  ova  of  the  frog 
can  be  made  to  undergo  cleavage  in  very  different  directions,  according  to  the  angle  between  the 
axis  of  the  egg  and  the  line  of  gravitation.  This,  of  course,  we  can  alter  as  we  please,  by  placing 
the  eggs  at  any  angle  to  the  line  of  gravitation.  By  the  axis  of  the  ovum  is  meant  a  line  connecting 
the  centre  of  the  black  surface  and  the  middle  of  the  white  part,  which,  in  the  fertilized  ovum,  is  always 
vertical.  In  such  cases  of  abnormal  cleavage  the  deposition  of  the  organs  takes  place  from  other 
constituents  of  the  egg  than  those  from  which  they  are  formed  under  normal  conditions.  Under 
normal  circumstances,  according  to  Roux,  the  first  line  of  cleavage  in  the  frog  is  in  the  same  direc- 
tion as  the  central  nervous  system.  The  second  intersects  the  first  at  a  right  angle,  so  as  to  divide  the 
mass  of  ovum  into  two  unequal -p^ris,  the  larger  of  which  forms  the  anterior  part  of  the  embryo. 

Blastoderm. — During  this  time  the  ovum  is  enlarging  by  absorption  of  fluid 
into  its  interior.  All  the  cells,  from  mutual  pressure  against  each  other,  become 
polyhedral,  and  are  so  arranged  as  to  form  a  cellular  envelope  or  bladder,  the 
blastoderm  or  germinal  membrane,  which  lies  on  the  internal  surface  of  the 
vitelline  membrane  {De  Graaf,  v.  Baer,  Bischoff,  Coste).  A  small  part  of  the  cells 
not  used  in  the  formation  of  the  blastoderm  is  found  on  some  part  of  the  latter. 
[In  the  ovum  of  the  bird,  where  there  is  only  partial  segmentation,  the  blasto- 
derm is  a  small,  round  body  resting  on  the  surface  of  the  yelk,  under  the  vitelline 
membrane,  so  that  it  does  not  completely  surround  the  yelk,  or  a  hollow  cavity,  as 
in  mammals.     In   mammals,  this   cavity  is  called  the   segmentation  cavity.] 


Fig.  660. 


cnh. 


Fig. 


Blastodermic  vesicle  of  a  rabbit,  ect, 
ectoderm,  or  outer  layer  of  cells ; 
f«^,  inner  layer  of  cells. 


Pr,    primitive  streak ;    R,    medullary    groove ;     U, 
first  proto-vertebra. 


The  hollow  sphere,  composed  of  cells,  is  called  the  blastodermic  vesicle  by 
Reichert  (Fig.  660),  and  in  the  human  embryo  it  is  formed  at  the  loth  to  12th  day, 
in  the  rabbit  at  the  4th,  the  guinea-pig  at  the  3)^,  the  cat  7th,  dog  nth,  fox  14th, 
ruminantia  at  the  loth  to  12th  day,  and  the  deer  at  the  60th  day. 

When  the  blastoderm  grows  to  2  mm.  (rabbit),  whereby  the  vitelline  membrane 
is  distended  to  a  very  thin,  delicate  membrane,  then  at  one  part  of  it  there  appears 
the  germinal  area,  the  area  germinativa,  or  the  embryonal  shield  (  Coste,  Kolli- 
ker),  as  a  round  white  spot,  in  which  the  blastoderm,  owing  to  the  proliferation  of 
its  cells,  becomes  double.  The  upper  layer  is  called  the  ectoderm  or  epiblast, 
and  in  some  animals  it  consists  of  several  layers  of  cells,  while  the  lower  layer  is 
the  endoderm  or  hypoblast.  The  hypoblast  continues  to  grow  at  its  edges,  so 
that  it  ultimately  forms  a  completely  closed  sac,  on  which  the  epiblast  is  applied 
concentrically.  The  embryonal  area  soon  becomes  more  pear-shaped,  and 
afterward  biscuit-shaped.  At  the  same  time  the  surface  of  the  zona  pellucida 
develops  numerous  small,  hollovv,  structureless  villi,  and  is  called  the  primitive 
chorion. 

At  the  posterior  part,  or  narrow  end,  of  the  embryonic  shield,  the  primitive 
streak  (Fig.  661,  I,  Fr)  appears  at  first  as  an  elongated  opaque  circular  thicken- 
ing, and  later  as  a  longer  streak  or  groove,  the  primitive  groove.     [The  opacity 


916 


STRUCTURE  OF  THE  BLASTODERM. 


is  due  to  the  fact  that  there  are  several  layers  of  cells  in  this  region  (Fig.  662). 
In  a  transverse  section  through  the  primitive  streak,  three  layers  of  cells  are  seen. 
They  form  part  of  the  middle  layer  or  mesoblast,  and  are  originally  derived  from 
the  hypoblast.  Tiiese  cells  fuse  with  those  of  the  epiblast.  The  remainder  of  the 
hypoplastic  cells  retain  their  stellate  character.]     At  the  same  time  a  new  layer  of 


Fig.  662. 


/4' » 


Transverse  section  of  the  primitive  streak  of  a  fowl's  blastoderm,     ep,  epiblast  ;  hy,  hypoblast  ;  in,  mesoblast  ;  pv, 
primitive  groove  ;  ^/i.yoke  of  germinal  wall. 

cells  is  developed  between  the  epiblast  and  hypoblast,  the  mesoderm  or  meso- 
blast (Fig.  662,  I),  which    soon   extends  over  the  embryonal  area,  and    into  the 

blastoderm.     [There  has  been 
Fio.  663.  much  discussion  as  to  the  origin 

of  the  mesoblast,  but  in  verte- 
brates it  seems  to  be  originally 
developed  from  the  hypoblast. 
Fig.  663  shows  a  portion  of  the 
hypoblast  in  its  axial  part,  in 
process  of  forming  the  noto- 
chord,  which  is  described  as 
mesoblastic]  Blood  vessels 
are    formed  within   the  meso- 

Transverse  section  of  an  embryo  newt,  a,  mesenteron  ;  a.r. /y,  axial  DiaSt,  and  are  UlStriDUteCl  OVet 
hypoblast,  forming  the  notochord  ;  ^f,  coelom  or  body  cavity  :  ep,  ^j^g  blaStodcrm  tO  fomi  tllC 
epiblast;  /y,  digestive  hypoblast;  som,  somatic  mesoblast;  sptn, 


»p.l*i. 


splanchnic  mesoblast;    np,  neural  plate. 


area  vascuiosa. 


Medullary  Groove. — A 

longitudinal  groove,  the  medullary  groove,  is  formed  at  the  anterior  part  of  the 
embryonal  shield,  but  it  gradually  extends  posteriorly,  embracing  the  anterior  part 
of  the  primitive  streak  with  its  divided  posterior  end,  while  the  primitive  streak 
itself  gradually  becomes  relatively  and  absolutely  smaller  and  less  distinct,  until  it 
disappears  altogether  (Fig.  661,  I,  and  II,  Pr). 

The  position  of  the  embryo  is  indicated  by  the  central  part  becoming  more 
transparent, — the  area  pellucida, — which  is  surrounded  by  a  more  opaque  part — 
the  area  opaca.  [The  area  opaca  rests  directly  upon  the  white  yelk  in  the  fowl, 
and  it  takes  no  share  in  the  formation  of  the  embryo,  but  gives  rise  to  structures 
which  are  temporary,  and  are  connected  with  the  nutrition  of  the  embryo.  The 
embryo  is  formed  in  the  area  pellucida  alone.] 

From  the  epiblast  {^neuro-epidertnal  /aye?-]  are  developed  the  central  nervous 
system  and  epidermal  tissues,  including  the  epithelium  of  the  sense  organs. 

From  the  mesoblast  are  formed  most  of  the  organs  of  the  body  [including  the 
vascular,  muscular,  and  skeletal  systems,  and,  according  to  some,'  the  connective 
tissue.     It  also  gives  rise  to  the  generative  glands  and  excretory  organs]. 


STRUCTURES    FORMED    FROM    THE    EPIBLAST. 


917 


Vertical  section  of  part  of  the  unincubated  blastoderm  of  a  hen.     a,  epiblast ; 
b,  hypoblast;  c,  formative  cells  resting  on  white  yelk;  y,  archenteron. 


From  the  hypoblast  epithelio-glandular  layer  [which  is  the  secretory  layer], 
arise  the  intestinal  epithelium,  and  that  of  the  glands  which  open  into  intestine. 
The  notochord  is  also  formed  from  its  axial  portion.  [The  mouth  and  anus  being 
formed  by  an  inpushing  of  the  epiblast,  are  lined  by  epiblast,  and  are  sometimes 
called  the  stomodaeum  and  proctodaeum  respectively.] 

[Structure  of  the  Blastoderm  (Fig.  664). — Originally  it  is  composed  of 
only  two  layers,  and  in  a  vertical  section  of  it  the  epiblast  consists  of  a  single 
row  of  nucleated  granular 

cells,    arranged    side    by  Fig.  664. 

side,  with  their  long  axes 
placed  vertically.  The 
hypoblast  consists  of 
larger  cells  than  the  fore- 
going, although  they  vary 
in  size.  They  are  spher- 
ical and  very  granular,  so 
that  no  nucleus  is  visible 
in  them.  The  cells  form 
a  kind  of  network,  and 
occur  in  more  than  one 
layer,  especially  at  the 
periphery.  It  rests  on  white  yelk,  and  under  it  are  large  spherical  refractive  cells, 
spoken  of  as  formative  cells  (<r).] 

The  cells  of  the  epiblast,  and  especially  those  of  the  hypoblast,  nourish  themselves  by  the  direct 
absorption  and  incorporation  of  the  constituents  of  the  yelk  into  themselves.  The  amoeboid  move- 
ments of  these  cells  play  a  part  in  the  process  of  absorption.  The  absorbed  particles  are  changed, 
or,  as  it  were,  digested  within  the  cells,  and  the  product  used  in  the  processes  of  growth  and  devel- 
opment {^Kolhnanti). 

440.  STRUCTURES  FORMED  FROM  THE  EPIBLAST.— 
Laminae  Dorsales. — Thie  medullary  groove  upon  the  epiblast  (also  called  outer, 
serous,  sensorial,  corneal,  or  animal  layer)  becomes  deeper  (Fig.  665,  II).  The 
two  longitudinal  elevations  or  laminae  dorsales  consist  of  a  thickening  of  the 
epiblast,  and  grow  up  over  the  medullary  groove,  to  meet  each  other  and  coalesce 
by  their  free  edges  in  the  middle  line  posteriorly.  Thus,  the  open  groove  is 
changed  into  a  closed  tube — the  medullary  or  neural  tube  (III).  The  cells 
next  the  lumen  of  the  tube  ultimately  become  the  ciliated  epithelium  lining  the 
central  canal  of  the  spinal  cord,  while  the  other  cells  of  the  nipped-off  portion  of 
the  epiblast  form  the  ganglionic  part  of  the  central  nervous  system  and  its  pro- 
cesses. 

Primary  Cerebral  Vesicles. — [The  laminae  dorsales  unite  first  in  the  region 
of  the  neck  of  the  embryo,  and  soon  this  is  followed  by  the  union  of  those  over 
the  future  head.]  The  medullary  tube  is  not  of  uniform  diameter,  for  at  the 
anterior  end  it  becomes  dilated  and  mapped  out  by  constrictions  into  the  primary 
vesicles  of  the  brain,  which  at  first  are  arranged  one  behind  the  other,  in  the  fol- 
lowing order,  each  one  being  smaller  than  the  one  in  front  of  it :  the  fore-brain 
(representing  the  structures  from  which  the  cerebral  hemispheres  are  developed) ; 
the  mid-brain  (corpora  quadrigemina)  ;  the  hind-brain  (cerebellum);  and  the 
after-brain  (medulla  oblongata),  which  is  gradually  continued  into  the  spinal 
cord  (IV  and  V).  The  posterior  part  of  the  medullary  tube  has  a  dilatation  at  the 
lumbar  enlargement.  In  birds,  the  medullary  groove  remains  open  in  this  situa- 
tion to  form  a  lozenge-shaped  dilatation,  the  sinus  rhomboidalis. 

Cranial  Flexures. — The  anterior  part  of  the  medullary  tube  curves  on  itself, 
especially  at  the  junction  of  the  spinal  cord  and  oblongata,  between  the  mid- 
brain and  hind  brain,  and  again  almost  at  right  angles  between  the  fore-brain  and 


yi8 


STRUCTURES    TuRMliD    FROM    THE    EITDl.AST, 
Fig.  665. 


I,  The  three  layers  of  the  blastoderm  of  a  mammalian  ovum — Z,  zona  pellucida ;  E,  epiblast ;  ;«,  mesoblast;  e, 
hypoblast.  II,  Section  of  an  embryo,  with  six  protovertebrse  at  the  ist  day — ^I,  medullary  groove;  h,  somato- 
pleure;  U,  protovertebrae  ;  c,  chorda  dorsalis  ;  b,  the  lateral  plates  divided  into  two  ;  f,  hypoblast.  Ill,  Section 
of  an  embryo  chick  at  the  2d  day  in  the  region  behmd  the  heart — M,  medullar^-  groove;  It,  outer  part  of 
somatopleure ;  k,  protovertebra ;  c,  chorda ;  lu.  Wolffian  duct;  K,  coelom  ;  jc,  inner  part  of  somatopleure ; 
y,  inner  part  of  splanchnopleure;  A,  amniotic  fold;  a,  aorta;  e,  hypoblast.  IV',  Scheme  of  a  longitudinal 
section  of  an  early  embrj'O.  V,  Scheme  of  the  formation  of  the  head  and  tail  folds — r,  head  fuld  ;  D,  anterior 
extremity  of  the  future  intestinal  tract ;  S,  tail  fold,  first  rudiment  of  the  cavity  of  the  rectum.  VI,  Scheme  of  a 
longitudinal  section  through  an  cmbrj'o  after  the  formation  of  the  head  and  tail  folds — A  o,  omphalo-mesenteric 
arteries  ;  V  o,  omphalo-mesenteric  veins  ;  a.  position  of  the  allantois  ;  A,  amniotic  fold.  VII,  Scheme  of  a  lon- 
gitudinal section  through  a  human  ovum — Z,  zona  pellucida;  S,  serous  cavity  ;  r,  union  of  the  amniotic  folds  ; 
A.  cavity  of  the  amnion;  a,  allantois ;  N,  umbilical  vesicle;  in,  mesoblast;  //,  heart;  U,  primitive  intestine. 
VIII,  Schematic  transverse  section  of  the  pregnant  utenis  during  the  formation  of  the  placenta  ;  U,  muscular  wall 
of  the  uterus  ;  /,  uterine  mucous  membrane,  or  decidua  vera  ;  t,  maternal  part  of  the  placenta,  or  decidua 
serotina  ;  r,  decidua  reflexa  ;  ch,  chorion  ;  A,  amnion ;  n,  umbilical  cord  ;  a,  allantois,  with  the  urachus  ;  N,  um- 
bilical vesicle,  with  D,  the  omphalo-mesenteric  duct;  /  I,  openings  of  the  Fallopian  tubes;  G,  canal  of  the  cervix 
uteri.  IX,  Scheme  of  a  human  embryo,  with  the  visceral  arches  still  persistent — A,  amnion  ;  V,  fore-brain  ;  M, 
mid-brain  ;  H,  hind-brain  ;  N,  after-brain  ;  U,  primitive  vertebra  :  a,  eye  :  /,  nasal  pits ;  S,  frontal  process  ;  y, 
internal  nasal  process  ;  k,  external  nasal  process  ;  r,  superior  maxillary  process  of  the  ist  visceral  arch  ;  i,  2,  3, 
and  4,  the  four  visceral  arches,  with  the  visceral  clefts  between  them;  iJ,  auditory  vesicle;  //,  heart,  with  e, 
primitive  aorta,  which  divides  into  five  aortic  arches;  /,  descending  aorta;  out,  omphalo-mesenteric  artery  ;  b, 
the  omphalo-mesenteric  arteries  on  the  umbilical  vesicle;  c,  omphalo-mesenteric  vein;  L,  liver,  with  vense 
advehentes  and  revehentes  ;  D,  intestine;  i,  inferior  cava;  T,  coccyx;  «//,  allantois,  with  z,  one  umbilical 
arterj-,  and  .r,  an  umbilical  vein. 


STRUCTURES    FORMED    FROM    THE    MESOBLAST. 


919 


mid-brain.  [Thus,  a  displacement  of  the  primary  vesicles  is  produced,  and  the 
head  of  the  future  embryo  is  mapped  off.]  At  first  all  the  cerebral  vesicles  are 
devoid  of  convolutions  and  sulci.  On  each  side  of  the  fore-brain  there  grows  out 
a  stalked  hollow  vesicle  (VI),  the  primary  optic  vesicle.  The  remainder  of 
the  epiblast  forms  the  epidermal  covering  of  the  body.  At  an  early  period  we 
can  distinguish  the  stratum  corneum  and  the  Malpighian  layer  of  the  skin  (§  283)  ; 
from  the  former  are  developed  the  hairs,  nails,  feathers,  etc. 

Partial  Cleavage  — Only  a  partial  cleavage  takes  place  in  the  eggs  of  birds  and  in  mero- 
blastic  ova,  i.  e.,  only  the  white  yelk  in  the  neighborhood  of  the  cicatricula  divides  into  numerous 
segmentation  spheres  [Coste,  1848).  The  cells  arrange  themselves  in  two  layers  lying  one 
over  the  other.  The  upper  layer  or  epiblast  is  the  larger,  and  contains  small  pale  cells;  the  lower 
layer,  or  hypoblast,  which  at  first  is  not  a  continuous  layer,  ultimately  forms  a  continuous  layer,  but 
its  periphery  is  smaller  than  the  upper 

layer,  while  its  cells  are  larger  and  Fig.  666. 

more  granular. 

Between  the  epiblast  and  hypoblast 
there  is  formed,  from  the  primitive 
streak  as  a  product  of  cell-prolifera- 
tion, the  mesoblast,  which  is  said  by 
Kolliker  to  be  due  to  the  division  of 
the  cells  of  the  epiblast.  It  gradually 
extends  in  a  peripheral  direction  be- 
tween the  two  other  layers.  All  the 
three  layers  grow  at  their  periphery. 
In  the  mesoblast  blood  vessels  are 
developed.  Ail  the  three  layers,  as 
they  grow,  come  ultimately  to  enclose 
the  yelk,  so  that  their  margins  come 
together  at  the  opposite  pole  of  the 
yelk. 

441.  STRUCTURES 
FORMED  FROM  THE 
MESOBLAST  AND  HY- 
POBLAST.—The  meso- 
blast (vascular  layer  or  middle 
layer)  forms  immediately  under 
the  medullary  groove,  a  cy- 
lindrical cellular  cord,  the 
chorda  dorsalis,  or  noto- 
chord,  which  is  thicker  at  the 
tail  than  at  the  cephalic  end 
(Fig.  665,  II,  III,  c).  It  is 
present  in  all  vertebrata,  and 
also  in  the  larval  form  of  the 
ascidians,  but  in  the  latter  it 
disappears  in  the  adult  form 
'yKowalewsky).  In  man  it  is 
relatively  small.  It  forms  the 
basis  of  the  bodies  of  the  ver- 
tebrae, and  around  it,  as  a  central  core,  the  substance  of  the  bodies  of  the  verte- 
brse  is  deposited,  so  that  they  are  strung  on  it,  as  it  were,  like  beads  on  a  string. 
After  it  is  formed,  it  becomes  surrounded  by  a  double  sheath-like  covering  {Gegen- 
baur,  Kd Hiker). 

The  recent  observations  of  L.  Gerlach  and  Strahl  show  that  the  chorda  dorsalis  is  derived  from 
the  hypoblast  (Fig.  663).     It  does  not  contain  chondriu  or  glutin,  but  albumin  {^Retziits). 

Protovertebrse. — The  cells  of  the  mesoblast,  on  each  side  of  the  chorda, 
arrange  themselves  into  cubical  masses,  always  disposed  in  pairs  behind  each  other. 


Embrj'O  fowl  of  the  2d  day,  ;<  5o-  ^0,  area  opaca ;  Ap,  area  pellu- 
cida;  ///z,  hind-brain  ;  J/A,  mid-brain  ;  KA,  fore-brain  ;  otn,  om- 
phalo-mesenteric  veins  ;  oinr,  point  where  the  closure  of  the  neu- 
ral groove  is  traveling  backward  with  the  protovertebrae ;  Viv, 
muscle  plates  ;  Ry,  posterior  part  of  widely-open  neural  groove ; 
Rw,  neural  ridge  ;  vA/,  anterior  amniotic  fold. 


920 


STRUCTURES    FORMED    FROM    THE    MESOBLAST. 


the  protovertebrae  (Fig.  665.  U  and  //).  The  first  pair  correspond  to  the  atlas. 
At  a  later  period  each  protovertebra  shows  a  marginal  cellular  area  and  a  nuclear 
area  (Fig.  665).  Only  part  of  it  goes  to  form  a  future  vertebra.  The  part  of  the 
mesoblast  lying  external  to  the  protovertebrii^,  the  lateral  plates  (Fig.  665,  II, 
s),  splits  into  two  layers,  an  upper  one  and  a  lower  one,  which,  however,  are  united 
by  a  median  plate  at  the  i)rotovertebrae.  The  space  between  the  two  layers  of 
the  mesoblast  is  called  the  pleuro-peritoneal  cavity,  or  the  ccelom  of  Haeckel 
(III,  K).  The  upper  layer  of  the  lateral  jilate  becomes  united  to  the  ei)iblast, 
and  forms  the  cutaneo-muscular  plate  of  German  authors,  or  the  somatopleure 
(Fig.  665,  III,  A-  ;  Fig.  667,  so),  while  the  inner  one  unites  with  the  hypoblast  to 
form  the  intestinal  plate  of  German  authors,  or  the  splanchnopleure  (Fig.  665, 
III,  J';  Fig.  667,  s/>).  On  the  surfaces  of  these  plates,  which  are  directed  toward 
each  other,  the  endothelium  lining  the  pleuro-peritoneal  cavity  is  developed.  On 
the  surface  of  the  median  plate,  directed  toward  the  ccelom,  some  cylindrical  cells, 

P'iG.  667. 


Transverse  section  of  an  embryo  duck,  am,  amnion  ;  aa,  aorta  ;  ca.7/,  cardinal  vein  ;  c/t,  notochord  ;  A)',  hypoblast  ; 
>«j,  muscle  plate  ;  j<7,  somatopleure  ;  j/,  splanchnopleure  ;  j/.c,  spinal  cord;  J/-^,  spinal  ganglion  ;  j/,  segmen- 
tal tube  ;  n'rf.  Wolffian  (segmental)  duct. 


of  VValdeyer,  remain,  which   form  the  ovarian   tubes 


the  "  germ   epithelium 

and  the  ova  (§  43^). 

According  to  Remak,  the  skin,  the  muscles  of  the  trunk,  and  the  blood  vessels,  and  according  to 
His,  only  the  musculature  of  the  trunk,  are  derived  from  the  somatopleure.  Both  observers  agree 
that  the  splanchnopleure  furnishes  the  musculature  of  the  intestinal  tract. 

Parablastic  and  Archiblastic  Cells. — According  to  His,  the  blood  vessels, 
blood,  and  connective  tissue  are  not  developed  from  true  mesoblastic  cells,  but  he 
asserts  that  for  this  purpose  certain  cells  wander  in  from  the  margins  of  the  blasto- 
derm between  the  epiblast  and  hypoblast,  these  cells  being  derived  from  outside 
the  ])osition  of  the  embryo,  from  the  elements  of  the  white  yelk.  His  calls  these 
structures />arad/as//c,  in  opposition  to  the  archiblastic,  which  belong  to  the  three 
layers  of  the  embryo.  Waldeyer  also  adheres  to  the  parablastic  structure  of  blood 
and  connective  tissue,  but  he  assumes  that  the  material  from  which  the  latter  is 
formed  is  continuous  protoplasm,  and  of  equal  value  with  the  elements  of  the 
blastoderm. 


HEAD    AND    TAIL    FOLDS HEART.  921 

The  hypoblast  does  not  undergo  any  change  at  this  time  ;  it  applies  itself  to 
the  inner  layer  of  the  raesoblast,  as  a  single  layer  of  cells,  to  form  the  splanchno- 
pleure. 

442.  FORMATION  OF  EMBRYO,  HEART,  PRIMITIVE  CIR- 
CULATION.—Head  and  Tail  Folds.— Up  to  this  time  the  embryo  lies 
with  its  three  layers  in  the  plane  of  the  layers  themselves.  The  cephalic  end  of 
the  future  embryo  is  first  raised  above  the  level  of  this  plane  (Fig.  665,  V).  In 
front  of,  and  under  the  head,  there  is  an  inflection  or  tucking-in  of  the  layers, 
which  is  spoken  of  as  the  head-fold  (V,  r).  [It  gradually  travels  backward,  so 
that  the  embryo  is  raised  above  the  level  of  its  surroundings.]  The  raised  cephalic 
end  is  hollow,  and  it  communicates  with  the  space  in  the  interior  of  the  umbilical 
vesicle.  The  cavity  in  the  head  is  spoken  of  as  the  head-gut  or  fore-gut  (V,  D.). 
The  formation  of  the  fore-gut,  by  the  elevation  of  the  head  from  the  plane  of 
the  three  layers,  occurs  on  the  second  day  in  the  chick,  and  in  the  dog  on  the  2  2d 
day.  The  tail-fold  is  formed  in  precisely  the  same  way,  in  the  chick  on  the  3d 
day,  and  in  the  dog  on  the  22d  day.  The  tail-fold,  S,  also  is  hollow,  and  the 
space  within  it  is  the  hind-gut,  d.  Thus,  the  body  of  the  embryo  is  supported  or 
rests  on  a  hollow  stalk,  which  at  first  is  wide,  and  communicates  with  the  cavity  of 
the  umbilical  vesicle.  This  duct  or  communication  is  called  the  omphalo-mes- 
enteric  duct,  or  the  vitello-intestinal  or  vitelline  duct.  The  saccular  vesicle 
attached  to  it  in  mammals  is  called  the  umbilical  vesicle  (VII,  N),  while  the 
analogous  much  larger  sac  in  birds,  which  contains  the  yellow  nutritive  yelk,  is 
called  the  yelk  sac.  The  omphalo-mesenteric  or  vitelline  duct  in  course  of  time 
becomes  narrower,  and  is  ultimately  obliterated  in  the  chick  on  the  5th  day.  The 
point  where  it  is  continuous  with  the  abdominal  wall  is  the  abdominal  umbilicus, 
and  where  it  is  inserted  into  the  primitive  intestine,  the  intestinal  umbilicus. 

[Sometimes  part  of  the  vitelline  duct  remains  attached  to  the  intestine,  and  may  prove  dangerous 
by  becoming  so  displaced  as  to  constrict  a  loop  of  intestine,  and  thus  cause  strangulation  of  the  gut.] 

Heart. — Before  this  process  of  constriction  is  complete,  some  cells  are  mapped 
off  from  that  part  of  the  splanchnopleure  which  lies  immediately  under  the  head- 
gut  ;  this  indicates  \\\&  position  of  the  heart,  which  appears  in  the  chick  at  the  end 
of  the  first  day,  as  a  small,  bright  red,  rhythmically  contracting  point,  \k\t  pimctum 
saliens,  or  the  (jTiyirq  y.tvouij.i'rq  of  Aristotle.     In  mammals  it  appears  much  later. 

The  heart,  VI,  begins  first  as  a  mass  of  cells,  some  of  which  in  the  centre  dis- 
appear to  form  a  central  cavity,  so  that  the  whole  looks  like  a  pale  hollow  bud 
(originally  a  pair)  of  the  splanchnopleure.  The  central  cavity  soon  dilates  ;  it 
grows,  and  becomes  suspended  in  the  coelom  by  a  duplicature  like  a  mesentery 
(mesocardium),  while  the  space  which  it  occupies  is  spoken  of  as  iht  fovea  cardica. 
The  heart  now  assunes  an  elongated  tubular  form,  with  its  aortic  portion  directed 
forward,  and  its  venous  end  backward  ;  it  then  undergoes  a  slight  /-shaped  curve 
(Fig.  675,  i).  From  the  middle  of  the  2d  day,  the  heart  begins  to  beat  in  the 
chick,  at  the  rate  of  about  40  beats  per  minute.  [It  is  very  important  to  note  that 
at  first,  although  the  heart  beats  rhythmically,  it  does  not  contain  any  nerve  cells.] 

From  the  anterior  end  of  the  heart,  there  proceeds  from  the  bulbus  aortge,  the 
aorta  which  passes  forward  and  divides  into  two  primitive  aortae,  which  then 
curve  and  pass  backward  under  the  cerebral  vesicles,  and  run  in  front  of  the  proto- 
vertebrse.  Opposite  the  omphalo-mesenteric  duct,  each  primitive  aorta  in  the 
chick  sends  off  one,  in  mammals  several  (dog  4  to  5),  omphalo-mesenteric  arteries 
(VI,  A,  6),  which  spread  out  to  form  a  vascular  network  within  the  mesoblast  of 
the  umbilical  vesicle.  From  this  network,  there  arise  the  omphalo-mesenteric 
veins,  which  run  backward  on  the  vitelline  duct,  and  end  by  two  trunks  in  the 
venous  end  of  the  tubular  heart.  In  the  chick,  these  veins  arise  from  the  sinus 
terminalis  of  the  future  vena  terminalis  of  the  area  vasculosa.  Thus,  the  first 
or  primitive  circulation  is  a  closed  system,  and  functionally  it  is  concerned  in 


922  FORMATION    OF   THE    BODY. 

carrying  nutriment  and  oxygen  to  the  embryo.  In  the  bird,  the  latter  is  supplied 
through  the  porous  shell,  and  the  former  is  supplied  uj)  to  the  end  of  incubation 
by  the  yelk.  In  mammals,  both  arc  sui)plied  by  the  blood  vessels  of  the  uterine 
mucous  membrane  to  the  ovum.  In  birds,  owing  to  the  absorption  of  the  con- 
tents of  the  yelk  sac,  the  vascular  area  steadily  diminishes,  until  ultimately, 
toward  the  end  of  the  period  of  incubation,  the  shriveled  yelk  sac  slijjs  into  the 
abdominal  cavity.  In  mammals,  the  circulation  on  the  umbilical  vesicle  /.  <r., 
through  the  omphalo-mesenteric  vessels,  soon  diminishes,  while  the  umbilical 
vesicle  itself  shrivels  to  a  small  appendix,  and  the  second  circulation  is  formed 
to  replace  the  omphalo-mesenteric  system.  The  first  blood  vessels  are  formed  in 
the  chick,  in  the  area  vasculosa,  outside  the  position  of  the  embryo,  at  the  last 
quarter  of  the  first  day,  l)efore  any  part  of  the  heart  is  visible.  The  .blood  vessels 
begin  in  vaso-formative cells  [constituting  the  "blood  islands"  of  Pander].  At 
first  they  are  solid,  but  they  soon  become  hollow  (§  7,  A). 

A  narrow-meshed  plexus  of  lymphatics  is  formed  in  the  area  vasculosa  of  the  chick  {His),  and 
it  communicates  with  the  amniotic  cavity  {A.  Btulge). 

443.     FORMATION      OF     THE     BODY.— Body-^A^  all.— (i)     The 

ccelom,  or  pleuro-peritoneal  cavity,  becomes  larger  and  larger,  while  at  the 
same  time  the  difference  between  the  body-wall  and  the  wall  of  the  intestine 
becomes  more  pronounced.  The  latter  becomes  more  separated  from  the  proto- 
vertebra;,  as  the  middle  jilate  begins  to  be  elongated  to  form  a  mesentery.  The 
body-wall,  or  somatoi)leure,  composed  of  the  epiblast  and  the  outer  layer  of  the 
cleft  mesoblast,  becomes  thickened  by  the  ingrowth  into  it  of  the  muscular  layer 
from  the  muscle-plate,  and  the  ])osition  of  the  bones  and  the  spinal  nerves  from 
the  protovertebrje.  These  grow  between  the  epiblast  and  the  outer  layer  of  the 
mesoblast  {Remali).  [The  somatopleure,  or  parietal  lamina,  from  each  side  grows 
forward  and  toward  the  middle  line,  where  they  meet  to  form  the  body-wall,  while 
at  the  same  time,  the  splanchnopleure,  or  visceral  lamina,  on  each  side  also  grow 
and  meet  in  the  middle  line,  and  when  they  do  so,  they  enclose  the  intestine. 
Thus,  there  is  one  tube  within  the  other,  and  the  space  between  is  the  pleuro-peri- 
toneal cavity.] 

(2)  Vertebral  Column. — A  dorsally  placed  structure,  called  the  muscle 
plate  (Fig.  667,  ]iis.),  is  differentiated  from  each  of  the  protovertebrre  ;  the 
remainder  of  the  protovertebrai,  the  protovertebra  proper,  coalesces  with  that  on 
the  other  side,  so  that  both  completely  surround  the  chorda,  to  form  the  mem- 
brana  reuniens  inferior,  in  the  chick  on  the  3d,  and  in  the  rabbit  on  the  loth 
day,  while,  at  the  same  time,  they  close  over  the  medullary  tube  dorsally,  in  the 
chick  at  the  4th  day,  to  form  the  membrana  reuniens  superior  {Reichert). 
Thus,  there  is  a  union  of  the  masses  of  the  protovertebra^  in  front  of  the  medul- 
lary tube,  which  encloses  the  chorda,  and  represents  the  basis  of  the  bodies  of 
all  the  vertebrae,  while  the  membrana  reuniens  superior,  pushed  between  the  muscle 
plates  and  the  epiblast  on  the  one  hand  and  the  medullary  tube  on  the  other, 
represents  the  position  of  the  entire  vertebral  lamincj;  as  well  as  the  intervertebral 
ligaments  between  them.  In  some  rare  cases  the  membrana  reuniens  superior  is 
not  developed,  so  that  the  medullary  tube  is  covered  only  by  the  epiblast  (epider- 
mis), either  throughout  its  entire  extent,  or  at  certain  parts.  This  constitutes  the 
condition  of  spina  bifida,  or,  when  it  occurs  in  the  head,  hemicephalia.  The 
vertebral  column  at  this  membranous  stage  is  in  the  same  condition  as  the  verte- 
bral column  of  the  cyclostomata  (Petromyzon).  The  membranes  of  the  spinal 
cord,  the  spinal  ganglia,  and  spinal  nerves  are  formed  from  the  membrana 
reuniens  superior. 

Lastly,  parts  of  the  somatopleures  also  grow  toward  the  middle  line  of  the  back, 
and  insinuate  themselves  between  the  muscle  plate  and  the  epiblast ;  thus,  the 
dorsal  skin  is  formed  {jRemak). 


VISCERAL   CLEFTS   AND    ARCHES.  923 

In  the  membranous  vertebral  column,  there  are  formed  the  several  cartilaginous 
vertebrae,  the  one  behind  the  other,  in  man  at  the  6th  to  7th  week,  although 
at  first  they  do  not  form  closed  vertebral  arches  ;  the  latter  are  closed  in  man  about 
the  4th  month.  Each  cartilaginous  vertebra,  however,  is  not  formed  from  a  pair 
of  protovertebrse,  i.e.,  the  6th  cervical  vertebra  from  the  6th  pair  of  protovertebrae, 
but  there  is  a  new  subdivision  of  the  vertebral  column,  so  that  the  lower  half  of 
the  preceding  protovertebra  and  the  upper  half  of  the  succeeding  protovertebra 
unite  to  form  the  final  vertebra.  While  the  bodies  are  becoming  cartilaginous  the 
chorda  becomes  smaller,  but  it  still  remains  larger  in  the  intervertebral  disks.  The 
body  of  the  first  vertebra  or  atlas  unites  with  that  of  the  axis  to  form  its  odontoid 
process,  and  in  addition  it  forms  the  arcus  anterior  atlantis  and  the  transverse 
ligament  (^Hasse).  The  chorda  can  be  followed  upward  through  the  ligamentum 
suspensorium  dentis  as  far  as  the  posterior  part  of  the  sphenoid  bone. 

The  histogenetic  formation  of  cartilage  from  the  indifferent  formative  cells  takes  place  by 
division  and  growth  of  the  cells,  until  they  ultimately  form  clear  nucleated  sacs.  The  cement  sub- 
stance is  probably  formed  by  the  outer  parts  of  the  cells  (parietal  substance)  uniting  and  secreting 
the  intercellular  substance.  It  is  supposed  by  some  that  the  latter  contains  fine  canals,  which  connect 
the  protoplasm  of  the  adjoining  cells. 

Visceral  Clefts  and  Arches. — Each  side  of  the  cervical  region  contains  four 
slit-like  openings — the  visceral  clefts  or  branchial  openings  (^Rathke^  ;  in  the  chick, 
the  upper  three  are  formed  at  the  3d,  and  the  fourth  on  the  4th  day.  Above  the 
slits  are  thickenings  of  the  lateral  wall,  which  constitute  the  visceral  or  branchial 
arches  (Fig.  671).  The  clefts  are  formed  by  a  perforation  from  the  fore  gut,  but 
this,  perhaps,  does  not  always  occur  in  the  chick,  mammal,  and  man  (His),  and 
they  are  lined  by  the  cells  of  the  hypoblast.  On  each  side  in  each  visceral  arch, 
i.e.,  above  and  below  each  cleft,  there  runs  an  aortic  arch,  five  on  each  side  (Fig.  665, 
IX).  These  aortic  arches  persist  in  fishes.  In  man,  all  the  slits  close,  except 
the  uppermost  one,  from  which  the  auditory  meatus,  the  tympanic  cavity,  and  the 
Eustachian  tube  are  developed.  The  four  visceral  arches  are  for  the  most  part 
made  use  of  later  for  other  formations  (p.  931). 

Primitive  Mouth  and  Anus. — Immediately  under  the  fore-brain,  in  the 
middle  line,  is  a  thin  spot,  where  there  is  at  first  a  small  depression,  and  ultimately 
a  rupture,  forming  the  primitive  oral  aperture,  which  represents  both  the  mouth 
and  the  nose.  Similarly,  there  is  a  depression  at  the  caudal  end,  and  the  depres- 
sion ultimately  deepens,  thus  communicating  with  the  hind  gut  to  form  the  anus. 
When  the  latter  part  of  the  process  is  incomplete,  there  is  atresia  ani,  or  imper- 
forate anus.  Several  processes  are  given  off  from  the  primitive  intestine,  including 
the  hypoblast  and  its  muscular  layers,  to  form  the  lungs,  the  liver,  the  pancreas, 
the  caecum  (in  birds),  and  the  allantois. 

The  extremities  appear  at  the  sides  of  the  body  as  short  unjointed  stumps  or 
projections  at  the  3d  or  4th  week  in  the  human  embryo. 

444.  AMNION  AND  ALLANTOIS.— Amnion.— During  the  elevation 
of  the  embryo  from  its  surroundings,  immediately  in  front  of  the  head  (at  the  end 
of  the  2d  day  in  the  chick),  there  rises  up  a  fold  consisting  of  the  ej^iblast  and  the 
outer  layer  of  the  mesoblast,  which  gradually  extends  to  form  a  sort  of  hood  over 
the  cephalic  head  of  the  embryo  (Fig.  665,  VI,  A).  In  the  same  way,  but  somewhat 
later,  a  fold  rises  at  the  caudal  end,  and  between  both  along  the  lateral  borders 
similar  elevations  occur,  the  lateral  folds  (Fig.  665,  III,  A).  All  these  folds  grow 
over  the  back  of  the  embryo  to  meet  over  the  middle  line  posteriorly,  where  they 
unite  at  the  3d  day,  in  the  chick,  to  form  the  amniotic  sac.  Thus,  a  cavity  vfhich 
becomes  filled  with  fluid — the  amniotic  fluid — is  developed  around  the  embryo 
[so  that  the  embryo  really  floats  in  the  fluid  of  the  amniotic  sac].  In  mammals, 
also,  the  amnion  is  developed  very  early,  just  as  in  birds  (Fig.  665,  VII,  A). 
From  the   middle  of  pregnancy  onward,  the  amnion  is  applied  directly  to   the 


924  FORMATIOX    or    THE    AMXIOX    AXD    ALLAXTOIS. 

dioraoo,  and  united  to  it  bj  a  gidaydiKms  iajer  of  tisoe,  die  tanica  media  of 
Bischoff. 

Aninintir  Find. — Tb  aaHoa,  jad  dhe  allwnw  ss  wdl,  ac  SaamtA  aaij  ia  ■tawak,  faiids, 
ami  rqptiles,  <rfciA  kwg  heace  heca  oMed  ■mninla,  whffle  »he  lower  volcfanfees,  vludi  are  devoid 
of  IB  aaaia^  nc  <aOed  ■mmnia.  ConqpositiaB. — ^The  ■mirioric  fluid  is  m  clesr.  seroos, 
■1  iHiw  iaiil ,  |i 1 1 riii  snray  1007  to  loii,  octBTwiwg, beadcs  i.|Mli<.i—,  Imafcu  lunis,  ^^  to  2  per 
orat.  of  faed  sofids.  Awag  the  bffia-  are  •B'TOiim  (^  to  \  per  oeaC^  —liiu,  £M>>fi>>  a  Titriiine- 
Ifte  body,  soBK  S'ape  s^ar,  area,  aaaBoaaBa  coatiumarp,  very  probaUy  demvd  ftvHi  tdte  deoampo- 
gD—  of  area,  uwiiaif  v>  hcnc  acid  aad  1  ii.Miaiii,  cakic  salphate  and  phoyhair,  and  ooiiion  sak. 
Abotf  the  ■addle of  lac^aaarj,  it  ■■iiaai  todboat  1-1.5  kila.  [2.2-3.3  ^b.],  and  m.  the  end  aboat 
o.5k9ik.  TWa^aBBOclBaidisof Cnrlalon^iiB^asisi^KMnl^'ilsoooaiTCnoeiabiids.and 
aoaasBdannatkrea^AeiBaalaieaJhunes.  Ia  BSHnlsi,  Ihe  anne  of  dK  fixtas  faims  pot  of  k 
Amms  dg  aecaad  InJf  of  lacgaaaLf  i{'Sm!xtneap\.  Ia  the palhnihifflcal  onadition  of  hydramnion, 
Ae  Mood  ^i^aA  of  Ae  aieriae  — coar  1  wlajite  secrete  a  wabny  flaid.    The  flaid  preserres  the 

daboAe^cEeisof  «heie«alfadaTsfcqaiTriMairal  ii^aries;  itpenaite  theli»bsto 
:  hedf,  aad  pratoo^  thea  inm  giuai^  to|;eidhcr;  said,  l^df,  it  is  iBportant  far  dilating  the 

AadaglabQK.    The  aaaaoa  is  enable  of  coatianiina  at  the  7th  day  ia  thechict;  aad  thb 
E  dae  to  ihe  aaoolh  aKscabr  Ores  ahich  are  devdoped  ia  theoataaeoas  plate  ia  its  iKsoblastic 


Anantois. — Tram  die  anterior  sncface  of  the  caudal  end  of  the  embryo,  theie 
grows  om  a  smaD  doidile  projection,  which  becomes  hollowed  oat  to  form  a  sac 
pnifectii^  into  the  cavirf  ^  die  cadom  or  pleaio-peritoneal  caTity  (Fig.  665) ;  it 
cwiVLJiuies  the  mffftrmimf,  and  is  fanned  in  the  duck  before  the  5tli  day,  and  in 
man.  daring  the  2d  week.  Beii^  a  trae  pra^ectiMi  fiom  the  hind  got,  the  allantois 
has  two  lajecs,  one  fitom  the  hypoblast,  and  the  other  from  die  moscdUr  layer,  so 
tint  it  K  an  ofl^ioot  from  the  sidanchnopleaie.  From  both  sides,  there  pass  <m  to 
the  allantois  the  umbilical  arteries  from  die  hypogastric  arteries,  and  they  ramify 
on  die  snr&oe  of  die  sac  The  aOantots  grows,  like  a  urinary  bladder  gradnaUy 
bong  distended,  in  front  oi  the  hind  got  in  the  jrienro-peritMieal  cavity  toward  the 
mnhilinB;  and  bedy,  it  grows  oat  of  the  mnbilicns,  and  {Hojects  beyond  it  along- 
side  ilie  omphalo-mesentetic  or  vitdline  diQCt,  its  vessds growing  widi  it  (Fig.  665, 
Ml.  <« )  I  hm.  aficer  tfak  stage,  it  behaves  diC<aendy  in  Inrds  and  mammal 

h  bwds,  aJBer  tihe  11IB1I ii  pames  o«at  of  Ae  ■mIiiIji  m\  ,  il  aadasoes  great  devdopaKBt,  so  that 

widaa  a  dnat  taae  it  fines  the  arhnOe  of  d>e  interior  of  &e  ^eJD  ss  a  li^illy  vascalar  and  saocolar 
iM*mne     lfeaBteries»e  JtfiBtbraarhfsof  thepriwilireaortaE,fant  with  thedewdopmentof  the 

poateiim   t  iitm  iniitrM  \  thn'  appear  as  lajanWi.  of   the  hypcgastnc  aiteries.    Two  alHantoidal  or 

■lafiffii  Ml"  iiiraii  |a»r>iiiii  iiiiimhi  miaii  iiiiiia  1  n[iii]llliarii  iinirnBM  iilDiliiai  They pag baci-wad thww^ 
AeaMMkag,arfMlS»aaaitear3&the<aiipBral<>-toi»qF>>«icwiMS  tojoiafliei«BO^ 
la  bads  Ab  eacalMiua  oa  Ae  afcamis,  or  setmmd  tanmleiiem,  is  irtipiialury  in  Amctian,  as  its 
^e»efe  acne  fir  Ae  csxha^ie  of  gases  Ana^  die  ponsas  ^elL  The  cirealatiaa  gtadaaiOy  asstones 
Ae  ic^piEritaEyiiacliaBsof  the  oailaKcall  xvatAt^as  the  taw»T  gm«fanilly  iw'nffif^  ■^iwillfT  mH  aaadler, 
aad  cei^s  to  be  a  swtBirarat  respiotanr'Cggam.  Towaid  the  ead  of  the  period  of  incdbotian  the  dndc 
■o^  brea^e  and  ory  wodia  the ^beSI  ^Arisioile) — aproof  that  AerBpnratxxy  fondiaBof  theaSaaAois 
ispa«^tAea<wnerbyAe3aBf;ii.  The  ajBaaaws  is  also  the  CMiietuty  o^gaaaof  the  arinaiy  oonstitB- 
eai&.  Lmo  xs  carity  ia  aaBtoals  the  dac^  of  the  primuiisx  Mdmej'e,  or  die  Wit^trnm  Auis,  open, 
boB  ia  baid^  aad  grjaiiHes,  wMch  r«»agwac  £  *^mt^^_  €aeat  opea  into  the  posterior  wall  of  the  t^^eir^ 
The  gaJaaJyiiwe  badoeys,  or  Woft&oa  bo^es,  ooaast  of  many  ^otoeiaii,  and  empty  their  secretion 
tftiiiiMigb  the  WoDfiaa  dncas  into  the  aHlbmiftnig  i{in  bmds  iato  d>e  doua),  and  the  seoetian  pasres 
BJinMigh  A^  wfliMiiiriir^  JUT  A»  laJhaliOTK  mbw  «w  pTTJyfltfyTi!!  pmt  of  thf  TaTJmury  3aC-  Remak  iband 
^atooaiaM  aad  Midiaai  acae,  affitaattoia,  grape  sigar,  and  salts  ia  the  caaiemtsrfdaerflanaois.  From 
Ac  SA  di7  oaanad,  da  aibwanit;  cf  the  cUdk  b  oawtractile  ( rib^Kca ),  omii^  to  Ae  piesenoe  of 
■wawA  fibres  deuwed  inan  the  fpilaarftiannifrani..     Lya^dniics   aooonpony  the  JuMirliwc  of  Ae 

Allantois  in  Mammals. — In  ntaimmly  and  man,  the  relation  of  the  aDantois 
KstMnewhat  diffiaent.  The  first  part  or  its  otigin  farms  the  minaiy  bladder,  and 
M»  the  vertex  dL  the  latter  there  proceeds  dnoi^  the  ombiUciB  a  tnbe,  the 
oradms,  whitji  is  t^pen  at  irst  {F%.  665,  Tm,  «).  Tbe  blind  part  of  die  sac  of 
die  allanlDB  ootside  Ae  abdomen  is  in  some  animads  filled  with  a  fluid  like  iirine. 
In  man,  howerer,  tins  sac  disappears  dming  the  2d  mgnth,  so  tiiat  there  remains 
oidy  Ae  vessds  whidi  lie  in  tl^  Twr^irwlar  part  of  die  allantok.     In  some  animaUj 


FCETAL   MEMBRANES. 


925 


however,  the  allantois  grows  larger,  does  not  shrivel,  but  obtains  through  the 
urachus  from  the  bladder  an  alkaline  turbid  fluid,  which  contains  some  albumin, 
sugar,  urea,  and  allantoin.  The  relations  of  the  umbilical  vessels  will  be  described 
in  connection  with  the  fcetal  membranes. 

445.  FCETAL  MEMBRANES,  PLACENTA,  FCETAL  CIRCU- 
LATION.— Decidua. — When  a  fecundated  ovum  reaches  the  uterus,  it  becomes 
surrounded  by  a  special  covering,  which  William  Hunter  (1775)  described  as  the 
membrana  decidua,  because  it  was  shed  at  birth.  We  distinguish  the  decidua 
vera  (Fig.  665,  YIII,/),  which  is  merely  the  thickened,  very  vascular,  softened, 
more  spongy,  and  somewhat  altered  mucous  membrane  of  the  uterus.  [Some- 
times in  a  diseased  condition,  as  in  dysmenorrhcea,  the  superficial  layer  of  the 
uterine  mucous  membrane  is  thrown  off  nearly  en  fnasse  in  a  triangular  form  (Fig. 
668).     This  serves  to  show  the 


shape  of  the  decidua,  which  is 
that  of  the  uterus.]  When  the 
o\aim  reaches  the  uterus,  it  is 
caught  in  a  crypt  or  fold  of  the 
decidua,  and  from  the  latter 
there  grow  up  elevations  around 
the  ovum  ;  but  these  elevations 
are  thin,  and  soon  meet  over  the 
back  of  the  ovum  to  form  the 
decidua  reflexa  (Fig.  665, 
VIII,  r).  At  the  2d  to  3d 
month,  there  is  still  a  space  in 
the  uterus  outside  the  reflexa ; 
in  the  4th  month,  the  whole 
cavity  is  filled  by  the  ovum.  At 
one  part  the  ovum  lies  directly 
upon  the  d.  vera  [and  that  part 
is  spoken  of  as  the  decidua 
serotina],  but  by  far  the  great- 
est part  of  the  surface  of  the 
ovum  is  in  contact  with  the  re- 


FiG.  668. 


Adysmeaorrh'sal  membrane  laid  open. 


flexa.     In  the  region  of  the  d.  serotina  the  placenta  is  ultimately  formed. 

Structure  of  the  Decidua  Vera. — The  d.  vera  at  the  3d  month  is  4  to  7  mm.  thick,  and  at  the 
4tli  only  I  to  3  mm.,  and  it  no  longer  has  any  epithelium;  but  it  is  very  vascular,  and  is  possessed 
of  lymphatics  around  the  glands  and  blood  vessels  (^Leopold),  and  in  its  loose  substance  are  large 
round  cells  (decidua  cells — A'tV/z'/J^r),  which  in  the  deeper  parts  become  changed  into  fibre  cells — 
there  are  also  ijTnphoid  cells.  The  uterine  glands,  which  become  greatly  developed  at  the  com- 
mencement of  pregnancy,  at  the  3d  to  the  4th  month  form  non-cellular,  wide,  bulging  tubes,  which 
become  indistinct  in  the  later  months,  and  in  which  the  epithelium  disappears  more  and  more.  The 
d.  reflexa,  much  thinner  than  the  vera  from  the  middle  of  pregnancy,  is  devoid  of  epithelium,  and 
is  without  vessels  and  glands.     Toward  the  end  of  pregnancy  both  deciduie  unite. 

The  o\ami,  covered  at  first  with  small  hollow  villi,  is  surrounded  by  the  decidua. 
From  the  formation  of  the  amnion  it  follows  that,  after  it  is  closed,  a  completely 
closed  sac  passes  away  from  the  embryo  to  He  next  the  primitive  chorion.  This 
membrane  is  the  "serous  covering"  of  v.  Baer  (Fig.  665,  VII,  s),  or  the  false 
amnion.  It  becomes  closely  applied  to  the  inner  surface  of  the  chorion,  and 
extends  even  into  its  villi.  The  allantois  proceeding  from  the  umbilicus  comes  to 
lie  directly  in  contact  with  the  fcetal  membrane;  its  sac  disappears  about  the  2d 
month  in  man,  but  its  vascular  layer  grows  rapidly  and  lines  the  whole  of  the  inner 
surface  of  the  chorion,  where  it  is  found  on  the  iSth  day  i^Coste).  From  the  4th 
week  the  blood  vessels,  along  with  a  covering  of  connective  tissue,  branch  and 


926 


THE    PLACENTA. 


penetrate  into  the  hollow  cavities  of  the  villi,  and  comi)letely  fill  them.  At  this 
time  the  primitive  chorion  disappears.  Thus,  we  have  a  stage  of  general  vasculari- 
zation of  the  chorion.  In  the  ])lace  of  the  derivative  of  the  zona  pellucida  we 
have  the  vascular  villi  of  the  allantois,  which  are  covered  by  the  epiblastic  cells 
derived  from  the  false  amnion.  This  stage  lasts  only  until  the  3d  month,  when 
the  chorionic  villi  disappear  all  over  that  part  of  the  surface  of  the  ovum  which  is 
in  contact  with  the  decidua  reflexa.  On  the  other  hand,  the  villi  of  the  chorion, 
where  they  lie  in  direct  contact  with  the  decidua  serotina.  become  larger  and  more 
branched.     Thus,  there  is  distinguished  the  chorion  laeve  and  c.  frondosum. 

The  chorion  laeve,  which  consists  of  a  connective-tissue  matrix  covered  externally  by  several 
layers  of  cells,  has  a  few  isolated  vilH  at  wide  intervals.  Between  the  chorion  and  the  amnion  is  a 
gelatinous  substance  (membrana  intermedia)  or  undeveloped  connective  tissue. 

Placenta. — The  large  villi  of  the  chorion  frondosum  penetrate  into  the  tissue 
of  the  decidua  serotina  of  the  uterine  mucous  membrane.  [It  was  formerly  sup- 
posed that  the  chorionic  villi  entered  the  mouths  of  the  uterine  glands,  but  the 
researches  of  Ercolani  and  Turner  have  shown  that,  although  the  uterine  glands 
enlarge  during  the  early  months  of  utero-gestation,  the  villi  do  not  enter  the 
glands.  The  villi  enter  the  crypts  of  the  uterine  mucous  membrane.  The  glands 
of  the  inner  layer  of  the  decidua  serotina  soon  disappear.]     As  the  villi  grow  into 

the  decidua  serotina,  they  push 
^'*^-  ^^9-  against  the  walls  of  the   large 

blood  vessels,  which  are  simi- 
lar to  capillaries  in  structure,' 
so  that  the  villi  come  to  be 
bathed  by  the  blood  of  the 
mother  in  the  uterine  sinuses, 
or  they  float  in  the  colossal 
decidual  capillaries  (Fig.  665, 
VH,  I?).  The  villi  do  not 
float  naked  in  the  maternal 
blood,  but  they  are  covered  by 
a  layer  of  cells  derived  from 
the  decidua.  Some  villi,  with 
bulbous  ends,  unite  firmly  with 
the  tissue  of  the  uterine  part  of 
the  placenta  to  form  a  firm 
bond  of  connection.  [The 
placenta  is  formed  by  the 
mutual  intergrowth  of  the 
chorionic  villi  and  the  decidua 
serotina.]  Thus,  it  consists  of 
a  foetal  part,  including  all 
the  villi,  and  a  maternal  or 
uterine  part,  which  is  the 
very  vascular  decidua  serotina.  At  the  time  of  birth,  both  parts  are  so  firmly 
united  that  they  cannot  be  separated.  Aroimd  the  margin  of  the  placenta  is  a  large 
venous  vessel,  ih^  marginal  sinus  of  the  placenta.  [Friedlander  found  the  uterine 
sinuses  below  the  placental  site  blocked  by  giant  cells  after  the  8th  month  of  preg- 
nancy. Leopold  confirms  this,  and  found  the  same  in  the  serotinal  veins.]  Func- 
tions.— The  placenta  is  the  nutritive,  excretory,  and  respiratory  organ  of 
the  ftetus  (§  368)  ;  the  latter  receives  its  necessary  pabulum  by  endosmosis  from 
the  maternal  sinuses  through  the  coverings  and  vascular  wall  of  the  villi  in  which 
the  fcetal  blood  circulates.     [The  placenta  also  con\.3\\\s  gIycogen.'\ 


Human  placental  villi.     Blood  vessels  black. 


UTERINE    MILK.  927 

[Structure. — A  piece  of  fresh  placenta  teased  in  normal  saline  solution,  shows  the  villi  provided 
Vi^ith  lateral  offshoots,  and  consisting  of  a  connective-tissue  framework,  containing  a  capillary  network 
with  arteries  and  veins,  while  the  villi  themselves  are  covered  by  a  layer  of  somewhat  cubical 
epithelium  (Fig.  669).] 

Uterine  Milk. — Between  the  villi  of  the  placenta  there  is  a  clear  fluid,  which 
contains  numerous  small,  albuminous  globules,  and  this  fluid,  which  is  abundant 
in  the  cow,  is  spoken  of  as  the  uterine  milk.  It  seems  to  be  formed  by  the  break- 
ing up  of  the  decidual  cells.  It  has  been  supposed  to  be  nutritive  in  function. 
[The  maternal  placenta,  therefore,  seems  to  be  a  secreting  structure,  while  the 
foetal  part  has  an  absorbing  function.  The  uterine  milk  has  been  analyzed  by 
Gamgee,  who  found  that  it  contained  fatty,  albuminous,  and  saline  constituents, 
while  sugar  and  casein  were  absent.] 

The  investigations  of  Walter  show,  that  after  poisoning  pregnant  animals  with  strychnin,  morphia, 
veratrin,  curara,  and  ergotin,  these  substances  are  not  found  in  the  foetus,  although  many  other 
chemical  substances  pass  into  it. 

[Savory  found  that  strychnin  injected  into  a  foetus  in  utero  caused  tetanic  convulsions  in  the 
mother  (bitch),  while  syphilis  may  be  communicated  from  the  father  to  the  mother  through  the 
medium  of  the  foetus  [Htitchinson).  A.  Harvey's  record  of  observations  on  the  crossing  of  breeds 
of  animals — chiefly  of  horses  and  allied  species — show  that  materials  can  pass  from  the  foetus  to  the 
mother.] 

On  looking  at  a  placenta,  it  is  seen  that  its  villi  are  distributed  on  large  areas  separated  from  each 
other  by  depressions.  This  complex  arrangement  might  be  compared  with  the  cotyledons  of  some 
animals. 

The  position  of  the  placenta  is,  as  a  rule,  on  the  anterior  or  posterior  wall  of  the  uterus, 
more  rarely  on  the  fundus  uteri,  or  laterally  from  the  opening  of  the  Fallopian  tube,  or  over  the 
internal  orifice  of  the  cervix,  the  last  constituting  the  condition  of  placenta  praevia,  which  is 
a  very  dangerous  form  of  placental  insertion,  as  the  placenta  has  to  be  ruptured  before  birth  can 
take  place,  so  that  the  mother  often  dies  from  hemorrhage.  The  umbilical  cord  may  be  inserted 
in  the  centre  of  the  placenta  {inserdo  centralis),  or  more  toward  the  margin  (ins.  marginalis), 
or  the  chord  may  be  fixed  to  the  chorion  laeve.  Sometimes,  though  rarely,  there  are  small  sub- 
sidiary placentas  (/>/.  sticcentia-iata),  in  addition  to  the  large  one.  'SMien  the  placenta  consists  of 
two  halves,  it  is  called  duplex  or  bipartite,  a  condition  said  by  Hyrtl  to  be  constant  in  the  apes 
of  the  old  world. 

Structure  of  the  Cord. — The  umbilical  cord  (48  to  60  cm.  [20  to  24  inches] 
long,  II  to  13  mm.  thick)  is  covered  by  a  sheath  from  the  amnion.  The  blood 
vessels  make  about  forty  spiral  turns,  and  they  begin  to  appear  about  the  second 
month.  [The  cause  of  the  twisting  is  not  well  understood,  but  Virchow  has  shown 
that  capillaries  pass  from  the  skin  for  a  short  distance  on  the  cord,  and  they  do  so 
unequally,  and  it  may  be  that  this  may  aid  in  the  production  of  the  torsion.]  It 
contains  two  strongly  muscular  and  contractile  arteries,  and  one  umbilical  vein. 
The  two  arteries  anastomose  in  the  placenta  (^Hyrtl).  In  addition,  the  cord  con- 
tains the  continuation  of  the  urachus,  the  hypoblastic  portion  of  the  allantois  (Fig. 
665,  VIII,  a),  which  remains  until  the  second  month,  but  afterward  is  much 
shriveled.  The  omphalo-mesenteric  duct  of  the  umbilical  vesicle  (N)  is  reduced 
to  a  thread-like  stalk  (Fig.  665,  VIII,  D).  Wharton's  jelly  surrounds  the 
umbilical  blood  vessels.  Wharton's  jelly  is  a  gelatinous-like  connective  tissue, 
consisting  of  branched  corpuscles,  lymphoid  cells,  some  connective-tissue  fibrils, 
and  even  elastic  fibres.  It  yields  mucin.  It  is  traversed  by  numerous  juice  canals 
lined  by  endothelial  cells,  but  other  blood  and  lymphatic  vessels  are  absent. 
Nerves  occur  3-8-1 1  cm.  from  the  umbilicus  {Schott,  Valentin). 

The  foetal  circulation,  which  is  established  after  the  development  of  the  allan- 
tois, has  the  following  course  (Fig.  670)  :  The  blood  of  the  foetus  passes  from  the 
hypogastric  arteries  through  the  two  umbilical  arteries,  through  the  umbilical  cord 
to  the  placenta,  where  the  arteries  split  up  into  capillaries.  The  blood  is  returned 
from  the  placenta  by  the  umbilical  vein,  although  the  color  of  the  blood  cannot 
be  distinguished  from  the  venous  or  impure  blood  in  the  umbilical  arteries.     The 


928 


THE    FCETAL    CIRCULATION. 


umbilical  vein  (Fig.  673,  3,  //)  returns  to  the  umbilicus,  passes  upward  under  the 
margin  of  the  liver,  gives  a  branch  to  the  vena  portje  (a),  and  runs  as  the  ductus 

venosus  into  the  inferior  vena  cava, 
Kic.  670.  which  carries  the  blood  into  the  right 

auricle.  Directed  by  the  Eustachian 
valve  and  the  tubercle  of  Lower  (Fig. 
675,  6,  /Z),  the  great  mass  of  the  blood 
passes  through  the  foramen  ovale  into 
the  left  auricle,  owing  to  the  i)resence 
of  the  valve  of  the  foramen  ovale.  From 
the  left  auricle  it  passes  into  the  left 
ventricle,  aorta,  and  hypogastric  arte- 
ries, to  the  umbilical  arteries.  The 
blood  of  the  superior  vena  cava  of  the 
f(etus  passes  from  the  right  auricle  into 
the  right  ventricle  (Fig.  675,  6,  Cs). 
From  the  right  ventricle  it  passes  into 
the  pulmonary  artery  (Fig.  675,  7,  />), 
and  through  the  ductus  arteriosus  of 
Botalli  (jB)  into  the  aorta.  There  are, 
therefore,  two  streams  of  blood  in  the 
right  auricle  which  cross  each  other,  the 
descending  one  from  the  head  through 
the  superior  vena  cava,  passing  in  front 
of  the  transverse  one  from  the  inferior 
vena  cava  to  the  foramen  ovale.]  Only 
a  small  amount  of  the  blood  passes 
through  the  as  yet  small  branches  of  the 
])ulmonary  artery  to  the  lungs  (Fig.  675, 
7,  I,  2).  The  course  of  the  blood  makes 
it  evident  that  the  head  and  upper  limbs 
of  the  foetus  are  nourished  by  purer 
blood  than  the  remainder  of  the  trunk, 
which  is  supplied  with  blood  mixed  with 
the  blood  of  the  superior  vena  cava. 
After  birth,  the  umbilical  arteries  are 
obliterated,  and  become  the  lateral  ligaments  of  the  bladder,  while  their  lower 
parts  remain  as  the  superior  vesical  arteries.  The  umbilical  vein  is  obliterated, 
and  remains  as  the  ligamentum  teres,  or  round  ligament  of  the  liver,  and  so  is  the 
ductus  venosus  Arantii.  Lastly,  the  foramen  ovule  is  closed,  and  the  ductus  arteri- 
osus is  obliterated,  the  latter  forming  the  lig.  arteriosus. 

The  condition  of  the  membranes  where  there  are  more  foetuses  than  one  :  (i)  With  twins 
there  are  two  completely  separated  ova,  with  two  placenta;  and  two  deciduje  reflexse.  (2)  Two 
completely  separated  ova  may  have  only  one  reflexa,  whereby  the  placentae  grow  together,  while 
their  blood  vessels  remain  distinct.  The  chorion  is  actually  double,  but  cannot  be  separated  into 
two  lamellx  at  the  point  of  union.  (3)  One  reflexa,  one  chorion,  one  placenta,  two  umbilical  cords, 
and  two  amnia.  The  vessels  anastomose  in  the  placenta.  In  this  case  there  is  one  ovum  with 
a  double  yelk,  or  wiih  two  germinal  vesicles  in  one  yelk.  (4)  As  in  (3),  but  only  one  amnion,  caused 
by  the  formation  of  two  embryos  in  the  same  blastoderm  of  the  same  germinal  vesicle. 

Formation  of  the  fcEtal  membranes. — The  oldest  mammals  have  no  placenta  or  umbilical 
vessels;  these  are  the  Mammalia  implacentalia,  including  the  monetremata  and  marsupials.  The 
second  group  includes  the  Mammalia  placentalia.  Among  these  (a)  the  non-deciduata  pos- 
sess only  chorionic  villi  supplied  by  the  umijihcal  vessels,  which  project  into  the  depressions  of  the 
uterine  mucous  membrane,  and  from  which  they  are  pulled  out  at  birth  (PI.  diffusa,  e.g.,  pachy- 
dermata,  cetacea,  solidungula,  camelidx).  In  the  ruviinants,  the  villi  are  arranged  in  groups  or 
cotyledons,  which  grow  into  the  uterine  mucous  menibrane,  from  which  they  are  pulled  out  at  birth. 


Course  of  the  fcetal  circulation  (Cleland). 


CHRONOLOGY  OF  HUMAN  DEVELOPMENT.  929 

(b)  In  the  deciduata,  there  is  such  a  firm  union  between  the  chorionic  villi  with  the  uterine  mucous 
membrane,  that  the  uterine  part  of  the  placenta  comes  away  with  the  foetal  part  at  birth.  In  this 
case  the  placenta  is  either  zonary  (carnivora,  pinnipedia,  elephant)  or  discoid  (apex,  insectivora, 
edentata,  rodentia). 

446.  CHRONOLOGY  OF  HUMAN  DEVELOPMENT.— Development  during  the 
ist  Month. — At  the  I2th-I3th  day  the  ovum  is  saccular  (5.5  mm.  and  3  mm.  in  diameter) ;  there  is 
simply  the  blastodermic  vesicle,  with  the  blastoderm  at  one  part,  consisting  of  two  layers;  the  zona 
pellucida  beset  with  small  villi  (^Reicherf).  At  the  15th— i6th  day  the  ovum  (5-6  mm.)  is  covered 
with  simple  cylindrical  villi.  The  zona  pellucida  consists  of  embryonic  connective  tissue  covered 
with  a  layer  of  flattened  epithelium.  The  primitive  groove  and  the  laminse  dorsales  appear.  Then 
follows  the  stage  when  the  allantois  is  first  formed.  At  the  I5th-i8th  day  Coste  investigated  an 
ovum.  It  was  13.2  mm.  long,  with  small  branched  villi;  the  embryo  itself  was  2.2  mm.  long,  of  a 
curved  form,  and  with  a  moderately  enlarged  cephalic  end.  The  amnion,  umbiUcal  vesicle  with  a 
wide  vitelline  duct,  and  the  allantois  were  developed,  the  last  already  united  to  the  false  amnion. 
The  S-shaped  heart  lies  in  the  cardiac  cavity,  shows  a  cavity  and  a  bulbous  aortas,  but  neither  auri- 
cles nor  ventricles.  The  visceral  arches  and  clefts  are  indicated,  but  they  are  not  perforated.  The 
omphalo-mesenteric  vessels  forming  the  first  circulation  on  the  umbilical  vesicle  are  developed,  the 
duct  (vitelhne)  is  still  quite  open,  and  two  primitive  aortse  run  in  front  of  the  protovertebras.  The 
allantois  attached  to  the  foetal  membranes  is  provided  with  blood  vessels.  The  two  omphalo-mesen- 
teric veins  unite  with  the  two  umbilical  veins,  and  pass  to  the  venous  end  of  the  heart.  The  mouth 
is  in  process  of  formation.    The  limbs  and  sense  organs  absent ;  the  Wolffian  bodies  probably  present. 

At  the  20th  day  all  the  visceral  arches  are  formed,  and  the  clefts  are  perforated.  The  mid-brain 
forms  the  highest  part  of  the  brain,  while  the  two  auricles  appear  in  the  heart.  The  connection  with 
the  umbilical  vesicle  is  still  moderately  wide.  The  embyro  is  2.6-3.3-4  mm.  long,  while  the  head 
is  turned  to  one  side  [His).  At  a  slightly  later  period  the  temporal  and  cervical  flexures  take  place, 
and  the  hemispheres  appear  more  prominently;  the  vitelline  duct  is  narrowed,  the  position  of  the  liver 
is  indicated,  while  the  \^mbs  are  still  absent  [His). 

At  the  2ist  day  the  ovum  is  13  mm.  long  and  the  embryo  4-4.5  mm.;  the  umbilical  vesicle  2.2 
mm.,  and  the  intestine  almost  closed.  Three  branchial  clefts.  Wolffian  bodies  laid  down,  and  the 
fi?-st  appearance  of  the  limbs,  three  cerebral  vesicles,  auditory  capsules  present  (R.  Wagner).  Coste 
also  observed,  in  addition,  the  nasal  pits,  eye,  the  opening  for  the  mouth,  with  the  frontal  and  superior 
maxillary  processes,  the  heart  with  two  ventricles  and  two  auricles. 

End  of  the  ist  Month. — The  embryos  of  25-28  days  are  characterized  by  the  distinctly  stalked 
condition  of  the  umbilical  vesicle  and  the  distinct  presence  of  limbs.  Size  of  the  ovum,  17.6  mm.; 
embryo,  13  mm.;  umbilical  vesicle,  5  5  mm.,  with  blood  vessels. 

2d  Month. — The  embryos  of  28-35  days  are  more  elongated,  and  all  the  branchial  clefts  are 
closed  except  the  first.  The  allantois  has  now  only  three  vessels,  as  the  right  umbilical  vein  is 
obliterated.  At  the  5th  week  the  nasal  pits  are  united  with  the  angle  of  the  mouth  by  furrows, 
which  close  to  form  canals  at  the  6th  week  [Toldt^.  At  35-42  days  the  nasal  and  oral  orifices  are 
separated,  the  face  is  flat,  the  limbs  show  three  divisions,  the  toes  are  not  so  sharply  defined  as  the 
fingers.  The  outer  ear  appears  as  a  low  projection  at  the  7th  week.  The  Wolffian  bodies  are 
much  reduced  in  size.     Length  of  body  at  7th  to  8th  week,  i. 6-4.1  cm. 

End  of  the  2d  Month. — Ovum,  61^  cm.;  vilh,  1.3  mm.  long;  the  circulation  on  the  imibilical 
vesicle  has  disappeared;  embryo,  26  mm.  long,  and  weighs  4  grammes.  Eyehds  and  nose  present, 
umbilical  cord  8  mm.  long,  abdominal  cavity  closed,  ossification  beginning  in  the  lower  jaw,  clavicle, 
ribs,  bodies  of  the  vertebrae;  sex  indistinct,  kidneys  laid  down. 

3d  Month. — Ovum  as  large  as  a  goose's  egg,  beginning  of  the  placenta,  embryo  7-9  cm.,  weigh- 
ing 20  grammes,  and  is  now  spoken  of  as  a  foetus.  External  ear  well  formed,  umbilical  cord  7  cm. 
long.  Beginning  of  the  difference  between  the  sexes  in  the  external  genitals,  umbilicus  in  the  lower 
fourth  of  the  linea  alba. 

4th  Month. — Foetus,  17  cm.  long,  weighing  120  grammes;  sex  distinct,  hair  and  nails  beginning 
to  be  formed,  placenta  weighs  80  grammes,  umbilical  cord  19  cm.  long,  umbilicus  above  the  lowest 
fourth  of  the  linea  alba,  contractions  or  movements  of  the  limbs,  meconium  in  the  intestine,  skin  with 
blood  vessels  shining  through  it,  eyelids  closed. 

5th  Month. — Foetus,  length  of  body,  9.7-14.7  cm.,  total  length  18  to  28  cm.,  weighing  2S4 
grammes;  hair  on  the  head  and  lanugo  distinct;  skin  still  somewhat  red  and  thin,  and  covered  with 
vernix  caseosa  [\  287,  2),  is  less  transparent;  weight  of  placenta,  178  grammes;  umbilical  cord,  31 
cm.  long. 

6th  Month. — Foetus,  length  of  body,  15-18. 7,  total  length,  29—37  cm.,  weighing  634  grammes; 
lanugo  more  abundant;  vernix  more  abundant;  testicles  in  the  abdomen;  pupillary  membrane  and 
eyelashes  present ;  meconium  in  the  large  intestine. 

7th  Month. — Foetus,  length  of  body,  18-22.8,  total  length,  35-38  cm.,  weighing  1218  grammes; 
the  descent  of  the  testicles  begins — one  testicle  in  the  inguinal  canal,  the  eyes  open,  the  pupillary 
membrane  often  absorbed  at  its  centre  in  the  28th  week.  In  the  brain  other  fissures  are  formed 
besides  the  primary  ones.  The  foetus  is  capable  of  living  independently.  At  the  beginning  of  this 
month  there  is  a  centre  of  ossification  in  the  os  calcis. 

59 


930  FORMATION    OF   THE    OSSEOUS    SYSTEM. 

8th  Month. —  Kcvtus,  length  of  body,  24-27. S.  total  length  42  cm.,  weighing  1.5  to  2  kilos.  (3.3 
to  4.4  11  >.  1;  hair  01  the  hend  abundant,  I  3  cm.  long,  nails  with  a  small  margin,  umbilicus  below 
the  middle  of  the  linca  alba,  one  testicle  in  the  scrotum. 

gth  Month. —  l-utus,  length  of  Iwly,  30-37,  total  length,  47-67  cm.,  weighing  2234  grammes, 
anil  is  not  distinguishable  from  the  chilil  at  the  full  j>eriod. 

.  FcEtus  at  the  Full  Period.  —  Length  of  body,  51  cm.  [20  inches],  weight,  3 '4  kilos.  [7  lbs.], 
lanugo  present  only  on  the  shoulders,  skin  white.  The  nails  of  the  fingers  project  beyond  the  tips 
of  the  fingers,  umbilicus  slightly  below  the  middle  of  the  linea  alba.  The  centre  of  ossification  in 
the  lower  epiphysis  of  the  femur  is  4  to  8  mm.  broad. 

Period  of  Gestation  or  Incubation  [Sc/unk). 
Pays.  D.iys.  Weeks.  I  Weeks. 

Coluber,     ....  12       Rabbit,  •    ■    •    •   ^  ,2       ^*°^' )  Sheep, 21 

Hen,       ••••)-,,        Hare,      .    .    .    .    1" -^         Vox \    9       ^odi\. 


.-,,        .      .....  --, ^- _       22 

Duck,     ....   J  "  Weeks.  Foumart,    ...   J  Roe 24 

Goose, 29       Rat, 5  Badger,       .    .    •   \  jq       Bear 1 

Stork, 42  '   Guinea-pig,    ...     7  Wolf,      .    .    .    .    j  Small  apes,    ../•'" 

Cassowary,     ...  65       Cat, "to  Lion,       14  Deer,      ....  36-40 

Mouse 24       Marten,      .    .    .   j  ,  I'ig, 17    ,  Woman 40 

Horse,  Camel,  13  months;  Rhinoceros,  18  months;  and  the  Elephant,  24  months. 
Limitation  of  the  supply  of  O  to  eggs  during  incubation,  leads  to  the  formation  of  dwarf  chicks. 

447.  FORMATION  OF  THE  OSSEOUS  SYSTEM.— Vertebral  Column.— The  ossifi- 
cation of  the  vertebrae  begins  at  the  Sth  to  the  9th  week,  and  first  of  all  there  is  a  centre  in  each 
vertebral  arch,  then  a  centre  is  formed  in  the  body  behind  the  chorda,  which,  however,  is  composed 
of  two  closely  apposed  centres.  At  the  5th  month  the  osseous  matter  has  reached  the  surface,  the 
chorda  within  the  body  of  the  vertebra  is  compressed;  the  three  parts  unite  in  the  1st  year.  The 
atlas  has  one  centre  in  the  anterior  arch  and  two  in  the  posterior;  they  unite  at  the  3d  year.  The 
epistropheus  has  a  centre  at  the  ist  year.  The  three  points  of  the  sacral  vertebrre  unite  or  anchylose 
between  the  2d  and  the  6th  year,  and  all  the  vertebrre  (sacral)  become  united  to  form  one  body 
between  the  I^>th  and  25th  years.  Each  of  the  four  coccygeal  vertebrae  has  a  centre  from  the  ist  to 
loth  year.  The  vertebra  in  later  years  produce  i  to  2  centres  in  each  process;  i  to -2  centres  in 
each  transverse  process;  i  in  the  mamillary  process  of  the  lumbar  vertebra;  and  I  in  each  articular 
process  (8  to  15  years).  Of  the  upper  and  under  surfaces  of  the  tody  of  a  vertebra  each  forms  an 
epiphyseal  thin  osseous  plate,  which  may  still  be  visible  at  the  20th  year.  Groups  of  the  cells  of  the 
chorda  are  still  to  be  found  within  the  intervertebral  disks.  As  long  as  the  coccygeal  vertebra*,  the 
odontoid  process,  and  the  base  of  the  skull  are  cartilaginous,  they  still  contain  the  remains  of  the 
chorda  (H.  Miiller).  The  coccygeal  vertebra.-  form  the  tail,  and  they  originally  project  in  man  like 
a  tail  (Fig.  665,  IX,  T),  which  is  ultimately  covered  over  Ijy  the  growth  of  the  soft  parts  (His). 

The  ribs  bud  out  from  the  prolovertebra%  and  are  represented  on  each  vertebra.  The  thoracic 
ribs  become  cartilaginous  in  the  2d  month  and  grow  forward  into  the  wall  of  the  chest,  whereby  the 
seven  upper  ones  are  united  by  a  median  portion  [Jiathke'),  which  represents  the  position  of  one-half 
of  the  sternum,  and  when  the  two  halves  meet  in  the  middle  line  the  sternum  is  formed.  When  this 
does  not  occur  we  have  the  condition  of  the  cleft  sternum.  At  the  6th  month  there  is  a  centre  of 
ossification  in  the  manubrium,  then  4  to  13  in  pairs  in  the  body,  and  I  in  the  ensiform  process. 
Each  rib  has  a  centre  of  ossification  in  its  body  at  the  2d  month,  and  at  the  8th  to  14th  one  in  the 
tubercle  and  another  in  the  head.  These  anchylose  at  the  14th  to  25th  year.  Sometimes  cervical 
ribs  are  present  in  man,  and  they  are  largely  developed  in  birds. 

The  skull. — The  chorda  extends  forward  into  the  axial  part  of  the  base  to  the  sphenoid  bone. 
The  skull  at  first  is  membranous,  or  the  primordial  cranium;  at  the  2d  month  the  basal  por- 
tion becomes  cartilaginous,  including  the  occipital  bone,  except  the  upper  half,  the  anterior  and 
posterior  part  and  wings  of  the  sphenoid  bone,  the  petrous  part  and  mastoid  process  of  the  temporal 
bone,  the  ethmoid  with  the  nasal  septum,  and  the  cartilaginous  part  of  the  nose.  The  other  parts  of 
the  skull  remain  membranous,  so  that  there  is  a  cartilaginous  and  membranous  primordial  cranium. 

I.  The  occipital  bone  has  a  centre  of  ossification  in  the  basilar  part  at  the  3d  month,  and  one  in 
the  condyloid  part  and  another  in  the  fossa  cerebelli,  while  there  are  two  centres  in  the  membranous 
cerebral  fossae.  The  four  centres  of  the  body  unite  during  intra-uterine  life.  All  the  other  parts 
unite  at  the  1st  to  2d  year. 

II.  The  post- sphenoid. — From  the  3d  month  it  has  two  centres  in  the  sella  turcica,  two  in  the 
sulcus  caroticus,  two  in  both  great  wings,  which  also  form  the  lamina  externa  of  the  pterygoid  pro- 
cess, while  the  non-cartilaginous  and  previously  formed  inner  lamina  arises  from  the  supeiior  maxil- 
lary process  of  the  first  branchial  arch.  During  the  first  half  of  fcetal  life  these  centres  unite  as  far 
as  the  great  wings ;  the  dorsum  sella  and  the  clinoid  process,  as  far  as  the  synchondrosis  spheno- 
occipitalis,  are  still  cartibginous,  but  they  ossify  at  the  13th  vear. 

III.  The  pre-sphenoid  at  the  Sth  month  has  two  centres  in  the  small  wings  and  two  in  the  body. 
At  the  6th  month  they  unite,  but  cartilage  is  still  found  within  them  even  at  the  13th  year. 


DEVELOPMENT   OF   THE    OSSEOUS    SYSTEM. 


931 


Fig.  671. 


r*"^ 


IV.  The  ethmoid  has  a  centre  in  the  labyrinth  at  the  5th  month,  then  in  the  1st  year  a  centre  in 
the  central  lamina.     They  unite  about  the  5th  or  6th  year. 

V.  Among  the  membranous  bones  are  the  inner  lamina  of  the  pterj-goid  process  (one  centre), 
the  upper  half  of  the  tabular  plate  of  the  occipital  (two  points),  the  parietal  bone  (one  centre  in  the 
parietal  eminence),  the  frontal  bone  (one  double  centre  in  the  frontal  eminence),  three  small  centres 
in  the  nasal  spine,  spina  trochlearis  and  zygomatic  process,  nasal  (one  centre),  the  edges  of  the  parie- 
tal bones  (one  centre),  the  tympanic  ring  (one  centre),  the  lachrymal,  vomer,  and  intermaxillary 
bone. 

The  facial  bones  are  intimately  related  to  the  transformations  of  the  branchial  arches  and  bran- 
chial clefts  (Fig.  671).  The  median  end  of  the  first  branchial  arch  projects  inward  from  each 
side  toward  the  large  oral  aperture.  It  has  two  processes, 
the  superior  maxillary  process  which  grows  more  laterally 
toward  the  side  of  the  mouth,  and  the  inferior  maxillary 
process,  which  surrounds  the  lower  margin  of  the  mouth 
(Fig.  665,  IX).  From  above  downward  there  grows  as  an 
elongation  of  the  basis  cranii  the  frontal  process  (i-),  a 
broad  process  with  a  point  (_;')  at  its  lower  and  outer  angle, 
the  inner  nasal  process.  The  frontal  and  the  superior  maxil- 
lary processes  (r)  unite  with  each  other  in  such  a  way  that 
the  former  projects  between  the  two  latter.  At  the  same 
time  there  is  anchylosed  with  the  superior  maxillary  process 
the  small  external  nasal  process  («),  a  prolongation  of 
the  lateral  part  of  the  skull,  and  lying  above  the  superior 
maxillary  process.  Between  the  latter  and  the  outer  nasal 
process  is  a  slit  leading  to  the  eye  [a).  Thus  the  mouth  is 
cut  off  from  the  nasal  apertm^es  which  lie  above  it.  But  the 
separation  is  continued  also  within  the  mouth  ;  the  superior 
maxillary  process  produces  the  upper  jaw,  the  nasal  process, 
and  the  intermaxillary  process  [Goethe) — the  latter  is  present 
in  man,  but  is  united  to  the  upper  jaw.  The  intermaxillary 
bone,  which  in  many  animals  remains  as  a  separate  bone  (os       > 

incisivum),  carries  the  incisor  teeth.     At  the  oth  week  the  Head  of  embri-o  rabbit  of  10  days  (><  12).  a 

•"   :                                     .                                     "^    ,                            eye;  at,  atFium   or  primitive  auricle  of 
hard  palate  IS  closed,  and  on  it  rests  the  septum  of  the  nose,         "  -.-...- 

descending  vertically  from  the  frontal  process.  The  lower 
jaw  is  formed  from  the  inferior  maxillary  process.  At  the 
circumference  of  the  oral  aperture  the  lips  and  the  alveolar 
walls  are  formed.  The  tongue  is  formed  behind  the  point  of 
the  union  of  the  second  and  third  branchial  arches   {His); 

while,  according  to  Born,  it  is  formed   by  an  intermediate  part  between  the  inferior  maxillary  pro- 
cesses. 

These  transformations  may  be  interrupted.  If  the  frontal  process  remains  separate  from  the  supe- 
rior maxillary  processes,  then  the  mouth  is  not  separated  from  the  nose.  This  separation  may  occur 
only  in  the  soft  parts,  constituting  hare-lip  (Fig.  672)  ;  or  it  m^ay  involve  the  hard  palate,  constitut- 
ing cleft  palate.     Both  conditions  may  occur  on  one  or  both  sides.     From  the  posterior  part  of  the 


heart ;  b,  aortic  bulb  ;  k' ,  k" ,  k'" ,  first 
(mandibular),  second  (hyoid),  third  (ist 
branchial)  visceral  arch  ;  ?«,  mouth;  s, 
superior,  and  u,  inferior  maxillary  pro- 
cess ;  s,  mid-brain  ;  v,  part  of  head  and 
fore-brain  ;  v,  ventricle  of  heart. 


Fig.  672. 


Fig.  673. 


Fig.  672.^Hare-lip  on  the  left  side. 

Fig.  673. — Inner  view  of  the  lower  jaw  of  an  embryo  pig  3  inches  long  (X  3%)-    f^k,  Meckel's  cartilage;  d,  dentary 
bone  ;  cr,  coronoid  process  ;  ar,  articular  process  (condyle) ;  ag;  angular  process ;  tnl,  malleus  ;  m6,  manubrium. 

first  branchial  arch  are  formed  the  malleus  (ossified  at  the  4th  month),  and  Meckel's  cartilage 
(Fig.  673),  which  proceeds  from  the  latter  behind  the  tympanic  ring  as  along  cartilaginous  process, 
extending  along  the  inner  side  of  the  lower  jaw,  almost  to  its  middle.  It  disappears  after  the  6th 
month;  still  its  posterior  part  forms  the  internal  lateral  ligament  of  the  maxillary  articulation.  ISTear 
where  it  leaves  the  malleus  is  the  processus  Folii  [Baumiiller).     A  part  of  its  median  end  ossifies, 


932        THE  BRANCHIAL  CLEFrS  AND  THEIR  RELATION  TO  NERVES. 

and  unites  with  the  lower  jaw.  The  lower  jaw  is  laid  down  in  memhrane  from  the  first  branchial 
arch,  while  the  angle  and  condyle  are  formed  from  a  cariiiaginous  process.  The  union  of  both  bones 
to  form  the  chin  occurs  at  the  1st  year.  I'rom  the  superior  maxillary  process  are  formed  the  inner 
lamella  of  the  pterj-goid  process,  the  jialaline  process  of  the  upper  jaw,  and  the  palatine  bone  at  the 
end  of  the  2d  month,  and  lastly  the  malar  bone. 

The  second  arch  [Ayoit/],  arising  from  the  temporal  bone,  and  running  parallel  with  the  first 
arch,  gives  rise  to  the  stapes  (although  acccirding  to  Salensky,  this  is  derived  from  tiie  first  arch),  the 
emmentia  pyramidalis,  with  the  stapedius  muscle,  the  incus,  the  styloid  process  of  the  temporal  bone, 
the  (foimerly  cartilt^inous)  stylohyoid  ligament,  the  smaller  cornu  of  the  hyoid  bone,  and  lastly 
the  gIoS!-o-palatine  arch  [His). 

The  third  arch  [t/iyro-hyoia)  forms  the  greater  cornu  and  body  of  the  hyoid  bone  and  the 
pharyngo-palatine  arch  {//is). 

The  fourth  arch  gives  rise  to  the  thyToid  cartilage  {//is). 

Branchial  Clefts. — The  fust  branchial  or  visceral  is  represented  by  the  external  auditory 
meatus,  the  tympanic  cavity,  and  the  Eustachian  tube ;  all  the  other  clefts  close.  Should  one 
or  other  of  the  clefts  remain  open,  a  condition  that  is  sometimes  hereditary  in  some  families, 
a  cervical  fistula  results,  and  it  may  be  formed  either  from  without  or  within.  Sometimes 
only  a  blind  diverticulum  remains.  IJranchiogenic  tumors  and  cysts  depend  upon  the  branchial 
arches  (A'.   I'o/kwnnn). 

[Relation  of  Branchial  Clefts  to  Nerves. — It  is  important  to  note  that  the  clefts  in  front  of 
the  mouth  (pre-oral),  and  those  behind  it  (post-oral),  have  a  relation  to  certain  nerves.  The  lac/t- 
ry ma  I  sVii  between  the  frontal  and  nasal  processes  is  supplied  by  Kh^/irs/  diTision  of  the  tris;emitius. 
Ihe  nasal  slil  between  the  superior  maxillary  process  and  the  nasal  process  is  supplied  by  the  bifur- 
cation of  the ////>,/ wf/tc.  The  orv;/ c/^//,  between  the  superior  maxillary  processes  and  the  mandi- 
bular arch,  is  supplied  by  the  second  and  third  divisions  of  the  trii^eminus.  The  first  post-oral  or 
tympanic- Eustachian  cleft,  between  the  mandibular  arch  (ist)  and  the  hyoid  arch,  is  su])plied  by 
the  portio  dura.  The  next  cleft  is  supplied  by  the  glosso-pharyni;eal,  and  the  succeeding  clefts  by 
branches  of  the  vai:;us.'\ 

The  thymus  and  thyroid  glands  are  formed  as  paired  diverticula  from  the  epithelium  covering 
the  branchial  arches.  The  epithelium  of  the  last  two  clefis  does  not  disappear  (pig),  but  prolifer- 
ates and  pushes  inward  cylindrical  processes,  which  develop  into  two  epithelial  vesicles,  the  paired 
commencement  of  the  thyroid  glands.  These  vesicles  have  at  first  a  central  .'■lit,  which  communi- 
cates w  ith  the  pharynx  ( IVo/jier).  According  to  His,  the  thyroid  gland  appears  as  an  epithelial 
vesicle  in  the  region  of  the  2d  pair  of  visceral  arches  in  front  of  the  tongue — in  man  at  the  4th 
week.  Solid  buds,  which  ultimately  become  hollow,  are  given  off  from  the  cavity  in  the  centre  of 
the  embryonic  thyroid  gland.  The  two  glands  ultimately  unite  together.  The  only  epithelial  part 
oi  ihe  thymus  \\\\\ch  remains  is  the  so-called  concentric  corpuscles  (p.  198).  According  to  Born, 
this  gland  is  a  diverticulum  from  the  3d  cleft,  while  His  xscribes  its  origin  to  the  4th  and  5th  aortic 
arches  in  man  at  the  4ih  week.  The  carotid  gland  is  of  epithelial  origin,  being  a  variety  of  the 
thyroid  (Stieda). 

The  Extremities. — The  origin  and  course  of  the  nerves  of  the  brachial  plexus  (p.  666)  show 
that  the  upper  extremity  was  originally  placed  much  nearer  to  the  cranium,  while  the  position  of  the 
posterior  pair  corresponds  to  the  last  lumbar  and  the  3d  or  4th  sacral  vertebrae  {//is). 

The  clavicle,  according  to  Bruch,  is  not  a  membrane  bone,  but  is  formed  in  cartilage  like  the 
furculum  of  birds  {Gegettbauer).  At  the  2d  month  it  is  four  times  as  large  as  the  upper  limb ;  it  is 
the  first  bone  to  ossify  at  the  7th  week.  At  puberty  a  sternal  epiphysis  is  formed.  Episternal  bones 
must  be  referred  to  the  clavicles  {Go/te).  Ruge  regards  pieces  of  cariilages  existing  between  the 
clavicle  and  the  sternum  as  the  analogues  of  the  episternum  of  animals.  The  clavicle  is  absent  in 
many  mammals  (camivora) ;  it  is  very  large  in  Hying  animals,  and  in  the  rabbit  is  half  membranous. 
The  furculum  of  birds  represents  the  united  clavicles. 

The  scapula  at  first  is  united  with  the  clavicle  (Rathke,  Gotte),  and  at  the  end  of  the  2d  month 
it  has  a  metlian  centre  of  ossification,  which  rapidly  extends.  Morphologically,  the  accessory  centre 
in  the  coracoid  process  is  interesting ;  the  latter  al>o  forms  the  upper  part  of  the  articular  surface. 
In  birds  the  corresponding  structure  forms  the  coracoid  bone,  and  is  united  with  the  sternum  ; 
while  in  man  only  a  membranous  band  stretches  from  the  tip  of  the  coracoid  process  to  the  sternum. 
The  long,  basal,  osseous  strip  corresponds  to  the  supra-scapular  bone  of  many  animals.  The  other 
centres  of  ossification  are — one  in  the  lower  angle,  two  or  three  in  the  acromion,  one  in  the  articu- 
lar surface,  and  an  inconstant  one  in  the  spine.     Complete  consolidation  occurs  at  puberty. 

The  humerus  ossifies  at  the  8th  to  the  gih  week  in  its  shaft.  The  other  centres  are — one  in  the 
upper  epiphysis,  and  one  in  the  capitellum  (1st  year);  one  in  the  great  tuberosity  and  one  in  the 
small  tuberosity  (2d  year);  two  in  the  condyles  (5th  to  loth  year) ;  one  in  the  trochlea  (12th  year). 
The  epiphyses  unite  with  the  shaft  at  the  l6th  to  20lh  year. 

The  radius  ossifies  in  the  shaft  at  the  3d  month.  The  rther  centres  are — one  in  the  lower  epi- 
physis (5ih  year),  one  in  the  upper  1 6th  year),  and  an  inconstant  one  in  the  tuberosity,  and  one  in  the 
styloid  process.     They  unite  at  puberty. 

The   ulna  also  ossifies  in  the  shaft  at  the  3d  month.     There  is  a  centre  in  the  lower  end  (6th 


DEVELOPMENT   OF   THE    BONES    OF   THE    IJMBS. 


933 


year),  two  in  the  olecranon  (nth  to  14th  year),  and  an  inconstant  one  in  the  coronoid  process,  and 
one  in  the  styloid  process.     They  consolidate  at  puberty. 

The  carpus  is  arranged  in  mammals  in  two  rows.  The  first  row  contains  three  bones — the 
radial,  intermediate,  and  ulnar  bones.  In  man  these  are  represented  by  the  scaphoid,  semi-lunar, 
and  cuneiform  bones ;  the  pisiform  is  only  a  sesamoid  bone  in  the  tendon  of  the  flexor  carpi  ulnaris. 
The  second  row  really  consists  of  as  many  bones  as  there  are  digits  {e.  ^^.,  salamander).  In  man 
the  common  position  of  the  4th  and  5th  fingers  is  represented  by  the  unciform  bone.  Morphologi- 
cally, it  is  interesting  to  observe  that  an  os  centrale,  corresponding  to  the  os  carpale  centrale  of 
reptiles,  amphibians,  and  some  mammals,  is  formed  at  first,  but  disappears  at  the  3d  month,  or  unites 
with  the  scaphoid.  Only  in  very  rare  cases  is  it  persistent.  All  the  carpal  bones  are  cartilaginous 
at  birth.  They  ossify  as  follows :  Os  mag- 
num, unciform  (ist  year),  cuneiform  (3d  year).  Fig.  674. 
trapezium,  semilunar  (5th  year),  scaphoid  (6th 
year),  trapezoid  (7th  year),  and  pisiform  (i2th 
year). 

The  metacarpal  bones  have  a  centre  in 
their  diapbyses  at  the  end  of  the  3d  month, and 
so  have  the  phalanges.  All  the  phalanges  and 
the  first  bone  of  the  thumb  have  their  cartilagi- 
nous epiphyses  at  the  central  end,  and  the  other 
metacarpal  bones  at  the  peripheral  end,  so  that 
the  first  bone  of  the  thumb  is  to  be  regarded  as 
a  phalanx.  The  epiphyses  of  the  metacarpal 
bones  ossify  at  the  2d,  and  those  of  the  pha- 
langes at  the  3d  year.  They  consolidate  at 
puberty. 

The  innominate  bone,  when  cartilaginous, 
consists  of  two  parts — the  pubis  and  the  ischium 
(^Rosenberg\.  Ossification  begins  with  three  cen- 
tres— one  in  the  ilium  (3d  to  4th  month),  one  in  I 
the  descending  ramus  of  the  ischium  (4th  to  5th 
month),  one  in  the  horizontal  ramus  of  the  pubis 
(5th  to  7th  month).  Between  the  6th  to  the 
14th  year,  three  centres  are  formed  where  the 
bodies  of  the  three  bones  meet  in  the  acetabu- 
lum, another  in  the  superficies  auricularis,  and 
one  in  the  symphysis.  Other  accessory  centres 
are :  One  in  the  anterior  inferior  spine,  the 
crests  of  the  ilium,  the  tuberosity  and  the  spine 
of  the  ischium,  the  tuberculum  pubis,  eminentia 
iliopectinea,  and  floor  of   the  acetabulum.     At 

first  the  descending  ramus  of  the  pubis  and  the  ascending  ramus  of  the  ischium  unite  at  the  7th 
to  8th  year;  the  Y-shaped  suture  in  the  acetabulum  remains  until  puberty  (Fig.  674). 

The  femur  has  its  middle  centre  at  the  end  of  the  2d  month.  At  birth,  there  is  a  centre  in  the 
lower  epiphyses;  slightly  later  in  the  head.  In  addition,  there  is  one  in  the  great  trochanter  (3d  to 
nth  year),  one  in  the  lesser  trochanter  (13th  to  14th  year),  two  in  the  condyles  (4th  to  8th  year) ;  all 
unite  about  the  time  of  puberty.  The  patella  is  a  sesamoid  bone  in  the  tendon  of  the  quadriceps 
femoris.     It  is  cartilaginous  at  the  2d  month,  and  ossifies  from  the  1st  to  the  3d  year. 

The  tarsus  generally  resembles  the  carpus.  The  os  calcis  ossifies  at  the  beginning  of  the  7th 
month,  the  astragalus  at  the  beginning  of  the  8th  month,  the  cuboid  at  the  end  of  the  loth,  the 
scaphoid  (ist  to  5th  year),  the  I  and  II  cuneiform  (3d  year),  and  the  III  cuneiform  (4th  year).  An 
accessory  centre  is  formed  in  the  heel  of  the  calcaneum  at  the  5th  to  loth  year,  which  consolidates 
at  puberty. 

The  metatarsal  bones  are  formed  like  the  metacarpals,  only  later. 

[Histogenesis  of  Bone. — The  great  majority  of  our  bones  are  laid  down  in  cartilage,  or  are 
preceded  by  a  cartilaginous  stage,  including  the  bones  of  the  limbs,  backbone,  base  of  the  skull, 
sternum,  and  ribs.  These  consist  of  solid  masses  of  hyaline  cartilage  covered  by  a  membrane, 
which  is  identical  with  and  ultimately  becomes  the  periosteum.  The  formation  of  bone,  when  pre- 
ceded by  cartilage,  is  called  endochondral  bone.  Some  bones,  such  as  the  tabular  bones  of  the 
vault  of  the  cranium,  the  facial  bones,  and  part  of  the  lower  jaw,  are  not  preceded  by  cartilage. 
In  the  latter  there  is  merely  a  membrane  present,  while  from  and  in  it  the  future  bone  is  formed.  It 
becomes  the  future  periosteum  as  well.  This  is  called  the  intra-membranous  or  periosteal  mode 
of  formation.] 

[Endochondral  Formation. — (i)  The  cartilage  has  the  shape  of  the  future  bone  only  in  minia- 
ture, and  it  is  covered  with  periosteum.  In  the  cartilage  an  opaque  spot  or  centre  of  ossification 
appears,  due  to  the  deposition  of  lime  salts  in  its  matrix.     The  cartilage  cells  proliferate  in  this  area, 


Centres  of  ossification  of  the  innominate  bone. 


934  DEVELOPMENT    AND    GROWTH    OF    BONE. 

but  the  first  bone  is  fonned  under  the  periosteum  in  the  shaft,  so  that  an  osseous  case  like  a  muff 
surrounds  the  cartilage.  This  bone  is  formed  by  the  sub-periosteal  osteoblasts.  (2)  Bloodvessels, 
accompanied  by  osteoblasts  and  connective  tissue,  grow  into  the  cartilage  from  the  osteogenic  layer  of 
the  periosteum  ( /<<^rios/i-ii/  /roiesses  of  N'irchow),  so  that  tlie  cartilage  becomes  channeled  and  vas- 
cular. As  these  channels  extend  they  open  into  the  already  enlarged  cartilage  lacun;v.  absorption 
of  the  matrix  taking  place,  while  other  parts  of  the  cartilaginous  matrix  become  calcified.  Thus  a 
series  of  cavities,  bounded  by  calcified  cartilage— the  primary  medullary  cavities — are  fonned. 
They  contain  the  primary  or  cartihu^e  marrcno,  consisting  of  blood  vessels,  osteoblasts,  and  osteo- 
clasts, carried  in  from  the  osteogenic  layer  of  the  jieriosteum,  and  of  course  the  carlilai^e  cells  that 
have  been  liberated  from  their  lacuniv.  (3)  The  osteoblasts  are  now  in  the  interior  of  the  cartilage, 
where  they  (lis]iose  themselves  on  the  calcified  cartilage,  and  secrete  or  fomi  around  them  an  osseous 
matrix,  thus  enclosing  the  calcified  cartilage,  while  the  osteoblasts  themselves  become  embedded  in 
the  products  of  their  own  activity  and  remain  as  bone  corpuscles.  Bone  therefore  is  at  first  spongy 
bone,  and  as  the  primar)-  medullary  spaces  gradually  become  filled  up  by  new  osseous  matter  it 
becomes  denser,  while  the  calcified  cartilage  is  gradually  absorbed.  It  is  to  be  remembered  that, 
pari  passu  witli  the  deposition  of  the  new  bone,  bone  and  cartilage  are  being  absorbed  by  the 
osteoclasts.] 

Chemical  Composition  of  Bone. — Dry  bone  contains  ■(  of  organic  matter  or  ossein,  from 
which  gelatin  can  be  extracted  by  prolonijed  boiling;  and  about  -3  mineral  matter,  which  consi.sis  of 
neutral  calcic  phosphate,  57  per  cent.;  calcic  carbonate,  7  per  cent.;  magnesic  phosphate,  I  to  2  per 
cent.;  calcic  lluoride,  I  per  cent.,  with  traces  of  chlorine ;  and  water,  about  23  per  cent.  The 
marrow  contains  fluid  fat,  albumin,  hypoxanthin,  cholesterin,  and  extractives.  The  reil  marrow- 
contains  more  iron,  correspDnding  to  its  larger  proportion  of  hii^moglobin  [iVasse). 

[The  medullary  cavity  of  a  long  bone  is  occupied  hy  yeiimu  marrow,  which  contains  about  96 
per  cent,  of  fat.  The  rt'd  marrow  occurs  in  the  ends  of  long  bones,  in  the  flat  bones  of  the  skull, 
and  in  some  short  bones.  It  contains  very  little  fat,  and  is  really  lymphoid  in  its  characters,  being, 
in  fact,  a  hlood-formini:;  tissue  (p.  53)-] 

Growth  of  Bones. — Long  bones  grow  in  thickness  by  the  deposition  of  new  bone  from  the 
periosteum,  the  osteoblasts  becoming  embedded  in  the  osseous  matrix  to  form  the  bone  corpuscles. 
Some  of  the  fibres  of  the  connective  tissue,  which  are  caught  up,  as  it  were,  in  the  process,  remain 
as  Sharpey's  fibres,  which  are  calcified  fibres  of  white  fibrous  tissue,  bolting  together  the  peripheric 
lamella;.  [Miiller  and  Schafer  have  shown  that  there  are  also  fibres  in  the  peripheric  lamella,  com- 
parable to  yellow  elastic  fibres;  they  branch,  stain  deeply  with  magenta,  and  are  best  developed  in 
the  bones  of  birds.] 

[At  the  same  time  that  bone  is  being  deposited  on  the  surface,  it  is  being  absorbed  in  the  marrow 
cavity  by  the  action  of  the  osteoclasts,  so  that  a  metallic  ring  placed  round  a  bone  in  a  young 
animal  ultimately  comes  to  lie  in  the  medullary  cavity  (Dtthaviel).  The  growth  in  length  takes 
place  by  the  continual  growth  and  ossification  of  the  epiphyseal  cartilage.  The  cartilage  is  gradually 
absorbed  from  below,  but  it  proliferates  at  the  same  time,  so  that  what  is  lost  in  one  direction  is  more 
than  made  up  in  the  other  {J.  Hunier).'\ 

When  the  growth  of  bone  is  at  an  end,  the  epiphysis  becomes  united  to  the  diaphysis,  the  epiphyseal 
cartilage  itself  becoming  ossified.  It  is  not  detinitely  proved  whether  there  is  an  interstitial  expansion 
or  growth  of  the  true  osseous  substance  itself,  as  maintained  by  Wolfi"  (^  244,  9). 

[Howship's  Lacunae. — The  osteoclasts  or  myeloplaxes  are  large  multinuclear  giant  cells, 
which  erode  bone.  They  can  be  seen  in  great  numbers  lying  in  small  depressions  corresponding  to 
them — Howship's  lacunae — on  the  fang  of  a  temporarj'  tooth,  when  it  is  being  absorbed.  They  are 
readily  seen  in  a  microscopical  section  of  spongy  bones  with  the  soft  parts  preserved.] 

The  form  of  a  bone  is  influenced  by  external  conditions.  The  bones  are  stronger  the  greater  the 
activity  of  the  muscles  acting  on  them.  If  pressure  acting  normally  upon  a  bone  be  removed,  the 
bone  develops  in  the  direction  of  least  resistance,  and  becomes  thicker  in  that  direction.  Bone 
develops  more  slowly  on  the  side  of  the  greatest  external  pressure,  and  it  is  curved  by  unilateral 
pressure  {Lesshaft). 

448.  DEVELOPMENT  OF  THE  VASCULAR  SYSTEM.  —  Heart.  —  [The  heart 
appears  as  a  solid  mass  of  cells  in  the  splanchnopleure,  at  the  front  end  of  the  embryo,  immediately 
under  the  "  foregut."  Very  soon  a  cavity  appears  in  this  mass  of  cells;  some  of  the  latter  float  free 
in  the  fluid,  while  the  cellular  wall  begins  to  pulsate  rhythmically.  This  hollow  cellular  structure 
elongates  into  a  tube,  which  very  soon  assumes  a  shape  somewhat  like  an  ,S  (Fig.  675,  i)],  and  there 
are  indications  of  its  being  subdivided  into  (a)  an  upper  aortic  part  with  the  bulbus  arteriosus  ; 
{b)  a  middle  or  ventricular  part ;  and  {v)  a  lower  venous  or  auricular  part.  The  heart  then 
curves  on  itself  in  the  form  of  a  horseshoe  (2),  so  that  the  venous  end  {A)  comes  to  lie  above  and 
slightly  behind  the  arterial  end.  On  the  right  and  left  side,  respectively,  of  the  venous  part  is  a 
blind  hollow  outgrowth,  which  forms  the  large  auricle  on  each  side  (3,  o,  0,).  The  flexure  of  the 
body  of  the  heart  corresponding  to  the  great  curvature  (2,  V)  is  divided  into  two  large  compart- 
ments (3),  the  division  being  indicated  by  a  slight  depression  on  the  surface.  The  large  truncus 
venosus  (4,  z-),  which  joins  with  the  middle  of  the  posterior  wall  of  the  auricular  part,  is  composed 
of  the  superior  and  inferior  venas  cava\     This  common  trunk  is  absorbed  at  a  later  period  into  the 


DEVELOPMENT    OF   THE    HEART. 


935 


enlarging  auricle,  and  thus  arise  the  separate  terminations  of  the  superior  and  inferior  venae  cavce. 
In  man,  the  heart  soon  comes  to  lie  in  a  special  cavity,  which  ia  part  is  bounded  by  a  portion  of  the 
■diaphragm  [His).  At  the  4th  to  5th  week,  the  lieart  begins  to  be  divided  into  a  right  and  a  left 
half.  Corresponding  to  the  position  of  the  vertical  ventricular  furrow,  a  septum  grows  upward  verti- 
cally in  the  interior  of  the  heart,  and  divides  the  ventricular  part  into  a  right  and  left  ventricle  (5, 
R,  L).  There  is  a  constriction  in  the  heart,  between  the  auricular  and  ventricular  portions,  forming 
the  canalis  auricularis.  It  contains  a  communication  between  the  auricle  and  both  ventricles, 
lying  between  an  anterior  and  posterior  projecting  lip  of  endothelium,  from  which  the  auriculo- 
ventricular  valves  are  formed  [F.  Schmidt).  The  ventricular  septum  grows  upward  toward  the 
canalis  auricularis,  and  is  complete  at  the  8th  week.  Thus,  the  large  undivided  auricle  communi- 
cates by  a  right  and  left  auriculo-ventricular  opening  with  the  corresponding  ventricle  (5).  At  the 
same  time  two  septa  (4,/  a)  appear  in  the  interior  of  the  truncus  arteriosus  (4,/),  which  ulti- 
mately meet,  and  thus  divide  this  tube  into  two  tubes  (5,  a  p),  the  latter  forming  the  aorta  and 


Development  of  the  heart,  i,  Early  appearance  of  the  heart — /?,  aortic  part,  with  the  bulbus,  b;  v,  venous  end.  2, 
Horseshoe-shaped  curving  of  the  heart — a,  aortic  end,  with  the  bulbus,  d ;  V,  ventricle ;  A,  auricular  part.  3, 
Formation  of  the  auricular  appendages,  o,  o-^,  and  the  external  furrow  in  the  ventricle.  4,  Commencing  division 
of  the  aorta,  /,  into  two  tubes,  a.  5,  View  from  behind  of  the  opened  auricle,  v,  v,  into  the  L,  and  R,  ventricles, 
and  between  the  two  latter  the  projecting  ventricular  septum,;  while  the  aorta  (a)  and  pulmonary  artery  (/) 
open  into  their  respective  ventricles.  6,  Relation  of  the  orifices  of  the  superior  (Cf)  and  inferior  vena  cava  [Ci)  to 
the  auricle  (schematic  view  from  above)— .r,  direction  of  the  blood  of  the  superior  vena  cava  into  the  right  auricle  ; 
_j',  that  of  the  inferior  cava  to  the  left  auricle;  tL,  tubercle  of  Lower.  7,  Heart  of  the  ripe  foetus — R,  right,  L, 
left  ventricle  ;  «,  aorta,  with  the  innominate,  c,  c,  carotid,  c,  and  left  subclavian  artery,  i- ;  B,  ductus  arteriosus ; 
J>,  pulmonary  artery,  with  the  small  branches  /  and  2,  to  the  lungs. 


pulmonary  artery,  and  are  disposed  toward  each  other  like  the  tubes  in  a  double-barreled  gun. 
The  septum  grows  downward  until  it  meets  the  ventricular  septum  (5),  so  that  the  right  ventricle 
comes  to  be  connected  with  the  pulmonary  artery,  and  the  left  with  the  aorta.  The  division  of 
the  truncus  arteriosus,  however,  takes  place  only  in  the  first  part  of  its  course.  The  division  does 
not  take  place  above,  so  that  the  pulmonary  artery  and  aorta  unite  in  one  common  trunk  above. 
This  communication  between  the  pulmonary  artery  and  the  aorta  is  the  ductus  arteriosus  Botalli 

In  the  auricle  a  septum  grows  from  the  front  and  behind,  ending  internally  with  a  concave  mar- 
gin. The  vena  cava  superior  (6,  Cs)  terminates  to  the  right  of  this  fold,  so  that  its  blood  will  tend 
to  go  toward  the  right  ventricle,  in  the  direction  of  the  arrow  in  6,  x.  The  cava  inferior,  on  the 
other  hand  (6,  Ci),  opens  directly  opposite  the  fold.  On  the  left  of  its  orifice  the  valve  of  the  fora- 
men ovale  is  formed  by  a  fold  growing  toward  the  auricular  fold,  so  that  the  blood  current  from  the 
inferior  vena  cava  goes  only  to  the  left,  in  the  direction  of  the  arrow,  j;  on  the  right  of  the  orifice 


936 


DEVELOPMENT   OF   THE    AORTIC    ARCHES. 


of  the  cava,  and  opposite  the  fold,  is  the  Eustachian  valve,  which,  in  conjunction  with  the 
tubercle  of  Lower  {tL),  directs  the  stream  from  the  inferior  vena  cava  to  the  left  into  the  left 
auricle,  through  the  ]>ervious  foramen  ovale.  Comjjare  the  fcttal  circulation  (p.  92cS).  After  birth, 
the  valve  of  the  foramen  ovale  closes  that  aperture,  while  the  ductus  arteriosus  also  becomes  imjier- 
vioiis,  so  that  the  blood  of  the  pulmonary  arlerj  is  forced  to  go  through  the  pulmonary  branches 
proceeding  to  the  expanding  lungs.  .Sometimes  the  foramen  ovale  remains  pervious,  giving  rise  to 
serious  syrnptoms  after  a  time,  and  constituting  morbus  ceruleus. 


Fic.  676. 


1. 


The  aortic  arches,  i.  The  first  position  of  the  1,2,  and  3  arches.  2.  5  aortic  arches  ;  tii,  common  aortic  trunl: ;  ad, 
descending  aorta.  3.  Disappearance  of  the  upper  two  arches  on  each  side — S,  subclavian  artery;  v,  vertebral 
artery;  aj-,  axillary  artery.  4.  Transition  to  the  final  stage — P,  pulmonary  artery ;  ./4,  aorta  ;  rfZ?,  ductus  arte- 
riosus (Sotalli) ;  S,  right  subclavian,  united  with  the  right  common  carotid,  which  divides  into  the  internal  (C7) 
and  external  carotid  (C<?);  a.r,  axillary  ;  t/,  vertebral  artery. 


Arteries. — With  the  formation  of  the  branchial  arches  and  clefts,  the  number  of  aortic  arches  on 
each  side  becomes  increased  to  5  (Fig.  676),  which  run  above  and  below  each  branchial  cleft,  in  a 
branchial  arch,  and  then  all  reunite  behind  in  a  common  descending  trunk  (2,  ad)  {Rathke).  These 
blood  vessels  remain  only  in  animals  that  breathe  by  gills.  In  man,  the  upper  two  arches  disappear 
completely  (3).  When  the  truncus  arteriosus  divides  into  the  pulmonary  artery  and  the  aorta  (4, 
/*,  A),  the  lowest  arch  on  the   left   side,  with  its  origin,  forms  the  pulmonary  artery  (4),  and  it 

springs  from  the  right  side  of  the  heart.    Of 


Fig.  677. 


First  appearance   of  the   veins  of  the   embrjo.      II,    Their 
transformations  to  form  the  final  arrangement. 

into  the  venous  part  of  the  heart. 


these  the  /e/t  lowest  arch  forms  the  ductus 
arteriosus  {dB),  and  from  the  commence- 
ment of  the  latter  proceed  the  pulmonary 
branches  of  the  pulmonary  artery.  Of  the 
remaining  arches  which  are  united  with  the 
aorta,  the  left  middle  one  {i.e.,  the  fourth 
left)  forms  the  permanent  aortic  arch  into 
which  the  ductus  arteriosus  opens,  while 
the  right  one  (fourth)  forms  the  .subclavian 
artery ;  the  third  arch  forms  on  each  side 
the  origin  of  the  carotids  [Ci,  Ce).  The 
arteries  of  the  first  and  second  circulations 
have  been  referred  to  already  (p.  921). 
When  the  umbilical  vesicle,  with  its  primary 
circulation,  diminishes,  only  one  omphalo- 
mesenteric artery  is  present,  which  gives  a 
branch  to  the  intestine.  At  a  later  period, 
the  omphalo-mesenteric  arteries  atrophy, 
while  the  artery  to  the  intestine — the  supe- 
rior mesenteric — becomes  the  largest  of  all, 
it  being  originally  derived  from  one  of  the 
omphalo-mesenteric  arteries. 

Veins  of  the  Body. — The  veins  first 
formed  in  the  body  of  the  embryo  itself 
are  the  two  cardinal  veins  ;  on  each  side 
an  anterior  (Fig.  677,  I,  cs),  and  a  posterior 
[ci),  which  proceed  toward  the  heart  and 
unite  on  each  side  to  form  a  large  trunk, 
the  duct  of  Cuvier  [DC),  which  passes 
The  anterior  cardinal  veins  give  off  the  subclavian  veins  {bb) 


DEVELOPMENT    OF    THE    VEINS. 


937 


and  tlie  common  jugular  veins,  which  divide  into  the  external  [le)  and  internal  [Ji\  jugular 
veins.  In  addition,  there  is  a  transverse  anastomosing  branch  passing  obliquely  irom  the  left 
(where  it  divides)  to  the  right,  which  joins  their  trunk  lower  down.  In  the  final  arrangement  (II) 
this  anastomosis  (^j)  becomes  very  large  to  form  the  left  innominate  vein,  while  with  the  growth 
of  the  arms  the  subclavian  veins  increase  (bb') ;  and  lastly,  the  calibre  of  the  jugular  vein  changes, 
the  internal  jugular  (ye)  becoming  very  large,  and  the  external  jugular  (/f)  smaller.  In  some 
animals,  e.g.,  the  dog  arid  rabbit,  the  large  embryonic  size  is  retained.  The  part  of  the  left  superior 
cardinal  vein,  from  the  anastomosis  downward  to  the  left  duct  of  Cuvier,  disappears.  The  posterior 
cardinal  veins  divide  in  the  pelvis  into  the  hypogastric  (I,  li)  and  external  iliac  (/",  /").  The 
inferior  cava  at  first  is  very  small  (I,  Vc),  divides  at  the  entrance  to  the  pelvis,  and  on  each  side  goes 
into  the  point  of  division  of  the  cardinal  veins.  There  is  also  a  transverse  ascending  anastomosis 
between  the  right  and  left  cardinal  veins.  For  the  final  arrangement,  the  cava  inferior  (II,  Ci\ 
dilates,  and  with  it  the  hypogastric  and  external  iliac  vein  on  each  side.  The  right  cardinal  vein 
remains  very  small  (  Vena  azygos,  Az,)  and  also  the  lower  part  from  the  left  one  to  the  transverse 
anastomosis.  The  latter  itself  also  remains  very  small  (  Vena  hemiazygos,  Hz).  On  the  other  hand, 
the  upper  part  above  the  anastomosis  to  the  duct  of  Cuvier  disappears.  Lastly,  the  common  large 
venous  trunk  is  so  absorbed  into  the  wall  of  the  auricle  ( V)  that  both  venae  cavae  have  each  a 
separate  orifice  (p.  928).     The  embryonic  condition  of  the  veins  persists  in  fishes. 

Veins   of  the  First  and  Second   Circulation,   and  Portal  System. — The  two  omphalo- 
mesenteric veins  (^om,  om-^    open  into   the  posterior  or  venous   end  of   the  tubular  heart    (Fig. 

Fig.  678. 


om 


Development  of  the  veins  and  portal  system.  H,  heart ;  R,  L,  right  and  left  side  of  the  body;  om,  right  omphalo- 
mesenteric vein;  oin\,  left;  u,  right  umbilical  vein;  «i,  left;  O',  vena  cava  inferior;  a,  venae  advehentes ;  r, 
vense  revehentes  ;  Z*,  intestine ;  zk,  mesenteric  vein  ;  4, /,  splenic  vein;  2, /,  liver. 


678,  I,  H).  The  right  vein,  however,  disappears  very  soon.  As  soon  as  the  allantois  is  formed, 
the  two  umbilical  veins  join  the  truncus  venosus(l,  u,  u-^).  At  first  the  omphalo-mesenteric  veins  are 
larger  than  the  umbilical  veins ;  at  a  later  period  this  is  reversed,  and  the  right  umbilical  vein  dis- 
appears. As  soon  as  veins  are  formed  within  the  body  proper  of  the  embryo,  the  inferior  cava  also 
opens  into  the  truncus  venosus  (2,  Ci).  Gradually  the  umbilical  vein  (2,  zi-^)  becomes  the  chief 
trunk,  while  the  small  omphalo-mesenteric  (2,  om-^)  carries  little  blood. 

Portal  System. — The  umbilical  and  omphalo-mesenteric  veins  pass  in  part  directly  under  the 
liver  to  reach  the  heart.  They  send  branches — carrying  arterial  blood — to  the  liver,  and  the  latter 
grows  round  these  vessels.  These  branches  are  the  venae  advehentes  (2  and  3,  a).  The  blood 
circulating  through  the  liver  from  the  vense  advehentes  is  returned  by  other  veins,  the  venae  reve- 
hentes (2  and  3,  ;'),  which  reunite  at  the  blunt  margin  of  the  liver  with  the  chief  trunk  of  the 
umbilical  vein.  The  umbilical  vein  (3,  z^j)  and  the  omphalo-mesenteric  vein  (3,  orn-^)  anastomose  in 
the  liver.  When  the  intestine  develops  (3,  D),  the  mesenteric  vein  (;«)  opens  into  the  omphalo- 
mesenteric vein,  and  the  splenic  vein  as  well  (4,  /).  when  the  spleen  is  formed.  At  a  later  period, 
when  the  omphalo-mesenteric  vein  (4,  om^)  disappears,  the  vein  from  the  intestine  now  becomes  the 
common  trunk  of  the  previously  united  vessel?.  It  unites  in  the  liver  with  the  umbilical  vein  to 
form  the  trunk  of  the  vena  portse.  When,  after  birth,  the  umbilical  vein  disappears  (4,  i(^),  the 
mesenteric  alone  remains  as  the  portal  vein.  As  the  ductus  venosus  is  obliterated,  the  portal 
vein  must  send  its  blood  through  the  liver,  and  thus  the  portal  circulation  is  completed. 


938 


FORMATION    OF   THE    INTESTINAL   CANAL. 


449.  FORMATION  OF  THE  INTESTINAL  CANAL.— The  primitive  intestine,  or 
gut,  consists  of  a  slrai<j;lit  tube  pioceedinjj  from  the  head  to  the  tail.  The  vitelline  duct  is  inserted 
at  that  point,  which  at  a  later  period  corresjionds  to  the  lower  part  of  the  ileum.  .\t  the  4th  week 
the  tube  makes  a  slight  bend  toward  the  umbilicus  (Fig.  679,  I).     As  already  mentioned,  the  vitel- 


Fir.:  680. 


Development  of  the  intestine,  z',  stomach  ;  o,  insertion 
of  the  vitelline  duct;  /,  small  intestine;  c,  colon  ;  r, 
rectum. 


Formation  of  the  lungs.  A,  Diverticula  of  the  lungs 
as  double  sacs — k,  mcsoblastic  layer;  /,  hypoblas- 
tic  layer  ;  m,  stomach  ;  s,  oesophagus.  B,  Further 
branching  of  the  Umgs— /,  trachea;  i,  e,  bronchi  ; 
y,  projecting  vesicles. 


line  duct  is  obliterated,  remaining  only  for  a  time  as  a  thread  attached  to  the  intestine,  being  still 
visible  at  the  3d  month.  Sometimes  it  remains  as  a  short  blind  tube  communicating  with  the  intes- 
tine. This  is  the  so  called  "  true  intestinal  diverticulum ;  "  occasionally  a  cord — the  obliterated 
omphalo- mesenteric  vessels — passes  from  it  to  the  umbilicus.     In  very  rare  cases,  the  duct  may 


Fig.  681. 


m 


Formation  of  the  omentum.  I  and  II — hg,  gastro-hepatic  ligament;  ;«,  great,  n,  lesser  curvature  of  the  stomach; 
s,  posterior,  and  /,  anterior  fold  or  plate  of  the  omentum;  ;«c,  mesocolon  ;  c,  colon.  Ill — L,  liver;  /,  small 
intestine;  i,  mesentery ;/,  pancreas  ;  rf,  duodenum  ;   r,  rectum  ;  A',  great  omentum. 


remain  open  as  far  as  the  umbilicus,  forming  a  congenital  fistula  of  the  ileum,  or  it  may  give  rise  to 
cystic  formations  (J/.  Roth).  In  a  human  fcetus  at  the  4th  week,  His  distinguished  the  cavity  of 
the  mouth,  pharynx,  oesophagus,  stomach,  duodenum,  mesenterial  intestine,  and  the  hind  gut,  with 
the  cloaca.     The  intestine  then  forms  \\\t,  first  coil  (Fig.  679,  II)  by  rotating  on  itself  at  the  intes- 


THE    GLANDS,    PERITONEUM    AND    MESENTERY. 


939 


tinal  umbilicus,  so  that  the  lower  part  of  the  intestine  lying  next  the  knee-like  bend  comes  to  lie 
above,  while  the  upper  part  lies  below.  From  the  lower  part  of  this  loop,  there  proceed  the  coils 
of  the  small  intestine  (III,  i),  which  gradually  grow  longer.  From  the  upper  limb  of  the  loop, 
which  also  elongates,  the  large  intestine  is  formed ;  first  the  descending  colon,  then  by  elonga- 
tion the  transverse  colon,  and  lastly  the  ascending  colon. 

Glands. — By  diverticula,  or  protrusions  from  the  intestine,  the  various  glands  are  formed.  The 
cells  of  the  hypoblast  proliferate  and  take  part  in  the  process,  as  they  form  the  secretory  cells  of  the 
glands,  while  the  mesoblastic  part  of  the  splanchnopleure  forms  the  membranes  of  the  glands, 
giving  them  their  shape.     The  diverticula  are  as  follows : — 

1.  The  salivary  glands,  which  grow  out  from  the  oral  cavity  at  first  as  simple  solid  buds,  but 
-afterward  become  hollow  and  branched.       [The  salivary  glands  are  developed  from  the  epiblast 

lining  the  mouth  (stomodaeum).] 

2.  The  lungs,  which  arise  as  two  separate  hollow  buds  (Fig.  680,  A,  2),  and  ultimately  have 
only  one  common  duct,  are  protrusions  from  the  oesophagus.  The  upper  part  of  the  united  tracheal 
tube  forms  the  larynx.  The  epiglottis  and  the  thyroid  cartilage  originate  fi-om  the  part  which  forms 
the  tongue  [Gangkofner) .  The  two  hollow  spheres  grow  and  ramify  like  branched  tubular  glands 
with  hollow  processes  (B,y).  In  the  first  period  of  development,  there  is  no  essential  difference 
between  the  epithelium  of  tlae  bronchi  and  that  of  the  primitive  air  vesicles  [Siteda),     The  spleen 


Development  of  the  internal  generative  organs.  I,  Undifferentiated  condition— D,  reproductive  gland,  Ij'ing  on  the 
tubules  of  the  Wolffian  body  ;  W,  Wolffian  duct ;  M,  MijUerian  duct ;  S,  uro-genital  sinus.  II,  Transformations 
in  the  female — F,  fimbria,  with  the  hydatid,  /i^  ;  T,  Fallopian  tube  ;  U,  uterus  ;  S,  uro-genital  sinus  ;  O,  ovary  ; 
P,  parovarium.  Ill,  Transformations  in  the  male — H,  testis;  E,  epididymis,  with  the  hydatid.  A;  a,  vas 
aberrans;  V,  vas  deferens;  S,  uro-genital  sinus;  ?<,  male  uterus.  4,  ^,  hind  gut;  a,  allantois;  «,  urachus ;  K, 
cloaca.     5,  M,  rectum;  ?«,  perineum  ;  3,  positioa  of  the  bladder;  S,  uro-genital  sinus. 

and  suprarenal  capsules,  however,  are  not  developed  in  this  way.     The  former  arises  in  a  fold 
of  the  mesogastrium  at  the   2d  month  (//w)  ;  the  latter  are  originally  larger  than  the  kidneys. 

3.  The  pancreas  arises  in  the  same  way  as  the  salivary  glands,  but  is  not  visible  at  the  4th 
week  [J7is). 

4.  The  liver  begins  very  early,  and  appears  as  a  diverticulum,  with  two  hollow  pri7mtive  hepatic 
ducts,  which  branch  and  form  bile  ducts.  At  their  periphery  they  penetrate  between  the  solid  masses 
of  cells — the  liver  cells — which  are  derived  from  the  hypoblast.  At  the  2d  month  the  liver  is  a  large 
organ,  and  secretes  at  the  3d  month  {\  182). 

5.  In  birds  two  small  blind  sacs  are  formed  from  the  hind  gut. 

6.  The  fcetal  respiratory  organ,  the  allantois,  is  treated  of  specially  (|  444). 

Peritoneum  and  Mesentery. — The  inner  surface  of  the  ccelom,  or  body  cavity,  the  surface  of 
the  intestine,  and  its  mesentery  are  covered  by  a  serous  coat — ihQ  peritoneum.  xAt  first  the  simple 
intestine  is  contained  in  a  fold,  or  duplicature  of  the  peritoneum ;  on  the  stomach,  which  is  merely 
at  first  a  spindle- shaped  dilatation  of  the  tube  placed  vertically,  it  is  called  mesogastrium.  Afterward, 
the  stomach  turns  on  its  side,  so  that  the  left  surface  is  directed  forward  and  the  right  backward. 
Thus,  the  insertion  of  the  mesogastrium,  which  originally  was  directed  backward  (to  the  vertebral 
column),  is  directed  to  the  left;  the  line  of  insertion  forming  the  region  of  the  great  curvature, 
which  becomes  still  more  curved.  From  the  great  curvature,  the  mesogastrium  becomes  elongated 
like  a  pouch  (Fig.  681,  I  and  II,  s,  i),  constituting  the  omental  sac,  which  extends  so  far  downward 


940 


DEVELOPMENT   OF    THE    URINARY    APPARATUS. 


as  to  pass  over  the  transverse  colon  and  the  loops  of  the  small  intestine  (III,  N).  As  the  mesogas- 
trium  originally  consists  of  two  plates,  of  course  the  omentum  must  consist  of  four  plates.  At  the 
4th  month,  the  posterior  surface  of  the  omental  sac  unites  with  the  surface  of  the  transverse  colon 

(Jo/i.  Miilkr). 

450.  URINARY  AND  GENERATIVE  ORGANS.— Urinary  apparatus.— The  first 
indication  of  this  apparatus  occurs  in  the  chick  at  the  2d  day  and  in  the  rabbit  at  the  9th,  as  the 
ducts  of  the  primitive  kidneys  or  Wolffian  ducts  (Fig.  682,  i,  \V),  which  are  formed  from  some 
cells  mapped  off  from  the  lateral  plate  above  and  to  the  side  of  the  protovertebrx-,  and  extending 
from  the  fifth  to  the  last  vertebra.  The  ducts  are  solid  at  first,  Init  soon  become  hollow,  and  from 
their  cavities  there  extend  laterally  a  series  of  small  tubes,  which  in  the  chick  communicate  freely 
with  the  peritoneal  cavity  {A'olliker).  Into  one  end  of  each  of  these  tubes  grows  a  tuft  of  blood 
vessels  forming  a  structure  resembling  the  glomeruli  of  the  kidney.  The  tubes  elongate,  form  con- 
volutions, and  increase  in  number.  The  upper  end  of  the  Wolffian  duct  is  closed  at  first,  its  lower 
end,  which  lies  in  a  projecting  fold — the  plica  urogenitalis  of  Waldeyer — in  the  peritoneal  cavity, 
opens  into  the  uro-genital  sinus.  Close  above  the  orifice  of  the  Wolffian  duct  appears  the  ureter  as 
the  duct  of  the  kidney.  The  duct  elongates,  and  branches  at  its  upper  end.  Each  canal  at  its  end 
is  like  a  stalked  caoutchouc  sac  ( Toldt),  and  into  it  there  grow  the  already  formed  glomeruli. 
The  duct  of  the  kidney  opens  independently  into  the  uro-genital  sinus,  and  forms  the  ureter.  The 
part  where  the  branching  of  the  duct  stops  forms  the  pelvis  of  the  kidney,  and  the  branches  them- 
selves the  renal  tubules.  Toldt  found  Malpighian 
corpuscles  in  the  human  kidney  at  the  2d  month,  and 
Henle's  loops  at  the  4lh.  The  first  appearance  of  the 
urinary  bladder  is  at  the  4th  week  {//is),  and  is 
more  distinct  at  the  2d  month,  as  the  dilated  first  part 
of  the  allantois  (Fig.  682).  The  upper  part  of  the 
allantois  remains  as  the  obliterated  urachus,  in  the 
middle  vesicle  ligament. 

Internal  Reproductive  Organs. — In  front  of  and 
internal  to  the  Wolffian  bodies,  there  arises  in  the 
mesoblast  the  elongated  reproductive  gland,  germ- 
ridge,  or  mass  of  germ  epithelium  (Fig.  682, 1,  D), 
which  in  both  sexes  is  originally  alike  (Fig.  683,  K, 
E).  In  addition,  there  is  formed  a  canal  or  duct 
parallel  to  the  Wolffian  duct  (W),  which  aho  opens 
into  the  uro-genital  sinus;  this  is  Miiller's  duct  (M), 
The  elevation  of  the  future  reproductive  gland  is 
covered  originally  by  germ  epithelium  (  Waldeye?-). 
The  upper  end  of  the  Sliillerian  duct  opens  free  into 
the  abdominal  cavity,  while  the  lower  ends  of  both 
ducts  unite  for  a  distance"  Some  of  the  germinal  cells 
covering  the  surface  of  the  future  ovary  enlarge  to 
form  ova,  and  sink  into  the  stroma  to  form  ova  em- 
bedded in  their  Graafian  follicles  (?  433)  (Fig.  683). 
In  the  female,  the  Miillerian  ducts  form  the  Fallopian 
tube  (II,  T),  and  the  lower  united  ends  the  uterus. 

In  the  male,  the  germ  epithelium  is  not  so  till. 
According  to  Waldeyer,  there  are  two  kinds  of  tubes 
in  the  Wolffian  lx)dies,  and  some  of  these  penetrate 
the  position  of  the  reproductive  gland.  These  tubes, 
which  are  connected  with  the  Wolffian  ducts,  become 
the  seminiferous  tubules  (v.  IVitlich),  and  the  Wolffian 
duct  itself  becomes  the  vas  deferens,  with  the  vesiculse 
seminiles.  According  to  some  other  observers,  however, 
tubes  which  become  the  seminiferous  tubules,  are  de- 
veloped within  the  reproductive  gland  itself,  and  these 
tubes  lined  w-ith  their  g'erm  epithelium  ultimately  form 
a  connection  with  the  Wolffian  ducts. 
The  Miillerian  ducts,  which  are  really  the  ducts  of  the  reproductive  glands,  disappear  in  man, 
all  except  the  lowest  i)art,  which  becomes  the  male  uterus  or  vesicula  prostatica  (III,  «), — the  homo- 
logue  of  the  uterus.  The  upper  tubules  of  the  Wolffian  body  unite  at  the  3d  month  with  the  repro- 
ductive gland  (which  has  now  become  the  body  of  the  testis),  and  become  the  coni  vasculosi  of  the 
epididymis,  which  are  lined  by  ciliated  epithelium  (E) ;  the  remainder  of  the  Wolffian  body  disap- 
pears. Some  detached  tubules  form  the  vasa  aberrantia  (a)  of  the  testicle  {Kobelt).  The  hydatid 
of  Morgagni  (//),  at  the  head  of  the  epididymis,  according  to  Luschka  and  others,  is  a  part  of  the 


Section  of  mammalian  ovary  showing  development 
of  ova  and  their  follicles.  Ei,  Ripe  ovum  ;  G, 
follicular  cells  of  germinal  epithelium  ;  g,  blood 
vessels ;  K,  germinal  vesicle  and  spot ;  KE, 
germinal  epitticlium  :  Lf,  liquor  foUiculi ;  Mg, 
membrana  granulosa  ;  Mp,  zona  pellucida  ;  PS, 
ingrowths  from  germinal  epithelium,  ovarian 
tubes,  by  means  of  which  some  of  the  nests 
retain  their  connection  with  the  epithelium  ;  S, 
cavity  which  appears  within  the  Graafian  fol- 
licle ;  So,  stroma  of  ovary  ;  Tf,  Theca  foUiculi 
or  ovi-capsule  ;   U,  primitive  ova. 


DEVELOPMENT   OF   THE    OVARY   AND    TESTICLE.  941 

epididymis — Fleischl  regards  it  as  tlie  rudiment  of  the  male  ovary.  The  organ  of  the  Giraldes  is 
part  of  the  Wolffian  body.  The  Wolffian  duct  itself  becomes  the  vas  deferens  (V)  from  which  the 
vesiculfe  seminales  are  developed.  The  two  Wolffian  and  two  Miillerian  ducts,  as  they  enter  the 
pelvis,  unite  to  form  a  common  cord- — the  genital  cord. 

In  the  female,  the  tubes  of  the  Wolffian  bodies  disappear,  all  except  a  few  tubules,  lined  with 
ciliated  epithelium,  constituting  the  parovarium,  or  organ  of  Rosenmiiller  (Fig.  646),  and  a  part 
analogous  to  the  organ  of  Giraldes  in  the  broad  ligament  of  the  uterus  (  Waldeyer)  (Fig.  682,  P). 
The  same  is  the  case  with  the  Wolffian  ducts.  In  some  animals  (ruminants,  pig,  cat  and  fox)  they 
remain  permanently  as  the  ducts  of  Gaertner. 

The  Miillerian  duct  is  frayed  oiit  at  its  upper  end  to  form  the  fimbriae  of  the  Fallopian  tube,  and 
it  is  often  provided  with  a  hydatid  (/z').  That  part  of  the  uro-genital  sinus  into  which  the  four 
ducts  open  grows  above  into  a  hollow  sphere,  which  forms  the  vagina  iyRathke).  According  to 
Thiersch  and  Leuckart,  however,  the  two  Miillerian  ducts  unite  at  their  lower  ends  to  form  the 
united  uterus  (U)  and  vagina,  while  their  free  upper  ends  form  the  Fallopian  tubes  (T).  The 
Miillerian  ducts  at  first  open  into  the  posterior  part  of  the  urinary  bladder  below  the  ureters  (uro- 
genital sinus,  S),  while  ultimately  this  part  of  the  bladder  becomes  so  elongated  posteriorly  that 
the  vagina  (the  united  Miillerian  ducts)  and  the  urethra  are  united  below  and  deeply  within  the 
vestibule  of  the  vagina.  At  the  3d  to  the  4th  month,  the  uterus  and  vagina  are  not  separate  from 
each  other,  but  at  the  5th  to  the  6th  month  the  uterus  is  defined  from  the  vagina. 

The  testicles  lie  originally  in  the  lumbar  region  of  the  abdominal  cavity  (Fig.  684,  V,  {),  and 
are  carried  by  a  fold  of  the  peritoneum — the  mesorchium  (;«).  From  the  hilum  of  the  testicle  a 
cord,  the  gubernaculum  testis,  runs  through  the  inguinal  canal  into  the  base  of  the  scrotum.  At 
the  same  time  a  septum-like  process  is  developed  independently  from  the  peritoneum  to  the  ba-e 
of  the  scrotum  {^pv).  The  testicle  passes  through  the  inguinal  canal  into  the  scrotum,  but  the 
mechanism  and  the  cause  of  the  descent  are  not  accurately  ascertained. — [Descent  of  testis, 
I  446.] 

The  ovaries  also  descend  somewhat.  The  round  ligament  of  the  uterus  corresponds  to  the 
gubernaculum  testis.  A  process  of  the  peritoneum  passes  in  the  female  into  the  inguinal  canal  as 
Nuck's  canal.     It  is  rare  to  find  the  ovaries  descending  into  the  labia  majora. 

[The  origin  of  the  urinary  and  generative  organs  is  undoubtedly  as  ociated  with  the  develop- 
ment of  the  Wolffian  bodies.  The  researches  of  Semper  and  Balfour  on  elasmobranch  fishes  show 
that  the  process  is  a  very  complex  one.  There  is  a  mass  of  cells  on  each  side  of  the  vertebral 
column,  which  is  divided  into  three  parts,  the  first  called  the  pronephros,  or  head  kidney  of  Balfour 
and  Sedgwick,  the  middle  one,  the  mesonephros  or  Wolffian  body,  and  the  posterior  one  or 
metanephros,  which  is  formed  after  the  other  two,  gives  origin  to  the  permanent  kidney  in  the 
amniota.  The  Miillerian  duct  is  connected  with  the  pronephros,  the  Wolffian  duct  with  the 
mesonephros,  and  the  ureter  with  the  metanephros.] 

[The  following  table,  modified  from  Quain,  shows  the  destiny  of  these  structures  : — 

MiJLLERiAN  Ducts  (Ducts  of  the  Pronephros). 
Female.  Male. 

Fallopian  tubes.  Hydatid  of  Morgagni. 

Hydatid.  .  Male  uterus. 

Uterus  and  vagina. 

W0LFFLA.N  Bodies  (Mesonephros). 
Parovarium.  Vasa  efferentia,  Coni  vasculosi. 

Paroophoron.  Organ  of  Giraldes,  Vasa  aberrantia. 

Round  ligament  of  the  uterus.  Gubernaculum  testis. 

Wolffian  Ducts. 
Chief  tube  of  parovarium.  Convoluted  tube  of  epididymis. 

Ducts  of  Gaertner.  Vas  deferens  and  vesiculse  seminales. 

Metanephros. 
Kidney.  Ureter.] 

The  external  genitals  are  at  first  not  distinguishable  in  the  two  sexes  (Fig.  684,  /).  At  the 
4th  week,  there  is  merely  an  orifice  at  the  posterior  extremity  of  the  trunk,  representing  both  the 
anus  and  the  opening  of  the  urachus,  and  forming  a  cloaca  (Fig.  682,  4,  K).  In  front  of  this  an 
elevation — the  genital  eminence — appears  about  the  6th  week,  and  on  each  side  of  the  orifice  a 
large  cutaneous  elevation  (//,  w).  At  the  end  of  the  2d  month,  there  is  a  groove  on  the  under 
surface  of  the  genital  eminence,  leading  back  to  the  cloaca,  and  with  distinct  walls  bounding  it 
( //,  r).  At  the  middle  of  the  3d  month,  the  cloacal  opening  is  divided  by  the  growth  of  the 
perineum,  between  the  urachus  (now  become  the  urinary  bladder)  (Fig.  682,  5,  ^)  and  the 
rectum  (M). 

In  the  male,  the  genital  eminence  enlarges,  its  groove  deepens  from  the  opening  of  the  bladder 
onward  to  the  apex  of  the  elevation  at  the  loth  week.  The  two  edges  unite  to  enclose  the  groove 
which  becomes  the  urethra.     When  this  does  not  take  place,  hypospadias   occurs.     At  the  4th 


942 


DEVELOPMENT   OF   THE    EXTERNAL    GENITALS. 


inonili  the  ^lans,  and  at  the   6tli  the  prepuce,  are  formed.     The  large  cutaneous  folds  meet  in  the 
middle  line  or  raphe  to  form  the  scrotum. 

In  the  female,  the  undirterenliated  condition  remains  to  a  certain  extent  permanent.  The  small 
t,'enital  eminence  remains  as  the  clitoris,  the  margins  of  its  furrow  become  the  nymphae,  the 
cutaneous  elevations  remain  sejiarate  to  form  the  labia  majora.  The  uro-genital  siims  remains 
short  as  the  vestibule  of  the  vagina,  while  in  man,  by  the  closing  of  the  genital  groove,  it  has  a 
long  additional  tube,  the  urethra.  [The  accompanying  illustrations,  after  Schroeder,  show  the 
changes  of  the  external   organs  of  generation   in  the  female.     In  the  early  period  (6th   week),  the 


Development  of  the  external  genitals,  /.and  //. — Genital  eminence;  r,  genital  groove;  s,  coccyx;  tc,  cutaneous 
elevations.  //-'—/',  penis;  /?,  raphe  penis;  S,  scrotum.  ///. — c,  clitoris;  /,  labia  minora;  L,  labia  majora; 
a,  anus.  y.  and  F/. — Descent  of  the  testicle  ;  /,  testis;  «/,  mesorchium  ;  /v,  processus  vaginalis  of  the  perito- 
neum ;  -1/,  abdominal  wall  ;  5,  scrotum. 

hind  gut  (Fig.  685,  R),  allantois  (ALL),  and  the  Miillerian  ducts  (M)  communicate,  but  not  with 
the  exterior.  About  the  loth  week  a  depression  or  inflection  of  the  skin  takes  place,  genital  cleft, 
until  it  meets  the  hind  gut  and  allantois,  whereby  the  cloaca  (Fig.  686,  CL)  is  formed.  The  cloaca 
is  then  divided  into  an  interior  part,  the  uro-genital  sinus,  into  which  the  Miillerian  ducts  open, 
and  a  posterior  part,  the  anus.  There  is  a  downward  growth  of  the  tissue  between  the  hind  gut 
and  the  allantois  to  form  the  perineum  (Fig.  687).     The  uro-genital  sinus  then  contracts  at  its  upper 


Fig.  685. 


R, 


rectum  contuiuous 
with  the  allantois 
(ALL— bladder) ;  M, 
duct  of  Miiller  (va- 
gina); A,  depression 
of  skin  below  genital 
eminence,  growing 
inward  to  form  the 
vulva. 


The  depression  has  be- 
come continuous 
with  the  rectum  and 
allantois  to  form  the 
cloaca  (CL). 


Fig.  687. 


The  cloaca  is  becoming  divided 
into  uro-genital  sinus  (SU) 
and  anus  by  the  downward 
growth  of  the  perineal  sep- 
tum. The  ducts  of  Miiller 
are  united  to  form  the  va- 
gina (V). 


Perineum  completely 
formed. 


part  to  form  the  short  urethra,  its  lower  part  remaining  as  the  vestibule  (Fig.  688,  SV),  while  the 
vagina  has  been  formed  by  the  union  of  the  lower  pans  of  the  two  Miillerian  ducts.  The  bladder 
(B)  is  the  expanded  lower  end  of  the  stalk  of  the  allantois.]  j[)|jj2)y 

The  causes  of  the  difference  of  sex  are  by  no  means  well  known.  From  a  statistical  analysis 
of  80,000  cases,  the  influence  of  the  age  of  the  parents  has  been  .shown  by  Hofacker  and  Sadler. 
If  the  husband  is  younger  than  the  wife  there  are  as  many  boys  as  girls  ;  if  both  are  of  the  same 
age,  there  are  1029  boys  to  1000  girls;  if  the  husband  is  older,  1057  boys  to  looo  girls.  In  insects, 
food  has  a  most  important  influence.     Ffluger's  investigations  on  frogs  show  that  all  external  con- 


FORMATION    OF   THE    CENTRAL    NERVOUS    SYSTEM. 


943 


ditions  during  development  are  without  effect  on  the  determination  of  the  sex,  so  that  the  latter 
would  seem  to  be  determined  before  impregnation. 

451.  FORMATION    OF    THE    CENTRAL  NERVOUS  SYSTEM.— Fore  brain.— 

At  each  side  of  the  fore  brain,  or  anterior  cerebral  vesicle,  which  is  covered  externally  by  epiblast 
and    internally    by    the    ependyma, 

there  grows  out  a  large  stalked  hoi-  Fig. 

low  vesicle,  the  rudiment  of  the 
cerebral  hemispheres.  The  rela- 
tively wide  opening  in  the  stalk,  or 
communication,  ultimately  becomes 
very  small,  and  is  the  foramen  of 
Monro.  The  middle  part  between 
the  two  cerebral  vesicles  remains 
small,  and  is  the  'tween  or  inter- 
brain  with  the  third  ventricle  in  its 
interior.  It  elongates  at  the  second 
month  toward  the  base  of  the  brain 
as  a  funnel-shaped  projection,  to 
form  the  tuber  cinereum  with  the 
infundibulum.  The  thalami  optici, 
projecting  and  enlarging  from  the 
sides  of  the  third  ventricle,  narrow 
the  foramen  of  Monro  to  a  semi- 
lunar slit.  At  the  base  of  the  brain 
are  formed,  in  the  second  month,  the 
corpora  albicantia,  at  the  third  the 
chiasma;  while  within  the  third  ven- 
tricle the  commissures  are  formed. 
The  hypophysis,  belonging  to  the 
mid  brain,  is  a  diverticulum  of  the 

nasal  mucous  membrane,  extending  Transverse  section  of  the  brain  of  an  embryo  sheep  2.7  cm.  long;  X  10 
through  the  base  of  the  skull  toward 
the  hollow  infundibulum,  which 
grows  to  meet  it  (Fig.  505,  T). 
There  is,  as  it  were,  a  tendency  to 
the  union  of  the  cavity  of  the  fore 
gut  with  the  medullary  tube.  In  the 
amphioxus       [Kowalewsky),      goose 

( Gasser).  and  lizard  [Strahl)  the  medullary  tube  communicated  originally  with  the  hind  gut  by  the  cana- 
lis  myeloentericus.  The  choroid  plexus,  which  grows  into  the  ventricles  of  the  hemispheres  through 
the  foramen  of  Monro,  is  a  vascular  development  of  the  ependyma.  At  the  fourth  month,  the  cona- 
rium  (pineal  gland)  is  formed,  and  at  this  time  the  corpora  quadrigemina  cover  the  hemispheres. 
The  corpora  striata  begin  to  be  developed  in  the  cerebral  (lateral)  ventricle  at  the  second  month, 
while  the  cornu  ammonis  is  formed  at  the  fourth  month.  [The  external  walls  and  floor  of  the  primi- 
tively simple  central  hemipheres  become  much  thickened,  the  thickenings  in  the  floor  constitute  the 
corpora  striata,  which  protrude  into  the  lateral  ventricles,  their  position  being  indicated  on  the  sur- 
face of  the  brain  by  the  Sylvian  tis^ure.  As  they  extend  backward,  they  become  connected  with  the 
optic  thalami  (Fig.  689,  s(,  tk).  The  corpora  striata  are  connected  together  by  the  anterior  com- 
missure. From  the  inner  wall  of  each  hemisphere,  there  grow  into  each  lateral  ventricle  two  pro- 
jections; the  upper  one  forms  the  hippocampus  major  or  cornu  ammonis  (Fig.  689,  h),  while  the 
lower  one  becomes  folded,  remains  thm,  receives  numerous  blood  vessels  from  the  falx  cerebri,  and 
forms  the  choroid  plexus  (Fig.  689,//).]  At  the  third  month  the  Sylvian  fissure  is  formed,  and 
the  basis  of  the  island  of  Reil.  The  permanent  cerebral  convolutions  are  formed  from  the  seventh 
month  onward. 

The  mid  brain,  or  middle  cerebral  vesicle,  is  gradually  covered  over  by  the  backward  growth  of 
the  hemispheres;  its  cavity  forms  the  aqueduct  of  Sylvius  (Fig.  690).  Depressions  appear  on  the 
surface  of  the  vesicle  to  divide  it  into  four,  the  corpora  quadrigemina,  in  birds  into  two,  the  cor- 
pora bigemina  (Fig.  690,  bg),  the  longitudinal  depression  being  formed  at  the  third,  and  the  trans- 
verse one  at  the  seventh  month.  The  cerebral  peduncle  is  formed  by  a  thickening  in  the  base 
of  this  vesicle. 

In  the  hind  brain  are  found  the  cerebellar  hemispheres,  which  grow  backward  to  meet  in  the 
middle  line.  The  vermis  is  foiTned  at  the  seventh  month.  The  cerebellum  covers  in  the  part  of  the 
medullary  tube  lying  below  it,  which  is  not  closed,  as  far  as  the  calamus.  The  pons  arises  in 
the  floor  of  the  hind  brain  at  the  third  month. 

The  spindle-shaped  narrow  after  brain  forms  the  medulla  oblongata,  with  the  opening  of  the 
medullary  tube  in  its  upper  part. 


cartilage  of  orbito-sphenoid ;  c,  peduncular  fibres;  ck,  optic 
chiasm  ;  _/,  median  cerebral  fissure  ;  h,  cerebral  hemispheres,  with  a 
convolution  upon  their  inner  wall,  projecting  into  the  lateral  ventricle, 
/;  ;«.  foramen  of  Monro;  <p,  optic  nerve;  /,  pharynx;  //,  lateral 
plexus;  J,  termination  of  the  median  fissure,  which  forms  the  roof  of 
the  third  ventricle ;  sa,  body  of  the  anterior  sphenoid ;  st,  corpus 
striatum;  t,  third  ventricle;  th,  anterior  deep  portion  of  the  optic 
thalamus  {Kolliker). 


044 


DEVELOPMLNT    OF   THE    SENSE    ORGANS. 


[The  following  table,  from  Quain,  shows  the  destiny  of  each  cerebral  vesicle : — 


I.   Anterior  Primary 
Vesicle, 


II.   Middle    Primary   f  3. 
Vesicle, ( 

(   ^' 
III.   Posterior    Pri-   | 

mary    Vesicle,  .    .         5. 


rrosctuephalon,  .    .    . 
(fore  brain) 

Thalamcncef'halon,    . 
(inter  or  'tween  brain) 

Mesencephalon,   .    .    . 
(mid  brain) 

Epencephalon^     .    .    . 

(hind  brain) 
Metenciphalon,   .    .    . 

(after  brain) 


Cerebral  hemispheres,  corpora  striata, 
corpus  callosum,  fornix,  lateral  ven- 
tricles, olfactory  bulb. 
Thalami  optici,  pineal  gland,  pituitary 
body,    crura    cerebri,    aqueduct    of 
Sylvius,  oplic  nerve. 
Corpora  quadrigemina,  cruri   cerebri, 
aqueduct  of    Sylvius,   optic    nerve 
(secondarily). 
(    Cerebellum,  ]X)ns,  anterior  part  of  the 
\       fourth  ventricle, 
f  Medulla   oblongata,  fourth   ventricle, 
\       auditory  nerve. 


Spinal   Cord. — The   spinal  cord    is   developed   from   the  medullary  tube  behind  the   medulla 
oblongata,  first  the  gray  matter  around  the  canal,  while  the  white  matter  is  atlded  afterward  outside 

this.     The  ganglionic  cells  increase  by  divi- 


FiG.  690. 


vaz 


6ce  ps 


sion  in  amphibians  [Loniirtsly).  At  first 
the  spinal  cord  reaches  to  the  coccyx.  In 
the  adult,  the  spinal  cord  reaches  only  to 
the  first  or  second  lumbar  verlebnx:,  so  that 
it  does  not  elongate  so  much  as  the  ver- 
tebrre  can.  It  is  a  question  how  far  this 
want  of  harmony  in  the  development  of  these 
two  structures  may  lead  to  disturbances  of 
sensibility  or  paralysis  of  the  lower  limbs  in 
children.  The  first  muscles  are  formed  in 
the  back  at  the  second  month  ;  at  the  fourth 
month  they  are  red.  The  spinal  ganglia 
are  formed  from  a  special  strip  of  epiblastic 
cells.  They  are  seen  at  the  4th  week,  and 
so  are  the  anterior  spinal  roots  and  some  of 
the  trunks  of  the  spinal  nerves,  while  the 
posterior  roots  are  still  absent.    At  this  period 


Diagram  of  an  embryonic  fowl's  brain,  ac,  anterior  com- 
missure; <j/«7/,  anterior  medullary  velum,  and  below  it  the 
aqueduct  of  Sylvius  and  the  cerebral  peduncles  ;  //a,  basilar 
artery  ;  Af,  corpora  bigemina  ;  cai,  internal  carotid  artery  ; 

cbi    cerebellum  ;    f/:»,  ch*,  choroid   plexuses  of  the  third     the    ganglia    of    the    fifth,    seventh,    eVhth, 
and  fourth  ventricles;  A,  cerebral  hemispheres;  /;//",  infun-  =■      °  ° 

dibulum  ;  //,  lamina  terminalis;  //.lateral  ventricle;  oH, 
medulla  oblongata;  pi/,  olfactory  lobe  and  nerve;  ofic, 
optic  commissure;  //«,  pineal  gland,  ///,  pituitary  body; 
ps,  pons  Varolii ;  r,  floor  of  fourth  ventricle  ;  si.  corpus 
striatum;  t/',  third  ventricle;  j/*,  fourth  ventricle  ( ^?«i/«, 
after  Mihalkovics). 


ninth,  and  tenth  nerves  and  part  of  their 
origins  are  present,  while  the  first,  second, 
third,  and  twelfth  nerves  and  the  sympa- 
thetic are  not  yet  far  differentiated  [His). 
The  peripheral  nerves  grow  out  from  the 
ganglia  of  the  spinal  cord  (first  the  motor 

and  afterward  the  sensory  nerves),  and  penetrate  into  the  other  parts  of  the  body  [His).     At  first 

they  are  devoid  of  myelin. 

452.  THE  SENSE  ORGANS. — Eye. — The  primary  optic  vesicle  grows  out  from  the  fore 
brain  toward  the  outer  covering  of  the  head  or  epiblast,  and  soon  becomes  folded  in  on  itself  (fourth 
week),  so  that  the  stalked  optic  vesicle  is  shaped  like  an  egg  cup  (Fig.  691,  I).  The  cavity  in  the 
inlerior  of  this  cup  is  called  the  secondary  optic  vesicle.  The  inflected  part  becomes  the  retina 
(IV,  r),  while  the  posterior  part  becomes  the  choroidal  epithelium  (IV, />).  The  stalk  becomes  the 
oplic  nerve.  At  the  under  surface  of  the  depression  there  is  a  slit— the  choroidal  fissure — 
which  permits  some  of  the  mesoblast  to  gain  access  to  the  interior  of  the  eye.  This  slit  forms  the 
coloboma  (II) ;  it  is  prolonged  backward  on  the  stalk,  and  contains  the  central  artery  of  the  retina. 
The  margins  of  the  coloboma  afterward  unite  completely  with  each  other,  but  in  some  rare  conditions 
this  does  not  take  jilace,  in  which  case  we  have  to  deal  with  a  coloboma  of  the  choroid  or  retina,  as 
the  case  may  be.  In  the  bird  the  embryonic  coloboma  slit  does  not  close  up,  but  a  vascular  process 
of  the  mesoblast  dips  into  it,  and  passes  into  the  eye  to  form  the  pecten  (p.  846).  The  same  is  the 
casein  fishes,  where  there  is  a  large  vascular  process  of  the  meso-  and  epiblast  forming  ihs processus 
falciformis  (p.  846). 

The  depression  or  inflection  of  the  optic  vesicle  is  due  to  the  downgrowth  into  it  of  a  thickening  of 
the  epiblast  ( I,  L).  It  is  hollow,  and  as  it  grows  inward  ultimately  becomes  spherical  and  separated 
from  the  epiblast  to  form  the  crystalline  lens,  so  that  the  lens  is  epiblastic  in  its  origin,  while  the 
capsule  of  the  lens  is  a  cuticular  structure  formed  from  the  epiblast.  That  part  of  the  epiblast  which 
covers  the  vesicle  in  front  of  the  lens  ultimately  becomes  the  stratified  epithelium  of  the  cornea.  The 
layer  of  pigment  of  the  invaginated  oplic  vesicle  is  applied  to  the  ciliary  body,  and  the  posterior  sur- 
face of  the  iris,  when  the  latter  is  formed.     The  cornea  is  formed  at  the  sixth  week.     The  substance 


DEVELOPMENT   OF   THE    SENSE   ORGANS. 


945 


•of  the  choroid,  sclerotic,  and  cornea  is  formed  around  the  position  of  the  eye  from  the  mesoblast  (w). 
The  capsule  of  the  lens  is  at  first  completely  surrounded  by  a  vascular  membrane — the  membrana 
capsulo-pupillaris.  Afterward,  the  lens  passes  more  posteriorly  into  the  eye — the  anterior  part 
of  the  capsulo  pupillary  membrane,  however,  remains  in  the  anterior  part  of  the  eye,  while  toward  it 
grows  the  margin  of  the  iris  (seventh  week),  so  that  the  pupil  is  closed  by  this  part  of  the  vascular 
capsule,  membrana  pupillaris.  The  blood  vessels  of  the  iris  are  continuous  with  those  of  the  pupillary 
membrane ;  those  of  the  posterior  capsule  of  the  lens  give  off  the  hyaloid  artery,  a  continuation  of  the 


Development  of  the  eye.  I,  Inflexion  of  the  sac  of  the  lens  (L)  into  the  primary  optic  vesicle  (P) — e,  epidermis  ;  tn, 
mesoblast.  II,  The  inflexion  seen  from  below — «,  optic  nerve  ;  e,  the  outer;  i,  the  inner  layer  of  the  inflected 
vesicle;  L,  lens.  Ill,  Longitudinal  section  of  II.  IV,  Further  development — <?,  corneal  epitlielium  ;  c,  cornea  ; 
in,  membrana  capsulo-pupillaris  ;  L,  lens  ;  a,  central  artery  of  the  retina  ;  s,  sclerotic  ;  ch,  choroid;  /,  pigment 
layer  of  the  retina  ;  r,  retina.     V,  Persistent  remains  of  the  pupillary  membrane. 

central  artery  of  the  retina;  its  veins  pass  into  those  of  the  iris  and  choroid.  The  vitreous  humor 
at  the  fourth  week  is  represented  by  a  cellular  mass  between  the  lens  and  the  retina.  The  pupillary 
membrane  disappears  at  the  seventh  month.     It  may  remain  throughout  life  (V). 

Organ  of  Smell. — On  the  under  surface  and  lateral  limit  of  the  fore-brain,  the  epiblast  forms  a 
groove  or  pit  with  thickened  epithelium,  which  forms  a  depression  toward  the  brain,  but  always 
remains  as  a  pit  or  depression;  this  is  the  olfactory  or  nasal  pit,  to  which  the  olfactory  nerve 
afterward  sends  its  branches.     For  the  formation  of  the  nose,  see  p.  931. 

Fig.  692. 


Early  stages  in  the  development  of  the  vertebrate  ear.  A-D,  Early  stages  in  the  chick  {Reissner).  E,  Transverse 
section  through  the  auditory  pit  of  a  50  hours'  chick  {^Marshall).  F,  Transverse  section  through  the  hind  brain 
of  a  foetal  sheep,  acz/,  anterior  cardinal  (jugular)  vein  ;  a??z,  amnion;  «(?,  aortic  arch;  c^,  cochlea  ;  rz*,  recessus 
(aqueductus)  vestibuli ;  v,  vestibulum  ;  vc,  vertical  semicircular  canal ;  viii,  auditory  nerve. 


Organ  of  Hearing. — On  both  sides  of  the  after-brain  or  posterior  brain  vesicle,  above  the  first 
visceral  or  hyoid  arch,  there  is  a  depression  or  pit  formed  in  the  epiblast,  which  gradually  extends 
deeper  toward  the  brain — this  is  the  labyrinth  pit  or  auditory  sac,  which  soon  becomes  flask- 
shaped  (Fig.  692,  A,  B). 

[The  stalk,  which  originally  connected  the  cavity  of  the  sac  with  the  surface,  persists  as  the  aque- 
ductus vestibuli ;  and  its  blind  swollen  distal  extremity  as  the  saccus  endolymphaticus,  or 
recessus  vestibuli  {^Haddon,  Fig.  692,  ;-,  &).]  The  pit  is  ultimately  completely  cut  off  from  the 
60 


946  niRTii. 

cpil)lasl,  just  like  the  lens,  and  is  now  called  the  vesicle  of  the  labyrinth  or  primary  auditory 
vesicle.  lis  related  portion  forms  the  utricle,  from  wliich,  at  tlic  2(1  month,  the  semicircular 
canals  and  the  cochlea  are  developed  (Fig.  6q2,  1)).  The  union  with  the  brain  occurs  later,  along 
witli  the  development  of  ihe  auiiitory  nerve.  Tlie  first  visceral  cleft  remains  as  an  irregular  passage 
from  tlic  Eustachian  tube  to  the  external  auditory  meatus.     The  culer  ear  appears  at  the  7th  week. 

Organ  of  Taste. — The  gustatory  papilla;  are  developed  in  the  later  period  of  intra-uterine  life,  and 
several  tiays  before  birth  the  taste-buds  appear  (/>-.  Hermann). 

453.  BIRTH. — With  the  growth  of  the  ovtim,  the  uterus  becomes  inore  dis- 
tended, hs  walls  more  muscular  and  more  vascular,  although  the  uterine  walls  are 
not  thicker  at  the  end  of  pregnancy.  Toward  the  end  of  gestation  the  cervical 
canal  is  intact  until  labor  begins,  or  at  any  rate  it  is  but  slightly  opened  up  at  its 
upper  part.  After  a  period  of  280  days  of  gestation,  "labor"  begins,  whereby  the 
contents  of  the  uterus  are  discharged.  The  labor  pains  occur  rhythmically  and 
periodically,  being  separated  from  each  other  by  intervals  free  from  pain.  F^ach 
pain  begins  gradually,  reaches  a  ma.ximum,  and  then  slowly  declinesj.  With  each 
pain  the  heat  of  the  uterus  increases  (§  303),  while  the  heart-beat  of  the  foetus 
becomes  slower  and  feebler,  which  is  due  to  stimulation  of  the  vagus  in  the  medulla 
oblongata  (§369,  3). 

[At  the  full  time  the  membranes  and  i)lacenta  line  the  uterus.  The  mem- 
branes consist,  from  within  outward,  of  amnion,  chorion,  decidua  reflexa,  and 
decidua  vera.  The  fundi  of  the  uterine  glands  persist  in  the  deep  part  of  the 
decidua  vera,  and  thus  form  a  spongy  layer,  the  part  above  this  being  the  compact 
layer  in  the  deep  part  of  the  placenta,  e.  g.,  near  the  uterine  wall;  we  have  also 
the  fundi  of  the  uterine  gland  persisting  in  the  decidua  serotina.  When  the  pla- 
centa and  membranes  are  expelled  after  birth,  the  line  of  separation  takes  place 
in  the  part  of  the  membranes  and  placenta  where  the  fundi  of  the  glands  persist. 
After  labor  is  completely  fini.shed,  the  uterus  is  lined  by  the  remains  of  the  spongy 
layer  of  the  decidua  vera  and  serotina,  e.  g.,  is  lined  by  a  layer  which  contains  the 
fundi  of  the  uterine  glands.  The  new  mucous  membrane  is  regenerated  by  the 
growth  of  the  epithelium  and  connective  tissue  in  this  part.  The  membranes 
expelled  are  made  up  of  amnion,  chorion,  deciduse  reflexae,  and  the  compact 
layer  of  the  decidua  vera.] 

The  uterine  movements  during  labor  proceed  in  a  peristaltic  manner  from  the 
Fallopian  tube  to  the  cervix,  and  occupy  20  to  30  seconds.  In  the  curve  registered 
by  these  movements  there  is  usually  a  more  steep  ascent  tl"ran  descent. 

[Power  in  Ordinary  Labor. — Sometimes  the  ovum  is  expelled  whole,  the  membranes  contain- 
ing the  liquor  amnii  remaining  unruj)lured.  Poppel  has  pointed  out  that  the  force  whicli  ruptures  the 
bag  of  meml)ranes  is  sufficient  to  complete  delivery,  so  that,  as  Matthews  Duncan  remarks,  the 
strength  of  the  memliranes  gives  us  a  means  of  ascertaining  the  power  of  labor  in  the  easiest  class 
of  natural  labors.  MaUhews  Duncan,  from  experiments  on  the  pressure  required  to  rupture  the 
membranes,  concludes  that  the  great  majority  of  labors  are  completed  by  a  propelling  force  not 
exceeding  40  II  s.] 

Polaillon  estimates  the  pressure  exerted  by  the  uterus  upon  the  foetus  at  each  pain  to  be  154  kilos. 
[338.8  lbs.],  so  that,  according  to  this  calcuhtion,  ihe  uterus  at  each  pain  performs  8820  kilogram- 
metres  of  work  {\  301).     [  Th  s  estimate  is  certainly  far  too  high.] 

After-Birth. — After  the  foetus  is  expelled,  the  placenta  remains  behind;  but  it  is  soon  expelled 
by  tht;  contractions  of  the  uterus.  During  the  comraciion  of  the  uterus  to  expel  the  placenta,  a  not 
inconsideial)le  amount  of  the  placental  blood  is  forced  into  the  child  (i)  40).  [It  is  more  probable 
that  the  child  aspirates  the  blood  from  the  foetus  portion  of  the  placenta.  This  can  be  seen  in  late 
ligature  of  the  cord.  The  child  may  thus  gain  two  ounces  of  blood.]  After  a  time  the  placenta, 
the  membranes  and  the  decidua — constituting  the  after-birth — are  expelled. 

Influence  of  Nerves  on  the  Uterus. —  i.  Stimulation  of  the  hypogastric  plexus  causes  con- 
traction of  the  uterus.  The  fibres  arise  from  the  spinal  cord,  from  the  last  dorsal,  and  upper  three  or 
four  lumbar  nerves,  run  into  the  sympathetic,  and  trien  reach  the  hypogastric  plexus  (Frafikeiihduser). 
2.  Stimulation  of  the  nervi  erigentes,  which  are  derived  from  the  sacral  plexus,  causes  movement 
(v.  Bascli  and  //o/mann).  3.  Stimulation  of  the  lumbar  and  sacral  parts  of  the  cord  causes 
powerful  movements  {Spie:,'elberg].  There  is  a  centre  for  the  act  of  parturition  in  the  lumbar 
region  of  the  cord  (^  362,6).  The  uterus,  like  the  intestine,  probably  contains  independent  or 
parenchymatous  nerve  centres  {/Corner),  which  can  be  excited  by  suspension  of  the  respiration,  and 


INFLUENCE  OF  NERVES  ON  THE  UTERUS.  947 

by  ansemia  (by  compressing  the  aorta,  or  rapid  hemorrhage).  Decrease  of  the  bodily  temperature 
diminishes,  while  an  increase  of  the  temperature  increases  the  movement,  which,  however,  ceases 
during  high  fever  (^Fronune).  The  experiments  made  by  Rein  upon  bitches  show  that,  if  all  the 
nerves  going  to  the  uterus  be  divided,  practically  all  the  functions  connected  with  conception,  preg- 
nancy, and  parturition  can  take  place,  even  although  the  uterus  is  separated  from  all  its  cerebro- 
spinal connections.  Hence,  we  must  look  to  the  presence  of  some  automatic  ganglia  in  the 
uterus  itself.  According  to  Dembo,  there  is  a  centre  in  the  anterior  wall  of  the  vagina  of  the  rabbit. 
According  to  Jastreboff,  the  vagina  of  the  rabbit  contracts  rhythmically.  Sclerotic  acid  greatly 
excites  the  uterine  conKxzsXxoxvs,  [v.  Swiecicki),  so  does  ax\xm\a.  (^Ki-oiiecker  and  Jastreboff).  4. 
The  uterus  contracts  reflexly  on  stimulating  the  central  end  of  the  sciatic  nerve  {v.  Basch  and  Hof- 
mann),  the  central  end  of  the  brachial  plexus  {^Schlesinge}-),  and  the  nipple  {Scanzoni).  5.  The 
uterus  is  supplied  by  vasomotor  nerves  (hypogastric  plexus),  which  come  from  the  splanchnic;  and 
also  by  vaso- dilator  fibres,  the  latter  through  the  nervi  erigentes.  The  vasomotor  nerves  are  affected 
reflexly  by  stimulation  of  the  sciatic  nerve  (y.  Basch  and  Hof77iann). 

[In  the  rabbit  the  vagina  and  uterine  cornua  exhibit  regular  movements  of  a  "peristaltic"  nature. 
These  exist  apart  from  any  extraneous  stimulus,  and  are  probably  a  vital  property  of  the  tissue. 
They  can  be  demonstrated  in  animals  a  few  weeks  old,  and  have  been  recorded  continuously  for 
many  hours.  JVequently  they  are  more  vigorous  six  hours  after  than  at  the  beginning,  showing  that 
they  are  not  due  to  the  irritation  of  the  operation  necessary  to  demonstrate  them. 

Their  rate  and  extent  vary.  In  young  animals  they  are  frequent  (l  to  4  per  minute),  but  irregular 
in  character.  In  nuUiparous  adults  they  are  less  frequent  and  somewhat  more  regular.  During  preg- 
nancy they  increase  greatly  in  extent,  and  their  rate  becomes  i  in  120  to  130  seconds.  These  char- 
acters are  retained  alter  pregnancy  for  many  months  at  least.  They  are  diminished  or  abolished  by 
chloroform  narcosis,  are  scarcely  affected  by  ether.  Water  at  100°  to  120°  F.  produces  a  persistent 
contraction  accompanied  by  blanching  of  the  tissue.  Similar  effects  are  produced  by  dilute  acetic 
acid  {^Milne  Murray). "] 

Lochia. — After  birth  the  whole  mucous  membrane  (decidua)  is  shed  ;  its  inner 
surface,  therefore,  represents  a  large  wounded  surface,  on  which  a  new  mucous 
membrane  is  developed.     The  discharge  given  off  after  birth  constitutes  the  lochia. 

Involution  of  the  Uterus. — After  birth  the  thick  muscular  mass  decreases 
in  size,  some  of  its  fibres  undergoing  fatt)'  degeneration.  Within  the  lumen  of  the 
blood  vessels  of  the  uterus  itself,  there  begins  in  the  interna  of  these  vessels  a  pro- 
liferation of  the  connective-tissue  elements,  whereby  within  a  few  months  the 
blood  vessels  so  affected  become  completely  occluded.  The  smooth  muscular  fibres 
of  the  middle  coat  of  the  arteries  undergo  fatty  degeneration.  The  relatively 
large  vascular  spaces  in  the  region  of  the  placenta  are  filled  by  blood  clots,  which 
are  ultimately  traversed  by  outgrowths  of  the  connective  tissue  of  the  vascular 
walls. 

Milk  Fever. — After  birth,  there  is  a  peculiar  action  on  the  vasomotor  system,, 
constituting  milk  fever,  while  at  the  2d  to  3d  day  there  is  a  more  copious  supply 
of  blood  to  the  mammary  gland  for  the  secretion  of  milk  (§  231).  [After  birth 
the  pulse  becomes  slow  and  remains  so  in  a  normal  puerperium.  The  so-called 
milk  fever  is  not  found  in  cases  where  strict  cleanliness  is  observed  during  the 
labor  and  puerperium.]  For  the  cause  of  the  first  respiration  in  the  child,, 
see  p.  717. 

454.  COMPARATIVE — HISTORICAL. — A  sketch  of  the  development  of  man  must  neces- 
sarily have  some  reference  to  the  general  scheme  of  development  in  the  Animal  Kingdom.  The 
question  as  to  how  the  numerous  forms  of  animal  life  at  present  existing  on  the  globe  have  arisen 
has  been  answered  in  several  ways.  It  has  been  asserted  that  each  species  has  retained  its  characters 
unchanged  from  the  beginning,  so  that  we  speak  of  the  "  constancy  of  species."  This  view,  developed 
by  Linnseus  Cuvier,  Agassiz,  and  others,  is  opposed  by  that  supported  by  Lamarck,  1809,  or  the 
doctrine  of  the  "  Unity  of  the  Animal  Kingdom,"  corresponding  to  the  ancient  view  of  Empedocles, 
that  all  species  of  animals  were  derived  by  variations  from  a  few  fundamental  forms  ;  that  at  first 
there  were  only  a  few  lower  forms  from  which  the  numerous  species  were  developed — a  view  sup- 
ported by  Geoffrey  St.  Hilaire  and  Goethe.  After  a  long  period  this  view  was  restated  and  eluci- 
dated in  the  most  brilliant  and  most  fruitful  manner  by  Charles  Darwin  in  his  "  Origin  of  Species  " 
(1859)  and  other  works.  He  attempted  to  show  how  modifications  may  be  brought  about  by  uniform 
and  varying  conditions  acting  for  a  long  time.  Among  created  beings  each  one  struggles  with  its 
neighbor,  so  that  there  is  a  real  "  struggle  for  existence."  Many  quahties,  such  as  vigor,  rapidity, 
color,  reproductive  activity,  etc.,  are  hereditary,  so  that  in  this  way  by  "  natural  selection  "  there 
may  be  a  gradual  improvement,  and  therewith  a  gradual  change  of  the  species.     In  addition,  organ- 


948  COMPARATIVE HISTORICAL. 

isms  can,  wiihin  certain  limits,  accommodate  themselves  to  their  surroundings  or  environment. 
Thus  certain  useful  organs  or  parts  may  undcrs^o  development,  while  inactive  or  useless  parts  may 
undergo  retrogres>ion,  and  form  "  rudimentary  organs."  This  procefs  of  "  natural  selection," 
causing  gradual  changes  in  the  form  of  ori^anisms,  fin. Is  its  counterpart  in  "  artificial  selection  " 
among  plants  and  animals.  Breeders  of  animals,  for  example,  by  .selecting  the  proper  crosses,  can 
within  a  relatively  short  time  produce  very  material  alterations  in  the  form  and  characters  of  the 
animals  which  they  hreed,  the  changes  being  more  pronounced  than  many  of  those  that  se[)arate 
well-defmed  species.  Hut,  just  as  with  artificial  selection,  there  is  s mietimes  a  sudden  "  reversion  " 
to  a  former  type,  so  in  the  development  of  species  by  natural  selection  there  is  sometimes  a  condition 
of  atavism.  ( )bviously,  a  wide  distribution  of  one  sjiecies  in  different  climates  must  increase  the 
liability  to  change,  as  very  different  conditions  of  environment  come  into  play.  Thus,  the  migration 
of  organi>ms  may  gradually  lead  to  a  change  of  species. 

Biological  Law. — Wiihout  di.'^cussing  the  development  of  different  organisms,  we  may  refer  to 
the  "/«/;</<j///<«/(j/  liio/o^'icn!  la-.o  "  of  Haeckel,  viz.,  ''  that  the  ontogeny  is  a  short  repetition  of  the 
phylogeny,"  [ontogeny  being  the  history  of  the  development  of  siiti;/e  beings,  or  of  the  individual 
from  the  ovum  onward,  while  phylogeny  is  the  history  of  the  development  of  a  -whole  stock 
of  organisms,  from  the  lowest  forms  of  the  series  upward]  (p.  ^t,).  When  applied  to  man,  this 
law  asserts  that  the  individual  stages  in  the  course  of  the  development  of  the  human  embryo,  e.  g., 
its  existence  as  a  unicellular  ovum,  as  a  group  of  cells  after  complete  cleavage,  as  a  blastodermic 
vesicle,  as  an  organism  without  a  body  cavity,  etc.;  that  these  stages  of  development  indicate  or 
represent  so  many  animal  forms,  through  which  the  human  species  in  the  course  of  untold  ages  has 
been  gradually  evolved.  The  individual  stages  which  the  human  race  has  passed  in  this  proce.'^s  of 
evolution  are  rapidly  rehearsed  in  its  eml)ryonic  development.  This  conception  has  not  passed  with- 
out challenge.  In  any  case,  the  comparison  of  the  human  development  and  its  individual  organs 
with  the  corresponding  perfect  organs  of  lower  vertebrates  is  of  great  importance.  Thus,  a  mammal 
during  the  development  of  its  organs  is  originally  possessed  of  the  tubular  heart,  the  branchial  clefts, 
the  undeveloped  brain,  the  cartilaginous  chorda  dorsalis,  and  many  arrangements  of  the  vascular 
system,  etc.  I,  which  are  permanent  throughout  the  life  of  the  lowest  vertebrates.  These  incomplete 
stages  are  perfected  in  the  ascending  classes  of  vertebrates.  Still,  there  are  many  difficulties  to 
contend  with  in  establishing  both  the  evolution  hypothesis  of  Darwin  and  the  biological  law  of 
Haeckel. 

Historical. — Although  the  impetus  to  the  study  of  the  history  of  development  has  been  most 
stimulated  in  recent  times,  the  ancient  philosophers  held  distinct  but  very  varied  views  on  the  ques- 
tion of  development.  Passing  over  the  views  of  Pyihagoras  (550  it  c.)  and  Anaxagoras  (500  li.  c), 
Kmpedocles  (473  u.  c.)  taught  that  the  embryo  was  nourished  through  the  umbilicus;  while  he 
named  the  chorion  and  amnion.  Hippocrates  observed  incubated  eggs  from  day  to  day,  noticed 
that  the  allantois  protruded  through  the  umbilicus,  and  observed  that  the  chick  escaped  from  the  egg 
on  the  20th  day.  He  taught  that  a  7  months'  foetus  was  viable,  and  explained  the  possibility  of 
superfrelation  from  the  horns  of  the  uterus.  The  writings  of  Aristotle  (born  3S4  B.  c  )  contain  many 
references  to  development,  and  many  of  them  are  already  referred  to  in  the  text.  He  taught  that 
the  embryo  receives  its  vascular  supply  thiough  the  umbilical  vessels,  and  that  the  placenta  sucked 
the  blood  from  the  vascular  uterus  like  the  rootlets  of  a  tree  absorbing  mi^islure.  lie  ditinguished 
the  polycolyledonary  from  the  diffuse  placenta;  and  he  referred  the  former  to  animals  without  a 
complete  row  of  teeth  in  both  jaws  In  the  incubated  egg  of  the  chick  he  distinguished  the  blood 
vessels  of  the  umbilical  vesicle,  which  carried  food  from  the  cavity  of  the  latter,  and  also  the  allan- 
t<^is.  He  also  observed  that  the  head  of  the  chick  lay  on  its  right  leg,  and  that  the  umbilical  sac 
was  ultimately  absorbed  into  the  body.  The  formation  of  double  monste:s  he  ascribed  to  the  union 
of  two  germs  or  two  eml^ryos  lying  near  each  other.  During  generation  the  female  produces  the 
matter,  the  male  the  principle  which  gives  it  form  and  motion.  There  are  also  numerous  references 
to  reproduction  in  the  lower  animals.  Erasislratus  (304  b.  c.)  described  the  embryo  as  arising  by 
new  formations  in  the  ovum — Epigenesis, — while  his  contemporary,  Herophilus,  found  that  the 
pregnant  uterus  was  closed.  He  was  aware  of  the  glandular  nature  of  the  prostate,  and  named  the 
vesiculje  seminalis  and  the  epididymis.  Galen  (131-203  A.  D.)  was  acquainted  with  the  existence 
of  the  foramen  ovale,  and  the  course  of  the  blood  in  the  ftt-tus  through  it,  and  through  the  ductus 
arteriosus.  He  was  also  aware  of  the  physiological  relation  between  the  breast  and  the  blood  vessels 
of  the  uterus,  and  he  described  how  the  uterus  contracted  on  pre>sure  being  applied  to  it.  In  the 
Talmud  it  is  stated  that  an  animal  with  its  uterus  extirpated  may  live,  that  thepubes  separates  during 
birth,  and  there  is  a  record  of  a  case  of  Ca^sarean  section,  the  child  being  saved.  Sylvius  described 
the  value  of  the  foramen  ovale;  Vesalius  (1543)  ihe  ovarian  follicles;  Eustachius  (f  1570)  the  ductus 
arteriosus  (Botalli)  and  the  branches  of  the  umbilical  vein  to  the  liver.  Arantius  investigated  the 
duct  which  bears  his  name,  and  he  asserted  that  the  umbilical  arteries  do  not  anastomose  with  the 
maternal  vessels  in  the  placenta.  In  Libavius  (1597)  it  is  stated  that  the  child  may  cry  in  utero. 
Riolan  ( 1618)  was  aware  of  the  existence  of  the  corpus  Elighmorianum  testis.  Pavius  (1657)  investi- 
gated the  position  of  the  testes  in  the  lumbar  region  of  the  foetus.  Harvey  (1633)  stated  the  funda- 
mental axiom,  "  Otmie  viviim  ex  ovo^  Fabricius  ab  Aquapendente  fl6oo)  collected  the  materials 
known  for  the  history  of  the  development  of  the  chick.     Regner  de  Graaf  described  more  carefully 


HISTORICAL.  949 

the  follicles  which  bear  his  name,  and  he  found  a  mammalian  ovum  in  the  P'allopian  tube.  Swam- 
merdam  (f  1685)  discovered  metamorphosis,  and  he  dissected  a  butterfly  from  the  chrysalis  before 
the  Grand  Duke  of  Tuscany.  He  described  the  cleavage  of  the  frog's  egg.  Malpighi  (f  1694) 
gave  a  good  description  of  the  development  of  the  chick  with  illustrations.  Hartsoecker  (1730) 
asserted  that  the  spermatozoa  pass  into  the  ovum.  The  first  half  of  the  1 8th  century  was  occupied 
with  a  discussion  as  to  whether  the  ovum  or  the  sperm  was  the  more  important  for  the  new  forma- 
tion (the  Ovulists  and  Spermatists ) ;  and  also  as  to  whether  the  fcetus  was  formed  or  developed 
within  the  ovum  (Epigenesis),  or  if  it  merely  increased  in  growth.  The  question  of  spontaneous 
generation  has  been  frequently  investigated  since  the  time  of  Needham  in  1745. 

New  Epoch. — A  new  epoch  began  with  Caspar  Fried.  Wolff  (1759),  who  was  the  first  to  teach 
that  the  embiyo  was  formed  from  layers,  and  that  the  tissues  were  composed  of  smaller  parts  (corres- 
ponding to  the  cells  of  the  present  period).  He  observed  exactly  the  formation  of  the  intestine, 
William  Hunter  (1775)  described  the  membranes  of  the  pregnant  uterus.  Soemmering  (1799) 
described  the  formation  of  the  external  human  configuration,  and  Oken  and  Kieser  that  of  the  intes- 
tines. Oken  and  Goethe  taught  that  the  skull  was  composed  of  vertebrse.  Tiedemann  described 
the  formation  of  the  brain,  and  Meckel  that  of  monsters.  The  basis  for  the  study  of  the  develop- 
ment of  an  animal  from  the  layers  of  the  embryo  was  laid  by  the  researches  of  Pander  (1817),  Carl 
Ernst  V.  Baer  (1828-1834),  Remak,  and  many  other  observers;  and  Schwann  was  the  first  to  trace 
the  development  of  all  the  tissues  from  the  ovum.  [Schlaiden  enunciated  the  cell  theory  with  refer- 
ence to  the  minute  structure  of  vegetable  tissues,  while  Schwann  applied  the  theory  to  the  structin-e 
of  animal  tissues.  Among  those  whose  names  are  most  prominent  in  connection  with  the  evolution 
of  this  theory  are  Martin  Barry,  von  Mohl,  Leydig,  Remak,  Goodsir,  Virchow,  Beale,  Max  Schultze 
Briicke,  and  a  host  of  recent  observers.] 


APPENDIX  A. 


General  Bibliography. 


SYSTEMATIC  WORKS  AND  TEXT-BOOKS —A.  v.  Haller,  Elementa  physiologire  cor- 
poris humani,  1757-1766,8  vols.,  Auctarium,  1780. — F.  Magendie,  Precis  elementaire  de  physi- 
ologic, 1816,  2cl  ed.,  1825. — ^Johannes  Miiller,  Ilandbuch  der  l*hysiolo<jie  des  Men.'^cheii,  2d  ed., 
185S-1861  (translated  by  W.  Ualy). — Donders,  I'hys.  d.  Mensch.,  pt.  i,  Leip.,  1856. — C.  Lud- 
wig,  Lelirbuch  der  Physiologic  des  Menschen,  2d  ed.,  ICS5S-1S61. — Otto  Funke,  Lehrbuch  der 
Physiologic,  7th  ed.,by  A.  C'.riinhagcn,  18S4. — G.  Valentin,  Lehrbuch  der  Physiologic,  1844  (trans- 
lated by  Briiiton,  1853). — Moleschott,  Phys.  d.  Xahtungsmittel,  2d  ed.,  Ciicssen,  1859. — F.  A. 
Longet,  Traite  de  physiologic,  2d  ed.,  1860-1S61. — ^Joh.  Ranke,  Grundziige  der  Physiologic,  4th 
ed.,  18S1. — E.  Briicke,  Vorlesungcn  iiber  Physiologic,  3d  ed.,  1885. — L.  Hermann,  Grundriss 
der  Phy.-iologie,  8th  ed.,  1S85  (translated  and  enlarged  by  A.  Gamgee,  2d  Engli>h  ed  ,  1878). — 
W.  Wundt,  Lehrbuch  der  Physiologic,  4th  ed.,  1878,  and  Grundziige  d.  physiol.  Psycholog.,  3d 
ed.,  Leip.,  1887. — M.  Fester,  Text-book  of  Physiology,  4th  ed.,  18S3. — H.  Milne-Edwards, 
Legons  sur  la  physiologic  et  I'analomie  comparee,  14  vols.,  1857-18S0. — G.  Colin,  Traile  de  Physi- 
ologic comparee  des  animaux,  Paris,  1871-1873. — Bernard,  Leg.  de  Pathol,  exper.,  Paris,  1872. — 
Marshall,  Phys.  (Diagrams  and  Text),  1875. —  Strieker,  \'orles.  ii.  allg.  u.  exp.  Path.,  Wien,  1878. 
— Munk,  Physiologic  d.  Menschen  u.  d.  Saugcthierc,  Berlin,  2d  ed.,  1888. — Schmidt-Mulheim, 
Grundriss  d.  spec.  Physiologic  d.  Ilaus-augethierc,  Leipzig,  1879. — Vierordt,  Grunrlriss  d.  Physiol- 
ogic d.  Menschen,  5th  ed.,  Tubingen,  1857. — Todd  and  Bowman's  Cyclopaedia  of  Anat.  and  Phys. 
— Hermann,  Expt.  Toxicologic,  1S74. — W.  Rutherford,  .V  Text-book  of  Physiology,  pt.  i,  Edin- 
burgh, 1S80. — W.  B.  Carpenter,  Princip.  of  Phys.,  8th  ed.,  edited  by  Power,  London,  1876. —J. 
Beclard,  Traite  elem.  de  Phys.,  Paris,  1880. — Cohnheim,  N'orlcsungen  ii.  allgem.  Pathologic, 
Berlin,  1880. — Huxley's  Ivlements,  1885. — H.  Beaunis,  Nouveaux  elements  de  Physiologic  hu- 
maine,  2d  ed.,  1881. — Flint,  Textbook,  New  York,  1876;  and  Phys.  of  Man,  1S66-1873. — Kirkes, 
Handbook  of  Physiology,  nth  ed.,  1884.— Dalton,  Text-book,  1882.— -J.  G.  M'Kendrick,  Text- 
book of  Physiology,  Glasgow,  18S8. — Samuel,  Ilandb.  d.  allg.  Path.,  Slutt.,  1879. — The  works 
of  Herbert  Spencer  and  G.  H.  Lewes. — E.  D.  Mapother,  Manual  of  Physiology,  3d  ed.,  re- 
written by  L  L.  Knott,  Dublin,  1882. — A.  Fick,  Compendium  d.  Phys.,  18S2. — Steiner,  Physiol- 
ogic, 4th  ed.,  Leipzig,  1S88. — Nuel  and  Fredericq,  Elem.  de  Phys.,  Gand,  1883.— Preyer,  Ele- 
mente  der  allgemeinen  Physiologic,  1883. — T.  Lauder-Brunton,  Pharmacology,  Therapeutics, 
and  Materia  Medica,  1887. — H.  Power,  Elements  of  Physiol.,  London,  18S4. — Wundt,  Phys. 
med.,  1878 — Daniell,  Text-book  of  the  Principles  of  Physics.  1884.— Fick,  Med.  Physik.,  2d  ed., 
1884. — M'Gregor  Robertson,  Physiological  Physics,  London,  1885.— Draper,  Med.  Phys-ics, 
1.885. — Yeo,  Manual  of  Physiology,  2d  ed.,  London,  1887. — L.  v.  Thanhoffer,  tirundziige  d. 
vergl.  Physiologic  u.  Histologic,  Stuttgart,  1885. — Ziegler,  Text-book  of  Path.  Anat.  (trans,  by  D. 
Macalister),  1883-1S84.— P.  H.  Pye-Smith,  Syllabus  of  Lectures  on  Physiology,  London,  1885. — 
Chapman,  Treatise  on  Human  Phys,  Philad.,  1S87. — Klein,  Microorganisms  and  Disease,  1884. 
— Magnin  and  Steinberg,  Bacteria,  1884. — W^oodhead  and  Hare,  Mycology,  1885. — Crook- 
shank,  Bacteriology,  1886. — Davis,  Text-book  of  Biol.,  London,  18S8. — Vines,  Physiology  of 
Plants. — Albertoni  and  Stefani,  Manualc  di  Fisiol.  umana,  1888. — Ellenberger,  Lehrb.  d.  verg- 
leich.  Histol.  u.  Physiol,  d.  Llaunhiere,  Berlin,  1887. —  Landois  and  Stirling,  Text-book,  ^d  ed., 
1888. 

YEARLY  REPORTS.  BIBLIOGRAPHICAL  WORKS.— 1834-1837  :  "  Jahresberichte  iiber 
die  Fortschritte  der  Physiologic,"  by  Job.  Muller,in  his  Archiv. — 1 838-1846  :  by  Th.  L.  Bischoff, 
ebenda. — 1836-1843:  in  "  Repertorium  fiir  Anatomic  und  Physiologic,"  by  G.  Valentin,  8  vols. — 
1856-1871  :  in  "  Zeitschrift  fiir  rationelle  Medicin,"  by  G.  Meissner,  and  continued  since  1872 
under  the  title — "Jahresberichte  iiber  die  Fortschritte  der  Anatomic  und  Physiologic,"  by  F.  Hof- 
mann,  and  G.  Schwalbe,  Leipzig. — 1841-1865  :  Jahresbericht  uber  die  Fortschritte  der  gcsammten 

950 


GENERAL   BIBLIOGRAPHY.  951 

Medicin,  by  Canstatt,  continued  by  Virchow  and  Hirsch. — 1822-1849  :  Froriep's  Notizen,  loi 
vols.  (References  and  Bibliogr=iphy). — Centralblatt  fiir  die  medicinisclien  Wissenschaften,  Berlin ; 
yearly  since  1863. — Biologisches  Centralblatt,  Erlangen,  since  1881. — 1817-1818:  Isis,  by  Oken. — 
Catalogue  of  Scientific  Papers  compiled  and  published  by  the  Royal  Society  of  London,  1800-1873, 
8  vols. — Engelmann,  1700-1846:  Bibliotheca  historico-naturalis  (Titles  of  Books  on  Comparative 
Physiology). — Jahrbuch  der  gesammten  Medicin,  by  Schmidt,  since  1826. — Bibliotheca  anatomica 
qua  scripta  ad  anatomen  et  physiologiam  facientia  a  reruni  initus  recensentur  auctore  Alberto  von 
Haller,  2  vols,  (important  for  the  older  literature  up  to  1776). — Yearly  Reports  on  Physiology,  in 
Journal  of  Anat.  and  Phys.,  by  Rutherford,  Gamgee,  and  Stirling  ;  also  Monthly  Reports  in 
London  Med.  Record,  since  its  commencement  in  1873. — Index  medicus. — Neurologisches  Central- 
blatt.— Med.  Bibliographic  by  A.  Wiirzburg,  since  1886. — Fortschritt  d.  Med. 

HISTORICAL. — Kurt  Sprengel,  Versuch  einer  pragmatischen  Geschichte  der  Arzneykunde, 
3d  ed.,  1821. — W.  Hamilton,  Hist,  of  Med.  Surg,  and  Anat.,  1831. — Bostock's  Syst.  of  Phys., 
3d  ed.,  1836. — ^J.  C.  Poggendorf,  Geschichte  der  exacten  Wissenschaft,  1863. — J.  Goodsir,  Titles 
of  Papers  on  Anat.  and  Phys.,  1849-1852,  Edin.,  1853. — Meyer,  Gesch.  d.  Botanik,  Konigs., 
1854-1857. — H.  Haeser,  Lehrbuch  der  Geschichte  der  Medicin,  Jena,  1875. — Julius  Sachs, 
Geschichte  der  Botanik  seit  16.  Jahrh.  bis  i860;  1875. — Bouchut,  Hist,  de  la  med.,  Paris,  1873. — 
Fournie,  Applic.  de  la  scien.  a  la  med.,  Paris,  1873. — Willis's  William  Harvey,  1878;  and  his 
Servetus  and  Calvin,  London,  1877.     Biographisches  Lexikon,  Vienna,  1884. 

ENCYCLOP.-EDIAS.— R.  Wagner,  Handworterbuch  der  Physiologic,  4  vols.,  1842-1853.— 
R.  B.  Todd,  The  Cyclopfedia  of  Anatomy  and  Physiology,  1836-1852. — Pierer  and  N.  Choulant, 
Anatomisch-physiologisches  Realworterbuch,  8  vols.,  1816-1829. — L.  Hermann,  Handbuch  der 
Physiologic,  1879-1884.     Real-Encyclop.  d.  gesam.  Med.,  edited  by  Eulenberg,  Wien,  1888. 

PRACTICAL  WORK  IN  THE  LABORATORY.— R.  Gscheidlen,  Physiol ogische  Meth- 
odik,  1876  (not  yet  completed). — E.  Cyon,  Methodik  der  physiologischen  Experimente  u.  Vivisek- 
tionen,  with  Atlas,  1876  (only  one  part  issued).  Ott,  The  Actions  of  Medicines,  Phil.,  1878. — 
Claude  Bernard  and  Huette  Precis  iconographique  de  medecine  operatoire  etd'anatomie  chirurgi- 
cale,  with  113  plates,  1873  '■>  ^^^o  Legons  de  physiologic  operatoire  (edited  by  Duval),  Paris,  1879. — 
Sanderson,  Foster,  Klein,  and  Brunton,  Handbook  for  the  Physiological  Laboratory  (Text  and 
Atlas).  The  French  edition  contains  additional  matter. — Rutherford,  Outlines  of  Pract.  Hist., 
1876. — Meade-Smith,  Trans,  of  Hermann's  Toxicol. — ^J.BurdonSanderson,  Practical  Exercises 
in  Physiology,  London,  1882. — Foster  and  Langley,  Pract.  Phys.,  London.  1884. — B.  Stewart 
and  Gee,  Pract.  Physics. — Vierordt,  Anat.  Physiol,  u.  Physik.  Daten  u.  Tabellen,  Jena,  1888  — 
Miiller-Pouillet,  Lehrb.  d.  Physik.,  8th  ed.,  Braunschweig. — Wiillner,  Lehrb.  d.  exp.  Physik. — 
Livon,  Manuel  de  Vivisect.,  Paris,  1882. — Harris  and  Power,  Manual  for  the  Phys.  Lab.,  5th  ed., 
1888. — Straus-Durckheim,  Anat.  descrip.  comp.  du.  chat,  Paris,  1845. — ^-  Krause,  Die  Anato- 
mic des  Kaninchens,  Leipzig,  2d  ed.,  1883  — A.  Ecker,  Die  Anatomic  des  Frosches,  1864-1S82, 
2d  ed.,  pt.  i,  1888. — Biolog.  Memoirs,  edited  by  Burdon-Sanderson. — Stirling,  Outlines  of 
Pract.  Physiol.,  Lond.,  1888. 

SPECIAL  LABORATORY  REPORTS.— Ludwig  and  his  pupils,  Arbeiten  aus  der  physio- 
logischen Anstalt  zu  Leipzig,  since  1866. — Burdon-Sanderson  and  Schafer,  Collected  papers 
from  the  Physiological  Laboratory  of  University  College,  London,  1876— 1885. — Gamgee,  .Studies 
from  the  Physiological  Laboratory  of  Owens  College,  Manchester,  1877-78. — Traube,  Beitr.  z. 
Path.  u.  Phys.,  Berlin,  1871. — ^J.  Czermak,  Gesammelte  Schriften,  1879. — Marey,  Physiologic  ex- 
perimentale,  Travaux  du  laboratoire,  Paris,  1875. — L.  Ranvier,  Laboratoire  d'histologie  du  College 
de  France,  Paris,  since  1875. — Loven,  Physiol.  Mittheil.,  Stockholm,  1882-84. — W.  Kiihne,  Un- 
tersuchungen  des  physiologischen  Instituts  der  Universitat,  Heidelberg,  since  1877. — R.  Heiden- 
hain,  Studien  des  physiologischen  Instituts  zu  Breslau,  1861-68. — Strieker,  Studien  aus  dem  Insti- 
tute fur  experimentelle  Pathologic,  Vienna. — John  Reid,  Physiological  and  Anatomical  Researches, 
Edinburgh,  1848. — Rollett's  Untersuch.  a.  d  Inst,  zu  Gratz,  since  1870. — Schenk,  Mitth.  a.  d. 
embryol.  Inst.  z.  Wien,  1877-. — Preyer,  Sammlung  phys.  Abhandl.,  Jena,  1877. — Von  Wit- 
tich,  Mitth.  a.  d.  Konigsb.  Phys.  Lab.,  1878. — Rossbach,  Pharmacol.  Unters.  Wiirzb.,  1873. — 
Fick,  Arb.  a.  d.  Wiirzburger  Hochschule,  Wiirzburg,  1872. — Hoppe-Seyler,  Med.-chem.  Unters., 
1866-71. — Laborde,  Travaux  de  Lab.  de  Phys.  de  la  Faculte  de  Med.,  Paris,  1885.  Studies  from 
the  Biol.  Lab.  of  Owens  College,  pt.  i,  1886. — Tigerstedt,  Mitth.  v.  d.  phys.  Lab.  in  Stockholm, 
1888. 

JOURNALS,  PERIODICALS.— Archiv  fur  die  Physiologic,  by  J.  C.  Reil  and  Autenreith,  12 
vols.,  Halle,  1796-1815.  Continued  as — Deutsches  Archiv  fiir  die  Physiologic,  by  J.  F.  Meckel, 
8  vols.,  Halle,  1815-1823.  Continued  as — Archiv  fiir  Anatomic  und  Physiologic,  by  J.  F.  Meckel, 
6  vols.,  Leipzig,  1826-1832.  Continued  as — Archiv  iiir  Anatomic  und  wissenschaftliche  Medicin, 
by  Johannes  Miiller,  25  vols.,  Berlin,  1834-1858.  Continued  under  the  same  titiehy — C.  B. 
Reichert  and  E.  du  Bois-Reymond,  1859-1876.  When  it  was  divided  into — Zeitschrift  fiir 
Anatomic  und  Entwickelungsgeschichte,  by  W.  His  and  Braune,  and  Archiv  fiir  Physiologic,  by 


952  GENERAL    BIBLIOGRAPHY. 

E.  du  Bois-Reymond,  until  1S77.  Is  ,oitliuued  as — Archiv  fiir  Anatomic  und  Physiologic  by 
W.  His,  W.  Braune,  and  E.  du  Bois  Reymond. — Archiv  fiir  die  gesamnite  Physiologic  des 
Menschcn  uinl  dcr  Thicro,  liy  E.  F.  W.  Pfliiger,  Bonn,  since  1S6S. — Zcitschrifl  fiir  Biologic,  edited 
from  1S65  hy  Buhl,  Pettenkofcr,  Voit,  and  Radlkofcr  ;  from  1S75  i)y  the  first  three,  and  since 
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presently  by  Waldeyer  and  La  Valette. — (Quarterly  Microscopical  Journal,  London. — Monthly 
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Mikrosk.  Untcrsuch.,  1838  (translated  by  the  Sydenham  Society,  1847). — W.  Kiihne,  Das  Proto- 
plasma,  Leipzig,  1864. — Max  Schultze,  Das  Protoplasma,  Leipzig,  1863. — R.  Virchow,  Die  Cel- 
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and  his  Icones  Histolog.,  Leip.,  1864. — J.  Goodsir,  Anatomical  and  Pathological  Observations, 
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954 


COMPARISON    OF    METRICAL   WITH    COMMON    MEASURES. 


APPENDIX  B. 

COMPARISON  OF  THE  METRICAL  WITH  THE  COMMON  MEASURES. 

By  Dr.  Warren  De  la  Rue. 


MEASURES  OF  LENGTH. 


In  English  Inches. 


In  English  Feet  = 
iz  Inches. 


In  English  Yards 
3  Feet. 


Millimetre 

Centimetre 

Decimetre 

Metre     .    . 

Decametre 

Hectometre 

Kilometre 

Myriometre 


003937 

0.39371 

3-93708 

39.37079 

393.70790 

3937.07900 

39370.79000 

393707.90000 


0.0032809 

0.0328090 

0.3280899 

3.2808992 

32.8089920 

328.0899200 

3280.8992000 

32808.9920000 


0.0010936 

0.0109363 

0.1093633 

1.0936331 

10.9363310 

109  3633100 

1C93. 6331000 

10936.3310000 


1  Inch  =  3.539954  Centimetres. 


I  Foot  =  3.0479449  Decimetres.       |       i  Yard  =  0.91438348  Metre. 


MEASURES  OF  CAPACITY. 


In  Cubic  Inches. 


In  Cubic  Feet  =  1728 
Cubic  Inches. 


In  Pints  ^  34.65923 
Cubic  Inches. 


Millilitre  or  cubic  centimetre  .  . 
Centilitre  or  10  cubic  centimetres 
Decilitre  or  loo  cubic  centimetres 
Litre  or  Cubic  decimetre     .... 

Decalitre  or  centistere 

Hectolitre  or  decistere 

Kilolitre  or  stere,  or  cubic  metre  . 
Myriolitre  or  decastere 


0.061027 

0.610271 

6. 102705 

61.027032 

610.270515 

6102.705152 

61027.051519 

610270.515194 


0.0000353 
0.0003532 
0.0035317 
0.0353166 
0.3531658 
3-53i658i 
35.3165807 
353.1658074 


0.001761 

0.017608 

0.176077 

1.760773 

17  607734 

176.077341 

1 760. 7734 14 

17607.734140 


1  Cubic  Inch  =  16.3861759  Cubic  Centimetres.  |  i  Cubic  Foot  =  28.3153119  Cubic  Decimetres. 

The  UNIT  OF  voLtjMB  is  I  Cubic  Centimetre. 


MEASURES  OF  WEIGHT. 


Milligramme  . 
Centigramme  . 
Decigramme  . 
Gramme  .  .  , 
Decagramme  . 
Hectogramme 
Kilogramme 
Myriogramme 


In  English  Grains. 


0.015432 

01 54323 

1-543235 

15-432349 

154.323488 

1543-234880 

15432.348800 

154323.488000 


In  Troy  Ounces  = 
480  Grains. 


0.000032 
0.000322 
0.003215 
0.032151 
0.321507 
3.215073 
32.150727 
321.507267 


In  Avoirdupois  Lbs. 
7000  Grains. 


O.O0O0O32 

o  0000220 
0.0002205 
0.0022046 
0.0220462 
0.2204621 
2.2046213 
22.0462126 


The  UNIT  OF  MASS  in  the  metrical  system  is  1  Gramme,  which  is  the  mass  or  weight  of  i  Cubic  Centimetre 
(1  c.c.)  of  water  at  4°  C,  i.e.,  at  its  temperature  of  maximum  density. 


CORRESPONDING  DEGREES  IN  THE  FAHRENHEIT  AND  CENTIGRADE  SCALES. 


Fahr.       Cent. 


500"  . 

450°  • 
400°  . 
350°. 
300^  • 

2H°  . 

210°  . 
205°  . 

aoo°  . 
195°. 
190°  , 
185°. 
180°  . 
175°. 
170°  , 
165O  , 
160° 
1550 
150° 
145° 


a6o°.o 

232°.2 

,  ao4°.4 
176°. 7 

•  '48°.9 
.  100°  .0 

■  98°  9 
.    96"^  1 

93°-3 

•  90°  5 
.  87°.  8 
.    85°.o 

.      82°.2 

•  79°-4 

•  76°. 7 

•  73°-9 
.  7i°.i 
.  68°. 3 

•  65°.S 
.  62°.8 


Fahr.      Cent. 


140" 
.35° 
130° 
125° 
120° 
115° 
110° 


95°. 
90°  . 

85°. 
80°  . 

75°. 
70°  , 
65°, 
60°. 
55° 

^o 
45° 


6o°.o 
57°.2 
S4°-4 
5i°.7 

48°.9 
,  46°.  1 
.  43°- 3 
.  40°. 5 
•37°.8 
■  35°-o 

.    32°.2 

.  29°.4 
.  26°. 7 
•  23°-9 

.  2I°.l 
.    18°  3 

.  iS°-5 

.    I2°.8 

.  iey°.o 

.      7°.2 


Fahr. 

40° 
35° 
32° 
30° 
25° 


—25" 
-30° 


—45" 
-50°, 


Cent. 

4°.4 
i°.7 
o°.o 

-  1^.1 

-  3°.9 

-  6°.7 

-  9°.4 

,  —12°.  2 
.  — 15°.0 

—17°  8 
,  —20°  5 

•  -23°.  3 
,—26°.  I 
.  — 28°.9 

-3i°-7 
.  -34°-4 

•  -37°-2 
.  — 40°.o 
.  —42°.  8 
.  -45°.6 


Cent.      Fahr, 

100°  ...  212°.0 

2o8°.4 
204°.8 

,  201°.2 

197°  6 

i94°.o 

190°. 4 

,  i86°.8 

.  183°. 2 

,  i79°.6 

1760.0 

,  I72°.4 

,  i68°.8 

.  i65°.2 

i6i°.6 

i58°.o 

1 54°- 4 

.  i5o°.8 

147°.2 

143°.6 


96°  . 

88° 
86° 
84° 
82° 
80° 

76° 
74° 

K 
70° 

68°- 

66° 

64° 

6.!° 


Cent. 

60°... 

58°  ... 
56°  ... 
54°  ... 

I   52q  ... 

48°  ... 
46°  ... 


4°"' 
38°. 

36°, 
M°. 
32°  . 
30°. 
28°  , 
26°  . 
24°, 


Fahr. 
i40°.o 

136°.4 
132°.8 
129°.  2 
125°6 
ia2°.o 
ii8°.4 
ii4°.8 

11I°.2 

io7°.6 
lo4°.o 
100°. 4 
96°.8 
93°-2 
89°.  6 
86°.o 
82°.  4 
78°.  8 
75O2 
7i°.6 


Cent.  Fahr. 
20°  ...  68°.o 
-  64°.4 
6o°.8 
57°.  2 
53°.6 
50°.o 
46°.4 
42°.8 
39O.2 
35°-6 
32°.o 
28°.4 
24°.  8 

21°.2 

17°.6 
i4°.o 
10°.  4 
6°.8 
3°-2 
-o°.4 
-4°.o 


16°  .., 


8°... 
6°.., 
4°.., 


—  6°  .., 

—  8°  ... 

—  10°  .. 


To  turn  C°  into  F°,  multiply  by  9,  divide  by  5,  and  add  32°. 
To  turn  F°  into  C°,  deduct  32,  multiply  by  5,  and  divide  by  9. 


INDEX. 


Abdominal  muscles   in  respira- 
tion, 217 
Abdominal  reflex,  692 
Abducens,  649 
Aberration,  chromatic,  807 
spherical,  807 
Abiogenesis,  893 
Absolute  blindness,  752 
Absorption  by  fluids,  80 
by  solids,  80 
forces  of,  342 
influence   of   nerves 

on,  347 
organs  of,  336 
Absorption  of- — ■ 
Carbohydrates,  344 
Coloring  matter,  346 
Digested  food,  342 
Effusions,  359 
Fat  soaps,  345 
Grape  sugar,  344 
Inorganic  substances,  344 
Nutrient  enemata,  347 
Oxygen,  232,  236 
Peptones,  345 
Small  particles,  346 
Solutions,  344 
Sugars,  344 

Unchanged  proteids,  345 
Absorption  spectra,  62 
Accelerans  nerve,  720 

in  frog,  722 
Accommodation  of  eye,  799 

defective,  805 
force  of,  805 
line  of,  803 
nerves  of,  803 
phosphene,  813 
range  of,  806 
spot,  813 
time  for,  803 
Accord,  861 
Acetic  acid,  429 
Aceton,  454,  464 
Acetylene,  66 
Achromatin,  893 
Achromatopsy,  828 
Achroodextrin,  262 
Acid  albumin,  425 
Acid  haematin,  66 
Acids,  free,  422 
Acoustic  nerve,  653 

tetanus,  600 
Acquired  movements,  758 


Acrylic  acid  series,  429 

Action  currents,  605 

Active  insufficiency,  552 

Addison's  disease,  200,  498 

Adelomorphous  cells,  285 

Adenin,  433 

Adenoid  tissue,  351 

Adipocere,  412 

Adventitia,  137 

^gophony,  225 

Aerobes,  325 

^sthesiometer,  882 

^sthesodic  substance,  695 

Afferent  nerves,  633 

After-birth,  946 

After-images,  829 

After-sensation,  782 

Ageusia,  877 

Agoraphobia,  655 

Agrammatism,  761 

Agraphia,  761 

Ague,  197 

Air,  changes  in  respiration,  231 
collection  of,  228 
composition  of,  230 
diffusion  of,  234 
expired,  231 
impurities  in,  244 
quantity  exchanged,  232 

Air  cells,  205 

Albumimeter,  459 

Albuminoids,  426 

Albumin  of  egg,  905 

Albumins,  423 

Albuminuria,  457 

Albumoses,  animal,  425 

vegetable,  425 

Alcohol,  400 

Alcohols,  430 

Alcoholic  drinks,  400 

Alcool  au  tiers,  50 

Aleurone  grains,  425 

Alexia,  763 

Alkali  albiunin,  425 

Alkali  hsematin,  66 

Alkaline  fermentation,  457 

Alkaloids,  400 

Allantoin,  402,  452 

Allantois,   924 

Allochiria,  8S9 

AUorhythmia,  150 

Alloxan,  449 

Almen's  test,  461 

Alternate  hemiplegia,  705 

955 


Alternate  paralysis,  705,  769 

Alternation  of  generations,  895 

Amaurosis,  637 

Amblyopia,  637 

American  crow-bar  case,  731 

Amido  acids,  432 

Amidoacetic  acid,  312,  432 

Amido -caproic  acid,  300 

Amimia,  761 

Amines,  432 

Ammonisemia,  479 

Amnesia,  761 

Amnion,  923 

Amniota,  924 

Amniotic  fluid,  924 

Amoeboid  movement,  55,  500 

Ampere's  rule,  593 

Amphiarthroses,  549 

Ampho  peptone,  292 

Amphoric  breathing,  224 

AmygdaUn,  359 

Amyloid  substance,  425 

Amylopsin,  299 

Amylum,  431 

Anabiosis,  893 

Anacrotism,  151 

Anaemia,  58,  89 

metabolism  in,  89 
pernicious,  58 
Anserobes,  325 
AnKsthesia  dolorosa,  890 
Ansesthetic  leprosy,  632 
Anjesthetics,  890 
Anabolic  nerves,  633 
Anabolism,  388 
Anakusis,  653 
Analgesia,  698 
Analgia,  891 
Anamnia,  924 
Anarthria,  760 
Anasarca,  359 
Anelectrotonus,  616 
Aneurism,  157,  158 
Angiograph,  143 
Angiometer,  151 
Angioneuroses,  728 
AnidrosiS,  497 
Animals,  characters  of,  39 
Animal  foods,  405 

magnetism,  736 
Anions,  594 

Anisotropous  substance,  504 
Ankle  clonus,  693 
Anode,  584 


•JoG 


INDEX. 


Anosmia,  634 
Antagonistic  muscles,  552 
Anihrncometer,  22S 
Anthracosis,  207 
Ami  albumin,  293 
Antiar,  358 
Anti-emetics,  277 
Amihydrotics,  496 
Antipeptone,  292 
Antiperistalsis,  278 
Antipyretics,  384 
Antisialics,  260 
Aortic  valves,  95 

insufficiency  of, 1 53 
Aperistalsis,  281 
Apex  beat,  102,  110 
Aphakia,  79 1 
Aphasia,  760 
Aphonia,  573 
Apncea,  713 

Appunn's  apparatus,  866 
Apselajihesia,  SS9 
Aqueous  humor,  792 
Arachnoid  mater,  776 
Archiblastic  cells,  920 
Area  opaca,  916 
pellucida,  916 
vasculosa,  922 
Argyll  Robertson  pupil,  810 
Arhythmia  cordis,  98 
Aristotle's  experiment,  8S4 
Aromatic  acids,  430 

oxyacids,  433 
Arrector  pili  muscle,  490 
Arterial  tension,  I47 
Arteries,  137 

blood  pressure  in,  165 
central,  740 
develoi>mcnt  of,  936 
emptiness  of,  723 
rhythmical    contraction 

of  725 
sounds  in,  184 
structure  of,  135 
tension  in,  165 
termination  in  veins,  iSl 
Arterioijram,  143 
Arthroidal  joints,  549 
Articular  cartilage,  548 
Articu  lation  nerve  corpuscles,  880 
Artificial    cold-blooded     condi- 
tion, 386 
Artificial  eye,  798 

digestion,  295 
gastric  juice,  291 
pancreatic  juice,  300 
respiration,  243 

^Iarshall  Hall's  me- 
thod, 243 
Sylvester's    method, 

243 
selection,  948 
Aspartic  acid,  301,  433 
Asphyxia,  241,  714 

artificial  respiration  in, 
243 


Asphyxia,  recovery  from,  242 
Aspirates,  572 
Aspiration  of  heart,  172 
thoracic,  172 
ventricles,  99 
Assimilation,  388 
Associated  movement,  810,  S37 
Astatic  needles,  594 
Asteatosis,  498 
Asthma  nenosum,  663 

dyspepticum,  663 
Astigmatism,  807 

correction  of,  808 
test  for,  808 
Atavism,  948 
Ataxaphasia,  761 
Ataxia,  668,  750,  759 
Ataxic  tabes,  697 
Atelectasis,  226,  243 
Atmospheric  pressure,  247 

diminution  of,  248 
increase  of,  248 
Atresia  ani,  923 
Atrophy,  554 

of  the  face,  648 
A  tropin,  524 

in  eye,  638,  810 
Attention,  time  for,  735 
Audible  tone,  lowest,  862 
Auditory  after-sensations,  870 

area,  753 

aurie,  754 

centre,  753 

delusions,  653 

meatus,  849 

nerve,  847 

ossicles,  851 

paths,  754 

perceptions,  860 

sac,  945 
Auerbach's  plexus,  281,  341 
Augmentor  nerves,  722 
Auricles  of  heart,  91,  93 

development  of,  935 
Auscultation  of  heart,  117 
of  lungs,  223 
Automatic  excitement,  675 
Autonomy,  737 
Auxocardia,  128 
Avidity,  290 
Axis  of  vision,  819 


Bacillus,  324 

acidi  lactici,  325 
anihracis,  90 
butyricus,  325 
I  subtilis,  326 

!  tubercle   and    others, 

244 
Bacterium,  90,  324,  330 
aceti,  325 
coh,  330 
fceiidum,  498 
I  lactis,  330 

synxanthum,  395 


l?nll  and  socket  joints,  549 
Hantingism,  413 
Hancsthesiometer,  885 
Basal  development,  943 

ganglia,  701,  765 
Basedow's  disease,  199,  728 
Bases,  422 

Basilar  membrane,  860 
Bass-deafness,  863 
Batteries,  galvanic,  594 
]>unsen's,  595 
Daniell's,  595 
Grennet's,  595 
j  Grove's,  595 

Leclanche's,  596 
Smee's,  595 
Beats,  868 

isolated,'  868 
successive,  868 
Bed-sores,  632 
Beef  tea.  397 
Beer,  401 
Bell's  law,  667 

deductions  from,  667 
Bell's  paralysis,  652 
Benzoic  acid,  451 
Bert'f  experiment,  624 
Bidder's  ganglion,  119 
Bile,  312 

acids,  312 

composition  of,  315 

crystallized,  312 

ducts,  306 

ligature  of,  307 
j  effects  of  drugs  on,  318 

I  excretion  of,  316 

fate  of,  320 

functions  of,  319 

gases  of,  314 

passage  of  drugs  into,  317 

pigments,  313 

pressure,  317 

reabsorption  of,  317 

secretion  of,  315 

spectrum  of,  314 

test  for,  313,  314 
Biliary  fistula,  316 
Bilicyanin,  314 
Bilifuscin,  314 
Biliprasin,  314 
Bilirubin,  313 
Biliverdin,  313 
Binocular  vision,  837 
Biological  law,  948 
Biology,  33 
Biot's  respiration,  216 
Birth,  946 
Biuret  reaction,  424 
Blastoderm,  903,  915 
Blastomere,  914 
Blastosphere,  914 
Blepharospasm,  652 
Blind  spot,  818 
Blood,  33 

abnormal,  87 
analysis,  69 


INDEX. 


957 


Blood,  arterial,  86 

carbon  dioxide  in,  85 
clot,  70 
coagulation,  72 
color,  33 

coloring  matter,  59 
composition  of,  61 
defibrinated,  70 
distribution  of,  187 
electrical     condition    of, 

629 
extractives,  80 
fats  in,  79 
fibrin  in,  58,  71 
gases  in,  80 
granules  of,  58 
islands,  51,  922 
lake- colored,  49 
loss  of,  89 
microscopic   examination 

of,  44  _ 
nitrogen  in,  86 
odor,  43 
organisms  in,  90 
oxygen  in,  83 
ozone  in,  84 
plasma,  70 
plates,  57 
portal  vein,  86 
proteids  of,  78 
quantity,  86 
reaction,  33 
salts  in,  80 
serum,  70 

specific  gravity  of,  43 
taste,  43 
temperature,  44 
transfusion  of,  87 
variations  in,  87 
venous,  86 
water  in,  80 
Blood     channels,     intercellular, 

137 
Blood  corpuscles — stroma,  49 
abnormal  changes,  58 
action  of  reagents  on,  47, 

49,56 
amoeboid  movements,  55 
change  of  form,  47 
chemical  composition,  59 
circulation,  180 
color,  47 
colorless,  53 
conservation  of,  49 
crenation,  47 
decay,  53 

diapedesis,  56,  182 
effect  of  drugs,  56 
effect  of  reagents,  47 
form,  44,  50 
Gower's  method,  46 
histology  of,  46 
human,  red,  44 

white,  53,  69 
intracellular  origin,  52 
Malassez's  method,  45 


Blood  corpuscles,  nucleated,  58 
number,  44,  58 
of  newt,  54 
origin,  5 1 
parasites  of,  59 
pathological  changes,  58 
proteids  of,  69 
rouleaux  of,  47 
size,  44,50,  58 
staining  of,  48 
stroma,  46 
transfusion  of,  87 
weight,  44 
white,  53 
Blood  current,  180 

in  capillaries,  181 
velocity  of,  177 
Blood  gases,  80 

estimation  of,  O,  COj,  and 

N,  83 
extraction,  81 
gas-pumps  for,  81 
quantity,  82 
Blood  glands,  192 
Blood  islands,  51,  922 
Blood  plasma,  70 
Blood  pressure,  161 
arterial,  165 
capillary,  1 71 
estimation  of,  161 
in  pulmonary  artery,  173 
in  veins,  171 
relation  to  pulse,  170 
variations  of,  165,  170 
Blood  vessels,  134 

action  of  drugs  on,  138 
cohesion  of,  139 
elasticity  of,  138 
lymphatics,  137 
pathology  of,  139 
properties  of,  137,  138 
structure  of,  134 
Blue  pus,  498 

sweat,  498 
Body,  vibrations  of,  158 
Body-wall,  formation  of,  922 
Bone,  chemical  composition  of, 

934 

callus  of,  418 
development  of,  933 
effect  of  madder  on,  418 
fracture  of,  418 
growth  of,  934 
histogenesis  of,  933 
red  marrow,  53 

Bones,  mechanism  of,  547 

Bottger's  test,  264 

Boutons  terminals,  88 1 

Bowman's  tubes,  785 
glands,  871 

Box  pulse-measurer,  140 

Bradyphasia,  761 

Brain,  700 

arteries  of,  777,  77^ 
blood  vessels  of,  777 
general  scheme  of,  700 


Brain  impulses,  course  of,  683 
in  invertebrata,  780 
membranes  of,  776 
motor  centres  of,  742 
movements  of,  777 
of  dog,  744 
pressure  on,  779 
protective    apparatus   of, 

776 
psychical     functions     of, 

731. 
pulse  in,  158 
pyramidal  tracts  of,  703, 

7S8 
topography  of,  756,  764 
we  ght  of,  700 
Branchial  arches,  923 

clefts,  923,  932 
Brandy,  401 
Bread,  398 

Brenner's  formula,  653 
Broca's  convolution,  760 
Bromidrosis,  498 
Bronchial  breathing,  223,  224 

fremitus,  224 
Bronchiole,  205 
Bronchophony,  225 
Bronchus,  extra-pulmonary,  204 
intra-pulmonary,  204, 

205 
small,  205 
Bronzed  skin,  200 
Brownian  movement,  261 
Bruit,  184 

de  diable,  185 
Brunner's  glands,  321,  339 
Buchanan's  experiments,  74 
Bulbar  paralysis,  712 
Bulbus  arteriosus,  934 
Butter,  393 
Butyric  acid,  325,  429 


Cachexia,  198 

Caffein,  400 

Calabar  bean  on  eye,  638 
Calcic  phosphate,  421 
CalcuU,  bihary,  314,  332 
salivary,  260,  331 
urinary,  468 
Callus,  418 
Calorimeter,  362 
Canal  of  cochlea,  857 
hyaloid,  791 
Nuck,  941 
of  spinal  cord,  676 
of  Stilling,  791 
Petit,  790 
Schlemm,  785 
semicircular,  859 
CanaHs  cochlearis,  857 

reuniens,  858 
Capillaries,  136 

action  of  silver  nitrate 

on, 136 
blood  current  in,  181 


958 


INDEX. 


Capillaries,  circulation,  l8l 

contractility  of,  139 
development  of,  53 
form    and    arrange- 
ment of,  I  So 
pressure  in,  171 
slijjmata  of,  136 
velocity  of  blood  in, 
178 
Capillary  electrometer,  603 
Capsule,  external,  767 
Cilisson's,  304 
internal,  766 
of  Tenon,  791 
Carbohydrates,  436 

fermentation    of, 

325 

Carbolic  acid  urine,  453 

Carbon   dioxide,  conditions   af- 
fecting, 232 
estimation  of,  229 
excretion  of,  232,  236 
in  air,  230 
in  blood,  85 
in  expired  air,  231 
where  formed,  238 

Carbonic  oxide  haemoglobin,  65 
oxide,  65 
poisoning  by,  65 

Cardiac  cycle,  98 

dullness,  117 
ganglia,  1 18 
hypertrophy,  IIO 
impulse,  102,  no 
movements,  107 
murmurs,  1 14 
nerves,  1 18 
nutritive  fluids,  120 
plexus,  118 
poisons,  127 
revolution,  98 
sounds,  1 12 

Cardinal  points,  796 

Cardiogram,  102 

Cardiograph,  102 

Cardio-inhibitory  centre,  1 68, 7 1 8 
nerves,  718 

Cardio  -  pneumatic     movement, 
12S 

Caricin,  301 

Carnin,  396 

Carotid   gland,    n8,   137,    200, 
201 

Cartilage.  548,  923 

Casein,  393,  425 

Catacrotic  pulse,  145 

Cataphoric  action,  598 

Cataract,  790 

Cathartics,  284 

Cathelectrotonus,  615 

Cathode,  594 

Caudate  nucleus,  765,  766 

Cavernous  formations,  137 

Cells,  division  of,  S93 

Cellulose,  262 

Cement,  268 


Cement,  action  of  silver  nitrate 
on,  136 
substance,  136 
Centre,  accelerans,  720 
ano-spinal,  694 
auditory,  763 
cardio-inhibitory,  718 
cilio-spinal,  693 
closure  of  eyelids,  710 
coughing,  711 
dilator  of  pupil,  693,  7 1 1 
ejaculation,  694 
erection,  694,  910 
for  coughing,  71 1 
for  defalcation,  694 
for  mastication  and  suck- 
ing, 7H 
for  saliva,  711 
gustatory,  763 
heat  regulating,  730 
micturition,  694 
olfactory,  763 
parturition,  694 
pupil,  711 
respiratory,  712 
sensory,  751 
sneezing,  710 
spasm,  730 
speech,  760 
swallowing,  71 1 
sweat,  694,  730 
vaso-dilator,  694,  729 
vasomotor,  694,  722 
vesico  spinal,  694 
visual,  763 
vomiting,  711 
Centre  of  gravity,  554 
Centrifugal  nerves,  63 1 
Centripetal  nerves,  633 
Centro-acinar  cells,  297 
Cereals,  398 
Cerebellum,  772 

Action  of  electricity  on,  775 
Connections  of,  702 
Function  of,  774 
Pathology  of,  776 
Removal  of,  774 
Structure  of,  772 
Cerebral  arteries,  740,  777,  778 
epilepsy,  745,  759 
fissures,  dog,  744 
inspiratory  centre,  713 
motor  centres,  756 
sensory  centres,  763 
vesicles,  918 
Cerebrin,  428,581 
Cerebro-spinal  Huid,  354 
Cerebrum,  700 

blood  vessels  of,  739, 

740,  777 
convolutions  of,  740 
epilepsy  of,  745 
excision  of    centres, 

750 
Flourens'     doctrine, 
732 


Cerebrum,    functions  of,  731 

(Joltz's     theory     of 

755 
imperfect     develop 

ment  of,  732 
lobes  of,  740 
motor      regions    of, 

744 
movements  of,  777 
removal  of,  732 
sensory  centres,  751 
structure  of,  737 
sulci    and    gyri    of, 

740,  741 
thermal    centres   of, 

755 
weight  of,  700 
Cerumen,  494 
Cervical  sympathetic,  section  of, 

673 
Chalazre,  904 
Charcot's  crystals,  247 
disease,  632 
Cheese,  395 
Chemical  affinity,  37. 
Chess-board  phenomenon,  842 
Chest,  dimensions  of,  220 
Cheyne  -  Stokes'      phenomenon, 

216 
Chiasma,  635 
Chitin,  428 
Chloasma,  495 
Chloral,  724 
Chlorophane,  790 
Chlorosis,  58 
Chocolate,  400 
Chokiemia,  317 
Cholalic  acid,  312,  430 
Cholesterrcmia,  319 
Cholesterin,  69,314,  320,  582 
Choletelin,  314 
Cholin.  581 
Choloidinic  acid,  313 
Choluria,  462 
Chondrin,  427 
Chondrogen,  427 
Chorda  dorsalis,  919 
Chorda  tympani,  650,  729 
Chordie  tenclineje,  ico 
Chorion  la;ve,  926 

frondosum,  926 
primitive,  925 
Choroid,  785 
Choroidal  fissure,  944 
Christison's  formula,  440 
Chromatic  aberration,  807 
Chromatin,  893 
Chromalophores,  499 
Chromatopsia,  637 
Chroraidrosis,  498 
Chromophanes,  790 
Chronograph,  530 
Chyle,  353 

movement  of,  356 

vessels,  348 
Chylous  urine,  467 


INDEX. 


959 


Chyme,  292 
Cicatricula,  903 
Cilia,  500 

conditions  for  movement, 

501 
effect  of  reagents  on,  501 
functions  of,  501 
Ciliary  ganglion,  641 
motion,  500 

force  of,  501 
muscle,  786,  801 
nerves,  641 
Ciliated  epithelium,  500 
Cilio-spinal  region,  693 
Circle  of  Willis,  778 
(circulating  albumin,  403 
Circulation,  capillary,  181 

duration  of,  179 
firvt,  921 
foetal,  927 
portal,  91 
pulmonary,  91 
schemata  of,  161 
second,  922 
systemic,  91 
Circumpolaiization,  265 
Circumvallate  papillae,  874 
Claustrum,  767 
Cleft  sternum,  109 

palate,  931 
Clerk  -  Maxwell's      experiment, 

814 
Cleavage  of  yelk,  914 
lines  of,  915 
partial,  917 
Climacteric,  906 
Clitoris,  942 
Closing,    continued   contraction, 

619 
Closing  shock,  599 
Clothing,  379 
Coagulable  fluids,  78 
Coagulated  proteids,  425 
Coagulation  experiments,  76 
Coagulation  of  blood,  71,  72,  74 

theories  of,  74,  77 
Cocaine,  810 

Coccygeal  gland,  137,  200 
Cochlea,  857 
Cocoa,  400 
Coecitas  verbalis,  763 
Coelom,  920 
Coffee,  400 

Cold-blooded_  animals,  365 
Cold  on  the  body,  385 

uses  of,  387 
Cold  spots,  887 
Collagen,  426 
Colloids,  343 
Coloboma,  944 
Colostrum,  394 
Color  associations,  870 
Color  blindness,  828 
acquired,  828 
testing,  829 
Color  sensation,  824 


Color,  Hering's  theory,  827 

Young-  Helmholtz   theory, 
826 
Colored  shadovs's,  S32 
Colorless  corpuscles,  53 
Color  top,  830 
Colors,  complementary,  824 
contrast,  830 
geometrical  table,  825 
methods  of  mixing,  824 
mixed,  825 
simple,  824. 
Columella,  870 
Columns  of  the  cord,  677 
Coma,  diabetic,  31 1 
Comedo,  498 
Common  sensation,  889 
Comparative — 

Circulation,  201 

Digestion,  334 

Hearing,  870 

Heat,  387 

Kidney  and  urine,  486 

Metabolism.  433 

Motor  organs,  558 

Nerve  centres,  779,  780 

Nerves  and  electro-physiology, 
629 

Peripheral  nerves,  674 

Reproduction    and    develop- 
ment, 947 

Respiration,  249 

Sight,  845 

Skin,  499 

Smell,  873 

Taste,  877 

Voice  and  Speech,  574 
Compensation,  604 
Complemenlal  air,  210 
Compleinenlary  colors,  824 
Compound  eye,  845 
Concretions,  330 
Condensed  milk,  395 
Condiments,  400 
Conduction  in    the    cord,    683, 

696 
Conductivity,  623 
Conglutin,  425 
Congo  red,  288 
Conjugate  deviation,  638,  758 
Conjugation,  895 
Connective-tissue  spaces,  348 
Consonance,  868 
Consonants,  572 
Constant  current,  action  of,  532 
Constant  elements — 

Bunsen's,  595 

Daniell's,  595 

Grennet,  595 

Grove's,  50,5 

Leclanche's,  596 

Smee's,  595 
Constipation,  332 
Contraction,  cardiac,  127 
fibrillar,  526 
initial,  537 


Contraction,  muscular  (see  Myo- 
grani) 
of    blood    vessels, 

137 
remainder,  530 
rhythmical,  523 
secondary,  609 
without  metals,  606 
Contracture,  529 
Contrast,  830 

colors,  824,  830 
Convergent  lens,  action  of,  793 
Cornea,  783,  784 
Coronary  vessels,  97 

effects  of  ligature  of,  97 
Corpora  quadrigemina,  700,  702, 

770 
Corpulence,  413 
Corpus  callosum,  765 
luteum,  909 
spongiosum,  909 
striatum,  700,  765 
Corresponding  points,  837 
Cortical  blindness,  752 
Corti's  organ,  857 
Cotyledons,  928 
Coughing,  226 

centre  for,  711 
Cracked-pot  sound,  223 
Cramp,  892 
Cranial  flexures,  918 
nerves,  634 
Cranioscopy,  732 
Creamometer,  394 
Cremasteric  reflex,  691 
Crepitation,  224 
Crescents  of  Gianuzzi,  253 
Crista  acustica,  859 
Crossed  reflexes,  688 
Crura  cerebri,  768 
Crusta,  769 

pelrosa,  268 
phlogislica,  71 
Crying,  227 
Crystallin,  424,  790 
Crystalline  lens,  790 

spheres,  845 
Crystallized  bile,  312 
Ciystalloids,  343 
Cubic  space,  245 
Curara,  action  of,  520,  523,  724 
Cutaneous  respiration,  238 

trophic  affections,  631 
Cuticular  membrane,  268 
Cyanogen,  66 
Cylindrical  lenses,  807 
Cynuric  acid,  452 
Cyrtometer,  220 
Cysticercus,  895 
Cystin,  464 
Cytozoon,  48 


Daltonism,  827 
Damping  apparatus,  851 
Darby's  fluid  meat,  294 


960 


INDEX. 


Death  of  a  nerve,  591 
I  )el>ove's  niemhrane,  203 
Decidua  rellexa,  925 
serotina,  925 
vera,  925 
Decubitus  :iculus,  632,  772 
I  )ecussation  of  pyramids,  707 
Def.ccaiion,  2S0 

centre  for,  694 
Degeneration,  fatty,  414,  5S9 
traumatic,  589 
Deglutition,  272 

nerves  of,  273 
Deiter's  cells,  859 
Delomori)hous  cells,  285 
Demarcation  current,  604 
Demodex  foUiculorum,  494 
Denis's  plasmine,  74 
1  )intine,  268 
1  )entilion,  270 
Depressor  fibres,  660,  662,  725 

nerve,  167,  660 
Deutero-albumose,  293 
Development,  chronology  of,  929 
Dextrin,  431 
Dextrose,  431 
Diabetes  mellitus,  310 
Diabetic  coma,  31 1 
1  )ialysis,  343 
Diapedesis,  182 
Di.iphanometer,  394 
1  )iaphoretics,  496 
Diaphragm,  217 
1  )iarrhnea,  ^^^ 
Diastatic   action,  262,  299,  323, 

428 
Diastole,  98 
Dichroism,  59 
I  )icrotic  pulse,  148 
wave,  145 
Diet,  ade(]uate,  406 

effect  of  age  on,  407 
effect  of  work  on,  407 
flesh,  409 
flesh  and  fat,  41 1 
of  carbohydrates,  410 
quality  of,  403 
(luantity,  403 
Difference  theory,  613 
Differential  rheotom.  610 

tones,  868 
Diffusion,  342 

circles,  799 
of  gases,  80 
Digestion  durmg  fever,  332 

in  plants,  334 
Digestion,  250 

artificial,  295,  300 
Digestive  apparatus,  266 
Dilatation  of  pupil,  centre  for, 

693 
Dilator  pupiilx,  809 
Dilemma,  735 
Dioptric,  S07 

observations,  792 
Diphthongia,  573 


Diphthongs,  57 1 

I  )iplacusis,  863 

Diplopia,  63S,  S37 

Direct  vision,  S19 

Direction,  869 

Discharging  forces,  519 

Discus  proligerus,  902 

Disdiaciasts,  51 1 

Dissociation,  237 

Dissonance,  868 

Distance,  esiimalion  of,  843 

false  estimate  ol,  843 
smallest     appreciable, 
884 

Diuretics,  471 

I  )ivision  of  cells,  893 

1  )ouble  conduction  in  nerve,  623 

Double  contact,  feeling  of,  882 

Double  images,  neglect  of,  839 

Dreams,  736 

Drcpanidium,  48 

Dromograph,  177 

Dropsy,  359 

Duct  of  Cuvier,  936 

Ciaertner,  941 

Ductus  arteriosus,  928 
venosus,  928 

Dura  mater,  776 

Dust  particles,  244 

Dvs  albumose,  293 

Dyschromatopsy,  828 

Dyslysin,  313 

Dysperistalsis,  281 

Dyspnoea,  215,  241,  714 


Ear,  S47 

conduction  in,  887 

development  of,  945 

external,  849 

fatigue  of,  869 

fineness  of,  862 

labyrinth  of,  946 

meatus  of,  849 

ossicles  of,  851 

sj-)eculum,  849 

tympanum  of,  849 
Earthy  jjhosphates,  455 
Eccentric  hypertrophy,  loi 
Echo  speech,  737 
Ectoderm,  915 
Ectopia  cordis,  109 
Efferent  nerves,  631 
Effusions,  359 
Egg  albumm,  424,  459 

Egk's,  395 

Ejaculation,  centre  for,  694 
Elastic  after  effect,  139,  541 
elevations,  147 
tension,  173 
tubes,  134 
Elasticity  of  blood  vessel^,  138 
lens,  801 
lungs,  209 
muscle,  541 
Elastin,  426 


Electrical  charge  of  body,  629 
lishes,  629 
nerves,  623 
organs,  529 
Electrical    currents   of    muscle, 
603,  607 
eye,  6n 
glands,  611 
heart,  608 
mucous   membranes, 

611 
nerve,  603,  607 
plants,  615 
skin,  611 
Electricity,   therapeutical    uses, 

624 
Electrodes,  non-polarizable,  596 

other  forms,  625 
Electrolysis,  594 
Electrometer,  603 
Eleclro-motive  force,  591 
Electro  physiology,  591 
Electro-therapeutics,  624 
Electrotonus,  611,  612 

currents  in,  61 1 
in  conductors,  6l2 
in     inhibitory 

nerves,  617 
in    motor    nerves, 

611,  615 
in  muscle,  617 
in  sensory  nerves, 
617 
Eleidin,  4S7 

Elementary  granules  of  blood,  58 
Embryo,  formation  of,  921 
Emetics,  276 

Emmetropic  eye,  800,  804 
Emotions,  expression  of,  573 
Emulsitication,  301 
Emulsin,  359 
Emulsion,  301 
Emydin,  425 
Enamel,  269 
Enamel  organ,  270 
Enchylema,  894 
End  arteries,  192 
bulbs,  880 
organs,  63 1 
plate,  507 
Endocardial  pressure,  109 
Endocardium,  95 
Endoderm,  915 
Endolymph,  858 
Endomysium,  502  ' 
Endoneurium,  580 
Endc-mometer,  342 
Endosmosis,  342 
Endosmotic  equivalent,  343 
Enemata,  347 
Energy,  conservation  of,  38 

potential,  38 
Eneuresis  nocturna,  486 
Entoptical  phenomena,  8l2 

pulse,  813 
Entotical  perceptions,  869 


INDEX. 


961 


Enzym,  427 
Epiblast,  915 
Epicardium,  92 
Epidermal  appendages,  416 
Epididymis,  897 
Epidural  space,  777 
Epigenesis,  949 
Epiglottis,  273 

injury  to,  273 
Epilepsy,  731,  745 
Epineurium,  579 
Epiphysis  cerebri,  772 
Epithelium,  ciliated,  203,  500 
Eponychium,  490 
Equator,  612 

Equilibrium,  653,  697,  732 
Erectile  tissue,  909 
Erection,  centre  for,  909 

of  penis,  909 
Erect  vision,  799 
Errhines,  227 
Erythrochlorophy,  828 
Erythro-dextrin,  262 

-granulosa,  431 
Esbach's  method,  459 
Eserine,  810, 
Ether,  34 
Eudiometer,  81 
Eukalyn,  432 
Euperistalsis,  281 
Eupnoea,  714 
Eustachian  catheter,  856 

tube,  855 
Excitability,    action   of   poisons 

on,  696 
Excitable  points  of  a  nerve,  591 
Excito-motor  nerves,  633 
Excretin,  328 

Excretion  of  fsecal  matter,  278 
Exophthalmos,  833 
Expectorants,  247 
Experimentum  mirabile,  737 
Expiration,  213 
Expiratory  muscles,  217 
Explosives,  572 
Extensor  tetanus,  687 
External  capsule,  767 

genitals,  941,  942 
Extra  current,  599 
Extrapolar  region,  615 
Extremities,    development    of, 

923  . 
Exudation,  360 
Eye,  783 

accommodation  of,  799 

artificial,  778 

astigmatism,  807 

chromatic  aberration  of,  807 

compound,  843 

development  of,  944 

effect  of  electrical  ciurents, 

813 
emmetropic,  800 
entoptical  phenomena,  812 
epiphyseal,  846 
excised,  81 1 

61 


Eye,  fundus  of,  816 

hypenmetropic,  804 
illumination  of,  814 
movements  of,  833 
muscles  of,  833 
myopic,  804 
pineal,  846 
presbyopic,  805 
protective  organs  of,  843 
refractive  power  of,  803 
structure  of,  783 
Eyeballs,  axis  of,  833 

movements  of,  835 
muscles  of,  835 
planes  of,  833 
positions  of,  834 
protrusion  of,  833 
retraction  of,  833 
simultaneous     move- 
ments of,  830 
Eye  currents,  611 
Eyehds,  843 


Facial  nerve,  649 
Fsecal  matter,  328 

excretion  of,  278 
Fainting,  102 
Fallopian  tubes,  905 
Fall-rhetom,  614 
Falsetto  voice,  568 
Faradic  current,  599 
Faradization  in  paralysis,  627 
Far  point,  803 
Fascia,  lymphatics  of,  357 
Fatigue  of  muscle,  545 

stuffs,  545 
Fats,  429 

decomposition  of,  301 
metabolism  of,  410 
origin  of,  411 
Fat-splitting  ferment,  301 
Fatty  acids,  429 

degeneration,  414 
Febrifuges,  384 
Fechner's  lavv^,  782 
Fehling's  solution,  264,  463 
Fermentation,  401 

in  intestine,  324 
test,  265 
Ferments,  428 

fate  of,  324 
organized,  428 
unorganized,  427 
Fertilization  of  ovum,  912 
Fever,  383 

after  transfusion,  189 
Fibres  of  Tomes,  268 
Fibrillar  contraction,  525 
Fibrin,  58,  71 
Fibrin  factors,  75 
Fibrin-ferment,  76 
Fibrinogen,  75,  424 
Fibrinoplastin,  75 
Fibroin,  426 
Field,  of  vision,  799 


Field  of  vision,  contest  of,  841 
Filaria  sanguinis,  467    ■ 
Filiform  papillse,  874 
Filtration,  344 

First    respiration,    discharge   of, 
717 
effects  of,  on  thorax,  226 
Fish  extract,  397 
Fission,  893 
Fistula,  biliary,  316 
gastric,  291 
intestinal,  322 
pancreatic,  298 
pyloric,  289 
Thiry's,  322 
Vella's,  322 
Flame  spectra,  62 
Flavor,  873 

Fleischl's    law    of    contraction, 
618 
hsemometer,  61 
Flesh,  396 
Flight,  559 
Floor  space,  245 
Flourens'  doctrine,  732 
Fluid  vein,  184 
Fluids,  flow  of,  132 

introduction  of,  267 
Fluorescence,  824 

of  eye,  799 
Fluorescin,  792 
Focal  distance,  793 
line,  802 
point,  794 
Foetal  circulation,  927 
membranes,  925 
Follicles,  solitary,  339 
Fontana's  markings,  582 
Fontanelle,  pulse  m,  158 
Foods,  isodynamic,  363 
plastic,  403 
quantity,  403,  406 
respiratory,  403 
utilization  of,  399 
vegetable,  397 
Foramen  ovale,  928 

of  Magendie,  776 
Force  of  accommodation,  805 
Forced  movements,  770 
Forces,  35 
Fore-gut,  921 
Formatio  reticularis,  709 
Formative  cells,  918 
Fovea  cardica,  921 

centralis,  789,  819 
Fractional  heat  coagulation,  70 
Free  acid,  formation  of,  290 
Fremitus,  224 
Friction  sounds,  224 
Frog  current,  607 
Fromann's  lines,  579 
Fruits,  399 

Fundamental  note,  863 
Fundus  glands,  285 
Fungi,  324 
Fungiform  papillae,  874 


961^ 


INDEX. 


Gaertner,  ducts  of,  941 
tialactorrha^a,  392 
Galactose,  431 
Gallop,  55S 
Gall  stones,  332 
Galton's  whistle,  862 
Galvanic  battery,  594 

excital)iliiy,  628 
Galvano-cautery,  629 
Galvanometer,  594 

rellecting,  597 
Galvano-puncture,  629 

tonus,  5S6 
Gamgee's  method,  76 
Ganglionic  arteries,  740 
Gangrene,  632 
Gargling,  227 
Gaseous  exchanges,  232 
Gases,  al)Sorpti()n  of.  So 

diffusion  of,  80 

extraction  of,  81 

in  blood.  So 

indifferent,  244 

in  lymph,  239 

in  stomach,  297 

irrespirable,  244 

poisonous,  244 

respired,  232 
Gaskell's  clamp,  122 
Gas-pump,  81 

Gasserian  ganglion,  641,  642 
Gas  sphygmoscope,  144 
Gastric  digestion,  292 

conditions  affecting,  294 
fistula,  291 
pathological     variations, 

331 
Gastric  giddiness,  655 
Gastric  juice,  287 

action  of  drugs  on,  291 

action  on  tissues,  296 

actions  of,  292 

artificial,  291 
Gaule's  experiment,  48 
Gelatin,  296,  410,  426 
Gelatin  v.  albumin,  410 
Gemmation,  894 
Genital  cord,  941 

corpuscles,  880 

eminence,  941 
Genu  valgum,  553 
varum,  553 
Geometrical  color  table,  825 
Gerlach's  theory,  6S0 
Germ  epithelium,  901,  920 
Germinal  area,  915 

membrane,  915 
Germinating  cells,  350 
Germs,  244 

Gestation,  period  of,  930 
Giddiness,  654,  655 
Ginglymus,  548 
Girald^s,  organ  of,  941 
Girdle  sensation,  699 
Gizzard,  275 
Glance,  841 


Glands,  album  nous,  250 

15o\vman's,  871 

Brunner's,  321,  339 

buccal,  250 

carotid,   118,   137,   200, 
201 

ceruminous,  494 

changes  in,  253 

coccygeal,  137,  200 

Ebner's,  251 

fundus,  2S5 

llarderian,  846 

lachrymal,  844 

Licberkiihn's,  322,  339 

lingual,  250 

lymph,  351 

mammary,  390 

Meibomian,  843 

mixed,  253 

Moll's,  492 

mucous,  250 

Nuhn's,  251 

parotid,  258 

peptic,  285 

I'eyer's,  339 

pyloric,  2S6 

salivary,  250 

sebaceous,  492 

serous,  250 

solitary,  339 

sublingual,  258 

submaxillary,  253 

sweat,  492 

uterine,  906 

\Vel)cr's,  250 
Glaucoma,  644 
Gliadin,  426 
Glisson's  capsule,  304 
Globin,  425 
Globulins,  424 
(Jlobuloses,  293 
(domerulus,  435 
Glosso-pharyngeal  nerve,  655 
Glossoplegia,  665 
Glossy  skin,  632 
Glottis,  561,  562 
Glucose,  310,  431,  462 

tests  for,  264,  265,  462 
Glucosides,  428 
Glutamic  acid,  433 
Gluteal  reflex,  691 
Gluten.  426 
Glycerin,  429,  430 

method,  263 
Glycerin-phosphoric  acid,  430 
Glycin,  432 
Glycocholic  acid,  312 
Glycogen,  308,  431 
Glycoiic  acid,  430 
Glycosuria,  310,  462 
Gmelin-IIeintz'  reaction,  314 
Goblet  cells,  337 
Goitre,  198 
Goll's  column,  683 
Goltz's   balancing    experiments, 
733 


Goltz's     croaking      experiment, 
68S 
embrace  experiment,688 
oesophagus  experiments, 
274 
Gorham's  pupil  photometer,  8n 
Gout,  89 

Graafian  follicle,  901 
Gracilis  experiment,  624 
Grandry's  corpuscles,  880 
Granules,  elementary,  58 
Granulose,  262 
Grape-sugar,  431,  462 

absorption  of,  344 
estimation  of,  265 
injection  of,  309 
fn  urine,  462 
tests  for,  264 
volumetric     analy- 
sis, 463 
Gravitation,  35 
Great  auricular  nerve,  725 
Green  blindness,  828 
Green  vegetables,  399 
Growth,  420 
Guanidin,  532 
Guanin,  489,  502 
Guarana,  400 
Gubernaculum  testis,  941 
Gum,  431 

Gustatory  centre,  754,  763 
fibres,  650 
region,  874 
sensations,  876 
Gymnastics,  553 
Gymnotus,  629 
Gyri,  700 


Hay's  reaction,  313,462 

ILtmacylometer,  46 

IIa:madroniometer,  1 75 

Ha^madyiiamometer,  161 

Ha?matin,  66,  67 

Hcematoblasts,  57 

Hsematohidrosis,  498 

Hasmatoidin,  68 

Haematoma  aurium,  632 

Hrematoporphyrin,  67 

Hremaluria,  460 

Hremautography,  144 

Htcmin  and  its  tests,  67,  461 

Hsemochromogen,  66 

Ha?mocyanin,  79 

Ilivmocytolysis,  48 

IIa?mocytometer,  46 

Haemocytotrypsis,  48 

Hremodynamometer,  161 

Haemoglobin,  59 

amount  of,  6 1 
analysis,  59 
carbonic  oxide,  65 
compounds  of,  62 
crystals,  59 
decomposition  of, 
66 


INDEX. 


963 


Haemoglobin,  estimation  of,  60 
nitric  oxide,  66 
pathological,  61 
preparation,  59 
proteids  of,  68 
reduced,  63 
spectrum,  62 
Hsemoglobinometer,  60 
Hsemoglobinuria,  460 
Hsemometer,  61 
Haemophilia,  72 
Hemorrhage,  death  by,  89 
effect  on,  723 
Hemorrhagic  diathesis,  72 
Hasmotachometer,  176 
Haidinger's  brushes,  814 
Hair,  490 

cells,  859 
follicle,  490 
Halisterisis,  553 
Hallucinations,  782 
Hammarsten,  75 

on  blood,  75 
Harderian  gland,  846 
Hare-lip,  931 
Harmony,  868 
Harrison's  groove,  215 
Hassall's  corpuscles,  198 
Hawking,  227 
Hay's  test,  313 
Head- fold,  921 
Head-gut,  921 
Hearing,  847 
Heart,  92 

accelerated  action,  108  ■ 
action  of  fluids  on,  123 
action  of  gases,  127 
action  of  poisons  on,  124, 

127 
apex,  124 
apex  beat,  102 
arrangement  of  fibres,  92 
aspiration  of,  172 
auricular  systole,  98 
automatic  centres,  121 
automatic  regulation,  96 

97 
blood  vessels  of,  97 
changes  in  shape,  106 
chordae  tendineae,  lOO 
cutting  experiments,  109 
development  of,  921,  934 
diastole,  98 
duration   of  movements, 

116 
endocardium,  95 
examination  of,  117 
frog's,  118 
ganglia  of,  1 18 
hypertrophy  of,  loi 
impulse  of,  102 
innervation  of,  117 
movements  of,  98 
muscular  fibres,  94 
myocardium,  92 
nerves,  118 


Heart  nutritive  fluids,  120 
palpitation  of,  loi 
pause  of,  100,  107 
pericardium,  95 
Purkinje's  fibres,  96 
regulation  of,  96,  97 
section  of,  122 
sounds  of,  112 
staircase    beats    of,    122, 

126 
systole,  98 
valves  of,  95 
weight,  96 
work  of,  180 
Heat-,  37 

balance  of,  379 
calorimeter,  371 
centres,  377,  755 
conductivity,  373 
dyspnoea,  215,  715 
employment  of,  384 
estimation  of,  371 
excretion  of,  377 
income  and  expenditure, 

380 
in  inflamed  parts,  387 
in  muscle,  543 
latent,  362 
production,  364 
regulating  centre,  376 
relation  to  work,  381 
sources  of,  362 
specific,  371 
stiffening,  517 
storage  of,  382 
units,  37,  363 
variations    in   production, 
380 
Helicotrema,  857 
Heller's  test,  265,  458 
blood  test,  461 
Helmholtz's  modification,  599 
Hemeralopia,  637 
Hemialbumin,  293 
Hemialbumose,  292,  293 
Hemianaesthesia,  744 
Hemianopsia,  636 
Hemicrania,  728 
Hemiopia,  636 
Hemipeptone,  292 
Hemiplegia,  757 
Hemisystole,  112 
Henle's  loop,  435 

sheath,  580 
Hen's  egg,  903 _ 
Hensen's  experiments,  867 
Hepatic  cells,  305 

chemical      composition 

of,  307 
zones,  305 
Hepatogenic  icterus,  317 
Herbst's  corpuscles,  881 
Hermann's  theory  of  tissue  cm-- 

rents,  613 
Herpes,  632 
Hetero-albumose,  293 


Hetero-xanthin,  450 
Heterologous  stimuli,  781 
Hewson's  experiments,  74 
Hibernation,  386 
Hiccough,  227 
Hippocampus,  738 
Hippuric  acid,  451 
Hippus,  638 
Histo-hsematin,  200 
Historical — 

Absorption,  361 

Circulation,  202 

Digestion,  334 

Hearing,  870 

Heat,  387 

Kidney  and  urine,  486 

Metabolism,  433 

Nerves  and  electro-physiology, 
629 

Nerve  centres,  780 

Peripheral  nerves,  674 

Reproduction    and     develop- 
ment, 948 

Respiration,  249 

Sight,  845 

Skin,  499 

Smell,  873 

Taste,  877 

Voice  and  speech,  573 
Hoarseness,  573 
Holoblastic  ova,  903 
Homoiothermal  animals,  365 
Homologous  stimuli,  781 
Horopter,  838 
Hot  spots,  887 
Howship's  lacunae,  934 
Humor,  aqueous,  792 
Hunger  and  starvation,  408 
Hyaloid  canal,  791 
Hybrids,  912 
Hydatids,  896 
Hydrsemia,  89 
Hydramnion,  924 
Hydrobilirubin,  314 
Hydrocele,  75 
Hydrocephalus,  778 
Hydrochinon,  453 
Hydrochloric  acid,  288 
Hydrocyanic  acid,  66 
Hydrogen  in  body, 421 
Hydrolytic  ferments,  427 
Hydronephrosis,  485 
Hydrostatic  test,  209 
Hydroxylbenzol,  453 
Hyo-cholalic  acid,  313 
Hypakusis,  653 
Hypalgia,  891 
Hyperaesthesia,  696 
Hyperakusis,  653 
Hyperalgia,  653 
Hyperdicrotism,  149 
Hypergeusia,  877 
Hyperglobulie,  88 
Hyperidrosis,  498 
Hyperkinesia,  696 
Hypermetropia,  804 


964 


INDEX. 


Hyperoptic,  S04 
Hyperosniia,  634 
Hy|)eri>selaphe.sia,  8S9 
Hypertrophy  of  heart,  loi,  in 

of  muscle,  554 
Hypnotism,  736 
Hypoblast,  915 
Hypogeusia,  S77 
Hypoglossal  nerve,  664 
Hypophysis  cerebri.  200,  772 
I  lypopselaphesia,  8S9 
Hyposmii,  634 
Hypospadias,  941 
Hypoxanthin,  433 


ichthidin,  425 

Icterus,  318 

Identical  points,  837 

Ileo  colic  valve,  277 

Ileus,  278 

Illumination  of  eye,  814 

Illusion,  782 

Images,  formation  of,  79S 

Imbibition  currents,  615 

Impregnation,  913 

Impulse,  cardiac,  I02 

Impulses  in  brain,  course  of,  704 

Inanition,  233 

Incisures,  578 

Income,  406 

Indican,  452 

Indifferent  point,  615 

Indigo  blue,  453 

Indigo  carmine  test,  463 

Indigogen,  453 

Indirect  vision,  819 

Indol,  300,  327 

Induction,  599 

Inductorium,  601 

Inferior  maxillary  nerve,  645 

Inhibition,  nature  of,  690 

Inhibition  of  reflexes,  689 

Inhibitory  action  of  brain,  756 
nerves,  633 
for  heart,  718 
for  intestine,  282 
for  respiration,  716 

Inion,  764 

Initial  contiaction,  537 

Inosinic  acid,  433 

Inosit,  432 

Insectivorous  plants,  334 

Inspiration,  213 

centre  for,  713 
muscles  of,  216 
ordinary,  216 

Intelligence,  degree  of,  734 

Intercellular     blojd     channels, 

Intercentral  nerves,  633 
Intercostal  muscles,  218 
Interference,  868 
Interglobular  spaces,  268 
Interlobular  vein,  304 
Internal  capsule,  766 


Internal  reproductive  organs,  940 

respiration,  203,  23S 
Intestinal  fistula,  322 

gases,  324 

juice,  323 

actions  of,  323 

paresis,  282 
Intestine,  278 

artificial      circulation, 

283 
development  of,  938 
effect  of  drugs  on,  283 
fermentation  processes 

in.  324 
large,  328,  342 
movements  of,  278 
small,  336 
Intra-labyrinthine  pressure,  860 
Intralobular  vein,  304 
Intraocular  pressure,  644,  792, 

811 
Intrathoracic  pressure,  225 
Intra-vascular  hemorrhage,  727 
Inulin,  432 
Inunction,  498 
Invertin,  326 
Invert  sugar,  326 
Inverted  miage,  798 
.Ions,  594 
Iris,  786 

action  of  poisons  on,  810 

blood  vessels  of,  787 

functions  of,  808 

movements  of,  809 

muscles  of,  S09 

nerves  of,  809 
Irradiation,  830 

of  pain,  698,  890 
Ischuria,  486 
Island  of  Reil,  741 
Isodynamic  foods,  363 
Isolated  beats,  868 
Isometrical  act,  537 
Isotropous,  511 


I  Jacksonian  epilepsy,  746,  759 

Jacobson's  organ,  872 

Jaeger's  types,  805 

Jaundice,  317 

Jaw  jerk,  693 
j  Joints,  54S 
I  arthrodial,  549 

ball  and  socket,  549 
ginglymus,  548 
'  mechanism  of,  547 

I  rigid,  549 

,  screw  hinge,  548 

]  Juice  canals,  348 


Karyokinesis,  894 

Karyomiton,  893 
Karyopla>ma,  893 
Katabolic  metabolism,  388 
nerves,  633 


Katalepsy,  737 
Kations,  594 
Keratin,  426 
Keratitis,  652 
Keys — 

Capillary  contact,  603 
Friction,  602 
Plug,  602 
Kidney,  434 

blood  of,  475 
chemistry  of,  475 
condit  ions  affecting,  476 
reabsorption  in,  473 
structure  of,  434 
volume  of,  477 
Kinxsodic  substance,  695 
Kinetic  energy,  362 
theory,  654 
Klang,  864 

Knee  phenomenon,  693 
jerk,  693 
reflex,  693 
Koenig's  monometric  flames,  866 
Koumiss,  395 
Krause's  end  bulbs,  880 
Kreatin,  433 
Kreatinin,  433,  449 

properties,  449 
quantity,  449 
test,  449 
Kresol,433 

Kryptophanic  acid,  454 
Kiihne's  ariiticia!  eye,  798 

experiments,  606,  625 
pancreas  powder,  301 
Kymograph,  162 

Kick's,  165 
Hcring's,  164 
Ludwig's,  l6z 
Kyphosis,  553 


Labials,  572 

Labor,  power  of,  946 

Labyrinth,  856 

Lachrymal  apparatus,  844 

Lacteals,  336,  348 

Lactic  acid,  288,  393,  430 
ferment,  296 

Lactometer,  394 

Lactoprotein,  393 

Lactoscope,  394 

Lactose,  431 

Lcevulose,  326,  431 

Lagophthalmus,  638 

Lambert's  meihod,  824 

Lamince  dorsalcs,  918 

Lamina  spiralis,  857 

Language,  761 

Lanoline,  494 

Lanutjo,  491 
i  Lapping,  267 
!  Lardacein,  425 
;  Large  intestine,  328,  342 
'  absorption 

I  -,28 


INDEX. 


965 


Laryngoscope,  566 

Larynx,  cartilages  of,  560 

during  respiration,  567 
experiments  on,  568 
illumination  of,  565 
mucous    membrane   of, 

564 
muscles  of,  561 
view  of,  566 
vocal  cords,  560 

Latent  heat,  362 

period,  528 

Lateral  plates,  920 

Laughing,  227 

Law  of  conservation  of  energy, 

contraction,  618 
isolated  conduction,  623 
peripheral     perception, 

881 
specific  energy,  781 
Leaping,  557 
Lecithin,  69,  429,  518 
Legumin,  398 
Lens,  chemistry  of,  790 
crystalline,  790 
development  of,  945 
Lenticular  nucleus,  766 
Leptothrix  epidermalis,  498 

buccalis,  261 
Leucic  acid,  430 
Leucin,  300 
Leucocytes,  54 
LeuCQderma,  632 
Leucomaines,  294 
Leuksemia,  59 
Levers,  551 
Lichenin,  432 
Lichen's  test,  454 
Lieberkiihn's  glands,  321 

jelly  ,425 
Liebermann's  reaction,  424 
Liebig's  extract,  397 
Life,  38 

Limbic  lobe,  754 
Limb  plexus,  669 
Liminal  intensity,  781 
Line  of  accommodation,  803 
Ling's  system,  553 
Lingual  nerve,  646 
Lipsemia,  88 
Liquor  sanguinis,  70 
Listing's  reduced  eye,  797 

law,  834 
Liver,  303 

action  of  drugs  on  cells, 

306 
chemical        composition, 

307  _ 
cirrhosis  of,  307 
development  of,  939 
fat  in,  309 
functions  of,  311 
glycogen  in,  308 
influence  on  metabolism, 

316 


Liver,  pathology  of,  307 
pulse  in,  186 
regeneration  of,  307 
structure  of,  303 
Lobes  of  brain,  740 
Locality,  sense  of,  882 

illusions  of,  884 
Lochia,  947 
Locomotor  ataxia,  697 
Lordosis,  553 
Loss  by  skin,  238 
Loss  of  weight,  409 
Lowe's  ring,  814 
Lungs,  203 

chemical  composition  of, 

209 
development  of,  939 
elastic   tension    of,    129, 

173,  210 
examination  of,  220 
excision  of,  209 
limits  of,  221 
physical  properties,  209 
structure  of,  205 
tonvis,  208 
Lunule,  489 
Lutein,  909 

Luxus  consumption,  403 
Lymph,  353 

movement  of,  356 
gases  of,  239,  354 
Lymphatics,  348 

of  eye,  791 
origin  of,  348 
Lymph  corpuscles,  352 

origin  and  decay  of,  355) 

356 
follicles,  351 
glands,  351 
hearts,  358 


Macropia,  638 

Macula  lutea,  789 

Maculae  acusticse,  859 

Madder,  feeding  with,  418 

Magnetization,  599 

Magneto-induction,  600 

Major  chord,  861 

Malapterurus,  629 

Malt,  401 

Maltose,  262,  431 

Mammary  glands,  390 

changes  in,  390 
development  of,  391 
structure  of,  390 

Manometer,  161 

frog,  123 
maximum,  lOO 
minimum,  lOO 

Manometric  flames,  866 

Marey's  tambour,  109 

Margarin,  489 

Marginal  convolutions,  74I 

Mariotte's  experiment,  818 

Massage,  553 


Mastication,  267 
Mastication,  muscles  of,  267 

nerves  of,  267 
Mat6,  400 
Matter,  34 

Maturation  of  ovum,  913 
Meat  soup,  397 
Meckel's  caitilage,  931 
ganglion,  645 
Meconium,  320 
Medulla  oblongata,  705 
Functions  of,  710 
Gray  matter  of,  708 
Reflex  centres  in,  710 
Structure  of,  705 
Medullary  groove,  916 

tube,  918 
Meibomian  glands,  843 
Meiocardia,  128 
Meissner's  plexus,  275,  281,  342 
Melansemia,  59 
Melanin,  429 
Melitose,  431 
Mellitsemia,  88 
Mellituria,  88 

Membrana  decidua  menstrualis, 
925 
flaccida,  849 
reticularis,  860 
reuniens,  922 
secundaria,  856 
tectoria,  859 
tympani,  849 
Membranes  of  brain,  776 
Meniere's  disease,  655 
Menopause,  906 
Menstruation,  907 
Mercurial  balance,  885 
Merkel's  cells,  880 
Meroblastic  ova,  903 
Mesentery,  development  of,  939 
Mesoblast,  916 
Mesonephros,  941 
Metabolic  equilibrium,  402 
phenomena,  388 
Metabolism,  388 

in  anaemia,  89 
on  flesh  and  other 
diets,  409 
Metakresol,  453 
Metalbumin,  424 
Metallic  tinkhng,  224 
Metalloscopy,  891 
Metamorphosis,  895 
Metanephros,  941 
Meteorism,  282 
Methsemoglobin,  64 
Methylamine,  432 
Meynert's  projection  systems,  700 

theory,  734 
Micrococci,  457 
Micrococcus  ure^e,  457 
Microcytes,  58 
Micropyle,  902 
Microscope,  iSo 
Microorganisms,  330 


9G6 


INDEX. 


Micro-spectroscope,  62 
Micturition,  4S3 

centre  for,  694 
Migration  of  ovum,  912 
Milk,  392 

action  of  dru<js  on,  392 
coagvilation  of,  393 
colostrum,  390 
comjK>siiion  of,  39I 
curdling  ferment,  288,  393 
digestion  of,  295 
fever,  392.  947 
globules  of,  392 
peptonized,  303 
plasma,  392 
preparations  of,  395 
substitutes  for,  394 
sugar,  393 
tests  for,  394 
Millon's  reagent,  423 
Mimetic  spasm,  652 
Mimicry,  574 
Minor  chord,  861 
Mitosis,  S94 
Mixed  colors,  S25 
Modiolus,  S57 

Molecular  basis  of  chyle,  353 
Molecules,  34 
Molisch's  test,  265 
Monoplegia,  759 
Monospasm,  760 
Moore's  test,  265 
Moreau's  experiment,  323 
Mormyrus,  629 
Morphology,  33 
Morula,  914 
Motion,  illusions  of,  S30 
Motor  areas,  756 
Motor  centres,  dog,  742,  744 
excision  of,  749 
in  man,  749 
in  monkey,  746 
nerves,  631 
paths,  703 

points  on  the  surface,  624, 
625 
Mouth,  250 

glands  of,  250 
Mouvements  de  manege,  771 
Movements  of  the  eye,  833 
acquired,  750 
forced,  770 
incoordinated,  668 
Mucedin,  426 
Mucigen,  337 
Mucin,  312,  426 
Mucous  membrane  currents,  611 

tissue,  791 
Mucus,  effect  of  dnigs  on,  247 
formation  of,  245,  312 
Mulberrj-  mass,  914 
Mulder's  test,  265 
Miiller's  ducts,  940 

experiment,  129,  154 
fibres,  7S9 
valve,  22S 


Multiplicator,  593 
Murexide  test,  449 
Murmurs,  cardiac,  115 
venous,  185 
Muscx  volitantes,  812 
Muscarin,  720 
Muscle,  502  ' 

action  of  two  stimuli  on, 

533 
action  of  veratrin,  532 
active  changes  in,  524 
arrangement  of,  549 
atrophic  proliferation  of, 

554 

blood  vessels  of,  506 

cardiac,  92,  509 

changes  during  contrac- 
tion, 524 

chemical      composition, 

5" 
current,  597 
ciu-ve  of,  528 
degenerations  of,  554 
development  of,  509 
effect  of  acids  on,  518 
effect  of  cold  on,  518 
effect  of  distilled  water 

on, 518 
effect  of    exercise     on, 

553 
effect  of  heat  on,  5 1 7 
elasticity  of,  541 
electric  currents  of,  604 
excitability  of,  519 
extractives  of,  514 
fatigue  of,  545 
ferments,  512 
fibrillar,  504 
formation  of  heat  in,  543 
gases  in,  513 
glycogen  in,  512,  514 
hypertrophy,  554 
involuntary,  502 
lymphatics  of,  507 
metabolism  of,  513 
myosin  of,  572 
nerves  of,  507 
nutrition  of,  553 
of  heart,  92,  509 
perimysium  of,  502 
physical  characters,  511 
plasma  of,  511 
plate,  922 

polarized  light  on,  5 1 1 
reaction,  511 
recovery  of,  547 
red  and  pale,  509 
relation  to  tendons,  506 
rhvthmical    contraction, 

'523 
rigor  mortis  of,  515 
rods,  505 

sensibility,  508,  543 
serum  of,  512 
smooth,  502,  509 
sound  of,  545 


Muscle,  spectrum  of,  509 
staircase  of,  535 
stimuli  of,  522 
structure  of  striped,  502 
tetanus,  534 
tonus,  543,  694 
uses  of,  549 
volume  of,  524 
voluntary,  502 
work  of,  538 
Muscle  current,  603 

theories,  613 
Muscular  contraction   (see  Myo- 

S^ram),  rate  of,  537 
Muscular  energy,  515 
exercise,  233 
sense,  89 1 
work,  514 

laws  of,  538 
Mutes,  572 
Mydriasis,  638 
Mydriatics,  810 
Myelin  forms,  577 
Myocardium,  92 
Myogram,  528 

effect  of  constant  cur- 
rent on, 532 
effect   of  fatigue    on, 

531 
effect   of  poisons  on, 

532 
effect  of  veratrin  on, 

532 
effect   of  weights  on, 

53' 
method  of   studying, 

526 
stages  of,  529 
Myograph,  Helmholtz's,  526 
pendulum,  526 
Pfliiger's,  528 
simple,  528 
spring,  528 
Myohoematin,  429,  509 
Myopia,  804 

Myoryctes  Weismanni,  5 1 1 
Myosin,  424,  512 

ferment,  512 
Myosis,  639 
Myotics,  811 
Myxoedema,  199,  632 


Nails,  4S9 

Narcotics,  890 

Nasal  breathing,  226 
timbre,  571 

Nasm>1;h's  membrane,  268 

Native  albumins,  424 

Natural  selection,  947 

Near  point,  803 

Neefs  hammer,  601 

Negative  accommodation,  800 
after  images,  83O 
pressure,  344 
variation,  607,  609 


INDEX. 


967 


Nephrozymose,  454  I 

Nerve  cells,  575,  5S0  | 

bipolar,  580  j 

multipolar,  580,  679 
of  cerebrum,  737 
Purkinje's,  773 
with  a  spiral  fibre,  581 
Nerve  centres,  general  functions, 

675 
Nerve  current,  603 
Nerve  fibres,  575 

action  of  nitrate  of  silver 

on,  579  .  . 

chemical    properties    of, 

581 
classification  of,  631 
death  of,  591 
degeneration  of,  587 
development  of,  580 
division  of,  579 
effect  of  a  constant  cur- 
rent on,  585 
electrical  current  of,  603 
electrical  stimuli,  585 
excitability  of,  583 
fatigue  of,  587 
incisures  of,  578 
mechanical  properties  of. 
582 

meduUated,  575 

metabolism  of,  582 

nutrition  of,  588 

Ranvier's  nodes,  578 

reaction  of,  582 

recovery  of,  587 

regeneration  of,  587,  589 

sheaths  of,  579 

stimuli  of,  583 

structure  of,  575 

suture  of,  590 

terminations  of,  878 

to  glands,  256 

traumatic      degeneration 

of,  589 
trophic  centres  of,  589 
unequal    excitability    of, 

586 
union  of,  590 
unipolar   stimulation    of, 

587 
Nerve  impulse,  rate  of,  620 

method     of    measuring, 

621 
modifying   conditions  of, 
620 
Nerve  motion,  623 
Nerve-muscle  preparation,  606 
Nerves,  631 

afferent,  633 
anabolic,  633 
centrifugal,  631 
centripetal,  633 
cranial,  634 
electrical,  623 
intercenlral,  633 
katabolic,  633 


Nerves,  motor,  63 1  | 

secretory,  631 
sensory,  633  | 

special  sense,  633 
spinal,  665  ■     j 

trophic,  631  ! 

union  of,  590 
vaso-dilator,  729 
vasomotor,  722  I 

visceral,  633 
Nerve  stretching,  583 
Nervi  nervorum,  580 
Nervous  system,  575 

development,  943 
Nervus  abducens,  649 
accelerans,  720 
accessorius,  664 
acusticus,  653 
depressor,  660 
erigens,  693,  729,  910 
facialis,  649 
glossopharyngeus,  655 
hypoglossus,  664 
oculomotorius,  637 
olfactorius,  634 
opticus,  634 
sympathicus,  670 
trigeminus,  640 
trochlearis,  639 
vagus,  657 
Neubauer  s  test,  265 
Neuralgia,  648 
Neurogha,  681,  682 
Neural  tube,  918 
Neurasthenia  gastrica,  331 
Neurin,  581 
Neuro-epithelium,  ^88 
Neuro-keratin,  578 
Neuro-muscular  cells,  522 
New-born  child,    digestion    of 
291 
pulse,  149 
size,  419 
temperature,  374 
urine  of,  440 
weight,  419 
Nictitating  membrane,  846 
Nitrites,  64 

on  pulse,  147 
I  Nitrogen  in  air,  230 
i  in  blood,  85 

in  body,  421 
given  off,  402 
Noeud  vital,  712 
Noises,  860 
Nose,  development  of,  931 

structure,  871 
Notochord,  919 
Nuclear  spindle,  861 
Nuclein,  426 
Nucleus  of  Pander,  904 
Number  forms,  870 
Nussbaum's  experiments,  472 
Nutrient  enemata,  347 
Nyctalopia,  6^7 
Nystagmus.,  654,  771 


Oatmeal,  398 
Octave,  861 
Oculomotorius,  637 
Odontoblasts,  268 
CEdema,  359 

cachectic,  360 
pulmonary,  226 
CT^sophagus,  274,  275 
Ohm's  law,  592 
Oleic  acid,  429 
OligJemia,  89 
Olivary  body,  707 
Olfactory  centre,  754,  763 
nerve.  634 
sensations,  872 
Omphalo-mesenteric  duct,  921 

vessels, 922 
Onamatopoesy,  574 
Oncograph,  195,  477 
Oncometer,  477 
Ontogeny,  948 
Opening  shock,  599 
Ophthalmia     neuro  -  paralytica, 
644 
intermittens,  644 
sympathetic,  644 
Ophthalmic  nerve,  641 
Ophthalmometer,  798 
Ophthalmoscope,  814 
Optic  nerve,  634,  813 
I  radiation,  635 

1  thalamus,  766 

tract,  634 
vesicle,  919 
Optical  cardinal  points,  795 
I  Optogram,  823 
1  Optometer,  805 
'  Ordmates,  164 
:  Organic  albumin,  403 
I  compounds,  423 

:  reflexes,  693 

j  Ortho-kresol,  453 
I  Orthopnoea,  215 
Orthoscope,  817 
Osmasome,  397 
Ossein,  427 
Osseous    system,    formation    of, 

930 
Osteoblasts,  934 
Osteoclasts.  934 
Osteomalacia,  553 
Otic  ganglion,  646 
Ovarian  tubes,  902 
Ovary,  901 
Overcrowding,  245 
Ovulation,  907 
i  theories  of,  90S 

]  Ovum,  901 

;  development  of,  902 

discharge  of,  908 
fertilization  of,  912 
impregnation  of,  913 
maturation  of,  913 
migration  of,  912 
structure  of,  901 
Oxalic  acid,  430,  450 


968 


INDEX. 


Oxalic  acid  series,  430  I 

Oxaluria,  430 

Oxaliiricacid,  429 

Oxy-acids,  454  | 

Oxyakoia,  652  j 

Oxygen  in  blood,  83  j 

estimation  of,  S3,  228 

forms  of,  85 

ill  body,  421 
Oxyhemoglobin,  62 
Ozone  in  blood,  84 


Pacchionian  bodies,  777 
Pacini's  corpuscles,  879 
Pain,  889 

irradiation  of,  890 
points,  882 
Painful  impressions,  conduction 

of,  697 
Palmitic  acid,  429 
Palpitation,  loi 
Pancreas,  297 

changes  in,  298 

development  of,  939 

fistula  of,  298 

juice  of,  299 

paralytic       secretion, 

303 
powder,  301 
salt,  302 
Pancreatic  secretion,  298 
actions  of,  299 
artificial  juice,  300 
action  of  nerves   on, 

302 
action  of  poisons  on, 

303 

com|)osition,  298,  299 

extracts,  302 
Panophtlialmia,  643 
Pansphygmograph,  102 
Papain,  301 
Papilla  foliata,  875 
Papilla;  of  tongue,  S74 
Parablastic  cells,  920 
Paradoxical  contraction,  612 
Paraglobulin,  78 
Parakresol,  433,  453 
Paralbumin,  423 
Paralgia,  890 
Paralytic  secretion  of  saliva,  258 

pancreatic  juice,  303 
Paramylum,  432 
Para  pe[)tone,  292 
Paraphasia,  761 
Paraxanthin,  433,  450 
Parelectronc.my,  613 
Paridrosis,  498 
Paroophoron,  941 
Parotid  gland  252,  258 
Parovarium,  941 
Parthenogenesis,  896 
Partial  pressure.  Si 
reflexes,  686 
Particles,  34 


Parturition,  centre  for,  694 

Passive  insufficiency,  552 

Patellar  reflex,  692 

Pavy's  test,  264 

Pecten,  846 

Pectoral  fremitus,  224 

IV'dunculi  cerebri,  768 

Tenis,  erection  of,  909 

Pepsin,  2S8 

Pepsinogen,  289 

Peptic  glands,  285 

changes  in,  289 

Peptogenic  substances,  291 

Peptone,  292,  294 

absorption  of,  345 
forming  ferment,  288 
injection  of,  73,  345 
metabolism  of,  410 
tests  for,  294 

Peptonized  foods,  303 

Peptonuria,  459 

Percussion  of  heart,  117 
lungs,  222 
sounds,  222 
wave,  145 

Perforating  ulcer  of  the  foot,  632 

Pericardium,  95 

fluid  of,  354 

Perilymph,  858 

Perimeter,  Aubert  and  Forster, 
S19 
M' Hardy's,  820 
Priestley  Smith's,  822 

Perimetric  chart,  820 

Perimetry,  S19 

Perimysium,  92,  502 

Perineurium,  5S0 

Periodontal  membrane,  268 

Peristaltic  movement  277 

action  of  blood  on,  281 
action    of   nerves  on, 
283 

Peritoneum,  development  of,  939 

Perivascular  spaces,  738 

Pernicious  an;omia,  58 

Pettenkofer's  test,  313 

apparatus,  229 

Peyer's  glands,  339 

Pfliiger's  law,  617 

law  of  reflexes,  688 

Phagocytes,  56 

Phakoscope,  S02 

Phanakistoscope,  830 

Phases,  displacement  of,  864 

Phenol,  327,  453 

Phenylsulphonic  acid,  453 

Phlebogram,  185 

Phloro-glucin-vanilin,  288 

Phonation,  564 

Phonograph,  866 

Phonometry,  223 

Phosphenes,  813 

Phosphoric  acid,  455 

Photohitmatachomeier,  1 77 

Photophobia.  653 

Photopsia,  637 


Phrenograph,  212 
Phrenology,  732 
Phylogeny,  948 
Physostigmin,  810 
Phytalbumose,  425 
Phytomycetes,  466 
Pia  mater,  676 
Picric  acid  test,  459 
Picro-saccharimeter,  463 
Pigment  cells,  501 
Pineal  eye,  772 

gland,  772 
Pitch,  861 
Pituitary  body,  772 
Placenta,  926 
Placental  bruit,  184 
Plantar  reflex,  691 
Plants,  characters  of,  39 

digestion  by,  334 

electrical  currents  in,  615 
Plasma  cells,  776 

of  blood,  70,  78 

of  invertebrates,  79 

of  lymph,  353 

of  milk,  392 

of  muscle,  511 
Plasmine,  74 
Plethora,  88 
Plethysmography,  187 
Pleura,  206 

Pleuro- peritoneal  cavity,  920 
Pleximeter,  221 
Pneumatic  cabinet,  155 
Pneumatogram,  214 
Pneumatometer,  226 
Pneumograph,  128,  213 
Pneumonia  after  section  of  vagi 

661 
Pneumothorax,  210 
Poikilothermal  animals,  365 
Poiseuille's  space,  181 
Poisons,  heart,   127 
Polar  globules,  913 
Polarization,  galvanic,  594 
internal,  598 
Polarizing  after-currents,  612 
Politzer's  ear  bag,  856 
Polyxmia,  87 

apocoptica,  87 
aquosa,  87 
hyperalbuminosa,  88 
polycytha;mica,  88 
serosa,  87 
Polyopia  monocularis,  808 
Pons  Varolii,  769 
Porret's  phenomenon,  598 
Portal  canals,  304 

circulation,  91 

system,  development  of, 

937 
vein  in  liver,  304 
Positive  accoinmodation,  800 

after-images,  829 
Potash  salts,  421 
Potassium   sulphocyanide,    260, 
I      454 


INDEX. 


969 


Potatoes,  398 

Presbyopia,  805 

Pressor  fibres,  724 

Pressure,  arterial,  165 

atmospheric,  247 
intra-labyrinlhine,   860 
of  blood,  161 
phosphenes,  813 
points,  882,  885 
respiratory,  225 
sense  of,  885 

Presystolic  sound,  115 

Prickle  cells,  487 

Primitive  anus,  923 
aorta,  921 
chorion,  915,  925 
circulation,  921 
groove,  915 
kidneys,  940 
mouth,  923 
streak,  915 

Primordial  cranium,  930 
ova,  902 

Principal  focus,  793 

Proctodseum,  918 

Proglottis,  895 

Progressive   muscular   atrophy, 

554 

Pronephros,  941 

Pronucleus,  male,  913 
female,  913 

Propepsin,  289 

Propeptone,  292 

Protagon,  428 

Proteids,  423 

coagulated,  425 
gastric  digestion  of,  292 
fermentation  of,  327 
metabolism  of,  409 
pancreatic  digestion  of, 

300 
reactions  of,  423 
vegetable,  425 

Proteolytic  ferments,  427 

Proteoses,  292 

Protistse,  33,  41 

Proto-albumose,  293 

Protovertebr^^,  919 

Pseudo-hypertropic     paralysis, 

554 
Pseudo-motor  action,  650,  653 
Pseudoscope,  841 
Pseudo-stomata,  206 
Psychical  activities,  731 

blindness,  752 

deafness,  753 

processes,  time  of,  735 
Psycho-physical  law,  781 
Ptomaines,  294 
Ptosis,  638 
Ptyalin,  263,  264 
Ptyalism,  259 
Puberty,  906 
Pulmonary  artery,    pressure   in, 

173 

vessels,  206 


Pulmonary  oedema,  226 
Pulp  of  tooth,  269 

of  spleen,  192 
Pulse,  139 

anacrotic,  153 

capillary,  161 

catacrotic,  145 

characters  of,  144 

conditions  affecting,  149 

curve,  144 

dicrotic,  148 

entoptical,  157 

hyperdicrotic,  149 

in  animals,  150 

in  jugular  vein,  186 

in  liver,  186 

influence  of  pressure  on, 

.    ^55 

influence    of   respiration 
on, 153 

instruments  for  investiga- 
ting, 140 

monocrotic,  148 

of  various  arteries,  151 

paradoxical,  155 

pathological,  158 

rate,  149,  170 

recurrent,  152 

tracing,  144 

trigeminal,  150 

variations  in,  150 

venous,  185 

wave,  156 
Pulses,  398 
Pulsus  alternans,  150 

bigeminus,  150 

caprizans,  149 

dicrotus,  149 

intercurrens,  150 

myurus,  150 
Pumping  mefhanisms,  357 
Pupil,  802 

action  of  poisons  on,  810 

Argyll  Robertson,  810 

functions  of,  808 

movements  of,  809 

photometer,  8ll 

size  of,  811 
Pupilometer,  8n 
Purgatives,  283 
Purkinje,  cells  of,  773 

fibres  of,  96,  509 
figure,  812 
Sanson's  images,  801 
Pus  corpuscles,  182 
Putrefaction,  pancreatic,  300 
Putrefactive  processes,  328 
Pyloric  glands,  286 

changes  in,  289,  290 

fistula,  289 
Pyramidal  cells,  739 
tracts,  684 

degeneration 
of,  758 
Pyrokatechin,  430,  453 
Pyuria,  465 


Quality  of  a  note,  861,  863 
Quantity  of  blood,  86 
of  food,  405 
of  gases,  232 


Rales,  dry,  224 

moist,  224 
Rami  communicantes,  670 
Range  of  accommodation,  806 
Ranvier's  nodes,  578 
Raynaud's  disease,  632 
Reaction  impulse,  105 
Reaction  of  degeneration,  627 
Reaction  time,  624,  735 
Recoil  wave,  145 
Rectum,  283 
Recurrent  pulse,  152 

sensibility,  667 
Red  blindness,  828 
Reduced  eye  of  Listing,  797 
Reducing  agents,  84 
Reductions  in  intestine,  328 
Reflex  acts,  examples  of,  687 

inhibition  of,  689 

law  of,  688 

movements,  686 
Reflex  movements,  theory  of,  691 

nerves,  633 

organic,  693 

spasms,  686 

tactile,  697 

time,  689 

tonus,  695 
Reflexes,  crossed,  688 
deep,  692 
spinal,  686 
organic,  694 
Refracted  ray,  794 
Refractive  indices,  794 
Regeneration  of  tissues,  416 
of  nerve,  589 
Regio  olfactoria,  871 

respiratoria,  871 
Regnault's  apparatus,  228 
Reissner's  membrane,  857 
Relative  proportions  of  diet,  405 
Remak's  ganglion,  1 19 
Renal  plexus,  476 
Rennet,  295,  393 
Reproduction,  forms  of,  893 
Requisites  in  a  proper  diet,  405 
Reserve  air,  210 
Residual  air,  210 
Resistance,  132 
Resonance  organs,  560 
Resonants,  572 
Resonators,  S67 
Resorcin,  453 
Respiration,  203 

amphoric,  224 
artificial,  243 
Biot's,  216 
bronchial,  224 
centre  for,  712 
chemistry  of,  227 


970 


INDEX. 


Respiration,  cog-wheel,  224 
cutaneous,  238 
first,  717 
forced,  216 
foreign  gases,  244 
in  a  closed  space, 

240 
in  animals,  212 
internal,  238 
mechanism  of,  209 
muscles  of,  216 
nasal,  226 
number  of,  211 
pathological,  215 
periodic,  216 
pressure  during,  225 
pressure    on    heart, 

128 
sounds  of,  223 
time  of,  212 
type,  214 
variations  of,  21 1 
vesicular,  223 
Respiratory  apparatus,  203 

Andral  and  Gavar- 

ret,  228 
centre,  712 
mechanism  of,  209 
v.  Pettenkofer,  229 
quotient,  231 
Regnault  and  Rei- 

set,  229 
Scharling,  229 
undulations,  167 
Restiform  bodies,  705 
Rete  mirabile,  91 
Retina,  787 

activity  in  vision,  818 
blood  vessels  of,  789 
capillaries,  movements 

in,  813 
chemistry  of,  790 
epithelium  of,  789 
rods  and  cones  of,  788, 

819 
stimulation  of,  829 
structure  of,  787 
visual  purple  of,  789 
Retinal  image,  formation  of,  798 

size  of,  798 
Retinoscopy,  817 
Reversion,  948 
Rheocord,  592 
Rheometer,  176 
Rheophores,  625 
Rheoscopic  limb,  6g6 
Rheostat,  593 
Rheotom,  610 
Rhinoscopy,  568 
Rhodophane,  790 
Rhodopsin,  789 
Ribs,  218 
Ricket's,  553 
Rigor  mortis,  515 
Ritter's  opening  tetanus,  618 
tetanus,  618 


Ritter-Valli  law,  591 
Rods  and  cones,  7SS,  S19 
Rods  of  Corti,  859 
Rosenthal's  modification,  521 
Rotatory  disk  for  colors,  824 
Rudimentary  organs,  948 
Rumination,  ^33 
Running,  555 


Saccharomycetes,  401 

Saccharose,  431 

Saccule,  857 

Saftcanalchen,  348 

Saline  cathartics,  284 

Saliva,  action  of  nerves  on,  256 
action  of  poisons  on,  257 
action  on  starch,  262 
chorda,  256 
composition  of,  261 
facial,  256 
functions  of,  263 
mixed,  261 
new-born  child,  262 
paralytic  secretion,  258 
parotid,  260 
pathological,  331 
ptyalin,  260,  263 
reflex  secretion  of,  258 
sublingual,  261 
submaxillary,  260 
sympathetic,  256 
theory  of  secretion,  260 

Salivary  corpuscles,  261 

Salivary  glands,  252 

changes  in,  253 
development  of, 

939 

extirpation     of, 
258 

nerves  of,  255 
Salts,  421 

Sanson-Purkinje's  images,  801 
Saponification,  301 
Sarcina  ventriculi,  332 
Sarcoglia,  508 
Sarcolactic  acid,  512 
Sarcolemma,  503 
Sarcolytes,  509 
Sarcoplasts,  509 
Sarcous  elements,  504 
Sarkin,  450 
Sarkosin,  433 
Saviotli's  canals,  298 
Scheiner's  experiment,  803 
Schiff 's  test,  449 
Schizomycetes,  90,  324 
Schmidt's  researches,  74 
Schreger's  lines,  268 
Schwann's  sheath,  578 
Sclerotic,  785 
Scoliosis,  553 
Scotoma,  822 
Screw-hinge  joint,  548 
Scrotum,  formation  of,  941 
1  Scurvy,  58 


Scyllit,  432 
Sebaceous  glands,  492 

secretion,  493 
Seborrhcea,  498 
Secondary  circulation,  922 
contraction,  609 
decompositions,  595 
degeneration,  683 
tetanus,  609 
Secretion  currents,  611 
Secretory  nerves,  631 
Sectional  area,  178 
Segmentation  sphere,  914 
Self-stimulation  of  muscle,  606 
Semen,  composition  of,  898 
ejaculation  of,  911 
reception  of,  911 
Semicircular  canals,  654,  859 
Sensation,  781 
Sense  organs,  781 

development  of,  944 
Sensory  areas,  751 

crossway,  705>  7^^ 
paths,  704 
sensations,  881 
Serin,  433 
Serous  cavities,  350 
Serum  of  blood,  71 
Serum  albumin,  78,  424 
Serum  globulin,  78,  424 
Setschenow's  centres,  690 
Sex,  difference  of,  942 
Shadows,  lens,  812 

colored,  832 
Sharpey's  fibres,  934 
Short-sightedness,  804 
Shunt,  598 
Sialogogues,  259 
Sighing,  227 
Silver  lines,  136 
Simple  colors,  824 
Simultaneous  contrast,  830 
Sinuses,  137 
Sitting,  555 
Size,  419,  420 

estimation  of,  841 
increase  in,  419 
false  estimate  of,  843 
Skatol,  300,327,454 
Skin,  absorption  by,  498 
chorium  of,  487 
currents  of,  607 
epidermis,  487 
functions  of  487 
galvanic     conduction     of, 

499 

glands  of,  492 

historical,  499 

pigments,  495 

protective  covering,  493 

respiratory  organ,  238, 493 

structure  of,  487 

varnishing  the,  493 
Skin  currents,  61 1 
Sleep,  735 
Small  intestine,  336 


INDEX. 


971 


Small  intestine,  absorption by,344 
structure  of,  336 
Smegma,  494 
Smell,  sense  of,  871 
Sneezing,  227 
Snellen's  types,  805 
Sniffing, 872 
Snoring,  227 
Sodic  chloride,  421 

salts,  421 
Solitary  follicles,  339,  342 
Somatopleure,  920 
Somnambulism,  734 
Sorbin,  432 
Sound,  848 

cardiac,  1 09 

conduction  to  ear,  848, 

857 
direction  of,  869 
distance  of,  869 
perception  of,  869 
reflection  of,  848 
Sounds,  cardiac,  112 

cracked  pot,  223 
respiratory,  223 
tympanitic,  223 
vesicular,  223 
Spasm  centre,  730 
Spasmus  nictitans,  653 
Specific  energy,  781,  823 
Spectacles,  806 
Spectra,  absorption,  62 
flame,  62 
ocular,  814 
Spectroscope,  61 
Spectrum  mucro-lacrimale,  812 
of  bile,  314 
of  blood,  62 
of  muscle,  509 
Speech,  569 

centre  for,  760 
pathological   variations, 

573 
Spermatin,  898 
Spermatozoa,   898 
Spermatoblasts,  899 
Spheno-palatine  ganglion,  645 
Spherical  aberration,  807 
Sphincters,  552 
Sphincter  ani,  279 

pupillse,  786 
urethras,  483 
Sphygmogram,  144 
Sphygmograph,  140 

Dudgeon's,  142 
Ludwig's,  142 
Marey's,  141 
SphygmometA-,  140 
Sphygmomanometer,  165 
Sphygmoscope,  144 
Sphygmotonometer,  139 
Spina  bifida,  776,  922 
Spinal  accessory  nerve,  664 
Spinal  cord,  676 

action  of  blood  and  poi- 
sons on,  696 


Spinal  cord,  blood  vessels  of,  682 
centres,  693 

conducting  paths  in,  683 
conducting  system  of,683, 

696 
degeneration  of,  685 
development  of,  944 
excitability  of,  695 
Flechsig's  systems,  683 
functions  of,  683 
ganglion,  666 
Gerlach's  theory,  680 
nerves,  665 
neuroglia  of,  681 
nutritive  centres  in,  685 
reflexes,  686 
regeneration  of,  731 
secondary     degeneration 

of,  685 
segment  of,  685 
structure  of,  676 
time  of  development,  686 
transverse  section  of,  699 
iinilateral  section  of,  699 
vasomotor  centres  in,  727 
Spinal  cord,  Woroschiloff's  ob- 
servations, 697 
Spinal  nerves,  665 

anterior  roots  of,  669 
posterior  roots  of,  669 
Spiral  joints,  549 
Spirillum,  90,  324 
Spirochseta,  90,  324 
Spirometer,  21 1 
Splanchnic  nerve,  282 
Splanchnopleure,  920 
Spleen,  192 

action  of  drugs  on,  197 
chemical      composition, 

194 
contraction  of,  195 
extirpation  of,  194 
functions  of,  194 
influence  of   nerves  on, 

196 
oncograph,  195 
regeneration  of,  194 
structure,  192 
tumors  of,  197 
Spongin,  426 

Spontaneous  generation,  893 
Spores,  326 

Spring  kymograph,  164 
Spring  myograph,  529 
Springing,  555 

Sputum,    abnormal     coloration, 
248 
normal,  247 
Squint,  638 
Staircase,  535 
Stammering,  573 
Standing,  554 
Stannius's  experiment,  121 
Stapedius,  854 
Starch,  431 
Starvation,  408 


Stasis,  183 

Statical  theory  of  Goltz,  654 

Stationary  vibrations,  848 

Steapsin,  301 

Stenopaic  spectacles,  807 

Stenosis,  112 

Stenson's  experiment,  517 

Stercobilin,  314,  329 

Stercorin,  329 

Stereoscope,  841 

Stereoscopic  vision,  839 

Sternutatories,  227 

Stethograph,  213 

Stigmata,  136 

Stilling,  canal  of,  791 

Stimuli,  519 

adequate,  781 
heterologous,  781 
homologous,  781 
muscular,  522 
Stoffwechsel,  41 
Stomach,  284 

cancer  of,  331 
catarrh  of,  331 
changes  in  glands,  288 
gases  in,  297 
glands  of,  285,  286 
movements  of,  275 
structure  of,  284 
Stomata,  182,  350 
Stomodseum,  918 
Storage  albumin,  403 
Strabismus,  771 
Strangury,  486 
Strassburg's  test,  462 
Strise  medullares,  767 
Strobic  disks,  830 
Stroboscopic  disks,  830 
Stroma-fibrin  and  plasma-fibrin, 

78 
Stromuhr,  176 
Struggle  for  existence,  947 
Struma,  728 

Strychnin,  action  of,  687 
Stuttering,  573 
Subarachnoid  space,  776 
fluid,  776 
Subdural  space,  776 
Subjective  sensations,  782 
Sublingual  gland,  258 
Submaxillary  ganglion,  647 
atropin  on,  257 
g'and,  253 
saliva,  260 
Substantia  gelatinosa,  678 
Successive  beats,  868 

contrast,  832 
light-induction,  832 
Succinic  acid,  454 
Succus  entericus,  323 

action  of  drugs  on,  323 
Suction,  267 
Sudorifics,  495 
Sugars,  435 

estimation  of,  265 
tests  for,  264 


972 


INDEX. 


Sulphindigotate  of  soda,  472 
Summation  of  stimuli,  534,  687 
Summational  tones,  869 
Superfecundation,  91 2 
Superficial  reflexes,  691 
Superfoetation,  912 
Superior  maxillary  nerve,  644 
Supplemental  air,  210 
Supra-renal  capsules,  200 
Surditas  verbal  is,  763 
Suture,  secondary,  590 
Sutures,  549 
Swallowing  fluids,  719 
Sweat,  494 

chemical  composition, 

494 

conditions  influencing  se- 
cretion, 495 

excretion    of    substances 

by,  495 
glands,  492 
insensible,  494 
nerves,  496 
pathological  variations  of, 

497 

Sweat  centre,  496,  497,  731 
spinal,  730 

Swimming,  559 

Sympathetic  ganglion,  671 
nerve,  670 
section  of,  673,  726 
stimulation  of,  673, 
726 

Symphyses,  549 

Synchondroses,  549 

Syncope,  102 

Synergetic  muscles,  552 

Synovia,  548 

Syntonin,  292,  425 

Systole,  cardiac,  98 


Tabes,  697 

Taches  cerebrales.  728 

Tactile  areas,  764 

corpuscles,  880 

sensations,  881 

sensations,  conduction  of, 
696 
Taenia,  895 
Tail- fold,  921 
Talipes  calcaneus,  553 

equinus,  553 

varus,  553 
Tambour,  Marey's,  142 
Tapetum,  Si 7 
Tapping  experiment,  718 
Taste,  centre  for,  754 
organ  of,  874 
testing,  876 
Taste  bulbs,  875 
Taurin,  433 
Taurocholic  acid,  433 
Tea,  400 

eftects  of,  264 
Tears,  844 


Tegmentum,  768 
Tel; stereoscope,  841 
Telolemma,  508 
Temperature  of  animals,  366 

accom  modation 

for,  381 
artificial      increase 

of,  384 
estimation  of,  366 
febrile,  383 
how        influenced, 

370 
lowering  of,  386 
post  mortem,  385 
regulation  of,  376 
topography  of,  369 
variations  of,  373 
Temperature  sense,  887 

illusions    of, 
889 
Tendon,  506 

nerves  of,  511,  881 
reflexes,  692 
Tensor  choroideae,  801 

tympani,  853 
Terminal  arteries,  181 
Testicle,  descent  of,  941 
Testis,  896 
Tetanomotor,  584 
Tetanus,  534,  536,  586 
secondary,  609 
Tetronerythrin,  79 
Theobromin,  400 
Thermal  centre,  376 
nerves,  376 
Thermo-electric  methods,  367 
needles,  368 
Thermogenesis,  364 
Thermometer,  366 

clinical,  366 
maximal     and 

minimal,  366 
metastatic,  368 
outflow,  367 
Thermometry,  366 
Thirst,  403 
Thiry's  fistula,  322 
Thomsen's  disease,  533 
Thoracometer,  220 
Thrombosis,  74 
Thymus,  197 

development  of,  932 
Thyroid,  198 

development  of,  932 
Tidal  air,  210 

wave,  145 
Timbre,  569,  571,  861 
Time  in  psychical  processes,  735 
Time  sense,  863 
Tinnitus,  655 
Tissue  formers,  403 

metabolism  of, 

405 
regeneration  of, 
406 
Tizzoni's  reaction,  309 


Tobin's  tubes,  245 
Tomes,  fibres  of,  268 
Tone  inductorium,  537 
Tones,  863 
Tongue,  glands  of,  250 

movements  of,  271 
nerves  of,  272 
taste  bulbs  of,  875 
Tonometer,  123 
Tonsils,  251 
Tonus,  694 
Tooth,  268 

action  of  drugs  on,  271 
chemistry  of,  269 
development  of,  270 
eruption  of,  270,  271 
permanent,  271 
pulp  of,  268 
structure  of,  268 
temporary,  270 
Topography,  cerebral,  "J $6,  764 
Toricelli's  theorem,  132 
Torpedo,  629 
Torticollis,  664 
Touch  corpuscles,  878 
Touch,  sense  of,  878 
Trachea,  203 
Transfusion,  189 

of  blood,  189 
of  other  fluids,  191 
Transitional  epithelium,  480 
Transplantation  of  tissues,  419 
Transudations,  360 
Trapezius,  spasm  of,  664 
Traube-Hering  curves,  168 
Traumatic       degeneration       of 

nerves,  589 
Trehalose,  431 
Trichina,  895 
Trigeminus,  640 

gangHaof,64l,645, 

646,  647 
inferior      maxillary 

branch,  645 
neuralgia  of,  648 
ophthalmic  branch, 

641 
paralysis  of,  649 
pathological,  648 
section  of,  643,  648 
superior    maxillary 

branch,  644 
trophic  functions  of, 

643 

Triple  phosphate,  457 

Trismus,  648 

Trochlearis,  639 

Trommer's  test,  2^4 

TropKolin,  288 

Trophic  centres,  589 
fibres,  589 
nerves,  589,  632 

Trophoneuroses,  632 

Trotting,  558 

Trypsin,  300 

Trypsinogen,  300 


INDEX. 


973 


Tryptone,  299 
Tube  casts,  466 
Tubes,  capillary,  134 

division  of,  134 

elastic,  134 

movements   of  fluids  in, 
134 

rigid,  134 
Tumultus  sermonis,  761 
Tunicin,  432 
Turacin,  429 
Tiirck's  meiiod,  691 
Twins,  912 
Twitch,  528 
Tympanic  membrane,  849 

artificial,  851 
Tyrosin,  300,  433,  465 


Ulcer  of  foot,  perforating,  632 
Umbilical  arteries,  924 
cord,  927 
veins,  924 
vesicle,  921 
Unipolar  induction,  600 

stimulation,  587 
Upper  tones,  863 
Urachus,  924 
Uraemia,  479 
Urates,  448 
Urea,  443 

antecedents  of,  445 
compounds  of,  445 
decomposition  of,  444 
effect  of  exercise  on,  444 
ferment,  457 
formation    of,    445,   473, 

.474 
nitrate  of,  445 
occurrence  of,  445 
oxalate  of,  446 
pathological,  445 
phosphate  of,  446 
preparation  of,  445 
properties  of,  443 
qualitative   estimation    of, 

446 
quantitative  estimation  of, 

446 
quantity  of,  444 
relation    of,    to   muscular 
work,  444 
Ureameter,  446 
Ureter,  ligature  of,  474 
pressure  in,  471 
structure   and    functions 
of,  480 
Uric  acid,  447 

diathesis,  480 
formation  of,  474 
occurrence,  448 
properties  of,  447 
qualitative  estimation,  449 
quantitative    estimation    of, 

449 
acid,  quantity,  447 


Uric  acid,  solubility,  448 

tests  for,  449 
Urinary  bladder,  481 
calculi,  468 
closure  of,  483 
deposits,  465 
development  of,  925 
organs,  434 
pressure  in,  485 
Urine,  440 

accumulation  of,  483 

aceton  in,  464 

acid  fermentation,  456 

acidity,  443 

albumin  in,  457 

alkaline        fermentation, 

457 
alkaloids,  480 
amount  of  solids,  441 
bile  in,  462 
blood  in,  460 
calculi,  468 
changes   of    in   bladder, 

485 
characters  of,  440 
color,  441 

coloring  matters  of,  452 
consistence,  442 
cystin  in,  465 
deposits  in,  465 
dextrin  in,  464 
effect  of  blood   pressure 

on,  470 
egg  albumin  in,  459 
electrical     condition    of, 

629 
excretion  of  pigments  by, 

473 
fermentations  of,  456 
ferments  in,  454 
fluorescence,  442 
fungi  in,  466 
gases  in,  456 
globulin  in,  459 
hemi-albumose,  459 
incontinence  of,  486 
influence   of  nerves   on, 

476 
inorganic       constituents, 

454 
inosit  in,  464 
leucin  in,  465 
milk-sugar  in,  464 
movement  of,  481 
mucin  in,  442,  460 
mucus  in,  442,  460 
organisms  in,  465 
passage      of     substances 

into,  475 
peptone  in,  459 
phosphoric  acid  in,  455 
physical     characters     of, 

440 
pigments  of.  452 
propeptone  in,  459 
quantity,  440 


Urine,  reaction,  442 

retention  of,  486 
secretion  of,  469 
siHcic  acid  in,  456 
sodic  chloride  in,  454 
solids  of,  441 
specific  gravity,  440 
spontaneous    changes  in, 

456 
sugar  in,  462 
sulphuric  acid  in,  455 
taste  of,  442 

taste  for  albumin  in,  458 
tube  casts  in,  466 
tyrosin  in,  465 

Urinometer,  440 

Urobilin,  67,  452 

Urochrome,  452 

Uroerythrin,  452 

Uro-genital  sinus,  942 

Uromelanin,  452 

Urorubin,  452 

Urostealith,  468 

Uterine  milk,  927 

Uterus,  905 

development  of,  940 
involution  of,  947 
nerves  of,  946 

Utricle,  858 

Uvea,  785 


Vagotomy,  716 

Vagus,  656 

cardiac  branches,  660 

depressor  nerve   of,  167, 
660 

effect  of  section,  66 1 

on  heart,  169 

pathological,  663 

pneumonia   after  section, 
661 

reflex  effects  of,  662 

stimulation  of,  169,  719 

unequal    excitability    of, 
663 
Valleix's  points  douloureux,  890 
Valsalva's  experiment,  129, 154 
Valve,  ileo-colic,  277 

pyloric,  275 
Valves  of  heart,  95 

disease  of,  iii 

injury  to,  lOl 

of  veins,  136  ■ 

sounds  of,  185 
Valvulse  conniventes,  336 
Varicose  fibres,  575 
Varix,  172 

Varnishing  the  skin,  387 
Vas  deferens,  897 
Vasa  vasorum,  137 
Vascular    system,    development 

of,  934 
Vaso  dilator  centre,  729 
nerves,  729 
Vaso-formative  cells,  52 


974 


INDEX. 


Vasomotor  centre,  4^2 

destruction  of,  723 
nerves,  722 
spinal,  727 

Vasomotor     nerves,   course   of, 

723 
Vater's  corpuscles,  879 
Vegetable  all)umin,  425 
casein,  425 
foods,  397 
preserveti,  399 
proteids,  425 
Veins,  136 

cardinal,  936 
development  of,  936 
movement    of  blood    in, 

183 
murmurs  in,  1S5 
pressure  in,  171 
pulse  in,  1S5 
structure  of,  137 
tonus  of,  723 
valves  in,  137,  1S5 
valvular  sounds  in,  1 85 
varicose,  172 
velocity  of  blood  in,  1S3 
Vella's  fistula,  322 
Velocity  of  blood  stream,  132 
Venous  blood,  86 
Ventilat  on,  245 
Ventricles,  94,  108 

aspiration,  99 
brain,  776 
capacity  of,  161, 179 
fibres  of,  94 
impulse  of,  104 
negative  pressure  in, 

100 
systole  of,  100,  108 
Veratrin,  532 
Vemix  caseosa,  494 
Vertebrct,  mobility  of,  554 
Vertebral  column,  922 
Vertigo,  655 
Vestibular  sacs,  859 
Vibrations  of  body,  158 
Vibralives,  572 
Vibrio,  90 
Villus,  intestinal,  337 

absorption  by,  346 
chorionic,  925 


Villus,  contractility  of,  339 

placental,  926 
Violet-blindness,  828 
Visceral  arches,  923 
clefts,  923 
1  Vision,  binocular,  837 

stereoscopic,  839 
Visual  angle,  79S 

apparatus,  783 
centre,  752,  763 
pur|)le,  789,  823 
Vital  capacity,  210 
Vitellin,  424 
Vitelline  duct,  921 
Vitreous  humor,  791 
Vocal  cords,  559 

conditionsinfluencing  the, 
568 
N'oice,  509 

falsetto,  568 
[  in  animals,  574 

pathological  variations  of, 

573 
physics  of,  560 
pitch  of,  560 
production  of,  569 
range  of,  569 
\olunie  pulse,  188 
\'olumetric  method,  447 
Vomiting,  276 

centre  for,  276,  711 
Vowels,  570 

analysis  of,  570,  864 
artificial,  864 
formation  of,  570 
Ka'nig's  apparatus  for, 
867 

Wagner's  corpuscles,  878 

Waking,  735 

Walking,  555 

Wallerian  law  of  degeneration, 
589 

Wandering  cells,  349 

Warm-blooded  animals,  365 

Washed  blood  clot,  74 

Water,  38S,  421 

absorbed  by  skin,  498 
absorption  of,  344 
exhaled    by    skin,    238, 
492 


Water,  exhaled   from  lungs,  232 

hardness  of,  389 

impurities,  388 

in  urine,  440 

vapor  of,  in  air,  231 
Wave  pulse,  145 

propagation  of,  154 
Wave  motion,  134 
Wave  movements,  848 
Waves,  in  elastic  tubes,  156 
Weber's  paradox,  543 

law,  782 
Weigert's  method,  579 
Weight,  419 
Weyi's  test,  449 
Wharton's  jelly,  927 
Whispering,  570 
White  of  egg,  423 
Wine,  401 

Wolffian  Ixidies,  940 
ducts,  940 
Word  blindness,  761 
Word  deafness,  754,  761 
Work,  539 

unit  of,  36 


Xanthin,  450 
Xanthokyanopy,  828 
Xanthophane,  990 
Xanthoproteic  reaction,  423 
Xerosis,  644 

Yawning,  227 

Yeast,  428 
Yelk,  904 

cleavage  of,  914 

sac,  921 
Yellow  spot,  814 
Young- Helniholtz  theory,  826 

Zero  temperature,  888 
Zimniemiann,  blood  particles  of, 

Zinn,  zonule  of,  790 
Zoetrope,  830 
Zollner's  lines,  843 
Zona  pellucida,  901 
Zooglrta,  325 
Zymogen,  300 


